Biomedical subjects

E M Tucker

Publications and source records attributed to E M Tucker.

At least 37 records · Page 2Linked to original sources

PubMed1988

Genetic control of red-cell nucleoside transport and its association with the B blood-group locus and nucleoside phosphorylase activity in sheep.

Nucleoside transport in sheep red cells is controlled by two allelomorphic genes, the gene for nucleoside transport deficiency (NuI) being dominant to that for the functional presence of carrier-mediated nucleoside transport activity (Nui). Sheep are also polymorphic with respect to their red-cell nucleoside phosphorylase (NP) activity, some having high activities and others low activities of this enzyme. The gene for high activity (NPH) is incompletely dominant to that for low activity (NPL). Inheritance data indicate that the Nu locus is genetically linked to that for the B blood-group system and, in addition, exerts a pleiotropic effect on NP activity, Nu permeability stabilizing the heat-labile NPL gene product. Nu-permeable cells have a higher ATP content than Nu-impermeable red cells, and within the Nu-impermeable subgroup, NP deficiency causes a further reduction in red cell ATP concentration. It is concluded that the nucleoside inosine supplements glucose as a physiological energy substrate in sheep red cells.

ABO Blood-Group System↗

PubMed1988

Hemoglobin types in Saanen goats and Barbary sheep: genetic and comparative aspects.

By the use of the Immobiline technique at pH ranges 7.0-7.6 and 6.9-7.9, 16 different hemoglobin (Hb) phenotypes were observed in 61 English Saanen goats. They are explained in this breed by a genetic theory of five beta-globin genes (A4, A6, A8, E, and D) and two closely linked alpha-globin loci ('alpha and "alpha) of which the "alpha has a variant allele, provisionally called "alpha X. Family data together with observed and expected Hb frequencies were in agreement with the genetic theory. Among six Barbary sheep there were three Hb phenotypes explained by the occurrence of the beta-chain alleles B and Cna.

Alleles↗

PubMed1988

Production and characterization of bovine monoclonal antibodies to respiratory syncytial virus.

Six interspecific hybridomas (heterohybridomas) secreting bovine monoclonal antibodies (MAbs) against respiratory syncytial (RS) virus were produced. Four of the heterohybridomas were formed using the mouse myeloma cell line NS1 as the fusion partner, one using NS0, and the remaining heterohybridoma was formed using a bovine X murine hybridoma as the fusion partner. Five heterohybridomas secreted bovine IgG1 and one secreted IgG2. All six MAbs recognized human subtype A and B viruses as well as bovine RS virus. They were specific for the fusion glycoprotein and reacted with a 140K dimer and a 70K monomer in a Western blot of native antigen; three also bound to the 46K F1 component and its 22K cleavage product in a blot of reduced antigen. Two of these MAbs neutralized RS virus infectivity, inhibited virus-induced fusion, lysed RS virus-infected cells in the presence of complement and protected mice against RS virus challenge.

Animals↗

PubMed1987

The effect of sodium periodate treatment on the modulation of the sodium pump in low-potassium type (LK) sheep red cells by the L antigen.

1. The action of sodium periodate and neuraminidase on active and passive K+ transport in low-potassium type (LK) sheep red cells was investigated in relation to the contribution of the Lp and Ll antigens. 2. Active K+ transport in LK sheep red cells was not affected by treatment with sodium periodate (2 mM), or with neuraminidase. 3. Passive K+ transport in LK sheep red cells was increased by sodium periodate treatment in a concentration-dependent manner. The increase was not Cl- dependent, and so differed from the increased passive K+ uptake resulting from N-ethylmaleimide treatment. 4. HK sheep red cells treated with sodium periodate showed small increases in passive K+ uptake, and N-ethylmaleimide treatment used sequentially with sodium periodate resulted in further small increases in passive K+ uptake. 5. In LK sheep red cells the stimulation of active K+ transport by anti-L was impaired by 50% in cells treated with sodium periodate (2 mM) and was slightly lowered in cells treated with neuraminidase. 6. In LK sheep red cells inhibition of passive K+ transport by anti-L was not impaired by sodium periodate treatment (2 mM), or by neuraminidase treatment.

