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Biomedical subjects

R M Galbraith

Publications and source records attributed to R M Galbraith.

At least 73 records · Page 4Linked to original sources
PubMed1981

Expression of transferrin receptors on mitogen-stimulated human peripheral blood lymphocytes: relation to cellular activation and related metabolic events.

Mitogen-activated normal human peripheral blood lymphocytes bind transferrin to specific membrane receptors. In this study, lymphocytes stimulated with phytohaemagglutinin for 0-66 hr were examined to determine the relation of this phenomenon to cellular activation and related metabolic events. Transferrin receptors were first detected at 20-24 hr. This event was consistently preceded by RNA and protein turnover which commenced during the first 6 hr of culture, whereas initiation of DNA synthesis was detected concurrently with the appearance of receptors or slightly later (24-30 hr). Exposure of cells to inhibitors of RNA and protein synthesis early during culture (at 0 or 24 hr) prevented the expression of transferrin receptors, but also caused generalized metabolic failure, and abrogated cellular activation. In contrast, later addition of these agents at 48 hr did not interfere significantly with the process of activation, but did suppress the terminal increase in receptor-bearing cells observed during the final 18 hr in control cultures lacking inhibitor. After deliberate thermal stripping of receptors from activated cells, the reappearance of membrance binding sites which normally occurred within 30 min, was also blocked by cycloheximide, puromycin and actinomycin D. However, similar inhibition of DNA which was induced by hydroxyurea had much less effect upon both the initial appearance of receptors and their reappearance after ligand-induced depletion. These results demonstrate that the appearance of transferrin receptors upon human lymphocytes is dependent upon cellular activation and requires synthesis of protein and RNA.

Antimetabolites↗
PubMed1981

Studies of the interaction between human transferrin and specific receptors on the trophoblast membrane.

The concept of specific receptors for maternal transferrin on the human syncytiotrophoblast membrane has been generally accepted for many years, but definitive evidence of their existence has been established only recently. In this study, experiments were performed to characterize transferrin receptors further, both on intact membranes and after solubilization. Intact, isolated membrane fragments were examined for transferrin binding, both qualitatively by immunofluorescence and quantitatively by radiobinding. The amounts of ligand bound varied inversely with the quantities of residual maternal transferrin remaining at the time of testing. Scatchard plots revealed that the calculated affinity (K alpha) and the number of receptors increased substantially when transferrin was removed by initial washing with chaotropic agents. After dissociation from the membrane by detergents, occupied receptors largely retained bound transferrin, and transferrin binding by unoccupied receptors was also preserved. The stability of such ligand:receptor complexes was considerably enhanced at pH 5.0, and was apparently unaffected by prior treatment with chaotropic agents. Specific immunoprecipitation of solubilized radioiodinated membrane with rabbit antiserum to human transferrin, followed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate under reducing conditions, indicated a relative molecular mass for the unoccupied receptor of 90,000. These results confirm the existence of high-affinity receptors for transferrin on the trophoblast, and also delineate certain potential pitfalls in studies of their interactions with ligand.

Chemical Precipitation↗
PubMed1981

Placental immunopathology in gestational diabetes.

Gestational diabetes and insulin-dependent diabetes are characterized by distinct pathophysiological mechanisms. However, their presence in pregnancy poses similar risks to the fetus. It is possible that factors common to both diseases are responsible for the increased morbidity and mortality in offspring of such pregnancies. Recent studies of placentae from insulin-dependent diabetics revealed evidence of immunopathological change which may support the possible role of immunological factors in the complications of diabetic pregnancy. In the present study, we have similarly examined placentae derived from 30 pregnancies complicated by gestational diabetes and from 10 normal pregnancies. The most striking differences detected by immunofluorescence were increased amounts of clotting factors related to areas of fibrinoid necrosis, and large quantities of complement components C4 and C3 in the intervillous spaces and trophoblast basement membrane respectively. These results are similar to those found in placentae from insulin-dependent diabetics, suggesting that glucose intolerance in pregnancy, even of minor degree, is frequently associated with immunopathological processes that are reflected in the placenta.

Animals↗
PubMed1981

Studies of antigenic components of the human syncytiotrophoblast membrane.

In order to initiate characterization of potentially immunogenic moieties on the human trophoblast membrane, antisera to native and detergent-solubilized normal trophoblast membranes were prepared in rabbits. By indirect immunofluorescence, these antisera reacted strongly with all villous structures in normal placentae and also with a panel of normal adult human tissues. Specificities to normal human serum components were then removed by solid-phase immunoabsorption. However, the resultant antisera still reacted weakly with differentiated, normal adult tissues, and additional absorption with normal adult liver homogenate was necessary to remove cross-reactivity completely. Such absorbed antisera gave undiminished and specific fluorescence of the syncytiotrophoblast plasma membrane, and specifically precipitated two protein species with approximate relative molecular masses of 148,000 and 62,000. However, they also reacted with PHA-activated peripheral blood lymphocytes, in addition to Chang liver and HeLa cell lines. These results indicate that, even after extensive absorption, trophoblast membrane antisera may retain reactivity for determinants shared with normal and transformed adult cells.

