Search PubMed⌕ Search

Biomedical subjects

A B Morrison

Publications and source records attributed to A B Morrison.

At least 37 records · Page 2Linked to original sources
PubMed1978

Humoral inhibitors of the immune response in uremia. I. Effect of serum and of the supernatant of spleen cultures from uremic rats on the mixed lymphocyte reaction.

The effects of the serum of rats with experimentally induced chronic renal failure and of the supernatant of cultured spleen cells obtained from these animals were tested in the mixed lymphocyte reaction (MLR). Serum of uremic rats with blood urea nitrogen levels greater than 35 mg. per 100 ml. and supernatant of spleen cultures from animals with blood urea nitrogen levels greater than 60 mg. per 100 ml. were found to be inhibitory to the MLR. The inhibitory activity of uremic serum was directly correlated with blood urea nitrogen levels. The inhibitory activities both of uremic serum and of the supernatant of cultured uremic spleen cells were further studied and compared. Dialysis in vitro does not remove the suppressing effect of serum or of supernatant on the MLR. Irreversible inhibition of the MLR is observed after 48 hours' exposure to the serum or to the supernatant; this inhibition occurs whether the MLR culture is exposed during the first 48 hours or last 48 hours of incubation. In some uremic rats the inhibitory activity of the serum disappears or is weakened after splenectomy, despite a continued rise in blood urea nitrogen levels.

Animals↗
PubMed1978

A stereologic study of glomerular hypertrophy in the subtotally nephrectomized rat.

Subtotal nephrectomy in the rat is followed by glomerular hypertrophy, glomerulosclerosis, and, ultimately, renal failure. To gain more insight into this sequence, we have made a morphometric study of the glomerular changes following subtotal nephrectomy in the rat during the period of functional compensation before glomerulosclerosis appears. We found a twofold increase in glomerular volume as compared with controls 2 weeks after operation (to approximately 2 X 10(6) cu mu) followed by a linear increase to approximately 5 X 10(6) cu mu at 21 weeks. The rate of increase in glomerular volume in controls did not significantly exceed that of body weight. The volume increase after subtotal nephrectomy is a true hypertrophy, since other morphometric parameters expressed per unit glomerular volume (surface and length densities) were approximately 80% of control values at 2 weeks and constant thereafter. Glomerular hypertrophy up to 21 weeks is accompanied by a stable BUN and a gradually increasing proteinuria. We conclude that glomerular hypertrophy in this system is a pathologic rather than a compensatory process and suggest that it may represent a counter-productive response to hemodynamic changes serving to increase the glomerular filtration rate.

Animals↗
PubMed1976

The Canadian influenza decision, 1976.

This paper explains the Canadian decision process following the isolation and identification of A/New Jersey/8/76 at Fort Dix, New Jersey in February 1976. The cause for concern was the emergence of a swine-like strain related to that which caused the 1918-19 pandemic, together with proved man-to-man transmission. This concern was reinforced since all new influenza A strains known to have infected the number of persons involved at Fort Dix have become strains of epidemic importance. The Fort Dix outbreak gave sufficient warning to allow implementation of a national vaccination program, to prevent and protect against influenza. In the past such an opportunity had not occurred, and vaccine use had, at best, constituted an intervention in the course of an outbreak. The National Advisory Committee on Immunizing Agents had all available information when it reached its decision to recommend vaccination with bivalent (A/Victoria and A/New Jersey) or with monovalent (A/New Jersey) vaccine for selective, high-risk groups. This was an independent, scientifically based decision.

Adolescent↗
PubMed1976

A decrease in cell-mediated immunity in uremia associated with an increase in activity of suppressor cells.

The graft-versus-host (GVH) reactivity of uremic and control spleen cells was studied by popliteal lymph node assay in the rat. The reaction evoked by cells from animals with severe uremia was conspicuously weaker than that evoked by control cells. The magnitude of the GVH reaction induced by control cells was directly proportional to dose, while with the uremic cells the same increases in dose led only to insignificant increases in the strength of the GVH reaction. When mixtures of syngeneic control and uremic cells were used, the GVH reactivity of the control cells was suppressed. The activity of uremic spleen cells can be enhanced (restored) by removal of the sub-population of cells adherent to glass wool. The GVH reaction induced by uremic cells so treated became directly proportional to dose. The removal of the adherent cell population from the uremic spleen cell suspension also led to the disappearance of the suppressor effect in mixtures of control and uremic cells. These results indicate that a decrease in GVH activity of rat uremic spleen cells is due to an increase in suppressor cell activity in the uremic spleen cell population.

