The compartmentalization of prolactin signaling in the mouse mammary gland

In mammary epithelial cells, prolactin (PRL) activates at least two signaling pathways: Jak/Stat and nitric oxide (NO). The former induces differentiation as measured by alpha-lactalbumin accumulation, while experiments with sodium nitroprusside (SNP) show that NO inhibits differentiation. In order to resolve this apparent contradiction, the kinetics, inducibility, and cellular localization of NO production and sensitivity in mammary cells were examined. First, mammary cells remained responsive to PRL throughout the incubation with respect to NO production. Second, although desensitization occurred with continuous PRL exposure, recovery began as quickly as 30 min after PRL withdrawal. Since PRL is secreted in pulses in vivo, complete desensitization was not a likely explanation for the cells' escape from NO inhibition. Finally, the cellular site of transduction was examined using the caveolar disrupting agent, methyl-beta-cyclodextrin (MBCD). MBCD inhibited the accumulation of PRL-induced NO but not alpha-lactalbumin. This finding was confirmed by membrane fractionation studies where the PRL-induced NO production occurred primarily in caveolae and PRL-stimulated tyrosine phosphorylation of Stat5, which transcribes the alpha-lactalbumin gene, occurred predominantly in noncaveolar membranes. Finally, endogenous elevations of NO by arginine did not inhibit differentiation. As such, the inhibition seen with SNP appeared to be an artifact of the ubiquitous generation of NO from SNP. Physiologically, PRL induces NO only in caveolae and this restricted distribution does not interfere with differentiation.     

Subclinical thyroid disease: scientific review and guidelines for diagnosis and management

Context  Patients with serum thyroid-stimulating hormone (TSH) levels outside the reference range and levels of free thyroxine (FT₄) and triiodothyronine (T₃) within the reference range are common in clinical practice. The necessity for further evaluation, possible treatment, and the urgency of treatment have not been clearly established. Objectives  To define subclinical thyroid disease, review its epidemiology, recommend an appropriate evaluation, explore the risks and benefits of treatment and consequences of nontreatment, and determine whether population-based screening is warranted. Data Sources  MEDLINE, EMBASE, Biosis, the Agency for Healthcare Research and Quality, National Guideline Clearing House, the Cochrane Database of Systematic Reviews and Controlled Trials Register, and several National Health Services (UK) databases were searched for articles on subclinical thyroid disease published between 1995 and 2002. Articles published before 1995 were recommended by expert consultants. Study Selection and Data Extraction  A total of 195 English-language or translated papers were reviewed. Editorials, individual case studies, studies enrolling fewer than 10 patients, and nonsystematic reviews were excluded. Information related to authorship, year of publication, number of subjects, study design, and results were extracted and formed the basis for an evidence report, consisting of tables and summaries of each subject area. Data Synthesis  The strength of the evidence that untreated subclinical thyroid disease is associated with clinical symptoms and adverse clinical outcomes was assessed and recommendations for clinical practice developed. Data relating the progression of subclinical to overt hypothyroidism were rated as good, but data relating treatment to prevention of progression were inadequate to determine a treatment benefit. Data relating a serum TSH level higher than 10 mIU/L to elevations in serum cholesterol were rated as fair but data relating to benefits of treatment were rated as insufficient. All other associations of symptoms and benefit of treatment were rated as insufficient or absent. Data relating a serum TSH concentration lower than 0.1 mIU/L to the presence of atrial fibrillation and progression to overt hyperthyroidism were rated as good, but no data supported treatment to prevent these outcomes. Data relating restoration of the TSH level to within the reference range with improvements in bone mineral density were rated as fair. Data addressing all other associations of subclinical hyperthyroid disease and adverse clinical outcomes or treatment benefits were rated as insufficient or absent. Subclinical hypothyroid disease in pregnancy is a special case and aggressive case finding and treatment in pregnant women can be justified. Conclusions  Data supporting associations of subclinical thyroid disease with symptoms or adverse clinical outcomes or benefits of treatment are few. The consequences of subclinical thyroid disease (serum TSH 0.1-0.45 mIU/L or 4.5-10.0 mIU/L) are minimal and we recommend against routine treatment of patients with TSH levels in these ranges. There is insufficient evidence to support population-based screening. Aggressive case finding is appropriate in pregnant women, women older than 60 years, and others at high risk for thyroid dysfunction.      

