Search PubMed⌕ Search

Biomedical subjects

S Thomas

Publications and source records attributed to S Thomas.

At least 649 records · Page 36Linked to original sources
PubMed1987

Inoperable aortic stenosis in the elderly: benefit from percutaneous transluminal valvuloplasty.

Eight patients with severe symptomatic calcific aortic stenosis were considered to be unsuitable for valve replacement. Four were admitted with pulmonary oedema and three in cardiogenic shock and one had angina at rest. With the use of echocardiographic and radiographic guidance percutaneous transluminal aortic valvuloplasty was carried out. Aortic gradients were reduced by an average of 40%. All four patients who presented with cardiac failure improved immediately and remained well six months later. The patient with angina was symptom free at nine months. Two of the three patients who presented in cardiogenic shock improved immediately and were well nine and three months later. The other patient died four hours after the procedure. Doppler echocardiographic studies showed a slight initial increase in aortic incompetence, but this did not worsen and valvar gradients remained improved three and six months later. Percutaneous valvuloplasty of the aortic valve is an effective therapeutic option in patients with severe calcific aortic stenosis who are unfit for surgery. Its role as an alternative to surgery has not been considered and should be investigated in a controlled clinical trial.

Aged↗
PubMed1987

Effects of graded exercise on blood gas tensions and acid-base characteristics of rainbow trout.

A swim tunnel respirometer and an extracorporeal blood circulation technique allowed continuous collection of data from exercising fish below and near their critical speed. Swimming at speeds below maximum showed no changes in plasma Na+, Cl- and lactate concentrations but increased levels of blood hemoglobin and plasma K+. PaO2 and PaCO2 showed an exponential decrease and increase respectively and related to swimming speed. Increased swimming speed changed the acid-base status toward a mixed respiratory and metabolic acidosis. Upon reaching maximum speed sudden and large increases in plasma Na+, K+ and lactate concentrations occurred associated with a large metabolic acidosis.

Acid-Base Equilibrium↗
PubMed1987

Length polymorphisms of the human Y chromosome in patients with chronic myelogenous leukemia.

The extent of length heteromorphisms of the human Y chromosomes was measured in 50 patients with chronic myelogenous leukemia and was compared with 50 normal controls. No significant difference (p greater than 0.05) in the size of the Y chromosome was noted between these two groups. These findings differ from an earlier investigation, where a longer heterochromatic segment of Y chromosome was noted in malignant tumors and it was stressed that constitutive heterochromatin plays a role in susceptibility of cancer. Present investigation, however, suggests that this is not the case in patients with chronic myelogenous leukemia.

Heterochromatin↗
PubMed1987

A CT based dosimetry system for intracavitary therapy in carcinoma of the cervix.

The physical dose distribution from intracavitary sources used in the treatment of carcinoma of the cervix can be accurately calculated in three dimensions. However, it is no simple matter to relate dose to critical tissues within the pelvis. We have studied 10 patients and have used CT scanning with dummy sources to determine the dose to lymph nodes, bladder and rectum. This technique may be superior to the use of orthogonal radiographs and highlights the limitations of the use of the flexible rectal dose meter. Further work will required to determine whether or not the morbidity of radical radiotherapy can be reduced using such detailed dosimetry to adjust therapy and eliminate small areas of high dose to critical normal tissues. In one case, CT showed a spontaneous and unexplained uterine perforation by the intrauterine tube one day after check films had shown a satisfactory position.

Adult↗
PubMed1987

Role of adrenergic-dependent H+ release from red cells in acidosis induced by hypoxia in trout.

The response to severe hypoxia is characterized in trout by a sudden drop in blood pH, which is of metabolic origin, and by an increase in the blood concentration of adrenaline. This acidification is biphasic in nature. The first phase of acidification is not associated with a rise in the blood lactate concentration and no longer occurs after pretreatment of the fish with a beta-blocker agent, propranolol. Thus an acid other than lactic acid is released into the blood at the onset of hypoxia and this release, which is under beta-adrenergic control, is responsible for the first phase of acidification. On the other hand the second phase of acidification is related to an increase in blood lactate and is not modified by a beta-blocker agent. We have also demonstrated that deep hypoxia promotes a rapid increase in red blood cell volume and that this cell enlargement is coincident with a large net uptake of Na+ and Cl-. In the presence of beta-blocking agents the Na+ uptake is blocked and the swelling of the cells is considerably inhibited. The residual swelling is clearly due to the chloride shift induced by both deoxygenation of hemoglobin and change in blood pH. In the light of data obtained in vitro on the effect of catecholamines on trout erythrocytes, it can be considered that the first phase of acidification occurring at the onset of hypoxia, and that is under beta-adrenergic control, is due essentially to the release of H+ by red blood cells in exchange with external sodium mediated by a beta-adrenergic-stimulated Na+-H+ exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1987

