Mechanisms of impulsive choice: Experiments to explore and models to map the empirical terrain

Impulsive choice is preference for a smaller-sooner (SS) outcome over a larger-later (LL) outcome when LL choices result in greater reinforcement maximization. Delay discounting is a model of impulsive choice that describes the decaying value of a reinforcer over time, with impulsive choice evident when the empirical choice-delay function is steep. Steep discounting is correlated with multiple diseases and disorders. Thus, understanding the processes underlying impulsive choice is a popular topic for investigation. Experimental research has explored the conditions that moderate impulsive choice, and quantitative models of impulsive choice have been developed that elegantly represent the underlying processes. This review spotlights experimental research in impulsive choice covering human and nonhuman animals across the domains of learning, motivation, and cognition. Contemporary models of delay discounting designed to explain the underlying mechanisms of impulsive choice are discussed. These models focus on potential candidate mechanisms, which include perception, delay and/or reinforcer sensitivity, reinforcement maximization, motivation, and cognitive systems. Although the models collectively explain multiple mechanistic phenomena, there are several cognitive processes, such as attention and working memory, that are overlooked. Future research and model development should focus on bridging the gap between quantitative models and empirical phenomena.

Effects of insect host chemical secretions on the entomopathogenic nematode Steinernema carpocapsae

Given the threat presented by parasites and pathogens, insects employ various defences to protect themselves against infection, including chemical secretions. The red flour beetle Tribolium castaneum releases a secretion containing the benzoquinones methyl-1,4-benzoquinone (MBQ) and ethyl-1,4-benzoquinone (EBQ) into the environment. These compounds have known antimicrobial effects; however, their role in defence against macroparasites is not known. Entomopathogenic nematodes, such as Steinernema carpocapsae, present a serious threat to insects, with successful infection leading to death. Thus, quinone-containing secretions may also aid in host defence. We tested how exposure to the individual components of this quinone secretion, as well as a mix at naturally-occurring proportions, affected the survival and thrashing behaviour of S. carpocapsae, as well as their virulence to a model host (Galleria mellonella). Exposure to high concentrations of MBQ and EBQ, as well as the quinone mix, significantly increased nematode death but did not consistently reduce thrashing, which would otherwise be expected given their toxicity. Rather, quinones may act as a host cue to S. carpocapsae by triggering increased activity. We found that exposure to quinones for 24 or 72 hours did not reduce nematode virulence, and surviving nematodes remained infective after non-lethal exposure. Our results indicate that quinone secretions likely serve as a defence against multiple infection threats by reducing S. carpocapsae survival, but further research is required to contextualize their roles by testing against other nematodes, as well as other helminths using insects as hosts.

Wastewater-based epidemiology in hazard forecasting and early-warning systems for global health risks

With the advent of the SARS-CoV-2 pandemic, Wastewater-Based Epidemiology (WBE) has been applied to track community infection in cities worldwide and has proven succesful as an early warning system for identification of hotspots and changingprevalence of infections (both symptomatic and asymptomatic) at a city or sub-city level. Wastewater is only one of environmental compartments that requires consideration. In this manuscript, we have critically evaluated the knowledge-base and preparedness for building early warning systems in a rapidly urbanising world, with particular attention to Africa, which experiences rapid population growth and urbanisation. We have proposed a Digital Urban Environment Fingerprinting Platform (DUEF) - a new approach in hazard forecasting and early-warning systems for global health risks and an extension to the existing concept of smart cities. The urban environment (especially wastewater) contains a complex mixture of substances including toxic chemicals, infectious biological agents and human excretion products. DUEF assumes that these specific endo- and exogenous residues, anonymously pooled by communities' wastewater, are indicative of community-wide exposure and the resulting effects. DUEF postulates that the measurement of the substances continuously and anonymously pooled by the receiving environment (sewage, surface water, soils and air), can provide near real-time dynamic information about the quantity and type of physical, biological or chemical stressors to which the surveyed systems are exposed, and can create a risk profile on the potential effects of these exposures. Successful development and utilisation of a DUEF globally requires a tiered approach including: Stage I: network building, capacity building, stakeholder engagement as well as a conceptual model, followed by Stage II: DUEF development, Stage III: implementation, and Stage IV: management and utilization. We have identified four key pillars required for the establishment of a DUEF framework: (1) Environmental fingerprints, (2) Socioeconomic fingerprints, (3) Statistics and modelling and (4) Information systems. This manuscript critically evaluates the current knowledge base within each pillar and provides recommendations for further developments with an aim of laying grounds for successful development of global DUEF platforms.

Generalizability of time-based interventions: Effects of choice procedure and smaller-sooner delay

Interventions exposing rats to delayed-reward contingencies attenuate suboptimal impulsive choices, a preference for a smaller-sooner (SS) over a larger-later (LL) reward. Interventions may potentially improve delay-tolerance, timing of delays, and/or discrimination of reward magnitudes. Generalization from the intervention to impulsive choice under different procedures can provide insights into the processes that underlie the intervention effects. Experiment 1 tested intervention effects on systematic-delay (SYS) and adjusting-delay (ADJ) procedures, predicting that intervention effects would be more effective on the SYS procedure with predictable delays. The ADJ procedure did not benefit significantly from intervention, but the SYS procedure, unexpectedly, showed greater impulsive choices following intervention. Experiment 2 tested whether short (5 s) SS intervention delays may have promoted greater impulsivity in the SYS impulsive choice procedure in Experiment 1. Short SS delays in choice and intervention procedures increased impulsive choices in comparison to longer (10 s) delays. Incongruent SS delays in the intervention/choice procedures resulted in negative intervention effects. The results suggest that short SS delays are detrimental to self-control and that specific temporal information generalizes from the intervention to the SYS choice task, but not the ADJ choice task.

The opioid crisis: 18 years of opioid prescriptions in spine patients

Background

The US opioid epidemic continues to afflict patients and the healthcare system. Surgery remains a risk factor for opioid misuse, and treatment of low back pain in orthopedics and neurosurgery is one of the largest introductions of opioids into the community. The objective of the study is to understand how opioid prescribing practices for spinal surgery have evolved in two academic hospital in the last 18 years.

Methods

Data were obtained from the Research Patient Data Registry for Brigham and Women's and Massachusetts General Hospital from January 2000 to December 2018. Patients included had a primary diagnosis of degenerative diseases, trauma, spinal infection, spinal deformities, or spinal pain symptoms/syndromes; were aged > 18 years; and had an opioid prescription. Covariates included demographics, diagnoses, comorbidities, procedures, opioid type, number of prescriptions, route of administration, doses and length of prescription.

Results

A total of 38,250 patients with spine-related diagnoses received an opioid prescription. The median age was 63 years (18-107), 50% male and 86% white. A total of 32,304 patients (84.4%) received at least one opioid prescription during their hospitalization. The sum of opioid prescriptions filled (inpatient and outpatient) were 889,868 between 2000 and 2018 (55.2% oral, 41.7% intravenous). Oxycodone was the most prescribed. The dose of ≥ 50 morphine milligram equivalents MME/day was reduced from 65.0% in 2000 to 17.3% in 2018, and doses ≥ 90 MME/day dropped from 26.9% in 2000 to 6.4% in 2018. However, the duration of prescription has increased from 4.1% having an opioid prescription for >7 days in 2000, to 21.7% in 2018.

Conclusions

Opioid prescription rates for spinal surgery patients have increased since 2000, declined temporarily in 2016, but are rising again. Physicians are prescribing fewer MMEs per day but have increased longitudinal dosing, which still leaves patients at risk for misuse and opioid use disorder.

