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T L Miller

Publications and source records attributed to T L Miller.

At least 37 records · Page 2Linked to original sources
PubMed1999

The rat growth hormone-releasing hormone receptor gene: structure, regulation, and generation of receptor isoforms with different signaling properties.

The interaction of GHRH with membrane-bound receptors on somatotroph cells of the anterior pituitary is an important step in the regulation of GH synthesis and secretion. The identification of a G protein-coupled receptor for GHRH has made it possible to investigate the pathway by which GHRH regulates pituitary somatotroph cell function. To initiate an analysis of the mechanisms regulating expression and function of the GHRH receptor, the structure of the gene and its promoter region were analyzed. The coding sequence of the rat GHRH receptor gene is contained within 14 exons spanning approximately 15 kb of genomic DNA. Four transcription start sites are located within 286 bp upstream of the initiation codon. The 5' flanking region of the GHRH receptor gene acts as a functional promoter in rat pituitary tumor GH3 cells, and basal promoter activity is enhanced in GH3 and COS7 cells by cotransfection of an expression construct encoding the pituitary-specific transcription factor Pit-1. The rat GHRH receptor gene is subject to at least 1 alternative RNA processing event that generates 2 receptor isoforms differing by 41 amino acids within the third intracellular loop (IL) of the protein. The short isoform of the GHRH receptor is predominant in pituitary cells. The MtT/S pituitary tumor cell line was found to express the GHRH receptor, and different populations of these cells produce predominantly the long or short isoforms of the receptor messenger RNA, suggesting that the alternative splicing can be regulated. Functional analysis of the two GHRH receptor isoforms demonstrates that both bind GHRH, but only the short isoform signals through a cAMP-mediated pathway. Neither receptor isoform is able to stimulate calcium mobilization from internal stores after GHRH treatment. Our findings indicate that the pituitary-specific transcription factor Pit-1 is involved in the somatotroph-specific expression of the GHRH receptor gene and that functionally distinct receptor proteins are generated by an alternative RNA processing mechanism.

Amino Acid Sequence↗
PubMed1999

Children's perceptions of parental drinking: the eye of the beholder.

OBJECTIVE: Children learn about alcohol and about how to drink through modeling experience, in part. Modeling is typically studied by asking parents to describe their drinking behavior. However, children's perception of parents' drinking may differ from the way parents describe it. This study examined the degree to which children's perceptions and parents' reports agreed. METHOD: A sample of 177 grade-school children and their parents was drawn from a public school in Kentucky. Children completed questionnaires inquiring about their perceptions of the quantity, frequency and the positive and negative consequences of their parents' drinking. Their parents completed similar questionnaires describing their own drinking and its consequences. RESULTS: As hypothesized, first and second grade children's perceptions of parents' drinking were unrelated to parents' self-reports: Most of these children perceived their parents as nondrinkers even though parents reported drinking. Also as hypothesized, children's perceptions and parents' reports were significantly correlated for third through sixth grade students. However, there was a great deal of reliable, but unshared variance between these older children's perceptions and parents' reports. Children's perceptions and parents' reports were consistently quite different, even when both child and parent described the parent as a drinker. CONCLUSIONS: Studies of modeling influences on children regarding drinking should assess children's perceptions of their parents' behavior rather than parents' self-reports.

Age Factors↗
PubMed1998

Design and synthesis of [2-(8,9-dioxo-2,6-diazabicyclo[5.2.0]non-1(7)-en-2-yl)-ethyl]phosphonic acid (EAA-090), a potent N-methyl-D-aspartate antagonist, via the use of 3-cyclobutene-1,2-dione as an achiral alpha-amino acid bioisostere.

