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Biomedical subjects

A Siddiqui

Publications and source records attributed to A Siddiqui.

At least 145 records · Page 8Linked to original sources
PubMed1981

Ground squirrel hepatitis virus DNA: molecular cloning and comparison with hepatitis B virus DNA.

Ground squirrel hepatitis virus (GSHV) shares many ultrastructural antigenic, molecular, and biological features with hepatitis B virus (HBV) of humans, indicating that they are members of the same virus group. Both viruses contain small circular DNA molecules which are partially single stranded. Here, we ligated an endonuclease EcoRI digest of GSHV DNA with EcoRI-cleaved plasmid vector pBR322 and cloned recombinant plasmids in Escherichia coli C600. Two cloned recombinants were characterized. One (pGS2) was found to contain only part of the GSHV genome, and the other (pGS11) was found to contain the entire viral DNA. A restriction endonuclease cleavage map of the GSHV insert in pGS11 and the locations of certain physical features of the virion DNA were determined. The relative positions of the single-stranded region, the unique 5' end of the short DNA strand, and the unique nick in the long DNA strand in GSHV DNA were found to be the same as those previously described for HBV DNA. Hybridization with an HBV [32P]DNA probe containing the apparent coding sequence for the major polypeptide of HBV surface antigen and a probe containing the putative coding sequence for the major polypeptide of the HBV core revealed specific homology with different restriction fragments of GSHV DNA. The two homologous regions had approximately the same locations relative to the single-stranded region, the 5' end of the short strand, and the nick in the long strand in the two viral DNAs. These results suggest that in both viruses the genes for the major HBV surface antigen and core polypeptides have the same locations relative to unique physical features of the viral DNAs.

Animals↗
PubMed1979

Restriction endonuclease cleavage map and location of unique features of the DNA of hepatitis B virus, subtype adw2.

DNA of hepatitis B virus (HBV) of hepatitis B surface antigen (HBsAg) subtype adw2 made fully double stranded by the virion DNA polymerase and radiolabeled either by the virion DNA polymerase reaction or by nick-translation with 32P-labeled deoxynucleoside triphosphates was used to establish a map of restriction endonuclease cleavage sites by the method double and triple enzyme digestion and to determine the relative positions of several unique physical features of this DNA. The five restriction sites for enzyme HincII, the two sites each for BamHI, Ava I, and Bgl II, and the single sites for EcoRI, Pst I, Hpa I, and Taq I were positioned relative to each other. Within this map, the single-stranded region in HBV DNA has been localized and the locations of nicks in each strand (a and b) have been determined with respect to restriction sites on the circular map. Comparison of restriction endonuclease cleavage patterns of DNAs of HBV of HBsAg subtypes adw2, ayw3, and adrq+ revealed consistent differences among subtypes and occasional differences within subtypes.

Chromosome Mapping↗
PubMed1979

Detection of the viral sarcoma gene product in cells infected with various strains of avian sarcoma virus and of a related protein in uninfected chicken cells.

Genetic analyses have defined a single gene (src) as that portion of the avian sarcoma virus (ASV) genome which encodes the protein directly responsible for ASV-induced neoplastic transformation. We have recently identified the polypeptide product of the src gene of the Schmidt-Ruppin (SR) strain of ASV, a 60,000-dalton phosphoprotein designated pp60(src), and have further determined that pp60(src) acts as a protein kinase. Essential to the identification and characterization of the pp60(src) protein of SR-ASV was the use of serum (TBR serum) from rabbits bearing SR-ASV-induced tumors. TBR serum was, however, strain specific, recognizing pp60(src) from SR-ASV-transformed cells only. We report here that sera from marmosets bearing tumors induced by the Bryan or SR strains of ASV (TBM sera) contain antibody which precipitates the transforming gene product from cells transformed by the SR, Bryan, Prague, or Bratislava strains of ASV. In contrast, rabbits bearing tumors induced by either the Bratislava or Bryan strains of ASV, or hamsters with SR-ASV-induced tumors did not produce antibody to pp60(src) from any strain of ASV. The 60,000-dalton polypeptides immunoprecipitated with TBM serum from cells transformed by each of the above virus strains are phosphoproteins. One-dimensional peptide mapping by limited proteolysis revealed that the pp60(src) proteins are structurally very similar, but not identical. Furthermore, all of the viral pp60(src) proteins have an associated phosphotransferase activity. In addition to detecting the viral src proteins, TBM serum was able to immunoprecipitate an antigenically related protein from normal uninfected avian cells.

Animals↗
PubMed1978

The lack of correlation of gallium (67Ga) scans with known prognostic indicators in childhood acute lymphocytic leukemia.

