Coding of amplitude modulation in the auditory midbrain of the bullfrog (Rana catesbeiana) across metamorphosis

The functional development of the auditory system across metamorphosis was examined by recording neural activity from the torus semicircularis of larval and postmetamorphic bullfrog froglets in response to amplitude-modulated sound. Multiunit activity in the torus semicircularis during early larval stages showed significant phase-locking to the envelopes of amplitude-modulated noise bursts, up to modulation rates as high as 250 Hz. Beginning at metamorphic climax and continuing into the froglet period, phase locking was restricted to the more limited frequency range characteristic of adult frogs. The onset of operation of the tympanic pathway does not reinstate the highly synchronous neural activity characteristic of the operation of the fenestral pathway. Modulation transfer functions based on spike count did not show tuning for modulation rate in early stage tadpoles, but a greater variety of shapes of these functions emerged as development proceeded. Most of the different kinds of modulation transfer functions seen in adult frogs were also observed in froglets, but band-pass functions were not as sharply peaked. These data suggest that different neural codes for processing of the periodicity of complex signals operate in early stage tadpoles than in postmetamorphic froglets. Accepted: 7 October 1998     

Glomerular permeability in the bullfrog Rana catesbeiana

Filtration studies suggest similar size pores in the glomerular filters of mammals and amphibians. However, the glomerular wall in the bullfrog exhibits several structural features not found in mammals. The subendothelial space of the basement membrane is often greatly enlarged and infiltrated by cellular elements. The lamina densa of the basement membrane shows extensive variation in thickness and packing of its filaments. On the other hand, the epithelial slits in the bullfrog are closed by a slit diaphragm which appears similar in size and structure to the slit diaphragm in mammals. Horse spleen ferritin, a protein with a hydrodynamic radius of 61 A, was used as an ultrastructural tracer to determine whether the highly variable structure of the basement membrane renders this layer more permeable than its mammalian counterpart. Within 10 min after intravenous injection, ferritin was found throughout the basement membrane and often in clusters within the subepithelial layer adjacent to the slit diaphragm. Virtually no ferritin was found within the urinary space, podocytes, or cells of the proximal tubule. Ferritin distribution was the same in both superficial glomeruli and more deeply lying glomeruli regardless of the method of fixation. These results indicate that in the bullfrog the slit diaphragm is a principal filtration barrier to ferritin and thus to smaller plasma proteins.     

Pharmacokinetics of kanamycin in the bullfrog, Rana catesbeiana

1. Kanamycin disposition was studied in bullfrogs (Rana catesbeiana) following single doses IP. Both plasma t1/2 and Vd of the drug increased with increasing time after drug indicating redistribution and tight binding of kanamycin to deep tissue compartments. 2. Kanamycin was eliminated unchanged with a t1/2 plasma = 27 hr; perilymph = 89 hr; endolymph = 183 hr; aqueous humor = 54 hr; and CSF = 58 hr. 3. Kanamycin was absorbed by frogs from environmental water. 4. Environmental conditions must be carefully specified and monitored, as well as the physiological state of the animals when studying the effects of drugs on Amphibia.     

Arachnoid mater of the bullfrog,Rana catesbeiana

Summary In the bullfrog, the meninges surrounding the central nervous system include an arachnoid mater that contains layers of cells with abundant intermediate filaments (IFs) having unique organizational characteristics. This membrane contains an inner lamina of cells that resemble fibroblasts and an outer lamina of flattened cells that are almost filled with IFs. The IFs of the outer arachnoid are arranged in compact, arching bundles that lie parallel to the outer surface of the central nervous system. Thus, sections cut tangentially to the membrane reveal bending of filament bundles, whereas transverse sections do not. In some cells bordering the subdural space, bundles of filaments are organized into highly-ordered spiral arrays. Attachments to the numerous desmosomes and, apparently, to the nuclear envelope suggest anchoring of cytoplasmic structures by the IF system. Microtubules occur primarily near the plasma membrane and the nucleus. Numerous caveolae also are associated with the plasma membrane.The unusual abundance, organization, and cytoplasmic relations of IFs in the bullfrog arachnoid suggest that this membrane may serve as an important model for study of fundamental cytoskeletal relations and function.     

