Cell-cycle-dependent regulation of cell motility and determination of the role of Rac1.

To study cell motility in different phases of the cell cycle, time-lapse recording by computer-assisted microscopy of unsynchronised cells from three mammalian cell lines (L929, BT4Cn, HeLa) was used for the determination of the displacements of individual cells. The displacements were used for calculation of three key parameters describing cell motility: speed, persistence time and rate of diffusion. All investigated cell lines demonstrated a lower cell displacement in the G2 phase than in the G1/S phases. This was caused by a decrease in speed and/or persistence time. The decrease in motility was accompanied by changes in morphology reflecting the larger volume of cells in G2 than in G1. Furthermore, L-cells and HeLa-cells appeared to be less adherent in the G2 phase. Transfection of L-cells with constitutively active Rac1 led to a general increase in the speed and rate of diffusion in G2 to levels comparable to those of control cells in G1. In contrast, transfection with dominant-negative Rac1 reduced cell speed and resulted in cellular displacements, which were identical in G1 and G2. These observations indicate that migration of cultured cells is regulated in a cell-cycle-dependent manner, and that an enhancement of Rac1 activity is sufficient for a delay of the reduced cell displacement otherwise seen in G2.

Intermediate filaments regulate astrocyte motility.

Intermediate filaments (IFs) compose, together with actin filaments and microtubules, the cytoskeleton and they exhibit a remarkable but still enigmatic cell-type specificity. In a number of cell types, IFs seem to be instrumental in the maintenance of the mechanical integrity of cells and tissues. The function of IFs in astrocytes has so far remained elusive. We have recently reported that glial scar formation following brain or spinal cord injury is impaired in mice deficient in glial fibrillary acidic protein and vimentin. These mice lack IFs in reactive astrocytes that are normally pivotal in the wound repair process. Here we show that reactive astrocytes devoid of IFs exhibit clear morphological changes and profound defects in cell motility thereby revealing a novel function for IFs.

[Changes in the topography of various proteins in cultured neurons after selective injury of various cytoskeletal elements with neurotoxins]. / Izmeneniia topografii nekotorykh belkov vneshnei membrany kul'tiviruemykh neironov pri izbiratel'nom povrezhdenii razlichnykh élementov tsitoskeleta neirotoksinami.

The spinal cord and hippocampal primary cultures were incubated with three neurotoxins (separately) known to impair the main components of the cytoplasmic cytoskeleton: 1) colchicine blocking the repolymerization of microtubules, 2) cytochalasin preventing elongation of actin filaments, and 3) beta, beta'-iminodipropionitrile (IDPN), causing disorganisation of neurofilaments. The distribution of surface membrane molecules on the surface of the neurons was evaluated in the ultrastructural study after treatment with the neurotoxins on the 5th, 12th, and 15th days in vitro (DIV). On the 12 DIV, the density of immunogold labelled neural cell adhesion molecules (NCAM) on IDPN-treated hippocampal neurons increased 1.45 times comparing to the controls. On the 5 DIV, the density of WGA (wheat germ agglutinin)-binding membrane glycoproteins increased 2.09 times on colchicine-treated neurons, and 3.98 times on cytochalasin-treated ones, whereas on the 12 DIV, the increase was 3.28 and 2.72 times, respectively, as compared to the control cultures of the same age. These data provide insights into the mechanisms of neurodegenerative changes in the nerve cells and into the relationship between the cytoskeletal elements and the surface molecules on the neuronal plasmatic membrane.

The influence of maternal hypothyroidism and radioactive iodine on rat embryonal development: thyroid C-cells.

There have been no works devoted to the study of the influence of (131)I and maternal (131)I-induced hypothyroidism on the state of the C-cells in the thyroid gland of the developing embryos. A study was made on the effect of a dose of 150 microCi (131)I (0.5 Gy) leading to hypothyroidism in rats, on 35 mother rats and 168 newborn pups. The mother rats were divided into control and four treated groups which were injected with (131)I before pregnancy, on gestation days 5, 10, and 16, respectively. Immunohistochemically, the thyroid gland was examined for calcitonin-positive cells. Maternal hypothyroidism induced by (131)I leads to the development of hyperplasia and hyperthrophy of calcitonin-positive cells in the pups at the time of birth. The discovery of separate C-cells in the peripheral zone of the thyroid lobe may be evidence of an unbalance in the development of the medial and lateral source of the thyroid. There is a verifiable increase in the quantity of C-cells per 1 mm(2) field of the localization in the central zone of the gestation days 10 and 16 groups. This might be a compensatory mechanism for regulating the activity of the thyroid gland under induced hypothyroidism. Thus, in cases when there is a breakdown in the normal external regulation of the embryonic morphogenesis, a reduction in the level of maternal thyroid hormones and also direct exposure to (131)I, there is also a change in the foetus' internal regulatory systems. A change in C-cell system could lead to the appearance of endocrinological disorders later in life.

