Effects of Midazolam/Dexmedetomidine with Buprenorphine or Extended-release Buprenorphine Anesthesia in C57BL/6 Mice

The effects of commonly used injectable combinations of anesthetics such as ketamine and xylazine, with or without acepromazine, vary widely across individuals, have a shallow-dose response curve, and do not provide long-term analgesia. These drawbacks indicate the importance of continuing efforts to develop safe and effective injectable anesthetic combinations for mice. In this study, a series of experiments was designed to validate the use of dexmedetomidine and midazolam to provide chemical restraint for nonpainful procedures and the addition of buprenorphine or extended-release buprenorphine to reliably provide a surgical plane of anesthesia in C57BL/6J mice. Loss of consciousness was defined as the loss of the righting reflex (LORR); a surgical plane of anesthesia was defined as the LORR and loss of pedal withdrawal after application of a 300 g noxious stimulus to a hind paw. The combination of intraperitoneal 0.25 mg/kg dexmedetomidine and 6 mg/kg midazolam produced LORR, sufficient for nonpainful or noninvasive procedures, without achieving a surgical plane in 19 of 20 mice tested. With the addition of subcutaneous 0.1 mg/kg buprenorphine or 1 mg/kg buprenorphine-ER, 29 of 30 mice achieved a surgical plane of anesthesia. The safety and efficacy of the regimen was then tested by successfully performing a laparotomy in 6 mice. No deaths occurred in any trial, and, when administered 1 mg/kg atipamezole IP, all mice recovered their righting reflex within 11 min. The anesthetic regimen developed in this study is safe, is reversible, and includes analgesics that previous studies have shown provide analgesia beyond the immediate postsurgical period. Buprenorphine-ER can be safely substituted for buprenorphine for longer-lasting analgesia.

Use of Ketamine or Xylazine to Provide Balanced Anesthesia with Isoflurane in C57BL/6J Mice

Balanced anesthesia-the use of a combination of drugs to achieve a desired anesthetic plane-offers many benefits, including smoother induction and recovery and fewer adverse effects than occur with individual drugs. Although premedication prior to inhalant anesthesia is routine in other species, mice are commonly induced with gas anesthesia alone. The hypothesis of this study was that premedication with ketamine or xylazine would safely reduce the stress of isoflurane induction and lower the minimum alveolar concentration (MAC) of isoflurane. Young adult male and female C57BL/6J mice were premedicated with ketamine (100 mg/kg), xylazine (4 mg/kg), or isotonic crystalloid (0.1 mL) and were used in 4 experiments. First, isoflurane induction was video recorded under all test conditions, and the videos were scored according to a behavioral ethogram to identify signs of distress. Mice in the ketamine group experienced tremors and ataxia before and dur- ing induction. Therefore, ketamine was given after induction with isoflurane in subsequent experiments. Second, the MAC value for each anesthetic protocol was determined by using quantal and bracketing analysis. Third, mice were anesthetized according to the 3 protocols, and vital parameters were monitored for 60 min. Finally, anesthetized mice were challenged with hypoxia and hypovolemia, and vital parameters were monitored. Premedication with xylazine significantly reduced the stress scores for isoflurane induction (control, 7.3 ± 1.5; ketamine, 6.0 ± 3.0; xylazine, 3.1 ± 1.0). Ketamine and xylazine both reduced the MAC of isoflurane (control, 1.89%; ketamine, 0.96%; xylazine, 1.20%). All mice survived 60 min of anesthesia and the hypoxia-hypovolemia challenge. Premedication with xylazine reduced the stress of induction and lowered the necessary dose of isoflurane in C57BL/6J mice to maintain a surgical plane of anesthesia. We recommend administering xylazine before isoflurane induction and anesthesia of healthy mice that are undergoing procedures in which 100% oxygen is provided and anticipated blood loss is less than 10% to 15% of the total blood volume.

Mouse Anesthesia: The Art and Science

There is an art and science to performing mouse anesthesia, which is a significant component to animal research. Frequently, anesthesia is one vital step of many over the course of a research project spanning weeks, months, or beyond. It is critical to perform anesthesia according to the approved research protocol using appropriately handled and administered pharmaceutical-grade compounds whenever possible. Sufficient documentation of the anesthetic event and procedure should also be performed to meet the legal, ethical, and research reproducibility obligations. However, this regulatory and documentation process may lead to the use of a few possibly oversimplified anesthetic protocols used for mouse procedures and anesthesia. Although a frequently used anesthetic protocol may work perfectly for each mouse anesthetized, sometimes unexpected complications will arise, and quick adjustments to the anesthetic depth and support provided will be required. As an old saying goes, anesthesia is 99% boredom and 1% sheer terror. The purpose of this review article is to discuss the science of mouse anesthesia together with the art of applying these anesthetic techniques to provide readers with the knowledge needed for successful anesthetic procedures. The authors include experiences in mouse inhalant and injectable anesthesia, peri-anesthetic monitoring, specific procedures, and treating common complications. This article utilizes key points for easy access of important messages and authors’ recommendation based on the authors’ clinical experiences.

Effects of Oxygen Supplementation on Injectable and Inhalant Anesthesia in C57BL/6 Mice

Oxygen supplementation is rarely considered when anesthetizing laboratory mice, despite reports that mice become profoundly hypoxic under anesthesia. Little is known about the effects of hypoxia on anesthetic performance. This article focuses on the effects of oxygen supplementation on physiologic parameters and depth of anesthesia in male and female C57BL/6 mice. Anesthesia was performed via common injectable anesthetic protocols and with isoflurane. Mice anesthetized with injectable anesthesia received one of 3 drug protocols. Low-dose ketamine/xylazine (100/8 mg/kg) was chosen to provide immobilization of mice, suitable for imaging procedures. Medium-dose ketamine/xylazine/acepromazine (100/10/1 mg/kg) was chosen as a dose that has been recommended for surgical procedures. High-dose ketamine/xylazine/acepromazine (150/12/3 mg/kg) was chosen after pilot studies to provide a long duration of a deep plane of anesthesia. We also tested the effects of oxygen supplementation on the minimum alveolar concentration (MAC) of isoflurane in mice. Mice breathed supplemental 100% oxygen, room air, or medical air with 21% oxygen. Anesthetized mice that did not receive supplemental oxygen all became hypoxic, while hypoxia was prevented in mice that received oxygen. Oxygen supplementation did not affect the MAC of isoflurane. At the high injectable dose, all mice not receiving oxygen supplementation died while all mice receiving oxygen supplementation survived. At low and medium doses, supplemental oxygen reduced the duration of the surgical plane of anesthesia (low dose with oxygen: 22 ± 14 min; low dose without supplementation: 29 ± 18 min; medium dose with oxygen: 43 ± 18 min; medium dose without supplementation: 61 ± 27 min). These results suggest that mice anesthetized with injectable and inhalant anesthesia without supplemental oxygen are routinely hypoxic. This hypoxia prolongs the duration of anesthesia with injectable drug protocols and affects survival at high doses of injectable anesthetics. Because of variable responses to injectable anesthetics in mice, oxygen supplementation is recommended for all anesthetized mice.

A Survey of Laboratory Animal Veterinarians Regarding Mouse Welfare in Biomedical Research

The quality of research animal welfare is undeniably linked to the quality of scientific results generated from the animals. Although mice are the most commonly used mammalian species in biomedical research, little information is available about what factors should be considered to promote future progress. To address this issue, the Animal Welfare Committee of the American Society of Laboratory Animal Practitioners (ASLAP) surveyed laboratory animal veterinarians to obtain their opinions about the welfare of mice and to consider the roles of 5 factors that significantly affect animal welfare in biomedical research: husbandry, clinical care, experimental use, regulatory oversight, and training. The survey revealed that 95% of veterinarians scored mouse welfare as acceptable to excellent, although areas for improvement remain. These areas include: 1) training of researchers performing experimental procedures; 2) the frequency of monitoring mice likely to experience pain and distress due to experimental manipulation; 3) inclusion of the institutional veterinary staff in the monitoring of mice likely to experience pain and distress; 4) continued improvement in the environmental enrichment provided to mice; 5) the ability of the IACUC to ensure that instances of noncompliance are fully addressed in order to prevent reoccurrence both within laboratories and among other research groups at the institution; and 6) reliance on non-veterinarians to perform examinations, diagnose disease, and prescribe the treatment of sick or injured mice.

