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Biomedical subjects

B Baker

Publications and source records attributed to B Baker.

At least 109 records · Page 6Linked to original sources
PubMed1989

Antagonism of xylazine hydrochloride sedation in raptors by yohimbine hydrochloride.

The mean time to initial reversal response (MTIRR) and the mean time to perching (MTP) were measured in 34 raptors sedated with xylazine hydrochloride with dosages ranging from 1.0 to 20 mg/kg intravenously (i.v.) and 2.5 to 20.0 mg/kg intramuscularly (i.m.). Yohimbine hydrochloride, given i.v. (0.2 mg/kg), 30 min after the injection of the xylazine, shortened the MTIRR and MTP compared to the controls. No adverse effects were noted due to the use of yohimbine. Yohimbine appeared to be a safe and effective antagonist for xylazine sedation in raptors.

Animals↗
PubMed1989

Unusual complications of antithyroid drug therapy: four case reports and review of literature.

Two cases of propylthiouracil-associated acute hepatitis, one case of fatal methimazole-associated hepatocellular necrosis and one case of propylthiouracil-associated lupus-like syndrome are described. The literature related to antithyroid drug side effects and the mechanisms for their occurrence are reviewed and the efficacy and complications of thyroidectomy and radioiodine compared to those of antithyroid drugs. It is concluded that in most circumstances 131I is the therapy of choice for hyperthyroidism.

Adult↗
PubMed1988

Characterization of the maize transposable element Ac by internal deletions.

We have used the ability of Ac to transpose in tobacco to determine which Ac sequences are required for transposition, using a phenotypic assay for Ac excision from an NPTII gene in which excisions of Ac result in calli resistant to the antibiotic kanamycin (Baker et al., 1987). Here we show that deletion of the Ac DNA which encodes the untranslated leader of the Ac transcript does not prevent Ac excision. A deletion which removes 110 bp including the first 75 bp of long open reading frame prevents Ac excision in tobacco cells. However, it will excise in tobacco cells previously transformed with Ac indicating that deletion of the region prevents the synthesis of a product required for Ac excision. Deletion of the Ac sequences between bp 44 and bp 92 or from bp 75 to bp 181 abolishes, or strongly reduces, transposition in cells which are already transgenic for an active Ac element. This indicates that these deleted elements have lost sequences which are required for the transposon to respond to the transposase, when the enzyme is produced in trans. We also describe a tobacco strain transformed with a Ds element stably inserted wtihin an NPTII gene. This strain is Km and was retransformed with a construct containing the open reading frame (ORF) of the 3.5-kb Ac transcript expressed from a plant promoter. Expression of the cDNA construct promotes excision of the Ds element. These data suggest that the 3.5-kb transcript of Ac encodes the only Ac product required for transposition, i.e. the transposase function.

Journal Article↗
PubMed1988

Endotoxaemia in racehorses following exertion.

Endotoxins (lipopolysaccharides-LPS) and anti-endotoxin IgG antibodies were measured in racehorses before and after races of 1,000, 2,000 and 2,800 m. Results show that the mean plasma concentration of endotoxin increased significantly (p less than 0.02) while the anti-LPS IgG concentration decreased significantly (p less than 0.005) in all horses following the races. Pre-race and post-race anti-LPS IgG levels in racing-fit racehorses were significantly higher than in untrained horses (p less than 0.05). The possibility therefore exists that training-induced stress leads to leakage of LPS into the systemic circulation which results in self-immunisation against LPS. The effects of plasma LPS and anti-LPS IgG concentrations on performance of racehorses require further studies.

Animals↗
PubMed1987

Phenotypic assay for excision of the maize controlling element Ac in tobacco.

We describe a phenotypic assay designed to detect excision of the maize controlling element Ac from a selectable marker gene, neomycin phosphotransferase II (NPT II). An NPT II gene which expresses kanamycin resistance in tobacco cells, and contains a unique restriction enzyme site in the untranslated leader region, was constructed. Ac, or a defective Ac element (Ac big up tri, open), was inserted into the leader region of this gene. The transposon insertions inactivated the NPT II gene as determined by transient NPT II expression assays. The three plasmids were inserted into the T DNA of Agrobacterium tumefaciens Ti plasmid vectors, and transferred to tobacco protoplasts. The transformed protoplasts were selected with 100 or 200 microg/ml kanamycin. Protoplasts transformed by the NPT II gene interrupted by Ac formed 25% as many calli resistant to 100 or 200 microg/ml kanamycin as protoplasts transformed by the uninterrupted NPT II gene. Protoplasts transformed by the NPT II gene interrupted by Ac big up tri, open did not form any calli resistant to 200 microg/ml of kanamycin when transformed under similar conditions. Southern blot hybridization analyses of seven kanamycin-resistant calli or plants obtained after transformation by the NPT II gene interrupted by Ac revealed that in all cases Ac had excised, restoring the structure of the NPT II gene. This assay is therefore useful to monitor the activity of a transposable element such as Ac and to define the regions of this element involved in transposition activity.