Key messages

Between 2000 and 2016 there was an increase of 140 times the number of opioid prescriptions for spine patients. More interventions and non-pharmacological solutions are needed to reduce this public health epidemic.

Outcome expectancy and suboptimal risky choice in nonhuman primates

Animals will favor a risky option when a stimulus signaling reward bridges the choice and the outcome. The present experiments investigated signal-induced risky choices and reward-outcome expectations in rhesus and capuchin monkeys. Risky choice was assessed by preference for a large-probabilistic reward over a modest-certain reward. Outcome expectancy was assessed by providing a truncation-response to shorten the delay period. In Experiment 1 both species generally favored the risky option compared to a safe option when the outcomes were signaled and generally shortened the delays except when a signaled-loss stimulus was presented. The use of the delay-truncation response suggested that the monkeys were sensitive to the information conveyed by the stimulus. Experiments 2 and 3 were designed to investigate whether the delay-truncation response used by capuchin monkeys was strategically used reflecting explicit decision-making versus a conditioned response to reward stimuli. A perceptual judgment task was included and the selective use of the delay-truncation response on unsignaled correct trials may suggest the involvement of metacognitive processes. The capuchin monkeys generally truncated the delays except under conditions where reward would not be expected (risky-loss or incorrect-judgment). When the outcomes were unsignaled during the delay some capuchin monkeys were less likely to truncate the delay following an incorrect task response. Overall, the monkeys: (1) made more risky choices when the outcomes were signaled - consistent with gambling-like behavior. (2) selectively truncated the unsignaled delays when rewards could be anticipated (even when metacognitive-like awareness guided anticipation) - suggesting that delay truncation responses reflect explicit outcome expectancy.

Age, pathology and CA-125 are prognostic factors for survival in patients with brain metastases from gynaecological tumours

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The largest cohort of brain metastases patients from gynaecological tumours.

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CA-125, age and primary tumour type are prognostic for survival.

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This will inform clinical practice and aid the development of new prognostic tools.

Background and purpose

Brain metastases originating from gynaecological tumours are a rare phenomenon, but have an increasing incidence due to better targeted therapies. This study aimed to identify factors that predict survival in these patients, which can be used in creating a robust prognostic tool for shared decision making.

Materials and methods

We identified a consecutive cohort of 73 patients treated for gynaecological brain metastases in two tertiary institutions. Baseline demographics, pathology and serum CA-125 were included in a multivariable Cox proportional hazards model.

Results

Median overall survival in our cohort was 14.4 months, with a one-year survival of 56.4% and a two-year survival of 39.1%. Thirty-eight patients (52.1%) had ovarian carcinoma as the primary malignancy. The following factors were significantly associated with survival: age (HR 1.05 per year), CA-125 (HR 1.02 par 50 U/ml), and uterine and vulvar primary tumours (when compared to ovarian carcinoma, with HRs 3.07 and 8.70). A post-hoc analysis with primary tumour site reclassified into ovary versus non-ovary showed a HR of 0.50 for ovarian primary tumour type.

Conclusion

We have found that age, pathology and CA-125 are prognostic factors for survival in patients with brain metastases from gynaecological tumours. Our findings may provide a foundation for future development of prediction models, for the benefit of both patients and physicians.

Capuchin monkeys (sometimes) go when they know: Confidence movements in Sapajus apella

To test for evidence of metacognition in capuchin monkeys (Sapajus apella), we analyzed confidence movements using a paradigm adapted from research with chimpanzees. Capuchin monkeys provide an interesting model species for the comparative assessment of metacognition as they show limited evidence of such cognitive-monitoring processes in a variety of metacognition paradigms. Here, monkeys were presented with a computerized delayed matching-to-sample (DMTS) memory test in one location but were rewarded for correct responses in a separate location. Movements could be made from one location to the other at any time, but movements between a response and reward feedback may reflect confidence in the accuracy of the response. Critically, DMTS tests included occasional "no sample" trials where monkeys' performance was at chance when the trial started without a sample and a 1-s interval to the response options. We predicted that monkeys would (1) perform less accurately (and less confidently) at longer retention intervals, (2) move to the dispenser early more often on trials completed correctly than incorrectly, and (3) show a relation between faster response latency and early movements. Analyses of response times and "go" or "no go" confidence movements before feedback to the reward location suggested that the monkeys were capable of monitoring confidence in their responses. However, their confidence movements were less precise and less flexible than chimpanzees. Overall, this paradigm can reveal potential metacognitive abilities in nonhuman animals that otherwise demonstrate these abilities inconsistently.

Limited evidence of number-space mapping in rhesus monkeys (Macaca mulatta) and capuchin monkeys (Sapajus apella)

Humans exhibit evidence of a mental number line that suggests a left-to-right, or sometimes right-to-left, representation of smaller to larger numbers. The Spatial Numerical Association of Response Codes (SNARC) effect is one example of this mental number line and has been investigated extensively in humans. Less research has been done with animals, and results have been inconclusive. Rugani, Vallortigara, Priftis, and Regolin (2015) found that young chicks showed a bias to respond to small quantities presented to their left and large quantities presented to their right when forced to move toward those stimuli to gain food reward. We replicated this design with rhesus macaques and capuchin monkeys using a computerized task, but we did not find this outcome. We also trained monkeys to choose between 2 arrays of dots, and then assessed biases in terms of choice location and response latency on trials with a numerical difference and on trials with equal numbers of items in both sets. There was no evidence of SNARC-like effects in equal trials, although when arrays differed in number, 12 of 19 monkeys showed differential performance depending on whether the smaller array was at the left or at the right onscreen. These results indicate that SNARC-like effects may not emerge in all contexts and may not be phylogenetically widespread. More effort is needed to broaden the number of species assessed and match other methods that are used with human participants so that we can better define the presence and extent of such effects. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Brain cancer survival in Canada 1996-2008: effects of sociodemographic characteristics

Background

Literature suggests that factors such as rural residence and low socioeconomic status (ses) might contribute to disparities in survival for Canadian cancer patients because of inequities in access to care. However, evidence specific to brain cancer is limited. The present research estimates the effects of rural or urban residence and ses on survival for Canadian patients diagnosed with brain cancer.

Methods

Adults diagnosed with primary malignant brain tumours during 1996-2008 were identified through the Canadian Cancer Registry. Brain tumours were classified using International Classification of Diseases for Oncology (3rd edition) site and histology codes. Hazard ratios (hrs) and 95% confidence intervals (cis) were estimated using Cox proportional hazards models. Events were restricted to individuals whose underlying cause of death was cancer-related. Postal codes were used to match patient records with Statistics Canada data for rural or urban residence and neighbourhood income as a surrogate measure of ses.

Results

Of 25,700 patients included in the analysis, 78% died during the study period, 21% lived in rural areas, and 19% were in the lowest income group. A modest variation in survival by rural compared with urban residence was observed for patients with glioblastoma (first 5 weeks after diagnosis hr: 0.86; 95% ci: 0.79 to 0.99) and oligoastrocytoma (first 3 years after diagnosis hr: 1.41; 95% ci: 1.03 to 1.93). Small effects of low compared with high income were seen for patients with glioblastoma (first 1.5 years after diagnosis hr: 1.15; 95% ci: 1.08 to 1.22) and diffuse astrocytoma (first 6 months after diagnosis hr: 1.17; 95% ci: 1.00 to 1.36).

Conclusions

Our analysis did not yield evidence of strong effects of rural compared with urban residence or ses strata on survival in brain cancer. However, some variation in survival for patients with specific histologies warrants further research into the mechanisms by which rural or urban residence and income stratum influences survival.

