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J Blackburn

Publications and source records attributed to J Blackburn.

14 recordsLinked to original sources
PubMed1992

Mechanical properties of microcallus in human cancellous bone.

Until now, the mechanical properties of the microcalluses that form in human cancellous bone have been unexplained. We measured the microhardnesses of microcalluses in cancellous bone, of the trabeculae within the microcalluses, of the trabeculae adjacent to microcalluses, and of trabeculae lacking microcalluses in a human tibia and femur. We observed no important differences between materials at the four different sites. Because the microhardness of bone is very closely related to its stiffness, this finding indicates that microcalluses are likely to stiffen the trabeculae in which they are formed, even though they may surround unhealed fractures of the cancellous trabeculae.

Adult↗
PubMed1992

The development of a radiometric assay for monocyte phagocytosis and killing.

Monocyte and macrophage phagocytosis and killing has an important role in host defence against infectious microorganisms. Established methods for investigating these activities in vitro are time-consuming, expensive and prone to subjective error. An in vitro assay has been developed which measures monocyte phagocytosis and killing of Candida albicans. In this system, monocyte function is assessed by a radiometric assay based on the incorporation of [3H]uridine into viable yeast cells. This technique allows the simultaneous but independent measurement of the average number of yeast cells ingested by monocytes and the percentage of the ingested organisms killed within a defined incubation period. These tests can be carried out on a single sample of peripheral blood, are relatively easy to perform, and provide objective results within 24 h of receipt of the specimen. This method gave consistent results when monocyte-enriched harvests were obtained by four different separation techniques. This assay could prove a valuable tool for the investigation of monocyte function in individuals with recurrent infections to determine the contribution this makes to their clinical condition. It may also be used to investigate in vitro the influence of cytokines and other chemical agents on monocyte function.

Blood↗
PubMed1986

Effect of glucose on amphetamine-induced motor behavior.

The effect of 1 g/kg D-glucose on amphetamine-induced increases in activity; stereotypy; and rotation in rats with unilateral 6-OHDA lesions of nigro-striatal neurons was examined. The amphetamine dose-response curve for stereotypy was shifted to the right by glucose but retained the same slope as the control curve, suggesting that glucose competes for amphetamine or dopamine receptors that mediate this behavior. The slope of the dose-response curve for activity was significantly decreased by glucose, suggesting that glucose reduces activity levels in a manner that is non-competitive with the action of amphetamine or dopamine. Amphetamine-induced turning was unaffected by glucose at all doses tested. These data suggest that the effect of amphetamine on each of the three motor behaviors may be mediated by different dopamine-containing neurons, or by different post-synaptic dopamine receptors. The findings are also consistent with other data suggesting that glucose antagonizes dopamine function, but they suggest that this antagonism may not be uniform over all dopaminergic neurons or receptor types.

Amphetamine↗
PubMed1985

Comparative immunohistologic studies in an adoptive transfer model of acute rat cardiac allograft rejection.

It has been shown that fulminant acute rejection of rat cardiac allografts across a full haplotype disparity may occur as a direct result of adoptive transfer of sensitized W3/25+ MRC OX8- SIg- T helper/DTH syngeneic spleen cells to sublethally irradiated recipients. In order to establish the immunohistologic parameters of this form of rejection, allografts and recipient lymphoid tissue were analyzed using a panel of monoclonal antibodies of known cellular distribution. These data were compared with those obtained following reconstitution of irradiated allograft recipients with unseparated sensitized spleen cells, with unreconstituted irradiated donor recipient pairs, with unmodified first-set rejection, and with induced myocardial infarction of syngeneic heart grafts transplanted to normal and to sublethally irradiated recipients. Rejecting cardiac allografts transplanted to all reconstituted irradiated recipients were characterized by extensive infiltration with MRC OX8+ (T cytotoxic-suppressor, natural killer) cells even when this subset was virtually excluded from the reconstituting inocula. A similar proportional accumulation of MRC OX8+ cells observed at the infarct margins of syngeneic heart grafts transplanted to irradiated unreconstituted recipients greatly exceeded that present in normal nonirradiated controls. These data provide evidence that under conditions of heavy recipient irradiation, MRC OX8+ cells may be sequestered within heart grafts in response to nonspecific injury unrelated to the rejection process. Although there was no significant degree of MRC OX8+ cellular repopulation within organized secondary lymphoid tissues of irradiated animals over the study period, the density of ileal mucosal MRC OX8+ lymphocytes approximated normal at 7 days post-irradiation, raising the possibility that these cells could share a common origin with those sequestered within the heart grafts. Carbon+ MRC OX6+ macrophages were a significant component of the infiltrate in all rejecting cardiac allografts, as well as in all infarcted syngeneic heart grafts--providing further evidence that macrophage "activation" with expression of class II determinants may occur in response to nonspecific injury. In unmodified first-set rejection there was an intense B cell reaction in recipient spleens and lymph nodes. In the adoptive transfer model, marked B cell expansion was exclusively confined to the parathymic lymph nodes of irradiated allograft recipients reconstituted with the sensitized W3/25+, MRC OX8-, SIg- T helper/DTH donor cell inocula.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Pulmonary lymphangiomyomatosis.

