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doi: 10.1002/jmor.1051270302pmid: N/A
The mechanism of respiration in the bullfrog has been analyzed by means of pressure recordings from the buccal cavity, the lungs and the abdominal cavity, by cinematography and cinefluorography, and by electromyography of buccal, laryngeal and abdominal muscles. Gas flow was investigated by putting frogs in atmospheres of changing argon and nitrogen content and monitoring the concentration of the nostril efflux.
Barrow, Mark V.; Taylor, W. Jape
doi: 10.1002/jmor.1051270303pmid: 4388962
A rapid method for examining rat fetuses is presented. The technique consists of fixing the fetuses in Bouin's solution, serially sectioning the head, neck and lower trunk with a razor blade and doing sagittal sections of the heart after opening the thoracic cavity. Examples of sections from normal 20 day rat fetuses are given as well as some with the following abnormalities: cleft palate produced by chlorcyclizine and eye and heart malformations resulting from anti‐adult rat kidney serum.
Ruby, John R.; Dyer, Robert F.; Skalko, Richard G.
doi: 10.1002/jmor.1051270304pmid: 15526403
A fine structural analysis of fetal mouse ovaries reveals the presence of intercellular bridges between developing oocytes. These bridges, which connect two or more oocytes, are most frequently seen prior to the dictyate stage of meiotic prophase. The intercellular connections are limited by a tri‐laminar membrane which is continuous with the oocyte plasmalemma. A characteristic feature of all bridges is the presence of an electron‐dense material on the cytoplasmic side of the limiting membrane. Since this dense material is a constant and conspicuous component of the entire bridge, identification of these connections is possible in all planes of section. In cross section, the bridges are usually cylindrical, while in longitudinal section, a variety of configurations are observed. Oocytes connected by intercellular bridges exhibit a highly developed Golgi complex which is frequently localized in the region of the cytoplasmic continuities. Vesicular elements, apparently derived from the Golgi, are routinely observed within the boundaries of the bridges. Other cytoplasmic organelles, including rough and smooth endoplasmic reticulum, free ribosomes and mitochondria, are also seen in these bridges. The presence of these vesicles and organelles within intercellular bridges suggests that these connections may provide a means for transfer of organelles and other substances from one oocyte to another. It may be, therefore, that intercellular bridges are important for the nourishment and maturation of certain selected oocytes as well as for the synchronization of meiotic events.
doi: 10.1002/jmor.1051270305pmid: N/A
Three‐dimensional, histological, and x‐ray techniques provide a picture of body segment and limb morphogenesis. Cell multiplication begins in the proliferation region (“meristem”) during the molt from the preceding instar. By four days post‐molt, the cells that will form the new segments are well under way in their anterior, lateral, and dorsal migration. It is suggested that after the anlagen for all the new segments are estabilshed, a mitotic wave commences in the most anterior anlagen and moves posteriorly during the remainder of the instar. When cell proliferation is complete, final differentiation of the segments takes place.
doi: 10.1002/jmor.1051270306pmid: N/A
The serigenous glands of a number of different sawfly larvae have been examined. Silk is secreted by pear‐shaped cells which may be fused together in pairs or triplets, or exist simply as free, single cells. The cells are arranged in numerous groups attached to a pair of wide silk reservoirs by means of short canals. Each gland cell contains a large, irregular, ramifying nucleus and an intracellular duct which receives droplets of synthesised silk protein. Two modifications of this basic arrangement are described. It is suggested that the secretory cells are dermal gland cells, and that the intracellular duct is a rudimentary end‐apparatus. A comparison is made between these and some other types of dermal gland cell found in insects.
Simnett, John D.; Balls, Michael
doi: 10.1002/jmor.1051270307pmid: N/A
Using the Colcemid technique, the mitotic incidence (MI) was measured in the epidermis, lung, spleen, liver, kidney and ovarian follicular cells of metamorphosed, immature Xenopus laevis laevis. The MI was higher at 25°C than at 20°C, and there was a significant ranking correlation between organs in respect of the MI in different animals. With the exception of the liver and kidney, organ cultures showed good preservation for up to six days in vitro using a medium supplemented with 10% fetal calf serum, and values for MI comparable with or even higher than in vivo were obtained.
Singer, Irwin I.; Palmer, John D.
doi: 10.1002/jmor.1051270308pmid: N/A
The complete regeneration of a new oral‐disc and tentacles has been observed and described for Aiptasia diaphana. These structures are regenerated quite rapidly: seven to ten days at 20°C. At three days post‐amputation, the new primary, secondary, and tertiary tentacle buds begin to develop in direct association with the underlying primary, secondary, and tertiary septae (respectively) of the column, suggesting that the latter organize the form of the regenerating oral‐disc. Two days after amputation, the zooxanthellae of the presumptive oral disc arrange themselves into a ring which quite precisely delimits the area from which the tentacle buds will form. In spite of its suggestive proximity, this accumulation of algae plays no role in the induction of tentacle buds as was shown by studying regeneration in anemones which essentially lacked large quantities of these symbiotic algae.
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