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Biomedical subjects

J S Wakefield

Publications and source records attributed to J S Wakefield.

At least 19 recordsLinked to original sources
PubMed2000

The histology and growth kinetics of canine renal oncocytoma.

A renal oncocytoma was diagnosed in a 10-year-old English springer spaniel with a 5-month history of anorexia, vomiting and weight loss. The tumour, which was localized to the kidney, was treated by simple nephrectomy and the dog made a full recovery. Histologically, the tumour consisted of cells with abundant eosinophilic cytoplasm forming acini and alveolar nests set within a loose fibrovascular stroma. The results of cell kinetic studies (AgNOR score 2.68, PCNA index 5.2%) were comparable with findings reported for benign human renal tumours. This appears to be the first reported case of renal oncocytoma in a dog.

Adenoma, Oxyphilic↗
PubMed1997

Ultrastructure of streptozotocin-induced renal tumours in mice.

Streptozotocin-induced tumours in the kidneys of experimental animals have been shown to be histologically similar to human renal cell carcinoma. We report the ultrastructural features of renal tumours induced in 15 mice by a single intravenous bolus of 2.5% streptozotocin administered in a dose of 250 mg streptozotocin/kg mouse body weight. Animals were sacrificed 232-361 days after the administration of streptozotocin. On examination both kidneys from each animal contained 1-4 dysplastic tubules and 1-3 discrete tumours per kidney. Twelve dysplastic proximal convoluted tubules showing varying degrees of epithelial atypia and nine tumours exhibiting either a papillary or solid architecture were examined. Dysplastic epithelial cells and tumours of papillary and solid type exhibited complex cell borders with well-developed junctional complexes. The majority of cells contained surface microvilli, and in some cells microvilli-lined intracytoplasmic lumina were observed. Occasional dysplastic epithelial cells and tumour cells contained double-membrane vesicles 120-200 nm in diameter. These were similar to the intracytoplasmic vesicles characteristic of human chromophobe renal cell carcinoma. Intracytoplasmic collections of glycogen granules and flocculant protein were identified in both dysplastic and neoplastic cells, and where prominent they resulted in compression of cytoplasmic organelles. Coated vesicles were commonly observed. These were free within the cytoplasm and were also seen budding from strands of rough endoplasmic reticulum. The distribution of these vesicles suggested a role in protein transport from the rough endoplasmic reticulum. It is concluded that while streptozotocin-induced renal tumours have some ultrastructural features in common with human chromophobe renal cell carcinoma, the overall ultrastructural morphology differs significantly from that described for the various histological types of human renal cell carcinoma.

Animals↗
PubMed1991

Therapeutic mineral enrichment of dental plaque visualized by transmission electron microscopy.

The form, location, and distribution of fluorhydroxyapatite deposited in dental plaque by a urease-mediated mineral enrichment process have been studied by transmission electron microscopy. Artificial plaque was formed in terylene gauze in the mouth of one subject and immersed for five min four times per day in a mineral-enriching solution. Contralateral control plaque remained untreated. The effect on natural plaque was studied in two subjects who withheld oral hygiene for four days and mouthrinsed with this solution for two min four times per day during the last two days. Mineral deposits were seen in all plaque samples exposed to the test solution. None was detected in any control sample. The deposits were scattered in the interbacterial matrix as needle-shaped crystals, the size and shape of apatite, together with amorphous material. The crystals appeared larger and more perfect, and the amorphous material less conspicuous, with longer in vivo rinsing periods. Platelet-shaped crystals of octacalcium phosphate were never seen. Mineral was also seen within the remnants of dead bacterial cells and within degenerating epithelial cells. Crystals were never seen within intact bacterial cells, as in calculus formation. The presence of a single crystal type and the relative absence of densely-mineralized foci are other differences between this mineral-enrichment process and supra-gingival calculus formation. A longer-term study is necessary to determine whether the solution promotes calculus by providing nucleation seeds.

Calcium Chloride↗
PubMed1991

A multi-station dental plaque microcosm (artificial mouth) for the study of plaque growth, metabolism, pH, and mineralization.

A plaque growth chamber was developed for long-term growth of five separate plaques from the same plaque or saliva sample under identical conditions of temperature and gas phase. Reagent addition and growth conditions for each plaque could be independently controlled, and each was accessible for sequential sampling and electrode insertion. Plaques were cultured for over six weeks on pellicle-coated Lux (TM) 25-mm diameter cover-slips at 35 degrees C under 5% CO2 in N2, and supplied with a medium containing 0.25% mucin (BMM) at 3.6 mL/h, and with periodic 5% sucrose. Electron microscopy and flora analysis of microcosm plaques showed that they had close similarities to reported characteristics of natural dental plaques. Diverse motile bacteria were present. Sucrose-induced Stephan pH curves and urea-induced pH rises were also similar to those reported for natural plaques. Changes in plaque urease, calcium, phosphate concentrations, and the flora were followed over five weeks in a plaque supplied with BMM containing additional 2.5 mmol/L calcium and 7.5 mmol/L phosphate. Despite this high environmental calcium phosphate concentration, there was no continuing increase in calcium levels, although plaque phosphate doubled. Urease levels fluctuated. Changes in the cultivable flora were minor. A urea-containing calcium phosphate/mono-fluorophosphate pH 5 solution, applied for six min every two h for seven days, increased plaque calcium, phosphate, and fluoride to high levels. Thus, plaques grown over several weeks in the multi-station artificial mouth exhibited metabolic and pH behavior typical of natural plaques, could be analyzed during development, and the system allowed manipulation of environmental variables important in plaque pH control and calcification.

