A CDKN2A mutation in familial melanoma that abrogates binding of p16INK4a to CDK4 but not CDK6.

The CDKN2A locus encodes two distinct proteins, p16INK4a and p14ARF, both of which are implicated in replicative senescence and tumor suppression in different contexts. Here, we describe the characterization of a novel strain of human diploid fibroblasts (designated Milan HDFs) from an individual who is homozygous for the R24P mutation in p16INK4a. As this mutation occurs in the first exon of INK4a (exon 1alpha), it has no effect on the primary sequence of p14(ARF). Based on both in vitro and in vivo analyses, the R24P variant is specifically defective for binding to CDK4 but remains able to associate with CDK6. Nevertheless, Milan HDFs behave as if they are p16INK4a deficient, in terms of sensitivity to spontaneous and oncogene-induced senescence, and the R24P variant has little effect on proliferation when ectopically expressed in normal fibroblasts. It can, however, impair the proliferation of U20S cells, presumably because they express more CDK6 than primary fibroblasts. These observations suggest that CDK4 and CDK6 are not functionally redundant and underscore the importance of CDK4 in the development of melanoma.

Distribution of Serum Uric Acid in Black Africans and Its Association With Cardiovascular Risk Factors.

Hyperuricemia is associated with cardiovascular disease and its prevalence is unknown in black Africans. This study reports hyperuricemia distribution and its association with cardiovascular risk factors in a selected Angolan population. A cross-sectional study in 585 black Africans was performed. Hyperuricemia was defined as uric acid >7.0 mg/dL in men or >5.7 mg/dL in women. Overall prevalence was 25%. Hyperuricemia was associated with hypertension (odds ratio [OR], 2.20; confidence interval [CI], 95% 1.41-3.47), high waist circumference (OR, 1.67; CI, 95% 1.05-2.65), and metabolic syndrome (OR, 1.66; CI, 95% 1.07-2.57). Compared to those with uric acid levels in the first quartile, individuals in the fourth quartile showed higher body mass index, waist circumference, systolic blood pressure, and plasma levels of creatinine and triglycerides. Hypertension, high waist circumference, and metabolic syndrome were the major cardiovascular risk factors associated with hyperuricemia.

Dental and Periodontal Conditions in Alcoholics from a Brazilian Recovery Centera

ABSTRACT: The aim of this study was to evaluate the dental and periodontal condition of alcohol-dependents from a Brazilian Recovery Center. Sixty male individuals (30 alcoholic and 30 non-alcoholic) and aged between 32 and 72 years old were clinically evaluated. Interviews, dental and periodontal clinical examinations were obtained from all participants. The Pearson Chi-Square Test and Exact Fisher test were used to compare categorical data. The t-Student's test was adopted for non-categorical data. Multiple logistic regressions were used to evaluate the association of variables in the groups. The alcoholics were younger, consumed more tobacco, had lower frequency of tooth brushing and dental flossing, higher number of missing and decayed teeth, more residual root, and more teeth with presence of visible plaque index (OR = 0.5, 95 % Cl = 4.4 to 5.5), when compared to the non-alcoholics. Alcoholics at the Recovery Center performed poor oral hygiene, had higher number of sites with periodontal disease, and worse oral hygiene than non-alcoholic individuals. As regards professional follow-up, there was similarity between the groups evaluated.

RESUMEN: El objetivo de este estudio fue evaluar las condiciones dentales y periodontales de los alcohólicos de un Centro de Recuperación de Brasil. Sesenta hombres (30 alcohólicos y 30 no alcohólicos) y con edades comprendidas entre 32 y 72 años fueron evaluados clínicamente. Se obtuvieron entrevistas, exámenes clínicos dentales y periodontales de todos los participantes. La prueba de Chi-cuadrado de Pearson y la prueba exacta de Fisher se utilizaron para comparar datos categóricos. La prueba de t-Student se adoptó para datos no categóricos. Se utilizaron regresiones logísticas múltiples para evaluar la asociación de variables en los grupos. Los alcohólicos eran más jóvenes, consumían más tabaco, tenían menor frecuencia de cepillado dental y uso de hilo dental, mayor número de dientes perdidos y cariados, más raíz residual y más dientes con presencia de índice de placa visible (OR = 0,5, 95 % Cl = 4,4 a 5,5), en comparación con los no alcohólicos. Los alcohólicos en el Centro de Recuperación realizan una mala higiene bucal, tenían un mayor número de sitios con enfermedad periodontal y una peor higiene bucal que los no alcohólicos. En cuanto al seguimiento profesional, hubo similitud entre los grupos evaluados.

Jak2 and proteasome activities control the availability of cell surface growth hormone receptors during ligand exposure.

