Biomedical subjects

D Carter

Publications and source records attributed to D Carter.

At least 19 recordsLinked to original sources

PubMed2006

Right precordial leads and lead aVR at exercise electrocardiography: does it change test results?

BACKGROUND: A recent study on exercise testing (ET) suggested that ST-segment changes in the right precordial leads (RPL) may increase its sensitivity substantially. However, this study looked at a highly selected population of patients who all underwent thallium-201 scintigraphy and coronary angiography. The present study evaluated the clinical utility of ST-segment changes in the RPL and lead aVR in an unselected population of patients undergoing ET. METHODS: A total of 906 consecutive patients who received ET were included in the study. ET was done using the Bruce Protocol with a 12-lead electrocardiogram (ECG) substituting V(4)R and V(6)R for V(1) and V(6). Leads V(1) and V(6) were selected for omission as these two leads hardly ever manifest changes in isolation. Substituting two leads would obviate the need for a more complex recording system, thus improving clinical utility. RESULTS: On the basis of horizontal/downsloping ST-segment depression (STD) of 1.0 mm or more (the usually accepted criterion for a positive ET), 159 (17.5%) patients had a positive ET. In those patients with a negative ET (545 patients), 4 patients (0.7%) manifested STD and 5 patients (0.9%) manifested ST-segment elevation (STE) in leads V(4)R and/or V(6)R, respectively. Of note, 44.7% of the positive ET group had STE in lead aVR. CONCLUSION: The use of ST-segment changes in RPL during exercise stress testing does not appreciably change the test results of a standard ET. If one was to consider an additional marker, STE in aVR may be more useful, as it shows a stronger correlation with positive tests and does not require the recording of additional leads.

Electrocardiography↗

PubMed2004

Modulation of the mouse testis transcriptome during postnatal development and in selected models of male infertility.

The aim of this study is to develop an overview of genetic events during spermatogenesis using a novel, specifically targeted gonadal gene set. Two subtracted cDNA libraries enriched for testis specific and germ cell specific genes were constructed, characterized and sequenced. The combined libraries contain >1905 different genes, the vast majority previously uncharacterized in testis. cDNA microarray analysis of the first wave of murine spermatogenesis and of selected germ cell-deficient models was used to correlate the expression of groups of genes with the appearance of defined germ cell types, suggesting their cellular expression patterns within the testis. Real-time RT-PCR and comparison to previously known expression patterns confirmed the array-derived transcription profiles of 65 different genes, thus establishing high confidence in the profiles of the uncharacterized genes investigated in this study. A total of 1748 out of 1905 genes showed significant change during the first spermatogenic wave, demonstrating the successful targeting of the libraries to this process. These findings highlight unknown genes likely to be important in germ cell production, and demonstrate the utility of these libraries in further studies. Transcriptional analysis of well-characterized mouse models of infertility will allow us to address the causes and progression of the pathology in related human infertility phenotypes.

Animals↗

PubMed2003

Fluoxetine improves functional work capacity in women with premenstrual dysphoric disorder.

Interference with social and occupational functioning is a key criterion for premenstrual dysphoric disorder (PMDD) and distinguishes it from the less severe premenstrual syndrome (PMS). We conducted a post hoc analysis of the results of a previously reported study evaluating the efficacy of fluoxetine in the management of PMDD, to determine the extent to which women with PMDD perceived impairment in their functional work capacity during the luteal phase of their menstrual cycle. The effects of two doses of fluoxetine vs placebo in alleviating PMDD symptoms and restoring normal work capacity during this period were assessed. We measured baseline follicular vs luteal phase presence of 8 patient-rated functional work capacity-related symptoms on the Premenstrual Tension Scale-Self Rated in 320 women who met diagnostic criteria for late luteal phase dysphoric disorder, now known as PMDD. Women were then randomized to double-blind treatment with either fluoxetine 20 mg/d, fluoxetine 60 mg/d, or placebo daily for 6 menstrual cycles. All 8 work capacity-related symptoms were more likely to be present in the baseline luteal phase than in the baseline follicular phase. A statistically significant improvement from baseline to the average treatment score for the work capacity subscale was detected for both fluoxetine groups compared to the placebo group. This beneficial response to fluoxetine was evident by the first cycle of treatment. Our results demonstrate that fluoxetine at a relatively low dose of 20 mg/d quickly reduced symptoms that negatively affect work capacity and was well tolerated.

