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Biomedical subjects

M J Hall

Publications and source records attributed to M J Hall.

At least 55 records · Page 3Linked to original sources
PubMed1996

Genetic probing of the first and second transmembrane helices of the plasma membrane H(+)-ATPase from Saccharomyces cerevisiae.

Structural features of the putative helical hairpin region comprising transmembrane segments 1 (TM1) and 2 (TM2) of the yeast plasma membrane H(+)-ATPase were probed by site-directed mutagenesis. The importance of phenylalanine residues Phe-116, Phe-119, Phe-120, Phe-126, Phe-144, Phe-159, and Phe-163 was explored by alanine replacement mutagenesis. It was found that substitutions at all positions, except Phe-120 and Phe-144, produced viable enzymes, although a range of cellular growth phenotypes were observed like hygromycin B resistance and low pH sensitivity, which are linked to in vivo action of the H(+)-ATPase. Lethal positions Phe-120 and Phe-144, could be replaced with tryptophan to produce viable enzyme, although the F144W mutant was highly perturbed. ATP hydrolysis measurements showed that Km was not significantly altered for most mutant enzymes, whereas Vmax was moderately reduced with two mutants, F144W and F163A, showing less than 50% of the normal activity. Double Phe-->Ala mutations in TM1 and TM2 were constructed to examine whether such substitutions would result in a higher degree of enzyme destabilization. Mutant F116A/F119A was viable and gave a normal phenotype, while F159A/F163A was not viable. Other double mutants, F116A/F159A and F119AF/159A, which are predicted to lie juxtaposed on TM1 and TM2, produced non-functional enzymes. However, a viable F119V/F159A mutant was isolated and showed hygromycin B resistance. These results suggest that double mutations eliminating 2 phenylalanine residues strongly destabilize the enzyme. A putative proline kink at Gly-122/Pro-123 in TM1 is not essential for enzyme action since these residues could be variously substituted (G122A or G122N; P123A, P123G, or P123F) producing viable enzymes with moderate effects on in vitro ATP hydrolysis or proton transport. However, several substitutions produced prominent growth phenotypes, suggesting that local perturbations were occurring. The location of Pro-123 is important because Gly-122 and Pro-123 could not be exchanged. In addition, a double Pro-Pro created by a G122P mutation was lethal, suggesting that maintenance of an alpha-helical structure is important. Other mutations in the hairpin, including modification of a buried charged residue, E129A, were not critical for enzyme action. These data are consistent with the view that the helical hairpin comprising TM1 and TM2 has important structural determinants that contribute to its overall stability and flexibility.

Cell Membrane↗
PubMed1996

Efficacy of ivermectin and moxidectin injection against larvae of Wohlfahrtia magnifica (Diptera: Sarcophagidae) in sheep.

The therapeutic efficacies of ivermectin (Ivomec injection, Merck Sharp & Dohme B.V.) and moxidectin (Cydectin 1% injection, American Cyanamid Company) were evaluated in sheep naturally infested with larvae of Wohlfahrtia magnifica. Sheep were randomly allocated to one of the 2 groups, each consisting of 19 animals. Sheep in one group received ivermectin and those in the other, moxidectin by subcutaneous injection at a dose of 0.2 mg/kg body weight. Evaluation was performed at 19, 24, 28, 39, 43, 48, 52, 63, 67, 72, 87, 96, 120, 144 and 168 h after treatment. At 144 and 168 h post-treatment, late third-instar larvae were collected from wounds of four sheep in both groups and from untreated, infested sheep. These larvae were reared in the laboratory to assess adult emergence. Neither ivermectin nor moxidectin was effective as a rapid acting treatment or as a long-term, or even short-term, prophylactic. Despite the treatment, 30-40% of sheep had live larvae at every evaluation. Although larvae disappeared from the wounds of some sheep in both groups after the treatment, the wounds in these animals failed to recover and were reinfested by larvae of W. magnifica. On day 7 post-treatment the trial had to be finished because the majority of treated sheep were severely infested by Wohlfahrtia maggots. The average number of infested sheep in the two groups and the number of adults that were produced from larvae collected from treated sheep indicate that ivermectin and moxidectin did not differ significantly in efficacy.

Animals↗
PubMed1996

Cycle length of periodic breathing in patients with and without heart failure.

