Urinary elimination of acetone in experimental and occupational exposure

Fifteen volunteers were exposed to an acetone vapor concentration of 964-8, 610 mumol/m3 (56-500 mg/m3) for 2-4 h in an exposure chamber. Ten subjects were at rest during the exposure, and five were exposed at alternate rest and light physical exercise. Subsequently 104 workers occupationally exposed to acetone were studied. The relative uptake averaged about 53%, and the ratio of the alveolar concentration to the environmental concentration averaged about 0.28. Both for the experimentally exposed subjects and the occupationally exposed workers the urinary acetone concentration showed a linear relationship to the corresponding environmental time-weighted average concentration. A linear equation also existed between urinary concentrations and the amounts of acetone absorbed. The findings enable a consideration of the urinary concentration of the unaltered acetone as an appropriate exposure indicator and the proposal of a "biological equivalent threshold" to be used in the field of biological monitoring.

Monoamine oxidase: an important intracellular regulator of gastrin release in the rat

The role of monoamine oxidase (MAO) in the meal-induced or amino acid-induced release of gastrin was investigated. Rats that were pretreated with the nonspecific MAO inhibitor nialamide (200 mg/kg) showed a greater rise in meal-induced serum gastrin than did untreated controls. In vitro experiments demonstrated that gastrin secretion from dispersed antral G cells in response to a stimulatory dose of phenylalanine or methylbenzylamine (10 mM) was markedly enhanced if the cells were treated with nialamide. Studies with the more specific MAO inhibitors clorgyline and deprenyl indicated that antral mucosa contained predominantly type A activity. Inhibition of MAO type A with clorgyline, both in vivo and in vitro, resulted in a greater release of gastrin after stimulation by a meal or phenylalanine. It is concluded that MAO may play an important role in the regulation of gastrin release from the G cell by partially controlling the level of amines within the cell.

A new method for estimation of nerve conduction velocity distribution in the frequency domain

Nerve conduction velocity (NCV) measurements have been widely used to assess the electrophysiological properties of peripheral nerves and to detect neuropathies at a subclinical stage. Conventional NCVs are usually expressed as the NCV for the fastest conducting fibers and the current standard methods do neither supply information about slower conducting fibers, nor detect information about individual fiber groups. We present a new analytical method, to estimate the distribution of conduction velocity (DCV), based upon spectral analysis of the wave forms of two compound action potentials (CAPs) recorded by surface electrodes from a nerve bundle. If the spectra of the two CAPs recorded at two different sites in response to supramaximal electrical stimulation at distances l1 and l2 are given as G11(omega) and G12(omega), the spectral representation of the latency distribution P12(omega) for the propagation distance l2 is expressed as follows: P12(l1 omega/l2) = [G11(omega)/G12(omega)]P12(omega), where omega is an angular frequency. We developed an algorithm that computes P12(omega) successively without using iterative calculation methods. Our estimation method is theoretically based upon the principle that the CAPs are recorded monopolarly to estimate the DCV, but in practical use, it is almost impossible to obtain appropriate CAP wave forms by monopolar recording methods, because of stimulation and muscle artefacts. In order to evaluate the efficacy of bipolarly recorded CAP wave forms for this computation algorithm, we examined the two CAP wave forms reconstructed by simulation techniques. We found that the difference between the monopolar and bipolar recording methods was reflected in the wave form extracted for the single fiber action potentials but not in the latency distribution. The distance between the bipolarly recorded electrodes (1.5 cm was the minimal distance used) did not affect the reproducibility of estimating the latency distribution. This new method is non-invasive and could be used for evaluation of peripheral neuropathies.

