Fast,persistent, Ca2+-dependent K+ current controls graded electrical activity in crayfish muscle

The early outward current in opener muscle fibres of crayfish (Procambarus clarkii) was studied using the two-electrode voltage-clamp technique. This current was abolished in Ca²⁺-free and 5 mM Cd²⁺ solutions, and was blocked by extra- or intracellular tetraethylammonium, indicating that it was a Ca²⁺-dependent K⁺ current [I _K(Ca)]. I _K(Ca) was voltage dependent, apamin insensitive and sensitive to charybdotoxin (CTX), which, in addition to its tetraethylammonium sensitivity, suggests that the channels mediating I _K(Ca) behave in a BK type manner. I _K(Ca) activation was extremely fast, reaching a maximum within 5 ms, and the inactivation was incomplete, stabilizing at a persistent steady-state. I _K(Ca) was insensitive to intracellular ethylenebis(oxonitrilo)tetraacetate (EGTA), but was abolished by injection of the faster Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N,N'-tetraacetic acid (BAPTA), suggesting that voltage-dependent Ca²⁺ channels and those mediating I _K(Ca) should be clustered closely on the membrane. Under two-electrode current-clamp recording mode, low amplitude, graded responses were evoked under control conditions, whereas repetitive all-or-none spikes were elicited by application of CTX or after loading the cells with BAPTA. We conclude that I _K(Ca) activates extremely quickly, is persistent and is responsible for the generation and control of the low amplitude, graded, active responses of opener muscle fibres.     

Seroprevalence of human herpesvirus-8 in blood donors from different geographical regions of Argentina, Brazil, and Chile

Human herpesvirus-8 (HHV-8) causes Kaposi's sarcoma (KS) and lymphoproliferative disorders in both HIV-infected and uninfected patients. HHV-8 has a worldwide occurrence but infection rates vary according to a combination of geographic and behavioral risks. The main transmission route seems to be sexual, nevertheless, nasal secretions, saliva, blood, and organ graft have been proposed. HHV-8 was postulated as a new infectious agent for screening in blood donors. The aim of this study was to evaluate the prevalence of antibodies against HHV-8 antigens in blood donors of South America. Serum samples from 2,470 blood donors from Argentina, Brazil, and Chile corresponding to five geographic regions were studied by indirect immunofluorescence assay (IFA). Seroprevalence rate was 3.7% (92/2,470; 95% CI 2.9-4.5) in the entire blood donor population distributed as follows: Argentina, 4.0% (Buenos Aires city, 4.3%; Bahia Blanca, 2.4%; and Córdoba, 4.0%), Campinas (Brazil), 2.8%; and Santiago de Chile, 3.0%. There was no difference (P>0.05) between men and women or age related, except in Brazil where positive cases were 30-49-year-old males. The present study, which includes different geographical areas of multiple countries from South America, has not been done before. The results show similar prevalence rates among the studied zones corresponding to low-prevalence regions. South America is a large sub-continent with a wide spectrum of population and geographical characteristics, thus, more HHV-8 prevalence studies should be necessary to establish possible regional differences.     

Cervicovaginal (Papanicolaou) smear findings in patients with malignant mixed Müllerian tumors

Malignant mixed Müllerian tumor is a rare neoplasm that occurs most frequently in elderly patients. It is characterized by a mixture of malignant epithelial and sarcomatous components. Little has been published about Papanicolaou smear findings pertaining to malignant mixed Müllerian tumors. We present our experience, with an emphasis on cytologic detail. Nine patients (median age, 65 yr) met our study criteria. All available smears and surgical specimens were reviewed. Four smears were positive for malignancy, with a sensitivity of 44% (3 adenocarcinoma, and 1 squamous-cell carcinoma, small-cell type). The results of our study showed that Papanicolaou smear findings pertaining to malignant mixed Müllerian tumors are seen in patients with advanced-stage disease with involvement of the lower uterine segment or cervix. The usual finding is large numbers of high-grade epithelial malignant cells in a necrotic background. The mesenchymal component rarely sheds cells visible on Papanicolaou smear.     

Familial testicular cancer: interest in genetic testing among high-risk family members.

PURPOSE: This study is part of an ongoing National Cancer Institute multidisciplinary, etiologically-focused, cross-sectional study of Familial Testicular Cancer (FTC). The current report targets interest in clinical genetic testing for susceptibility to FTC. METHODS: Demographics, knowledge, health beliefs, and psychological and social factors were evaluated as covariates related to interest in genetic testing. RESULTS: The majority (66%) of 229 participants (64 affected men, 66 unaffected men, and 99 women) from 47 multiple-case FTC families expressed interest in having a genetic test within 6 months, should such a test become available. Interest was similar among the three subgroups mentioned above. Worries about insurance discrimination based on genetic test results were associated with a significantly lower interest in testing. Alternatively, participants were more likely to be interested in genetic testing if they were younger and had higher levels of family support, a physician's recommendation supporting testing, cancer distress, and a need for information to inform the health care of their children. CONCLUSIONS: This study reveals social and relationship factors that FTC survivors and their relatives considered important when contemplating the use of new genetic technologies. This is the first study describing hypothetical interest in genetic testing for familial testicular cancer.     

