Comparison of statistics for candidate-gene association studies using cases and parents.

Studies of association between candidate genes and disease can be designed to use cases with disease, and in place of nonrelated controls, their parents. The advantage of this design is the elimination of spurious differences due to ethnic differences between cases and nonrelated controls. However, several statistical methods of analysis have been proposed in the literature, and the choice of analysis is not always clear. We review some of the statistical methods currently developed and present two new statistical methods aimed at specific genetic hypotheses of dominance and recessivity of the candidate gene. These new methods can be more powerful than other current methods, as demonstrated by simulations. The basis of these new statistical methods is a likelihood approach. The advantage of the likelihood framework is that regression models can be developed to assess genotype-environment interactions, as well as the relative contribution that alleles at the candidate-gene locus make to the relative risk (RR) of disease. This latter development allows testing of (1) whether interactions between alleles exist, on the scale of log RR, and (2) whether alleles originating from the mother or father of a case impart different risks, i.e., genomic imprinting.     

Suppressive effects of soluble histocompatibility antigens on the in vitro generation of cytotoxic T cells to D-end alloantigens

Murine histocompatibility antigens were solubilized from the spleens and lungs of C57BL/6 (H-2b) animals with hypertonic salt (3 M KC1). Aggregate-free soluble antigens were incubated with nonadherent lymph node cells from BALB/c (H-2d) mice for 18 hr prior to their use as responder cells in the mixed-lymphocyte reaction (MLR). It was found that the generation of cytotoxic cells was suppressed while the proliferative response was not affected. The observed suppression was not due to a shift in the kinetics of the generation of cytotoxicity as determined throughout a 10-day culture period. The suppression was specific in that the response in MLR to unrelated H-2f stimulator cells and the subsequent generation of cytotoxic cells were unchanged. Using various H-2 recombinant strains as target cells in the assay of cell-mediated lympholysis, suppression of cytotoxicity was observed when the D end, but not the K end, was shared with the C57BL/6 strain from which the antigens were derived.     

The unusual social organization of the antPachycondyla tridentata (Formicidae,ponerinae)

Colonies of the ponerine antPachycondyla tridentata from Malaysia occur with and without queens. In a total of 7 colonies we found more than 80% of the workers to be mated, irrespective of the presence or absence of queens. This is a hitherto unknown social organisation in ants. Queens and workers competed equally for reproduction. In the colonies investigated several ants were laying eggs. Behavioral observations revealed persistent dominance interactions between colony members. A few ants, but not necessarily a queen, occupied top positions. Removal of the most dominant ants led to a new hierarchy in which subordinate ants with developed ovaries were attacked significantly more frequently than non-reproductive ants. On the average, callows were more aggressive than older subordinate ants, displacing most of the older laying workers in one colony. Nestmate recognition tests revealed that non-reproductive ants were much more aggressive towards foreign ants than were ants with developed ovaries.     

Die Belichtungsreaktionen sessiler Crustaceen(Balanus balanus) als Alternative zu den Schutzreaktionen bodenbewohnender mariner Wirbelloser

Shadow responses, including reactions to both increase (on) and decrease (off) in light intensity have been hitherto described in the adults of various bottom-dwelling marine invertebrates. These reactions as expressed by decrease in activity are assumed to be protective (withdrawal responses, kinetic rigidity after v. Buddenbrock, 1952). By contrast, the free-swimming larvae of these species normally show increase in activity to both increase and decrease in light intensity as expressed by negative or positive photoresponses. In the sessile barnacleBalanus balanus L. reactions to increase in light intensity are demonstrated which, contrary to the withdrawal responses or kinetic rigidity, result in an increase of cirral activity. The shadow responses of the barnacles (off responses) are described as withdrawal responses. The light responses are expressed by two different modes of behaviour: (a) If an active barnacle is stimulated by increase in light intensity, the frequency of cirral activity increases; (b) if an inactive barnacle is stimulated by increase in light intensity, the cirral activity arises a short time later. The light responses observed are interpreted as a metamorphosis of larval swimming activity.

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Gefördert von der Deutschen Forschungsgemeinschaft     

Ammonia volatilization after injection of anhydrous ammonia into arable soils of different moisture levels

Laboratory experiments have shown appreciable losses of ammonia after injection of anhydrous ammonia into dry and wet soils. In this study losses of ammonia injected into a moist (tension 10 kPa), dry (tension 160 kPa) and a wet (tension 1.6 kPa) sandy loam were measured under field conditions using wind tunnels. Losses were insignificant from a moist soil. However losses from a dry and a wet soil were 20% and 50% of injected ammonia, respectively. From the dry soil, losses of gaseous ammonia took place within the first hours after injection, which indicates a rapid transport through cracks and voids. From the wet soil, 20% of the injected ammonia was lost more gradually between 6 h and 6 d. This indicates that upward movement of water due to evaporation may be the cause of these ammonia losses which proceeded for longer periods.     

Direct sequencing of the dopamine D2 receptor (DRD2) in schizophrenics reveals three polymorphisms but no structural change in the receptor.

The dopamine D2 receptor gene (gene symbol DRD2) is a candidate gene for schizophrenia because the potency of certain neuroleptics correlates with their affinity for this receptor. Seven regions of likely functional significance including the coding sequences and the splice junctions were fully sequenced in the dopamine D2 receptor of 14 schizophrenics (and partially in several others) meeting DSM-III-R diagnostic criteria and in four unaffected non-Caucasians (97 kb of total sequence). No structural changes were found, suggesting that alteration in the structure of the dopamine D2 receptor is not commonly involved in the etiology of schizophrenia. However, two common and one uncommon intragenic polymorphisms were found. At least one of the polymorphisms was informative for linkage in 70% of Caucasians and 78% of Koreans.     

Co-curing of plasmids affecting killer double-stranded RNAs of Saccharomyces cerevisiae: [HOK], [NEX], and the abundance of L are related and further evidence that M1 requires L.

We describe two sets of plasmid-plasmid interactions in the yeast Saccharomyces cerevisiae. [HOK], [EXL], [NEX], and [KIL-k1] are genetically defined plasmids, and M1 and L are biochemically defined double-stranded RNA plasmids. We show that (i) [HOK], [NEX], and the abundance of L are related, and (ii) under submaximal curing conditions, all colonies retaining M1 also retain L. There are three pieces of evidence that either [NEX] required [HOK] for replication or [NEX] and [HOK] are on the same plasmid. The evidence is as follows. (i) The great majority of strains containing [HOK] also contain [NEX]. However, two [HOK] [NEX-o] strains do exist. (ii) Growth at 39 degrees C or growth at 34 degrees C with 3% ethanol or 2-propanol cures [HOK] and [NEX]. In a [HOK] [NEX] strain, the two plasmids are always co-cured. (iii) [HOK] and [NEX] are both maintained in mak4, mak6, and mak27 strains (mak = maintenance of [KIL-k1]), but not in mak3, mak10, and pet18 strains. Strains containing [HOK] and [NEX] have about fourfold more L double-stranded RNA than their isochromosomal, cured derivatives. In addition, a cytoductant which has acquired [HOK] and [NEX] has fourfold more L than its parent. These results are consistent with either [HOK] being a form of L or [HOK] increasing the copy number of L. Using a K1 killer strain in which L, as well as M1, could be cured by growth at 38 degrees C, we examined the distribution of loss of M1 and L under conditions giving 98% M-o colonies and at least 50% L-o colonies. No M1L-o colonies were observed, supporting the previous suggestion by others that M1 requires L.