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Biomedical subjects

R O'Connor

Publications and source records attributed to R O'Connor.

At least 109 records · Page 6Linked to original sources
PubMed1982

cDNA cloning and analysis of chick-embryo-liver cytochrome P-450 mRNA induced by porphyrinogenic drugs.

Hepatic microsomal cytochrome P-450 was elevated in 17-day chick embryos by combined administration of the porphyrinogenic drugs 2-allyl-2-isopropylacetamide and 3,5-diethoxycarbonyl-1,4-dihydrocollidine. Increased apoprotein levels were the result of de novo protein synthesis; in vitro obtained translation data suggested that cytochrome P-450 mRNA levels were elevated. A 1000-base cDNA sequence for the drug-induced cytochrome P-450 mRNA was isolated from a chick embryo cDNA 'library' and this was used as a specific probe to investigate drug-mediated induction of cytochrome P-450 mRNA. RNA-DNA 'dot' hybridisation studies demonstrated that drug treatment led to a 3-5-fold increase in the level of this mRNA and that the mRNA was predominantly associated with membrane-bound polyribosomes. Treatment of embryos with the drugs individually demonstrated that both of them induced synthesis of the same mRNA. These studies show directly that treatment of chick embryos with 2-allyl-2-isopropylacetamide or 3,5-diethoxycarbonyl-1,4-dihydrocollidine caused increased levels of cytochrome P-450 mRNA and suggest that this involved increased transcription of the gene.

Acetamides↗
PubMed1982

Experimental ocular toxoplasmosis in primates.

The rabbit serves as the only existing experimental model for ocular toxoplasmosis. This model has many deficiencies. Our technique for the production of acute toxoplasmic retinitis in monkeys is described herein. This primate model should be more representative than the rabbit model of human ocular toxoplasmosis.

Animals↗
PubMed1981

In vitro cyclic nucleotide responsiveness of leukocytes and platelets in patients suffering from atopic dermatitis.

Peripheral blood leukocytes from patients with severe atopic dermatitis (serum IgE levels between 1,560 and 28,000 U/ml) showed a significantly weaker increase in intracellular cAMP after stimulation with epinephrine (10(-5)-10(-3) M) than leukocytes from normals. At the same time stimulation with methylcholine (10(-10)-(10(-4) M) induced a significantly higher increase in intracellular levels of cGMP in the atopic group compared to normals. The immunomodulating agent levamisole induced a slight increase in cAMP and cGMP response both in leukocytes from atopic patients and in normals. Platelet cAMP concentrations were lowered by epinephrine stimulation both in atopics and controls. There was no effect of methylcholine upon platelet cyclic nucleotide levels in the dose range examined. The data support the concept that abnormal cyclic nucleotide responsiveness--not only as beta-adrenergic blockade but also as cholinergic hyperreactivity--may plays a role in the pathogenesis of atopic dermatitis.

Adult↗
PubMed1980

Ascorbic acid requirements of the trained monkey as determined by blood ascorbate levels.

The ascorbate requirements of 4 monkeys were investigated by comparison of the plasma and whole blood ascorbate levels to known amounts of ascorbate supplements. The monkeys were conditioned to the experimental procedures to minimize environmental stress which increases ascorbate requirements. Trained monkeys required 3 and 6 mg AA/kg body weight fed daily to mature and young monkeys, respectively, to maintain blood ascorbate levels proposed as necessary to prevent the development of scurvy. Young monkeys (sexually immature) required twice the amount of the vitamin to maintain acceptable ascorbate levels than did the mature monkeys. Smaller amounts of ascorbate were required by the monkeys to maintain similar blood ascorbate levels when the vitamin was incorporated into the diet in comparison to the single and oral supplement. Only small variations were measured between the plasma and whole blood ascorbate levels in the same monkey. The leucocyte ascorbate levels suggest that the tissue ascorbate concentration may be minimal although the blood ascorbate concentration is in an acceptable range.

Aging↗
PubMed1979

In vitro histamine and serotonin release studies in atopic dermatitis.

6 patients suffering from severe atopic dermatitis with high serum IgE were investigated. 3 of the patients had elevated plasma histamine levels (1.5-2.0 ng/ml). Compared to 9 nonatopic normal volunteers, the patient showed increased in vitro histamine release from peripheral leukocytes after stimulation with iothalamate and methacholine: while there was no significant histamine release at a methacholine concentration of 10(-4) M in normals, 4 of the patients with atopic dermatitis showed measurable histamine release under these conditions in vitro. The uptake of radiolabeled serotonin by platelets in vitro was decreased in 2 of the patients. There was no significant difference in serotonin release induced in vitro by different concentrations of thrombin, epinephrine and methacholine; 2 patients showed an increased platelet release reaction after iodipamide stimulation. It is concluded that a general tendency to release vasoactive mediators, even after 'nonimmunologic' stimulation, might play a role in the pathogenesis of atopic dermatitis.

Adult↗
PubMed1978

Isolation of human tumour-specific antigens associated with beta2 microglobulin.