Biomechanics of vibration reception in the bullfrog,Rana catesbeiana

The opercularis system (OPS) of amphibians consists of an opercularis muscle that connects the shoulder girdle skeleton to the operculum, a movable element in the oval window of the otic capsule. The role of the OPS in reception of vibrations was examined in bullfrogs (Rana catesbeiana) tested in various postures that manipulated differential motion between the shoulder girdle (the origin of the opercularis muscle) and skull (including the inner ear). Amplitude and phase relationship of motions of the suprascapular cartilage of the shoulder girdle and the posterior skull were also measured during these tests. 1. Microphonic responses to vertical vibrations from 25-200 Hz were typically highest when frogs were in a normal, sitting posture with the head held off the vibrating platform. Responses from animals in which the head directly contacted the platform were often less (by up to 10 dB at certain frequencies). Responses from all test positions were highest at lower frequencies, especially between 50-100 Hz. 2. Suprascapular accelerations were typically highest in the normal, sitting posture, and at lower frequencies (50-75 Hz) were often greater than that of the vibrating platform by up to 8 dB. The shoulder girdle skeleton of the bullfrog is therefore readily affected by vertical substrate motion. 3. The amplitude of microphonic responses in the different test postures did not correspond well with head acceleration. Rather, response amplitude corresponded best with the absolute difference between shoulder and head motion. For example, in the normal posture, suprascapular motion was much greater than head motion, and responses were relatively high. If only the head was vibrated, head motion was high and shoulder motion low, and responses also were relatively high. If the head and body were vibrated together, their motions were similar, and responses to the same platform accelerations were often reduced. Phase differences between shoulder and head motions were small at the frequencies examined and may be of little functional significance. The importance of differences in shoulder and head motion suggests that the resulting differential motion of the operculum and inner ear fluids can produce waves that stimulate appropriate end organs (such as the saccule). 4. Removal of the opercularis muscle reduced responses up to 18 dB at certain frequencies in some of the test postures. The most significant reductions were observed in those postures with a significant difference between shoulder and head motion (such as the normal posture).(ABSTRACT TRUNCATED AT 400 WORDS)     

Central respiratory pattern generation in the bullfrog, Rana catesbeiana

There are two components to breathing pattern generation the production of the pattern of neural discharge associated with individual breaths, and the pattern in which breaths are produced to effect ventilation. Bullfrogs typically breathe with randomly distributed breaths. When respiratory drive is elevated, breathing becomes more regular and often episodic. Studies on in vitro brainstem-spinal cord preparations of the adult bullfrog and in situ preparations of decerebrate, paralyzed, unidirectionally ventilated animals suggest that output from the central rhythm generator in frogs is conditional on receiving some input and that a host of central inputs remain even in the most reduced preparations. There appear to be descending inputs from sites in the dorsal brainstem just caudal to the optic chiasma that cluster breaths into episodes, a strong excitatory input caudal to this site but rostral to the origin of the Vth cranial nerve and, possibly, segmental rhythm generators throughout the medulla that are normally entrained to produce the normal breathing pattern. The data also suggest that the shape of the discharge pattern (augmenting, decrementing) and timing of outputs (alternating vs synchronous) associated with motor outflow during each breath are also dependent on the interconnections between these various sites.     

