Search PubMed⌕ Search

Biomedical subjects

J B Weiss

Publications and source records attributed to J B Weiss.

215 records · Page 12Linked to original sources
PubMed1965

[Anisometropia].

Explore the source record for details and available documents.

Humans↗
PubMedDate not supplied

Factors involved in capillary growth in the heart.

Growth of capillaries in the heart occurs under physiological circumstances during endurance exercise training, exposure to high altitude and/or cold, and changes in cardiac metabolism or heart rate elicited by modification of thyroid hormone levels. Capillary growth in all these conditions can be linked with increased coronary blood flow, decreased heart rate, or both. This paper brings evidence that, although increased blood flow due to long-term administration of coronary vasodilators results in capillary growth, a long-term decrease in heart rate induced by electrical bradycardial pacing in rabbits and pigs, or by chronic administration of a bradycardic drug, alinidine, in rats, stimulates capillary growth with little or no change in coronary blood flow. Decreased heart rate results in increased capillary wall tension, increased end-diastolic volume and increased force of contraction, and thus stretch of the capillary wall. This could lead to release of various growth factors possibly stored in the capillary basement membrane. Correlation was found between capillary density (CD) and the levels of low molecular endothelial cell stimulating angiogenic factor (ESAF) both in rabbit and pig hearts with CD increased by pacing. There was no relation between expression of mRNA for basic fibroblast growth factor and CD in sham-operated and paced rabbit hearts. In contrast, mRNA for TGF beta was increased in paced hearts, and the possible role of this factor in the regulation of capillary growth induced by bradycardia is discussed.

Angiogenesis Inducing Agents↗
PubMedDate not supplied

Low-molecular-mass endothelial cell-stimulating angiogenic factor in relation to capillary growth induced in rat skeletal muscle by low-frequency electrical stimulation.

The involvement of endothelial cell-stimulating angiogenic factor (ESAF) in capillary growth was studied in adult rat skeletal muscles (tibialis anterior, TA, and extensor digitorum longus, EDL) in which capillary growth was induced by chronic unilateral electrical stimulation (10 Hz, 8 h/day for 7 days), and in sham-operated and unoperated control muscles. ESAF was assayed by its ability to activate latent collagenase in units per hour per milligram protein. Anatomical capillary density (CD, number of capillaries per mm2) and capillary per fibre ratio (C/F) were estimated in frozen sections from the same muscles after staining for endothelial alkaline phosphatase. In control muscles, ESAF levels were inversely related to capillary supply, being highest (1.82 +/- 0.25 units) in the glycolytic cortex of TA (CD 273 +/- 18/mm2, C/F 1.26 +/- 0.07), lowest (1.04 +/- 0.02 units) in its oxidative highly capillarized core (CD 862 +/- 60/mm2, C/F 2.05 +/- 0.04), and intermediate in EDL (ESAF 1.59 +/- 0.37 units, CD 527 +/- 26/mm2, C/F 1.44 +/- 0.06). Neither capillary supply nor ESAF levels were affected by sham operation. However, chronic electrical stimulation increased capillary supply significantly in EDL (CD 61% greater than in controls, C/F 45% greater) and ESAF levels were elevated 3-fold to 4.77 +/- 0.74 units. In TA muscles, stimulation increased capillary supply specifically in the glycolytic cortex (C/F 2.51 +/- 0.09, p < 0.0001 vs. control) and ESAF levels were increased significantly in this region to 3.19 +/- 0.55 units (p < 0.05, vs. control). C/F ratio and ESAF in the oxidative core of TA (2.31 +/- 0.05 and 1.48 +/- 0.23 units, respectively) were not significantly different from control values. Thus, chronic electrical stimulation, which is known to increase both shear stress and wall tension in capillaries and induce angiogenesis, also increased ESAF activity.

Animals↗
PubMedDate not supplied

Measurement of blood flow in the chick egg yolk sac membrane.

Blood vessels of the yolk sac membrane are the transport route by which a chick embryo obtains nutrients from the egg yolk. After 4 days of incubation at 37 degrees C a sparse network of blood vessels are visible within the membrane and they become denser over the following days. The preparation has been used to assess angiogenesis. Using visual inspection to assess the growth of new vessels towards pellets of test substances placed on the membrane surface, responses are judged negative or positive. Laser Doppler flowmetry has been used to investigate the potential of this technique to quantify blood flow through the yolk sac membrane. Measurements have been taken from capillary beds and single larger vessels over a range of temperatures and from avascular yolk and egg white using a Perimed PF3 with PF310 bent-tipped probe. Capillary beds exhibited vasomotion (about one cycle per minute) and oscillations of longer duration (about five cycles per hour). Cardiac pulses, strongly present in larger vessels (mean 90 pu, pulse 75 pu), were not easily identified in the capillary bed. Avascular yolk measurements gave flux values (due to Brownian motion of yolk proteins) which were greater than for capillary beds but without oscillations. Angiogenesis was stimulated by pellets containing 2 micrograms of basic fibroblast growth factor. There were significant increases in single vessel blood flow after 24 h compared with blank control pellets placed on the same egg.

Animals↗
PubMedDate not supplied

Collagenolytic enzyme systems in human intervertebral disc: their control, mechanism, and their possible role in the initiation of biomechanical failure.

Changes in the macromolecular matrix of the intervertebral disc may predispose to biomechanical failure of the disc. Such changes would involve extracellular enzymes capable of altering the collagen and proteoglycan of the disc matrix. In this study, extracts from homogenates of both annuli fibrosi and nuclei pulposi of human lumbar discs were found to contain neutral collagenolytic, gelatinolytic, and elastinolytic enzymes in all samples assayed. The specific activity of the collagenase was higher in extracts from nuclear than from annular tissue, a difference not seen with gelatinase or elastase. The collagenase was present as both a latent and active enzyme, the other enzymes being fully active. Human intervertebral discs therefore contain enzymes capable of degrading their extracellular macromolecular matrix.

Age Factors↗
PubMedDate not supplied

Raised endothelial cell stimulating angiogenesis factor in ankylosing spondylitis.

Endothelial cell stimulating angiogenesis factor (ESAF) is important in the neovascularisation that precedes new bone formation, and raised levels are found in association with healing fractures and osteoarthritis. We investigated its relevance to the new bone growth that is found at inflammatory sites in ankylosing spondylitis (AS). Forty-one patients with AS were studied clinically and radiographically and had their serum ESAF levels measured. In comparison to age-matched controls the AS patients had significantly raised ESAF levels (p < 0.0001). Within the AS group, patients with relatively higher ESAF levels had no characteristic clinical or radiological features.

Adult↗