Search PubMed⌕ Search

Biomedical subjects

D Williams

Publications and source records attributed to D Williams.

At least 433 records · Page 24Linked to original sources
PubMed1988

Fuchs' heterochromic iridocyclitis in blacks.

Fuchs' heterochromic iridocyclitis (FHI) is a frequently overlooked cause of anterior uveitis. Improper diagnosis may lead to unnecessary therapy. Dark brown irides may demonstrate heterochromia poorly. We believe that FHI may be overlooked in blacks because of a frequent lack of obvious heterochromia and the frequent presence of iris nodules. Heterochromia is not necessary for the diagnosis of FHI if other clinical features of the syndrome are present. In our series of 54 whites and 13 blacks with FHI, heterochromia occurred in 50 (92%) whites and ten (76%) blacks (nonsignificant difference). Iris nodules occurred in 11 (20%) whites and four (30%) blacks (not significant). Statistically significant differences occurred with cataract/aphakia in 41 (75%) whites and three (23%) blacks and with glaucoma in six (11%) whites and five (38%) blacks.

Age Factors↗
PubMed1988

A cluster of chromosome 11p13 translocations found via distinct D-D and D-D-J rearrangements of the human T cell receptor delta chain gene.

Human T cell tumours have few consistently occurring translocations which provide markers for this disease. The translocation t(11;14)(p13;q11), however, seems to be an exception, since it has been repeatedly observed in T-ALL. We have analysed a number of T-ALL samples carrying the t(11;14) with a view to assessing the nature of the translocated sequences on chromosomes 11 and 14. Three of the tumours studied have breakpoints, at 14q11, within the T cell receptor delta chain locus, while a fourth appears to break in the J alpha region. The TCR delta sequences involved in the translocation junctions are made from D delta-D delta-J delta joins or from D delta-D delta joins, allowing us to define distinct human D delta and J delta segments. These results allow us to make a comparison between the human and mouse TCR delta loci, both as regards sequence and rearrangement hierarchies. The disparate translocation breakpoints at chromosome 14q11 contrast with the marked clustering of breaks at chromosome 11p13; in all four cases, the breakpoint occurs within a region of less than 0.8 kb of chromosome 11. The analysis of junctional sequences at the 11p13 breakpoint cluster region only shows a consensus heptamer-like sequence in one out of four tumours analysed. Therefore, recombinase-mediated sequence specific recognition is not the only cause of chromosomal translocation.

Animals↗
PubMed1988

The demonstration of tissue clonality by X-linked enzyme histochemistry.

We report here the first demonstration in normal, as opposed to chimaeric mice, of the clonal architecture of the small intestine, oesophagus, breast, and thyroid, using polymorphism of the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) as a clonal marker. Reproducible results using X-linked histochemistry were found to depend upon the simultaneous study of tissue from normal mice, mice homozygous for abnormal enzyme levels, and heterozygous mice. In tissues from homozygous animals where levels of enzyme activity normally vary, the use of a physiological stimulus to reduce this metabolic heterogeneity allowed interpretation of clonality in the heterozygotes. The details of the histochemical technique used require modification for each of the different tissues studied. A dual population of cells was seen in the heterozygous animals in all tissues studied. Oesophageal epithelium showed sharply separated alternating patches of positive and negative cells. Small intestinal crypts were always monophenotypic, while villi were polyphenotypic, indicating that crypts are monoclonal and villi derive from more than one crypt, confirming work in allophenic animals. In contrast, thyroid follicles and breast acini showed a mixture of mono- and polyphenotypia, consistent with a polyclonal origin. These results, which have important implications for the study of the clonal origins of normal and neoplastic growth, require the direct in situ demonstration of the cellular phenotype.

Animals↗
PubMed1988

Pulmonary endocrine cells in various species in the Himalaya.

The numbers, morphology and distribution of pulmonary endocrine cells in goats, sheep and the yak and its interbreeds with cattle, dzos and stols, were studied after their demonstration by means of the peroxidase-antiperoxidase technique with a polyclonal antiserum raised in the rabbit to human neuron-specific enolase, a marker for neuroendocrine cells. The numbers, morphology and distribution were related to species and not to residence at high altitude. Pulmonary endocrine cells were common and mainly distributed as solitary cells in the epithelium of the bronchial tree in sheep. They were much less common and found mainly as clusters in the alveolar capillary walls in goats and in the yak and its interbreeds with cattle.

Altitude↗
PubMed1988

Automatic and effortful processing after severe closed head injury.

