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Biomedical subjects

G H Cope

Publications and source records attributed to G H Cope.

At least 37 records · Page 2Linked to original sources
PubMed1979

Comparative studies on the nature of purified cytomembranes of the rabbit parotid gland.

Centrifugation procedures have been evolved for isolating purified samples of rough endoplasmic reticulum, Golgi, zymogen granule and plasmalemmal membranes from homogenates of rabbit parotid gland tissue. The purification process was monitored using morphometry and enzyme and chemical marker assays. The membrane preparations were analysed by sodium dodecylsuphate (SDS) polyacrylamide gel electrophoresis, quantitative phospholipid thin layer chromatography and by enrichment studies. The results were used to evaluate various possible general models for the behaviour of membranes during the secretory cycle of parotid acinar cells.

Animals↗
PubMed1978

Stereological analysis of the duct system of the rabbit parotid gland.

The duct system of the rabbit parotid gland constitutes about 5% of gland tissue volume and is divisible into intercalated and striated ducts in a volumetric ratio of about 3:2. The intercalated duct consists of low cuboidal epithelial cells (375 micrometer 2) surrounded by a myoepithlium, and the cells contain a few small secretion granules, particularly at the proximal end of the duct. The cells of the striated duct are larger (531 micrometer 3), columnal in shape, and show a mitochondrial compartment three times that of intercalated duct cells (16.5% of cell volume). These mitochondria are concentrated in a basal and perinuclear position, but they are largely absent from the apical cytoplasm, which is permeated with microfilaments and contains numerous small smooth membraned vesicles, but no clearly recognisable secretion granules. The lateral plasmalemma of these cells is complexly folded, and basal processes interdigitate with those of adjacent cells. This results in an increase in the ratio of apical to lateral/basal plasmalemma from 1:5 in intercalated cells to 1:24 in striated cells. Some slight changes in cell morphology were detected following isoprenaline-induced secretion of the gland in vivo. These included a small increase in the volume fraction of nuclei and mitochondria in intercalated duct cells, and depletion of their secretion granules. Change in striated cells was confirmed to a small increase in the volume of smooth membraned cytoplasmic vesicles. The structure of the duct and changes wrought by isoprenaline are discussed in the context of the role of the duct in the production of saliva.

Animals↗
PubMed1977

Compartmentation of enzymes in the rabbit parotid salivary gland. A study by enzyme histochemical, tissue fractionation and morphometric techniques.

Rabbit parotid gland was chosen as a suitable model tissue for studying the role of membranes in enzyme secretion by acinar cells. The study was initiated using subcellular fractionation techniques. During these experiments the effects of various tissue disruption conditions such as the medium and the duration and vigour of homogenization were explored and the results assessed by enzyme and chemical assays and both quantitatively and qualitatively by electron microscopy. A series of basic fractions was isolated and marker enzyme or chemical assays selected for each of the relevant membrane types (rough endoplasmic reticulum, Golgi apparatus, zymogen granule, plasmalemma). A parallel study was effected using enzyme histochemical methods applied to frozen sections. Interesting comparisons could then be made between histochemical and biochemical methods of enzyme demonstration. These comparisons are discussed. The basic fractions provide the material from which specimens of purified membranes of the four species can be obtained. The isolation and characterization of such purified membranes is the subject of another report.

Acid Phosphatase↗
PubMed1977

Stereological analysis of the mitochondrial compartment of the rabbit parotid gland before and after isoprenaline-induced degranulation.

A stereological analysis of the mitochondrial compartment of the rabbit parotid gland has been carried out before and after isoprenaline-induced degranulation. Normally, mitochondria constitute about 5% of acinar cell volume, 6% of intercalcate duct cell volume and 16% of striated duct cell volume. The ratio of inner electron transport membrane to outer limiting membrane is in the range 2.3:1. Two hours after the induction of secretion by isoprenaline a significant (P less than 0.10) increase in the volume fraction of mitochondria in acinar and intercalated duct cells was noted and this may reflect increased oxidative phosphorylation at this time. Other parameters measured suggest that there is some rounding up of mitochondria Another significant feature was an increase in the number of damaged mitochondrial profiles (+80% to +250%, P less than 0.05) after isoprenaline treatment. This finding is discussed in the context of changes in mitochondrial enzyme levels which have been reported in similar situations.

