Mosaicism of the CAG repeat sequence in the Huntington disease gene in a pair of monozygotic twins

We report on a pair of monozygotic twins belonging to a family segregating Huntington disease (HD). In routine DNA analysis of blood cells, they displayed three alleles of the CAG repeat sequence in the HD gene. Two different cell lines, carrying the normal allele together with either an expanded allele with 47 CAGs or an intermediate allele with 37 CAGs, were detected in blood and buccal epithelium from both twins. To our knowledge, this is the first case described of HD gene CAG repeat length mosaicism in blood cells. Haplotype analysis established that the 37 CAG allele most likely arose by contraction of the maternal 47 CAG allele. The contraction must have taken place postzygotically, possibly at a very early stage of development, and probably before separation of the twins. One of the twins has presented symptoms of HD for 4 years; his skin fibroblasts and hair roots carried only the cell line with the 47 CAG repeat allele. The other twin, who is without symptoms at present, displayed mosaicism in skin fibroblasts and hair roots. If the proportion of the two cell lines in the brain of each twin resembles that of their hair roots (another tissue originating from the ectoderm), the mosaicism in the unaffected twin would mean that only a part of his brain cells carried the expanded allele, which could explain why he, in contrast to his brother, has no symptoms at this time.     

Replicative multivirus infection with cytomegalovirus, herpes simplex virus 1, and parvovirus B19, and latent Epstein-Barr virus infection in the synovial tissue of a psoriatic arthritis patient.

BACKGROUND: Psoriatic arthropathy occurs as complicating feature in about 5-7% of psoriasis patients. Infectious mechanisms including viral antigens have been suggested by serologic data as CD8 T cellular specifity towards viral epitopes. OBJECTIVE AND RESULTS: We here reported a case of a 32-year-old male psoriatic arthritis patient, where we could demonstrate simultaneous infection with cytomegalovirus (CMV), herpes simplex virus type I (HSV1) and parvovirus B19 (B19), as well as latent Epstein-Barr virus (EBV) infection within the synovial tissue by immunohistochemistry (CMV, parvovirus B19, HSV1, EBV-LMP) and DNA-in situ-hybridization (CMV). Serologic examination revealed positive EBV and parvovirus B19-IgG-antibodies, but no antibody response to HSV1 and CMV. CONCLUSION: This case is of special interest, since replicative viral infections have not yet been demonstrated localised in the psoriatic arthritis synovia. Thus, with particular regard to the limited information of the serologic data and the possible need of immuno suppressive therapy direct synovial testing for viral antigenes may be considered in psoriatic arthritis patients.     

Cardiac auscultation training of medical students: a comparison of electronic sensor-based and acoustic stethoscopes

Background  

To determine whether the use of an electronic, sensor based stethoscope affects the cardiac auscultation skills of undergraduate medical students.     

Neonatal outcome in a Danish national cohort of 3438 IVF/ICSI and 10,362 non-IVF/ICSI twins born between 1995 and 2000

BACKGROUND: In Denmark, one-third of twin pregnancies are the result of IVF/ICSI treatment. Limited data on neonatal outcome in IVF/ICSI twins are available in the literature. METHODS: A register study was conducted on neonatal morbidity and mortality in a complete national twin cohort including all 3438 (3393 live-born) IVF/ICSI and 10,362 (10,239 live-born) non-IVF/ICSI twins born between 1995 and 2000. Twins were identified in the National Medical Birth Registry and dichotomized into IVF/ICSI and non-IVF/ICSI by cross-reference with the Danish IVF Registry. Data on neonatal morbidity and mortality were retrieved from the Danish Patient Registry and the Danish Registry of Causes of Deaths. In order to exclude monozygotic twins, sub-analyses on unlike-sex twins were conducted. RESULTS: A birth weight discordance of >20% was observed in 20.6% of IVF/ICSI versus 15.7% of control twin pairs (P < 0.001). The risk of discordant birth weight >20% was OR 1.29 (95% CI 1.04-1.58) in unlike-sex IVF/ICSI twins versus control twins. The risk of delivery at <37 completed weeks and birth weight <2500 g was similar in the two cohorts; however, in unlike-sex IVF/ICSI versus control twins the risk of delivery at <37 weeks and birth weight <2500 g was OR 1.22 (95% CI 1.09-1.38) and OR 1.25 (1.11-1.40) respectively. After stratification for maternal age and parity, these risks disappeared. IVF/ICSI twins carried a higher risk of admittance to a neonatal intensive care unit (NICU) than control twins (OR 1.18, 95% CI 1.09-1.27), and this was even more pronounced in unlike-sex twins [OR 1.34 (95% CI 1.19-1.51)]. No differences were observed in malformation or mortality rates between the two cohorts. CONCLUSIONS: Despite higher birth weight discordance and more NICU admissions among IVF/ICSI twins, neonatal outcome in IVF/ICSI twins seems to be comparable with that of non-IVF/ICSI twins, when only dizygotic twins were considered in the comparisons.     

Glucose Ingestion Attenuates Interleukin-6 Release from Contracting Skeletal Muscle in Humans

To examine whether glucose ingestion during exercise affects the release of interleukin-6 (IL-6) from the contracting limb, seven men performed 120 min of semi-recumbent cycling on two occasions while ingesting either 250 ml of a 6.4 % carbohydrate (GLU trial) or sweet placebo (CON trial) beverage at the onset of, and at 15 min intervals throughout, exercise. Muscle biopsies obtained before and immediately after exercise were analysed for glycogen and IL-6 mRNA expression. Blood samples were simultaneously obtained from a brachial artery and a femoral vein prior to and during exercise and leg blood flow was measured by thermodilution in the femoral vein. Net leg IL-6 release, and net leg glucose and free fatty acid (FFA) uptake, were calculated from these measurements. The arterial IL-6 concentration was lower (   P < 0.05  ) after 120 min of exercise in GLU, but neither intramuscular glycogen nor IL-6 mRNA were different when comparing GLU with CON. However, net leg IL-6 release was attenuated (   P < 0.05  ) in GLU compared with CON. This corresponded with an enhanced (   P < 0.05  ) glucose uptake and a reduced (   P < 0.05  ) FFA uptake in GLU. These results demonstrate that glucose ingestion during exercise attenuates leg IL-6 release but does not decrease intramuscular expression of IL-6 mRNA.     