The diazabicyclic amino acid phosphonate 15, [2-(8,9-dioxo-2,6-diazabicyclo[5.2.0]non-1(7)-en-2-yl)ethyl]phosphonic acid, was identified as a potent NMDA antagonist. It contains the alpha-amino acid bioisostere 3,4-diamino-3-cyclobutene-1,2-dione and an additional ring for conformational rigidity. Compound 15 was as potent as CGS-19755 (5) in the [3H]CPP binding assay, the stimulated [3H]TCP binding assay, and the NMDA-induced lethality model in mice. A single bolus dose of compound 15, administered intravenously following permanent occlusion of middle cerebral artery (MCA) in the rat, reduced the size of infarcted tissue by 57%. Structure-activity relationship (SAR) studies have indicated that the six- and eight-membered ring derivatives had diminished activity and that the two-carbon side chain length was optimum for NMDA receptor affinity. Substitution on the ring was found to be counterproductive in the case of sterically demanding dimethyl groups and of no consequence in the case of an H-bonding hydroxyl group. Replacement of the phosphonic acid group by either a carboxylic acid or a tetrazole group was unproductive. The potent bicyclic NMDA antagonists were synthesized efficiently by virture of their achiral nature and the ease of vinylgous amide formation from squaric acid esters. Compound 15, being a unique NMDA antagonist structural type with a favorable preclinical profile, may offer advantages over existing NMDA antagonists for the treatment of neurological disorders such as stroke and head trauma. Compound 15 is currently under clinical evaluation as a neuroprotective agent for stroke.

Animals↗
PubMed1998

Phylogenetic analysis of Methanobrevibacter isolated from feces of humans and other animals.

Comparative 16S rRNA gene sequence and genomic DNA reassociation analyses were used to assess the phylogenetic relationships of Methanobrevibacter fecal isolates. The 16S rRNA gene sequences of Methanobrevibacter smithii strain PS and the human fecal isolates B181 and ALI were essentially identical, and their genomic DNA reassociated at values greater than 94%. The analysis of 16S rRNA sequences of the horse, pig, cow, rat, and goose fecal isolates confirm that they are members of the genus Methanobrevibacter. They had a high degree of sequence similarity (97-98%) with the 16S rRNA gene of M. smithii, indicating that they share a common line of descent. The 16S rRNA genes of the horse and pig isolates had 99.3% sequence similarity. Sequence analysis of the 16S rRNA gene of the sheep fecal isolate showed that it formed a separate line of descent in the genus Methanobrevibacter. Genomic DNA reassociation studies indicate that the horse, pig, cow, and goose fecal isolates represent at least three new species. The horse and pig isolates were the only animal isolates that had > 70% genomic DNA reassociation and represent strains of a single species. The cow, goose, and sheep isolates had little or no genomic DNA reassociation with M. smithii or with each other. The relationship of the rat isolate to the other animal isolates was not determined. An evaluation of the relationship of 16S rRNA gene sequence similarity and genomic DNA reassociation of Methanobrevibacter and other methanogenic archaea indicated that genomic DNA reassociation studies are necessary to establish that two methanogenic organisms belong to the same species.

Animals↗
PubMed1998

Like mother, like child: intergenerational patterns of age at first birth and associations with childhood and adolescent characteristics and adult outcomes in the second generation.

A 30-year follow-up of 1,758 inner-city children and their mothers in the Pathways to Adulthood Study revealed significant associations in transgenerational timing of age at 1st birth between mothers and their daughters and sons. Intergenerational age patterns were associated with the children's family and personal characteristics during childhood and adolescence and self-sufficiency at age 27-33. Continuity in teenage parenthood was associated with family and personal characteristics unfavorable for optimal child development and successful adult outcomes. Delay in 1st parenthood to age 25 or older was associated with significantly greater odds of more favorable environmental and developmental characteristics and greater adult self-sufficiency. The authors concluded that age at 1st birth of both mothers and children contributes, but in subtly different ways for daughters and sons, to the children's development and adult self-sufficiency.

Adolescent↗
PubMed1998

Changes in production of ethanol, acids and H2 from glucose by the fecal flora of a 16- to 158-d-old breast-fed infant.

