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Biomedical subjects

J H Jones

Publications and source records attributed to J H Jones.

At least 55 records · Page 3Linked to original sources
PubMed1994

Dental surgery assistants' roles in cross-infection control in general dental practice: their knowledge and use of autoclaves.

This study investigated dental surgery assistants' (DSAs) role in providing cross-infection control in general dental practice. DSAs' knowledge about using autoclaves and their compliance with the recommended procedures were used as measures. Eighty-nine practices in three districts of the North Western Region of England were approached. Fifty-six agreed to permit the study and DSAs in these practices were observed at work and questioned, a response rate of 63%. Eighteen tasks relating to use of autoclaves (eg correct loading of instruments and correct storage) were observed and knowledge about them was assessed by questioning. Each was scored positively if correctly undertaken and answered. Scores for compliance varied between 2 and 12 and between 3 and 15 in the case of knowledge. In all instances certificated DSAs scored more highly than uncertificated DSAs. The study illustrated the value of certification, background education and membership of a vocational organisation. It supports the belief that all DSAs should be educated to the level of certification and that this improved education and training would improve cross-infection control in general dental practice.

Certification↗
PubMed1994

Skeletal muscle mitochondrial myopathy as a cause of exercise intolerance in a horse.

Although exertional myopathies are commonly recognized in horses, specific etiologies have not been identified. This is the first report in the horse of a deficiency of Complex I respiratory chain enzyme associated with profound exercise intolerance. Physical examination, routine blood tests, endoscopy, and ultrasonograms of the heart and iliac arteries were unremarkable. With slow, incremental exercise (speeds 1.5-7 m/s), the Arabian mare showed a marked lactic acidosis, increased mixed venous PVO2, and little change in oxygen consumption. Muscle biopsies contained large accumulations of mitochondria with bizarre cristae formations. Biochemical analyses revealed a very low activity of the first enzyme complex in the mitochondrial respiratory chain (NADH CoQ reductase). The exercise intolerance and muscle stiffness in this horse were attributed to a profound lactic acidosis resulting from impaired oxidative energy metabolism during exercise.

Acidosis, Lactic↗
PubMed1994

Factors affecting the role of dental surgery assistants in cross-infection control in dental practice.

A study of cross-infection control in general dental practices in the North Western Health Region of England suggested that much of its quality might lie in the hands of dental surgery assistants (S. Doohan, 1991, personal communication). The present paper describes part of a programme of work intended to improve cross-infection control in general dental practices and to discover any factors which might affect this control. A qualitative study of dental surgery assistants' behaviour was used to devise an interview schedule for making quantitative assessments; these were made in visits to 82 general dental practices. A high proportion of DSAs were aware that they are failing to carry out cross-infection control procedures and were worried by this.

Cross Infection↗
PubMed1994

Endoscopic anatomy and map of the equine bronchial tree.

To develop a bronchoscopic map of the equine respiratory tree, the major airways of the lungs of 6 healthy Thoroughbred horses were systematically explored with a flexible fibreoptic endoscope through a tracheostomy while the horses were sedated in stocks. With the carina as the reference point, measurements were made of distances to the branches of the major airways using markers on the shaft of the endoscope. All branches were explored until the narrowing of their diameters prevented further advancement of the endoscope. Positions of origins of branches from the parent bronchus were recorded in relation to a 12 h clock. Branching patterns of the right and left lungs were similar. Seventeen branches of the principal and caudal lobar bronchi of the left lung, and 18 branches of the principal and caudal lobar bronchi of the right lung were identified. Mean explorable distances from the carina to the ends of the right and left caudal lobar bronchi were 34.0 +/- 3.5 (sd) and 34.5 +/- 3.0 cm, respectively. Generally, smaller horses had shorter explorable bronchial lengths. Branching patterns of the parent bronchi were fairly consistent among horses, particularly the branches closest to the carina. After endoscopy and euthanasia, the lungs were removed, and dried with pressurised air flowing through them for 7-10 days. Attempts to explore the airways of the dried lungs endoscopically were relatively unsuccessful, because airways were much smaller in the dried lungs, and many of the branches were distorted when compared with their antemortem appearances. However, having a dried lung specimen as a reference during the bronchoscopic procedure was useful for maintaining orientation in the lungs. Radiographs were used to estimate the location of the origin and destination of each airway branch in relation to the nearest intercostal space. This makes the airway map useful when lesions identified radiographically are to be lavaged.

Animals↗
PubMed1994

Body position and direction preferences in horses during road transport.

