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Biomedical subjects

R Sullivan

Publications and source records attributed to R Sullivan.

At least 91 records · Page 5Linked to original sources
PubMed1995

Comparative immunoreactivity of mouse and hamster sperm proteins recognized by an anti-P26h hamster sperm protein.

The binding of the spermatozoon to the zona pellucida is a species-specific phenomenon. We have previously shown that the binding of hamster sperm to the homologous zona pellucida involves a sperm 26-kDa glycoprotein, the P26h, originating in the epididymis. In order to establish to what extent this sperm protein is involved in the species-specific recognition of the egg's extracellular coat, we have compared the inhibitory properties of anti-P26h antibodies in a sperm-zona pellucida assay using hamster and mouse gametes. Anti-P26h IgGs inhibit, in a dose-dependent manner, gamete interactions in both species, although in a less efficient manner in the mouse than in the hamster. While anti-26kDa Fab fragments are as efficient as the intact IgG to inhibit hamster sperm-zona pellucida binding, they have no effect on mouse gamete interaction. ELISA, Western blot, and immunohistochemical experiments have been performed in order to characterize the mouse antigen(s) recognized by the anti-P26h antiserum. ELISA and Western blots showed that this antiserum recognized two proteins on mouse spermatozoa that are less reactive than the hamster P26h. These antigens are localized in the acrosomal region of epididymal spermatozoa of both species. These results indicate that the hamster P26H involved in zona pellucida interaction has certain unique epitopes, while others are common to the sperm of both species.

Animals↗
PubMed1995

Expression of a connexin 43/beta-galactosidase fusion protein inhibits gap junctional communication in NIH3T3 cells.

Gap junctions contain membrane channels that mediate the cell-to-cell movement of ions, metabolites and cell signaling molecules. As gap junctions are comprised of a hexameric array of connexin polypeptides, the expression of a mutant connexin polypeptide may exert a dominant negative effect on gap junctional communication. To examine this possibility, we constructed a connexin 43 (Cx43)/beta-galactosidase (beta-gal) expression vector in which the bacterial beta-gal protein is fused in frame to the carboxy terminus of Cx43. This vector was transfected into NIH3T3 cells, a cell line which is well coupled via gap junctions and expresses high levels of Cx43. Transfectant clones were shown to express the fusion protein by northern and western analysis. X-Gal staining further revealed that all of the fusion protein containing cells also expressed beta-gal enzymatic activity. Double immunostaining with a beta-gal and Cx43 antibody demonstrated that the fusion protein is immunolocalized to the perinuclear region of the cytoplasm and also as punctate spots at regions of cell-cell contact. This pattern is similar to that of Cx43 in the parental 3T3 cells, except that in the fusion protein expressing cells, Cx43 expression was reduced at regions of cell-cell contact. Examination of gap junctional communication (GJC) with dye injection studies further showed that dye coupling was inhibited in the fusion protein expressing cells, with the largest reduction in coupling found in a clone exhibiting little Cx43 localization at regions of cell-cell contact. When the fusion protein expression vector was transfected into the communication poor C6 cell line, abundant fusion protein expression was observed, but unlike the transfected NIH3T3 cells, no fusion protein was detected at the cell surface. Nevertheless, dye coupling was inhibited in these C6 cells. Based on these observations, we propose that the fusion protein may inhibit GJC by sequestering the Cx43 protein intracellularly. Overall, these results demonstrate that the Cx43/beta-gal fusion protein can exert a dominant negative effect on GJC in two different cell types, and suggests that it may serve as a useful approach for probing the biological function of gap junctions.

3T3 Cells↗
PubMed1995

New directions for research in prevention and treatment of delinquency: a review and proposal.

The past century has witnessed a number of approaches to the prevention and treatment of delinquency. Some approaches have emphasized physiological, psychological, and other individual characteristics; others have focused on the structure of the family; and still others have considered the structure of social relations within the broader society. More recent approaches have attempted to conceptualize an integrated complex of factors which includes community characteristics. This article reviews the various approaches which have dominated the field over the last few decades and concludes with a methodological proposal which may facilitate the systematic consideration of these various factors.

Adolescent↗
PubMed1995

A brief journey into medical care and disease in ancient Egypt.

Ancient Egypt was one of the greatest civilizations to have arisen, becoming the cradle of scientific enquiry and social development over 3 millennia; undoubtedly its knowledge of medicine has been vastly underestimated. Few artefacts survive which describe the medical organization, but from the extent of the diseases afflicting that ancient populus there would have been much to study. Evidence from papyri, tomb bas reliefs and the writings of historians of antiquity tell of an intense interest in the sciences, humanities and medicine born of an educated society which had overcome the superstitions of its nomadic ancestors.

