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Biomedical subjects

M A Baker

Publications and source records attributed to M A Baker.

At least 145 records · Page 8Linked to original sources
PubMed1977

Thermosensitive midbrain neurons in the cat.

Responses of single neurons in the midbrain of cats anesthetized with chloral hydrate were studied during manipulations of midbrain temperature produced with a bilateral water-perfused thermode. Temperatures of the thermodes and the anterior hypothalamus were monitored while single neuron activity was recorded between the thermodes and correlated with the midbrain temperature. Q10's and thermal coefficients were calculated from the estimated temperature at the neuron itself. A surprisingly high percentage (72%) of the 72 neurons recorded in the caudal paramedian midbrain of 11 cats were thermoresponsive. Most of these were heat sensitive and exhibited a variety of frequency/temperature curves. Explorations of more rostral regions of the midbrain in 9 cats yielded only 18% thermoresponsive units out of the 99 neurons sampled. We suggest that the concentrated pool of warm-sensitive neurons in the caudal midbrain is part of an extensive system of brain stem thermosensors which are involved in establishing and controlling normal brain temperature.

Animals↗
PubMed1977

Albumin phylogeny for clawed frogs (Xenopus).

Comparisons of albumin indicate that the frogs commonly used by North American molecular and developmental biologists under the name of Xenopus muelleri belong to another species, X. borealis. Phylogenetic analysis of the albumin data reveals two major groups of Xenopus species, one containing only X. tropicalis and the other, called the X. laevis grou, containing the remaining species of the genus. The phylogenetic tree, in conjunction with evidence from chromosomes and DNA content, leads to the hypothesis that total genome duplication occurred in the common ancestor of the X. laevis group.

Animals↗
PubMed1977

Rapid brain cooling in exercising dogs.

In alert, resting dogs, the brain is warmer than arterial blood in the common carotid artery. When dogs run, brain temperature drops, despite a sharp rise in carotid blood temperature, and is maintained 1.3 degrees C below carotid temperature during exercise. This brain cooling apparently results from countercurrent heat exchange between warm arterial blood supplying the brain and cool venous blood draining the nose and mouth. The heat exchange occurs in the arteries at the base of the brain, which form a rudimentary carotid rete in the dog, and is greatest during exercise, when respiratory evaporation is at a peak. In animals with a carotid rete, the brain is protected against overheating during the severe thermal stress of exercise.

Animals↗
PubMed1977

Sex of listener and hormonal correlates of auditory thresholds.

The present study investigates changes in auditory threshold during 4-6 week intervals for men, women on birth control pills, and normal cycling women not on birth control pills. Thresholds were determined at 250, 500, 1,000, 2,000, 4,000, 6,000, 8,000 Hz. Normal cycling females had significantly lower thresholds during first half of the menstrual cycle than during the second half. Females on birth control pills showed significantly and consistently lower thresholds than other listeners at several frequencies. Explanations for the phenomena are proposed.

Adolescent↗
PubMed1976

The use of oral BCG in the treatment or metastatic malignant melanoma.

This study assess the effects of oral BCG, as a single agent, on tumor progression and on cell-mediated immune function in patients with metastatic malignant melanoma. Thirty patients were studied including 22 with measurable metastatic lesions and 8 with no detectable disease, following treatment of metastases by surgery, radiotherapy, or 5-(3, 3-dimethyl-1 -triazeno)-imidazole-4-carboxamide (DTIC; DIC). Oral BCG was given in doses of 120--240 mg, 1--3 times per week for periods ranging from 9 to 80 weeks and to total doses of from 1.2 to 20.1 gm. Patients were assessed by direct measurements of tumor mass, PPD skin test and in vitro blastogenic responses to PPD PHA. Of the 22 patient with measureable disease, 19 showed tumor progression and none showed regression of any lesion. Of the 8 without apparent disease, 5 remained stable and 3 had tumor recurrence. Of the total group of 30 patients, 8 showed some increased sensitivity to skin testing with PPD. Of 19 tested, 3 showed an increased PPD response in vitro, while 3 showed a decreased response. Six of 20 tested showed an increased PHA response in vitro. Oral BCG alone was not effective as an antitumor agent in patients with metastatic malignant melanoma.

Adult↗
PubMed1976

Platelet-induced tolerance in the production of heteroantisera to human leukemia-associated antigens.

A method is described for raising antisera to human leukemia cells of an individual patient in mice rendered tolerant with cyclophosphamide to platelets obtained from the same patient. The resulting antisera are able to distinguish serologically between leukemic blast cells and remission cells of patients with acute leukemia and may be recognizing leukemia-associated antigens. The antisera are similar in activity to antisera raised following tolerance-induction with remission leukocytes, but larger volumes of anti-leukemia antiserum can be raised using the more easily obtainable platelets. This technique provides further evidence that human platelets share many of the antigens present on human leukocytes.

Acute Disease↗
PubMed1976

Detection of monocyte specific antigen on human acute leukaemia cells.

