Isolation of the light-harvesting chlorophyll a/b--protein complex from thylakoid membranes of barley by adsorption chromatography on controlled-pore glass.

The light-harvesting chlorophyll $\text{a}\text{b}$-protein complex has been isolated from barley thylakoids by a rapid, single-step procedure involving adsorption chromatography on controlled-pore glass columns. The Triton X-100-solubilized complex contains a polypeptide of apparent molecular weight, 26,000; the 0.25% Triton X-100 light-harvesting chlorophyll $\text{a}\text{b}$-protein has spectral characteristics consistent with its assumed in vivo state. On the same column free chlorophyll and carotenoids have been separated from chlorophyll-protein complex 1, but this complex contained many polypeptides other than those associated with chlorophyll. This method is potentially suitable for the isolation of other thylakoid membrane proteins. It may also be generally applicable for fractionation of intrinsic membrane proteins from other sources and for separation of mixed Triton X-100-lipid micelles.     

Distribution of the molossinus allele of Sry, the testis-determining gene, in wild mice

When the Y chromosome of the laboratory inbred mouse strain C57BL/6 (B6) is replaced by the Y of certain strains of Mus musculus domesticus, testis determination fails and all XY fetuses develop either as hermaphrodites or XY females (XY sex reversal). This suggests the presence of at least two alleles of Sry, the male-determining gene on the Y:M. m. domesticus and B6. The B6 Y chromosome is derived from the Japanese house mouse, M. m. molossinus and therefore carries a molossinus Sry allele. As a first step to determine how the molossinus Sry allele evolved, its distribution pattern was determined in wild mice. The cumulative data of 96 M. musculus samples obtained from 58 geographical locations in Europe, North Africa, and Asia show the molossinus Sry allele is restricted to Japan and the neighboring Asian mainland and confirm that Japanese M. m. molossinus mice were derived in part from a race of M. m. musculus from Korea or Manchuria. Sry polymorphisms, as illustrated by the molossinus Sry allele, can serve as molecular markers for studies on the evolution of wild M. musculus populations and can help determine the role sex determination plays in speciation.      

The conversion of ATP to IMP by muscle surface enzymes

These experiments showed that an isolated muscle bundle could be used to study, simultaneously, ion transport and the activity of surface enzymes. Frog muscles were carefully dissected and incubated for four hours in Ringer's solution containing a tris buffer and 3 mM ATP; at various times samples of the medium were chromatographed and analysed spectrophotometrically for nucleotide content. Samples of the final medium were analysed for inorganic phoshpate and for ammonia. The results demonstrated the conversion of adenosine triphosphate to inosine monophosphate, via adenosine diphosphate and adenosine monophosphate. Under the conditions of the experiment IMP was detected on chromatograms within 20 minutes of incubation; at the end of four hours the media had concentrations of 2.3 mM IMP, 4.4 mM inorganic phosphate and 2.6 mM ammonia, showing a stoichiometric relation among the products formed. There was convincing evidence that the enzymes involved (ATPase, adenylate kinase and AMP deaminase) must be situated close to or on the muscle surface. No effect of ouabain (1 μM) on the activity of the ATPase, adenylate kinase or deaminase could be found in these experiments, but the drug inhibited Na and K recovery from a Na-loaded, K-depleted state.     

Chromatin,gene silencing and HIV latency

One of the cellular defenses against virus infection is the silencing of viral gene expression. There is evidence that at least two gene-silencing mechanisms are used against the human immuno-deficiency virus (HIV). Paradoxically, this cellular defense mechanism contributes to viral latency and persistence, and we review here the relationship of viral latency to gene-silencing mechanisms.     

Smoking and health care patterns among pregnant women

A population-based hospital survey of 3628 women in the postpartum period was conducted in the Ottawa-Carleton region in 1983 to determine the prevalence of smoking before and during pregnancy, the demographic and socioeconomic characteristics of women who smoke during pregnancy and the use of health care services by these women. Of the 3628 women 91% completed a full-length questionnaire and 4% completed a shorter questionnaire. Before pregnancy 37.4% of the women smoked cigarettes. Overall, 61.1% of the smokers changed their smoking habit: 31.1% stopped, 28.1% decreased the amount smoked and 2.0% increased the amount smoked. Two thirds of the women who stopped smoking did so as soon as they realized they were pregnant. Over 50% of teenagers, single women, women living common-law and women with less than a grade 11 education smoked after the 3rd month of pregnancy. The physician is in an ideal position to identify as soon as possible pregnant women who smoke and to initiate a health education program. Only a few women who smoked during pregnancy attended early prenatal classes. Physicians and class organizers must work to improve this situation if such classes are to have an impact on smoking during pregnancy.     

