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Biomedical subjects

D A Herbert

Publications and source records attributed to D A Herbert.

28 records · Page 2Linked to original sources
PubMed1979

Effects of dopamine, norepinephrine and 5-hydroxytryptamine on the carotid body of the dog.

The effects of bolus intracarotid (IC) infusions of dopamine (DA), norepinephrine (NE), and 5-hydroxytryptamine (5-HT) on activity in single or few-fiber carotid chemoreceptor afferent nerve preparations were studied in pentobarbital anesthetized dogs. In addition, the effects of intravenous (IV) infusions of DA were also assessed. IC injections of DA (10 microgram) and (5-HT) (1 microgram) consistently produced a burst of intense activity followed by a period of inhibition. A similar effect was seen with IC NE (20--40 microgram) injections, but the burst of excitation occurred in only 45% of the injections. Inhibition of activity was seen in 88% of the IC NE injections. Low IC doses of all 3 amines produced inhibition of chemoreceptor afferent activity. High doses of DA IV (approximately 60 microgram/kg/))produced excitation followed by depression, while lower doses (approximately 21 microgram/kg) produced only inhibition. The excitatory effects of all 3 amines were blocked by d-tubocurarine (50--435 microgram/kg IV). Inhibitory effects of all 3 amines were blocked by dihydroergotamine (140--270 microgram/kg). The inhibitory effect produced by DA was specifically blocked by haloperidol (50--400 microgram/kg IV). We conclude that DA, NE and 5-HT can modulate carotid body activity by increasing or decreasing responses to physiologic stimuli.

Animals↗
PubMed1978

Properties of apneusis produced by reversible cold block of the rostral pons.

Reversible cold block of the rostral pons was used to compare properties of normal and apneustic respiration in anesthetized, vagotomized, artificially ventilated cats. During apneusis we observed high frequency oscillations (HFO) in phrenic nerve activity which were reduced in frequency compared with those during a normal inspiration. Apneusis produced by mid-pontine transection or punctate pneumotaxic center (PC) lesion produced similar HFO changes. The minimal intensity of superior laryngeal nerve electrical stimulation needed to terminate a breath was higher early in an apneusis than at the same time during a normal breath. Later in apneusis the intensity required became constant and was approximately the same as that needed to end a normal inspiration at its natural termination. With intact vagi lung inflation produced a greater prolongation of expiration during apneustic respiration than during normal respiration. Apneustic type activity was observed in both phrenic and vagal inspiratory motoneurons. We suggest that: (1) HFO are generated without the PC, but the PC elevates the oscillation frequency; and (2) apneusis may result in part from a delayed activation of the normal inspiratory off-switch mechanism.

Action Potentials↗
PubMed1975

Potencies of doxapram and hypoxia in stimulating carotid-body chemoreceptors and ventilation in anesthetized cats.

The effects of doxapram on carotid chemoreceptor activity and on ventilation (phrenic-nerve activity) were tested before and after denervation of the peripheral chemoreceptors in cats. Doxapram was found to be a potent stimulus to the carotid chemoreceptors; the stimulation produced by 1.0 mg/kg doxapram, iv, equalled that produced by a Pao2 of 38 torr. Doxapram also increased phrenic-nerve activity in doses as low as 0.2 mg/kg, iv. After denervation of the peripheral chemoreceptors, doxapram in doses as large as 6 mg/kg failed to stimulate ventilation. It is concluded that (in anesthetized cats) doxapram in doses of less than 6 mg/kg increases ventilation by direct stimulation of the carotid, and, probably, the aortic, chemoreceptors, not by a direct effect on the medullary respiratory center.

Anesthesia↗
PubMedDate not supplied

Hepatitis B vaccine: low postvaccination immunity in hospital personnel given gluteal injections.

Although other investigators have found excellent response rates to the hepatitis B vaccine, we report here an unusually low rate of seroconversion following hepatitis B vaccination in a group of apparently healthy medical center personnel. Only 67% of these individuals developed adequate postvaccination antibodies to HBsAg, in contrast to 85 to 96% in other studies. A significant decrease in seroconversion with increasing age was noted with a 54% seroconversion rate in vaccines over the age of 40; all of whom had received gluteal injections. Employees at another facility had been given deltoid injections from the same vaccine lot and had an overall seroconversion rate of 90%. Subsequently, nonresponders from the first group were revaccinated. Seven of the ten individuals tested developed anti-HBs. We believe the relatively low rate of seroconversion in individuals above the age of 40 may have been related to gluteal injection of the hepatitis B vaccine, and further investigation is warranted.

Adult↗
PubMedDate not supplied

Canned foods.

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Food Preservation↗