Depression and survival of glioma patients: A systematic review and meta-analysis

INTRODUCTION

There is currently a lack of a well-formed consensus regarding the effects of depression on the survival of glioma patients. A more thorough understanding of such effects may better highlight the importance of recognizing depressive symptoms in this patient population and guide treatment plans in the future.

OBJECTIVE

The aim of this meta-analysis was to study the effect of depression on glioma patients' survival.

METHODS

A meta-analysis was conducted according to the PRISMA guidelines. PubMed, Embase, and Cochrane databases were searched for studies that reported depression and survival among glioma patients through 11/06/2016. Both random-effects (RE) and fixed-effect (FE) models were used to compare survival outcomes in glioma patients with and without depression.

RESULTS

Out of 619 identified articles, six were selected for the meta-analysis. Using RE model, the various measures for survival outcomes displayed worsened outcomes for both high and low-grade glioma patients with depression compared to those without depression. For binary survival outcomes, the overall pooled risk ratio for survival was 0.70 (95% CI: 0.47, 1.04; 6 studies; I² = 54.9%, P-heterogeneity = 0.05) for high grade gliomas (HGG) and 0.28 (95% CI: 0.04, 1.78; I² = 0%, P-heterogeneity = 1.00; one study) for low grade gliomas (LGG) was. A sub-group analysis in the HGG group by depression timing (pre- versus post-operative) revealed no differences between depression and survival outcomes (P-interaction = 0.47). For continuous survival outcomes, no statistically significant difference was found among the high and low-grade glioma groups (P-interaction = 0.31). The standardized mean difference (SMD) in survival outcomes was -0.56 months (95%CI: -1.13, 0.02; 4 studies, I² = 89.4%, P-heterogeneity < 0.01) for HGG and -1.69 months (95%CI: -3.26, -0.13; one study; I² = 0%, P-heterogeneity = 1.00) for LGG. In patients with HGG, the pooled HR of death also showed a borderline significant increased risk of death among depressive patients (HR 1.42, 95% CI: 1.00, 2.01). Results using the FE model were not materially different.

CONCLUSIONS

Depression was associated with significantly worsened survival regardless of time of diagnosis, especially among patients with high-grade glioma.

Task switching in rhesus macaques (Macaca mulatta) and tufted capuchin monkeys (Cebus apella) during computerized categorization tasks

The present experiments extended to monkeys a previously used abstract categorization procedure (Castro & Wasserman, 2016) where pigeons had categorized arrays of clipart icons based upon two task rules: the number of clipart objects in the array or the variability of objects in the array. Experiment 1 replicated Castro and Wasserman by using capuchin monkeys and rhesus monkeys and reported that monkeys' performances were similar to pigeons' in terms of acquisition, pattern of errors, and the absence of switch costs. Furthermore, monkeys' insensitivity to the added irrelevant information suggested that an associative (rather than rule-based) categorization mechanism was dominant. Experiment 2 was conducted to include categorization cue reversals to determine (a) whether the monkeys would quickly adapt to the reversals and inhibit interference from a prereversal task rule (consistent with a rule-based mechanism) and (b) whether the latency to make a response prior to a correct or incorrect outcome was informative about the presence of a cognitive mechanism. The cue reassignment produced profound and long-lasting performance deficits, and a long reacquisition phase suggested the involvement of associative learning processes; however, monkeys also displayed longer latencies to choose prior to correct responses on challenging trials, suggesting the involvement of nonassociative processes. Together these performances suggest a mix of associative and cognitive-control processes governing monkey categorization judgments. (PsycINFO Database Record

Gambling in rhesus macaques (Macaca mulatta): The effect of cues signaling risky choice outcomes

Preference for a larger-variable "risky" option over a smaller-reliable "safe" option often depends upon the likelihood that the risky option will deliver a sufficiently sized reward to have an equivalent or superior expected value. However, preference for the risky option has been shown to increase under conditions where informative stimuli signaling the outcome of a risky choice is included between the choice and the outcome and this risk-prone preference persists even when the risky option has a lower expected value than the alternative safe option. In the present study, rhesus macaques chose between a risky option and a safe option across two experimental phases to determine whether the outcome signal affected the degree of preference for the risky option. Overall, six out of seven macaques showed a greater preference for the risky option in the signaled condition than in the unsignaled condition. The macaques' risky choices were sensitive to the expected value of the risky option and the signaled condition produced a general increase in risky choices independently of the expected value of the risky outcome. Overall, these results are consistent with those obtained with other animals, and this may relate to a process where animals show a biased preference for "good news." This process may model some of the relevant factors that explain the psychology of gambling in humans.

LY293558, a Novel AMPA/GluR5 Antagonist, is Efficacious and Well-Tolerated in Acute Migraine

Glutamatergic hyperactivity is implicated migraine pathogenesis. Also, LY293558, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate (KA) receptor antagonist, is effective in preclinical models of migraine. We therefore tested LY293558 in acute migraine. We conducted a randomized, triple-blind, parallel-group, double-dummy, multicentre trial of 1.2 mg/kg intravenous (IV) LY293558, 6 mg subcutaneous (SC) sumatriptan, or placebo in the treatment of acute migraine. The primary efficacy variable was the headache response rate, i.e. headache score improvement from moderate/severe at baseline to mild/none at 2 h. Of 45 enrolled patients, 44 patients (20M:24F; mean age ± SD = 40 ± 9 years) completed the study. Response rates were 69% for LY293558 ( P = 0.017 vs. placebo), 86% for sumatriptan ( P < 0.01 vs. placebo) and 25% for placebo. LY293558 and sumatriptan were superior to placebo ( P < 0.01 for all comparisons) on all other measures of improvement in pain and migraine associated symptoms. Fifteen percent of patients who took LY293558 reported adverse events (AEs) ( n = 2; one mild, one severe). Fifty-three percent of patients who took sumatriptan ( n = 8; seven mild, one moderate) and 31% of those who received placebo reported AEs ( n = 5; four mild, one severe). The efficacy and safety results of LY293558 in this small migraine proof of concept trial, together with supportive preclinical data, provide evidence for a potential role of nonvasoactive AMPA/KA antagonists in treating migraine. Larger trials are needed to further test the hypothesis.

Simple tone discriminations are disrupted following experimental frontal traumatic brain injury in rats

PRIMARY OBJECTIVE

To assess cognitive deficits in a rat model of brain injury.

RESEARCH DESIGN

Cognitive deficits are some of the most pervasive and enduring symptoms of frontal traumatic brain injury (TBI) in human patients. In animal models, the assessment of cognitive deficits from TBI has primarily been limited to tests of spatial learning. Recently, simple discrimination performance has been shown to be sensitive to frontal brain damage. The current study provides a detailed characterization of deficits in a two-choice tone discrimination following a bilateral frontal controlled cortical impact injury.

METHODS AND PROCEDURES

Rats were trained on a two-tone discrimination task in a standard operant chamber, then either a frontal brain injury was delivered or sham procedures performed. Following recovery, they were re-tested on the discrimination task and then tested on a reversal of the discrimination.

MAIN OUTCOMES AND RESULTS

Frontal injury caused substantial deficits in responding and discrimination accuracy as well as an increase in side bias.

CONCLUSIONS

Based on the outcomes seen in this study, discrimination and other operant tasks may provide a sensitive tool to assess the effect of therapeutic agents on cognitive deficits in animal models, which could lead to improved characterization of deficits and yield an improved assessment tool to aid in drug discovery.

Chronic lung disease and HIV infection are risk factors for recurrent tuberculosis in a low-incidence setting

SETTING

Programmatic data from the United States on tuberculosis (TB) recurrence are limited.