Effects of Standard and Sustained-release Buprenorphine on the Minimum Alveolar Concentration of Isoflurane in C57BL/6 Mice

Both standard and sustained-release injectable formulations of buprenorphine (Bup and BupSR, respectively) are used as preemptive analgesics, potentially affecting gas anesthetic requirements. This study tested the effects of Bup and BupSR on isoflurane requirements and confirmed that buprenorphine could reduce isoflurane requirements during a laparotomy in mice. We hypothesized that both Bup and BupSR would significantly decrease the required minimum alveolar concentration (MAC) of isoflurane. C57BL/6 mice received either isotonic crystalloid fluid (control), Bup (0.1 mg/kg), or BupSR (1.2 mg/kg) subcutaneously 10 min prior to the induction of anesthesia. Each anesthetized mouse was tested at 2 isoflurane concentrations. A 300-g noxious stimulus was applied at each isoflurane concentration, alternating between hindfeet. In addition, a subset of mice underwent terminal laparotomy or 60 min of anesthesia after injection with Bup, BupSR, or saline to ensure an appropriate surgical plane of anesthesia. Mice were maintained at the lowest isoflurane concentration that resulted in 100% of mice at a surgical plane from the aforementioned MAC experiments (control, 2.0%; Bup and BupSR, 1.7%). Analysis showed that both Bup and BupSR significantly decreased isoflurane requirements by 25.5% and 14.4%, respectively. The isoflurane MAC for the control injection was 1.80% ± 0.09%; whereas Bup and BupSR decreased MAC to 1.34% ± 0.08% and 1.54% ± 0.09%, respectively. Sex was not a significantly different between the injection groups during MAC determination. All of the mice that underwent surgery achieved a surgical plane of anesthesia on the prescribed regimen and recovered normally after discontinuation of isoflurane. Lastly, heart and respiratory rates did not differ between mice that underwent surgery and those that were anesthetized only. Bup and BupSR are MAC-sparing in male and female C57BL/6 mice and can be used for effective multimodal anesthesia.

Continuous Rate Infusion of Alfaxalone during Ketamine-Xylazine Anesthesia in Rats

Alfaxalone is an injectable anesthetic agent that is used in veterinary medicine for general anesthesia. We evaluated the safety and efficacy of alfaxalone delivered through continuous rate infusion by comparing ketamine-xylazine-alfaxalone (KXA) anesthesia with ketamine-xylazine (KX) anesthesia in Sprague-Dawley rats. Anesthesia was induced in male and female rats by using subcutaneous KX. After induction, rats in the KXA group received alfaxalone (10 mg/kg/h IV) for 35 min, whereas rats in the KX group did not receive alfaxalone. At the end of the trial, alfaxalone was discontinued, and xylazine was reversed in all rats by using atipamezole. Throughout anesthesia, we assessed forepaw withdrawal reflex (FPWR), hindpaw withdrawal reflex (HPWR), response to surgical stimulation, heart rate, respiratory rate, SpO₂, body temperature, and time to standing. KXA produced a reliable surgical plane of anesthesia, as evidenced by the loss of both FPWR and HPWR and lack of response to surgical stimulation in all 16 rats, whereas only 6 of the 16 rats in the KX group lost HPWR. No rat in the KXA group regained a paw withdrawal reflex during alfaxalone administration, whereas 3 of the 12 rats (25%) in the KX group that reached a surgical plane of anesthesia exited that plane within the 35-min timeframe. Neither heart rate, respiratory rate, SpO₂, body temperature, nor time to standing differed between KXA and KX groups; and there were no sex-associated differences in anesthesia response. These results indicate that alfaxalone (10 mg/kg/h IV) delivered through continuous rate infusion, in combination with ketamine and xylazine, provides a safe, prolonged, and reliable surgical plane of anesthesia in rats.

Hydromorphone-induced Neurostimulation in a Yorkshire Swine (Sus scrofa) after Myocardial Infarction Surgery

Opiates play an important role in the control of pain associated with thoracotomy in both people and animals. However, key side effects, including sedation and respiratory depression, could limit the use of opiates in animals that are lethargic due to cardiac disease. In addition, a rare side effect-neuroexcitation resulting in pathologic behavioral changes (seizures, mania, muscle fasciculation)-after the administration of morphine or hydromorphone is well-documented in many species. In pigs, however, these drugs have been shown to stimulate an increase in normal activity. In the case presented, we describe a Yorkshire-cross pig which, after myocardial infarction surgery, went from nonresponsive to alert, responsive, and eating within 30 min of an injection of hydromorphone. This pig was not demonstrating any signs associated with pain at this time, suggesting that the positive response was due to neural stimulation. This case report is the first to describe the use of hydromorphone-a potent, pure μ opiate agonist-for its neurostimulatory effect in pigs with experimentally-induced cardiac disease.

Postapproval Monitoring Practices at Biomedical Research Facilities

Federal regulations and policies require institutions to establish procedures for ongoing IACUC oversight of approved animal care and use program activities including animal procedures. To fulfill these requirements, research institutions implement postapproval monitoring (PAM) programs designed to assure compliance in animal activities. Although several references commenting on the requirement to conduct PAM are available, few publications discuss actual best practices for accomplishing PAM. Here we use information collected through a survey of large academic research institutions to identify common practices for conducting PAM reviews. Many similarities and differences exist between institutions, which may or may not influence the overall quality of an institution's PAM program.

Alfaxalone-Xylazine Anesthesia in Laboratory Mice (Mus musculus)

Since its recent reformulation, alfaxalone has gained popularity as an injectable veterinary anesthetic, including promising studies demonstrating the use of alfaxalone-xylazine for anesthesia in mice. Here we sought to expand these studies by testing additional dose ranges, elaborating on physiologic monitoring, testing sex- and strain-associated differences, and evaluating efficacy during actual surgical conditions. C57BL/6J mice showed significant sex-associated differences in anesthetic sensitivity, with males requiring higher doses of alfaxalone (80-120 mg/kg IP alfaxalone with 10 mg/kg IP xylazine) than females (40-80 mg/kg IP alfaxalone with 10 mg/kg IP xylazine) to achieve a surgical plane of anesthesia. In addition, female outbred CD1 mice were less sensitive to alfaxalone than female inbred C57BL/6J mice. When used during actual surgery, alfaxalone-xylazine administered intraperitoneally provided adequate anesthesia for a model of orthopedic surgery, whereas the same anesthetic regimen during laparotomy resulted in unacceptably high mortality; survival during laparotomy increased when drugs were administered subcutaneously. These results indicate that alfaxalone-xylazine may be a viable option for injectable surgical anesthesia in mice, although strain- and sex-associated differences and alternative routes of administration should be considered when optimizing the anesthetic regimen for specific experimental conditions.

Effects of Rodent Thermoregulation on Animal Models in the Research Environment

To best promote animal wellbeing and the efficacy of biomedical models, scientific, husbandry, and veterinary professionals must consider the mechanisms, influences, and outcomes of rodent thermoregulation in contemporary research environments. Over the last 2 decades, numerous studies have shown that laboratory mice and rats prefer temperatures that are several degrees warmer than the environments in which they typically are housed within biomedical facilities. Physiologic changes to rodents that are cage-housed under standard temperatures (20 to 26 °C) are attributed to 'cold stress' and include alterations in metabolism, cardiovascular parameters, respiration, and immunologic function. This review article describes common behavioral and physiologic adaptations of laboratory mice and rats to cold stress within modern vivaria, with emphasis on environmental enrichment and effects of anesthesia and procedural support efforts. In addition, potential interventions and outcomes for rodents are presented, relative to the importance of repeating and reproducing experiments involving laboratory rodent research models of human disease.

Effectiveness of Rapid Cooling as a Method of Euthanasia for Young Zebrafish (Danio rerio)

Despite increased use of zebrafish (Danio rerio) in biomedical research, consistent information regarding appropriate euthanasia methods, particularly for embryos, is sparse. Current literature indicates that rapid cooling is an effective method of euthanasia for adult zebrafish, yet consistent guidelines regarding zebrafish younger than 6 mo are unavailable. This study was performed to distinguish the age at which rapid cooling is an effective method of euthanasia for zebrafish and the exposure times necessary to reliably euthanize zebrafish using this method. Zebrafish at 3, 4, 7, 14, 16, 19, 21, 28, 60, and 90 d postfertilization (dpf) were placed into an ice water bath for 5, 10, 30, 45, or 60 min (n = 12 to 40 per group). In addition, zebrafish were placed in ice water for 12 h (age ≤14 dpf) or 30 s (age ≥14 dpf). After rapid cooling, fish were transferred to a recovery tank and the number of fish alive at 1, 4, and 12-24 h after removal from ice water was documented. Euthanasia was defined as a failure when evidence of recovery was observed at any point after removal from ice water. Results showed that younger fish required prolonged exposure to rapid cooling for effective euthanasia, with the required exposure time decreasing as fish age. Although younger fish required long exposure times, animals became immobilized immediately upon exposure to the cold water, and behavioral indicators of pain or distress rarely occurred. We conclude that zebrafish 14 dpf and younger require as long as 12 h, those 16 to 28 dpf of age require 5 min, and those older than 28 dpf require 30 s minimal exposure to rapid cooling for reliable euthanasia.

