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J M Overhage

Publications and source records attributed to J M Overhage.

8 recordsLinked to original sources
PubMed1990

Developing renal innervation in the spontaneously hypertensive rat: evidence for a role of the sympathetic nervous system in renal damage.

The spontaneously hypertensive rat (SHR) exhibits increased renal sympathetic nerve activity and neurotransmitter levels compared with the control Wistar-Kyoto rat (WKY). These renal nerve abnormalities have been implicated as the cause of hypertension in the SHR. The aims of the present study were to characterize the ontogeny of renal sympathetic innervation in SHR in order to determine any functional implications. Glyoxylic acid histofluorescent and radio-enzymatic norepinephrine assays demonstrated an accelerated development of renal innervation in newborn and 1-, 2-, 3- and 6-week-old SHR compared with WKY. Sympathetic nervous system function was blocked in developing male SHR by treating pups from days 0 to 14 with: (1) guanethidine, (2) combined alpha- and beta-receptor antagonists (prazosin and timolol), or (3) vehicle (5% sucrose). Blood pressure (mean), renal function (plasma creatinine) and histologic renal damage were assessed at 42 weeks of age. Although the blood pressure of the drug-treated rats remained elevated, renal damage was reduced and renal function was improved compared with control (sucrose-treated) SHR. The data demonstrate that the SHR kidney develops a precocious sympathetic innervation and that inhibition of the development of sympathetic function ameliorates renal damage independently of systemic hypertension.

Animals↗
PubMed1986

Morphological evaluation of vascular smooth muscle cell: length and width from a single scanning electron micrograph of microvessels.

Accurate three-dimensional data on the structure of vascular smooth muscle cells is essential for understanding the microvascular system in both normal or disease conditions. The laborious serial reconstruction methods have limited the amount of data collected on the structure of individual vascular smooth muscle (VSM) cells. The circumferential viewing of whole vessel segments via scanning electron microscopy provides an alternative approach, but even this technique is highly specialized and tedious. This study presents a simplified method to determine the average cell length and width of individual VSM cells by using only one view of a microvessel (single view). The vessels do not have to be isolated for circumferential viewing and can be left in their host tissue if desired. Values for the average VSM cell length and width were obtained by both circumferential- and single-view approach on the same vessels. The average cell length and width obtained from the single-view method (using one-third circumference) duplicated the mean length and width measurements obtained by circumferential viewing.

Animals↗
PubMed1985

Hypertrophy of arteriolar smooth muscle cells in the rat small intestine during maturation.

The purpose of this study was to define structural characteristics for vascular smooth muscle (VSM) cells from the submucosal arteriolar system of the rat small intestine during maturation. Arterioles from 6- to 8-week-old and 10- to 12-week-old male WKY animals were selected from tissue prepared for scanning electron microscopy and mounted on end so that the entire circumference of each vessel could be observed by serial photography using scanning electron microscopy. From each vessel segment, the following measurements were made: outer vessel diameter, number of VSM cells occupying a length of vessel, the number of resolutions each VSM cell makes around the vessel, length of individual VSM cells, and width of lateral processes along their length. At a given age, the length and width of the VSM cell was statistically similar for all types of arterioles. However, the VSM cell increased substantially in length and width from the 6-8- to 10-12-week time periods. The outer diameter for a particular arteriolar type also increased with age. These data suggest that the intestinal vasculature as a common population of smooth muscle cells at a given age in terms of their length, size, and process morphology for the various types of arterioles. Furthermore, maturation of the microvessels is associated with a uniform hypertrophy of the VSM cells from the majority of arterioles such that cells of young adult rats and those of juvenile animals represent distinctly different populations.

Aging↗
PubMed1984

Effect of denervation on the afferent arteriole in the SHR.

To study the role the renal nerves may play in the hypertension of the SHR, we conducted a morphometric study of the afferent arteriole of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) which were subjected to renal denervation (or sham-operation). Methacrylate casts were made of the renal vasculature after perfusion fixation with glutaraldehyde. These vascular casts were then examined and measurements made with the scanning electron microscope (SEM). Afferent arterioles of the denervated SHR were dilated in comparison to the sham-operated SHR, but there was no difference between the afferent arteriolar diameters of the 2 groups of WKYs. However, the afferent arteriolar diameters of the SHR (either group) were smaller than those of the WKY. Renal denervation caused a reduction in systolic blood pressure compared to sham-operated in both strains of rat. We concluded that the dilation changes of afferent arterioles of denervated SHRs may be related to renal autoregulation resulting from the decreased blood pressure. However, the effect of the loss of sympathetic innervation of the arterioles cannot be ruled out.

Animals↗