Transmission of haplotypes of microsatellite markers rather than single marker alleles in the mapping of a putative type 1 diabetes susceptibility gene (IDDM6)

Allelic association methods based on increased transmission of marker alleles will have to be employed for the mapping of complex disease susceptibility genes. However, because the extent of association of single marker alleles with disease is a function of the relative frequency of the allele on disease-associated chromosomes versus non disease-predisposing chromosomes, the most associated marker allele in a region will not necessarily be closest to the disease locus. To overcome this problem we describe a haplotype-based approach developed for mapping of the putative type 1 diabetes susceptibility gene IDDM6. Ten microsatellite markers spanning a 550 kb segment of chromosome 18q21 in the putative IDDM6 region were genotyped in 1708 type 1 diabetic Caucasian families from seven countries. The most likely ancestral diabetogenic chromosome was reconstructed in a stepwise fashion by analysing linkage disequilibrium between a previously defined haplotype of three adjacent markers and the next marker along the chromosome. A plot of transmission from heterozygous parents to affected offspring of single marker alleles present on the ancestral chromosome versus the physical distance between them, was compared with a plot of transmission of haplotypes of groups of three adjacent markers. Analysing transmission of haplotypes largely negated apparent decreases in transmission of single marker alleles. Peak support for association of the D18S487 region with IDDM6 is P = 0.0002 (corrected P = 0.01). The results also demonstrate the utility of polymorphic microsatellite markers to trace and delineate extended and presumably ancient haplotypes in the analysis of common disease and in the search for identical-by-descent chromosome regions that carry an aetiological variant.      

Multilocus linkage identifies two new loci for a mendelian form of stroke, cerebral cavernous malformation, at 7p15-13 and 3q25.2-27

Cerebral cavernous malformation (CCM) is a Mendelian model of stroke, characterized by focal abnormalities in small intracranial blood vessels leading to hemorrhage and consequent strokes and/or seizures. A significant fraction of cases is inherited as an autosomal dominant trait with incomplete penetrance. Among Hispanic Americans, virtually all CCM is attributable to a founder mutation localized to 7q ( CCM1 ). Recent analysis of non-Hispanic Caucasian kindreds, however, has excluded linkage to 7q in some, indicating at least one additional CCM locus. We now report analysis of linkage in 20 non-Hispanic Caucasian kindreds with familial CCM. In addition to linkage to CCM1, analysis of linkage demonstrates linkage to two new loci, CCM2 at 7p13-15 and CCM3 at 3q25.2-27. Multilocus analysis yields a maximum lod score of 14.11, with 40% of kindreds linked to CCM1, 20% linked to CCM2 and 40% linked to CCM3, with highly significant evidence for linkage to three loci (linkage to three loci supported with an odds ratio of 2.6 x 10(5):1 over linkage to two loci and 1.6 x 10(9):1 over linkage to one locus). Multipoint analysis among families with high posterior probabilities of linkage to each locus refines the locations of CCM2 and CCM3 to approximately 22 cM intervals. Linkage to these three loci can account for inheritance of CCM in all kindreds studied. Significant locus- specific differences in penetrance are identified. These findings have implications for genetic testing of this disorder and represent an important step toward identification of the molecular basis of this disease.      

Arterial epigastricocavernous anastomosis for the treatment of sexual impotence

Previous histologic and phalloarteriographic studies that we have performed suggest that stenoses and occlusions of the arteries supplying the penis play a very important role in the etiology of sexual impotence in many patients. This report describes the results of direct arterial anastomosis to the cavernous bodies of the penis, using the inferior epigastric artery and microsurgical technique, in 21 impotent males ranging in age from 40 to 63 years. The objective of the operation was to increase basal penile blood flow to a level, determined by preoperative studies, just below that necessary to maintain an effective erection. A limited capacity to increase blood flow in response to an erotic stimulus could then suffice to produce an erection. The anastomosis became occluded in 6 patients, and the complication of priapism developed in 3. The bypass remained patent in 13 patients, 11 of whom experienced improved erection. Nine patients resumed normal sexual activity that, prior to operation, was impossible.

