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Biomedical subjects

H O'Sullivan

Publications and source records attributed to H O'Sullivan.

13 recordsLinked to original sources
PubMed1997

The use of povidone iodine in exit site care for patients undergoing continuous peritoneal dialysis (CAPD).

Exit site infection is a major risk factor for the development of peritonitis in continuous ambulatory peritoneal dialysis. The frequency of infection can be reduced by scrupulous exit site care with or without topical antiseptics. A randomized trial was performed of 149 catheters in 130 patients to assess any additional benefits conferred by the use of povidine iodine dry powder spray at dressing changes over an existing strict protocol of exit care. Exit infections occurred in 14 (18%) of 77 patients using spray and in 15 (21%) of 72 patients not using spray. The risk of peritonitis was also similar in each group. The proportion of infections caused by Staphylococcus aureus was reduced in the spray group, but those caused by Pseudomonas aeruginosa were increased. Rash occurred in 6% of those using the spray. The use of the spray did not therefore seem justified.

Aged↗
PubMed1997

GnRH perikarya in medial basal hypothalamus of pubertal female rhesus macaque are ensheathed with glia.

A previous study in our laboratory revealed that the cell bodies of gonadotropin releasing hormone (GnRH) neurons in the preoptic area (POA) of early to midpubertal female rhesus monkeys were extensively invested with thick glial processes. Because the medial basal hypothalamus (MBH) plays a critical role in the control of pulsatile and cyclic gonadotropin release in the primate, we have now focused on the ultrastructural milieu of GnRH neurons of this region in the same sample of monkeys. The ensheathment of the perikarya of GnRH neurons in the MBH with such glial processes was more pronounced than in the POA. Whereas the mean proportion of the cell membrane covered by these glia was 57% in the POA, it was 72% in the MBH. In addition, the cell bodies of GnRH neurons in the MBH of the pubertal monkey (unlike those in the POA) were less well innervated than were those in the adult cycling monkey, further highlighting differences between these brain regions. Differences in the anatomical milieu of the MBH between immature monkeys, in which GnRH release is still relatively quiescent, and adult cycling monkeys are consistent with the hypothesis that GnRH neurons within the MBH are under particular constraint in the immature animals. The functional significance of these observations must, however, await further studies.

Animals↗
PubMed1995

Organelle-cytoskeletal interactions: actin mutations inhibit meiosis-dependent mitochondrial rearrangement in the budding yeast Saccharomyces cerevisiae.

During early stages of meiosis I, yeast mitochondria fuse to form a single continuous thread. Thereafter, portions of the mitochondrial thread are equally distributed to daughter cells. Using time-lapse fluorescence microscopy and a membrane potential sensing dye, mitochondria are resolved as small particles at the cell periphery in pre-meiotic, living yeast. These organelles display low levels of movement. During meiosis I, we observed a threefold increase in mitochondrial motility. Mitochondrial movements were linear, occurred at a maximum velocity of 25 +/- 6.7 nm/s, and resulted in organelle collision and fusion to form elongated tubular structures. Mitochondria do not co-localize with microtubules. Destabilization of microtubules by nocodazole treatment has no significant effect on the rate and extent of thread formation. In contrast, yeast bearing temperature-sensitive mutations in the actin-encoding ACT1 gene (act1-3 and act1-133) exhibit abnormal mitochondrial aggregation, fragmentation, and enlargement as well as loss of mitochondrial motility. In act1-3 cells, mitochondrial defects and actin delocalization occur only at restrictive temperatures. The act1-133 mutation, which perturbs the myosin-binding site of actin without significantly affecting actin cytoskeletal structure in meiotic yeast, results in mitochondrial morphology and motility defects at restrictive and permissive temperatures. These studies support a role for the actin cytoskeleton in the control of mitochondrial position and movements in meiotic yeast.

Actins↗
PubMed1995

Glial ensheathment of GnRH neurons in pubertal female rhesus macaques.

During the period of development, prior to full sexual maturity, gonadotropin hormone-releasing hormone (GnRH) neurons are fully capable of synthesizing and processing the GnRH decapeptide. Nonetheless, the secretion of the hormone is not adequate to stimulate adult patterns of gonadotropin release. The present study was undertaken to examine ultrastructural characteristics of the GnRH neuron and its relationship to its environment in early-midpubertal female rhesus monkey. The neurons bore all the ultrastructural immunocytochemical characteristics of those in mature animals, but quantitative morphometrics revealed that they were extensively apposed by glial processes. Such ensheathment was described earlier in ovariectomized adult animals and was found to be reversible by administration of gonadal steroids. The density of synaptic input to GnRH neurons in the pubertal animals did not differ significantly from that of adult intact or ovariectomized animals from a previous study. Chemical identification will be required to determine whether there are age or hormonal differences in the innervation of these neurons. These results provide anatomical evidence in support of indications from other studies that the ovarian steroidal milieu affects GnRH-glial relationships. Further testing will be required to determine whether the attainment of sexual maturity in the female rhesus macaque is dependent upon a reduction in glial ensheathment of GnRH neurons.

