Abstract TMP115: Nox-2 and Cerebrovascular Function in Metabolic Syndrome After a Stroke

Introduction: The aim here is to elucidate the mechanisms involved in post-stroke cerebrovascular impairments in metabolic syndrome (MetS) that pre-dispose obese patients to more severe post-stroke deficits.

Methods: 1 hr middle cerebral artery occlusion was performed in 17 week old lean (LZR) and obese Zucker (OZR: MetS model) rats. At 24 hr or 15 days post-stroke, the ipsilateral middle cerebral artery (MCA) was cannulated in an ex-vivo microvessel preparation to examine MCA reactivity. Cerebrovascular microvessel density (MVD) was examined 15 days post-stroke via IHC. To examine a potential role of Nox2 and oxidative stress, a specific inhibitor of Nox2 oxidase Nox2-dstat (i.p 10mg/kg) was given during the stroke procedure in OZR.

Results: In LZR, MCA reactivity was impaired vs. non-stroke control at 24hr post-stroke and remained stable at 15 days post-stroke. In LZR, NO bioavailability was reduced at 24hrs vs. controls, which remained stable at 15 days. In OZR, the MCA impairment was greater at 24 hr vs. LZR, and worsened significantly at 15 days post stroke. NO bioavailability for OZR at 24 hr was similar to LZR stroke, but by 15 days had fallen. MVD was reduced 15 days post-stroke, with a larger loss in OZR vs. LZR. Stroke mortality and infarct size were higher for OZR. Nox2 inhibition restored MCA reactivity, improved MVD and NO levels, and limited stroke infarct size in OZR post-stroke.

Discussion: Our data suggest that the MetS increases stroke severity and drives a progressive decline in cerebrovascular dysfunction following ischemic stroke. Inhibiting Nox2 production improved stroke outcome in MetS.

The reliability of muscle function analysis using different methods of stimulation

BACKGROUND

The purpose of our study was to determine the reliability of nonvolitional muscle function analysis (MFA) by determining the day-to-day and within-day reliability of conventional electrical stimulation and a newer, magneto-electrical stimulation method, using standard laboratory methodology.

METHODS

Ten healthy, human immunodeficiency virus-negative adult men volunteered as subjects. MFA consisted of measuring the maximal relaxation rate, for magneto-electrical stimulation at 1 Hz and conventional electrical stimulation at 20 Hz, and force-frequency ratios using conventional electrical stimulation at 10 Hz:20 Hz and 10 Hz:50 Hz. Within-day and day-to-day reliability were determined by calculating the coefficient of variation (CV) for all subjects.

RESULTS

Maximal relaxation rate using magneto-electrical stimulation had a significantly lower CV compared with the other nonvolitional MFA methods (p = .002).

CONCLUSIONS

Maximal relaxation rate using magneto-electrical stimulation was more reliable and technically easier than the other muscle function parameters examined. However, the day-to-day CV of muscle function parameters is larger than traditional nutrition assessment techniques. Development within the field should strive to improve testing techniques so that the reliability of MFA will allow definition of a range of normal values against which an individual's value can be compared. Until this is available, the precision and reliability of MFA restrict its use to research and population studies.

Cirrhosis mortality and occupation

Cirrhosis, the ninth leading cause of death in the United States, has been associated with abusive alcohol consumption patterns. Since the workplace serves as a major exposure variable for alcohol consumption over a significant portion of the lifecourse, and since heavy drinking has been shown to differ by type of occupation, this study examines the relationship between type of occupation and cirrhosis mortality. The California Occupational Mortality Study data set (1979 to 1981) provided the information on primary occupation and liver cirrhosis mortality. Crude and sex-specific mortality rates were calculated based on information from a 20% sample of the 1980 California census (included in the data set). Ninety-five percent confidence intervals were calculated around all rates to determine if any were significantly different from rates for the entire state. The findings uphold the view that an association exists between occupation and cirrhosis mortality. The highest mortality rates were found among persons with blue-collar type jobs (e.g., construction laborers and machinists) or jobs where alcohol was easily available (e.g., bartenders and waitresses). Future research needs to specify the factors associated with occupation that may promote the chronic heavy drinking that leads to cirrhosis.

