PubMed Health⌕ Search

Biomedical subjects

C A Harrington

Publications and source records attributed to C A Harrington.

At least 19 recordsLinked to original sources
PubMed1992

Basal forebrain neurons and memory: a biochemical, histological, and behavioral study of differential vulnerability to ibotenate and quisqualate.

The differential vulnerability of basal forebrain cells to ibotenate (IBO) or quisqualate (QUIS) was investigated in rats. IBO was also coinjected with cystine (CYS) or zinc (Zn). Cortical choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) activity, neurotensin receptors, and high-affinity choline uptake sites were quantified in conjunction with radioimmunoassays for neurotensin, substance P, and somatostatin; immunocytochemistry for neurotensin-, somatostatin-, Leu-enkephalin-, and ChAT-positive cells; and in situ hybridization histochemistry of somatostatin, substance P, and enkephalin mRNAs. Compared with the performance of controls, continuous alternation performance in a T maze of IBO+Zn or IBO+CYS rats was better than that of IBO rats, whereas the performance of QUIS rats was unimpaired. Of those neurotransmitter systems examined, only ChAT-immunoreactive cells were vulnerable to IBO or QUIS. However, cholinergic cell loss did not correlate with impaired performance.

Animals↗
PubMed1990

Steroid hormone regulation of ribosomal RNA in rat hypothalamus: early detection using in situ hybridization and precursor-product ribosomal DNA probes.

In the female rat, behavioral and endocrine aspects of reproduction are controlled, in part, by the action of the steroid hormone estradiol on several regions of the brain, including the ventrolateral portion of the ventromedial hypothalamus (VL-VMN) and the arcuate nucleus of the hypothalamus (ARC). Quantitative assessment of the effects of estradiol on the regulation of ribosomal RNA in rat hypothalamus was accomplished in this study by tandem in situ hybridization experiments with 2 ribosomal DNA probes specific to the initial transcript (precursor) or mature, stable (product) rRNA. This novel approach allowed the regulation of RNA processing by steroid hormones to be analyzed in the individual neuron, a particularly important concern in heterogeneous tissue such as the brain. Estradiol was administered subcutaneously to ovariectomized rats for 15 min, 30 min, or 2 hr, or a discontinuous schedule of 2 hr on/7 hr off/2 hr on. Levels of precursor and product rRNA were measured in VL-VMN and ARC neurons using a computerized image-analysis system. Significant increases in the levels of precursor rRNA were observed only in the VL-VMN as early as 30 min after hormone exposure, with a doubling in the amount of precursor rRNA occurring at 2 hr. No changes in product rRNA were observed in either brain region at these early times. These data, in conjunction with our previous findings of increases in product rRNA after longer hormone exposure times, lead us to conclude that rRNA gene transcription is activated in rat hypothalamic neurons within 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Tyrosine hydroxylase mRNA in the neurons of the tuberoinfundibular region and zona incerta examined after gonadal steroid hormone treatment.

The dopamine-producing neurons of the tuberoinfundibular region are known targets of estrogen and progesterone, and are of considerable neuroendocrine importance. To determine the anatomical distribution, and number of cells that contain tyrosine hydroxylase (TH) mRNA in the tuberoinfundibular region and other regions of the brain we carried out in situ hybridization on sections prepared from ovariectomized female rats given either oil vehicle, or estrogen, or estrogen plus progesterone. The intensity of label per cell was assessed to compare the relative amount of mRNA found per cell among TH-mRNA containing cells. [3H]cRNA probes to the rat TH sequence were used. Autoradiograms demonstrated the presence of TH-mRNA in the cytoplasm of cells in the arcuate and periventricular nuclei, zona incerta, substantia nigra, and the adrenal medulla. The number and anatomical distribution of cells that contained TH-mRNA was identical to the number and distribution of cells previously demonstrated by others to contain TH immunoreactivity. In the arcuate and periventricular nuclei, compared to treatment with estrogen alone, estrogen plus progesterone did lead to a statistically significant decrease in the number of TH mRNA-containing cells we could detect. No alteration in the mean number of grains per cell, among cells detected as containing TH-mRNA was found in any group. In contrast, these same hormone treatments had no effect on the number TH-mRNa producing cells we could detect in the zona incerta. Most of the cells in the zona incerta are found within the same tissue sections as arcuate/periventricular cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1988

Quantitation of thiothixene in plasma by high-performance thin-layer chromatography and fluorometric detection.