Because apnea length during periodic breathing varies according to the preceding increase in ventilation and reduction in PaCO 2, differences in the cycle length of periodic breathing among patients with normal and impaired cardiac function might be explained by the influence of lung-to-carotid body circulatory delay, as reflected by lung-to-ear circulation time (LECT), on hyperpnea length rather than on apnea length. It was therefore hypothesized that circulatory delay is an important determinant of periodic-breathing hyperpnea length but not apnea length. To test this hypothesis, LECT, periodic-breathing cycle length, apnea length, and hyperpnea length were compared in 10 patients with idiopathic central sleep apnea (ICSA), whose cardiac function was normal, as opposed to 10 with Cheyne-Stokes respiration and central sleep apnea (CSR-CSA) in association with congestive heart failure (CHF). As compared with ICSA patients, cycle length was significantly longer in patients with CSR-CSA (37.3 +/- 3.0 s versus 59.0 +/- 4.9 s, p < 0.005). This difference was due to significantly longer hyperpnea length in the CSR-CSA patients (16.7 +/- 2.8 s versus 36.7 +/- 3.4 s, p < 0.001), since apnea length was similar in the two groups. In addition, LECT was longer in the CSR-CSA patients (24.3 +/- 2.0 s versus 10.3 +/- 1.0 s, p < 0.001), and correlated strongly with cycle length (r = 0.88, p < 0.001) and hyperpnea length (r = 0.90, p < 0.001) but not with apnea length. LECT correlated inversely with cardiac output (r = -0.72, p < 0.006), indicating that LECT is a valid measure of circulatory delay. Thus, circulatory delay is an important determinant of hyperpnea length but not of apnea length in patients with ICSA and CSR-CSA.

Cardiac Output↗
PubMed1996

Patients, carers and the medical profession: a co-operative approach.

This article is reprinted (with minor editing) from the Queensland Council of Carers newsletter for members. The Council's Public Policy Forum, held in September 1994, raised problems faced by carers, some of which related to the relationship between patients, carers, and the medical profession. Their concerns were circulated to the Divisions of General Practice, who in turn delegated the author to contact the Queensland Council of Carers, with a view to improving co-operation and clarifying mutual expectations.

Caregivers↗
PubMed1995

Does occupational exposure to argon laser radiation decrease colour contrast sensitivity in UK ophthalmologists?

The objects of the study were to determine: (1) whether United Kingdom ophthalmologists who used argon lasers had the elevation of colour-contrast thresholds previously discovered and (2) whether other users of argon lasers showed any unusual loss of colour vision. A total of 1072 UK ophthalmologists filled in a questionnaire about their professional use of lasers, the length of time spent operating, and their out-of-doors activities. Their colour vision was then tested by a new sensitive system, and if any abnormality was detected, a clinical eye examination was performed. The results were as follows: (1) Colour vision testing was shown to be reliable. Any self-selection bias was excluded. Test-retest variability was small. Normal results did not change during the survey. (2) A number of men with high red-green thresholds were discovered. Some were aware of their congenital insensitivity. The frequency of all such defects was less than the known incidence of congenital colour deficiency in the male population. (3) Additionally a number of high tritan (blue-yellow) thresholds were encountered, some associated with reported diabetes and hypertension. In other cases of this type, undetected or unacknowledged systemic disease may be present. (4) After making allowance for all these incidental causes of loss of colour vision, and for the effect of age on colour vision (which is very small) only four of the sample were > 2 SD above normal. (5) However, the average blue-yellow thresholds of ophthalmologists were slightly and highly significantly raised compared with normal, in the first year of the survey. During the second and third years, the mean thresholds declined to normal. Similar but less significant findings were found for protan thresholds. It is concluded that the enhanced safety precautions recently introduced are associated with a recovery of colour vision in this population, demonstrating that any changes to individuals were reversible. Colour vision screening has proved able to detect mild ocular abnormalities due to systemic and congenital disease.

Adult↗
PubMed1995

Trapping the flies that cause myiasis: their responses to host-stimuli.

A critical phase in the life cycle of the fly species that cause myiasis is host location by the adult females, whether by direct location of and contact with the host, or by indirect location through the selection of sites frequented by hosts. The stimuli to which these flies respond in host location, principally visual and olfactory, are discussed here in the context of their use to enhance the performance of trapping systems used in research, monitoring and control. The three major families of flies encountered in myiasis can be divided into two groups for comparison of host-location strategies: (1) Oestridae; and (2) Calliphoridae and Sacrophagidae. The former are all obligate parasites, the latter include obligate and primary facultative parasites. In the Oestridae, the majority of Cuterebrinae deposit their eggs at sites likely to be visited by the host, whereas the majority of Oestrinae, Hypodermatinae and Gasterophilinae deposit their eggs or larvae directly onto the host. It is presumed that most host location is, like that of haematophagous insects, by response to olfactory and visual cues released by healthy hosts, but the subject is very under-researched. In the Calliphoridae and Sacrophagidae, most species that cause myiasis deposit their eggs or larvae directly onto the host at some predisposing site, such as those caused by wounding, necrosis and/or bacterial contamination. Healthy hosts are much less attractive, even for obligate species such as Wohlfahrtia magnifica, which can invade undamaged tissues. The last decade has seen a renewed interest in the potential for using traps in control of myiasis, leading to significant advances in trap and bait efficiency. However, there is great potential for further research and development, particularly on the general responses of Oestridae to hosts and in the precise identification of the olfactory cues for Calliphoridae and Sarcophagidae.

