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At least 595 records · Page 33Linked to original sources
PubMed1986

Abnormal visual cortex development in the kitten associated with maternal dietary taurine deprivation.

We have examined the visual cortex of newborn and 8-week-old kittens born to mothers consuming a taurine-supplemented or taurine-free diet using the rapid Golgi technique. Kittens from taurine-supplemented mothers exhibited normal development of the visual cortex. Kittens from taurine-depleted mothers showed striking differences. In newborn kittens, neuroblasts are aggregated both at the ventricular and pial zones, having failed to migrate and differentiate normally. Eight weeks after birth, only few pyramidal and nonpyramidal neurons are found. Those present have heavily spined dendritic processes indicative of poor arborization. Protoplasmic astrocytes are represented by undifferentiated cellular masses. The taurine concentration in the cortex of such kittens is four- to fivefold smaller than in kittens from taurine-supplemented mothers. These results suggest that normal concentrations of taurine in visual cortex, as well as cerebellum, are required for normal ontogeny of neurons. Once such deficits are established in the prenatal and immediate postnatal period, they result in permanent abnormalities. These findings have clear implications for vegetarian women who intend to have children, since virtually no taurine is present in plants and vegetables.

Aging↗
PubMed1989

Implantation of rabbit embryo brain fragments into newborn mice: integration and survival of xenogeneic astrocytes.

Brain fragments containing embryonic rabbit glia were implanted into the brains of newborn mice. The hosts developed an astroglial reaction around the transplants and along the needle tracks. Transplant-derived astrocytes were identified in the operated brain by their expression of rabbit GFAP. During the first few days post-implantation (PI) glial cells were exchanged between the transplant and the host. Less than 3 to 5 days PI, the transplant was extensively invaded by host astrocytes. Xenogeneic astroglial cells were first detected 10 days PI in the immediate proximity of the transplant. At 2 to 11 weeks, they could be detected either close to or at distance from the point of implantation. Most often, transplant-derived astrocytes presented a morphology similar to that of neighboring host astrocytes. Xenogeneic glial cells were found to participate in various types of astroglial features: sub-pial, pericapillary, fibrous, and protoplasmic. This morphological integration suggests that they are physiologically integrated, at least to a certain degree, in the host tissue. In spite of their integration into the host, xenogeneic astrocytes disappear after 3 months without signs of an inflammatory reaction.

Animals↗
PubMed1990

Isolation of cDNAs from a mouse astroglial cell line by a subtracted cDNA library.

Astrocytes belong to the glial cell population and represent a major subclass of the CNS. Although different subtypes of astrocytes have been described according to their morphological characteristics, biochemical markers of each subtype of astrocytes are not yet available. We have thus undertaken to compare gene expression pattern of different astroglial subtypes. In this study we have taken advantage of two astroglial cell clones derived from 8 day postnatal mouse cerebellar explants and which might be the in vitro equivalents of the velate protoplasmic (D19) and of the Golgi-Bergmann (C8S) astrocytes (Alliot and Pessac, Brain Res., 306: 283-291, 1984). We have constructed a subtracted cDNA library derived from cytoplasmic poly(A)+ RNAs of the D19 cell line. This library was enriched 12-fold for D19 specific sequences by subtractive hybridization with an excess of cytoplasmic poly(A)+ RNAs purified from the C8S astroglial clone. This subtracted library was differentially screened with cDNA probes derived from D19 and C8S cell lines; both probes were subtracted with C8S poly(A)+ RNAs. Eight cDNA clones corresponding to transcripts overexpressed in D19 were selected. Three cDNAs encode for smooth muscle actin, one for fibronectin and one for polyadenylate binding protein. The three other gene products have not been previously reported. The in vivo distribution pattern of these sequences in various mouse adult tissues shows that all these transcripts are expressed in the cerebellum and/or in the brain.

Actins↗
PubMed1997

Physiological and biochemical characterization of intergeneric hybrids of thermotolerant and non-thermotolerant yeasts.

Kluyveromyces-like intergeneric hybrids of thermotolerant Kluyveromyces marxianus and non-thermotolerant Saccharomyces cerevisiae, produced in a previous study by protoplasmic fusion, have been characterized. On molasses, these strains produced ethanol in excess of 6% (v/v) both at 30 and 45 degrees C as against 3% and 4.2% (v/v) by the former parent at 30 and 45 degrees C, respectively. In hybrids, the increase in ethanol production appeared to be a sequel to increased activities of alcohol dehydrogenase and pyruvate kinase, derived probably from S. cerevisiae parent. Hybrid ADH-isozyme pattern on polyacrylamide gel corroborated the presence of S. cerevisiae ADH in the tested hybrids. Regression analyses indicated a positive correlation between ethanol production and ADH or PK or both (r approximately 0.76-0.84).