The DeltaF508 mutation in Ecuador, South America.

There are few reports about the incidence of the DeltaF508 mutation in Latin American countries. We show the study of the DeltaF508 mutation and the seven most common "European" mutations in 10 Ecuadorian CF affecteds. The incidence of DeltaF508 mutation found was 25% and none of the other seven was detected in our population, which indicates that at least 60% of the mutations in the studied population are different from most common in Europe. Similar data have been reported in other Amerindian populations, therefore it is suggested that Cystic Fibrosis in Ecuador-and other Amerindian countries in Latin America-have a different ethiology than that of Caucasian populations.     

Aberrant cellular retinol binding protein 1 (CRBP1) gene expression and promoter methylation in prostate cancer

AIMS: Retinoids are involved in cell growth, differentiation, and carcinogenesis. Their effects depend on cytosolic transport and binding to nuclear receptors. CRBP1 encodes a protein involved in this process. Because altered CRBP1 expression and promoter hypermethylation occur in several tumours, these changes were investigated in prostate tumorigenesis. METHODS: The CRBP1 promoter was assessed by methylation specific polymerase chain reaction on tissue samples from 36 radical prostatectomy specimens (paired normal tissue, adenocarcinoma, and high grade prostatic intraepithelial neoplasia (HGPIN)), 32 benign prostatic hyperplasias (BPHs), and 13 normal prostate tissue samples from cystoprostatectomies. Methylation of DNA extracted from microdissected tissue was examined blindly. CRBP1 expression was assessed by immunohistochemistry on formalin fixed, paraffin wax embedded tissue. RESULTS: Loss of CRBP1 expression was seen in 15 of 36 adenocarcinomas and 18 of 36 HGPINs. Fifteen adenocarcinomas and nine HGPINs showed overexpression, whereas the remainder showed normal expression. BPH displayed normal expression. No significant associations were found between CRBP1 expression and Gleason score or stage. CRBP1 promoter hypermethylation was found in 17 of 36 adenocarcinomas, three of 35 HGPINs, one of 36 normal prostate tissues from the same patients, none of 32 BPHs, and none of 13 normal prostate tissues from cystoprostatectomies. Loss of expression and hypermethylation of CRBP1 were not significantly associated. CONCLUSIONS: Altered CRBP1 expression and hypermethylation are common in prostate carcinoma, although CRBP1 hypermethylation is not an early event in tumorigenesis. Moreover, both adenocarcinoma and HGPIN show frequent CRBP1 overexpression. The molecular mechanisms underlying altered CRBP1 expression in prostate cancer deserve further study.     

Two new mutations and three novel polymorphisms in the<Emphasis Type="Italic"> RB1</Emphasis> gene in Ecuadorian patients

RB1 is the gene responsible for retinoblastoma, the most common malignant intraocular tumor of infancy and early childhood. There are no reports about this gene in Ecuadorian populations, and only a few studies have been published in Latin America about this subject. There is a spectrum of more than 370 mutations described in the RB1 gene mutation database (http://www.d-lohmann.de/Rb/mutations.html), and alterations have been found in 25 of the 27 exons. During the exon-by-exon analysis of 31 tumor and blood samples from Ecuadorian patients, we found two new mutations and three novel polymorphisms. One of the polymorphisms is located in intron 26 where no alterations of the gene have been described previously. The polymorphisms were found in all of the patients tumor samples, but not in normal population, suggesting there might be a relationship between these polymorphisms and the development of retinoblastoma in the Ecuadorian population.The nucleotide sequence data reported are available in the GenBank database under the accession numbers: AY243567, AY260472, AY260473, AY273783     

Extracellular taurine increase in rat hippocampus evoked by specific glutamate receptor activation is related to the excitatory potency of glutamate agonists

Taurine increases in brain extracellular space due to glutamate agonists were studied in vivo in the rat hippocampus using a dialysis technique, both in the absence and in the presence of glutamate receptor antagonists. Extracellular taurine levels increased during perfusions of agonists, listed in descending order of potency: kainate (KA), N-methyl-D-aspartate (NMDA), and quisqualate (QA). While taurine increases due to KA or QA perfusions were inhibited by 6,7-dinitro-quinoxaline-2,3-dione (DNQX), those induced by NMDA were abolished in the presence of 3-(carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP). These results indicate that increases in extracellular taurine levels evoked by NMDA, KA or QA in the rat hippocampus are caused by activation of their specific receptors. Field potentials, concomitantly recorded, were quickly abolished during NMDA or KA perfusions (0.1 mM), while QA (0.25 mM) induced the appearance of bicuculline-like evoked responses. Since taurine has been proposed as an osmoregulatory substance in the rat brain, and cell swelling is known to be an early component of glutamate agonists neurotoxicity, the increases in extracellular taurine reported here could be due to taurine released through an osmoregulatory process, counteracting the neurotoxic cellular oedema induced by glutamate agonists.