Animals↗
PubMed1995

Cardiovascular disease and sleep apnea.

A number of novel and important observations have recently arisen that emphasize the interaction between sleep apnea and cardiovascular function. New evidence of a role for obstructive sleep apnea as an independent factor in the genesis of hypertension and nocturnal myocardial ischemia has been described. Advances have been made in the understanding of the acute impact of sleep-disordered breathing on hemodynamic function, and a better understanding of the interaction between sleep-disordered breathing and congestive heart failure is now emerging. There is now strong evidence that reversal of sleep-related breathing disorders by nasal continuous positive airway pressure leads to improvements in markers of cardiovascular outcome in selected patients with congestive heart failure. These findings augur well for the development of new diagnostic approaches and treatment strategies for patients with sleep apnea and coexisting cardiovascular disease.

Cardiovascular Diseases↗
PubMed1995

Orientation of agents of wound myiasis to hosts and artificial stimuli in Hungary.

The orientation of adults of the myiasis species Wohlfahrtia magnifica and Lucilia sericata to artificial visual stimuli (cloth targets) and olfactory stimuli ('swormlure-4', a potent screwworm attractant), was studied in sheep pastures near to Sárbogard in Hungary. Experiments with odour-baited cloth targets, enclosed in electrocuting grids, demonstrated that colour was an important factor influencing catches on targets: a black target caught most flies of both species, with other colours in the following order of effectiveness, blue > white > yellow. Wohlfahrtia magnifica did not respond to swormlure-4 in the strong manner that L.sericata did. The sex ratios of W.magnifica caught on targets (67.2% males) and hand-netted from fence posts (68.8% males) were similar and biased towards males, whereas that of L.sericata on targets was strongly biased towards females (15.6% males), indicating a fundamental difference in the response of these two myiasis species towards the swormlure-baited targets. The orientation of these two species towards hosts was also recorded together with that of a third species, Phormia regina. Electric nets placed beside infested sheep caught significantly more flies of all three species than those placed beside uninfested sheep or in the absence of sheep. The sex ratio of W.magnifica caught around infested sheep was the reverse of that on targets, with 68.5% females. Wohlfahrtia magnifica responded more strongly to healthy, uninfested sheep than did L. sericata and P.regina. The potential for use of targets both for population monitoring and control is discussed.

Animals↗
PubMed1994

Exercise, potassium, and muscle deconditioning post-thoracic organ transplantation.

Although muscle deconditioning appears to significantly limit peak exercise performance post-thoracic organ transplantation, few confirmatory data exist. Potassium (K+) regulation during exercise may reflect muscle deconditioning, since both peak plasma K+ concentration ([K+]) and the increase in plasma [K+] relative to energy expenditure (delta [K+]/W) are reduced in healthy individuals after training. This study compares delta [K+]/W during graded exercise and the change in [K+] (delta [K+]) during both exercise and recovery in 12 heart transplant (HT) recipients, 14 lung transplant (LT) recipients, and 7 healthy subjects. Plasma [K+] was determined from arterial blood sampled at rest; during the final 15 s of each power output; and at 1, 2, and 5 min postexercise. Peak oxygen consumption was significantly lower (P < 0.0001), whereas delta [K+]/W was significantly higher (P < 0.002) among the HT and LT groups. When delta [K+] during recovery was expressed relative to delta [K+] detected during activity, no difference at 1, 2, or 5 min postexercise was detected, although the absolute fall in plasma [K+] was greater among the healthy subjects in the 1st min (P < 0.0001). The rate of delta [K+] during recovery appears to reflect the rise seen during activity in all groups. These results suggest that [K+] regulation is altered during exercise in both HT and LT recipients and may reflect muscle deconditioning.

Adult↗
PubMed1994

Violence in patients with narcissistic personality pathology: observations of a clinical series.

This paper presents clinical observations on a group of nine patients whose action consisted of either the commission of violent acts or of seriously threatening behaviors suggestive of precursors to violence. A cluster of common features was observed to be present to some degree in all patients: (1) significant narcissistic personality pathology, (2) recent narcissistic injury, (3) inability to acknowledge or express affect related to this injury, (4) some history of impulsiveness when stressed, and (5) the availability of a weapon. Discussion is presented that the clinician's ability to predict the potential for violence may be enhanced by special attention to these features.

