[Risk factors for surgical site infection after emergency abdominal surgery: a multicenter cross-sectional study in China]

Objective: Surgical site infection (SSI) is the most common infectious complication after emergency abdominal surgery (EAS). To a large extent, most SSI can be prevented, but there are few relevant studies in China. This study mainly investigated the current situation of SSI occurrence after EAS in China, and further explored risk factors for SSI occurrence. Methods: Multi-center cross-sectional study was conducted. Clinical data of patients undergoing EAS in 33 hospitals across China between May 1, 2019 and June 7, 2019 were prospectively collected, including perioperative data and microbial culture results from infected incisions. The primary outcome was the incidence of SSI after EAS, while the secondary outcomes were postoperative hospital stay, ICU occupancy rate, length of ICU stay, hospitalization cost, and mortality within postoperative 30 days. Univariate and multivariate logistic regression models were used to analyze the risk factors of SSI after EAS. Results: A total of 660 EAS patients aged (47.9±18.3) years were enrolled in this study, including 56.5% of males (373/660). Forty-nine (7.4%) patients developed postoperative SSI. The main pathogen of SSI was Escherichia coli [culture positive rate was 32.7% (16/49)]. As compared to patients without SSI, those with SSI were more likely to be older (median 56 years vs. 46 years, U=19 973.5, P<0.001), male [71.4% (35/49) vs. 56.1% (343/611), χ(2)=4.334, P=0.037] and diabetes [14.3% (7/49) vs. 5.1% (31/611), χ(2)=5.498, P=0.015]; with-lower preoperative hemoglobin (median: 122.0 g/L vs. 143.5 g/L, U=11 471.5, P=0.006) and albumin (median: 35.5 g/L vs. 40.8 g/L, U=9452.0, P<0.001), with higher blood glucose (median: 6.9 mmol/L vs. 6.0 mmol/L, U=17 754.5, P<0.001); with intestinal obstruction [32.7% (16/49) vs. 9.2% (56/611), χ(2)=25.749, P<0.001], with ASA score 3-4 [42.9% (21/49) vs. 13.9% (85/611), χ(2)=25.563, P<0.001] and with high surgical risk [49.0% (24/49) vs. 7.0% (43/611), χ(2)=105.301, P<0.001]. The main operative procedure resulting in SSI was laparotomy [81.6%(40/49) vs. 35.7%(218/611), χ(2)=40.232, P<0.001]. Patients with SSI experienced significantly longer operation time (median: 150 minutes vs. 75 minutes, U=25 183.5, P<0.001). In terms of clinical outcome, higher ICU occupancy rate [51.0% (25/49) vs. 19.5% (119/611), χ(2)=26.461, P<0.001], more hospitalization costs (median: 44 000 yuan vs. 15 000 yuan, U=24 660.0, P<0.001), longer postoperative hospital stay (median: 10 days vs. 5 days, U=23 100.0, P<0.001) and longer ICU occupancy time (median: 0 days vs. 0 days, U=19 541.5, P<0.001) were found in the SSI group. Multivariate logistic regression analysis showed that the elderly (OR=3.253, 95% CI: 1.178-8.985, P=0.023), colorectal surgery (OR=9.156, 95% CI: 3.655-22.937, P<0.001) and longer operation time (OR=15.912, 95% CI:6.858-36.916, P<0.001) were independent risk factors of SSI, while the laparoscopic surgery (OR=0.288, 95% CI: 0.119-0.694, P=0.006) was an independent protective factor for SSI. Conclusions: For patients undergoing EAS, attention should be paid to middle-aged and elderly patients and those of colorectal surgery. Laparoscopic surgery should be adopted when feasible and the operation time should be minimized, so as to reduce the incidence of SSI and to reduce the burden on patients and medical institutions.