Small Ca2+ releases enable hour-long high-frequency contractions in midshipman swimbladder muscle

The swimbladder muscle of the Pacific midshipman fish contracts up to 360,000 times in an hour while generating mating calls. Using experimental measurements and computational modeling, Nelson et al. reveal the Ca²⁺ handling that permits these superfast muscle fibers to sustain high-frequency calling.

Type I males of the Pacific midshipman fish (Porichthys notatus) vibrate their swimbladder to generate mating calls, or “hums,” that attract females to their nests. In contrast to the intermittent calls produced by male Atlantic toadfish (Opsanus tau), which occur with a duty cycle (calling time divided by total time) of only 3–8%, midshipman can call continuously for up to an hour. With 100% duty cycles and frequencies of 50–100 Hz (15°C), the superfast muscle fibers that surround the midshipman swimbladder may contract and relax as many as 360,000 times in 1 h. The energy for this activity is supported by a large volume of densely packed mitochondria that are found in the peripheral and central regions of the fiber. The remaining fiber cross section contains contractile filaments and a well-developed network of sarcoplasmic reticulum (SR) and triadic junctions. Here, to understand quantitatively how Ca²⁺ is managed by midshipman fibers during calling, we measure (a) the Ca²⁺ pumping-versus-pCa and force-versus-pCa relations in skinned fiber bundles and (b) changes in myoplasmic free [Ca²⁺] (Δ[Ca²⁺]) during stimulated activity of individual fibers microinjected with the Ca²⁺ indicators Mag-fluo-4 and Fluo-4. As in toadfish, the force–pCa relation in midshipman is strongly right-shifted relative to the Ca²⁺ pumping–pCa relation, and contractile activity is controlled in a synchronous, not asynchronous, fashion during electrical stimulation. SR Ca²⁺ release per action potential is, however, approximately eightfold smaller in midshipman than in toadfish. Midshipman fibers have a larger time-averaged free [Ca²⁺] during activity than toadfish fibers, which permits faster Ca²⁺ pumping because the Ca²⁺ pumps work closer to their maximum rate. Even with midshipman’s sustained release and pumping of Ca²⁺, however, the Ca²⁺ energy cost of calling (per kilogram wet weight) is less than twofold more in midshipman than in toadfish.

Results of Survey Regarding Prevalence of Adventitial Infections in Mice and Rats at Biomedical Research Facilities

Control of rodent adventitial infections in biomedical research facilities is of extreme importance in assuring both animal welfare and high-quality research results. Sixty-three U.S. institutions participated in a survey reporting the methods used to detect and control these infections and the prevalence of outbreaks from 1 January 2014 through 31 December 2015. These results were then compared with the results of 2 similar surveys published in 1998 and 2008. The results of the current survey demonstrated that the rate of viral outbreaks in mouse colonies was decreasing, particularly in barrier facilities, whereas the prevalence of parasitic outbreaks has remained constant. These results will help our profession focus its efforts in the control of adventitial rodent disease outbreaks to the areas of the greatest needs.

Intraperitoneal Administration of Ethanol as a Means of Euthanasia for Neonatal Mice (Mus musculus)

The humane euthanasia of animals in research is of paramount importance. Neonatal mice frequently respond differently to euthanasia agents when compared with adults. The AVMA's Guidelines for the Euthanasia of Animals includes intraperitoneal injection of ethanol as "acceptable with conditions," and recent work confirmed that this method is appropriate for euthanizing adult mice, but neonatal mice have not been tested. To explore this method in neonatal mice, mouse pups (C57BL/6 and CD1, 162 total) were injected with 100% ethanol, a pentobarbital-phenytoin combination, or saline at 7, 14, 21, 28, or 35 d of age. Electrocardiograms, respiratory rates, and times to loss of righting reflex and death were recorded. Time to death (TTD) differed significantly between ethanol and pentobarbital-phenytoin at 7, 14, and 21 d and between ethanol groups at 7, 14, and 21 d compared with 35 d. The average TTD (± 1 SD) for ethanol-injected mice were: 7 d, 70.3 ± 39.8 min; 14 d, 51.7 ± 30.5 min; 21 d, 32.3 ± 20.8 min, 28 d, 14.0 ± 15.2; and 35 d, 4.9 ± 1.4. Mean TTD in pentobarbital-phenytoin-injected mice were: 7 d, 2.8 ± 0.4 min; 14 d, 2.9 ± 0.5 min; 21 d, 3.9 ± 1.2 min; 28 d, 3.9 ± 0.7 min; and 35 d, 4.4 ± 0.5. Although TTD did not differ between ethanol and pentobarbital-phenytoin at 28 d of age, the TTD in 3 of 12 mice was longer than 15 min after ethanol administration at this age. Therefore, ethanol should not be used as a method of euthanasia for mice younger than 35 d, because the criteria for humane euthanasia were met only in mice 35 d or older.

Intraperitoneal Continuous-Rate Infusion for the Maintenance of Anesthesia in Laboratory Mice (Mus musculus)

Intraperitoneal injectable anesthetics are often used to achieve surgical anesthesia in laboratory mice. Because bolus redosing of injectable anesthetics can cause unacceptably high mortality, we evaluated intraperitoneal continuous-rate infusion (CRI) of ketamine with or without xylazine for maintaining surgical anesthesia for an extended period of time. Anesthesia was induced in male C57BL/6J mice by using ketamine (80 mg/kg) and xylazine (8 mg/kg) without or with acepromazine at 0.1 mg/kg or 0.5 mg/kg. At 10 min after induction, CRI for 90 min was initiated and comprised 25%, 50%, or 100% of the initial ketamine dose per hour or 50% of the initial doses of both ketamine and xylazine. Anesthetic regimens were compared on the basis of animal immobility, continuous surgical depth of anesthesia as determined by the absence of a pedal withdrawal reflex, and mortality. Consistent with previous studies, the response to anesthetics was highly variable. Regimens that provided the longest continuous surgical plane of anesthesia with minimal mortality were ketamine-xylazine-acepromazine (0.1 mg/kg) with CRI of 100% of the initial ketamine dose and ketamine-xylazine-acepromazine (0.5 mg/kg) with CRI of 50% of the initial ketamine and xylazine doses. In addition, heart rate and respiratory rate did not increase consistently in response to a noxious stimulus during CRI anesthesia, even when mice exhibited a positive pedal withdrawal reflex, suggesting that these parameters are unreliable indicators of anesthetic depth during ketamine-xylazine anesthesia in mice. We conclude that intraperitoneal CRI anesthesia in mice prolongs injectable anesthesia more consistently and with lower mortality than does bolus redosing.

Intraperitoneal Injection of Ethanol for the Euthanasia of Laboratory Mice (Mus musculus) and Rats (Rattus norvegicus)

Compassion, professional ethics, and public sensitivity require that animals are euthanized humanely and appropriately under both planned and emergent situations. According to the 2013 AVMA Guidelines for the Euthanasia of Animals, intraperitoneal injection of ethanol is "acceptable with conditions" for use in mice. Because only limited information regarding this technique is available, we sought to evaluate ethanol by using ECG and high-definition video recording. Mice (n = 85) and rats (n = 16) were treated with intraperitoneal ethanol (70% or 100%), a positive-control agent (pentobarbital-phenytoin combination [Pe/Ph]), or a negative-control agent (saline solution). After injection, animals were assessed for behavioral and physiologic responses. Pain-assessment techniques in mice demonstrated that intraperitoneal injection of ethanol was not more painful than was intraperitoneal Pe/Ph. Median time to loss of consciousness for all mice that received ethanol or Pe/Ph was 45 s. Median time to respiratory arrest was 2.75, 2.25, and 2.63 min, and time (mean ± SE) to cardiac arrest was 6.04 ± 1.3, 2.96 ± 0.6, and 4.03 ± 0.5 min for 70% ethanol, 100% ethanol, and Pe/Ph, respectively. No mouse that received ethanol or Pe/Ph regained consciousness. Although successful in mice, intraperitoneal ethanol at the doses tested (9.2 to 20.1 g/kg) was unsuitable for euthanasia of rats (age, 7 to 8 wk) because of the volume needed and prolonged time to respiratory effects. For mice, intraperitoneal injection of 70% or 100% ethanol induced rapid and irreversible loss of consciousness, followed by death, and should be considered as "acceptable with conditions."

