Antiatherogenic effect of a low lysine: arginine ratio of protein involves alteration in the aortic glycosamihoglycans and glycoproteins

The effect of alteration of lysine: arginine ratio of the protein on the aortic glycosaminoglycans and glycoproteins was studied in rats fed cholesterol free and atherogenic diet. The concentration of total glycosaminoglycans and of individual fractions was significantly lower in the aorta in the case of diet with lysine: arginine ratio of 1.0, than the diet with a ratio of 2.0. Rats fed globulin fraction isolated from sesame seeds, which has a lysine: arginine ratio of 0.67 also showed significantly lower concentration of total and individual glycosaminoglycan fractions in the aorta than those fed casein (lysine:arginine ratio 2.0). Concentration of total hexose and fucose in the glycoproteins was also lower in the aorta in the case of lysine: arginine ratio 1.0. These results in the light of previous reports of increase in the aortic glycosaminoglycans in the early stages of atherosclerosis and increase in the total hexose and fucose in the glycoproteins in the atherosclerotic aorta indicate that the antiatherogenic effect of a low lysine: arginine ratio in the protein involves alteration in the aortic glycosaminoglycans and glycoproteins.     

Influence of the egg parasitoidPlatytelenomus busseolae [Hym.: Scelionidae] on the population ofSesamia nonagrioides [Lep.: Noctuidae] in central greece

The egg parasitoid,Platytelenomus busseolae (Gahan) (Hymenoptera: Scelionidae) was recorded from egg masses of the corn stalk borer,Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) on maize in the area of Istiaea, Central Greece. Natural parasitism was studied during the years 1986, 1987. A total of 3,382 egg masses, containing 205,227 eggs, was collected from corn fields. Parasitized eggs were found from end July to mid-October. In 1986. 76.2% of the egg masses and 42.8% of all eggs were parasitized, while in 1987, respective values were 27.6% and 12.9%. The inferior performance of the parasitoid in 1987 may be due to the unfavorable winter and summer conditions. Parasitism decreased when the host population was at its peak, but it increased again within 1 to 3 weeks. A small percentage of egg masses was completely parasitized (9.5% and 4.7% for the 2 years respectively). In 1987, the sex ratio, ♀♀/♂♂ was 1.5: 1 and 26.2% of the egg masses produced only ♂♂. Mated ♀♀ produced 3 times more ♀♀ than ♂♂. It seems that the parasitoid, under favorable weather conditions, can play a significant role in the control of the corn stalk borer.      

Seasonal water uptake and movement in root systems of Australian phraeatophytic plants of dimorphic root morphology: a stable isotope investigation

A natural abundance hydrogen stable isotope technique was used to study seasonal changes in source water utilization and water movement in the xylem of dimorphic root systems and stem bases of several woody shrubs or trees in mediterranean-type ecosystems of south Western Australia. Samples collected from the native treeBanksia prionotes over 18 months indicated that shallow lateral roots and deeply penetrating tap (sinker) roots obtained water of different origins over the course of a winter-wet/summer-dry annual cycle. During the wet season lateral roots acquired water mostly by uptake of recent precipitation (rain water) contained within the upper soil layers, and tap roots derived water from the underlying water table. The shoot obtained a mixture of these two water sources. As the dry season approached dependence on recent rain water decreased while that on ground water increased. In high summer, shallow lateral roots remained well-hydrated and shoots well supplied with ground water taken up by the tap root. This enabled plants to continue transpiration and carbon assimilation and thus complete their seasonal extension growth during the long (4–6 month) dry season. Parallel studies of other native species and two plantation-grown species ofEucalyptus all demonstrated behavior similar to that ofB. prionotes. ForB. prionotes, there was a strong negative correlation between the percentage of water in the stem base of a plant which was derived from the tap root (ground water) and the amount of precipitation which fell at the site. These data suggested that during the dry season plants derive the majority of the water they use from deeper sources while in the wet season most of the water they use is derived from shallower sources supplied by lateral roots in the upper soil layers. The data collected in this study supported the notion that the dimorphic rooting habit can be advantageous for large woody species of floristically-rich, open, woodlands and heathlands where the acquisition of seasonally limited water is at a premium.     

Ecophysiology and distribution of the endemic leafless spurgeEuphorbia aphylla and the introducedE. tirucalli (Euphorbiaceae,Euphorbia sect.Tirucalli) in the Canary Islands

The leafless spurgeEuphorbia aphylla (Euphorbiaceae), an endemic species restricted to several of the Canary Islands where it inhabits coastal and arid localities, expresses Crassulacean Acid Metabolism (CAM) when it is subjected to summer drought. A flexible CAM is consistent with the general ecology of the species. It is the only member of sect.Tirucalli native to the Canary Islands and is at the north-western edge of the section's biogeographical range. The other members of the section have a paleotropic distribution and are found throughout Africa. Many of them are regarded as obligate CAM plants, includingE. tirucalli which was used as a comparison in ecophysiological experiments examining the response ofE. aphylla to drought and temperature.     