To investigate the automatic versus effortful distinction following severe closed head injury (CHI), we administered free recall and frequency of occurrence tasks to patients and controls. In Experiment 1 we found that both free recall (an effortful task) and judgment of relative frequency of occurrence (an automatic task) were impaired in 15 CHI patients as compared to 14 controls. In Experiment 2 we corroborated this finding and showed that absolute estimates of frequency were also impaired in new samples of 16 patients and 16 controls. We infer that cognitive tasks which normal individuals can perform without practice, feedback, or instructions may demand more effortful strategies following severe CHI.

Adult↗
PubMed1988

Usefulness of pyridoxal-containing blood agar as a primary plating medium to enhance recovery of nutritionally deficient streptococci.

We evaluated the use of horse blood agar containing 0.0005% pyridoxal hydrochloride (HBAP) mainly for use as a primary plating medium for blood cultures, other sterile fluids, wounds, and abscesses in order to facilitate the isolation of nutritionally deficient streptococci (NDS). Our results showed that the addition of pyridoxal hydrochloride (pxl) permitted good growth of NDS within 24 h and did not inhibit or significantly alter the colony morphology of 34 different species of microorganisms and 296 isolates of beta hemolytic streptococci presumptively identified as Group A streptococci. The use of pxl-supplemented blood agar such as HBAP is recommended for primary plating as well as subculturing of blood cultures, and may also increase recovery of NDS from wounds and abscesses.

Agar↗
PubMed1988

DHFR coamplification of t-PA in DHFR+ bovine endothelial cells: in vitro characterization of the purified serine protease.

High-level expression of human tissue-type plasminogen activator was accomplished in endothelial cells by a novel approach to dihydrofolate reductase (DHFR) coamplification in DHFR+ cells. A tripartite mammalian expression vector coding for DHFR, neomycin phosphotransferase, and the t-PA gene was introduced into bovine endothelial cells by transfection and selection for G418 resistance. Upon methotrexate selection of these transformants, we obtained endothelial cells that had amplified the plasmid-encoded DHFR and t-PA genes. As a result, cell lines were isolated that efficiently produced t-PA (greater than 4 pg/cell.day). This t-PA was purified and compared with recombinant t-PA produced in Chinese hamster ovary cells. These two t-PA samples differed in carbohydrate composition, and amounts of 530 and 527 amino acid forms but had similar in vitro activity.

Animals↗
PubMed1988

Isolation and Characterization of Xylan-Degrading Strains of Butyrivibrio fibrisolvens from a Napier Grass-Fed Anaerobic Digester.

Six new xylanolytic bacterial strains have been isolated from a Napier grass-fed anaerobic digester. These strains were identified as Butyrivibrio fibrisolvens and were similar in many respects to ruminal isolates described previously. The new isolates exhibited a high degree of DNA homology with several ruminal strains of B. fibrisolvens. Xylan or xylose was required to induce the production of enzymes for xylan degradation, xylanase and xylosidase. Production of these enzymes was repressed in the presence of glucose. Xylanase activity was predominantly extracellular, while that of xylosidases was cell associated. The new isolates of B. fibrisolvens grew well in defined medium containing xylan as the sole carbon source and did not produce obvious slime or capsular layers. These strains may be useful for future genetic investigations.

Journal Article↗
PubMed1988

Comparative study of the degree of differentiation of neuroblastoma and mean numbers of nucleolar organiser regions.

Twenty confirmed cases of childhood neuroblastoma diagnosed over six years were reviewed and classified according to the subtyping proposed by Shimada et al. The tumours were stained using a silver colloid method for nucleolar organiser regions (NORs), and the mean number of NORs for every 200 cells was calculated. The correlation between the mean number of NORs and histology and survival was studied. There was a significant correlation between the mean numbers of NORs and differentiation, and with the mitosis-karyorrhexis index (MKI) in the stroma poor group (p = 0.01-0.001). A trend to increased survival with decreased numbers of NORs was observed in the study group as a whole (rank order of correlation = -0.57, p = 0.05-0.02). It is suggested that mean number of NORs is of prognostic value in neuroblastomas.

Cell Count↗
PubMed1988

Relationship of depth of brain lesions to consciousness and outcome after closed head injury.

Magnetic resonance (MR) imaging was performed in 94 patients who sustained closed head injury of varying severity. Results of MR studies obtained after the intensive care phase of treatment disclosed that intracranial lesions were present in about 88% of the patients. Consistent with the centripetal model of progressive brain injury proposed in 1974 by Ommaya and Gennarelli, the depth of brain lesion was positively related to the degree and duration of impaired consciousness. Further analysis indicated that the relationship between depth of brain lesion and impaired consciousness could not be attributed to secondary effects of raised intracranial pressure or to the size of intracranial lesion(s).

Adolescent↗