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Biomedical subjects

H I Rosenberg

Publications and source records attributed to H I Rosenberg.

7 recordsLinked to original sources
PubMed1997

Cardiovascular responses of snakes to hypergravity.

Snakes have provided useful vertebrate models for understanding circulatory adaptation to gravity, attributable to their elongate body shape and evolutionary diversificaton in terms of ecology and behavior. Recently we have studied cardiovascular responses of snakes to hypergravic acceleration forces produced acutely in the head-to-tail direction (+Gz) on a short-arm centrifuge. Snakes were held in a nearly straight position within a horizontal plastic tube and subjected to a linear force gradient during acceleration. Carotid blood flow provided an integrated measure of cardiovascular performance. Thus, cardiovascular tolerance of snakes to stepwise increments of Gz was measured as the caudal Gz force at which carotid blood flow ceased. Tolerance to increasing Gz varies according to adaptive evolutionary history inferred from the ecology and behavior of species. With respect to data for six species we investigated, multiple regression analysis demonstrates that Gz tolerance correlates with gravitational habitat, independently of body length. Relative to aquatic and non-climbing species, carotid blood flow is better maintained in arboreal or scansorial species, which tolerate hypergravic forces of +2 to +3.5 Gz. Additionally, semi-arboreal rat snakes (Elaphe obsoleta) exhibit plasticity of responses to long-term, intermittent +1.5 Gz stress. Compared to non-acclimated controls, acclimated snakes show greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of prostaglandin ratios favorable to maintenance of arterial blood pressure, and medial hypertrophy in major arteries and veins. As in other vertebrates, Gz tolerance of snakes is enhanced by acclimation, high arterial pressure, comparatively large blood volume, and body movements. Vascular studies of snakes suggest the importance to acclimation of local responses involving vascular tissue, in addition to centrally mediated responses to fluid shifts.

Adaptation, Physiological↗
PubMed1995

Cephalic morphology of the honey possum, Tarsipes rostratus (Marsupialia: Tarsipedidae); an obligate nectarivore.

The sharply tapering skull of the honey possum is delicately constructed and has only a few, minute teeth; its mandible is reduced to a thin, flexible rod. The mandibular fossa has been displaced caudally to the caudomedial corner of the squamosal. Head skeletons of the feathertail glider and western pygmy-possum, omnivores that are closely related to the honey possum, bear greater resemblance to the distantly related carnivorous fat-tailed dunnart than to the honey possum. Selected muscles associated with the jaws, hyoid, and tongue of these four mouse-sized (9-22 g) marsupials are described for the first time. The honey possum is characterized by a greatly reduced temporalis that is almost completely hidden by the eye. Its digastric consists of a single belly that inserts onto the caudal margin of the mylohyoid. The lateral pterygoid is relatively long as it extends caudally to insert onto the elongated mandible. The stylohyoid originates high up on the caudal surface of the tympanic bulla; it curves around the caudal and ventral surfaces of the bulla to reach the basihyoid. The insertion of the genioglossus is restricted to the caudal quarter of the tongue. Homologous muscles of the feathertail glider and western pygmy-possum are more similar to those of the fat-tailed dunnart. In addition to the very different musculoskeletal system, the honey possum has an unusual tongue that tapers to a fine point.

Animals↗
PubMed1992

The secretion of Duvernoy's gland of Malpolon monspessulanus induces haemorrhage in the lungs of mice.

A toxic protein that induces death of mice with profuse bleeding from the nostrils was isolated from the secretion of Duvernoy's gland of Malpolon monspessulanus (Colubridae). The toxic protein, referred to as CM-b, showed mainly one band on SDS-PAGE corresponding to a mol. wt of 24,000. Its intravenous LD50 in mice was 1 microgram/g and i.v. injections of lethal or sublethal doses induced haemorrhage in the lungs. When injected into the skin of mice, however, the toxin was not haemorrhagic. CM-b showed no proteolytic or procoagulant activity. The nature of this and other components from Duvernoy's secretion of colubrids that cause similar effects remains to be established.

Animals↗
PubMed1985

Lethal factors and enzymes in the secretion from Duvernoy's gland of three colubrid snakes.

Secretion from Duvernoy's gland of the colubrid snakes Malpolon, Spalerosophis, and Thamnophis was obtained by pilocarpine stimulation and tested for lethality and selected enzymatic activities. Pools of secretion from Malpolon and Spalerosophis were fractionated by gel filtration, and several major active fractions were examined. The secretion from Malpolon had an LD50 of 6.5 micrograms/gm in mice; two lethal fractions with LD50's of 2.75 micrograms/gm and 4.5 micrograms/gm were isolated. One of these fractions appears to be a basic phospholipase A with a molecular weight of about 17,000. Spalerosophis had a secretion with an LD50 of 2.75 micrograms/gm in mice; one main lethal fraction with an LD50 of 2.5 micrograms/gm was isolated. Secretion from Thamnophis had an LD50 of 33.3 micrograms/gm; it was not fractionated owing to a paucity of material. At least two of the snake species examined have toxic secretions that may be important during feeding by killing or weakening and helping to subdue the struggling prey.

Animals↗
PubMed1978

Air flow in snake ventilation.

Ventilation in resting, unrestrained Boa constrictor, Python regius and Thanmophis s. sirtalis was monitored using various combinations of a closed Kopfkappe (head chamber), intratracheal pressure catheters, strain gauges around the trunk, and a flow meter connected to one of the nostrils. Records of intratracheal pressure with and without closing the Kopfkappe show that the latter device induces artifacts in the normal ventilatory pattern. Flow meter readings from quiescent snakes indicate that ventilation is biphasic (outflow-inflow-pause) rather than triphasic (outflow-inflow-outflow-pause), while simultaneous pressure and strain gauge records are variably tri- or quadriphasic.

Animals↗