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Biomedical subjects

J Dark

Publications and source records attributed to J Dark.

At least 55 records · Page 3Linked to original sources
PubMed1990

T tube intubation in the management of seriously ill patients with oesophagopleural fistulae.

Ten patients referred late with oesophagopleural fistulae were managed by T tube intubation of the oesophageal defect. Seven survived and six had radiographic evidence of closure of the defect. One patient who removed his T tube early was discharged to convalesce with a small oesophagocutaneous fistula. Three patients died as a consequence of pre-existing renal failure, upper gastrointestinal haemorrhage and adult respiratory distress syndrome. Patients presenting late with multisystem complications and ongoing sepsis secondary to oesophagopleural fistulae pose a major management problem. Our preliminary results suggest that T tube intubation offers a potential alternative to major surgical intervention, when more conservative measures have failed.

Acute Kidney Injury↗
PubMed1990

Isolated lung transplantation for pulmonary fibrosis.

The peri-operative anaesthetic management of 11 patients with pulmonary fibrosis undergoing single-lung transplantation is presented. Intra-operative problems, the early postoperative phase of recovery and intensive care, and other incidents in which general anaesthesia was required for the management of complications, are featured. Results, both short- and long-term, are mentioned. Major intra-operative events that cause concern appear to be related to the severity of the presenting illness and the development of respiratory failure. Others have reported the development of intra-operative cardiac failure. All cases were successfully managed operatively using conventional one-lung anaesthesia, although resort to partial cardiopulmonary bypass may have been indicated in some. The indications and attitudes to utilising cardiopulmonary bypass in the evolution of techniques for facilitating single-lung transplantation are reviewed.

Adult↗
PubMed1990

Role of mediastinoscopy in the diagnosis of mediastinal masses.

In order to assess the diagnostic efficiency of mediastinoscopy in patients with undiagnosed mediastinal masses, a retrospective review was undertaken of the results obtained in a consecutive series of 42 patients presenting over a 5-year period. In 28 (67%) patients, a tissue diagnosis was made. Ten (24%) patients underwent a negative mediastinoscopy but were found to have significant pathology on further investigation (eight in a location outside the range of conventional mediastinoscopy). Four (10%) patients had negative findings and were confirmed to have no significant pathology on further investigation and follow-up. Overall, mediastinoscopy had a sensitivity of 74%, a specificity of 100% and an accuracy of 76%; however, for lesions within the range of mediastinoscopy, the sensitivity was 93%, the specificity 100% and the accuracy 94%. The predictive value of a negative examination was 66%. Mediastinoscopy is a valuable technique in the diagnosis of mediastinal masses but, because of the low predictive value of a negative examination, further evaluation, including thoracotomy if necessary, is still indicated if mediastinoscopy is unhelpful.

Adolescent↗
PubMed1989

Adipose tissue dynamics during cyclic weight loss and weight gain of ground squirrels.

Ad libitum fed golden-mantled ground squirrels undergo marked annual fluctuations in body mass; during the first cycle, peak and trough masses were approximately 291 and approximately 192 g, respectively. Peak masses were significantly higher (9%) during the second than the first cycle, reflecting a 15% increase in fat-free dry mass and a 12% increase in lipid reserves. The reduction in body mass during the weight loss phase was almost entirely due to an 84% decrease in total lipid reserves and reflected a decrease in adipocyte size but not number. All measured fat depots decreased at similar rates, and there was no evidence of preferential utilization or sparing of individual depots. Fat cell size decreased progressively in each depot during the transition from peak to trough masses and did not vary among the several depots at any stage of annual cycle. Adipocyte number increased in parametrial and retroperitoneal depots but not in the subcutaneous fat between the first and second body mass peaks; fat cell size in these two depots decreased by 28 and 20%, respectively, from the first to the second peak in body mass. Reduced lipid filling of adipocytes at the second peak mass, concomitant with adipocyte hyperplasia, suggests that total lipid mass, not simply fat cell size, is regulated during the annual body mass cycle. Maturation of the subcutaneous fat depot before the initial entry into hibernation may be adaptive in providing insulation during dormancy.

Adipose Tissue↗
PubMed1988

Lipectomy influences white adipose tissue lipoprotein lipase activity and plasma triglyceride levels in ground squirrels.

Golden-mantled ground squirrels undergo marked fattening and fat depletion during the prehibernatory and hibernatory phases, respectively, of their annual body weight cycle. Fat regulation was studied by surgical removal (lipectomy) of most of the inguinal-subcutaneous, retroperitoneal, and parametrial fat depots from female squirrels during the weight-gain phase of the annual cycle. Seven weeks after surgery, body weights of lipectomized (Lipx) and Sham-Lipx squirrels were equivalent, although white adipose tissue was not completely recovered in Lipx animals. Lipoprotein lipase (LPL) activity was markedly elevated in subcutaneous adipose tissue of Lipx squirrels, but not in other depots. Plasma triglyceride (TG) levels also were higher in Lipx squirrels 7 weeks after surgery. Changes in LPL activity and plasma TG may contribute to body mass and lipid restoration following lipectomy.

