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Biomedical subjects

J H Jones

Publications and source records attributed to J H Jones.

At least 91 records · Page 5Linked to original sources
PubMed1987

Comparison of computer-assisted learning with tutorial teaching in a group of first-year dental students.

Two identical groups of first-year dental students were instructed in the pathology of dental caries and periodontitis using computer-assisted learning (CAL) or tutorial teaching (TT). A cross-over arrangement, in which the first group was taught about dental caries by CAL and periodontitis by TT and the second group in the reverse order, allowed comparison of the two methods. The comparison included a knowledge test and completion of a questionnaire. CAL and TT were equally effective as far as acquisition of knowledge was concerned. Students felt pressurized with CAL and had problems with note-taking. They liked a teacher to be present. Nevertheless, CAL was an acceptable method of instruction and was more economical, in terms of staff involvement, than TT.

Computer-Assisted Instruction↗
PubMed1987

Substrate and O2 fluxes during rest and exercise in a high-altitude-adapted animal, the llama.

Llamas were trained to exercise on a treadmill at graded speeds. O2 uptake values at rest, at modest exercise (ME, 0.58 m/s), and at heavy exercise (HE, 1.84 m/s) were 0.069, 0.297, and 0.594 ml O2 X kg-1 X s-1. Corresponding values for cardiac output were 1.64, 4.39, and 6.85 ml X kg-1 X s-1. Palmitate, glucose, and lactate replacement rates (Ra values) were determined at these varying work rates using a single-bolus injection of 14C- or 3H-labeled metabolites, two at a time. Ra values for palmitate, glucose, and lactate at rest were 6.2, 61.4, and 36.1 mumol X kg-1 X min-1, respectively. During ME, the Ra values for glucose and palmitate increased about twofold but showed no further increase when exercise intensity was increased about twofold. In contrast to these results, Ra values for lactate increased much more with increasing work rate. A combination of increased perfusion (increased cardiac output) and increased lactate availability (increased plasma concentration) could account for the lactate Ra data. During prolonged ME, the Ra for lactate decreased because lactate availability decreased; concurrently, both the plasma free fatty acid availability and the Ra values for palmitate greatly increased. Because O2 carrying capacity is low in the llama (as in all high-altitude-adapted mammals), a given level of exercise required exaggerated increases in cardiac output (and hence in perfusion rates of working muscles). As a result, the flux rates of palmitate, glucose, and lactate through the plasma compartment could readily account for O2 flux rates even at relatively high sustainable rates of exercise.

Acclimatization↗
PubMed1986

Trial of strategy for reducing the use of laboratory tests.

Clinical guidelines and a weekly review of medical records were introduced into a medical unit in a teaching hospital to promote a more discriminating use of laboratory tests. This strategy resulted in an immediate reduction in the average number of requests each week from 74 to 27 haematological tests (64%) and 158 to 58 biochemical tests (64%). During a period of 10 weeks after the strategy was introduced (the intervention period) the mean number of haematological tests for each person decreased from 2.0 during the baseline period to 1.1 (45% reduction; p less than 0.01) and the mean number of biochemical tests decreased from 4.4 to 2.7 (39%; p less than 0.0001). The decrease in the number of repeat requests was greater than that for new requests and accounted for half the reduction in use. There was no significant change in the number of tests requested from an adjacent medical unit that was not exposed to the interventions. This strategy is worthy of trial in other specialties and hospitals, but attention will have to be paid to possible difficulties in sustaining reductions in use over long periods of time.

Clinical Laboratory Techniques↗
PubMed1986

Industrial hygiene and control technology assessment of ion implantation operations.

