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[Study of calcium ion binding by merlang parvalbumin according to changes in the parameters of the proteins own fluorescence].

The binding of Ca+ to whiting parvalbumin has been studied by intrinsic (tryptophan) protein fluorescence. It has been shown that parvalbumin can exist in three states, which are interpreted as the protein without Ca2+ (P), with one bound Ca2+ (PC) and with two bound Ca2+ (CPC). The spectra of the states have been identified and the protein fluorescence spectra at different Ca2+ concentration have been decomposed on the components corresponding to these states. Relative populations of the P, PC and CPC states have been plotted against Ca2+ concentration. On the basis of a scheme of the successive Ca2+ binding; P+Ck1 in equilibrium PC; PC+Ck2 in equilibrium CPC, corresponding theoretical dependences have been computed and fitted to the experimental ones. The fitted equilibrium constants K1 and K2, are 5.10(8) and 6.10(6)M-1, correspondingly. The schemes are in a good agreement with the experimental data on EGTA-titration of Ca2+-saturated parvalbumin and on pH-titration of parvalbumin in the presence of EGTA.

Animals↗

Neurochemical development of the hippocampal region in the fetal rhesus monkey, III: calbindin-D28K, calretinin and parvalbumin with special mention of cajal-retzius cells and the retrosplenial cortex.

In spite of continuing controversy on the precise function of the calcium-binding proteins expressed in the hippocampal formation, nothing is known about their prenatal development in primates. In this study, calbindin-D28K, calretinin, and parvalbumin were localized in the hippocampal formation of seven rhesus monkey fetuses aged E47 to E90 (term 165 days). All of the three markers were expressed during the first half of gestation in distinct subsets of nonpyramidal neurons: calretinin-containing cells were the most numerous and relatively differentiated contrasting with a more restricted, less mature, parvalbumin-labeled population and a poor calbindin-positive nonpyramidal contingent. The granule cells and pyramidal neurons were calbindin-positive, including the pyramids of CA3 and the subicular complex, in contrast to the situation found in the adult monkey. The presubiculum and retrosplenial cortex, whose merging formed the caudal pole of the hippocampal formation, also expressed precociously the three calcium-binding proteins. A heterogeneous population of Cajal-Retzius-like cells was demonstrated in the marginal zone of the ventral hippocampal formation. The majority co-expressed calbindin-D28K and calretinin and displayed acetylcholinesterase activity but no GABA-like immunoreactivity. Major intrinsic and extrinsic pathways of the hippocampal system (mossy fiber system, alveus, fimbria, angular, and cingular bundles) were immunoreactive for calretinin and/or calbindin. The distinct developmental time course and regional pattern of distribution of calbindin-D28K, calretinin, and parvalbumin in the nonprincipal neurons suggests a precocious but asynchronous prenatal development of different inhibitory circuits in the hippocampal formation of primates. The labeling of several fiber systems in keeping with comparable early events in the entorhinal cortex (Berger et al.: Hippocampus 3:279-305, 1993), suggests the possibility of earlier functional circuits than hitherto inferred from the observations available in rodents, a hypothesis that deserves further investigation.

Animals↗

Distribution of GABAergic interneurons immunoreactive for calretinin, calbindin D28K, and parvalbumin in the cerebral cortex of the lizard Podarcis hispanica.

The types and distribution of cells containing three calcium-binding proteins, calretinin, calbindin D28K, and parvalbumin, have been studied by immunocytochemistry in different areas of the cerebral cortex of lizards. Cross-reactivity of the antisera has been excluded by demonstrating the existence of several cell groups immunoreactive for one but not the other two calcium-binding proteins. In the dorsal and dorsomedial cortices all three proteins coexist in a single subpopulation of gamma-aminobutyric acid (GABA)ergic neurons, the terminals of which form pericellular baskets around cell bodies of bipyramidal neurons. The somata of these neurons are largely restricted to the cellular and inner plexiform layers, but the dendrites usually penetrate all layers, allowing the neurons to sample input from all possible sources. A small number of parvalbumin-containing neurons in the outer plexiform layer do not contain the other two proteins. The medial cortex, which is likely to be homologous to the mammalian dentate gyrus, only contains parvalbumin-immunoreactive neurons. The dendritic trees of these cells appear to avoid the Timm-positive fields receiving input from zinc-rich fiber collaterals, originating from principal cells. The lateral cortex contains calbindin D28K-immunoreactive GABAergic neurons, which lack the other two calcium-binding proteins. These neurons have horizontally running dendrites in the outer plexiform layer, but their axon terminals could not be visualized. The present study uncovered important similarities and differences between the lizard and the mammalian archicortex in the types of neurons containing calcium-binding proteins. As in mammals, different cell types evolved in the lizard to inhibit the perisomatic versus the distal dendritic region of principal cells, the calcium-binding protein-containing neurons being responsible for the former, and neuropeptide-containing neurons for the latter. The results also suggest that further neurochemical diversion of GABAergic interneurons coupled to a functional specialization took place during phylogenetic development from reptiles to mammals.

