Preliminary study of synergism of acid rain and diflubenzuron.
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Acid Rain↗
Biomedical subjects
J M Clark
Publications and source records attributed to J M Clark.
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↗
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↗
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↗
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↗
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↗
Rapid construction of nested deletions of recombinant plasmid DNA for dideoxy sequencing.
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Base Sequence↗
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↗
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↗
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↗
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↗
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↗
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↗
Nurse managers' perceptions of contracting for nurse education, Part 2: Contracting and post-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). This is the second of two papers, and focuses on senior health service managers views on the purchasing and provision of post-registration nurse education. 24 managers from one region were interviewed. The aim was to identify their post-registration education needs, the criteria they use to choose between post-registration courses held in different colleges, and how they identify 'value for money' in post-registration education. The findings showed a limited understanding of the financial issues involved and considerable variation in opinion regarding the purpose, type and academic level of post-registration education. Cost emerged as a potentially more influential factor than quality in determining which courses managers will purchase. The managers interviewed are predominantly looking to contract with colleges who will be communicative, receptive to their needs, and willing to work in partnership with them.
Attitude of Health Personnel↗
Encephalopathy due to severe hyponatremia in an ultramarathon runner.
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Humans↗
N-methyl-D-aspartate lesions of the lateral hypothalamus do not reduce amphetamine or fenfluramine anorexia but enhance the acquisition of eating in response to tail pinch in the rat.
These experiments examine the acquisition of tail pinch-induced eating and responses to the anorectic agents d-amphetamine and d,l-fenfluramine by rats bearing N-methyl-D-aspartate (NMDA) lesions of the lateral hypothalamus. Lesioned rats lost weight following surgery but had no significant eating or drinking difficulties in the home cage (Clark et al. 1990). The acquisition of eating in response to tail pinch was enhanced in lateral hypothalamic-lesioned rats: they ate on earlier test sessions than controls and less pressure was required to elicit eating. Home cage food intake over the period when tail pinch was being examined was not affected by the lateral hypothalamic lesions. There were no significant differences between lateral hypothalamic-lesioned and control rats in terms of their anorectic responses to either d-amphetamine or d,l-fenfluramine, though the lesioned rats had a lower baseline intake. These data suggest that the lateral hypothalamus is not an important site for the mediation of amphetamine or fenfluramine anorexia but is involved in the acquisition of tail pinch-induced eating. The disinhibition of responding to tail pinch by lateral hypothalamic lesions is discussed in terms of the possible role the lateral hypothalamus plays in regulating cortical activity. The role of the medial hypothalamus and non-hypothalamic systems in the response to anorectic drugs and tail pinch is discussed.
Amphetamine↗
NMDA lesions of lateral hypothalamus enhance the acquisition of schedule-induced polydipsia.
Schedule-induced polydipsia (SIP) is affected by damage to various limbic structures that have connections with the lateral hypothalamus. The present experiment sought to determine whether or not SIP could be induced in rats bearing NMDA-induced lesions of the lateral hypothalamus. Following surgery, lesioned rats lost weight and were hypophagic and hypodipsic. Drinking, in response to systemic injection of hypertonic saline, was impaired in lesioned rats. Prior to testing for SIP, all rats were placed on a food-restriction regime to maintain body weight at 85% of normal. There was no statistically significant difference in mean body weight between lesioned and control groups before deprivation began, though lesioned rats were hypodipsic in their home cages. The lateral hypothalamic-lesioned rats acquired SIP significantly more rapidly than controls over the first six sessions, but over four following sessions no differences were present. The enhanced acquisition of SIP by lateral hypothalamic-lesioned rats cannot be accounted for by postoperative recovery of body weight or by hypodipsia in the home cage, neither of which correlated with SIP. It is suggested that the lateral hypothalamus has a role in cueing appropriate and inhibiting inappropriate behavior in conditions of motivational excitement. SIP is suggested to have two CNS components--one excitatory and one inhibitory.
Animals↗
Dynamic heterogeneity of cerebral hypoperfusion after prolonged cardiac arrest in dogs measured by the stable xenon/CT technique: a preliminary study.
After prolonged cardiac arrest and reperfusion, global cerebral blood flow (gCBF) is decreased to about 50% normal for many hours. Measurement of gCBF does not reveal regional variation of flow or permit testing of hypotheses involving multifocal no-flow or low-flow areas. We employed the noninvasive stable Xenon-enhanced Computerized Tomography (Xe/CT) local CBF (LCBF) method for use in dogs before and after ventricular fibrillation (VF) cardiac arrest of 10 min. This was followed by external cardiopulmonary resuscitation (CPR) and control of cardiovascular pulmonary variables to 7 h postarrest. In a sham (no arrest) experiment, the three CT levels studied showed normal regional heterogeneity of LCBF values, all between 10 and 75 ml/100 cm3 per min for white matter and 20 and 130 ml/100 cm3 per min for gray matter. In four preliminary CPR experiments, the expected global hyperemia at 15 min after arrest, was followed by hypoperfusion with gCBF reduced to about 50% control and increased heterogeneity of LCBF. Trickle flow areas (LCBF less than 10 ml/100 cm3 per min) not present prearrest, were interspersed among regions of low, normal, or even high flow. Regions of 125-500 mm3 with trickle flow or higher flows, in different areas at different times, involving deep and superficial structures migrated and persisted to 6 h, with gCBF remaining low. These preliminary results suggest: no initial no-reflow foci (less than 10 ml/100 cm3 per min) larger than 125 mm3 persisting through the initial global hyperemic phase; delayed multifocal hypoperfusion more severe than suggested by gCBF measurements; and trickle flow areas caused by dynamic factors.
Animals↗