OBJECTIVES

To determine the TB recurrence rate and to determine if chronic lung disease (CLD) and human immunodeficiency virus (HIV) infection are risk factors for recurrence in this population.

DESIGN

Nested case-control study among TB cases reported to the Tennessee Department of Health between 1 January 2000 and 31 December 2006. Time at risk for recurrence was through 31 December 2007. Multiple imputation accounted for missing data.

RESULTS

Of 1431 TB cases, 20 cases recurred (1.4%, 95%CI 0.9-2.1). Median time at risk for recurrence was 4.5 years (interquartile range 2.7-6.1). Initial and recurrent Mycobacterium tuberculosis isolates were available for genotyping for 15 patients; 12 were consistent with relapse (0.8%, 95%CI 0.4-1.5) and three with re-infection (0.2%, 95%CI 0.04-0.6). HIV infection (OR 5.01, P = 0.04) and CLD (OR 5.28, P = 0.03) were independently associated with recurrent TB, after adjusting for a disease risk score. HIV infection was a risk factor for TB re-infection (P < 0.001).

CONCLUSIONS

In this low-incidence US population, the TB recurrence rate was low, but CLD and HIV were independent risk factors for recurrence. HIV infection was also a risk factor for TB re-infection.

Combination therapy with amlodipine/valsartan in essential hypertension: a 52-week, randomised, open-label, extension study

BACKGROUND

A majority of hypertensive patients require > or = 2 agents to achieve target blood pressure (BP).

METHODS

This 52-week, multicentre, open-label, randomised extension trial to a previously reported double-blind, placebo-controlled study evaluated the safety and efficacy of amlodipine/valsartan (Aml/Val) combination. Patients who successfully completed the core study without serious drug-related adverse events (AEs) and mean sitting systolic BP (MSSBP)/mean sitting diastolic BP (MSDBP) < or = 150/95 mmHg were eligible to enter the extension and be treated with Aml/Val 2.5/80 or 5/80 mg. After 4 weeks of treatment, patients underwent force-titration to receive 5/160 mg (low dose) or 10/160 mg (high dose) for 48 weeks. Addition of hydrochlorothiazide (HCTZ) 12.5 mg was permitted if BP was > or = 140/90 mmHg at Week 8 or later. Patients could be down-titrated to the prior lower combination dose with or without HCTZ if an intolerable AE occurred. Safety evaluations included monitoring of AEs. Efficacy variables were change from baseline in MSDBP (primary) and MSSBP (secondary).

RESULTS

Of 1246 patients randomised, 1075 (86.3%) completed the extension study. At week 52 end-point, change in MSSBP/MSDBP from core study baseline was -22.1/-17.2 mmHg for low-dose regimen and -22.8/-18.1 mmHg for high-dose regimen. For both regimens, reductions in BP were sustained over 52 weeks and mean BP maintained below approximately 135/85 mmHg at all visits. Frequent AEs in the low- and high-dose regimens were peripheral oedema (9.7% and 17.1% respectively), nasopharyngitis (8.1% and 7.2%), and dizziness (5.2% and 7.0%). Incidence of serious AEs was 3.7% with low dose and 4.1% with high dose.

CONCLUSION

The combination of Aml/Val with the optional addition of HCTZ produced clinically significant and persistent reductions in BP over 52 weeks with a favourable tolerability profile.

Effects of sibutramine and rimonabant in rats trained to discriminate between 22- and 2-h food deprivation

OBJECTIVE

The objective of the study was to evaluate whether sibutramine and rimonabant, drugs that decrease food intake in human and non-human animals, affect the discriminative stimulus effects associated with acute food deprivation ("hunger").

MATERIALS AND METHODS

Rats were trained to discriminate between 22- and 2-h food deprivation in a two-lever choice procedure. After rats acquired the discrimination, subjects were food-restricted for 22 h and administered with sibutramine (0.32-10 mg/kg, p.o.) or rimonabant (0.32-10 mg/kg, s.c.) before a generalization test session.

RESULTS

Sibutramine (3.2 mg/kg) produced significant decreases in 22-h deprivation-appropriate responding, response rates (resulting in lever pressing rates similar to those following 2-h food deprivation), and food intake measured 1 h after the generalization test. A larger sibutramine dose eliminated responding and significantly reduced food intake. Rimonabant did not alter the discriminative stimulus effects of 22-h food deprivation, but rimonabant did significantly reduce both response rates and food intake.

CONCLUSION

Sibutramine appears to decrease food intake by reducing hunger sensations associated with food deprivation. In contrast, rimonabant does not alter the discrimination of acute food deprivation. The use of food-deprivation discrimination techniques may be useful in identifying the role of specific neuroactive compounds in eating stimulated by a sense of hunger and may aid in medication development for more effective treatments for obesity and other eating-related conditions.

Environmental stress-corrosion cracking of fiberglass: lessons learned from failures in the chemical industry

Fiberglass reinforced plastic (FRP) composite materials are often used to construct tanks, piping, scrubbers, beams, grating, and other components for use in corrosive environments. While FRP typically offers superior and cost effective corrosion resistance relative to other construction materials, the glass fibers traditionally used to provide the structural strength of the FRP can be susceptible to attack by the corrosive environment. The structural integrity of traditional FRP components in corrosive environments is usually dependent on the integrity of a corrosion-resistant barrier, such as a resin-rich layer containing corrosion resistant glass fibers. Without adequate protection, FRP components can fail under loads well below their design by an environmental stress-corrosion cracking (ESCC) mechanism when simultaneously exposed to mechanical stress and a corrosive chemical environment. Failure of these components can result in significant releases of hazardous substances into plants and the environment. In this paper, we present two case studies where fiberglass components failed due to ESCC at small chemical manufacturing facilities. As is often typical, the small chemical manufacturing facilities relied largely on FRP component suppliers to determine materials appropriate for the specific process environment and to repair damaged in-service components. We discuss the lessons learned from these incidents and precautions companies should take when interfacing with suppliers and other parties during the specification, design, construction, and repair of FRP components in order to prevent similar failures and chemical releases from occurring in the future.

Evaporative Tunnel Cooling of Dairy Cows in the Southeast. I: Effect on Body Temperature and Respiration Rate

The techniques used to mitigate the effects of heat stress on lactating dairy cows are often overwhelmed in the southeastern United States, where elevated heat and humidity often persist for extended periods. A model free-stall barn located at the North Mississippi Branch Experiment Station in Holly Springs was used to evaluate the potential of tunnel ventilation with evaporative cooling to alleviate heat stress in lactating dairy cows. Two studies were conducted using 2 groups of 10 lactating Holsteins housed in the tunnel barn (inside) and 2 groups of matched herdmates housed in an adjacent covered free-stall barn (outside), which was cooled by fans and sprinklers during 2001 or by shade and fans alone in 2003. Peak daytime temperatures inside were 5.2 +/- 0.18 degrees C below that outside in 2001 and 3.1 +/- 0.20 degrees C lower in 2003. Although evaporative cooling increased humidity by 22%, cows housed in the tunnel barn received 84% less exposure to moderate heat stress (temperature-humidity index > 80) in both years. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 15.5 +/- 0.56 breaths/min and rectal temperatures by 0.6 +/- 0.02 degrees C compared with shade and fans alone in 2003. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 13.1 +/- 0.78 breaths/min and rectal temperatures by 0.4 +/- 0.03 degrees C compared with fans and sprinklers in 2001. Thus, tunnel ventilation cooling dramatically reduced the exposure to heat stress and improved the comfort of lactating dairy cows when compared with traditional cooling technologies under the conditions present in the southeastern United States.

