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High-density polyethylene (PE) foils were modified by an Ar(+) plasma discharge and subsequent grafting with biomolecules, namely glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C) or BSA and C (BSA + C). As revealed by atomic force microscopy (AFM), goniometry and Rutherford Backscattering Spectroscopy (RBS), the surface chemical structure and surface morphology of PE changed dramatically after plasma treatment. The contact angle decreased for the samples treated by plasma, mainly in relation to the formation of oxygen structures during plasma irradiation. A further decrease in the contact angle was obvious after glycine and PEG grafting. The increase in oxygen concentration after glycine and PEG grafting proved that the two molecules were chemically linked to the plasma-activated surface. Plasma treatment led to ablation of the PE surface layer, thus the surface morphology was changed and the surface roughness was increased. The materials were then seeded with vascular smooth muscle cells (VSMC) derived from rat aorta and incubated in a DMEM medium with fetal bovine serum. Generally, the cells adhered and grew better on modified rather than on unmodified PE samples. Immunofluorescence showed that focal adhesion plaques containing talin, vinculin and paxillin were most apparent in cells on PE grafted with PEG or BSA + C, and the fibres containing alpha-actin, beta-actin or SM1 and SM2 myosins were thicker, more numerous and more brightly stained in the cells on all modified PE samples than on pristine PE. An enzyme-linked immunosorbent assay (ELISA) revealed increased concentrations of focal adhesion proteins talin and vinculin and also a cytoskeletal protein beta-actin in cells on PE modified with BSA + C. A contractile protein alpha-actin was increased in cells on PE grafted with PEG or Gly. These results showed that PE activated with plasma and subsequently grafted with bioactive molecules and colloidal C particles, especially with PEG and BSA + C, promotes the adhesion, proliferation and phenotypic maturation of VSMC.

The adhesion, growth and differentiation of human osteoblast-like MG 63 cells were investigated in cultures grown on nanostructured nanocrystalline diamond (NCD) films with either low surface roughness (rms of 8.2 nm) or hierarchically organized surfaces made of low roughness NCD films deposited on Si surfaces with the original microroughness (rms of 301.0 nm and 7.6 nm, respectively). The NCD films were grown using a microwave plasma-enhanced CVD method in an ellipsoidal cavity reactor. The films were treated in oxygen plasma to enhance the hydrophilic character of the diamond surface (water drop contact angle approx. 20 degrees). The samples were then sterilized by 70% ethanol, inserted into 12-well polystyrene multidishes (diameter 2.2 cm), seeded with human osteoblast-like MG 63 cells (40,000 cells/dish, 10,530 cells/cm2) and incubated in 2 ml of DMEM medium with 10% of fetal bovine serum. On day 3 after seeding, the cell numbers were significantly higher on the nanostructured NCD films (72,020 +/- 6540 cells/cm2) and also on the hierarchically micro- and nanostructured films (60200 +/- 6420 cells/cm2) than on the control polystyrene culture dish (40750 +/- 2,530 cells/cm2). The cells on hierarchically micro- and nanostructured diamond substrates also adhered over a significantly larger area (3730 +/- 180 microm2 compared to 2740 +/- 130 microm2 on polystyrene). The cell viability, measured by a LIVE/DEAD viability/cytotoxicity kit, reached 98% to 100% on both types of NCD films. The XTT test showed that the cells on both nanodiamond layers had significantly higher metabolic activity than those on the control polystyrene dish (approx. 2 to 3 times). Immunofluorescence staining of the cells on both NCD films revealed talin-containing focal adhesion plaques and beta-actin filaments, well apparent particularly at the cell periphery, as well as the presence of considerable amounts of osteocalcin, i.e., a marker of osteogenic cell differentiation. These results suggest that nanocrystalline diamond films give good support for adhesion, growth and differentiation of osteogenic cells and could be used for surface modification of bone implants in order to improve their integration with the surrounding bone tissue.

