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Biomedical subjects

J H Jones

Publications and source records attributed to J H Jones.

At least 37 records · Page 2Linked to original sources
PubMed1999

Neodymium: YAG transconjunctival laser revision of late-failing filtering blebs.

OBJECTIVE: To study the effectiveness of neodymium:YAG (Nd:YAG) laser transconjunctival revision of late-failing filtering blebs. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Thirty consecutive patients from a glaucoma referral practice at the Ohio State University Department of Ophthalmology. INTERVENTION: Transconjunctival Nd:YAG laser revision of blebs diagnosed as failing secondary to episcleral fibrosis. MAIN OUTCOME MEASURE: Reduction in intraocular pressure (IOP) and survival of bleb. RESULTS: Reduction in IOP was attained in 24 (80%) of 30 patients with a mean prelaser IOP of 21.21 mmHg and a mean 1-week postlaser IOP of 13.97 mmHg (P < 0.0001). These results were maintained at the 1-, 3-, and 12-month follow-up visits with mean IOPs of 16.31 mmHg (P = 0.0008), 14.81 mmHg (P < 0.0001), and 15.25 mmHg (P = 0.0003), respectively. Two-year data were available on a small number of patients (4) with a mean of 15.25 mmHg (P = 0.0085). Mean time interval between trabeculectomy and laser revision was 31 months. CONCLUSION: Late-failing filtering blebs are often amenable to Nd:YAG transconjunctival revision.

Aged↗
PubMed1999

Is ventilation during maximal exercise limited by dynamic airway closure?

A study was undertaken to find if the reason why horses hypoventilate when running is that they experience expiratory flow limitation due to dynamic airway closure. To test this hypothesis, we measured peak expiratory flows on a Thoroughbred galloping on a treadmill and hypoventilating and compared those flows with the peak dynamically-limited flow that the same horse could achieve during a forced expiratory flow-volume manoeuvre. At the approximate lung volumes at which the horse was ventilating while running, it did not appear to be mechanically limited and appeared to have reserve capacity available potentially to increase its expiratory flow.

Animals↗
PubMed1999

Changes in left ventricular dynamics during graded exercise.

Three mature Thoroughbred horses were prepared surgically with ultrasonic sonomicrometer crystals affixed to their ventricular pericardia. Signals from crystals recorded dimensions of axes across the left ventricle. Cubic algorithms were fitted to dimensional data to generate volume estimates that matched stroke volumes simultaneously measured using the Fick principle. As horses stood at rest or exercised at various intensities (approx 7, 12, 24, 47 and 100% maximal rate of O2 consumption VO2max[), left ventricular dimensions were recorded and 20 consecutive diastolic and systolic volumes calculated. Although Fick estimates detected no difference in stroke volume at different exercise intensities, sonomicrometer measurements of stroke volume were significantly lower at rest and higher at VO2max. These differences mirrored changes in end-diastolic volume, although end-systolic volume did not change. At all exercise intensities, stroke volume was most variable and end-diastolic volume the least. The pattern conforms to the Frank-Starling mechanism, and indicates that at high exercise intensities ventricular myocytes generate high pressures with higher myocardial wall stress due to the increased size of the chamber.

Animals↗
PubMed1999

Cardiac output measurements using sonomicrometer crystals on the left ventricle at rest and exercise.

Eight horses were fitted surgically with 8 ultrasonic sonomicrometer crystals each attached to their left ventricular pericardia and a left atrial catheter. Three horses returned to treadmill performance with a maximum rate of oxygen consumption similar to their presurgical values. These horses were evaluated to determine how well sonomicrometer estimates of cardiac output agreed with those obtained by a steady-state method, the Fick principle. Variance between the 2 was similar to the coefficient of variation (approximately 12.5%) of the Fick estimates. We conclude that left ventricular sonomicrometer measurements in horses appear to give a reasonable estimate of ventricular dimensions and can, therefore, be used potentially to evaluate such variables as diastolic flow.

Animals↗
PubMed1999

Effects of frusemide on electrolyte and acid-base balance during exercise.

This study was undertaken to evaluate the effects of frusemide on the concentration of plasma electrolytes and the relationship between changes in electrolyte concentration and the simultaneous changes in acid-base balance in arterial and venous blood during intense exercise. Five exercise-conditioned Thoroughbred horses were exercised on a high-speed treadmill at a slope of 10% at speeds known to exceed VO2max. Horses participated in 3 randomised exercise trials in which they received either placebo (control), low-dose frusemide (0.5 mg/kg bwt), or high-dose frusemide (1.0 mg/kg) 4 h prior to exercise. Arterial and mixed venous blood samples were drawn before, during and after intense exercise. Packed cell volume (PCV), plasma protein, plasma electrolyte, plasma lactate concentrations and acid-base balance were determined. Frusemide at both dosages induced a significant metabolic alkalosis associated with a decrease in plasma çhloride[ in both arterial and mixed venous blood. There was a highly significant correlation between the strong ion difference (SID) and bicarbonate[ in all blood samples. The effects of frusemide on electrolyte concentration and acid-base balance were largely due to changes in SID.

