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Biomedical subjects

L O Simpson

Publications and source records attributed to L O Simpson.

At least 109 records · Page 6Linked to original sources
PubMed1982

A hypothesis proposing increased blood viscosity as a cause of proteinuria and increased vascular permeability.

Currently accepted concepts of renal and vascular physiology are inadequate to explain the reversible increases in vascular permeability which occur during episodes of increased blood viscosity. On the basis that all basement membranes exhibit biological thixotropy, it has been suggested that basement membranes are pressure dependent. The physiological significance of increased blood viscosity lies in the associated increase in peripheral vascular resistance which develops because of altered blood rheology. In order to overcome the peripheral resistance, intravascular pressure rises, and if adequate pressures develop, plasma proteins may deform and pass through the vascular basement membrane. This is considered to be the mechanism of proteinuria. In the treatment of high blood viscosity disorders it is suggested that the immunosuppressant drug, Thiamphenicol, may be useful because of its ability to induce a reversible dose-related depression of erythropoiesis, and thereby reduce blood viscosity.

Blood Viscosity↗
PubMed1981

Increased blood viscosity as the pathogenic agent in minimal change nephrosis: a new hypothesis.

It is proposed that minimal change nephrosis (MCN) is the result of impaired glomerular blood flow to slightly increased blood viscosity or to an abnormality of an autoregulatory mechanism controlling glomerular perfusion pressure or to unusually small efferent arterioles, or to combinations of these factors. The functional response to any of such changes would be an increase in intraglomerular pressure. If the pressure exceeded a critical level albumin would be able to pass into Bowman's space after deforming the pressure-dependent thixotropic basement membrane. In response to the presence of albumin in Bowman's space, epithelial cell foot process retraction would be initiated. The concentration of albumin capable of stimulating this reversible change in unknown. If it can be shown that MCN is a consequence of increased blood viscosity, then drugs having direct effects on blood viscosity might offer alternatives to steroid treatment.

Albuminuria↗
PubMed1981

Basal processes on duodenal epithelial cells of man, mouse and rat.

Localized ischaemia of duodenal mucosa induced either by ligation or cautery of a small branch of the coeliac artery resulted in the loss of epithelial cells of duodenal villi in young mature inbred mice. Biopsies from normal human duodenum and mouse duodenum placed in non-oxygenated physiological saline for 20 min showed a similar loss of epithelial cells. In all cases, scanning electron microscope (SEM) examination revealed that processes extended from the base of epithelial cells through the underlying basement membrane. When duodenal tissues were bathed in solutions of EDTA or sodium azide, basal processes were not seen by SEM. Transmission electron microscopy (TEM) of duodenal tissues from man, rat, and mouse revealed basal processes. Because all duodenal epithelial cells appear to have basal processes, it is proposed that they may play an important role in moving absorbed substances across the villous basement membrane barrier along an intracellular concentration gradient, and in thus facilitating absorption. There are no indications which would suggest that basal processes are the result of a pathological process, and the presence of similar basal processes in other tissues is noted.

Animals↗
PubMed1981

Pseudo-lymphocyte monocytes--the memory cells responsible for the development of epitheloid cell granulomata. A new hypothesis.

This hypothesis proposes that, in individuals with an appropriate genetic background, monocyte memory cells are formed when histiocytes and macrophages undergo mitosis following first exposure to a granulomagenic agent and circulate as pseudolymphocytes in the lymphocyte null cell population. It is proposed that epithelioid cell granulomata develop from a clone of cells formed from monocyte memory cells on the second or subsequent exposure to the same granulomagenic agent. Epithelioid cell granuloma formation is therefore not dependent on T-cell function, although the cellular nature of the granuloma appears to depend upon the nature of a concomitant but independent classical immune response. The implications of pseudolymphocyte memory cells on the development of granulomata of both exogenous and endogenous origin, and the relationships between lymphocytes and cells of the monocytic phagocyte series are discussed.

Animals↗
PubMed1980

Experimental granulomatous inflammation: the ultrastructure of the reaction of guinea pigs to bentonite injection.

Bentonite, a silicate, induces a classical non-immunological foreign body reaction when injected intradermally into guinea pigs. The cellular response consists of a mass of macrophages and large macrophage polykaryons, surrounded and infiltrated by an extensive fibrous reaction. The bentonite granuloma shows no signs of intercellular organisation of the reacting cells. Study of its ultrastructure suggests a low turnover lesion with a stable, long-lived cell population. The bentonite granuloma is contrasted with the tuberculous, immunologically mediated epithelioid cell granuloma produced in sensitised guinea pigs.

Animals↗
PubMed1980

A new periodontal membrane biology based upon thixotropic concepts.

The biology of the periodontal membrane is not completely understood, and tissue changes associated with orthodontic tooth movement are assumed to be the result of a recoverable pathologic process. The response of this tissue to dynamic loading may, however, be explained by changes in viscosity of the collagenous matrix.

Biology↗
PubMed1980

Biological thixotropy of glomerular basement membrane and the implications of thixotropic in explaining basement membrane permeability.

Glomerular basement membranes (GBMs) are considered to exhibit the characteristics of biological thixotropic systems, and because of this GBM permeability is determined by intravascular pressure. The significance of pressure as the major determinant of GBM permeability is discussed. Factors leading to GBM permeability to albumin following interruption of renal blood flow are examined, and a possible explanation for the phenomenon is proposed.

Animals↗
PubMed1980

A mouse model of spontaneous renal hypertension. blood pressure, heart weight, kidney weight and proteinuria relationships in NZB x OUW F1 hybrid female mice.

Data concerning blood pressure, kidney weight, heart weight and proteinuria were obtained from different groups of BW mice. Relatively early in life, systolic blood pressures as measured by a tail-cuff method, were above the upper limits of normal, continued to rise with increasing age and had peak average values coinciding with the peak death period and increased proteinuria. Any relationships which might exist among age, body weight and heart weight or kidney weight were sought by computerized polynomial multivariate analysis. It was found that, although there was only a slight effect with increasing body weight, both heart weight and kidney weight showed a steady increase with increasing age. These data support the proposal that the BW female mouse is a good model of spontaneous renal hypertension.

Aging↗
PubMed1979

Experimental granulomatous inflammation: the ultrastructure of the granuloma induced by injection of tubercle bacilli into Freund adjuvant-sensitised guinea-pigs.

Injection of killed tubercle bacilli into a sensitised guinea pig produces a characteristic biphasic response with the development of an organised epithelioid cell granuloma in the second phase. Previous sensitisation to tubercle bacilli is a requirement for development of the organised granulomatous response. The main components of the granuloma are epithelioid cells, although multinucleate cells of both Langhans and foreign-body type are present. Epithelioid cells appear to evolve from monocytes, probably in the sequence: (a) monocyte, (b) monocytic transition form, (c) immature epithelioid cell, (d) mature epithelioid cell, although some may possibly develop through a macrophage stage. Differentiation of monocytes into epithelioid cells is a continual process in the experimental tuberculous granuloma with monocytes migrating into the lesion at all stages examined. Epithelioid cells are not obviously phagocytic. Their differ4ntiation has a phase suggestive of biosynthesis during which RER is the predominant cytoplasmic component. This is followed by a storage/secretory phase in which the cytoplasm contains membrane-lined vesicles and prominent Golgi apparatus. The vesicles and, where distended, the RER laminae contain a lightly staining, finely granular material the biological activity of which is unknown.

Animals↗