Haemoglobin A/F ratio in neonates at 7 days correlated with birth weight and estimated gestational age.

Haemoglobin (Hb) A and Hb F has been determined in neonates of Afro-Caribbean and North European origin with gestational ages varying from 32 to 42 weeks. There was no difference in the distribution of Hb A/F ratios between the two groups. Only weak correlations could be established between the Hb A/F ratio and the estimated gestational age or birth weight. This would indicate that there is a considerable interindividual variation in the timing of the switching of haemoglobin synthesis from Hb F to Hb A and erythrocyte production from liver to bone marrow and of oxygen affinity of fetal blood. Thus, intra-uterine adjustments of the oxygen release capacity of haemoglobin would have to rest on biochemical mechanisms during the third trimester.

Birth Weight↗
PubMed1986

Lower esophageal pressure changes with tube gastrostomy: a causative factor of gastroesophageal reflux in children?

In children, Stamm tube gastrostomy can initiate gastroesophageal reflux (GER) or worsen preexisting GER. We identified a possible mechanism for this problem in 25 children with GER who had esophageal manometry performed in conjunction with an antireflux operation. Intraoperative lower esophageal high pressure zone (LEHPZ) pressure and length were recorded for a simulated gastrostomy in all patients prior to performing the antireflux operation. These same parameters were then recorded for a simulated (11 patients) or real gastrostomy (14 patients) following the antireflux procedure. The LEHPZ pressure decreased with simulated Stamm gastrostomy (7.8 +/- 1.1----6.6 +/- 1.1 mm Hg, NS: Normal = 11.2 +/- 0.9 mm Hg). This decrease was less significant than the decrease in LEHPZ length (1.1 +/- 0.1----0.8 +/- 0.1 cm, P less than .01: Normal = 1.3 +/- 0.1 cm). Following Boerema gastropexy, simulated gastrostomy produced a similar decrease in LEHPZ pressure (20.8 +/- 3.8----17.1 +/- 2.7 mm Hg, NS) and length (3.3 +/- 0.4----2.5 +/- 0.3 cm, P less than .025). The LEHPZ pressure and length were not decreased by real gastrostomy performed with modified Thal fundoplication or with Nissen fundoplication. Thus, a decrease in LEHPZ length may be one mechanism whereby GER is initiated or worsened by tube gastrostomy in children. Tube gastrostomy has a similar effect when performed with a Boerema gastropexy, but not when performed with a Nissen or modified Thal fundoplication.

Child↗
PubMed1986

Effects of a low carbohydrate isoenergetic diet on sleep behavior and pulmonary functions in healthy female adult humans.

To study the effects of a low carbohydrate, isoenergetic diet on pulmonary physiology and sleep behavior, we measured pulmonary functions and respiratory gas exchange and carried out ambulatory electroencephalographic studies after a week's intake of isoenergetic diet containing only 50 g carbohydrate per day in 6 healthy female adult humans in a free-living condition. Compared with their normal intake, during the week of low carbohydrate intake there was a rise in the level of fasting plasma 3-hydroxybutyrate from 0.12 +/- 0.07 (mean +/- SD) to 1.01 +/- 0.40 mmol/L(P less than 0.01, paired t-test); a fall in serum bicarbonate from 26.2 +/- 0.75 to 25.0 +/- 1.41 mmol/L (P less than 0.05) and in serum chloride from 107 +/- 1.3 to 105 +/- 1.8 mmol/L (P less than 0.05). Serum urea rose from 4.3 +/- 0.71 to 5.7 +/- 0.70 mmol/L (P less than 0.01), and serum uric acid from 0.34 +/- 0.08 to 0.39 +/- 0.10 mmol/L (P less than 0.05). Functional residual capacity was increased from 2.07 +/- 0.35 to 2.26 +/- 0.34 L (P less than 0.01). Respiratory gas exchange ratio fell from 0.81 +/- 0.05 to 0.75 +/- 0.04 (P less than 0.05) and partial pressure of expired carbon dioxide reduced from 22 +/- 3.3 to 21 +/- 3.1 mmHg (P less than 0.05). There was a reduction in endogenous carbon dioxide production and arterial carbon dioxide tension. An analysis of ambulatory electroencephalogram showed that REM latency increased from 66 +/- 8 to 111 +/- 38 min (P less than 0.05), with no significant changes in sleep time and stages. These studies show that a low carbohydrate isoenergetic diet is tolerable, influences sleep behavior, reduces carbon dioxide production and respiratory gas exchange ratio, and may be therapeutically useful in patients with hypercapnic respiratory failure.

