PubMed Health⌕ Search

Biomedical subjects

J Kaas

Publications and source records attributed to J Kaas.

8 recordsLinked to original sources
PubMed1999

Interview with John Kaas.

Jon Kaas received a Ph.D. in Psychology with Irving Diamond at Duke University and completed a postdoctoral fellowship with Clinton Woolsey in neurophysiology at the University of Wisconsin, where he also collaborated with Ray Guillery. After 4 years as an Assistant Professor in Neurophysiology at Wisconsin, he moved to the Department of Psychology at Vanderbilt University where he is currently Centennial Professor. Awards include the Earl Sutherland Prize, Javits Neuroscience Investigator Award, Krieg Cortical Discoverer Award, and American Psychological Association Distinguished Scientific Contribution Award.

Animals↗
PubMed1998

Myogenic effects enhance norepinephrine constriction: inhibition by nitric oxide and felodipine.

Myogenic, pressure-induced vasoconstriction may amplify the effects of circulating vasoconstrictors. Through intravital microscopy in cremaster arterioles (31 to 115 microm diameter), the relative contribution of myogenic responses (MR) to norepinephrine (NE)-induced constriction and the inhibitor potency of nitric oxide (NO) or a Ca2+ entry blocker (CEB), felodipine (F), were examined. In 24 anesthetized hamsters, a vessel occluder was placed around the aorta to control cremaster vessel inflow pressure (IP). NE infusion increased blood pressure (by 50 +/- 2 mm Hg) and induced significant constriction (24% +/- 9%) in small arterioles (< 65 microm) only. The constriction, which was not altered by adrenergic blockade, was dependent on the actual IP and was abolished when the IP increase was blocked. NO synthase (NOS) blockade unmasked a significant MR in large arterioles. F inhibited the MR predominantly in large vessels. In isolated microvessels, F completely blocked the pressure-induced Ca2+ increase and MR. We conclude that circulating NE constricts muscle arterioles mainly by a myogenic mechanism. NO effectively opposes MR in larger arterioles, thus restricting MR and vasoconstrictor reinforcement to a small section of the vasculature being tightly controlled by metabolic signals. MR, which otherwise would impair adjustment of peripheral resistance, is reduced by CEB predominantly in larger arterioles, similar to NO.

Animals↗
PubMed1997

Organization of sensory cortex in a Madagascan insectivore, the tenrec (Echinops telfairi).

We identified subdivisions of somatosensory cortex, and the borders and extents of auditory and visual cortex in Madagascan tenrecs (Echinops telfairi) by using microelectrode recording techniques and cortical myeloarchitecture. There was evidence for three distinct somatosensory fields. The primary somatosensory area (S1) contained an orderly representation of the contralateral body surface that stained darkly for myelin. Neurons were activated by light touch, and receptive fields were often small, especially for the snout. Immediately rostral to S1, a lightly myelinated rostral field (R) also contained a representation of the contralateral body, although the internal topography was not fully determined. Neurons in R responded to manipulations of body parts and tissue displacements. A small, moderately myelinated area lateral to S1 was termed PV/S2 because it possessed features that were similar to both the parietal ventral area (PV) and the second somatosensory area (S2) in other mammals. Neurons in PV/S2 responded to light tactile stimulation. A densely myelinated oval of cortex caudal to PV/S2, the auditory area (A), contained neurons that responded to clicks, and the densely myelinated caudomedial visual area (V) contained neurons that were activated by stimulation of one or both eyes. Some characteristics of V were similar to the primary visual area (V1) described in other mammals. A visual area located in rostromedial cortex (RV) contained neurons that were highly responsive to visual stimulation. Area RV may be a specialization of tenrecs or an elaboration of a visuomotor field that has been retained in most extant mammals. The results support the view that most of the neocortex of primitive mammals was composed of a few sensory areas. J. Comp. Neurol. 379:399-414, 1997.

Animals↗
PubMed1994

Interactions of hormones with the vascular endothelium. Effects on the control of vascular tone.

Due to their anatomical location vascular endothelial cells are an obvious target for hormones which are transported by the bloodstream. Studies on cultured endothelial cells, isolated vessels and the intact organism revealed the existence of multiple interactions between endothelial cells and circulating hormones. Not only are endothelial cells involved in the clearance of some specific circulating hormones, but they also form a tight barrier for other hormones thus preventing or attenuating their direct effects on vascular smooth muscle. Endothelial cells are also involved in the production of circulating angiotensin II by the angiotensin converting enzyme. Probably the most significant effect of hormones in vascular control is the ability of many of them to modulate the release of vasoactive autacoids such as nitric oxide, prostaglandins and endothelin-1. Aside from acute stimulating effects on autacoid production, some hormones, particularly steroids, exert chronic effects on vasoactive-factor gene expression. Apparently, in the control of vascular tone, interactions between circulating hormones and the endothelium play a major role. However, the functional significance of these interactions, especially in pathophysiologic conditions remains to be determined.

Animals↗
PubMed1990

Convergence of processing channels in the extrastriate cortex of monkeys.

The first (V-I) and second (V-II) visual areas of primates contain three types of anatomical segregations of neurons as parts of hypothesized "P-B" or "color", "P-I" or "form," and "M" or "motion" processing channels. These channels remain distinct in relays of P-B and P-I information to the inferior temporal lobe via V-II and dorsolateral visual cortex for object recognition, and "M" information to posterior parietal cortex via the middle temporal visual area (MT) for visual tracking and attention. The present anatomical experiments demonstrate another channel where "P-B" modules in V-I and "P-B" and "M" modules in V-II merge in the projections to the dorsomedial visual area (DM), which relays to MT and posterior parietal cortex. This integrative area may function in unifying our perception of the visual world, and may allow "color" as well as "motion" to play a role in visual tracking and attention.

Animals↗