Acid-Base Equilibrium↗
PubMed1999

Swimming overuse injuries.

Swimming injuries are unique in that they involve upper limb overuse more than lower limbs and that swimming is performed in a non-weight-bearing fluid setting. Identifying the mechanism of injury and prescribing appropriate management is not easy unless one has a thorough understanding of proper technique of the four competitive strokes. Understanding the psychology of swimming athletes will improve outcome and compliance. The goals of this article are to familiarize the reader with the diagnosis and management of swimming injuries and to improve the physician's effectiveness in dealing with swimmers through a thorough understanding of technique and psychology.

Athletic Injuries↗
PubMed1998

Optimization of the mammalian respiratory system: symmorphosis versus single species adaptation.

Taylor and Weibel's principle of symmorphosis hypothesized optimal design of the mammalian respiratory system, with no excess structure relative to its maximal O2 flux, VO2max. Although they found symmorphosis not to be a general principle of design, it might apply to a highly adapted aerobic athlete, e.g. the Thoroughbred racehorse. Using a mathematical model based on empirical data of the equine O2 transport system at normoxic VO2max, the fraction of the total limitation to O2 flux contributed by each of the respiratory transport steps is calculated as either the fractional change (F) in VO2max for a 1% change in each component, or as the fraction of total O2 pressure drop (R(int)) across each component at VO2max. When calculated as F, alveolar ventilation (VA) and pulmonary diffusing capacity (DLO2) are major limiting factors, circulatory convection (Q) is nearly as limiting, and peripheral tissue diffusing capacity (DTO2) is only one-third as important. When calculated as R(int), DLO2 is the major factor, VA and DTO2 contribute significantly, and Q is smallest. These patterns contrast with analogous studies in humans, in which Q is the single major limiting factor. The results suggest that strong selection for aerobic power in horses has maximized the malleable components of their respiratory systems until the least malleable structure, the lungs, has become a major limitation to O2 flux. Symmorphosis cannot determine if such a design is or is not optimized, as every system falls on a continuous distribution of relative optimization among species. However, the concept of symmorphosis is useful for establishing a framework within which a single species can be compared with a quantitatively defined hypothesis of optimal animal design, and compared with other species according to those criteria.

Adaptation, Biological↗
PubMed1997

Gradient elution reversed-phase chromatographic isolation of individual glycerophospholipid molecular species.

We describe a gradient elution reversed-phase high-performance liquid chromatographic approach for isolation of individual glycerophospholipid molecular species which greatly improves resolution and reduces run time compared to isocratic techniques. Separations were optimized and elution order and retention time data established by synthesizing 37 different homogeneous phospholipids comprising the major alkylacyl, diacyl and plasmalogen molecular species in samples derived from mammalian sources. Empirical equations which predict the elution order of individual species were derived. The method was validated with the use of complex mixtures of choline and ethanolamine glycerophospholipid species from isolated rabbit cardiomyocytes and porcine endothelial cells.

Animals↗
PubMed1996

Structural determinants of maximal O2 transport in muscles of exercising foxes.

The arctic blue fox (Alopex lagopus) has a specific maximal oxygen consumption (VO2 max/Mb = 3.6 ml O2.s-1.kg-1) that is approximately 1.6-fold greater than those of dogs and horses. The fox has one of the highest body mass specific skeletal muscle mitochondrial volumes (V(mt,m)/Mb = 44 cm3.kg-1) among mammalian athletic species matching its higher VO2 max/Mb. The structural components related to capillaries, such as specific capillary length density (J(c)/Mb = 348 km.kg-1) and specific capillary volume (V(c)/Mb = 4.8 ml.kg-1), are not greater in the fox than in the larger athletes. Because a greater specific muscle diffusing capacity for oxygen (DTO2/Mb) is not utilized by the fox to achieve a higher VO2 max/Mb, a higher pressure difference for diffusion in the muscle capillaries is the alternative explanation for the fox's higher VO2 max/Mb. This mechanism is suggested by the fox's higher arterial and mixed venous capillary PO2 (120 mm Hg and 37 mm Hg, respectively) and its shorter mean muscle capillary transit time for blood (tc = 0.28 sec) compared to larger species.

