Variation at the ADAM10 gene locus is not associated with Creutzfeldt-Jakob disease

Prion diseases are characterized by the accumulation in the brain of a misfolded and protease-resistant form of the prion protein (PrP(c)). PrP(c) contains an amyloidogenic, neurotoxic sequence that is essential for conversion into PrP(Sc), the pathological isoform. During normal processing, PrP(c) is cleaved at a site within this sequence, and this cleavage is thought to destroy the amyloidogenic potential of the protein. ADAM10, a disintegrin and metalloprotease that plays a key role in the pathogenesis of Alzheimer's disease, was recently shown to use PrP(c) as a substrate. We investigated whether variability in the ADAM10 gene could contribute to the pathogenesis of Creutzfeldt-Jakob disease (CJD), by analyzing a single nucleotide polymorphism (SNP) within ADAM10, as a genetic marker potentially in linkage disequilibrium with a functional polymorphism, in patients with sporadic or variant CJD. We observed no significant differences in ADAM10 genotype or allele frequencies between CJD patients and healthy individuals. Moreover, the distribution of ADAM10 SNP genotypes and alleles did not differ between groups of patients based on genotype at the polymorphic codon 129 of the prion protein gene--the sole major genetic risk factor for CJD identified to date. Our data indicate that ADAM10 is unlikely to confer genetic susceptibility to CJD.     

Genotype-phenotype correlation in von Hippel-Lindau families with renal lesions

von Hippel-Lindau (VHL) disease arises from mutations in the VHL gene and predisposes patients to develop a variety of tumors in different organs. In the kidney, single or multiple cysts and renal cell carcinomas (RCC) may occur. Both inter- and intrafamilial heterogeneity in clinical expression are well recognized. To identify VHL-dependent genetic factors, we investigated the renal phenotype in 274 individuals from 126 unrelated VHL families in whom 92 different VHL mutations were characterized. The incidence of renal involvement was increased in families with mutations leading to truncated protein (MLTP) or large rearrangement, as compared to families with missense changes (81 vs. 63%, respectively; P=0.03). In the latter group, we identified two mutation cluster regions (MCRs) associated with a high risk of harboring renal lesions: MCR-1 (codons 74-90) and MCR-2 (codons 130-136). In addition, the incidence of RCC was higher in families with MLTP than in families with missense changes (75 vs. 57%; P=0.04). Furthermore, mutations within MCR-1 but not MCR-2 conferred genetic susceptibility to develop RCC. Overall, our data argued for a substantial contribution of the genetic change in the VHL gene to susceptibility to renal phenotype in VHL patients.     

Cytologic grade independently predicts survival of patients with pancreatic adenocarcinoma

Our objectives were to devise a cytologic grading system and determine whether it would predict survival of patients with solid-type pancreatic adenocarcinoma. We evaluated 116 consecutive patients from July 2000 to November 2002; they were followed up until September 2003. We scored the following features on rapid Romanowsky-stained endoscopic ultrasound-guided fine-needle aspiration smears: cell group architecture, single cells, nuclear grade, mucus, bizarre cells, and necrosis. A cytologic grade (low vs high) was assigned. The Kaplan-Meier estimate of 6-month survival was 76% (SE, 7%) for patients with low-grade tumors vs 50% (SE, 6%) for patients with high-grade carcinoma. The median survival for patients with low-grade vs high-grade tumors was 1 year vs 6 months, respectively (chi2 = 4.45; P = .035). Cox proportional hazards regression showed tumor stage, cancer-specific treatment, and cytologic grade to be independent predictors of survival (P = .001). No other factors (age, mass location, placement of stent, presence of concomitant chronic pancreatitis, race, sex) predicted survival. We devised a grading system that independently predicted survival in patients with pancreatic adenocarcinoma.     

Outcrossing in the homothallic oomycete,Pythium ultimum,detected with molecular markers

The oomycete Pythium ultimum is homothallic, thus a single isolate completes the sexual stage in pure culture. It has been generally assumed that homothallic oomycetes are predominantly inbreeding. In P. ultimum, antheridia occasionally develop from hyphae not directly connected to the oogonium and appear to participate in fertilization, suggesting a possible mechanism for outcrossing. We have used molecular markers to confirm that outcrossing can occur between isolates of P. ultimum. Genetic markers based on randomly amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLP) were used to distinguish isolates in a collection of P. ultimum. Two isolates displaying a high level of polymorphism were mixed and placed on media which allows the development of the sexual stage. RAPD markers were used to screen single oospore progeny to identify potential hybrids between the two parental isolates. Subsequent self-fertilization of one putative F₁ yielded a F₂ population which demonstrated segregation and independent assortment of RAPD and RFLP markers. A similar strategy was used to show that an isolate which is incapable of producing oospores in pure culture can outcross when mixed with a homothallic isolate. These results suggest that other homothallic oomycetes may be capable of outcrossing, and sexual reproduction may, therefore, play an important role in the generation of variation in homothallic oomycetes.     

