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Biomedical subjects

D L Jones

Publications and source records attributed to D L Jones.

At least 217 records · Page 12Linked to original sources
PubMed1983

The repetitive ventricular response: relationship to ventricular fibrillation threshold in dogs.

The experiments investigated the hypothesis that the occurrence of repetitive ventricular responses elicited by the ventricular extrasystole (VES) technique are an indicator of ventricular vulnerability to fibrillation. A comparison was made between the incidence of repetitive responses elicited by the VES technique and the minimum electrical energy (VFT technique) necessary to elicit repetitive responses and ventricular fibrillation in normal dogs, dogs with acute infarction, and dogs with chronic infarction. The VES technique produced repetitive responses in 14 of 46 sites. Responses were of at least three types: (1) bundle branch re-entry; (2) activation at the pacing site, and (3) activation at the infarct zone. In contrast repetitive responses and the onset of fibrillation produced by the VFT technique appeared to be a single type with earliest activation at the pacing site. There were no differences in the ventricular fibrillation thresholds between dogs with and without repetitive responses produced by the VES technique. Thus the incidence of VES technique-induced repetitive responses is not a reasonable predictor of ventricular vulnerability to fibrillation. However, in 2 dogs with lower ventricular fibrillation thresholds, repetitive responses originating at the infarct zone were induced by the VES technique. Occurrence of these repetitive responses may be indicative of ventricular vulnerability to fibrillation.

Animals↗
PubMed1983

Effects of benzo(a)pyrene on Friend viral leukemogenesis in B10SJF1 mice.

A single intraperitoneal injection of benzo(a)pyrene (BP) given 1, 2, or 3 days before an ip injection of Friend leukemia virus (FLV) significantly increased the leukemogenic effect of the virus in B10SJF1 mice. These hybrids are the offspring of C57BL/10 females and SJL/J males and are highly resistant to FLV leukemogenesis when the virus is injected alone.

Animals↗
PubMed1983

Potentiation of Friend viral leukemogenesis by 9,10-dimethyl-1,2-benzanthracene in two strains of mice.

The polycyclic aromatic hydrocarbon, 9,10-dimethyl-1,2-benzanthracene (DMBA) produced malignancy involving the spleen in SJL/J and B10SJF1 mice when injected ip at 500 micrograms per mouse either alone or in combination with threshold doses of Friend leukemia virus (FLV). The mice that received both chemical and virus died significantly sooner than mice that received either chemical or virus alone, and a synergism between DMBA and FLV was demonstrated in both the virus-resistant B10SJF1 hybrids and virus-sensitive SJL/J mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

An inexpensive automatic activity monitor for small primates.

An activity cage has been designed to provide a quantitative measure of locomotor activity in small primates. Movement is detected by the interruptions of photocell beams, which are counted electronically and stored in on-board memory for subsequent display or entry into a computer. The device functions independently, and does not require a computer to be on-line during data collection. Data thus obtained have proven reliable, and are a valid record of the activity of the animal.

Animals↗
PubMed1982

Central injections of spiperone and GABA: attenuation of angiotensin II stimulated thirst.

This study investigated the effects of injecting spiperone or gamma-aminobutyric acid (GABA) into the brain on drinking induced by angiotensin II injected into a lateral cerebral ventricle of the rat. Injections of 12.5 pM of angiotensin II elicited water intakes averaging 10 mL in 15 min with latencies of less than 3 min. Spiperone, a dopamine antagonist injected into the nucleus accumbens produced dose-dependent reductions in water intake and number of laps while increasing the latency to drink. Injections of GABA into the ventral tegmental area produced dose-dependent reductions in water intake and number of laps without altering latency to drink or lap volume. GABA injected into the globus pallidus reduced drinking in a manner similar to that described for spiperone injected into the nucleus accumbens when angiotensin II was the dipsogenic agent but was totally without effect on drinking induced by carbachol injections. These results indicate that a proposed neuronal circuit composed of GABA input to ventral tegmental area neurons, dopamine input from the ventral tegmental area to nucleus accumbens neurons, and subsequent GABA input from the nucleus accumbens to globus pallidus neurons may interact with the goal-directed behaviour, drinking, elicited by central angiotensin II administration. Further, they provide evidence that this neuronal circuit may be part of a functional interface for response initiation.

Angiotensin II↗
PubMed1981

Testing the hearing level of schoolchildren: comparison of several currently used screening techniques.

An attempt was made to validate several currently used methods of screening the hearing level of children in schools (selecting the quietest area available in the school). Each child was screened with watch tick, hand-held beeper (frequencies, 600 Hz and 2500 Hz at 25 dB HL), whispered voice, and pure-tone audiometry. Screening audiometry is currently the most effective technique for the detection of deafness in the school population, but only if background noise is minimal. The watch and whispered voice methods are unreliable for identification of mild conductive hearing impairment for English-speaking children and are useless for screening children whose grasp of the English language is inadequate. This latter category may include deaf children.

Adolescent↗
PubMed1981

Biphasic locomotor response to intra-accumbens dopamine in a nonhuman primate.

