A Second Gene for Cerulean Cataracts Maps to the β Crystallin Region on Chromosome 22

Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitageet al.(Nature Genet.9: 37–40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodkeret al.(Am. J. Med. Genet.37: 54–59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two β crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers.     

Suppression of programmed neuronal death by a thapsigargin-induced Ca2+ influx

Rat sympathetic neurons undergo programmed cell death (PCD) in vitro and in vivo when they are deprived of nerve growth factor (NGF). Chronic depolarization of these neurons in cell culture with elevated concentrations of extracellular potassium ([K⁺]_o) prevents this death. The effect of prolonged depolarization on neuronal survival is thought to be mediated by a rise of intracellular calcium concentration ([Ca²⁺]_i) caused by Ca²⁺ influx through voltage-gated channels. In this report we investigate the effects of chronic treatment of rat sympathetic neurons with thapsigargin, an inhibitor of intracellular Ca²⁺ sequestration. In medium containing a normal concentration of extracellular Ca²⁺ ([Ca²⁺]_o), thapsigargin caused a sustained rise of intracellular Ca²⁺ concentration and partially blocked death of NGF-deprived cells. Elevating [Ca²⁺]_o in the presence of thapsigargin further increased [Ca²⁺]_i, suggesting that the sustained rise of [Ca²⁺]_i was caused by a thapsigargin-induced Ca²⁺ influx. This treatment potentiated the effect of thapsigargin on survival. The dihydropyridine Ca²⁺ channel antagonist, nifedipine, blocked both a sustained elevation of [Ca²⁺]_i and enhanced survival caused by depolarization with elevated [K⁺]_o, suggesting that these effects are mediated by Ca²⁺ influx through L-type channels. Nifedipine did not block the sustained rise of [Ca²⁺]_i or enhanced survival caused by thapsigargin treatment, indicating that these effects were not mediated by influx of Ca²⁺ through L-type channels. These results provide additional evidence that increased [Ca²⁺]_i can suppress neuronal PCD and identify a novel method for chronically raising neuronal [Ca²⁺]_i for investigation of this and other Ca²⁺-dependent phenomena. © 1995 John Wiley & Sons, Inc.     

Polymorphic Admixture Typing in Human Ethnic Populations

A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (δ). The distribution of frequency differences (δ values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high δ values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066–.098), and <10% of the measured overall molecular genetic diversity in these human samples can be attributed to “racial” differentiation. The median δ values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies.     

Shifting Narratives and Mutable Meanings

In and Out of Africa . 1993. 59 minutes, color. A film by Ilisa Barbash and Lucien Taylor. For information contact University of California Extension Center for Media and Independent Learning, 2000 Center Street, Fourth Floor, Berkeley, CA 94704, 510–642–0460.     

Effect of vertebrate predation on the spatio-temporal distribution of cladocerans in a temperature eutrophic lake

We analysed the spatio-temporal distribution of zooplankton along a profile of 10 stations from the shore to the pelagic zone from April to September 1988, the period when the larvae and juveniles Rutilus rutilus, the most abundant species in the Lake, are in the littoral zone. The digestive tracts of the young roach were analysed. They fed essentially on rotifers and on cladocerans. For comparison, zooplankton was also analysed at one littoral area without fish fry. There was an increase of cladoceran density from the vegetated nearshore zone to the offshore zone. Considering the density of Bosmina longirostris, Daphnia longispina, Chydorus sphaericus and Ceriodaphnia quadrangula, we observed a different distribution pattern in the course of the year. In the nearshore zone, the relative abundance of small species, Bosmina and Chydorus, was much higher than that of the larger Daphnia. From April to September, predation pressure mainly affected the smallest species: in contrast to the inshore station without fish fry, the density of Bosmina decreased in May in the littoral with fish. Chydorus was concentrated in the littoral between February and April, then grew into the pelagic zone, where predation pressure obviously was low during the warm season. The number of Daphnia, which was eaten by the fish fry at any time, remained low in the nearshore zone, which suggests that the presence of fish may cause Daphnia to avoid this zone. Ceriodaphnia which was not affected by this predation, was scarce in the nearshore zone during mid-summer. The low density of the cladocerans in the nearshore zone is likely associated with vertebrate predation by roach fry and juveniles, the result of such a process being either a depletion in density of the prey, or an avoidance behaviour.     

Mutations affecting a regulated, membrane-associated esterase in Salmonella typhimurium LT2

Mutations at the apeA locus in Salmonella typhimurium lead to loss of a soluble enzyme (protease I) that hydrolyzes the chromogenic endoprotease substrate N-acetyl phenylalanine -naphthyl ester. We have isolated pseudorevertants of S. typhimurium apeA mutations that have regained the ability to hydrolyze this compound. These pseudorevertants contain mutations (apeR) that lead to overproduction of a membrane-bound esterase different from protease I. The apeR locus is phage P1 cotransducible with ilvC (83 map units) and is unlinked to apeA. Mutations at still another locus, apeE, lead to loss of the membrane-associated esterase. The apeE locus is P1 cotransducible with purE (12 map units). In an apeE-lacZ operon fusion strain, an apeR mutation increases the level of -galactosidase approximately 60-fold. We propose that apeR encodes a repressor of apeE. The evidence available suggests that the ApeE protein is not a protease.     

Inhibition of cuticular lipid synthesis and its effect on insect survival

A new approach to insect control—using sodium trichloroacetate (NaTCA) to inhibit synthesis of the hydrophobic cuticular lipids that protect insects from dehydration—was tested on Triatoma infestans. In vivo and in vitro studies of incorporation of radioactive precursors showed diminished cuticular hydrocarbon synthesis after NaTCA treatment. Thin layer chromatography and scanning electron microscopy showed disruption of the cuticular lipid layer of NaTCA-treated insects, which also have increased mortality and altered molting cycles. NaTCA treatment enhanced the penetration and increased the lethality of a contact insecticide. © 1994 Wiley-Liss, Inc.     

Hydrocarbon biosynthesis in Triatoma infestans eggs

Triatoma infestans eggs are shown to synthesize hydrocarbons. Radio-gas chromatography was used to demonstrate metabolism of [1-¹⁴C]propionate into precursor methyl-branched fatty acids and into methyl-branched hydrocarbons in T. infestans eggs. These reactions have not been demonstrated previously in insect eggs. An in vivo study showed that hydrocarbons are also transported to eggs by the hemolymph. Inhibition of hydrocarbon synthesis by sodium trichloroacetate (NaTCA) was correlated with reduced oviposition, reduced hatchability, and reduced insect survival. Scanning electron microscopy showed impoverishment of the eggs' epicuticular waxes following NaTCA treatment. © 1994 Wiley-Liss, Inc.