Multicolor in situ hybridization and linkage analysis order Charcot-Marie-Tooth type I (CMTIA) gene-region markers.

This study demonstrates a clear and current role for multicolor in situ hybridization in expediting positional cloning studies of unknown disease genes. Nine polymorphic DNA cosmids have been mapped to eight ordered locations spanning the Charcot-Marie-Tooth type 1 (CMT1A) disease gene region in distal band 17p11.2, by multicolor in situ hybridization. When used with linkage analysis, these methods have generated a fine physical map and have firmly assigned the CMT1A gene to distal band 17p11.2. Linkage analysis with four CMT1A pedigrees mapped the CMT1A gene with respect to two flanking markers (8B10-5 cM[LOD 5.2]-CMT1A-3.5 cM[LOD 5.3]-10E4). Additional loci were physically mapped and ordered by in situ hybridization and analysis of phase-known recombinants in CMT1A pedigrees. The order determined by multicolor in situ hybridization was 17cen-LEW301-8B10-5H5/6A9-VAW409- 5G7-6G1-4A11-VAW412-10E4-pter. Two ordered probes, 4A11 and 6G1, reside on the same 440-kb partial SfiI restriction fragment. These data demonstrate the ability of in situ hybridization to resolve loci within 0.5 Mb on early-metaphase chromosomes. Multicolor in situ hybridization also excluded the possibility of pericentric inversions in two unrelated patients with CMT1 and neurofibromatosis type 1. When used with pulsed-field gel electrophoresis, multicolor in situ hybridization can establish physical location, order, and distance in closely spaced chromosome loci.     

植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

Genetic Analysis of a Kindred With X-linked Mental Handicap and Retinitis Pigmentosa

A kindred is described in which X-linked nonspecific mental handicap segregates together with retinitis pigmentosa. Carrier females are mentally normal but may show signs of the X-linked retinitis pigmentosa carrier state and become symptomatic in their later years. Analysis of polymorphic DNA markers at nine loci on the short arm of the X chromosome shows that no crossing-over occurs between the disease and Xp11 markers DXS255, TIMP, DXS426, MAOA, and DXS228. The 90% confidence limits show that the locus is in the Xp21-q21 region. Haplotype analysis is consistent with the causal gene being located proximal to the Xp21 loci DXS538 and 5'-dystrophin on the short arm of the X chromosome. The posterior probability of linkage to the RP2 region of the X chromosome short arm (Xp11.4-p11.23) is .727, suggesting the possibility of a contiguous-gene-deletion syndrome. No cytogenetic abnormality has been identified.     

Altered free calcium transients in pig kidney cells (LLC-PK1) cultured with penicillin/streptomycin

Summary The effect of a conventional antibiotic (penicillin/streptomycin) mixture on the widely used kidney epithelial cell line, LLC-PK₁, was investigated by measuring growth and intracellular free calcium. Free calcium concentration was the same in cells cultured for 3 to 7 wk with (“plus”) and without (“minus”) antibiotics both at rest and when challenged with high (14 mM) external calcium. When exposed to vasopressin, minus cells exhibited significantly smaller calcium transients than plus cells. A similar difference existed for transients elicited by a calcium ionophore, 4-br-A23187. After longer periods of culture (>20 wk), minus cells grew slower than plus cells but on reaching confluence (minus cells took 1 day longer) the morphologies and viabilities were indistinguishable. The finding that culture with penicillin/streptomycin reversibly modified some properties of LLC-PK₁ cells, at least partly through altered calcium homeostasis, is of importance for workers using this cell model to study drug effects and raises the general possibility of similar effects on other cultured cells.     

Chromosome 14 and late-onset familial Alzheimer disease (FAD)

Familial Alzheimer disease (FAD) is genetically heterogeneous. Two loci responsible for early-onset FAD have been identified: the amyloid precursor protein gene on chromosome 21 and the as-yet-unidentified locus on chromosome 14. The genetics of late-onset FAD is unresolved. Maximum-likelihood, affected-pedigree-member (APM), and sib-pair analyses were used, in 49 families with a mean age at onset ≥60 years, to determine whether the chromosome 14 locus is responsible for late-onset FAD. The markers used were D14S53, D14S43, and D14S52. The LOD score method was used to test for linkage of late-onset FAD to the chromosome 14 markers, under three different models: age-dependent penetrance, an affected-only analysis, and age-dependent penetrance with allowance for possible age-dependent sporadic cases. No evidence for linkage was obtained under any of these conditions for the late-onset kindreds, and strong evidence against linkage (LOD score ≤ –2.0) to this region was obtained. Heterogeneity tests of the LOD score results for the combined group of families (early onset, Volga Germans, and late onset) favored the hypothesis of linkage to chromosome 14 with genetic heterogeneity. The positive results are primarily from early-onset families. APM analysis gave significant evidence for linkage of D14S43 and D14S52 to FAD in early-onset kindreds (P < .02). No evidence for linkage was found for the entire late-onset family group. Significant evidence for linkage to D14S52, however, was found for a subgroup of families of intermediate age at onset (mean age at onset ≥60 years and <70 years). These results indicate that the chromosome 14 locus is not responsible for Alzheimer disease in most late-onset FAD kindreds but could play a role in a subset of these kindreds.     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