Adult↗
PubMed1993

Long-stay patients in short-stay hospitals.

In 1980 and 1990, only 4-5 percent of patients in short-stay hospitals were hospitalized for more than 3 weeks. The number of discharges and days of care for these long-stay patients were lower in 1990 as compared with 1980, but they continued to use more than a quarter of all hospital days in 1990. Long-stay patients were more likely than all patients to be 65 years of age and over and have Medicare as their expected principal source of payment. For long-stay and all patients, private insurance covered smaller proportions of discharges and days of care, and Medicaid covered larger proportions in 1990 than in 1980. Long-stay patients were more likely than all patients to be discharged dead or transferred to other hospitals or nursing homes. Long-stay and all patients were more likely to be transferred at discharge in 1990 than in 1981. The Northeast Region had a larger proportion of long-stay patients than of all patients, and that proportion increased from 1980 to 1990. The proportion of long-stay discharges and days of care in the Midwest decreased during this period. In 1980 and 1990, more than 50 percent of the discharges and days of care for long-stay patients were for diseases of the circulatory system, mental disorders, neoplasms, or injury and poisoning. Despite the overall decreases in hospital use by long-stay patients, their discharges and days of care increased significantly from 1980 to 1990 for diagnoses such as septicemia, psychoses, and miscellaneous complications of surgical and medical care. Over time, decreases were seen in long-stay discharges and days of care for a variety of diagnostic categories, including malignant neoplasm of trachea, bronchus, and lung; diabetes mellitus; and fracture of the neck of the femur. Long-stay patients had a higher rate of procedures per 1,000 discharges in 1990 than in 1980, and a higher rate than all patients in both years. Approximately half of all the procedures performed on long-stay patients in 1980 and two-thirds in 1990 were miscellaneous diagnostic and therapeutic procedures, operations on the cardiovascular system, or operations on the digestive system. The rates of numerous procedures, especially diagnostic tests, increased for long-stay and all patients from 1980 to 1990.

Age Distribution↗
PubMed1993

Attracting adult New World screwworm, Cochliomyia hominivorax, to odour-baited targets in the field.

A field study in Libya investigated aspects of Cochliomyia hominivorax behaviour relevant to the operation of a target-based control system. Flies were readily caught by electrified targets, but only when baited with the attractant 'swormlure-4'. Target size (0.25-1 m2) did not affect catch, but black targets caught twice as many flies as red ones. Omitting the most volatile component of swormlure-4, dimethyl disulphide, significantly reduced catches of both sexes of C.hominivorax in wind-orientated traps, but only reduced the capture of females significantly on targets. A new polythene sachet dispenser for odours was tested; four to six such sachets filled with swormlure-4 less dimethyl disulphide gave an equivalent catch to one of the standard bottle plus wick dispensers using the same attractant, although they dispensed odour at about half the rate. From direct observations, fewer than 40% of flies contacted the target for more than 10 s on any one visit. From catches on an intermittently-active electrocuting grid, it was calculated that there is a c. 40% rate of multiple contacts of flies with the target.

Animals↗
PubMed1993

Ophthalmomyiasis in Kuwait: first report of infections due to the larvae of Oestrus ovis before and after the Gulf conflict.

We report for the first time four cases of ophthalmomyiasis due to the larvae of Oestrus ovis in Kuwait, before and after Operations Desert Shield and Desert Storm. The larvae were easily removed under local anaesthetic. The symptom complex of acute foreign body sensation, irritation, redness, lacrimation and photophobia resolved rapidly. Ophthalmic antibiotic and corticosteroid drops were also instilled and recovery was uneventful. The ophthalmomyiasis may not always be associated with contact with sheep-rearing per se. Medical personnel should therefore be aware that in cases of what might appear initially as acute, non-specific catarrhal conjunctivitis, patients with the persistent symptom complex should be re-examined to exclude ophthalmomyiasis due to the larvae of O. ovis in endemic areas.

Adult↗
PubMed1993

An examination of narcissistic personality traits as seen in a military population.

Various studies examining the prevalence of personality disorders in civilian inpatient and outpatient populations have consistently found narcissistic personality disorder to be one of the least common. In striking contrast to this, a recently published study showed narcissistic personality features to be among the most common personality features in a military outpatient clinic population. This paper examines several possible explanations for this finding. This surprisingly high relative incidence of narcissistic personality features may be related to a self-selection bias on the part of persons choosing a military career. Narcissistic personality traits may confer adaptive advantage in certain military professional roles. Kohut's theory of specific transference requirements in individuals with narcissistic character structure serves as a useful explanatory model for these findings.

Humans↗