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Résumé Précédemment, des études histologiques et artériographiques des artères de la verge nous avaient donné l'impression que les sténoses et occlusions de ces artères jouaient un rôle très important dans l'étiologie de nombreuses impuissances sexuelles. Nous avons, chez 21 hommes âgés de 40 à 63 ans et atteints d'impuissance, réalisé, avec des techniques de microchirurgie, une anastomose directe entre l'artère épigastrique et les corps caverneux. Le but de l'opération est d'élever le débit sanguin de base jusqu'à un niveau juste inférieur à ce qui est nécessaire pour obtenir l'érection. Ce niveau est déterminé par les études préopératoires. Il suffit alors d'un accroissement modéré de débit en réponse à un stimulus érotique pour que l'érection soit obtenue. Les complications ont été 6 thromboses de l'anastomose et 3 priapismes. Chez 13 malades, l'anastomose est restée perméable et chez ll l'érection est améliorée: 9 d'entre eux ont une activité sexuelle normale.

     

Differential trafficking of the Niemann-Pick C1 and 2 proteins highlights distinct roles in late endocytic lipid trafficking

The cellular location of Niemann-Pick C2 protein (NPC2) in cultured human fibroblasts and Chinese hamster ovary cells was examined immunocytochemically and in living cells by expression of a functional red fluorescent protein chimeric analogue. Results : NPC2 is present in the lysosomes of both cholesterol-depleted and -replenished cells, unlike Niemann-Pick C1 protein (NPC1) which is recruited to late endosomes only upon uptake of low-density lipoprotein. With mobilization of cholesterol from lysosomes, immunocytochemical detection of NPC2 in lysosomes is greatly diminished, whereas NPC1 remains in the late endosomal compartment. We found a partial overlap in the trafficking and organellar sites of accumulation of NPC2 and NPC1. In living cells, NPC2 traffics with NPC1 in late endosomal tubules. However, in contrast to NPC1, which remains either in late endosomal vesicles and tubules or at the peripheries of cholesterol-laden lysosomes, NPC2 moves into the central core of lysosomes. Glycolipid analysis reveals that, in contrast to null mutant NPC1 cells, which accumulate G_M2 ganglioside only at the plasma membrane, with no endocytic storage, absence of NPC2 protein in null mutant NPC2 cells does not block internalization of G_M2 into endocytic vesicles. This difference in the cellular distribution of G_M2 in NPC1 and NPC2 null mutants is the first report of a variation in the phenotypic expression of these genotypically distinct lesions.
Conclusion : We speculate that while NPC1 may play a major role in the sorting of glycolipids as well as cholesterol within the late endosomes, NPC2 primarily plays a role in the egress of cholesterol and, potentially, glycolipids from lysosomes. These proteins appear not to be integrated into a tightly bound biological complex, but rather represent separate functional entities that complement each other.     

Reproducibility of BOLD-based functional MRI obtained at 4 T.

The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.     

Genus Tabanus. Tabanids (horseflies). What is this insect and how does it affect man?

The insect family Tabanidae (Order: Diptera) comprises approximately 3000 species of flies worldwide, including the commonly known horseflies and deerflies. Females of most species require a blood meal to complete egg development and many species are important in human and animal medicine. This article briefly discusses the life cycle, biology, and medical significance of tabanids.     

Safety and Efficacy of I-Leucovorin Rescue Following High-Dose Methotrexate for Osteosarcoma

High-dose methotrexate with leucovorin rescue (HDMTX-LCV) is an important component of regimens used in the treatment of osteosarcoma. As of this writing the commercially available form of leucovorin is a racemic mixture of d- and l-diastereoisomers; the l-isomer is the active component. This study describes the efficacy and safety of l-leucovorin in HDMTX-LCV regimens. Fifteen patients with osteosarcoma who were enrolled into or treated according to Pediatric Oncology Group protocols 8759 and 8651 received l-leucovorin (7.5 mg every 6 hours) in place of d,l-leucovorin following high-dose methotrexate. Safety data were collected for 1 week after each course or until any toxicities resolved. The mean number of l-leucovorin doses per course was 16.2 and the mean total dose per course was 126 mg. Adverse experiences were generally mild or moderate and occurred in 54 (60%) of 90 courses of l-leucovorin therapy. One l-leucovorin patient, who had inadequate methotrexate rescue, developed severe typhlitis. There were no instances of severe, acute methotrexate toxicity. Myelosuppression was seen but, in general, was not severe. These results support the conclusion that l-leucovorin effectively rescues patients from the toxicity of high-dose methotrexate. © 1995 Wi1ey-Liss, Inc.