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Biomedical subjects

J Lehmann

Publications and source records attributed to J Lehmann.

At least 307 records · Page 17Linked to original sources
PubMed1980

Visna virus synthesized in absence of host-cell division and DNA synthesis.

Visna virus is similar to the avian and the murine oncornaviruses. Oncornavirus replication is dependent upon the provirus being integrated into the host cell's DNA but integration and subsequent oncornavirus synthesis is blocked when the host cells are prevented from synthesizing cellular DNA or dividing. The synthesis of visna virus is restricted in vivo and may be dependent upon the host cell's ability to synthesize cellular DNA or divide. Treatment of sheep choroid plexus (SCP) cells with ultraviolet light or with mitomycin C prior to infection irreversibly inhibited plexus (ScP) cells with ultraviolet light or with mitomycin C prior to infection irreversibly inhibited both cell division and cellular nucleic acid synthesis but did not inhibit visna virus synthesis. Similarly, the synthesis of visna virus in cultures of SCP cells which had been prevented from dividing by being deprived of serum and in cultures of SCP cells which were incapable of synthesizing host cell nucleic acids by being treated with miracil D or sodium hexachloroiridate was equivalent to the synthesis of visna virus in cultures of SCP cells which were allowed to both synthesize cellular nucleic acids and divide. The synthesis of visna virus in the presence of ethidium bromide further demonstrated that integration of the visna provirus into the host cell's DNA is not required for visna virus synthesis to occur.

Animals↗
PubMed1979

Sedative effects of apomorphine in an animal model of Huntington's disease.

The sedative effectiveness of apomorphine in a newly developed animal model of Huntington's disease was examined. The motor responses of rats with kainic acid lesions of the neostriatum to a sedative dose of apomorphine (50 micrograms/kg) was similar to that observed in intact controls. In contrast, compared to controls, a marked potentiation of the motor stimulant effects of dextroamphetamine was confirmed in the kainic acid-lesioned group. We suggest that the pathological changes underlying the symptoms observed in this animal model and in Huntington's disease do not include abnormalities in presynaptic dopamine receptors in the neostriatum.

Animals↗
PubMed1979

The ineffectiveness of analogs of D-galactal as competitive inhibitors of, and substrates for, beta-D-galactosidase from Escherichia coli.

2,6-Anhydro-3-deoxy-aldehydo-D-lyxo-hept-2-enose (7) and 2,6-anhydro-3-deoxy-D-lyxo-hept-2-enitol (8) were synthesized as half-chair analogs of D-galactal (1). As 1 is a strong inhibitor of, as well as a substrate for, beta-D-galactosidase from Escherichia coli, the same properties were expected for 7 and 8; however, both were ineffective. This result, together with those of other authors, allows speculative conclusions on the tight binding of 1 to the enzyme only, when water or an alcohol is bound as a co-substrate.

Escherichia coli↗
PubMed1979

Bimodal distribution of serum trypotphan level.

Serum levels of total L-tryptophan (L-TP) were determined before and during treatment in patients suffering from endogenous depression, who were treated with L-TP, 6 g daily, and unilateral electroconvulsive therapy (ECT). The gaussian curve of initial L-TP concentrations changed into a bimodal distribution during treatment. The patients with initially lower L-TP levels also had lower L-TP levels during the treatment, thus forming the low-concentration group within the bimodal distribution. In the patients with higher initial concentrations, the L-TP levels increased to a much greater degree, forming the high-concentration group. Patients in this group needed a larger number of ECT's, probably owing to L-TP's property of shortening the seizure duration. No other background data or clinical variables showed significant differences between the groups. It is suggested that the bimodality of L-TP levels is genetically determined.

Adult↗
PubMed1978

The use of kainic acid in the localization of enzymes in the substantia nigra.

The selective destruction of neuronal perikarya via intracerebral injections of kainic acid was used to elucidate the cellular location of four neurotransmitter-related enzymes in the substantia nigra (SN). Two weeks after intranigral injections of kainic acid, dopamine-sensitive adenylate cyclase, glutamic acid decarboxylase (GAD), choline acetyltransferase (CAT) and acetylcholinesterase (AChE) were measured in the SN. Histological examination of the SN, and a reduction of striatal tyrosine hydroxylase (TH) activity by 94%, confirmed the extensive loss of neuronal cell bodies in the SN. Dopamine stimulation of adenylate cyclase was not reduced in the lesioned SN, supporting the view that dendritically-released dopamine can regulate cyclic AMP synthesis in afferent terminals to these dendrites. Nigral GAD activity was significantly reduced by the lesions, suggesting that there are GAD-containing perikarya in the SN. CAT activity was not affected by the kainic injections, indicating the absence of cholinergic perikarya in the SN. Nigral AChE activity was significantly decreased after kainic injections, thus confirming the presence of AChE within the nigral perikarya. The results suggest that dopamine-sensitive adenylate cyclase and CAT are located within afferents to the SN, while GAD and AChE are found, to some extent at least, in neuronal soma of the SN. The differentail effects of kainic acid on these enzymes suggest that this compound may be a useful neurochemical tool with which to determine the cellular distribution of enzyme systems in the central nervous system.

Acetylcholinesterase↗
PubMed1978

Tetrakis(acetoxymercuri)methane: a polymetallic reagent for labeling sulfur in nucleic acids.

Tetrakis(acetoxymercuri)methane binds to the sulfur atom of 6-thioguanosine and also to the 4-thiouridine residue of Escherichia coli tRNAVal. A 4:1 complex is formed between 6-thioguanosine and tetrakis(acetyoxymercuri)methane. Addition of 3 equivalents of N,N-dimethyl-2-amino-ethanethiol hydrochloride to tetrakis(acetoxymercuri)methane effectively blocks three of the four mercury atoms, rendering the compound monofunctional toward 6-thioguanosine. Under appropriate conditions, tetrakis(acetyoxymercuri)methane, in the presence or absence of N,N-dimethyl-2-amino-ethanethiol hydrochloride, binds to the 4-thiouridine residue in E. coli tRNAVal without forming intermolecular crosslinks. These results suggest that tetrakis(acetoxymercuri)methane will be a useful polymetallic reagent for labeling sulfur sites in polynucleotides. It may also prove to be a valuable reagent for preparing heavy metal derivatives of proteins for x-ray crystallographic study.

Chemical Phenomena↗