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Biomedical subjects

D E Levy

Publications and source records attributed to D E Levy.

124 records · Page 7Linked to original sources
PubMed1978

Reversed immunosorbents: a simple method for specific antibody immobilization.

A method is presented for permanently converting an antigen immunosorbent into a purified antibody immunosorbent which retains specific reactivity for antigen. Following immunological reaction of the antibodies in an antiserum with the antigen adsorbent, the specific immunoglobulin is chemically bound to the antigen by means of the divalent crosslinking agent. Various such agents, including glutaraldehyde, suberimidate, a diazide, and isocyanates, were employed. The conditions of preparation using the first two were optimized, and the characteristics of the resulting immobilized antibodies were investigated. Applications in radioimmunoassay, preparative chromatography, and affinity-constant studies discussed in view of the unique attributes of these reagents.

Animals↗
PubMed1977

Platelet activation in acute cerebral ischaemia. Serial measurements of platelet function in cerebrovascular disease.

Circulating platelet aggregates formed in vivo were serially measured, and platelet-aggregation thresholds were determined in vitro in 82 patients with acute cerebral ischaemia. The percentage of aggregated platelets was increased in 53 patients with completed stroke (30.9% +/- 2.0) and in 29 patients with transient ischaemic attacks (34.1% +/- 2.3), all studied within 10 days of the acute event. These values were higher (P less than 0.001) than levels of aggregated platelets in 30 patients with non-vascular neurological disease (16.8% +/- 2.3). The percentage of aggregated platelets returned to normal 10 days to 6 wk after acute cerebral ischaemia. Aspirin and dipyridamole did not affect either the increase in or subsequent normalisation of circulating-platelet-aggregate levels in these patients. Platelet-aggregation sensitivity to adenosine diphosphate and adrenaline was also increased in patients with acute cerebral ischaemia, but this abnormally resolved during convalescence. Platelet activation is abnormal in acute cerebral ischaemia but usually returns to normal with or without anti-platelet therapy. This activation of platelets may contribute to the clinical manifestations of occlusive vascular disease.

Acute Disease↗
PubMed1977

A prospective study of nontraumatic coma: methods and results in 310 patients.

Neurological signs and outcome are compared in the first 310 patients from a continuing prospective study of coma not caused by trauma or drugs. Sixteen percent of the patients achieved an independent existence within a month; severe disability or the vegetative state developed in 25% of patients comatose for six hours and in 79% of those still in coma after a week. The chance of regaining an independent existence was greater in patients who, by one day, obeyed commands or moved the limbs appropriately in response to noxious stimuli or who had attained any of the following: orienting eye movements, normal responses to oculocephalic or oculovestibular stimulation, or normal muscle tone. Conversely, the chance of regaining an independent existence fell in patients who, after one day, had either extensor responses of the limbs or failed to move them in response to noxious stimuli or who lacked eye opening, pupillary reactions, corneal responses, or any eye movement in response to oculovestibular or oculocephalic stimulation. Beyond these general guidelines, numbers of patients with particular signs are presently too small for confident prediction of outcome.

Adolescent↗
PubMed1975

Brief hypoxia-ischemia initially damages cerebral neurons.

Rats were studied during cerebral hypoxic ischemia to determine whether neurons or blood vessels suffered the first damage. Ten or more minutes of unilateral carotid artery occlusion combined with systemic hypoxemia (PaO-2, 21 mm Hg) produced neuronal but not vascular damage in the ipsilateral cerebral hemispheres of 18 of 29 rats (62%); two and five minute stresses caused no visible neuronal abnormalities. The longer exposures produced more widespread damage, and neuronal loss and gliomesodermal reaction were evident after prolonged survival. Early neuronal changes correlated with abnormalities of motor behavior (P less than .005). Despite neuronal damage that was sometimes extensive, vascular no-reflow developed in only one of 24 animals after 20 and 30 minutes of hypoxia-ischemia. Production of neuronal and neurological abnormalities in the absence of hypotension or vascular no-reflow indicates that hypoxia-ischemia initially damaged cerebral neurons.

Anesthesia, Inhalation↗
PubMed1975

Ischaemic brain damage in the gerbil in the absence of 'no-reflow'.

Approximately 40% of gerbils subjected to one hour of unilateral carotid artery occlusion displayed neurological abnormalities during that time. Most such animals were subsequently found to have ischaemic neuronal alterations within the territory of the ipsilateral middle cerebral artery. In contrast, impaired reperfusion ('no-reflow') rarely occurred and cannot therefore be implicated in the pathogenesis of ischaemic brain damage.

Animals↗
PubMedDate not supplied

The virus battles: IFN induction of the antiviral state and mechanisms of viral evasion.

Response to IFN involves a rapid and direct signal transduction mechanism that quickly reports that presence of extracellular cytokine to the cell nucleus, preserving the specificity inherent in cytokine-receptor interactions to transcriptionally induce expression of a set of genes encoding important antiviral proteins. Establishment of the resulting antiviral state provides a crucial initial line of defense against viral infection. Studies of IFN-deficient cells and animals derived by gene targeting have demonstrated the essential nature of IFN-mediated innate immunity. The long co-evolutionary history of viruses with their hosts has seen the development of a variety of evasive adaptations that allow viruses to circumvent or inactivate host antiviral mechanisms. Further understanding of both host and viral components of this battle may provide important new strategies for vaccine development and creation of novel antiviral compounds.