Nanocomposite Ti/hydrocarbon plasma polymer (Ti/ppCH) films were deposited by DC magnetron sputtering of titanium target in n-hexane, argon, or a mixture of these two gases. The resultant films were heterogeneous, with inorganic regions of nanometer scale distributed within a plasma polymer matrix. The titanium content was controlled by adjusting the argon/n-hexane ratio in the working gas. In the pure n-hexane atmosphere, the Ti concentration was found to be below 1 at %, whereas in pure argon it reached 20 at %, as measured by Rutherford backscattering spectroscopy and elastic recoil detection analysis (RBS/ERDA). A high level of titanium oxidation is detected with TiO(2), substoichiometric titania, and titanium carbide, composing an inorganic phase of the composite films. In addition, high hydrogen content is detected in films rich with titanium. Ti-deficient and Ti-rich films proved equally good substrates for adhesion and growth of cultured human osteoblast-like MG 63 cells. In these cells, the population densities on days 1, 3, and 7 after seeding, spreading area on day 1, formation of talin-containing focal adhesion plaques as well as concentrations of talin and osteocalcin (per mg of protein) were comparable to the values obtained in cells on the reference cell culture materials, represented by microscopic glass coverslips or a polystyrene dish. An interesting finding was made when the Ti/ppCH films were seeded with calf pulmonary artery endothelial cells of the line CPAE. The cell population densities, the spreading area and also the concentration of von Willebrand factor, a marker of endothelial cell maturation, were significantly higher on Ti-rich than on Ti-deficient films. On Ti-rich films, these parameters were also higher or similar in comparison with the reference cell culture materials. Thus, both types of films could be used for coating bone implants, of which the Ti-rich film remains effective in enhancing the endothelialization of blood contacting artificial materials.

Objectives: Neurochemical studies on the etiopathogenesis of depression are also focusing on the transduction system beyond receptors. Trimeric G-proteins play a crucial role in the transmembrane signalling, signal amplification and intracellular processing. Abnormalities of G-protein levels are observed in subjects with depression, G-protein modulation is considered to play a role in the antidepressant mode of action., Methods: We studied acute or chronic administration of antidepressants from different pharmacological groups. We used immunochemical estimation (ELISA) of the main types of G-protein alpha subunits from isolated membranes of C6 glioma cells and rat brain tissue., Results: Significant elevation of G alpha q/11 subunits after chronic administration of sertraline and significant reduction of G alpha s subunit levels following both acute and chronic administrations of sertraline were found. In contrast, no significant effects on G alpha subunit levels following acute desipramine and moclobemide administration were observed in vitro. Chronic moclobemide effect in vivo is causing significant elevation of Galpha s and Galpha i1,2 subunit levels., Conclusions: Results show involvement of antidepressant drugs in the C6 glioma signal transduction cascades modulation in dependence on the antidepressant class. Significant influence in the cAMP system modulation is observed after administration both SSRI and MAOA inhibitors. Astrocytoma cells - C6 glioma cells also can offer a model system of the glia where modulation of cell signalization cascades can influence cell functioning and production of neurotrophic factor molecules relevant to the antidepressant treatment and depression etiopathogenesis.

The multifunctional cytokine interleukin-18 (IL-18) is an important mediator in intestinal inflammatory processes. The aim of this study was to evaluate the constitutive expression of IL-18 and its receptors (IL-18Ralpha and IL-18Rbeta) in intestinal epithelial cells (IEC) stimulated by tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). In addition, cellular proliferation and evaluation of brush border enzymes as differentiation markers were studied. Nontransformed rat intestinal epithelial IEC-6 cells were grown on an extracellular matrix (ECM) in medium with or without TNF-alpha, IFN-gamma, or a combination of both. Gene expression of IL-18, its receptors and apoptotic markers was evaluated using real-time PCR. Expression of IL-18Ralpha protein was demonstrated by flow cytometry and Western blot. Enzymatic activities of brush border enzymes and caspase-1 were determined. The constitutive expression of IL-18, IL-18Ralpha and IL-18Rbeta mRNAs and proteins were detected in IEC-6 cells. The biologically active form of IL-18 was released in response to TNF-alpha and IFN-gamma treatment. Exogenous IL-18 had no effect on cellular proliferation, brush border enzyme activities, and gene expression of apoptotic markers. However, the addition of IL-18 stimulated production and release of the chemokine IL-8. These data suggest that IEC-6 cells may be not only a source of IL-18 but also a target for its action.

