Steroid Producing Cells during Ovarian Differentiation of the Tilapia, Sarotherodon niloticus

In order to examine the initial appearance and development of the steroid producing cells (SPCs) during the process of ovarian differentiation, histology and ultrastructure of tilapia ( Sarotherodon niloticus ) ovaries were investigated from 10 to 50 days after hatching. In gonads of fry at 23–26 days after hatching, initial ovarian differentiation was confirmed by the differentiation of stromal aggregations in the proximal and distal region of the gonad on the side facing the lateral wall. This represents the initial formation of the ovarian cavity. At the same time as ovarian differentiation, a few large cells appeared initially in the vicinity of blood vessels. They have some of the ultrastructural features characteristic of SPCs such as a moderate number of mitochondria with tubular cristae, a large amount of smooth endoplasmic reticulum and many free ribosomes. Based on these ultrastructural criteria, together with the present finding that these cells further differentiated into the typical SPCs at older stages, these cells were identified as SPCs. Thereafter, by 30–50 days, SPCs increased gradually in number in the area enclosing the blood vessels of ovaries. The increase in SPCs coincided with the development of germ cells, including the multiplication of oogonia and the transformation from oogonia to oocytes.     

The Ontogeny of Thymic Myoid Cells in the Chicken

The ontogeny of thymic myoid cells in the chick was studied electron microscopically and immunohistochemically. An anticreatine kinase antibody which reacts specifically to skeletal muscle cells was used. This antibody reacts only to myoid cells in the thymus. Myoid cells were found in the medulla or in the interlobular region, though the number of the myoid cells was small. Immunohistochemically, myoid cells were detected on the 18th day of incubation. Mature myoid cells showed clear cross striations after immunohistochemical staining around the time of hatching. Electron microscopically, myoid cells were detectable on the 19th day of incubation. The discrepancy between immunohistochemical and electron microscopical detection may be due to the low number of myoid cells.     

Influence of Temperature on Glucose Metabolism of Round Spermatids of Rats

Glucose utilization by spermatids was found to be 17.37±0.37 nmoles/hr/10⁶ cells at 34°C and 28.94±1.12nmoles/hr/10⁶ cells at 40°C. A good parallelism was observed between the increased rate of glucose utilization and lactate production at 40°C. There was no significant change in the levels of glycolytic intermediates in the cells, except for marked accumulations of fructose-1, 6-diphosphate, dihydroxyacetone phosphate and glyceraldehyde-3-phosphate in the presence of glucose (1 mM). Glucose oxidation in the citrate cycle by spermatids was higher at 40°C than at 34°C, but was never greater than 2% of the overall rate of glucose utilization. In addition, glucose did not prevent decrease of ATP at either 34 or 40°C. The effects of temperature on the activities of 11 glycolytic enzymes were examined. The activities of aldolase and phosphoglyceromutase were similar between 30 and 34°C, but increased markedly at 40°C. The higher temperature increased the V_max values, without affecting the Kms. The activities of other glycolytic enzymes were similar at the different temperatures. These findings indicate that the increased overall rate of glucose utilization in glycolysis at higher temperature is due to increased Vmax values of aldolase and phosphoglyceromutase.     

A bimodal germination response to temperature in cocklebur seeds. II. ATP and adenylate pool

Abstract. The mechanism involved in a bimodal germination-temperature response in pre-soaked cocklebur (Xanthium pennsylvanicum Wallr.) seeds was studied with special reference to adenylate metabolism. Exposure to either low (optimal at 8°C) or high (optimal at 34°C) temperature which was effective in inducing the germination of the seeds brought about the accumulation of ATP in them. The ATP level remained unchanged at temperatures around 23°C. Pretreatment with KCN, stimulating germination even at 23°C, subsequently increased the ATP content, total adenylate pool and energy charge (EC) in the axial tissue prior to germination above those of the untreated controls. The lower the treatment temperature, the greater the inhibitory effect of KCN on ATP formation. An increase in germination following an increasing duration of pre-soaking at 8°C was comparable to increasing both the ATP content and total adenylate pool of axes, but not the EC value. Similarly, changes in germination following an increased exposure duration at 8°C correlated with changes in ATP content rather than EC value in the axes. Unlike the case of chilling, an increase in ATP level in response to 34°C was greater in the early period of water imbibition, during which times its germination-stimulating effect appeared more striking than in the later period, and it occurred without a concomitant rise in EC value because of the increased supply of AMP. Such a supply of AMP was reduced in the presence of benzohydroxamic acid or propyl gallale, inhibitors of an alternative respiratory pathway. It was thus concluded that both low temperature, coupled with warm temperature, and high temperature, by itself, can induce seed germination by increasing the ATP level as well as the total adenylate pool, but not the EC value, in the axial tissue. Further, that increases in both the ATP level and the adenylate pool especially are required for seed germination to proceed, probably depending on the activities of the cytochrome and alternative respiration pathways, respectively.     

MECHANICAL PROPERTIES OF THE CELL SURFACE IN STARFISH EGGS

The mechanical properties of the cell surface of the starfish egg at various stages of maturation have been investigated using the cell elastimeter. When constant negative pressure was applied to a part of the cell with a micropipette closely in contact with it, it bulged out, and the bulge rapidly increased at first and then gradually reached a steady value within one min. The relation between the deformation of the cell surface (i.e. degree of bulging) and applied negative pressure was almost linear in both oocytes at the germinal vesicle stage and mature eggs. The surface force and the elasticity value: i.e., the product of the elastic modulus of the surface membrane (layer) and its thickness, were determined from the relation between the deformation and the negative pressure. The elasticity value was about 5 times the surface force in both oocytes at the germinal vesicle stage and mature eggs. When maturation of the oocyte was induced by 1-methyladenine, the stiffness of the cell surface decreased shortly before the breakdown of the germinal vesicle. The stiffness transiently increased at the time of formation of the first and second polar-bodies.     

Enzymic synthesis of floridean starch in a red alga, Serraticardia maxima

ADP-glucose: -l,4-glucan -4-glucosyltransferase was obtainedfrom a marine red alga Serraticardia maxima in a form boundwith floridean starch granules. The enzyme catalyzed the transferof glucosyl residue from ADP-glucose, UDP-glucose and GDP-glucoseto floridean starch added as a primer. ADP-glucose was the mostefficient glucosyl donor in the reaction. Maltose was producedby ß-amylolysis of the glucan synthesized by the algalenzyme. The optimum pH for enzyme activity was at 8.4. The enzymewas not obtained in a soluble form from either the chloroplastextract or the whole algal cell extract. Electron micrographsof algal cells revealed that floridean starch granules are localizedexclusively outside chloroplasts. Hence, it appears that mostof the synthetase is present outside chloroplasts. ¹ Contribution from the Shimoda Marine Biological Station, TokyoKyoiku University, No. 202. This work was supported by a Grant-in-Aidfor Cooperative Research from the Ministry of Education, Japan. ² Present address: Department of Biology, Faculty of Science,Science University of Tokyo, Kagurazaka, Tokyo 162, Japan. ³ Present address: Laboratory of Biology, Faculty of Science,Toho University, Narashino, Chiba 275, Japan. (Received May 25, 1970; )