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Biomedical subjects

R G Rowland

Publications and source records attributed to R G Rowland.

83 records · Page 5Linked to original sources
PubMed1980

Effects of urine and continued exposure to carcinogen on progression of early neoplastic urinary bladder lesions.

Based on reports of regression of superficial bladder tumors after urinary diversion, a study was designed to measure the effects of urine and continued exposure to carcinogen on the incidence of progression of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide-induced early urinary bladder lesions to invasive tumor. After being fed 0.2% N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide diet for 14 weeks, one-half of the male Fischer rats had urinary diversion by ureterosigmoidostomy, and the remainder were sham operated. One-half of each of these two groups was continued on the N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide diet while the remaining animals were fed regular chow postoperatively. One-half of each of the four groups was sacrificed at 3 months, and the remainder were sacrificed at 6 months after ureterosigmoidostomy or sham-operation. The incidence and mean number of tumors as well as the incidence of invasive tumor were tabulated. The combined 3- and 6-month data indicate that excreted carcinogen in the urine influences progression of the preinvasive lesions more than urine alone or systemic carcinogen alone. However, urine alone had a significant effect (p < 0.025) on tumor incidence (8 of 19 sham-operated animals with tumor versus 1 of 18 diverted animals with tumor). Urine acts as a promoter in this experimental system. These findings may have clinical applications in the treatment of early transitional cell carcinoma.

Animals↗
PubMed1979

Ureterosigmoidostomy in rats: a model for the study of bladder tumour carcinogenesis and cocarcinogenesis.

A modified Coffey I ureterosigmoidostomy has been developed in rats as a model of urinary diversion for studying bladder carcinogenesis and co-carcinogenesis. Diverted and sham-operated animals were killed at 1, 3 and 6 months. Excretory urograms revealed minimal hydroureteronephrosis in most diverted animals. Upper tract bacterial colonisation was 9 times more frequent in diverted animals. Approximately one-third of the diverted animals had focal cortical scarring; however, renal function was normal in all groups as assessed by serum creatinine and electrolytes. These studies indicate that ureterosigmoidostomy in rats is a satisfactory model of urinary diversion for studying carcinogenesis.

Animals↗
PubMed1978

Polychlorinated biphenyls may alter marine trophic pathways by reducing phytoplankton size and production.

Polychlorinated biphenyls at concentrations of 1 to 10 micrograms per liter reduced phytoplankton biomass and size in natural estuarine phytoplankton communities grown within dialysis bags in situ in an estuarine marsh. In polychlorinated biphenyls-contaminated waters, these changes could increase the number of trophic levels and divert the flow of biomass from harvestable fish to jellyfish and other gelatinous predators.

Carbon Dioxide↗
PubMed1977

Response to polychlorinated biphenyls of marine phytoplankton isolates cultured under natural conditions.

Polychlorinated biphenyls (PCB) at a concentration of 10 mug/liter substantially but temporarily suppressed the growth rate and photosynthesis of two species of Thalassiosira recently isolated from Long Island Sound and grown in dialysis membrane bags suspended in the tidal channel of an estuarine marsh. Inhibition of carbon fixation was apparently due to reduced levels of chlorophyll a per PCB-treated cell, but no significant loss of function per unit of existing chlorophyll a was observed. Cell concentrations in all size classes (3.2- to 18.6-mum-equivalent spherical diameters) were markedly lower in PCB-treated cultures, with toal biomass equaling only 30% of that in control cultures throughout the experiment.

Aroclors↗
PubMed1973

Adrenal corticosteroid-induced renal cystic disease in the newborn hamster.

A new model of renal cystic disease was developed in newborn Syrian hamsters by the repeated injection of 9-fluoroprednisolone acetate (9-FPA), a long-acting adrenal corticosteroid. Kidneys harvested from the tenth to the fourteenth day of age showed diffuse cystic dilatation of nearly all cortical convoluted tubules. Microdissection revealed that cystic changes primarily involved proximal convoluted tubules and, to a lesser degree, the distal tubules. Electron microscopy showed immaturity of development and varying degrees of degeneration of the cells of the proximal convoluted tubule. Intraluminal obstruction was not detected and therefore could not account for the cystic changes. Analysis of electrolytes in serum and selected tissues showed a significant reduction in potassium and sodium of serum, and significant depletion of potassium, magnesium and calcium in the skeletal muscle. Thus, there was no direct relationship between an electrolyte deficiency and the cystic changes.

Animals↗