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Biomedical subjects

R Sullivan

Publications and source records attributed to R Sullivan.

At least 55 records · Page 3Linked to original sources
PubMed1998

cDNA sequence and deduced amino acid sequence of bovine oviductal fluid catalase.

A bovine oviductal fluid catalase (OFC) which preferentially binds to the acrosome surface of some mammalian spermatozoa has recently been purified. The objectives of this study were to clone the OFC, obtain the full-length cDNA and protein sequence and determine which characteristics of the proteins are associated with the binding of the enzyme to sperm surface. Northern blot analysis revealed low levels of catalase mRNA in bovine oviducts and uterus compared to the liver and kidney. Screening of a cDNA library from the cow oviduct permit to obtain a full-length cDNA of 2282 bp, with an open reading frame of 1581 bp coding for a deduced protein of 526 amino acids (59,789 Da). The deduced protein contained four potential N-glycosylation sites and many potential O-glycosylation sites. The OFC protein exhibited high identity with catalase from other bovine tissues, likewise with catalases from human fibroblast and kidney, and with rat liver catalase. The homology of amino acid sequence of OFC with bovine liver catalase was about 99%. However the OFC possess an extended carboxyl terminus of 20 amino acids not present on the liver catalase. This result is supported by a lower mobility of the OFC compared to the liver catalase when both proteins are submitted on SDS-PAGE.

Amino Acid Sequence↗
PubMed1998

Binding of a bovine oviductal fluid catalase to mammalian spermatozoa.

Hydrogen peroxide (H2O2) is a reactive oxygen species that at low concentration is toxic to sperm. H2O2 inhibits not only sperm viability but also the acrosome reaction, sperm-egg binding, and oocyte penetration. Catalase activates the decomposition of H2O2 into water and oxygen, thus removing an initiator of free radical chain reactions leading to lipid peroxidation. Since the oviduct is known to enhance sperm survival, we hypothesized that it might secrete catalase. We found that oviductal fluid, harvested from washed cells collected at the slaughterhouse, possessed catalase-specific activity that varied during the estrous cycle. Catalase activity increased during the cycle and reached its maximal level just before ovulation (Days 18-20). No significant difference in activity was seen between fluid from the isthmus and that from the ampulla. Indirect immuno-staining of spermatozoa incubated in the oviductal fluid revealed the association of catalase in the region of the acrosomal cap. Addition of a commercial antibody directed against bovine liver catalase completely inhibited catalase activities from the oviductal fluid. Catalase activity was also detected in porcine oviductal fluid, human oviductal fluid, and cervical mucus. Western blots of oviductal fluid probed with the anti-catalase antibody revealed two major bands at 60 and 40 kDa. An immunoaffinity column was used to purify oviductal catalase, showing a unique band at about 60 kDa when analyzed by SDS-PAGE. The purified protein was incubated with bovine, boar, and human sperm, and Western blots of these sperm after several washes detected a band at 60 kDa, indicating that the protein was bound to sperm membranes. However, bovine liver catalase did not bind to sperm. Since H2O2 is one of the key reactants in the chain reaction of free radical production, this enzyme may play an important role in sperm survival within the female tract.

Animals↗
PubMed1998

Cariostatic effects of a xylitol/NaF dentifrice in vivo.

Xylitol has been shown to reduce plaque acids, but its topical cariostatic effect has been equivocal. The purpose of the studies reported here was to optimise the xylitol/NaF combination in dentifrices for an improved anticaries activity. In the first study, the combination of 10 per cent xylitol with 1100 ppm F (NaF), 1100 ppm F (NaF), and placebo dentifrices were tested in a rat caries model to assess the cariostatic effect. The combination was significantly more effective than fluoride by itself (P = 0.05). The xylitol/NaF combination provided significantly more remineralisation of dentine than fluoride by itself. Collectively, results of these investigations confirm the improved anticaries effectiveness of the xylitol/NaF combination in a variety of animal and intra-oral models. A three-year clinical study confirmed these findings.

Acids↗
PubMed1998

Analysis of a Ca2+-activated K+ channel that mediates hyperpolarization via the thrombin receptor pathway.

