Electrophoretic analysis of liver and testis histones of the frog Rana pipiens

Histones were extracted from frog livers and testes and analyzed by electrophoresis on long polyacrylamide gels and on sodium dodecyl sulfate (SDS)-containing polyacrylamide gels. Frog histones were found to be similar to those of calf thymus except that frog histone fraction F2A2 showed a marked dependence on the temperature at which the long gels were run, and frog histone fraction F3 could be separated from frog F2B on SDS-containing gels. Comparisons between frog liver and frog testis histones indicated that the testis contains as its major F1 component a fast migrating species not found in liver. Testis histones also showed less microheterogeneity of fractions F3 and F2A1 than liver histones. These were the only differences observed between liver and testis histones, even when testis histones were prepared from sperm suspensions that were rich in cells in the late stages of spermiogenesis. Thus it seems that, in Rana, the electrophoretic properties of the basic proteins of sperm differ from those of somatic cells only in the nature of histone F1 and in the degree of microheterogeneity of fractions F2A1 and F3.     

The initiation of diving apnoea in the frog, Rana pipiens.

1. Diving apnoea in Rana pipiens was initiated by submerging the external nares. As the water level was raised above the frog, both buccal and lung pressure increased by an amount corresponding to the water head. During submergence the external nares remained closed, although the apnoeic period was punctuated by ventilation movements which moved gas between the lungs and buccal cavity. 2. Bilateral section of the ophthalmic nerves did not alter the normal pattern of ventilation in air, although it often resulted in the intake of water into the buccal cavity on submergence. Introduction of water into the buccal cavity, either naturally as in denervates or by injection through a catheter in intact frogs, triggered sustained electromyographical activity in some respiratory muscles. 3. Electroneurograms recorded from the cut peripheral end of an ophthalmic nerve showed that receptors in the external narial region were stimulated by movement of a water meniscus across them. Activity could also be recorded in the ophthalmic nerve in response to water flow past the submerged nares. Punctate stimulation of the narial region confirmed that these receptors were mechanosensitive. 4. Bilateral electrical stimulation of the central ends of cut ophthalmic nerves in lightly anaesthetized frogs caused apnoea with a latency of less than 200 ms. The external nares remained closed throughout the period of stimulation although buccal pressure events, resembling underwater ventilation movements, occurred when stimulation was prolonged.     

The ear and hearing in the frog, Rana pipiens

The development of electric organ spindles of Gymnarchus niloticus has been investigated with respect to the exact time and place of origin and the process of formation of the adult plan. The results are compared with those of Dahlgren ('14). A common primordium for all the electroplates of of a spindle as held by Dahlgren ('14) is not supported by the present work.     

Directionality of the pressure-difference receiver ears in the northern leopard frog, Rana pipiens pipiens

We studied the directional response of the coupled-eardrum system in the northern leopard frog, Rana pipiens pipiens. Eardrum behavior closely approximates a linear time-invariant system, with a highly correlated input–output relationship between the eardrum pressure difference and the eardrum velocity. Variations in the eardrum transfer function at frequencies below 800 Hz indicate the existence of an extratympanic sound transmission pathway which can interfere with eardrum motions. The eardrum velocity was shown to shift in phase as a function of sound incident angle, which was a direct result of the phase-shift of the eardrum pressure difference. We used two laser-Doppler vibrometers to measure the interaural vibration time difference (IVTD) and the interaural vibration amplitude difference (IVAD) between the motions of the two eardrums. The coupled-eardrum system enhanced the IVTD and IVAD by a factor of 3 and 3 dB, respectively, when compared to an isolated-eardrum system of the same size. Our findings are consistent with the time-delay sensitivity of other coupled-eardrum systems such as those found in crickets and flies.     

