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PubMed1976

On the diversity of sperm histones in the vertebrates. I. Changes in basic proteins during spermiogenesis in the newt Notophthalmus viridescens.

Sperm histones display great variability in contrast to the conservation of most classes of somatic histones. To study this paradox, this series of papers examines the variation of histone patterns in the testis and sperm of vertebrates, particularly amphibians and reptiles, and attempts to relate such variation to genetically based sex determination as hypothesized by Bloch [Genetics Supplement 61, 93 (1969)]. In the present study we have investigated spermiogenesis in the newt Notophthalmus viridescens viridescens. Cytochemical experiments indicate that the basic nuclear proteins undergo progressive shifts from somatic type histone leads to very arginine-rich "stable protamine" in the later spermatids leads to protamine in the mature sperm. Electrophoresis of Notophthalmus histones extracted from chromatin reveals that the pattern of testes specific basic proteins in the urodele is distinct from the pattern of testicular proteins in the anurans Bufo americanus and Xenopus laevis. Species within the class Amphibia therefore exhibit considerable diversification in their type of basic sperm proteins.

Animals↗
PubMed1989

Cytokeratin filaments and desmosomes in the epithelioid cells of the perineurial and arachnoidal sheaths of some vertebrate species.

Using electron microscopy and immunohistochemistry with a large panel of antibodies to various cytoskeletal proteins we have noted that the single- or multi-layered sheaths of epithelioid cells ("neurothelia") surrounding peripheral nerves (perineurial cells) or structures of the central nervous system, including the optic nerve (arachnoid cells), show remarkable interspecies differences in their cytoskeletal complements. In two anuran amphibia examined (Xenopus laevis, Rana ridibunda), the cells of both forms of neurothelia, i.e., perineurial and arachnoid, are interconnected by true desmosomes and are rich intermediate-sized filaments (IFs) of the cytokeratin type. Among higher vertebrates, a similar situation is found in the bovine and chicken nervous systems, in which the arachnoid cells of the meninges contain desmosomes and IFs of both the cytokeratin (apparently with restricted epitope accessibilities in the chicken) and the vimentin type, whereas the perineurial cells of many nerves contain cytokeratin IFs, often together with vimentin, but no desmosomes. In contrast, in rat arachnoidal and perineurial cells significant reactions have been observed neither for cytokeratins nor for desmosomes. In the human nervous system, cytokeratins and desmosomes have also not been seen in the various perineuria studied whereas desmosomes are frequent in arachnoidal cell layers which are dominated by vimentin IFs and only in certain small regions of the brain contain some additional cytokeratins. The occurrence of cytokeratins in the tissues found positive by immunohistochemistry has been confirmed by gel electrophoresis of cytoskeletal proteins, followed by immunoblotting. Our results emphasize both similarities and differences between the neurothelia on the one hand and epithelia or endothelia on the other, justifying classification as a separate kind of tissue, i.e., neurothelium. The observations of interspecies differences lead to the challenging conclusion that neither desmosomes nor cytokeratins are essential for the basic functions of neurothelial sheaths nor does the specific type of IF protein expressed in these cells appear to matter in this respect. The results are also discussed in relation to the cytoskeletal characteristics of other epithelioid tissues and of human neurothelium-derived tumors.

Animals↗
PubMed1980

Activities of 3-hydroxybutyrate dehydrogenase, 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase in relation to ketone-body utilisation in muscles from vertebrates and invertebrates.

1. The activities of 3-hydroxybutyrate dehydrogenase were non-detectable in muscles of invertebrates and marine teleost fish; activities were found in muscles of amphibia, reptiles and mammals and also in an elasmobranch fish. Muscles were classified into three groups according to the activities of 3-oxoacid CoA-transferase: muscles with very low activities (less than 0.01 mumol x min-1 x g-1) which obtain energy for contraction from anaerobic glycolysis; muscles with low activities (greater than 0.01 less than 5 mumol x min-1 x g-1) which include insect flight muscles, muscles of other invertebrates and skeletal muscles of higher vertebrates; muscles with high activities of 3-oxoacid CoA-transferase (greater than 5 mumol x min-1 x g-1) which are characterised by continuous mechanical activity for long periods of time, e.g. heart, diaphragm, postural and some smooth muscles of mammals. 2. It is suggested that ketone bodies may be important fuels for muscles in the very low and low activity groups during starvation, when the muscle is at rest. The muscles in the high activity group may use ketone bodies when they are available in the blood to provide energy for mechanical activity. Since these muscles provide a continuous vital physiological function, they must always be provided with a fuel for respiration and, in a similar manner to brain, they may utilise either glucose or ketone bodies.