Animals↗

Parvalbumin, calbindin D-28k, and calretinin immunoreactivity in the ascending auditory pathway of horseshoe bats.

In the subcortical auditory system of Rhinolophus rouxi, antibodies directed against the calcium-binding proteins parvalbumin, calbindin D-28k, and calretinin yield partly overlapping and partly complementary labeling patterns which are described in detail for each nucleus. The most general features of the labeling patterns are that: 1) Parvalbumin is a potent marker for large and heterogeneous populations of cells and puncta (presumed axon terminals) throughout the auditory pathway. 2) Immunostaining with the monoclonal calbindin-antiserum was typically absent or sparse in most auditory brainstem centers, but prominent in auditory nerve fibers and in cells of the medial geniculate body (MGB). 3) Calretinin label is abundant but more restricted to subsets of auditory nuclei or subpopulations of cells than parvalbumin. 4) Calcium-binding proteins are useful markers to define particular subregions or cell types in auditory nuclei: for example, i) different labeling patterns are obtained within the nuclei of the lateral lemniscus and adjacent tegmental zones; ii) in the inferior colliculus both calbindin- and calretinin-antisera yield similar regional specific staining patterns, but label different cell types; iii) subregions of the medial geniculate body have characteristic profiles of calcium-binding proteins; and iv) analyses of different nuclei showed that there is no simple common denominator for cells characterized by the expression of particular calcium-binding proteins, nor does labeling correspond in a straightforward way with specific functional systems. 5) there are profound differences between the calbindin labeling patterns seen in Rhinolophus and those in other mammals.

Animals↗

Immunohistochemical distribution of calbindin D-28k and parvalbumin in the head of the caudate nucleus and substantia nigra of the cat.

The heterogeneous anatomy of both the dorsal striatum at the level of the head of the caudate nucleus and of the substantia nigra of cats was analyzed immunohistochemically using two calcium-binding proteins, namely, calbindin D-28k and parvalbumin. The striatal histochemical markers nicotinamide-adenine dinucleotide phosphate diaphorase and acetylcholinesterase were revealed in sections adjacent to those used for the immunohistochemical procedure. The distribution of both the calbindin D-28k and the parvalbumin immunoreactivities is heterogeneous in dorsal, ventral, lateral, and medial areas of the head of the caudate nucleus and is in register with the striosome/matrix pattern displayed by the histochemical markers. These calcium-binding proteins preferentially are located in the matrix compartment of the rostral caudate nucleus. Moreover, in some areas of the rostral two-thirds of the substantia nigra, calbindin D-28k and parvalbumin immunoreactivities appear to follow a complementary pattern that is quite different from the mesencephalic distribution of these two calcium-binding proteins.

Acetylcholinesterase↗

Nitric oxide synthase-positive neurons in the rat superior colliculus: colocalization of NOS with NMDAR1 glutamate receptor, GABA, and parvalbumin.

We analyzed the potential input and output components of nitric oxide synthase (NOS)-containing neurons in the rat superior colliculus (SC). To identify whether NOS-positive neurons receive glutamatergic input we investigated the colocalization of NOS with NMDA receptor subunit R1 (NMDAR1). In addition, to examine whether putative nitric oxide synthesizing neurons represent a neurochemically specific or distinct subpopulation of cells in the SC we studied the colocalization of NOS with the neurotransmitter GABA, the calcium-binding proteins parvalbumin, calbindin and calretinin and with neuropeptides such as somatostatin, substance P and neuropeptide Y. We found that 90% of NOS-positive neurons in the superficial layers of the rat SC express NMDAR1. Nearly 20% of the population of nitridergic neurons also expresses GABA and 15% of them express parvalbumin. NOS-positive neurons in the superior colliculus did not contain calretinin, calbindin or either of the neuropeptides tested. The results of this study show that the capacity for synthesizing NO in the SC is largely restricted to neurons that receive glutamatergic inputs and that some of these neurons express GABA or parvalbumin.

Animals↗

Deafferentation removes calretinin immunopositive terminals, but does not induce degeneration of calbindin D-28k and parvalbumin expressing neurons in the hippocampus of adult rats.