A specific and sensitive assay procedure to measure thiothixene (Navane) in plasma has been developed and used to measure plasma concentrations in patients receiving thiothixene. The procedure involves in situ fluorescent detection after separation by high-performance thin-layer chromatography. Fluorescent detection permits a limit of detectability of approximately 0.1 ng/ml in plasma and the coefficient of variation is less than 6% at 2 ng/ml. Thirty samples may be processed through the entire procedure in less than 6-h period and up to 60 samples may be simultaneously spotted and chromatographed with a larger-capacity spotter and plate. Plasma levels (n = 62) drawn 10-12 h after dosage ranged from 0 to 42 ng/ml from dosages of 4-100 mg/day.

Chromatography, Thin Layer↗
PubMed1987

Identification and cell type specificity of the tyrosine hydroxylase gene promoter.

Genomic DNA encoding the rat tyrosine hydroxylase (TH) gene was isolated from a lambda phage library using a nick-translated fragment from a cDNA clone for rat TH. We have determined the initiation site for TH RNA synthesis and have sequenced 1100 bases of the primary transcript and 5' flanking region. The 5' end of the transcript is the same in several rat tissues in which TH is expressed as well as in rat pheochromocytoma cells (PC). RNA prepared from PC cells that had been stimulated with dexamethasone also mapped to the same transcription start site. Sequence upstream from the initiation site contains the canonical TATA box, but no apparent CAAT box. When a portion of the 5' flanking region of the TH gene (-773 to + 27) is fused to the chloramphenicol acetyltransferase (CAT) gene, it promotes expression of CAT in pheochromocytoma cells and GH4 cells, but not in two neural tumour lines, RT4-D and B103, nor in several non neural cell lines. This suggests that this region of the TH gene has features that confer tissue-restricted expression on the TH promoter.

Adrenal Gland Neoplasms↗
PubMed1987

Transcriptional regulation of the tyrosine hydroxylase gene by glucocorticoid and cyclic AMP.

Glucocorticoid and cyclic AMP increase tyrosine hydroxylase (TH) activity and mRNA levels in pheochromocytoma cultures. The transcriptional activity of the TH gene, as measured by nuclear run-on assay, is also increased when cultures are treated with the synthetic glucocorticoid dexamethasone or agents that increase intracellular cyclic AMP, such as forskolin and 8-BrcAMP. Both inducers effect transcriptional changes within 10 min after treatment and are maximal after 30 min for forskolin and after 60 min for dexamethasone. The 5' flanking sequences of the TH gene were fused to the bacterial gene chloramphenicol acetyltransferase (CAT), and the hybrid gene was transfected into pheochromocytoma cultures and GH4 pituitary cells. In both cell lines, a region of the TH gene containing bases -272 to +27 conferred induction of CAT by cyclic AMP, but not by glucocorticoid. The same results were found when a region of the TH gene containing -773 to +27 was used. Thus, the sequences required for induction of TH by cyclic AMP are contained within 272 bases of 5' flanking sequence, but sequences sufficient for glucocorticoid regulation are not contained within 773 bases.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Transcription of spacer sequences flanking the rat 45S ribosomal DNA gene.

The transcriptional activity of spacer sequences flanking the rat 45S ribosomal DNA (rDNA) gene were studied. Nascent RNA labeled in in vitro nuclear run-on reactions hybridized with both 5' and 3' spacer regions. The highest level of hybridization was seen with an rDNA fragment containing tandem repeats of a 130-base-pair sequence upstream of the 45S rRNA initiation site. Synthesis of RNA transcripts homologous to this internally repetitious spacer region was insensitive to high levels of alpha-amanitin, suggesting that it is mediated by RNA polymerase I. Analysis of steady-state RNA showed that these transcripts were present at extremely low levels in vivo relative to precursor rRNA transcripts. In contrast, precursor and spacer run-on RNAs were synthesized at similar levels. This suggests that spacer transcripts are highly unstable in vivo; therefore, it may be the process of transcription rather than the presence of spacer transcripts that is functionally important. Transcription in this upstream rDNA region may be involved in regulation of 45S rRNA synthesis in rodents, as has been suggested previously for frog rRNA. In addition, the presence of transcriptional activity in other regions of the spacer suggests that some polymerase I molecules may transcribe through the spacer from one 45S gene to the next on rodent rDNA.