The Effects of Acute Blood Loss for Diagnostic Bloodwork and Fluid Replacement in Clinically Ill Mice

Despite the great value of diagnostic bloodwork for identifying disease in animals, the volume of blood required for these analyses limits its use in laboratory mice, particularly when they are clinically ill. We sought to determine the effects of acute blood loss (ABL) following blood collection for diagnostic bloodwork in healthy mice compared with streptozotocin-induced diabetic and dextran sulfate sodium (DSS)-treated dehydrated mice. ABL caused several mild changes in the control mice, with significant decreases in body weight, temperature, and activity in both experimental groups; increased dehydration and azotemia in the DSS-treated mice; and a significant drop in the blood pressure of the diabetic mice. To determine whether these negative outcomes could be ameliorated, we treated mice with intraperitoneal lactated Ringers solution either immediately after or 30 min before ABL. Notably, preABL administration of fluids helped prevent the worsening of the dehydration and azotemia in the DSS-treated mice and the changes in blood pressure in the diabetic mice. However, fluid administration provided no benefit in control of blood pressure when administered after ABL in the diabetic mice. Furthermore, fluid therapy did not prevent ABL-induced drops in body weight and activity. Although one mouse not receiving fluid therapy became moribund at the 24-h time point, no animals died during the 24-h study. This investigation demonstrates that blood for diagnostic bloodwork can be collected safely from clinically ill mice and that preemptive fluid therapy mitigates some of the negative changes associated with this blood loss.

Dose regimens, variability, and complications associated with using repeat-bolus dosing to extend a surgical plane of anesthesia in laboratory mice

Extending a surgical plane of anesthesia in mice by using injectable anesthetics typically is accomplished by repeat-bolus dosing. We compared the safety and efficacy of redosing protocols administered either during an anesthetic surgical plane (maintaining a continuous surgical plane, CSP), or immediately after leaving this plane (interrupted surgical plane, ISP) in C57BL/6J mice. Anesthesia was induced with ketamine, xylazine, and acepromazine (80, 8, and 1 mg/kg IP, respectively), and redosing protocols included 25% (0.25K), 50% (0.5K), or 100% (1.0K) of the initial ketamine dose or 25% (0.25KX) or 50% (0.5KX) of the initial ketamine-xylazine dose. In the ISP group, the surgical plane was extended by 13.8 ± 2.1 min (mean ± SEM) after redosing for the 0.25K redose with 50% returning to a surgical plane, 42.7 ± 4.5 min for the 0.5K redose with 88% returning to a surgical plane, and 44.3 ± 15.4 min for the 1.0K redose, 52.8 ± 7.2 min for the 0.25KX redose, and 45.9 ± 2.9 min for the 0.5KX redose, with 100% of mice returning to a surgical plane of anesthesia in these 3 groups. Mortality rates for ISP groups were 0%, 12%, 33%, 12%, and 18%, respectively. Mice in CSP groups had 50% mortality, independent of the repeat-dosing protocol. We recommend redosing mice with either 50% of the initial ketamine dose or 25% of the initial ketamine-xylazine dose immediately upon return of the pedal withdrawal reflex to extend the surgical plane of anesthesia in mice, optimize the extension of the surgical plane, and minimize mortality.

Antibiotic administration in the drinking water of mice

Although antibiotics frequently are added to the drinking water of mice, this practice has not been tested to confirm that antibiotics reach therapeutic concentrations in the plasma of treated mice. In the current investigation, we 1) tested the stability of enrofloxacin and doxycycline in the drinking water of adult, female C57BL/6 mice; 2) measured the mice's consumption of water treated with enrofloxacin, doxycycline, amoxicillin, or trimethoprim-sulfamethoxazole; and 3) used HPLC to measure plasma antibiotic concentrations in mice that had ingested treated water for 1 wk. Plasma concentrations of antibiotic were measured 1 h after the start of both the light and dark cycle. The main findings of the study were that both enrofloxacin and nonpharmaceutical, chemical-grade doxycycline remained relatively stable in water for 1 wk. In addition, mice consumed similar volumes of antibiotic-treated and untreated water. The highest plasma antibiotic concentrations measured were: enrofloxacin, 140.1 ± 10.4 ng/mL; doxycycline, 56.6 ± 12.5 ng/mL; amoxicillin, 299.2 ± 64.1 ng/mL; and trimethoprim-sulfamethoxazole, 5.9 ± 1.2 ng/mL. Despite the stability of the antibiotics in the water and predictable water consumption by mice, the plasma antibiotic concentrations were well below the concentrations required for efficacy against bacterial pathogens, except for those pathogens that are exquisitely sensitive to the antibiotic. The findings of this investigation prompt questions regarding the rationale of the contemporary practice of adding antibiotics to the drinking water of mice for systemic antibacterial treatments.

Incidence rates of spontaneous disease in laboratory mice used at a large biomedical research institution

A detailed epidemiologic survey of spontaneous diseases of mice used in biomedical research has not been performed in more than 4 decades. The current study examined all mouse disease reports for a subset of the University of Pennsylvania vivaria from October 2010 through September 2011. Mortality logs were examined over the same period of time. After eliminating protocol-related cases, the incidence rates for more than 30 diseases were calculated in terms of number of cases per 1000 cages per month. The average daily census for the facilities analyzed exceeded 29,000 cages and included more than 180 research groups. No single research group accounted for more than 4% of the total number of cases reported, indicating that this study did not simply quantify the spontaneous disease incidence in a limited number of research groups. Spontaneous mortality with unknown cause in adult and neonatal mice without prior reported illness was the most commonly reported issue, followed by dermatitis, ocular disease, and nonspecific clinical signs including lethargy, poor hair coat, and muscle wasting. These results indicate that improving the ability to identify sick mice is important in refining the care and use of mice in biomedical research. The information provided in the current study can help to provide a baseline for comparison, guide the field in directing mouse welfare research toward areas of need, and identify optimal methods of care for mice in biomedical research.

Comparison of thermoregulatory devices used during anesthesia of C57BL/6 mice and correlations between body temperature and physiologic parameters

General anesthesia affects several body systems, including thermoregulation. Decreased body temperature during anesthesia has potential negative effects, including delayed recovery to consciousness. Thermoregulatory support devices are used to maintain temperature in anesthetized rodents. We analyzed 2 novel thermoregulatory devices, thermogenic gel packs and reflective foils, to compare their effectiveness in maintaining temperatures with that of a standard circulating-warm-water blanket (CWWB) in C57BL/6 mice. Mice were grouped randomly: control (no thermal support), reflective foil, gel pack, gel pack plus reflective foil, CWWB on medium setting, CWWB on high setting, and CWWB on high setting plus reflective foil. Mice were anesthetized with isoflurane for 30 min, and temperature and heart and respiratory rates were monitored. Results indicated that the temperatures of mice with reflective foil only (start temperature, 36.2 ± 0.38 °C; end temperature, 28.8 ± 0.78 °C) did not differ significantly from those of control mice; however, the inclusion of foil heightened thermogenic properties when combined with other devices. Thermogenic gel packs and CWWB on high setting, both with and without reflective foil, caused significant temperature increases (that is, 1.6 °C to 4.4 °C) in mice. CWWB on medium setting (blanket temperature, 37.5 °C) maintained mice at temperatures within 1 °C of the 36.1 °C baseline. Strong correlations existed between temperature, heart and respiratory rates, and recovery time to consciousness. This information provides guidance regarding the use of thermoregulatory devices in anesthetized rodents and demonstrates the effect of maintaining a consistent core temperature on physiologic parameters.

Effects of Rho-kinase inhibition on myosin light chain phosphorylation and obstruction-induced detrusor overactivity

OBJECTIVES

To study the relationship between myosin light chain phosphorylation of the detrusor muscle and spontaneous smooth muscle contractions in a rabbit model of partial outlet obstruction.

