Individual admixture estimates: disease associations and individual risk of diabetes and gallbladder disease among Mexican-Americans in Starr County, Texas

The ethnic and geographic distributions of several common chronic diseases show distinct patterns that are consistent with the distribution of genes and genetic admixture. For example, diabetes and gallbladder disease occur most frequently among Amerindians, while those genetically admixed with them (such as Mexican-Americans) have intermediate rates, and lowest rates are found among Whites and Blacks. Because there will be heterogeneity from individual to individual in ancestral affinity within an admixed population, a method is developed for estimating each person's admixture probability. Results confirm that there is substantial heterogeneity of individual admixture among Mexican-Americans in Starr County, Texas, with a mean value indicating that 65% of genes in this population are Caucasian derived and 35% Amerindian derived. The individual estimates are shown to be unrelated to the probability of being diabetic and only marginally related to gallbladder disease, with those having the most Amerindian affinity being at increased risk. These results are a consequence of the independent assortment of loci and indicate that unless the markers employed are related (including linkage) to the disease of interest, the method will have limited utility. Individual admixture estimates will be useful, however, for examining aspects of population structure and will find increased utility for predicting disease and examining disease associations as more and more of the genome is represented by markers, a very probable prospect with the abundance of DNA polymorphism being identified by restriction enzymes.     

Ecological aspects of a silicified bivalve fauna from the Silurian of Gotland

The silicified Wenlockian (Silurian) bivalve fauna from MÖllbos, Gotland, is part of a life assemblage. The vast number of shells show unusual phenomena, e.g. shell repair, pearl and tumour formation, etc. A number of shells contain epibionts and bored, round holes. Presumptive predators of the bivalve community are discussed. Size-frequency distribution of the two most abundant species possibly reflects age classes. The fauna, comprising eleven species, is dominated by deposit-feeders (90 %). They exhibit niche diversification, including at least three different feeding levels within the sediment.     

The impact of zooplankton size structure on phosphorus cycling in field enclosures

Plastic bag field enclosures (1570 1) were used to investigate the relationship between zooplankton size distributions and the turnover rate of pelagic phosphorus. Water within the enclosures was filtered to simulate either low (200 µm mesh net) or high (80 µm) planktivory. The bags were then spiked with radiolabelled phosphorus and sampled 7 times during the following 24 h period. Zooplankton communities dominated by smaller size classes cycled more phosphorus than those composed of larger species. These experiments reveal that higher trophic level interactions, such as size selective predation, may have a significant impact upon nutrient regeneration rates and, hence, primary production.     

冬小麦对不同海拔气候条件的反应 Ⅲ.植株光合作用特征

我们在原地测量了840米和2150米两地种植的冬小麦“凤麦13”苗期、拔节期、抽穗期和灌浆初期的光合作用速率的日变化,光合作用速率对光量子通量密度的反应和CO_2补偿点。结果表明生育前期(苗期和拔节期)和后期(抽穗期和灌浆初期)光合作用速率的一日内变化形式相反,而且低地种植的冬小麦其光合速率在前期高于高地种植的,后期高地种植的冬小麦有比低地高的光合速率。光饱和点基本相同。光补偿点在生育前期高地小麦比低地小麦低,而后期低地小麦的的光补偿点减低,并低于高地小麦的。高地小麦的光补偿点比较稳定。CO_2补偿点高地小麦比低地的较低。并就两地气候条件讨论了上述差异。     

Compensation by locusts for changes in dietary nutrients: behavioural mechanisms

ABSTRACT. The detailed behavioural mechanisms underlying an instance of compensation for changes in dietary nutrients are described for the first time in an insect. Nymphs of Locusta migratoria L. were given one of four artificial diets on the third day of the fifth instar, and their feeding patterns recorded in detail for 12 h. The diets represented combinations of two protein and two digestible carbohydrate levels (28% and 14% dry weight) presented in an otherwise complete nutrient mix. At the nutrient levels used, locusts regulated their intake of food with respect to protein but not digestible carbohydrate in the diet. They ate more of the lower protein diets by eating the same sized meals more frequently than insects fed on the higher protein diets. Compensation was not complete over the 12 h observation period: insects on the lower-protein diets ingested and absorbed 72% as much nitrogen as those insects fed on the higher-protein diets. Possible physiological mechanisms underlying the behavioural mechanisms are discussed.     