Adolescent↗

PubMed2003

Differential effects of metformin on bile salt absorption from the jejunum and ileum.

AIMS: The antidiabetic drug metformin is often associated with a small reduction in total circulating cholesterol, but the mechanism responsible is unknown. As bile salts contribute significantly to cholesterol homeostasis, this study has investigated the effect of metformin on the absorption of bile salts by the jejunum and ileum, and their transfer into bile. METHODS: Sodium-[1-14C]-glycocholate was administered into the jejunum or ileum of anaesthetized rats with and without metformin (250 mg/kg). Appearance of 14C-glycocholate in plasma and bile was followed for 150 min. RESULTS: Absorption of 14C-glycocholate from the ileum, which is a high-capacity active process, was 10-fold greater than absorption from the jejunum, which is mainly a passive process. Metformin increased threefold the absorption of 14C-glycocholate from the jejunum. Metformin similarly increased the appearance of jejunal 14C-glycocholate in plasma and bile. In contrast to the jejunum, absorption of 14C-glycocholate from the ileum was suppressed by more than half with metformin. This was associated with corresponding reductions of 14C-glycocholate in plasma and bile. DISCUSSION: Thus, metformin induced a large suppression of active bile salt absorption from the ileum compared with a small increase in passive absorption from the jejunum. This suggests that the ileal effect of metformin to reduce overall bile salt absorption could contribute to the modest cholesterol-lowering effect of this drug.

Animals↗

PubMed2002

Effects of metformin on bile salt transport by monolayers of human intestinal Caco-2 cells.

The antidiabetic biguanide metformin has been shown to increase faecal excretion of bile salts in type 2 diabetes. Cultured human intestinal Caco-2 cell monolayers provide a model of human enterocytes. These monolayers are used here to determine the effect of metformin on the secondary-active, sodium-linked transfer of 14C-glycocholate from the apical (brush border) to the basolateral (serosal) surface. During 24-h incubations, 10-2 mol/l metformin significantly reduced 14C-glycocholate transfer. This could not be attributed to alterations of monolayer integrity or Na+-K+ ATPase pump activity. For example, the secondary-active transport of glucose and proline was not interrupted, and the inhibitory effect of metformin on bile salt transport was additive to the inhibitory effect of ouabain. The results suggest that metformin can act directly on intestinal enterocytes to reduce the active transfer of bile salts by a mechanism that is independent of Na+-K+ ATPase activity.

Bile Acids and Salts↗

PubMed2002

Environmental sampling for Cryptococcus neoformans var. gattii from the Blue Mountains National Park, Sydney, Australia.

The environmental association of Cryptococcus neoformans var. gattii with decaying wood in tropical and subtropical regions of the world is well documented. In Australia, the yeast appears confined to certain species of Eucalyptus or very closely related tree species. In this study, we attempted to isolate C. n. var. gattii from different gum tree species in the Blue Mountains National Park. Out of 99 samples from 9 different tree species, only 3 yielded viable yeast colonies; 2 were from turpentine gums (Syncarpia glomulifera) and 1 was from a decayed stump of an unknown species. All of the colonized trees occurred in close proximity in urbanized areas of the Park, and all isolates shared identical DNA fingerprinting profiles. We suggest that domestic animal vectors may be responsible for the introduction and transmission of the yeast in this region, but that propagation and dispersal are very limited. This study indicates that C. n. var. gattii may occur on trees and in areas that were not previously expected to host it. However, the low incidence in the Blue Mountains National Park means this yeast is unlikely to pose any hazards to humans and animals living in or visiting this area.