METHODS

New Zealand white rabbit urinary bladders were partially obstructed for 2 weeks. Rabbits were euthanized, detrusor muscle strips were hung on a force transducer and spontaneous activity was measured at varying concentrations (0-0.03 μM/L) of the Rho-kinase inhibitors GSK 576371 or 0.01 μM/L Y27632. Basal myosin light chain phosphorylation was measured by 2-D gel electrophoresis in control and GSK 576371-treated strips.

RESULTS

Both drugs suppressed the force of spontaneous contractions, whereas GSK 576371 had a more profound effect on the frequency of the contractions. The IC₅₀ values for the inhibition of frequency and force of spontaneous contractions were 0.17 μM/L and 0.023 μM/L for GSK 576371, respectively. The compound significantly decreased the basal myosin light chain phosphorylation from 28.0 ± 3.9% to 13.5 ± 1.9% (P < 0.05). At 0.01 μM/L, GSK 576371 inhibited spontaneous bladder overactivity by 50%, but inhibited carbachol-elicited contractions force by just 25%.

CONCLUSIONS

These data suggest that Rho-kinase regulation of myosin light chain phosphorylation contributes to the spontaneous detrusor activity induced by obstruction. This finding could have therapeutic implications by providing another therapeutic option for myogenic, overactive bladder.

There is no slowing of motility speed with increased body size in rat, human, horse and rhinoceros independent on temperature and skeletal muscle myosin isoform

AIM

The predictions of scaling of skeletal muscle shortening velocity made by A.V. Hill 60-years ago have proven to be remarkably accurate at the cellular level. The current investigation looks to extend the study of scaling of contractile speed to the level of the molecular motor protein myosin at both physiological and unphysiological low temperatures.

METHODS

A single muscle cell in vitro motility assay to test myosin function, i.e. myosin extracted from short single muscle fibre segments, was used in four species representing a 5 500-fold difference in body mass (rat, man, horse and rhinoceros) at temperatures ranging from 15 to 35 °C.

RESULTS

The in vitro motility speed increased as the temperature of the assay increased, but a more profound effect was observed on the slower isoforms, narrowing the relative differences between fast and slow myosin heavy chain (MyHC) isoforms at physiological temperature in all species. The in vitro motility speed varied according to MyHC isoform within each species: I < IIa < IIx < IIb, but the expected scaling relationship within orthologous myosin isoforms was not observed at any temperature.

CONCLUSION

The scaling effect of body size and limb length on shortening velocity at the muscle fibre level, i.e. the decreasing shortening velocity associated with increasing body weight and limb length, was not confirmed at the motor protein level when including mammals of very large size. Thus, other factors than myosin structure and function appear to cause this scaling effect and thin filament isoform expression or myofilament lattice spacing are forwarded as alternative underlying factors.

Influence of oral contraceptive use on growth hormone in vivo bioactivity following resistance exercise: responses of molecular mass variants

The purpose was to examine effects of oral contraceptive (OC) use on plasma growth hormone (GH) responses to heavy resistance exercise. Sixty untrained women were placed into one of two groups: currently using OC (Ortho Tri-Cyclen) (n=25; mean+/-SD: 24.5+/-4.2y, 160.4+/-7.1cm, 64.1+/-11.3kg) or not currently using OC (NOC) (n=35; 23.6+/-4.6y, 165.9+/-6.0cm, 65.7+/-10.3kg). Participants performed an acute heavy resistance exercise test (AHRET; six sets of 10 repetition squats; 2min rest between sets) during days 2-4 of the follicular phase (NOC group) or of inactive oral contraceptive intake (OC group). Plasma was obtained before and immediately after AHRET and subsequently fractionated based on apparent molecular weight (>60kD, 30-60kD, and <30kD). GH was determined in unfractionated plasma and each plasma fraction using 4 methods: (1) Nichols Institute Diagnostics immunoradiometric assay (Nichols), (2) National Institute of Diabetes and Digestive Kidney Diseases (NIDDK) competitive radioimmunoassay, (3) DSL immunofunctional enzyme-linked immunoabsorbent assay (IFA) and (4) rat tibial line bioassay. GH increased (P<0.05) in all fractions post-AHRET for the Nichols, NIDDK, and IFA. The OC group displayed higher resting GH for the NIDDK, and higher exercise-induced GH for the IFA, Nichols, and NIDDK in unfractionated plasma and >60kD subfraction compared to NOC group. No differences were observed for the tibial line bioassay. OC use augmented immunological GH response to AHRET in unfractionated plasma and >60kD molecular weight subfraction. However, OC use only increased biological activity of GH in one of two bioassays. These data demonstrated that GH concentrations at rest and following exercise are assay-dependent.

Partial bladder outlet obstruction selectively abolishes protein kinase C induced contraction of rabbit detrusor smooth muscle

PURPOSE

Despite the acute onset, partial bladder outlet obstruction in the rabbit induces detrusor remodeling similar to that in men with benign prostatic hyperplasia in terms of its impact on structural and functional alterations in smooth muscle. We determined if partial bladder outlet obstruction induced remodeling alters the protein kinase C signaling pathway that leads to contraction.

MATERIALS AND METHODS

Smooth muscle from control animals and those subjected to 2 weeks of partial bladder outlet obstruction were mounted for isometric force recording, measurement of myosin light chain phosphorylation and levels of adducin phosphorylation. Bladder muscle strips were stimulated by phorbol dibutyrate or carbachol in the presence and absence of bisindolylmaleimide-1.

RESULTS

Smooth muscle strips from animals subjected to partial bladder outlet obstruction showed little to no increase in stress in response to phorbol dibutyrate and no increase in myosin light chain phosphorylation levels. Muscle strips from control animals produced a robust contraction with concomitant increases in myosin light chain phosphorylation. Inhibition of protein kinase C by bisindolylmaleimide-1 significantly depressed carbachol induced contractions of muscle strips from control animals but it had no effect on carbachol induced contractions of muscle strips from outlet obstructed animals. Phorbol dibutyrate increased phospho-adducin levels in muscle strips from the 2 animal sources, suggesting that protein kinase C could be activated.

CONCLUSIONS

We propose that partial bladder outlet obstruction does not alter protein kinase C activation, but rather abolishes or uncouples the pathway(s) downstream of protein kinase C, leading to contraction. Loss of this pathway may contribute to the loss of normal voiding behavior and the resultant decompensated state.

Chronic resistance training in women potentiates growth hormone in vivo bioactivity: characterization of molecular mass variants

This investigation determined the influence of acute and chronic resistance exercise on responses of growth hormone (GH) molecular variants in women. Seventy-four healthy young women (23 +/- 3 yr, 167 +/- 7 cm, 63.8 +/- 9.3 kg, 26.3 +/- 4.0% body fat) performed an acute bout of resistance exercise (6 sets of 10 repetition maximum squat). Blood samples were obtained pre- and postexercise. Resulting plasma was fractionated by molecular mass (fraction A, >60 kDa; fraction B, 30-60 kDa; and fraction C, <30 kDa) using chromatography. Fractionated and unfractionated (UF) plasma was then assayed for GH using three different detection systems (monoclonal immunoassay, polyclonal immunoassay, and rat tibial line in vivo bioassay). Subjects were then matched and randomly placed into one of four resistance exercise training groups or a control group for 24 wk. All experimental procedures were repeated on completion of the 24-wk resistance training programs. After acute exercise, immunoassays showed consistent increases in UF GH samples and fractions B and C; increases in fraction A using immunoassay were seen only in the monoclonal assay. No consistent changes in bioactive GH were found following acute exercise. Conversely, chronic exercise induced no consistent changes in immunoassayable GH of various molecular masses, whereas, in general, bioassayable GH increased. In summary, although acute exercise increased only immunoactive GH, chronic physical training increased the biological activity of circulating GH molecular variants. Increased bioactive GH was observed across all fractions and training regimens, suggesting that chronic resistance exercise increased a spectrum of GH molecules that may be necessary for the multitude of somatogenic and metabolic actions of GH.

