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Biomedical subjects

J M Clark

Publications and source records attributed to J M Clark.

At least 109 records · Page 6Linked to original sources
PubMed1995

Cloning and sequencing of a cDNA encoding acetylcholinesterase in Colorado potato beetle, Leptinotarsa decemlineata (Say).

A cDNA encoding acetylcholinesterase (AChE, EC 1.1.1.7) was cloned from a cDNA library constructed from an insecticide-susceptible strain of Colorado potato beetle, Leptinotarsa decemlineata (Say). The complete amino acid sequence of AChE deduced from the cDNA consisted of 29 residues for the putative signal peptide and 600 residues for the mature protein with a predicted molecular weight of 67,994. Northern blot analysis of poly(A) RNA showed an approx 13.1-kb transcript. The mature protein sequence had 57 and 61% of amino acid residues identical to those of Drosophila melanogaster and Anopheles stephensi, respectively, and produced a remarkably similar hydropathy profile when compared to those of the two dipterous species. The three residues (Ser, Glu and His) that putatively form the catalytic triad and the six Cys that form intra-subunit disulfide bonds were completely conserved when compared to the other seven AChEs from a broad range of animal species reported to date. Other properties of the deduced protein of AChE, including molecular weight and amino acid composition, agreed well with those of a previously reported study on the purified AChE from the same insect species. All these features firmly established that the cloned cDNA encodes AChE in Colorado potato beetle.

Acetylcholinesterase↗
PubMed1995

Quantitative analysis of the lens cell microstructure in selenite cataract using a two-dimensional Fourier analysis.

Using two-dimensional (2-D) Fourier methods, we analysed the cellular microstructure of three rat lenses: normal transparent, selenite-induced cataractous and selenite-treated plus a phase separation inhibitor (PSI) to prevent cataract. 2-D Fourier analysis of electron micrographs of the lens cells quantified the dimensions of the spatial fluctuations in electron density of the lens cell microstructure. The 2-D Fourier spectra of the transparent normal and PSI-treated lens cells were remarkably similar while those of the opaque selenite-treated lens cells were dramatically different. In the opaque cells the contributions of large Fourier components (larger than half the wavelength of light) in the 2-D Fourier spectra were much greater than in the transparent cells. The results of the 2-D Fourier analysis of electron micrographs are consistent with the theory of transparency of the eye.

Amifostine↗
PubMed1995

Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen.

STUDY OBJECTIVE: Carbon monoxide (CO) poisoning is a major clinical problem. The risk of morbidity and the most effective treatment have not been clearly established. We measured the incidence of delayed neurologic sequelae (DNS) in a group of patients acutely poisoned with CO and tested the null hypothesis that the incidence would not be affected by treatment with hyperbaric oxygen (HBO). DESIGN: We conducted a prospective, randomized study in patients with mild to moderate CO poisoning who presented within 6 hours. Patients had no history of loss of consciousness or cardiac instability. INTERVENTIONS: The incidence of DNS was compared between groups treated with ambient pressure 100% oxygen or HBO (2.8 ATA for 30 minutes followed by 2.0 ATA oxygen for 90 minutes). DNS were defined as development of new symptoms after oxygen treatment plus deterioration on one or more subtests of a standardized neuropsychologic screening battery. RESULTS: In 7 of 30 patients (23%), DNS developed after treatment with ambient-pressure oxygen, whereas no sequelae developed in 30 patients after HBO treatment (P < .05). DNS occurred 6 +/- 1 (mean +/- SE) days after poisoning and persisted 41 +/- 8 days. At follow-up 4 weeks after poisoning, patients who had been treated with ambient pressure oxygen and had not sustained DNS exhibited a worse mean score on one subtest, Trail Making, compared with the group treated with HBO and with a control group matched according to age and education level. There were no differences in scores between the control group and the hyperbaric oxygen group. CONCLUSION: DNS after CO poisoning cannot be predicted on the basis of a patient's clinical history or CO level. HBO treatment decreased the incidence of DNS after CO poisoning.

Adolescent↗
PubMed1995

Morphological and life-cycle aspects of the parasitic mite Trichosurolaelaps crassipes Womersley, 1956 of trichosurid possums.

All four life-cycle stages of the ubiquitous parasitic possum mite Trichosuroluelups crassipes Womersley, 1956 are illustrated. They comprise the ephemeral, quiescent and nonfeeding larva, an active feeding protonymph, an active feeding deutonymph and the adults. Morphological adaptations with viviparity allow the entire life-cycle of the mite to be completed on the host. The lack of a nidicolous egg or larva and the absence of a quiescent deutonymph implies transmission is via host-host contact.