Dami human leukemia cells express G protein-coupled thrombin receptors that operate through the phospholipase C pathway. When these receptors are activated by alpha-thrombin or by thrombin receptor-activating peptide, an elevation in cytosolic Ca2+ concentration develops that is accompanied by hyperpolarization of the plasma membrane. This transitory phase of hyperpolarization is primarily mediated by inwardly rectifying, Ca2+-activated K+ channels that have an inward conductance of approximately 24 pS. In cell-attached patches the channels open within seconds after superfusion of the cell with thrombin receptor-activating peptide. In inside-out patches, perfusion of submicromolar Ca2+ onto the cytosolic surface of the membrane is sufficient to activate the channels. In outside-out patches, channel opening can be blocked by nanomolar concentrations of charybdotoxin. The function of these intermediate-sized inwardly rectifying, Ca2+-activated K+ channels has not been established; however, by analogy with other cell systems, they may serve to regulate cell volume during cellular activation or to increase the electromotive drive that sustains Na+ and/or Ca2+ influx through ligand-gated cation channels.

Calcium↗
PubMed1998

Proto-surgery in ancient Egypt.

This article investigates the evidence we have for the existence of proto-surgery in ancient Egypt during the Dynastic Period (c.3200-323 BC). Climate and chance have preserved medical literature as well as paleoarcheological specimens and these artefacts, along with extant Greek and Roman treatises appear to support the conclusion that proto-surgery was practised in ancient Egypt (the prefix proto-designates an original or early form). Elements of proto-surgical development including analgesia and sedation, the incision, trephination, proto-surgery of trauma, mythical proto-surgery and antisepsis, drawing on primary sources, surviving artefacts and modern commentary are discussed. Where appropriate comparisons are made with proto-surgery in ancient Mesopotamia and the Bronze Age Aegean.

Egypt, Ancient↗
PubMed1997

Results from the Mars Pathfinder camera.

Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.

Atmosphere↗
PubMed1997

Cx43 gap junction gene expression and gap junctional communication in mouse neural crest cells.

Although gap junctions are not known to be important in mediating cell-cell interactions amongst migratory cells, our studies showed that the connexin 43 (Cx43) gap junction gene is widely expressed in mouse neural crest cell lineages. Using in situ hybridization analysis, Cx43 expression was detected in presumptive neural crest cells emerging from the neural folds of the early postimplantation embryo. Neural crest expression of the Cx43 gap junction gene was also indicated by the analysis of transgenic mice containing a lacZ reporter construct driven by the Cx43 promoter. In neural tube explant cultures of these transgenic mice, lacZ expression was observed in the emerging neural crest outgrowths. Whole mount X-gal staining of these transgenic embryos at various stages of development showed lacZ expression in neural crest cells distributed along the entire craniocaudal axis, with expression found in both cranial and trunk neural crest cells contributing to a wide range of embryonic tissues. This included presumptive cardiac neural crest cells localized in the heart. In light of the widespread expression of Cx43 in neural crest cell lineages, dye injection studies, were carried out to determine if neural crest cells are functionally coupled via gap junctions. Such studies revealed extensive dye coupling among presumptive neural crest cells, thus demonstrating that these migratory cells are indeed gap junctional communication competent. In total, these observations suggest that gap junctions may play a role in mouse neural crest development. This possibility is particularly intriguing given the recent finding that the Cx43 knockout mice die of defects associated with the outflow tract [Reaume et al., 1995], a region of the heart in which neural crest cells are required for normal development.

Animals↗
PubMed1997

Learning-induced changes in rat piriform cortex activity mapped using multisite recording with voltage sensitive dye.

The piriform cortex (PCx) has a potential role in storage and recall of olfactory information. This study is a first extensive investigation of the spatiotemporal distribution of activity in the PCx induced by learned sensory inputs following conditioning. In a conditioned group, rats chronically implanted with four electrodes in the olfactory bulb were trained to associate the electrical stimulation of a given bulbar electrode with a positive reinforcement, while stimulation of a different electrode predicted a negative reinforcement. In a familiarized group, rats received the same protocol of daily electrical stimulation with no associated reinforcement. At the end of the conditioning or familiarization episode, activity evoked in the PCx was optically mapped using a 144 photodiode array. In the anaesthetized rats, PCx maps were recorded in response to stimulation of each of the four bulbar electrodes using either high (0.5-1 mA) or low (0.1 mA) test current intensities. Low intensity stimulation revealed that conditioning selectively enhanced the probability of occurrence of a signal composed of a single late (56-73 ms) component which occurred almost simultaneously on a large PCx area. In the conditioned group, high intensity stimulation through either of the four electrodes revealed a potentiation of the early (17-30 ms) disynaptic component of the PCx response in the most posterior part of the PCx as well as a homogeneous increase of the late (39-52 ms) component spread over the PCx areas. These data suggest that learning induces synaptic changes at different nodes of the PCx circuitry.

