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Biomedical subjects

J Hobbs

Publications and source records attributed to J Hobbs.

At least 55 records · Page 3Linked to original sources
PubMed1979

The hemolytic anemias.

Hemolytic anemias usually present with persistent reticulocytosis, a characteristic that differentiates them from other types of anemia. Once the presence of a hemolytic process has been documented, simple observation of red blood cell morphology will yield important etiologic information. Hemolysis may result from inherent defects in the red cell or from excessive environmental stress on normal cells. Immune mechanisms of hemolysis should be investigated early because of the frequency of their occurrence.

Anemia, Hemolytic↗
PubMed1978

Inhibition of primase, the dnaG protein of Escherichia coli by 2'-deoxy-2'-azidocytidine triphosphate.

2'-Deoxy-2'-azidocytidine-5'-triphosphate was investigated as an inhibitor in two reconstructed enzyme systems which catalyze the replication of two viral DNAs. During replication of the duplex replicative form of phiX174 DNA, DNA polymerase III holoenzyme was weakly inhibited and inhibition was reversed by dCTP. A more pronounced inhibition, not reversed by either dCTP or CTP, was observed during replication of the single-stranded DNA of the bacteriophage G4, a close relative of phiX174. This effect depended on the incorporation of 2'-deoxy-2'-azidocytidine-5'-triphosphate by primase (dnaG protein) which synthesizes a 29-residue RNA primer at the unique origin of bacteriophage G4 DNA replication. Extension of the primer strand, terminated by 2'-deoxy-2'-azidocytidine-5'-triphosphate is then severely inhibited. Primase was also inhibited by the 2'-deoxy-2'-azido derivatives of ATP, GTP, and UTP.

Coliphages↗
PubMed1978

Effects of hydrogen ion dissociation and concentration of the reactivity of dichromate-fixed tissue components to the PAS procedure: recommendations for reducing undesirable background staining.

The undesirable PAS reactivity of cytoplasmic aldehydes after dichromate fixation can be suppressed without affecting selective staining by lowering the pH of Lillie's Cold Schiff reagent to 1.5. Alternatively, dilution of pH 2.2 Cold Schiff reagent with distilled water (1:2) is recommended. Hydrogen ion concentration and dissociation effect the rate of color formation in various PAS positive sites differentially with respect to the time of incubation in Schiff reagent. Based on the experiments, aldehydes exposed in different tissue components appear to be chemically distinct and separable depending on the rate of color formation and duration of incubation in Schiff reagent.

Aldehydes↗
PubMed1977

2'-Deoxy-2'-azidocytidine, a new inhibitor of DNA replication in mammalian cells.

Cell growth is reversibly inhibited by the nucleoside analogue, 2'-deoxy-2'-azidocytidine and the inhibition is a result of interference with DNA replication. The 5'-diphosphate of the analogue was earlier shown to specifically inactivate the enzyme ribonucleotide reductase in vitro. However, measurements of the pools of deoxyribonucleoside triphosphates in cells incubated in azidocytidine showed only minor changes which appeared to result from and not to be the cause of the inhibition of DNA replication. The DNA synthesized in polyoma-infected cells after incubation in azidocytidine showed a sedimentation pattern quite different from that seen after inhibition of DNA synthesis with arabinosyl cytosine or hydroxyurea. Experiments with nuclei isolated from azidocytidine-inhibited, polyoma-infected cells indicated (a) that the number of replicating molecules is decreased during the inhibition and (b) that upon incubation of the nuclei there is a rapid synthesis of DNA occurring in a new class of DNA molecules which are at a very early state of replication. Neither the 5'-triphosphate of azidocytidine nor the nucleoside itself inhibit DNA synthesis in vitro in isolated nuclei from polyoma-infected cells and at present the nature of the DNA-synthesis-inhibiting compound acting in the cells after addition of azidocytidine is unknown. Taken together the results suggest that azidocytidine inhibits DNA synthesis at an early stage, possible by blocking the initiation of DNA synthesis at the origin or by interfering with the elongation of newly initiated DNA molecules.

Cell Line↗
PubMed1977

Malaria field studies in a high-incidence coastal area of El Salvador, C.A.

A three-year investigation was made of the incidence patterns and characteristics of malaria in a small high-incidence coastal area of El Salvador with a resident population of about 6,000 persons and a migrant population of 3,000 to 4,000 others. It found a significant increase in the incidence of Plasmodium falciparum cases during the three-year period, combined with relative stability in the annual number of Plasmodium vivax cases. A close correlation was observed between the seasonal occurence of P. falciparum cases in 1973 and vector densities, and between vector densities and aerial application of agricultural insecticides. Cases of P. vivax appeared about twice as common in the 5 to 14 year age group as in older or younger groups, and cases of P. falciparum seemed only about one-third as frequent in the 0 to 4 year group as in older groups. The attack rate in 1973 was somewhat higher in males than in females. There appeared to be a decrease in parasite densities with age, as well as a direct correlation between parasite densities and the degree of disability (symptoms and "in bed" time) reported by patients.

Adolescent↗
PubMed1975

Inhibition of oncornavirus functions by 2'-azido polynucleotides.

The 2'-azido analogs of poly(U) and poly(C), poly(dUz) [poly(2'-azido-2'-deoxyuridylic acid)], and poly-(dCz [poly(2'-azido-2'-deoxycytidylic acid)], were found to inhibit the RNA-directed DNA polymerase (reverse transcriptase) activity of murine leukemia (Moloney, Rauscher) and sarcoma (Moloney) virus, and feline leukemia (Theilen) and sarcoma (Gardner) virus, while under the same conditions the unsubstituted parent compounds failed to do so. In addition, poly(dUz) and poly(dCz) inhibited the replication of exogenous murine sarcoma virus (Moloney) in nontransformed cells (as assessed by an infectious center assay), but poly(dUz) failed to suppress the formation of endogenous sarcoma and leukemia viruses in transformed cell lines (MO-P, JLSV5). In these same cells, poly(dUz) failed to inhibit the multiplication of vesicular stomatitis virus. These data add further strength to the contention that reverse transcriptase is necessary for the productive infection and transformation of normal cells by oncornaviruses but is not essential maintenance of this transformed state and the continuous production of new viruses particles by these transformed cells.

Animals↗
PubMed1975

Hydrolysis in 2'-chloro-2'-deoxy nucleosides, -nucleotides and -polynucleotides to arabinose-derivatives.

The rate of hydrolysis of 2'-chloro-2'-deoxycytidine and -uridine, and their 5'-phosphates, -diphosphates and polymers to the corresponding arabinocytidine and arabinouridine derivatives in the presence of Tris-HCL pH 8.9 is determined. This rate is highest for the nucleosides, less for the 5'-phosphates and 5'-diphosphates and even less for the polynucleotides. In the the 2'-chloro-2'-deoxyuridine series the O2, 2'-cyclonucleoside was formed in addition to the arabinonucleoside.

Alkaline Phosphatase↗
PubMed1975

Natural infections of Anopheles albimanus with Plasmodium in a small malaria focus.

Entomologic surveys conducted in a small village in an area of known high malaria transmission in El Salvador yielded a high rate of infection in Anopheles albimanus collected inside houses in which cases of malaria had occurred. Of 324 specimens dissected, 12 were found to harbor sporozoites or oocysts. This is in contrast to prior reports of extremely low infection rates in collections of this species from malarious areas, and suggests that under some circumstances A. albimanus does meet the criteria of an effective malaria vector.

Anopheles↗