Evaporative Tunnel Cooling of Dairy Cows in the Southeast. II: Impact on Lactation Performance

Heat stress has a dramatic impact on the dairy industry, reducing production and profitability throughout the southeastern United States. In many regions, management techniques can be used to mitigate the effects of heat stress, but available cooling technologies are often overwhelmed by the conditions of chronic heat stress present in southeastern United States. Although combining tunnel ventilation and evaporative cooling (evaporative tunnel cooling) seems to provide superior cooling for dairy cows, there is a dearth of reports on the impact of this technology on milk production. A model evaporative tunnel cooling facility in northern Mississippi was studied using 2 groups of 10 lactating Holstein cows housed in the tunnel barn and 2 groups of 10 matched herdmates housed in an adjacent naturally ventilated free-stall barn. Two 10-wk trials were performed in 2 yr beginning June 25, 2001, and May 26, 2003, in which cows housed outside were cooled by traditional fans and shade alone (2003) or with sprinklers (2001). In both years, the use of evaporative tunnel cooling decreased exposure to conditions of moderate heat stress by 84%. Cows cooled by evaporative tunnel ventilation increased feed intake by 12 and 11% over cows housed outside in 2001 and 2003, respectively. Evaporative tunnel cooling had no effect on milk composition, but increased milk yield over the 10-wk trial by 2.6 +/- 0.27 and 2.8 +/- 0.19 kg/cow per day in 2001 and 2003, respectively. In addition, somatic cell count was decreased 27 to 49% by evaporative tunnel cooling. Thus, under the range of environmental conditions present, evaporative tunnel cooling reliably reduced exposure to conditions of heat stress and improved milk production of lactating dairy cows during the summer season.

Establishing principles for migraine management in primary care

Published guidelines for the management of migraine in primary care were evaluated by an international advisory board of headache specialists, to establish evidence-based principles of migraine management that could be recommended for international use. Twelve principles of migraine management were identified, covering screening, diagnosis, management and treatments: Almost all headaches are benign/primary and can be managed by all practising clinicians. Use questions/a questionnaire to assess the impact on daily living and everyday activities, for diagnostic screening and to aid management decisions. Share migraine management between the clinician and the patient. Provide individualised care for migraine and encourage patients to manage their migraine. Follow up patients, preferably with migraine calendars or diaries. Regularly re-evaluate the success of therapy using specific outcome measures and monitor the use of acute and prophylactic medications regularly. Adapt migraine management to changes that occur in the illness and its presentation over the years. Provide acute medication to all migraine patients and recommend it is taken at the appropriate time, during the attack. Provide rescue medication/symptomatic treatment for when the initial therapy fails. Offer to prescribe prophylactic medications, as well as lifestyle changes, to patients who have four or more migraine attacks per month or who are resistant to acute medications. Consider concurrent co-morbidities in the choice of appropriate prophylactic medication. Work with the patient to achieve comfort with mutually agreed upon treatment and ensure that it is practical for their lifestyle and headache presentation. Using these principles, practising clinicians can screen and diagnose their headache patients effectively and manage their migraine patients over the long-term natural history of the migraine process. In this way, the majority of migraine patients can be well treated in primary care, ensuring a structured and individualised approach to headache management, and conserving valuable healthcare resources.

Pitfalls in migraine diagnosis and management

The decade of the 90s brought about a revolution in our understanding of migraine and in medications to treat this disorder. Indeed, our understanding of the pathophysiology of migraine and the pharmacology involved in its treatment has exploded. Nonetheless, there are still many pitfalls that may occur in the clinical assessment and management of migraine that may prevent the patient from receiving the full benefits of the advances of the past 10 years. This article explores the reasons for the unsuccessful diagnosis and treatment of migraine and presents suggestions for improving its management.

Evaluation of alternative algorithms used to simulate pasture intake in grazing dairy cows

Four algorithms used to simulate pasture intake in grazing dairy cows in a dairy decision support system were proposed and evaluated with data from the literature. The algorithms proposed were: 1) an algorithm combining the approach used in a published model to determine dry matter intake based on neutral detergent fiber intake as a percentage of the BW, energy requirements, pasture availability and a standard supplementation (PIest), 2) the previous algorithm modified to consider the type and amount of supplementation (PIsup), 3) an algorithm which considers the effect of selection of pasture (PIsel), and 4) the combination of algorithms 2 and 3 (PIsupsel). Pasture intake data of 27 grazing experiments from the literature were used to evaluate those algorithms. Two methods of evaluation were used: 1) simple linear regression between reported and simulated values, and 2) analysis of variance for the difference between reported and simulated values considering pasture availability and type of supplementation. The R2 of the linear regression and average proportional bias between reported values and simulated values were 0.24 and 19% for PIest, 0.42, and 23% for PIsup, 0.45 and 2% for PIsel and 0.41 and 10% for PIsupsel. Those results showed that PIsel had the lower variability and the values closer to pasture intake. The algorithm PIsup had low variability but tended to underpredict pasture intake. The algorithm PIest values were closer to reported values for low pasture availability. The modeling results show the influence of pasture selection in grazing systems.

CT appearance of some colonic villous tumors

OBJECTIVE

A review was made of the CT studies and pathology reports of four patients with surgically resected colonic villous adenomatous tumors, two of whom had focal carcinomatous invasion.

CONCLUSION

Two patients had villous tumors with IV contrast-enhancing convolutional gyral patterns. The other two patients had tumor masses that showed oral contrast medium collecting in surface interstices, analogous to findings with barium enemas. One of the latter also had an unusual cluster of mesenteric vessels adjacent to the lesion.

Amino acid substitution variants of APE1 and XRCC1 genes associated with ionizing radiation sensitivity

Although several variants of DNA repair genes have been identified, their functional significance has not been determined. Using samples collected from 135 cancer-free women, this study evaluated whether amino acid substitution variants of DNA repair genes contribute to ionizing radiation (IR) susceptibility as measured by prolonged cell cycle G2 delay. PCR-restriction fragment length polymorphism (RFLP) assays were used to determine four genotypes: X-ray repair cross complementing group 1 (XRCC1, exon 6, C/T, 194 Arg/Trp and exon 10, G/A, 399 Arg/Gln), XRCC group 3 (XRCC3, exon 7, C/T, 241 Thr/Met) and apurinic/apyrimidinic endonuclease 1 (APE1, exon 5, T/G, 148 Asp/Glu). Fluorescence-activated cell sorter (FACS) analysis was used to measure cell cycle delay. APE1 (exon 5) genotype was significantly associated with mitotic delay (P = 0.01), with the Glu/Glu genotype having prolonged delay compared with the other two genotypes. The mitotic delay index (mean +/- SD) in women with the APE1 codon 148 Asp/Asp, Asp/Glu and Glu/Glu genotypes was 30.95 +/- 10.15 (n = 49), 30.65 +/- 10.4 (n = 60) and 39.56 +/- 13.12 (n = 21), respectively. There was a significant interaction between family history (FH) and APE1 (exon 5) genotype (P = 0.007) as well as FH and XRCC1 (exon 10) genotype (P = 0.005) in mitotic delay. Lastly, prolonged cell cycle delay was significantly associated with number of variant alleles when APE1 Asp148Glu and XRCC1 Arg399Gln genotypes were evaluated in a four-level model (chi(2) for linear trend = 10.9; P = 0.001). These results suggest that amino acid substitution variants of XRCC1 and APE1 may contribute to IR hypersensitivity.