Ion implantation is a process used to create the functional units (pn junctions) of integrated circuits, photovoltaic (solar) cells and other semiconductor devices. During the process, ions of an impurity or a "dopant" material are created, accelerated and imbedded in wafers of silicon. Workers responsible for implantation equipment are believed to be at risk from exposure to both chemical (dopant compounds) and physical (ionizing radiation) agents. In an effort to characterize the chemical exposures, monitoring for chemical hazards was conducted near eleven ion implanters at three integrated circuit facilities, while ionizing radiation was monitored near four of these units at two of the facilities. The workplace monitoring suggests that ion implantation operators routinely are exposed to low-level concentrations of dopants. Although the exact nature of dopant compounds released to the work environment was not determined, area and personal samples taken during normal operating activities found concentrations of arsenic, boron and phosphorous below OSHA Permissible Exposure Limits (PELs) for related compounds; area samples collected during implanter maintenance activities suggest that a potential exists for more serious exposures. The results of badge dosimetry monitoring for ionizing radiation indicate that serious exposures are unlikely to occur while engineering controls remain intact. All emissions were detected at levels unlikely to result in exposures above the OSHA standard for the whole body (1.25 rems per calendar quarter). The success of existing controls in preventing worker exposures is discussed. Particular emphasis is given to the differential exposures likely to be experienced by operators and maintenance personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1985

Lung volume changes during respiration in ducks.

The avian lung has been considered to be rigid and to remain isovolumetric during the respiratory cycle. We tested this hypothesis by implanting radiopaque markers of tantalum on the dorsal pulmonary surfaces and ventral pulmonary aponeuroses of Pekin ducks (Anas platyrhynchos) and measuring changes in lung thickness during the respiratory cycle using high speed cineradiography. We found small but regular changes in lung thickness that were synchronous with respiratory phase. Lung thickness was greatest at mid-inspiration (0.6% greater than mean) and least at mid-expiration (0.8% less than mean). Measurements made on ostrich (Struthio camelus) respiratory structures suggest that the maximal force that could be generated by the muscles (Mm. costopulmonales) at the margins of the ventral pulmonary aponeurosis is more than two orders of magnitude greater than would be required to resist pressure-induced changes in lung volume during respiration at rest. The action of these muscles could account for the very small magnitude of the volume changes measured during the respiratory cycle.

Animals↗
PubMed1985

Release of arsenic from semiconductor wafers.

The production of integrated circuits and other semiconductor devices requires the introduction of impurities or dopants into the crystal lattice of a silicon substrate. This "doping" or junction formation is achieved through one of two processes: thermal diffusion or ion implantation. Ion implantation, the more contemporary and more accurate of the two processes, accomplishes junction formation by bombarding selected areas of the silicon wafer with a beam of dopant ions. Inorganic arsenic, which is regulated by the Occupational Health and Safety Administration (OSHA) as a carcinogen, is frequently used as dopant material. Silicon wafers are found to emit inorganic arsenic following ion implantation. Data collected during this experiment demonstrate that arsenic is released over a 3.5-hour period following implantation and that the total amount of arsenic emitted may approach 6.0 micrograms per 100 wafers processed within 4 hours after implantation. The discovery and quantification of this phenomenon suggest that newly implanted silicon wafers are a potential source of arsenic contamination--a source that may impact both the quality of the work environment and the integrated circuit product.

Air Pollutants, Occupational↗
PubMed1985

Mortality of lead smelter workers.

To examine patterns of death in lead smelter workers, a retrospective analysis of mortality was conducted in a cohort of 1,987 males employed between 1940 and 1965 at a primary lead smelter in Idaho. Overall mortality was similar to that of the United States white male population (standardized mortality ratio (SMR) = 98). Excess mortality, however, was found from chronic renal disease (SMR = 192; confidence interval (CI) = 88-364), and the risk of death from renal disease increased with increasing duration of employment, such that after 20 years employment, the standardized mortality ratio reached 392 (CI = 107-1,004). Excess mortality was also noted for nonmalignant respiratory disease (SMR = 187, CI = 128-264). Eight of 32 deaths in this category were caused by silicosis; at least five workers who died of silicosis had been miners for a part of their lives. An additional 11 deaths resulted from tuberculosis (SMR = 139; CI = 69-249); in six of these cases, silicosis was a contributory cause of death. Cancer mortality was not increased overall (SMR = 95; CI = 78-114). An increase, however, was noted for deaths from kidney cancer (six cases; SMR = 204; CI = 75-444). Finally, excess mortality was noted for injuries (SMR = 138; CI = 104-179); 13 (23%) of the 56 deaths in this category were caused by mining injuries. The data from this study are consistent with previous reports of increased mortality from chronic renal disease in persons exposed occupationally to lead.