Animals↗
PubMed1976

Correlative morphological and biochemical study of the effects of isoprenaline on the organelle and membrane content of the rabbit parotid gland.

A quantitative study has been made on the enzymic, chemical and ultrastructural changes that occur in the parotid glands of rabbits as a result of Isoprenaline-induced secretion. Emphasis has been placed on correlating changes in organelle and membrane content which are evident 2 hr after Isoprenaline administration and which have been measured stereologically with the levels of appropriate enzymic or chemical markers, taking into account the contribution made by both the acinar and duct tissue. Lower protein, alpha-amylase and beta-glycerophosphatase levels correlated with reductions in zymogen granule and lysosome volume with whilst plasmalemmal and Golgi membrane areas and their marker enzyme concentrations remained unchanged. However, declines in alkaline phosphatase and succinate dehydrogenase activity (illustrated histochemically), and p-nitrophenyl phosphatase activity at pH 4-5 in the presence of tartrate occurred without any detectable decrease in membrane area. Conversely, an increase in rough endoplasmic reticulum area was measured stereologically but no increases in chemical markers were detected. The extent of correlation of the data is discussed in the context of the mechanism of secretion and the action of Isoprenaline.

Amylases↗
PubMed1970

Liquid-scintillation-spectrometer data processing by desk-top computer.

A desk-top computing system has been programmed to store accurately the quench curves necessary for the calculation of total disintegrations/minute (d.p.m.) of samples containing either one or two radioactive isotopes. In producing d.p.m. values background counts are subtracted, and in binary-labelled samples the counts attributable to each radioactive isotope are separated. The programme also relates d.p.m. to the weight, volume and density of the sample. Each variable is easily recalled and adjustments can be made for different batches of samples without reprogramming. Equally easily changes of radioactive isotope, quenching agent, scintillator or window setting can be accommodated. Quadratic equations are used to express the quench curves. Counting efficiencies obtained when the coefficients in the quadratic equations are derived from three carefully chosen points on a quench curve are compared with those obtained when the coefficients are derived by the method of least squares. The results of both mathematical approximations are compared with the efficiencies read by the eye from graphs.

Carbon Isotopes↗
PubMedDate not supplied

Biphasic expression of IGF-I following subtotal renal ablation.

Insulin-like growth factor-I (IGF-I) has been implicated in the pathogenesis of experimental renal growth. This study was designed to investigate the quantitative and qualitative changes in renal IGF-I which occur during the course of progressive renal scarring in rats submitted to extensive renal ablation. Analyses were carried out at 7, 15, 21, 30, 90 and 150 days after subtotal nephrectomy. Compensatory renal growth occurred over the first 30 days, amounting to a 161% increase in the protein content per remnant kidney (272 +/- 22 vs. 104 +/- 3 mg at the outset, p < 0.001, means +/- SD, n = 6) but DNA per remnant kidney continued to rise, reaching a 285% increase by day 90 (5.12 +/- 0.06 vs. 1.33 +/- 0.06 mg at the outset, p < 0.001), probably reflecting the continued recruitment of inflammatory cells. Changes in extractable renal IGF-I (eIGF-I) were measured by radioimmunoassay. Seven days after subtotal nephrectomy eIGF-I had increased by 70% compared with controls (2.37 +/- 0.22 ng/mg protein vs. 1.39 +/- 0.2 ng/mg at the outset, p < 0.001) but had returned to normal by 30 days. This coincided with a transient increase in the immunostainable IGF-I (iIGF-I) within the cortical collecting ducts which, again, had subsided by 30 days. However, at 90 and 150 days, as severe scarring was detected, a different pattern of immunostaining (iIGF-I) was noted. Strong staining was evident in the injured cells of the distal tubules and within the fibrosed interstitium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