Animals↗
PubMed1997

Complexity of the outward K+ current of the rat megakaryocyte.

Megakaryocytes isolated from rat bone marrow express a voltage-dependent, outward K+ current with complex kinetics of activation and inactivation. We found that this current could be separated into at least two components based on differential responses to K+ channel blockers. One component, which exhibited features of the "transient" or "A-type" K+ current of excitable cells, was more strongly blocked by 4-aminopyridine (4-AP) than by tetrabutylammonium (TBA). This current, which we designated as "4-AP-sensitive" current, activated rapidly at potentials more positive than -40 mV and subsequently underwent rapid voltage-dependent inactivation. A separate current that activated slowly was blocked much more effectively by TBA than by 4-AP. This "TBA-sensitive" component, which resembled a typical delayed rectifier current, was much more resistant to voltage-dependent inactivation. The relative contribution of each of these components varied from cell to cell. The effect of charybdotoxin was similar to that of 4-AP. Our data indicate that the voltage-dependent K+ current of resting megakaryocytes is more complex than heretofore believed and support the emerging concept that megakaryocytes possess intricate electrophysiological properties.

4-Aminopyridine↗
PubMed1997

Pyrexia after total knee replacement. A cause for concern?

Ninety patients who had undergone 92 total knee replacements were reviewed to determine predictors of postoperative pyrexia and to evaluate the relative value of septic screening in this group of patients. Postoperative pyrexia was defined as an axillary temperature greater than 37 degrees C (98.4 degrees F) on any or all of the 5 days after surgery. All of the patients in this series developed a postoperative pyrexia after knee arthroplasty. None of 16 patients (17% of arthroplasties) with a temperature of 39 degrees C (102 degrees F) or greater had evidence of infection. None of the 4 patients with urinary tract infections developed a pyrexia exceeding 38 degrees C (101 degrees F). At a minimum of 2 years' follow-up, none of the 90 patients had developed an infected arthroplasty. Logistic regression analysis showed that the risk of becoming significantly febrile (temperature > 39 degrees C) doubled for every unit drop in hematocrit and increased fourfold for each unit of blood transfused after surgery. Perioperative blood loss and pyrexia were correlated, but the correlation was not statistically significant. The duration of procedure, tourniquet time, and patient age or sex were not associated with risk of pyrexia. In this series, there was no association between a pyrexia greater than 37 degrees C, septic screening, and the presence of an infective focus. Early postoperative pyrexia after arthroplasty is a normal physiological response, and a significant pyrexia can be predicted by a drop in hematocrit and/or after postoperative transfusion. Pyrexia in the early postoperative period following total knee arthroplasty warrants detailed laboratory and radiographic investigation only in the presence of positive physical findings.

Aged↗
PubMed1996

Thrombin receptors activate potassium and chloride channels.

We used DAMI human megakaryocytic leukemia cells to study transmembrane ion currents activated through the G-protein-coupled thrombin receptor pathway. When the cells were stimulated by thrombin receptor-activating peptide, an increase in cytosolic Ca2+ ([Ca2+]i) developed as predicted by the known effect that thrombin exerts in the platelet. We then monitored the membrane potentials of individual DAMI cells during this response and observed complex, triphasic changes that could not be accounted for by Ca2+ fluxes alone. These consisted of rapid hyperpolarization, followed by depolarization to values more positive than the resting potential and then by slow repolarization. For the purpose of this study, we focused on the hyperpolarizing current that developed immediately after thrombin receptor activation. This proved to be composed of (1) a Ca(2+)-independent, outwardly rectifying Cl- current and (2) a strongly hyperpolarizing, inwardly rectifying, Ba(2+)-sensitive K+ current that required an increase of [Ca2+]i for activation. By analogy with their functions in other cell systems, it is logical to conclude that these prominent K+ and Cl- conductances may serve to regulate the complex volume changes that accompany thrombin receptor activation and/or to increase the electromotive drive that supports Ca2+ influx under these conditions through hyperpolarization of the cell membrane.