Unilateral combined transections of the fimbriafornix and angular bundle in adult Fischer 344 rats were used to study the effects of deafferentation on hippocampal expression of calretinin, calbindin D-28k, and parvalbumin. Reflecting the widespread degeneration of synaptic contacts, immunostaining for glial fibrillary acidic protein 6 days after the lesions was increased in lacunosum-molecular and oriens layers of CA1, 2, and 3 in ipsi- and contralateral hippocampus and in the ipsilateral dentate gyrus outer molecular layer. At 21 days the immunoreactivity had decreased to control levels except for a still slightly increased signal in the oriens layer of CA1-3. At 6 and 21 days after the combined lesions the numbers of hippocampal neurons containing calretinin, parvalbumin, and calbindin D-28k was unaltered. The combined lesions abolished calretinin containing terminals in the dentate gyrus inner molecular layer on the deafferentated side. This could be reproduced by single unilateral fimbria-fornix transections, suggesting that the axons of these calretinin positive terminals project to the hippocampus through the fimbria-fornix. The most likely origin of the calretinin positive terminals are neurons in the supramammillary hypothalamic nucleus. Our findings demonstrate that the extensive lesion-induced synaptic rearrangements in the adult hippocampus do not induce degeneration of hippocampal neurons expressing calretinin, calbindin D-28k, and parvalbumin, but do remove calretinin containing terminals which reach their targets in the hippocampus through the fimbria-fornix.

Animals↗

Divalent ion-binding properties of the two avian beta-parvalbumins.

Birds express three parvalbumins, one alpha isoform and two beta isoforms. The latter are known as avian thymic hormone (ATH) and avian parvalbumin 3. Although both were discovered in thymus tissue, and presumably function in T-cell maturation, they have been detected in other tissue settings. We have conducted detailed Ca2+- and Mg2+-binding studies on recombinant ATH and the C72S variant of CPV3, employing global analysis of isothermal titration calorimetry data. In Hepes-buffered saline, ATH binds Ca2+ with apparent microscopic binding constants of 2.4 +/- 0.2 x 10(8) and 1.0 +/- 0.1 x 10(8) M(-1). The corresponding values for CPV3-C72S are substantially lower, 4.5 +/- 0.5 x 10(7) and 2.4 +/- 0.2 x 10(7) M(-1), a 1.9-kcal/mol difference in binding free energy. Thus, the beta-parvalbumin lineage displays a spectrum of Ca2+-binding affinity, with ATH and the mammalian beta isoform at the high- and low-affinity extremes and CPV3 in the middle. Interestingly, despite its decreased Ca2+ affinity, CPV3-C72S exhibits increased affinity for Mg2+, relative to ATH. Whereas the latter displays Mg2+-binding constants of 2.2 +/- 0.2 x 10(4) and 1.2 +/- 0.1 x 10(4) M(-1), CPV3-C72S yields values of 5.0 +/- 0.8 x 10(4) and 2.1 +/- 0.3 x 10(4) M(-1).

Amino Acid Sequence↗

Heme binding to calmodulin, troponin C, and parvalbumin, as a probe of calcium-dependent conformational changes.

Heme-CO binds to the active (calcium-bound) form of calmodulin (CaM), but not to the inactive form. Despite a similarity in structure of another calcium-binding protein, skeletal muscle troponin C, both the affinity and the spectral red-shift of the absorption of the heme group are greatly decreased for troponin C relative to calmodulin. Parvalbumin, another calcium-binding protein, shows a twofold greater affinity for heme-CO relative to CaM. Unlike calmodulin and troponin C, the affinity of parvalbumin for heme-CO is even greater in the absence of calcium. The affinity of the tryptic and thrombic fragments of CaM for heme-CO are decreased relative to the entire calmodulin. The binding of heme-CO is specific as demonstrated by the discrimination of the calmodulin, troponin C, and parvalbumin pockets. The interaction of heme-CO with active (calcium-bound) CaM is rapid (ms) as determined by stopped flow measurements. No difference in kinetics was observed for mixing inactive (calcium free) CaM with a solution of [heme-CO plus calcium], indicating that the calcium-binding step and subsequent change in protein conformation are rapid.

Animals↗

Detection of a beta-parvalbumin isoform in the mammalian inner ear.