Animals↗

PubMed1987

Bovine monoclonal antibodies to the F5 (K99) pilus antigen of E. coli, produced by murine/bovine hybridomas.

Lymph node cells from calves immunized with purified pilus antigen of K99+ enterotoxigenic E. coli (ETEC) were fused with mouse myeloma (NSO) cells, and with non-Ig producing mouse/calf hybridomas or with a bovine Ig-producing mouse/calf/calf secondary hybridoma. Lines secreting bovine monoclonal IgG1 specific for K99 pilus antigen in an ELISA were obtained in each case. The two lines derived from xenohybridoma fusion partners have been secreting anti-K99 bovine monoclonal antibody for over one year in continual passage. None of the antibodies cross-reacted with other pilus types including K88, CFAI, CFAII, 987P or CP; they all inhibited agglutination of horse RBC (which have a K99 receptor) in the presence of K99 antigen; they showed positive fluorescence in an indirect binding assay on K99+ ETEC and inhibited K99+ ETEC adhesion to piglet enterocytes. These antibodies have potential prophylactic and therapeutic use in control and treatment of diarrhoea.

Animals↗

PubMed1987

L-antigen and active potassium transport in HK and LK red cells of Barbary sheep (Ammotragus lervia).

1. The potassium concentration in red cells of 21 Barbary sheep showed a bimodal distribution, with five animals of LK type (K+ conc. 30-45 mM) and 16 of HK type (K+ conc. 80-95 mM). 2. Evidence is presented that both Lp and Ll antigens are present on LK Barbary sheep red cells. 3. Active K+ transport in LK Barbary sheep red cells was stimulated 3-5 fold by sheep and goat anti-L. 4. Active K+ transport in HK Barbary sheep red cells was higher than in LK red cells. Five out of six HK animals tested showed no stimulation of active K+ transport with anti-L. One HK animal (2BA2) showed some stimulation of active K+ transport, and also absorbed some anti-L from antisera, suggesting that Lp antigen is present on these red cells. 5. Ouabain-sensitive ATPase in membranes from HK and LK Barbary sheep red cells showed kinetics characteristic of HK and LK membranes of domestic goats and sheep; the ATPase of LK Barbary sheep membranes sensitized with anti-L was stimulated 2-fold due to an alteration in the internal sodium and potassium affinities in favour of sodium.

Adenosine Triphosphatases↗

PubMed1987

Hormonal regulation of inhibin production by cultured Sertoli cells.

The hormonal regulation of inhibin production by cultured rat Sertoli cells was examined using a specific radioimmunoassay (RIA) which detects the N-terminal portion of the porcine inhibin alpha chain. FSH, but not hCG or prolactin caused a dose-dependent increase in inhibin production (EC50 for FSH = 2.4 ng/ml); both secreted and intracellular levels of inhibin were increased, but the secreted form represented one-half to two-thirds of the total. The FSH-stimulated production of inhibin was augmented by addition of a phosphodiesterase inhibitor, and could be mimicked by cholera toxin, forskolin, or dibutyryl cAMP, all of which are known to increase intracellular cAMP levels. Inclusion of either dihydrotestosterone or estradiol in the cultures had no effect on inhibin production, both in the presence and absence of FSH. Examination of the conditioned media from forskolin-treated Sertoli cells by gel filtration chromatography revealed a single peak of bioactive and immunoreactive inhibin, at a molecular weight of approximately 32,000, similar to that observed for the porcine and bovine follicular fluid inhibins. Thus, FSH activated the cAMP pathway to stimulate Sertoli cell production of inhibin which in turn suppresses pituitary FSH release to form a closed-loop feedback system.

Animals↗

PubMed1987

Murine/bovine hybridomas producing monoclonal alloantibodies to bovine red cell antigens.