It has been hypothesised that horses have a preference for facing backward in a trailer during road transport in order to minimise shifts of body weight due to accelerations and decelerations. To determine if horses have preferences for facing forward vs. backward in a horse trailer, the authors analysed the percentages of time horses spent in different body positions and directions while standing in a moving or parked horse trailer. Body positions and directions of 8 Thoroughbred geldings were videotaped while horses were transported singly and untethered in a 4-horse stock trailer over a 32 km route of country roads; or while the same horses were untethered in the same trailer stationary in a parking lot. Analysis of the logit-transformed percentages of time horses spent in different directions indicated that they spent significantly more time facing backward when the trailer was in motion, but not when it was parked. Several horses displayed strong individual preferences for the directions they faced during road transport.

Animals↗
PubMed1994

Capillary blood transit time in muscles in relation to body size and aerobic capacity.

The mean minimal transit time for blood in muscle capillaries (tc) was estimated in six species, spanning two orders of magnitude in body mass and aerobic capacity: horse, steer, dog, goat, fox and agouti. Arterial (CaO2) and mixed venous (CvO2) blood O2 concentrations, blood hemoglobin concentrations ([Hb]) and oxygen uptake rates were measured while the animals ran on a treadmill at a speed that elicited the maximal oxygen consumption rate (VO2max) from each animal. Blood flow to the muscles (Qm) was assumed to be 85% of cardiac output, which was calculated using the Fick relationship. Total muscle capillary blood volume (Vc) and total muscle mitochondrial volume were estimated by morphometry, using a whole-body muscle sampling scheme. The tc was computed as Vc/Qm. The tc was 0.3-0.5 s in the 4 kg foxes and agoutis, 0.7-0.8 s in the 25 kg dogs and goats, and 0.8-1.0 s in the 400 kg horses and steers. The tc was positively correlated with body mass and negatively correlated with transcapillary O2 release rate per unit capillary length. Mitochondrial content was positively correlated with VO2max and with the product of Qm and [Hb]. These data suggested that Qm, Vc, maximal hemoglobin flux, and consequently tc, are co-adjusted to result in muscle O2 supply conditions that are matched to the O2 demands of the muscles at VO2max.

Aerobiosis↗
PubMed1994

Circulatory function during exercise: integration of convection and diffusion.

The cardiovascular system has frequently been hypothesized to be the limiting step for O2 transport that determines VO2 max in many species of mammals. Careful analysis of the factors that determine how O2 is transported by the circulation demonstrate that such a single-step limitation cannot exist. Evaluation of the results of experiments in which circulatory O2 transport capacity was experimentally altered demonstrates no direct or absolute relationship between changes in O2 transport capacity and changes in VO2 max. Furthermore, experimental evidence collected during maximal exercise in hypoxia and hyperoxia supports the concept that multiple components of the O2 transport system contribute to limiting O2 flux at VO2 max. Consideration of the basic equations that describe O2 transport through the respiratory system shows that changes in PO2 at each step of the system required to increase O2 flux through that step conflict with the changes in PO2 required to increase flux through adjacent steps. Changes in convection, capacitance, or conductance at one step affect gas transport through the adjacent steps. Hence, no single-step limitation to O2 transport is possible, because the convective and diffusive gas exchangers are interdependent. Increasing QT at VO2 max always increases O2 flux (although not necessarily in proportion to the increase in QT), unless VO2 max is limited by mitochondrial oxidative capacity, as in goats. Cardiovascular structure and function in mammals reflects allometric, adaptive and induced variation. Maximal heart rate is determined strictly by body size, thus maximal QT/Mb is inevitably lower in larger mammals. Adaptive and induced variation elicit hypertrophy of muscle, capillaries, and mitochondria, increasing circulatory capacity and VO2 max. When selection for maximal respiratory function is weak, as in most species of mammals, any component(s) of the respiratory system may be underdeveloped, relative to other structures in the system, and contribute disproportionately to limiting O2 flux. When selection for aerobic capacity is strong, as in racehorses, malleable elements of the respiratory system, including the cardiovascular structures, may hypertrophy until their capacities for O2 transport match that of the least malleable structure, the lung. Amplifying circulatory function so greatly in a large animal may lead to functional demand exceeding structural capacity, resulting in the nearly ubiquitous occurrence of exercise-induced pulmonary hemorrhage in racehorses.

Animals↗
PubMed1994

Effect of body direction on heart rate in trailered horses.