Photocatalytic and adsorption property of ZnS–TiO2/RGO ternary composites for methylene blue degradation

The visible light–driven ZnS–TiO2/RGO nanocomposites, with good visible light–driven photocatalytic activity, utilizing graphene oxide as precursor, were successfully synthesized via a facile solvothermal thermal method with graphene oxide as precursor. Ti4+ ions were derived from titanium dioxide powder (TiO2, P25) and tetrabutyl titanate. S2− ions and Zn2+ ions were provided by sodium sulfide and zinc acetate, respectively. The photocatalytic and absorbance activity of the nanocomposites was investigated through the photocatalytic degradation of methylene blue in aqueous solution. The results showed that the ZnS–TiO2/RGO nanocomposite prepared by tetrabutyl titanate exhibited better photocatalytic and adsorbance activity for methylene blue under visible light irradiation and its photocatalytic efficiency reached 90% in 60-min light irradiation, almost 1.5 times that of the synthesized ZnS–TiO2/RGO by P25, which was attributed to a cooperative reaction because of an increase of photo-absorption effect of graphene sheets and photocatalytic effect of ZnS nanoparticles. The adsorbance activity for ZnS–TiO2/RGO–tetrabutyl titanate) reached 48%, which was almost 1.7 times higher than that of ZnS–TiO2/RGO-P25 and almost 3.7 times higher than that of ZnS/RGO.

Opposite effects of genistein on the regulation of insulin-mediated glucose homeostasis in adipose tissue

BACKGROUND AND PURPOSE

Genistein is an isoflavone phytoestrogen found in a number of plants such as soybeans and there is accumulating evidence that it has beneficial effects on the regulation of glucose homeostasis. In this study we evaluated the effect of genistein on glucose homeostasis and its underlying mechanisms in normal and insulin-resistant conditions.

EXPERIMENTAL APPROACH

To induce insulin resistance, mice or differentiated 3T3-L1 adipocytes were treated with macrophage-derived conditioned medium. A glucose tolerance test was used to investigate the effect of genistein. Insulin signalling activation, glucose transporter-4 (GLUT4) translocation and AMP-activated PK (AMPK) activation were detected by Western blot analysis or elisa.

KEY RESULTS

Genistein impaired glucose tolerance and attenuated insulin sensitivity in normal mice by inhibiting the insulin-induced phosphorylation of insulin receptor substrate-1 (IRS1) at tyrosine residues, leading to inhibition of insulin-mediated GLUT4 translocation in adipocytes. Mac-CM, an inflammatory stimulus induced glucose intolerance accompanied by impaired insulin sensitivity; genistein reversed these changes by restoring the disturbed IRS1 function, leading to an improvement in GLUT4 translocation. In addition, genistein increased AMPK activity under both normal and inflammatory conditions; this was shown to contribute to the anti-inflammatory effect of genistein, which leads to an improvement in insulin signalling and the amelioration of insulin resistance.

CONCLUSION AND IMPLICATIONS

Genistein showed opposite effects on insulin sensitivity under normal and inflammatory conditions in adipose tissue and this action was derived from its negative or positive regulation of IRS1 function. Its up-regulation of AMPK activity contributes to the inhibition of inflammation implicated in insulin resistance.

Serum high-density lipoprotein cholesterol and progression to arterial stiffness in middle-aged and elderly Chinese

BACKGROUND AND AIMS

Low high-density lipoprotein cholesterol (HDL-c) is a risk factor for cardiovascular disease. Brachial-ankle pulse wave velocity (baPWV) is an indicator of arterial stiffness, which is recognized as a predictor of cardiovascular disease. The aim of this study was to investigate the association between HDL-c and baPWV among middle-aged and elderly Chinese.

METHODS

A total number of 1133 Chinese (430 men, 703 women) aged from 50 to 90 years old were recruited from Shanghai downtown district. The baPWV and major cardiovascular risk factors of the participants were measured.

RESULTS

Serum HDL-c was negatively correlated with baPWV (r = -0.143, P < 0.001) after adjustment for age and gender. Multivariate linear regression analysis demonstrated that age (P < 0.001), systolic blood pressure (P < 0.001), HDL-c (P < 0.001), smoking (P = 0.001), BMI (P = 0.002), fasting plasma glucose (P = 0.004), and white blood cell (P = 0.005) were independently associated with baPWV. After multiple adjustments, participants in the highest quartile of HDL-c had an odds ratio of 0.442 (95% CI 0.268-0.729) for developing high arterial stiffness compared with participants in the lowest quartile. The association remained significant after further adjustment for major cardiovascular risk factors.

