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Biomedical subjects

D Levy

Publications and source records attributed to D Levy.

At least 379 records · Page 21Linked to original sources
PubMed1986

Immunocompetence of sheep experimentally infected with bovine leukemia virus.

The humoral and cellular immunological reactivity of sheep were studied throughout the first 32 weeks following experimental infection with bovine leukemia virus (BLV). Seroconversion of BLV-inoculated sheep occurred within 4 weeks, but infection was not transmitted to contact control sheep. Despite the persistence of the viral infection, no differences were demonstrated in leukograms, serum IgG concentrations, humoral response to immunization with an irrelevant antigen (rabbit red blood cells), phytomitogen (Concanavalin A and Pokeweek mitogen)-induced lymphocyte blastogenesis, or chemical (1-chloro, 2-4 dinitrobenzene) skin contact hypersensitivity, between BLV-infected and uninfected contact control sheep. These results demonstrate the absence of a nonspecific immunosuppressive effect of BLV and further negate the influence of a generalized immunological deficit on the development of clinical disease in BLV-infected animals.

Animals↗
PubMed1986

Sleep patterns and problems in adolescents.

A sleep questionnaire was administered to 390 students in an urban high school. Total sleep hours per week appeared to decrease between the ages of 12 and 18 years. In general, girls slept more than boys. The quality of sleep and the perception of sleep adequacy also decreased with age. Reporting of the occasional use of sleep medications and alcohol at bedtime was 4.6% and 10.5%, respectively. These findings suggest that sleep problems among adolescents represent normal physiologic processes as well as some serious disturbances that may reflect the social pressures prevalent during adolescence.

Adolescent↗
PubMed1986

Interferon-stimulated transcription: isolation of an inducible gene and identification of its regulatory region.

A human gene (termed ISG-54K) that is induced from near undetectable levels to high transcriptional activity by alpha- and beta-interferons has been cloned. The genomic structure and nucleotide sequence of the coding region were determined and the RNA initiation site was identified. The 5' portion of the gene was fused with a heterologous gene lacking an active promoter in recombinant plasmid and adenoviral vectors. These fusion genes were used to assess the activity of the ISG-54K promoter in response to interferon. RNA was formed in HeLa cells from recombinant plasmids only in response to interferon. Furthermore, in human diploid fibroblasts, infection with the recombinant adenovirus vector resulted in a 50-fold increase in specific RNA in response to interferon, followed by a subsequent decrease, imitating the natural regulated transcriptional cycle of the endogenous gene.

Amino Acid Sequence↗
PubMed1985

A quaternary anti-cholinesterase probe for determining the integrity of the blood--brain barrier.

7-(Methylethoxyphosphinyloxy)-1-methyl quinolinium iodide (MEPQ), a new quaternary anti-cholinesterase (anti-ChE) compound was prepared and evaluated as a potential probe for assessing changes in the blood-brain barrier (B-BB) permeability. MEPQ was found to be 170 times more potent in its cholinesterase inhibitory activity than phospholine iodide, a previously reported anti-ChE probe in B-BB research. In rats and mice with impaired B-BB induced by osmotic opening, MEPQ readily penetrated through the damaged site as demonstrated by considerable reduction of ChE activity. In controls, brain ChE activity remained unaffected. It is suggested that MEPQ is a useful probe for both qualitative (histological staining) and quantitative (brain homogenated) assessment of permeability changes in the B-BB.

Animals↗
PubMed1985

Changes in the H-1 histone complement during myogenesis. I. Establishment by differential coupling of H-1 species synthesis to DNA replication.

Proportions of the four major chicken H-1 histones (referred to as H-1's a-d) change during in vitro skeletal myogenesis. As myoblasts fuse and differentiate into myotubes, the relative amount of H-1c increases dramatically. The change occurs primarily because synthesis of the H-1 species is coupled to DNA synthesis to different extents. H-1c synthesis is least tightly coupled to DNA replication in precursor myoblasts and in differentiated myotubes. Thus H-1c synthesis predominates after dividing myoblasts fuse into postmitotic myotubes. This results in the replacement of pre-existing H-1 and therefore increases the relative amount of H-1c. Differences in the stability of the H-1's are also involved in changing H-1 proportions. The results show that changes in H-1 proportions during myogenesis are a consequence of withdrawal from the cell cycle. The data provides a general mechanistic explanation of how tissue-specific H-1 proportions are established.

Animals↗
PubMed1985

Gastrointestinal manifestations of the acquired immunodeficiency syndrome: a review of 22 cases.

Patients with acquired immunodeficiency syndrome (AIDS) frequently have diarrhea and weight loss. We prospectively examined the upper and lower gastrointestinal tracts in 22 AIDS patients, although severe medical problems often precluded full evaluation. Ninety-six percent (21 of 22) lost weight, and 55% (12 of 22) had diarrhea. The mean (+/- SD) weight loss was 34 +/- 19 lb. Steatorrhea was found in 4 of 14 patients, and D-xylose tests were abnormal in 8 of 14 patients. Mean serum albumin was 3.3 +/- 0.8 g/dl. A significantly diminished plasma selenium level, which can influence immune function, was noted in these AIDS patients. Gastrointestinal infections were identified in 45% of patients. Although diarrhea and malabsorption were more common in the infected group, weight loss and albumin were similar in those with and without demonstrated infections. Flexible sigmoidoscopy showed that of 15 patients, there were two with Kaposi's sarcoma, 10 normals, and three with nonspecific endoscopic changes of colitis. Infection was documented in all patients with colitis. Panendoscopy of the upper gastrointestinal tract was positive for AIDS-related pathology in five of 10 patients, including two with Kaposi's sarcoma, one with Candida esophagitis, one with herpetic esophagitis, and one with gastroduodenitis (biopsy positive for cryptosporidia); five patients had a normal-appearing tract. Small bowel or colonic biopsies frequently showed nonspecific inflammatory changes, although pathogens were identified in six patients (27% of all biopsies). We conclude that a wide variety of gastrointestinal pathology, which includes infectious agents, neoplasms, and inflammatory changes, may occur in AIDS patients. Therefore, AIDS patients, particularly those with diarrhea or weight loss, deserve an intensive evaluation for remediable lesions of their gastrointestinal tracts.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Synthesis and transport characteristics of photoaffinity probes for the hepatocyte bile acid transport system.

