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1.
Histological and histochemical studies of oocyte development in the bass, Dicentrarchus labrax L., showed that three types of inclusions are formed during vitellogenesis. Lipid yolk accumulates first as lipid droplets, followed by protein yolk in the form of discrete protein yolk granules. The third type of inclusion are the small cortical alveoli (intravesicular yolk/yolk vesicles, i.e.'carbohydrate yolk') which form in the peripheral cytoplasm after both the lipid and protein yolk have started to accumulate. While the protein yolk granules maintain their structural integrity through to maturation, forming a densely packed zone in the mid-outer cortex, the lipid yolk droplets continually coalesce and migrate centripetally, forming a prominent zone of large lipid droplets in the inner-mid cortex. From the histological study of oocyte development, a number of distinct developmental stages are delineated, while gross examination of the paired ovary revealed that, depending on its stage of development, it can be placed into one of seven maturity stages. 相似文献
2.
Isolation and characterization of plasma membrane-associated cortical granules from sea urchin eggs 总被引:9,自引:6,他引:3
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Cortical granules, which are specialized secretory organelles found in ova of many organisms, have been isolated from the eggs of the sea urchins Arbacia punctulata and Strongylocentrtus pupuratus by a simple, rapid procedure. Electron micropscope examination of cortical granules prepared by this procedure reveals that they are tightly attached to large segments of the plasma membrane and its associated vitelline layer. Further evidence that he cortical granules were associated with these cell surface layers was obtained by (125)I-labeling techniques. The cortical granule preparations were found to be rich in proteoesterase, which was purified 32-fold over that detected in a crude homogenate. Similarly, the specific radioactivity of a (125)I-labeled, surface glycoprotein was increased 40-fold. These facts, coupled with electron microscope observations, indicate the isolation procedure yields a preparation in which both the cortical granules and the plasma membrane-vitelline layer are purified to the same extent. Gel electrophoresis of the membrane-associated cortical granule preparation reveals the presence of at least eight polypeptides. The major polypeptide, which is a glycotprotein of apparent mol wt of 100,000, contains most of the radioactivity introduced by (125)I-labeling of the intact eggs. Lysis of the cortical granules is observed under hypotonic conditions, or under isotonic conditions if Ca(2+) ion is present. When lysis is under isotonic conditions is induced by addition of Ca(2+) ion, the electron-dense contents of the granules remain insoluble. In contrast, hypotonic lysis results in release of the contents of the granule in a soluble form. However, in both cases the (125)I-labeled glycoprotein remains insoluble, presumably because it is a component of either the plasma membrane or the vitelline layer. All these findings indicate that, using this purified preparation, it should be possible to carry out in vitro studies to better define some of the initial, surface-related events observed in vivo upon fertilization. 相似文献
3.
Biomechanics of chelipeds in some decapod crustaceans 总被引:2,自引:0,他引:2
The major chelipeds of five species of decapod crustaceans were studied with reference to lever system mechanical advantage, pattern of occlusive geometry, and force/pressure developed during cheliped closure by intact animals. Every cheliped type was found to possess a linear array of two to four distinctive regions of occlusion. The factors responsible for the differences in occlusive design are discussed. It is suggested that crustacean major chelipeds must be regarded as regionally-specialized, multifunctional appendages. 相似文献
4.
Carolina Mazo‐Molina Samantha Mainiero Benjamin J. Haefner Ryland Bednarek Jing Zhang Ari Feder Kai Shi Susan R. Strickler Gregory B. Martin 《The Plant journal : for cell and molecular biology》2020,103(4):1433-1445
The Ptr1 (Pseudomonas tomato race 1) locus in Solanum lycopersicoides confers resistance to strains of Pseudomonas syringae pv. tomato expressing AvrRpt2 and Ralstonia pseudosolanacearum expressing RipBN. Here we describe the identification and phylogenetic analysis of the Ptr1 gene. A single recombinant among 585 F2 plants segregating for the Ptr1 locus was discovered that narrowed the Ptr1 candidates to eight nucleotide‐binding leucine‐rich repeat protein (NLR)‐encoding genes. From analysis of the gene models in the S. lycopersicoides genome sequence and RNA‐Seq data, two of the eight genes emerged as the strongest candidates for Ptr1. One of these two candidates was found to encode Ptr1 based on its ability to mediate recognition of AvrRpt2 and RipBN when it was transiently expressed with these effectors in leaves of Nicotiana glutinosa. The ortholog of Ptr1 in tomato and in Solanum pennellii is a pseudogene. However, a functional Ptr1 ortholog exists in Nicotiana benthamiana and potato, and both mediate recognition of AvrRpt2 and RipBN. In apple and Arabidopsis, recognition of AvrRpt2 is mediated by the Mr5 and RPS2 proteins, respectively. Phylogenetic analysis places Ptr1 in a distinct clade compared with Mr5 and RPS2, and it therefore appears to have arisen by convergent evolution for recognition of AvrRpt2. 相似文献
5.
Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae 总被引:10,自引:2,他引:8
Arginine decarboxylase (ADC) is an important enzyme in the production of
putrescine and polyamines in plants. It is encoded by a single or low-copy
nuclear gene that lacks introns in sequences studied to date. The rate of
Adc amino acid sequence evolution is similar to that of ndhF for the
angiosperm family studied. Highly conserved regions provide several target
sites for PCR priming and sequencing and aid in nucleotide and amino acid
sequence alignment across a range of taxonomic levels, while a variable
region provides an increased number of potentially informative characters
relative to ndhF for the taxa surveyed. The utility of the Adc gene in
plant molecular systematic studies is demonstrated by analysis of its
partial nucleotide sequences obtained from 13 representatives of
Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order
Capparales) and 1 from the related order Malvales. Two copies of the Adc
gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied
to data except the basal genus Aethionema. The resulting Adc gene tree
provides robust phylogenetic data regarding relationships within the
complex mustard family, as well as independent support for proposed tribal
realignments based on other molecular data sets such as those from
chloroplast DNA.
