Effects of selective opioid agonists on feline colonic transit.

The mu agonist morphine and the non-specific opioid antagonist naloxone both may accelerate feline colonic transit; the effects of morphine are dose dependent. Kappa and delta receptor function was studied in the present work. Colonic transit of a radionuclide marker instilled into the cecum was quantitated for 6 hr in a crossover study. The delta agonist [D-Pen2,D-pen5]enkephalin (1 mg/kg, i.m.) prolonged the cecum and ascending colon half-emptying time by 337% (P less than 0.05), and delayed the progression of the geometric center over time. The kappa agonist U-50,488 (1 mg/kg, i.m.) had no apparent effect on the cecum and ascending colon, but delayed filling of the descending colon. Loperamide, an antidiarrheal agent, also delayed colonic transit. Thus, selective opioid agonists have both site and functional differences in their effect on feline colonic transit.     

Molecular characterization of biologically diverse envelope variants of human immunodeficiency virus type 1 derived from an individual.

The envelope genes of six viruses derived from a single sampling from an individual chronically infected with human immunodeficiency virus type 1 (RJS-4) have been analyzed. Here we present the nucleotide and predicted amino acid sequences of these variants and show a correlation between biological properties and disturbance of the envelope reading frame.     

Gene expression in nematode-infected plant roots

Summary A major pathogen of potato plants (Solanum tuberosum) is the potato cyst nematode (Globodera spp.), which induces localized redifferentiation of a limited number of host cells to form a specialized feeding-site termed the syncytium. A novel strategy utilizing the polymerase chain reaction (PCR) was employed to construct a cDNA library from dissected potato roots highly enriched in syncytial material. The library was differentially screened with cDNA probes derived from the infected root tissue from a compatible interaction and from healthy root tissue. Characterization of one gene identified by the library screen indicated an expression pattern that correlated with events in the immediate vicinity of the pathogen after syncytial establishment. The strategy for library construction and screening could be applicable to the study of gene expression in any plant-pathogen interaction in which the limited supply of cells at the interface of the two organisms precludes a more traditional approach.     

The influence of maternal age on radiation-induced chromosome aberrations in mouse oocytes

The relative sensitivities of dictyate oocytes from young and old female mice to radiation-induced chromosome damage were examined in 2 separate experiments. Firstly, females were given either 2 or 4 Gy of X-rays and metaphase I stage oocytes collected 16.5 days later. Analysis of these cells showed dose-related increases in chromosome aberrations in both age groups. The response was significantly greater in oocytes of older females. In the second experiment, females were given 4 Gy of X-rays and metaphase I stage oocytes collected 3.5 days later. Again, a significantly larger frequency of aberrations was present in cells from older animals. Overall, these 2 experiments provide unambiguous evidence that the radiosensitivity of mouse dictyate oocytes increases with advancing maternal age.     

Human cyclin E, a new cyclin that interacts with two members of the CDC2 gene family.

A new human cyclin, named cyclin E, was isolated by complementation of a triple cln deletion in S. cerevisiae. Cyclin E showed genetic interactions with the CDC28 gene, suggesting that it functioned at START by interacting with the CDC28 protein. Two human genes were identified that could interact with cyclin E to perform START in yeast containing a cdc28 mutation. One was CDC2-HS, and the second was the human homolog of Xenopus CDK2. Cyclin E produced in E. coli bound and activated the CDC2 protein in extracts from human G1 cells, and antibodies against cyclin E immunoprecipitated a histone H1 kinase from HeLa cells. The interactions between cyclin E and CDC2, or CDK2, may be important at the G1 to S transition in human cells.     

Murine erythrocyte ankyrin cDNA: highly conserved regions of the regulatory domain

Ankyrin is an essential link between cytoskeletal proteins, such as spectrin, and membrane bound proteins, such as protein 3, the erythrocyte anion exchanger. Although the amino acid structure of human ankyrin is known, the functional regions have been only partially defined. Sequence comparisons between mouse and human ankyrin offer one mechanism of identifying highly conserved regions that probably have functional significance. We report the isolation and sequencing of a series of overlapping murine erythroid ankyrin (Ank-1) cDNAs from spleen and reticulocyte libraries (total span 6238 bp) and identify potentially important regions of murine-human reticulocyte ankyrin homology. Comparison of the predicted peptide sequences of mouse and human erythroid ankyrins shows that these ankyrins are highly conserved in both the N-terminal, protein 3 binding domain (96% amino acid identity) and in the central spectrin-binding domain (97% identity), but differ in the C-terminal regulatory domain (79% identity). However, the C-terminal regulatory domain contains two regions of peptide sequence that are perfectly conserved. We postulate these regions are important in the regulatory functions of this domain.     

Immunohistochemical localization of PGF2 alpha receptor in the rat ovary.

As a step towards understanding the role of prostaglandin F2 alpha (PGF2 alpha) in ovarian function, a rabbit antiserum against purified PGF2 alpha receptor (PGF2 alpha-R) was produced. This report details the use of this antiserum in immunohistochemical staining of ovaries of non-pregnant and pregnant rats to ascertain which cell types, in vivo, possess PGF2 alpha-R. In non-pregnant rats, three ovarian cell subpopulations contain immunoreactive PGF2 alpha-R. These include: a subpopulation of the cells found in corpora lutea, a subpopulation of the thecal cells surrounding secondary and mature (Graafian) follicles, and a subpopulation of primary and secondary interstitial cells. The ovarian tissues and cell types in which immunoreactive PGF2 alpha-R cannot be demonstrated include: the serosa overlying the ovary and its vessels, the coelomic epithelium and its underlying cortical stroma, medullary stroma and vessels, granulosa cells of primary, secondary and mature follicles, the oocyte, and the blood vessels and stroma within corpora lutea. PGF2 alpha-R immunohistochemical staining of corpora lutea from non-pregnant animals was examined both prior to the start of luteolysis and during luteolysis. During luteolysis, cells undergoing apoptosis stained for the presence of PGF2 alpha-R. PGF2 alpha-R immunohistochemical staining was also examined in corpora lutea during pregnancy and until 4 days postpartum. The major findings here were the apparent large increase in staining intensity of granulosa-lutein cells during pregnancy, and the loss of PGF2 alpha-R immunopositivity of the granulosa-lutein cells during the postpartum period. In summary, three ovarian cell subpopulations, all of which can secrete steroids, possess immunoreactive PGF2 alpha-R.