Facilitation of Pituitary-Induced Frog Ovulation by Progesterone in Early Fall.

Wright, Paul A.; Flathers, Ann R.

doi:10.3181/00379727-106-26333

Cited by 42 publications

(8 citation statements)

References 1 publication

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“…Ovulation of adult Rana pipiens (Hazen & Co., Alburg, VT) was induced by injecting progesterone (Eli Lilly, Indianapolis, IN) and/or pituitary glands (modified from Wright and Flathers, 1961). Eggs were fertilized in 5% Holtfreter solution according to standard procedures (Hamburger, 1960) and were then kept for a few days in dechlorinated tapwater that contained penicillin (100 U/ ml) and streptomycin (100 pg d m l ) .…”

Section: Materials and Methods Frogsmentioning

confidence: 99%

In vitro behavior of thymic nurse cell‐like complexes from mechanically and enzymatically dissociated frog tadpole thymuses

Holtfreter

Cohen

1987

Am. J. Anat.

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Cellular complexes, analogous by virtue of their external appearance, size, and number of seemingly internalized thymocytes to thymic nurse cells (TNCs) of endothermic vertebrates, were seen in short-term cultures (6-8 days) of mechanically and enzymatically dissociated thymuses of leopard frog tadpoles. Most TNC-like complexes from mechanically disrupted thymuses were covered with many thymocytes that morphologically resembled the "internalized" thymocytes. With time in culture, most complexes remained spherical and lost their externally adherent and "internalized" thymocytes. Some complexes, however, adhered to the glass substratum by means of macrophage-like cells. After one typically appearing TNC from a mechanically dissociated thymus had released its "internalized" thymocytes and spread completely over the glass substratum, it could be seen to consist actually of 9-10 stromal cells with the appearance of epithelial cells, macrophages, and dendritic cells. TNC-like structures from enzymatically dissociated thymuses had few, if any, attached thymocytes. Although these structures closely resembled murine TNCs initially, they displayed abnormal transformations within a few days of culture. Our observations led us to question the assumption that all TNCs from mechanically as well as enzymatically isolated TNCs from vertebrate thymuses are single cells. Rather, some if not all of the so-called TNC may actually be entities composed of several stromal cell types that enclose thymocytes. We suggest that this configuration seen in vitro may reflect the architecture of the compartmentalized reticular stromal cell meshwork that characterizes the intact thymus.

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Section: Materials and Methods Frogsmentioning

confidence: 99%

In vitro behavior of thymic nurse cell‐like complexes from mechanically and enzymatically dissociated frog tadpole thymuses

Holtfreter

Cohen

1987

Am. J. Anat.

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“…Sexually mature northern Rana pipiens were obtained from Arnold Nasco, Ltd ., Fort Atkinson, Wis., in the fall and stored in the dark at -4°C . Frogs were induced to ovulate by the injection of one or two macerated pituitary glands into the body cavity and by intramuscular injection of progesterone, depending upon the season (43) . Eggs were fertilized at l8°C with minced testis for 15 min, rinsed, and then allowed to develop in 10% Steinberg's solution (37) before injection .…”

Section: Microinjection Of Eggsmentioning

confidence: 99%

Effect of microinjected N-ethylmaleimide-modified heavy meromyosin on cell division in amphibian eggs.