Cryptococcus neoformans↗

PubMed2001

Breast carcinoma in situ: risk factors and screening patterns.

BACKGROUND: Risk factors associated with invasive breast cancer are well documented, but those associated with breast carcinoma in situ are not well defined. METHODS: We conducted a population-based, case-control study among female residents of Connecticut to identify risk factors for breast carcinoma in situ. Case patients, diagnosed with ductal carcinoma in situ (DCIS) (n = 875) or lobular carcinoma in situ (LCIS) (n = 123), were matched by 5-year age groups with control subjects (n = 999). Case patients were diagnosed between September 15, 1994, through March 14, 1998, and all subjects were between the ages of 20 and 79 years. Information on risk factors and cancer-screening history was collected by telephone interviews. Conditional logistic regression was used to determine odds ratios (ORs) for the association of these factors with the risk of DCIS and LCIS. RESULTS: Case patients with DCIS were more likely than control subjects to report a family history of breast cancer (OR = 1.48; 95% confidence interval [CI] = 1.19 to 1.85) or previous breast biopsy (OR = 3.56; 95% CI = 2.86 to 4.43). They also had fewer full-term pregnancies (OR = 0.86; 95% CI = 0.80 to 0.93) and were older at first full-term pregnancy (OR for being 20-29 years old relative to being <20 years old = 1.68; 95% CI = 1.17 to 2.43) and at menopause (OR for being > or =55 years old relative to being <45 years old = 1.71; 95% CI = 1.05 to 2.77). DCIS case patients were more likely than control subjects to have had a mammographic examination (OR = 2.46; 95% CI = 1.78 to 3.40) or an annual clinical breast examination (OR = 1.83; 95% CI = 1.48 to 2.26). DCIS patients and control subjects did not differ with respect to oral contraceptive use, hormone replacement therapy, alcohol consumption or smoking history, or breast self-examination. Associations for LCIS were similar. CONCLUSIONS: The risk factors associated with DCIS and LCIS are similar to those associated with invasive breast cancer. Diagnosis of DCIS is associated with increased mammography screening.

Adult↗

PubMed2001

Adenoid cystic carcinoma: a retrospective clinical review.

Adenoid cystic carcinoma (ACC) are uncommon tumors, representing about 10% to 15% of head and neck tumors. We compare the survival and control rates at our institution with those reported in the literature, and examine putative predictors of outcome. All patients registered with the tumor registry as having had ACC were identified. Demographic and survival variables were retrieved from the database. Additionally, a chart review of all patients was done to obtain specific information. Minor gland tumors were staged using the American Joint Committee on Cancer's criteria for squamous cell carcinomas in identical sites. Histopathologic variables retrieved included grade of the tumor, margins, and perineural invasion. Treatment modalities, field sizes, and radiation doses were recorded in applicable cases. An effort to retrieve archival tumor specimens for immunohistochemical analysis was undertaken. A total of 69 patients were treated for ACC from 1955 to 1999. One patient, who presented with fatal brain metastasis, was excluded from further analysis. Of the remaining 68 patients, 30 were men and 38 were women. The average age at diagnosis was 52 years, and mean follow-up was 13.2 years. Mean survival was 7.7 years. Overall survival (OS) rates at 5, 10, and 15 years were 72%, 44%, and 34%, and cause-specific survival was 83%, 71%, and 55%, respectively. Recurrence-free survival rates were 65%, 52%, and 30% at 5, 10, and 15 years, with a total of 29 of 68 (43%) eventually suffering a recurrence. Overall survival was adversely affected by advancing T and AJCC stage. Higher tumor grades were also associated with decreased OS, although the numbers compared were small. Primaries of the nasosinal region fared poorly when compared with other locations. Total recurrence-free survival, local and distant recurrence rates were distinctly better in primaries of the oral cavity/oropharynx when compared with those in other locations. Reduced distant recurrence-free survival was significantly associated with increasing stage. No other variables were predictive for recurrence. Additionally, we found that nasosinal tumors were more likely to display higher stage at presentation, and were more often associated with perineural invasion. Also of interest was the association of perineural invasion with margin status, with 15 of 20 patients with positive margins displaying perineural invasion, while only 5 of 17 with negative margins showed nerve invasion (P = 0.02). On immunohistochemistry, 2 cases of the 29 (7%) tumor specimens found displayed HER-2/neu positivity. No correlation between clinical behavior and positive staining could be demonstrated. Our data concur with previous reports on ACC in terms of survival and recurrence statistics. Stage and site of primary were important determinants of outcome. Grade may still serve a role in decision making. We could not demonstrate any differences attributable to primary modality of therapy, perhaps due to the nonrandomization of patients into the various treatment tracks and the inclusion of palliative cases. Similarly, perineural invasion, radiation dose and field size, and HER-2/neu positivity did not prove to be important factors in our experience.

