Rationing is a desperate measure.
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Health Care Rationing↗
Biomedical subjects
R Dunn
Publications and source records attributed to R Dunn.
Hormonal status affects the reactivity of the cerebral vasculature.
OBJECTIVE: We compared the blood velocity and vascular resistance in the central retinal and ophthalmic arteries in healthy nonpregnant, pregnant, and postmenopausal women (before and after estrogen replacement therapy). STUDY DESIGN: Color flow Doppler ultrasonography was used to determine systolic, diastolic, and mean velocity, as well as the resistance index in the central retinal and ophthalmic arteries in 10 nonpregnant women, 10 third-trimester pregnant women, and 10 hypoestrogenic postmenopausal women. The postmenopausal patients were again studied 2 months after starting daily oral therapy with 2 mg of micronized 17 beta-estradiol. RESULTS: Pregnant women had a significantly (p < 0.05) higher diastolic blood velocity (4.2 +/- 0.8 cm/sec) and a lower resistance index (0.56 +/- 0.05) in the central retinal artery, when compared with nonpregnant women (diastolic velocity 2.8 +/- 0.8 cm/sec, resistance index 0.68 +/- 0.1), and hypoestrogenic postmenopausal women (diastolic velocity 2.6 +/- 0.9 cm/sec, resistance index 0.73 +/- 0.08). Significant differences were not seen in the ophthalmic artery. In the postmenopausal patients estradiol therapy was associated with an increase in diastolic velocity (2.6 +/- 0.9 cm/sec vs 4.1 +/- 1.6 cm/sec) and a decrease in the resistance index (0.73 +/- 0.08 vs 0.66 +/- 0.1) in the central retinal artery but not in the ophthalmic artery. CONCLUSIONS: The blood velocity and vascular resistance in the cerebral microcirculation appear to change according to the phases of a woman's reproductive life. This may be related, in part, to estrogen levels, because estradiol vasodilates small-diameter cerebral vessels in hypoestrogenic postmenopausal women.
Adult↗
The oxygen distribution in the prelaminar optic nerve head of the cat.
Oxygen-sensitive microelectrodes were used to measure oxygen profiles from the prelaminar region of the cat optic nerve head. From the profiles, the oxygen distribution of this tissue was determined. Changes in oxygen levels in response to flicker stimulation were obtained. Also, the regulatory ability of this tissue was assessed by acutely increasing IOP and by presenting the cat with periods of hyperoxia. The cells in the optic nerve head were found to exist in the same oxygen environment as cells of the inner retina. Oxygen tensions usually varied between 0 and 40 mmHg, with the mean being between 10 and 20 mmHg. There was no difference in oxygen levels between central and peripheral parts of the optic nerve head, nor was there a difference as a function of depth. Different levels of light adaptation of the retina had no effect on oxygen levels in the optic nerve head, but flicker stimulation of the retina resulted in decreases in tissue oxygen tension. A small number of experiments in which the intraocular pressure was raised showed that oxygen levels in the optic nerve head were not drastically altered during acute decreases in perfusion pressure. Based on the size of changes in tissue oxygen tensions during hyperoxia, it appeared that blood vessels in the optic nerve head constricted in response to systemic hyperoxia.
Adaptation, Ocular↗
Vitamin supplements improve the fertility potential of a subfertile male with macrocytic anemia--a case study.
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Anemia, Macrocytic↗
Managing low back pain: attitudes and treatment preferences of physical therapists.
BACKGROUND AND PURPOSE: We surveyed physical therapists about their attitudes, beliefs, and treatment preferences in caring for patients with different types of low back pain problems. SUBJECTS AND METHODS: Questionnaires were mailed to all 71 therapists employed by a large health maintenance organization in western Washington and to a random sample of 331 other therapists licensed in the state of Washington. RESULTS: Responses were received from 293 (74%) of the therapists surveyed, and 186 of these claimed to be practicing in settings in which they treat patients who have back pain. Back pain was estimated to account for 45% of patient visits. The McKenzie method was deemed the most useful approach for managing patients with back pain, and education in body mechanics, stretching, strengthening exercises, and aerobic exercises were among the most common treatment preferences. There were significant variations among therapists in private practice, hospital-operated, and health maintenance organization settings with respect to treatment preferences, willingness to take advantage of the placebo effect, and mean number of visits for patients with back pain. CONCLUSIONS AND DISCUSSION: These variations emphasize the need for more outcomes research to identify the most effective treatment approaches and to guide clinical practice.