In an effort to characterize the hepatocyte bile acid transport system, a photoreactive derivative of taurocholate, (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid (7-ADTC) has been synthesized and its transport properties compared to those of the natural substrate. Both the bile acid and its synthetic analog were shown to be transported against an electrochemical gradient as well as a chemical gradient. Transport as a function of concentration and the presence of sodium indicated that both substrates were taken up by a sodium-dependent and a sodium-independent route. Taurocholate had Km values of 26 and 57 microM and Vmax values of 0.77 and 0.15 nmol/mg of protein/min, respectively. In comparison, 7-ADTC had very similar kinetic properties with Km values of 25 and 31 microM and Vmax values of 1.14 and 0.27 nmol/mg of protein/min. Each compound was shown to inhibit competitively the transport of the other, suggesting that these substrates utilized a common membrane carrier. The transport properties of the photoreactive anion transport inhibitor, N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine) were also characterized in the hepatocyte system. Transport occurred via a sodium-dependent and a sodium-independent route with Km values of 210 and 555 microM and Vmax values of 0.57 and 1.62 nmol/mg of protein/min. As in the case of 7-ADTC, NAP-taurine and taurocholate were also shown to be mutual competitive inhibitors. In the absence of light, 7-ADTC was a reversible inhibitor of taurocholate uptake. Upon irradiation, irreversible photoinactivation of the taurocholate uptake system was observed. These results indicate that 7-ADTC and NAP-taurine can be utilized as photoaffinity probes for the identification of the bile acid carrier protein(s) in hepatocyte plasma membranes.

Affinity Labels↗
PubMed1983

Characterization of the bile acid transport system in normal and transformed hepatocytes. Photoaffinity labeling of the taurocholate carrier protein.

The taurocholate transport system in normal and transformed hepatocytes has been characterized using transport kinetics and photoaffinity labeling procedures. A photoreactive diazirine derivative of taurocholate, (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino [ 1,2-3H ]ethanesulfonic acid (7-ADTC), which has been shown to be a substrate for the bile acid carrier system, was photolyzed in the presence of intact hepatocytes, hepatoma tissue culture (HTC) cells, and plasma membranes derived from the hepatocyte sinusoidal surface. Irradiation of membranes in the presence of 7-ADTC resulted in the incorporation of the photoprobe into two proteins with Mr = 68,000 and 54,000. The specificity of labeling was confirmed by the significant inhibition of labeling observed when photolysis was carried out in the presence of taurocholate. The 68,000-Da protein was easily extracted with water and was shown to exhibit electrophoretic properties identical with rat serum albumin. The 54,000-Da protein required Triton X-100 for solubilization, indicating a strong association with the plasma membrane. Labeling of intact hepatocytes also resulted in specific labeling of the 54,000-Da protein. In contrast to hepatocytes, HTC cells derived from Morris hepatoma 7288C as well as H4-II-E cells derived from Reuber hepatoma H-35 exhibited a total loss of mediated bile acid uptake. Photolysis of 7-ADTC in the presence of HTC cells did not result in the labeling of any proteins, a result consistent with the loss of transport activity, and further supporting the specificity of the labeling reaction. The anion transport inhibitor N-(4-azido-2-nitrophenyl)-2-aminoethyl-[ 35S ]sulfonate, which has been shown to be a substrate for the bile acid carrier system also labeled the 54,000-Da plasma membrane protein when photolyzed in the presence of intact hepatocytes. These results suggest that the 54,000-Da protein is a component of the hepatocyte bile acid transport system and that the activity of this system is greatly reduced in several hepatoma cell lines.

ATP-Binding Cassette Transporters↗
PubMed1983

Price and income elasticities of demand for alcoholic beverages.

Estimating the demand for alcoholic beverages represents a difficult statistical problem. A number of studies have attempted to estimate the demand for beer, wine, distilled spirits, or total alcohol consumption. The results vary widely according to country of study, data used, and model and statistical technique. For the United States, most studies find the demand for beer to be relatively price inelastic, at around -0.3. The demand for distilled spirits appears to be unitary price elasticity or somewhat greater, around -1.5. The evidence on wine is too sketchy to draw any conclusions. There is no strong evidence of substitutability among beer, wine, and distilled spirits based on econometric models, nor evidence that advertising plays a strong role in the aggregate demand for beer, wine, or distilled spirits. The main policy implication is that price increases to control consumption will have a stronger impact on the consumption of distilled spirits than on beer.

Alcohol Drinking↗
PubMed1983

Congenital adrenal hypoplasia: two new cases.

Two male adolescents with the X-linked form of congenital adrenal hypoplasia are described. Both grew slowly during childhood and adolescence and did not undergo pubertal development because of hypogonadotropic hypogonadism associated with the congenital adrenal hypoplasia. The severely delayed bone age in childhood is probably due to the adrenal androgen deficiency and suggests a role of these hormones in the prepubertal skeletal maturation. The failure of gonadotropin secretion still remains unexplained. A hypothalamic defect has been suggested, but further studies are necessary to clarify this hypothesis.

Adolescent↗