Animals↗
PubMed1986

Effects of smoking on haloperidol and reduced haloperidol plasma concentrations and haloperidol clearance.

Plasma concentrations of haloperidol and its reduced metabolite (reduced haloperidol) were investigated in cigarette smokers (N = 23) and nonsmokers (N = 27). Steady-state plasma concentrations were obtained 12 h post bedtime dose. Haloperidol and reduced haloperidol concentrations were determined by RIA. Reduced haloperidol was separated by selective succinylation and liquid chromatography. Patients were clinically assessed with the Clinical Global Impression Scale (CGIS). Smokers had significantly lower haloperidol and reduced haloperidol plasma concentrations than nonsmokers (P less than 0.01, P less than 0.05). Clearance of haloperidol was significantly greater in smokers compared to nonsmokers (P = 0.0052). CGIS assessments did not show significant differences between smokers and nonsmokers. Plasma concentrations should be carefully monitored when patients either start or stop smoking.

Adult↗
PubMed1986

In situ hybridization detection of estradiol-induced changes in ribosomal RNA levels in rat brain.

In this study, quantitative assessment of estradiol (E2)-induced changes in levels of ribosomal RNA within brain regions concentrating the hormone was accomplished by in situ hybridization with nick-translated tritiated ribosomal DNA probes and use of a computer-based image analysis system. Ovariectomized rats were either implanted with estradiol capsules for 6 h, 24 h, or 15 days, or sham-implanted under the same time course to serve as controls. The mean number of grains, somal area, and grain density of neurons within three E2-concentrating brain regions, the ventrolateral portion of the ventromedial and the arcuate nuclei of the hypothalamus (VL-VMN and ARC, respectively) and the corticomedial nucleus of the amygdala (AMY) were determined. In the VL-VMN and ARC, levels of rRNA were significantly increased after 6 h of E2 treatment (70% and 30%, respectively) and after 24 h of E2 treatment (60% and 62%, respectively). However, these effects on rRNA levels in VL-VMN and ARC were not observed after prolonged exposure of 15 days to the hormone. Neuronal hypertrophy was present only after 24 h of E2 treatment in the VL-VMN and ARC (32% and 14%, respectively). No changes were found in the AMY. As an additional internal control, measurements were also collected from the dorsomedial portion of the VMN (DM-VMN), a region with few E2-concentrating neurons. No changes in any of the parameters were found in DM-VMN at any time after exposure to the hormone. By extending the in situ hybridization technique to the quantitative level, these findings demonstrate differential estrogenic regulation of a known gene product, rRNA, in rat brain that is temporally and regionally specific.

Animals↗
PubMed1985

Quantification of reduced haloperidol and haloperidol by radioimmunoassay.

A radioimmunoassay for reduced haloperidol and haloperidol has been developed by using a simple derivatization-separation step prior to assay with an antibody cospecific for both compounds. The detection limit of the assay is less than 25 pg and shows no cross reactivity to other metabolites. The intraassay coefficient of variation for reduced haloperidol and haloperidol were 9.0 and 8.2% respectively and the interassay coefficients of variation were 9.0 and 10.6% respectively at 5-10 ng/ml. As many as 30 patient samples can be analyzed for both compounds in a single day.

Chromatography, Liquid↗
PubMed1984

Quantitative determination of chlorpromazine and thioridazine by high-performance thin layer chromatography.

An assay for quantitation of chlorpromazine and thioridazine in patient plasma is developed. The procedure utilizes high-performance thin layer chromatography for separation and in situ absorption densitometry for quantitation. Depending upon the HPTLC plate size, 30 to 60 samples may be processed in less than 6 hr, with an intra-assay coefficient of variation of less than 4%. The procedure can be used to measure as little as 10 ng/ml of drug in plasma, well below expected concentrations in patients receiving these medications. Investigations of extraction procedures, sample application procedures, chromatographic conditions, sample derivatization, and in situ absorption densitometry are described.

