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Biomedical subjects

N Greenberg

Publications and source records attributed to N Greenberg.

66 records · Page 4Linked to original sources
PubMed1979

Role of the paleostriatum in species-typical display behavior of the lizard (Anolis carolinensis).

In a comparative study of forebrain mechanisms of species-typical behavior, unilateral lesions were placed in the subpallial telencephalon of male green anolis lizards (Anolis carolinsis), in which there is an almost complete decussation of the optic nerve. Responses to a conspecific male antagonist in a territorial confrontation were then tested when the subject's vision was limited to an eye leading to either the normal or lesioned hemisphere. In lizards with lesions involving the paleostriatum and lateral forebrain bundle, there was an elimination of or marked deficit in the performance of the challenge display while signature displays and measures of general activity were not significantly affected. Lesions predominantly in anterior or posterior dorsal ventricular ridge resulted in no significant deficit in any behavioral measure.

Animals↗
PubMed1979

Composition and molecular organization of lipids and proteins in the envelope of mycoplasmavirus MVL2.

MVL2 virus was purified from culture supernatants of infected Acholeplasma laidlawii cells by differential centrifugation, followed by velocity centrifugation in sucrose gradients. The purified virus contained 0.08 to 0.1 mumol of lipid phosphorous per ml of viral protein. Thin-layer chromatography of viral lipids revealed the presence of phospho-, glyco-, and phosphoglycolipids identical with those found in the host cell membrane, but the relative amount of phosphatidylglycerol was much lower than that in the virus. The fatty acid composition of lipids incorporated into the virus included lipids synthesized before and after infection. The freedom of motion of spin-labeled fatty acids in MVL2 depended markedly on temperature and on the position of the nitroxide group on the hydrocarbon chain of the probe, suggesting that the local environment of the probe has the properties of a lipid bilayer. Nevertheless, the lipid hydrocarbon chains in MVL2 appear to be less mobile than those in membranes of the host cells. Polyacrylamide gel electrophoresis of purified MVL2 revealed four major and about five minor polypeptide bands. None of the polypeptide bands gave a positive periodic acid-Schiff reaction. Lactoperoxidase-mediated iodination, followed by proteolytic digestion of intact MVL2 particles, revealed that at least two major polypeptides are localized on the external surface of the viral envelope.

Acholeplasma laidlawii↗
PubMed1979

Empirical description of effects of exercise on mood.

18 experienced joggers showed altered Mood Adjective Check List responding after jogging 12.5 miles, highlighted by increased pleasantness. Results support a broad-spectrum, unipolar approach to quantification of exercise-induced mood change.

Adolescent↗
PubMed1978

Antitumor 1-(X-aryl)-3,3-dialkyltriazenes. 2. On the role of correlation analysis in decision making in drug modification. Toxicity quantitative structure-activity relationships of 1-(X-phenyl)-3,3-dialkyltriazenes in mice.

A series of 11 triazenes (X-C6H4N=NNRCH3) was characterized for toxicity in mice (LD50). The quantitative structure-activity relationship (QSAR) obtained for toxicity was compared with the QSAR for antitumor activity. The close correspondence of the two QSAR leaves essentially no means for the synthesis of more potent, less toxic triazenes.

Animals↗
PubMed1977

Uridine kinase activities and pyrimidine nucleoside phosphorylation in fluoropyrimidine-sensitive and -resistant cell lines of the Novikoff hepatoma.

Uridine kinase, the rate-limiting enzyme in the activation (phosphorylation) of uridine and the corresponding chemotherapeutic analogues, is present as two isoenzymes localized exclusively in the cytosol of rapidly growing neoplasms, including the S-37 sarcoma, EL-4 leukaemia, HeLa cells (a human carcinoma) and the Novikoff hepatoma. The activities of the isolated isoenzymes are markedly decreased when the concentrations of ATP, phosphate or Mg2+ that are optimum in vitro are replaced by concentrations of ATP, phosphate or Mg2+ that are optimum in vitro are replaced by concentrations approximating to those found in vivo. Further, comparisons of the Km values of isolated uridine kinases with those for cellular uptake of pyrimidine nucleosides and their rate of intracellular phosphorylation suggest that nucleoside-transport systems play a rate-limiting role in nucleoside analogue activation and consequently that it is impossible to estimate the Km of uridine kinase in the intact cell. During the development of tumour-cell resistance to 5-fluorouracil or 5-fluorouridine in vivo there was an early differential increase in the activity of a low-affinity (high-Km) uridine kinase isoenzyme, as measured in cell extracts, and a 7-fold increase in the Km values for the uptake of both uridine and 5-fluorouridine into the intact resistant cells.