Achondroplasia↗
PubMed1994

Induction of polyspermy in sea urchin eggs by antibodies raised against a hamster sperm protein.

Polyclonal antibodies raised against a hamster sperm protein (P26h) induce polyspermic fertilizations in the green sea urchin without affecting the fertilizing ability of the spermatozoa nor the elevation of the fertilization membrane. While the adsorption of the antibodies on sperm decreased the polyspermic effect, preincubation of unfertilized eggs with the anti-P26h did not cause polyspermy. These results suggest that common epitopes are involved in fertilization processes in phylogenetically distant species.

Animals↗
PubMed1994

Expression of fibronectin and a fibronectin-binding molecule during preimplantation development in the mouse.

Using an indirect immunofluorescent technique, expression of cell surface fibronectin and a cell surface fibronectin-binding molecule was studied during mouse embryo preimplantation development. We also studied the expression of fibronectin on immunosurgically isolated inner cell masses (ICMs) and regenerated mouse blastocysts. Fibronectin and the fibronectin-binding molecule were not detected at the morula stage. From the early to late blastocyst stage, fibronectin expression increased on the trophectoderm. Expression of the fibronectin-binding molecule was found only in the polar trophectoderm region of the early blastocyst, then in the polar and mural trophectoderm regions of the middle blastocyst. In the late blastocyst stage, this fibronectin-binding molecule was only present in the mural trophectoderm. Fibronectin expression by ICMs of early blastocysts was more intense than that of late blastocysts. After 24 h of culture, 10% of ICMs isolated from early blastocysts regenerated a trophectoderm which stained intensively for fibronectin in the mural and polar trophectoderm regions. After 48 h of culture, regenerated blastocyst-like structures closely resembled the normally obtained late blastocysts and stained for fibronectin in the mural and polar trophectoderm regions. The significance of the results is discussed in relation to mouse embryo development, trophectoderm formation and blastocyst implantation.

Amino Acid Sequence↗
PubMed1994

Human sperm-zona pellucida interaction is inhibited by an antiserum against a hamster sperm protein.

During epididymal transit, mammalian spermatozoa acquire new surface antigens that may participate in gamete interaction. We have previously described a 26-kDa (P26h) epididymal hamster sperm protein that we propose to be involved in fertilization. In this study, we have searched for an antigenically related protein in the human, and have found that an anti-P26h antiserum recognizes a 34-kDa (P34H) protein on Western blot of human sperm proteins. Immunostaining showed that this protein is localized on the acrosomal cap of human epididymal spermatozoa but not on testicular gametes. The effect of the anti-P26h antiserum on the fertilizing ability of human spermatozoa was evaluated by use of a human zona pellucida binding assay. Compared to the preimmune serum, the antiserum caused a highly significant decrease in the number of sperm bound per zona pellucida. This inhibition was not due to the induction of a premature acrosomal reaction nor to an effect on the motility of the spermatozoa. The antiserum recognizing the P34H human sperm protein had no effect on gamete fusion as determined by the zona-free hamster test. Our results suggest that the human spermatozoon acquires an epididymal protein that shares a common epitope(s) with the P26h hamster sperm protein. The possible involvement of this human sperm antigen in the binding to the zona pellucida is discussed.

Acrosome↗
PubMed1994

Inhibition of in vivo fertilization by active immunization of male hamsters against a 26-kDa sperm glycoprotein.

We have identified a 26-kDa (P26h) epididymal hamster sperm glycoprotein with a species-specific affinity for zona pellucida glycoprotein. Two immunological procedures have been used to document the biological function of this sperm component; active immunization of males against P26h and inhibition of sperm-zona pellucida binding in vitro by anti-P26h antibodies. The immunized male hamsters produced circulating antibodies specific to P26h. Indirect immunofluorescence studies showed that these antibodies bind to the surface of the sperm covering the acrosome. These males were mated with superovulated females, and although spermatozoa were recovered from the genital tract, none of the 194 oocytes recovered were fertilized. In contrast, control males immunized with hamster albumin fertilized 97.4% of the oocytes. Unlike control spermatozoa, those recovered from the cauda epididymidis of males immunized with P26h were characterized by the presence of antibodies at the surface of the acrosome. To establish whether the inhibition of in vivo fertilization by active immunization was occurring at the level of sperm-zona pellucida interaction, a polyclonal antiserum against P26h was raised, and the IgG fraction was added to an in vitro sperm-zona pellucida assay. Compared to the preimmune serum, the IgG inhibited the binding of spermatozoa in a dose-dependent manner. The Fab fragments generated from these IgGs were almost as efficient in inhibiting the binding. These results are discussed with regard to a possible function of P26h in hamster gamete interaction.

Acrosome↗
PubMed1994

Oxygen-induced retinopathy in the mouse.

