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Biomedical subjects

H E Hoff

Publications and source records attributed to H E Hoff.

At least 19 recordsLinked to original sources
PubMed1986

Central origin vs. reflex feedback in the respiratory heart rate relationship.

In the midcollicular decerebrate cat we have observed unique respiratory variation in heart rate (respiratory-heart rate relationship, RHRR) in respiratory intervals of 2-7 s or Biot's breathing of paired breaths at 16-s intervals. Cardiac slowing that marked the respiratory segmentation of the heartbeat showed consistent relationship with the breath it preceded by 1 to 5 s. Thus, association of respiration and heartbeat must include synergistically central interrelated origins for respiration cardiac rates constituting the RHRR.

Animals↗
PubMed1986

Respiratory heart rate relationship in the decerebrate cat.

The respiratory heart rate relationship was examined in 10 decerebrate cats. The relationship appears to be a multi-part phenomenon consisting of (1) the inspiratory acceleration of the heart rate, which is well known, plus (2) the tendency toward small numbered relationships of integers between heart and respiration, as for example 2:1 to 5:1 heart rate to respiratory rate rather than complete randomness in the multiples of cardiac intervals in the respiratory cycle, and (3) registry of the heart and respiratory cycles upon each other in conformity to definitions of linear autonomous systems. So the phenomenon can be attributable to the influence of respiration upon the heart, the influence of the heart upon respiration, resulting in the mutual influence of both in supplying the physiological needs of perfusion of the periphery revealing higher integrations which an autonomous system would require.

Animals↗
PubMed1983

The site of the integration of muscular activity and respiration.

Acutely decerebrate (midcollicular) cats do not, or rarely if ever, walk spontaneously; nor do they show phasic movements of progression. After low thoracic cordotomy in a Schiff-Sherrington preparation with enhanced forelimb rigidity, approximately 50% of the preparations begin to show spontaneous locomotory movements in the forelimbs. In some cases these movements are in periodic bursts, and at these times are associated with waxing hyperpnea beginning before the onset of the forelimb movements. This indicates the presence of an intrinsic exercise hyperpnea mechanism mediated within the central nervous system in centers caudal to the hypothalamus.

Animals↗
PubMed1981

Physiological responses to spirometer load.

A transient time-dependent increase in tidal volume (TV) and respiratory rate has been observed as a spirometric loading effect in experiments on 22 decerebrate cats. Respiration was recorded via the impedance pneumograph throughout the entire experiment while tidal volume was measured at intervals of 10-60 min on a spirometer. A total of 233 spirograms was recorded. The mean control tidal volume was 14 ml/kg, followed by an average increase of 30%, 43%, 51%, and 64% at 30, 60, 90, and 120 sec on the spirometer respectively. Spirometric respiratory rate also increased and as a result instantaneous minute volumes (MV) showed increases up to nearly 400% of control. Maximal effects occurred within 80 sec reflecting a sequential combination of reflex (via vagal afferents) and chemical (increased CO2) factors reaching a new equilibrium. We also noted a spirometric regularization of previously irregular or periodic (Biot's) breathing. It is apparent that the spirometer introduces small and graded perturbations into respiratory control systems.

Animals↗
PubMed1975

An analysis of the circadian rhythmicity of atrial and ventricular rates in complete heart block.

A 19 year old female human subject with complete heart block was put at complete bed rest for 63 hours during which a Lead II EKG was monitored at half hour intervals. Atrial and ventricular rates demonstrated cyclic activity with peaks during the day and troughs during the night. A correlation coefficient of plus 0.85 and a slope of plus 1.0 from a linear regression between atrial and ventricular rates demonstrated a close parallel. Calculation of the crosscovariances confirmed the observed cyclic activity with a period of 24 hours and phase angle of zero degrees between the two chambers. The data may be explained by one or all of the following mechanisms: (1) both chambers are subject to the same internal milieu, (2) autonomic nervous system discharge and associated reflexes may integrate relative changes in rate, (3) direct mechanical or electrotonic forces may result in alteration of rates in direct proportion to the magnitude of the dominant chamber, (4) program which operates independent of external factors. The question remains for direct experimental data to demonstrate whether the observed phenomenon is an intrinsic biologic rhythm within the heart or in its control system.

Adult↗
PubMed1975

Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta.

This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent with outflow tract obstruction. The pony was also hypotensive and this condition was interpreted as a long-term compensation for the obstructive lesion. It is likely that the changes in systolic time intervals were at this stage predominantly affected by the hypotension. The report notes that the existence of such a case of spontaneous cardiovascular disease in the pony population might suggest the utility of the animal as a resource in comparative cardiovascular physiology and medicine.

Animals↗