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181.
Ass. Prof. Dr. A. Römmler W. Seinsch A. S. Hasan F. Haase 《Cell and tissue research》1978,190(1):135-149
The effects of single and repeated LH-RH injections at 120 min intervals on female rat LH gonadotrophs and on pituitary and serum LH levels were investigated using electronmicroscopy and radioimmunoassay. A temporary stimulation of granule release, of protein and new granule synthesis and of the accumulation of lysosomal structures was found in LH cells after the first LH-RH injection. The temporary stimulations were massively enhanced after the second injection. These consecutive yet in their time-sequence overlapping processes account for the initial depletion of secretory granule content (3--15 min after LH-RH injection), for the subsequent regranulation and accumulation of granules above control levels (60--120 min after injection) and also for the reduction in the number of granules to control levels (150 min after LH-RH injection and thereafter). Increased polymorphic lysosomal structures are believed to be responsible for this reduction of excess granules. The amount of assayable pituitary and serum LH generally corresponds with the morphological changes observed in LH-gonadotrophs, thus further substantiating the above observations. A schema which summarizes the observed morphological and hormonal changes in their time-sequence in response to LH-RH stimulation depicts the short-term regulation of secretory processes in female gonadotrophs. 相似文献
182.
183.
Light and Electron Microscopic Observations of Gametogenesis in Hastigerina pelagica (Foraminifera)*
M. SPINDLER O. R. ANDERSON C. HEMLEBEN A. W. H. B 《The Journal of eukaryotic microbiology》1978,25(4):427-433
SYNOPSIS. During gametogenesis mother individuals of Hastigerina pelagica (d'Orbigny) undergo significant morphological changes. Thirty h before gamete release, the cytoplasm changes from pale orange to bright red, possibly due to transport of stored lipids from the inner region to more peripheral parts of the cytoplasm. During the next 10 to 15 h the bubble capsule which surounds the calcareous shell is discarded. After all bubbles have disappeared, the individual sheds its spines by resorbing the spine bases close to the shell surface. A single mother nucleus divides into some hundreds of thousands of gamete nuclei within a span of ~ 20 h. A bulge of cytoplasm is extruded from the aperture and increases in size during the next 5 to 10 h. This bulge consists of cytoplasmic strands in which gametes and spherical bodies are embedded. The gametes and spherical bodies mature and are released during the afternoon and early evening. The gametes have 2 unequal acronematic flagella. A previously undescribed structure in foraminiferal reproduction is the spherical body which consists of a large vacuole surrounded by a thin cytoplasmic layer in which several nuclei, various typical cell organelles and multiple flagella are present. The spherical bodies are believed to play a role as receptacles of waste material, possibly including residual digestive enzymes, thereby protecting the gametes from lysis during the reproductive process. Fusion of gametes and further development into the next generation have not been observed. 相似文献
184.
Initiation of mammalian protein synthesis. II. The assembly of the initiation complex with purified initiation factors 总被引:39,自引:0,他引:39
The assembly of initiation complexes is studied in a protein synthesis initiation assay containing ribosomal subunits, globin [125I]mRNA, [3H]Met-tRNAf, seven purified initiation factors, ATP and GTP. By omitting single components from the initiation assay, specific roles of the initiation factors, ATP and GTP are demonstrated. The initiation factor eIF-2 is required for the binding of Met-tRNAf to the 40 S ribosomal subunit. The initial Met-tRNAf binding to the small ribosomal subunit is a stringent prerequisite for the subsequent mRNA binding. The initiation factors eIF-3, eIF-4A, eIF-4B and eIF-4C together with ATP promote the binding of mRNA to the 40 S initiation complex. The association of the 40 S initiation complex with the 60 S ribosome subunit to form an 80 S initiation complex is mediated by the initiation factor eIF-5 and requires the hydrolysis of GTP. The factor eIF-1 gives a twofold overall stimulation of initiation complex formation. A model of the sequential steps in the assembly of the 80 S initiation complex in mammalian protein synthesis is presented. 相似文献
185.
Summary Application of a granular formulation of hexachlorocyclohexane (HCH) to the potted soil at flooding decreased the concentration
of iron and. to some extent, manganese in rice plants, especially at concentrations above 3 ppm active ingredient (a.i.) Likewise,
HCH, applied to rice fields at transplanting (several days after submergence) caused a significant decrease in the concentration
of iron, and not manganese, in the rice plant but only at concentrations above 12.5 kg a.i./ha despite high levels of reduced
iron in the soil. Inhibition of iron reduction by HCH was more pronounced when applied at flooding than at several days after
flooding. 相似文献
186.