Hybridization, Genetic↗
PubMed1978

Spectrin binding and the control of membrane protein mobility.

Transmembrane proteins of the human erythrocyte show restricted in-plane mobility. Many of the restrictions on mobility are attributable to the molecules of spectrin which are located on the protoplasmic surface of the erythrocyte membrane. These molecules are elongate, form end-to-end heterodimer associations, and bind selectively to protein (or proteins) accessible on inside-out, but not right-side out, membrane vesicles.

Actins↗
PubMed1991

The molecular environment of intracellular sodium: 23Na NMR relaxation.

The comprehensive approach described in the accompanying paper is illustrated here with the 23Na signal of a concentrated solution of bovine serum albumin (BSA) in saline and the intracellular (Nai) 23Na resonance of a dense suspension of Na(+)-loaded yeast cells. We use frequency shift reagents to discriminate the latter from the extracellular resonance. We find that the Nai signal corresponds to that of an effective single population of Na+ ions exhibiting a single type c spectrum. This is true despite the fact that the yeast protoplasm is too large and too compartmentalized for a given Na+ ion to sample its entirety on the relevant NMR timescale. Our results show clearly that, in addition to the decay of transverse magnetization, the recovery of longitudinal magnetization is biexponential. This is required for a type c spectrum but has not often been detected. The temperature dependence of the relaxation rate constants of the Nai resonance is not consistent with either a simple Debye process or a discrete exchange mechanism connecting two sites in the fast limit. We have fitted the data using an asymmetric continuous distribution of correlation times for the fluctuations of electric field gradients sensed by the Nai nuclei. The analogous distribution function for the Na+ in a 44% (w/w) BSA solution is quite similar to that of the Nai at the same temperature. This suggests that while the macromolecular environment of the Nai ions is quite congested, it is also isotropic on quite a small spatial scale. Also, one can use the correlation time distribution function, obtained from fitting the relaxation data, to calculate a relaxometry curve. This is useful because experimental 23Na relaxometry is difficult. The calculated curve may be a reasonable model for the mostly extracellular 23Na resonance encountered in vivo.

Calibration↗
PubMed2004

Effects of progesterone derivatives, dihydroprogesterone and tetrahydroprogesterone, on the subependymal layer of the adult rat.

Indirect evidence suggests that in the subependymal layer (SEL) steroid hormones could be partially involved in the modulation of neurogenesis, but little or nothing is known about a direct effect of these molecules on this cellular system. The possible effect of progesterone (P) and/or its neuroactive metabolites, dihydroprogesterone (DHP) and tetrahydroprogesterone (THP), on the two cellular components of the SEL (i.e., proliferating/migrating neuroblasts and protoplasmic astrocytes) has been analyzed in adult male rat. P, DHP, and THP were administered by intraventricular injections and after 2 days the SEL was analyzed by immunohistochemistry by using anti-glial fibrillary acidic protein (GFAP) and anti-vimentin antibodies, to label the glial compartment, anti-polysialylated form of the neural cell adhesion molecule (PSA-NCAM), anti-Stathmin, and anti-beta III Tubulin antibodies to label the migrating neuroblasts. Furthermore, the newly formed cells were identified by using intraventricular injections of 5-bromo-2'-deoxyuridine (BrdU) detected immunohistochemically. Our results demonstrate that DHP and THP treatments drastically decrease the number of BrdU-labeled cells within the SEL. THP, DHP, and to a lesser extent P, administrations also induce molecular and structural modifications of the SEL glial compartment. On the whole, the present results indicate that neuroactive derivatives of P (i.e., DHP and THP) exert direct effects on adult neurogenesis, strongly affecting both neuroblasts and astrocytes of the SEL.

20-alpha-Dihydroprogesterone↗
PubMed1992

Expression of a novel nuclear protein is correlated with neuronal differentiation in vivo.

