Comparison of gas-liquid chromatography and EMIT assay for serum valproic acid

We describe a simple direct extraction method for the gas-liquid chromatography determination of serum valproic acid. The working range for the assay is 2-180 mg/L and our within-run precision was 5.8 and 4.3% at the 40 and 90 mg/L concentrations respectively. Hemolyzed and lipemic sera as well as samples from patients with hyperbilirubinemia and from patients with decreased renal function were put through the assay and no interfering peaks were noted. Interference occurred when teflon-lined screw caps were used during the extraction step. The method was proven to be accurate by linear regression analysis of samples containing weighed-in amounts of valproic acid. The above assay was compared to an enzyme immunoassay technique (EMIT). The working range for the latter is 10-150 mg/L and the with-run precision was 10.8 and 5.9% and 90 mg/L concentration respectively. Samples were run by both the gas-liquid chromatograph and enzyme immunoassay methods and gave very similar results over the range 16-139 mg/L.     

Identification of accessory bile ducts at cholecystectomy

The presence of accessory channels between the liver and extrahepatic bile ducts has long been recognised by anatomists and the division of such ducts may be a cause of bile leakage following cholecystectomy. However, visualisation of accessory bile ducts at operation is difficult as they are often small and sometimes less than 1 mm in diameter. Cholangiography has been used to help in the identification of accessory ducts in 50 patients included in a prospective trial. X-rays were taken after dissection of the gall bladder from its bed and extravasation of contrast was seen on five occasions (10%) suggesting leakage from divided accessory ducts. The identification of damage to accessory bile ducts in 10% of patients suggests that this may occur more frequently than previously supposed.     

Effects of partial hepatectomy on organ-specific toxic response to 1,2-dibromo-3-chloropropane (DBCP)

The organ-specific toxic potency of subcutaneously administered 1,2-dibromo-3-chloropropane (DBCP) was compared in partially hepatectomized and sham-operated rats over a dose range of 20--80 mg kg-1 to assess the roles of hepatic and extrahepatic metabolism in protection against acute renal and gonadal injury. Relative kidney weight and the severity of DBCP-induced renal proximal tubular cell necrosis were increased in rats subjected to a partial (70%) surgical hepatectomy 48 h prior to treatment with DBCP at 80 mg kg-1. Relative liver weight was reduced by DBCP in the hepatectomized, but not in the sham-operated rats. The severity of DBCP-induced (80 mg kg-1) hepatocellular centrilobular necrosis was greater in hepatectomized than in sham rats. DBCP reduced the relative weights of the testis and epididymis in a progressive manner and produced dose-dependent seminiferous tubular atrophy within 12 days of treatment. The morphologically apparent lesions of the testis and epididymis were enhanced by hepatectomy. The concentration of non-protein sulfhydryl groups (NPS) in rat liver was increased by partial hepatectomy. Because of the resulting decrease in liver size, however, the total amount of hepatic NPS per kg body weight 48 h post-surgery was lower than in sham rats. The surgery had no effect on renal, testicular or epididymal NPS concentrations of organ weights. Partial hepatectomy greatly increased pentobarbital and ethanol sleeping times, while sleep induction time for pentobarbital was decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

HLA-DR typing in identical twins with insulin-dependent diabetes: difference between concordant and discordant pairs

A total of 106 pairs of identical twins, of whom 56 were concordant and 50 discordant for insulin-dependent diabetes, were typed for HLA-DR. In both the concordant and discordant groups there was a high prevalence of the antigens DR3 and DR4, a low prevalence of DR5 and DR7, and a virtual absence of DR2. The heterozygous phenotype DR3,DR4 was more prevalent in concordant than discordant pairs. This was therefore the first demonstration of a genetic difference between concordant and discordant identical twin pairs. These findings suggest that possession of both DR3 and DR4 antigens confers a greater genetic predisposition to insulin-dependent diabetes than does the possession of either antigen alone.     

Long-term neurotoxicity of chlorpyrifos: spatial learning impairment on repeated acquisition in a water maze.

