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J B Burch

Publications and source records attributed to J B Burch.

54 records · Page 3Linked to original sources
PubMed1987

Developmental regulation of the estrogen receptor and the estrogen responsiveness of five yolk protein genes in the avian liver.

The magnitude of the expression of five yolk protein genes in the avian liver in response to exogenous estradiol is shown to be developmentally regulated. Though each of these yolk protein genes gains the capacity to respond to estradiol during embryonic development, we demonstrate that maximal responses for the different genes are achieved at distinct ages between 1 and 6 weeks after hatching. This observation prompted us to look for possible correlations between yolk protein gene expression and changes in the expression of estrogen receptors that might also occur after hatching. We discovered that indeed the maximal level of nuclear estrogen receptors (assayed following the administration of estradiol) increases progressively over this same period of development from approximately 1000 receptors per cell at 1 week after hatching to approximately 3500 receptors per cell at 6 weeks after hatching. The latter number represents the fully mature state, as comparable levels of receptors are present in the livers of egg-laying hens. Thus, though increases in the expression of estrogen receptors during embryonic liver development have previously been reported, our results indicate that the changes that occur after hatching are quantitatively far more significant to the developmental program for this transcription factor.

Age Factors↗
PubMed1986

A genetic analysis of nicotine effects on open field activity.

The genetics of the effects of nicotine on the open field activity of mice were studied using a 5 by 5 diallel cross. The five inbred strains used were: A, BALB, C57BL, DBA, and C3H. These strains differ both in basal open field activity as well as activity after injection of nicotine. Analysis of the results of baseline activity indicated that both additive and dominance variance affected the activity of the animals. The dominance was non-directional. Likewise, the responses observed after injection of 0.75 mg/kg nicotine displayed both additive and dominance components. However, after correcting the results for differences in basal activity, the dominance item was primarily directional. This directional dominance was towards a more intense response to the effects of the drug, that is, a decrease in open field activity.

Animals↗
PubMed1986

Chromatin structural transitions and the phenomenon of vitellogenin gene memory in chickens.

We have previously shown that the steroid hormone-mediated transcriptional activation of the chicken vitellogenin II gene (VTGII) in the liver is accompanied by a series of chromatin structural changes, including the formation of two sets of 5'-proximal nuclease-hypersensitive sites and the demethylation of a single 5'-flanking MspI site which lies within a region of DNA that recently has been shown by Jost and co-workers to specifically bind the estrogen receptor complex in vitro. To assay the stability and possible functional significance of these induced structural changes, we transiently activated the VTGII gene during embryonic development and then allowed the chickens to hatch and grow for various periods of time before analyzing their livers. By 7 weeks posthatching all of the induced 5'-flanking hypersensitive sites had decayed. Moreover, the loss of these sites occurred without consequence to the "memory effect," that is, these structural features did not need to be present in hormone withdrawn birds to allow this gene to be activated more rapidly in response to a secondary presentation of estradiol. Although the demethylation was more stable, it also appeared not to be the basis of the memory phenomenon. The birds that still exhibited memory after 25 weeks of hormone withdrawal were not more extensively demethylated within the receptor-binding site than were the birds which failed to show memory at this age. A similar uncoupling of these two parameters was also observed when embryos were first injected with submaximal doses of estradiol and then assayed 1 week after hatching; the chickens which acquired memory were not demethylated to any greater extent than those which did not acquire memory. Other parameters that may be relevant to memory are discussed.

Animals↗
PubMed1984

Identification and sequence analysis of the 5' end of the major chicken vitellogenin gene.

We have precisely determined the positions of the first three exons for the major chicken vitellogenin gene (VTG II) by a combination of S1 nuclease protection, primer extension and DNA sequencing experiments. In addition, we have determined the nucleotide sequences of the 5' flanking nuclease hypersensitive sites that we have previously shown are induced during the estrogen mediated activation of the VTG II gene in liver (1). One of these sites is found to be nearly identical to the enhancer core sequence of SV40. A computer assisted analysis of the DNA sequences upstream from the VTG II gene has revealed four short (7 to 9 base pair) sequence elements that are present in similar positions flanking the other major estrogen inducible gene for liver, very low density apolipoprotein II (apoVLDL II). For VTG II, these sequences are located between two of the induced nuclease hypersensitive sites that are liver specific. Sequences homologous to one element, located approximately 100 base pairs upstream from the mRNA cap sites of the VTG II and apoVLDL II genes, are also observed for three estrogen inducible genes that are expressed in the oviduct, although for each of these genes the sequence falls further upstream, between -220 and -200. We suggest that these conserved sequences may be important in mediating the tissue specific responses of these genes to estrogen.