The metabolism of [3H]formate has been examined in etiolated and greening leaves of barley (Hordeum vulgare), dwarf bean (Phaseolus vulgarls), broad bean (Vicia faba) and corn (Zea mays). Tritium was extensively incorporated by primary leaves incubated for 20-min periods in light or dark. The organic acids and free amino acids were the principal products of formate metabolism but these and other products were more heavily labelled in green tissues. Time course experiments with barley leaves revealed a rapid labelling of serine, accompanied by increasing amounts of 3H in glycine and aspartate as the feeding period was extended. These amino acid products were formed throughout a 4-day greening period with an approximate doubling in total incorporation being due to large accumulations of tritiated glycine and aspartate. The involvement of tetrahydrofolate-dependent reactions in formate metabolism was indicated by inhibition of [14C] and [3H]formate incorporation by the folate antagonist, aminopterin. Labelling of glycine and serine was also strongly inhibited (up to 90%) when the leaves were incubated with increasing concentrations of isonicotinylhydrazide. 相似文献
187.
Summary The concentration, uptake and element use efficiency of N, P and K in one C3 annual (Polypogon monspeliensis) and two C4 (Echinochloa colonum, an annual, andDichathium annulatum, a perennial) grasses were determined during winter and summer seasons in monocultures raised in field plots at three moisture
levels,viz. full, half and one-fourth of field capacity. At each moisture regime the plants were clipped thrice at moderate and severe
levels corresponding to 40 and 80% of live green. The concentration of these elements was characteristic of the growth habit
of these plants;e.g. the build up of concentration was maximum in leaf of the annuals while it was comparable in crown and leaf of Dichanthium.
The N level was maximum in Polypogon. The nutrient use effiency was comparable in the two annuals and maximum K and N use
were obtained in Polypogon and Dichanthium, respectively. 相似文献
188.
Summary Organic components leaked fromSorghum bicolor seedlings (‘root exudates’) were examined by recovering14C labelled compounds from root solutions of seedlings inoculated withAzospirillum brasilense, Azotobacter vinelandii orKlebsiella pneumoniae nif-. Up to 3.5% of the total14C recovered from shoots, roots, and nutrient solutions was found in the root solutions. Inoculation with Azospirillum and
Azotobacter increased the amounts of14C and decreased the amounts of carbohydrates in the root solutions. When sucrose was added as a carbon source for the bacteria,
the increase of14C in the solutions did not occur. Quantities of14C found in the root solutions were proportional to amounts of mineral nitrogen supplied to the plants. Bacterial growth also
was proportional to nitrogen levels. When sorghum plants were grown in soil and labelled with14CO2, about 15% of the total14C recovered within 48 hours exposure was found in soil leachates. 相似文献
189.
Four groups of intracellular structures can be recognized according to bismuth and uranyl staining and phosphorus content. (1) Those which contain phosphorus and stain strongly with uranyl acetate but not with bismuth (ribosomes, heterochromatin and mature ribosomal precursor granules), presumably because of their nucleic acid content. (2) Those which contain phosphorus and stain with uranyl acetate and bismuth (interchromatin granules, immature ribosomal precursor granules and mitochondrial granules), presumably because at least some of their phosphate is available to react with bismuth. (3) Those which contain little phosphorus but which stain strongly with bismuth and weakly with uranyl acetate (Golgi complex beads), perhaps because some ligand in addition to phosphate reacts with bismuth, and (4) those which do not contain phosphorus and stain with neither uranyl acetate nor bismuth (portasomes). Uranyl staining correlates strongly with the phosphorus content of nucleic acids, proteins and inorganic deposits. Bismuth will stain some phosphorylated molecules but not all. Thus only some phosphates stain with bismuth. 相似文献
190.
A simple and sensitive colorimetric method for the determination of long-chain free fatty acids in subcellular organelles 总被引:12,自引:0,他引:12
A colorimetric assay for the determination of long-chain free fatty acids (FFA) is described. The FFA were extracted from subcellular organelles with chloroform:heptane:methanol. The copper soaps of FFA were determined colorimetrically with diphenylcarbazide. There are three advantages to employing the present modified procedure. (a) The sensitivity has been increased approximately twofold over that of the previous procedure of K. Falholt, B. Lund, and W. Falholt (1973, Clin. Chim. Acta46, 105–111); (b) it takes less time to complete the assay compared to the tedious procedures currently available; and (c) the presence of bovine serum albumin, a known FAA-binding protein, does not interfere with the assay procedure. The assay shows a linear response over the range of 10 to 130 nmol of FFA. The recovery of free fatty acids from mitochondria is 99%. 相似文献