CONCLUSION

HDL-c has an independent protective effect on arterial stiffness in middle-aged and elderly Chinese. Early detection of HDL-c level is important in high risk populations with arterial stiffness. Increasing HDL-c level may be an attractive therapeutic target for the prevention of arterial function and subsequent disease.

Evaluation of health-related quality of life of rheumatoid arthritis patients treated with celecoxib

OBJECTIVE

To study the functional status and health-related quality of life (HRQOL) of patients with rheumatoid arthritis (RA) after treatment with celecoxib, compared with placebo and naproxen.

METHODS

This was a prospective, randomized, double-blind, parallel group trial conducted at 79 sites in the United States and Canada over a 12-week treatment period. Patients were randomly assigned to 5 groups: placebo, 100 mg twice a day of celecoxib, 200 mg twice a day of celecoxib, 400 mg twice a day of celecoxib, and 500 mg twice a day of naproxen. The Health Assessment Questionnaire (HAQ) disability index was used to measure functional status. The Medical Outcomes Study Short Form 36 (SF-36) was used to measure general HRQOL.

RESULTS

Enrollees were 1,149 patients with diagnosed and active RA. At the end of the treatment period, patients in the 4 active treatment groups had significant improvement in both functional status and overall HRQOL in comparison with the placebo group. Patients in the twice-daily 100 mg celecoxib group significantly differed from placebo at weeks 2 and 6 on HAQ scores and at week 12 on 5 domains and both summary scores of the SF-36. Patients treated with twice-daily 200 mg celecoxib had significantly better functional status than placebo at all times of testing with the HAQ, and also had significantly better function than those treated with naproxen after 2 and 12 weeks of treatment. Patients in the twice-daily 200 mg and 400 mg celecoxib groups showed similar improvement in HRQOL as determined by the 8 domain scores and 2 summary scores of the SF-36.

CONCLUSION

Celecoxib was better than placebo and comparable with naproxen in improving functional status and overall HRQOL among RA patients.

Efficacy and safety of valdecoxib in treating the signs and symptoms of rheumatoid arthritis: a randomized, controlled comparison with placebo and naproxen

OBJECTIVE

To compare the efficacy of the COX-2 specific inhibitor valdecoxib with the conventional NSAID naproxen and placebo in treating rheumatoid arthritis (RA).

METHODS

This multi-centre, randomized, double-blind, placebo-controlled trial compared the efficacy and safety of valdecoxib 10 mg (n=209), 20 mg (n=212) or 40 mg once daily (q.d.) (n=221) with naproxen 500 mg b.i.d. (n=226) or placebo (n=222), in treating the signs and symptoms of RA. Efficacy was assessed by the number of patients responding to treatment according to the American College of Rheumatology-Responder Index (ACR-20).

RESULTS

ACR-20 response was recorded for all randomized patients who received a single dose of study medication (above). Valdecoxib, at all administered doses, produced significant improvements in the ACR-20 Responder Index at weeks 2, 6 and 12 compared with placebo (P<or=0.01). Valdecoxib and naproxen did not differ in terms of ACR-20 response rate and the three doses of valdecoxib were similar to one another. All three doses of valdecoxib were well tolerated.

CONCLUSIONS

Single daily doses of valdecoxib 10, 20 and 40 mg demonstrated efficacy that was superior to placebo and similar to naproxen in treating the signs and symptoms of RA. All three doses provided similar levels of efficacy.

Reduced incidence of gastroduodenal ulcers with celecoxib, a novel cyclooxygenase-2 inhibitor, compared to naproxen in patients with arthritis

OBJECTIVE

Nonsteroidal anti-inflammatory drugs (NSAIDs) block prostaglandin production by inhibiting cyclooxygenase (COX); they are believed to cause gastroduodenal damage by inhibiting the COX-1 isoform and to have analgesic and anti-inflammatory effects by inhibiting the COX-2 isoform. As compared to conventional NSAIDs, celecoxib, a COX-2 specific inhibitor, has been shown in previous single posttreatment endoscopy studies to be associated with lower gastroduodenal ulcer rates. In response to concerns that such studies may under-represent ulceration rates, the present serial endoscopy study was designed to compare cumulative gastroduodenal ulcer rates associated with the use of celecoxib to those of naproxen, a conventional NSAID.