Acetyl-CoA C-Acetyltransferase↗
PubMed2005

Testosterone-immunopositive primordial germ cells in the testis of the bullfrog, Rana catesbeiana.

In amphibia, steroidogenesis remains quiescent in distinct seasonal periods, but the mechanism by which spermatogenesis is maintained under low steroidogenic conditions is not clear. In the present study, testosterone location in the testes of Rana catesbeiana was investigated immunohistochemically during breeding (summer) and nonbreeding (winter) periods. In winter, the scarce interstitial tissue exhibited occasional testosterone immunopositivity in the interstitial cells but the cytoplasm of primordial germ cells (PG cells) was clearly immunopositive. By contrast, in summer, PG cells contained little or no immunoreactivity whereas strong immunolabelling was present in the well-developed interstitial tissue. These results suggest that PG cells could retain testosterone during winter. This androgen reservoir could be involved in the control of early spermatogenesis in winter and/or to guarantee spermiogenesis and spermiation in the next spring/summer. The weak or negative immunoreaction in the summer PG cells might reflect consumption of androgen reservoir by the intense spermatogenic activity from spring to summer. Thus, besides acting as stem cells, PG cells of R. catesbeiana could exert an androgen regulatory role during seasonal spermatogenesis.

Animals↗
PubMed1981

Interspecies comparison of brain ganglioside patterns studied by two-dimensional thin-layer chromatography.

Brain gangliosides from four vertebrate classes (fish, amphibia, aves, and mammalia) were studied by patterns generated with the use of two-dimensional thin-layer chromatography. In an effort to retain possible alkalilabile gangliosides, samples were not base-hydrolyzed. Resultant chromatograms revealed complex patterns of the major known gangliosides and a number of minor and trace molecular species previously unresolved. More than 30 resorcinol-positive components were detected in mammalian neural samples. Our data indicate both qualitative and quantitative differences in the chromatogram patterns between the vertebrate classes, but potentially greater qualitative similarity exists between the lower and higher classes than has previously been noted.

Animals↗
PubMed1982

Myelin gangliosides in vertebrates.

A phylogenetic survey of brain myelin ganglioside patterns and concentrations has been carried out on 16 vertebrate species. Gangliosides were isolated from purified myelin and found to vary in concentration from 25 micrograms of sialic acid per 100 mg of myelin for goldfish to a value of 395 for turkey. The latter species had approximately equivalent amounts of GM1 and GM4 as the two major gangliosides. The 11 mammals studied all had GM1 as the major ganglioside, with variable amounts of GM4; rhesus monkey and human had 20-25% GM4, whereas the others had less than 10%. Amphibia and fish myelin contained the least total ganglioside, with patterns that showed relatively little GM1 and no detectable GM4. Alligator myelin was unique in having a total concentration as high as the avian species, but a pattern with predominantly di- and trisialo gangliosides.

Aged↗
PubMedDate not supplied

Isolation of a thermotolerant Paravahlkampfia sp. from lizard intestine: biology and molecular identification.

An amoeba was isolated from the intestines of several moribund pink-tongued skinks (lizards), Hemisphaeriodon gerrardi. Unusual features of this isolate were its ability to grow at temperatures of > or = 37 degrees C, and its inability to use Escherichia coli as a food source or to grow axenically on a variety of enriched culture media suitable for other soil amoeba isolates. Growth was abundant, however, on tissue culture cells, with amoebae clearing cell monolayers in approximately 48 h at 37 degrees C. Trophozoites had a vahlkampfiid-like morphology, moving by means of an anterior eruptive pseudopod. Cysts, round to slightly ovoid and lacking exit pores, were formed in culture. Tests for enflagellation of trophic amoebae were negative. Indirect immunofluorescence staining was negative for Naegleria fowleri and Willaertia sp. The isolate was sensitive to azithromycin, but not to amphotericin B, pentamidine isethionate, fluconazole, 5-fluorocytosine, and sulfadiazine. Phylogenetic analysis based on the PCR-amplified small subunit ribosomal DNA, identified the organism as Paravahlkampfia ustiana, an amoeba not previously isolated from either poikilothermic or homeothermic hosts. No evidence of pathology was seen in stained sections of lizard intestine, suggesting that the ameba was part of the normal fauna of the lizard gut. Its diet in the lizard intestine is unknown and the organism may have unusual growth requirements. Thus, P. ustiana joins other soil amoebae that have been isolated from mammals, amphibia, fish, and reptiles, which have the potential of becoming opportunistic pathogens.

