Growth Rate Of Oocytes Research Articles

Reproductive cycles in oregon populations of the echinoid, Strongylocentrotus purpvratus (Stimpson). II. Seasonal changes in oocyte growth and in abundance of gametogenic stages in the ovary

During the annual reproductive cycle in the echinoid, Strongylocentrotus purpuratus (Stimpson) two major seasonal events in oogenesis have been demonstrated by several different quantitative methods. Both seasonal changes in size and frequency distributions of stages of the oocytes indicate that in the intertidal populations studied, there is an abrupt increase in the growth rate of oocytes during October, accompanied by an increase in the rate at which oogonia become primary oocytes. Between March, just after spawning is completed, and October, oocytes increase in volume at a rate of ≈ 2 % per day. In October and November, the growth rate of oocytes approaches 6 % per day, and thereafter declines for oocytes reaching maturity in December. The absolute numbers of oocytes and oogonial clusters/mm 2 of ovary wall were estimated and adjusted for changes produced by volume changes in the gonad. The lowest numbers of oogonial clusters occur from December to March. Renewed proliferation begins soon after spawning. There is a significant increase in number of clusters in March, and the absolute cluster number increases to a maximum in June, reaching approximately four times the initial number. The proliferation rate during this period is ≈ 180 clusters/mm 2/month; some proliferation continues into September. The number of small oocytes present remains the same from March to August, when it begins to increase. The total number of oocytes produced during the fall period is approximately three times the number initially present at the start of the annual cycle in March. Two populations studied differ in the absolute numbers of oogonial clusters and oocytes produced in the annual cycle; environmental factors must influence the processes involved. In S. purpuratus the large majority of oocytes differentiate from oogonia during the same reproductive cycle in which they reach maturity as ova.

Yolk formation by transplanted cockroach oocytes.

AbstractIntraspecific transplantation of ovaries in 18 species of cockroaches resulted in the initiation of yolk formation and oocyte growth rates similar to sham‐operated controls. Host vitellogenins were sequestered by transplanted oocytes in concentrations equal to those observed in oocytes of unoperated cockroaches. Ovaries transplanted interspecifically sequestered host vitellogenins and grew to terminal stages only when donor and host were closely related. Yolk formation did not occur when ovaries were transplanted between species of different superfamilies or families, whereas several cases of successful ovary transplantations were observed between species of different subfamilies. Unsuccessful transplants either failed to take up host vitellogenins and did not increase in size or were encapsulated and degenerated.

Studies on oogenesis in the polychaete annelid Nereis grubei (Kinberg) : II. Oocyte growth rates in intact and hormone-deficient animals

Nereis grubei appears to maintain normal oocyte growth rates when maintained in the laboratory for a month without feeding. The necessary use of unfed controls in hormone deprivation experiments in nereids thus appears to provide conclusions valid for animals in the field. The rate found for both fed and unfed animals with oocytes over 95 μ in diameteris about 1.5 μ/day. Oocytes under 95 μ in diameter, expected to grow more slowly, were found to exhibit variable growth rates which could reach the average for the larger cells, and which could not be distinguished with certainty from those of the larger cells. Analysis of oocyte responses to hormone deprivation (decapitation) indicates increased oocyte growth rates only in animals with oocytes between 50 μ and 130 μ in diameter. Smaller oocytes are completely resorbed within 2–3 weeks of the operation. Growth rates of oocytes greater than 130 μ in diameter do not differ significantly from unoperated controls. Only operated animals with an initial oocyte diameter greater than 95 μ achieve a morphology close to that of normal mature oocytes. Responses of oocytes of increasing diameter to hormone deprivation resemble results obtained earlier for metamorphosis. The hypothesis that both processes are controlled by a single hormone, which is present in decreasing concentration for nearly a month, is thus strongly supported. Observations on the relationships between oocytes and eleocytes (a class of coelomic cells circumstantially implicated in oocyte nutrition) are also included.

Inhibition of blood digestion and oocyte growth in Aedes aegypti by 5-fluorouracil.

1. Oviposition in Aedes aegypti females is inhibited by 5-fluorouracil (FU); 0.01% FU fed in the blood meal causes about 99% inhibition of oviposition. The inhibition of oviposition by FU is temporary; some of the females which laid no eggs after their first blood meal recover their ability to oviposit after a second blood meal. The eggs laid by the FU-treated females hatch normally.2. Oviposition in mosquitoes is also inhibited by feeding FU in sugar solution before the blood meal; 0.05% causes about 95% inhibition of oviposition when given in sugar solution for two days. This effect is also temporary. The eggs laid by females treated with FU in sugar solution batch normally even when both sexes have been treated.3. FU slows down the growth of oocytes; the treated females oviposit later than the controls. The rate of oocyte growth and the percentage of females developing mature eggs is proportional to the amount of FU.4. Blood digestion is retarded by FU-treatment. The delay in blood digestion is already evident one day after feeeding by the color of the blood mass. The period of blood digestion in females treated with 0.05% FU in sugar solution is more than twice that in the controls.5. Midgut proteolytic activity is inhibited in FU-treated females. The extent of inhibition is proportional to the amount of FU and the time interval between FU-treatment and the blood meal.6. FU does not inactivate protease in vitro.7. A close correlation between the stage of ovarian development and the amount of midgut protease has been found.8. Soy bean trypsin inhibitor, which inactivates mosquito protease in vitro, also retarded the maturation of eggs in vivo.9. The effect of FU on oocyte maturation in mosquitoes could be an indirect effect (oocyte growth is inhibited because of a lack of midgut protease) or a direct effect of FU on the synthesis of specific proteins in all parts of the insect body.