Carcinoma, Adenoid Cystic↗

PubMed2001

BAG-1: a novel biomarker predicting long-term survival in early-stage breast cancer.

PURPOSE: Among women with early-stage breast cancer treated with lumpectomy and radiation therapy, 30% to 40% will develop metastatic disease, which is often fatal. A need exists therefore for biomarkers that distinguish patients at high risk of relapse. We performed a retrospective correlative analysis of BAG-1 protein expression in breast tumors derived from a cohort of early-stage breast cancer patients. PATIENTS AND METHODS: Archival paraffin blocks from 122 women with stages I to II breast cancer treated with lumpectomy and radiation therapy (median follow-up, 12.1 years) were analyzed by immunohistochemical methods using monoclonal antibodies recognizing BAG-1 and other biomarkers, including Bcl-2, estrogen receptor, progesterone receptor, p53, and HER2/Neu. Immunostaining data were correlated with distant metastasis-free survival (DMFS) and overall survival (OS). RESULTS: Cytosolic immunostaining for BAG-1 was upregulated in 79 (65%) of 122 invasive breast cancers (P <.001) compared with normal breast. Elevated BAG-1 was significantly associated with longer DMFS and OS, overall (stages 1 and II) and in node-negative (stage I only) patients, on the basis of univariate and multivariate analyses (DMFS, P =.005; OS, P =.01, in multivariate analysis of all patients; DMFS, P =.005; OS, P =.001, in multivariate analysis of node-negative patients). All other biomarkers failed to reach statistical significance in multivariate analysis. Clinical stage was an independent predictor of OS (P =.04) and DMFS (P =.02). CONCLUSION: These findings provide preliminary evidence that BAG-1 represents a potential marker of improved survival in early-stage breast cancer patients, independent of the status of axillary lymph nodes.

Adult↗

PubMed2001

Species- and tissue-specific physiological regulation of vasopressin mRNA poly(A) tail length.

Transgenic experiments can be used to test the extent to which genes from different species can be swapped around, but still retain function, and be appropriately regulated. A vector has been developed that directs the expression of foreign genes to specific groups of vasopressin (VP) hypothalamic neurons in transgenic rats. Using this vector, we have expressed the bovine VP (bVP) RNA in the rat brain. In contrast to the situation in a mouse host, but like its endogenous rat counterpart, the mRNA encoded by the bVP transgene is subject to posttranscriptional physiological regulation in the hypothalamus; its poly(A) tail dramatically lengthens as a consequence of 3 days of dehydration. Transgene expression is also seen in the adrenal cortex, but here, despite a marked increase in transgene RNA levels with dehydration, there is no change in poly(A) tail length. These data suggest that the mouse hypothalamus and the rat adrenal gland do not have the transcript recognition or enzymatic machinery required for the physiologically responsive poly(A) tail length modulation seen in the rat brain.