To determine whether body direction in a trailer affects the degree to which a horse is excited (and presumably stressed) during transport, heart rates were measured in 8 Thoroughbred geldings transported over a 32-km route of county roads while tethered facing forward or backward in a 4-horse stock trailer. Heart rates also were measured on the horses while they were tethered facing forward or backward in the same trailer while it was parked. Heart rates decreased during the first 10 minutes for both groups, and remained stable after the first 15 minutes. Heart rates were not significantly different between horses facing forward or backward during transport or while parked. Heart rates were significantly (P < 0.05) higher for horses during transport, compared with those of horses in a parked trailer whether facing forward or backward.

Animals↗
PubMed1994

Factors affecting dental surgery assistants' job satisfaction in general dental practice.

Reported studies suggested that job satisfaction, was low among non-operating dental auxiliaries. Clearly this might affect the quality of their work. The study reported in the present article evaluated dental surgery assistant (DSA) job satisfaction in general dental practices in the northwestern region of England. An initial qualitative study determined the factors that DSAs thought affected their job satisfaction and these were evaluated in a quantitative study. Although the majority of DSAs found their work satisfying and enjoyable, a number found some aspects unsatisfactory and changes are proposed which may improve the quality of their working lives.

Adolescent↗
PubMed1993

Synthesis and evaluation of 2-pyridinone derivatives as HIV-1-specific reverse transcriptase inhibitors. 4. 3-[2-(Benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one and analogues.

A new series of potent specific 2-pyridinone reverse transcriptase (RT) inhibitors was developed based on the preliminary development lead 3-[(phthalmido)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one (3), a non-nucleoside derivative which exhibited weak antiviral activity in cell culture against HIV-1 strain IIIB. One compound, 3-[(benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one (9,L-696,229), which was a highly selective antagonist of the RT enzyme (IC50 = 23 nM) and which inhibited the spread of HIV-1 IIIB infection by > 95% in MT4 human T-lymphoid cell culture (CIC95 = 50-100 nM), was selected for clinical evaluation as an antiviral agent.

Antiviral Agents↗
PubMed1993

Assessment of arsenic exposures and controls in gallium arsenide production.

The electronics industry is expanding the use of gallium arsenide in the production of optoelectronic devices and integrated circuits. Workers in the electronics industry using gallium arsenide are exposed to hazardous substances such as arsenic, arsine, and various acids. Arsenic requires stringent controls to minimize exposures (the current OSHA PEL for arsenic is 10 micrograms/m3 and the NIOSH REL is 2 micrograms/m3 ceiling). Inorganic arsenic is strongly implicated in respiratory tract and skin cancer. For these reasons, NIOSH researchers conducted a study of control systems for facilities using gallium arsenide. Seven walk-through surveys were performed to identify locations for detailed study which appeared to have effective controls; three facilities were chosen for in-depth evaluation. The controls were evaluated by industrial hygiene sampling. Including personal breathing zone and area air sampling for arsenic and arsine; wipe samples for arsenic also were collected. Work practices and the use of personal protective equipment were documented. This paper reports on the controls and the arsenic exposure results from the evaluation of the following gallium arsenide processes: Liquid Encapsulated Czochralski (LEC) and Horizontal Bridgeman (HB) crystal growing, LEC cleaning operations, ingot grinding/wafer sawing, and epitaxy. Results at one plant showed that in all processes except epitaxy, average arsenic exposures were at or above the OSHA action level of 5 micrograms/m3. While cleaning the LEC crystal pullers, the average potential arsenic exposure of the cleaning operators was 100 times the OSHA PEL. At the other two plants, personal exposures for arsenic were well controlled in LEC, LEC cleaning, grinding/sawing, and epitaxy operations.

Air Pollutants, Occupational↗
PubMed1993

Limits to maximal performance.

Body size fundamentally affects maximal locomotor performance in mammals. Comparisons of performances of different-sized animals yield different results if made using relative, rather than absolute scales. Absolute speed may be a reasonable way to evaluate the locomotor performance of an animal that must escape predators in real time. However, comparisons of metabolic power in animals of different size can only be made meaningfully on a mass-specific basis. Numerous factors associated with the mechanics, energetics, and storage of elastic energy during locomotion change with body size, which results in allometric relationships that make the energetic cost of locomotion (alpha Mb-0.3) more expensive for small mammals than for large mammals. Small mammals have lower enzymatic capacities for anaerobic glycolysis (alpha Mb0.15) and higher specific aerobic capacities (alpha Mb-0.13) than large mammals. However, the energetic cost of transport increases more than aerobic power as mammals get smaller. The higher ratio of cost to available power in small mammals may explain why they run more slowly than large mammals, as a rule. Maximum aerobic capacity is allometrically related to body size. Limits to VO2max can be imposed by mitochondrial oxidative capacity, as in goats, or by the O2 transport system, as in humans and horses. No single step in the O2 transport system can limit the flux of O2 by itself; however, in an average non-athletic species of mammal, any of the steps in the system might appear to be the weakest link. In highly aerobic athletic species, and possibly elite athletic individuals of other species (e.g. humans), the malleable elements of the O2 transport system may develop to the point that their O2 transport capacities approach that of the least malleable element in the system, the lung. VO2max is very high in such individuals, and appears to be limited by simultaneous failure of all components of the O2 transport system.

