Journal of Experimental Zoology 

About: Journal of Experimental Zoology is an academic journal. The journal publishes majorly in the area(s): Sperm & Population. It has an ISSN identifier of 1932-5223. Over the lifetime, 11514 publications have been published receiving 360433 citations. The journal is also known as: Journal of experimental zoology. Part A, Ecological genetics and physiology.

Cytoplasmic control of nuclear behavior during meiotic maturation of frog oocytes.

Abstract: Fully grown oocytes of the frog (Rana pipiens) undergo cytoplasmic and nuclear maturation when treated with progesterone after the follicular envelopes have been removed. The mechanism of this maturation was investigated by injection of cytoplasm from progesterone-treated oocytes at various stages of maturation into fully grown but immature oocytes. The injected cytoplasm becomes effective in inducing maturation by 12 hours after progesterone administration, reaches a maximum effectiveness around 20 hours, and then declines after the donor oocytes complete maturation. However, even cytoplasm from early embryos retains some capacity to induce oocyte maturation. The frequency with which maturation is induced is proportional to the volume of the injected cytoplasm. Progesterone itself is not directly responsible for the maturation-producing effect of injected cytoplasm since injected progesterone does not promote maturation. However, externally applied progesterone does induce the completion of the first meiotic division, presumably by releasing a cytoplasmic “maturation promoting factor.” The production of this cytoplasmic factor was not affected by removal of the nucleus. After completion of the first meiotic division, oocytes cease further development at the metaphase of the second meiotic division, where they remain until fertilized or activated to develop. Cytoplasm from such secondary oocytes when injected into one of the blastomeres at the two-cell stage of development suppresses mitosis as well as cleavage. Mitosis is usually arrested at metaphase. No such inhibition was brought about by injection of cytoplasm from cleaving blastomeres. Thus, the arrest of mitosis and cleavage can be attributed to a specific “cytostatic factor” in the cytoplasm of the secondary oocyte. Activation of donor secondary oocytes by insemination or pricking with a glass needle soon destroys the cytostatic factor. Likewise, addition of cortical cytoplasm to endoplasm from the secondary oocyte rapidly destroys the cytostatic capacity. This result implies that cortical material is involved in the process of removing the cytostatic factor at the time of normal activation or fertilization. Enucleation of oocytes demonstrated that production and removal of the cytostatic factor is independent of the nucleus.

Proliferation, differentiation and degeneration in the spinal ganglia of the chick embryo under normal and experimental conditions.

Abstract: In this paper Viktor Hamburger [5] and Rita Levi-Montalcini [6] collaborated to examine the effects of limb transplantation [7] and explantation on neural development [8]. In 1947 Hamburger invited Levi-Montalcini to his lab at Washington University [9] in St. Louis to examine this question. Independently, each had previously arrived at opposing conclusions based on the same data. Hamburger concluded that limb transplantations caused the ganglia to develop more connections and grow larger while LeviMontalcini concluded that the ganglia first produce a large amount of neurons, then degenerate the unsuccessful neurons. She concluded that larger ganglia must be due to the increase in successful connections. This joint paper, published in the Journal of Experimental Zoology [10] in 1949, corroborated the findings reported by Levi-Montalcini and established that nerve degeneration is an integral part of development.

Selective growth stimulating effects of mouse sarcoma on the sensory and sympathetic nervous system of the chick embryo.

Abstract: In “Selective Growth Stimulating Effects of Mouse Sarcoma on the Sensory and Sympathetic Nervous System of the Chick Embryo,” Rita Levi-Montalcini [5] and Viktor Hamburger [6] explored the effects of two nerve growth stimulating tumors; mouse [7] sarcomas 180 and 37. This experiment led to the discovery that nerve growth factor [8] was a diffusible chemical and later to discoveries that the compound was a protein. Although this paper was an important step in the discovery of nerve growth factor [8], the term “nerve growth factor” was not used in this paper. It was instead referred to as a “growth promoting agent.” The discovery of nerve growth factor [8] earned Levi-Montalcini and Stanley Cohen [9], who also discovered epidermal growth factor, the 1986 Nobel Prize in Physiology or Medicine [10].