Morphology of neurons in the torus semicircularis of the northern leopard frog,Rana pipiens pipiens

The neuronal morphology of the torus semicircularis of the northern leopard frog, Rana pipiens pipiens, was examined in Golgi-impregnated material. Neurons in each of the five subdivisions of the torus semicircularis (Potter, '65a) have distinct morphologies which are characteristic of the subdivision. Laminar nucleus neurons are mostly multipolar with spherical or ovoidal somata and smooth dendrites oriented primarily parallel and perpendicular to the cell laminae. Principal nucleus neurons have variable soma shapes with short dendrites ( < 100 μm) radiating in all directions. In the magnocellular nucleus, there are three major cell types: neurons characterized by small, spherical-shaped somata, with short, thin, radiating dendrites and many varicosities; bi- or tripolar neurons with ovoidal somata, and long (100–200 μm) and smooth dendrites orienting primarily dorsoventrally and mediolaterally; and multipolar neurons with triangular-shaped somata and very long (200–350 μm) dendrites, which are either smooth or highly spiny. Neurons in the commissural nucleus are mostly multipolar cells with ovoidal somata and beaded dendrites projecting mostly dorsally and ventrally. The subependymal midline nucleus contains mostly uni- or bipolar neurons with small ovoidal somata and straight, spiny dendrites. In addition to revealing the morphological features of neurons in the torus, the counterstained material shows further cytoarchitectural organization of the principal nucleus, i.e., the presence of a circular lamellar organization. The functional significance of these anatomical features is discussed.     

Pineal regeneration in the frog, Rana pipiens, following embryonic extirpation

This report describes the capacity of larvae of the Leopard frog, Rana pipiens, to regenerate pineal tissue after embryonic pinealectomy, and presents experimental evidence for frontal organ dependence on the epiphysis. In addition, it was found that the “brow spot,” a pigment-free region located in the epidermis betweeen the eyes, is dependent on the frontal organ for its formation. This report also substantiates that the absence of the pineal organ in larval animals does not affect growth or development through metamorphosis.     

Morphological observations on cultured lampbrush-stage Rana pipiens oocytes.

Early lampbrush-stage oocytes are characterized by small lampbrush chromosome loops, a small amount of ribonucleoprotein (RNP) matrix on the loops, small nucleoli, few RNP particles in the nucleoplasm, and a smooth germinal vesicle contour. In vitro culture of these oocytes in serum-free culture medium for 24 hr at 18°C promotes a number of morphological changes in the oocytes: The lampbrush loops increase in diameter and acquire extensive RNP matrix, the nucleoli increase in size and complexity, the nucleoplasm accumulates numerous polymorphic RNP particles, and the germinal vesicle envelope acquires a sacculated contour. These characteristics are typical of the in vivo maximum lampbrush stage, and their appearance is due to an apparent in vitro acceleration of the lampbrush phase. Two possible interpretations of these observations are discussed.     

Histochemical study of skeletal muscles of the frog, Rana temporaria

Histochemical profiles of muscles were identified based on staining for myosin ATPase activity. They reveal typical arrangement of muscular fibres with a zoned pattern. Tonic fibres have a unique histochemical profile and are mixed with the most oxydative fast fibres to form toxic zones. Muscles show fast profiles in thigh and tonic or mixed profiles in fore-arm.     

Vitellogenic cycles in laboratory-maintained females of the leopard frog, Rana pipiens

As a part of studies on the reproduction of laboratory maintained frogs, wild-caught Rana pipiens were ovulated and maintained at 22-27 degrees C for up to 18 months. Vitellogenic oocytes were periodically staged and counted, and a "maturity index" was calculated to assess the progress of the vitellogenic cycle. The initial cycle was similar to that of wild frogs except that the first oocytes to reach stage 5 (mature eggs) usually began to degenerate before later starting oocytes became mature. In addition, a second cycle began before the first was completed. After more than 1 year at room temperature, abnormal cycles were common. Ovaries of such animals contained very few mature eggs. Many of their oocytes were in early stages of vitellogenesis or, if pigmented, had begun to degenerate. These deficiencies were partially corrected in females placed in 4 degrees C for 4-6 weeks. The average number of mature eggs increased 15-fold and ovary weights more than doubled. Oviduct weights almost doubled. Although the rates of cooling, photoperiod, and nutritional status could be important influences, the results imply that cold treatment alone increases estrogen secretion. We suggest that low estrogen secretion may account for the reproductive deficiencies seen in R. pipiens cultured at room temperature.