Assignment of the gene encoding the catalytic subunit Cβ of CAMP-dependent protein kinase to the p36 band on chromosome

Summary A cDNA for the human catalytic subunit (C) of cAMP-dependent protein kinase (PKA) has been cloned from a testis cDNA library. In the present study, we have determined the chromosomal localization of this gene using a cDNA for C as a probe. Southern blot analysis of genomic DNA from human/mouse cell hybrids revealed that the presence or absence of a 20-kbXbaI fragment, which hybridized with the C probe, was concordant with the presence of human chromosome 1.In situ hybridization to metaphase chromosome confirmed the somatic cell hybrid data and regionally mapped the C gene of PKA to the p36 band on chromosome 1.     

Rainbow trout p53: cDNA cloning and biochemical characterization.

We have cloned and sequenced the p53-encoding cDNA of rainbow trout (Salmo gairdneri). The encoded product contains the characteristics found in all p53 proteins: (i) the five highly conserved domains, (ii) an acidic N terminus, (iii) a hydrophilic C terminus, and (iv) a penultimate serine residue. Furthermore, we demonstrate that the rainbow trout p53 is able to specifically interact with the SV40 large T antigen.     

Group size and stability: Why do gibbons and spider monkeys differ?

Gibbons and spider monkeys have similar diets, body size, and locomotor patterns. They are therefore expected to be subject to similar socioecological rules. However their grouping patterns differ. Gibbons live in small stable groups, whereas spider monkey form unstable sub-groups that vary from small to large during different seasons. If similar principles apply to the two species, food abundance should vary more for spider monkeys than for gibbons; food density should be similar for the two species when spider monkey sub-groups are the same size as gibbon groups; and the highest level of food abundance should be higher for spider monkeys than for gibbons. These predictions are upheld for a comparison of particular populations ofHylobates muelleri andAteles geoffroyi.     

Age-dependent choice of sexual partners and the transmission dynamics of HIV in Sub-Saharan Africa.

A mathematical model of the transmission of HIV-1 within heterosexual populations in Sub-Saharan Africa is described and its properties analysed. The model incorporates epidemiological and demographic processes and extends previous work in this area via the inclusion of age and sex dependency in rates of sexual partner change, and sexual partner choice dependent on age. Parameter assignments are made on the basis of current data on the transmission dynamics of HIV-1 and the demography of human populations in Africa. Both age-dependent rates of sexual activity and the sexual contact of males with females younger than themselves act to enhance the predicted demographic impact. With realistic parameter values, the model suggests AIDS is able to reverse the sign of population growth rates from positive to negative values over a timescale of a few decades. The sensitivity of this prediction is examined in relation to changes in the pattern of sexual contact between different age classes of females and males, different patterns of change in the age-dependent rate of sexual partner change, different assumptions concerning the doubling time of the epidemic in its early stages, and the relative efficiencies of viral transmission between men and women, and vice versa. The impact AIDS is predicted to have on the number of young and elderly persons as a fraction of the number of productive adults (the dependancy ratio) is examined under various assumptions concerning the weighting to be applied to mirror the burden imposed by the care of those with AIDS. The paper includes an assessment of the influence of the timing of changes in sexual behaviour, or the promotion of the use of condoms, on the predicted course of the epidemic. The paper concludes with a discussion of data needs and the model refinements required to more accurately mirror current understanding of the epidemiology of HIV-1.     

Immunohistochemical localization of porcine diazepam-binding inhibitor (DBI) to rat endocrine pancreas

Summary The occurrence of diazepam-binding inhibitor (DBI), isolated and characterized from porcine upper intestine, was examined in the pancreas of Sprague-Dawley albino rats using indirect immunofluorescence. The polypeptide was found in the endocrine Langerhans islets and, utilizing double-labelling controls, it was shown to be present within the peripherally located glucagon-containing cells. Regulation of islet hormone production may therefore be under DBI control.     

Intranuclear distribution of SV40 large T-antigen and transformation-related protein p53 in abortively infected cells

The intranuclear localization of SV40 T-antigen (T-Ag) and the cellular protein p53 was studied in SV40 abortively infected baby mouse kidney cells using two complementary methods of ultrastructural immunocytochemistry in combination with preferential staining of nuclear RNP components and electron microscope autoradiography. Both proteins were revealed in association with peri- and interchromatin RNP fibrils containing the newly synthesized hnRNA. In addition, T-Ag and p53 remained bound, at least in part, to the residual internal nuclear matrix following nuclease and salt extractions of infected cells. The localization of T-Ag was different in SV40 lytically infected monkey kidney cells since, in addition to hnRNP fibrils, the viral protein was also associated with cellular chromatin. However, when lytic infection was performed in conditions of blocked viral DNA replication, T-Ag was no longer associated with the cellular chromatin but remained bound to the hnRNP fibrils. We conclude that the transforming and lytic functions of T-Ag can be distinguished by different subnuclear distributions. The significance of the association of T-Ag and p53 with hnRNP fibrils and the internal nuclear matrix is discussed in relation to the role of these structures in the control of cellular mRNA biogenesis.     

The role of a low pH intracellular compartment in the processing, storage, and secretion of ACTH and endorphin

To determine whether a low pH intracellular "sorting" step is required to route peptides into secretory granules, the effects of pH altering drugs on the biosynthesis and secretion of peptides by AtT-20 mouse corticotrope tumor cells and rat intermediate pituitary cells were examined. Doses of each drug maintaining normal protein synthesis and cell morphology, while obliterating the intracellular pH gradients detected by acridine orange fluorescence, were experimentally determined. Regions of the cell rich in secretory granules were localized by immunocytochemistry and were found to coincide with organelles with a low internal pH. Biosynthetic labeling experiments were coupled with immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel analyses to examine the biosynthesis and secretion of corticotropin (ACTH(1-39], alpha-melanotropin, ACTH(18-39), beta-endorphin, gamma-melanotropin, alpha-amidated joining peptide, and the NH2-terminal region of pro-ACTH/endorphin. Chloroquine (20-40 microM) and a mixture of NH4Cl and methylamine (2-5 mM each) dissipated pH gradients but had no effect on the synthetic rate of pro-ACTH/endorphin, the extent and rate of precursor processing to smaller peptides, the rate of basal secretion of the various peptides, or the extent to which secretion of each of the peptides could be stimulated by secretagogues. Monensin (0.1-1 microM) had no discernible effect on intracellular pH gradients yet totally blocked proteolytic processing of pro-ACTH/endorphin. Thus, a monensin-blockable step occurs in peptide processing, presumably in the trans Golgi region; however, a low pH chloroquine-sensitive sorting step is not required for processing or for routing peptides to a stable storage form which can be released in response to secretagogues.