PURPOSE: To develop oxygen-induced retinopathy in the mouse with reproducible and quantifiable proliferative retinal neovascularization suitable for examining pathogenesis and therapeutic intervention for retinal neovascularization in retinopathy of prematurity (ROP) and other vasculopathologies. METHODS: One-week-old C57BL/6J mice were exposed to 75% oxygen for 5 days and then to room air. A novel fluorescein-dextran perfusion method has been developed to assess the vascular pattern. The proliferative neovascular response was quantified by counting the nuclei of new vessels extending from the retina into the vitreous in 6 microns sagittal cross-sections. Cross-sections were also stained for glial fibrillary acidic protein (GFAP). RESULTS: Fluorescein-dextran angiography delineated the entire vascular pattern, including neovascular tufts in flat-mounted retinas. Hyperoxia-induced neovascularization occurred at the junction between the vascularized and avascular retina in the mid-periphery. Retinal neovascularization occurred in all the pups between postnatal day 17 and postnatal day 21. There was a mean of 89 neovascular nuclei per cross-section of 9 eyes in hyperoxia compared to less than 1 nucleus per cross-section of 8 eyes in the normoxia control (P < 0.0001). Proliferative vessels were not associated with GFAP-positive astrocyte processes. CONCLUSIONS: The authors have described a reproducible and quantifiable mouse model of oxygen-induced retinal neovascularization that should prove useful for the study of pathogenesis of retinal neovascularization as well as for the study of medical intervention for ROP and other retinal angiopathies.

Animals↗
PubMed1994

Evaluation of a new dentifrice for the treatment of sensitive teeth.

A dentifrice containing 5% potassium nitrate, 1.3% soluble pyrophosphate, 1.5% polyvinylmethyl ether and maleic acid (PVM/MA) copolymer and 0.243% sodium fluoride in a silica base (Sensitive/Tartar Control) has been developed to concomitantly control tartar, caries and dentinal hypersensitivity. In vitro and animal studies show that the fluoride in this product effectively inhibits formation of enamel and dentine caries. In vitro studies also demonstrate that this dentifrice effectively reduces hydraulic conductance by occluding dentine tubules with a mixed surface deposit of copolymer and silica. Using an in vitro model that simulates in vivo conditions, this dentifrice also allows a rapid penetration of potassium nitrate through the dentine matrix. These findings demonstrate a correlation under in vivo conditions between the occlusion of dentine and the ability to deliver topically applied agents to target sites within or below dentine. The results indicate that this new dentifrice should provide multiple clinical therapeutic benefits including controlling tooth decay and tartar formation, and reducing and preventing dentinal hypersensitivity.

Animals↗
PubMed1993

Structure, sequence and expression of the mouse Cx43 gene encoding connexin 43.

Gap junctions, membrane channels that mediate the diffusion of ions and small molecules between cells, are hypothesized to play a role in development and growth regulation. The Cx43 gene (encoding connexin 43) is one member of the gap junction gene family whose transcripts are expressed in a highly regionalized manner during mouse development. We cloned and sequenced Cx43 cDNAs from a 7.5-day mouse embryo cDNA library. These cDNA clones encode the authentic 43-kDa connexin. Analysis of RNA isolated from different regions of the 7.5-day mouse embryo revealed that Cx43 transcripts are differentially expressed, with expression detected in the embryo proper, but not in the extraembryonic region containing the ectoplacental cone. Using one of the newly isolated mouse Cx43 cDNA probes, we screened a mouse genomic DNA library and cloned the Cx43 gene. Restriction mapping and sequencing of the cloned genomic inserts revealed that Cx43 contains two exons and a 10.5-kb intron located in the 5' untranslated region (5'-UTR). We mapped the Cx43 transcription start point (tsp) by RNase protection and primer extension analyses and showed that transcripts expressed in the 7.5-day mouse embryo and in adult tissues are initiated from the same tsp. The DNA sequence immediately upstream from the tsp contains a putative AP1-binding site and a degenerate TATA consensus sequence. A comparison of mouse, rat, human and bovine Cx43s showed that the 3'-UTR has an unexpectedly high degree of sequence homology. This includes conservation of four AUUUA motifs, a sequence associated with transcript instability in immediate early genes.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗
PubMed1993

The effect of immigration on aggregate native unemployment: an across-city estimation.

"This study investigates the relationship between the rate of immigration into various [U.S.] cities in various years and the level and change in unemployment. In pooled regressions, immigration lagged one year does not show a statistically significant effect either by itself or when other lags are added. Individual regressions using the difference in unemployment rates over time show a slight, but statistically insignificant, positive displacement effect over two-year periods. The evidence indicates that there is little or no observed increase in aggregate native unemployment due to immigration, even in the relatively short run during which adjustment frictions should be most severe."

Americas↗