Microbes in the adult human colon ferment dietary substrates chiefly to acetic, propionic and butyric acids and CO2, H2 and CH4. How this fermentation evolves after microbial colonization of the neonate is unknown. We examined the fermentation of glucose by fecal suspensions of a breast-fed infant from d 16 to 158 and found that the fermentation changed with age. Acetate, ethanol, succinate, lactate, formate and H2 were formed up to 117 d of age. Production of succinate, lactate, formate and H2 ceased after 117 d and acetate production increased. Butyrate and propionate were minor products up to 117 d. Afterwards, there was a slight increase in propionate production with no change in butyrate formation. Acetate was always the major product of glucose fermentation by the fecal suspensions. Approximately the same amounts of ethanol were formed throughout the study period. The fermentations were similar to fermentations of Escherichia coli and streptococci through 117 d. Nuclear magnetic resonance (NMR) analysis of the acetate formed from 1-13C- and 3-13C-glucose showed that the dominant fermentation pathway used by the colonic microbes switched from the Embden-Meyerhof-Parnas pathway at 16 d of age to the Bifidobacterium pathway at 158 d of age. An increase in the contribution of the Bifidobacterium fermentation to the overall colonic fermentation after 117 d would account for the increase in the formation of acetate from glucose. Chemical and NMR analyses of products of fecal fermentations from two other breast-fed infants <1 mo old were similar to those of the infant examined between 16 and 158 d.

Acetates↗
PubMed1998

NMR detection of 13CH313COOH from 3-13C-glucose: a signature for Bifidobacterium fermentation in the intestinal tract.

The gastrointestinal tracts of breast-fed infants are colonized more easily with bifidobacteria than are those of formula-fed infants. Colonization is thought to reduce infant diarrhea. Amendments to formulas that improve colonization by bifidobacteria are being actively investigated. Colonization studies almost invariably require measurements of the concentration of the bifidobacteria in feces to assess their importance in the colon. We investigated the use of nuclear magnetic resonance (NMR) analysis of products of fermentations of 1- and 3-13C-glucose to evaluate the importance of bifidobacteria in the colonic ecosystem. Bifidobacteria use a unique pathway of hexose catabolism to produce primarily acetate and lactate. The fermentation yields 3 mol of acetate from 2 mol of glucose. Two of the acetates are formed from C1 and C2 of glucose and the third is formed entirely from C3 of glucose. We first employed high resolution NMR to verify the pathway used by a pure culture of Bifidobacterium bifidum. The major products of fermentation of 1- and 3-13C-glucose were acetate and lactate. Most of the 13C from 3-13C-glucose was in 13CH313COOH with equal enrichment in the methyl and carboxyl groups. The 13C-acetate from 1-13C-glucose was almost entirely enriched in the methyl of acetate and no 13CH313COOH was produced. NMR analysis of glucose fermentation by the colonic flora of a 158-d-old strictly breast-fed infant showed production of 13CH313COOH from 3-13C-glucose. The amount of 13CH313COOH formed established that the Bifidobacterium pathway was the major pathway used for glucose fermentation by this infant's colonic microbes.

Acetic Acid↗
PubMed1998

Decompression sickness risk in rats by microbial removal of dissolved gas.

We present a method for reducing the risk of decompression sickness (DCS) in rats exposed to high pressures of H2. Suspensions of the human colonic microbe Methanobrevibacter smithii were introduced via a colonic cannula into the large intestines of the rats. While the rats breathed H2 in a hyperbaric chamber, the microbe metabolized some of the H2 diffusing into the intestine, converting H2 and CO2 to methane and water. Rate of release of methane from the rats, which was monitored by gas chromatography, varied with chamber H2 pressure. This rate was higher during decompression than during compression, suggesting that during decompression the microbe was metabolizing H2 stored in the rats' tissues. Rats treated with M. smithii had a 25% (5 of 20) incidence of DCS, which was significantly lower (P < 0.01) than the 56% (28 of 50) incidence of untreated controls, brought on by a standardized compression and decompression sequence. Thus using a microbe in the intestine to remove an estimated 5% of the body burden of H2 reduced DCS risk by more than one-half. This method of biochemical decompression may potentially facilitate human diving.