Journal Article↗
PubMed1995

The diet of the parasitic mite Trichosurolaelaps crassipes Womersley, 1956 and its potential to act as a disease vector.

The anatomy of the gaster of Trichosurolaelaps crassipes is illustrated. Protonymphs, deutonymphs and adults were all seen with a scarlet gut and gave strongly positive results to occult blood tests. Host blood cells were identified in a gut smear from a female mite. An adult female gut could hold about 7.1 x 10(-6) ml. The mite was seen frequenting small open skin lesions. Gram-negative bacteria identified in the mite's gut are most likely to be endosymbionts. Mite larvae have their gastric caeca invaded by these bacteria before birth. There is a potential for this mite to act as a weak vector of disease from one possum to another.

Journal Article↗
PubMed1995

Health promotion: a concept analysis.

Health promotion is a concept which is frequently used, but is often ill defined. Current health care trends, and the emphasis on the nurse of the future as a promoter of health suggest that it would be useful to attempt to clarify the concept. This paper develops a conceptual analysis of health promotion using the process developed by Rodgers (1989). Attributes, antecedents, consequences and references are described following an examination of the ongoing debate in the literature surrounding the meaning of the concept. Empirical work is also reviewed which suggests that nurses' understandings of the concept are firmly embedded in the more traditional approach rather than the more modern or new paradigm approach to health promotion. A model case is described, and the analysis results in a proposed definition of health promotion which it is hoped will stimulate further discussion.

Attitude to Health↗
PubMed1995

Resistance to avermectins: extent, mechanisms, and management implications.

The avermectins represent a group of natural compounds with potent pesticidal activities. Because of their novel mode of action, they represent an important resource for pest control and resistance management. In the Colorado potato beetle, the house fly, and the two-spotted spider mite, resistance to abamectin is usually autosomal, recessive, and polygenic. Although these aspects are beneficial in resistance management, the fact that resistance could be readily selected for suggests that abamectin needs to be used in moderation. Furthermore, several major resistance mechanisms (e.g. excretion, oxidative metabolism, penetration) and minor factors (e.g. altered target site, conjugation, hydrolysis/sequestration) have been implicated in abamectin resistance. Thus, the question is not whether resistance to abamectin will occur but is simply when and how it will occur. To address this problem, we have gathered information on the genetics, biochemical mechanisms, effectiveness of synergists, and cross-resistances to other insecticides from three abamectin-resistant insects. Judicious implementation of this information may prove useful in the resistance management of this natural pesticide.

Animals↗
PubMed1995

Vertical gaze palsies from medial thalamic infarctions without midbrain involvement.

BACKGROUND: Although the supranuclear pathways for vertical gaze control are not well defined, lesions of the mesencephalic reticular formation including the nucleus of Darkschewitsch, the rostral interstitial medial longitudinal fasciculus, the interstitial nucleus of Cajal, and the posterior commissure are known to produce vertical gaze palsies. MRI studies have not previously reported isolated thalamic lesions as the cause of vertical gaze palsies. CASE DESCRIPTIONS: Three patients with acute paralysis of vertical gaze were imaged with MRI. Sagittal T1 and axial T1, T2, and proton-weighted images were obtained. All three patients had repeated scans performed from 3 days to 6 weeks after the original study. Two patients exhibited unilateral right thalamic infarcts (polar and paramedial territory), and one patient had a bilateral paramedian thalamic infarction. There was no evidence of midbrain involvement on any of the images. CONCLUSIONS: Vertical gaze palsies are known to be produced by lesions of the rostral interstitial medial longitudinal fasciculus. This MRI study reveals thalamic infarctions without associated midbrain infarctions in three patients with vertical gaze palsies. This may be explained by interruption of supranuclear inputs.

Aged↗
PubMed1995

Tryptase inhibitors block allergen-induced airway and inflammatory responses in allergic sheep.

