Linkage of Alzheimer's disease to chromosome 21 and chromosome 19 markers: Effect of age of onset assumptions

Age of onset heterogeneity in Alzheimer's disease families was modelled by allowing for different liability classes for affected individuals according to their age of onset when calculating lod scores to chromosome 21 and chromosome 19 markers. Linkage to chromosome 21 was supported in the Boston data set, and the method of age correction did not greatly change the lod scores when only affected individuals were analyzed. The location of a gene on chromosome 19 for late age of onset illness was affected by the assumptions about early onset individuals. © 1993 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Schedule dependent potentiation of antitumor drug effects by α-difluoromethylornithine in human gastric carcinoma cells in vitro

A clone of human gastric cancer cells (AGS-6) and the parental line (AGS-P) from which it was isolated were used in cell survival studies to determine whether pretreatment for 24, 48 or 72h with -difluoromethylornithine (DFMO, 5mM) would increase the cell's sensitivity to 5-Fluorouracil (5FU), Adriamycin (Adria), 1-(2-chloroethyl)-3-(4-methyl cyclohexyl)-1-nitrosourea (MeCCNU), or Bleomycin (Bleo). Generally, the AGS parental cells were most sensitive to the anticancer agents after exposures to DFMO. However, there was no way to predict in advance from DFMO-induced changes in ornithine decarboxylase (ODC), polyamine or cell kinetics values, how long an exposure to DFMO was required before sensitization to an anticancer agent occurred. The degree of potentiation for a single drug was variable from time to time during exposure to DFMO, and broad differences in the sensitizations were demonstrated among the four anticancer drugs. The AGS-6 clone exhibited little or no increased sensitivity as a result of pretreatment with DFMO, even though the DFMO-induced reductions in ODC and polyamine values in these cells were similar to those produced in the more sensitive parental line.     

A Dutch family with progressive sensorineural hearing impairment linked to the DFNA2 region

We studied a Dutch family with DFNA2-linked progressive sensorineural hearing impairment (SNHI). Recent audiograms were obtained from 18 of the affected persons (age 7–81 years) and were used in a gene-linkage analysis. Linear regression analysis of the audiograms, using binaural mean thresholds, disclosed on average a descending slope of approximately 10 dB/octave at any age and an annual threshold increase at any frequency of about 0.7 dB/year. There may have been substantial congenital impairment at higher frequencies, but longitudinal analysis of hearing impairment in the youngest case, who was followed from age 5 years, suggested that the most significant changes in hearing may have occurred in the first two decades of life. Linkage analysis was carried out with special attention to the DFNA2 region because hearing trends were very similar to families previously linked to DFNA2. Linkage to DFNA2 was established with maximum lod scores of 4.7 and 3.2 for the flanking markers of the DFNA2 region (D1S432;MYCL1). Received: 25 February 1999 / Accepted: 11 June 1999     

多巴胺转运载体基因多态性及帕金森病遗传易感性的关系

目的 探讨多巴胺转运载体（ＤＡＴ）基因３’ＶＮＴＲ多态性与帕金森病（ＰＤ）遗传易感性的关系。方法 选择确诊的ＰＤ患者１７１例和正常人１８０名,利用ＰＣＲ扩散增片段长度多态性（Ａｍｐ－ＦＬＰ）技术检测ＤＡＴ基因３’ＶＮＴＲ多态性,并分析比较ＰＤ组与对照组之间多态性频率的差异。结果 发现ＰＤ组和对照组之间ＤＡＴ基因３’ＶＮＴＲ多态位点基因型分布和等位基因频率差异均有显著意义（Ｐ〈０．０５）。ＤＡＴ基因     

Heterogeneity of Na+/K+-ATPase from rectal gland of Squalus acanthias is not due to α isoform diversity