Adult↗
Abdominal surgery in patients with severe morbid obesity.
At the University of Massachusetts Medical Center, from 1984 to 1992, we performed laparotomy or panniculectomy on 42 individuals weighing from 290 to 600 pounds, each with a height-weight index of over 55. All patients weighted more than 220 percent of ideal body weight. Follow-up ranged 8 to 52 months. All patients underwent panniculectomy except one. Pannus resection was performed by means of a large transverse ellipse. A suprapubic wedge resection often was used to minimize the discrepancy between the lengths of the upper and lower transverse incisions. With severe discrepancy, lateral V-flaps also were utilized to minimize the lateral dog-ear. To facilitate preparation, pannus exsanguination, and surgical resection, 10 to 12 towel clips or 4 to 5 large K-wires or Steinmann pins were passed through the central pannus. These were then suspended by rope from the overhead lighting. A two-team approach appears to have distinct advantages, including minimized blood loss, operative time, pulmonary compromise, and hospital stay. The technical difficulties of manipulating a large pannus were simplified by pannus suspension. Early preoperative involvement of the entire operative team, particularly the plastic surgeon, the anesthesiologist, and the nursing staff, allows for proper evaluation of underlying medical problems and appropriately detailed anesthetic and surgical planning. Surgical management of the abdominal pannus in the morbidity obese patient in this series was performed with apparent clinical efficacy, reasonable safety, and long-term functional improvement.
Adipose Tissue↗
Environmental factors and child pedestrian injuries.
The aim of this study was to provide information on modifiable environmental factors at sites of child pedestrian injuries which would be useful for the design of preventive strategies. A total of 103 child pedestrian injuries was identified over a one-year surveillance period. Of these, 71 per cent occurred on public roads, 24 per cent occurred in residential driveways and 4 per cent occurred in car parks. For roadway injury sites, the median traffic flow was 635 vehicles per hour and the median speed was 49.0 kph. For 31 (42 per cent) roadway injury sites the median vehicle speed was in excess of the posted speed limit. The majority of roadway injuries occurred on residential streets. For driveway injuries there was no separation of the driveway from the children's play area in 75 per cent. Changes to the urban traffic environment which reduce traffic flows and vehicle speeds have the potential to prevent child pedestrian injuries. Controlled epidemiologic studies which examined the magnitude of the risks associated with modifiable environmental factors are required.
Accidents, Traffic↗
Preventing child pedestrian injury: pedestrian education or traffic calming?
The traditional approach to the prevention of child pedestrian injuries in New Zealand is pedestrian education. However, none of the programs currently being implemented in New Zealand have ever been shown to reduce injury rates. The allocation of scarce resources to pedestrian education must therefore be questioned. In this paper we estimate the number of serious child pedestrian injuries which might be prevented if the resources allocated to pedestrian education were allocated instead to environmental approaches, in particular, to traffic calming. It is estimated that approximately 18 hospitalisations of child pedestrians could be prevented each year under this alternative resource allocation, disregarding any other benefits of traffic calming. These results emphasise the need to consider the potential sacrifices involved in the allocation of scarce resources to child pedestrian education.
Accidents, Traffic↗
Context specificity of conditioned-reinforcement effects on discrimination acquisition.
