Suppression of quinacrine banding of human chromosomes by mounting in organic media

When Q-banded human chromosomes mounted in water are transferred to an organic mounting medium, the chromosomes show uniform bright quinacrine fluorescence. This change is reversible. It is inferred that quinacrine is bound uniformly along the chromosomes, and that Q-banding is a consequence of a non-uniform distribution along the chromosomes of chemical groups, probably proteinaceous, which affect the fluorescence efficiency of the bound quinacrine.     

Relative DNA contents of somatic nuclei of ox,sheep and goat

Diploid ox nuclei contain about 14% more DNA than nuclei from sheep of the same sex. Goat nuclei have a similar DNA content to those of sheep. In view of the similar chromosome banding patterns in these species, it appears that chromosome evolution must have involved numerous minute interstitial deletions or additions of DNA. Although chromosomes which have similar banding patterns in these three species may be regarded as homologous in this respect, and can be regarded as having a common evolutionary origin, they are not homologous for the quantity of their DNA.     

Alfalfa,Medicago sativa L., in highly weathered,acid soils

Summary Seedlings of a broad based population of alfalfa, (Medicago sativa L.), were visually selected for 2 generations (cycles) in an acid Cecil soil (pH=4.8). Simultaneously, 2 generations of selections were made in a limed Cecil soil (pH=6.2) amended with phosphorus. When tested in acid soil (pH=4.8) with added P, the cycle 2 acid selections yielded significantly more top yield than either the limed selections or the original seed. When grown in the limed soil (pH=6.2) without added P, the acid selections yielded significantly less. There were no significant differences among selections in other soil conditions (pH=4.8, no P added and pH=6.2, P added). Root weight and length and nodule fresh weight correlated well with top yield in all treatments. The yield of the 10 parent varieties and polycrossed seed of their cycle 1 acid and cycle 1 limed selections were compared under two soil conditions (acid and limed). The results of this test indicate that some varieties were more responsive to acid soil selection than other. Overall, none of the 10 varieties showed any decreases in total top yield due to one cycle of selection in either the acid or limed soil conditions.     

Limited effect of anthropogenic habitat fragmentation on molecular diversity in a rain forest skink, Gnypetoscincus queenslandiae

To examine the effects of recent habitat fragmentation, we assayed genetic diversity in a rain forest endemic lizard, the prickly forest skink (Gnypetoscincus queenslandiae), from seven forest fragments and five sites in continuous forest on the Atherton tableland of northeastern Queensland, Australia. The rain forest in this region was fragmented by logging and clearing for dairy farms in the early 1900s and most forest fragments studied have been isolated for 50-80 years or nine to 12 skink generations. We genotyped 411 individuals at nine microsatellite DNA loci and found fewer alleles per locus in prickly forest skinks from small rain forest fragments and a lower ratio of allele number to allele size range in forest fragments than in continuous forest, indicative of a decrease in effective population size. In contrast, and as expected for populations with small neighbourhood sizes, neither heterozygosity nor variance in allele size differed between fragments and sites in continuous forests. Considering measures of among population differentiation, there was no increase in FST among fragments and a significant isolation by distance pattern was identified across all 12 sites. However, the relationship between genetic (FST) and geographical distance was significantly stronger for continuous forest sites than for fragments, consistent with disruption of gene flow among the latter. The observed changes in genetic diversity within and among populations are small, but in the direction predicted by the theory of genetic erosion in recently fragmented populations. The results also illustrate the inherent difficulty in detecting genetic consequences of recent habitat fragmentation, even in genetically variable species, and especially when effective population size and dispersal rates are low.     

Effect of hydrogen peroxide and other protease inhibitors on Cryptosporidium parvum excystation and in vitro development

This study was undertaken to observe the effects of hydrogen peroxide on Cryptosporidium parvum oocysts with respect to protease activity in comparison to known protease inhibitors. In assessing the possible mechanisms of action of hydrogen peroxide, treatment effectiveness was analyzed using 3 assays and the potential roles of proteases and cations were considered. Treatment of C. parvum oocysts with hydrogen peroxide inhibited protease activity up to 50% compared with untreated controls. Treatment of oocysts with chemicals that affect sulfhydryls, including N-ethylmaleimide and dithiolthreitol, inhibited protease activity by >90%. Treatment of oocysts with these chemicals, along with the protease inhibitors, phenylmethylsulfonyl fluoride (PMSF), ethylenediamine-tetraacetic acid, and cystatin, inhibited protease activity as well as in vitro excystation and infection in a cell culture assay. Several mechanisms may result in the successful inhibition of infection and excystation by hydrogen peroxide treatment, including: oxidation of oocyst wall proteins or lipids, chelating of cations necessary for infection, or hydroxyl radical-induced DNA damage to sporozoites, or both.     