Several mechanisms participate in the down-regulation of growth hormone receptor (GHR) signalling under ligand exposure. In CHO cells expressing GHR, we show that ligand stimulation induces degradation of the total cell GHR content. Experiments with 125I-hGH indicate that ligand-bound internalized receptors are not immediately replaced. Using cell surface biotinylation, we demonstrate for the first time that, concomitantly with the degradation of cell surface receptors, GHRs from the intracellular compartments are also degraded. We thus suggest that under prolonged ligand exposure, some GHRs are targeted to the cell surface, while others are routed to degradation compartments. Inhibitors of Jak2 and of the proteasome partially inhibited degradation of cell surface receptors, while these compounds completely inhibit the degradation of intracellular GHRs, resulting in their accumulation. We therefore propose that Jak2 and proteasome activities control the amount of intracellular GHRs, and thus the availability of receptors at the cell surface, during ligand exposure.

Autocrine growth hormone production prevents apoptosis and inhibits differentiation in C2C12 myoblasts.

Although C2C12 myoblasts express low levels of growth hormone receptor (GHR), we failed to see any effect of exogenous growth hormone (GH) on cell proliferation or differentiation. C2C12 cells stably overexpressing (sixfold) more in GHR (C2C12(GHR)) grew faster than parental cells in media containing 2% serum, and proliferated while parental cells died, in the absence of serum. These effects were independent of exogenous GH but were inhibited by anti-GH and anti-insulin-like growth factor (anti-IGF-1) antibodies, consistent with a local production of GH, which we confirmed by RT-PCR and radioimmunoassay. In C2C12(GHR) cells, we observed an increased activation of the Janus kinase 2 (Jak2), signal transducers and activator of transcription 5 (Stat5), mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) upon acute GH stimulation. GHR overexpression also inhibited the formation of myotubes and the expression of markers for myoblast differentiation. Taken together, our data suggest that GH acts as an autocrine factor in C2C12 cells, to enhance proliferation and to inhibit differentiation.

QT interval prolongation associated with low magnesium in chronic alcoholics.

BACKGROUND: Alcoholism is a psychoactive drug-dependence with high prevalence throughout the world. Alcoholism has already been shown to be associated with electrical heart disorders, such as QT interval prolongation. Long QT, rare among healthy individuals (0.0017-0.31%), can trigger tachyarrhythmias and sudden death and might be caused by alcohol consumption itself and the resulting hypomagnesaemia. METHODS: This case-control study assessed active alcoholics and alcoholics who have been abstinent for at least seven days to compare changes in electrocardiographic, clinical and laboratory analyses among groups. RESULTS: A total of 166 alcoholics were evaluated, of which 62 were active and 104 abstinent alcoholics. Long QT was more prevalent among active alcoholics compared to abstinent alcoholics (16% vs. 2%, respectively, odds ratio (OR) 9.81, p=0.011), as was hypomagnesaemia (23% vs. 10%, OR 3.11, p=0.013). Serum magnesium levels were inversely proportional to the length of the corrected QT interval among active alcoholics (ß=-35.1ms, p=0.005). CONCLUSIONS: Active chronic alcoholics exhibited a higher association of long QT and hypomagnesaemia. Low serum magnesium levels were predictive of QT interval prolongation. Because the above changes potentially trigger fatal arrhythmias, it is of fundamental importance to consider the diagnostic possibility by routinely requesting electrocardiograms and serum magnesium level assessment during the treatment of chronic alcoholic patients.

Development of pure prolactin receptor antagonists.

Prolactin (PRL) promotes tumor growth in various experimental models and leads to prostate hyperplasia and mammary neoplasia in PRL transgenic mice. Increasing experimental evidence argues for the involvement of autocrine PRL in this process. PRL receptor antagonists have been developed to counteract these undesired proliferative actions of PRL. However, all forms of PRL receptor antagonists obtained to date exhibit partial agonism, preventing their therapeutic use as full antagonists. In the present study, we describe the development of new human PRL antagonists devoid of agonistic properties and therefore able to act as pure antagonists. This was demonstrated using several in vitro bioassays, including highly sensitive assays able to detect extremely low levels of receptor activation. These new compounds also act as pure antagonists in vivo, as assessed by analyzing their ability to competitively inhibit PRL-triggered signaling cascades in various target tissues (liver, mammary gland, and prostate). Finally, by using transgenic mice expressing PRL specifically in the prostate, which exhibit constitutively activated signaling cascades paralleling hyperplasia, we show that these new PRL analogs are able to completely revert PRL-activated events. These second generation human PRL antagonists are good candidates to be used as inhibitors of growth-promoting actions of PRL.