In attempts to produce stable lines secreting bovine monoclonal antibodies, murine/bovine hybridomas (1 degree xenohybridomas) were selectively cultured in 8-azaguanine to derive HAT-sensitive lines that were then used as myeloma partners for further fusions with bovine lymphocytes. The resulting 2 degrees xenohybridomas were further selected to produce 3 degrees xenohybridomas. Four stable lines secreting bovine monoclonal antibodies recognizing blood group determinants X1 (an IgG1), E'2 (an IgM) and SU" (an IgGI) and another (an IgGI) as yet unidentified were produced from fusions of 2 degrees xenohybridomas with lymphocytes from calves that had been immunized with bovine red cells.

Animals↗

PubMed1987

Search for genetic variation in the blood of Norwegian dairy goats reveals a new polymorphism at the Hb beta A locus.

A total of 150 blood samples tested for serum albumin and transferrin and for red cell carbonic anhydrase, phosphoglucomutase, phosphogluconate dehydrogenase, phosphohexose isomerase, nucleoside phosphorylase, acid phosphatase, 'X'-protein and potassium concentration only showed variation at the 'X' protein and nucleoside phosphorylase loci. Isoelectric focusing over pH range 6-8 showed 145 samples to be of haemoglobin type A and 5 type AD. The haemoglobin A type was resolved into further types by separation over pH 6.9-7.5 in Immobiline polyacrylamide gels. A 2- or 4-band pattern was present in 136 of the samples; a genetic hypothesis based on four or more different haemoglobin A variants is proposed. 14 samples had a 3-, 5- or 6-band pattern. It is assumed that these are heterozygous for a variant of the II alpha gene.

Animals↗

PubMed1986

Relationship between cell age, glutathione and cation concentrations in sheep erythrocytes with a normal and a defective transport system for amino acids.

Percoll density gradients were used to separate sheep erythrocytes according to cell age. Erythrocytes with low intracellular levels of glutathione (GSH) caused by an inherited deficiency of the System C amino acid transporter exhibited large age-related decreases in GSH and K+ content. In contrast, there was no age-related loss of intracellular GSH in normal sheep erythrocytes or in sheep erythrocytes with low GSH resulting from a diminished activity of gamma-glutamylcysteine synthetase. Loss of GSH from amino acid transport-deficient erythrocytes was paralleled by the progressive appearance of Heinz bodies in the cells, indicating an increased susceptibility to oxidative damage.

Amino Acids↗

PubMed1986

Monoclonal antibodies to bovine blood group antigens.

Hybridomas were made by fusing mouse myeloma cells with spleen cells from mice immunized with bovine red cells. Sixteen cloned lines which secreted haemolytic monoclonal antibodies reacting with antigens in the A, B, F, Z and S blood group systems were established; one of the antibodies identified a new factor in the B system. Extensive tests on red cells from 1000 animals indicated that several of the antibodies are suitable for use in routine blood typing; others are of potential use for genetic studies of the bovine blood group systems.

Animals↗

PubMed1986

Hormonal regulation of granulosa cell inhibin biosynthesis.

The hormonal regulation of inhibin production by cultured granulosa cells from immature hypophysectomized, estrogen-treated rats was examined using a specific RIA which detects the N-terminal portion of the inhibin alpha-chain. The RIA measured bioactive inhibin of Mr about 32,000 in granulosa cell conditioned media fractionated by fast protein liquid chromatography. In the presence of 10(-7) M androstenedione, FSH stimulated inhibin production in a dose-dependent manner during a 2-day culture. Inclusion of a phosphodiesterase inhibitor decreased the EC50 for FSH from 2.6 to 0.8 ng/ml (n = 3). The stimulatory effect of FSH could be mimicked with forskolin (an adenyl cyclase activator) and with a cAMP analog, (Bu)2cAMP, consistent with FSH action mediated through a cAMP dependent pathway. Intracellular levels of inhibin were unmeasureable, suggesting that inhibin is not stored to any great extent by the granulosa cells. This finding was consistent with in vivo studies which showed that whereas FSH treatment for 2 days doubled serum inhibin levels when compared with basal levels, there was no increase in the concentration of extractable inhibin in ovarian tissue. Granulosa cells which had been exposed to 20 ng/ml FSH for 2 days to induce LH receptors produced inhibin in response to both LH and human CG during the subsequent 2-day culture, with the levels of inhibin equalling the amount inducible by FSH. In contrast, neither PRL nor terbutaline, a beta 2-adrenergic agonist, had any effect on inhibin production even though receptors for these hormones are also induced by FSH. GnRH was found to inhibit the FSH-stimulated production of inhibin (IC50, 10(-7) M), consistent with previous observations that GnRH can act at the ovarian level to inhibit granulosa cell differentiation. This inhibition by GnRH could be reversed by inclusion of a specific GnRH antagonist. On the other hand, another regulatory peptide, vasoactive intestinal peptide, slightly stimulated inhibin production. The effect of several growth factors was also tested. Insulin-like growth factor I raised not only FSH-stimulated inhibin levels, but basal levels as well. Insulin was also effective, but only at 100-fold higher concentration. Epidermal growth factor inhibited FSH-stimulated inhibin production (IC50 = 0.1 ng/ml), whereas fibroblast growth factor had no effect. Thus, granulosa cell inhibin secretion is regulated by FSH and LH but not by PRL, presumably via a cAMP-mediated pathway.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