Animals↗
PubMed1996

Cross-infection control: the role of "in-training" dental nurses.

OBJECTIVES: This paper reports the findings of a study on the roles of dental nurses in cross-infection control in general dental practices and who were undergoing training for their initial certificate. The research aimed to find out what factors in their vocation gave them satisfaction, what caused stress and the bearing of these factors on cross-infection control. The study complemented previous research on the same matters carried out face-to-face in dental practices and aimed to test the validity of this previous research. METHODS: The study was made anonymously by means of self-administered questionnaires completed by respondents attending evening classes. RESULTS: Sixty per cent of respondents reported suffering anxiety in their work, the list of causes being headed by lack of experience, language barriers and taking part in general anaesthetic sessions. A third thought their workload was too great and a third quoted lack of time as the reason for not always completing cross-infection control procedures. Half were worried about cross-infection control. Clinical work was the most, and adequate pay the least important of five factors that gave respondents satisfaction in their work. Respondents always welcomed a word of thanks from their dentists and relied on them for information about their tasks. CONCLUSIONS: In order to carry out their work thoroughly, uncertificated dental nurses need sufficient time. They benefit from support and encouragement from their dentist. These are important factors in cross-infection control so that stress is prevented and job satisfaction enhanced. Our two studies validate each other.

Adolescent↗
PubMed1996

Effects of road transport on indices of stress in horses.

Stress associated with road transport is believed to be a significant contributor to the pathogenesis of post transport respiratory disease in horses. To determine the effects of road transport on pulmonary function, pulmonary aerosol clearance rates were measured in 4 horses 24 h before, and immediately after, 24 h of road transport by delivering aerosolised 99mtechnetium-labelled diethylenetriaminepentacetate (99mTc-DTPA) to the lungs and monitoring its washout. Each horse was transported twice, once while the trailer was equipped with a leaf-spring suspension and bias-ply tyres (trailer's original equipment, smooth ride) and once while the trailer was equipped with a torsion-bar suspension and normal pressure radial tyres (rough ride) in order to generate different ride characteristics. Before transport, blood was drawn from each horse for haematology and measurement of serum cortisol concentration; 24 h rates of hay and water intake and faecal output were recorded for each horse. Horses were then transported, 2 at a time, over a 128 km circular route of predominantly rural freeways at a constant speed of 72 km/h for 24 h. Horses were rested by stopping the trailer every 3.75 h for 0.25 h. During transport, heart rates (continuous 1 min averages), rates of hay and water intake and rates of faecal output were measured. Ammonia (NH3) and carbon monoxide (CO) concentrations were measured within the trailer and temperatures (wet bulb [WB], dry bulb [DB] and black globe [BG]) within the trailer were recorded each minute. Immediately after each experiment blood was drawn for haematology and measurement of pulmonary aerosol clearance rates were measured. For control studies, horses were housed in their stalls while heart rates were measured for 24 h. Slopes calculated from the 99mTc-DTPA clearance curves for pretransport horses were not significantly different from post transport clearance slopes. Pretransport mean 99mTc-DTPA clearance half-lives (T50, left lung mean +/- s.d. 41.7 +/- 15.8 min, right lung 44.6 +/- 19.1 min) were not significantly different from post transport T50 (left lung 53.5 +/- 14.0 min, right lung 52.0 +/- 11.6 min). Heart rates during transport were not affected by suspension type or trip order (the horse's first or second transport experiment) and were not significantly different from stall controls after the first 120 min of the experiment. Horses had increased red blood cell count, packed cell volume, haemoglobin, plasma protein and cortisol concentrations, and decreased body weights immediately post transport, indicating slight dehydration. Water and hay intake rates were significantly lower during transport than pretransport. Temperatures within the trailer were highest in the midafternoon and lowest in the early morning hours, but all temperatures measured in the trailer were within the comfort zone for large homeotherms. Ammonia and CO concentrations in the trailer during the transport period were within acceptable limits for human exposure. However, respirable articulates in the atmosphere were elevated above safe concentrations for human exposure.

Aerosols↗
PubMed1996

Quantitation of individual phospholipid molecular species by UV absorption measurements.