Nocturnal growth hormone secretory dynamics are altered after resistance exercise: deconvolution analysis of 12-hour immunofunctional and immunoreactive isoforms

To characterize the effects of daytime exercise on subsequent overnight growth hormone (GH) secretion and elimination dynamics, serum was sampled, and GH was measured every 10 min for 12 h (1800 to 0600) in a control (CON) condition and after a 50-set resistance exercise protocol (EX) from 1500 to 1700. GH was measured with a conventional immunoreactive (IR) and an immunofunctional (IF) assay, and values were analyzed via a multi-parameter deconvolution analysis. EX resulted in a higher overnight secretory burst frequency [CON: 7.6 (SD 2.4) < EX: 9.4 (2.2) bursts per 12 h, P = 0.005] but lower mean burst mass [CON: 9.2 (4.7) > EX: 6.0 (2.9) μg/l, P = 0.019] and secretory rate [CON: 0.68 (0.29) > EX: 0.48 (0.23) μg/l/min; P = 0.015; ANOVA main effect means presented]. Approximate entropy (ApEn) was greater after EX, indicating a less orderly GH release process than CON. The estimated half-life of IF GH was significantly lower than IR GH [IF: 15.3 (1.1) < IR 19.8 (1.6) min, P < 0.001] but similar between the CON and EX conditions (∼17 min). Despite the changes in secretory dynamics, 12-h mean and integrated GH concentrations were similar between conditions. The results suggest that although quantitatively similar total amounts of GH are secreted overnight in CON and EX conditions, resistance exercise alters the dynamics of secretion by attenuating burst mass and amplitude yet increasing burst frequency.

Scaling of skeletal muscle shortening velocity in mammals representing a 100,000-fold difference in body size

To fully understand the effect of scaling on skeletal muscle shortening velocity (V (0)), it is important to know which phenotypic characteristics drive the changes between species. The purpose of the current investigation was to compare the effects of body mass and femur length, as an estimate of total limb length, on V (0) in species that cover a 100,000-fold range of body masses. Using the slack test procedure, V (0) was determined for fibers expressing types I and IIa myosin heavy chain (MyHC) isoforms in the mouse, rat, dog, human, horse, and rhinoceros under identical experimental conditions. A significant scaling effect on V (0) was detected when compared to body mass (type I fibers, r=0.95, p<0.01; type IIa fibers, r=0.83, p<0.05). However, the horse's V (0) for both fiber types was faster than the human's, despite having a 5-fold greater body mass than the human. When V (0) was scaled vs limb length, the strength of the relationships improved in fibers expressing both types I and IIa MyHC (r=0.98, p<0.001, and r=0.89, p<0.05, respectively) and scaled with the expected relationship, with the species with the shorter femur, the horse, having the faster V (0). A similar effect can be seen with stride frequency scaling more closely with limb length than body mass. These results suggest that limb length, not body mass, is a more relevant factor driving the scaling effect on skeletal muscle shortening velocity.

Growth hormone molecular heterogeneity and exercise

There are more than 100 molecular isoforms of circulating growth hormone (GH), but the traditional measurement approach in the exercise literature has only focused on the main isoform (i.e., 22 kDa). New assay methodologies now can assess various GH isoforms. The current data suggest that exercise results in the preferential release of GH isoforms with extended half-lives, thereby sustaining biological actions.

Influence of muscle strength and total work on exercise-induced plasma growth hormone isoforms in women

The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on human growth hormone (GH) variants to a heavy resistance exercise protocol in untrained women. From a distribution of 100 healthy, untrained women, the strongest 10 women (S) and the weakest 10 women (W) were compared for GH responses pre- and post an acute heavy resistance exercise test (AHRET, 6 sets of 10 RM squats, 2 minutes rest between sets). Blood samples were obtained pre-exercise and immediately post-exercise and subsequently analysed in total as well as fractionated by Sephacryl S-100R column chromatography into three molecular weight size classes: fraction A: > 60 kD, fraction B: 30-60 kD, fraction C: < 30 kD. For each total sample as well as each fraction, immunoreactive GH was measured via the Nichols IRMA, while bioactive GH was measured via the hypox rat tibial line bioassay and Diagnostic Systems Laboratory's immunofunctional GH ELISA. No exercise-induced changes or differences between groups were observed in the tibial line bioassay. However, the S group displayed a significantly higher pre-exercise resting value in the total fraction than the W group. Conversely, the W group exhibited a significantly higher pre-exercise value in the smaller molecular weight fraction C. With regards to the immunofunctional and immunoreactive assays, the total fraction, fraction A, and fraction B demonstrated significant (P < or = 0.05) exercise-induced increases in both the S and W group despite no group differences. For the Nichols and immunofunctional assays significant exercise-induced changes were observed in the smaller molecular weight C fraction in the W group but not the S group. However, the S group displayed a significantly higher pre-exercise value in fraction C relative to the W group. These data demonstrate for the first time that differences exist in the GH molecular weight variants between strong and weak untrained women, with the lower molecular weight variants seemingly less responsive to greater amounts of exercise in stronger women, thus suggesting differential regulation of GH molecular weight variants during resistance exercise due to pre-existing physical parameters.

Strength, workload, anaerobic intensity and the immune response to resistance exercise in women

AIM

The mechanism linking exercise intensity to the magnitude of the immune response is not completely understood. The purpose of this investigation was to determine whether the immune response to resistance exercise was associated with (1) changes in workload or (2) anaerobic exercise intensity.

METHODS

Previously untrained women underwent 6 months of resistance training for lower and upper body (TOTAL, n = 34) or for upper body alone (UPPER, n = 30). Lymphocyte subsets [T (CD3+), CD4+, CD8+, NK and B], functional markers (CD45RA+ and CD45RO+), and mitogen (phytohemagglutinin-M, concanavalin A and pokeweed mitogen) and superantigen (staphylococcus a. cowans)-stimulated proliferation were measured from blood samples collected pre- and post-exercise for a squat resistance exercise consisting of six sets of 10 repetitions at 75% of one repetition maximum. This protocol was performed before (T0) and after 3 (T3) and 6 months (T6) of training.

RESULTS

Lymphocyte recruitment to the circulation and proliferation following resistance exercise did not differ between training groups at any time, although the TOTAL group performed at a higher workload as training progressed. With respect to anaerobic intensity, exercise-induced increases in NK, CD4+, CD8+ and B lymphocyte concentrations were 42 (P = 0.07), 76 (P < 0.05), 72 (P < 0.05) and 242% (P < 0.01) greater in women in the highest compared with the lowest post-exercise lactate quartiles. Lymphocyte proliferation did not differ between lactate quartiles.

CONCLUSIONS

Anaerobic intensity, rather than increased strength and workload, is associated with the number of lymphocytes recruited to the circulation, but not T and B cell proliferation responses.

Effects of resistance training on resting immune parameters in women

The aim of this investigation was to determine whether intense resistance training of 6 months duration influenced resting immune parameters. Previously untrained women underwent one of four training programs or were non-training controls (CON, n=7). The resistance-training groups trained for total body power (TP, n=16), total body hypertrophy (TH, n=18), upper body power (UP, n=15) or upper body hypertrophy (UH, n=15). Immune parameters were measured from a fasting morning blood draw in September/October (0 months, t(0)), November/December (3 months, t(3)), and April/May (6 months, t(6)). Lymphocyte subsets [CD4+ T cells, CD8+ T cells, natural killer cells (NK), and B cells], and mitogen-stimulated proliferation were measured. The concentration of NK cells increased ( P<0.001) after 3 months of training for the resistance-training groups but not the CON group. This increase was not present after 6 months of training, thus it was a transient change. Lymphocyte proliferation responses were similar across time for the resistance-trained and CON groups for all stimulation conditions. Thus, resistance training induces a transient increase in NK cells but has little effect on lymphocyte trafficking or proliferation. This was consistent despite differences in the volume of muscle mass trained or the manner of training (power verses hypertrophy).

Effects of aging on human skeletal muscle myosin heavy-chain mRNA content and protein isoform expression

The purpose of this investigation was to determine the role played by pretranslational events in the decreased rate of myosin heavy-chain (MyHC) protein synthesis in old age. It was hypothesized that the decreased rate of MyHC protein synthesis reported in the elderly population is, at least in part, related to lower MyHC messenger RNA (mRNA) in old age. MyHC protein expression and mRNA levels for the three MyHC isoforms expressed in human muscle, that is, types I, IIa, and IIx/d, were measured in percutaneous vastus lateralis muscle biopsies from 16 young and 16 old healthy men. The MyHC isoform mRNA content was determined by quantitative, real-time reverse transcriptase polymerase chain reaction, and it was normalized to 18S ribosomal RNA; the relative MyHC protein isoform content was measured on silver-stained 7% sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. The old men demonstrated signs of sarcopenia, such as loss of muscle force, a trend toward a loss in lean body mass, and an increased percentage of body fat. Statistically significant correlations were observed between the isoform expression of different MyHCs at the protein and mRNA levels. However, the expression of the different MyHC isoforms at the mRNA and protein levels did not differ between the young and old men. Thus, the present results do not support the hypothesis that pretranslational events in MyHC protein synthesis are playing a significant role in the development of sarcopenia.