Lymphangiomyomatosis is an interesting disease with distinctive clinical and histopathologic findings. We report herein two additional cases of lymphangiomyomatosis, including one with clinical improvement after therapy with progesterone. This case is of particular significance in view of the patient's negative sex steroid receptor analysis. These findings open new avenues for future considerations in the therapy of this unusual but interesting disease.

Adult↗
PubMed1982

"No two fields ever grow grass the same way": assessment of conservation abilities in the elderly.

Within the past ten years, standard cognitive assessment procedures, including Piagetian tasks, have often been used with the elderly. The present paper examines several possible difficulties in interpreting the results of studied which employ Piagetian tasks, especially conservation tasks, with older individuals. First, it is noted that Piaget's clinical method allows more flexibility in the assessment of competence than do the more quantifiable, American techniques. However, most of the research studies suggesting a cognitive decline with age have utilized rigid assessment procedures. Second, the paper examines the possibility of task misinterpretation by the elderly. Examples from recent research, in which older persons stressed reality-based problem solving strategies rather than the more abstract strategies traditionally associated with Piagetian tasks, are provided. The possibility of cognitive change instead of cognitive decline with age is discussed, and the importance of utilizing procedures which can measure this change is stressed.

Aged↗
PubMed1981

The effect of a thirty per cent reduction in physician fees on Medicaid surgery rates in Massachusetts.

In this paper, we use an interrupted time series analysis to assess the effect of a 30 per cent reduction in the Medicaid reimbursement fee for physician services on the rate at which eight elective surgical procedures were performed in the Massachusetts Medicaid population. Tonsillectomy/adenoidectomy is the only procedure in which there was a statistically significant decline in the rate of surgery in most areas of the state following the fee cut. There is some evidence of an increase in the rate of disc surgeries/spinal fusions. The rate of other procedures increased in some areas of the state and decreased in other areas in the period after the fee cut.

Adenoidectomy↗
PubMed1980

Training cognitive functioning in the elderly--inability to replicate previous findings.

This study was designed to replicate Hornblum and Overton's study which trained conservation ability in elderly women [1]. Thirty-four elderly women volunteers were given a pretest battery of area and volume conservation tasks; participants also completed an extensive life history questionnaire. Conservation scores were the highest yet recorded by elderly participants. Thirty-two women received perfect conservation scores; only two were "partial conservers"; no participant was a "nonconserver." Consequently, training was not implemented. These women had high levels of education, good health, adequate income, satisfying leisure activities, and positive attitudes about aging. Advanced chronological age does not guarantee poor conservation performance. The mechanism(s) whereby life history variables influence cognitive functioning needs to be determined.

Aged↗
PubMed1975

Upper-respiratory tract complaint protocol for physician-extenders.

A protocol for upper-respiratory tract complaints was administered to 226 patients in a walk-in clinic. The protocol, for use by a physician-extender in conjunction with a physician, specified the collection of data necessary for management. A decision-making algorithm separated the major causes of upper respiratory infection (URI) complaints and led to one of four plans: a physician referral, a culture only, antibiotic treatment, or symptomatic treatment only. Each patient was seen by a physician following the health assistant's interview. Of 226 patients, 96 (42 percent) would have been sent home by the protocol without seeing the physician. None of these had a complication of URI. Sixteen (seven percent) of the 226 had serious complications - all would have been referred to the physician. The protocol proved to be safe and efficient, acceptable to patients, and a reliable approach to physician-extender management of URI.

Anti-Bacterial Agents↗