Substance use and sexual risk: a participant- and episode-level analysis among a cohort of men who have sex with men

Prior reports associating substance use with sexual risk behavior have generally used summary measures and have not adjusted for participants' background levels of substance use. In this 1999-2001 US study (the EXPLORE study), the authors determined whether substance use during sex was independently associated with sexual risk during recent sexual episodes, as reported by 4,295 human immunodeficiency virus-negative men who have sex with men. The main outcome measure was serodiscordant unprotected anal sex (SDUA). The influence of participant-level characteristics was examined by using repeated-measures logistic models. In assessing the influence of episode-level predictors on SDUA, the influence of participant-level characteristics, including 6-month substance use, was removed by using conditional logistic regression, in effect making each participant his own control. The authors also adjusted for partner characteristics. Eleven percent of participants reported heavy alcohol use, 37% used poppers, 19% sniffed cocaine, and 13% used amphetamines. In the participant-level analysis, use of poppers, amphetamines, and sniffed cocaine as well as heavy alcohol use in the prior 6 months were independently associated with SDUA. In the conditional analysis, consumption of > or = 6 alcoholic drinks or use of poppers, amphetamines, or sniffed cocaine just before or during sex was independently associated with SDUA. The authors concluded that programs aimed at preventing human immunodeficiency virus transmission should emphasize the influence of substance use during sex on increased risk behavior.     

Single dose of the antivascular agent, ZD6126 (N-acetylcolchinol-O-phosphate), reduces perfusion for at least 96 hours in the GH3 prolactinoma rat tumor model

Tumor vasculature is an attractive therapeutic target as it differs structurally from normal vasculature, and the destruction of a single vessel can lead to the death of many tumor cells. The effects of antivascular drugs are frequently short term, with regrowth beginning less than 24 hours posttreatment. This study investigated the duration of the response to the vascular targeting agent, ZD6126, of the GH3 prolactinoma, in which efficacy and dose-response have previously been demonstrated. GH3 prolactinomas were grown in the flanks of eight Wistar Furth rats. All animals were treated with 50 mg/kg ZD6126. The tumors were examined with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) 24 hours pretreatment and posttreatment, and at a single time between 48 and 96 hours posttreatment. No evidence of recovery of perfusion was observed even at the longest (96-hour) time point. Involvement of a statistician at the project planning stage and the use of DCE-MRI, which permits noninvasive quantitation of parameters related to blood flow in intact animals, allowed this highly significant result to be obtained using only eight rats.     

Automated classification of short echo time in in vivo 1H brain tumor spectra: a multicenter study.

Automated pattern recognition techniques are needed to help radiologists categorize MRS data of brain tumors according to histological type and grade. A major question is whether a computer program "trained" on spectra from one hospital will be able to classify those from another, particularly if the acquisition protocol is different. A subset of 144 histopathologically validated brain tumor spectra in the INTERPRET database, obtained from three of the collaborating centers, was grouped into meningiomas, low-grade astrocytomas, and "aggressive tumors" (glioblastomas and metastases). Spectra from two centers formed the training set (94 spectra) while the third acted as the test set (50 spectra). Linear discriminant analysis successfully classified 48/50 in the test set; the remaining two were atypical cases. When the training and test sets were combined, 133 of the 144 spectra were correctly classified using the leave-one-out procedure. These spectra had been obtained using different sequences (STEAM and PRESS), different echo times (20, 30, 31, and 32 ms), different repetition times (1600 and 2000 ms), and different manufacturers' instruments (GE and Philips). Pattern recognition algorithms are less sensitive to acquisition parameters than had been expected.     

Tumor vascular architecture and function evaluated by non-invasive susceptibility MRI methods and immunohistochemistry

PURPOSE: To investigate the physiological origins responsible for the varying blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) responses to carbogen (95% O(2)/5% CO(2)) breathing observed with different tumor types. MATERIALS AND METHODS: Susceptibility contrast-enhanced MRI using the exogenous blood pool contrast agent NC100150 to determine blood volume and vessel size, and immunohistochemical-derived morphometric parameters, were determined in GH3 prolactinomas and RIF-1 fibrosarcomas, both grown in mice, which exhibited very different BOLD responses to carbogen. RESULTS: Administration of NC100150 increased the R(2)* and R(2) rates of both tumor types, and indicated a significant four-fold larger blood volume in the GH3 tumor. The ratio deltaR(2)*/deltaR(2) showed that the capillaries in the GH3 were two-fold larger than those in the RIF-1, in agreement with morphometric analysis. Carbogen breathing induced a significant 25% decrease in R(2)* in the GH3 prolactinoma, whereas the response in the RIF-1 fibrosarcoma was negligible. CONCLUSION: Low blood volume and small vessel size (and hence reduced hematocrit) are two reasons for the lack of R(2)* change in the RIF-1 with carbogen breathing. BOLD MRI is sensitive to erythrocyte-perfused vessels, whereas exogenous contrast agents interrogate the total perfused vascular volume. BOLD MRI, coupled with a carbogen challenge, provides information on functional, hemodynamic tumor vasculature.