Effect of alkalosis on plasma epinephrine responses to high intensity cycle exercise in humans

The purpose of this study was to determine the effects of alkalosis on epinephrine concentrations in response to a 90 s maximal exercise test. A group of ten healthy men ingested either a bicarbonate (BS) supplement (0.3 g x kg(-1) of body mass of sodium bicarbonate) or placebo mixture (P) prior to performing a 90 s maximal cycle ergometer test. An indwelling Teflon cannula was placed in the antecubital vein and blood samples were drawn at three times at rest separated by 10 min, immediately following the protocol, and at 2.5, 5, and 10 min post exercise to determine plasma epinephrine concentrations. Sodium bicarbonate ingestion significantly ( P<0.05) induced alkalosis both at rest [mean (SD) pH=7.42 (0.02) BS, 7.38 (0.02) P] and after the exercise protocol [pH=7.16 (0.02) BS, 7.12 (0.02) P]. Plasma epinephrine concentrations were not significantly different immediately post exercise between the two conditions [4.2 (0.6) compared to 4.2 (0.7) pmol x ml(-1) in BS and P, respectively]. Work performed and power output attained were not significantly different between the two treatment conditions [mean power=258.7 (35.1) W BS, 260.3 (35.4) W P; peak power=534.7 (61.6) W BS, 535.7 (54.4) W P]. The primary finding of this investigation was that orally-induced alkalosis does not significantly affect plasma epinephrine concentrations or performance following 90 s of maximal cycle exercise in untrained men.

The relationship of natural killer cell counts, perforin mRNA and CD2 expression to post-exercise natural killer cell activity in humans

The aim of this study was to further investigate the mechanism of suppression of natural killer (NK) cell cytotoxic activity in peripheral blood following strenuous exercise. Blood was collected for analysis of NK cell concentration, cytotoxic activity, CD2 surface expression and perforin gene expression from runners (RUN, n=6) and resting controls (CONTROL, n=4) pre-exercise, 0, 1.5, 5, and 24 h following a 60-min treadmill run at 80% of VO2 peak. Natural killer cytotoxic activity, measured using a whole blood chromium release assay, fluctuated minimally in the CONTROL group and increased by 63% and decreased by 43% 0 and 1.5 h post-exercise, respectively, in the RUN group (group x time, P < 0.001). Lytic index (cytotoxic activity per cell) did not change. Perforin mRNA, measured using quantitative real-time polymerase chain reaction (QRT-PCR) decreased from pre- to post-exercise and remained decreased through 24 h. The decrease from pre- to 0 h post-exercise was seen predominately in the RUN group and was inversely correlated (r=- 0.95) to pre-exercise perforin mRNA. The NK cell surface expression of CD2 (lymphocyte function-associated antigen-2) was determined using fluorescent antibodies and flow cytometry. There was no change in the proportion of NK cells expressing CD2 or CD2 density. We conclude that (1) numerical redistribution accounted for most of the change in NK cytotoxic activity following a strenuous run, (2) decrease in perforin gene expression during the run was inversely related to pre-exercise levels but did not parallel changes in cytotoxic activity, and (3) CD2 surface expression was not affected by exercise.

Testosterone responses after resistance exercise in women: influence of regional fat distribution

Regional fat distribution (RFD) has been associated with metabolic derangements in populations with obesity. For example, upper body fat patterning is associated with higher levels of free testosterone (FT) and lower levels of sex-hormone binding globulin (SHBG). We sought to determine the extent to which this relationship was true in a healthy (i.e., non-obese) female population and whether RFD influenced androgen responses to resistance exercise. This study examined the effects of RFD on total testosterone (TT), FT, and SHBG responses to an acute resistance exercise test (ARET) among 47 women (22+/-3 years; 165+/-6 cm; 62+/-8 kg; 25+/-5%BF; 23+/-3 BMI). RFD was characterized by 3 separate indices: waist-to-hip ratio (WHR), ratio of upper arm fat to mid-thigh fat assessed with magnetic resonance imaging (MRI ratio), and ratio of subscapular to triceps ratio (SB/TRi ratio). Skinfolds were measured for the triceps, chest, subscapular, mid-axillary, suprailaic, abdomen, and thigh regions. The ARET consisted of 6 sets of 10 RM squats separated by 2-min rest periods. Blood was obtained pre- and post- ARET. TT, FT, and SHBG concentrations were determined by radioimmunoassay. Subjects were divided into tertiles from the indices of RFD, and statistical analyses were performed by an ANOVA with repeated measures (RFD and exercise as main effects). Significant (p < or = .05) increases following the AHRET were observed for TT (approximately 25%), FT (approximately 25%), and SHBG (4%). With multiple regression analysis, anthropometric measures significantly predicted pre- concentrations of FT, post-concentrations of TT, and pre-concentrations of SHBG. The SB/TRi and MRI ratios but not the WHR, were discriminant for hormonal concentrations among the tertiles. In young, healthy women, resistance exercise can induce transient increases in testosterone, and anthropometric markers of adiposity correlate with testosterone concentrations.

Effects of aging on regulation of muscle contraction at the motor unit, muscle cell, and molecular levels

Rodent motor units, muscle fibers, and motor proteins undergo significant aging-related changes. Such changes include spatial organization and physiological properties of fast- and slow-twitch single motor units, regulation of contractile speed and force generation capacity at the muscle fiber level, and altered functional properties of the motor protein myosin. In addition to specific changes, there also appears to be a "disorganization" of the coordinated expression of contractile, sarcoplasmic reticular, and mitochondrial protein isoforms in aging skeletal muscle. This is suggested to have a strong impact on aging-related impairments in muscle function in addition to the changes in specific muscle proteins.

Characteristics of circulating growth hormone in women after acute heavy resistance exercise

The effects of exercise on the molecular nature of secreted human growth hormone (GH) or its biological activity are not well understood. Plasma from women (average age 23.6 yr, n = 35), drawn before and after an acute heavy resistance exercise test, was fractionated by size exclusion chromatography into three size classes, namely, > 60 kDa (fraction A), 30-60 kDa (fraction B), and < 30 kDa (fraction C), before GH assay. Concentrations of GH in these fractions, as well as in unfractioned plasma, were measured by the Nichols immunoradiometric assay, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) polyclonal competitive RIA, Diagnostic Systems Laboratory's immunofunctional assay (measures dimerization-capable species), and the rat tibial bioassay. Significantly increased circulating GH concentrations of two- to fourfold were observed when immunoassays in unfractionated plasma samples were used, but they showed no significant change with use of the rat tibial bioassay. Significant exercise-induced increases in GH were found in fractions B and C but not in fraction A. Because chemical reduction of the samples before GH immunoassay significantly increased GH concentrations in fractions B and C (Nichols and NIDDK kits) after exercise, it is concluded that exercise may specifically increase release of disulfide-linked hormone molecules and/or fragments. Finally, because most of the GH released after exercise was able to dimerize the GH receptor in vitro, it is also concluded that these forms have the two intact binding sites required to initiate signal transduction in target cells.

LH secretion and testosterone concentrations are blunted after resistance exercise in men

This study examined the hypothesis that exercise-induced changes in circulating testosterone would be centrally mediated via hypothalamic-pituitary release of luteinizing hormone (LH). We tested this hypothesis by examining overnight LH, total and free testosterone (TT and FT), and cortisol (C) concentrations in 10 young healthy men (21 +/- 1 yr) during two experimental sessions: a control and an acute heavy-resistance exercise bout (50 total sets consisting of squats, bench press, leg press, and latissimus dorsi pull-down). Exercise was performed from 1500 to 1700, and blood sampling began at 1700 and continued until 0600 the next morning. Blood was sampled every 10 min for LH and every hour for TT, FT, and C. Hormonal concentrations were determined via RIA, and the secretion characteristics of LH were analyzed with deconvolution analysis. When overnight postexercise concentrations were compared with control concentrations, no statistically significant (P < or = 0.05) differences were observed for LH half-life, LH pulse frequency, interpulse interval, pulse amplitude, or pulse mass. Significant differences were observed for LH production rate (13.6 +/- 4 and 17.9 +/- 5 IU. l distribution volume(-1) x day(-1) for exercise and control, respectively, a 24% reduction). For the ANOVA marginal main effect means due to condition, C was significantly elevated (5.9 +/- 0.7 vs. 4.0 +/- 0.4 microg/dl), while TT (464 +/- 23 vs. 529 +/- 32 ng/dl) and FT (15.6 +/- 0.7 vs. 18.3 +/- 0.9 pg/ml) were significantly decreased for the exercise condition. These data demonstrate that the decline in overnight testosterone concentrations after acute heavy-resistance exercise is accompanied by a blunted LH production rate and elevated C concentrations.

