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Biomedical subjects

A Williams

Publications and source records attributed to A Williams.

At least 577 records · Page 32Linked to original sources
PubMed1984

Use of an ammonia electrode to study bacterial deamination of amino acids with special reference to D-asparagine breakdown by campylobacters.

A method using an ammonia electrode is being developed for investigating the deamination of amino acids and amides by bacteria. Application of this method to Campylobacter jejuni and C. coli has led to the demonstration of D-asparaginase activity in some strains. This has allowed the subdivision of both species into D-asparaginase-positive and -negative biotypes. Even though the method is in the developmental stage, it was found to be generally reproducible and easy to perform. Areas for further improving the procedure have been identified. The ammonia electrode offers the theoretical possibility of investigating the breakdown of any amino acid by bacteria. It thus opens up a new and practical approach for separating species and strains, particularly in those bacterial groups that are difficult to subdivide by conventional means.

Amino Acids↗
PubMed1984

Ophthalmological signs and prognosis in patients with a subarachnoid haemorrhage.

In cases of subarachnoid haemorrhage from various causes, ophthalmological signs can be a feature. In the clinical examination they can be of assistance in determining the site of the aneurysm or other responsible lesion, and they can also be of prognostic value. In a series of 48 cases the significance of these ocular signs is evaluated and discussed.

Adult↗
PubMed1984

Home monitoring for central apnoea.

Between July 1978 and December 1981, 64 infants thought to be at increased risk from sudden infant death syndrome (SIDS) were monitored at home for central apnoea. Twenty four of the infants had had a 'near miss' episode at age, median (range), 6 (1 to 33) weeks, and of these infants 22 had had 335 alarms for apnoea by age 6 months. Stimulation by shaking was carried out on 38 occasions and bag and mask resuscitation on one. The remaining 40 infants were siblings of SIDS victims and of these, 35 were monitored from age 1 week (usually after discharge home). Thirty four of the SIDS siblings had had 573 alarms for apnoea by age 6 months: stimulation by shaking was carried out on 32 occasions and bag and mask resuscitation on one. The duration of home monitoring was, median (range), 34 (8 to 87) weeks for 'near miss' infants and 45 (12 to 70) weeks for SIDS siblings. All infants survived. As part of an over all support system monitors were accepted and greatly appreciated by most parents, especially those with previous experience of SIDS. Home monitoring was practicable but the commitment in time and expertise was great and objective benefits to the infant remain unproved.

Apnea↗
PubMed1984

The pituitary fossa: a correlative anatomic and MR study.

This study characterizes the normal appearance of the pituitary fossa in partial saturation magnetic resonance (MR) images. In sagittal images, the pituitary fossa appears inhomogeneous. Correlation of sagittal MR images in normal subjects with sagittal cryomicrotomic images in cadavers suggests that the highest intensity signal from the posterior-inferior pituitary fossa is due to a fat pad. This conclusion was supported by MR images and postmortem cryotome sections obtained in normal subhuman primates. The cause of the less constant, low intensity signal was less certain. The height of the pituitary gland in sagittal images was usually less than 8 mm, and the upper surface was flat or concave.

Adipose Tissue↗
PubMed1984

Alpha-adrenergic receptors in orthostatic hypotension syndromes.

Alpha-adrenergic receptor function was measured in platelets from patients with orthostatic hypotension and normotensive controls. Patients with idiopathic orthostatic hypotension (IOH) or multiple system atrophy (MSA) had more alpha-receptors than controls. Patients with IOH, but not MSA, produced less prostaglandin E1 (PGE1)-stimulated cyclic AMP (cAMP) than controls. Patients with sympathotonic orthostatic hypotension (SOH) were similar to controls in receptor number and cAMP production. The percent norepinephrine (NE) inhibition of PGE1-stimulated cAMP production was similar in patients and controls. An increase in alpha-receptor number may result from decreased peripheral NE secretion in IOH and MSA. Increased alpha-receptor number and decreased cAMP production, which accompany essential hypertension, may contribute to the supine hypertension of IOH, and an increase in alpha-receptor number may contribute to the supine hypertension of MSA. SOH patients appear to have no abnormalities of alpha-receptor function.