Organophosphate compounds are cholinesterase inhibitors widely used in agriculture, industry, household products, and even as chemical weapons. Their major mechanism of acute toxic action is the inhibition of acetylcholinesterase, which is responsible for the degradation of the neurotransmitter acetylcholine. An organophosphorus ester-induced chronic neurotoxicity (OPICN) syndrome has been proposed. The OPICN syndrome could result from both long-term exposure to subclinical doses of OPs and after acute poisoning. Development of animal models for the cognitive decline are required and could later help to elucidate the mechanisms involved in this long-term effect on the central nervous system. Previously, we have found performance decrements in a four-trial repeated acquisition spatial task in a water maze. The present study includes two experiments to extend the long-term behavioral effects observed. Rats were injected either once or twice with chlorpyrifos (CPF) and then tested months after in a two-trial repeated acquisition task in a water maze. Our results confirm and extend the long-term behavioral effects of subcutaneous administration of CPF. The two treatments used produced performance decrements that suggest functional central nervous system alterations.     

Hemangioma of the nasal vault: MR and CT features

Six patients with a history of epistaxis (five patients) or nasal obstruction (one patient) were found to have a capillary hemangioma of the nasal vault that involved one or more nasal turbinates. Four patients underwent computed tomographic (CT) examination; two of these also underwent magnetic resonance (MR) imaging. Four others underwent only MR imaging. At CT and MR, all of the lesions were well circumscribed and intensely enhancing, with contralateral deviation of the nasal septum. Remodeling of the surrounding bone was present in three patients. On T1-weighted MR images, the masses were intermediate in signal intensity. Varying degrees of T2 shortening were shown on T2-weighted MR images, with an appearance that suggested the presence of blood products surrounding an inner matrix of higher-signal-intensity tumor. Intense enhancement at CT and MR assisted differentiation of tumor from retained sinonasal secretions. In two patients, external carotid arteriography revealed small foci of pooling contrast material; in one of these patients, arteriovenous shunting was also present. Pathologic examination in all patients demonstrated capillary hemangiomas with varying degrees of fibrosis and hemosiderin deposition.     

The brain/mind complex. An epistemological approach.

It is stressed that the brain/mind complex constitutes a monolithic system that functions with emergent properties at several levels of hierarchical organization. These hierarchical levels are non-reducible to one another; they are at least three (neuronal, functional, and semantic), and they function within an interactional plan. From the epistemological view-point, the brain/mind complex uses logical and non-logical mechanisms to deal with day-to-day problems. Logic is necessary for the thinking process, but it is not sufficient. Emphasis is given to non-logical mechanisms; fuzzy logic and heuristics, which allow the mind to develop strategies to find solutions, are analysed.     

Extracellular characteristics of putative cholinergic neurons in the rat laterodorsal tegmental nucleus

The extracellular electrophysiological properties of neurons in the laterodorsal tegmental nucleus (LDT), a major source of cholinergic afferents to the thalamus, were studied in chloral hydrate-anesthetized rats. A combination of antidromic activation from the thalamus and histological verification of recording sites was used to correlate the identity of extracellular recordings in the rat LDT with cholinergic neurons in that region. All neurons antidromically activated by stimulation of the anteroventral thalamus were histologically verified to be within clusters of cholinergic (NADPH-d-positive) cells in the LDT or in the adjacent nucleus locus coeruleus (LC). The thalamically projecting LDT neurons had a homogeneous neurophysiological profile consisting of long duration action potentials (mean = 2.5 ms), slow conduction velocities (mean = 0.78 m/s), and lengthy chronaxie values (mean = 0.725 ms). The appearance and axonal characteristics of these neurons resembled those of noradrenergic LC neurons, but the two populations exhibited substantially different spontaneous activity patterns and sensory responsiveness. These characteristics may be useful in the preliminary identification of putative cholinergic neurons in vivo, and thereby provide a foundation for exploring the neuropharmacology, afferent modulation, sensory responsiveness and behavioral correlates of the brainstem cholinergic system.     

Diabetes mellitus. II: Routine chest radiography.

Chest radiographs of 43 consecutive diabetic patients were evaluated with a view to determine their role as a routine investigation of patients with diabetes mellitus. 22 (51.2%) patients had normal chest radiographs. The remaining 21 patients had 61 abnormalities found in their chest radiographs. 26 (42.6%) of these were significant abnormalities while 35 (57.4%) were non-significant. Of the former, 42.3% were due to cardiomegaly while in the latter group, aortic unfolding was the main finding. Radiological abnormalities were more commonly observed in patients aged 40 years and over, than in those below, with a ratio of 3:1. Chest radiographs corroborated clinical diagnosis in 19 of the 21 cases in whom abnormalities were observed. This study shows that routine chest radiograph in diabetic patients is useful in those with clinical symptoms and in older diabetics above the age of 40 years.