In the present study the tube LAI assay was used to monitor the isolation of the TSA of 4 different types of human cancers. Each tumour antigen was found to be specific for tumours arising in the organ from which the TSA was initially derived and which were histopathologically similar. Immunochemical studies revealed that these molecules co-isolate with normal human HLA antigens and are associated with beta2m. On Sephadex G-150, the majority of the papain-solubilized tumour antigen eluted in the mol. wt range 70,000-150,000. Analysis of this material by SDS-PAGE and 6M guanidine-HC1 column chromatography indicated that the material is composed of smaller subunits with prominent peaks at approximately 40,000, 25,000 and 12,000 mol. wt. Immunoadsorbent affinity chromatography of the solubilized tumour-membrane constituents on AH-Sepharose-linked horse anti-human-beta2m indicated that the tumour antigens, like HLA molecules, contain a beta2m subunit. The specificity of binding of TSA to the immunoadsorbent columns and the immunologically specific abrogation of LAI reactivity were clearly shown. The present study, therefore, indicates that by the isolation of beta2m, human tumour antigens can also be isolated, since human tumour antigens are associated with beta2m. Whether human TSAs may perhaps be modified histocompatibility antigens remains to be answered. Although the change upon malignant transformation in the pattern of the cell-surface proteins expressing the TSA determinant remains obscure, it would appear that for tumours arising within a given organ, a consistent alteration of cell-surface proteins occurs.

Antigens, Neoplasm↗
PubMed1978

The natural history of antitumour immunity in human breast cancer assayed by tube leucocyte adherence inhibition.

The specificity of the tube LAI in breast cancer was examined in a study with coded samples of PBL. In addition, 64 patients with breast cancer had their LAI reactivity monitored and correlated with their clinical status for up to 3 years after mastectomy. When patients were assayed by tube LAI, 83, 72, and 29% with Stage I, and II and III breast cancer respectively were positive. In Stage IV brest cancer, 88% of those with local recurrence and 15% of those with disseminated cancer were positive. By contrast, 3% of control subjects were LAI+. A select group of patients admitted to hospital with suspicious breast lumps that histopathologically proved to be benign breast disease (BBD) had a higher incidence of LAI+ (12%), whereas of outpatients with BBD only 2% were LAI+. Most breast cancer patients LAI reactivity became negative 2--4 months after mastectomy, even when some harboured micrometastases. LAI reactivity remained absent in those patients who remained clinically "cancer-free". In the follow-up patients, LAI activity returned about 4 months before local recurrence. LAI reactivity was observed in 7/8 patients in the coded study and 14/15 patients in the follow-up study preceding and/or at the time of local recurrence. A few patients (15%) progressed to widespread cancer without preceding positive LAI activity. The results suggest that tumour-specific immunity rapidly fades after surgery and may play no role in the rejection of micrometastases by 6 months after surgery. In addition, the present study has shown that the human hose manifests tumour-specific immunity when the cancer is small, and suggests that the early detection of human cancer would depend upon reliable methods to measure the tumour-specific immune response.

Breast Neoplasms↗
PubMed1978

A study of false positive and negative responses in the tube leucocyte adherence inhibition (tube LAI) assay.

A panel of 5 different breast-cancer and 2 other cancer extracts was used to clarify the false-negative responses in patients with Stage I and II breast cancer and the false-positive responses in control subjects. Most patients with Stage I and II breast cancer who had an initially negative LAI response were positive when tested against the panel. The false negatives occurred because of (1) the experimental errors of the assay; (2) changes in the antigenic strength of the extracts; (3) antigenic heterogeneity of a few tumours and (4) lack of tumour-specific reactivity of the host. 3% of control subjects had a false-positive LAI response. The leucocytes from most of these positive patients did not react to the panel of antigens, and hence the false positives appeared to result from experimental error. In-hospital patients with benign breast disease had a 12% positivity rate when initially assayed, and 63% of these patients reacted to the panel of breast-cancer antigens. Those patients with benign breast disease who reacted to the panel of breast-cancer antigens had cytophilic anti-breast-cancer antibody in their serum; their leucocyte LAI reactivity was blocked in an immunologically specific manner by serum from advanced Stage IV breast-cancer patients; their leucocytes reacted to extracts of breast cancer and not fibrocystic breast tissue; their leucocyte reactivity was blocked by isolated breast-cancer TSA that was linked to beta 2 microglobulin, but not by normal breast-tissue proteins; and the kinetics of the LAI response after excision of the breast mass was identical to that observed with breast-cancer patients after mastectomy. In these patients, the breast tissue within the breast lump expressed breast TSA similar to unequivocal breast cancer.

Antigens, Neoplasm↗
PubMed1978

Modulation of an apparent mRNA pool for extracellular protease in Bacillus amyloliquefaciens.

Late-log-phase cells of Bacillus amyloliquefaciens have the unusual capacity to produce extracellular protease for over 60 min in the presence of rifampin or actinomycin D at levels which strongly inhibit incorporation of amino acids into cellular protein. If cells are incubated in the presence of high levels of amino acids for 75 min this capacity is exhausted, but it is retained if the incubation is carried out in low levels of amino acids. Transfer of exhausted cells from high to low concentrations of amino acids results in a progressive recovery of the capacity for rifampin-actinomycin-insensitive protease production. The results seem best explained on the basis of the accumulation of a reserve pool of mRNA for extracellular protease. Measurement of the apparent mRNA pool size over 12 h shows a cyclical rise and fall, and these changes correlate with a periodic variation of the rate of protease production. A working hypothesis is presented to account for these observations in terms of a novel control situation over protease mRNA transcription.

Amino Acids↗
PubMed1977

Fitness trails.

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Gymnastics↗