Comparative study of a combination of isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate in the treatment of migraine

OBJECTIVE

To compare the safety and efficacy of isometheptene mucate, dichloralphenazone with acetaminophen to sumatriptan succinate for the treatment of mild-to-moderate migraine, with or without aura, when taken at the first sign of an attack.

BACKGROUND

The Food and Drug Administration approved sumatriptan succinate and the combination of isometheptene mucate, dichloralphenazone with acetaminophen for the treatment of migraine. As part of the stratified treatment of migraine, those patients whose headaches are mild or moderate may benefit from nontriptan medications. Additionally, early treatment of acute migraine before the headache has become moderate or severe may improve response to treatment.

METHODS

This was a multicenter, double-blind, randomized, parallel-group study to assess the safety and efficacy of the combination of isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate in the early stages of a single migraine attack. Patients diagnosed with migraine, with or without aura, as defined by the International Headache Society diagnostic criteria were enrolled.

RESULTS

One hundred thirty-seven patients were enrolled in the study. Data for efficacy were available for 126 patients; safety data were available for 128 patients. No statistically significant difference between the two active agents in the patient's response to treatment was demonstrated. Headache recurrence was not significantly different over the 24-hour evaluation period for those patients responding in the first 4 hours. In those with headache recurrence, it was statistically significantly more severe in those patients treated with sumatriptan succinate. Improvement in functional disability was, in general, better among those treated with isometheptene mucate, dichloralphenazone with acetaminophen. Global analysis of efficacy was similar in the two active groups. Patients treated with sumatriptan succinate were somewhat more likely to have adverse effects than the isometheptene mucate, dichloralphenazone with acetaminophen group.

CONCLUSIONS

Both isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate are safe and effective when used early in the treatment of an acute migraine. Several parameters suggest that isometheptene mucate, dichloralphenazone with acetaminophen may have a slight advantage compared with sumatriptan succinate in the early treatment of mild-to-moderate migraine.

Factors affecting pasture intake and total dry matter intake in grazing dairy cows

We investigated the most relevant variables for estimating pasture intake and total dry matter (DM) intake in grazing dairy cows using 27 previously published studies. Variables compared were pasture allowance, days in milk, amount of forage, amount of concentrate and total supplementation, pasture allowance and supplementation interaction, fat-corrected milk, body weight (BW), metabolic BW, daily change in BW, percentage of legumes in pasture, neutral detergent fiber (NDF) contents of pasture, and NDF in pasture selected. The variables were selected using stepwise regression analysis for total DM intake and pasture DM intake. Variables selected in the total DM intake regression equation (R2 = 0.95) were pasture allowance, total supplementation, interaction of pasture allowance and supplementation, fat-corrected milk, BW, daily change in BW, percentage of legumes and pasture NDF content. Pasture DM intake regression equation (R2 = 0.90) was similar to total DM intake equation, but supplementation coefficient was negative, showing substitution effect in supplementing grazing cows. The intake of NDF as a percentage of BW was higher than 1.3% when considering NDF content of the pasture allowance. Low pasture allowance groups had values higher than 1.3%.

Hyperventilation increases muscle protein synthesis in critically ill trauma patients

BACKGROUND

Critically ill trauma patients are often in negative nitrogen balance and demonstrate advanced muscle protein wasting, which is in part due to a decrease in muscle protein synthesis. Previous studies have been performed on the relationship between pH and protein metabolism. Some evidence suggests that alkalosis might enhance protein synthesis. The purpose of the present study is to determine whether protein synthesis is increased in trauma patients who have a respiratory alkalosis from hyperventilation.

METHODS

Trauma patients in the intensive care unit (n = 8) who were treated with hyperventilation for elevated intracranial pressures were enrolled. Muscle protein synthesis rates were determined in vivo using the flooding method with l-[(2)H(5)]phenylalanine. Measurements were performed twice on each patient within a 36-h period, first during hyperventilation and then after hyperventilation was discontinued. Hemoglobin oxygen saturation was maintained above 95% for all measurements.

RESULTS

Protein synthesis in muscle was 1.38 +/- 0.11%/day during hyperventilation (pH 7.50 +/- 0.02, pCO(2) 27.3 +/- 1.0 mm Hg) and 0.93 +/- 0.15%/day after respiratory parameters were normalized (pH 7.39 +/- 0.01, pCO(2) 39.4 +/- 1.5 mm Hg). The synthesis rate was significantly higher (P < 0.01, paired t test), 0.46 +/- 0.13%/day (32.6%), at the time of hyperventilation.

CONCLUSION

Muscle protein synthesis is elevated during hyperventilation in critically ill patients with traumatic brain injury. We believe this preliminary study provides data that warrant confirmation in larger clinical studies. It suggests that this ventilatory therapeutic strategy may have a role in mitigating the negative nitrogen balance and muscle protein wasting that can impair the recovery of these patients.

Hsp70 and a 54 kDa protein (Osp54) are induced in salmon (Salmo salar) in response to hyperosmotic stress

Hsp70 and a 54 kDa osmotic stress protein (osp54) were induced in isolated tissues of anadromous Atlantic salmon (Salmo salar) upon exposure to hyperosmotic conditions. Incubation of branchial lamellae, hepatic tissue, and erythrocytes in medium supplemented with 200-600 mM NaCl dramatically reduced protein synthesis. Although general protein synthesis remained depressed following transfer of tissues from 450 mM supplemental NaCl to iso-osmotic medium, hsp70 was prominently induced in branchial lamellae and hepatic tissue. Accumulation of hsp70 mRNA and a decrease in actin mRNA suggest preferential upregulation of the hsp70 gene. Induction of osp54 was observed in branchial lamellae and erythrocytes, but not in hepatic tissue, during exposure to 75-125 mM supplemental NaCl. Use of glycerol in place of NaCl to create hyperosmotic conditions stimulated induction of hsp70 in branchial lamellae. Substitution with mannitol resulted in induction of osp54 in both branchial lamellae and erythrocytes. The solute-specific and temporal patterns of response suggest that hsp70 and osp54 might function in concert to restore osmotic homeostasis and renature proteins destabilized or denatured during the early stages of osmotic shock.

When courts review medical appropriateness

OBJECTIVES

The authors examined how the courts have responded to public and private insurers' use of medical appropriateness criteria to establish coverage and payment policies.

METHODS

A structured review of all federal and state court health insurance cases decided between 1960 and June 1994 that involved a dispute involving medical appropriateness was performed. A total of 3,215 published court decisions were analyzed, of which 203 met the criteria of relevance and 124 explicitly mentioned medical appropriateness criteria. The main outcome variable was whether the court ordered the insurer to provide coverage.

RESULTS

In 185 cases, a definitive decision was rendered, and the insurer was required to pay in 57% of the decisions. Whether the insurer relied on an assessment or not, whether the assessment process was formal or informal, and who conducted the assessment did not appear to influence courts' decisions, nor did the specificity of the coverage exclusion. Significant predictors of courts ordering coverage were court jurisdiction, contract language assigning discretion to the insurer, severity of patient's condition, and whether the treatment appeared to work for the particular patient.

CONCLUSIONS

For practice guidelines to be accepted by the courts, it is more important to focus on how insurance contracts are written than on how medical assessments are performed.