Occupation and alcohol-related causes of death

The purpose of the present investigation is to determine if various alcohol-related causes of death are associated with similar occupational groups. The California Occupational Mortality Study data set (1979-1981) provided information on primary occupation and deaths from cirrhosis, digestive cancers, injury, suicide and homicide. Age-adjusted mortality rates were calculated along with 95% confidence intervals. Findings indicate that farming/forestry/fishing personnel and handlers/equipment cleaners/helpers/labourers seem to be at risk of dying from alcohol-related causes. Due to the various methodological issues discussed, these findings need to be interpreted with caution.

Characterization of a halothane-induced humoral immune response in rabbits

An animal model of halothane-induced liver injury has been developed in the rabbit to study the production of humoral immunity towards a biotransformation intermediate of halothane. Rabbits exposed many times to halothane in a 75% O2/25% N2 atmosphere produce an antibody that cross-reacts with the trifluoroacetyl moiety of trifluoroacetylated rabbit serum albumin (TFA-RSA). The generation of this halothane-induced immunogen is dependent upon high oxygen tension as shown by the minimal anti-TFA antibody response seen in rabbits exposed to halothane in a 14% O2/86% N2 atmosphere. In addition, halothane exposure of rabbits specifically immunized with the metabolite-carrier complex, TFA-RSA, induces a secondary antibody response toward the immunogen. In rabbits, either immunized with TFA-RSA or not, multiple halothane exposures induce populations of antibodies with varying specificities. Evidence suggests that predominance of the metabolic intermediate, the ensuing immunogen, and the subsequent antibody response depends upon the oxygen tension during successive exposures to halothane. These successive exposures could potentially generate many different immunogens resulting in varied antibody specificities.

Carnitine in the streptozotocin-diabetic rat

Rats made moderately diabetic by streptozotocin (decreased growth without decreased body mass, blood glucose, 588-840 mg/dl) and nondiabetic rats were either fed a purified diet with no measurable carnitine (diet 1), the same diet supplemented with carnitine (44.5 nmol/g food, diet 2), or a closed formula, nonpurified diet (3.3 nmol/g food, diet 3). Levels of total carnitine (free + acyl) were lower (P less than 0.05) in plasma, heart, soleus, extensor digitorum longus and kidney of rats fed diet 1 compared to those fed diet 2. Liver carnitine in diabetic animals was 2.6- to 4.4-fold higher than in nondiabetic animals with urinary carnitine of rats fed diet 1 being four times greater in diabetic than in nondiabetic rats. Other changes in tissue total carnitine were less pronounced. Compared to diabetic rats, insulin-treated diabetics had lower urinary excretion of carnitine and blood glucose levels (P less than 0.05), and tissue carnitine approximating nondiabetic levels. Significant catabolism of carnitine was not found. Apparent carnitine biosynthesis (diet 1) showed no difference between nondiabetic and diabetics (31.5 +/- 1.6 and 31.2 +/- 2.2 nmol/g of body weight per day, respectively) suggesting elevated liver levels resulted from redistribution.

Toxicity and biotransformation of volatile halogenated anesthetics in rat hepatocyte suspensions

This study examines the toxicity (as measured by reduced intracellular K+) and metabolism (defluorination) of halothane and enflurane in rat hepatocytes in suspension (RHS) with regards to O2 tension, time, and concentration. In 95% O2 halothane is more toxic than enflurane when RHS are exposed to 5-20 microliters of these anesthetics. At these levels halothane is not metabolized while enflurane is metabolized. At 21% O2 a similar pattern was seen with regards to toxicity. However, metabolism of halothane rapidly reached an elevated level while that of enflurane is reduced when compared to 95% O2. Thus toxicity of halothane and enflurane at these dose levels appears to be unrelated to metabolism and due solely to a solvent effect.