A small, acidic calcium-binding protein (CBP-15) has been detected in the guinea pig organ of Corti, the auditory receptor organ. The apparent molecular weight (15,000) and very low isoelectric point (pI approximately 3.1) suggest that CBP-15 is a beta-parvalbumin isoform. Consistent with this hypothesis, CBP-15 exhibits extreme homology to the mammalian oncofetal parvalbumin called oncomodulin. Sequence data have now been obtained for 30 residues in the N-terminal third of CBP-15. Identity with oncomodulin is observed at all 30 positions. This finding could necessitate revision of the assumption that postnatal mammals utilize a single alpha-parvalbumin isoform in muscle and nonmuscle settings alike.

Amino Acid Sequence↗

Relative resistance of striatal neurons containing calbindin or parvalbumin to quinolinic acid-mediated excitotoxicity compared to other striatal neuron types.

To evaluate the relative ability of those striatal neuron types containing calbindin or parvalbumin to withstand a Ca(2+)-mediated excitotoxic insult, we injected the NMDA receptor-specific excitotoxin quinolinic acid (QA) into the striatum in mature adult rats and 2 months later examined the relative survival of striatal interneurons rich in parvalbumin and striatal projection neurons rich in calbindin. To provide standardization to the survival of striatal neuron types thought to be poor in Ca2+ buffering proteins, the survival was compared to that of somatostatin-neuropeptide Y (SS/NPY)-containing interneurons and enkephalinergic projection neurons, which are devoid of or relatively poorer in such proteins. The various neuron types were identified by immunohistochemical labeling for these type-specific markers and their relative survival was compared at each of a series of increasing distances from the injection center. In brief, we found that parvalbuminergic, calbindinergic, and enkephalinergic neurons all showed a generally comparable gradient of neuronal loss, except just outside the lesion center, where calbindin-rich neurons showed significantly enhanced survival. In contrast, striatal SS/NPY interneurons were more vulnerable to QA than any of these three other types. These observed patterns of survival following intrastriatal QA injection suggest that calbindin and parvalbumin content does not by itself determine the vulnerability of striatal neurons to QA-mediated excitotoxicity in mature adult rats. For example, parvalbuminergic striatal interneurons were not impervious to QA, while cholinergic striatal interneurons are highly resistant and SS/NPY+ striatal interneurons are highly vulnerable. Both cholinergic and SS/NPY+ interneurons are devoid of any known calcium buffering protein. Similarly, calbindin does not prevent striatal projection neuron vulnerability to QA excitotoxicity. Nonetheless, our data do suggest that calbindin may offer striatal neurons some protection against moderate excitotoxic insults, and this may explain the reportedly slightly greater vulnerability of striatal neurons that are poor in calbindin to ischemia and Huntington's disease.

Animals↗

Distribution of calbindin, parvalbumin, and calretinin immunoreactivity in the reticular thalamic nucleus of the marmoset: evidence for a medial leaflet of incertal neurons.

The placement of the reticular thalamic nucleus (RTN) between the dorsal thalamus and the cortex and the inhibitory nature of reticulothalamic projections has led to suggestions that it "gates" the flow of sensory information to the cortex. The New World diurnal monkey, the marmoset, Callithrix jacchus is emerging as an important "model primate" for the study of sensory processing. We have examined the distribution of Nissl-stained somata and calbindin, parvalbumin, and calretinin immunoreactivity in the ventral thalamus for comparison with other species. Cells were labeled using standard immunohistochemistry, ExtraAvidin-HRP, and diaminobenzidine reaction products. The RTN is constituted by a largely homogeneous population of parvalbumin immunoreactive cells with respect to size and orientation. Calbindin and calretinin immunoreactive cells were only found along the medial edge of the RTN adjacent to the external medullary lamina of the dorsal thalamus and laterally near the ventral RTN. These cells were considered to be part of the zona incerta (ZI). The marmoset ZI could be subdivided into dorsal and ventral regions on the basis of its immunoreactivity to calcium binding proteins. Both the ZI and nucleus subthalamicus Luysi contained scattered calbindin and calretinin immunoreactive cells with well-defined dendritic processes. These cells were clearly different to cells in the dorsal thalamus. Parvalbumin immunoreactive cells in RTN, ZI, and subthalamic nucleus were on average larger than neurons positive for the other calcium binding proteins. Future studies reporting the afferent and efferent projections to the RTN must view their results in terms of the close apposition of RTN and ZI somata.

Animals↗

Formation of calcium-parvalbumin complex during contraction. A source of "unexplained heat"?

Computer simulation of the kinetics of the distribution of Ca between troponin, parvalbumin and the sarcoplasmic reticulum, during contraction and relaxation shows that parvalbumins can contribute significantly to the rate of relaxation and to the post contractile translocation of calcium. The binding of Ca to parvalbumin is an exothermic process which may account for about 20% of the 'unexplained heat' during contraction.