Animals↗
PubMed1980

The human materno-foetal relationship in malaria: I. Identification of pigment and parasites in the placenta.

To facilitate investigations of the consequences of malarial infection during human pregnancy, several methods for the recognition of pigment and parasites in the placenta were evaluated. Pigment was visualized in infected blood smears and placental tissue using both white light and modified fluorescence microscopy. However, the characteristic pigment dots observed with fluorescent light were also apparent in unstained cryostat and deparaffinized placental sections, and following reaction with immunohistological reagents. Intact parasites were recognized immunohistologically in placental sections and blood smears using rabbit antisera to Plasmodium falciparum and P. berghei. Using these procedures, numerous erythrocytes containing parasites associated with small pigment dots were seen in intervillous spaces in heavily infected placentae. In these organs, larger irregular pigment aggregates were present within maternal cells which were shown to be monocytes by esterase staining. Pigment was also observed in the cytoplasm of the trophoblast and not infrequently in the mesenchymal stroma, but no intact parasites were observed within chorionic villi. These simple and sensitive methods thus confirm placental localization of parasites and pigment. Furthermore, the finding of pigment in all Gambian placentae examined, of which seven were thought initially to be uninfected, indicates that malaria may complicate pregnancy more frequently than hiterto anticipated.

Esterases↗
PubMed1980

The human materno-foetal relationship in malaria. II. Histological, ultrastructural and immunopathological studies of the placenta.

Histological and ultrastructural studies of four placentae heavily infectd with Plasmodium falciparum revealed large intervillous accumulations of erythrocytes containing parasites together with monocytes which had ingested pigment. These appearances were associated with focal syncytial necrosis, loss of syncytial microvilli and proliferation of cytotrophoblastic cells. In addition, marked irregular thickening of trophoblastic basement membranes and protrusion of tongue-like projections of syncytiotrophoblast into the basement membrane were observed. In six other placentae which contained scanty amounts of pigment but no parasites, representing past or inactive infection, no large collections of monocytes or abnormalities of trophoblast were apparent but basement membrane thickening was evident. Immunohistological studies revealed no significant differences between placentae positive for parasites and those containing pigment only, although the amount of certain immunoproteins and clotting factors was clearly increased above normal. These findings establish that P. falciparum infection in the placenta may result in substantial damage although lesions within the villus are rare. Furthermore, previous infection, although adequately controlled, may leave a heritage of pigment deposition, basement membrane thickening and immunopathological lesions. These results may thus account for both the high frequency of intra-uterine growth retardation and the rarity of congenital malaria in the presence of P. falciparum malaria.

Female↗
PubMed1980

Transferrin binding to peripheral blood lymphocytes activated by phytohemagglutinin involves a specific receptor. Ligand interaction.

Immunohistological studies have indicated that membrane sites binding transferrin are present upon activated human peripheral blood lymphocytes. In this study, we have investigated transferrin uptake in human lymphocytes exposed to phytohemagglutinin (PHA), by quantitative radiobinding and immunofluorescence in parallel. In stimulated lymphocytes, binding was maximal after a 30-min incubation, being greatest at 37 degrees C, and greater at 22 degrees C than at 4 degrees C. Although some shedding and endocytosis of transferrin occurred at 22 degrees and 37 degrees C, these factors, and resulting synthesis of new sites, did not affect measurement of binding which was found to be saturable, reversible, and specific for transferrin (K(a) 0.5-2.5 x 10(8) M(-1)). Binding was greater after a 48-h exposure to PHA than after 24 h, and was maximal at 66 h. Sequential Scatchard analysis revealed no significant elevation in affinity of interaction. However, although the total number of receptors increased, the proportion of cells in which binding of ligand was detected immunohistologically increased in parallel, and after appropriate correction, the cellular density of receptors remained relatively constant throughout (60,000-80,000 sites/cell). Increments in binding during the culture period were thus due predominantly to expansion of a population of cells bearing receptors. Similar differences in binding were apparent upon comparison of cells cultured in different doses of PHA, and in unstimulated cells binding was negligible. Transferrin receptors appear, therefore, to be readily detectable only upon lymphocytes that have been activated.

Dose-Response Relationship, Drug↗
PubMed1980

Demonstration of transferrin receptors on human placental trophoblast.

It has been postulated that the transplacental passage of maternal iron to the developing fetus requires binding of maternal transferrin to the trophoblast. We have therefore examined the ability of the human placenta to bind transferrin in vitro. Transferrin was demonstrated on trophoblast of human chorionic villi by immunohistologic methods. Moreover, after removal of transferrin bound in vivo by treatment of tissue with chaotropic solution or phosphate-buffered saline, freshly added transferrin was shown to bind in vitro in the same characteristic distribution. These findings suggest that placental iron transport is initiated by uptake of maternal transferrin iron to specific trophoblast binding sites.