Animals↗
PubMed1975

A stereological study of the glomerular filter in the rat. Morphometry of the slit diaphragm and basement membrane.

Kidney from normal male albino rats, of body weight 170-200 g, was fixed by arterial perfusion with buffered tannic acid-glutaraldehyde, and postfixed with osmium tetroxide. Random and isotropic ultrathin sections from 23 different glomeruli from five rats were mounted on slot grids for staining and electron microscopy. Prints of whole glomeruli at a magnification of 3,909 were analyzed by stereological methods. The mean glomerular volume was (8.048 +/- 0.474) X 10(5) mum3 if the glomeruli are treated as spheres. The area of the basement membrane was 0.281 +/- 0.017 mm2 per glomerulus, of which 0.184 +/- 0.011 mm2 represents peripheral basement membrane. The aggregate epithelial slit length per glomerulus was 65.19 +/- 3.84 cm, of which 48.69 +/- 2.87 cm represents epithelial slits abutting on the peripheral basement membrane. Assuming that a slit diaphragm is 390 A wide, and that the pores of the slit diaphragm represent 26% of its area, the mean pore area is 3.96 cm2, of which 2.96 cm2 represents the area of peripheral pores. These findings are discussed in the context of the hydrodynamic theory of glomerular ultrafiltration. We conclude that the porous substructure of the glomerular slit diaphragm is significant in determining the hydraulic conductivity of the glomerulus and hence also solute flux during ultrafiltration.

Animals↗
PubMed1975

Wide-field electron microscopy. A rapid method for the study of histologic material that provides a bridge between light and electron microscopy.

Wide fields of tissue can be rapidly examined by electron microscopy by use of Formvar films for the support of ultrathin sections on slot grids. The intervention of the grid bars of conventional mesh grids is avoided, and a continuous micrograph of the specimen at scanning magnifications can be obtained. Enough material is sublimed from the section and the supporting film by deliberate exposure to the electron beam to permit one to obtain an image with good contrast. This method of examination, which takes in all about two hours, permits examination of an extensive area of tissue in relation both to its topography at low magnifications and to its ultrastructural detail, and accordingly adds to electron microscopy a dimension characteristic of the lower powers of the light microscope. It offers the histopathologist the option of using micrographs taken during the scanning survey of a tissue to detect regions that can be readily re-examined at high magnification in the same ultrathin section.

Animals↗
PubMed1975

Stabilization and clarification of sections mounted on formvar-coated slot grids by deliberate irradiation in the electron beam.

Epon-Araldite sections supported on Formvar-coated slot grids can be stabilized by exposing the area of interest in the column of the electron microscope to irradiation of 0-5C/cm-2. With this procedure one can obtain electron micrographs of high quality, without drift or distortion, from any part of the open slot area. After treatment the support film is not only stable and transparent but robust enough to permit repeated removal and replacement of the specimen in the microscope column. We illustrate the method with a series of electron micrographs with initial magnifications ranging from x300 to x500,000 to show the quality of image that can be achieved. The effect of the irradiation on tissue architecture is checked by resectioning the irradiated sections. We recommend this method of local irradiation of sections for investigations using low or intermediate magnifications for the wide field it permits, for the durability it confers on the specimen and for its convenience.

Cell Membrane↗
PubMed1975

A progressive glomerulosclerosis occurring in partial five-sixths nephrectomized rats.

A chronic renal disease was induced by 5/6 nephrectomy in young adult Wistar albino male rats. Groups of 3 rats were killed at varying time intervals from 10 to 50 weeks after nephrectomy, and the glomerular structure was studied by light and electron microscopy. By light microscopy, increase in glomerular size and hypertrophy of the visceral glomerular epithelial cells were evident as early as the tenth week. Significant degree of glomerular hyalinization started on the 25th week and gradually became more extensive in involvement towards the 50th week. By electron miscroscopy, the hypertrophied glomerular epithelia showed many osmiophilic bodies and vacuoles in their cytoplasm and fusion of foot processes. Beginning on the 30th week, increase of the mesangial matrix was quite evident, and endothelial and epithelial cells disappeared from the areas where the increase was prominent. The increased matrix gradually encroached and occluded capillary lumina and Bowman's space, leading to a formation of obsolescent glomeruli. Whether or not these glomerular changes are due to the glomerular hyperfiltration which has been known to occur after 5/6 nephrectomy remains to be elucidated.

Animals↗
PubMed1973

Halifax drug abuse.

Explore the source record for details and available documents.

Heroin Dependence↗