Alterations in dipeptidyl peptidase-IV (DPP-IV) enzymatic activity are characteristic of malignant transformation. Through its well-characterized functionality in regulating the activity of bioactive peptides by removal of the N-terminal dipeptide, DPP-IV activity may have profound effects upon metastatic potential and cell growth. Although DPP-IV/CD26 (EC 3.4.14.5) is the canonical representative of the group, a number of other proteins including DPP-7, 8, 9, and seprase/fibroblast activation protein-alpha (FAP-alpha) have been shown to have similar enzymatic activity. This study was set up to address the relative representation and enzymatic activity of plasma membrane localized DPP-IV/CD26 and FAP-alpha in human brain and astrocytic tumours. In parallel, expression of CXCR4, receptor for glioma cell growth stimulator chemokine SDF-1alpha known to be a DPP-IV substrate, was investigated. This is the first report showing that non-malignant brain tissue contains a DPP-IV-like enzymatic activity attributable mostly to DPP-8/9, while the substantial part of the activity in glioma is due to increased DPP-IV/CD26, localized in both the vascular and parenchymal compartments. DPP-IV enzymatic activity increased dramatically with tumour grade severity. A grade-related increase in CXCR4 receptor paralleled the rise in DPP-IV expression and activity. These data might support a role for DPP-IV regulation of the CXCR4-SDF-1alpha axis in glioma development.

The surface of poly(L-lactide) (PLLA) films deposited on glass coverslips was modified with poly(DL-lactide) (PDLLA), or 1:4 mixtures of PDLLA and PDLLA-b-PEO block copolymers, in which either none, 5% or 20% of the copolymer molecules carried a synthetic extracellular matrix-derived ligand for integrin adhesion receptors, the GRGDSG oligopeptide, attached to the end of the PEO chain. The materials, perspective for vascular tissue engineering, were seeded with rat aortic smooth muscle cells (11,000 cells/cm(2)) and the adhesion, spreading, DNA synthesis and proliferation of these cells was followed on inert and bioactive surfaces. In 24-h-old cultures in serum-supplemented media, the number of cells adhering to the PDLLA-b-PEO copolymer was almost eight times lower than that on the control PDLLA surface. On the surfaces containing 5% and 20% GRGDSG-PEO-b-PDLLA copolymer, the number of cells increased 6- and 3-fold respectively, compared to the PDLLA-b-PEO copolymer alone. On PDLLA-b-PEO copolymer alone, the cells were typically round and non-spread, whereas on GRGDSG-modified surfaces the cell spreading areas approached those found on PDLLA, reaching values of 991 microm(2) and 611 microm(2) for 5% and 20% GRGDSG respectively, compared to 958 microm(2) for PDLLA. The cells on GRGDSG-grafted copolymers were able to form vinculin-containing focal adhesion plaques, to synthesize DNA and even proliferate in a serum-free medium, which indicates specific binding to the GRGDSG sequences through their adhesion receptors.

Lily mottle virus (LMoV), genus Potyvirus, an important virus of lily that also causes flower-breaking in tulip (1), is considered to have a natural host range restricted to the family Liliaceae. In 1996, escarole (Cichorium endivia L. var. latifolium LAM) plants growing in fields close to Torino, Italy, and showing mosaic and necrotic spots on outer leaves were infected by a potyvirus related to LMoV. The virus was identified by immunoelectron microscopy (IEM) done on experimentally infected Nicotiana benthamiana and Chenopodium quinoa. The virus isolated from escarole (LMoV-E) had an experimental host range similar to that of lily isolates of LMoV, although species within the Liliaceae were not tested. LMoV-E systemically infected all nine escarole cultivars and six of seven endive cultivars (C. endivia L. var. crispum LAM) but did not infect any of six lettuce and two chicory cultivars (C. intybus L. var. foliosum HEGI). Symptoms ranged from mild to severe mosaic and were generally more severe on escarole than on endive. Some of the same escarole, endive, and lettuce cultivars were inoculated with a typical LMoV isolate from lily (Le97/49, from A. F. L. M. Derks, the Netherlands), which induced mild systemic infections in only one escarole and one endive cultivar. Both cultivars were also susceptible to LMoV-E. LMoV-E was purified from N. benthamiana, and an antiserum was prepared. IEM decoration titer experiments were done with LMoV-E and four other LMoV isolates from Liliaceae and their homologous antisera. Heterologous titers ranging from identity to serological differentiation index values of 2 to 4 were obtained, confirming the identity of the escarole isolate as a LMoV strain and indicating considerable serological variability among LMoV isolates. In a field survey of endive and escarole crops in 1998, in the area where LMoV-E was first identified, the virus was again detected by enzyme-linked immunosorbent assay in 4 of 80 escarole plants tested. LMoV-E appears to be a LMoV strain particularly adapted to escarole. To our knowledge, this is the first report of LMoV identified in a naturally infected host outside monocotyledonous plants. Reference: (1) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993.