We report the production of a monoclonal antibody (MAb 526) that recognizes a novel, developmentally regulated nuclear protein expressed in neurons throughout the rat nervous system. Analysis of whole brain and cell nuclear extracts by SDS-PAGE and immunoblotting determined that MAb 526 recognizes a single nuclear protein (np) of apparent molecular weight 42 kD, designated np526, as well as a slightly larger (ca. 44 kD) cytoplasmic protein. Light microscopic immunocytochemistry showed np526 to be present in neurons of all types throughout the central and peripheral nervous systems. Nuclei of both fibrous and protoplasmic astrocytes were also immunoreactive, but oligodendrocyte nuclei were negative. Positive, but highly variable immunocytochemical staining of nonneural cell nuclei in a variety of other tissues was also observed. Electron microscopic (EM) immunocytochemistry using pre-embedding peroxidase methods revealed that np526 is associated with euchromatin or with the edges of condensed chromatin bundles in neurons, indicating that it is likely to be a chromosomal protein. Most interestingly, the expression of np526 was found to be developmentally regulated in brain. Immunocytochemical analysis of the developing cerebral cortex from embryonic day (E) 16 to postnatal day (P) 4 and cerebellum from P4 to P18 revealed that np526 first appears in central neurons following the cessation of mitosis and that the intensity of nuclear staining increases during subsequent neuronal maturation. To our knowledge, np526 is the first presumptive chromosomal protein whose expression has been precisely correlated with the early postmitotic differentiation of mammalian neurons.

Animals↗
PubMed1980

Experimental limb dysmorphogenesis as a model of chemical injury response in undifferentiated embryonic tissues: a light and electron microscopical study.

A histopathological and ultrastructural analysis of the early stage of limb dysmorphogenesis from 1 hr to 48 hr, following citral administration is presented as a model for studying the reaction to injury of undifferentiated embryonic tissues. Early lesions such as cloudy swelling, hydropic degeneration, enlargement of the extracellular space and retraction of protoplasmic extensions were observed 1 hr after treatment, affecting both epiderm and mesenchyme of the limb. Few pyknotic cells were encountered during the early stages. Cell necrosis and autophagocytosis became more conspicuous at 12 hr post-injection. About the same time the first signs of healing were observed, charcterised by heterophagocytosis and return of mitotic activity. The epiderm being more differentiated, regenerates ad integrum and more rapidly than the mesenchyme. The evolution of these pathological events, which proceed in a spatio-temporal cascade, seem to reflect the pharmacokinetic gradient of the cell-teratogen interactions. The type of limb malformation will depend mainly on the extent of injury and/or healing of the mesenchymal mass, rather than on the injury and/or healing of the surface ectoderm. It is concluded that the reaction to chemical injury of undifferentiated tissues partially mimics the destructive and repair process in adult tissues, but differs in lacking some basic constituents such as oedema, monocyte exudation and granulation tissue formation.

Abnormalities, Drug-Induced↗
PubMed1995

Localization of carbohydrate and DNA in cyst-like structures from a human intestinal spirochaete.

This study examined the cyst-like structures found in human intestinal spirochaetes by transmission electron microscopy and by histochemical and immunocytochemical analysis. A human intestinal spirochaete which morphologically resembled other intestinal spirochaetes was grown anaerobically on blood agar plates and in Tryptone Soya broth (Oxoid) and harvested by centrifugation after 8 days growth. Specimens were either conventionally fixed for transmission electron microscopy or fixed in 0.5% glutaraldehyde in 0.1M sodium cacodylate buffer and embedded in LR White resin for immunocytochemistry. En bloc histochemical investigation using a periodic acid-thiosemicarbazide-silver proteinate technique was undertaken for the localization of carbohydrate. A post-embedding immunogold labelling technique was used on ultrathin sections to label DNA. Results from the histochemical study demonstrated a reaction product which was confined to the cytoplasm of mature spirochaetes and in the central bodies within the cysts. Immunogold labelling demonstrated the presence of DNA in both the mature protoplasmic cylinders and in the central bodies. The results of the present study indicate that spirochaetal cysts are highly organized structures, which contain both DNA and carbohydrate. These findings are compatible with the view that these structures have a functional role rather than representing degenerative artifacts.

Journal Article↗
PubMed1994

Identification and characterization of parathyroid hormone/parathyroid hormone-related peptide receptor in cultured astrocytes.

Parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor expressed in rat cultured cortical type I astrocytes was identified and characterized. Northern blot analysis demonstrated that the PTH/PTHrP receptor mRNA is expressed in astrocytes. A human PTH fragment, PTH [1-34], stimulated adenylate cyclase with the EC50 value of 3 nM, but not phospholipase C. PTH [1-34] changed the morphology of protoplasmic type astrocytes into process-bearing ones. Thus, type I astrocytes possess PTH/PTHrP receptor that is coupled to an adenylate cyclase-activating system but not to phospholipase C.

Adenylyl Cyclases↗
PubMed1995

Stochastic behavior of organelle motion in Nitella internodal cells.

The stochastic behavior of organelles during the recovery process of protoplasmic streaming is investigated in Nitella internodal cells at a nanometer space resolution. The motions of organelles in the components parallel and perpendicular to the alignment of actin filaments in the cell are analysed from the traces of displacement of 860 organelles in 1/30s (= video rate). The analysis of those traces shows that the generation of motive forces to the organelle follows the Poisson process. Therefore, we have been able to estimate the step size corresponding to the single force generation as approximately 100 nm.

Actins↗
PubMed1996

Inhibition of vanadate-induced astrocytic stress fiber formation by C3 ADP-ribosyltransferase.

Mechanisms of vanadate-induced actin reorganization were examined in cultured astrocytes. Treatment of protoplasmic astrocytes with 0.5 mM dibutyryl cAMP (DBcAMP) caused the disappearance of stress fibers (SFs) and focal adhesions (FAs) accompanied with cellular stellation. A subsequent addition of 1 mM orthovanadate (VO4(3-) reorganized SFs and FAs in DBcAMP-treated cells. The newly formed FAs had increased phosphotyrosine levels. VO4(3-) reorganized SFs and FAs in stellate astrocytes induced by 5 microM cytochalasin B, 50 microM ML-9 and 20 microM W-7. Cytoplasmic microinjection of 20 micrograms/ml C3 ADP-ribosyltransferase of C. botulinum, which inactivates rho proteins, caused disappearance of SFs. The effect of C3 enzyme on SFs was not reversed by a subsequent addition of VO4(3-). These results suggest that rho proteins are involved in vanadate-induced reorganization of cytoskeletal actin.

ADP Ribose Transferases↗
PubMed1997

Rapid volume expansion in the Torpedo electric organ associated with its postsynaptic potential.

By electrically stimulating Torpedo electric organs enclosed in a sealed plastic chamber, it was demonstrated that the production of a postsynaptic potential is accompanied by a rapid increase in the volume of the organ. This increase started almost simultaneously with the onset of the postsynaptic potential and reached its maximum at about the end of the potential. The volume returned slowly to its resting level. Repetitive stimulation produced a summation of volume changes. The maximum change evoked by a single electric shock was roughly 10(-6) times the electrocyte volume. The thermal expansion of the organ associated with the production of a postsynaptic potential accounts for roughly 25% or less of this volume increase. The possibility is pointed out that a cation-exchange process involving Ca2+ on anionic sites in the electrocyte protoplasm may be at the base of the volume changes.

Animals↗
PubMed1994

The centrosome and its mode of inheritance: the reduction of the centrosome during gametogenesis and its restoration during fertilization.

Neither the restoration of the centrosome during fertilization nor its reduction during gametogenesis is fully understood, but both are pivotal events in development. During each somatic cell cycle, the chromosomes, cytoplasm, and centrosomes duplicate in interphase, and all three split in two during each cell division. While it has long been recognized that both the sperm and the egg contribute equal haploid genomes during fertilization and that the vast majority of the cytoplasm is contributed by the egg, the relative contributions of the centrosome by each gamete are still in question. This article explores centrosome inheritance patterns and considers nine integral and secondarily derived activities of the centrosome. Boveri once hypothesized that "The ripe egg possesses all of the elements necessary for development save an active division-center. The sperm, on the other hand, possesses such a center but lacks the protoplasmic substratum in which to operate. In this respect the egg and sperm are complementary structures; their union in syngamy thus restores to each the missing element necessary to further development." This article reviews the evidence gathered from 11 experimental strategies used to test this theory. While the majority of these approaches supports the hypothesis that the sperm introduces the centrosome at fertilization, the pattern did not reveal itself as universal, since parthenogenesis occurs in nature and can be induced artificially, since centrosome and centriole form de novo in extracts from unfertilized eggs and since the centrosome is derived from maternal sources during fertilization in some systems--notably, in mice. Models of the centrosome are proposed, along with speculative mechanisms which might lead to the cloaking of the reproducing element of the maternal centrosome during oogenesis and the retention of this structure by the paternal centrosome during spermatogenesis. Proteins essential for microtubule nucleation, like gamma-tubulin, are retained in the cytoplasm during oogenesis, but are largely lost during spermatogenesis. It is further postulated that the restoration of the zygotic centrosome at fertilization requires the attraction of maternal centrosomal components (in particular, gamma-tubulin and the 25S "gamma-some" particle) to the paternal reproducing element; this, along with post-translational modifications (including phosphorylation, disulfide reduction, and calcium ion binding), creates a functional zygote centrosome by blending both maternal and paternal constituents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Ciliary neurotrophic factor stimulates astroglial hypertrophy in vivo and in vitro.

