Search PubMed⌕ Search

Biomedical subjects

C Wood

Publications and source records attributed to C Wood.

At least 181 records · Page 10Linked to original sources
PubMed1994

UREA PRODUCTION, ACID-BASE REGULATION AND THEIR INTERACTIONS IN THE LAKE MAGADI TILAPIA, A UNIQUE TELEOST ADAPTED TO A HIGHLY ALKALINE ENVIRONMENT

The Lake Magadi tilapia, Oreochromis alcalicus grahami, thrives in highly alkaline geothermal springs and pools surrounding Lake Magadi, Kenya (control pH=9.9, CCO2=173 mmol l-1), has a functional hepatic ornithine­urea cycle (OUC) and excretes all nitrogenous waste as urea-N at variable rates (JUrea) related to O2 consumption (M·O2). The mean value of JUrea/M·O2 (N/O2=0.183) was high for fish but below the theoretical maximum (approximately 0.27) for 100 % aerobic respiration of protein, so an exogenous source of substrates is not required to explain the observed JUrea. JUrea was insensitive to thiourea. Urea excretion occurred largely (80 %) through the gills, but urea-N was also present in bile and urine. Control blood pHe, pHi and [HCO3-] (approximately 8.1, 7.6 and 15 mmol l-1, respectively, at approximately 32°C) were extremely high. When fish were exposed to lake water titrated with HCl and aerated to remove CO2, N/O2 progressively declined. At a lake water pH of 7.05 and CCO2 of 0 mmol l-1, N/O2 was reduced by 80 % and an intense metabolic acidosis occurred (pHe=7.04, [HCO3-]=1.5 mmol l-1). Restoration of control water pH 9.9 at a CCO2 of 0 mmol l-1 resulted in intermediate levels of N/O2 and internal acid­base status. Additional experiments confirmed that urea production was inhibited by low pHe, was dependent on blood [HCO3-] with a Km of 3.06 mmol l-1 and was insensitive to acetazolamide. While metabolic acidosis clearly inhibited OUC ureagenesis, the system appeared to be saturated with HCO3- under control conditions so that additional basic equivalent loading would not stimulate ureagenesis. Urea production in the Lake Magadi tilapia does not appear to remove exogenous HCO3- or to play a role in normal acid­base regulation.

Journal Article↗
PubMed1994

AMMONIA EXCRETION IN FRESHWATER RAINBOW TROUT (ONCORHYNCHUS MYKISS) AND THE IMPORTANCE OF GILL BOUNDARY LAYER ACIDIFICATION: LACK OF EVIDENCE FOR Na+/NH4+ EXCHANGE

Net ammonia fluxes (JAmm) were measured in adult freshwater rainbow trout in vivo under a variety of conditions designed to inhibit unidirectional sodium uptake (JinNa; low external [NaCl], 10(-4) mol l-1 amiloride), alter transbranchial PNH3 and NH4+ gradients [24 h continuous (NH4)2SO4 infusion, or exposure to 1 mmol l-1 external total ammonia at pH 8] and prevent gill boundary layer acidification (5 mmol l-1 Hepes buffer). Inhibition of JinNa with amiloride or low external [NaCl] under normal conditions reduced JAmm by about 20 %, but did not prevent the net excretion of ammonia during exposure to high concentrations of external ammonia. Increasing the buffer capacity of the ventilatory water with Hepes buffer (pH 8) reduced JAmm by 36 % and abolished the effect of amiloride on ammonia excretion. No evidence could be found to support a directly coupled apical Na+/NH4+ exchange. We suggest that any dependence of ammonia excretion on sodium uptake is caused by alteration of transbranchial PNH3 gradients within the gill microenvironment secondary to changes in net H+ excretion. Under normal conditions (pH 8, low external ammonia) gill boundary layer acidification facilitates over one-third of the total ammonia excretion. During exposure to high concentrations of external ammonia in poorly buffered water, estimates of transbranchial PNH3 gradients from measurements of bulk water pH and total ammonia concentration (TAmm) may be grossly in error because of boundary layer acidification. Prevention of boundary layer acidification with Hepes buffer during exposure to high cocncentrations of external ammonia revealed that the local transbranchial PNH3 gradient at the gill may in fact be positive (blood to water), negating the need for an active NH4+ transport mechanism. In freshwater trout, NH3 diffusion may account for all ammonia excretion under all experimental conditions used in the present study.