Predation and parasitism of cotton leafworm eggs,Alabama argillacea [Lep.: Noctuidae]

The identification and efficiency of arthropod predator and parasites related to natural control of cotton leafworm eggs,Alabama argillacea (Huebner), were studied in a cotton field, Jaboticabal, SP, Brazil. Plants were marked randomly and the eggs found on them were indicated by arrow tapes for predation and parasitism observations. To evaluate and identify the arthropod fauna in the row-meter containing the marked plant, visual countings and collections using D-Vac ® and “beat sheet” were used. The average predation rate during the season, in the presence of 23.0 predators per row-meter, was 50.6% and the parasitism byTrichogrammatoidea annulata was 44.9% totaling 95.5% of egg reduction. In decreasing order of abundance, the arthropod predators found were the antPheidole sp., the spiderChrysso clementinae Petrunkevitch, the hemipteraOrius insidiosus Say andCeratocapsus mariliensis Carvalho & Fontes, and the coccinellidHyperaspis festiva (Mulsant).     

The osmaterial glands of the swallowtail butterfly Eurytides marcellus as a defence against natural enemies

ABSTRACT.

• 1 Natural enemies account for almost all mortality of zebra swallowtail caterpillars (Eurytides marcellus [Cramer]) feeding on pawpaw (Asimina spp.) in Florida.
• 2 The osmaterial glands of the third instar caterpillars reduce predation rates in the spring, but not later in the season.
• 3 The seasonal decline in effectiveness of osmateria in deterring natural enemies probably stems from a reduction in the importance of the predators that are repelled by osmateria.

     

Environmental implications of recombinant DNA technology

Applications of recombinant DNA technology are discussed as a backdrop for evaluation of the environmental impacts of this technology. Some of applications include using traditional biological techniques for specific purposes, including nitrogen fixation, microbial pesticides, and waste treatment. In these instances the final product lies along a continuum, beginning with an organism marginally performing its function, and ending with one that is highly specialised and very efficient in what it does. One may move along this continuum toward the ‘perfect’ microorganism by using traditional methodologies of mutagenesis and selection, recombinant DNA technology, or a combination of the two.     

Specific photoperiodic stimulation of dry matter production in a high-latitude cultivar of Poa pratensis

Vegetative plants of Poa pratensis L. cv. Holt (origin 69°N) raised in short days gave large and significant increases in plant dry weight, plant height and leaf area upon exposure to continuous light, compared with 8-h short days, at essentially identical daily inputs of radiant energy (8-h summer daylight ± low intensity extension). For example, by the fourth harvest (after 26, 34 and 46 days at 21, 15 and 9°C, respectively), the dry weights of plants in long days were 81, 163 and 195% greater than those of the corresponding short-day controls at the respective temperatures. Plant leaf areas in long days were between two and four times as large as control values by the end of the experiment. This was mainly due to increased leaf length caused by long-day stimulation of cell extension and division. However, the photoperiod did not affect the partitioning of assimilates amongst leaves, culms and stolons. Most of these effects could also be brought about by exogenous gibberellin application to plants in short days. However, in contrast to the effect of long days, gibberellin treatment also induced stem internode elongation even in these vegetative plants. Examination by standard growth analysis procedures revealed that the observed increases in relative growth rate were due primarily to increased net assimilation rate followed, several days later, by increases in leaf area ratio when newly-emerged leaves began to constitute a significant proportion of the leaf area. It is concluded that these reactions are of great adaptive significance for growth at the marginal temperatures prevailing at high latitudes.     

The fish community structure in Tjeukemeer in relation to fishery and habitat utilization

The fish community in Tjeukemeer was monitored from 1971 to 1988 by trawling, and during the summer of 1988 the distribution of the more abundant species was determined in relation to size and location. Bream, pikeperch and smelt were the most dominant fishes, whereas roach, white bream, perch and ruffe comprised <10% of the total catches. After the termination in 1977 of the intensive gillnet fishery both pikeperch >50 cm and bream >30 cm increased in biomass, but roach >15 cm and perch >15 cm virtually disappeared and pikeperch <50 cm substantially decreased. Only smelt, ruffe, white bream and bream <30 cm hardly changed in biomass. Bream, pikeperch, perch and smelt were restricted to the open water zone, but roach <15 cm and 0 + bream were confined to the littoral zone. White bream and ruffe did not show a distinct habitat preference. Because the recruitment of smelt is largely dependent on immigration from the IJsselmeer, a feed-back between the smelt and pikeperch population is lacking. Because the carrying capacity of the pikeperch population is mainly determined by smelt, the other fish <15 cm are very vulnerable to predation when the smelt population is consumed, before a new year-class of smelt is recruited, or when the smelt fails to recruit. The vulnerability to predation of the different species and their feeding habits are discussed in relation to their distribution.