Adolescent↗
PubMed1984

Glycosylated hemoglobin (HbA1) and hemoglobinopathies in pregnancy.

Glycosylated hemoglobin (HbA1) is considered to be representative of prior blood-glucose levels and is being used in pregnant and nonpregnant diabetic patients as a possible index of both long and short-term glucose-control. Factors other than blood-glucose concentration have been reported to affect its value. Variant hemoglobin is one of them. HbA1 and blood-glucose levels were measured in pregnant patients at high risk for diabetes for screening for abnormal carbohydrate metabolism. HbA1 was measured by cation exchange column chromatography and glucose was measured by hexokinase reaction. The mean HbA1 in patients with normal blood sugars was 6.17 +/- 0.6 percent. A value of HbA1 of less than 5 percent as measured by cation exchange column chromatography was highly predictive (P less than 0.001) of hemoglobinopathies (S or C). The mean HbA1 of randomly selected matched patients with "normal" Hb was 5.94 +/- 0.72 percent. In patients with thalassemia, HbA1 values as measured by cation exchange column chromatography were elevated despite normal carbohydrate tolerance. While interpreting the results of HbA1 in the management of pregnant diabetics, the above fact should be kept in mind.

Blood Glucose↗
PubMed1983

A microcolorimetric assay of inorganic pyrophosphatase.

A procedure is described for the assay of inorganic pyrophosphatase in tissues by a microcolorimetric procedure, taking advantage of the marked color intensification of phosphomolybdate by malachite green. Conditions are described for optimum enzyme activity, color stability, and sensitivity. With 1-cm cuvettes the AM660 is 100,000, allowing accurate measurement of Pi in the 1-nmol range. Reaction is conducted at 25 degrees C for 10 min in 0.5 ml of a 50 mM histidine buffer, pH 7.2, containing 0.2 mM inorganic pyrophosphate and 4 mM Mg2+, terminated by addition of 0.05 ml 2.4 M HClO4, cooled in ice, and 0.45 ml of color reagent is added. After standing 10 min at 0 degrees C, the contents are transferred to 1-cm cuvettes and the absorbance is read at 660 nm. Blanks are low, nonenzymatic hydrolysis of PPi is negligible, and color is stable without addition of detergents. The high sensitivity makes this procedure well-adapted to measurement of optimal activities in crude tissue preparations.

Animals↗
PubMed1983

RBE of spleen CFU-S to low dose rate Cf-252 neutron or photon radiation.

The RBE of Cf-252 neutron irradiation was determined for hemopoietic tissue using spleen CFU-S. Radiosensitivity was compared to acute Cobalt-60 radiation and low dose rate Cesium-137 under identical irradiation conditions. The RBE for the neutron component of the Cf-252 radiation was 2.1. No dose rate effect was observed for hemopoietic CFU-S to acute doses or low dose rate photon irradiation.

Animals↗
PubMed1983

ORG NC45 for short intra-abdominal operations: a comparison with succinylcholine.

ORG NC45 was compared with succinylcholine to produce muscle relaxation for short, intra-abdominal operations in 40 patients during nitrous oxide-oxygen-enflurane anaesthesia. Intubating conditions after ORG NC45, 100 micrograms/kg, were similar to those after succinylcholine 1 mg/kg, although this was achieved at a mean time of 229.9 +/- 10.8 sec compared with 129.8 +/- 14.2 sec after succinylcholine. Muscle relaxation during surgery, mean duration 32.5 minutes, was provided in the succinylcholine group with an infusion and in the ORG NC45 group by repeated boluses, 10 micrograms/kg, which were required in four patients. At the end of surgery ORG NC45 was antagonized with atropine, 17 micrograms/kg, and neostigmine, 36 micrograms/kg, which were repeated in two patients. Postoperative recovery of neuromuscular function was indistinguishable between the two groups. We conclude that ORG NC45 is a suitable relaxant for short, intra-abdominal operations if sufficient time, three to four minutes, is allowed to produce good intubating conditions.

Adult↗
PubMed1983

RBE of spleen CFU-S to low dose rate Cf-252 or photon radiation in vivo.

