Functional muscle ischemia in neuronal nitric oxide synthase-deficient skeletal muscle of children with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a fatal disease caused by mutation of the gene encoding the cytoskeletal protein dystrophin. Despite a wealth of recent information about the molecular basis of DMD, effective treatment for this disease does not exist because the mechanism by which dystrophin deficiency produces the clinical phenotype is unknown. In both mouse and human skeletal muscle, dystrophin deficiency results in loss of neuronal nitric oxide synthase, which normally is localized to the sarcolemma as part of the dystrophin-glycoprotein complex. Recent studies in mice suggest that skeletal muscle-derived nitric oxide may play a key role in the regulation of blood flow within exercising skeletal muscle by blunting the vasoconstrictor response to alpha-adrenergic receptor activation. Here we report that this protective mechanism is defective in children with DMD, because the vasoconstrictor response (measured as a decrease in muscle oxygenation) to reflex sympathetic activation was not blunted during exercise of the dystrophic muscles. In contrast, this protective mechanism is intact in healthy children and those with polymyositis or limb-girdle muscular dystrophy, muscle diseases that do not result in loss of neuronal nitric oxide synthase. This clinical investigation suggests that unopposed sympathetic vasoconstriction in exercising human skeletal muscle may constitute a heretofore unappreciated vascular mechanism contributing to the pathogenesis of DMD.     

Molecular cloning and structural analysis of genes from Zea mays (L.) coding for members of the ras-related ypt gene family.

We have isolated, cloned, and characterized two cDNAs from Zea mays (L.), denoted yptm1 and yptm2, encoding proteins related to the ypt protein family. Amino acid similarity scores with YPT1 from yeast and ypt from mouse are in the range of 70% for yptm1 and 74% for yptm2, respectively, whereas similarities with p21 ras and other ras-related proteins are less than 40%. Most amino acid residues showing identity are clustered in the GTP/GDP binding domain. In addition, two cysteine residues close to the C-terminal ends, known to be palmitoylated and necessary for membrane binding in all eukaryotic ras-related proteins that have been characterized so far, are conserved in the maize genes as well. Northern blot hybridization analysis of poly(A)+ mRNA from etiolated maize coleoptiles revealed single mRNA species of approximately the same size as the isolated cDNAs. The gene for yptm1 is expressed at very low levels in maize coleoptiles and tissue culture cells. The gene for yptm2 is expressed at higher levels and is differentially represented in RNAs isolated from various organs of maize plants, with its highest level in leaves and flowers. The structural similarity of the genes identified suggests that they could be involved in the control of secretory processes.     

B-cell lymphoma after angioimmunoblastic lymphadenopathy: a case with oligoclonal gene rearrangements associated with Epstein-Barr virus

We describe a patient with angioimmunoblastic lymphadenopathy with dysproteinemia (AILD), who subsequently developed large-cell immunoblastic lymphoma of B-cell immunophenotype. At the time of the initial diagnosis, histologic examination of an inguinal lymph node showed typical features of AILD, and there was no evidence of a monoclonal B-cell population by immunohistochemical analysis. In situ hybridization and Southern blot analysis for Epstein-Barr virus (EBV) were negative. At autopsy 2 years later, the patient had widespread lymph node and organ involvement by large-cell immunoblastic lymphoma of B-cell immunophenotype. Southern blot analysis performed on DNA extracted from lymph nodes, liver, and spleen showed two patterns of Ig heavy chain and kappa light chain gene rearrangements. The T-cell receptor beta chain gene was in the germline configuration. Analysis with an EBV terminal repeat region probe showed two clonal populations that paralleled the Ig gene rearrangement studies. Double-labeling immunohistochemistry and in situ hybridization confirmed the presence of EBV within the neoplastic B cells. The data support the hypothesis that EBV was not etiologically related to AILD in this case, and that EBV proliferation may occur after the onset of the disease. Further, the data suggest that some B-cell lymphomas that arise in the setting of AILD resemble EBV-associated B-cell lymphomas that arise in other immunodeficiency states.     