Spatial and spectral dependence of the auditory periphery in the northern leopard frog

We investigated directionalities of eardrum vibration and auditory nerve response in anesthetized northern leopard frogs (Rana pipiens pipiens). Simultaneous measures of eardrum velocities and firing rates from 282 auditory nerve fibers were obtained in response to free-field sounds from eight directions in the horizontal plane. Sound pressure at the external surface of the ipsilateral eardrum was kept constant for each presentation direction (± 0.5 dB). Significant effects of sound direction on eardrum velocity were shown in 90% of the cases. Maximum or minimum eardrum velocity was observed more often when sounds were presented from the lateral and posterior fields, or from the anterior and contralateral fields, respectively. Firing rates of 38% of the fibers were significantly affected by sound direction and maximum or minimum firing rate was observed more frequently when sounds were delivered from the lateral fields, or from the anterior and contralateral fields, respectively. Directionality patterns of eardrum velocity and nerve firing also vary with sound frequency. Statistically significant correlation between eardrum velocity and nerve fiber firing rate was demonstrated in only 45% of the fibers, suggesting that sound transmission to the inner ear through extratympanic pathways plays a non-trivial role in the genesis of directionality of auditory nerve responses.Abbreviations CF characteristic frequency - SVL snout-vent length - TM tympanic membrane     

牛蛙外周血细胞的形态学特点

本研究对雌雄牛蛙(Rana catesbeiana)外周血细胞的组成、形态、大小和数量进行了观察和统计。牛蛙外周血细胞由红细胞、白细胞以及血栓细胞组成,其中红细胞体积最大,平均大小(长径×短径)为(25.68±1.88)μm×(16.49±1.53)μm,扫描电镜下发现红细胞表面光滑;血栓细胞呈卵圆形或纺锤形,其体积最小,平均大小为(8.62±1.04)μm×(7.47±1.11)μm;白细胞由淋巴细胞、单核细胞、浆细胞、嗜中性粒细胞、嗜酸性粒细胞和嗜碱性粒细胞组成,扫描电镜下白细胞表面粗糙不平,有许多不规则的凸起。白细胞中淋巴细胞最多,其中小淋巴细胞约占白细胞的32.66%±4.29%,大淋巴细胞约占6.03%±1.54%;嗜碱性粒细胞最少,只占4.78%±0.83%;浆细胞胞体大小不一,常呈椭圆形,平均大小为(23.51±0.59)μm×(22.86±0.67)μm;此外,牛蛙外周血细胞中单核细胞、淋巴细胞和嗜碱性粒细胞的数量比例以及淋巴细胞和嗜碱性粒细胞的大小均有性别的差异(P0.05)。     

Albumin synthesis during induced and spontaneous metamorphosis in the bullfrog Rana catesbeiana

Treatment of premetamorphic tadpoles with triiodothyronine (T₃) alters the in vivo distribution of radioactive amino acids among serum protein fractions. The effects on the albumin fraction have been interpreted as reflections of the relative rate of synthesis. About 12 hr after intraperitoneal injection of 2.5 × 10^?10 mole of T₃ per gram, there is an increase in the relative rate of albumin synthesis. The effect peaks on day 3 at 5 × the untreated level and returns to near the untreated level by day 6. Continuous immersion in 1 × 10^?7M T₃ results in a similar stimulation of albumin synthesis, but with no decline after day 3. The timing of the response is independent of dose or route of T₃ administration. The effect of T₃ on the relative rate of albumin synthesis is also observed in froglets. There is a 6-fold increase in the relative rate of albumin synthesis during spontaneous metamorphosis peaking at stage XXI and returning to the premetamorphic level by stage XXV. The following was concluded: (1) The increase in the relative rate of albumin synthesis during metamorphosis results from increased endogenous thyroid levels. (2) Following a peak, the decline in albumin synthesis observed in induced and spontaneously metamorphosing animals is a result of decreasing thyroid hormone levels. (3) The effect of T₃ on albumin synthesis may be the summation of two effects, a direct effect of T₃ and a stimulation by amino acids from the resorbing tail. (4) A decreased relative rate of albumin degradation or a sparing of albumin is probably responsible for the elevated relative concentration of albumin in the serum of postmetamorphic animals.     

