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Biomedical subjects

M Buchanan

Publications and source records attributed to M Buchanan.

At least 55 records · Page 3Linked to original sources
PubMed1991

Results of extracapsular cataract surgery and intraocular lens implantation in Ghana.

Neither outpatient surgery nor intraocular lenses have been widely used in developing countries. We performed extracapsular cataract extraction with posterior chamber intraocular lens implantation in a simple outpatient clinic in Ghana, West Africa. Forty-nine (64%) of 77 eligible patients with follow-up times of 12 to 29 months after surgery underwent an eye examination and an interview related to activities of daily life. Preoperative visual acuity was counting fingers or worse in all but one patient. Visual acuity improved in 44 patients (90%) after surgery. Twenty-six patients (53%) had a corrected visual acuity of 20/40 or better, 11 (22%) had a corrected visual acuity of 20/50 to 20/100, and 12 (25%) had a corrected visual acuity of 20/200 or worse. Subjectively, 94% of patients believed that their vision improved after surgery. No major late complications occurred following the immediate postoperative period. In addition, our population experienced no complications attributable to the outpatient format of this surgery. Every patient, all of whom lived within a 32-km radius of the clinic, reliably returned for postoperative appointments. Our results demonstrate that outpatient surgery may be a safe and practical alternative to routine hospitalization for eye surgery in developing countries.

Adult↗
PubMed1990

Reactive haemophagocytic syndrome in human immunodeficiency virus infection.

The reactive or virus-associated haemophagocytic syndrome (RHS) has been described in association with several different infections and is regarded as clinically and pathologically distinct from malignant histiocytosis. A case is described of this syndrome in a 30-year-old HIV-antibody positive homosexual male who presented with fever, pancytopenia, lymphadenopathy, and massive splenomegaly. The fever and haematological abnormalities resolved following splenectomy, and the patient remains well after 12 months. Prominent histiocytic haemophagocytosis was seen in both the spleen and an abdominal lymph node. Exhaustive tests failed to demonstrate any infectious agent other than human immunodeficiency virus, indicating this to be a case of this syndrome occurring in association with HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Changes in bone mineralization pattern: a response to local stimulus in maxilla and mandible of dogs.

A pilot study was carried out in order to verify the pattern of changes in mineralization of bone in the maxillas and mandibles of dogs which had a tooth extraction or luxation. Bone mineral content was determined using computerized microdensitometry. Significant changes in patterns of mineralization were found for alveolar bone, cortical bone and trabecular bone at the sites adjacent to the area of operation. These findings suggest that the three envelopes of jaw bones of the dogs are influenced by Regional activation phenomenon (RAP). These results have important implications for the design of clinical studies of periodontium. A more detailed study should elucidate the cellular mechanisms by which these changes occur.

Animals↗
PubMed1985

Rationale behind the development of low molecular weight heparin derivatives.

There is now considerable evidence that the antithrombotic and the hemorrhagic effects of heparin can be dissociated by using low molecular weight heparins and by using heparin with low affinity to AT III. The findings with low-affinity heparin suggest that hemorrhage is contributed to by heparin properties that are independent of AT III binding and thus of their major anticoagulant effect. The current evidence supports the suggestion that the hemorrhagic effect of heparin is contributed to by a reversible platelet functional defect that is relatively less important than its AT III dependent anticoagulant effect for preventing experimental venous thrombosis. Whether these promising results in animals also apply to human thromboembolism disease will require careful evaluation by suitably designed clinical trials.

Animals↗
PubMed1985

Effects of pedal frequency on VO2 and work output at lactate threshold (LT), fixed blood lactate concentrations of 2 mM and 4 mM, and max in competitive cyclists.

To determine the effects of differing pedal frequencies on VO2 and work output values at the lactate threshold (LT), fixed blood lactate concentrations of 2 mM and 4 mM (2 mM, 4 mM), and at max, nine male competitive road racing cyclists (USCF category I or II) completed three VO2 max tests; on a Monark bicycle ergometer, at pedal frequencies of 60, 90, and 120 rpm. Each stage was 3 min in duration, starting at 0 kgm/min with subsequent stages increased by either 180 kgm/min (60 and 120 rpm) or 178 kgm/min (90 rpm). Blood samples were taken during the last 30 s of each stage. VO2 and work output at LT, 2 mM, and 4 mM were determined from individual blood lactate-work rate and VO2-work rate relationships. VO2 max and maximal work output were chosen as the peak values observed during the VO2 max tests. Results indicated that work output at LT, 2 mM, and 4 mM was affected by choice of pedal frequency (1278, 1140, 999 kgm/min at LT; 1533, 1450, 1182 kgm/min at 2 mM; 1780, 1703, 1487 kgm/min at 4 mM; for 60, 90, and 120 rpm, respectively, P less than 0.05). Max work output at 60 and 90 rpm was significantly greater (P less than 0.05) than at 120 rpm (2035, 2053, 1879 kgm/min for 60, 90, and 120 rpm, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Aluminum associated bone disease: clinico-pathologic correlation.