Amino Acid Sequence↗
PubMed1996

Contributions to senescence: non-enzymatic glycosylation of proteins.

Non-enzymatic glycosylation (NEG) of in vivo proteins is believed to play an important role in the process of senescence. Diabetes mellitus also provides a convenient model to study senescence, as many of its sequalae, e.g. neuropathy, retinopathy, may be found in the post seventy year old normoglycaemic population. Discoveries of the mechanisms by which proteins become irreversibly modified by chronic high levels of glucose and other reducing sugars, has led to an increased understanding of the pathophysiological consequences of senescence. This may eventually enable the development of suitable therapies to improve age-related morbidity.

Aging↗
PubMed1996

Surface localization of P34H an epididymal protein, during maturation, capacitation, and acrosome reaction of human spermatozoa.

During epididymal transit, spermatozoa acquire new surface antigens that are involved in the acquisition of their fertilizing ability. We have previously described a 34-kDa (P34H) human epididymal sperm protein that shows antigenic and functional homologies with the hamster P26h. P34H is localized on the acrosomal cap of human spermatozoa and has been proposed to be involved in the interaction with the zona pellucida. The aim of this study was to document the expression of P34H on the sperm surface during transit along the male and female genital tracts. Immunohistochemical techniques were performed on human testes and epididymides by means of an antiserum specific for P34H. No labelling was detected on those spermatozoa found within the seminiferous tubules or in the vasa efferentia. P34H first appeared in the caput epididymidis and was restricted to the acrosomal cap. Signal intensity then increased considerably from the proximal corpus to the cauda region of the epididymis. After ejaculation, the same pattern of P34H distribution was observed, but the intensity was much lower than that characterizing the cauda epididymal spermatozoa. Strong labeling was restored after incubation in B2 medium and was maximal after 5 h of capacitation. After acrosomal exocytosis induced by a Ca2+ ionophore, the percentage of P34H-labeled spermatozoa decreased proportionally to the number of acrosome-reacted spermatozoa as determined by Pisum sativum-fluorescein isothiocyanate (FITC) labeling. P34H appeared to be strongly anchored to the sperm plasma membrane during epididymal transit as indicated by the requirement for detergent to extract this surface antigen from ejaculated spermatozoa. This confirms the importance of P34H binding to the sperm plasma membrane during epididymal maturation. We have previously proposed that P34H is involved in sperm-zone pellucida interaction. The appearance and accumulation of P34H on the sperm plasma membrane during epididymal maturation, followed by its inaccessibility associated with ejaculation, its unmasking during capacitation, and finally its elimination after the acrosome reaction, are in agreement with te proposed function of this sperm antigen.

Acrosome↗
PubMed1996

Cases of human infertility are associated with the absence of P34H an epididymal sperm antigen.

The interaction of spermatozoa with the zona pellucida is a critical step of fertilization. Specific sperm surface proteins involved in this process can be added or modified during epididymal transit. We have previously described a 34-kDa human epididymal sperm protein (P34H) that we proposed to be involved in sperm-zona pellucida interaction. In this study, Western blot analysis were performed to determine the level of P34H protein present on the spermatozoa of 16 men with idiopathic infertility. These levels were compared with the amount of P34H protein found in men of proven fertility. In addition, a sperm-zona pellucida binding assay was performed with spermatozoa from fertile and infertile men. Spermatozoa obtained from different semen samples from a given individual had similar P34H levels. However, the amount of P34H varied from one man to another. Nine of 16 infertile men had a P34H level that was less than 30% of the normal value based on a population of fertile men, while the remaining 7 males were in the normal range. Sperm from infertile subjects with a normal P43H determination bound to zonae pellucidae as efficiently as those from controls. However, spermatozoa from subjects with a low amount of P34H exhibited a dramatic diminution in their ability to interact with zonae pellucidae. Our results show that the quantity of the epididymal protein P34H varied from one male to another and that low levels of this epididymal sperm protein are associated with certain cases of idiopathic infertility. Results are discussed with regard to the function of human epididymis in sperm maturation.

Adult↗