67Gallium-citrate scans were performed on 45 patients with acute lymphoblastic leukemia (ALL) at the time of diagnosis. The extent of uptake and distribution of gallium were compared to known prognostic indicators of age, initial white count, and bone marrow lymphoblast immune markers (T, B, and null cell). Selective increased uptake was noted in bone, kidney, liver/spleen, lymph nodes, or other sites in 29 patients, and 16 patients had "normal" scans. A scoring system giving one point for selective uptake in each organ system was used. Patients were grouped according to scores of zero, 1--2, and 3 or greater. There was no significant correlation found between total gallium scores and any of the three prognostic indicators. There was also no significant correlation when prognostic factors were compared to uptake in the individual organ systems except that T cell disease was associated with a significantly greater propensity for lymph node uptake. There was a suggestion that children with "normal" gallium scans may have a better long-term prognosis, since 6 of 7 nonrelapsers observed for longer than 18 months had scores of zero at diagnosis compared to 4 of 6 early deaths with scores greater than zero. This study indicates that the 67Ga scan does not significantly correlate with known prognostic indicators, with the possible exception of lymph node uptake in T cell disease, and its value as an independent indicator of long-term survival will require longer follow-up.

Adolescent↗
PubMed1977

Arteriovenous malformation simulating Meckel's diverticulum on 99mTc-pertechnetate abdominal scintigraphy.

99mTc-pertechnetate scintigraphy in a 67-year-old woman with chronic gastrointestinal bleeding showed an area of increased activity in the right lower quadrant which appeared at the same time the stomach was visualized. At first this was thought to be a Meckel's diverticulum; however, superior mesenteric angiography subsequently revealed a small arteriovenous malformation which proved to be the bleeding site on laparotomy. This false-positive finding emphasizes the importance of comparative evaluation of early and late images in scintigraphy for suspected Meckel's diverticulum.

Aged↗
PubMed1976

Efficiency of in vivo labeling of red blood cells with 99mTc.

The effectiveness of three commercial bone scintigraphic agents and freshly made stannous chloride in labeling erythrocytes with 99mTc was compared. Our results indicate that tin pyrophosphate is the agent of choice and that it is most effective when injected at least 15 minutes before the 99mTc-pertechnetate is administered. This technique of labeling red blood cells in vivo could be applied in performing blood pool studies.

Animals↗
PubMed1976

Evaluation of labeling procedures and in vivo stability of 99mTc-red blood cells.

Stable labeling of red blood cells (RBCs) with 99mTc, in yields of about 66%, was achieved by using stannous chloride as a reducing agent. In a study of 12 patients, the stability of technetium-labeled RBCs in the circulation varied significantly among individuals, but the average biologic half-life of the labeled cells was 16.8 hr. Although the labeling yield was lower when the labeling was carried out without EDTA with the addition of stannous chloride after the pertechnetate, this sequence appears to be the best for labeling RBCs for use in obtaining images of the blood pool or the cardiovascular system because of the increased viability of the RBCs.

Erythrocytes↗
PubMed1975

Intrageneric transformation of neisseria gonorrhoeae and neisseria perflava to streptomycin resistance and nutritional independence.

Auxotrophic mutants of Neisseria gonorrhoeae and Neisseria perflava were transformed to prototrophy using homologous and heterologous deoxyribonucleic acid (DNA). Within either species the efficiencies of transformation for nutritional markers were found to be very similar to the values obtained for transformation to streptomycin resistance. The number of transformants in the interspecific N. perflava (donor) - - leads to N. gonorrhoeae (recipient) cross was 100-fold lower than the number obtained in the intraspecific N. gonorrhoeae - - leads to N. gonorrhoeae cross for streptomycin resistance, as well as for several nutritional markers. In the reciprocal experiment the difference in the number of transformants in the interspecific N. gonorrhoeae - - leads to N. perflava cross and the number obtained in the intraspecific N. perflava - - leads to N. perflava cross varied from 600 to 1,000-fold for the streptomycin resistance marker. Of greater interest was the finding that N. perflava auxotrophs, although transformable to prototrophy with wild-type N. perflava DNA, were not transformed to nutritional independence by gnoncoccal DNA. These same mutants were transformable to streptomycin resistance using the heterologous gonococcal DNA. When the DNAs of N. meningitidis, N. flava, and N. lactamicus were used to transform N. gonorrhoeae to prototrophy or streptomycin resistance, the transformation frequencies obtained fell along a gradient that in general reflected taxonomic relationships. On the other hand, with N. perflava as the recipient for these same DNAs, only N. flava DNA could transform auxotrophs to prototrophy, although transformation to streptomycin resistance occurred in all cases. DNA from N. perflava - - leads to N. gonorrheae streptomycin-resistant or Ade+ intergenotic transformants transformed N. gonorrhoeae cells at a 100-fold-higher efficiency than did DNA from N. perflava. Our findings suggest that (i) N. gonorrhoeae and N. perflava are more closely related than hitherto suspected and (ii) N. perflava is more selective with respect to heterologous DNA than is N. gonorrhoeae.