METHODS

In this double-blind, parallel-group, multicenter study, 537 patients with osteoarthritis (OA) or rheumatoid arthritis (RA) were randomized to treatment with celecoxib 200 mg b.i.d. (n = 270) or naproxen 500 mg b.i.d. (n = 267) for 12 wk. Gastroduodenal damage was determined from esophagogastroduodenoscopy after 4, 8, and 12 wk of therapy. Arthritis efficacy was evaluated with Patient's and Physician's Global Assessments.

RESULTS

Gastroduodenal ulcer rates after celecoxib and naproxen treatment were 4% versus 19% in the 0-4 wk interval (p < 0.001), 2% versus 14% in the 4-8 wk interval (p < 0.001), and 2% versus 10% in the 8-12 wk interval (p < 0.001), respectively. After 12 wk of treatment, the cumulative incidence of gastroduodenal ulcers was 9% with celecoxib and 41% with naproxen. In the celecoxib group, gastroduodenal ulcers were significantly associated with Helicobacter pylori status (p < 0.05), concurrent aspirin usage (p = 0.001), and a history of ulcer (p = 0.010), but not with disease type (OA/RA), age, gender, other relevant medical histories, or concurrent corticosteroid or disease-modifying antirheumatic drugs usage (p > 0.05). Celecoxib produced a significantly lower incidence rate of both gastric (p < 0.001) and duodenal (p < 0.030) ulcers. The two agents produced similar improvements in Patient's and Physician's Global Assessments of arthritis efficacy. The incidence of adverse events and withdrawal rates did not differ significantly between treatments.

CONCLUSIONS

As compared to naproxen (500 mg b.i.d.), use of celecoxib (200 mg b.i.d.), a COX-2 specific agent, at the recommended RA dose and twice the most frequently prescribed OA dose, was associated with lower rates of gastric, duodenal, and gastroduodenal ulcers but had comparable efficacy, in patients with OA and RA.

Gastrointestinal toxicity with celecoxib vs nonsteroidal anti-inflammatory drugs for osteoarthritis and rheumatoid arthritis: the CLASS study: A randomized controlled trial. Celecoxib Long-term Arthritis Safety Study

CONTEXT

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs) are associated with a spectrum of toxic effects, notably gastrointestinal (GI) effects, because of inhibition of cyclooxygenase (COX)-1. Whether COX-2-specific inhibitors are associated with fewer clinical GI toxic effects is unknown.

OBJECTIVE

To determine whether celecoxib, a COX-2-specific inhibitor, is associated with a lower incidence of significant upper GI toxic effects and other adverse effects compared with conventional NSAIDs.

DESIGN

The Celecoxib Long-term Arthritis Safety Study (CLASS), a double-blind, randomized controlled trial conducted from September 1998 to March 2000.

SETTING

Three hundred eighty-six clinical sites in the United States and Canada.

PARTICIPANTS

A total of 8059 patients (>/=18 years old) with osteoarthritis (OA) or rheumatoid arthritis (RA) were enrolled in the study, and 7968 received at least 1 dose of study drug. A total of 4573 patients (57%) received treatment for 6 months.

INTERVENTIONS

Patients were randomly assigned to receive celecoxib, 400 mg twice per day (2 and 4 times the maximum RA and OA dosages, respectively; n = 3987); ibuprofen, 800 mg 3 times per day (n = 1985); or diclofenac, 75 mg twice per day (n = 1996). Aspirin use for cardiovascular prophylaxis (</=325 mg/d) was permitted.

MAIN OUTCOME MEASURES

Incidence of prospectively defined symptomatic upper GI ulcers and ulcer complications (bleeding, perforation, and obstruction) and other adverse effects during the 6-month treatment period.

