蓖麻蚕两种凝集素在蚕体内的出现与分布

蓖麻蚕Philosamia cynthia ricni血淋巴含两种凝集素,一种凝集兔新鲜红血球,凝血活力被L-鼠李糖和D-半乳糖抑制;另一种凝集戊二醛固定的人和鸡的红血球,凝血活力被岩藻糖抑制.它们在蚕的不同生长阶段及在蚕体各组织中的分布和凝血活力显著不同.血淋巴中这两种凝集素的凝血活力明显比其他组织中高.卵中测不到这两种凝集素活力.本文对这两种凝集素在蚕体中可能的生理功能进行了讨论.     

Sulfur dioxide inhibition of photosynthesis in isolated spinach chloroplasts

Photosynthetic oxygen evolution by isolated spinach (Spinacia oleracea L.) chloroplasts approached complete inhibition in the presence of a 5 mm concentration of sulfur dioxide. A similar inhibition was observed in the presence of equimolar concentrations of bisulfite ions, suggesting a parallel mode of action. In contrast, an equimolar concentration of sulfite ions was markedly less inhibitory and sulfate ions caused negligible inhibition of apparent photosynthesis. The mode of action of sulfur dioxide and related sulfur anions in inhibiting photosynthesis was found to be essentially independent of direct hydrogen-ion effects. Supplements of inorganic pyrophosphate lessened the inhibition of oxygen evolution caused by sulfur dioxide and the sulfur anions.Sulfur dioxide and the sulfur anions were almost equally effective in inhibiting cyclic and noncyclic photophosphorylation in chloroplast suspensions. However, the extent of the inhibition of these photosynthetic reactions does not appear sufficient to account for the inhibition of photosynthetic oxygen evolution by sulfur dioxide.     

The status of ribosomal RNA genes during nuclear DNA reversion in flax

Heritable changes in plant weight and nuclear DNA content may be induced in certain varieties of flax by different fertilizer environments. The large stable form (L) has 16% more nuclear DNA that the small stable form (S). In subsequent generations in particular environments the nuclear DNA difference disappears, although the plant weight differences remain, while in other environments both DNA and plant weight differences are maintained. The large stable form has 56-70% more rRNA genes than the small stable form. The majority of this difference in rDNA is maintained in types where the nuclear difference has reverted. It is suggested that the expression of the flax genome may be susceptible to a reduction in the multiplicity of rRNA genes which limits the availability of protein synthetic machinery needed for growth.     

Molecular integrity of plant ribosomal ribonucleic Acid

Thermal denaturation of plant ribosomal RNA followed by gel fractionation shows that although a large percentage of molecules contain breaks in the polynucleotide chain, 25S and 18S RNAs do exist as unique molecular species. Values for the rate constant of hydrolysis under routine denaturing conditions are of the order of 10⁻⁷ to 10⁻⁸ sec^{− 1} and these are shown not to be a result of ribonuclease activity. This high rate of hydrolysis and the use of insensitive fractionation procedures may account for the reported absence of a 25S rRNA molecule and its apparent conversion to a molecule similar in size to 18S RNA.     

A decoy set for the thermostable subdomain from chicken villin headpiece,comparison of different free energy estimators

Background  

Estimators of free energies are routinely used to judge the quality of protein structural models. As these estimators still present inaccuracies, they are frequently evaluated by discriminating native or native-like conformations from large ensembles of so-called decoy structures.     

Effect of switch trimming on udder and teat hygiene of dairy cows

The study objective was to determine the effects of trimming the switch of dairy cows on teat-end bacterial counts and udder hygiene scores. Cows (n = 102) were blocked by days in milk, milk production, and parity and then assigned to (a) treatment (trimming of their tail switch using a commercially available trimmer), or (b) control (unaltered tails). Udder hygiene was recorded for cows on Days 0 (initiation of treatment), 32, and 64. A subset of cows (n = 21) was used to assess Streptococci and coliform bacterial populations on teat ends. Samples were collected by swabbing the left front teat end before milking on Days 0, 32, and 64 and were cultured within 24 hr of sampling. The GLIMMIX and PROC Frequency (SAS Version 9.3) were used to analyze data. There were no treatment effects of switch trimming on hygiene scores or bacterial counts. These findings suggest that udder hygiene may not be driven by tail status. Environmental and management factors, such as cleanliness, stall bedding, and stall design, may be more important contributing factors in maintaining udder health.     