Journal Article↗
PubMed1994

UREA TRANSPORT BY HEPATOCYTES AND RED BLOOD CELLS OF SELECTED ELASMOBRANCH AND TELEOST FISHES

Although urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. This study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (Scyliorhinus canicula), Atlantic stingray (Dasyatis sabina), turbot (Scopthalmus maximus), redfish (Scianops ocellatus), gulf toadfish (Opsanus beta) and oyster toadfish (Opsanus tau). Urea appeared to be passively distributed in both tissues (i.e. there was no difference between plasma and tissue urea concentrations). Additionally, a number of in vitro experiments examining [14C]urea flux were performed. In red blood cells from all species except redfish, urea transport occurred via simple passive diffusion, but redfish red blood cells showed a small (25 %) phloretin-sensitive uptake component. In hepatocytes of the two elasmobranch species (dogfish and stingray), urea efflux was also by simple passive diffusion. However, urea efflux in toadfish (both O. beta and O. tau) hepatocytes exhibited a marked phloretin-sensitivity, and O. beta hepatocytes were used in further experiments with other inhibitors and treatments. Urea transport in O. beta had a relatively high specificity for urea compared with the urea analogues acetamide, thiourea and N-methylurea, was unaffected by phloridzin and extracellular Na+ removal, and was not inhibited by physiological levels of glucose (0.5­10 mmol l-1). A phloretin-sensitive glucose transport, that was not inhibited by physiological levels of urea, was discovered in O. beta hepatocytes. The results are discussed in terms of patterns of species distribution and similarities between urea and glucose transport.

Journal Article↗
PubMed1994

CARBONIC ANHYDRASE INJECTION PROVIDES EVIDENCE FOR THE ROLE OF BLOOD ACID-BASE STATUS IN STIMULATING VENTILATION AFTER EXHAUSTIVE EXERCISE IN RAINBOW TROUT

This study tests the hypothesis that the increase in blood PCO2 and associated respiratory acidosis after exhaustive exercise play an important role in stimulating ventilation during post-exercise recovery in fish. Injection of bovine carbonic anhydrase (10 mg kg-1) into the bloodstream of rainbow trout caused a persistent 40 % increase in the HCO3- dehydration capacity of the blood. The treatment was designed to increase CO2 excretion and therefore to reduce PCO2 build-up and acidosis after exercise. Aerobic and anaerobic swimming performance were not affected by carbonic anhydrase, and there were only very minor effects on arterial blood acid­base status in resting fish. However, carbonic anhydrase attenuated post-exercise increases in PaCO2 and decreases in pHa by about 50 % without altering arterial O2 variables, red cell swelling or the intracellular pH of the brain or muscle tissues. The effects on arterial pH (pHa) resulted largely from alleviation of the increase in PaCO2. In accordance with the original hypothesis, normal post-exercise hyperventilation was greatly attenuated, through reductions in both ventilatory stroke volume and frequency, and excess post-exercise O2 consumption was reduced. Post-exercise increases in plasma levels of adrenaline and noradrenaline were also reduced by the carbonic anhydrase treatment. Overall, there was a strong correlation between increases in relative ventilation and decreases in pHa after exhaustive exercise. The results provide functional significance for the phenomenon of PaCO2 elevation and associated respiratory acidosis after exercise and are consistent with other recent studies indicating an important secondary drive to ventilation in fish based on arterial acid­base status, in addition to the primary drive based on arterial O2 levels.

Journal Article↗
PubMed1994

Brain injury: personality, psychopathology and neuropsychology.

This study investigated the relationship between brain injury and personality, using the Luria-Nebraska Neuropsychological Battery and the Clinical Analysis Questionnaire as measurement tools. Psychopathological factors, as opposed to normal personality traits, were highly correlated with measures of brain injury. Depression, in particular, was found to be substantially involved in the sequelae of brain injury for this sample. A trend in the data revealed that suicidal depression and anxious depression were differentially related to deficits on two scales of the LNNB. Patients with evidence of suicidal depression were also more sensitive to emotional dysfunction in other areas. Few differences were found between patients with traumatic brain injury and those with other types of brain injuries. Results suggest that measures of psychopathology can provide important supplementary information to neuropsychological assessment, above that obtained from measures of brain functioning alone. Controlled studies should investigate the relationship between psychopathology and neuropsychology more thoroughly to provide clearer determinations of its involvement in the rehabilitation of the brain-injured person.

Adolescent↗
PubMed1994

[Pre- or neonatal corticotherapy: what are the long-term consequences?].

This paper is a literature overview on the potential long-term side effects of steroid therapy in the prenatal and neonatal period. Incomplete and transient suppression of adrenal function without growth impairment has been reported in prolonged treatment with steroids for bronchopulmonary dysplasia. There seems to be no secondary chronic immune dysfunction. There is evidence for deleterious effects on lung and brain development in experimental animals. In human preterm neonates, no pulmonary and cerebral secondary effects were observed after short prenatal steroid courses, but it is as yet uncertain whether this applies also to prolonged steroid therapy which requires further long-term investigations, including school performance.