Adrenal Cortex↗

PubMed2001

Pathobiologic findings in DCIS of the breast: morphologic features, angiogenesis, HER-2/neu and hormone receptors.

With the increasing incidence of ductal carcinoma in situ (DCIS) of the breast and its relationship to invasive breast carcinoma, it is important to understand the biology of this entity. We report on a hospital-based survey of 219 case subjects with DCIS of the breast without associated invasive carcinoma diagnosed between 1982 and 1994. The cases of DCIS were analyzed for architectural type, size, nuclear grade, necrosis, calcification, periductal fibrosis, neovascularization, estrogen receptor (ER), progesterone receptor (PR), and HER-2/neu expression. Periductal neovascularization was associated with tumor size, microcalcifications, periductal fibrosis, and HER-2/neu overexpression. Expression of ER and PR was observed in 60 and 62% of the cases, respectively, and HER-2/neu overexpression in 28% of the cases. ER and PR expression were both inversely associated with comedo histology and nuclear grade. HER-2/neu overexpression was positively associated with comedo histology, high nuclear grade, and periductal neovascularization and was inversely correlated with both ER and PR expression. High nuclear grade was positively associated with comedocarcinoma, necrosis, microcalcification, and periductal fibrosis. The role of these molecular/pathologic markers in the biology of DCIS and their potential clinical implications are discussed.

Breast Neoplasms↗

PubMed2001

Chemical deglycosylation can induce methylation, succinimide formation, and isomerization.

Interpretation of deglycosylation studies relies heavily on the absence of modifications to the polypeptide chain. We have found that by using a common chemical deglycosylation technique, one can effect at least three changes in a peptide's structure: methylation, isomerization, and ring formation. It was determined that the conditions of chemical deglycosylation introduce a +14 Da shift in the masses of our model peptides, RKDVY, RKEVY, and horseradish peroxidase. This shift is localized to acidic functional groups and is interpreted as methylation of the free carboxylates in our models. An additional shift in mass of -18 Da is found in the model peptide RKDVY consistent with the loss of water associated with succinimide ring formation in this peptide. Chemical treatment induced isomerization of aspartyl residues to isoaspartyl residues in another model peptide, tetragastrin. These results indicate that one should use caution when interpreting the results of chemical deglycosylation experiments.

Amino Acid Sequence↗

PubMed2001

An exploration of midwives' and obstetricians' knowledge of genetic screening in pregnancy and their perception of appropriate counselling.

OBJECTIVE: to describe levels of knowledge relevant to genetic screening in a sample of midwives and obstetricians in the late 1990s, and to compare these with those found by Smith et al. in London and Wales, and reported in 1994; to describe health professionals' perceptions of an appropriate counselling process relating to genetic screening in comparison with recognised good practice; and to consider links between knowledge and perceptions of the counselling process. DESIGN: a questionnaire study, including responses to a counselling scenario. PARTICIPANTS AND SETTING: responses were obtained from 81 midwives and obstetricians from maternity services in the North West of England. FINDINGS: knowledge about procedures was very good, but knowledge about the probability of genetic abnormality was relatively poor, and respondents overestimated the efficacy and usefulness of tests. These findings were similar to those of Smith et al. (1994), suggesting that they are a good reflection of the national picture. In terms of reported information-giving and counselling practice, there were some respondents who would not check the woman's understanding of her baby's risk of a genetic abnormality, or the risk of a false result. Some respondents would give information based on their own (necessarily limited) experience, rather than national statistics, and give advice based on the choices they themselves would make. These findings reflect earlier, basic research on people's understanding of probabilistic information. IMPLICATIONS: the findings of this study, together with those of earlier work cited, suggest a need for education and training which includes a specific focus on biases in understanding this type of probabilistic information. They also raise the question as to why tests which provide probabilistic data have been introduced without consideration of the known problems in understanding such information.

Attitude of Health Personnel↗

PubMed2001

The efficacy of fluoxetine in improving physical symptoms associated with premenstrual dysphoric disorder.