Amoeba↗
PubMed1997

The site and time of expression of MIF in frog development.

A ventrally localized melanization-inhibiting factor (MIF) has been suggested to play a role in the expression of dorsal-ventral pigment patterns in amphibia. Here we investigate the onset and localization of MIF appearance in frog development. The expression of MIF was analyzed in the wild-type and gray-eyed mutant (g/g) of Rana japonica by immunoblotting and immunohistochemistry using an anti-MIF neutralizing monoclonal antibody. Western blot analysis revealed that the anti-MIF antibody recognized approximately 51 kDa and approximately 58 kDa bands. The 51 kDa band first appeared at the external gill stage, while 58 kDa band was additionally detected at the hindlimb bud stage. With the use of immunohistochemistry, it was found that the anti-MIF antibody stained the whole epidermis of the embryos at the external gill stage; however, the staining was stronger in lateral and ventral epidermis than in dorsal. Staining with the anti-MIF antibody was observed only in the outer epidermis of the ventral skin, but not in the dorsal skin during and after metamorphosis. The spatial expression of MIF in the wild-type was the same as that in the gray-eyed mutant. The same immunohistochemical result was obtained in the adults of R. nigromaculata. These results suggest that MIF is involved in the formation of the dorsal-ventral pigment pattern.

Animals↗
PubMed1977

Immunoglobulin gamma chains of a monotreme mammal, the echidna (Tachyglossus aculeatus): amino acid composition and partial amino acid sequence.

The echidna represents the lowest stage in phylogeny at which molecules clearly homologous to IgG antibodies appear to occur. We provide evidence that a fraction of gamma chains possess an unblocked N terminal sequence comparable to the VHIII sub-group of human gamma chains and that glycine is the C-terminal residue. Statistical comparison of amino acid composition of the component chains with other immunoglobulin heavy chains suggests that echidna gamma chains are more closely related to eutherian gamma chains than to the 7S Ig heavy chains from amphibia or aves. The results are consistent with our view that true gamma-type heavy chains did not appear in evolution until after the mammalian line diverged from the stem reptiles.

Amino Acid Sequence↗
PubMed1977

Morphology of motor units in cat extraocular nodule.

Muscle fibers from single motor units in cat inferior oblique were marked iontophoretically with procion red injected through an intracellular pipette. The fibers were isolated by dissection and characterized by electron microscopy. A fiber in a slow motor unit with non-conducted electrical responses showed slow fiber morphology of the amphibia-type. Fast, twitch motor units contained fibers with twitch fiber morphology. Thus, a good correlation between muscle fiber structure and function was obtained in these eye motor units, examined with both physiological and morphological techniques.

Animals↗
PubMed1969

Changes in extracellular potassium concentration produced by neuronal activity in the central nervous system of the leech.

1. Experiments were made on single neurones and glial cells in the central nervous system of the leech to study the accumulation of K that occurs in the extracellular spaces around neurones as a result of impulse activity.2. The resting potential of a neurone is too insensitive to be used for the estimation of small changes in K concentration. The undershoot of the action potential, however, provided a reliable indicator of the K accumulation that occurs around a neurone during activity.3. After a single impluse the amplitude of the undershoot of a second action potential was decreased; the effect corresponded to a peak increase in K concentration of about 0.8 mM/l. immediately after the spike and declined exponentially with a time constant of about 100 msec. With trains of impulses the K concentration increased exponentially, again with a time constant of about 100 msec. The final value of K depended on the frequency and could build up to about double the normal concentration of 4 mM/l.4. The build-up of K was markedly reduced when the extracellular space surrounding a neurone was enlarged by removing its glial investment.5. Synchronous, repetitive activation of groups of neurones caused a slow depolarization of neighbouring glial cells in the C.N.S. of the leech, similar to that observed in amphibia and mammals. The change in glial membrane potential was also used to estimate the changes in K concentration and these values agreed with measurements derived from the undershoot.6. Increases of K concentration in the bathing fluid of the same order as those caused by neural firing markedly affected the frequency of ;spontaneous' neuronal discharges and synaptic potentials occurring within certain neurones in the C.N.S.7. The possible effects of physiologically occurring increases of K concentration on integration are discussed.

