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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
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↗
PubMed1993

Surgery for Crohn's disease.

In the last 12 years, 72 operations have been performed on 41 patients for Crohn's disease in this hospital. The patients were predominantly young (mean age 32 yrs) and there were more females than males. 28 had ileocolic disease, three small intestinal, two pan-enteric and eight colonic. Pain (in 76%), diarrhoea (56%) and weight loss (66%) were the main presenting symptoms. Diarrhoea occurred in all those with colonic disease, but in only 43% of those with ileocolic disease. A right hemicolectomy (28 patients), colonic resection (12) and small intestinal resection (9) were the commonest operations. There were no deaths. 22 patients had a total of 26 complications after surgery, eight necessitating further surgery. The mean post-operative stay was 15 days, being lowest in those with ileocolic disease. 19 patients have required only one operation, with a mean follow-up of 5.3 years. These patients also had significantly less complications (p < 0.05). Half of the patients requiring surgery for Crohn's disease have done very well. The other half require many operations and have a substantial morbidity.

Adolescent↗
PubMed1992

Constriction of environmental space and the behavioral response to the dopamine agonist quinpirole.

The present study examines the influence of size of testing environment on the behavioral profile seen following injection of the dopamine D2 receptor agonist quinpirole (0.5 mg/kg, n = 16) or saline (n = 16). All rats were tested in a counterbalanced order in both a small and large environment. Oral (licking) behaviors were observed exclusively in the small environment and only in drug-treated rats; moreover, quinpirole increased rearing in the small but not large environment. Other behaviors--sniffing, face and body grooming--were affected by quinpirole but not in an environment-dependent manner. It is concluded that limiting environmental space promotes emergence of oral responding under quinpirole. The self-directed nature of this licking (paw- and tail-licking) may reflect a hierarchical transformation of quinpirole-induced hyperactivity from exploration of space to investigation of body parts.

Animals↗
PubMed1992

Effect of the method of preparing monochloramine upon inactivation of MS2 coliphage, Escherichia coli, and Klebsiella pneumoniae.

Monochloramine prepared in situ by first adding chlorine to a suspension of microorganisms, followed by subsequent addition of ammonia, inactivated the MS2 coliphage more rapidly than did exposure of phage to monochloramine prepared either by adding chlorine to ammonia or by adding chlorine and ammonia simultaneously. The rapid viral inactivation was apparently due to the exposure of MS2 to free chlorine before the addition of ammonia. The average 99% CT value of MS2 when exposed to free chlorine was 1.3 and 1.1 at 5 and 15 degrees C, respectively. The average 99% CT values of MS2 briefly exposed to the combined action of free chlorine followed by the addition of ammonia to form monochloramine in situ were 19.3 and 1.5 at 5 and 15 degrees C, respectively. No 99% CT values were calculated for the inactivation of MS2 with preformed monochloramine because less than 1 log (90%) of inactivation occurred during a 4-h contact time. Inactivation of MS2 by monochloramine was more rapid at 15 than at 5 degrees C and when the chlorine to nitrogen weight ratio was 5:1 compared with 3:1. Monochloramine was a more efficient inactivating agent for the coliforms Escherichia coli and Klebsiella pneumoniae than it was for the MS2 coliphage.

Chloramines↗
PubMed1992

Biochemical effects of human granulocyte-macrophage colony-stimulating factor (GM-CSF) on the human neutrophil.