Animals↗
PubMed1977

Uridine kinase activities in normal and neoplastic lymphoid cells.

Both adult (I) and embryonic (II) forms of uridine kinase have been identified in the transplantable EL-4 leukemia of C57BL/6 mice and in the P815Y mastocytoma of DBA/2 mice. Only Species I is found in primary tumor cells of lymphoid orgin (virus-induced feline lymphosarcoma, human acute and chronic lymphocytic leukemia) and in normal calf thymocytes and porcine peripheral blood lymphocytes; Species I was induced 4-fold upon stimulation of the normal blood lymphocytes with phytohemagglutinin. The level of uridine kinase activity in the feline lymphosarcoma of thymus-dependent lymphocyte orgin and childhood lymphocytic leukemia of possible thymus-dependent lymphocyte or null-cell origin was similar to the induced level in phytohemagglutinin-stimulated normal lymphocytes, i.e., thymus-dependent lymphocytes. In contrast lymphocytes of a patient with chronic lymphocytic leukemia of thymus-independent lymphocyte origin had a level of uridine kinase activity comparable to that of the unstimulated normal lymphocytes or thymocytes. The uridine kinase activity in the EL-4 tumor cells was repressed by acute treatment of the mice with 5-azacytidine.

Animals↗
PubMedDate not supplied

Molecular organization and selective solubilization of lipids and proteins in the envelope of mycoplasmal virus L2.

The composition and molecular organization of mycoplasmal virus L2 (MVL2) were studied and compared with those of the cell membrane of the host, Acholeplasma laidlawii strain JA1. The virus contained 0.2-0.25 mumol of polar lipids per mg of viral protein. The lipid species of the MVL2 were the same as those of the host cells. Nevertheless, the proportions between the various polar lipids were different, with a much lower content of phosphatidylglycerol in the viral lipids. Despite these quantitative differences, the fatty acid composition of MVL2 was similar to that found in the host cells, a similarly allowing alteration of the fatty acid composition and study of its effect on viral absorption, penetration, and release. Pulse-chase experiments revealed that the lipids incorporated into the virus were synthesized before and after infection. Electron paramagnetic resonance spectrometry suggested that the viral lipid domain had the properties of a lipid bilayer. Nevertheless, the hydrocarbon chains in the MVL2 envelope were less mobile than those in membranes of the host cells, a difference apparently due to the different content, composition, and disposition of proteins in the MVL2 envelope. The electrophoretic pattern of MVL2 polypeptides was dominated by four major and five minor bands distinct from the polypeptides present in A. laidlawii membranes. None of the polypeptides gave a positive periodic acid-Schiff reaction, a result suggesting the absence of glycoproteins. Selective solubilization experiments excluded the possibility that one or more of the major polypeptides was associated with a capsid structure. Lactoperoxidase-mediated iodination of intact viral particles revealed that at least two of the major polypeptides were localized on the external surface of the viral envelope. The susceptibility of these polypeptides to brief proteolytic treatment and the finding that the infectivity of the virus was dramatically affected by such treatment suggested that these polypeptides were playing a role in recognition and/or attachment of the virus to the host cells.

Acholeplasma laidlawii↗
PubMedDate not supplied

Binding of MVL-2 virus to A. laidlawii cells.

Binding of MVL-2 virus, whose envelope lipids were radioactively labeled, to A. laidlawii JA1 cells was determined and characterized. The binding followed first-order kinetics and was temperature-dependent. All MVL-2 particles were capable of binding to A. laidlawii cells. At least 75 percent of radioactive MVL-2 bound represented specific binding which was markedly inhibited by EDTA. Virus infectivity was not essential for binding as inactivation of the virus by ultraviolet irradiation did not affect binding. Nevertheless, protein denaturing agents or proteolytic enzymes markedly inhibited MVL-2 binding, suggesting that the binding site of MVL-2 is of proteinaceous nature.

Acholeplasma laidlawii↗