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Biomedical subjects

J D Walker

Publications and source records attributed to J D Walker.

At least 109 records · Page 6Linked to original sources
PubMed1988

Survival of twenty-two months in a patient with primary plasma cell leukaemia treated with melphalan and prednisolone.

In the majority of cases plasma cell leukaemia is a rapidly fatal disease with a mean survival time of five months. There have been reports of increased survival using various regimens of chemotherapy although most cases eventually relapse. We describe a patient with primary plasma cell leukaemia who responded to a combination of oral melphalan and prednisolone with control of the disease in the bone marrow but relapsed with extramedullary disease in the central nervous system and testes, and died 22 months after diagnosis. Melphalan poorly penetrates the central nervous system and its testicular penetration is unknown.

Administration, Oral↗
PubMed1985

Declining incidence of multiple sclerosis in the Orkney Islands.

The incidence of MS in the Orkney Islands has been updated from 1941 to September 21, 1983. Since 1965, MS incidence rates have fallen significantly when compared with those for 1941 to 1964. Alterations in age-specific prevalence, mean duration of illness, and mean age of the MS population are consistent with the decline in incidence of MS in recent years. Although the reason for the decreasing incidence is uncertain, it is consistent with the hypothesis that MS may be caused by canine distemper virus.

Adult↗
PubMed1983

Transepithelial chemotaxis of rat peritoneal exudate cells.

The migration of peritoneal exudate (PE) cells into plain Millipore filters mounted in Boyden chambers occurs under random, chemokinetic and chemotactic conditions. Significant migration of such cells in vivo, however, involves both transendothelial and transepithelial penetration and occurs predominantly under pathological conditions where chemotactic agents are presumed to be present in gradient form. When Madin-Darby canine kidney (MDCK) epithelial cells are grown as a confluent monolayer on the Millipore filter of a Boyden chamber, transepithelial migration is seen only under chemotactic conditions thus modelling in vivo behaviour more effectively. The MDCK cell line exists as 2 variant strains which model different regions of the mammalian nephron. Strain I MDCK cells share features of the distal and collecting tubules and have relatively high junctional resistance (greater than 1k omega cm2). Strain II MDCK cells model the proximal segment of the nephron and have relatively low junctional resistance (c. 70 omega cm2). We have found that PE cells penetrate the less resistant strain II MDCK monolayer at a faster rate (as assessed by leading front migration) than they penetrate the tighter strain I monolayer. We have also utilized the electrophysiological features of MDCK monolayers to monitor transepithelial penetration. Our electrophysiological data indicate that rat PE cells penetrate MDCK monolayers of either strain by a transjunctional route with consequent reversible dissolution of the junctional complex. This extracellular path of PE cell migration was confirmed by ultrastructural observations. The extent of junctional dissolution and the delay in re-establishment of monolayer integrity (as assessed by electrophysiological means) are related to the concentration of PE cells added to the MDCK monolayer. Brief treatment (10 min) of the MDCK monolayer with the cation chelating agent EDTA also disrupts monolayer integrity, although its re-establishment is significantly faster than when disruption occurs by PE cell transmigration. Our results show a clear parallel between PE cell migration across an MDCK monolayer and changes in its electrophysiological parameters and thus suggest that transepithelial chemotaxis may be directly assessed by electrophysiological means. The use of Boyden chambers modified by the incorporation of epithelial monolayers may prove useful in in vitro studies of inflammation and could be adapted for studies of other pathological processes, such as metastasis, where considerable cell invasion is involved.

Animals↗
PubMed1982

Cytomegalovirus infection of the skin.

A case of fatal generalized cytomegalovirus infection with particular attention to lesions involving the skin is reported. Characteristic cytomegalovirus inclusion bodies were present within nuclei of endothelial cells in the dermis beneath ulcerations. Skin biopsy may be useful in the diagnosis of disseminated infections by cytomegalovirus.

Biopsy↗
PubMed1978

Growth of Prototheca isolates on n-hexadecane and mixed-hydrocarbon substrate.

Prototheca zopfii, an achlorphyllous alga, was capable of using hydrocarbons as sole carbon and energy source. The ability of P. zopfii to use hydrocarbons did not correlate with source of isolation. Seventy-five percent of the P. zopfii cultures recovered from sewage, plants, or animals utilized hydrocarbons. Other Prototheca species and P. zopfii that did not utilize hydrocarbons were isolated simultaneously from several sources with isolates that did use hydrocarbons. Species type rather than source of isolation was the predominant factor that determined hydrocarbon utilization.

Alkanes↗
PubMed1977

Diverticulitis in women: an unappreciated clinical presentation.

A final diagnosis of diverticulosis or diverticulitis was made in 1,031 women over a 10 year period. The 69 patients who underwent abdominal operation for what proved to be diverticulitis are discussed in detail. Thirty-eight per cent of these women were believed to have gynecologic disease because of the presence of a pelvic mass. Diverticulitis is an important differential diagnosis of a pelvic mass with or without clinical and laboratory indications of infection and with or without history of diverticulosis or diverticulitis. The increasing awareness of ovarian carcinoma and its ominous prognosis make this differential diagnosis especially important. Diverticular disease should always be considered among such patients and preparations made to allow optimal treatment at that operation, whatever the ultimate cause of the mass.

Adult↗
PubMed1977

Numerical taxonomy and ecology of petroleum-degrading bacteria.

A total of 99 strains of petroleum-degrading bacteria isolated from Chesapeake Bay water and sediment were identified by using numerical taxonomy procedures. The isolates, together with 33 reference cultures, were examined for 48 biochemical, cultural, morphological, and physiological characters. The data were analyzed by computer, using both the simple matching and the Jaccard coefficients. Clustering was achieved by the unweighted average linkage method. From the sorted similarity matrix and dendrogram, 14 phenetic groups, comprising 85 of the petroleum-degrading bacteria, were defined at the 80 to 85% similarity level. These groups were identified as actinomycetes (mycelial forms, four clusters), coryneforms, Enterobacteriaceae, Klebsiella aerogenes, Micrococcus spp. (two clusters), Nocardia species (two clusters), Pseudomonas spp. (two clusters), and Sphaerotilus natans. It is concluded that the degradation of petroleum is accomplished by a diverse range of bacterial taxa, some of which were isolated only at given sampling stations and, more specifically, from sediment collected at a given station.

Bacteria↗
PubMed1976

Measuring the potential activity of hydrocarbon-degrading bacteria.

[14C]hydrocarbons were utilized as a means of estimating the hydrocarbon-degrading potential of bacteria in estuarine and marine environments. Evaporation of the hydrocarbons must be considered in estimates of oxidation. Amount of mineralization of [14C]hexadecane can be equated with the total number of petroleum-degrading bacteria and the percentage of the total heterotrophic population, which they represent. Mineralization activity was found to be related to the activity of the bacterial populations during in situ incubation. Rates of mineralization were observed, as follows, for [14C]hexadecane greater than [14C]naphthalene greater than [14C]toluene greater than [14C]cyclohexane. Increased rates of uptake and mineralization were observed for bacteria in samples collected from an oil-polluted harbor compared with samples from a relatively unpolluted, shellfish-harvesting area, e.g., turnover times of 15 and 60 min for these areas, respectively, using [14C]hexadecane.

Bacteria↗