Association analysis of sequence variants of GABA(A) alpha6, beta2, and gamma2 gene cluster and alcohol dependence

Quantitative trait analyses in mice suggest a vulnerability locus for physiological alcohol withdrawal severity on a chromosomal segment that harbors the genes encoding the alpha1, alpha6, beta2, and gamma2 subunits of the gamma-aminobutyric acid type-A receptor (GABR). We tested whether genetic variation at the human GABA(A) alpha6, beta2, and gamma2 gene cluster on chromosome 5q33 confers vulnerability to alcohol dependence. The genotypes of three nucleotide substitution polymorphisms of the GABRA6, GABRB2, and GABRG2 genes were assessed in 349 German alcohol-dependent subjects and in 182 ethnically matched controls. To eliminate some of the genetic variance, three more homogeneous subgroups of alcoholics were formed by: (1) a history of alcohol withdrawal seizure or delirium (n = 106); (2) a history of parental alcoholism (n = 120); and (3) a comorbidity of dissocial personality disorder (n = 57). We found no evidence that any of the investigated allelic variants confers vulnerability to either alcohol dependence or severe physiological alcohol withdrawal symptoms or familial alcoholism (p > 0.05). The frequency of the T allele of the GABRA6 polymorphism was significantly increased in dissocial alcoholics [f(T) = 0.799] compared with the controls [f(T) = 0.658; p = 0.002; OR(T+) = 7.26]. Taking into account the high a priori risk of false-positive association findings due to multiple testing, further replication studies are necessary to examine the tentative phenotype-genotype relationship of GABRA6 gene variants and dissocial alcoholism.     

Prevention of Mother-to-Child Transmission of HIV: Compliance with the Recommendations of the Brazilian National STD/AIDS Control Program for Prenatal and Perinatal HIV Testing in Porto Alegre, Brazil

In order to benefit from antiretroviral therapy, pregnant women infected with HIV must be tested and diagnosed. Not infrequently, however, women present in labor without prior prenatal care and are thus unable to benefit fully from HIV testing and, if infected, antiretroviral therapy. In this study we evaluated the need for rapid perinatal HIV testing for untested mothers presenting in labor in a public maternal–child hospital that provides care for metropolitan Porto Alegre, Brazil, and potentially modifiable risk factors for noncompliance with national recommendations. We surveyed a consecutive sample of women who gave birth at Hospital Materno–Infantil Presidente Vargas (Presidente Vargas Mother-and-child Hospital) in August–October 2001and administered a structured questionnaire to consenting participants. The questionnaire consisted of demographic data, information on health-seeking behavior, knowledge of HIV infection, and testing during pregnancy. We confirmed information on HIV testing, syphilis, and hepatitis B by examination of the patient's prenatal records. We also obtained data regarding laboratory testing and treatment during labor and delivery (e.g., HIV testing, antiretroviral treatment, and suppression of lactation) from hospital inpatient charts. Of 214 eligible participants, 209 (98%) agreed to participate in the study. Overall 173 (83%) of the 209 participants had had a previous HIV test and 36 (17%) had not. Women with fewer pregnancies were more likely to have been tested (p = .017), as were women with lower family incomes (p = .007). No women had received rapid tests in the delivery room. Of the 209 participants, 201 (96%) had had at least one prenatal visit and 169 (81%) had had three or more visits; 12 (6%) of these reported that they had not been offered an HIV test, 5 (2%) did not know if testing had been offered or not, and 191 (95%) reported that they had been offered a test. We were able to obtain prenatal records for 190 (95%) of the 201participants who had received prenatal care. HIV testing was not mentioned in 9% of charts. Results of syphilis tests were recorded on prenatal records or hospital charts for 167 (80%)participants, and results of hepatitis B surface antigen were found for 93 (45%). Women who to 30pchad had three or more prenatal visits were significantly more likely to have been tested for to 30pcHIV (OR 46.96, 95% CI, 15.92–144.85, .0001), syphilis (OR 31.64, 95% CI, 11.81–87.42, p < .0001) or HBsAg (OR, 4.88, 95% CI, 1.91–12.99, p < .0001) than women who had had two prenatal visits or fewer. Our study showed shown that in 12% of the pregnancies included in our sample national recommendations for prenatal or perinatal testing were not followed, and in an additional 5%, HIV testing, though offered, was not obtained. These women could potentially have benefited from rapid HIV testing. As knowledge of HIV and risk factors for transmission were almost universal in our sample, we believe that the passive health-seeking behavior we observed may offer an opportunity for targeting new efforts to promote the importance of prenatal care and prenatal diagnosis of HIV.