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Biomedical subjects

A Williams

Publications and source records attributed to A Williams.

At least 541 records · Page 30Linked to original sources
PubMed1986

Leaving group dependence in the phosphorylation of Escherichia coli alkaline phosphatase by monophosphate esters.

Values of kcat and Km have been measured for the Escherichia coli alkaline phosphatase catalyzed hydrolysis of 18 aryl and 12 alkyl monophosphate esters at pH 8.00 and 25 degrees C. A Brønsted plot of log (kcat/Km) (M-1 s-1) vs. the pK of the leaving hydroxyl group exhibits two regression lines: log (kcat/Km) = -0.19 (+/- 0.02) pKArOH + 8.14 (+/- 0.15) log (kcat/Km) = -0.19 (+/- 0.01) pKROH + 5.89 (+/- 0.17) Alkyl phosphates with aryl or large lipophilic side chains are not correlated by the above equations and occupy positions intermediate between the two lines. The observed change in effective charge on the leaving oxygen of the ester (-0.2) is very small, consistent with substantial electrophilic participation of the enzyme with this atom. Cyclohexylammonium ion is a noncompetitive inhibitor against 4-nitrophenyl phosphate substrate at pH 8.00, and neutral phenol is a competitive inhibitor (Ki = 82.6 mM); these data and the 100-fold larger reactivity of aryl over alkyl esters are consistent with the existence of a lipophilic binding site for the leaving group of the substrate. The absence of a major steric effect in kcat/Km for substituted aryl esters confirms that the leaving group in the enzyme--substrate complex points away from the surface of the enzyme. Arguments are advanced to exclude a dissociative mechanism (involving a metaphosphate ion) for the enzyme-catalyzed substitution at phosphorus.

Alkaline Phosphatase↗
PubMed1986

Gallium scanning and tomography in the preoperative evaluation of lung cancer.

Discrepant reports on the utility of gallium scanning in the preoperative evaluation of patients with lung cancer prompted a prospective study of the test. The authors studied 47 patients with lung cancer who underwent preoperative gallium scanning and frontal tomography of the mediastinum. Both tests were found to be most accurate in predicting the presence of mediastinal metastases among patients with squamous cell carcinoma. Both test may help direct surgical planning in patients with known squamous cell carcinoma of the lung.

Carcinoma, Squamous Cell↗
PubMed1986

Epidemiologic study of Holstein dairy cow performance and reproduction near a high-voltage direct-current powerline.

The development and operation of a high-voltage direct-current (HVDC) transmission line in rural Minnesota generated public concern over potential adverse effects to nearby residents and their livestock. Electrical environmental parameters near an HVDC line decline rapidly with distance, but effects on ambient space charge have been detected out to 1 mile. Previous studies of powerline effects on livestock have involved the more common alternating-current (HVAC) lines, which create a different electrical environment. To identify potential adverse effects of HVDC line operation on livestock, case-control and cohort study methods were used to examine various indices of Holstein performance in relation to distance from the line and the onset of line operation. It was believed that these indices would reflect changes in physiologic function or overt health effects that might arise from the HVDC environment. High-quality performance data from existing Dairy Herd Improvement Association (DHIA) records were obtained for 97% of qualifying herds located within 10 miles of the line. The large number of animals and years of observation provided high statistical power to detect even small systematic changes in performance. No significant differences in milk production or reproductive capacity were associated with presumed exposure to the HVDC environment. The absence of measurable effects in a large "sentinel" animal population may have implications for the assessment of human health risks related to HVDC transmission lines.

Abortion, Veterinary↗
PubMed1986

Sleep apnoea during upper respiratory infection and metabolic alkalosis in infancy.

Three to four hour polygraphic sleep studies were carried out in 10 infants, five with upper respiratory infection and five with metabolic alkalosis secondary to vomiting during and after recovery from illness. During upper respiratory infection, the main abnormality detected was brief (greater than 3 less than 6 seconds) or prolonged (greater than 6 seconds) attacks of obstructive apnoea. Other indices of apnoea were similar to recovery data. Gross body movements were also increased. In infants with metabolic alkalosis indices of central apnoea were significantly increased when compared with recovery or case control data. Prolonged (greater than 15 seconds) attacks of central apnoea and obstructive apnoea (greater than 6 seconds) were only observed during illness. Gross body movements and periodic breathing were also increased. These findings suggest that the functional consequences of apparently 'mild' illnesses in young infants may be greater than is generally suspected and perhaps relevant to mechanism(s) of death in sudden infant death syndrome.

Alkalosis↗
PubMed1986

Sleep apnoea in infants with congenital stridor.