Macroalgae Biorefinery from <Emphasis Type="Italic">Kappaphycus alvarezii:</Emphasis> Conversion Modeling and Performance Prediction for India and Philippines as Examples

Marine macroalgae are potential sustainable feedstock for biorefinery. However, this use of macroalgae is limited today mostly because macroalgae farming takes place in rural areas in medium- and low-income countries, where technologies to convert this biomass to chemicals and biofuels are not available. The goal of this work is to develop models to enable optimization of material and exergy flows in macroalgal biorefineries. We developed models for the currently widely cultivated red macroalgae Kappaphycus alvarezii being biorefined for the production of bioethanol, carrageenan, fertilizer, and biogas. Using flux balance analysis, we developed a computational model that allows the prediction of various fermentation scenarios and the identification of the most efficient conversion of K. alvarezii to bioethanol. Furthermore, we propose the potential implementation of these models in rural farms that currently cultivate Kappaphycus in Philippines and in India.     

Rate of digesta passage in the Philippine flying lemur,Cynocephalus volans

The rate of digesta passage was measured in five captive Philippine flying lemurs (Cynocephalus volans). These animals were force fed capsules containing known quantities of either particulate or soluble markers. The volumes of the gastrointestinal tracts of three flying lemurs were determined based on the wet weight of the contents of each section of the gut. The mean rate of digesta passage was 14.37±3.31 h when determined using the particulate marker and 21.9±0.03 h when determined using the soluble marker. The values based on the particulate marker are between 2% and 10% of similar values for other arboreal folivores. The morphology of the gastrointestinal system of the Philippine flying lemur is similar to that of other hindgut fermenters. Flying lemurs have a simple stomach and a large caecum. The total gut capacity of the Philippine flying lemur is similar to that of other herbivores, but is slightly smaller than that of either the koala (Phascolarctos cinereus), a hindgut fermenter, or the three-toed sloth (Bradypus variegatus), a foregut fermenter. These data suggest that flying lemurs deal with the problems of a folivorous diet very differently than some other arboreal mammals. Phascolarctos cinereus and Bradypus variegatus may represent one extreme with Cynocephalus volans representing the other extreme along a continuum of foraging strategies that are compatible with the arboreal folivore lifestyle.Abbreviations bw body weight - EDTA ethylenediaminetetraaceticacid - MR metabolic rate - i mean rate of passage - t _exp expected time to appearance - t _o time to first appearance     

The regulation of activity of the enzymes involved in the assimilation of nitrate by higher plants

1. Possible mechanisms regulating the activities of three enzymes involved in nitrate assimilation, nitrate reductase, nitrite reductase and glutamate dehydrogenase, were studied in radish cotyledons. 2. Nitrate-reductase and nitrite-reductase activities are low in nitrogen-deficient cotyledons, and are induced by their substrates. 3. Glutamate dehydrogenase is present regardless of the nitrogen status, and the enzyme can be increased only slightly by long-term growth on ammonia. 4. Although nitrate is the best inducer of nitrate reductase, lower levels of induction are also obtained with nitrite and ammonia. The experiments did not distinguish between direct or indirect induction by these two molecules. 5. Nitrite reductase is induced by nitrite and only indirectly by nitrate. 6. The induction of both nitrate reductase and nitrite reductase is prevented by the inhibitors actinomycin D, puromycin and cycloheximide, indicating a requirement for the synthesis of RNA and protein. 7. The decay of nitrate reductase, determined after inhibition of protein synthesis, is slower than the synthesis of the enzyme. Nitrite reductase is much more stable than nitrate reductase. 8. The synthesis of nitrate reductase is not repressed by ammonia, but is repressed by growth on a nitrite medium. 9. There is no inhibition of nitrate reductase, nitrite reductase or glutamate dehydrogenase by the normal end products of assimilation, but cyanate is a fairly specific inhibitor of nitrate reductase.