Histology of the oviduct of the leopard frog,Rana pipiens

The first one to three mm of each of the paired female oviducts in Rana pipiensconsists of a folded mucosa lacking tubular glands and enclosed by a serosa. Most of the remainder of the oviduct is lined by a folded mucosa richly endowed with simple tubular, jelly-secreting glands. The final one to two cm of the uterine portion of the oviduct, however, has a smooth mucosal lining which lacks tubular glands. Jelly-secreting glands penetrate to the base of the mucosa and open to the lumen between ridges capped with ciliated or mucous secreting epithelial cells. As cells of the jelly-secreting glands grow and differentiate during the summer, they accumulate a granular secretory product which exhibits basohpilia in hematoxylinstained specimens. This is the essential change in the histological structure of the gland throughout the growing season. The adult male oviduct is a solid cord of cells for about one-third of its length. The inferior two-thirds, however, is like the female oviduct at an intermediate stage of seasonal growth with gland cells containing secretory granules which exhibit basophilia.     

Bone marrow reconstitution of immune responses following irradiation in the leopard frog, Rana pipiens

The bone marrow of Rana is an important source of cells capable of maintaining individual viability, responding to Concanavalin A (Con A) and producing PFC against sheep erythrocyte (SRBC) antigens. Frog marrow is more effective than the spleen in maintaining life. Radiation destroys the ability of frogs to respond to SRBC immunization (lack of bone marrow and spleen PFC, serum antibody) and bone marrow/spleen cells to respond to Con A, i.e., bone marrow and spleen contain radiation-sensitive cells. Shielding one hind leg during irradiation leads to reconstitution of bone marrow/spleen PFC responses, antibody synthesis and individual viability. Our results suggest that bone marrow is: a) the source of stem cells, and b) the source of mature T- and B- lymphocytes that can recirculate within the immune system.     

Temporal processing in the dorsal medullary nucleus of the Northern leopard frog (Rana pipiens pipiens).

1. Single-unit responses to different temporal acoustic parameters were characterized in the dorsal medullary nucleus (DMN) of the Northern leopard frog, Rana pipiens pipiens. Our goal was to provide both a quantitative and a qualitative assessment of the neural representation of behaviorally relevant temporal acoustic patterns in the frog's DMN. 2. Acoustic stimuli included tone bursts having different durations, rise times, or rates of amplitude modulation (AM). Several metrics were used to compute temporal response functions for each of these, including mean spike count, average firing rate, and/or peak firing rate. Synchronization coefficients were also used to characterize responses to stimuli presented at different AM rates. 3. On the basis of mean spike count, the temporal response functions of DMN neurons with respect to signal rise time could be characterized as 1) all-pass, in which the mean spike count was largely independent of rise time, or 2) fast-pass, in which the mean spike count decreased with increasing rise time. Fast-pass response functions were of two types, those that decayed rapidly and those that decayed gradually from their peak values. 4. The minimum threshold varied with signal rise time for cells showing fast-pass but not all-pass response functions. Minimum response thresholds for fast-pass neurons were typically higher with slower signal rise time. 5. The filtering characteristics of cells displaying fast-pass rise time response functions were dependent on signal level, becoming all-pass when signal levels exceeded 30-40 dB above the minimum threshold. 6. Approximately 44% of DMN neurons exhibiting fast-pass response functions for signal rise time showed all-pass filtering characteristics when broadband noise rather than best frequency tones were used, thereby signifying an influence of signal spectrum on the pass-band characteristics of these cells. 7. All DMN neurons, regardless of discharge pattern, showed maximal instantaneous firing rates to signals having short (less than 25 ms) rise times. Response functions based on instantaneous firing rate were, therefore, fast-pass in nature. These responses were independent of signal level and spectrum. 8. There was an ordinal relationship between signal duration and the duration of tonic but not phasic unit discharges. This relationship was not intensity dependent. 9. On the basis of mean spike count, the temporal response functions of DMN neurons with respect to signal duration were characterized as 1) all-pass, in which the mean spike count was largely independent of signal duration, or 2) long-pass, in which the mean spike count increased with increasing signal duration.(ABSTRACT TRUNCATED AT 400 WORDS)     

Anatomical evidence for brainstem circuits mediating feeding motor programs in the leopard frog, Rana pipiens