Through studies of the stimulus-response coupling of GM-CSF in the neutrophils, important clues to the nature of the signal transduction of GM-CSF receptors are starting to emerge. GM-CSF receptors which have to date been identified and characterized biochemically appear to be too small to contain internal tyrosine kinase domains. Nonetheless, tyrosine phosphorylation of five separate proteins results when neutrophils are incubated with GM-CSF (73). The most appealing explanation for this interesting observation is that one or more tyrosine kinases lie distal to GM-CSF receptors in their signal transduction pathway. While less likely, the possibility exists that another class of GM-CSF receptors which exhibit intrinsic tyrosine kinase activity remains to be identified. Characterization of the specific proteins which are phosphorylated on tyrosine residues ought to provide important insights into the signal transduction of this cytokine. On the other hand, direct activation of protein kinases C has not been observed following exposure of neutrophils to GM-CSF (19,22,80). GM-CSF induces the release of small quantities of arachidonic acid from the plasma membrane of the neutrophil (22). Arachidonic acid is primarily released directly through the effects of phospholipases A2 on membrane phospholipids or indirectly through activation of phospholipases C or D, which release compounds that can serve as a source of arachidonic acid when hydrolyzed by specific enzymes. Direct activation of phospholipases C in the neutrophil by GM-CSF appears most unlikely, since GM-CSF does not elevate [Ca2+]i or induce the release of detectable quantities of inositol trisphosphates or diacylglycerols in these cells. Therefore, the possibility that GM-CSF may directly activate phospholipases A2 is quite plausible. GM-CSF directly activates Na+/H+ antiporters in the plasma membrane of the neutrophil, resulting in alkalinization of the cytoplasm of approximately 0.1-0.25 pH unit (73). The function of cytoplasmic alkalinization in the priming of mature neutrophils is unclear. However, evidence exists in other cell systems that cytoplasmic alkalinization may be important in inducing cell proliferation, since the pH optima of several enzymes necessary for DNA synthesis are slightly more alkaline than the resting pH of the cytosol. Many types of growth factors which initiate cell division through occupancy of surface receptors give rise to cytoplasmic alkalinization through just such a mechanism (52). Therefore, it seems likely that GM-cSF may activate Na+/H+ antiporters in the plasma membranes of hemic progenitor cells which bear GM-CSF receptors and which proliferate in response to this cytokine.(ABSTRACT TRUNCATED AT 400 WORDS)

Granulocyte-Macrophage Colony-Stimulating Factor↗
PubMed1991

Identification of epididymal proteins associated with hamster sperm.

The electrophoretic analysis of the proteins that were extracted from immature caput and mature cauda sperm showed evidence of accumulation of several proteins during the epididymal transit of the sperm. An antiserum, raised against detergent-extracted proteins from mature spermatozoa, immunostained six epididymal proteins with apparent molecular masses of 16, 22.5, 26, 37, 60, and 80 kDa on Western blots of epididymal fluid. Of these proteins, only the 26 kDa protein was significantly immunodetected in proximal caput epididymal fluid. Its biosynthesis by caput epididymis was confirmed by immunoprecipitation of an in vitro translated product of caput poly (A) RNA. The homology of the 26 kDa epididymal protein with the 26 kDa sperm protein was verified by epitope mapping. The other epididymal proteins were found in the fluid of the more distal portions of the organ. Their presence in the epididymal fluid coincided with their detection on the sperm. These epididymal proteins were considered to be sperm-coating proteins.

Animals↗
PubMed1991

Impact of a second insemination on the results of an in vitro fertilization-embryo transfer (IVF-ET) program.

In an attempt to increase the fertilization and pregnancy rates in our program, a second insemination was carried out when the first insemination yielded fewer than two fertilized oocytes. One hundred eighty consecutive patients were studied retrospectively and thirty-four required second insemination, 35% of them by donor semen. Fifty-five and nine-tenths percent of the patients had at least one fertilized oocyte for embryo transfer, but only 21.9% of the oocytes exposed to a second insemination were fertilized. No pregnancy resulted from the transfer of oocytes fertilized by the second insemination. There were no significant correlations between the success of fertilization after a second insemination and the number of oocytes retrieved, the protocol for the induction of superovulation, or the age of the female patient. Considering that the first insemination was done at a variable time after oocyte retrieval to allow oocyte maturation, we expected all oocytes to be mature at the time of first insemination and we considered the possibility of delayed fertilization as negligible since second insemination was done at least 24-30 hr after oocyte retrieval. Even though a second insemination provides further hope for the patient, by yielding additional fertilized oocytes for embryo transfer, its main value is that it may provide additional information about male fertility.

Adult↗
PubMed1991

Ethical and legal responsibilities of the neurosurgeon: selected topics.

There are many ethical and legal implications in a variety of activities in the neurosurgeon's day-to-day practice. Awareness of and proper attention to these issues are a professional responsibility that should be attended to, to ensure that the practice of medicine is carried out efficiently and effectively, to maintain public confidence, and to try to avoid micromanagement by third parties. The authors discuss four such subjects of particular interest to them, namely: 1) reporting of certain diseases and conditions to authorities and third parties; 2) acting without the consent of the patient to prevent harm to him or her and/or others; 3) reporting problems with drugs and devices; and 4) the detection and treatment of colleagues impaired by alcohol, drugs, or mental or physical illness.

Confidentiality↗
PubMed1991

Multilaboratory evaluation of methods for detecting enteric viruses in soils.