Animals↗
PubMed1997

Endoscopy of the upper gastrointestinal tract as a diagnostic tool for children with human immunodeficiency virus infection.

OBJECTIVE: The purpose of this study was to determine the prevalence of upper gastrointestinal tract lesions in children with human immunodeficiency virus (HIV) infection who undergo endoscopy of the upper gastrointestinal tract and to identify important clinical predictors of abnormal endoscopic results. METHODS: All HIV-infected children who underwent endoscopy and were followed at Children's Hospital, Boston, from January 1985 to August 1994 were studied. The main outcome measure was endoscopic results, which were categorized into observational, histologic, and microbiologic findings. Potential predictors included height, weight, nutritional interventions, HIV disease stage, CD4 T-lymphocyte count, medications, active infections, and indications for endoscopy. RESULTS: Forty-three endoscopies in unique patients are reported. Most children had advanced HIV infection (67% acquired immunodeficiency syndrome, mean CD4 T-lymphocyte count z score = -2.71, weight z score = -2.04). An abnormal endoscopic finding was discovered in 93% of children and confirmed by histologic, microbiologic, or a combination of these studies in 72% of children. Thirty-five percent of children had an opportunistic pathogen identified endoscopically; 65% of these pathogens were previously undiagnosed. Observational findings often were poor indicators of histologic and microbiologic abnormalities. Independent predictors of abnormal histologic findings include younger age at endoscopy (odds ratio (OR) = 1.16 per year, 95% confidence interval (CI) (1.02, 1.33)) and guaiac-negative stools (OR = 16.7, 95% CI (1.92, 142.9)). Independent predictors of finding a pathogen at the time of endoscopy include a greater number of indications for endoscopy (OR = 2.6 per indication, 95% CI (1.3, 5.3)) and diagnosis of acquired immunodeficiency syndrome (OR = 16.4, 95% CI (1.3, 213)). No other gastrointestinal, nutritional, or immunologic parameters were significantly predictive of endoscopic outcomes. Medical management was changed in 70% of children because of the endoscopic findings. CONCLUSIONS: Endoscopy is a useful tool to direct therapy against peptic and infectious disorders of the upper gastrointestinal tract in children with HIV infection. Specific gastrointestinal symptoms are not useful predictors of abnormal results.

Bacterial Infections↗
PubMed1997

Nutritional status and cardiac mass and function in children infected with the human immunodeficiency virus.

Malnutrition, skeletal muscle wasting, and changes in cardiac muscle mass and function have been described in children infected with the human immunodeficiency virus (HIV). This report analyzes the relation of nutritional status to cardiac muscle mass and function in HIV-infected children. Thirty-six children with symptomatic HIV infection underwent simultaneous anthropometric and echocardiographic evaluations before antiretroviral therapy or supplemental feedings. Nutritional measurements included weight, height, triceps skinfold thickness, and arm muscle circumference. Cardiac measurements included left ventricular mass, contractility, end-diastolic dimension, fractional shortening, blood pressure, and heart rate. In a cross-sectional analysis, children infected with HIV were significantly below age-adjusted standards for height (P = 0.0001), weight (P = 0.0001), triceps skinfold thickness (P = 0.001), and arm muscle circumference (P = 0.04). Left ventricular mass normalized to body surface area was below standard, but contractility was normal. Correlation analyses found an inverse relation between left ventricular mass and weight z score (r = -0.45, P = 0.01), height z score (r = -0.47, P = 0.006), and arm muscle circumference percentile (r = -0.51, P = 0.003). An inverse relation was also found between heart rate and weight z score (r = -0.47, P = 0.007) and arm muscle circumference percentile (r = -0.46, P = 0.007). In malnourished children with HIV infection, a paradoxical relation exists between nutritional status and cardiac muscle mass. The inverse relation between heart rate and nutritional status may suggest altered metabolic rates with possible increased sympathetic tone.

Anthropometry↗
PubMed1997

Acarbose enhances human colonic butyrate production.