RESULTS

For all patients, the annualized incidence rates of upper GI ulcer complications alone and combined with symptomatic ulcers for celecoxib vs NSAIDs were 0.76% vs 1.45% (P =.09) and 2. 08% vs 3.54% (P =.02), respectively. For patients not taking aspirin, the annualized incidence rates of upper GI ulcer complications alone and combined with symptomatic ulcers for celecoxib vs NSAIDs were 0.44% vs 1.27% (P =.04) and 1.40% vs 2.91% (P =.02). For patients taking aspirin, the annualized incidence rates of upper GI ulcer complications alone and combined with symptomatic ulcers for celecoxib vs NSAIDs were 2.01% vs 2.12% (P =.92) and 4.70% vs 6.00% (P =.49). Fewer celecoxib-treated patients than NSAID-treated patients experienced chronic GI blood loss, GI intolerance, hepatotoxicity, or renal toxicity. No difference was noted in the incidence of cardiovascular events between celecoxib and NSAIDs, irrespective of aspirin use.

CONCLUSIONS

In this study, celecoxib, at dosages greater than those indicated clinically, was associated with a lower incidence of symptomatic ulcers and ulcer complications combined, as well as other clinically important toxic effects, compared with NSAIDs at standard dosages. The decrease in upper GI toxicity was strongest among patients not taking aspirin concomitantly. JAMA. 2000;284:1247-1255

Anti-inflammatory and upper gastrointestinal effects of celecoxib in rheumatoid arthritis: a randomized controlled trial

CONTEXT

In vitro studies have shown that celecoxib inhibits cyclooxygenase 2 (COX-2) but not COX-1, suggesting that this drug may have anti-inflammatory and analgesic activity without adverse upper gastrointestinal (GI) tract effects that result from COX-1 inhibition.

OBJECTIVE

To test whether celecoxib has efficacy as an anti-inflammatory and analgesic with reduced GI tract mucosal damage compared with conventional nonsteroidal anti-inflammatory drugs in patients with rheumatoid arthritis.

DESIGN

Randomized, multicenter, placebo-controlled, double-blind trial lasting 12 weeks, with follow-up at weeks 2, 6, and 12, from September 1996 thorugh February 1998.

SETTING

Seventy-nine clinical sites in the United States and Canada.

PATIENTS

A total of 1149 patients aged 18 years or older with symptomatic rheumatoid arthritis who met inclusion criteria were randomized; 688 (60%) of these completed the study.

INTERVENTIONS

Patients were randomized to receive celecoxib, 100 mg, 200 mg, or 400 mg twice per day (n = 240, 235, and 218, respectively); naproxen, 500 mg twice per day (n = 225); or placebo (n = 231).

MAIN OUTCOME MEASURES

Improvement in signs and symptoms of rheumatoid arthritis as assessed using standard measures of efficacy and GI tract safety as assessed by upper GI tract endoscopy before and after treatment, compared among treatment groups.

RESULTS

All dosages of celecoxib and naproxen significantly improved the signs and symptoms of arthritis compared with placebo. Maximal anti-inflammatory and analgesic activity was evident within 2 weeks of initiating treatment and was sustained throughout the 12 weeks. The incidence of endoscopically determined gastroduodenal ulcers in placebo-treated patients was 4 (4%) of 99, and the incidences across all dosages of celecoxib were not significantly different (P>.40): 9 (6%) of 148 with 100 mg twice per day, 6 (4%) of 145 with 200 mg twice per day, and 8 (6%) of 130 with 400 mg twice per day. In contrast, the incidence with naproxen was 36 (26%) of 137, significantly greater than either placebo or celecoxib (P<.001). The overall incidences of GI tract adverse effects were 19% for placebo; 28%, 25%, and 26% for celecoxib 100 mg, 200 mg, and 400 mg twice per day, respectively; and 31 % for naproxen.

CONCLUSION

In this study, all dosages of celecoxib were efficacious in the treatment of rheumatoid arthritis and did not affect COX-1 activity in the GI tract mucosa as evidenced by less frequent incidence of endoscopic ulcers compared with naproxen.

Evaluation of the functional status aspects of health-related quality of life of patients with osteoarthritis treated with celecoxib

STUDY OBJECTIVE

To evaluate the functional status of patients with signs and symptoms of osteoarthritis of the knee after treatment with celecoxib compared with placebo and naproxen.

DESIGN

Prospective, randomized, double-blind, parallel-group, 12-week trial.