Two candidate methods for the recovery and detection of viruses in soil were subjected to round robin comparative testing by members of the American Society for Testing and Materials D19:24:04:04 Subcommittee Task Group. Selection of the methods, designated "Berg" and "Goyal," was based on results of an initial screening which indicated that both met basic criteria considered essential by the task group. Both methods utilized beef extract solutions to achieve desorption and recovery of viruses from representative soils: a fine sand soil, an organic muck soil, a sandy loam soil, and a clay loam soil. One of the two methods, Goyal, also used a secondary concentration of resulting soil eluants via low-pH organic flocculation to achieve a smaller final assay volume. Evaluation of the two methods was simultaneously performed in replicate by nine different laboratories. Each of the produced samples was divided into portions, and these were respectively subjected to quantitative viral plaque assay by both the individual, termed independent, laboratory which had done the soil processing and a single common reference laboratory, using a single cell line and passage level. The Berg method seemed to produce slightly higher virus recovery values; however, the differences in virus assay titers for samples produced by the two methods were not statistically significant (P less than or equal to 0.05) for any one of the four soils. Despite this lack of a method effect, there was a statistically significant laboratory effect exhibited by assay titers from the independent versus reference laboratories for two of the soils, sandy loam and clay loam.

Enterovirus↗
PubMed1991

Glomerular nitrite synthesis in in situ immune complex glomerulonephritis in the rat.

Nitrite (NO2-) is the major end product of nitric oxide (NO) production in cell culture. The authors have examined nitrite production by glomeruli in in situ immune complex glomerulonephritis in the rat. Glomerulonephritis was induced by unilateral renal perfusion of cationized human gamma G immunoglobulin (IgG) in preimmunized rats. NO2- was measured in culture supernatants of isolated glomeruli after 48 hours. NO2- was produced by nephritic glomeruli with a maximum 4 days after induction of glomerulonephritis (24.4 +/- 11.4 pmol/glomerulus/48 hours). Production was increased by lipopolysaccharide (LPS; 1 micrograms/ml) (54 +/- 4.9 pmol/glomerulus; P less than 0.001). NO2- production was inhibited by the nitric oxide synthase inhibitor NG-monomethyl-L-arginine demonstrating synthesis through NO. Dexamethasone (10(-7) mol/l [molar]) reduced LPS-stimulated production by peritoneal macrophages and nephritic glomeruli (P less than 0.01). Macrophages isolated from nephritic glomeruli produced NO2- (4.9 +/- 0.6 nmols/10(5) cells). The production of NO by nephritic glomeruli has implications for mechanisms of glomerular injury and glomerular hemodynamics. The effect of dexamethasone may explain in part the ameliorative effect of steroids in glomerulonephritis.

Animals↗
PubMed1990

The biology of GM-CSF: regulation of production and interaction with its receptor.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a small glycoprotein growth factor which stimulates the production and function of neutrophils, eosinophils and monocytes. GM-CSF can be produced by a wide variety of tissue types, including fibroblasts, endothelial cells, T cells, macrophages, mesothelial cells, epithelial cells and many types of tumor cells. In most of these tissues, inflammatory mediators, such as interleukin 1, interleukin 6, tumor necrosis factor or endotoxin, are potent inducers of GM-CSF gene expression, which occurs at least partly by post-transcriptional stabilization of the GM-CSF mRNA. The biological effects of GM-CSF are mediated through binding to cell surface receptors, which appear to be widely expressed by hematopoietic cells and also by some non-hematopoietic cells, such as endothelial cells. Receptor expression is characterized by low number (20-200/cell) and high affinity (Kd = 20-100 pM). At least two different functional classes of GM-CSF receptor have been identified. The neutrophil GM-CSF receptor exclusively binds GM-CSF, while interleukin 3 competes for binding of GM-CSF to a second class of receptors detected on some leukemic cell lines, such as KG1 and MO-7E. Signal transduction involves activation of a tyrosine kinase and possibly G protein-coupled stimulation of Na+/H+ exchange. The exact relationship of the two receptors needs further clarification.

Animals↗
PubMed1990

Identification of a cadherin cell adhesion recognition sequence.

The molecular mechanisms by which the cadherins interact with one another to promote cell adhesion have not been elucidated. In particular, the amino acid sequences of the cadherin cell adhesion recognition sites have not been determined. Here we demonstrate that synthetic peptides containing the sequence HAV, which is common to all of the cadherins, inhibit two processes (compaction of eight-cell-stage mouse embryos and rat neurite outgrowth on astrocytes) that are known to be mediated by cadherins. The data suggest that the tripeptide HAV is a component of a cadherin cell adhesion recognition sequence.

Amino Acid Sequence↗