Adrenal Cortex Hormones↗
PubMed1994

Minimally invasive surgery in assisted conception.

Minimally invasive surgery enables the avoidance of, preparation for, participation in, and treatment of complications following assisted reproductive technology (ART). The major recent changes are, the development of surgical techniques to diagnose and treat intrafallopian tubal abnormalities; the use of operative endoscopy to avoid radical surgery in the treatment of severe endometriosis and large myomas; the use of endoscopy in the selection of patients for ART; the extension of gamete intrafallopian transfer (GIFT) procedures to include operative laparoscopy for endometriosis and adhesions; the ability to collect unripe oocytes from small follicles, thereby reducing the need for stimulated ovarian cycles in patients with polycystic ovaries; the ability to produce normal pregnancies from the intra-oocyte injection of a single sperm, which facilitates the treatment of severe male infertility; and the development of a promising technique to transfer an embryo to the uterus through the myometrium, thereby avoiding the cervical canal.

Embryo Transfer↗
PubMed1993

IVF and related technology. The present and the future.

OBJECTIVE: To describe the current status of in-vitro fertilisation (IVF) and related technologies, including: the indications for the procedures and the problems associated with the use of stimulated cycles; the use of frozen embryos and donor eggs; and the newer procedures of gamete micromanipulation for male infertility, immature egg collection as a possible alternative to the stimulated cycle, and preimplantation genetic diagnosis. DATA SOURCES AND STUDY SELECTION: The clinical experience and research at Monash IVF and the Centre for Early Human Development, Monash University, were reviewed in association with key original or review articles in the world literature. DATA SYNTHESIS: Cumulative pregnancy rates for IVF and the gamete intrafallopian transfer (GIFT) procedure at Monash IVF demonstrate that 29% of IVF patients and 55% of GIFT patients will have a live baby, the average number of treatments pursued being 3.4. Analogues of gonadotrophin releasing hormone (GnRH) have improved pregnancy rates, reduced blood sampling, and prevented natural ovulation. Disadvantages of stimulated cycles include a higher risk of multiple pregnancy, a higher risk of hyperstimulation, and behavioural changes due to the effects of drugs. Natural cycles or immature egg collection at incidental laparoscopy may become alternatives to the use of the stimulated cycle. In Australia the GIFT procedure is more successful than IVF and is nearly always used if the fallopian tubes are normal. Multiple pregnancies may be reduced, particularly triplets, by reducing the number of eggs or embryos transferred to two when egg or embryo quality is high. Embryo freezing has made a small but important contribution to overall pregnancy rates by enabling patients to use excess eggs and embryos. The social and legal concerns resulting from the use of frozen embryos have required new ethical and legal considerations. Donor eggs have made a small contribution to achieving pregnancy in women with absent or inappropriate eggs and increased the chance of conception in women over the age of 40. Micromanipulation of sperm and eggs has enabled fertilisation and conception when sperm are defective in quantity or quality. Sampling of cells in early embryos enables genetic diagnosis and may be used in selecting chromosomally normal embryos in IVF procedures or in couples at risk of recessive genetic disease. CONCLUSION: Assisted reproductive technology has developed over a decade to become useful for couples with infertility which cannot be cured by simpler treatments. The birth rates are comparable to natural conception and the incidence of congenital malformation is not increased. The costs and complexity of treatment have been reduced to in turn reduce the stress and social inconvenience of therapy. Problems related to the high risk of multiple pregnancy and the use of the stimulated cycle are being reduced and new techniques for severe male infertility and the detection of genetic abnormalities in the embryo are being introduced.

Female↗
PubMed1993

Percutaneous ultrasound guided uterine needle biopsy.

OBJECTIVE: To determine the safety, accuracy and usefulness of percutaneous ultrasound guided uterine needle biopsy. SETTING: Transabdominal uterine biopsy was performed with an ultrasound directed biopsy gun. The biopsy was performed as an outpatient procedure under local anaesthesia. MAIN OUTCOME MEASURES: The safety, accuracy and clinical value of the procedure; a comparison of the clinical and ultrasound diagnoses with the biopsy and surgical histological diagnoses; and the effect of the biopsy result on the choice of treatment by the surgeon and patient. RESULTS: There were no complications. Accuracy was validated in all seven patients who subsequently had surgical procedures and more extensive myometrial histological investigation. Biopsy diagnosis improved clinical diagnosis in nine of the ten patients, and altered or assisted in the ultrasound diagnosis in eight of the ten patients. Decisions concerning choice of treatment by the doctor or patient were assisted by the biopsy result in seven patients. CONCLUSION: Percutaneous ultrasound guided uterine needle biopsy is a useful procedure in the diagnosis of myometrial disease.