Bacteria, Aerobic↗
PubMed1982

Is Percoll innocuous to cells?

Peritoneal macrophages from mice, isolated rat liver Kupffer cells and rat testis Leydig cells ingested large numbers of Percoll particles, a gradient medium widely used for separation of cells and subcellular organelles by density-gradient centrifugation. A decrease in the percentage of macrophages adhering to plastic also occurred after exposure of the cells to Percoll, even at 4 degrees C, a temperature at which Percoll was not ingested. The effect of Percoll on macrophage adherence may involve a loose association between the density medium and the cell surface. Other cell-surface-related phenomena may also be affected by prior exposure of cells to Percoll.

Animals↗
PubMed1982

The induction of rat bladder cancer by 2-naphthylamine.

The widely held belief that 2-naphthylamine is not carcinogenic for the rat has been re-examined. Twenty female Wistar rats were dosed by gastric intubation weekly for 57 weeks with 2-naphthylamine, 300 mg/kg body wt, in arachis oil and 20 controls were given arachis oil alone. Animals which became moribund were killed during the course of the experiment and the remainder after 100 weeks. A 2-naphthylamine-treated animal died at 21 weeks; all others survived 57 weeks or longer. The urinary tracts of all but two 2-naphthylamine-treated animals, which were found dead and cannibalized, were examined histologically.No neoplastic disease of the urinary tract was present in control animals. In 10 of the 2-naphthylamine-treated rats there was neither neoplasia nor hyperplasia of the urothelium, but 4 of the 18 examined histologically had large, macroscopically visible bladder cancers; one of these also had bilateral transitional cell tumours of the kidney calyces and multiple tumours in both ureters. Another animal had bilateral urothelial cancers in the ureters. The histology and ultrastructure of these urothelial cancers were comparable to those of rat transitional-cell carcinomas experimentally induced with other chemical carcinogens.These results, considered in the context both of early and more recently published biochemical studies of 2-naphthylamine metabolism in the rat, support the possibility that production of the active carcinogenic metabolite in this species may be influenced by a pH-dependent, non-enzymic mechanism in the urine, which could account for individual, strain- and diet-related variations in response in the rat.

2-Naphthylamine↗
PubMed1982

Isolation of rat Leydig cells by density gradient centrifugation.

A rapid method for preparing Leydig cells from rat testes is described. An interstitial cell suspension, prepared by collagenase treatment of decapsulated testes, was centrifugal for 10 min over a cushion of 60% (v/v) Percoll to remove red blood cells, and then centrifuged for 20 min in a 0-60% linear density gradient of Percoll. Seventy-four per cent of the cells present in that fraction of the gradient comprising 35-50% Percoll were Leydig cells; the yield from each testis was about 1.5 x 10(6) cells. The Leydig cells appeared viable, excluded Trypan blue, possessed high-affinity binding sites for human chorionic gonadotrophin (hCG) and synthesized increased quantities of testosterone in response to hCG. The cells could be stored overnight in 20% (v/v) glycerol at -20 degrees C, with only minimal effect on the specific activities of a number of enzymes used as markers of subcellular components. Testosterone production in vitro by the cells after storage for 20 h was greater than that of hCG-stimulated fresh cells and was not further increased by hCG.

Animals↗
PubMed1981

Microvilli of the human term placenta. Isolation and subfractionation by centrifugation in sucrose density gradients.

Human placental microvilli were isolated and separated into two fractions by centrifugation in sucrose density gradients. Electron-microscopic morphology and morphometry, the distribution of enzymic activities and the results of sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of proteins were used to assess the purity of the final preparations and to define their properties. The combined evidence strongly suggested that the preparations contained negligible material that was not plasma membrane. The two fractions of microvilli differed in buoyant density, protein composition, enzyme specific activities and microscopic appearance. Some of these differences were explained by the absence of internal structure in the microvilli of the lighter fraction.

Cell Fractionation↗
PubMed1978

Cilia and sperm tail abnormalities in Polynesian bronchiectatics.

Sperm tails and bronchial cilia from Polynesians with bronchiectasis were examined in the electron microscope. The outer doublet tubules of the axonemal skeleton in these organelles either lacked dynein arms or had only partial arms. Various other cilial abnormalities were common. The sperm were immotile and pulmonary mucociliary clearance was reduced or absent.

Bronchi↗