The role of the skin of Rana pipiens in sulfate excretion

• 1.1. The intact whole skin of Rana pipiens excretes sulfate and this excretion is increased by sulfate loading of the animal,
• 2.2. Ninety-five percent of the excretion of sulfate seen following sulfate loading is via the skin, while a small amount is handled by the urinary system.

     

The ultimobranchial body in Rana pipiens

Summary Hypercalcemia was induced in male frogs by injection of Vitamin D₂ and maintaining animals in calcium chloride water. The fine structure of the Ultimobranchial gland was examined 3, 7 and 14 days after the initial injection. The initial response observed after the third day was a depletion of secretory granules in addition to an alteration of nuclear shape and cytoplasmic hypertrophy. After seven days secretory granule depletion continued and early cell types occurred which indicated an increase in mitotic activity. There was also a demonstrable increase in the amount of ergastoplasm and hypertrophy of the Golgi apparatus. On the fourteenth day, the height of the epithelium was markedly increased while the underlying vascular network was enlarged and more intimately associated with the secretory parenchyma. The homeostatic mechanisms of the Ultimobranchial gland appear to include both a rapid secretory response upon stimulation and a cellular renewal system to replace exhausted cells. This suggests that such a glandular system provides a mechanism to supply a rapidly expanding cell population to meet the demands of an excessive depletion of secretory materials. The response of this gland to hypercalcemia supports previous studies which suggest that the Ultimobranchial gland is the probable source of the hypocalcemic hormone, calcitonin.This project was supported in part by funds provided by the Department of Anatomical Sciences and National Institutes of Health, Grant No. AM-11795.     

The ultimobranchial body in Rana pipiens

Summary Autoplastic transplants of ultimobranchial glands of male Rana pipiens were bilaterally or unilaterally placed in a homeotopic or heterotopic site. Serum calcium levels were maintained at normal values in bilateral autotransplants, while total ultimobranchialectomy resulted in hypercalcemia. Electron microscopy verified the viability and functional state of transplanted, denervated glands. During the periods of denervation, ergastoplasm and Golgi membranes exhibited hypertrophy which was reversed when unmyelinated nerves reappeared in the pericapillary space. Autotransplants under hypercalcemic conditions indicated that the process of secretion is primarily an intrinsic cellular activity and independant of innervation. The present evidence suggests that the sympathetic axons which innervate the parenchyma probably are inhibitory in nature and may allow depression of glandular functions during periods of hypercalcemia.The technical assistance of Mrs. Lilly Weeks is gratefully acknowledged. This project was supported by N. I. H. Grant No. AM-11795; The National Institutes of Arthritic and Metabolic Diseases.     

A role for action potentials in maturing Rana pipiens oocytes

Intracellular electrical recording and voltage-clamp techniques were used to investigate possible roles for the action potentials (ap's) of Rana pipiens oocytes. The peak of each spontaneous or evoked ap is at or near the equilibrium potential for Na; therefore, the internal Na+ activity (aiNa) can be calculated from the Nernst equation. During maturation from metaphase I to metaphase II, aiNa increases from about 5 to 23 mM. By using three methods to prevent ap's from firing (voltage clamping, increasing the mechanical damage, adding 5 mM CoCl2 to the Ringer's) it was shown that the increase in aiNa required the existence of ap's. External Co2+ appeared to prevent the ap's by blocking only the Na+ current. Calculations showed that the Na+ influx during an ap could account for the observed increase in aiNa if a gradient or nonuniform distribution of Na+ exists within the oocyte. Preventing the ap's also delayed the onset of shock activatibility, a criterion of maturity. I propose that ap's load the oocyte with Na+ which may regulate the rate of maturation either directly or indirectly.     

Observations on Mexican Rana pipiens

Mexican Rana pipiens now commonly sold in the United Statesdiffer morphologically and physiologically from their northerncounterparts. They resemble Arizona pipiens in appearance andbehavior, but their breeding cycle is distinctive. They aremost reproductively active in July and August. During late springand summer they can be ovulated readily and their pituitarygonadotropin levels are apparently high. Such is not the caseduring other times of the year. The role of Mexican frogs inteaching and research is discussed.     