Serum bioactive follicle-stimulating hormone during the human menstrual cycle and in hyper- and hypogonadotropic states: application of a sensitive granulosa cell aromatase bioassay.

A sensitive in vitro assay based on the stimulation of estrogen production by cultured rat granulosa cells was recently developed for the measurement of biologically active FSH. This bioassay system is specific for FSH, highly sensitive, and capable of measuring basal FSH levels in rat serum. The granulosa cell aromatase bioassay was improved by the use of additives known to enhance FSH activity and by pretreatment of serum with 12% polyethylene glycol to remove inhibitory substances. We applied this method to the measurement of bioactive FSH levels in serum samples from human subjects. As determined in daily blood samples during ovulatory menstrual cycles in seven women, bioactive FSH levels exhibited a pattern closely resembling that of immunoreactive FSH. The mean bioactive serum FSH levels were 29.9, 20.5, 39.2, and 14.8 mIU/ml for the early follicular phase, late follicular phase, preovulatory surge, and luteal phase, respectively. The bio- to immunoratio (B:I) throughout the menstrual cycle ranged from 1.4-3.4, with a mean of 2.5. The ratios for early follicular phase, late follicular phase, preovulatory surge, and luteal phase were 2.7, 2.3, 1.4, and 2.6, respectively. The correlation coefficient (r) of the serum FSH values obtained by bioassay and RIA was 0.91. FSH bioactivity was also measured in patients in each of the following categories with the following mean values: oral contraceptive pill users (undetectable), hypothalamic amenorrhea (18.7 mIU/ml; B:I, 2.6), premature ovarian failure (163 mIU/ml; B:I, 1.7), and postmenopausal women (191 mIU/ml; B:I, 1.6). These findings suggest that measurement of immunoreactive FSH levels correctly reflects the biological activity of FSH in serum of cycling women and patients in certain hyper- and hypogonadotropic states. The granulosa cell aromatase bioassay represents a new tool for future assessments of biologically active FSH in physiological and pathophysiological conditions.

Adult↗

PubMed1986

Antibodies to ovine lymphocytes exist in bovine alloantisera.

Forty-six percent of 149 reagents against class 1 antigens of the bovine major histocompatibility system reacted with lymphocytes from 1 or more sheep in a microlymphocytotoxicity test. The reactions fell into six groups. The majority of antisera defined an antigen present on both erythrocytes and lymphocytes. This antigen is probably the R blood group antigen and the reactions were unrelated to the presence of anticlass I activity and are probably due to the additional presence of antibodies of R specificity. The other antigens are not identical to any of the 14 red blood cell factors or seven lymphocyte antigens examined, nor did they correspond to any of the class I bovine lymphocyte antigens defined by the alloantisera.

Animals↗

PubMed1985

Characterization of normal, glutathione-deficient and arginase-deficient sheep erythrocytes by 1H-NMR spectroscopy.