Tryptase, a mast cell serine protease, has been implicated in the pathophysiology of allergic asthma, but formal evidence to support this hypothesis has been limited by the lack of specific inhibitors for use in vivo. Therefore, in this study we examined the effects of two inhibitors of tryptase, APC 366 [N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride] and BABIM [bis(5-amidino-2-benzimidazolyl)methane] on antigen-induced early and late responses, airway responsiveness as measured by carbachol provocation, microvascular permeability as measured by bronchoalveolar lavage (BAL) albumin concentrations, and tissue eosinophilia from biopsies in allergic sheep. APC 366 and BABIM were administered by aerosol in all experiments. In vehicle control trials, antigen challenge resulted in peak early and late increases in specific lung resistance (SRL) of (mean +/- SE, n = 6) 259 +/- 30% and 183 +/- 27% over baseline, respectively. Treatment with APC 366 (9 mg/3 ml H2O given 0.5 h before, 4 h after, and 24 h after antigen challenge) slightly reduced the peak early response (194 +/- 41%), but significantly inhibited the late response (38 +/- 6%, p < 0.05 versus control trials). Twenty-four hours after challenge, APC 366 also completely blocked the antigen-induced airway hyperresponsiveness to inhaled carbachol observed in the control trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1995

The potential utility of animal poisoning data to identify human exposure to environmental toxins.

The database of the National Animal Poison Control Center (NAPCC) was evaluated as a source for animal poison data indicating human health hazards in indoor and outdoor environments. From 14,150 calls in the 1985 database, 259 cases were identified with histories suggesting human exposure. A subgroup of 25 cases with known human exposure was found. Dogs were the most common sentinel animal, but bird cases represented the highest proportional selection from the total 1985 call list. Indoor exposures represented 43.2% of cases; the most common toxicants were insecticides, lead and toxic fumes. Exposures associated with lawns were mainly due to insecticides and herbicides and constituted 25.5% of cases. Other outdoor exposures composed the remaining 31.7% of cases, with insecticides, herbicides and unidentified toxins the leading categories. Many of the specific agents identified, such as organophosphate insecticides, lead, gas and fume toxins, and phenoxy herbicides are also risk factors in human diseases. This study indicates that databases such as NAPCC could serve as sources of sentinel animal intoxications for followup studies to evaluate known and potential human health hazards.

Animals↗
PubMed1995

Human tolerance and physiological responses to exercise while breathing oxygen at 2.0 ATA.

Multiple physiological functions were monitored in ten men who performed two 30-min periods of 150-W ergometer exercise during 120-min exposures to O2 at 2.0 ATA. There were no convulsions or electroencephalographic manifestations of increased excitability. Sequential measurements of peripheral visual fields, pulmonary mechanical function, mental performance, and cardiovascular function during the resting recovery after each of the two exercise periods were not detectably altered from pre-exercise control values. Pre- and post-exposure measurements of visual acuity, accommodation, pupil diameter, visual cortical activity, and retinal electrical activity also revealed no significant differences. While CNS symptoms were absent, average arterial PCO2 rose by about 5 mm Hg during both exercise periods. This finding was confirmed in six subjects who performed four 6-min periods of continuous exercise at 50, 100, 150, and 200 W while breathing O2 at 2.0 ATA. Average arterial PCO2 rose nearly linearly from 34.3 mm Hg at rest to 44.0 mm Hg at 200 W. Arterial PCO2-related increments in brain blood flow and PO2 may explain part or all of the known detrimental influence of exercise on CNS O2 tolerance.

Atmospheric Pressure↗
PubMed1994

Retrieval mechanisms in the development of instance and superordinate naming of pictures.

Children's use of superordinate names lags behind their use of instance names, and production lags behind comprehension. The hypothesis that both of these developmental delays reflect underlying retrieval difficulties predicts an interaction between name generality (instance vs. superordinate) and task (comprehension vs. production). Specifically, production of superordinate names should be more difficult for children than the separate name generality and task effects would predict. To examine this hypothesis, 32 junior kindergarten and 32 Grade 1 children in Experiment 1 performed an instance and superordinate name comprehension task for 96 single-exemplar pictures from 12 categories, and 32 junior kindergarten and 32 Grade 1 children in Experiment 2 produced instance or superordinate names for the same pictures. As predicted, the combination of superordinate names and language production was particularly difficult, especially for junior kindergarten children. High rates of instance name intrusions and other findings suggest that superordinate name production may be interfered with by more readily available instance names. Weak inhibition of competing instance names and other mechanistic explanations for the effects are considered.

Child↗
PubMed1994

Pharmacokinetics and antiviral activity of a novel isonucleoside, BMS-181165, against simian varicella virus infection in African green monkeys.

A novel nucleoside analog BMS-181165 with potent activity against varicella-zoster virus was tested for efficacy in a simian varicella virus infection in African green monkeys. BMS-181165 was effective in preventing the development of a rash, decreasing the development of viremia and preventing death in infected monkeys when administered orally at 4, 16 or 64 mg/kg/day. The compound is well orally absorbed in monkeys, between 44 to 50% oral bioavailability, and may prove of value in therapy of varicella-zoster infections in humans.