The effects of cycloheximide on in vitro response of Rana pipiens pituitaries to continuously superfused gonadotropin-releasing hormone

An in vitro superfusion system was used to examine the effects of cycloheximide on the responsiveness of hemipituitaries from male Rana pipiens chronically treated with gonadotropin-releasing hormone (GnRH). Control hemipituitaries superfused with medium (DME) alone showed a rapid initial response to 100 ng/ml GnRH, and LH (luteinizing hormone) and FSH (follicle-stimulating hormone) levels remained above baseline throughout up to 13 h of treatment with GnRH. Subsequent to a 2-h rinse with DME alone following the initial treatment with GnRH, these control tissues showed a highly augmented increase in gonadotropin secretion in response to a final hour of GnRH superfusion, suggesting self-priming with as little as 5 h of initial GnRH treatment. Hemipituitaries treated with 71 microM cycloheximide showed a similar rapid initial response to 100 ng/ml GnRH, but levels declined to less than in control tissues within 3 h. Moreover, these tissues exhibited only slight responses when challenged with GnRH a second time. There were also no significant differences in response to GnRH by glands pretreated with cycloheximide for either 3 or 9 h. These results indicate the presence of a rapidly releasable pool of gonadotropin responsible for the initial response to GnRH that has minimal requirements for protein synthesis, and a second pool dependent upon protein synthesis that is involved in the maintenance of elevated gonadotropin secretion in response to chronically superfused GnRH, and for self-priming.     

Immunohistochemical localization of thyrotropin-releasing hormone (TRH) in skin of Rana pipiens

Summary Using immunofluorescent techniques thyrotropin releasing hormone (TRH) is demonstrated in skin of Rana pipiens and R. catesbeiana. The immunofluorescent-TRH is localized in all cell layers of the epidermis and in the epithelium lining the various cutaneous glands, but not in the dermal layer.We wish to thank Dr. Ronald DeLellis and Ms. Mary Blount for their expert advice and guidance in the immunohistochemical techniques.This investigation was supported by NIH National Research Service Award # 1F32 AMO6018-01 from the NIAMDD to Janice L. Bolaffi and NIH Grant AM 21863 to Ivor M.D. Jackson.     

The role of microtubules and microfilaments in the hydrosmotic response to antidiuretic hormone

To test the effects of colchicine and cytochalasin B on the ADH-induced response, unidirectional and net water fluxes were measured at one or two minutes intervals in frog urinary bladder. The action of these agents on the appearance of intramembrane particles aggregates in the luminal membrane of target cells under oxytocin stimulation and the changes in the tissue ultrastructure induced by cytochalasin B were also studied. It was observed that: the time-course of the response to oxytocin was strongly slowed by colchicine while the washout was not affected; the time-course of the 'on and off' of the response to oxytocin was not modified by cytochalasin B; cytochalasin B pretreatment proportionally reduced unidirectional and net water fluxes measured after glutaraldehyde fixation; the combined action of colchicine and cytochalasin B proportionally reduced the net water flux and the number of intramembrane particles aggregates, observed in freeze-fracture studies; after cytochalasin B action the dilation of intercellular spaces classically observed under oxytocin stimulation is strongly reduced. It is concluded that: microtubules probably play an important role in the water channels plug-in, but not in their removal; microfilaments integrity is necessary for the mechanisms inducing intercellular space dilation and the observed results confirm that water permeability is controlled by the number of permeation units present in the luminal border of granular cells and probably represented by the intramembrane particle aggregates.     

Role of calmodulin in antidiuretic hormone mediated water transport

Several classes of tricyclic antidepressants inhibit the action of antidiuretic hormone (ADH) and cyclic adenine monophosphate (cAMP) on osmotic water flow across toad urinary bladder without any effect on sodium transport. This finding suggests that calmodulin is involved in the hydroosmotic action of ADH (and of serosal hypertonicity), possibly in inducing exocytosis at the luminal border of vesicles rich in water channels.     

Migration and Gene Dispersal in Rana pipiens

Although the dominant burnsi gene is widely distributed in Minnesotapopulations of the leopard frog (Rana pipiens) at uniformlylow frequencies, estimates of the effective size of the breedingpopulations suggest that a wider range of gene frequencies mightbe expected due to random genetic drift. Observations of thespring, summer, and fall migrations, however, indicate a levelof migratory activity sufficient to prevent local divergencein gene frequencies. Temperature appears to play a major rolein the springtime migratory and breeding behavior of Rana pipiensin Minnesota.