Adipose Tissue↗
PubMed1988

Pineal and photoperiodic influences on fat deposition, pelage, and testicular activity in male meadow voles.

Pinealectomy completely prevented gonadal regression as well as reduction in body weight and white adipose tissue content of the gonadal and retroperitoneal fat deposits in male meadow voles transferred from long to short day lengths. Pineal influences on pelage characteristics depended on which parameter was assessed. For instance, the increase in guard hair length observed in short-day control voles was blocked by pinealectomy; however, a similar increase in underhair length was unaffected by removal of the pineal gland. Photoperiod-dependent changes in fat deposition, testicular activity, and guard hair length presumably rely on altered pineal secretory activity to transduce the effects of day length on the neuroendocrine axis; however, mechanisms independent of pineal activity may be capable of mediating photoperiodic control of underhair growth.

Adipose Tissue↗
PubMed1987

Long day lengths increase brain weight and DNA content in the meadow vole, Microtus pennsylvanicus.

Male voles reared in long (spring) day lengths had heavier brains with greater total DNA content than did males housed in short (fall) day lengths; these effects were not observed in female littermates kept in the two photoperiods. Male brains were heavier than female brains in long but not in short photoperiods. Day length affected brain mass during early postnatal development, but not when treatments were initiated in adulthood. Seasonal differences in brain development, including the numbers of neurons and glia, may reflect different metabolic and behavioral demands faced by males born in spring and fall, respectively.

Animals↗
PubMed1987

Androgens exert opposite effects on body mass of heavy and light meadow voles.

The influence of gonadal hormones on body mass of adult male meadow voles varied systematically as a function of the animals' baseline body weight; heavier voles decreased and lighter voles increased their body mass after castration. Testosterone replacement reversed the effects of castration; changes in body mass during hormone treatment were negatively correlated with changes observed after castration. Body mass of intact males was not correlated with plasma testosterone titers. Individual differences in body mass of male voles appear to reflect variations among animals in substrate responsiveness to hormones rather than differences in circulating hormone levels.

Androgens↗
PubMed1987

Sensory innervation of white adipose tissue.

The presumption that sensory information does not arise from white adipose tissue was reevaluated using the neuroanatomical tracer, "true blue." Fluorescent cell bodies were observed in dorsal root ganglia of rats after tracer was implanted into inguinal or dorsal subcutaneous fat depots. Sensory information from adipose tissue may play an important role in the regulation of regional and total body fat mass.

Adipose Tissue↗
PubMed1987

Effect of acute diaphragm paralysis on ventilation in awake and sleeping dogs.

The mechanisms responsible for hypoventilation during rapid-eye-movement (REM) sleep in patients with diaphragmatic weakness are not clear. Therefore, we studied the effects of unilateral (UDP) and bilateral (BDP) diaphragmatic paralysis on ventilation during wakefulness (W), slow-wave sleep (SWS), and REM sleep. Studies were performed in 3 trained dogs in which small silicone cuffs had been implanted surgically around the phrenic nerves. Reversible diaphragmatic paralysis was induced during wakefulness or sleep by bathing the phrenic nerves in local anesthetic injected through a catheter attached to the phrenic cuffs. The UDP reduced abdominal expansion and increased rib cage expansion, but had no effect on minute volume of ventilation (VI) or end-tidal PCO2 (PACO2). The BDP produced marked abdominal paradox, but did not reduce VI during W or SWS and had no effect on tidal volume or respiratory frequency. In contrast, during REM sleep, VI was decreased by an average of 21% mainly because of a fall in tidal volume, and PACO2 increased by 2.4 mm Hg compared with that during the intact state. Furthermore, addition of extra dead space to the breathing circuit, which was well tolerated in intact dogs, led to a progressive increase in PACO2 during BDP and to arousal from sleep. The findings indicate that acute BDP does not impair ventilation during quiet W or SWS, but reduces ventilation during REM sleep, supporting the concept that during REM sleep maintenance of ventilation is critically dependent on diaphragmatic compensation for intercostal and accessory muscle inhibition.

Animals↗
PubMed1987

Influence of daylength experienced by dams on post-natal development of young meadow voles (Microtus pennsylvanicus).

Meadow voles born to dams kept in short days (SD) beginning 5 or 11 weeks before parturition (SD-5, SD-11) had less developed testes, gained weight more slowly and built larger nests than did young gestated and maintained in long days (LD). Pelage development was greater in SD than in LD young at 21 and 45 days of age. At weaning, SD-5 young had less dense fur and shorter guard hairs than did SD-11 young, indicating that the photoperiodic history of dams before insemination affects the post-natal pelage development of their progeny. Short daylengths experienced by dams before mating may facilitate winter preparedness of their offspring.

