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1.
Yamuna Narayanan 《Genetics》1973,73(2):319-350
The phylogenetic relationships among the species of the D. robusta group were investigated by the analysis of chromosomal differences. Six of the ten known members of the D. robusta group were available for the study: D. colorata and D. robusta from the United States, and D. sordidula, D. pseudosordidula, D. lacertosa, and D. moriwakii from Japan. Analysis of the metaphase chromosomes from larval ganglion cells suggests that D. moriwakii and D. colorata, with rod-shaped X-chromosomes, are the more ancestral species, while D. sordidula, D. pseudosordidula, D. robusta, and D. lacertosa, with V-shaped X-chromosomes, are derived. The ancestral position of D. colorata and D. moriwakii is further strengthened by the fact that these are the two species in the D. robusta group that are cytologically closest to D. nigromelanica of the related D. melanica group. Of the four derived species, D. sordidula was found to be the closest to the ancestral species. The phylogeny based on the analysis of the gene sequences in the homologous chromosomes agreed with that indicated by the metaphase chromosomes. Since all attempts to obtain hybrids were unsuccessful except for the cross involving D. moriwakii females and D. colorata males, photographic maps of the salivary chromosomes were used to determine homology between the chromosomes of the different species. Evidence is presented to indicate that the D. robusta group originated in Asia (Japan), and that there were two migrations to the New World, the first leading to D. robusta, and the second to D. colorata. It is suggested that the route of migrations was across the Bering Land Bridge, and further, that the migrations occurred during the period from late Oligocene to middle Miocene, 20-25 million years ago. 相似文献
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N Narayanan P Bedard T S Waraich 《Canadian journal of physiology and pharmacology》1989,67(9):999-1006
In the present study, the effects of the cytosolic Ca2+ transport inhibitor on ATP-dependent Ca2+ uptake by, and unidirectional passive Ca2+ release from, sarcoplasmic reticulum enriched membrane vesicles were examined in parallel experiments to determine whether inhibitor-mediated enhancement in Ca2+ efflux contributes to inhibition of net Ca2+ uptake. When assays were performed at pH 6.8 in the presence of oxalate, low concentrations (less than 100 micrograms/mL) of the inhibitor caused substantial inhibition of Ca2+ uptake by SR (28-50%). At this pH, low concentrations of the inhibitor did not cause enhancement of passive Ca2+ release from actively Ca2+-loaded sarcoplasmic reticulum. Under these conditions, high concentrations (greater than 100 micrograms/mL) of the inhibitor caused stimulation of passive Ca2+ release but to a much lesser extent when compared with the extent of inhibition of active Ca2+ uptake (i.e., twofold greater inhibition of Ca2+ uptake than stimulation of Ca2+ release). When Ca2+ uptake and release assays were carried out at pH 7.4, the Ca2+ release promoting action of the inhibitor became more pronounced, such that the magnitude of enhancement in Ca2+ release at varying concentrations of the inhibitor (20-200 micrograms/mL) was not markedly different from the magnitude of inhibition of Ca2+ uptake. In the absence of oxalate in the assay medium, inhibition of Ca2+ uptake was observed at alkaline but not acidic pH.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
A fatty acid spin label, 16-doxyl-stearic acid, was used to determine the percent interdigitated lipid in mixtures of a neutral phospholipid and an acidic phospholipid. Interdigitation of the acidic lipid was induced with polymyxin B (PMB) at a mole ratio of PMB to acidic lipid of 1:5. This compound does not bind significantly to neutral lipids or induce interdigitation of the neutral lipids by themselves. The neutral lipids used were dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), or dipalmitoylphosphatidylethanolamine (DPPE), and the acidic lipids were dipalmitoylphosphatidylglycerol (DPPG) or dipalmitoylphosphatidic acid (DPPA). The percent interdigitated lipid was determined from the