Adult↗
PubMed1986

Response to ACTH in the newborn.

Adrenocortical function was studied in 52 newborn infants who had been divided into three groups: preterm well, preterm ill, and term ill. Basal plasma 17-hydroxyprogesterone concentrations were significantly increased in both groups of preterm infants. There was no significant difference in basal plasma cortisol concentrations, although they were highest in preterm ill infants. All infants responded to adrenocorticotrophic hormone (ACTH) stimulation (36 micrograms/kg intramuscularly) with a two to three fold increase in the concentration of both steroids. The peak plasma 17-hydroxyprogesterone response was significantly higher in preterm ill infants. A subgroup of five infants, who were highly stressed but had undetectable basal plasma cortisol concentrations, also showed an appropriate response to ACTH. The results provide useful reference data to assess adrenal function in the infant of a mother given glucocorticoids during pregnancy. There is also a change from the pattern of fetal adrenal steroidogenesis soon after birth, which may be affected by exogenous ACTH stimulation. Roughly 10% of stressed newborns failed to synthesise cortisol basally; temporary glucocorticoid replacement for such infants may be appropriate.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Effect of deep hypoxia on acid-base balance in trout: role of ion transfer processes.

Continuous recordings were made of pH, Po2, and Pco2 of arterial blood in an extracorporeal circulation during a 20-min period of deep hypoxia (inspired Po2 = 40 Torr) and subsequent normoxia in rainbow trout. Blood concentrations of lactate, Na+, K+, and Cl- and net fluxes of electrolytes across gills and kidney were also continuously monitored. Deep hypoxia induced a short respiratory alkalosis followed by a marked metabolic acidosis. The acidification is biphasic in nature. The first rapid phase of acidification is not related to lactic acid production. On the other hand, the second phase of acidification is associated with lactic acid diffusion into the blood. However, a considerable proportion of the lactate ions is balanced by Na+ ions coming from a shift in the distribution of this cation between intra- and extracellular compartments. Most of the H+ ions formed from the dissociation of lactic acid are buffered in the intracellular space. The acidification period is also characterized by a very small increase in plasma Cl- content, much less than that of Na+, and by the apparent accumulation of an unknown anion in the blood. Recovery from hypoxia is associated with a pH readjustment, a large and identical decline of blood Na+ and Cl- contents without modification of the concentrations of K+, lactate, and the unknown anion. During this period the branchial ionic exchanges are slightly stimulated, but in the acid-base regulation as a whole, the branchial regulatory processes only play a minor part, the ionic movements being mainly performed by transfer between intra- and extracellular spaces.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1986

Acute low back pain: patients' perceptions of pain four weeks after initial diagnosis and treatment in general practice.

In a nationwide study of the treatment of acute low back pain with and without radiation in general practice in the Netherlands the subjective well-being of patients was evaluated by means of a short questionnaire sent to patients four weeks after the initial contact with their general practitioner.After this period pain had disappeared in 28% of the patients, was diminished in 47%, was unchanged in 2% and was aggravated in 4%. There was no difference in the pain score of patients with and without follow-up encounters with their general practitioner. In all instances patients with low back pain without radiation fared significantly better than those with radiation. Radiation of pain was not constant - during the four-week follow-up period it developed in 19% of the patients originally without radiation and it disappeared in 44% of the patients originally suffering radiation.

Acute Disease↗