Albumins↗
PubMed1980

Metabolic and cytoskeletal modulation of transferrin receptor mobility in mitogen-activated human lymphocytes.

The transferrin receptors which appear on mitogen-activated human peripheral blood lymphocytes were found by the use of immunofluorescence techniques to display temperature-dependent patching and capping reactions upon binding of transferrin. Lateral mobility of ligand-occupied membrane sites was accompanied by both shedding and endocytosis of receptor-transferrin complexes. In the presence of sodium azide or the microfilament inhibitor cytochalasin B, cap formation and shedding were markedly inhibited. In contrast, endocytosis of patched receptor-ligand complexes was inhibited by azide and microtubule inhibitors, including colchicine, vinblastine and vincristine. Co-capping experiments performed to elucidate further the alterations in membrane configuration involved in these reactions failed to reveal any topographical relationship between transferrin receptors and lectin-binding sites in these cells. These studied indicate that temperature-dependent mobility of transferrin receptors upon mitogen-activated peripheral blood lymphocytes is dependent upon the integrity of the cytoskeletal system and metabolic function of the cell.

Binding Sites↗
PubMed1980

Induction and suppression of immunoglobulin synthesis in cultures of human lymphocytes: effects of pokeweed mitogen and Staphylococcus aureus Cowan I.

The synthesis and secretion of immunoglobulins by human peripheral blood mononuclear cells in cultures stimulated with pokeweed mitogen or Staphylococcus aureus Cowan I were evaluated by enumeration of cells containing cytoplasmic immunoglobulins and cells actively secreting immunoglobulins, and by quantitation of immunoglobulins released into culture supernatants. The two mitogens caused comparable stimulation of immunoglobulin production; however, in contrast to pokeweed mitogen, S. aureus was active in cultures depleted of T lymphocytes, and its stimulatory effects were resistant to the influence of suppressor T cells generated by co-stimulation with concanavalin A or by preincubation without mitogenic stimulus. These results indicate distinct pathways of induction and suppression of immunoglobulin synthesis for these two polyclonal B cell activators, and suggest that stimulation by S. aureus is less thymus dependent than that induced by pokeweed mitogen.

Aging↗
PubMed1979

Non-A non-B hepatitis associated with chronic liver disease in a haemodialysis unit.

To clarify the aetiology of an outbreak of HBsAg-negative acute hepatitis in the renal unit at Fulham Hospital in 1968--70, serological tests for antibody to hepatitis-A virus (anti-H.A.V.) were done retrospectively on serum samples obtained at the time of the outbreak. 7 patients had had two previous episodes of clinical HBsAg-negative hepatitis. Serum samples were available from 24 of the 29 infected patients, and these were paired in 12 instances. There was a slight increase in the titre of anti-H.A.V. in 1 patient, and a further 2 patients who subsequently developed chronic hepatitis showed a decrease in titre, but no changes in titre were detected in the remaining 21 cases. These findings do not provide evidence for the involvement of hepatitis-A virus in the outbreak of hepatitis and effectively exclude a role for this virus in the chrnoic liver disease which developed subsequently in 8 (28%) of the patients. This outbreak is therefore probably non-A non-B hepatitis, which has not been reported previously in Great Britain in a haemodialysis unit. The results confirm that this form of hepatitis may be related to a high frequency of persistent hepatic dysfunction.

Antibodies, Viral↗
PubMed1979

Association between immunoglobulin allotypes and immune responses to Haemophilus influenzae and Meningococcus polysaccharides.

Serum samples were collected from 20 healthy White and 33 Black infants before and after immunisation with three doses of diphtheria-pertussis-tetanus vaccine and with one dose of Haemophilus influenzae type b polyribose phosphate vaccine and meningococcal group A and group C polysaccharide vaccines. Antibodies to these immunogens were measured and sera were allotyped for several Gm, A2m, and Km antigens. A highly significant association was found between the Km(1) allotype and the immune responses (difference between post-immunisation and pre-immunisation antibody levels) to H. influenzae and meningococcus C polysaccharides in the White children.

Antibodies, Bacterial↗
PubMed1979

Pi phenotypes of alpha1-antitrypsin in Southern England: identification of M subtypes and implications for genetic studies.

Phenotypes of alpha1-antitrypsin (A1AT) were determined by isoelectric focusing in blood samples from 926 healthy Caucasians living in South-West England. Three subtypes of the most common allele product (M), designated M1, M2, and M3, were identified. Routine determination of these subtypes should considerably amplify the usefulness of the A1AT polymorphism in population genetics and, in view of the possible association of clinical disorders with heterozygous deficient M phenotypes, may enhance the value of Pi determinations in clinical genetics.

Alleles↗