Journal Article↗
PubMed1987

An investigation into the role of ganglion cells in the regulation of division and death of other retinal cells.

The patterns of cell death and division are described in the normal postnatal rat retina and following transection of the optic nerve on the day of birth. Optic nerve transection on the day of birth results in the rapid degeneration of the ganglion cells. Mitosis at the outer retinal surface ceases first in the temporal retina, then in the nasal retina and becomes progressively more restricted to peripheral regions. Mitotic activity was not affected by the loss of ganglion cells. Cell death takes place in a wave passing from the ganglion cell to the inner nuclear to the outer nuclear layer. The time course of cell death is not affected by the loss of ganglion cells following optic nerve transection, and there is no significant increase in the number of cells which degenerate in the inner nuclear layer. The effects of removing a major postsynaptic target of local circuit neurones appears to be less pronounced than has been reported for relay neurones.

Age Factors↗
PubMed1987

The Parental Bonding Instrument: factorial structure.

The Parental Bonding Instrument was administered to 49 schizophrenic out-patients attending a depot injection clinic. Subjects were instructed to rate each of their parents as they remembered them in their first 16 years. Principal components analyses followed by orthogonal varimax rotations were performed separately for mothers and fathers. The results suggested that the instrument is measuring two dimensions of parental characteristics; namely, care and overprotection. The findings lend further support to the internal structure of the instrument. The implications of the results for the prediction of relapse in schizophrenics and the expressed emotion construct are discussed.

Adult↗
PubMed1986

Transposition of the maize controlling element "Activator" in tobacco.

Transposition of the maize autonomous controlling element Activator (Ac) and a nonautonomous derivative, Dissociation (Ds), was investigated in tobacco cells. Tobacco protoplasts were transformed with Ti-plasmid vectors that contained Ac or Ds flanked by short maize wx gene sequences. The structures of the elements and surrounding wx and T-DNA sequences were investigated in nine Ac and five Ds tobacco transformants by digestion with restriction enzymes, Southern blotting, and hybridization using specific probes. In four of the nine Ac transformed lines, Ac had excised from its original position in the T-DNA and inserted at new sites in the tobacco genome. Ds did not excise from its original T-DNA position in any of the transformants examined. Two Ac fragments and cellular flanking sequences were cloned from a line of tobacco in which Ac had transposed. Fragments, comprised of sequences flanking the newly integrated Ac elements, were used as hybridization probes to normal tobacco DNA and to the tobacco DNA from which they were isolated. The Ac copies were integrated into repetitive tobacco DNA sequences. Two tobacco fragments containing empty Wx donor sites were cloned from the DNA of the same Ac transformant and sequenced. Both sequences are among the types of excision products observed to result from Ac-catalyzed excision events in maize. Our results indicate that the maize controlling element Ac is capable of self-catalyzed transposition in tobacco.

Journal Article↗
PubMed1986

Studies of the structure and functional organization of foreign DNA integrated into the genome of Nicotiana tabacum.

In transgenic plants obtained either by Agrobacterium tumefaciens-mediated transformation or by direct DNA transfer, the structure of integrated chimeric donor DNA remains stable during vegetative proliferation, during sexual transmission, and under various selection conditions. We correlate the level of expression of the introduced gene in independent transformants and their offspring with the particular arrangement and modification of their integrated DNAs. Genetic analysis of transgenic plants shows that the chimeric gene is transmitted in a Mendelian fashion to the F1 and F2 progeny as a single dominant trait. Deviations from the expected segregation pattern are discussed with respect to different levels of gene activity. We compare the gene activity in heterozygotes versus homozygotes, and show variation in activity between plants regenerated independently from the same transformed callus. Cotransformation studies with two physically unlinked and partly homologous plasmids carrying two different marker genes indicate that they are physically linked after integration into the host genome.

