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Biomedical subjects

E Thomas

Publications and source records attributed to E Thomas.

At least 253 records · Page 14Linked to original sources
PubMed1993

Venous air embolism during cesarean section: more common than previously thought.

To confirm the incidence of venous air embolism (VAE), we simultaneously monitored expired nitrogen concentration (FEN2) and precordial Doppler in 30 patients undergoing cesarean delivery during general anesthesia. Patients were randomized into two groups and the effect of a 10 degrees reverse Trendelenburg tilt versus the horizontal position was evaluated. Forty-two episodes of VAE, defined by an increase in FEN2 of 0.1%, were detected in 97% (29/30) of patients. Doppler ultrasound failed to detect 9 of the episodes and 23 (41%) changes in Doppler tones were not associated with an increase in FEN2. These spurious Doppler signals were synchronous with compression of retroperitoneal structures, suggesting turbulent venous return to be the cause. The reverse Trendelenburg position did not reduce the incidence of VAE. Compared with the preinduction baseline, mean arterial blood pressure decreased by 31.5 +/- 10.1 mm Hg in this position and 22.6 +/- 13.4 mm Hg in the supine position after hysterotomy. We conclude that VAE in cesarean delivery during general anesthesia occurs very frequently, and that changes in Doppler tones may not be reliable indicators of this complication. Measures to reduce the size and effect of air emboli therefore should be applied routinely in all patients.

Adult↗
PubMed1993

Measurement of the bone mineral density of the os calcis as an indication of vertebral fracture in women with lumbar osteoarthritis.

In women with lumbar osteoarthritis, measurement of the os calcis bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA) as an indication of vertebral fracture was evaluated. The in vivo precision of the method was 1.28%. Age- and sex-matched control curves were evaluated using a control of 193 females. The correlation between spine BMD and os calcis BMD was significant (r = 0.65, p << 0.001). For the osteoporotic women without osteoarthritis (n = 34), there was no significant difference in the spine and the os calcis Z-scores (-1.99SD and -1.83SD respectively). Whereas for osteoporotic women with osteoarthritis (n = 30) the spine Z-score was -0.49SD the os calcis Z-score was -1.92SD. The difference was significant (p < 0.001). Receiver operating characteristic (ROC) curves demonstrate the superiority of the os calcis as a measurement site over the lumbar spine, in correlation with existing crush fractures in the presence of osteoarthritis. It is concluded that when lumbar osteoarthritis occurs measurement of the os calcis BMD using DEXA is clinically useful for the estimation of bone mass.

Absorptiometry, Photon↗
PubMed1993

Early ultrastructural studies on local acid phosphatase activity in rat sciatic nerve after nerve crush.

Rat sciatic nerve was crushed at mid thigh level. 30 minutes up to 24 hours after the lesion, the nerve was excised, fixed, stained for acid phosphatase activity, and embedded in araldite. The nerve was cut lengthwise over a distance of 6 mm proximally and distally to the lesion and examined by electron microscopy. Not more than 30 minutes after damage fundamental changes were found to take place, with little difference between the proximal and the distal "stump". Changes affect the axon itself, the axolemma and the Schwann cell. In the axoplasm, structures not existent in normal axons became visible during the first hour. Acid phosphatase activity appeared in the endoplasmatic reticulum, vesicles and cisterns, along the axolemma, and in the Schwann cell. Enzyme filled vesicles were released from the Schwann cell into the axoplasm. Mitochondria were found in increasing numbers in the axoplasm next to the lesion, being mainly small and round in shape and prominent where various organelles and enzymes had accumulated. It is concluded that the axon itself is capable of enzyme activation and organelle production, and that there is a complex interaction between the Schwann cell and the axoplasm after nerve crush.

Acid Phosphatase↗
PubMed1993

[Determination of the instantaneous center of rotation of the shoulder using the ELITE system. Application to the study of normal and pathological abduction].

The authors determined the in vivo displacement of the instantaneous center of rotation (ICR) of the shoulder from data supplied by an optoelectronic system (ELITE System) which uses a specifically designed software program to achieve 3-dimensional analysis of abduction. The study involved 10 control subjects and 20 patients suffering from a periarticular disorder of the shoulder capsule retraction in 10 cases and rotator cuff tears before and after rehabilitation in 10 cases. This method provides an objective assessment of humeral head misalignment in relation to the glenoid cavity induced by the periarticular shoulder disorder and of the realignment achieved through rehabilitation. The proposed ICR calculation technique is entirely harmless for the patient in (particular because it requires no radiation analysis).

Adult↗
PubMed1993

Leukotriene generation and metabolism in dogs: inhibition of biosynthesis by MK-0591.