Normal sheep erythrocytes as well as glutathione- (GSH-) deficient and arginase-deficient sheep erythrocytes have been characterized by 1H nuclear magnetic resonance spectroscopy. The GSH deficiency is a result of defective amino acid transport (lesion 1), diminished gamma-glutamylcysteine synthetase activity (lesion 2), or both (lesions (1 + 2)). 1H-NMR spectra of normal sheep erythrocytes are similar to those for human erythrocytes, and consist of resonances from a number of small intracellular molecules, including GSH. In contrast, the resonances for GSH in the GSH-deficient erythrocytes are much weaker, and strong resonances are observed for lysine, threonine and ornithine or arginine, depending on the arginase activity, in erythrocytes with lesion 1 and lesions (1 + 2). A comparison of the intensity of GSH resonances in spectra for normal and GSH-deficient erythrocytes with GSH levels determined spectrophotometrically following reaction with the nonspecific thiol reagent 5,5'-dithiobis(2-nitrobenzoate) (DTNB) indicates that either not all of the GSH determined with Ellman's reagent is free and observable by 1H-NMR or that not all of the thiol determined by Ellman's reagent is GSH. If the latter is the case, the GSH levels determined with Ellman's reagent for erythrocytes with lesions (1 + 2) are most affected, which might account for their high susceptibility to oxidative stress.

Alanine↗

PubMed1985

Sheep twin chimaeras with admixtures of red cell amino acid and potassium transport phenotypes.

A pair of sheep twins each had two populations of red cells. Population 1 was positive for antigens Aa, Ma and Mb, was low-potassium type, possessed an amino acid transport system and was lysine-negative phenotype. Population 2 was negative for antigens Aa, and Mb, was high-potassium type, lacked the amino acid transport system and was lysine-positive phenotype. Population 2 disappeared from both sheep over a period of 8 years.

Age Factors↗

PubMed1985

Cytogenetic and blood group studies of sheep/goat chimaeras.

Aggregation chimaeras were composed of quarter (or 1 cell) contributions from 4-cell blastocysts of sheep or goats, or of an 8-cell blastocyst of one species enveloped in three 8-cell blastocysts of the other. Gestation was in sheep or goat recipient females. Of the 10 living animals born, 3 were identified as interspecific chimaeras by body conformation and coat type among the 7 quarter/quarter aggregations and 1 among the 3 giant aggregates. Interspecific chimaerism was identified by cytogenetic study of umbilicus and blood lymphocytes respectively of 2 of these, one from each type of aggregate. Intraspecific sex chimaerism was found in 3 other animals; 2 were of giant aggregate origin, but the 1 of quarter/quarter origin must have acquired it by placental anastomosis with a twin conceptus. Tests using species-specific monoclonal antibodies and electrophoretic separation of haemoglobins and isoenzymes demonstrated sheep and goat erythrocytes in one giant aggregate chimaera; their relative proportions and those of the blood lymphocytes changed over a period of 31 months from approximately 60% goat and 40% sheep to more than 90% sheep. The plasma transferrins and amylases did not show similar relative changes from their predominantly goat-like character and, by implication, neither did their tissues of origin.

Animals↗

PubMed1985

Supraophthalmic carotid infusion for brain chemotherapy. Experience with a new single-lumen catheter and maneuverable tip.

A single-lumen catheter with a maneuverable tip which does not incorporate a balloon has been developed for supraophthalmic intracarotid infusion of chemotherapeutic agents for central nervous system neoplasms. Supraophthalmic carotid catheterization was accomplished in 48 (96%) of the first 50 consecutive infusions in which this catheter was used. None of the 31 patients who underwent this procedure developed optic neuropathy or loss of vision. Ten patients developed Marcus-Gunn pupils, ipsilateral to the infused carotid artery in two and contralateral to the infused carotid artery in eight. Thrombosis of the carotid artery occurred after infusion in one patient. Problems associated with the technique include a tendency for the catheter to retract proximally during infusion in some patients, and the necessity for surgical exposure of the carotid artery. The infusion technique protects the eye from the high-concentration first-pass of chemotherapeutic agents administered via the carotid artery. Since the tip of this catheter can be hydraulically guided, it may prove to be useful in other areas of transarterial neurosurgical procedures.

Antineoplastic Agents↗