Sphingomyelinase has an insulin-like effect on glucose transporter translocation in adipocytes

Rat epididymal adipocytes were incubated with 0, 0.1, and 1 mU sphingomyelinase/ml for 30 or 60 min, and glucose uptake and GLUT-1 and GLUT-4 translocation were assessed. Adipocytes exposed to 1 mU sphingomyelinase/ml exhibited a 173% increase in glucose uptake. Sphingomyelinase had no effect on the abundance of GLUT-1 in the plasma membrane of adipocytes. In contrast, 1 mU sphingomyelinase/ml increased plasma membrane content of GLUT-4 by 120% and produced a simultaneous decrease in GLUT-4 abundance in the low-density microsomal fraction. Sphingomyelinase had no effect on tyrosine phosphorylation of either the insulin receptor beta-subunit or the insulin receptor substrate-1, a signaling molecule in the insulin signaling pathway. It is concluded that the incubation of adipocytes with sphingomyelinase results in insulin-like translocation of GLUT-4 to the plasma membrane and that this translocation does not occur via the activation of the initial components of the insulin signaling pathway.

Deciphering posttranslational processing events in the pituitary of a neopterygian fish: cloning of a gar proopiomelanocortin cDNA

A cDNA that codes for the polypeptide hormone precursor proopiomelanocortin (POMC) was cloned and sequenced from a gar (Lepisosteus osseus) pituitary cDNA library. The gar POMC cDNA is 1237 bp and contains a 780-bp open reading frame. The deduced amino acid sequence for gar POMC is 259 amino acids in length. The general organization of gar POMC is very similar to that of other gnathostome POMC sequences. The beta-endorphin sequence had 91% sequence identity with sockeye A beta-endorphin and 71% sequence identity with Xenopus laevis beta-endorphin. Three melanocyte-stimulating hormone (MSH) core sequences [HFR(W)] were detected. The gar alpha-MSH sequence was identical to the alpha-MSH sequence in rat POMC. The gar beta-MSH sequence had 77% sequence identity with salmonid forms of beta-MSH and 53% sequence identity with tetrapod forms of beta-MSH. The gamma-MSH region of gar POMC only had 26% primary sequence identity with tetrapod gamma-MSH sequences. Gar gamma-MSH had an incomplete MSH core sequence (HRF), an apparent internal deletion of five amino acids, and lacked flanking paired basic amino acids essential for proteolytic cleavage. The apparent degenerate nature of gar gamma-MSH is discussed in light of the absence of this sequence in salmonid fish.

Metabolic characteristics of induced ketosis in normal and obese dairy cows

Four groups of 6 cows were used to determine the effects of body condition on induction of ketosis. At calving, obese cows were heavier by 108 kg and had a higher body condition score by 0.74 units than did normal cows. Susceptibility to induced ketosis was evaluated by restricting dry matter intake by 20% and feeding 7% 1,3-butanediol from 15 to 49 d in milk (DIM) to one group of obese cows and to one group of normal cows. No normal or obese cows fed the control diet developed ketosis. Two normal and 2 obese cows developed ketonemia because of the induction protocol, and 1 cow in each of the two groups developed clinical ketosis. Obese cows lost 59% more body weight during the first 14 DIM than did normal cows, and cows fed the restricted diet plus 7% 1,3-butanediol lost 15% more body weight than did cows fed the control diet during the induction period. Concentrations of nonesterified fatty acids increased at parturition, peaked at 7 to 14 DIM, and returned to prepartum concentrations by 21 DIM. Plasma beta-hydroxybutyrate concentrations increased after calving and was increased additionally by the induction protocol. At the onset of lactation, plasma insulin decreased, plasma glucagon increased, hepatic triacylglycerols increased, and hepatic glycogen decreased. The incidence of ketonemia and clinical ketosis was the same for obese and normal cows, but, on the basis of changes of blood and liver composition, incidence of ketosis would probably increase if obese cows were overfed throughout the entire dry period.

Effect of monensin on 2-deoxyglucose uptake, the insulin receptor and phosphatidylinositol 3-kinase activity in rat muscle

Preincubation of rat soleus muscle with 1 and 10 microM monensin for 2 h increased the subsequent basal 2-deoxyglucose uptake by muscle 76 and 121% respectively. Under the same conditions, monensin decreased the insulin-stimulated (1 mU/ml) 2-deoxyglucose uptake by 29 and 37% respectively. The monensin-induced augmentation of basal 2-deoxyglucose uptake was inhibited 92% by cytochalasin B suggesting that the uptake is mediated by glucose transporters. Monensin did not increase the cellular accumulation of L-glucose in muscle indicating that it does not affect the cell membrane integrity. Neither the stimulatory effect of monensin on basal 2-deoxyglucose uptake nor the opposite, inhibitory action of monensin on the insulin-stimulated 2-deoxyglucose uptake were influenced by the removal of Ca2+ from the medium or by dantrolene, an inhibitor of Ca2+ release from the sarcoplasmic reticulum, suggesting that the actions of monensin are not mediated by calcium. Monensin had no effect on muscle ATP concentration. The monensin-induced augmentation of basal 2-deoxyglucose uptake was neither associated with stimulation of muscle phosphatidylinositol 3-kinase activity nor inhibited by wortmannin, demonstrating that the increase in basal 2-deoxyglucose uptake is not mediated by activation of phosphatidylinositol 3-kinase. The inhibition of insulin-stimulated 2-deoxyglucose uptake by monensin was associated with a 31% decrease in the abundance of insulin receptors in muscles, a 64% decrease in the insulin-induced autophosphorylation of the insulin receptor beta-subunit, and a 44% reduction of the insulin-stimulated phosphatidylinositol 3-kinase activity. Addition of monensin into the phosphatidylinositol 3-kinase reaction had no effect on the activity of the enzyme, demonstrating that the inhibition in monensin-treated muscles is indirect and occurs upstream of phosphatidylinositol 3-kinase. It is concluded that monensin has a dual effect on 2-deoxyglucose uptake by skeletal muscle: it stimulates basal uptake but inhibits the insulin-stimulated uptake. The primary cause of the latter, inhibitory effect of monensin is at the level of the insulin receptor.

Growth hormone-induced insulin resistance: role of the insulin receptor, IRS-1, GLUT-1, and GLUT-4

Treatment of rats with growth hormone (GH; 1 mg/kg sc) twice daily over 2.5 days did not alter fasting plasma glucose or glucose tolerance but increased fasting plasma insulin levels 65% and peak insulin response to a glucose load 35% over controls, indicating the development of insulin resistance. Studies on partially purified insulin receptors from soleus muscles showed that GH increased the abundance of insulin receptor beta-subunits by 48% as measured by immunoblotting. Despite this increase, GH abolished the increase in autophosphorylation of the insulin receptor beta-subunit in response to physiological hyperinsulinemia and diminished by 28% the response to supraphysiological hyperinsulinemia. Similarly, insulin-stimulated phosphorylation of insulin receptor substrate-1 (IRS-1) was decreased 25% by GH, but the abundance of IRS-1 was not affected. Studies on rats pretreated with streptozotocin suggested that the effects of GH are direct and not secondary to GH-induced hyperinsulinemia. GH decreased basal GLUT-1 abundance in the low-density microsome and plasma membrane fractions of epididymal adipocytes by 50 and 42%, respectively, but decreased basal GLUT-4 abundance only in the low-density microsome fraction by 24%. Despite these alterations, the abundance of both transporters in the plasma membrane fraction of adipocytes incubated with 0.1 U insulin/ml was not diminished by GH.