Animals↗
PubMed1984

Chronic scopolamine treatment and brain cholinergic function.

Scopolamine was either continuously infused or injected once daily into C3H mice. Chronic infusion resulted in mice that were supersensitive to the hypothermia and tremor produced by the muscarinic agonist, oxotremorine. Chronic scopolamine infusion did not alter brain acetylcholinesterase (AChE) or choline acetyltransferase (ChAT) activities but it did produce an increase in brain muscarinic receptors, as measured by quinuclidinyl benzilate (QNB) binding. The maximal increase in QNB binding was seen at the 0.2 mg/kg/hr dose. Further increase in dose resulted in a return to control QNB binding in all brain regions studied except cortex. These animals were still supersensitive to oxotremorine, suggesting a dissociation between receptor number and response to agonist. Animals injected once daily for 10 days with 5 mg/kg exhibited an increase in QNB binding while no increase was seen at 20 mg/kg/day. Chronic oxotremorine infusion resulted in tolerance to the hypothermia-producing effects of oxotremorine. This was accompanied by a decrease in brain QNB binding. Coinfusion of scopolamine with oxotremorine blocked both the tolerance development and receptor changes. These experiments demonstrate that chronic scopolamine treatment can elicit an increase in brain muscarinic receptors which is accompanied by supersensitivity to agonists. However, this effect is not clearly dose related, and a strict relationship between receptor number and agonist response does not exist.

Acetylcholine↗
PubMed1984

A diallel analysis of nicotine-induced hypothermia.

The hypothermic responses of mice that occur after acute injection of nicotine show genetic influences. The body temperatures of mice of all five strains tested decreased after injection of either 0.75 or 1.5 mg/kg nicotine, but mice of the C3H strain were less affected than were those of the DBA, BALB, or C57BL strains. Mice of the A strain were the most sensitive to nicotine's effects. Genetic effects on nicotine-induced hypothermia were further examined using a five-by-five diallel cross. Additive genetic variance occurred at both nicotine doses. Substantial dominance variance, including directional dominance toward a large hypothermic response induced by injection of a low dose of nicotine (0.75 mg/kg), suggested that an intense response to a low drug dose is adaptive. The directional dominance was absent after treatment with a high dose (1.5 mg/kg) of the drug. Epistatic interactions occurring in crosses involving C57BL mice were pronounced.

Alleles↗
PubMed1983

Temporal order of chromatin structural changes associated with activation of the major chicken vitellogenin gene.

The major chicken vitellogenin (VTG II) gene is marked at the chromatin level in hormone-responsive cells by a set of nuclease-hypersensitive sites that exist prior to hormone-mediated expression. When the gene is transcriptionally activated in the liver by treatment with 17 beta-estradiol, three additional hypersensitive sites are induced, which map near the 5' end of the gene. Two of these sites are stable and, moreover, appear to be propagated to daughter cells after hormone is withdrawn. In contrast, the third site (located 0.7 kb upstream from the gene) is observed only during periods of hormone treatment, perhaps due to a transient interaction with hormone receptor complex at this site. Whereas none of these nuclease-hypersensitive sites is observed in erythrocytes, brain, or fibroblasts, a subset is present in differentiated oviduct cells that have estrogen receptors, but do not express VTG II.

Animals↗
PubMed1983

Genetics of nicotine response in four inbred strains of mice.