Locomotor activity of ten squirrel monkeys, Saimiri sciureus, was evaluated by means of a photocell activity cage following intracranial application of dopamine (DA). A biphasic response consisting of an initial quiet period followed by increased locomotor activity was seen following intra-accumbens DA, 12.5--100 micrograms bilaterally. Both the length of the quiet phase and intensity of locomotor activity were positively related to DA dose. Intra-caudate DA (50 micrograms) was significantly less effective in producing locomotor effects. The specificity of the DA response was substantiated by dose-related inhibition with both systemic (0.1 or 0.05 mg/kg) and intra-accumbens (2--10 micrograms) administration of the DA antagonist haloperidol. Additionally, the intra-accumbens application of haloperidol was found to be ineffective in inducing catalepsy, a state readily produced by systemically administered haloperidol.

Animals↗
PubMed1981

Potentiating effect of benzo[a]pyrene and caffeine on Friend viral leukemogenesis.

The effect of exposing mice to both a chemical carcinogen and leukemia virus with and without an inhibitor of DNA repair were compared. The data indicated that benzo[a]pyrene (BP) could exert a potentiating effect of Friend viral leukemogenesis in mice, which was dependent on the relative times of administration of the chemical and virus. The addition of caffeine as an inhibitor of DNA repair further enhanced the potentiating effect of BP on the leukemia, but in the absence of BP, caffeine showed no carcinogenic effect either when given alone or in conjunction with Friend leukemia virus.

Animals↗
PubMed1980

Nucleus accumbens to globus pallidus GABA projection: electrophysiological and iontophoretic investigations.

Extracellular recordings were obtained from neurons in the nucleus accumbens and globus pallidus of urethane anesthetized rats. Eight neurons in the nucleus accumbens were activated antidromically following stimulation of the globus pallidus. Calculated conduction velocities were 0.4-1.5 m/sec, indicative of small unmyelinated fibers. A total of 74 of 153 neurons in the globus pallidus responded to stimulation of the nucleus accumbens. Of these neurons 4 (2.7%) were excited only, 46 (30.1%) were inhibited only and 24 (15.7%) had sequential effects to excitation and inhibition. Iontophoretic application of picrotoxin was found to attenuate or abolish the poststimulus inhibition in one-half of the neurons examined. The 74 neurons which responded to stimulation of the nucleus accumbens had slower firing frequencies and generally more random firing patterns than neurons which did not respond to stimulation. Fifty-three per cent of all globus pallidus neurons examined had increased spontaneous firing frequencies following the iontophoretic administration of picrotoxin alone. This is indicative of the removal of a tonic GABA input onto these neurons. Most neurons examined had decreased spontaneous firing frequencies following the iontophoretic application of GABA which could be blocked by the iontophoretic application of picrotoxin. The results from antidromic activation, slow conduction velocity, sensitivity to GABA and picrotoxin, and picrotoxin attenuation of the poststimulus inhibitory effect provide evidence of a direct GABAergic projection from the nucleus accumbens to the globus pallidus in the rat.

Animals↗
PubMed1980

Nucleus accumbens to globus pallidus GABA projection subserving ambulatory activity.

The present experiments investigated the hypothesis of a projection relating to the release of gamma-aminobutyric acid (GABA) from the nucleus accumbens to the globus pallidus subserving ambulatory activity in the rat. The GABA antagonist picrotoxin, microinjected into the globus pallidus, elicited dose-dependent increases in ambulatory activity. The administration of dopamine into the nucleus accumbens had a synergistic effect and further stimulated ambulatory activity. GABA injected into the ventral posterior globus pallidus significantly attenuated the ambulatory activity stimulated by injecting dopamine into the nucleus accumbens. These observations provide evidence of a GABAergic projection from the nucleus accumbens to the globus pallidus and implicate it in the initiation of ambulatory activity.

Animals↗
PubMed1980

Microscopically controlled surgery for carcinomas in patients with nevoid basal cell carcinoma syndrome.

The basal cell carcinomas of the nevoid basal cell carcinoma syndrome present a serious challenge in therapy because of the large number of cancers that eventually develop and because a notable proportion of them are highly aggressive neoplasms. Microscopically controlled surgery provides a means to ensure eradication of both the highly malignant and the more benign-behaving neoplasms. Since microscopic control obviates the need to remove an extra margin of normal tissue, elimination of the tumors is accomplished with conservation of the greatest possible amount of normal tissues. These conclusions are based on a study of 30 patients with nevoid basal cell carcinoma syndrome who were treated in chemosurgery clinics during the past 30 years.

Adult↗
PubMed1979

Oral motor performance following central dopamine receptor blockade.

Oral motor responses were recorded in water-deprived rats receiving injections of spiroperidol, the dopamine blocker, into the nucleus accumbens and caudate nucleus. Spiroperidol injected into the nucleus accumbens resulted in dose dependent decreases in lap volume and tongue extension. Injections of spiroperidol into adjacent sites or into the caudate nucleus did not significantly reduce lap volume even with an 8 fold larger dose administered into the caudate. These observations implicate the mesolimbic dopaminergic projections to the nucleus acumbens in oral motor responses and indicate the need for systematic comparisons of the contributions of mesolimbic and nigrostriatal dopaminergic systems to ingestive behaviors.

Animals↗