Evidence from twins for acquired cellular immune hyperactivity in type 1 diabetes

Type 1 diabetes has been associated with an increased frequency of activated T cells and T-cell hyperactivity to non-specific and disease-specific stimuli including the islet autoantigen glutamic acid decarboxylase 65 (GAD). To address whether T-cell hyperactivity is genetic or acquired we measured whole blood cytokines in vitro in response to GAD or tetanus in 18 identical twin pairs, nine discordant for type 1 diabetes. In addition, the activity of 2', 5' oligoadenylate synthetase (OAS) in blood mononuclear cells was measured as a marker of viral infection. Interleukin-2 (IL-2) basally and IL-2 and interferon-gamma (IFN-gamma) in response to GAD, were detected more frequently and at higher levels in diabetic compared to non-diabetic twins. IL-10 was not different between groups. OAS activity was increased in diabetic compared to non-diabetic twins and showed a correlation with basal IL-2 and GAD-stimulated IFN-gamma and IL-10. These findings suggest that T-cell hyperactivity in type 1 diabetes is an acquired trait and could reflect persisting virus expression.     

Transport of Proteins Across the Human Placenta

PROBLEM: The transport of various proteins across the human placenta was investigated by comparing maternal and fetal concentrations of tetanus antigen (TT-AG), anti-tetanus (TT)-immunoglobulin G (IgG) (following maternal vaccination), IgA, human chorionic gonadotropin (hCG), human placental lactogen (hPL), and alpha-fetoprotein (AFP) at term. METHOD OF STUDY: The concentrations of the six proteins were determined using enzyme-linked immunosorbent assay in serum of maternal venous and umbilical (fetal) vein samples obtained at delivery from uncomplicated term pregnancies (n = 16). RESULTS: The ratios (mean ± standard deviation) of fetal (umbilical) to maternal level were 1.41 ± 0.33 (anti-TT-IgG), 0.91 ± 0.37 (TT-AG), 0.002 ± 0.001 (IgA), 0.003 ± 0.001 (hCG), and 0.008 ± 0.004 (hPL), while the maternal:fetal concentration ratio of AFP was 0.002 ± 0.002. IgA, hCG, hPL, and AFP showed a close correlation between maternal and fetal levels varying between r² = 0.47 to 0.73 (P < 0.004–0.0001). Because AFP is produced by the fetus while IgA originates in the mother, the appearance of small amounts of these two proteins in the maternal or fetal compartment, respectively, suggests a slow rate of diffusion following a high concentration gradient. The detection of hCG and hPL in fetal serum is also interpreted as diffusion from the maternal into the fetal blood. Anti-TT-IgG has a significantly higher concentration in the fetal as compared with the maternal serum, which is in line with the well-documented active transfer of IgG. Fetal TT-antigen levels were similar to maternal concentrations, showing a close correlation (r² = 0.74, P < 0.0001) between the two proteins. CONCLUSIONS: The correlation between maternal and fetal concentrations of various proteins like IgA (150,000 Da), hCG (42,000 Da), and hPL (21,000 Da) suggests passive diffusion of these macromolecules across the placenta from the maternal to the fetal side, albeit at a slow rate. A similar process is postulated for AFP (70,000 Da) diffusing in the opposite direction from the fetus to the mother. There was no significant difference between the transplacental fetomaternal gradient of IgA and hCG and the maternal-fetal gradient of AFP. In view of the substantially larger volume of circulating maternal as compared with fetal blood, a significantly higher rate of crossing of AFP as compared with the other proteins must be assumed. It is uncertain whether a difference in the rate of transplacental transfer in the two directions or an additional source of AFP production in the maternal compartment explains the high maternal level. Anti-TT-IgG concentration is significantly higher in fetal than in maternal serum suggesting active transfer from the mother to the fetus. Furthermore, there is considerable transfer of TT-AG and a close correlation of fetal:maternal ratios of anti-TT-IgG (150,000 Da) and TT-AG (150,000 Da) could be an indication for a specific transfer of the antigen antibody complex.     

Human T lymphocyte activation induces tyrosine phosphorylation of α-tubulin and its association with the SH2 domain of the p59fyn protein tyrosine kinase

A glutathione-S-transferase-src-homology domain 2 (GST-SH2) fusion protein was employed to identify molecules interacting with the protein tyrosine kinase p59^fyn. Among several proteins which bound to the fyn SH2 domain in lysates of human Jurkat T lymphocytes, α- and β-tubulin were identified by N-terminal sequencing. Further analysis established that α-tubulin exists as a tyrosine-phosphorylated protein in Jurkat cells, where it interacts with p59^fyn, but not with p56^lck. By contrast, in untransformed resting human T lymphocytes α-tubulin is not detectable as a tyrosine phosphorylated protein. However, following T cell activation, it becomes rapidly phosphorylated on tyrosine residues and subsequently associates with the SH2 domain of fyn. Interestingly, constitutively tyrosine-phosphorylated α-tubulin that is able to interact with the fyn-SH2 domain is expressed in peripheral blood T lymphoblasts isolated from leukemic patients in the absence of external stimulation.