Animals↗

Parvalbumin and calretinin in the avian thymus.

The avian thymic hormone, known to support the maturation of T-lymphocytes, is biochemically similar to parvalbumin. However, its exact cellular distribution in the thymus is unknown. We have therefore studied the occurrence of parvalbumin and other related calcium-binding proteins in this organ by immunohistochemistry during development and after hatching. Parvalbumin immunoreactivity appears in the epithelial cells on embryonic day 9, and is expressed in the cortical reticular cells in the adult. Calretinin is found in the clusters of medullary epithelial cells from embryonic day 11, whereas calbindin D-28k is absent from this organ. Thus, calcium binding-proteins are excellent markers for different compartments of the avian thymus in embryonic life and after hatching, and their expression seems to coincide with their functional maturation.

Animals↗

Regulatory effects of S-100 protein and parvalbumin on protein kinases and phosphoprotein phosphatases from brain and skeletal muscle.

In the eluted fractions of histone-treated crude extracts separated by Sephadex G-200 filtration, multiple protein kinase (PK) activities, including three from brain and two from skeletal muscle, were augmented by both S-100 protein and parvalbumin on the phosphorylation of endogenous substrates. One additional PK activity suppressed by both S-100 and parvalbumin was also found in muscle. In comparison, phosphoprotein phosphatases (PPase), which were also prepared by the same procedure of initial step of histone-treatment followed by the steps of Bio-Gel P-6DG for brain and DNA-cellulose for muscle, were all activated by S-100 while inhibited by parvalbumin and phosphatidylserine.

Animals↗

Cellular distribution of parvalbumin immunoreactivity in the peripheral vestibular system of three rodents.

The cellular distribution of parvalbumin immunoreactivity in the vestibular peripheral system of mouse, rat, and guinea pig was investigated by light and electron microscopy. Parvalbumin was found in all neurons of the vestibular ganglia of these species but in the sensory epithelia immunoreactivity was restricted to type I hair cells localized exclusively in the central areas. The very intense staining pattern was similar in the cristae ampullares and utricles of all three species but a faint immunoreaction was also detectable in sensory cells of peripheral areas of rat cristae. The parvalbumin-immunoreactive type I sensory cells are connected by nerve fibres of the calyx unit type which are known selectively to contain calretinin.

Animals↗

Exercise-induced fibre type transitions with regard to myosin, parvalbumin, and sarcoplasmic reticulum in muscles of the rat.

Effects of a long-term, high intensity training program upon histochemically assessed myofibrillar actomyosin ATPase, myosin composition, peptide pattern of sarcoplasmic reticulum (SR), and parvalbumin content were analysed in muscles from the same rats which were used in a previous study (Green et al. 1983). Following 15 weeks of extreme training, an increase in type I and type II A fibres and a decrease in type II B fibres occurred both in plantaris and extensor digitorum longus (EDL) muscles. In the deep portion of vastus lateralis (VLD), there was a pronounced increase from 10 +/- 5% to 27 +/- 11% in type I fibres. No type I fibres were detected in the superficial portion of vastus lateralis (VLS) both in control and trained animals. An increase in slow type myosin light chains accompanied the histochemically observed fibre type transition in VLD. Changes in the peptide pattern of SR occurred both in VLS and VLD and suggested a complete transition from type II B to II A in VLS and from type II A to I in VLD. A complete type II A to I transition in the VLD was also suggested by the failure to detect parvalbumin in this muscle after 15 weeks of training. Changes in parvalbumin content and SR tended to precede the transitions in the myosin light chains. Obviously, high intensity endurance training is capable of transforming specific characteristics of muscle fibres beyond the commonly observed changes in the enzyme activity pattern of energy metabolism. The time courses of the various changes which are similar to those in chronic nerve stimulation experiments, indicate that various functional systems of the muscle fibre do not change simultaneously.

Adenosine Triphosphatases↗

Thermodynamic analysis of calcium binding to frog parvalbumin.

The enthalpy of calcium binding to frog parvalbumin (Rana temporaria isoenzyme IVb, pI 4.75) has been measured by microcalorimetry. The reaction is exothermic; the heat of the reaction in 100 mM KCl, 50mM Tris, pH 8.0 at 12 degrees C is -19 kJ (mol site)-1 and -33 kJ (mol site)-1 in the presence of 1 mM magnesium. The shape of the titration curve indicates that the properties of the two calcium binding sites are different. The thermodynamic parameters measured for frog parvalbumin are compared with those of related parvalbumins from carp and whiting.

Animals↗