Chlorpromazine↗
PubMed1984

Haloperidol and reduced haloperidol plasma levels in selected schizophrenic patients.

The first measurements of haloperidol (HL) and its reduced metabolite hydroxyhaloperidol (RH) in plasma versus clinical response in five chronic schizophrenic patients are reported. HL and RH were measured by a radioimmunoassay with a low coefficient of variation. Patients were selected based on poor response or the need for high dosage and were rated with the Clinical Global Impression Scale. Daily HL dosage range was 0.5 to 1.5 mg/kg. HL plasma concentrations ranged from 14 to 98 ng/ml. RH plasma concentrations ranged from 10 to 319 ng/ml. Four patients did not respond to HL therapy; two of these improved dramatically when switched to fluphenazine. The four nonresponding patients had higher RH than HL concentrations. RH seems to be present in plasma in significant concentrations, and further investigation of the relationships of RH and HL plasma levels versus response is needed.

Adult↗
PubMed1983

Genomic organization of rat rDNA.

A detailed restriction map was determined for a 10.9 KB region that contains the initiation site for 45S pre-rRNA and the first 1.7 KB of the 18S rRNA coding region. When the restriction pattern of the cloned rDNA was compared with that of total rat DNA, the rDNA regions of both Sprague-Dawley and BD-9 rats were identical to each other and to that of the cloned rDNA. However, both strains exhibit a major polymorphism consisting of an insertion of 0.9 KB of DNA in the nontranscribed spacer between 0.29 KB and 1.8 KB upstream from the 45S RNA initiation site. This region consists of tandem repeats approximately 130 base pairs in length. These repeats contain large poly T tracts and are similar in sequence to analogous elements 5' to the origin of mouse rRNA transcription. Regions containing highly repetitious DNA sequences were located at sites 2.8 KB and 4.3 KB upstream from the initiation site. The repetitive sequence at 2.8 KB from the initiation site anneal to a known Alu-equivalent type 2 sequence derived from the second intron of the rat growth hormone gene.

Animals↗
PubMed1983

Identification and sequence of the initiation site for rat 45S ribosomal RNA synthesis.

The transcription initiation site for rat 45S precursor ribosomal RNA synthesis was determined by nuclease protection mapping with two single-strand endonucleases. S1 and mung bean, and one single-strand exonuclease, ExoVII. These experiments were performed with end-labeled ribosomal DNA from double-stranded pBR322 recombinants and from single-stranded M13 recombinants. Results from experiments using both kinds of DNA and all three enzymes showed that the 5' end of 45S RNA mapped to a unique site 125 bases upstream from the Hind III site in the ribosomal DNA gene. The DNA surrounding this site (designated +1) was sequenced from -281 to +641. The entire sequence of this region shows extensive homology to the comparable region of mouse. This includes three stretches of T residues in the non-coding strand between +300 and +630. Two sets of direct repeats adjacent to these T-rich regions are observed. Comparison of the mouse and human ribosomal DNA transcription initiation sites with the rat sequence reported in this paper demonstrates a conserved sequence at +2 to +16, CTGACACGCTGTCCT. This suggests that this region may be important for the initiation of transcription on mammalian ribosomal DNAs.

Animals↗
PubMed1983

Norepinephrine causes alpha 1-adrenergic receptor-mediated decrease of phosphatidylinositol in isolated rat liver plasma membranes supplemented with cytosol.

When purified rat liver plasma membranes were incubated with norepinephrine, rat liver cytosol, and Ca2+, the amount of membrane-bound phosphatidylinositol was reduced by up to 50%. The levels of other major membrane phospholipids underwent negligible change. The decrease in phosphatidylinositol levels was not observed if norepinephrine was omitted or cytosol was absent. The disappearance of phospholipid persisted when soluble Ca2+ was depleted by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The decrease was prevented by phentolamine, benextramine, and prazosin, but not by sotalol. The results show that norepinephrine elicits a specific alpha 1-adrenergic receptor-mediated breakdown of phosphatidylinositol in isolated plasma membranes which is dependent on the presence of cytosol.

Animals↗