Actuarial Analysis↗
PubMed1985

Experimental oral candidal infection and carriage of oral bacteria in rats subjected to a carbohydrate-rich diet and tetracycline treatment.

Oral candidal infection and the carriage of oral bacteria in rats has been studied in animals on a high carbohydrate diet and treated with tetracycline. Candidal infection was not significantly enhanced by carbohydrate alone but was promoted by tetracycline; carbohydrate plus tetracycline was no more effective than tetracycline alone. Carriage of lactobacilli was enhanced by carbohydrate but streptococcal carriage was depressed; there was no effect on the number of rats carrying enterobacteria. Administration of tetracycline reduced the carriage of all three groups of bacteria but the isolation rate for enterobacteria increased towards the end of the experiment, becoming nearly the same as at the start. The prevalence of C. albicans did not vary with these changes in bacterial populations.

Animals↗
PubMed1985

Selectivity of (+)-4-propyl-9-hydroxynaphthoxazine [(+)-PHNO] for dopamine receptors in vitro and in vivo.

The intrinsic activity of the potent dopamine (DA) agonist 4-propyl-9-hydroxynaphthoxazine [(+)-PHNO] was examined in receptor binding assays for the following receptors: DA, alpha-1 and alpha-2 adrenergic, serotonin-1 and -2, neuroleptic, beta adrenergic, anxiolytic, adenosine A-1, gamma-aminobutyric acid, muscarinic and opiate. (+)-PHNO exhibited strong to moderate potencies [IC50 (nanomolars) in parentheses] in binding to DA (24), "neuroleptic" (67), alpha-2 adrenergic (77) and serotonin-1 (277) sites. The pharmacological activity of the naphthoxazine both in vivo and in vitro was contrasted with the known DA agonists apomorphine, pergolide, lisuride and 6-ethyl-9-oxaergoline in tests of DA, alpha-2 adrenergic and serotonergic function. Each compound was examined in vitro in receptor binding assays for interactions with DA, alpha-2 adrenergic, serotonin-1 and serotonin-2 receptors and for alpha-2 adrenergic activity in inhibiting field-stimulated contractions of the vas deferens of the rat. In vivo, alpha-2 adrenergic activity was assayed via measurement of mydriasis after i.v. injections in the rat, whereas serotonin activity was assayed by measuring drug-induced inhibition of 5-hydroxytryptophan accumulation, and DA activity was assessed by quantifying stereotyped behavior after both i.p. and i.v. injections. Selectivity ratios for the DA receptor were derived from effective dose values determined in these tests and demonstrated that only apomorphine was more selective as a DA agonist than (+)-PHNO in vivo. (+)-PHNO was the least active agent at the alpha-2 receptors in the vas deferens and with serotonergic mechanisms in vivo to reduce 5-hydroxytryptophan accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Synthesis of 4-substituted 2H-naphth[1,2-b]-1,4-oxazines, a new class of dopamine agonists.

A series of tricyclic oxazines, namely, the 4-substituted 2H-naphth[1,2-b]-1,4-oxazines, have been synthesized and assayed for dopamine agonist activity. One of the members of this series, compound (+)VII-15, was found to be a remarkably potent agonist in vivo when tested in the standard 6-hydroxydopamine lesioned rat assay. The absolute configuration of the compound corresponds to that found in the active isomer of apomorphine. Its activity at the alpha 2 receptor (vs. [3H]clonidine) is relatively low. It also failed to stimulate the synthesis of cAMP in the carp retina assay, thus giving the compound a highly selective profile in favor of the D2 receptor.