The influence of low doses 131I-induced maternal hypothyroidism on the development of rat embryos.

The aim of our research was to create and verify a model for studying the effects of a low dose of 131I and 131I-induced maternal hypothyroidism on the development of the embryo's thyroid gland and brain. The given dose (150 microCi) corresponds to the absorbed dose of 0.5 Gy. This dose is similar to that dose received by large numbers of the population of the C.I.S. regions polluted by radioactive isotopes of iodine as a result of the Chernobyl accident in 1985. Thirty-five female Wistar rats and their 168 newborn pups were used for observation. The females were divided into a control group and four experimental groups (each distinguished by the time of 131I injection: group I - no less than 12 days before mating; groups II, III and IV - on 5th, 10th and 16th days of gestation, respectively). In all the experimental female groups the incorporate dose of 131I led to hypothyroidism accompanied by a 43% reduction in the thyroxin level and by a nearly 8-fold increase in the TSH level. However, the influence of maternal hypothyroidism on the development of the thyroid gland and brain of embryos depends on the time when 131I took effect. There is a reduction in the weight of the newborns' brain and thyroid gland, total body mass. The hormonal status of the newborns' thyroid gland also changes. The proposed model will allow us to study many aspects of induced changes in the brain and thyroid gland of the embryos which develop under conditions of maternal hypothyroidism resulting from a low dose of 131I, administered at the critical times of development.

Immunohistochemical study of fibronectin and thyroglobulin in the thyroid gland of female rats after exposure to radioactive iodine.

The aim of this work was to study the effect of a dose of 150 microCi 131I on the barrier properties of the thyroid epithelium in pregnant female rats. Thirty-five female Wistar rats were divided into a control and four experimental groups (each distinguished by the time of 131I injection: group I--no less then 12 days before mating; groups II, III, and IV--on 5th, 10th, and 16th days of gestation, respectively). The thyroid glands were fixed in Bouin's fluid, embedded in paraffin, and stained immunohistochemically for thyroglobulin and fibronectin. In group IV the appearance of follicles with fibronectin-positive colloid demonstrates the penetration of blood plasma into the follicular lumen. There are more fibronectin positive follicles in group III. Regardless of the nature of the follicles' contents, numerous thyrocytes with an intensive fibronectin positive reaction begin to appear in the follicles. In group II the number of fibronectin positive follicles and thyrocytes is clearly reduced, and in group I only a few remain. In group IV there is a noticeable reduction in the quantity of colloid inside the follicles and often an absence of any thyroglobulin positive reaction. There are thyrocytes in which thyroglobulin positive granules localized in the basal zone. There is thyroglobulin positive staining in the stroma and blood vessels. In group II thyroglobulin is no longer found in the stroma. Small doses of 131I provoke a serious breakdown in the thyroid epithelium's barrier properties, although these changes are of a transient nature. The central zone of the thyroid gland reacts more actively and dynamically to exposure to radioactive iodine than the peripheral zone.

Studies on the teratogen pharmacophore of valproic acid analogues: evidence of interactions at a hydrophobic centre.

Propyl-4-yn-valproic acid (2-propyl-4-pentynoic acid), an analogue of valproic acid with a triple bond in one alkyl side chain, potently induces exencephaly in mice. Given that propyl-4-yn-valproic acid is a branched chain carboxylic acid, we synthesized a series of analogues with n-alkyl side chains of increasing length and correlated their potential to induce neural tube defects and to inhibit proliferation and induce differentiation in cells of neural origin, the latter being crucial to the orderly structuring of the embryo. All analogues significantly increased the incidence of neural tube defects in the embryos of dams exposed to a single dose of 1.25 mmol/kg on day 8 of gestation. This effect occurred in a dose-dependent manner and the rate of exencephaly increased with the progressive increase in n-alkyl side chain length. Moreover, increasing chain length resulted in a dose-dependent inhibition of C6 glioma proliferation rate over a concentration range of 0-3 mM and this was independent of the cell type employed and mode of estimating proliferative rate. The antiproliferative action of these analogues was associated with profound shape change in neuro-2A neuroblastoma involving extensive neuritogenesis and an associated increase in neural cell adhesion molecule (NCAM) prevalence at points of cell-cell contact, the latter exhibiting a dose-dependent increase when the n-alkyl chain was extended to five carbon units. These results suggest an interaction with a specific site in which the n-alkyl side is proposed to serve as an 'anchor' within a hydrophobic pocket to facilitate the ionic and/or H-bonding of the carboxylic acid and high electron density of the carbon-carbon triple bond.