Peptidoleukotriene metabolism in dogs was investigated to determine the suitability of this species for the development of in vivo biochemical models of asthma and inflammation. Circulatory metabolism of [3H]leukotriene (LT)C4 (0.5 microCi/kg, i.v.) to [3H]LTE4 and subsequent clearance was rapid (T1/2 = 100 sec). After 3 h, the major urinary metabolite was [3H]16-carboxydihydrotetranor LTE4 (identified by radiochromatography), with [3H]LTE4 accruing to a significant 1.7 +/- 0.9% (n = 3) of the original [3H]LTC4 dose. Immunoreactive LTE4 was excreted into canine urine at 1.85 +/- 0.35 to 2.35 +/- 0.57 ng/h (n = 4) over a 6-h period, suggesting that this metabolite may be an index of acute in vivo 5-lipoxygenase activity. MK-0591, a high-affinity ligand for the canine homolog of the human 5-lipoxygenase activating protein, dose-dependently inhibited the systemic generation of peptidoleukotrienes as measured by urinary LTE4 excretion (ED50 1 microgram/kg/min), the time course of disappearance of LTE4 from the urine being similar to that of the clearance of [3H]LTE4. Because the therapeutic improvements in human allergic asthmatics treated with LT synthesis inhibitors and challenged with antigen appear to be related to the degree of in vivo inhibition of LT biosynthesis (measured by urinary LTE4), the dog may be an appropriate species for preclinical assessment of LT inhibitors.

5-Lipoxygenase-Activating Proteins↗
PubMed1993

[Color echo-doppler of the ureterovesical stream. Normal aspects. Application to the acute ureteral obstruction].

A colour Doppler ultrasound study of the ureterovesical was performed to define the normal features, variants and abnormalities of the ureteric stream by comparing 50 normal subjects and 19 subjects with renal colic due to ureteric stones. The examination included assessment of the frequency, intensity, morphology and symmetry of the ureterovesical stream. In normal subjects, the stream was either absent, especially in the case of fluid restriction (36%), present and symmetrical (34%) or asymmetrical (30%). In patients with ureteric stones, during a non-painful period and in the absence of obstruction on IVU, the stream was normal and symmetrical (9%) while during a painful period with obstruction on IVU, the ureteric stream was either absent (47%) or abnormal and asymmetrical (31%). A continuous stream, very suggestive of obstruction, was observed in 5 cases. Colour Doppler ultrasound is a new, simple method which may be helpful in the diagnosis of renal colic, particularly in cases in which the pyelocaliceal cavities are not dilated.

Acute Disease↗
PubMed1992

Diminutive polyps found on flexible sigmoidoscopy. Management and follow-up.

Diminutive polyps found on flexible sigmoidoscopy are predominantly hyperplastic, but it is impossible to rely on endoscopic appearance to make an accurate diagnosis. Colonoscopy, polypectomy, and full pathologic evaluation are recommended for all such polyps. Follow-up care varies depending on the nature of the lesion.

Humans↗
PubMed1992

A computational model of vertical signal propagation in the primary visual cortex.

A computational model of the flow of activity in a vertically organized slab of cat primary visual cortex (area 17) has been developed. The membrane potential of each cell in the model, as a function of time, is given by the solution of a system of first order, coupled, non-linear differential equations. When firing threshold is exceeded, an action potential waveform is "pasted" in. The behavior of the model following a brief simulated stimulus to afferents from the dorsal lateral geniculate nucleus (dLGN) is explored. Excitatory and inhibitory post-synaptic potential (E and IPSP) latencies, as a function of cortical depth, were generated by the model. These data were compared with the experimental literature. In general, good agreement was found for EPSPs. Many disynaptic inhibitory inputs were found to be "masked" by the firing of action potentials in the model. To our knowledge this phenomenon has not been reported in the experimental literature. The model demonstrates that whether a cell exhibits disynaptic or polysynaptic PSP latencies is not a fixed consequence of anatomical connectivity, but rather, can be influenced by connection strengths, and may be influenced by the ongoing pattern of activity in the cortex.

Action Potentials↗
PubMed1992

Malignant rhabdoid tumor: primary intracranial manifestation in an adult.

Clinical, histopathological, and ultrastructural features of an extended intracranial malignant neoplasm are presented. Following incomplete extirpation of a large epidural tumor at the temporal base of the skull, the 21-year-old male patient suffered from several local recurrences and died at the age of 27. The neoplasm was defined by its histopathological and ultrastructural characteristics and by the pattern of its antigenicity as a malignant rhabdoid tumor (MRT). Considering previous publications on MRT, this case may be the first of primary intracranial MRT appearing in an adult.

Adult↗
PubMed1992

Fatal Legionella maceachernii pneumonia in Canada.