Adult↗
PubMed1993

Identification and characterization of glycoprotein gH of human herpesvirus-6.

Sequence analysis of an 8-kb BamHI-G DNA fragment from human herpesvirus-6 variant A strain GS (HHV-6A(GS)) has identified a gene encoding a glycoprotein homologous to glycoprotein gH of other herpesviruses and this gene was designated as HHV-6 gH (Josephs et al., J. Virol. 65, 5597). The open reading frame (ORF) of HHV-6A(GS) gH gene was amplified by polymerase chain reaction and was expressed as a trpE fusion protein in bacteria. Stable fusion protein was made only with constructs containing amino acids 15 to 469 of the ORF and this fusion protein was used to raise rabbit antisera. In the in vitro transcription-translation analysis of the gH gene, addition of microsomal membranes resulted in the processing of an unprocessed precursor to a polypeptide product of about 108 K. These in vitro-synthesized precursor and product forms were immunoprecipitated by the rabbit antibodies against the gH fusion protein. Rabbit anti-gH antibodies neutralized the infectivity of both HHV-6 variant A strain GS and variant B strain Z-29, and immunoprecipitation reactions identified a virion envelope-associated 102 K polypeptide as the glycoprotein gH of HHV-6 variants A and B. In addition to the 102 K glycoprotein, nonglycosylated polypeptides of about 58 and 164 K with different partial peptide maps were also consistently coimmunoprecipitated from [35S]methionine-labeled HHV-6A(GS)-infected cells, but not from HHV-6B(Z-29)-infected cells. The similarity in the molecular weights of glycoprotein gH among the two strains belonging to the two variant groups of HHV-6 and neutralization of infectivity of both groups by rabbit antibodies against HHV-6A(GS) gH suggests conserved functions of glycoprotein gH among the two variant groups of HHV-6.

Antibodies, Viral↗
PubMed1993

Disseminated cutaneous and vascular invasion by Fusarium moniliforme in a fatal case of acute lymphocytic leukemia.

A 35 year old female patient with acute lymphocytic leukemia developed fusariosis in which dissemination appeared to be limited to cutaneous and vascular invasion. The first evidence of fungemia occurred nearly seven months after initial hospitalization. The fungus was identified as Fusarium sp. and was considered a contaminant. Two weeks later blood cultures were again positive for Fusarium sp. and the patient was placed on amphotericin B and 5-fluorocytosine therapy. The following day developing lesions were noted on her forearms and face; lesions ultimately spread to her trunk, abdomen, and lower extremities. Skin lesion biopsy sections revealed abundant septate and branching hyphae throughout the dermis and within capillaries. Twenty-six days after the initial isolation the patient died. Post-mortem blood cultures gave rise to the same fungus, which was identified as Fusarium moniliforme. Postmortem cultures and stains of spleen, liver, lung, and brain specimens were all negative for fungi. The primary source and portal of entry of the organism remained undetermined.

Adult↗
PubMed1993

Laparoscopic endocorporeal mobilization followed by extracorporeal sutureless anastomosis for the treatment of carcinoma of the left colon.

Surgery has become progressively more reliant on technology. The technique of colonic anastomosis utilizing the biofragmentable anastomotic ring (BAR) is one such example. The benefits of therapeutic laparoscopy have been applied to the arena of colorectal surgery. A case is presented that combines these two modalities in a patient with colon cancer, laparoscopic mobilization of the large bowel, exteriorized resection, and BAR anastomosis.

Adenocarcinoma↗
PubMed1993

In vitro detection of bovine immunodeficiency-like virus using monoclonal antibodies generated to a recombinant gag fusion protein.

An Escherichia coli recombinant fusion protein containing the major core protein of bovine immunodeficiency-like virus (BIV) was used to immunize mice for generation of monoclonal antibodies to BIV p26. Eight hybridomas specific for BIV p26 were identified and two antibodies, designated 104 and 142, were further characterized. Both 104 and 142 antibodies were isotyped as IgG1; they reacted specifically with both BIV p26 and the recombinant fusion protein in Western immunoblot analyses. However, the epitope specificity of the antibodies was different. Immunoperoxidase assays were used to determine if antibodies 104 and/or 142 could detect BIV replication in cell culture. Both antibodies were found to react with BIV-induced syncytia and individual BIV-infected cells. The antibodies were also used successfully in a focal immunoassay for quantitation of BIV-infected cells. These antibodies will provide valuable reagents for detection and quantitation of BIV replication in studies of viral pathogenesis and immunity.

Animals↗