Action Potentials↗
PubMed1970

The contribution by glial cells to surface recordings from the optic nerve of an amphibian.

1. The contribution by glial cells to surface recordings has been examined in the optic nerve of the amphibian Necturus maculosus. The method of current injection was employed selectively to alter the membrane potential of glial cells without affecting that of the axons. The resulting changes in potential were recorded simultaneously from the surface of the nerve using the sucrose gap method and intracellularly from a glial cell near the gap.2. The sucrose gap method recorded 40% of the changes in glial membrane potential. This percentage was not affected when the current electrode was inserted into different glial cells while maintaining the recording conditions constant.3. Following axonal degeneration, produced by removing the eye 2-3 months earlier, the percentage contribution by glia increased to 84%.4. By measuring sucrose gap responses to changes in K(o) it was possible to estimate that the sucrose gap method recorded 31-60% of changes in axonal membrane potential. It was also determined that the axons, unlike glial cells, are relatively insensitive to reductions in K(o). Surface responses to decreases in external potassium thus reflect the magnitude of the glial contribution.5. It is concluded that changes in glial membrane potential contribute about as much to surface recordings from the optic nerve of Necturus as do equivalent changes in axonal membrane potential. The contributions by the glial cells and axons are related to the relative volumes of tissue they respectively occupy. The significance of these findings to the analysis of surface recordings from the mammalian brain is discussed. Since mammalian glial cells, like those in Amphibia and the leech, become depolarized during neuronal activity and on the basis of electron microscopic evidence appear to be electrically coupled, it is likely that they contribute to the electroencephalogram.

Animals↗
PubMed1975

The formation of synapses in amphibian striated muscle during development.

1. A study has been made of the formation of synapses in developing reinnervated and cross-reinnervated amphibian twitch muscles which receive either a focal (iliofibularis) or a distributed (sartorius) innervation from 'en plaque' nerve terminals using histological, ultrastructural and electrophysiological techniques. 2. During the development of the tadpole through metamorphosis to the adult frog, the sartorius myofibres increased in length at about twice the rate of the iliofibularis myofibres, due to a fast rate of growth at their insertions on to the pelvic tendon. 3. The short iliofibularis and sartorius myofibres of young tadpoles (800 mum long) possessed only a single synapse and the iliofibularis myofibres did not receive any further innervation during development. However the sartorius myofibres received further transient innervation on the new muscle laid down during development at the fast growing pelvic insertion, until the distance between the original synapse formed on the myofibres and the synapse at the pelvic end of the muscle was about 12 mm. 4. During development synapses possessed either skewed, multimodal, or unimodal m.e.p.p. amplitude-frequency distributions; the intervals between m.e.p.p.s. were not distributed randomly according to a Poisson process, as m.e.p.p.s. of similar amplitudes tended to be separated by very short intervals; the unit-size e.p.p. had a similar amplitude-frequency distribution as the m.e.p.p.s. if these had a unimodal distribution. 5. Reinnervation or cross-reinnervation of the sartorius and the iliofibularis muscles in adults or at a late stage of development simply reconstituted the normal focal and distributed innervation patterns of the muscles, as found in the control muscles of the contralateral and unoperated legs. 6. These observations on synapse formation in amphibia are consistent with the hypothesis that during development the axon making the initial synaptic contact on the muscle cells induces a property over a length of muscle membrane adjacent to this site which makes it refractory to synapse formation; thus during reinnervation or cross-reinnervation of adult muscles this refractory property constrains synapse formation to these sites.

Amphibians↗
PubMed2004

Adenosine decreases both presynaptic calcium currents and neurotransmitter release at the mouse neuromuscular junction.