To validate the utility of on-line measurements of UV absorption for the direct quantitation of individual phospholipid molecular species isolated by reverse-phase HPLC, we synthesized 37 different individual molecular species of diacyl choline glycerophospholipids. UV absorbance response factors (integrate UV absorbance/nmole phospholipid) were calculated for all diacyl, alkenylacyl, and alkylacyl species by injecting varying amounts of the purified molecular species in the 2-100 nmole range and integrating the UV absorbance at 203 nm. There was excellent agreement between the results of the quantitation of individual molecular species determined by measurements of phospholipid mass in HPLC fractions with that based on measurements of total integrated UV absorption and the use of absorbance response factors. The on-line quantitation of individual phospholipid molecular species by UV absorption measurement should prove useful as an adjunct to other techniques of phospholipid quantitation, as a means to assist in the identification of individual molecular species in complex biologic mixtures, and as a stand-alone approach to phospholipid quantitation to facilitate studies of the metabolism of individual species particularly when coupled with radiolabeling techniques.

Chromatography, High Pressure Liquid↗
PubMed1995

Cross-infection control in general dental practice: dentists' behaviour compared with their knowledge and opinions.

This study aimed to establish how dentists' knowledge, opinion and behaviour about cross-infection control were related and how they were affected by their ages, gender and the sizes of the practices in which they worked. In 1990/91 all general dental practitioners in the North Western Health Region of England were asked to complete a questionnaire about cross-infection control; 917 (75%) did so. Responses from all single-handed and one dentist selected randomly from each group practice were analysed (n = 546). The score to measure behaviour was based on guidelines on cross-infection control issued by the British Dental Association and this was correlated with scores for knowledge and opinion. The more knowledgeable not only tended to hold favourable opinions about the guidelines but also to practise them. Younger dentists were more knowledgeable about cross-infection control measures than older and more likely to wear gloves. Irrespective of age, all female dentists were more likely to wear gloves than their male colleagues. Single-handed dentists were less willing to treat carriers of HIV and HBV. Although 65% thought that recommended control procedures are feasible, 43% considered them prohibitively expensive.

Adult↗
PubMed1995

Estimation of metabolic energy cost and heat production during a 3-day-event.

The metabolic power required for sustained exercise in the horse is proportional to running speed. Moderately fast speeds require substantial energy expenditure and result in the generation of a massive metabolic heat load. Quantitative estimates of energy expenditure and heat production of horses at various running speeds were developed using empirically derived data from treadmill studies. Total metabolic power represents the sum of aerobic power indicated by the rate of oxygen consumption and net anaerobic power indicated by the rate of plasma lactate accumulation. These data were applied to typical running speeds and distances for each of the 4 phases of the endurance day of an Olympic level (CCI) 3-day-event to provide an estimate of the energy expenditure and heat production during each phase. In a given horse, the rates of energy expenditure and heat production are determined by running speed, while total energy expenditure and heat production are determined by a combination of running speed and duration of exercise at that intensity. The highest calculated rate of energy expenditure and heat production occurred during Phase B, the steeplechase, followed closely by Phase D, the cross-country course. Interestingly, the highest total energy expenditure and heat production occurred on Phase C, Roads and Tracks, which is usually considered a period for cool down and recovery between the relatively high speed steeplechase and the demanding cross-country course. Nevertheless, because the rate of energy expenditure is low during this phase, the horses would be expected to lose heat and lower body temperature during this interval. In hot and humid climates, dissipation of the exercise-induced heat load may be compromised, leading to a narrower range of safety between the rate of heat production and the ability of the horse to dissipate this heat to the environment. The results of this study could be used, should environmental conditions dictate, to provide quantitative guidelines as to how specific alterations of speed or distance of the various phases of the event would affect heat production.

Animals↗
PubMed1995

Allometry of pharmacokinetics and pharmacodynamics of the muscle relaxant metocurine in mammals.

We investigated the effects of body size on the pharmacokinetics and pharmacodynamics of the renally cleared muscle relaxant metocurine. We hypothesized that pharmacokinetics of the drug would change allometrically in proportion to physiological time [infinity Mb0.25, where Mb is body mass] and that pharmacodynamics would be independent of size because of the highly conserved structure of the acetylcholine receptor. Metocurine effects during general anesthesia were examined in 17 rats, 8 cats, 6 dogs, 5 pigs, 7 sheep, and 12 horses. Allometric analysis demonstrated size dependence for pharmacokinetics, which were affected by physiological time (Mb0.25). Pharmacodynamics were size independent, except for the value for effect compartment concentration associated with 50% twitch paralysis (IC50). Data from individual species had a bimodal distribution that was significant: pigs and sheep were more sensitive than other large species, and their IC50 appeared size independent. IC50 was size dependent in more active species (horse, dog, cat, rat). Although the mechanism is unknown, we speculate that this trend might relate to receptor density within the end plate. Thus pharmacokinetics changed in proportion to physiological time, and pharmacodynamics were in part size independent.

Anesthesia, General↗