An HTLV-III peptide produced by recombinant DNA is immunoreactive with sera from patients with AIDS

Human T-cell lymphotropic retrovirus type III (HTLV-III), also called lymphadenopathy-associated virus (LAV), has been identified as the aetiological agent of acquired immune deficiency syndrome (AIDS). The sera of most patients with AIDS or AIDS-related complexes, and of asymptomatic individuals infected with HTLV-III, contain antibodies against antigens of HTLV-III. The characterization of these antibodies and their corresponding viral antigens is important not only for understanding immunity against HTLV-III and the pathology of AIDS, but also for the development of diagnostic methods and preventive vaccine for AIDS. Following the successful establishment of a long-term T-cell line permissive for HTLV-III replication, large quantities of virus have been produced, facilitating the purification of viral proteins and the development of mouse monoclonal antibodies against several viral antigens. More recently, the structure of HTLV-III proviral DNA has been elucidated. We now report the production, by genetic engineering methods, of a peptide encoded by a gene segment of HTLV-III. A 1.1-kilobase (kb) EcoRI DNA segment from an isolate of HTLV-III was inserted into a lpp and lac promoter-coupled expression vector, pIN-III-ompA. Escherichia coli transformants of this plasmid produced a peptide of relative molecular mass (Mr) 15,000 (15K) which was strongly immunoreactive with anti-HTLV-III antibodies present in sera from AIDS patients. Lysates of the clones expressing this 15K peptide inhibited the reactivity of the p31 virion protein with AIDS sera, suggesting that it is a fragment of the viral p31 protein. The peptide reacted with sera from all 20 AIDS patients but none of the 8 normal controls tested. These results suggest that the peptide may be useful for detecting anti-HTLV-III antibodies in blood samples.

Expression in Escherichia coli of open reading frame gene segments of HTLV-III

Human T-cell lymphotropic virus type III (HTLV-III), the causative agent of the acquired immune deficiency syndrome (AIDS), was recently isolated and its genomic structure analyzed by DNA cloning methods. In the studies reported here a combined cloning and expression system was used to identify HTLV-III encoded peptides that react immunologically with antibodies in sera from AIDS patients. Cloned HTLV-III DNA was sheared into approximately 500-base-pair fragments and inserted into an "open reading frame" expression vector, pMR100. The inserted DNA was expressed in Escherichia coli transformants as a polypeptide fused to the lambda CI protein at its amino terminus and to beta-galactosidase at its carboxyl terminus. Sera from AIDS patients containing antibodies to HTLV-III were then used to screen for immunoreactive fusion proteins. Twenty clones, each specifying a fusion protein strongly reactive with AIDS serum, were identified. DNA sequence analysis indicated that the HTLV-III fragments were derived from the open reading frame DNA segments corresponding to the gag and pol gene coding regions and also the large open reading frame region (env-lor) located near the 3' end of the viral genome.

Electron microscopic assessment of bile regurgitation of humans in extrahepatic obstructive jaundice

Thirty-seven patients were studied on the anatomic routes of bile regurgitation into the blood stream by electron microscopy. The aim was to identify the relationship between the clinical results and pathway of bile regurgitation. These patients were classified into 3 groups; recovered, delayed, and fatal. Transcellular, paracellular, direct communication, necrotic hepatocyte and ruptured ductule pathway were found. In the recovered group, the transcellular pathway was most frequent with an incidence of 54.17%, and a direct communication pathway was found to be 54.55% in the fatal group with a significant difference between that of the recovered and delayed group. Long-duration bile duct obstruction creates bile regurgitation by way of direct communication between the canaliculi and Disse's space, and usually with a poor prognosis, since the serum bilirubin reached the high level of 22.65 mg%. Therefore, it is better to relieve the intrabiliary pressure as early as possible to prevent the jaundice from producing the irreversible change of hepatic canaliculi and Disse's space.

Zinc-induced seizures: a new experimental model of epilepsy

Seizures produced by intracerebral injection of zinc sulfate in rabbits are a new chronic model of experimental epilepsy. The main features of this model are: the animals are easily controlled, the electrocorticogram is conveniently recorded, the endpoints are definite, and the rate of seizure is higher than with other methods. The commonly used antiepileptic drugs, such as phenobarbital (30 mg/kg), diphenylhydantoin (30 mg/kg), nitrazepam (3 mg/kg), and sodium valproate (300 mg/kg), have therapeutic effects in treating this experimental epilepsy, when they are given intravenously. But they can not protect the rabbits from death, except phenobarbital.