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Biomedical subjects

J Williams

Publications and source records attributed to J Williams.

At least 811 records · Page 45Linked to original sources
PubMed1989

Solitary bone cyst of the radius containing Liesegang's rings.

The authors describe the case of a 33-year-old man with a solitary cystic lesion of the left distal radius with central radiodensities that radiographically suggested a chondroid matrix. Curettage of the lesion revealed numerous calcospherites with a lamellar structure. This lamellar pattern is thought to be a result of alternating precipitation and diffusion of supersaturated solutions. This biochemical process has been called the Liesegang's phenomenon, and the structures have been termed Liesegang's rings. The presence of these structures in this benign lesion contributed to atypical roentgenographic and pathologic findings.

Adult↗
PubMed1989

Evaluation of assay techniques for the measurement of antiepileptic drugs in serum: a study based on external quality assurance measurements.

The accuracy and precision of eight techniques used to measure a range of eight antiepileptic drugs in human serum were compared using data from 80 samples from the Heathcontrol External Quality Assurance scheme. The fluorescence polarization immunoassay was significantly more precise than other techniques for several analytes, producing the lowest number of measurements rejected as outliers and measurements with the lowest coefficient of variation. Other techniques had a significantly lower precision. Nephelometry (Neph) produced most outliers for phenytoin and carbamazepine and had the highest variability for phenytoin. Gas-liquid chromatography (GLC) with derivatization was most variable for phenobarbitone and primidone. Measurements by GLC with or without derivatization contained greater than 10% of outliers and were least precise for carbamazepine. Differences between the majority of techniques were in many cases, however, not significant. The accuracy of techniques was assessed from differences between sample means and spiked drug concentrations. Neph was notable in producing overestimates at lower concentrations. Immunoassay methods had a 16-21% cross-reactivity with carbamazepine 10,11-epoxide when measuring carbamazepine. All techniques reported underestimates for valproic acid that were thought to result from the hygroscopic nature of the salt used for spiking.

Anticonvulsants↗
PubMed1989

External quality assurance of tricyclic antidepressant measurements in serum: eight years of progress?

Comparison of the precision and accuracy of measurements made between December 1979 and January 1988 of tricyclic antidepressant drug concentrations in freeze-dried external quality-assurance samples of human serum showed only occasional significant differences between the different chromatographic techniques used for drug assay. Larger differences between data collected in different years correlated with changes in the source of the sample matrix and the personnel responsible for sample preparation. Measurements of amitriptyline and imipramine were more precise than those of nortriptyline and desipramine; the mean coefficients of variation of measurements were 20.2, 19.6, 26.6 and 25.3%, respectively. The data indicate the need for further interlaboratory studies directed at reducing the high level of variability in tricyclic measurements.

Amitriptyline↗
PubMed1989

The effect of vigabatrin on brain and platelet GABA-transaminase activities.

1. The inhibition profiles of GABA-transaminase (GABA-T) in rat brain and platelet have been compared following a single intraperitoneal dose of vigabatrin. The inhibition profiles exhibit similarities. The inhibition produced by the drug is dose-dependent and, in the dose range used in man, the dose-response curves are comparable. The pharmaco-dynamic effects of the drug (inhibition of central and peripheral GABA-T) remain after the drug has been eliminated from plasma. It is suggested that the measurement of rat platelet GABA-T may be used as a non-invasive assessment of the efficacy of GABA-T inhibitors in the rat CNS. 2. Human blood platelet GABA-T was significantly inhibited by the administration of a single oral dose of vigabatrin. Chronic administration also produces a significant inhibition of platelet GABA-T. As with rats, the pharmacodynamic effects on the platelet enzyme remained after the drug had been eliminated from plasma. If the situation in man is assumed to parallel that found in the rat then measurement of platelet GABA-T inhibition could prove to be a useful indicator of central inhibition.

4-Aminobutyrate Transaminase↗
PubMed1989

A case of two inversion (10) recombinants in a family.