Phosphatidylinositol 3-kinase and dynamics of insulin resistance in denervated slow and fast muscles in vivo

Regulation of glucose uptake by 1- and 3-day denervated soleus (slow-twitch) and plantaris (fast-twitch) muscles in vivo was investigated. One day after denervation, soleus and plantaris muscles exhibited 62 and 65% decreases in insulin-stimulated 2-deoxyglucose uptake, respectively, compared with corresponding control muscles. At this interval, denervated muscles showed no alterations in insulin receptor binding and activity, amount and activity of phosphatidylinositol 3-kinase, and amounts of GLUT-1 and GLUT-4. Three days after denervation, there was no increase in 2-deoxyglucose uptake in response to insulin in soleus muscle, whereas plantaris muscle exhibited a 158% increase in basal and an almost normal absolute increment in insulin-stimulated uptake. Despite these differences, denervated soleus and plantaris muscles exhibited comparable decreases in insulin-stimulated activities of the insulin receptor (approximately 40%) and phosphatidylinositol 3-kinase (approximately 50%) and a pronounced decrease in GLUT-4. An increase in GLUT-1 in plantaris, but not soleus, muscle 3 days after denervation is consistent with augmented basal 2-deoxyglucose uptake in plantaris muscle at this interval. These results demonstrate that, in denervated muscles, there is a clear dissociation between insulin-stimulated 2-deoxyglucose uptake and upstream events involved in insulin-stimulated glucose uptake.

Anomalous inferior vena cava associated with horseshoe kidneys

Two cases are presented in which anomalies of the inferior vena cava were associated with horseshoe kidneys. Radiological demonstration of such combined variation is rare, only one case of duplicated inferior vena cava with horseshoe kidney having been found in the literature. The embryological basis for these anomalies is reviewed. A possible explanation for their coexisting occurrence is also speculatively raised.

Use of lactation curves for analysis of milk production data

Nonlinear equations were compared with categorical analysis to account for DIM effects on milk production. Five different models for lactation curves were evaluated. Derived from a multiphasic lactation curve, the selected lactation curve appeared to result in random residuals and performed more consistently than the multiphasic curve. Residuals from the fitting of lactation curves were then used for split-plot analysis (continuous model) to estimate treatment effects. Statistical performance of this model was compared with split-plot analysis based on a discrete model with regularly spaced intervals to account for DIM effects (discrete model). The fitting of lactation curves accounted for herd, lactation number, and interaction effects of herd and lactation number and accounted for 34.1 and 44.3% of variance among cows for primiparous and multiparous cows, respectively. The continuous model detected interactions of genetic and management factors with treatment of multiparous cows that were not detected by the discrete model. No statistically significant differences were detected between the two modeling approaches. The continuous model appeared to violate fewer assumptions regarding data distribution than did the discrete model, which reduced the risk of introducing bias during the estimation of treatment effects. The continuous model seemed to be more sensitive to subtle interactions of treatment and other factors.

Sphingomyelinase stimulates 2-deoxyglucose uptake by skeletal muscle

The effects of sphingomyelinase, phosphorylcholine, N-acetylsphingosine (C2-ceramide), N-hexanoylsphingosine (C6-ceramide) and sphingosine on basal and insulin-stimulated cellular accumulation of 2-deoxy-D-glucose in rat soleus muscles were investigated. Preincubation of muscles with sphingomyelinase (100 or 200 m-units/ml) for 1 or 2 h augmented basal 2-deoxyglucose uptake by 29-91%, and that at 0.1 and 1.0 m-unit of insulin/ml 32-82% and 19-25% respectively compared with control muscles studied at the same insulin concentrations. The sphingomyelinase-induced increase in basal and insulin-stimulated 2-deoxyglucose uptake was inhibited by 91% by 70 microM cytochalasin B, suggesting that it involves glucose transporters. Sphingomyelinase had no effect on the cellular accumulation of L-glucose, which is not transported by glucose transporters. The sphingomyelinase-induced increase in 2-deoxyglucose uptake could not be reproduced by preincubating the muscles with 50 microM phosphorylcholine, 50 microM C2-ceramide or 50 microM C6-ceramide. Preincubation of muscles with 50 microM sphingosine augmented basal 2-deoxyglucose transport by 32%, but reduced the response to 0.1 and 1.0 m-unit of insulin/ml by 17 and 27% respectively. The stimulatory effect of sphingomyelinase on basal and insulin-induced 2-deoxyglucose uptake was not influenced by either removal of Ca2+ from the incubation medium or dantrolene, an inhibitor of Ca2+ release from the sarcoplasmic reticulum. This demonstrates that Ca2+ does not mediate the action of sphingomyelinase on 2-deoxyglucose uptake. Sphingomyelinase also had no effect on basal and insulin-stimulated activities of insulin receptor tyrosine kinase and phosphatidylinositol 3-kinase. In addition, 1 and 5 microM wortmannin, an inhibitor of phosphatidylinositol 3-kinase, failed to inhibit the sphingomyelinase-induced increase in 2-deoxyglucose uptake. These results suggest that sphingomyelinase does not increase 2-deoxyglucose uptake by stimulating the insulin receptor or the initial steps of the insulin-transduction pathway. The data suggest the possibility that sphingomyelinase increases basal and insulin-stimulated 2-deoxyglucose uptake in skeletal muscle as the result of an unknown post-receptor effect.

Effects of nicotinamide on milk composition and production in dairy cows fed supplemental fat

Thirty-two cows, averaging 112 DIM, were assigned to four dietary treatments: 1) control, 2) Ca salts of fatty acids, 3) nicotinamide, and 4) Ca salts of fatty acids blended with nicotinamide during manufacture. Preliminary studies showed that nicotinamide survives blending with Ca salts of fatty acids during manufacture and that a blended mixture of nicotinamide and Ca salts of fatty acids gave results similar to those from nicotinamide plus Ca salts of fatty acids supplemented separately. Calcium salts of fatty acids increased milk fat percentage, decreased milk protein percentage, but had no effect on production of milk, FCM, fat, or protein. Nicotinamide increased production of milk and protein, decreased fat percentage, but had no effect on either production of FCM and protein or percentage of protein. Calcium salts of fatty acids increased NEFA in blood, and dietary nicotinamide increased concentrations of nicotinamide in blood, but glucose and BHBA in blood were unaffected by either dietary ingredient. Therefore, in these midlactation cows, the decreased milk protein percentage caused by supplemental dietary fat was prevented by nicotinamide. Supplementation with only nicotinamide increased total production of milk protein.

Metabolic evaluation of the criteria used to fit elbow crutches by measurement of oxygen consumption

OBJECTIVE

To investigate if elbow crutches fitted using conventional guidelines are the most metabolically efficient.

DESIGN

Repeated measure connivance sample using crutch length as the independent variable.

SETTING

A university exercise physiology laboratory. OTHER PARTICIPANT: Connivance sample of 10 students free from cardiovascular disease, with previous experience in crutch ambulation, and between heights of 160 and 175 cm. Four potential subjects refused to participate in the study.

INTERVENTIONS

Crutch length was adjusted using conventional guidelines, and to lengths 2.5 cm above and below this setting. Oxygen consumption was measured using indirect open-circuit spirometry during the final 3 minutes of ambulation using self-selected walking speeds.

MAIN OUTCOME MEASURE

Crutches adjusted to the convention setting are not the most efficient in terms of metabolic energy expenditures.

RESULTS

A significant reduction in oxygen rate (p = .012), oxygen cost (p = .010), and respiratory exchange ratio (p = .009) were observed when comparing crutches adjusted to -2.5 cm of the standard height with conventional crutch height. Crutches adjusted 2.5 cm above the standard height also required less energy, but these values failed to reach any statistical significance (p > .05).

CONCLUSION

The importance of fitting crutches to the correct length using conventional guidelines has not been substantiated in this study. Clinically, there should be a move away from adherence to crutch-fitting criteria and more incorporation of patient feedback to fit crutches to the optimal height. Future research should evaluate the reliability of practical clinical measures such as heart rate and perceived exertion to fit crutches to the optimal height.