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Biomedical subjects

R Osterby

Publications and source records attributed to R Osterby.

At least 91 records · Page 5Linked to original sources
PubMed1979

Early functional and morphologic vascular renal consequences of the diabetic state.

Renal hyperfunction and hypertrophy are characteristic findings in the early diabetic state, both in diabetes mellitus and in experimental diabetes. A number of structure-function relationships and their likely mechanisms are discussed. The metabolically induced hypertrophy of glomerular capillaries possibly plays a central role. Its cause is not known, but recent results on its time-course emphasize the probable long-term consequences of the irreversibility of the accumulation of basement membrane material.

Albuminuria↗
PubMed1979

Determination of membrane thickness distribution from orthogonal intercepts.

This report deals with the reconstruction of the distribution of membrane thickness T from that of orthogonal length Lo, measured in random section planes. In such planes the membrane appears as a band and the linear distance from one of its boundaries perpendicular to the opposite one is the length of the orthogonal intercept. Using a membrane model, an integral equation relating the probability density functions of orthogonal intercept length f(lo) and membrane thickness g(tau) is derived. Relations between moments are derived and the analytic solution to the problem of reconstructing g(tau) from f(lo) is given. The parametric approach by which it assumed that g(tau) has some known analytic form with unknown parameters is considered, and the use of a suggested analytic form for describing the thickness distribution of the human glomerular basement membrane is discussed.

Basement Membrane↗
PubMed1978

Growth hormone enhances basement membrane thickening in experimental diabetes. A preliminary report.

Injection of porcine growth hormone (200 microgram) or saline 5 days a week for 16 to 20 weeks in streptozotocin-diabetic rats showed that compared to saline growth hormone produced a 2 1/2-fold larger increase in glomerular capillary basement membrane thickness (2p = 0.027). The possible significance of this effect of an elevated level of growth hormone for diabetic microangiopathy is discussed.

Animals↗
PubMed1978

Distribution of membrane thickness determined by lineal analysis.

The expected statistical distributions of intercept length are derived in terms of geometrical probability density functions pertaining to plates with known thickness penetrated by lines with random orientation. These expressions provide arithmetic and graphical solutions for obtaining distributions of membrane thickness and reciprocal membrane thickness from empirical distributions of intercept lengths. Furthermore, general relationships between probability density functions of distributions of intercept length and membrane thickness are derived as well as those between their moments. Examples of the application of the method to biological samples are given, and estimated distributions of glomerular basement membrane thickness are compared to those obtained by an independent, direct method. Various sources of bias, which in practice may occur due to departures from the sample model, are discussed and the influence of some of them is estimated. The knowledge of the probability density function of reciprocal intercepts makes it possible to perform a correction of the distribution of measured intercept length, which to some extent eliminates bias.

Animals↗
PubMed1977

Glomerular size and structure in diabetes mellitus. II. Late abnormalities.

A study of autopsy kidney material from six long-term diabetics and four controls was performed in order to elucidate the mechanism of the glomerular enlargement in long-term diabetics. The volume and the severity of the glomerular lesions were measured in each of a number of randomly selected, open glomeruli. The relative amount of solid material was taken as an expression of the severity of the glomerular lesion. In the long-term diabetics the volume of open glomeruli was almost doubled compared to that of controls and in the individual subject the enlargement was found to be inversely related to the relative amount of solid material in the glomeruli. This indicates that the enlargement of open glomeruli in long-term diabetics is due to a compensatory hypertrophy rather than to the excessive deposition of basement membrane material. The number of nuclei per open glomerulus was increased in long-term diabetics, but nuclear size was unchanged. Most of the long-term diabetics had a large number of occluded glomeruli and the individual, relative number of such glomeruli correlated closely both with the duration of diabetes above 15 years and the concentration of creatinine in serum. It is concluded that the destruction of glomeruli due to diabetic microangiopathy is compensated for some years by hypertrophy of the least affected glomeruli. This compensatory hypertrophy of glomeruli might well account for the preservation of renal funtion in long-term diabetics for a number of years despite the progressive basement membrane lesions of diabetic microangiopathy.

Adult↗
PubMed1977

Glomerular size and structure in diabetes mellitus. III. Early enlargement of the capillary surface.

The present electron microscopic study shows that the kidney hyperfunction in early diabetes can be due to a significant morphological change: an increased glomerular filtration surface. Applying standard stereological methods, the area of the peripheral wall of the glomerular capillaries was measured in biopsy specimens obtained from 7 patients with early diabetes and 7 controls.--An 80% enlargement of the capillary wall (the surface of the peripheral basement membrane) was found in the diabetics (2p=0.0096). Also the total area of the interface between the tuft and the urinary space was increased by 70% (2p=0.029). Since the thickness of the peripheral basement membrane is known to be unchanged in patients with early diabetes the finding of an increased area of the membrane implies that an increased quantity of basement membrane material is present in these patients. The significance of this phenomenon for the understanding of the metabolism of the basement membrane is discussed, and a working hypothesis is advanced for the pathogenesis of the diabetic microangiopathy.

Basement Membrane↗
PubMed1975

Glomerular size and structure in diabetes mellitus. I. Early abnormalities.

The volume of the glomerular tuft and its components was estimated in juvenile diabetics at onset and after one to six year's duration of the disease. An enlargement of the glomerular tuft was demonstrated in the newly diagnosed diabetics. In these patients the volume of both the individual capillary lumina and of the individual glomerular cells was enlarged, whereas the number of cells was unchanged. Although a partial normalization is seen in diabetics after a few years' disease, such patients still have an elevated capillary volume. The possible relationship between these findings and the well-documented elevation of the glomerular filtration rate in diabetics is discussed. It is suggested that the mechanism behind the morphological and functional changes is either a pressure-induced unfolding of the capillary wall or an increase of the capillary wall area, but the present study permits no distinction between these possibilities.

Capillaries↗