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Biomedical subjects

J Cronshaw

Publications and source records attributed to J Cronshaw.

At least 37 records · Page 2Linked to original sources
PubMed1975

The effect of several crude oils and some petroleum distillation fractions on intestinal absorption in ducklings (Anas platyhynchos).

Ducklings given hypertonic saline drinking water show significant increases in the rates of Na+ and water transfer across the intestinal mucosa. These increased rates of transfer are maintained as long as the birds are fed dypertonic saline. Oral administration of a single small dose of crude oil had no effect on the basal rate of mucosal transfer in freshwater-maintained ducklings but the adaptive response of the mucosa is suppressed in birds given hypertonic saline. When crude oils from eight different geographical locations were tested, the degree of inhibition varied between them; the greatest and smallest degrees of inhibition being observed following administration of Kuwait and North Slope, Alaska, crude oils respectively. The effects of distallation fractions derived from two chemically different crude oils were also examined. The volume of each distallation fraction administered corresponded to its relative abundance in the crude oil from which it was derived. The inhibitory effect was not associated exclusively with the same distallation fractions from each oil. A highly naphthenic crude oil from the San Joaquin Valley, California, showed the greatest inhibitory activity in the least abundant (2%), low boiling point (smaller than 245 degrees C) fraction and the least inhibitory activity in the highest boiling point (greater than 482 degrees C) most abundant (47%) fraction. In contrast, a highly paraffinic crude oil from Paradox Basin, Utah, showed the greatest inhibitory effect with the highest boiling point fraction and a minimal effect with the lowest boiling point fraction; the relative abundances of these two fractions in the crude oil represented 27 and 28% respectively. Water-soluble extracts of both crude oils also had inhibitory effects on mucosal transfer rates and these roughly proportionate to the inhibitory potency of the low boiling point fraction of each oil. Weathered samples of San Joaquin Valley, California, and the Paradox Basin, Utah, oils showed greater effects than corresponding samples of unweathered oils even though most of the low molecular weight material from both oils was either evaporated or solubilized in the underlying water during the 36-h weathering period.

Animals↗
PubMed1974

A biochemical and cytochemical study of adenosine triphosphatase activity in the phloem of Nicotiana tabacum.

A biochemical and cytochemical study has been made of the distribution of ATPase in mature and differentiating phloem cells of Nicotiana tabacum and of the substrate specificity and effects of fixation on enzyme activity. Homogenates of unfixed leaf midveins and midveins fixed in formaldehyde-glutaraldehyde were assayed for enzyme activity by determining the amount of P(i), liberated per milligram of protein from various substrates in a 30 min period at pH 7.2. In fresh homogenates, hydrolysis of ATP was not significantly different from that of ITP, CTP, and UTP. Hydrolysis of GTP was slightly higher than that of ATP. ATP hydrolysis by fresh homogenates was 17% more extensive than that of ADP, 76% more extensive than that of 5'-AMP, and was inhibited by fluoride and p-chloromercuribenzoate (PCMB). There was little or no hydrolysis of the competitive inhibitors 2'- and 3'-AMP nor with the alternate substrates p-nitrophenylphosphate (PNP) or beta-glycerophosphate (beta-GP). In homogenates of material fixed in formaldehyde-glutaraldehyde for 1(1/4) h, ATPase activity was 13% preserved. Hydrolysis of ATP by fixed homogenates was not significantly different from that of ADP, 5'-AMP, ITP, CTP, and GTP. Hydrolysis of UTP was lower. Fluoride and PCMB inhibited fixed ATPase activity. The results of cytochemical localization experiments using a lead phosphate precipitation technique were in agreement with the biochemical results. Similar localization patterns were obtained with the nucleoside triphosphates ATP, CTP, GTP, ITP, and UTP. Activity was also localized with ADP and 5'-AMP but not with the competitive inhibitors 2'- and 3'-AMP, nor with PNP or beta-GP. Little or no reaction product was deposited in other controls incubated without substrate or with substrate plus fluoride, PCMB, or N-ethylmaleimide. ATPase activity was demonstrated chiefly at the plasma membrane of mature and differentiating phloem cells and was associated with the P-protein of mature sieve elements. It is suggested that the phloem transport system derives its energy from the demonstrated nucleoside triphosphatase activity.

Adenosine Monophosphate↗
PubMed1968

P protein in the phloem of Cucurbita. I. The development of P-protein bodies.

Light and electron microscopical observations of the cells of the phloem of Cucurbita maxima have shown that two distinct types of P-protein bodies are formed: a larger type which arises as fine fibrils and a smaller type which apparently arises as groups of tubules. The tubules of the smaller type of body measure 242 +/- 3.6 (SE) A (n = 48) and appear morphologically identical with the P1-protein tubules of Nicotiana tabacum L. In some of these P1-protein bodies the tubules are arranged in a regular manner with a center-to-center distance of 295 A. The P protein of the larger type of P-protein body is first apparent in the cytoplasm as small aggregates of fine fibrils. This P-protein component has been designated P3 protein. As the P3 protein accumulates it is organized into large bodies. Some of these bodies contain only P3 protein, others a tubular form of protein, and still others a combination of P3 protein and a tubular form. This variability indicates that there is a developmental sequence of the formation of tubules from the P3-protein fibrils. These tubules measure 179 +/- 8.2 (SE) A (n = 31) and have been designated P4 protein.

Microscopy↗