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Biomedical subjects

A Edwards

Publications and source records attributed to A Edwards.

At least 55 records · Page 3Linked to original sources
PubMed1985

Cardiac function in acute hypothyroidism.

It has been established that chronic hypothyroidism may affect cardiac function by several mechanisms. It is not known how long the patient has to be hypothyroid for cardiac involvement to develop. This study was undertaken to assess the effect of a short period of hypothyroidism (10 days) on cardiac function. Nine patients who had had total thyroidectomy, had received ablative radioiodine for thyroid cancer and were euthyroid on replacement therapy were studied while both euthyroid and hypothyroid. Cardiac assessment was performed by X-ray, ECG, echocardiography and gated blood-pool scans. After 10 days of hypothyroidism, the left-ventricular ejection fraction failed to rise after exercise in 4 of the 9 patients studied, which was significant (P less than 0.002). No significant changes in cardiac size or function at rest were detected. This functional abnormality in the absence of any demonstrable change in cardiac size and the absence of pericardial effusion with normal basal function suggest that short periods of hypothyroidism may reduce cardiac reserve, mostly because of alterations in metabolic function.

Acute Disease↗
PubMed1985

Effects of recombinant leukocyte interferon (rIFN-alpha A) on tumour growth and immune responses in patients with metastatic melanoma.

Studies were initiated to assess the response of patients with disseminated melanoma to recombinant alpha interferon (rIFN-alpha A) and to monitor effects of rIFN-alpha A on several tests of immune function. Twenty patients were treated with rIFN-alpha A given by i.m. injection in escalating doses from 15 to 50 X 10(6) um-2. The responses of two patients were considered unevaluable. Of the remainder there was complete remission of tumour in two and stable disease in two. Subsequent progression of tumour in one of the latter patients coincided with development of antibodies to IFN. Side effects (usually fatigue) were dose rate limiting in 11 patients. Laboratory tests on samples taken 6 hours after rIFN-alpha A indicated a marked lymphopenia and a reduction in natural killer (NK) cell activity particularly against K562 target cells. Longer term changes measured in samples taken 2 days after the previous rIFN-alpha A injections consisted of neutropenia and an increase in the T4/T8 ratio due mainly to a relative increase in OKT4 positive T cells compared to OKT8 positive T cells. NK activity against the K562 target cell increased in most patients during the first week of treatment and then returned to below or near pretreatment levels thereafter against the K562 target cell. This contrasted with NK activity against the melanoma target cell which showed a more gradual increase over the duration of the treatment in 6 patients. The latter correlated with an increase in mitogen stimulated IL 2 production from their blood lymphocytes and may indicate that the cytotoxic activity resulted from lymphokine-activated killer (LAK) cells. These results confirm the activity of rIFN-alpha A against melanoma in certain patients. They suggest that further studies are needed to select patients who may respond to rIFN-alpha A and to optimize treatment regimens. Tests of IL 2 production and LAK activity may assisted in achieving these objectives.

Adult↗
PubMed1985

Influence of endogenous and exogenous oestrogens on posterior pituitary secretion in women.

Four normally menstruating subjects were studied throughout the menstrual cycle to investigate changes in plasma LH, arginine vasopressin (AVP), oxytocin (OT) and oxytocin associated neurophysin (NPOT). A clear mid-cycle LH peak was observed in each subject. Mean levels of AVP, OT and NPOT were 2.2 pmol/l, 1.1 pmol/l and 39 pmol/l, respectively. There were no significant differences between plasma levels during follicular, mid-cycle and luteal phases for each of these. Two further subjects with anovulatory cycles were studied in a similar way. In the first subject, with polycystic ovarian disease, posterior pituitary peptide levels were in the normal range, whereas the other subject, recovering from anorexia nervosa, had raised plasma levels of all posterior pituitary peptides (AVP 8.1 pmol/l, OT 1.8 pmol/l, NPOT 131 pmol/l, mean values) despite a normal osmolality. Administration of ethinyl oestradiol, 100 micrograms or 500 micrograms, had no effect of either AVP or OT, but 100 micrograms caused a marked rise in NPOT levels in all cases within 12 h (from mean 64 pmol/l to mean 196 pmol/l) and the levels remained elevated for 3 d.

Adult↗
PubMed1985

Differences in the fine specificities of monoclonal (Class A) antibodies to human myeloid cells.