Far-red enrichment and photosynthetically active radiation level influence leaf senescence in field-grown sunflower

Basal leaves frequently senesce before anthesis in high population density crops. This paper evaluates the hypothesis that quantitative and qualitative changes in the light environment associated with a high leaf area index (LAI) trigger leaf senescence in sunflower ( Helianthus annuus L.) canopies. Mean leaf duration (LD, time from achievement of maximum leaf area) of leaf 8 was significantly ( P < 0.05) reduced from 51 to 19 days as crop population density was increased from 0.47 to 4.76 plants m⁻². High compared to low plant population density was associated with earlier reduction in the photosynthetically active radiation (PAR) and red/far-red ratio (R/FR) reaching the target leaf. However the changes in R/FR preceded those in PAR. When the light environment of individual leaves of isolated plants growing under field conditions was manipulated using filters and FR-reflecting mirrors, LD was positively and linearly related with the mean daily PAR (MDR) received in the FR- (no FR enrichment) treatments. FR enrichment of light reaching the abaxial surface of the leaf significantly ( P < 0.05) reduced LD by 9 days at intermediate PAR levels with respect to FR-controls, but did not affect LD at the maximum PAR used in these experiments. However, when light reaching both leaf surfaces was enriched with FR, LD (for leaves receiving maximum PAR) was 13 days shorter than that of the FR- control. These results show that basal leaf senescence in sunflower is enhanced both by a decrease in PAR and by a decrease in R/FR.     

Shoot Sr concentrations in relation to shoot Ca concentrations and to soil properties

This work was aimed to investigate whether shoot Sr concentrations of plant species are related to respective Ca concentrations and to soil properties and to compare the Sr-Ca observed ratios (OR), defined as the quotient of the ratios Sr/Ca in shoots and in the soil solution or in the extractable form, among species and soils. Ten pasture plant species were grown in pots (1-L volume) filled with eight soils differing in the various physicochemical characteristics. Each pot received 50 mg Sr except those of the soil with the highest cation exchange capacity (C.E.C.) that received 100 mg Sr per pot. For each soil, shoot Sr concentrations of species were linearly and positively related with the respective Ca concentrations. C.E.C, organic matter content and Ca in the soil solution or in the extractable form were the only soil properties that were related, all negatively, with shoot Sr concentrations. The ratio of extractable Sr and Ca was positively and linearly related with the ratio of Sr and Ca. in the soil solution. OR was affected by both species and soils. Most of OR values of all species in all soils ranged between 0.8 and 1.5, except for the grass Agrostis capillaris which had the highest values for most of soils. This indicates that Agrostis capillaris compared to other species, takes up proportionally more Sr than Ca.     

Distribution and fitness effects of the son-killer bacterium inNasonia

Summary Maternally inherited microorganisms that kill male (but not female) progeny are widespread in nature. Three hypotheses have been proposed for the evolution of male-killing microorganisms: inbreeding reduction, release of resources to remaining females and inoculum for horizontal transmission. The sonkiller bacterium,Arsenophonus nasoniae, is a maternally inherited bacterium that causes lethality of male embryos of infected females in the parasitoid wasp,Nasonia vitripennis. In this paper we describe the geographical distribution and frequency of the son-killer bacterium in North American populations ofN. vitripennis andNasonia longicornis. We tested the resource release hypothesis using the body size measurements of infected and uninfected females from natural populations. No evidence was found for a fitness increase of females infected with the bacterium compared to uninfected females. We propose a modification of the existing models, termed the incremental gain hypothesis. According to this model, the bacteria are maintained in host populations due to horizontal transmission and male killing provides an incremental gain in the fitness of infected females relative to females infected with non-male-killing bacteria.     

Sex ratio regulation in the waspEupelmus vuilleti (crwf.), an ectoparasitoid on bean weevil larvae (Hymenoptera: Pteromalidae)

In Africa, the seeds and/or pods ofVigna unguiculata andVigna radiata (Papilionacea) are attacked in fields and storage structures by bruchid beetlesCallosobruchus maculatus andBruchidius atrolineatus, on which parasitoid communities can develop. One of these parasitoids is the solitary ectoparasitoidEupelmus vuilleti (Eupelmidae). The storage conditions ofV. unguiculata andV. radiata favor the overlapping of all host stages during several months. These conditions suggest that female parasitoids would vary the sex ratio of their offspring according to the different sizes or developmental stages of hosts. The sex ratio ofE. vuilleti was strongly related to the developmental stage of the hostC. maculatus. Under our experimental conditions, where superparasitism is rare, the proportion of daughters varied between 5 and 25% on the third larval stage but reached 70 to 90% on the pupae. The increase in the proportion of daughters was also observed in the absence of superparasitism. In this case, there was an absolute coincidence between the sex ratio of eggs laid and that of emerged adults. Manipulation of the sex of the egg by the females seems to take place at the time of the egg's fertilization. The relation between host weight and egg sex showed that the male eggs are preferentially laid on lighter host larvae and the female eggs on heavier ones.     

Sex-related growth rate differences in mouse preimplantation embryos in vivo and in vitro

Sex-related growth rate differences in preimplantation mouse embryos were investigated. In experiment I, Day 3 embryos were recovered from reproductive tracts, classified according to developmental stage, and cultured for 24 hr in CZB medium containing glucose. Each embryo was then reclassified and stained for measurement of number of nuclei and finally sexed using the polymerase chain reaction. In experiment II, Day 4 embryos were recovered, classified, stained, and sexed as in experiment I immediately after recovery. Morphologically, there were no differences between the sexes in either of the experiments on Day 4. However, based on number of nuclei, the data showed that in vitro conditions support the development of male embryos to the blastocyst stage compared to female embryos. Furthermore, growth rate differences were observed in vivo on Day 3, as females compacted earlier than males. These results suggest that the increased cell proliferation in cultured male embryos is an artifact caused by the in vitro environment. The variation may be due to sex differences in embryonal energy metabolism during the preimplantation stage. The growth difference implies different in vitro requirements of male and female embryos. © 1995 Wiley-Liss, Inc.