After insult or trauma, astrocytes become activated and endeavor to restore the brain's delicately balanced microenvironment. An index of their activated state is that they become enlarged or hypertrophic. Ciliary neurotrophic factor (CNTF), a member of the alpha helical family of cytokines, is synthesized by astrocytes and is generally regarded to be an autocrine and paracrine injury signal. To determine whether CNTF might be an endogenous signal that stimulates astrocyte hypertrophy in vivo, we intracerebrally injected 200 ng of recombinant human CNTF into the adult rat neocortex. To study the astrocytes their cytosol was stained with antibodies against S100beta and their nuclei were stained with propidium iodide (PI). Fluorescent images of astrocytic nuclei and somas were acquired using a confocal laser-scanning microscope and their areas were measured using the NIH image software. Within 24 h of treatment, CNTF induced a volume increase of the somas and nuclei of protoplasmic and fibrous astrocytes in vivo, and this effect persisted for at least 48 h. To determine whether CNTF activates astrocytes directly, glial cultures were treated with CNTF (10 ng/ml) and were evaluated by measuring the area of PI stained nuclei. CNTF stimulation increased the size of both polygonal and process-bearing astroglia. Since our studies in vivo have shown that CNTF induces other key aspects of gliosis (S. W. Levison et al., 1996; Exp. Neurol. 141, 256), we conclude that CNTF is a powerful activator of astrocytes and that it is likely responsible for the persistent glial hypertrophy observed following injuries and diseases of the CNS.

Animals↗
PubMed1998

Modelling the qualitative response of fungal mycelia to heterogeneous environments

Many species of fungi form a mycelium, an indeterminate system of protoplasm-filled, apically extending, branching tubes (hyphae). At the macroscopic level, mycelia produce organisational patterns that are found in many other indeterminate systems (e.g. nervous and vascular systems). Therefore they provide an experimentally and observationally accessible model system for investigating the dynamic origins of phenotypic patterns in such systems. Moreover, mycelial fungi form a vital link in the ecosystem allowing for the redistribution and reutilisation of nutrients and minerals over a far wider spatial domain than would be possible without their presence. In vivo these networks grow and function in heterogeneous environments and therefore to gain any true understanding of their form and function such heterogeneity must be taken into account. In this paper we develop a model based on a system of partial differential equations for the interaction of the fungal mycelium with a heterogeneous environment. Using this model we are able to test the hypothesis that mycelia react to their environment in a global manner and by close comparison with experimental results, we are also able to highlight two specific mechanisms in this global response which are central to the macroscopic distribution of biomass: uptake of nutrients in excess of local needs and subsequent internal redistribution (translocation) of this excess. Copyright 1998 Academic Press

Journal Article↗
PubMed1999

Reaction-diffusion-advection model for pattern formation of rhythmic contraction in a giant amoeboid cell of the physarum plasmodium

The plasmodium of Physarum polycephalum is a large amoeboid organism showing rhythmic contraction everywhere within an organism, and moves by forming spatio-temporal patterns of the rhythmic contraction. We propose a reaction-diffusion-advection model for the pattern formation. This model is constructed under physiological suggestions that the chemical oscillator acts as a clock regulating the rhythmic contraction and interacts spatially not only by diffusion but also by advection of protoplasm. Behavior of the model is studied by numerical calculation, especially the effects of the advection term on a simple reaction-diffusion system. The advection effect reproduces experimentally observed phenomena of fluctuating propagation of the contraction wave. Concept of the reaction-diffusion-advection system is promising for modeling the mechanism of amoeboid behaviour in the Physarum plasmodium. Copyright 1999 Academic Press.

Journal Article↗