Among 13 monoclonal antibodies to human myelomonocytic cells, six could be assigned to a group designated Class A with the following properties: (a) they react almost exclusively with granulocytes among cells of the peripheral blood, (b) they resemble the previously described anti-granulocyte antibodies, VEP8 and VEP9, and the anti-mouse embryo, anti-SSEA-1, in their strong reactions with human meconium glycoproteins and ovarian cyst mucins of non-secretor type and (c) they recognize the carbohydrate antigen 3-fucosyl-N-acetyllactosamine (alpha 1----3fucosylated Type 2 blood group chains). The binding of these anti-myeloid antibodies is more strongly inhibited by lacto-N-fucopentaose III than by the trisaccharide-fucosyl-N-acetyllactosamine, in contrast to anti-SSEA-1 which is more strongly inhibited by the trisaccharide. These observations suggest that the myeloid Class A antibodies recognize additional determinants on the neolacto (Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4) backbone of the pentasaccharide which occurs on the glycoproteins and glycolipids of myeloid cells. However, no two of the anti-myeloid antibodies were identical in their inhibition patterns with the glycoproteins and the two oligosaccharides. They also differed in their cellular reactivities, for example, the proportion of cells in the K-562 cell line reacting with each antibody ranged from 15-57%.

Antibodies, Monoclonal↗
PubMed1984

Effect of isoprinosine on natural killer cell activity of blood mononuclear cells in vitro and in vivo.

Addition of isoprinosine to cultures of blood mononuclear cells was shown to inhibit natural killer (NK) cell activity against the K562 myeloid cells and melanoma cells. This appeared to be due to inhibitory influences of monocytes in that after removal of adherent cells isoprinosine appeared to stimulate NK activity. Similar effects were noted on T cells separated by E rosette procedures. Administration of isoprinosine in vivo had variable effects on NK activity during drug administration but there was a significant increase in NK activity 3 days after cessation of the drug. These changes in NK activity may reflect different threshold levels of the drug on suppressor and NK cell populations and the relative proportions of different lymphocyte populations in individual subjects. Further studies with a wider range of drug doses and more frequent monitoring of responses are required to further evaluate the effect of isoprinosine on NK activity.

Adult↗
PubMed1983

Effects of cigarette smoking on the immune system. Follow-up studies in normal subjects after cessation of smoking.

Previous reports of an association between cigarette smoking and the depression of immune function were investigated by studies of 35 subjects before, and three months after, they had ceased to smoke cigarettes. The studies included tests of natural killer cell (NK) activity against several target cells and the measurement of immunoglobulin levels in sera and saliva. Similar tests were conducted on 29 control subjects who continued to smoke. The results indicated a significant decrease in lymphocyte counts and a significant increase in NK activity against cultured melanoma cells in subjects who ceased smoking. Serum IgG and IgM levels rose significantly in those who ceased smoking cigarettes, but there was no change in IgA levels. Similar increases in immunoglobulin levels (IgA and IgG) in mucosal secretions (saliva) were noted after cessation of smoking. The NK activity and immunoglobulin levels of smokers who continued to smoke did not show significant changes. These results were consistent with the reversal of changes in immune function associated with smoking. We suggest that these findings may provide further insight into the association of smoking with an increased incidence of certain malignant diseases and respiratory infections.

Adult↗
PubMed1983

Immunological effects of solarium exposure.

Normal volunteers underwent a standard course of treatment to acquire a suntan in a commercial solarium, and tests of immune function were carried out before, on completion, and 2 weeks after completion of radiation exposure. Compared with age and sex matched concurrent controls, the test subjects had reduced skin test responses to dinitrochlorobenzene (DNCB), slightly reduced blood lymphocyte numbers, and changes in the proportion of lymphocyte subpopulations. This included a relative increase in total (OKT3+) T-cell numbers which was attributable to an increase in the OKT8+ suppressor/cytotoxic subset of T cells. OKT4+ helper T cells were reduced and there was a significant decrease in the OKT4/OKT8 ratio. Other changes included a significant increase in suppressor T-cell activity against IgG production in vitro and depression of natural killer cell activity. These changes were still present in some subjects 2 weeks after solarium exposure.

Adult↗
PubMed1983

Clearance rates and systemic effects of intravenously administered interleukin 2 (IL-2) containing preparations in human subjects.