Pigeons were trained on a series of reversals of a simultaneous form discrimination in which the trial outcomes were separated from the choice responses by an 8-s delay interval. Different conditions were defined by the stimuli occurring during the two halves of the delay interval. Discrimination learning was greatly facilitated by having differential stimuli during the delay following correct versus incorrect choices. When the differential stimuli appeared only at the midpoint of the delay, some facilitation occurred relative to when no different stimuli occurred, but there was substantially less facilitation than when the differential stimuli occurred immediately contingent on choice. A reversed-stimulus condition, in which the stimulus at the onset of the delay following a correct choice was the same as that during the last segment of the delay following an incorrect choice, and the stimulus at the onset of the delay following an incorrect choice was the same as that preceding food during the last segment of the delay following a correct choice, also facilitated discrimination learning relative to the nondifferential stimulus conditions.
Journal Article↗
What will we be?
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Electronic Data Processing↗
Direct measurement of retinal microvascular pressures in the live, anesthetized cat.
Microvascular pressures in retinal circulation were measured in living, anesthetized cat by the servonull micropuncture technique. Of the total vascular pressure drop 32% was in the segment proximal to the large retinal arteries when intraocular pressure was set at 10 mm Hg and decreased to 27% when intraocular pressure was increased to 20 mm Hg. The pressure in the retinal veins was substantially (> 7 mm Hg) greater than intraocular pressure at both values of intraocular pressure. There was negligible pressure drop within venous segment; however, the pressure drop from the retinal veins to the systemic veins was large and cannot be explained on the basis of a venous waterfall within the retina.
Animals↗
In vivo micropuncture of retinal vessels.
Micropuncture has proven to be a valuable tool for the local study of vascular parameters in many organ systems; however, it has not been applied to the study of the circulation of the retina. We report here our extension of micropuncture techniques [4] to use in the intact retina of the anesthetized cat. We use extremely sharp micropipettes with tip sizes much smaller than the diameter of erythrocytes to avoid hemorrhage. The micropipette is held by a microdrive which in turn is mounted on a precision goniometric micromanipulator. We micropuncture retinal arteries and veins with diameters ranging from 20 to 130 microns with no apparent damage to the vessel wall and no observed hemorrhage. During micropuncture we routinely inject nanoliter quantities of dyed saline, which we observe flowing in a plume from the micropipette tip within the lumen of the vessel. Micropuncture techniques may be used in the laboratory to study retinal autoregulatory mechanisms by microinfusion of vasoactive substances and by measuring blood pressure in retinal microvessels. In the clinic micropuncture may be useful for treating disorders such as retinal vascular occlusion.
Animals↗
Radial and ulnar artery repairs: assessing patency rates with color Doppler ultrasonographic imaging.
This study was undertaken to evaluate the patency rate of radial and ulnar artery repairs performed with use of the magnification afforded by the operative microscope. Color Doppler ultrasonographic imaging was chosen as a reproducible, noninvasive technique to evaluate patency and graphically display vascular flow characteristics. Twenty-eight consecutive patients with 35 arterial injuries form the study group. Twenty-four patients with 31 arterial lacerations were available for enrollment in the protocol. Follow-up ranged from 1 to 40 months (average, 10 months). Eighteen male and six female patients sustained 13 radial and 18 ulnar artery lacerations, all sharp. Four patients required interposition vein grafting. Overall patency after repair was found to be 84%, with 82% of single vessels and 86% of double vessels patent. The patency of single vessels repaired without the use of vein grafts was 100%. These results indicate that microscope-assisted repairs of the radial and ulnar arteries remain patent at a higher rate than is commonly cited.
Color↗
Delay reduction: current status.
Delay-reduction theory states that the effectiveness of a stimulus as a conditioned reinforcer may be predicted most accurately by the reduction in time to primary reinforcement correlated with its onset. We review support for the theory and then discuss two new types of experiments that assess it. One compares models of choice in situations wherein the less preferred outcome is made more accessible; the other investigates whether frequency of conditioned reinforcement affects choice beyond the effect exerted by frequency of primary reinforcement.
Animals↗
Oxygen distribution in the macaque retina.