OBJECTIVE: To determine the effectiveness of fluoxetine in alleviating physical symptoms of premenstrual dysphoric disorder. DESIGN: Randomised, double-blind, placebo controlled, parallel study. SETTING: Canadian University based outpatient clinics. Participants Four hundred and five subjects, of whom 320 with prospectively determined premenstrual dysphoric disorder were randomised. METHODS: Randomised women were assigned to fluoxetine 20 or 60 mg/day or placebo. Common physical symptoms associated with premenstrual dysphoric disorder including breast tenderness, bloating, and headache were evaluated by visual analog scales and the self-rated and observer premenstrual tension syndrome scales. OUTCOME MEASURES: Luteal phase change from mean baseline scores to mean treatment scores for all scales. RESULTS: Fluoxetine treatment was statistically superior to placebo, with no significant differences between the two fluoxetine dosages in their effects on physical symptoms. CONCLUSION: Daily fluoxetine treatment is superior to placebo in improving the most common physical symptoms associated with premenstrual dysphoric disorder.

Adult↗

PubMed2001

Phenotypic switching and genetic diversity of Cryptococcus neoformans.

Niger seed agar was used as a primary plating medium for the isolation of Cryptococcus neoformans from cerebrospinal fluid specimens from AIDS patients with untreated primary cryptococcosis. The medium was used as the primary means to detect variations in the colony morphology of the yeast. To search for phenotypic and genetic variations, nine patients individually harboring two or three types of colony morphology were studied. Intraindividual isolates from nine patients had minor variations in the API 20C profile, and the MICs of one or more antifungal agents (amphotericin B, fluconazole, and itraconazole) for isolates from three patients were significantly different. Intraindividual isolates from three patients had minor karyotype differences, and one showed a dramatic chromosomal length polymorphism. In addition, three serial isolates from a patient with two episodes of infection showed similar karyotypes, confirming persistent infection by the same strain. Random amplified polymorphic DNA products were identical for all isolates (including three isolates from a relapse case). Our results provided evidence suggesting that (i) in humans, C. neoformans may undergo phenotypic and genetic changes during early infection prior to antifungal agent administration; (ii) dramatic variations in electrophoretic karyotypes and in phenotypes, as demonstrated during the early infection of one patient, may be due to infection by different strains; and (iii) the use of niger seed agar as a primary plating medium is useful for studying antifungal susceptibility, phenotypic switching, genetic diversity, and multiple-strain infections.

AIDS-Related Opportunistic Infections↗

PubMed2001

Molecular determinants of peptide binding to two common rhesus macaque major histocompatibility complex class II molecules.

Major histocompatibility complex class II molecules encoded by two common rhesus macaque alleles Mamu-DRB1*0406 and Mamu-DRB*w201 have been purified, and quantitative binding assays have been established. The structural requirements for peptide binding to each molecule were characterized by testing panels of single-substitution analogs of the two previously defined epitopes HIV Env242 (Mamu-DRB1*0406 restricted) and HIV Env482 (Mamu-DRB*w201 restricted). Anchor positions of both macaque DR molecules were spaced following a position 1 (P1), P4, P6, P7, and P9 pattern. The specific binding motif associated with each molecule was distinct, but largely overlapping, and was based on crucial roles of aromatic and/or hydrophobic residues at P1, P6, and P9. Based on these results, a tentative Mamu class II DR supermotif was defined. This pattern is remarkably similar to a previously defined human HLA-DR supermotif. Similarities in binding motifs between human HLA and macaque Mamu-DR molecules were further illustrated by testing a panel of more than 60 different single-substitution analogs of the HLA-DR-restricted HA 307-319 epitope for binding to Mamu-DRB*w201 and HLA-DRB1*0101. The Mamu-DRB1*0406 and -DRB*w201 binding capacity of a set of 311 overlapping peptides spanning the entire simian immunodeficiency virus (SIV) genome was also evaluated. Ten peptides capable of binding both molecules were identified, together with 19 DRB1*0406 and 43 DRB*w201 selective binders. The Mamu-DR supermotif was found to be present in about 75% of the good binders and in 50% of peptides binding with intermediate affinity but only in approximately 25% of the peptides which did not bind either Mamu class II molecule. Finally, using flow cytometric detection of antigen-induced intracellular gamma interferon, we identify a new CD4(+) T-lymphocyte epitope encoded within the Rev protein of SIV.