percent of the spin label which is motionally restricted, assuming that the spin label is homogeneously distributed in the lipid. Assuming further that 100% of the acidic lipid is interdigitated at this saturating concentration of PMB, the percentage of the neutral lipid which can become interdigitated along with it was calculated. The results indicate that about 20 mole % DPPC can be incorporated into and become interdigitated in the interdigitated bilayer of PMB/DPPG at 4 degrees C. As the temperature approaches the phase transition temperature, the lipid becomes progressively less interdigitated; this occurs to a greater degree for the mixtures than for the single acidic lipid. Thus the presence of DPPC promotes transformation of the acidic lipid to a non-interdigitated bilayer at higher temperatures. At the temperature of the lipid phase transition little or none of the lipid in the mixture is interdigitated. Thus the lipid phase transition detected by calorimetry is not that of the interdigitated bilayer. The shorter chain length DMPC can be incorporated to a greater extent than DPPC, 30-50 mol%, in the interdigitated bilayer of PMB-DPPG. This may be a result of reduced exposure of the terminal methyl groups of the shorter myristoyl chains at the polar/apolar interface of the interdigitated bilayer. Less than 29% of the total lipid was interdigitated in a DPPC/DPPA/PMB 1:1:0.2 mixture indicating that none of the DPPC in this mixture becomes interdigitated. This is attributed to the lateral interlipid hydrogen bonding interactions of DPPA which inhibits formation of an interdigitated bilayer. DPPE was found to be incorporated into the interdigitated bilayer of PMB-DPPG to a similar extent as DPPC if the amount of PMB added is sufficient to bind to only the DPPG in the mixture. Differential scanning calorimetry showed that the remaining non-interdigitated DPPE-enriched mixture phase separates into its own domain.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
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The critical relationship between free radicals and degrees of ischemia: evidence for tissue intolerance of marginal perfusion 总被引:8,自引:0,他引:8
M F Angel S S Ramasastry W M Swartz K Narayanan D B Kuhns R E Basford J W Futrell 《Plastic and reconstructive surgery》1988,81(2):233-239
Skin-flap ischemia has been associated with the presence of free radicals. In this study, two enzyme systems involved in free-radical metabolism were used to compare a distal skin flap to a skin graft. Forty-two rats were divided into several test groups. A 10 X 3 cm dorsal rat flap was used, and tissue biopsies for xanthine oxidase and malonyldialdehyde (MDA) were obtained 2.5, 5.5, and 8.5 cm from the base of the flap at the hours given. In group I (control), the flap was outlined but not elevated, and biopsies were obtained. In group II, the flap was elevated, and biopsies were obtained at 6 hours. In group III, the flap was elevated, the distal 4 X 3 cm was amputated and replaced as a full-thickness skin graft, and biopsies were obtained at 6 hours. In group IV, the flap was elevated, and biopsies were obtained at 12 hours. In group V, the flap was treated as in group III, and biopsies were obtained at 12 hours. In group VI, the flap was elevated, and biopsies were obtained at 24 hours. In group VII, the flap was treated as in group III, and biopsies were obtained at 24 hours. Results: Xanthine oxidase was significantly higher in all distal biopsies compared to proximal biopsies. Xanthine oxidase also increased with time. Malonyldialdehyde increased over time as well as with distance from the flap base. Distal flap biopsies at 24 hours had greatly increased levels of malonyldialdehyde compared to skin grafts (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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Cytosol from rabbit heart and slow and fast skeletal muscles was fractionated using (NH4)2SO4 to yield three cytosolic protein fractions, viz., CPF-I (protein precipitated at 30% saturation), CPF-II (protein precipitated between 30 and 60% saturation), and cytosol supernatant (protein soluble at 60% saturation). The protein fractions were dialysed and tested for their effects on