Meeusen¹,

Bennett²,

Cande³

1980

The Journal of Cell Biology

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N-Ethylmaleimide-modified heavy meromyosin (NEM-HMM) microinjected into amphibian eggs inhibits cytokinesis and the cortical contractions associated with wound closure. Injection of NEM-HMM into two-cell Rana pipiens embryos produces a zone of cleavage inhibition around the point of injection. Early furrows followed by time-lapse microcinematography are seen to slow and stop as they enter the NEM-HMM-injected zone . Arrested furrows slowly regress, leaving a large region of cytoplasm uncleaved. Few nuclei are found in these regions of cleavage inhibition . Wound closure is often inhibited by NEM-HMM, especially when this inhibitor is injected just beneath the egg cortex . We observe that the surface of an unfertilized Rana egg is covered with microvilli that disappear during the course of development. The surfaces of NEM-HMM-inhibited zones remain covered with microvilli and resemble the unfertilized egg surface.Cytokinesis in animal cells is accomplished by an equatorial constriction of the cortex that progressively pinches the cell in two, much like the action of a purse string . The discovery that a band of actin microfflaments, the contractile ring, forms in association with the developing cleavage furrow gave rise to a model of cytokinesis based on the role of actomyosin in the muscle sarcomere (1, 3, 26, 27, 29-32, 35, 38, 40).Evidence supporting an actomyosin-based model for cytokinesis has come largely from studies at the light and electron microscope levels that demonstrate that both actin and myosin are present in the cleavage furrow (11,17,28). Microinjection of an antibody against myosin has been shown to prevent cytokinesis in starfish (18) and sea urchin blastomeres (15), and studies using cytochalasin B, although limited by questions regardingthe drug's specificity, likewise suggest an actomyosinbased mechanism for cleavage (33) .We have previously demonstrated that rabbit skeletal muscle heavy meromyosin (HMM) treated with the sulfhydryl reagent N-ethylmaleimide (NEM) serves as a specific inhibitor of muscle-type force-generating systems (21) . N-Ethylmaleimidemodified heavy meromyosin (NEM-HMM) binds tightly to actin and does not release in the presence of MgATP. After decoration with NEM-HMM, the actin becomes unavailable to native myosin. Inhibition of in vitro actomyosin interactions, the contraction of demembranated muscle myofibrils, and contractility of Chaos cytoplasm also result (21) . It is not known whether NEM-HMM interferes with actin polymerization and the organization of actin gels . However, NEM-HMM inhibits neither the beat of demembranated cilia nor in vitro microtubule polymerization (21) .We report here that microinjection of NEM-HMM into blastomeres of fertilized Rana pipiens eggs inhibits cleavage in a zone surrounding the injection point and can prevent wound closure. We also report that changes in microvilli distribution are inhibited by NEM-HMM.Our findings confirm the involvement of an actomyosin force-generating mechanism in cleavage and are consistent with the...

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“…Ovulation and insemination were done by the method of Wright and Flathers (1961). Tadpoles were kept in enamel pans of dechlorinated water, were fed boiled and rinsed spinach, and were maintained at a water temperature of 20 to 22" under a 12-hr light:l2-hr dark light regime.…”

Section: Materials and Methods Animal Maintenancementioning

confidence: 99%

A comparison of adrenalin and glucagon effects on carbohydrate levels of larval and adult Rana pipiens

Farrar

Frye

1979

General and Comparative Endocrinology

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Hyperglycemia was observed in frogs after single ip injections of doses above 50 &kg of adrenalin and glucagon. Blood glucose responses were maximal at 3 hr and lasted at least 5 hr. Lactacidemia was apparent after treatment with adrenalin at doses of 50 &kg and above. The increase in lactate was apparent by 1 hr and had dropped to control levels by 5 hr. Tissue giycogen loss was not observed after treatment with either hormone in adults. Preliminary studies with tadpoles indicated a hyperglycemic response to adrenalin and glucagon at doses of 1.0 mgikg and an increase in lactate after injection of a 1 .O mg/kg dose of adrenalin. Liver glycogen loss was observed following glucagon but not adrenalin. Both hormones stimulated glucose release from liver slices of frogs and tadpoles.

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Facilitation of Pituitary-Induced Frog Ovulation by Progesterone in Early Fall.

Cited by 42 publications

References 1 publication

In vitro behavior of thymic nurse cell‐like complexes from mechanically and enzymatically dissociated frog tadpole thymuses

In vitro behavior of thymic nurse cell‐like complexes from mechanically and enzymatically dissociated frog tadpole thymuses

Effect of microinjected N-ethylmaleimide-modified heavy meromyosin on cell division in amphibian eggs.

A comparison of adrenalin and glucagon effects on carbohydrate levels of larval and adult Rana pipiens

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