Animals↗
PubMed1987

Role of photoperiod during pregnancy and lactation in the meadow vole, Microtus pennsylvanicus.

The influence of daylength on body mass and food intake of pregnant and lactating voles was tested by comparing animals housed in long versus short daylengths. Pregnancy rates were approximately 50% in long-day females and in voles kept in short days beginning 2 weeks before mating, but were significantly lower in voles preadapted to short days for 8 weeks before mating. Body mass and food intake increased substantially during pregnancy and lactation and the magnitude of the increase was unaffected by daylength; by contrast, body weight was significantly reduced in non-impregnated voles kept in short as compared to long days. The suppressive effects of short photoperiods on body weight were completely counteracted during pregnancy and lactation. Voles that breed during the short days of winter face extreme energetic challenges but the advantages of early breeding appear to justify the costs.

Animals↗
PubMed1987

Interaction of daylength and lactation in the control of pelage development and nest-building in female meadow voles (Microtus pennsylvanicus).

Pregnancy and lactation inhibited moult into winter pelage in voles maintained in short daylengths; development of a winter pelage was, however, greatly accelerated once the short-day dams weaned their litters. The presumed elevation of prolactin titres during lactation appears to mask full development and expression of pelage changes induced by short daylengths. Nest-building behaviour, by contrast, was increased in response to short photoperiods and was further augmented during lactation and may thereby facilitate thermoregulation in short-day dams that do not develop a winter pelage.

Animals↗
PubMed1987

Transplantation of the lungs.

After years of disrepute, single-lung transplant now seems to be a suitable form of treatment for a carefully selected group of patients with end-stage pulmonary fibrosis. In addition, there is the prospect of treating a wider range of pulmonary diseases in the near future, with the appropriate use of double-lung and heart-lung transplants.

Forecasting↗
PubMed1986

Photoperiodic regulation of body mass and fat reserves in the meadow vole.

Short photoperiods reduce both body mass and food intake of male meadow voles. To help determine whether the primary effect of short day lengths is on regulation of some component of body mass or on the control of food consumption, voles housed in a long photoperiod were provided rations equivalent to those consumed by animals in short day lengths. Animals were transferred to a short photoperiod and after either 3 or 6 weeks of food restriction were fed ad lib. Both groups of voles overate after termination of food restriction and achieved seasonally appropriate body masses that were influenced by the duration of short photoperiod treatment. We conclude that short photoperiods gradually alter the regulated level of one or more components of body mass. We tested and failed to support the hypothesis that the subcutaneous fat depot is selectively spared during seasonal weight loss and thereby increases surface insulation. Thus, the proportion of adipose tissue reduction did not differ significantly among the epididymal, retroperitoneal, and inguinal-subcutaneous fat depots of voles housed in short day lengths.

Adipose Tissue↗
PubMed1986

Short day lengths decrease body mass of overweight female meadow voles.

Groups of adult ovariectomized (ovx) voles and sham-ovx controls were placed in a short photoperiod or left in the original long photoperiod (10 or 14 hr light/day). In the next 12 weeks long-day ovx voles increased their body mass by 11.3%, whereas animals transferred to the short-day photoperiod manifested an 11.9% decline in body mass. Short photoperiods not only reversed pre-existing weight gains attributable to ovariectomy, but also prevented further increases in body mass associated with the withdrawal of ovarian hormones. Fat-free dry carcass mass was increased by ovariectomy and decreased by short photoperiods; lipoprotein lipase activity of white adipose tissue was unaffected by ovariectomy or photoperiod. We suggest that reductions in body mass in voles transferred to the short photoperiod are mediated by changes in pineal melatonin secretion.

Adipose Tissue↗
PubMed1986

Fat ablation and food restriction influence reproductive development and hibernation in ground squirrels.

The role of white adipose tissue in development of the reproductive apparatus of male golden-mantled ground squirrels was assessed by surgical removal of fat (lipectomy) immediately prior to onset of hibernation or by manipulation of fat levels through food restriction for 5 wk preceding hibernation. Animals then were maintained without food at 6 degrees C, and they hibernated from November 1983 until April 1984. At that time, blood plasma was assayed for hormone levels, and body mass, body composition, and masses of the testes and seminal vesicle-prostate complex were determined. At autopsy, testes and sexual accessory organs were heavier in Control squirrels than in Food-Restricted or Lipectomized (LIPX) animals. Paired-testes mass was positively correlated with body mass. Testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels were uniformly low in animals sampled during torpor, but were elevated in 2 animals that had regained the euthermic state. The Food-Restricted animals spent more time in torpor than did the other two groups, and the percentage of decrease in body mass over the hibernation season was less for Food-Restricted than for LIPX or Control animals. Adequate lipid stores may be essential for the normal development of the reproductive apparatus of male ground squirrels. In the field, animals with insufficient fat stores may forego reproduction and thereby conserve energy for survival.

Adipose Tissue↗