Ranunculus white mottle virus (RWMV) (1), genus Ophiovirus, has been reported in crops of several cultivars of commercial ranunculus (Ranunculus asiaticus hybrids) during the 1990s in Liguria in Northwest Italy. Symptoms associated with RWMV in ranunculus are not clear-cut owing to the presence of mixed viral infections. During autumn 1999, a severe disease in commercial crops of anemone (Anemone coronaria) was noted in the same area. Plants appeared stunted with young leaves showing curling, deformation, and necrotic spotting. Disease incidence in some fields reached 40 to 50%. DAS- and TAS-enzyme-linked immunosorbent assays (ELISAs) for presence of RWMV and for the viruses most frequently infecting anemone in Italy were run on 24 field samples. Seven proved to be infected by RWMV in mixed infection with Cucumber mosaic virus subgroup II or with Tobacco necrosis virus. Ophiovirus-like particles were detected by negative staining and electron microscopy from sap extracts of field plants that were RWMV-positive by ELISA. Sap from these plants was also mechanically inoculated to indicator plants. Total RNAs were extracted from RWMV-infected field samples and from inoculated Nicotiana benthamiana and N. clevelandii and used in molecular tests. A DIG-DNA probe targeting the 1.8-kb RNA2 of RWMV was used in Northern blots and dot blots of total RNAs, confirming the infection in field samples and multiplication of the virus in test plants, unfortunately still in mixed infection. At present, it is difficult to evaluate RWMV symptomatology in anemone, but the presence of this virus in mixed infection seems to produce serious effects. This is the first report of RWMV in anemone. Reference: (1) A. M. Vaira et al. Arch. Virol. 142:2131, 1997.

The pharmacological modulation of the uptake of porphyrin derivatives in cultured C6 glioma cells was investigated by means of spectrofluorometric analysis both in single cells and in cell homogenates. The influence of drugs acting as beta-receptor agonists or antagonists was studied in cells grown to semiconfluency. Isoproterenol (ISO), a beta-receptor agonist, enhanced the intracellular fluorescence intensity of both Photofrin and protoporphyrin IX (PpIX). A treatment with a beta-receptor antagonist I-propranolol (PRO), simultaneous with ISO, resulted in an intracellular Photofrin fluorescence signal comparable to that of the control cells, indicating the specificity of the pharmacological action. The pharmacological treatment seemed particularly effective with the aggregated species. This is suggested by the relative increase of the band at 670 nm, being greater than that in the 630 nm band in the emission spectra of Photofrin and PpIX, and by the comparison of the fluorescence intensity on cell homogenates measured both in the absence and in the presence of cetyltrimethyl-ammonium bromide as a detergent.