The present study was designed to examine the feasibility of in vivo administration of interleukin 2 (IL-2) to induce cytotoxic cell activity against tumours in human subjects. IL-2 was prepared from blood leukocytes stimulated with phytohaemagglutinin (PHA) and partially purified by membrane chromatography to exclude PHA. Administration of different amounts of IL-2 in vivo to 2 patients with melanoma revealed that the initial level of IL-2 in the circulation was related to the dose given and had a half-life of approximately 22.5 minutes. The initial and subsequent levels of IL-2 were lower than that expected to occur from equilibration in plasma and extracellular fluid. This was not apparently due to inactivation by serum factors because fresh human serum had little effect in vitro on the induction of mitogenic or cytotoxic activity by IL-2. Spontaneous division of lymphocytes was increased following IL-2 administration and it is suggested that clearance of IL-2 in vivo may reflect, in part, absorption by activated lymphocytes in the circulation. Side effects noted shortly after administration of the partially-purified IL-2 preparations included transient pyrexia, hypoglycaemia, increased cortisol levels, lymphocytopenia and signs of mild intravascular coagulation. No long-term effects were noted. These initial results suggest that systemic injection of purified preparations of II-2 may be a feasible approach to induce cytotoxic T cells in vivo.

Adult↗
PubMed1983

Characterization of an S antigen synthesized by several isolates of Plasmodium falciparum.

The S antigen of a Papua New Guinean isolate of Plasmodium falciparum was identified by immunoblotting as the dominant antigen in culture supernatants. An antigen identical in molecular weight (Mr 220,000), isoelectric point (pI 4.2), and immunoreactivity with sera from individuals exposed to malaria was expressed by four Papua New Guinean isolates and one isolate of unknown origin. The Mr 220,000 antigen was not detected in culture supernatants derived from two isolates from Thailand and one from Ghana. The Mr 220,000, pI 4.2 S antigen may characterize a subpopulation of parasites common to many isolates of P. falciparum, which is selected for by continuous culture in vitro. A variant S antigen, 30 kilodaltons larger but with similar immunoreactivity, was expressed by 1 of 26 clonal populations derived by limit-dilution culture from one of the Papua New Guinean isolates of P. falciparum. The characteristics of the S antigen, defined by immunoblotting, allowed it to be identified in two-dimensional separations of [35S]methionine-labeled parasite proteins, thus confirming the parasite origin of the antigen.

Animals↗
PubMed1983

Alteration of T cell subsets and induction of suppressor T cell activity in normal subjects after exposure to sunlight.

The effects of exposure to natural sunlight on the immune system were studied in 15 normal human subjects. Exposure was for 1 hr each day for 12 days over 2 wk and tests were carried out before, on completion, and 2 wk after completion. In comparison to concurrent studies on 13 age- and sex-matched controls, sun-exposed subjects had a significant increase in their circulation of T cells recognized by OKT8 monoclonal antibodies and a decrease in OKT4 positive T cells. Suppressor T cell activity measured in pokeweed mitogen-stimulated cultures of T and B cells was significantly increased against IgG and IgM production. These changes were still evident in many of the subjects 2 weeks after completion of the sun exposure. A trend for depression of natural killer cell activity against a melanoma target cell was noted in the present study, but this did not appear as marked as that noted previously in subjects exposed to radiation in solariums. The differences between the effect of radiation from solariums and natural sunlight on the immune system may result from the higher dosage of UV-A in radiation from solariums. The results suggest that exposure to sunlight may favor the induction of suppressor pathways in response to antigenic stimuli and that this may limit immune responses against tumor cells such as melanoma. They support the idea from animal studies that systemic changes in the immune system may be an important factor in the association of UV radiation with malignancy.

Adult↗
PubMed1983

Prognostic significance of leukocyte-dependent antibody activity in melanoma patients.

Sera from patients with melanoma and control subjects were examined for leukocyte-dependent antibody (LDA) activity against cultured melanoma and control nonmelanoma target cells in 51Cr release cytotoxicity assays. In over a third of 344 melanoma patients, LDA activity against melanoma cells was related to tumor growth, shown by disappearance of the LDA after surgical removal of melanoma. Tumor-related LDA activity was not detected in 143 controls with various nonmelanoma malignant conditions and benign skin lesions. Approximately 5% of the patients had high-titer melanoma LDA that was unchanged by surgical removal of the tumor, and 15% had melanoma LDA revealed in their sera only after the sera had been treated to dissociate immune complexes. In patients with stage I melanoma, the disease-free interval was significantly longer in those with tumor-related LDA compared to those with no LDA. Analysis of the data in relation to known prognostic variables suggested that the main influence of LDA on prolongation of the disease-free interval was in males. An association between tumor-related LDA and a longer disease-free interval was also apparent in patients with stage II melanoma at first presentation but not in those with recurrence after prior treatment of primary melanoma. The results suggest that LDA activity against melanoma cells in the sera of patients after surgical removal of stage I or stage II melanoma is a favorable prognostic factor. Further studies are needed to determine whether induction of melanoma LDA by immunotherapy may improve the outcome in patients without naturally occurring LDA.