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Effect of resistance training on women's strength/power and occupational performances

PURPOSE

The effects of resistance training programs on strength, power, and military occupational task performances in women were examined.

METHODS

Untrained women aged (mean +/- SD) 23 +/- 4 yr were matched and randomly placed in total- (TP, N = 17 and TH, N = 18) or upper-body resistance training (UP, N = 18 and UH, N = 15), field (FLD, N = 14), or aerobic training groups (AER, N = 11). Two periodized resistance training programs (with supplemental aerobic training) emphasized explosive exercise movements using 3- to 8-RM training loads (TP, UP), whereas the other two emphasized slower exercise movements using 8- to 12-RM loads (TH, UH). The FLD group performed plyometric and partner exercises. Subjects were tested for body composition, strength, power, endurance, maximal and repetitive box lift, 2-mile loaded run, and U.S. Army Physical Fitness Tests before (T0) and after 3 (T3) and 6 months of training (T6). For comparison, untrained men (N = 100) (MEN) were tested once.

RESULTS

Specific training programs resulted in significant increases in body mass (TP), 1-RM squat (TP, TH, FLD), bench press (all except AER), high pull (TP), squat jump (TP, TH, FLD), bench throw (all except AER), squat endurance (all except AER), 1-RM box lift (all except aerobic), repetitive box lift (all), push-ups (all except AER), sit-ups (all except AER), and 2-mile run (all).

CONCLUSIONS

Strength training improved physical performances of women over 6 months and adaptations in strength, power, and endurance were specific to the subtle differences (e.g., exercise choice and speeds of exercise movement) in the resistance training programs (strength/power vs strength/hypertrophy). Upper- and total-body resistance training resulted in similar improvements in occupational task performances, especially in tasks that involved upper-body musculature. Finally, gender differences in physical performance measures were reduced after resistance training in women, which underscores the importance of such training for physically demanding occupations.

Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise

This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.

Low-volume circuit versus high-volume periodized resistance training in women

PURPOSE

The purpose of this investigation was to determine the long-term training adaptations associated with low-volume circuit-type versus periodized high-volume resistance training programs in women.

METHODS

34 healthy, untrained women were randomly placed into one of the following groups: low-volume, single-set circuit (SSC; N = 12); periodized high-volume multiple-set (MS; N = 12); or nonexercising control (CON) group (N = 10). The SSC group performed one set of 8-12 repetitions to muscular failure 3 d x wk(-1). The MS group performed two to four sets of 3-15 repetitions with periodized volume and intensity 4 d x wk(-1). Muscular strength, power, speed, endurance, anthropometry, and resting hormonal concentrations were determined pretraining (T1), after 12 wk (T2), and after 24 wk of training (T3).

RESULTS

1-RM bench press and leg press, and upper and lower body local muscular endurance increased significantly (P < or = 0.05) at T2 for both groups, but only MS showed a significant increase at T3. Muscular power and speed increased significantly at T2 and T3 only for MS. Increases in testosterone were observed for both groups at T2 but only MS showed a significant increase at T3. Cortisol decreased from T1 to T2 and from T2 to T3 in MS. Insulin-like growth factor-1 increased significantly at T3 for SSC and at T2 and T3 for MS. No changes were observed for growth hormone in any of the training groups.

CONCLUSION

Significant improvements in muscular performance may be attained with either a low-volume single-set program or a high-volume, periodized multiple-set program during the first 12 wk of training in untrained women. However, dramatically different training adaptations are associated with specific domains of training program design which contrast in speed of movement, exercise choices and use of variation (periodization) in the intensity and volume of exercise.

The effects of 10 days of spaceflight on the shuttle Endeavor on predominantly fast-twitch muscles in the rat

The primary purpose of this investigation was to determine the effects of microgravity on muscle fibers of the predominantly fast-twitch muscles in the rat. Cross sectional area and myosin heavy chain (MHC) composition were assessed in order to establish the acute effects of microgravity associated with spaceflight. The extensor digitorum longus (EDL) and gastrocnemius muscles were removed from 12 male Fisher 344 rats which had undergone 10 days of spaceflight aboard the space shuttle Endeavor and from 12 age- and weight-matched control animals. Both groups of animals received similar amounts of food and water and were synchronized for photoperiods, environmental temperature, and humidity. Significant (P < 0.05) reductions in muscle fiber size were observed in the gastrocnemius (fiber types I, IIA, IIDB, and IIB) and EDL (fiber type IIB) muscles after spaceflight. Significant MHC isoform transformations also resulted during this brief period of microgravity exposure with a significant decrease in MHC IId isoform in the EDL muscle. A significant decrease was also observed in the MHC IId isoform in the superficial (white) component of the gastrocnemius muscle after spaceflight, although no alterations in MHC profile were demonstrated in the deep (red) component of this muscle. These findings highlight the rapid plasticity of skeletal muscle during short-term spaceflight. If such pronounced adaptations to spaceflight also occur in humans, then astronauts are likely to suffer severe decrements in skeletal muscle performance with long-term space flight and upon return to earth after both short- and long-term missions. Thus, countermeasures aimed at slowing or even preventing muscle fiber atrophy are warranted.

Regional body composition changes in women after 6 months of periodized physical training

Data are lacking regarding regional morphological changes among women after prolonged physical training. This study employed dual-energy X-ray absorptiometry to assess changes in whole body and regional (i.e., trunk, legs, arms) fat mass, lean mass, and bone mineral content body composition adaptations in 31 healthy women pre-, mid-, and post-6 mo of periodized physical training. These results were compared with those of 1) a control group of women who had not undergone the training program and were assessed pre- and post-6 mo and 2) a group of 18 men that was tested only once. Additionally, magnetic resonance imaging was used to assess changes in muscle morphology of the thigh in a subset of 11 members of the training group. Physical training consisted of a combination of aerobic and resistance exercise in which the subjects engaged for 5 days/wk for 24 wk. Overall, the training group experienced a 2.2% decrease, a 10% decrease, and a 2.2% increase for body mass, fat mass, and soft tissue lean mass, respectively. No changes in bone mineral content were detected. The women had less of their soft tissue lean mass distributed in their arms than did the men, both before and after the women were trained. Novel to this study were the striking differences in the responses in the tissue composition of the arms (31% loss in fat mass but no change in lean mass) compared with the legs (5.5% gain in lean mass but no change in fat mass). There was a 12% fat loss in the trunk with no change in soft tissue lean mass. Dual-energy X-ray absorptiometry and magnetic resonance imaging fat mass measurements showed good agreement (r = 0. 72-0.92); their lean mass measurements were similar as well, showing approximately 5.5% increases in leg lean tissue. These findings show the importance of considering regional body composition changes, rather than whole body changes alone when assessing the effects of a periodized physical training program.

Effects of exercise and alkalosis on serum insulin-like growth factor I and IGF-binding protein-3

This investigation examines the effects of orally induced alkalosis on serum IGF-I and IGFBP3 concentrations in response to an acute 90-s bout of high intensity cycle exercise. Ten healthy, active men, ages 24.60 +/- 4.90 years, participated in a randomized, double-blind, counterbalanced trial order with a cross-over design. Subjects ingested an experimental bicarbonate solution or a placebo solution. Blood was sampled at baseline; pre-exercise; and 0, 5, 10, and 30 min postexercise. The pH between groups for pre-exercise and postexercise time points differed significantly (p < or = .05) in the experimental condition (from 7.42 +/- 0.01 to 7.35 +/- 0.02) versus the placebo condition (from 7.36 +/- 0.01 to 7.25 +/- 0.03). Increases in IGF-I over resting conditions occurred with placebo conditions at 5 and 10 min postexercise and in the experimental condition at 5 min postexercise. Concentrations of IGFBP3 were elevated above baseline at IP in both experimental and placebo conditions.

The effects of short-term resistance training on endocrine function in men and women

This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5 min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly (P < or = 0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.