Animals↗
PubMed1993

Stress failure of pulmonary capillaries in racehorses with exercise-induced pulmonary hemorrhage.

Bleeding into the lungs in thoroughbreds is extremely common; there is evidence that it occurs in essentially all horses in training. However, the mechanism is unknown. We tested the hypothesis that exercise-induced pulmonary hemorrhage (EIPH) is caused by stress failure of pulmonary capillaries. Three thoroughbreds with known EIPH were galloped on a treadmill, and after the horses were killed with intravenous barbiturate the lungs were removed, inflated, and fixed for electron microscopy. Ultrastructural studies showed evidence of stress failure of pulmonary capillaries, including disruptions of the capillary endothelial and alveolar epithelial layers, extensive collections of red blood cells in the alveolar wall interstitium, proteinaceous fluid and red blood cells in the alveolar spaces, interstitial edema, and fluid-filled protrusions of the endothelium into the capillary lumen. The appearances were consistent with the ultrastructural changes we have previously described in rabbit lungs at high capillary transmural pressures. Actual breaks in the endothelium and epithelium were rather difficult to find, and they were frequently associated with platelets and leukocytes that appeared to be plugging the breaks. The paucity of breaks was ascribed to their reversibility when the pressure was lowered and to the fact that 60-70 min elapsed between the gallop and the beginning of lung fixation. Capillary wall stress was calculated from pulmonary vascular pressures measured in a companion study (Jones et al. FASEB J. 6: A2020, 1992) and from measurements of the thickness of the blood-gas barrier and the radius of curvature of the capillaries. The value was as high as 8 x 10(5) dyn/cm2 (8 x 10(4) N/m2), which exceeds the breaking stress of most soft tissues. We conclude that stress failure of pulmonary capillaries is the mechanism of EIPH.

Animals↗
PubMed1992

Synthesis and evaluation of 2-pyridinone derivatives as HIV-1-specific reverse transcriptase inhibitors. 2. Analogues of 3-aminopyridin-2(1H)-one.

A series of nonnucleoside 3-aminopyridin-2(1H)-one derivatives was synthesized and evaluated for HIV-1 RT inhibitory properties. Several analogs proved to be potent and highly selective antagonists with in vitro IC50 values as low as 19 nM in the enzyme assay using rC.dG as template-primer. Two compounds from this series, 3-[[(4,7-dimethylbenzoxazol-2-yl)methyl]-amino]-5-ethyl-6-methy lpyridin-2(1H)-one (34, L-697,639) and the corresponding 4,7-dichloro analogue (37, L-697,661) inhibited the spread of HIV-1 IIIb infection by 95% in MT4 cell culture at concentrations of 25-50 nM and were selected for clinical trials as antiviral agents.

Aminopyridines↗
PubMed1992

Estimating transit time for capillary blood in selected muscles of exercising animals.

The mean minimal capillary transit time was estimated in muscles of various animals using a combination of physiological and morphometric methods. Radioactive microspheres were injected intravascularly in various animals running on a treadmill at maximum oxygen consumption rate (VO2,max) to label blood flow to individual muscles. The muscles were then removed and preserved by standard methods for electron microscopy. The volume density of mitochondria was measured to assess muscle oxidative capacity. Capillary densities in muscle cross-sections, capillary diameters and tortuosities were incorporated into an estimate of capillary volume per unit muscle mass. Mean capillary transit time (tc) in the exercising muscles was estimated by dividing mass-specific capillary volume by mass-specific blood flow. Estimates of tc ranged from values near 1 s in horse heart and thigh muscles to 0.2 s in duck gastrocnemius. The relationship between muscle blood flow and tc was hyperbolic. The experimental data indicate a limiting value of 0.2 s for transit times at very high blood flows. There was no correlation between tc and body-mass-specific VO2,max.

Animals↗