Indices of central apnoea, respiration rate, heart rate, and body movements were comparable in seven infants with congenital stridor (infantile larynx) and matched controls. Obstructive sleep apnoea was only observed in three of seven infants with stridor. Periodic breathing was less common in infants with stridor than in controls.

Female↗
PubMed1986

Subacute combined degeneration of the cord due to folate deficiency: response to methyl folate treatment.

Subacute combined degeneration of the cord is a rare complication of folate deficiency. Disturbance of methylation reactions in nervous tissue probably underlie subacute combined degeneration of the cord arising from folate as well as vitamin B12 deficiency. Methyl tetrahydrofolate is the form in which folic acid is transported into the CNS. Therefore methyl tetrahydrofolate treatment of the neurological and psychiatric manifestations of folate deficiency would seem to be theoretically advantageous. A case of subacute combined degeneration of the cord due to dietary folate deficiency and associated with an organic brain syndrome is reported. There was striking haematological, neurological and psychiatric response to methyl folate treatment.

Female↗
PubMed1986

Anterior commissure: anatomic-MR correlation and use as a landmark in three orthogonal planes.

Correlation of cryomicrotomic and myelin-stained sections of human cadaver heads with spin-echo magnetic resonance (MR) images documents that MR imaging routinely displays the anterior commissure in three orthogonal planes as a distinct white-matter tract that resembles bicycle handlebars. The anterior commissure crosses the midline at the upper end of the lamina terminalis, just anterior to the anterior columns of the fornices. To each side of midline, it curves antero-inferolaterally and then postero-inferolaterally through the lateral nucleus of the globus pallidus to course with the white matter of the external and extreme capsules toward the middle and inferior temporal gyri. Because the anterior commissure is easily recognizable in all three planes at differing pulse sequences, the commissure has proved to be a major landmark for identification of the complex anatomy of this region, especially in sagittal sections.

Brain↗
PubMed1986

Percutaneous transjejunal biliary dilatation: alternate management for benign strictures.

Since 1980, 23 patients with diffuse benign biliary strictures underwent percutaneous retrograde biliary dilatation through a surgically created jejunal access route. Bile ducts of 15 patients with sclerosing cholangitis, five with traumatic strictures, and three with strictures of diverse etiology were dilated with 25-atm balloons during 88 separate sessions. Individual dilatation intervals ranged between 2 and 36 months. Three patients with sclerosing cholangitis died. One uncomplicated bile duct rupture occurred in the trauma group because of balloon oversizing. Our 5-year experience indicates that bile duct patency can be safely maintained by repeated retrograde dilatations without the need for biliary catheters or stents.

Adolescent↗
PubMed1986

Nocardiosis mimicking Wegener's granulomatosis.

A 45-year-old man presented with persistent nasal discharge and later developed arthropathy, cutaneous vasculitis, a macular rash and radiographic lung opacities. Early relapse after starting immunosuppressive therapy consisted of new cavitating lung opacities, as seen in Wegener's granulomatosis, and subcutaneous nodules. Lymph node biopsy showed Nocardia asteroides. One month after high dose cotrimoxazole the chest X-ray was normal.

Diagnosis, Differential↗
PubMed1986

Primary care of parenteral substance abusers.

Parenteral substance abuse is widespread. Although treatment for opiate dependence and cocaine abuse takes place in specialized programs, abusers frequently present in primary care settings for management of associated health problems. This article reviews the two drugs that are most commonly abused parenterally (heroin and cocaine); treatment options, including methadone maintenance and narcotic antagonists; and the primary care and health maintenance issues of this population. Psychological aspects of caring for these patients are discussed. Physical findings and diagnosis and management of the complications of parenteral drug abuse are presented.

Acquired Immunodeficiency Syndrome↗
PubMed1986

MPTP toxicity: clinical features.

MPTP causes acute irreversible Parkinsonism in man that mimics the idiopathic condition exactly. It is therefore a better model of the naturally occurring disease than previously described cases secondary to other chemicals or viruses.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1986

Gastric emptying of glucose in the dog.

The 30-minute gastric emptying of test meals consisting of 2.5%, 4%, 7%, 15%, or 25% glucose was evaluated in healthy, nonoperated dogs, using an orogastric intubation technique. An inversely proportional exponential relationship was found between test meal glucose concentration and amount of test meal emptied from the stomach in 30 minutes. For the 7%, 15%, and 25% glucose test meals, a mean (+/- SEM) of 1.11 +/- 0.03 kcal/min emptied into the duodenum, which represented 0.054 +/- 0.004 kcal/min/kg of body weight. Test meals of 2.5% and 4% glucose supplied significantly fewer kcal per minute to the duodenum than did the other 3 meals, indicating that control of gastric emptying of hypotonic glucose meals may be different than that of isotonic or hypertonic test meals in the dog.

Animals↗