Animals↗
PubMed1984

Pharmacologic profile of a novel potent direct-acting dopamine agonist, (+)-4-propyl-9-hydroxynaphthoxazine [(+)-PHNO].

The (+)-enantiomer of 1,2,3,4a,5,6-hexahydro-9-hydroxy-4-n-propyl-4H-naphth[1,2-b][ 1,4]-oxazine [(+)-PHNO] is demonstrated to be a potent and direct dopamine (DA) agonist in several in vivo and in vitro test procedures. In vitro (+)-PHNO inhibited binding of [3H]apomorphine (IC50 = 23 nM) or [3H]spiperone (IC50 = 55 nM) to rat striatal membranes. Because (+)-PHNO failed to stimulate adenylate cyclase in carp retina, it was classified as a D-2 agonist. ED50 values (shown in parentheses) derived in DA receptor-related in vivo tests were as follows: in mice, (+)-PHNO produced hypothermia (13 micrograms/kg i.p.) and postural asymmetry in the unilaterally caudectomized animal (4 micrograms/kg i.p.). In the rat, (+)-PHNO produced stereotypy (10 micrograms/kg i.p.) and contralateral turning in 6-hydroxydopamine-lesioned animals (5 micrograms/kg i.p.) that lasted 1 to 3 hr. Whereas both of the latter effects were blocked by haloperidol, prior treatment with depletors of endogenous catecholamines, reserpine or alpha-methylparatyrosine failed to reduce (+)-PHNO-induced stereotypy. The naphthoxazine also produced emesis in beagles (0.05 micrograms/kg i.v.) that was blocked by L-646,462, a peripherally selective DA receptor antagonist. (+)-PHNO was well absorbed when given p.o., producing contralateral turning (10 micrograms/kg) with a ratio of p.o. to i.p. ED50 values of 2. This ratio was much lower than those derived for n-propylnorapomorphine (60) and apomorphine (54). At the DA autoreceptor, (+)-PHNO inhibited the accumulation of dOPA in the gamma-butyrolactone-treated rat (11 micrograms/kg i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1983

Different actions of TL-99 and 3-PPP in producing contraversive turning in the 6-OHDA-lesioned rat.

The putatively selective dopamine autoreceptor agonists TL-99 and 3-PPP were compared with apomorphine for the production of contraversive turning in the 6-hydroxydopamine-lesioned rat. Although less potent than apomorphine, 3-PPP produced dose-related contralateral turning. The contralateral turning produced by TL-99 plateaued at the 3 mg/kg i.p. dose level. Yohimbine significantly enhanced the TL-99-induced turning, whereas it failed to modify the 3-PPP turning. The results suggest that the alpha 2-adrenergic properties of TL-99 at doses of greater than 3.0 mg/kg masked its dopaminergic effects. Hence, 3-PPP is clearly the more selective agent for DA receptors.

Adrenergic alpha-Agonists↗
PubMed1983

Panting in the emu causes arterial hypoxemia.

The purpose of this study was to determine the effect of heavy thermal panting on arterial oxygen (PaO2) and carbon dioxide (PaCO2) tension in emus. The birds showed no significant change in body temperature during a 3-4 h heat stress caused by increasing ambient air temperature from 21 to 46 degrees C. However, the emus increased their respiratory frequency 10-fold (from 5.3 to 52.9 breaths X min-1). The high respiratory frequency resulted in a slight but significant decrease in PaCO2 (from 33.5 to 29.8 mm Hg), coupled with a slight increase in pH (from 7.449 to 7.469). Paradoxically, these changes were accompanied by a significant decrease in the arterial oxygen tension (from 99.7 to 84.6 mm Hg). The arterial hypoxia suggests hypoventilation while the hypocapnia suggests hyperventilation of the lungs. This could result from various spatial and/or temporal changes in ventilation/perfusion ratios.

Acid-Base Equilibrium↗