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1.
2.
High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans 总被引:1,自引:0,他引:1
We compared male-reproductive-tract polypeptides of Drosophila melanogaster
and D. simulans by using two-dimensional gel electrophoresis. Approximately
64% of male-reproductive-tract polypeptides were identical between two
randomly chosen isofemale lines from these two species, compared with 83%
identity for third-instar imaginal wing-disc polypeptides. Qualitatively
similar differences were found between reproductive tracts and imaginal
discs when D. sechellia was compared with D. melanogaster and with D.
simulans. When genic polymorphism was taken into account, approximately 10%
of male- reproductive-tract polypeptides were apparently fixed for
different alleles between D. melanogaster and D. simulans; this proportion
is the same as that found for soluble enzymes by one-dimensional gel
electrophoresis. Strikingly, approximately 20% of male-reproductive- tract
polypeptides of either D. melanogaster or D. simulans had no detectable
homologue in the other species. We propose that proteins of the Drosophila
male reproductive tract may have diverged more extensively between species
than have other types of proteins and that much of this divergence may
involve large changes in levels of polypeptide expression.
相似文献
3.
Localization of calcium in skeletal and cardiac muscle 总被引:3,自引:0,他引:3
Summary The requirement of calcium (Ca2+) in the excitation-contraction coupling of both skeletal and cardiac muscle is well established. However, the exact location of the intracellular storage sites of Ca2+ is not firmly established. We report here on the ultrastructural distribution of Ca2+ in white and red skeletal muscle and in cardiac muscle of the rat using combined phosphate-pyroantimonate (PPA) and oxalate-pyroantimonate (OPA) procedures. The methods are based on (a) stabilization and/or trapping of Ca2+ during the primary fixation step in glutaraldehyde by potassium phosphate or oxalate; (b) subsequent wash-out of all non-trapped cations such as Na+ and Mg2+ in potassium phosphate or oxalate; (c) conversion of the complexed or trapped Ca2+ into an electron-dense calcium pyroantimonate salt in 100 m-thick tissue sections; and (d) wash-out of the excess potassium pyroantimonate at alkaline pH.With the OPA procedure, mitochondria of all muscle types showed little precipitate. The junctional sarcoplasmic reticulum was stongly reactive in relaxed white skeletal muscle, negative in contracted white fibres and negative in red skeletal and cardiac muscle, independent of the state of relaxation-contraction. Other organelles were essentially free of deposits.With the PPA method, the precipitate was almost exclusively confined to the sarcolemma and its T-tubular invaginations in cardiac and slow skeletal muscle, and was absent in fast skeletal muscle. Apart from occasional deposits in mitochondria, all other organelles were free of precipitate. The sarcolemma-associated deposits were clearly confined to the inner leaflet of the lipid bilayer. The amount of precipitate varied within the contraction cycle, relaxed cells possessing the highest density.Exposure of the tissue to La3+ resulted in the complete absence of sarcolemma-bound precipitate suggesting that the Ca2+ is exchangeable. Furthermore, these cytological data suggest a basic difference in Ca2+ storage between white skeletal muscle on the one hand, and red skeletal and cardiac muscle on the other. 相似文献
4.
Csillag A. Bourne R. C. Patel Sanjay N. Stewart Michael G. Tömböl Teréz 《Brain Cell Biology》1989,18(3):369-379
Brain Cell Biology - The distribution of GABA-like immunoreactivity (GABA-LI) in the ectostriatal core (Ec) of domestic chicks (one to two days old) was investigated using (1) preembedding GABA... 相似文献
5.
A double blind study was undertaken to determine the effectiveness or oral prostaglandin E2 as a means of improving the pelvic score prior to induction of labour. 48 patients who were greater than 37 were gestation and who had Bishop scores of less than 6 entered the study. Ten tablets were given on an hourly regime. Of 25 patients in the prostaglandin group, 17 were considered successes (68.0%), whereas of 23 patients who received a placebo, 9 were successes (39.1%). No adverse effects were recorded. Prostaglandin E2 is therefore considered a safe and effective method for priming the unfavourable cervix prior to induction of labour. 相似文献
6.
Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed. 相似文献
7.