SETTING

Multicenter study conducted at 71 sites in the United States and Canada.

PATIENTS

One thousand four patients with active osteoarthritis of the knee in a flare state.

INTERVENTIONS

Patients were assigned randomly to one of five treatment groups: placebo; celecoxib 50 mg twice/day, 100 mg twice/day, and 200 mg twice/day; and naproxen 500 mg twice/day.

MEASUREMENTS AND MAIN RESULTS

The Western Ontario and McMaster Universities Osteoarthritis Index was used to measure functional status. At the end of the treatment period, patients in the four active treatment groups had significantly better functional status than those receiving placebo. Patients treated with celecoxib 100 mg twice/day had significantly better improvements in pain scores than those treated with placebo and naproxen.

CONCLUSION

Celecoxib was better than placebo and comparable with naproxen in improving aspects of functional status in patients with osteoarthritis.

Treatment of osteoarthritis with celecoxib, a cyclooxygenase-2 inhibitor: a randomized controlled trial

OBJECTIVE

To compare the efficacy and safety of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, with those of naproxen, a nonsteroidal anti-inflammatory drug (NSAID), and placebo in the treatment of osteoarthritis of the knee.

METHODS

In this multicenter, randomized, double-blind, placebo-controlled trial, 1003 patients with symptomatic osteoarthritis of the knee were randomly assigned to receive celecoxib at doses of 50, 100, or 200 mg twice a day; naproxen, 500 mg twice a day; or placebo for 12 weeks. Patients were evaluated with standard measures of efficacy 2 to 7 days after discontinuing previous NSAID or analgesic therapy and after 2, 6, and 12 weeks of treatment with the study drug.

RESULTS

Celecoxib treatment led to significant improvement in the signs and symptoms of osteoarthritis as determined by all efficacy measures. Significant pain relief occurred within 2 days of the initiation of treatment, and maximum anti-inflammatory and analgesic activity, evident within 2 weeks, was sustained throughout the 12-week study. All celecoxib doses were efficacious compared with placebo, although the 50-mg twice-daily dosage regimen was minimally effective. The higher doses of celecoxib (100 and 200 mg twice a day) were similarly efficacious, and the magnitude of improvement observed with these dosing regimens was comparable to that seen with naproxen at a dose of 500 mg twice a day. All doses of celecoxib and naproxen were well tolerated.

CONCLUSION

COX-2 inhibition with celecoxib is an effective approach for the treatment of osteoarthritis, as seen by clinical improvement in signs and symptoms comparable to treatment with naproxen.

Ovulatory delay alters postnatal growth, behavior, and brain structure in rats

To investigate the effect of a delay in ovulation on postnatal growth and development in resultant rat offspring, a 1-day ovulatory delay was induced by sodium pentobarbital, animals mated, and the offspring monitored. There were no differences between control and 1-day delayed offspring in the number of live or dead births, number of males or females, nor in the ratio of sexes. Delayed pups had a slightly lower birth weight, but then recovered to weigh more than controls by day 12. In the first two weeks post-parturition, delayed pups displayed an earlier ability to reorient themselves in a negative geotaxis test, but no differences by the righting reflex and reflex suspension tests. At postnatal day (pnd) 28, delayed pups exhibited decreased activity in a continuous corridor test, but no alterations in gait. At this time, the brains of delayed animals revealed thickening of cortical layers V plus VI. There were significant correlations between various developmental endpoints (body weight, negative geotaxis, continuous corridor activity, and gait) and the cortical layer thicknesses. The results indicate that ovulatory delay produces changes in brain cortical thickness, with correlative changes in growth and behavior. Although the mechanisms by which ovulatory delay alters postnatal development and brain structure are unknown, ovulatory delay may alter the uterine environment during early pregnancy.

