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Biomedical subjects

G Clough

Publications and source records attributed to G Clough.

At least 37 records · Page 2Linked to original sources
PubMed1982

The effects of temperature on ferritin transport by endothelial cell vesicles in the capillaries of the frog mesentery.

Using electron microscopy we have determined the appearance of ferritin in the endothelial cell vesicles of frog mesenteric capillaries after varying periods of exposure of the luminal surface of the cell to a ferritin solution, at 17-20 degrees C and at 4-7 degrees C. At 17-20 degrees C, the pattern of labelling observed in the absence of flow through the capillary is very similar to that previously described by us in continuously perfused capillaries [1]. Some vesicles are labelled after the shortest exposures (less than 1 sec) and labelling increases with exposure to reach steady values at 40-60 s. At 4-6 degrees C, a similar initial level of labelling is observed. There is, however, no further increase in labelling as the period of exposure is increased. The effect of temperature on the uptake and transfer of ferritin by the endothelial cell vesicles is consistent with our previous view. We suggest that the cavities of the rapidly labelling vesicles communicate directly with the capillary lumen [1], and their labelling should be unaffected at low temperatures. The secondary, slow rise in labelling, we suggested, resulted from fusions of adjacent vesicles and we would expect this process to be abolished at low temperature.

Animals↗
PubMed1981

The role of vesicles in the transport of ferritin through frog endothelium.

1. The transport of ferritin molecules by endothelial cell vesicles has been quantitatively investigated by electron microscopy. Single mesenteric capillaries of pithed frogs were perfused with solutions containing 6.7 g ferritin 100 ml.-1 for known periods before fixation in situ with osmium tetroxide. 2. Two series of experiments were carried out: in the first series the perfusate contained bovine serum albumin (1.0 g 100 ml.-1); in the second series the perfusate contained no protein other than the ferritin. To assess the molecular radius of ferritin in solution, the free diffusion coefficient of ferritin was measured in the presence and absence of albumin. 3. The free diffusion coefficient of ferritin in saline solution (110 m-mole 1.-1) was found to be 0.35 X 10(-6) cm2 sec-1 at 21 degrees C and was not affected by the presence of bovine serum albumin. This indicates that there is no significant binding of albumin to ferritin in solution and yields a value for the Stokes-Einstein radius of ferritin of 6.1 nm. 4. In all perfusion experiments the percentage of luminal vesicles containing ferritin exceeded the percentage of labelled cytoplasmic vesicles, which in turn exceeded the percentage of labelled abluminal vesicles. 5. Labelling of all vesicle populations was seen after perfusions lasting less than 1 sec. At this time luminal vesicles were more heavily labelled in the absence of albumin. 6. The labelling of luminal vesicles increased with lengthening perfusion times up to 30-40 sec, after which steady levels of labelling were achieved. The rate of rise in luminal labelling and the steady-state levels reached were both greater in the absence of albumin. By contrast cytoplasmic labelling increased above its initial value only after perfusions of longer than 10 sec. 7. In the steady state, labelled cytoplasmic vesicles contained, on average, fewer ferritin molecules than labelled luminal vesicles. This finding is inconsistent with translocation of labelled luminal vesicles across the cell. 8. It is suggested that the early constant labelling of cytoplasmic and abluminal vesicles is consistent with the existence of vesicular channels. Later cytoplasmic labelling may result from the transient fusion of cytoplasmic vesicles with labelled luminal vesicles for periods long enough to allow mixing of vesicular contents. Albumin may affect vesicular transport by its interaction with the endothelial glycocalyx.

Animals↗
PubMed1978

Simultaneous measurement of pressure in the interstitium and the terminal lymphatics of the cat mesentery.

1. Simultaneous measurements of the pressure in terminal lymphatics and interstitial tissue have been made in the exteriorized cat mesentery superfused with either physiological salt solution (Krebs solution) or a water-immiscible fluorocarbon, FC-80. 2. The pressures within individual terminal lymphatics were measured using glass micropipettes attached to a servo pressure-measuring system. Tissue pressures were recorded using saline-filled cotton-wool wicks. 3. Mean pressure recorded in the terminal lymphatics of the Krebs-superfused mesentery were slightly above atmospheric (+0.2 mmHg, n = 45), while those recorded in the FC-80-superfused mesentery were slightly below atmospheric (-0.2 mmHg, n = 46). 4. Tissue pressures were also slightly subatmospheric in the in situ mesentery, and the recently exposed tissue. Continuous superfusion with Krebs solution caused the tissue pressure to rise to atmospheric pressure or above; with FC-80-superfusion the tissue pressure also rose, but never to above atmospheric pressure. 5. Isolated strips of mesentery immersed in Krebs solutions of different concentrations gained weight, but when immersed in FC-80 no change in weight was detected. 6. It was concluded that the interstitial gel of the mesentery is normally unsaturated and that superfusion with Krebs solution leads to tissue oedema. This tendency is less marked in FC-80-superfused preparations. Possible mechanisms for lymph formation and propulsion are discussed.

Animals↗
PubMed1976

Ammonia build-up in animal boxes and its effect on rat tracheal epithelium.

Some common laboratory species are now considered unsuitable for the study of the toxicity of inhalants because of the natural incidence of abnormal respiratory histology. Levels of ammonia commonly encountered in animal boxes and cages have been shown to cause histopathological changes in the tracheal epithelium of rats, and it is suggested that 'abnormal respiratory histology" could be a reflection of the standard of husbandry employed before and during an experiment.

Ammonia↗