Antibodies, Neoplasm↗
PubMed1982

Deficient natural killer cell activity in a patient with Fanconi's anaemia and squamous cell carcinoma. Association with defect in interferon release.

A child with Fanconi's anaemia diagnosed at 7 years of age presented in adult life with lymphopenia, recurrent warts and Bowen's disease. The latter resulted in the development of multiple cutaneous squamous cell carcinomas which metastasized to the skeleton. Investigation of her immune function revealed selective defects in natural killer (NK) cell activity. Humoral immunity and several tests of cell-mediated responses were within normal or became normal after treatment with levamisole or transfer factor. Analysis of the defect in NK activity revealed that low levels could be induced in vitro by fibroblast interferon. Stimulation of blood lymphocytes from the patient with the interferon inducer poly (I)-poly (C) resulted in an increase in NK activity but incubation of her lymphocytes on tumour cells did not result in an increase in NK activity or the release of interferon. This contrasted with the marked increase in NK activity and interferon release observed when lymphocytes from normal controls were incubated on tumor cells. These findings suggested the absence of NK activity in this patient was secondary to a defect in interferon release from lymphocytes on exposure to tumour antigens. It is considered that these defects may have been an important predisposing factor in the development of malignancy in this patient and possibly other patients with Fanconi's anaemia.

Adult↗
PubMed1981

A double-blind controlled trial of the effect of sodium cromoglycate in preventing relapse in ulcerative colitis.

A double-blind controlled trial of the effect of sodium cromoglycate (SCG) in preventing relapse in ulcerative colitis has been completed in 100 subjects. In patients already taking sulphasalazine, SCG did not prove to be of any additional benefit. However, in patients not on any other maintenance therapy, the relapse rate was 40% for SCG as compared with 75% for placebo. A large study of the effect of SCG in patients intolerant of sulphasalazine is indicated.

Adult↗
PubMed1980

Regulation of gene expression in primary cultures of adult rat hepatocytes on collagen gels.

The studies described in this paper demonstrate rather conclusively the efficacy of the study of the regulation of gene expression in primary cultures of adult rat hepatocytes. The utilization of these cells in completely defined medium allows one to determine the exact environmental conditions for the regulation of the expression of specific genes. In the studies described in this work, we have demonstrated that the regulation of glucokinase involved three hormones, insulin, corticosteroids, and T3. In contrast, the regulation of an enzyme involved primarily in fatty acid metabolism, ATP-citrate lyase, required only insulin and T3 for its full expression. Cyclic GMP appeared to be involved in the regulation of glucokinase, but not ATP-citrate lyase, a fact that would be extremely difficult to demonstrate clearly in vivo. The regulation of the gluconeogenic enzyme, ornithine aminotransferase, in vitro involved only a single hormone, glucagon, the inhibition of induction by corticoid steroids demonstrable in vivo being absent in cell culture. However, the repressive effect of glucose on the induction of this enzyme was quite comparable to that seen in vivo and was not mediated through cyclic AMP or insulin, based on findings in cell culture. Thus, the requirements for and the mechanisms involved in enzyme induction and repression by hormones and glucose may be much more easily studied in primary cultures of rat hepatocytes than in vivo, or even in hepatoma cell lines, where relatively few genes are expressed as compared with adult liver. In addition to the regulation of enzyme levels, the characteristics of protein secretion may be investigated in primary cultures of rat hepatocytes and compared with the biochemical and physiological parameters in the whole organism. This was exemplified by the study of the synthesis and secretion of alpha 2u-globulin that was secreted into the culture medium in both glycosylated and nonglycosylated forms but was maintained in the circulation in vivo, principally as the glycosylated form. Furthermore, the function of glycosylation in this particular instance may be deduced from a combination of the in vivo and in vitro approaches. The advantages of the use of primary hepatocyte cultures for the study of the regulation of gene expression in mammalian tissue has only recently been explored. Future investigations of the regulation of a variety of enzymes in these cultures as well as a study of the regulation of the synthesis of their messenger RNA are now possible and should provide an exciting system in which to understand at a molecular level the regulation of the expression of a number of genes.

ATP Citrate (pro-S)-Lyase↗