Using injections of small molecular weight fluorescein dextran amines, combined with activity-dependent uptake of sulforhodamine 101 (SR101), brainstem circuits presumed to be involved in feeding motor output were investigated. As has been shown previously in other studies, projections to the cerebellar nuclei were identified from the cerebellar cortex, the trigeminal motor nucleus, and the vestibular nuclei. Results presented here suggest an additional pathway from the hypoglossal motor nuclei to the cerebellar nucleus as well as an afferent projection from the peripheral hypoglossal nerve to the Purkinje cell layer of the cerebellar cortex. Injections in the cerebellar cortex combined with retrograde labeling of the peripheral hypoglossal nerve demonstrate anatomical convergence at the level of the medial reticular formation. This suggests a possible integrative region for afferent feedback from the hypoglossal nerve and information through the Purkinje cell layer of the cerebellar cortex. The activity-dependent uptake of SR101 additionally suggests a reciprocal, polysynaptic pathway between this same area of the medial reticular formation and the trigeminal motor nuclei. The trigeminal motor neurons innervate the m adductor mandibulae, the primary mouth-closing muscle. The SR101 uptake clearly labeled the ventrolateral hypoglossal nuclei, the medial reticular formation, and the Purkinje cell layer of the cerebellar cortex. Unlike retrograde labeling of the peripheral hypoglossal nerve, stimulating the hypoglossal nerve while SR101 was bath-applied labeled trigeminal motor neurons. This, combined with the dextran labeling, suggests a reciprocal connection between the trigeminal motor nuclei and the cerebellar nuclei, as well as the medulla. Taken together, these data are important for understanding the neurophysiological pathways used to coordinate the proper timing of an extremely rapid, goal-directed movement and may prove useful for elucidating some of the first principles of sensorimotor integration. Electronic Publication     

The theoretical small signal impedance of the frog node,Rana pipiens

Summary The small signal impedance of the frog node is calculated for frequencies from 1 Hz to 10,000 Hz and transmembrane potentials from –80 mV to –30 mV by linearizing the voltage clamp equations of Dodge [7] and Hille [8]. The modulus of the impedance is presented for the total system, and separately for the potassium and sodium systems as a function of frequency and voltage. There is a broad resonance in the total impedance with a voltage-dependent peak frequency. At 22°C, in the range –75 mV to –45 mV, the peak frequencies occur between 50 and 500 Hz. Removing the potassium system leaves a relatively shapr resonance centered around 200 Hz at –45 mV.     

The organization of descending tectofugal pathways underlying orienting in the frog,Rana pipiens

We have studied the visually triggered orienting behavior of frogs following complete unilateral transection of the neuraxis at the junction of the medulla and spinal cord, as well as after smaller lesions at the same level. Complete transection produces the same behavioral deficit as previously reported (Kostyk and Grobstein 1982, 1987a) for a similar lesion at the junction between midbrain and medulla. Lesioned frogs failed to turn toward stimuli at all locations in the ipsilateral visual hemifield, responding instead with forwardly directed movements in which there was a persistance of variations related to stimulus elevation and distance. Responses to stimuli in the contralateral visual hemifield were normal. Similar deficits were seen after smaller lesions restricted to a medial white tract. Partial damage to the tract resulted in turns of reduced amplitude for stimuli throughout the ipsilateral hemifield. Lesions to adjacent tissue were without effect on the behaviors studied. In all animals, we observed a strong correlation between turn amplitude for lateral stimuli and the distance at which the animals switched from snapping to hopping. These observations provide new evidence that a transformation from a retinocentric to a lateralized and parcellated form of spatial representation occurs in going from the retinotectal projection to the descending tectofugal pathway in the caudal midbrain, and that this form of representation remains stable until the spinal cord. A second transformation involved in determining the actual movement to be triggered must occur subsequently. Our findings also suggest that the signals underlying orienting turns may not descend into the spinal cord on tectospinal axons, and suggest that the lateralization of descending signals probably occurs coincidentally with a synaptic relay in the midbrain tegmentum.     

The organization of descending tectofugal pathways underlying orienting in the frog,Rana pipiens