 Purified Na⁺/K⁺-ATPase (EC 3.6.1.37) isolated from the rectal gland of Squalus acanthias was characterized in ouabain-binding studies and with respect to isoform(s) of the α peptide. To avoid enzyme inactivation [³H]ouabain equilibrium binding was carried out at 20°C. The heterogeneity of Na⁺/K⁺-ATPase isolated from shark rectal gland was similar in [³H]ouabain binding as previously seen in hydrolytic studies. The binding isotherms were compatible with the existence of a high-affinity (K _dis 0.69 nM) and a low-affinity (K _dis 42 nM) component of 1.46 and 0.79 nmol^.(mg protein)^–1, respectively. In Western blots the α peptide of the enzyme hybridized with an isoform-specific polyclonal antibody raised to an α₃-specific region of the large intracellular domain of rat Na⁺/K⁺-ATPase, but not with the supposed α₃-specific monoclonal antibody MA3-915 with its epitope near the N-terminus. Semi-quantitative analysis of the reaction of the α₃-specific polyclonal antibody with the α peptide from the shark enzyme compared to the reaction with α peptide from rat brain enzyme indicated that this region is not exactly the same in the two species. The α peptide of shark enzyme was not recognized by α₁- or α₂-specific polyclonal antibodies, or by the α₁-specific monoclonal antibodies 3B and F6. The large intracellular domain of Na⁺/K⁺-ATPase from shark rectal gland thus seems to be α₃-like and no α isoform heterogeneity seems able to account for the heterogeneity seen in ouabain binding. Received: 7 August 1998 / Accepted: 6 November 1998     

MDA in plasma as a biomarker of exposure to pyrolysed MDI-based polyurethane: correlations with estimated cumulative dose and genotype for N-acetylation

The object of this study was to investigate whether exposure of pipe-layers to thermal degradation products of diphenylmethane diisocyanate (MDI) could be assessed by analysing 4,4-methylenedianiline (MDA) in hydrolysed plasma and urine, and whether the genotype for N-acetylation affected these biomarker levels. Blood and urine samples were drawn from 30-pipe-layers who had been welding polyurethane (PUR) insulated pipes during the preceding 3 months. MDA in hydrolysed plasma and urine was determined with a gas chromatography-mass spectrometry technique, and genotype for N-acetylation was analysed with a polymerase chain reaction technique. MDA in plasma was detected in 18 of the 30 pipe-layers. Their plasma concentrations of MDA varied from 0.05 to 8.48 g/1. There was a significant negative correlation between time since last welding of PUR-insulated pipes and P-MDA (r _s = 0.50, P = 0.005). There was also a significant positive correlation between the estimated number of welded PUR-insulated pipes during the preceding 3 months and P-MDA (r _s = 0.68, P = < 0.001). No significant association between genotype of N-acetylation and P-MDA was observed in a multiple regression analysis when adjustment was made for the estimated cumulative exposure to thermal degradation products of MDI. MDA in urine was detected in only four of the 30 pipe-layers. These four subjects had been welding PUR pipes on the same day as the sampling, or on the day before. The present results indicate the spot plasma samples analysed for MDA may give a rather good estimate of exposure to MDI during the preceding months. P-MDA, but not U-MDA, therefore seems to be a useful biomarker of long-term exposure to MDI. The individual N-acetylation capacity did not affect the plasma levels of MDA.     

Diffusion of information about genetic risk within families

Recent developments in genetics are likely to exacerbate the ethical issues in clinical practice, especially with regard to privacy and disclosure of genetic information. To evaluate the behaviour of patients with respect to transmitting carrier information, we undertook a survey of 283 families with a balanced chromosomal rearrangement as a model. In these families, 1816 relatives were considered at risk and 806 of them were karyotyped (44.4%). The percentage of karyotypes performed is significantly related to the number of living children of the index couple, the reason for referral, the nature of the anomaly, the training of the counsellor and the age of the index case. This study shows the limits of the screening of at risk individuals within families, based on the willingness of the patients, and addresses practical and ethical issues around family disclosure in medical genetics.     

A genetic analysis of the hyperthermic response to d-amphetamine in two inbred strains of mice

A genetic analysis of amphetamine-induced hyperthermia was conducted in inbred mice of the strains Balb/c and C₃H and in their F₁F₂ and backcross generations. The results of biometric analysis indicate that the effect of amphetamine on body temperature is genetically determined. The mode of inheritance characterized by a partial dominance (Balb/C over C₃H strain). However, a possible matermal effect of C₃H can overcome the dominant effect in male progenies and inhibit amphetamine hyperthermic effect.