Earlier studies suggest that butyrate has colonic differentiating and nutritional effects and that acarbose increases butyrate production. To determine the effects of acarbose on colonic fermentation, subjects were given 50-200 mg acarbose or placebo (cornstarch), three times per day, with meals in a double-blind crossover study. Fecal concentrations of starch and starch-fermenting bacteria were measured and fecal fermentation products determined after incubation of fecal suspensions with and without added substrate for 6 and 24 h. Substrate additions were cornstarch, cornstarch plus acarbose and potato starch. Dietary starch consumption was similar during acarbose and placebo treatment periods, but fecal starch concentrations were found to be significantly greater with acarbose treatment. Ratios of starch-fermenting to total anaerobic bacteria were also significantly greater with acarbose treatment. Butyrate in feces, measured either as concentration or as percentage of total short-chain fatty acids, was significantly greater with acarbose treatment than with placebo treatment. Butyrate ranged from 22.3 to 27.5 mol/100 mol for the 50-200 mg, three times per day doses of acarbose compared with 18.3-19.3 mol/100 mol for the comparable placebo periods. The propionate in fecal total short-chain fatty acids was significantly less with acarbose treatment (10.7-12.1 mol/100 mol) than with placebo treatment (13.7-14.2 mol/100 mol). Butyrate production was significantly greater in fermentations in samples collected during acarbose treatment, whereas production of acetate and propionate was significantly less. Fermentation decreased when acarbose was added directly to cornstarch fermentations. Acarbose effectively augmented colonic butyrate production by several mechanisms; it reduced starch absorption, expanded concentrations of starch-fermenting and butyrate-producing bacteria and inhibited starch use by acetate- and propionate-producing bacteria.

Acarbose↗
PubMed1997

Glucocorticoids regulate pituitary growth hormone-releasing hormone receptor messenger ribonucleic acid expression.

Glucocorticoids regulate GH synthesis and secretion by influencing both hypothalamic and pituitary function. With respect to GH-releasing hormone (GHRH), an important GH secretagogue, glucocorticoids are reported not only to suppress hypothalamic GHRH expression but also to augment pituitary responsiveness to GHRH. To investigate further this latter observation, we have determined the effects of this steroid on expression of the GHRH receptor (GHRH-R) gene in the rat pituitary in vivo and in pituitary cells in vitro. Adult male rats were adrenalectomized or sham operated and treated with s.c. implants of cholesterol or corticosterone. Adrenalectomized animals showed substantially reduced pituitary GHRH-R mRNA levels, when compared with untreated sham-operated animals. Conversely, administration of corticosterone increased pituitary GHRH-R mRNA levels in intact, as well as adrenalectomized rats. We also analyzed the effects of the synthetic glucocorticoid, dexamethasone, on GHRH-R mRNA expression in cultured rat anterior pituitary cells. GHRH-R mRNA was significantly increased by dexamethasone, with a maximal response observed in the presence of 100 nM hormone. This dose of dexamethasone substantially elevated GHRH-R mRNA after 6 h, 12 h, and 24 h of treatment. Dexamethasone did not increase GHRH-R mRNA in the presence of the transcriptional inhibitor actinomycin D, indicating that the predominant effect of the hormone is to increase transcription of the GHRH-R gene. These data demonstrate that GHRH-R mRNA levels are directly stimulated by glucocorticoids, both in the presence and absence of hypothalamic influences, providing a probable explanation for the ability of this steroid to alter pituitary responsiveness to GHRH.

Adrenal Glands↗
PubMed1997

Adolescent childbearing revisited: the age of inner-city mothers at delivery is a determinant of their children's self-sufficiency at age 27 to 33.