Summary In the frog, identical orienting deficits, involving a failure to turn toward stimuli in the ipsilateral hemifield, can be produced by small white matter lesions either in the caudal mesencephalon (Kostyk and Grobstein, 1987a) or in the caudal medulla (Masino and Grobstein, 1989). These findings suggest that descending turn signals may run uninterrupted from the midbrain to the spinal cord, and that something other than tectospinal axons may carry such signals. We here report studies to determine whether there is a tecto-recipient structure whose axons pass through the known critical lesion sites in the caudal mesencephalon and medulla, and whether damage to such a structure, sparing tectospinal pathways, produces an orienting deficit. Horseradish peroxidase (HRP) was applied to behaviorally effective lesions in the caudal medulla and the resulting labelling patterns compared with those resulting from application of HRP to nearby but behaviorally ineffective lesions at the same rostrocaudal level. A column of large cells in the ventrolateral midbrain tegmentum (including nMLF as well as parts of AV and PV) was robustly labelled in all effective lesion cases, and less frequently labelled in ineffective cases. A quantitative analysis showed labelling in this region to be more highly correlated with the existence of a behavioral deficit than that in any other brain region. Reconstructions of single retrogradely labelled cells in the rostral part of the column (nMLF) showed that they have dendrites in a position to receive tectal input and axons which pass through the critical lesion sites in both the caudal mesencephalon and the caudal medulla. Tegmental lesions, sparing the tectospinal tracts, produced ipsilateral turning deficits in cases where the large cell column was completely removed but did not when the column was spared. The findings support the hypothesis that tectofugal signals involved in orienting turns descend uninterrupted to the spinal cord on something other than tectospinal axons, and suggest that the critical projections derive from the large cell column of the ventral tegmentum.Abbreviations A Anterior Thalamic nucleus - AD Anterodorsal nucleus - AV Anteroventral nucleus - B Neuropil Bellonci - BO Basal Optic nucleus - CbN Cerebellar nucleus - Cb Cerebellum - CG Central Grey - CPG Corpus Geniculatum Thalamicum - DH Dorsal Horn - Ent Entopeduncular nucleus - Hb Habenular nucleus - IP Interpeduncular nucleus - LA Lateral Anterior Thalamic nucleus - LCC Tegmental Large Cell Column - LP nucleus Lateralis Profundus - LPD Lateral Posterodorsal nucleus - LPV Lateral Posteroventral nucleus - Mg Magnocellular Thalamic nucleus - NB Nucleus Bellonci - nMLF Nu. Medial Longitudinal Fasciculus - NLM Nu. Lentiformis Mesencephalicus - NPC Nucleus of the Posterior Commissure - OT Optic Tectum - PD Posterodorsal Tegmental nucleus - P Posterior Thalamic nucleus - PTG Pretectal Grey - PV Posteroventral Tegmental nucleus - Ris Isthmic Reticular nucleus - Rinf Inferior Reticular nucleus - Rmed Medial Reticular nucleus - Rsup Superior Reticular nucleus - SC Suprachiasmatic nucleus - SF Solitary fasciculus - SO Superior olivary nucleus - SV Secondary visceral nucleus - T6 Tectal layer 6 - T8 Tectal layer 8 - Tel Telencephalon - TP Posterior tubercle - TSL Torus semicircularis laminaris - TSmg Torus semicircularis magnocellular - TSp Torus semicircularis principalis - VH Ventral horn - VLD Ventrolateral dorsal nucleus - VLV Ventrolateral ventral nucleus - VM Ventromedial nucleus - 2V Secondary visceral nucleus - 3 Oculomotor nucleus - 4 Trochlear nucleus - 5me Mesencephalic trigeminal nucleus - 5m Trigeminal motor nucleus - 7m Facial motor nucleus - 8V Ventral vestibular nucleus - 8d Dorsal vestibular nucleus - n8 Vestibular nerve - 9m Glossopharyngeal motor nucleus     

The vomeronasal organ in the frog, Rana esculenta. An electron microscopy study

The ultrastructure of the vomeronasal organ (Jacobson's VNO) of the frog, Rana esculenta, was studied under the transmission and scanning electron microscope. Four cell types were identified: ciliated, bipolar, glial-like, and basal. Ciliated cells are unique to the frog VNO and show morphological evidence of secretion; bipolar (neuronal) cells are arranged in columns and reach the free surface of the epithelium with knobs bearing microvilli. The latter are in contact with amorphous material not described previously. Glial-like cells wrap bipolar cells in the epithelium and poorly differentiated basal cells are found just over the basal lamina. The vascular pump described in mammal VNO is not present at all in the frog VNO. We conclude that in the frog the VNO is closer to the reptilian than the mammalian VNO, although the frog VNO shows some unique morphological characteristics.     