Animals↗
PubMed1995

Novel associations among gonadotropin-releasing hormone neurons.

GnRH is secreted in bursts into the hypophyseal portal vasculature by a small dispersed population of neurons. The means by which the activity of these intrinsically pulsatile cells is coordinated are unknown. This study was initiated as a continuation of our examination of the synaptic input to these cells and their anatomical relationships. Brain tissue from female rhesus monkeys and male and female rats was prepared for the immunocytochemical demonstration of GnRH. At the light microscopic level, GnRH neurons were occasionally found to be in close apposition. Such pairs (or small groups) were randomly distributed throughout the population of GnRH neurons from the diagonal band of Broca through the anterior hypothalamic area in rats and monkeys and in the medial basal hypothalamus in monkeys. The percentage of neurons found in such associations was small (2-7% in rats and 3-15% in monkeys) and was independent of the hormonal condition of the animal. GnRH neurons, either singly or in pairs, were serially sectioned for electron microscopic examination. The sparsity of synaptic input to the cell body that we had reported earlier on the basis of random sampling was confirmed. No soma had more than a dozen synapses, but none totally lacked innervation. The most significant result of serial reconstruction was the discovery of intercellular bridges or passageways between contiguous pairs of GnRH neurons. These were formed by the fusion of processes extending from the two cells or by fusion and opening of passageways in the membranes along regions of contiguity between the two cells. They were found in four of seven pairs of neurons examined in the rat and in four of eight pairs in the monkey. This syncytial arrangement along with GnRH-GnRH synaptic interactions could contribute to the coordination of dispersed influences on these neurons and the propagation of coordinated pulsatile release of GnRH.

Animals↗
PubMed1981

Human bone marrow biochemical function and megaloblastic hematopoiesis after nitrous oxide anesthesia.

Prolonged exposure to nitrous oxide (N2O) inhibits bone marrow function. The duration of exposure to nitrous oxide necessary to induce these changes and their permanence is unknown. The possible prophylactic effect of prior treatment with folinic acid has not been examined previously. Bone marrow function in patients receiving nitrous oxide was assessed by the deoxyuridine (dU) suppression test. Morphologic changes in the bone marrow were also studied. One group was exposed for under 6 h, the next for between 12 and 24 h and a control group who received nonitrous oxide. The control group and the short exposure group showed no abnormality of bone marrow function. The long exposure group had abnormal dU supression tests and a megaloblastic hematopoiesis. The changes observed in this group resolved 12 h after discontinuance of the anesthetic. The changes observed could be prevented by the preoperative administration of folinic acid. The absence of either morphologic or dU suppression test abnormalities following N2O anesthesia for periods of less than 6 h confirms the safety of this anesthetic for the majority of operations for which it is used. It has been confirmed that prolonged exposure to the gas causes impaired marrow function which is of a temporary nature and may be prevented by the prior administration of folinic acid.

Anemia, Aplastic↗
PubMedDate not supplied

Quantitative detection of hepatitis C virus RNA in patients undergoing hemodialysis.

The purpose of the current study was to detect quantitatively hepatitis C virus (HCV)-RNA among patients undergoing maintenance hemodialysis. Study subjects were 88 patients on hemodialysis at the Miami Veterans Administration Medical Center and the REN Dialysis Unit at the University of Miami School of Medicine. There were 66 men and 22 women, mean age 52 years (range, 22-87 years), and mean duration of dialysis was 2.8 years (range 0.2-12.5 years). Seventy-three percent had a history of blood transfusion. Anti-HCV was determined by enzyme linked immunosorbent assay (ELISA), confirmed by four antigen strip immunoblot assay (RIBA 2.0 SIA). HCV-RNA was quantitated directly in human sera using a branched DNA (bDNA) signal amplification assay. Twenty-seven of 88 (31%) patient samples were found to be anti-HCV reactive by ELISA. Twenty-two of 27 were confirmed reactive, 2 were indeterminate, and 3 were nonreactive by RIBA HCV. Eighteen of 22 (82%) reactive by RIBA 2.0 HVC were found to have detectable (> 3.5 X 10(5) Eq/ml) HCV-RNA levels (mean [&/- SD], 43.3 +/- 35.4 X 10(5) Eq/ml; range 4.9-123.3). No additional cases were identified with reverse transcription polymerase chain reaction (RT-PCR) using 5' untranslated region "nested" primers. HCV-RNA was not detected in four RIBA HCV 2.0 reactive, the two intermediate, or the 64 patient samples nonreactive for anti-HCV. The two epitopes most commonly associated with HCV-RNA were c22-3 and c33c. Sixteen of 18 (89%) patients with detectable levels of HCV-RNA had normal alanine aminotransferase (ALT). Three patients with the highest levels of HCV-RNA were infected with the human immunodeficiency virus. The authors conclude that HCV-RNA by bDNA assay is a sensitive, specific, and simple test that can be used in association with antibody assays and a PCR-based assay to study the prevalence and management of HCV infection in the dialysis setting.

Adult↗