Amino Acid Sequence↗

PubMed2001

Tissue-specific transgenic knockdown of Fos-related antigen 2 (Fra-2) expression mediated by dominant negative Fra-2.

Fos-related antigen 2 (Fra-2) is a member of the Fos family of immediate-early genes, most of which are rapidly induced by second messengers. All members of this family act by binding to AP-1 sites as heterodimeric complexes with other proteins. However, each appears to have a distinct role. The role and biology of Fra-2 are less well understood than those of its relatives c-Fos, Fra-1, and FosB; moreover, Fra-2 target genes remain largely unknown, as does the basis of its selective effects on transcriptional activity. To pursue these issues, we created a transgenic rat line (NATDNF2) in which a dominant negative fra-2 (DNF2) gene is strongly expressed in the pineal gland; tissue selectivity was achieved by putting the DNF2 gene under the control of the rat arylalkylamine N-acetyltransferase (AANAT) regulatory region, which targets gene expression to a very restricted set of tissues (pineal gland >> retina). Expression of AANAT is normally turned on after the onset of darkness in the rat; as a result, pineal DNF2 expression occurs only at night. This was associated with marked suppression of the nocturnal increase in fra-2 mRNA and protein levels, indicating that DNF2 expression inhibits downstream effects of Fra-2, including the maintenance of high levels of fra-2 gene expression. Analysis of 1,190 genes in the NATDNF2 pineal gland, including the AANAT gene, identified two whose expression is strongly linked to fra-2 expression: the genes encoding type II iodothyronine deiodinase and nectadrin (CD24).

3T3 Cells↗

PubMed2001

Nocturnal light pulses selectively induce Egr-1/NGFI-A protein in periventricular hypophysiotrophic somatostatinergic neurons.

Recent reports showing that circadian light cues may induce gene-specific patterns of expression in periventricular hypothalamic neurons has extended the functional correlates of light-pulse stimuli, which are conventionally restricted to circadian phase-setting actions within the suprachiasmatic nucleus (ScN). The aims of the present study were, first, to broaden these observations to the protein level using an Egr-1/NGFI-A antibody, and second to investigate the cell-type specificity of induction with respect to associated hypophysiotrophic neurons. In order to co-localize Egr-1 with neuroendocrine peptides, a same-species, double immunofluorescence protocol has been used. The Egr-1 antibody used for immunohistochemistry was first characterized by Western analysis, and we have shown that the C19 antisera detects a single 75 kDa protein species, which has a primarily nuclear subcellular localization. Immunohistochemical analysis has shown that Egr-1 protein is markedly induced by a 1 h nocturnal light pulse both in the body of the suprachiasmatic nucleus and in a dorsal ScN zone, which extends up into the periventricular nucleus (PeN). In contrast, induction of Egr-1 was not observed within the arcuate region of the hypothalamus. Double immunofluorescence histochemistry has shown that Egr-1 is extensively, although not exclusively, co-localized with somatostatin in PeN neurons. The selective induction of the 75 kDa protein product of the egr-1 gene in PeN somatostatinergic neurons, as contrasted with hypophysiotrophic (somatostatin and growth hormone-releasing hormone [GH-RH]) neurons of the arcuate nucleus is indicative of a cell- and stimulus-specific neuroendocrine paradigm, which may be used to address temporal characteristics of somatostatin function that determine pulsatile growth-hormone secretion.

Animals↗