The transneuronal transport of horseradish peroxidase in the visual system of the frog, Rana pipiens

During the course of experiments designed to study synaptic relationships between the terminals of retinal axons and the various cell populations in the optic tectum of the frog, Rana pipiens, we found that neurons in many of the retinorecipient nuclei, including the tectum, are labeled transneuronally following injections of horseradish peroxidase into the optic nerve. In the optic tectum, particular cell groups are labeled to the extent that their dendrites as well as their somas are filled with reaction product while other cell types, which, on the basis of the location of their somas or dendrites, seem equally likely to receive direct retinal projections, remain free of label. Electron microscopic investigation of the optic tectum reveals that the label is confined to pre- and postsynaptic processes. These results suggest that the transneuronal transport depends on a transfer of horseradish peroxidase from presynaptic terminals to postsynaptic cells rather than on a widespread diffusion of the enzyme through the neuropil followed by a selective uptake by particular cell groups. These results also suggest that only some of the tectal cell groups which receive direct retinal projections may be transneuronally labeled. The transneuronal transport of horseradish peroxidase is useful since it reveals the morphology as well as the location of at least some of the retinorecipient cells. Moreover, the robust nature of this phenomenon makes the frog a good choice for future studies of the mechanism of transneuronal transport.     

Auditory input to a vocal nucleus in the frog Rana pipiens: hormonal and seasonal effects

Summary In Rana pipiens, single unit recordings from the pretrigeminal nucleus (pre-V), a nucleus involved in call production, demonstrated neurons that respond to auditory stimuli. Most of these neurons had V-shaped tuning curves, with best excitatory frequencies between 200–1400 Hz, thresholds between 31–87 dB SPL, latencies between 10–50 ms, and Q (10 dB) between 1.3–5.1. The number of pre-V neurons that responded to acoustic stimulation increased after gonadotropin injections, and appeared to increase during the breeding season. In addition, a small number of neurons with more complex response properties, such as W-shaped tuning curves or sensitivity to white noise but not to pure tones, appeared after hormone treatments. The hormonal and possible seasonal effects on pre-V auditory activity suggest that the auditory input to this vocal nucleus may play a role in reproductive behavior.     

The effects of temperature and metabolic inhibitors on the spontaneous relaxation of the potassium contracture of the heart of the frog Rana pipiens

1. The spontaneous relaxation of the potassium contracture and the relaxation induced by the removal of extracellular calcium or the restoration of the original potassium concentration, in the frog heart, show a strong dependence on temperature.2. The energy of activation of the later exponential phase of the spontaneous relaxation is 10.43 kcal mole(-1), a value close to that reported for the binding of calcium ions by isolated sarcoplasmic reticulum, but larger than that for the calcium efflux from mammalian heart.3. The use of metabolic inhibitors shows that relaxation can be sustained when glycolysis is poisoned, but the disruption of oxidative phosphorylation slows relaxation.4. Poisoning of both glycolysis and oxidative phosphorylation blocks all but the small initial part of the spontaneous relaxation of the potassium contracture and also interferes with relaxation induced by other means.5. The results are considered to favour the existence, in frog heart, of an active intracellular relaxing system which uses ATP as its substrate to lower the sarcoplasmic calcium concentration. This system is likely to be the sarcoplasmic reticulum but the mitochondria could also be involved.     

Distribution and morphometric quantitation of pancreatic endocrine cell types in the frog, Rana pipiens

Cells reactive to anti-anglerfish insulin, anti-porcine glucagon, anti-synthetic somatostatin, and anti-bovine pancreatic polypeptide were identified in adult Rana pipiens male pancreases using peroxidase anti-peroxidase immunohistochemistry. Insulin positive cells are columnar shaped and arranged in cords. Glucagon positive and somatostatin positive cells are located around the core of insulin positive cells. Isolated cells and clusters of cells of only one cell type are also found. Adjacent sections stained with anti-glucagon and anti-bovine pancreatic polypeptide showed that glucagon positivity and pancreatic polypeptide positivity are found in the same cells. Comparison of double stained adjacent sections confirmed the presence of these two antigens in the same cells, and further showed the occasional presence of cells which are positive to only glucagon or pancreatic polypeptide. Staining of rat pancreas with these two antisera showed that glucagon and pancreatic polypeptide are present in two distinct cell populations. Morphometric quantitation of immunohistochemically stained sections of Rana pipiens pancreases showed that about 2% of the pancreas is endocrine tissue. Of this, 43% is comprised of insulin positive cells, and 43% is occupied by glucagon-pancreatic polypeptide positive cells. Somatostatin positive cell occupy about 14% of the total islet volume. The presence of glucagon and pancreatic polypeptide in the same cell population in the frog, but in different cell populations in mammals, may reflect special functional adaptation in this species, or a close relation of these two hormones and their cells of production during evolution.