A chemical, aurine tricarboxylic acid was used to identify aluminum in bone in a group of chronic renal failure patients with severe osteomalacia. Thirteen out of 49 (26%) patients had a positive stain at the bone-osteoid junction. The presence of aluminum at the staining site was confirmed by electron dispersion x-ray analysis. The patients' biopsies staining negative with this clinical, although having high bone aluminum levels, had more significant features of hyperparathyroidism, both biochemically and histologically than those having a positive stain. The usefulness of this technique to diagnose presymptomatic aluminum related osteomalacia is emphasized.

Adolescent↗
PubMed1982

Lidocaine reversibly inhibits fertilization in Chlamydomonas: a possible role for calcium in sexual signalling.

A flagellar adhesion-induced signal sent during the mating reaction of the biflagellate alga, Chlamydomonas reinhardtii, initiates release of cell-wall-degrading enzymes, activation of mating structures, and cell fusion. The nature of this signal is unknown, but it may be mediated by an adhesion-induced change (activation) of flagellar tips. The studies reported here show that lidocaine, a local anesthetic that is reported to interfere with the movement of divalent cations across cell membranes, reversibly blocks cell wall loss and gametic fusion without blocking adhesion or flagellar tip activation. In these experiments lidocaine inhibited both the initial rates and the extent of wall loss and zygote formation. Studies with gametes of a paralyzed flagellar mutant, pf 17, revealed that lidocaine also blocked flagellar surface motility (visualized as movement of polystyrene beads) at concentrations of the inhibitor which also prevented gametic fusion. The concentration of lidocaine required to block cell fusion was dependent on the concentration of calcium or magnesium in the medium. In the absence of added calcium, 0.5 mM lidocaine inhibited fusion by 70%. In 0.5 mM calcium, 0.5 mM lidocaine had no effect on fusion and 2 mM lidocaine was required for 90% inhibition. The results suggest that divalent cations may play a critical role in sexual signalling in Chlamydomonas.

Calcium↗
PubMed1979

Postoperative swelling and trismus after mandibular third molar removal with the lingual split bone technique.

Several factors have been suggested as possible causes for the development of the swelling and trismus which occur after the surgical removal of impacted third molar teeth. In this investigation, measurements of swelling and trismus were made before and after lower third molar removal by the lingual split technique, in a series of 53 patients. No single cause of these surgical sequelae was identified and the duration and pattern of both swelling and trismus were recorded.

Edema↗
PubMed1979

Shortening of the bleeding time in rabbits by hydrocortisone caused by inhibition of prostacyclin generation by the vessel wall.

The effect of hydrocortisone on thrombocytopenic bleeding has been studied in rabbits using a jugular vein bleeding-time technique and a microvascular bleeding-time technique. An inverse relationship was found between the bleeding time and platelet count with both techniques in rabbits made thrombocytopenic by either X-irradiation or injection of heterologous platelet antiserum. Hydrocortisone shortened both bleeding times in thrombocytopenic animals when given in single large doses intravenously (25-100 mg/kg), in daily doses (6 mg/kg) intramuscularly, and shortened the jugular bleeding time when applied to the outside of the jugular vein or instilled intraluminally into the vein. This effect was also noted in normal animals. The effect on thrombocytopenic bleeding was dose related. When given daily, the effect was greater when hydrocortisone was given for 10 d than for 5 d. Both indomethacin and tranylcypromine also reduced the jugular vein bleeding time when instilled intraluminally into the jugular vein, whereas exogenously provided arachidonic acid reversed the effect of hydrocortisone but did not reverse the effect of indomethacin or tranylcypromine. Exogenously provided linoleic acid did not have any effect. Perfusion of the vessel segment with prostacyclin (PGI(2)) reversed the effect of intraluminally administered hydrocortisone, indomethacin, and tranylcypromine. Similarly, hydrocortisone, indomethacin, and tranylcypromine all reduced the rate of loss of fluid from a standard wound in isolated vessels emptied of blood and perfused with saline under constant pressure. PGI(2) reversed the action of these three agents, however, arachidonic acid reversed only the effect of hydrocortisone and did not reverse the effect of indomethacin and tranylcypromine. The generation of PGI(2)-like material and 6-keto-prostaglandinF(1) alpha from jugular vein strips was prevented by prior exposure of the animals or vessel wall to hydrocortisone. These results are compatible with the hypothesis that the vessel wall releases smooth muscle-relaxing prostaglandins when injured and that inhibition of prostaglandin formation by hydrocortisone enhances hemostasis by allowing vasoconstriction to be maintained.

Animals↗