The biological effects of low dose rate (LDR) Cf-252 radiation were compared to LDR Cs-137 photon radiation and acute 60Co radiation. The RBEn for endogenous CFU-S in vivo was 2.1 for neutron radiation at a dose rate of 9.9 cGy/hr of Cf-252 radiation. The value was consistent with previous in vitro experiments where a value of 2.1 was found. For the low doses and low dose rates studied, we tested an acute assay dose following the LDR irradiation to determine dose-effect and RBEn. Organ size shrinkage and regeneration patterns after LDR Cf-252 and Cs-137 were also studied and showed greater growth delay for Cf-252 irradiated lympho-hemopoietic tissues.

Animals↗
PubMed1983

The serotype and biotype distribution of clinical isolates of Campylobacter jejuni and Campylobacter coli over a three-year period.

Two hundred eighty-five isolates of Campylobacter jejuni-Campylobacter coli from children with gastroenteritis at The Hospital for Sick Children (Toronto, Canada) over a three-year period were biotyped by the hippurate hydrolysis test and serotyped on the basis of thermostable, soluble antigens by the passive hemagglutination technique. Hippurate-negative strains (C. coli) were only 3.2% of the isolates. Ninety-seven percent of the isolates were serotypable with 55 antisera. About half of the strains belonged to one of four serotypes (2, 4, 3, or 1); about three-quarters belonged to one of 10 serotypes. Serotype 2 was consistently the commonest serotype in each of the three years of the study, accounting for 15%-20% of all isolates tested.

Campylobacter↗
PubMed1983

Inability of thoracic duct drainage to prevent hyperacute rejection.

Serum and lymph albumin and Ig levels were measured during 6 weeks of lymphocyte depletion by thoracic duct drainage (TDD) in 21 patients prior to renal allotransplantation. In ten of these patients, the amount of protein lost from all sources (blood sampling, dialysis, and lymph centrifugation) was measured. The total amount of albumin lost was significantly greater than the amount of IgG lost. However, serum IgG declined at a faster rate and to a greater extent than albumin. Hyperacute or acute humoral rejection occurred in 14 grafts in 10 patients prepared by TDD despite negative crossmatch tests. These data suggest that removal of lymphocytes by TDD, rather than protein loss alone, affects IgG levels. On the other hand, TDD and IgG depletion do not prevent hyperacute or acute humoral rejection. This is most likely due to the inability of currently employed crossmatch tests to predict accurately which patients will manifest antibody-mediated graft rejection.

Drainage↗
PubMed1983

Subcellular distribution of inorganic pyrophosphatase activity in various normal and neoplastic cell types.

Inorganic pyrophosphatase (PPiase) activity was measured in cell fractions of rat, mouse, and human erythrocytes; normal rat liver; Novikoff hepatoma; Morris 3924A hepatoma; and mouse Ehrlich and Sarcoma 37 ascites tumors. Despite high intracellular activities, when precautions were taken to maintain cell integrity, only negligible activities were found on the surface of intact erythrocytes, Novikoff ascites hepatoma, Ehrlich carcinoma, and Sarcoma 37 cells. Suspensions of intact Ehrlich and Sarcoma 37 cells exhibited low PPiase activity, but this was only about 1 to 2% of the intracellular activity and was completely accounted for by activity present in the suspension medium. It is considered to be due to extrusion of the intracellular enzyme. Systematic fractionation of subcellular components revealed that 92% of the total PPiase activity of rat liver and 97.5% of that of Hepatoma 3924A were in the cytosol. The soluble activity consisted of a major form, accompanied by very low activities of two minor forms, all of which migrate toward the anode on electrophoresis. About 4.5% of the liver activity was present in the mitochondria in two forms, one remaining at the origin and one migrating toward the cathode. The same cytosolic isozymes were present in Hepatoma 3924A, and the cathodic form was present in mitochondria but in much reduced amount. No evidence was obtained for specific isozymes in nuclei or microsomes. Only negligible PPiase activities were found in cell membranes isolated by sucrose gradient centrifugation. These results discount the occurrence of PPiase activity as an ectoenzyme or in the plasma membrane of these cells and point to the cytosol as the major and mitochondria as a minor locus of intracellular PPiase activity.

Animals↗