Role of the opercularis muscle in seismic sensitivity in the bullfrog Rana catesbeiana

The inner ear of anuran amphibians appears to be exceptionally sensitive to substrate vibration. The opercularis system, consisting of an opercularis muscle running from the shoulder girdle to a movable, cartilaginous operculum lying next to the inner ear, has been hypothesized to be involved in driving these seismic responses. Removal of the opercularis muscle of adult bullfrogs, Rana catesbeiana, caused clear decreases in microphonic responses of the inner ear to vibrations from 20-250 Hz and 0.05-5.0 cm/sec2 accelerations. Degree of decrease in responsiveness was variable between individuals and between different frequencies of stimulation, ranging up to 90% reduction at certain frequencies and in certain specimens. Decreases were most marked at lower frequencies below about 50 Hz. Additional removal of the levator scapulae superior muscle, which runs alongside the opercularis muscle from the shoulder girdle to ventrolateral portions of the otic capsule, also tended to depress responses, although this effect was substantially less (generally less than 10%) and also less consistent. As the opercularis muscle appears to be derived from the levator scapulae musculature, it is speculated that primitively seismic sensitivity was enhanced by a muscular connection that could transmit motion from the forelimb to the otic region, responsiveness being further enhanced by the subsequent evolution of the specialized opercularis system.     

Metabolism of C26 bile alcohols in the bullfrog, Rana catesbeiana

Metabolism of C26 bile alcohols in the bullfrog, Rana catesbeiana, was studied. [24-14C]-24-Dehydro-26-deoxy-5 beta-ranol (3 alpha,7 alpha,12 alpha-trihydroxy-27-nor-5 beta-cholestan-24-one) was chemically synthesized from [24-14C]cholic acid and incubated with bullfrog liver homogenate fortified with NADPH. 24-Dehydro-26-deoxy-5 beta-ranol was shown to be converted into both 26-deoxy-5 beta-ranol and 24-epi-26-deoxy-5 beta-ranol [(24S)- and (24R)-27-nor-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24-tetrols] in addition to 5 beta-ranol [(24R)-27-nor-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,26-pentol], which is the major bile alcohol of the bullfrog. [24-3H]-26-Deoxy-5 beta-ranol and [24-3H]-24-epi-26-deoxy-5 beta-ranol were prepared from 24-dehydro-26-deoxy-5 beta-ranol by reduction with sodium [3H] borohydride and administered respectively to two each of four bullfrogs by intraperitoneal injection. After 24 h, labeled 5 beta-ranol was isolated from the bile of the bullfrogs that received [24-3H]-26-deoxy-5 beta-ranol. In contrast little if any radioactivity could be detected in 5 beta-ranol or its 24-epimer after administration of [24-3H]-24-epi-26-deoxy-5 beta-ranol.     

Changes in serum lipoproteins during metamorphosis of the bullfrog,Rana catesbeiana

Serum lipoproteins of the bullfrog, Rana catesbeiana, were studied during metamorphosis. Adult bullfrog has essentially one lipoprotein, designated β-lipoprotein. This β-lipoprotein migrates during electrophoresis to β-globulin region and it has a low hydrated density such that it exhibits floatation in a solvent of density 1.063. On the other hand, tadpole serum has one more lipoprotein, designated as α-lipoprotein, in addition to the β-lipoprotein. The α-lipoprotein migrates to the α-globulin region in zone electrophoresis and corresponds to the so called high density lipoprotein judging from ultracentrifugal behavior. Serum α-lipoprotein disappears and β-lipoprotein content decreases during metamorphosis.     

Optimal hematocrit theory during activity in the bullfrog (Rana catesbeiana).