The effects of nicotine on five behavioral and physiological measures were determined in four inbred mouse strains (BALB, C57BL, DBA and C3H). In addition, the binding characteristics of nicotine and alpha-bungarotoxin, two ligands which appear to label different nicotinic receptors, were measured in seven discrete brain regions, as well as in whole brain. A number of differences in response to nicotine were found among the four inbred strains. Whereas nicotine depressed open-field activity of BALB, C57BL and DBA mice in a dose-dependent manner, low doses of nicotine increased locomotor activity in C3H mice. The doses of nicotine tested reduced Rotarod performance in DBA and C57BL mice but not in C3H and BALB mice. All four strains displayed a dose-dependent decrease in body temperature after nicotine administration. The BALB mice were more sensitive to the drug than were the C3H, whereas the effects on C57BL and DBA mice were intermediate. All four strains showed a transient increase in respiration only after a high (2.0 mg/kg) nicotine dose. No dose of nicotine was found to have an effect on the startle response after auditory stimulation in three of the strains; only the C3H mice exhibited enhanced startle after nicotine was administered. Differences in DL-[ 3H ]nicotine binding among the seven brain regions were noted in each strain, but no differences among strains were observed. The IC50 values for inhibition of this binding by nicotine did not differ among brain regions within any strain or within any region among strains. Similarly, nicotine inhibited alpha-[125I]bungarotoxin binding with equal potency in all brain regions of each of the four strains; however, the binding of this ligand was significantly lower in the midbrain and hippocampus of DBA mice than it was in these regions in the other three strains. Thus, genetic factors influence response to nicotine, but variation in response is not easily explained by differences in brain nicotinic receptors.

Animals↗
PubMed1982

Tissue-specific and species-specific monoclonal antibodies to avian red cell nuclear proteins.

In order to identify potential red cell-specific regulatory proteins and to define additional red cell-specific markers, we have isolated a series of hybridomas that produce monoclonal antibodies that react with nuclear preparations from avian red blood cells. Several antibodies have been well characterized for their tissue- and species-specific reactions by using solid-phase and protein-transfer radioimmunoassays as well as immunofluorescence. These antibodies should allow isolation and characterization of individual nuclear proteins that are tissue and species specific and may prove useful for the study of gene expression in the erythropoietic system. The majority of the well-characterized antibodies appear to have tissue-specific properties. However, three antibodies react with all tested chicken tissues; one of these reacts with multiple peptides in a pattern that varies qualitatively and quantitatively between the tissues. This may reflect a common protein domain or modification that is used in several different tissues for similar functions but is nevertheless present in an overall protein framework that is tissue specific. Because the major fraction of the hybridomas initially produced is tissue specific, we presume that the immune system selects for tissue-specific determinants. This property of the immune system may prove to be a useful general feature of this type of analysis.

Animals↗
PubMed1981

Iodination of nucleosomes at low ionic strength: conformational changes in H4 and stabilization by H1.

Radioactive iodine has been used to probe the relative reactivities of nucleosomal H4 tyrosine residues under various conditions of subphysiological ionic strength. We observe that tyrosine 72 of H4, which is not reactive over the range 20-150 mM NaCl, becomes the predominant site of iodination within H4 when nucleosomes are subjected to conditions of very low ionic strength. Conversely, the other H4 tyrosine residues, which are reactive within nucleosomes in solutions of moderate ionic strength (20-150 mM NaCl), become nonreactive when the ionic strength is reduced. This "flip-flop" in the H4 iodination pattern is the manifestation of a reversible nucleosomal conformational change. A method is presented which enables the conformational status of H4 in nucleosomes to be determined by simply electrophoresing the histones on a Triton gel after probing nucleosomes with labeled iodine. Using this technique, we demonstrate that the presence of H1 on one side of the nucleosome stabilizes a histone core domain on the other side so that all four tyrosines of H4 are maintained in their physiological ionic strength conformation even under conditions of no added salt.

Animals↗
PubMed1981

Genetic influences on cholinergic drug response.