Gene Expression Regulation↗
PubMed1985

Nervous control of mucin secretion into human bronchi.

Pieces of ferret trachea and human bronchi were mounted in Ussing chambers and given [35S]sulphate as a radiolabelled precursor of mucous glycoproteins (mucins). The output of 35S bound to macromolecules was studied as an index of mucin secretion. In the ferret trachea, electrical field stimulation increased the rate of mucin secretion. Tetrodotoxin (10(-7) M or 10(-6) M) abolished this effect. Pilocarpine (25 microM) stimulated the output of mucins from human bronchus. Atropine (10(-5) M) abolished this effect. Electrical field stimulation of human bronchus stimulated mucin secretion. Tetrodotoxin (10(-6) M) abolished this effect. Field stimulation in the presence of either atropine (10(-5) M) or atropine with l-propranolol (10(-5) M) and phentolamine (10(-5) M) caused no stimulation of mucin secretion rate. Some bronchi were treated with noradrenaline (10(-5) M) for 1 h to allow the adrenergic nerves to take up transmitter. Even in these, atropine prevented the effect of field stimulation. We conclude that activity in cholinergic nerves can stimulate mucin secretion in the bronchi in man. Our results provide no evidence that the adrenergic nerves or non-adrenergic, non-cholinergic nerves have a direct action on bronchial secretory cells in man.

Adult↗
PubMed1985

Effect of thyroid hormone excess on action, secretion, and metabolism of insulin in humans.

To determine the effect of thyroid hormone excess on insulin secretion, metabolism and action in humans, we examined intravenous glucose tolerance, glucose-induced insulin secretion, insulin clearance, monocyte insulin receptor binding, and the dose-response characteristics for the effects of insulin on glucose production, uptake, oxidation, and nonoxidative disposal in 10 normal volunteers for 14 days before and after oral administration of triiodothyronine (T3) in doses that increased plasma T3 to levels observed in spontaneous thyrotoxicosis (P less than 0.001). After T3 postabsorptive plasma glucose (P less than 0.05) and insulin (P less than 0.05) both increased; intravenous glucose tolerance was unaffected, but plasma insulin responses were increased (P less than 0.01); basal glucose production, uptake, and oxidation all increased (all P less than 0.05), whereas nonoxidative glucose disposal was unaffected (P = NS); monocyte insulin receptor binding increased (P less than 0.01) due to increased receptor affinity (P less than 0.05); and receptor number was not significantly altered (P = NS). Insulin clearance was increased. Insulin-induced suppression of glucose production was impaired (Km 22 +/- 3 vs. 37 +/- 7 microU/ml, P less than 0.02); maximal insulin-induced glucose uptake (10.7 +/- 0.6 vs. 13.0 +/- 0.9 mg X kg-1 X min-1, P less than 0.001) and oxidation (3.41 +/- 0.30 vs. 5.34 +/- 0.59 mg X kg-1 X min-1, P less than 0.001) were increased without a significant change in Km. However, submaximal rates of nonoxidative glucose disposal and glucose uptake were inappropriately low for the increased insulin receptor binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Subcutaneous versus intramuscular growth hormone therapy: growth and acute somatomedin response.

To determine the optimal route of growth hormone administration, a comparison was made of the acute somatomedin response and chronic growth response to either intramuscular or subcutaneous growth hormone in 20 children with growth hormone deficiency. None of the children had received growth hormone for at least 2 weeks prior to their random selection to receive growth hormone by either the subcutaneous (N = 11) or intramuscular (N = 9) route. Plasma samples for determination of levels of insulin-like growth factors I and II (IGF-I and IGF-II) were obtained prior to therapy and 20 hours after the first and fourth of four daily injections of growth hormone. Growth rate and growth hormone antibody levels were determined before and after 6 months of therapy. IGF-I levels tripled in both treatment groups after four days of growth hormone injections, whereas IGF-II levels nearly doubled, with no significant difference between the intramuscular or subcutaneous group. After 6 months of therapy, there was no significant difference in growth rate and only two patients had developed growth hormone antibodies. Both patients and parents expressed a preference for the subcutaneous method. The identical rises in the IGF-I and IGF-II levels following a brief course of either subcutaneous or intramuscular injections of growth hormone, the similar growth rates, the low incidence of antibody development, and the preference for the subcutaneous route all suggest that the subcutaneous route is the method of choice for chronic growth hormone therapy.

Adolescent↗