Heteroantisera with specificity for human monocyte and macrophage antigens (HuMa) have been tested for activity against peripheral blood cells from patients with acute leukaemia. Using indirect immunofluorescence, blast cells from 25/27 patients with acute myelomonocytic leukaemia were reactive with anti-HuMa antisera, whereas blasts from 19/20 patients with acute myeloblastic leukaemia and 13/13 patients with acute lymphoblastic leukaemia were not reactive. The F(ab1)2 fragment of the antibody retained specific activity. Activity of whole serum against myelomonocytic blast cells was specifically removed by absorption with macrophages. These observations indicate that circulating blast cells from patients with acute myelomonocytic leukaemia may carry differentiation antigens characteristic of monocytes and macrophages.

Animals↗
PubMed1976

Variability of skin temperature in the waking monkey.

Temperatures of the brain, skin, and nasal mucosa were recorded along with the cortical electroencephalogram (EEG) in chaired, conscious pigtail monkeys at 25 degrees C air temperature. In undisturbed animals, skin temperatures ranged from 34 to 37 degrees C. When the animal was alerted by visual or auditory stimuli, temperatures on the extremities, tail, nose, ears, and nasal mucosa dropped rapidly to 22-29 degrees C. Temperatures on the proximal limbs and trunk and most of the head remained steady at all times. Average hypothalamic temperature was 0.91 degrees C higher when the extremities, tail, nose, ears, and nasal mucosa were cool than when they were warm, the brain temperature change beginning 80-120 s after the change in peripheral temperatures. A slight decrease in EEG frequency, but no change in amplitude, occurred during skin warming. Anesthetic doses of barbiturate led to a rapid rise in temperature of the extremities, tail, nose, ears, and nasal mucosa and a drop in brain temperature. These large changes in skin temperature in conscious monkeys reflect changes in cutaneous blood flow, the resulting alteration in heat loss leading to a rapid change in deep body temperature. The experiments demonstrate the importance of the state of arousal on autonomic nervous control of peripheral vasomotor tone in the monkey.

Animals↗
PubMed1975

Antibody responses to leukemia-associated antigens during immunotherapy of chronic myelocytic leukemia.

We have studied immunologic reactivity to leukemia-associated antigens in patients with chronic myelocytic leukemia (CML) treated with chemotherapy and adjunctive immunotherapy. All patients were immunologically competent as measured by skin test reactivity to dinitrochlorobenzene. Immunotherapy consisted of allogeneic irradiated leukemic myeloblasts injected intradermally, with BCG vaccine (Research Foundation, Chicago, Ill.) given by multiple puncture at the same site. 10(9) cells plus BCG were given weekly for 4 wk, and 10(8) cells plus BCG were given at monthly intervals thereafter. Eight patients judged clinically to be in the stable phase of their disease developed circulating antibody against the immunizing blast cells demonstrable by cytotoxicity and immunofluorescence assays. The antibody also showed reactivity against a panel of myeloblasts (12 paients) but not against the corresponding remission lymphocytes (five patients) or normal lymphocytes (20 donors). In two cases the antibody showed reactivity against the patient's own leukemic blasts. Seven of these eight patients have maintained a steady clinical course ranging from 20 to 40 mo, while one entered the blastic phase and died. Six patients were judged to be in the aggressive phase of CML because of progressive leukocytosis and splenomegaly or increasing myeloblastosis; five died an average of 16 mo after diagnosis. Humoral antibodies were not detected in these patients after repeated courses of BCG and allogeneic leukemic cells. We conclude that specific active immunotherapy of patients with CML can abet the production of humoral antibody against blast cell antigens and that this response may be impaired during the aggressive phase of the disease.

Adult↗
PubMed1974

Specificity of heteroantisera to human acute leukemia-associated antigens.

Antisera have been raised to human leukemic blast cells from individual patients in mice rendered tolerant with cyclophosphamide to remission leukocytes from the same individual. 10 antisera were raised against acute myelogenous leukemia (AML) cells and 5 antisera were raised against acute lymphoblastic leukemia (ALL) cells. Antisera to AML cells were absorbed with ALL cells, and antisera to ALL cells were absorbed with AML cells. Unabsorbed and absorbed antisera as well as antisera raised in nontolerant mice were tested for cytotoxicity against various cells of a panel containing myeloblasts from 35 patients with AML, lymphoblasts from 7 patients with ALL, myeloblasts from 7 patients with chronic myelogenous leukemia (CML) in blast crisis, peripheral blood leukocytes from 12 patients with acute leukemia in remission and 30 nonleukemic patients, and nucleated bone marrow cells from 10 nonleukemic patients. Unabsorbed antisera to AML or ALL cells raised in tolerant mice were highly cytotoxic to leukemic blasts cells but significantly less cytotoxic to remission and control cells. Antisera to AML cells absorbed with ALL cells retained measurable cytotoxicity against AML cells but were not cytotoxic to ALL cells or control cells. Similarly, antisera to ALL cells absorbed with AML cells retained significant cytotoxicity only to ALL cells. Control antisera raised in nontolerant mice were cytotoxic to all cells tested. Although species specific, histocompatibility, differentiation, maturation, and cell cycle-associated antigens may be responsible in part for the cytotoxic activity of the unabsorbed antisera, the absorbed antisera are probably detecting antigens specific for their leukemic cell type.

Animals↗