Administration, Oral↗
PubMed1994

pH testing of feeding-tube aspirates to determine placement.

Although radiologic confirmation of tube placement remains the "gold standard," there is growing evidence that pH testing of feeding-tube aspirates can reduce (although not totally eliminate) reliance on x-rays used for this purpose. This article describes that evidence and tells how it was obtained. Reducing the number of x-rays needed to confirm tube position can have far-reaching financial benefits.

Adolescent↗
PubMed1994

Modification of oxygen tolerance in rats by adaptation to combined hypoxia and hypercapnia.

Tolerance to 100% O2 or to O2 with 60 torr PICO2 (O2-CO2) was determined at pressures of 1.0-4.0 atm abs in normal rats and in rats adapted to combined hypoxia and hypercapnia (HHA) before O2 or O2-CO2 exposure. Results were compared with previous studies of tolerance to O2 or O2-CO2 after adaptation to hypoxia or hypercapnia alone. Both the positive effect on pulmonary O2 tolerance and the negative effect on CNS O2 tolerance found in hypoxia-adapted rats were reduced or eliminated in HHA rats. The increased CNS tolerance to O2-CO2 found in hypercapnia-adapted rats was also reduced in HHA rats. The observation that some of the O2 tolerance modifications associated with adaptation to hypoxia or hypercapnia were reduced or eliminated by adaptation to both stresses concurrently may be because physiologic responses to chronic hypoxia and chronic hypercapnia are opposite in some ways. Results of the present and previous related studies indicate that physiologic adaptations to chronic alterations in the oxygen and acid-base environments have prominent influences on O2 tolerance over a range of useful pressures.

Adaptation, Physiological↗
PubMed1993

Synthesis and antiviral activity of novel isonucleoside analogs.

A series of branched-chain sugar isonucleosides was synthesized and evaluated for antiviral activity against herpesviruses. The preparation of homochiral [3S-(3 alpha, 4 beta, 5 alpha)]-2-amino-1, 9-dihydro-9-[tetrahydro-4,5-bis(hydroxymethyl)-3-furanyl]-6H-purin-6-one (7, BMS-181,164) and related compounds was stereospecifically achieved starting from 1,2-isopropylidene-D-xylofuranose (10). An efficient two-step reduction of the anomeric center of bis-acetate 18 involved formation of the chloride intermediate 19, followed by diisobutylaluminum hydride reduction. Tosylation of the resulting alcohol 20 provided the key intermediate 21, which was coupled with a variety of nucleobase anions. Several members of this new class of compounds possess activity against herpes simplex virus types 1 and 2 (HSV-1 and -2), varicella-zoster virus (VZV), and human cytomegalovirus (HCMV). Compound 7 exhibits potent and selective activity against thymidine kinase encoding herpesviruses, in particular, HSV-1 and HSV-2. Evaluation of compound 7 for inhibition of WI-38 cell growth indicated an ID50 of > 700 microM. Although the antiherpetic activity in vitro of 7 is less than that of acyclovir (1), compound 7 displays superior efficacy in mouse model infections. The (bromovinyl)uridine analog 8 (BMS-181,165) also exhibits selective activity against HSV-1 and VZV, with no cytostatic effect on WI-38 cell growth at > 800 microM. Compound 8 is active against simian varicella virus and is efficacious in the corresponding monkey model.

Animals↗
PubMed1993

Nurse managers' perceptions of contracting for education, Part 1: Contracting and pre-registration education.

The introduction of the 'purchaser/provider' split into nurse education alters the relationship between service units (or the education purchasers) and colleges of health studies (the education providers). The aim of this study was to identify how education purchasers view the new contracting arrangements, with regard to the provision of pre-registration and post-registration nurse education. In the first of two papers, findings are reported in relation to purchasers' views of pre-registration education. 24 people from one region, comprising senior nurses, and some non-nurse executives involved in the Working Paper 10 initiative, were interviewed. The findings indicate that most of the respondents want a close working relationship with an education provider. They hope that this relationship will be responsive to, and understanding of the needs of the service, and that it will be enhanced by the contracting process. The majority see the need to formally monitor the quality of the output of the college, to ensure that their educational needs are being met by their provider, but they are unsure as to how this can be done. Finally, although it is understood that if service units become dissatisfied with their local college, they can contract with alternative colleges for pre-registration education, the majority of these respondents believe that this will not be desirable or feasible.

Attitude of Health Personnel↗