相似文献
6.
Annerieke C van Groenestijn Ingrid GL van de Port Carin D Schröder Marcel WM Post Hepke F Grupstra Esther T Kruitwagen Harmen van der Linde Reinout O van Vliet Margreet GH van de Weerd Leonard H van den Berg Eline Lindeman 《BMC neurology》2011,11(1):1-11
Background
Neuropathic pain must be correctly diagnosed for optimal treatment. The questionnaire named Neuropathic Pain Symptom Inventory (NPSI) was developed in its original French version to evaluate the different symptoms of neuropathic pain. We hypothesized that the NPSI might also be used to differentiate neuropathic from non-neuropathic pain.Methods
We translated the NPSI into German using a standard forward-backward translation and administered it in a case-control design to patients with neuropathic (n = 68) and non-neuropathic pain (headache and osteoarthritis, n = 169) to validate it and to analyze its discriminant properties, its sensitivity to change, and to detect neuropathic pain subgroups with distinct profiles.Results
Using a sum score (the NPSI-G score), we found sensitivity to change (r between 0.37 and 0.5 for pain items of the graded chronic pain scale) and could distinguish between neuropathic and other pain on a group basis, but not for individual patients. Post hoc development of a discriminant score with optimized diagnostic properties to distinguish neuropathic pain from non-neuropathic pain resulted in an instrument with high sensitivity (91%) and acceptable specificity (70%). We detected six different pain profiles in the patient group with neuropathic pain; three profiles were found to be distinct.Conclusions
The NPSI-G potentially combines the properties of a diagnostic tool and an instrument to identify subtypes of neuropathic pain. 相似文献7.
8.
The zooxanthellate macrocnemic zoanthid Parazoanthus parasiticus lives at densities of 3–10 cm−2 in the chimney sponge Callyspongia vaginalis in Bermuda. It is gonochoric and oviparous. Small oocytes appear in the mesenteries in February–March, grow slowly at first,
then increase volume rapidly as seawater temperature passes 27 °C in July. In 1993, oocytes were found to have been shed over
2–3 days around the full moon on 1 September, with inferred small spawnings over the preceding and following full moons. Reproduction
had finished by November. In 1999, spawning of azooxanthellate eggs ∼ 250 μm diameter took place on 28 August, two nights after full moon. Spawnings therefore precede those known for four oviparous
scleractinians and one gorgonian in Bermudian waters by about a week. The eggs are not shed in bundles and lack zooxanthellae.
The unknown embryonic development and larval type in macrocnemic zoanthids is discussed and remains to be resolved by further
study with P. parasiticus.
Contribution number 1662 from the Bermuda Biological Station for Research. 相似文献
9.
Ryland Young 《Journal of microbiology (Seoul, Korea)》2014,52(3):243-258
The lysis of bacterial hosts by double-strand DNA bacteriophages, once thought to reflect merely the accumulation of sufficient lysozyme activity during the infection cycle, has been revealed to recently been revealed to be a carefully regulated and temporally scheduled process. For phages of Gramnegative hosts, there are three steps, corresponding to subversion of each of the three layers of the cell envelope: inner membrane, peptidoglycan, and outer membrane. The pathway is controlled at the level of the cytoplasmic membrane. In canonical lysis, a phage encoded protein, the holin, accumulates harmlessly in the cytoplasmic membrane until triggering at an allele-specific time to form micron-scale holes. This allows the soluble endolysin to escape from the cytoplasm to degrade the peptidoglycan. Recently a parallel pathway has been elucidated in which a different type of holin, the pinholin, which, instead of triggering to form large holes, triggers to form small, heptameric channels that serve to depolarize the membrane. Pinholins are associated with SAR endolysins, which accumulate in the periplasm as inactive, membrane-tethered enzymes. Pinholin triggering collapses the proton motive force, allowing the SAR endolysins to refold to an active form and attack the peptidoglycan. Surprisingly, a third step, the disruption of the outer membrane is also required. This is usually achieved by a spanin complex, consisting of a small outer membrane lipoprotein and an integral cytoplasmic membrane protein, designated as o-spanin and i-spanin, respectively. Without spanin function, lysis is blocked and progeny virions are trapped in dead spherical cells, suggesting that the outer membrane has considerable tensile strength. In addition to two-component spanins, there are some single-component spanins, or u-spanins, that have an N-terminal outer-membrane lipoprotein signal and a C-terminal transmembrane domain. A possible mechanism for spanin function to disrupt the outer membrane is to catalyze fusion of the inner and outer membranes. 相似文献
10.
Meto T. Leach Alistair L. Wilkins Ryland G. Fortney-Zirker Brian K. Nicholson 《Inorganica chimica acta》2011,375(1):228-235
The reactions of cis-[PtCl2L2] [L = PPh3, PMe2Ph or L2 = Ph2P(CH2)2PPh2 (dppe)] with endo-8-camphanylphosphonic acid (CamPO3H2) and Ag2O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O3PCam)L2]. The X-ray crystal structure of [Pt(O3PCam)(PPh3)2]·2CHCl3 shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh3 ligands. This allows the O3P-CH2 group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh3 and dppe derivatives, which contain inequivalent phosphine ligands in their 31P NMR spectra. These findings are backed up by theoretical calculations on the PPh3 and PPhMe2 derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh3 and PPhMe2 complexes. The X-ray crystal structure of CamPO3H2 is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups. 相似文献