A controversy currently exists as to the mechanism of action by which adenosine, an endogenous mediator of neurotransmitter depression, reduces the evoked release of the neurotransmitter acetylcholine (ACh) at the skeletal neuromuscular junction. Specifically, it is uncertain whether adenosine inhibits ACh release from mammalian motor nerve endings by reducing Ca(2+) calcium entry through voltage-gated calcium channels or, as is the case at amphibian motor nerve endings, by an effect downstream of Ca(2+) entry. In an attempt to address this controversy, the effects of adenosine on membrane ionic currents and neurotransmitter release were studied at neuromuscular junctions in adult mouse phrenic nerve hemidiaphragm preparations. In wild-type mice, adenosine (500 microm-1 mm) reduced prejunctional Ca(2+) currents simultaneously with a reduction in evoked ACh release. In Rab3A knockout mice, which have been shown to have an increased sensitivity to adenosine, the simultaneous reduction in Ca(2+) currents and ACh secretion occurred at significantly lower adenosine concentrations (< or = 50 microM). Measurements of nerve terminal Na(+) and K(+) currents made simultaneously with evoked ACh release demonstrated that the decreases in Ca(2+) currents were not attributable to changes in cation entry through voltage-gated Na(+) or K(+) channels. Furthermore, no effects of adenosine on residual ionic currents were observed when P/Q-type calcium channels were blocked by Cd(2+) or omega-agatoxin-IVA. The results demonstrate that inhibition of evoked neurotransmitter secretion by adenosine is associated with a reduction in Ca(2+) calcium entry through voltage-gated P/Q Ca(2+) channels at the mouse neuromuscular junction. Whilst it may be that adenosine inhibits ACh release by different mechanisms at amphibia and mammalian neuromuscular junctions, it is also possible that the secretory apparatus is more intimately coupled to the Ca(2+) channels in the mouse such that an effect on the secretory machinery is reflected as changes in Ca(2+) currents.

Acetylcholine↗
PubMed2005

Modulation of calcium currents is eliminated after cleavage of a strategic component of the mammalian secretory apparatus.

Adenosine inhibits neurotransmitter secretion from motor nerves by an effect on the secretory apparatus in amphibia. In contrast, the inhibitory effect of adenosine is associated with decreases in calcium currents at mouse motor nerve endings. To determine if the action of adenosine in the mouse is mediated thorough a direct effect on calcium channels or through the secretory machinery, the effects of cleavage of the SNARE proteins on the action of adenosine were examined. Cleavage of the SNARE syntaxin with botulinum toxin type C (Botx/C) prevented the inhibitory effect of adenosine on nerve terminal calcium currents. Cleavage of the other SNAREs (synaptobrevin with Botx/D or SNAP-25 with Botx/A) failed to affect the inhibitory action of adenosine. The results provide evidence for an intimate coupling of nerve terminal calcium channels with a plasma membrane component of the SNARE complex, such that modulation of calcium currents by a G-protein coupled receptor cannot occur when syntaxin is cleaved.

Adenosine↗
PubMed1964

IDENTITY OF TARICHATOXIN AND TETRODOTOXIN.

Tarichatoxin (C(11)H(17)N(3)O(8)), a potent neurotoxin recently isolated in pure form from the eggs of the California newt, Taricha torosa, has been found to be identical to tetrodotoxin from the ovaries of Sphoeroides rubripes, the Japanese Fugu or puffer fish. As yet this substance has been detected only in a single family of fish, Tetraodontidae, and in a single family of amphibia, Salamandridae.

Amphibians↗
PubMed1969

Toxin from skin of frogs of the genus Atelopus: differentiation from Dendrobatid toxins.

A potent, dialyzable toxin (atelopidtoxin) occurs in the skin of frogs of the genus Atelopus. A concentrate of atelopidtoxin from Atelopus zeteki has an LD(50) in mice of 16 micrograms per kilogram. It differs from batrachotoxin, tetrodotoxin, and saxitoxin, the only known nonprotein substances of greater toxicity, as well as from all toxins previously isolated from amphibia.

Animals↗
PubMed1980

Immunohistochemical localization of amelogenins in enameloid of lower vertebrate teeth.

The indirect method of immunofluorescence was used to demonstrate the presence of amelogenins in the enameloid of teeth and dermal denticles of Chondrichthyes; in the enameloid of Teleostei and Amphibia; and in the enamel of Reptilia. Nonmammalian amelogenins are formed in the ectodermal cells of tooth organs and chemically are so similar to mammalian amelogenins that they interact with antiserum prepared from bovine enamel matrix.

Amelogenesis↗