OBJECTIVES: Data from recent interviews with 1758 inner-city children, born between 1960 to 1965 and followed with their mothers in the Pathways to Adulthood Study to age 27 to 33 years, were used to address two related questions. 1) Is maternal age, across the reproductive age range, a determinant of child's adult outcome? and 2) Do covariates of maternal age at delivery reduce or eliminate the effect of maternal age on child's adult outcome? METHODS: An intergenerational life course model of development identified significant maternal and child characteristics at birth associated with the child's self-sufficient outcomes in adulthood: education (more than or equal to a high school diploma); financial independence of public support; and delay of first birth until age 20 or older. Bivariate and multiple logistic regression techniques were used to identify independent relationships between dependent and independent variables and to adjust the outcomes to compensate for the effect of possible confounding of maternal age at delivery by maternal education, parity, poverty status, and the child's race and gender. RESULTS: Each covariate was independently associated with maternal age at delivery. Adjustment for their effects reduced, but did not eliminate, the association between maternal age at birth and the child's outcome at age 27 to 33 years. As a group, children of the oldest mothers (>/=25 years of age) had the most favorable outcomes, and those of teenage mothers (<20 years of age) had the least favorable outcomes; 22% of daughters and 6% of sons of the oldest mothers versus 38% and 18%, respectively, of the youngest mothers became teenage parents. CONCLUSION: The mother's age at delivery is an independent determinant of the child's adult status.

Adolescent↗
PubMed1996

The growth-hormone-releasing hormone receptor: signal transduction, gene expression, and physiological function in growth regulation.

We now summarize key issues that we have investigated and highlight additional areas that need to be addressed. We are interested in two basic aspects of the GHRH pathway, those occurring in the brain, involving the synthesis of GHRH, and those occurring in the pituitary, involving signaling by GHRH. We have a long-term interest in the activity and regulation of the hypothalamic neurosecretory cells that synthesize GHRH. With respect to human disease, it is interesting that, despite the primal role played by GHRH in growth-hormone secretion, no mutations in the GHRH gene have yet been identified in association with growth disorders. Focusing on the downstream signaling components of the GHRH pathway, we now know quite a lot about the structure of the GHRH receptor and about some aspects of the signal transduction pathways that mediate the actions of GHRH. With respect to human disease, we have found that in an animal model, the little mouse, a mutation of the GHRH receptor results in growth-hormone deficiency and a dwarf phenotype, and there are ongoing attempts in several laboratories to try to identify similar inactivating mutations in the GHRH receptor in patients with isolated growth-hormone deficiency. Conversely, there is also substantial interest in whether activating mutations in this receptor might be identified in patients with growth-hormone-secreting pituitary tumors. We are also interested in whether there are additional receptors that might mediate some of the extrapituitary actions of GHRH. Finally, a major direction we are taking in the laboratory at the present time is toward understanding the developmental, hormonal, and tissue-specific regulation of the GHRH receptor gene.

Amino Acid Sequence↗
PubMed1996

Analysis of human breast cancer nuclear proteins binding to the promoter elements of the c-myc gene.

The expression of the c-myc gene is essential for the proliferation of both hormone-dependent and -independent human breast cancer cells. The regulation of c-myc gene expression in MCF-7 (hormone-dependent, estrogen-receptor (ER)-positive) and MDA MB 231 (hormone-independent, ER-negative) human breast cancer cells differs, with the c-myc gene of MCF-7 but not MDA MB 231 cells being regulated at the transcriptional level by estrogen. We have shown previously that the DNAase I hypersensitive (DH) sites in the c-myc chromatin of hormone-dependent and -independent human breast cancer cells were similar, with the exception of DH site II2. DH site II2, which maps near the P0 promoter, was less sensitive in hormone-dependent than in hormone-independent cells. As DH sites generally indicate the presence of sequence-specific DNA-binding proteins, we undertook a study to identify the nuclear proteins isolated from MCF-7 and MDA MB 231 cells that bound to the P0 and P2 promoter regions of the c-myc gene in vitro. The studies presented here provide evidence that Sp1 and/or Sp1-like proteins bind to the P0 and P2 promoter regions of the c-myc gene of MCF-7 and MDA MB 231 cells. Furthermore, evidence is presented for the presence of several previously unidentified sequence-specific DNA-binding proteins binding to these promoters. The DNA-binding activities of these latter proteins differed in the nuclear extracts of the MCF-7 and MDA MB 231 human breast cancer cells.

Base Sequence↗