ATP-dependent, oxalate-supported Ca2+ uptake by sarcoplasmic reticulum from heart and slow and fast skeletal muscles. CPF-I from heart and slow muscle, but not from fast muscle, caused marked inhibition (up to 95%) of Ca2+ uptake by sarcoplasmic reticulum from heart and from slow and fast muscles. Neither unfractionated cytosol nor CPF-II or cytosol supernatant from any of the muscles altered the Ca2+ uptake activity of sarcoplasmic reticulum. Studies on the characteristics of inhibition of sarcoplasmic reticulum Ca2+ uptake by CPF-I (from heart and slow muscle) revealed the following: (a) Inhibition was concentration- and temperature-dependent (50% inhibition with approx. 80 to 100 μg CPF-I; seen only at temperatures above 20°C). (b) The inhibitor reduced the velocity of Ca2+ uptake without appreciably influencing the apparent affinity of the transport system for Ca2+. (c) Inhibition was uncompetitive with respect to ATP. (d) Sarcoplasmic reticulum washed following exposure to CPF-I showed reduced rates of Ca2+ uptake, indicating that inhibition results from an interaction of the inhibitor with the sarcoplasmic reticulum membrane. (e) Concomitant with the inhibition of Ca2+ uptake, CPF-I also inhibited the Ca2+-ATPase activity of sarcoplasmic reticulum. (f) Heat-treatment of CPF-I led to loss of inhibitor activity, whereas exposure to trypsin appeared to enhance its inhibitory effect. (g) Addition of CPF-I to Ca2+-preloaded sarcoplasmic reticulum vesicles did not promote Ca2+ release from the vesicles. These results demonstrate the presence of a soluble protein inhibitor of sarcoplasmic reticulum Ca2+ pump in heart and slow skeletal muscle but not in fast skeletal muscle. The characteristics of the inhibitor and its apparently selective distribution suggest a potentially important role for it in the in vivo regulation of sarcoplasmic reticulum Ca2+ pump, and therefore in determining the duration of Ca2+ signal in slow-contracting muscle fibers. 相似文献
9.
Tarikere L. Gururaja Narayanan Ramasubbu Michael J. Levine 《Letters in Peptide Science》1996,3(2):79-88
Summary Short glycopeptides derived from salivary mucin have been synthesized in order to delineate the O-glycosylation pattern that is important in the biological activity of mucin. Two glycopoptides, APPETT*AAP-OMe and PAPPSS*SAP-OMe (*=-d-GalNAc), were prepared by solid-phase peptide synthesis integrating the Fmoc and Boc strategies. Since these peptides contain a C-terminal proline, we devised an efficient strategy using facile Boc chemistry, where the glycosylation at the desired position in the sequence was achieved using corresponding Fmoc-glycoamino acid esters A and B as building blocks. The transformation of the 2-azido group into the acetamido derivative was performed with thioacetic acid on the polymer-bound glycopeptides. Corresponding nonglycosylated peptides were also synthesized to study the influence of -d-GalNAc on peptide backbone conformation. 相似文献
10.
K. K. Narayanan P. Senthilkumar V. V. Sridhar G. Thomas J. Thomas 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(7-8):1087-1093
In the fertile rice line IR 36 there are two copies of the apocytochrome b (cob) gene: a functional copy, cob 1, and a pseudogene, cob 2 (Kaleikau et al. 1992). In a survey of diverse rice lines, we found that cob 2 was absent in the wild abortive(WA)-type cytoplasmic male-sterile cytoplasm, but was present in the fertile lines. While cob 1 was conserved among all the lines, fertile and sterile, the cob 2 region was different in the fertile lines tested. The 5′ regions of most cob 2 loci were similar to cob 1 (about 4 kb of the flanking region and most of the coding region), but the 3′ region varied among different fertile lines. The point of divergence, the break-point, from the cob 1 sequence was conserved in all the cob 2 regions tested. In all the cob 2 regions, this break-point seems to be linked to the variable region of cob 2 through a conserved 192-bp segment, which is not a part of cob 1. It is proposed that the cob 2 regions could have been produced by recombination or insertion events involving cob 1 and the 192-bp segment which is present at different locations in the mitochondrial genomes of the various rice lines. 相似文献