Distribution of N-cadherin and NCAM in neurons and endocrine cells of the human embryonic and fetal gastroenteropancreatic system.

For the first time, the distribution of N-cadherin and neural cell adhesion molecule (NCAM) as well as some neuropeptides in nerve cells and endocrine cells of the human embryonic and fetal gastroenteropancreatic system has been detected in early stages (from the 6th postovulatory week onwards). Epithelial cells of the stomach and small intestine contained gastrin and somatostatin and the epithelium of the small intestine also bombesin-positive cells. Myenteric ganglionic cells showed both bombesin and VIP and were NCAM- and N-cadherin-positive at all ages studied. Some basally granulated epithelial cells of stomach, duodenum and the upper part of jejunum contained N-cadherin. The number of these cells increased from 6th to 10th postovulatory weeks. Nerve cells and the cytoplasm of individual epithelial cells of pancreatic ducts were immunoreactive for NCAM and N-cadherin. NCAM- and N-cadherin-positive cells also appeared in Langerhans islets (> 10 weeks), mainly in their peripheral part. NCAM- and N-cadherin-positive endocrine cells were less numerous than endocrine cells producing somatostatin, bombesin, and VIP, probably reflecting the features of embryonic/fetal histogenesis of Langerhans islets from epithelial endocrine cells of pancreatic ducts. NCAM and N-cadherin were localized on the surface of endocrine islets cells as well as in the cytoplasm of single islet cells. This suggests the involvement of both membrane and soluble forms of adhesion proteins in embryonic/fetal histogenesis of human pancreatic islets. The early occurrence of N-cadherin (6th postovulatory week) in enteroendocrine cells supports the existence of a common precursor. The expression of NCAM and N-cadherin in nerve cells and endocrine cells of the human fetal gastroenteropancreatic system may indicate the involvement of neuronal adhesion mechanisms in the development of neuro-endocrine complexes of fetal stomach, small intestine and pancreas.

[Isolation and purification of a membrane hyaluronate-binding protein from embryonic human brain]. / Vydelenie i ochistka membrannogo gialuronatsviazyvaiushcego belka iz mozga émbrionov cheloveka.

A membrane hyaluronate-binding protein from cerebral cortex of human embryonic brain (22-24 weeks) was purified by affinity, ion exchange chromatographies and gel-filtration. While gel-filtration analysis the protein had Mm 250 kDa. Electrophoresis under reduction conditions in the presence of DS-Na revealed a major band with Mm 85 kDa and two minor binds with Mm 68 and 36 kDa. The isolated protein did not react with antibodies against known hyaluronate-binding and other proteins with similar mass. The results show that a new membrane hyaluronate-binding protein was isolated and purified from human embryonic brain.

Some morphological changes in the rat thyroid gland during experimental hyperphenylalaninemia.

BACKGROUND: Little is known about the effect of phenylketonuria on the thyroid gland. In the present study, this problem was investigated by using a defined experimental model of hyperphenylalaninemia (HPA). METHODS: The experimental group was subjected to an HPA regimen (Matsuo and Hommes, 1988. Neurochem. Res., 13:867-870) from the 5th day of postnatal development. The pups were decapitated on the 7th, 14th, 21st, 28th, and 35th days. The thyroid glands were fixed in Bouin's fluid and routinely embedded in paraffin. The staining techniques used were Mallory-Slinchenko's method, toluidin blue, silver impregnation of the basement membrane, immunohistochemical staining of the proliferating cell nuclear antigen (PCNA), and neuron-specific enolase (NSE). RESULTS: The size of the follicles was less than that in the control group. There were no substantial changes in the epitheliomer structures. In almost all of the treated groups, a reduction in the number of PCNA+, NSE+, and mast cells was observed until the 28th day. On the 28th day of HPA, the level of mast cell degranulation was higher (61%) than that in the control group. On the 35th day, these parameters began to reach normal levels. From the 28th day, degenerative changes in the thyroid glands of treated animals were observed in the NSE+ cells. CONCLUSIONS: The HPA condition mainly has an influence on the number and structure of the NSE+ cells of the thyroid gland. One may assume that under HPA the increase in mast cell degranulation plays a significant role in the normalisation of the parameter of the thyroid gland.