A MOLECULAR AND MORPHOLOGICAL ANALYSIS OF THE GYMNOGONGRUS DEVONIENSIS (RHODOPHYTA) COMPLEX IN THE NORTH ATLANTIC1

The Gymnogongrus devoniensis (Greville) Schotter complex in the North Atlantic Ocean was elucidated by comparative molecular, morphological, and culture studies. Restriction fragment length patterns and hybridization data on organellar DNA revealed two distinct taxa in samples from Europe and eastern Canada. Nucleotide sequences for the intergenic spacer between the large and small subunit genes of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and the adjoining regions of both genes, differed by 12.5–13.4% between the two taxa. One of the taxa, which included material from the type locality of G. devoniensis at Torbay, Devon, England, was taken to represent authentic G. devoniensis. Within this taxon, samples from Ireland, England, northern France, northern Spain, and southern Portugal showed great morphological variation, particularly in habit, but their Rubisco spacer sequences were identical or differed by only a single nucleotide. Constant morphological features included the development, from a single auxiliary cell, of the spherical cystocarp with a thick mucilage sheath that appears to be typical of Gymnogongrus species with internal cystocarps. Two life-history types were found. Northern isolates underwent a direct-type life history, recycling apomictic females by carpospores, whereas the Portuguese isolate followed a heteromorphic life history in which carpospores gave rise to a crustose tetrasporophyte. The second group of samples, from Nova Scotia and Northern Ireland, provisionally referred to as Gymnogongrus sp., showed little morphological variation. The life history in both areas consists of apomictically reproducing diploid female gametophytes and diploid crustose bisporophytes and tetrasporophytes. Rubisco spacer sequences of the samples were identical, and the plasmid previously described in the Nova Scotian samples was also present in the Northern Ireland population. This species is widely distributed in the western Atlantic, from Newfoundland to Massachusetts. In Europe, gametophytes are known only at one site, but crusts are distributed from Denmark, Scotland (and probably Norway) to France. It is very likely that this species was introduced from one side of the North Atlantic to the other by shipping during the early nineteenth century. Several morphological features are unusual within the genus but are shared with G. leptophyllus J. Agardh from the eastern Pacific Ocean, and further work is necessary to determine whether Gymnogongrus sp. and G. leptophyllus are conspecific.     

Tomato exo-(1-->4)-beta-D-galactanase. Isolation, changes during ripening in normal and mutant tomato fruit, and characterization of a related cDNA clone.

An exo-(1-->4)-beta-D-galactanase was isolated from ripe tomato fruit (Lycopersicon esculentum Mill. cv Ailsa Craig and cv Better Boy) using anion-exchange, gel filtration, and cation-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the most active fraction revealed a predominant protein band at 75 kD and several minor bands. A 30-amino acid N-terminal sequence from this 75-kD protein showed a high degree of homology with other recently identified beta-galactosidase/ galactanase proteins from persimmon and apple fruits (I.-K. Kang, S.-G. Suh, K.C. Gross, J.-K. Byun [1994] Plant Physiol 105: 975-979; G.S. Ross, T. Wegrzyn, E.A. MacRae, R.J. Redgwell [1994] Plant Physiol 106: 521-528) and with the predicted polypeptide sequence encoded by the ethylene-regulated SR12 gene in carnation (K.G. Raghothama, K.A. Lawton, P.B. Goldsbrough, W.R. Woodson [1991] Plant Mol Biol 17: 61-71). The enzyme focused to a single band of beta-galactosidase activity on an isoelectrofocusing gel at pH 9.8. The enzyme was specific for (1-->4)-beta-D-galactan substrates with a pH optimum of 4.5. The only reaction product detected was monomeric galactose, indicating that the enzyme was an exo (1-->4)-beta-D-galactanase. beta-Galactanase activity increased at the onset of ripening in normal fruit, but no similar increase was detected in the nonripening mutants nor and rin. A tomato homolog (pTombetagal1) was isolated using the SR12 cDNA clone from carnation as a probe. This clone showed 73% identify at the amino acid level with beta-galactosidase-related sequences from apple and asparagus and 66% identity with SR12. pTombetagal1 is a member of a gene family. Northern analysis demonstrated that pTombetagal1 expression was ripening related in normal fruits, with lower levels apparent in the nonsoftening mutants.