A family is described in which the mother's four pregnancies resulted in one spontaneous abortion, one healthy boy, and a male and female sib with developmental delay and multiple minor dysmorphic features. Chromosome analysis showed a large pericentric inversion of chromosome 10, involving the region between bands p15.1 and q25.2, in the father and the healthy son: 46,XY,inv(10) (p15.1q25.2), and an unbalanced karyotype in the two affected sibs: rec(10),dup p,inv(10) (p15.1q25.2). The unbalanced chromosome has been produced by meiotic recombination between the inversion chromosome and its normal homologue. The two affected sibs have partial duplication of 10p and partial deficiency of 10q, and share a large number of clinical features, several of which have previously been described in both of these chromosome imbalances. We believe this to be the largest pericentric inversion of chromosome 10 reported to have produced recombinant offspring.

Abnormalities, Multiple↗
PubMed1989

Platypnea-orthodeoxia and progressive autonomic failure.

Platypnea-orthodeoxia has been described in patients with pulmonary shunts, intracardiac shunts, and severe lung disease. We report a case of platypnea-orthodeoxia in a patient with minimal obstructive lung disease and progressive autonomic failure. We have shown our patient's symptoms to be the result of an orthostatic increase in ventilation-perfusion mismatching and to be corrected with fluid challenge.

Autonomic Nervous System Diseases↗
PubMed1989

Mechanistic approaches in the study of testicular toxicity: toxicants that affect the endocrine regulation of the testis.

This review will expand on the themes presented by Heindel and Treinen (1988). As a prelude to describing where selected compounds act on the endocrine regulation of the testis and the theories about their mechanisms, we will briefly review some of the central pathways that underlie this control. After reviewing some studies that define the site of action of lead on the reproductive system, we will discuss the "signature" lesion caused by androgen deficiency, and then move on to an evaluation of the effects of an antiandrogen (flutamide) on the male reproductive system. Finally, some consideration will be given to alterations in hepatic function which modify circulating levels of androgens.

Animals↗
PubMed1989

An evaluation and survey of enzyme immunoassay and fluorometric enzyme immunoassay tests for TSH and HCG.

Assays for human choriogonadotropin (HCG) and thyroid stimulating hormone (TSH) have typically been performed using radioisotopic procedures. Two newer, nonradioisotopic approaches, enzyme immunoassay (EIA) and fluorometric enzyme immunoassay (FEI), were evaluated for the determination of HCG and TSH. Two TSH EIA assays (Abbott, Hybritech) and one FEI assay (Dade) were compared with each other and an immunoradiometric (IRMA) assay. The FEI assay performed better than the EIA assays with a sensitivity of 0.3 microIU/ml, within-run closing volumes (CVs) of less than 4.5%, and a carryover of 0.7%. All of the assays correlated well with each other and the IRMA assay. Three HCG EIA assays (Abbott, Hybritech, Roche) and one FEI assay (Dade) were evaluated. Again, the FEI assay performed better than the EIA assays with a sensitivity of 1.3 mIU/ml, within-run CVs of 4.0% or less, and a carryover of 1.7%. The new generation of nonradioisotopic assays offers performance comparable to radioisotopic assays coupled with various degrees of automation. A clinical laboratory may not only take advantage of these methods but can choose an assay system that is well suited to its particular requirements.

Chorionic Gonadotropin↗
PubMed1989

Psittacosis pneumonia.

A 57-year-old man with symptoms and signs consistent with atypical pneumonia had epidemiologic and later serologic evidence of psittacosis pneumonia. Therapy with tetracycline resulted in rapid resolution.

Ciprofloxacin↗
PubMed1989

Reduced incidental light exposure: effect on the development of retinopathy of prematurity in low birth weight infants.

In a recent study, it was reported that incidental lighting within the newborn intensive care unit setting may play a role in the development of retinopathy of prematurity. Consequently, the routine clinical management in the intensive care nursery at Yale-New Haven Hospital was modified to include shielding each premature infant's isolette, thereby decreasing the intensity of the nursery lights on an infant's eyes from a median light level of 55 foot-candles to 15 foot-candles. The effect of this reduction of light level on the incidence of retinopathy of prematurity in 161 premature infants was prospectively investigated. This group was then compared with a historic control group of 129 premature infants with similar characteristics who had been exposed to standard nursery lighting. There was no difference in the incidence and severity of retinopathy of prematurity between the two groups.

Connecticut↗