Summary Moorland pools are shallow oligotrophic soft water lakes on poorly buffered sandy soils. Diatom assemblages of samples from 16 pools taken in 1920 and 1978 were compared by analysis of pH-spectra, diversity, dissimilarity and multivariate statistical techniques.The pH-spectra of pools in the southern (S) and central (C) part of the country indicate a fall in pH from 4.5–6.0 in the old samples to 3.7–4.6 in the recent ones. The pH-spectra of the northern pools (N) do not indicate a significant shift from the original pH (ca 4.5).The number of species in the count and the diversity (indices of Simpson and Shannon) decreased significantly in S+C, and that goes also for the dissimilarity index of Dyer. No changes were found in N.The first component (PC 1) of the principal component analysis explains 61% of total variance. PC 1 is correlated with log [SO4] (r=0.83, p<0.001) and even better (r=0.95, p<0.001) with the relative sulphate concentration,i.e. the ratio of sulphate to all major anions (sulphate, chloride, bicarbonate). All old samples have low scores on PC 1, recent samples have low scores on the second (PC 2) and third (PC 3) principal component. Old samples have high scores on PC 2 and PC 3, explaining 9 and 6% of total variance, respectively.The orginal variation, caused by regional factors, is replaced by a SO4
2– controlled variation. PC 1 is nearly completely determined by the relative abundance ofEunotia exigua. This species, which is known to be very resistant to pollution by sulphur, aluminium and heavy metals, increased largely from 1920 to 1978.In spite of the rather homogeneous distribution of wet sulphate deposition in the Netherlands, substantial differences in SO4
2– content in the pools are observed, being lowest in N (0.13–0.48 meq.l–1) and highest in S+C (0.38–1.65 meq.l–1). Sulphate is positively correlated with calcium, aluminum and magnesium but negatively with factors that characterize humic acid waters (e.g. permanganate-consumption, iron and the ratio of univalent to divalent cations). Sulphate concentration depends on the intensity of sulphate reduction, accumulation by dry deposition in surrounding forests of Scots pine, drought and atmospheric deposition. 相似文献
8.
Prado Valentina Cinelli Marco Ter Haar Sterre F. Ravikumar Dwarakanath Heijungs Reinout Guinée Jeroen Seager Thomas P. 《The International Journal of Life Cycle Assessment》2020,25(12):2393-2406
The International Journal of Life Cycle Assessment - Weighting in life cycle assessment (LCA) incorporates stakeholder preferences in the decision-making process of comparative LCAs. Research... 相似文献
9.
Jean‐Pierre Desforges Floris M. van Beest Gonalo M. Marques Stine H. Pedersen Larissa T. Beumer Marianna Chimienti Niels Martin Schmidt 《Ecology and evolution》2021,11(1):338-351
Animals have adapted behavioral and physiological strategies to conserve energy during periods of adverse conditions. Heterothermy is one such adaptation used by endotherms. While heterothermy—fluctuations in body temperature and metabolic rate—has been shown in large vertebrates, little is known of the costs and benefits of this strategy, both in terms of energy and in terms of fitness. Hence, our objective was to model the energetics of seasonal heterothermy in the largest Arctic ungulate, the muskox (Ovibos moschatus), using an individual‐based energy budget model of metabolic physiology. We found that the empirically based drop in body temperature (winter max ~−0.8°C) overwinter in adult females resulted in substantial fitness benefits in terms of reduced daily energy expenditure and body mass loss. Body mass and energy reserves were 8.98% and 14.46% greater in modeled heterotherms compared to normotherms by end of winter. Based on environmental simulations, we show that seasonal heterothermy can, to some extent, buffer the negative consequences of poor prewinter body condition or reduced winter food accessibility, leading to greater winter survival (+20%–30%) and spring energy reserves (+10%–30%), and thus increased probability of future reproductive success. These results indicate substantial adaptive short‐term benefits of seasonal heterothermy at the individual level, with potential implications for long‐term population dynamics in highly seasonal environments. 相似文献
10.
L. Santana M. Teijeira E. Uriartea C. Terán G. Andrei R. Snoeck 《Nucleosides, nucleotides & nucleic acids》2013,32(7-9):1337-1339
Abstract A series of new o ne t wo subtituted c arbonucleoside analogues (OTC) of purine was synthesized and evaluated against cytomegalovims and varicella-zoster virus in human embryonic lung (HEL) cells. 相似文献