PURPOSE: Oxygen distribution was characterized in the macaque retina, which is more like the human retina than others studied previously. METHODS: Profiles of oxygen tension (PO2) as a function of distance were recorded in a parafoveal region about halfway between the fovea and optic disk, and from the fovea in one animal. A one-dimensional diffusion model was used to determine photoreceptor oxygen consumption (QO2). RESULTS: In the parafovea, the PO2 decreased as the electrode was withdrawn from the choroid toward the inner retina, reaching a minimum value during dark adaptation of about 9 mmHg at about 70% retinal depth, and then increasing more proximally. Approximately 90% of the oxygen requirement of the photoreceptors was supplied by the choroidal circulation and 10% by the retinal circulation. In light adaptation, there was a monotonic PO2 gradient from the choroid to the inner retina, indicating that all of the oxygen used by photoreceptors was supplied by the choroid. In the fovea, the choroid supplied almost all the oxygen in both dark and light adaptation, with a minor supply from the vitreous humor. Dark-adapted foveal oxygen consumption was lower than parafoveal oxygen consumption. Light reduced the oxygen consumption of the photoreceptors, in both regions studied, by 16-36%. CONCLUSIONS: The results show that oxygenation of the parafoveal monkey retina is similar to that previously observed in the cat area centralis. In the fovea, the oxygen distribution differs as expected considering the thinner retina and the absence of inner retinal neurons and retinal circulation.
Animals↗
Decreased synthesis of ciliary neurotrophic factor in degenerating peripheral nerves.
The mRNA for ciliary neurotrophic factor in normal and injured sciatic nerves has been assayed by an RNase protection assay. The endoneurial concentration of ciliary neurotrophic factor mRNA is diminished in the distal nerve stump within three days of sciatic nerve transection, is less than one tenth of normal after one week, and remains low if regeneration does not occur. The synthesis of ciliary neurotrophic factor in injured peripheral nerves is decreased when and where the synthesis of nerve growth factor is increased.
Animals↗
Allelic loss on chromosome 11p is a less frequent event in bilateral than in unilateral Wilms' tumours.
Analyses to detect loss of heterozygosity (LOH) were performed at 11 polymorphic loci on chromosome 11 and, using a polymorphic CA repeat sequence in the WT1 gene, on a series of 39 tumours from 28 unilateral and 10 tumours from 6 bilateral Wilms' tumour (WT) patients. LOH was seen in 13 out of 35 patients including 12 out of 29 unilateral tumours, but only one of 10 bilateral tumours. This suggests that bilateral WT represents a subgroup of WT in which tumour initiating events less frequently involve LOH on chromosome 11 and that either epigenetic events, point mutations or another non-chromosome 11p locus are important in bilateral tumours. The observation of LOH in one WT but not another WT in a bilateral WT patient provides evidence that these tumours arising in the same patient are not monoclonal proliferations and most likely arise via different molecular pathways.
Alleles↗
Equivalent expression of paternally and maternally inherited WT1 alleles in normal fetal tissue and Wilms' tumours.
Observations of non-random maternal 11p allele loss in Wilms' tumour (WT) have implied the possible involvement of an imprinted 11p locus in WT aetiology. A proposed 11p13 Wilms' tumour gene, WT1, has recently been isolated and encodes a zinc finger DNA-binding protein, the 3' untranslated region of which contains a polymorphic dinucleotide repeat (CA repeat) motif. We have exploited this transcribed CA repeat to examine the allelic expression pattern of WT1 and thereby determine whether transcriptional imprinting of this gene occurs. DNA and reverse-transcribed RNA from tumours and normal tissue were subjected to the polymerase chain reaction (PCR) using radiolabelled primers flanking the CA repeat. The gene was seen to be expressed from both of the constitutive alleles in 9-week human fetal kidney, all informative Wilm's tumours and neonatal kidney tissue adjacent to the tumours. In one tumour, known to be heterozygous for a point mutation in zinc finger 2, direct sequencing confirmed that both mutant and wild-type transcripts were being expressed. These results demonstrate that this gene is not subject to transcriptional imprinting in tumours or normal fetal kidney.
Alleles↗