Sensitivity of periprosthetic stress-shielding to load and the bone density-modulus relationship in subject-specific finite element models

Subject-specific finite element (FE) computer models of the proximal femur in hip replacement could potentially predict stress-shielding and subsequent bone loss in individual patients. Before such predictions can be made, it is important first to determine if between subject differences in stress-shielding are sensitive to poorly defined parameters such as the load and the bone material properties. In this study we investigate if subject-specific FE models provide consistent stress-shielding patterns in the bone, independent of the choice of the loading conditions and the bone density-modulus relationship used in the computer model. FE models of two right canine femurs with and without implants were constructed based on contiguous computed tomography (CT) scans so that subject-specific estimates of stress-shielding could be calculated. Four different loading conditions and two bone density-modulus relationships were tested. Stress-shielding was defined as the decrease of strain energy per gram bone mass in the femur with the implant in place relative to the intact femur.The analyses showed that for the four loading conditions and two bone density-modulus relationships the difference in stress-shielding between the two subjects was essentially constant (1% variation) when the same loading condition and density-modulus relationship was used for both subjects. The severity of stress-shielding within a subject was sensitive to these input parameters, varying up to 20% in specific regions with a change in loading conditions and up to 10% for a change in the assumed density-modulus relationship. We conclude that although the choice of input parameters can substantially affect stress-shielding in an individual, this choice had virtually no effect on the relative differences in femoral periprosthetic stress-shielding between individuals. Thus, while care should be taken in the interpretation of the absolute value of stress-shielding calculated with these type of models, subject-specific FE models may be useful for explaining the variation in bone adaptation responsiveness between different subjects in experimental or clinical studies.     

PPAR-gamma: a nuclear receptor with affinity for cannabinoids

An increasing number of cannabinoid actions are being reported that do not appear to be mediated by either CB1 or CB2, the known cannabinoid receptors. One such example is the synthetic analog ajulemic acid (AJA), which shows potent analgesic and anti-inflammatory effects in rodents and humans. AJA binds weakly to CB1 only at concentrations many fold higher than its therapeutic range, and is, therefore, completely free of psychotropic effects in both normal subjects and pain patients suggesting the involvement of a target site other than CB1. AJA as well as several other cannabinoids appear to have profound effects on cellular lipid metabolism as evidenced by their ability to transform fibroblasts into adipocytes where the accumulation of lipid droplets can be readily observed. Such transformations can be mediated by the activation of the nuclear receptor PPAR-gamma. A variety of small molecule ligands including AJA have been shown to induce the activation of PPAR-gamma and, in some cases this has led to the introduction of clinically useful agents. It is suggested that PPAR-gamma may serve a receptor function for certain actions of some cannabinoids.     

Metabolic profiling of Medicago truncatula cell cultures reveals the effects of biotic and abiotic elicitors on metabolism

GC-MS-based metabolite profiling was used to analyse the response of Medicago truncatula cell cultures to elicitation with methyl jasmonate (MeJa), yeast elicitor (YE), or ultraviolet light (UV). Marked changes in the levels of primary metabolites, including several amino acids, organic acids, and carbohydrates, were observed following elicitation with MeJa. A similar, but attenuated response was observed following YE elicitation, whereas little response was observed following UV elicitation. MeJa induced the accumulation of the triterpene beta-amyrin, a precursor to the triterpene saponins, and LC-MS analysis confirmed the accumulation of triterpene saponins in MeJa-elicited samples. In addition, YE induced a slight, but significant accumulation of shikimic acid, an early precursor to the phenylpropanoid pathway, which was also demonstrated to be YE-inducible by LC-MS analyses. Correlation analyses of metabolite relationships revealed perturbation of the glycine, serine, and threonine biosynthetic pathway, and suggested the induction of threonine aldolase activity, an enzyme as yet uncharacterized from plants. Members of the branched chain amino acid pathway accumulated in a concerted fashion, with the strongest correlation being that between leucine and isoleucine (r2=0.941). While UV exposure itself had little effect on primary metabolites, the experimental procedure, as revealed by control treatments, induced changes in several metabolites which were similar to those following MeJa elicitation. Sucrose levels were lower in MJ- and YE-elicited samples compared with control samples, suggesting that a portion of the effects observed on the primary metabolic pool are a consequence of fundamental metabolic repartitioning of carbon resources rather than elicitor-specific induction. In addition, beta-alanine levels were elevated in all elicited samples, which, when viewed in the context of other elicitation responses, suggests the altered metabolism of coenzyme A and its esters, which are essential in secondary metabolism.