1. There is an exponential relationship between blood viscosity (cP) and hematocrit (%) for the bullfrog; eta = 1.81 e0.033Hct. The in vitro optimal hematocrit calculated for blood flow through tubes, from this relationship for bullfrog blood, is 30%. 2. Amphibian blood is a non-Newtonian fluid with viscosity dependent on shear rate. It has a finite yield shear stress of about 1.5 dynes cm-2. 3. Hematocrit of bullfrogs was increased from 27% (control) to 57% by isovolemic erythrocythemia (constant volume blood-doping). There was a slight increase in systolic, diastolic and venous blood pressure with elevated hematocrit. 4. Systemic arch blood flow rate was inversely related to blood viscosity for erythrocythemic bullfrogs. The decrease in systemic arch blood flow at high hematocrits was due primarily to reduced pulse volume rather than reduced heart rate. 5. Systemic arch blood flow, when standardised between individuals, was inversely related to blood viscosity; Qbl = 0.185 + 3.73 eta -1. This relationship was significantly different from that predicted by the Poiseuille-Hagen flow formula. The in vivo optimal hematocrit calculated from this relationship was 41%. 6. Optimal hematocrit theory appears to be generally applicable for Rana catesbeiana in vitro and in vivo. Most individuals had an in vivo optimal hematocrit, but the absence of a clear optimal hematocrit for some individuals could reflect methodological variability, or in vivo physiological compensation for the increased blood viscosity at high hematocrit.     

Testicular morphological changes during the seasonal reproductive cycle in the bullfrog Rana catesbeiana

Spermatogenesis and steroidogenesis undergo seasonal variations during the reproductive cycle in amphibians. Testicular morphological and morphometric seasonal variations as well as interstitial lipidic inclusions and intralobular glycoconjugates were evaluated during seasonal cycle of Rana catesbeiana. Testes of frogs collected during the annual seasons were weighed for calculation of GSI (Gonadosomatic index). Seminiferous lobule diameters (DSL) and volume densities of seminiferous lobules (VvSL), excretory ducts (VvED), and interstitial tissue (VvIT) were analyzed. Semithin sections were submitted to Periodic Acid-Schiff (PAS) and Alcian Blue (AB) methods for detection of glycoconjugates, while lipidic inclusions were detected by Sudan Black B. GSI showed no significant variations during the year. Since VvED and VvIT increased significantly during summer and were inversely proportional to VvSL, a compensatory effect between the testicular compartments may be related to the maintenance of GSI. During autumn/winter, larger lobular diameters were observed in comparison to spring/summer when spermiogenesis and spermiation were commonly observed. The increased VvIT and the numerous lipidic inclusions in the interstitial cells during summer suggest a relationship between spermiogenesis and steroidogenesis. Besides the structural stability variations occurring in the IT and SL, a possible paracrine interaction between ED and IT should be also involved in the IT development during summer. The presence of PAS and AB-positive globular structures were observed in the seminiferous lobules and excretory ducts. These structures containing acid glycoconjugates appear to be Sertoli cell apical portions, which are accumulated in the lumen of the seminiferous lobules mainly during spermiation.     

Fine structure of the rhombencephalic tela of the bullfrog,Rana catesbeiana

Summary The posterior rhombencephalic tela choroidea of the bullfrog was examined by electron microscopy. This membrane, the pia-ependymal roof of the caudal hindbrain, contains a large central region characterized by cuboidal ependymal cells which surround sizable microscopic apertures — the interependymal pores.Ultrastructurally ependymal cells of this area are characterized by infrequent apical microvilli and cilia. They contain irregularly shaped nuclei and few cytoplasmic organelles that are largely apical in position. The most striking feature is an abundance of cytoplasmic filaments forming an extensive cytoskeleton. Laterally these cells are joined by numerous elaborate desmosomes. The majority of the ependymal cells have a basal lamina consisting of single, double, or triple laminae lying parallel to the basal plasma membrane.Several unusual specializations are seen at the margins of the interependymal pores. The ependymal cells have lateral cytoplasmic processes that form the actual border of each pore. These processes originate from the apical surface of the cell and partially enclose an elaborate network of basal lamina associated with the interependymal pores.These findings demonstrate microscopic apertures in the roof of the fourth ventricle in the bullfrog that are associated with an unusual form of supportive ependyma.