A case of pneumonia and acute tubular necrosis was caused by an initially unknown species of Legionella. The organism was later identified as Legionella maceachernii by a combination of cultural, biochemical, and serological methods along with a gas-liquid chromatographic profile.

Canada↗
PubMed1992

High-volume spinal anaesthesia. A dose-response study of bupivacaine 0.125%.

The clinical effects of high-volume spinal anaesthesia with bupivacaine 0.125% were studied in 30 patients presenting for postpartum sterilisation. Group A, B and C patients received 6, 8 and 10 ml of bupivacaine 0.125% respectively. Onset, duration and regression of sensory block and motor blockade, haemodynamic parameters and postoperative complications were studied. A sensory level of T10 was reliably obtained in Group B and C but not in Group A. Similarly motor blockade was unreliable in Group A compared with Group B (P < 0.05) and Group C (P < 0.05). Two segment regression times were similar in all three groups. L1 regression times were 47.9, 94.3 and 99.0 minutes in Groups A, B and C respectively. The corresponding times for complete recovery of motor power were 120, 212.3 and 182.7 minutes respectively (P < 0.01 when Group A compared to B and C). A significant incidence of high spinal anaesthesia occurred when 10 ml bupivacaine 0.125% was administered (P < 0.05 when compared with Group A). No patient experienced respiratory discomfort in spite of sensory levels of up to T1. Hypotension responded readily to intravenous fluids and small doses of ephedrine (three patients). Only one patient (Group A) developed a postdural puncture headache. In this study, high-volume spinal anaesthesia with bupivacaine 0.125% was found to be satisfactory for postpartum tubal ligation. The optimal volume of bupivacaine 0.125% was 8 ml.

Adult↗
PubMed1992

Dietary management of inborn errors of amino acid metabolism with protein-modified diets.

This paper presents experiences encountered with protein-modified diets (PMD) in the management of 67 patients, aged 1 day to 14 years, followed in the Pediatric Nutrition Clinic in the past 5 years. All had inborn errors of amino acid metabolism: maple syrup urine disease (MSUD), 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency, propionic acidemia (PPA), or methylmalonic aciduria (MMA). In early infancy, the diet prescription is frequently adjusted to search for the infant's tolerance level of restricted amino acids. The levels must be established when natural foods other than milk are added to the PMD. The amino acids restricted are leucine, isoleucine, and valine in MSUD; leucine in HMG-CoA lyase deficiency; and isoleucine, methionine, threonine, and valine in PPA and MMA. Efficacy of the PMD depends on accuracy in prediction of the restricted amino acid requirement and the willingness and ability of parents and patients to conform to its demands.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

An overview of the role of calcium antagonists in the treatment of achalasia and diffuse oesophageal spasm.

Early studies confirmed the beneficial effects of calcium channel blockers on the normal oesophagus, which included a decrease in lower oesophageal sphincter tone in achalasia and a decrease in oesophageal contractions and amplitude in diffuse oesophageal spasm. This resulted in the enthusiastic use of the drugs in both disorders. With further experience, and with increased recognition of side effects, the role of these drugs in the 2 disorders has been better clarified. Clinical trials in general have not reflected the improvement observed in the manometric parameters. Only a minority of patients appear to derive sustained symptomatic benefit. Calcium channel blockers may be the initial choice for high or moderate risk patients with achalasia prior to proceeding with pneumatic dilatation or surgical myotomy. In diffuse oesophageal spasm, they are a reasonable first choice for all risk categories.

Calcium Channel Blockers↗
PubMed1992

Trisomy 15 with loss of the paternal 15 as a cause of Prader-Willi syndrome due to maternal disomy.

Uniparental disomy has recently been recognized to cause human disorders, including Prader-Willi syndrome (PWS). We describe a particularly instructive case which raises important issues concerning the mechanisms producing uniparental disomy and whose evaluation provides evidence that trisomy may precede uniparental disomy in a fetus. Chorionic villus sampling performed for advanced maternal age revealed trisomy 15 in all direct and cultured cells, though the fetus appeared normal. Chromosome analysis of amniocytes obtained at 15 wk was normal in over 100 cells studied. The child was hypotonic at birth, and high-resolution banding failed to reveal the deletion of 15q11-13, a deletion which is found in 50%-70% of patients with PWS. Over time, typical features of PWS developed. Molecular genetic analysis using probes for chromosome 15 revealed maternal disomy. Maternal nondisjunction with fertilization of a disomic egg by a normal sperm, followed by loss of the paternal 15, is a likely cause of confined placental mosaicism and uniparental disomy in this case of PWS, and advanced maternal age may be a predisposing factor.

Adult↗