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.     

Clinical and pathological characterization of an osteoma in a barred owl

Osteomas are rare in birds. An osteoma of the left proximal radius was diagnosed in an adult barred owl based on gross, radiographic, and pathologic findings.     

A case of 46,XX,r(X) (p1q1) diagnosed by in situ hybridization

A small marker chromosome was identified as an X-derived ring chromosome by in situ hybridization with a biotinylated X-chromosome specific a-satellite DNA probe. This procedure clearly determined the chromosomal origin of the marker chromosome, which had been impossible to define by conventional cytogenetic techniques including high resolution banding.     

H-reflexes are less depressed following muscle stretch in spastic spinal cord injured patients than in healthy subjects

The size of the soleus H-reflex was measured after a slow (17 deg/s) passive stretch of ankle plantarflex ors and compared to its control size without muscle stretch in ten neurologically healthy subjects and in six spastic spinal-cord-injured patients. Two seconds after the end of the stretch, the size of the H-reflex was reduced to about 30% of its pre-stretch size in the healthy sub jects. The depression remained for 10–15 s. In the spastic, spinal-cord-injured patients, stretch caused significantly less reduction in the size of the H-reflex. The H-reflex also regained its pre-stretch size much faster than in healthy subjects. We suggest that the smaller depression of the H-reflex observed in spastic patients may be involved in the pathophysiology of spasticity.     

An association study of the cholesteryl ester transfer protein TaqI B polymorphism with late onset Alzheimer's disease

Cholesteryl ester transfer protein (CETP) is reportedly able to affect the amount of cholesterol available for deposition and/or removal from peripheral tissues, in its capacity to mediate the transfer of cholesterol from high density lipoprotein (HDL) to very low density lipoprotein, in exchange for triacylglycerols from the latter. The TaqI B polymorphism of the human CETP gene has been associated with decreased CETP mass and an increase in HDL-cholesterol. While many studies have addressed the atherogenic or anti-atherogenic potential of this polymorphism, little is known about its effect on neurodegeneration, despite the fact that CETP is expressed in the brain and the disturbance of cholesterol homeostasis appears to be an important factor in the pathogenesis of Alzheimer's disease (AD). In this report, we have compared the distribution of the TaqI B polymorphism in an independent population of 102 clinically diagnosed late onset AD patients and a spousal control group of 97 individuals. We have also examined the possible interaction between this polymorphism and two other polymorphisms suspected of affecting cholesterol flux, namely apolipoprotein E APOE epsilon4, and lipoprotein lipase LPLS447X. No statistically significant differences have emerged with respect to either genotype or allele frequencies between the AD and control populations. CETP TaqI B did not interact significantly with either APOE epsilon4 or LPLS447X, in this study.     

The effects of cycle racing on pulmonary diffusion capacity and left ventricular systolic function

The purpose of this study was to examine the effects of a 20 km cycle race (TT) on left ventricular (LV) systolic and pulmonary function in 12 endurance cyclists. Spirometry, single-breath diffusion capacity (DLCO) with partitioning of membrane (DM) and capillary blood volume (Vc) components and 2-D echocardiograms were performed before and after the TT. During the TT mean oxygen consumption was 3.79 +/- 0.5 L x min(-1) (83 +/- 5.5% of VO2max) and mean blood lactate was 8.4 +/- 2.4 mM. Following the TT, spirometry values were unchanged, however, DLCO and DM were significantly (P<0.05) reduced. LV systolic function was increased (P<0.05) immediately after exercise, while end-diastolic area was decreased (P<0.05) at all points during recovery. The reduction in DM was correlated with LV systolic function following the TT. This relationship suggests a cardiovascular contribution to pulmonary diffusion impairment following exercise.     

A chimeric T cell receptor with super-signaling properties

A key question yet to be resolved concerns the structure and function relationship of the TCR complex. How does antigen recognition by the TCR-alphabeta chains result in the activation of distinct signal transduction pathways by the CD3-gammadeltaepsilon/zeta complex? To investigate which part of the TCR-beta chain is involved in TCR signaling, we exchanged different domains of the constant regions of the TCR-beta chain with the corresponding TCR-gamma chain domains. We show here that hybridoma cells expressing a chimeric TCR-beta chain (betaIII) containing intracellular and transmembrane TCR-gamma amino acids, together with a wild-type TCR-alpha (alphawt) chain, were 10 times more sensitive to antigenic stimulation compared to cells expressing TCR-alphawt/betawt chains. This super-signaling phenotype of the betaIII chain was observed in two different TCRs. One specific for an alloantigen (I-A(bm12)) and one for an autoantigen (I-A(b)/MOG(35-55)). We found that this chimeric alphawt/betaIII TCR had normal association with CD3-gammadeltaepsilon and zeta chains. To investigate the effect of the chimeric betaIII chain in transgenic T cells, we made MOG(35-55)-specific TCR transgenic mice expressing either the alphawt/betawt or chimeric alphawt/betaIII TCR. Similar to what was observed in hybridoma cells, transgenic alphawt/betaIII T cells showed a super-signaling phenotype upon antigenic stimulation. Further studies may help us understand the effect of increased TCR signaling on autoimmunity and may lead to the identification of signaling molecules that can be targeted to stop the progression of autoimmune disorders such as multiple sclerosis.     

Pseudodicentric chromosome 18 diagnosed by chromosome painting and primed in situ labelling (PRINS).

We report on a newborn white male infant with marked dysmorphic features and various congenital malformations. The initial clinical evaluation showed Crouzon-like features as well as some features of trisomy 18 syndrome and trisomy 13 syndrome. The results from conventional cytogenetic analysis showed a structurally abnormal chromosome replacing one normal chromosome 18, but only by applying molecular cytogenetic methods could the architecture of this abnormal chromosome be characterised clearly. The primed in situ labelling (PRINS) technique, using a newly synthesised alpha 18 oligonucleotide, showed the dicentric pattern and direct chromosome painting established the origin to be from chromosome 18. The combination of conventional cytogenetics and molecular cytogenetics showed the karyotype in the proband to be 45,XY,-14,-18,-21,+t(14;21),+psu dic(18) (qter-->cen-->p11.3: :p11.3-->psu cen-->qter). This was supported by molecular analysis using chromosome 18 specific DNA markers, which showed the paternal origin of the abnormal chromosome.