Three mouse strains were tested for oxotremorine effects on open-field activity and body temperature. Open-field activity was depressed less severely in C3H mice than in C57BL, which were less affected than DBA. While no differences in the hypothermic effects of oxotremorine were observed 15 min after injection, the time courses of the drug effect on body temperature indicated that C3H were less affected than C57BL or DBA. No differences in the activities of acetylcholinesterase of choline acetyltransferase were found among the three strains in cortex, cerebellum, hindbrain (pons-medulla), or total midbrain. While no differences in muscarinic receptor levels were found in the four large brain areas, finer dissection of the midbrain revealed small differences in total receptor number in striatum, hippocampus, and remaining midbrain areas. C3H mice exhibited greater QNB binding than C57BL and DBA mice in striatum; DBA mice exhibited greater QNB binding in hippocampus than C57BL (C3H mice were not different from either strain); and C57BL had less QNB binding than the other two strains in midbrain. All of these differences were small (20% or less). No differences in KD were observed. The inhibition of receptor binding by either oxotremorine or nicotine was the same in all strains, but the IC50 for oxotremorine varied from region to region. While behavioral differences in the effects of oxotremorine are clear, there is no obvious biochemical explanation for these differences.

Acetylcholinesterase↗
PubMed1980

The roles of H1, the histone core and DNA length in the unfolding of nucleosomes at low ionic strength.

Calf thymus nucleosomes exhibit two different and independent hydrodynamic responses to diminishing salt concentration. One change is gradual over the range 40 to 0.2 mM Na+ and is accompanied by decreases in contact-site cross-linking efficiency. The other change is abrupt, being centered between 1 and 2 mM Na+. We found only one abrupt change in sedimentation rate for particles ranging in DNA content fom 144 to 230 base pairs. This response to decreasing ionic strength is similar for particles of both 169 and 230 base pairs. Core particles (144 base pairs) exhibit a somewhat diminished response. The abrupt change is blocked by formaldehyde or dimethylsuberimidate cross-linking. The blockage by dimethylsuberimidate demonstrates that the abrupt conformational change requires the participation of the core histones. H1 completely blocks the abrupt but not the gradual conformational change. Thus H1 uncouples the different responses to low ionic strength and exerts an important constraint on the conformational states available to the nucleosome core.

Animals↗
PubMed1979

Specific histone-histone contacts are ruptured when nucleosomes unfold at low ionic strength.

The ordered unfolding of the nucleosome core within chromatin at low ionic strengths has been studied. The results show that, when nuclei are lysed gently in solutions of very low ionic strength, their constituent nucleosomes rupture at a major H2B-H4 binding site but remain unperturbed at the site of the H2A-H2B interaction. These conclusions are based on data which show that at least four separate but closely spaced H2B-H4 contacts, identifiable by contact-site cross-linking in intact nuclei, are broken when nuclei are suspended in very dilute buffers. Appropriate controls on purified nucleosomes monomers demonstrate that the H2B-H4 contacts being broken are indeed intranucleosomal. Sedimentation of nucleosomes in the ultracentrifuge at various salt concentrations reveals that a significant conformational transition occurs in the range of ionic strength over which the H2B-H4 binding site ruptures.

Animals↗
PubMed1979

Semihistone protein A24 replaces H2A as an integral component of the nucleosome histone core.

The semihistone protein, A24, was shown to be a stable minor component of purified salt-washed nucleosome core particles. A24 was also shown to become integrated into nucleohistone during reconstitution in a manner characteristic of the core histones. Purified A24 in solution was shown to exhibit the same specificity of interaction with histone H2B as is exhibited by histone H2A. We conclude that A24 in chromatin replaces H2A as a stable integral component of certain nucleosome histone cores.

Animals↗
PubMedDate not supplied

A genetic analysis of ethanol, pentobarbital, and methyprylon sleep-time response.

The sleep-time responses to ethanol, pentobarbital, and methyprylon were assessed in various generations derived from crossing the long-sleep (LS) and short-sleep (SS) mouse lines in order to assess whether common or different genes regulate response to these agents. The LS and SS mice were selectively bred for differences in duration of ethanol-induced sleep time. Ethanol and pentobarbital responses segregate in a different fashion into F1 and F2 generations derived from the LS and SS lines, indicating different genic control and probably different mechanisms of action for these two agents. Ethanol and methyprylon response segregated similarly but fewer genes seem to influence methyprylon response. These results support the notion that water-soluble depressants have common mechanisms of action.

Anesthetics↗