Amino Acids↗
PubMed1975

Visualization of nonvascular cranial tumor in cerebral flow study: case report.

Unusual results were obtained from a cerebral blood flow study and a brain scan performed on a patient with an uncommon, nonvascular scalp tumor eventually identified as a proliferating trichilemmal cyst with acanthosis. The tumor accumulated the radionuclide during the early phase of the cerebral flow study, and the increased radioactivity was persistent, being prominently observable in a scan made 3 min and 2 hr after the radionuclide injection. This unusual, positive finding in a cerebral blood flow study of a nonvascular tumor was thought to be a consequence of the higher counting efficiency resulting from the lack of shielding by the skull and from the larger volume of the tumor tissue.

Aged↗
PubMed1974

Rapid plate method for the isolation of lysogenic bacteriophages.

We have devised a rapid plate method for the detection and isolation of lysogenic phages and have used the procedure to screen 15 strains of Staphylococcus aureus. This method should prove applicable to a wide variety of bacterial species and should be especially valuable for those pathogens for which no phage-typing system is available.

Bacteriophage Typing↗
PubMedDate not supplied

Morphine induces reproductive changes in female rats and their male offspring.

The effect of intrauterine morphine exposure on the development of reproductive functions has been investigated in the rat. Female rats were treated daily ip with morphine sulfate, doses increasing at 10-d intervals from 5, 7.5, 10, to 15 mg/kg. These rats were mated between day 38 and 45, and morphine treatment continued at 20 and 30 mg/kg over pregnancy and at up to 40 mg/kg for 10 d postpartum. The treatment mainly disrupted ovarian cyclicity; only 48% exhibited normal cyclicity. Of these, 43% became pregnant when mature male rats were placed with them. Litter size was normal but with significantly more stillbirths in each litter and live pups had decreased body weights. Male offspring had reduced body weight at the time of weaning that persisted until 60 d of age. At 120 d, animals showed complete abolition of spermatogenesis and drastically reduced testicular steroidogenesis. Plasma LH levels were low, and hypothalamic noradrenaline was high.

Animals↗
PubMedDate not supplied

Isolation of a novel human voltage-dependent anion channel gene.

The voltage-dependent anion channel of the mitochondrial outer membrane (VDAC) is a small, abundant pore-forming protein found in the outer membranes of all eukaryotic mitochondria. The VDAC protein is believed to control the movement of adenine nucleotides through the outer membrane and to be the mitochondrial binding site for hexokinase and glycerol kinase. Two human VDAC cDNAs (HVDAC1 and HVDAC2) have been previously isolated and mapped on chromosome X and 21, respectively. Here, we report the isolation of a novel third human VDAC cDNA, corresponding to the mouse MVDAC3 gene. The expression of this gene in various tissues and its chromosomal localization by polymerase chain reaction (PCR) using a human/rodent somatic cell mapping panel and by fluorescence in situ hybridization is also presented.

Amino Acid Sequence↗
PubMedDate not supplied

Differential effects of oxygen on human dermal fibroblasts: acute versus chronic hypoxia.

The observation that many chronic wounds are ischemic has spurred a series of studies evaluating the response of cells exposed to hypoxia. To date, these studies have shown largely beneficial effects from hypoxia, such as increased cellular replication and procollagen synthesis. These findings are counter-intuitive from a clinical standpoint because cellular growth and synthetic function are known to be retarded in chronic ischemic wounds. We have established an in vitro system in which human dermal fibroblasts grown chronically at 5 +/- 3 mm Hg will proliferate at a rate three times slower than those fibroblasts grown under standard culture conditions (namely an oxygen partial pressure of 150 mm Hg). No phenotypic changes are noted in chronically hypoxic cells, and the growth-retarding effects are reversible when the cells are returned to standard oxygen conditions. Competitive reverse transcription-polymerase chain reaction showed that acute exposure to hypoxia (up to 1 week) results in a 6.3-fold increase in the relative expression of transforming growth factor-beta1 messenger RNA, whereas chronic exposure to hypoxia leads to a 3.1-fold decrease in this message. Collagen production measured at both the mRNA and protein level is also decreased in the setting of chronic hypoxia. We propose that this system may be the most appropriate setting for studying the role of oxygen on dermal fibroblasts in ischemic, nonhealing wounds.

Journal Article↗