Effect of experimental hyperphenylalaninemia on the postnatal rat brain.

The molecular mechanism of the disturbance of brain development caused by phenylketonuria remains mostly unknown. We have studied three molecular markers that reflect the development of neurons, glia and the extracellular matrix of the postnatal rat brain in an animal model of hyperphenylalaninemia, in order to elucidate the possible mechanism by which increased phenylalanine influences brain development. The content of NCAM, GFAP and hyaluronate-binding activity were compared in cerebellum and telencephalon of normal rats and those subjected to high phenylalanine. No statistically significant changes were found in telencephalon when experimental animals were compared to controls. In the hyperphenylalaninemic cerebellum, the developmental dynamic of NCAM content (represented by two peaks at about postnatal days 5 and 22 during normal development) is dramatically altered. The GFAP content in the cerebellum of treated rats exceeded those in controls significantly during late developmental stages (postnatal days 28-35). Hyaluronate-binding activity in the extracellular protein fraction from treated rat cerebellum was increased compared to normal rat at the early stages of development only (postnatal day 7). These results suggest that high serum phenylalanine may lead to permanent brain dysfunction through a disturbance of a wide range of developmental events.

[Effects of low-intensity electromagnetic radiation of extremely high frequency on the animal body within the framework of total low-dose x-ray irradiation]. / Vozdeistvie nizkointensivnogo élektromagnitnogo izlucheniia v diapazone kraine vysokikh chastot na zhivotnyi organizm na fone obshchego rentgenovskogo oblucheniia v malykh dozakh.

Effect of low-intensive electromagnetic radiation of extremely high frequency (EMR EHF) on the rats, subjected to the low-dose X-ray irradiation (6.192 mC/rg) was investigated. Content of glial fibrillary acidic protein as well as glucose content and activity of glutamate dehydrogenase and malate dehydrogenase was studied. It was shown than EMR EHF modifies the X-ray irradiation effect: filament GFAP concentration in brain and glucose content in serum were restored. The authors suggest central nervous system participation in realization of EMR EHF effects on the organism.

A novel method for evaluation of carbohydrate-binding activity: enzyme-linked carbohydrate-binding assay (ELCBA).

A highly sensitive method for detection of the carbohydrate-binding activity of proteins is described. The method is based on interactions of carbohydrate-binding proteins, immobilized on a solid phase, with an enzyme-labeled soluble polysaccharide (peroxidase conjugated glycosaminoglycans-heparin, chondroitin sulfate or hyaluronic acid. Binding capacity was measured spectrofotometrically after enzymatic reaction with chromogenic substrate. The reliability of the assay was tested by use of two heparin-binding proteins-i) fibronectin (soluble) and ii) heparin-binding protein purified from the human brain (water-insoluble). Binding of heparin was dependent on metal ions, detergents and urea. The assay is believed to be applicable for the identification and characterization of a variety of carbohydrate(glycosaminoglycan)-binding proteins, especially, when traditional methods can not be applied (e.g., when proteins are water-insoluble).

[A study of membrane glycoproteins from the rat brain using D-galactose-specific lectin]. / Izuchenie membrannykh glikoproteinov mozga krysy s ispol'zovaniem D-galaktozospetsificheskogo lektina.

Immobilized D-galactose-specific lectin from Zea mais was used to purify rat brain membrane glycoproteins. The membrane glycoproteins preliminarily washed from soluble proteins were solubilized consecutively by 2% triton X-100 and 1% SDS. PAG-electrophoresis with SDS and 2-mercaptoethanol revealed 10 polypeptide bands (Mm 109, 62, 59, 54, 51, 42, 16, 14, 12.5 and 12 kDa) in the membrane fraction of glycoproteins solubilized with triton X-100. Additional solubilization with SDS revealed 3 bands (Mm 109, 62, and 54 kDa). Only 3 polypeptide bands (Mm 62, 59, 42 kDa) were identified when analogous procedure was used for purification of the rat liver glycoproteins. Horse radish peroxidase labelled D-galactose-specific lectin from Zea mais was found to bind to neuron bodies and neurites in the cerebellum. It is suggested that the identified brain-specific membrane glycoproteins may take part in the cell adhesion between neurons.