Age-related accumulation of congophilic fibrillar inclusions in endocrine cells

Summary Intracellular fibrillar congophilic inclusions are well known as neurofibrillary tangles in neurons and as Biondi bodies in choroid plexus epithelial cells. Recently similar amyloid-like inclusions in adrenal cortical cells were described (Eriksson and Westermark 1990). This study on 150 adrenal glands confirms these observations. In our material the age-related accumulation of congophilic inclusions starts earlier (in the sixth decade) and reaches a higher incidence (42.7%). We found similar intracellular inclusions in other endocrine organs, for example in the anterior lobe of the pituitary, in the cells of parathyroid glands and in Sertoli cells. The age-related incidence of these fibrillar inclusions in the pituitary was 68%; the co-incidence with interstitial amyloid deposits was 49.5%. Thus the intracellular accumulation of congophilic fibrils in old age is a widespread phenomenon and occurs not only in neurons but also in endocrine cells (adrenal, pituitary and parathyroid glands) and in active secretory cells (choroid plexus and Sertoli cells).     

Cytogenetic analysis of the Asian Plethodontid salamander, Karsenia koreana: Evidence for karyotypic conservation, chromosome repatterning, and genome size evolution

A cytogenetic analysis, including the karyotype, C-bands, silver-stained nucleolus organizer regions and genome size, was performed on the recently discovered species, Karsenia koreana, the first plethodontid salamander from Asia. The karyotype consists of 14 pairs of bi-armed chromosomes, with no evidence of heteromorphic sex chromosomes. C-banding reveals a concentration of heterochromatin at the centromeres as well as at interstitial locations. The smallest chromosome (pair number 14) has symmetrical interstitial C-bands in each arm, resembling chromosome no. 14 of North American species of its sister group taxon, supergenus Hydromantes. Acomparative analysis of C-band heterochromatin and silver-stained nucleolus organizer regions of Karsenia and other plethodontid genera reveals that chromosomal evolution may have featured chromosome 'repatterning' within the context of conserved chromosome number and shape in this clade. Genome size is correlated with geographic distribution in plethodontids and appears to have important phenotypic correlates as well. The genome size of Karsenia is relatively large, and resembles that of the geographically closest plethodontids from western North America, especially species of the genus Hydromantes. The biological significance of these cytogenetic characteristics of plethodontid salamanders is discussed within an evolutionary context.     

Characterization of an influenza A virus from seals

An influenza A virus antigenically similar to A/FPV/Dutch/27 (Hav1Neq1) [H7N7] was isolated from harbor seals (Phoca vitulina) that had died of acute hemorrhagic pneumonia on Cape Cod Peninsula, beginning in the winter of 1979–1980. High titers of virus were obtained from the lungs and lower titers from the brains of the seals. Although antigenic analyses and characterization of the RNAs show that all of the genes and gene products are closely related to different avian influenza viruses, biologically the virus behaves more like a mammalian strain. The seal virus replicated and produced pneumonia in experimentally infected harbor seals, but the clinical course and pathology were less severe than in the natural infection; the virus also replicated in ferrets, cats, and pigs but produced no disease. In avian species, the seal influenza virus replicated poorly, produced no disease signs, and was not shed in the feces. Although the seal influenza virus can cause conjunctivitis in humans who have known contamination of the eyes from infected animals, serological studies detected no evidence of seroconversion among persons working with infected seals or with the virus. Preliminary studies detected antibodies to this virus in harbor seals on the New England coast but not in harbor seals, gray seals, or fur seals from other areas, suggesting that this virus may be a new introduction to this species. An Hav1Neq1 [H7N7] virus was also isolated from feral ducks in Iceland in 1980, but the two viruses could be distinguished by analysis of their RNAs and host range. The A/Seal/Mass/1/80 influenza virus provides the first evidence suggesting that a strain deriving all of its genes from one or more avian influenza viruses can be associated with severe disease in a mammalian population in nature. Whether this breach of species specificity represents a unique event in influenza evolution remains to be determined, but raises the possibility that human or animal influenza viruses may be derived directly from avian strains.     

Hyperpolarizing current of the Na/K ATPase contributes to the membrane polarization of the Purkinje cell in rat cerebellum

 The contribution of the Na/K ATPase (pump) current to the polarization of the Purkinje cell has been studied using slices of the rat cerebellum by blocking the pump with dihydro-ouabain (DHO) while recording the membrane potential with microelectrodes in the somata. From our recordings, it appeared that blocking the pump depolarized the Purkinje cells more rapidly than might be expected from shifts in Na⁺ and K⁺ concentrations, suggesting the removal of a hyperpolarizing current. Application of DHO, in the presence of tetrodotoxin (TTX), led to calcium spike firing and plateau-like discharges suggesting activation of voltage-dependent calcium channels in the dendrites. Adding 2 mM Co²⁺ to the medium did not prevent the depolarizations. Removing calcium from the bathing medium containing 2 mM Co²⁺ blocked the spiking activity but DHO application still produced a depolarization. Experiments to measure the current inhibited by DHO indicated that the Na/K pump supplies a constant current of 240 pA. Substitution of the sodium with choline produced a hyperpolarization, during which DHO had no effect on the membrane potential. Substitution of the sodium with lithium produced only a slowly developing depolarization. It is concluded that in the cerebellar Purkinje cell, a continuous sodium ion influx activates the pumps which produce a current that directly contributes to the membrane polarization. Possible pathways for this sodium influx are discussed. Received: 3 April 1997 / Received after revision and accepted: 12 May 1997