Chromosomal assignment of genes encoding the alpha, beta, and gamma subunits of human complement protein C8: identification of a close physical linkage between the alpha and the beta loci

The eighth component of human complement (C8) is a serum protein containing three nonidentical subunits (alpha, beta, gamma) that are arranged as a disulfide-linked alpha-gamma dimer and a noncovalently associated beta chain. In earlier genetic studies, electrophoretic analysis of C8 protein polymorphisms revealed several allelic variants of alpha-gamma and beta. These were governed by separate loci designated C8A and C8B for alpha-gamma and beta, respectively. Genetic linkage analyses indicated that these loci were linked to each other and to chromosome 1 marker loci PGM1 and Rh, but it was unclear at the time if C8A was a single locus coding for a single-chain precursor form of alpha-gamma or if separate loci existed for alpha and gamma. Since evidence now indicates that alpha, beta, and gamma are encoded by separate genes, cDNA probes corresponding to each subunit were used to make direct assignments of the individual loci. Analysis of somatic cell hybrids revealed that only the alpha and beta loci are located on chromosome 1. Parallel analysis of genomic DNA digests using 5' and 3'-specific cDNA probes showed they are physically linked (less than 2.5 kb) and oriented 5' alpha-beta 3'. Further probing of the hybrid panel revealed that gamma is located on chromosome 9q. Thus, the observed genetic linkage of alpha-gamma to beta must be determined solely by alpha. In accordance with these findings, the C8 loci should now be designated C8A, C8B, and C8G for alpha, beta and gamma, respectively.     

Rab5-family guanine nucleotide exchange factors bind retromer and promote its recruitment to endosomes

The retromer complex facilitates the sorting of integral membrane proteins from the endosome to the late Golgi. In mammalian cells, the efficient recruitment of retromer to endosomes requires the lipid phosphatidylinositol 3-phosphate (PI3P) as well as Rab5 and Rab7 GTPases. However, in yeast, the role of Rabs in recruiting retromer to endosomes is less clear. We identified novel physical interactions between retromer and the Saccharomyces cerevisiae VPS9-domain Rab5-family guanine nucleotide exchange factors (GEFs) Muk1 and Vps9. Furthermore, we identified a new yeast VPS9 domain-containing protein, VARP-like 1 (Vrl1), which is related to the human VARP protein. All three VPS9 domain–containing proteins show localization to endosomes, and the presence of any one of them is necessary for the endosomal recruitment of retromer. We find that expression of an active VPS9-domain protein is required for correct localization of the phosphatidylinositol 3-kinase Vps34 and the production of endosomal PI3P. These results suggest that VPS9 GEFs promote retromer recruitment by establishing PI3P-enriched domains at the endosomal membrane. The interaction of retromer with distinct VPS9 GEFs could thus link GEF-dependent regulatory inputs to the temporal or spatial coordination of retromer assembly or function.     

Effects of temporal patterning of predation threat on movement of a stream fish: evaluating an intermediate threat hypothesis

The addition of nocturnal, Hoplias malabaricus, and diurnal, Crenicichla alta, predatory fishes downstream of barrier waterfalls increases predation threat for a killifish, Rivulus hartii, in Trinidadian streams. We hypothesized that the diel patterning of predation risk would affect prey movement rates, and tested this hypothesis by comparing movement in river sites/zones containing both the nocturnal and diurnal predator with movement in river sites/zones containing only the nocturnal taxon. We evaluated this prediction in the framework of an intermediate threat hypothesis (ITH) that holds that movement will be highest at some intermediate level of threat. We marked prey fish in study sites in two watersheds of a river, each with waterfalls that divided the river into three zones: a predator absent zone (P0), a zone with one nocturnal predator (P1), and a zone with one nocturnal and one diurnal predator (P2), and tested the ITH prediction that movement will be ordered as P0<P1>P2. The single predator promoted longitudinal movement by Rivulus (P0<P1), while zones with the two predators retarded movement for small Rivulus (P1>P2) as predicted by the ITH. However, movement by larger, less vulnerable Rivulus remained elevated (P1=P2 or P2>P1). A displacement experiment in each zone found that threat tended to reduce the probability of a displaced fish reaching home, but the two predator zones did not differ from one another in their effect on this probability. Hence, the prediction that predator activity over the full 24 h diel cycle would retard movement, P2<P1, was not supported with respect to homing. Because habitat and predator communities change predictably from headwater streams to larger rivers in many lotic ecosystems, we present a conceptual model for predicting fish movement behavior along this continuum. The model posits an important role for predation threat, and the size and spacing of refuge patches, suggesting that human alterations of these factors will affect the natural movement of fish in streams.     

Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance

We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler.     

Heterobiaryl purine derivatives as potent antiproliferative agents: Inhibitors of cyclin dependent kinases. Part II

C-6 Biarylmethylamino purine derivatives of roscovitine (1) inhibit cyclin dependent kinases and demonstrate potent antiproliferative activity. Replacement of the aryl rings of the C-6 biarylmethylamino group with heterobiaryl rings has provided compounds with significantly improved activity. In particular, derivatives 18g and 9c demonstrated 1000-fold and 1250-fold improvements, respectively, in the growth inhibition of HeLa cells compared to roscovitine (1).     

The immediate effect of individual manipulation techniques on pulmonary function measures in persons with chronic obstructive pulmonary disease

Background

The use of manipulation has long been advocated in the treatment of chronic obstructive pulmonary disease (COPD), but few randomized controlled clinical trials have measured the effect of manipulation on pulmonary function. In addition, the effects of individual manipulative techniques on the pulmonary system are poorly understood. Therefore, the purpose of this study was to determine the immediate effects of four osteopathic techniques on pulmonary function measures in persons with COPD relative to a minimal-touch control protocol.

Methods

Persons with COPD aged 50 and over were recruited for the study. Subjects received five, single-technique treatment sessions: minimal-touch control, thoracic lymphatic pump (TLP) with activation, TLP without activation, rib raising, and myofascial release. There was a 4-week washout period between sessions. Protocols were given in random order until all five techniques had been administered. Pulmonary function measures were obtained at baseline and 30-minutes posttreatment. For the actual pulmonary function measures and percent predicted values, Wilcoxon signed rank tests were used to test within-technique changes from baseline. For the percent change from baseline, Friedman tests were used to test for between-technique differences.

Results

Twenty-five subjects were enrolled in the study. All four tested osteopathic techniques were associated with adverse posttreatment changes in pulmonary function measures; however, different techniques changed different measures. TLP with activation increased posttreatment residual volume compared to baseline, while TLP without activation did not. Side effects were mild, mostly posttreatment chest wall soreness. Surprisingly, the majority of subjects believed they could breathe better after receiving osteopathic manipulation.

Conclusion

In persons with COPD, TLP with activation, TLP without activation, rib raising, and myofascial release mildly worsened pulmonary function measures immediately posttreatment relative to baseline measurements. The activation component of the TLP technique appears to increase posttreatment residual volume. Despite adverse changes in pulmonary function measures, persons with COPD subjectively reported they benefited from osteopathic manipulation.