Animals↗
PubMedDate not supplied

Effects of low dose aspirin on platelet function in patients with recent cerebral ischemia.

We tested the antiplatelet effects of low-dose aspirin in patients with occlusive cerebrovascular disease, because conventional dosage aspirin inhibits vascular synthesis of prostacyclin at the same time that it inhibits platelets. The effects on platelet function and thromboxane A2 synthesis of 40 mg of aspirin daily or 40 mg aspirin plus dipyridamole were measured in 23 patients starting within a week after the onset of cerebral ischemia. All patients had normal baseline platelet aggregation responses to four stimuli: arachidonate, epinephrine, adenosine diphosphate and collagen. The generation of thromboxane A2 by platelets, measured as serum thromboxane B2, was also normal. After 3 to 7 days of low dose aspirin therapy, platelet aggregation responses were suppressed to the extent observed with higher dosage aspirin. Serotonin release during platelet aggregation was inhibited by more than 95% and thromboxane B2 levels in clotted blood fell by more than 95%. Responses to aspirin treatment were similar in patients with transient ischemic attacks and in those with stroke and were also similar in both sexes. No differences in platelet responses were observed between patients receiving aspirin alone and aspirin plus dipyridamole. Thus 40 mg aspirin daily inhibited platelet responses as effectively as higher doses of aspirin in patients who had recent cerebral ischemia and showed a cumulative antiplatelet effect.

Aged↗
PubMedDate not supplied

Regional brain blood flow in the conscious gerbil.

Regional brain blood flow was determined in 23 awake, unparalyzed gerbils with a simplified indicator-fractionation technique. The use of intravenous 14C-butanol, an indicator that is freely diffusible into the brain, eliminated the need for repetitive sampling of arterial and cerebral venous blood and reduced the period of indicator circulation of 10 seconds. Gerbils spontaneously breathing room air (PaCO2 = 32 +/- 1 (SE) mm Hg) had blood flows in whole cerebrum, cerebellum, and brainstem of 102 +/- 4, 93 +/- 5, and 114 +/- 6 ml/100 gm/min respectively. Cerebral blood flow increased linearly with elevations in PaCO2 (r=0.969) and averaged 3.14 +/- 0.17 ml/100gm/min per mm Hg increase in PaCO2. Interpolated cerebral blood flow at a PaCO2 of 40 mm Hg was 127 +/- 2 ml/100 gm/min. This technique is easy and convenient to use, involves no intracranial surgery, requires steady state conditions for only 10 seconds, and minimizes blood loss in small animals. In more discrete brain regions a less volatile indicator is needed.

Animals↗
PubMedDate not supplied

Assessment of quality of life in adolescent patients with orthopaedic problems: are adult measures appropriate?

New pressures of accountability brought on by a rapidly evolving system of health care financing have underscored the need for standardized, valid measures of patient outcome that reflect the effect of clinical intervention on all aspects of quality of life. In response, there has been a burgeoning interest in the area of outcomes assessment and measurement of quality of life after orthopaedic intervention in adults, but less attention has been focused on the assessment of broadly defined outcomes in children. In an effort to borrow from the broader adult experience in this area, the authors sought to examine whether the Medical Outcomes Study Short Form 36 (SF-36) or the EuroQol questionnaire, widely accepted adult health status measures, would be valid in this setting. These two measures were administered to 196 adolescent patients (10-18 years old) seeking orthopaedic evaluation. Tests of scale properties and construct validity show that these properties are maintained in this population, but neither instrument reflected known differences in health status among this cohort. Most importantly, both the SF-36 and the EuroQol exhibited serious ceiling effects (most respondents scored at the top of their scales), despite evidence indicating those patients often had suboptimal health status. Thus, neither the SF-36 nor the EuroQol is valid for use in this population. The assessment of pediatric health status demands outcomes measures specifically designed to reflect the unique needs of this population.

Adolescent↗
PubMedDate not supplied

Capturing quality of life in pediatric orthopaedics: two recent measures compared.

There is a clear need for standardized measures to assess health status that are valid and appropriate to the needs of children with orthopaedic problems. The Child Health Questionnaire and the American Academy of Orthopaedic Surgeons Pediatric Outcomes Data Collection Instrument, two new pediatric health status measures, were assessed for their ability to detect differences in health states in a pediatric orthopaedic population. The instruments have a range of scales designed to measure various aspects of physical and psychosocial health. Two hundred forty-two patients with wide-ranging diagnoses were enrolled in this cross-sectional study. The instruments exhibited ceiling effects in some domains but generally performed as they were intended in this large cohort. Using secondary factor analysis, it was shown that the domains of the instruments appropriately distinguish physical and psychosocial health. Several domains from each instrument discriminated between diagnosis groups and patients with varying numbers of comorbidities. Both of these measures show significant promise and have an important role in helping define the outcomes of children with orthopaedic problems.

Adolescent↗