Attitudes and practices of primary care physicians in the management of elevated serum cholesterol levels.

We conducted a telephone survey of 102 randomly selected Ottawa family physicians to determine their attitudes and practices regarding the treatment of hypercholesterolemia. Of the 102, 56% routinely measured serum cholesterol levels in all their patients over the age of 30 years, and 24% did so for patients in more restricted age ranges. The level at which they started dietary therapy averaged 6.95 mmol/L (270 mg/dl); for 25% it was less than 6.22 mmol/L (240 mg/dl). The level at which they started drug therapy averaged 8.9 mmol/L (345 mg/dl); for only 15% was it 7.23 mmol/L (280 mg/dl) or less. Two-thirds were unable to give numerical values to the serum cholesterol levels at which they started diet therapy, and 38% used the upper limits of laboratory normal values as an indication to start therapy. Our findings contrast markedly with results reported for US family physicians, who treat hypercholesterolemia much more aggressively. The variability in practices must be addressed if public campaigns to lower serum cholesterol levels are to be undertaken.     

To clean or not to clean: Cleaning mutualism breakdown in a tidal environment

The dynamics and prevalence of mutualistic interactions, which are responsible for the maintenance and structuring of all ecological communities, are vulnerable to changes in abiotic and biotic environmental conditions. Mutualistic outcomes can quickly shift from cooperation to conflict, but it unclear how resilient and stable mutualistic outcomes are to more variable conditions. Tidally controlled coral atoll lagoons that experience extreme diurnal environmental shifts thus provide a model from which to test plasticity in mutualistic behavior of dedicated (formerly obligate) cleaner fish, which acquire all their food resources through client interactions. Here, we investigated cleaning patterns of a model cleaner fish species, the bluestreak wrasse (Labroides dimidiatus), in an isolated tidal lagoon on the Great Barrier Reef. Under tidally restricted conditions, uniquely both adults and juveniles were part‐time facultative cleaners, pecking on Isopora palifera coral. The mutualism was not completely abandoned, with adults also wandering across the reef in search of clients, rather than waiting at fixed site cleaning stations, a behavior not yet observed at any other reef. Contrary to well‐established patterns for this cleaner, juveniles appeared to exploit the system, by biting (“cheating”) their clients more frequently than adults. We show for the first time, that within this variable tidal environment, where mutualistic cleaning might not represent a stable food source, the prevalence and dynamics of this mutualism may be breaking down (through increased cheating and partial abandonment). Environmental variability could thus reduce the pervasiveness of mutualisms within our ecosystems, ultimately reducing the stability of the system.     

An assessment of the performance of a resistivity fish counter

Closed-circuit television was used to provide a visual record of the events associated with the counts recorded by a resistivity fish counter. The fish seen were classified as' large'fish > 50 cm length and' small'fish of < 50 cm. Some of the' large' fish escaped detection by the counter, some' small'fish were counted and some counts were registered when nothing was seen. The sensitivity of the counter varied inversely with water conductivity which varied inversely with discharge.
Evidence was obtained suggesting that fish ascending a weir tend to swim closer to the bottom than do those descending. It was found that fish tended to move upstream just after sunset and downstream just before sunrise except when the water was turbid and when the fish were very close to spawning. The numbers of fish movements recorded increased during those periods when discharge was decreasing after a spate but when spawning activity was at its peak, increased activity occurred in the complete absence of any change in discharge. Instances of the same fish re-crossing the counting zone several times were recorded and the simultaneous passage of more than one fish through the counting zone was observed.     

BioGraph: unsupervised biomedical knowledge discovery via automated hypothesis generation

We present BioGraph, a data integration and data mining platform for the exploration and discovery of biomedical information. The platform offers prioritizations of putative disease genes, supported by functional hypotheses. We show that BioGraph can retrospectively confirm recently discovered disease genes and identify potential susceptibility genes, outperforming existing technologies, without requiring prior domain knowledge. Additionally, BioGraph allows for generic biomedical applications beyond gene discovery. BioGraph is accessible at .