PGE2 inhibits acetylcholine release from cholinergic nerves in canine but not equine airways

The effects of exogenous prostaglandin E2 (PGE2) and endogenous prostanoids on cholinergic neurotransmission were determined by measurement of acetylcholine (ACh) release from canine and equine airway tissues. Trachealis strips and bronchial segments were suspended in 2 ml tissue baths. ACh release was induced by electrical field stimulation (EFS), and its content in tissue bath liquid was measured by high pressure liquid chromatography (HPLC) with electrochemical detection. In canine airways, exogenous PGE2 (10(-9) to 10(-7) M) inhibited ACh release concentration-dependently, whereas inhibition of endogenous prostanoid production by indomethacin (3 x 10(-6) M) augmented ACh release. By contrast, in equine airways, exogenous PGE2 had no effect on ACh release in bronchi but at 10(-7) M augmented ACh release in the trachea. Cyclooxygenase inhibition by either indomethacin or meclofenamate (10(-6) M) did not influence ACh release. We conclude that exogenous PGE2 and endogenous prostanoids inhibit ACh release from cholinergic nerves in canine but not equine airways.

[Effect of the central noradrenergic system on carotid sinus reflex in rats]

In order to study the effect of central noradrenergic system on the regulation of mean arterial pressure (MAP) by intracarotid sinus pressure (ISP), ISP-MAP relationship curves were constructed using isolated carotid sinus under the condition of injection of 6-OHDA (200 micrograms) into lateral ventricle or cauterization of locus coeruleus (LC) and compared with that obtained under the condition of control. All ISP-MAP curves can be fitted by a logistic functional plot whose characteristics can be defined by two parameters, i.e. coordinates of the inversion point of the slope of the curve and the MAP range related to the rate of change of slope factor with which carotid sinus pressure exerts its control. The results were as follows: After injection of 6-OHDA, the rate of change of the slope of the ISP-MAP curve is considerably slower than that of the normal control, thus showing a much compressed range of MAP by ISP, while the abscissa (i.e. position of ISP) of the slope inversion point of the curve shows practically no change. In comparison with the control, cauterization of LC causes a similar but less striking change of ISP-MAP curve than that of 6-OHDA injection experiment. All such differences were illustrated in Fig. 3. The above results indicated that the central noradrenergic system facilitates carotid sinus reflex and LC plays a dominant role.

The method of time-resolved spin-probe oximetry: its application to oxygen consumption by cytochrome c oxidase

This work broadens the scope and improves the time resolution of spin-probe oximetry, a technique in which small nitroxide spin probes detect oxygen consumption via change in their relaxation properties [Froncisz, W., Lai, C.-S., & Hyde, J. S. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 411-415]. For rapid oxygen kinetic studies we combined the methodology of spin-probe oximetry with a recently developed loop-gap resonator, stopped-flow EPR system [Hubbell, W. L., Froncisz, W., & Hyde, J. S. (1987) Rev. Sci. Instrum. 58, 1879-1886]. The technique used microliter volumes of reactant solutions. Enzymatic consumption of oxygen by cytochrome c oxidase in the presence of ferrocytochrome c substrate was followed continuously in time under limited-turnover conditions, where the concentration of oxygen consumed often was comparable to or less than the amount of enzyme present. In detecting less than micromolar oxygen concentration changes, we have achieved a time resolution of the order 30 ms when flow is stopped. Oxygen consumption was followed under two different limited-turnover conditions: In the first, the amount of oxygen consumed was limited by available ferrocytochrome c, and the time course of oxygen consumption and its pH dependence were compared with the optically detected ferrocytochrome c consumption. In the second, the oxygen consumed was ultimately limited by the availability of oxygen itself while ferrocytochrome c was regenerated and remained in excess.(ABSTRACT TRUNCATED AT 250 WORDS)

[Dynamic changes in depolarization of action potentials by high frequency stimulation in guinea pig papillary muscles]

The effect of high frequency stimulation on rate-dependent depression of depolarization of action potentials was studied with computer and standard microelectrode techniques in guinea pig papillary muscles. After increasing driving frequency from 0.5 to 6 Hz, decreases in Vmax, APA and OS were found. Changes of upstroke velocity during phase 0 between driving frequency 6 and 0.5 Hz could be described as a parabola. The rate-dependent depression of depolarization was exaggerated by tetrodotoxin (TTX), particularly during the accelerating period of phase 0. A progressive decline in Vmax, which could be fitted by a power function curve, was observed after changing driving frequency from 1 to 5 Hz. TTX significantly influenced the decline in Vmax and the regression coefficients in fitted equations.