Objective: The aim of this study was to evaluate the influence of rescuer fatigue on the quality of chest compressions and the influence of the rescuer's gender, age, weight, height or professional status on the reduction of quality of chest compressions caused by fatigue., Material and Methods: The study was carried out with the Laerdal Skillmeter Resusci Anne manikin. The participants were doctors and nurses who work in the Intensive Care and Emergency departments, with an age ranging from 25 to 45 years and trained in cardiopulmonary resuscitation (CPR). Statistical analysis of results includes analysis variance and three models of multiple linear regression., Results: Thirty-eight people took part in the experiment; 20 (52.6%) were females; 15 (39.5%) staff physicians, 15 (39.5%) nurses and eight residents. Mean age was 34.1 years (SD = 4.1). We found a significant reduction in correct compression performance over the course of time: in the first minute 79.7%, in the second 24.9%, in the third 18%, in the fourth 17.7% and in the last minute 18.5%. There were no differences related to the rescuer's gender or profession. The median interval until rescuers appreciated the effect of the fatigue on chest compressions quality was 186 s (SD = 84.1); that appreciation was not influenced by gender, age, weight, height or profession. There were no differences in the percentage of correct compressions related to gender (P = 0.07), insufficient sternal depression (P = 0.23) or total number of compressions in the first minute., Discussion: A decrease of compressions quality after the first minute of CPR is produced. This effect does not depend on gender, age, weight, height or rescuer's profession and it is not adequately perceived by the person who performs the chest compressions.

Unusual symptoms were observed in summer 1997 in field zucchini of several cultivars grown in central Italy. Symptoms included reduction in growth, severe mosaic, blistering and deformation of leaves, and malformation on fruits. Plants gave negative results in enzyme-linked immunosorbent assay (ELISA) for cucumber mosaic cucumovirus, squash mosaic comovirus, papaya ringspot, zucchini yellow fleck, zucchini yellow mosaic, and watermelon mosaic 2 potyviruses. Positive reactions were obtained in ELISA with a monoclonal antibody that reacts with many potyviruses (from J. Vetten, Braunschweig) and with polyclonal antibodies (Sanofi, France) to Moroccan watermelon mosaic potyvirus (MWMV). Field symptoms were reproduced in zucchini cvs. Genovese and Striato d'Italia by mechanical inoculation of samples from symptomatic field plants. Chenopodium amaranticolor, C. quinoa, and Gomphrena globosa gave local lesions, while Citrullus lanatus cv. Crimson Sweet, Cucumis melo cv. Top Mark, C. metuliferus, C. sativus cvs. Marketer, MM76, and Sweet Slice, and Cucurbita maxima reacted with systemic mosaic. C. melo cv. Doublon formed necrotic local lesions followed by systemic necrosis. No infection occurred in Nicotiana benthamiana, N. clevelandii, N. glutinosa, Phaseolus vulgaris cv. Black Turtle, Pisum sativum cv. Alaska, tobacco White Burley, and Vigna unguiculata. These data are in agreement with the known host range of MWMV. MWMV is a tentative species in the genus potyvirus, widely present in Africa and occasionally found in Spain (1,2). Further spread of this virus in the Mediterranean area will create new problems for commercial cucurbit production and breeding, and for diagnosis. References: (1) E. Kabelka and R. Grumet. Euphytica 95:237, 1997. (2) N. M. McKern et al. Arch. Virol. 131:467, 1993.

Background: Only one third of patients who have suffered a myocardial infarction can benefit from thrombolytic treatment in the daily clinic practice. The aim of this study is to know the percentage of patients who were treated in a General Hospital and the main exclusion causes to receive thrombolytic treatment., Methods: A descriptive study in patients with infarction who were admitted to the Critical Care Unit of a 550 beds Hospital between September-95 and August-96., Results: 188 patients were admitted with suspicion of myocardial infarction. The 50.53% of them received thrombolytic treatment. The main exclusion causes to receive this treatment were: delay of the patient (18.10%), normal ECG or descended ST (16.50%), contraindications (8%), patient's refusal to receive treatment (0.53%) an uncertain indication of therapy (6.40%)., Conclusions: A high percentage of patients received thrombolytic therapy, maybe because these drugs can be used until 12 hours the infarction and they haven't limit of age.

An undescribed virus, here named ranunculus white mottle virus, was isolated in Italy from cultivated ranunculus showing mottle and distortion of leaves. The virus was mechanically transmissible to several herbaceous hosts. In negative stain, the particles appeared as circularised supercoiled threads 3 nm in diameter of different contour lengths; in some conditions the circles collapsed to form linear pseudobranched structures 9 nm in diameter. Immunolabeling of thin sections showed that viral antigen was widely distributed in the cytoplasm of parenchyma cells. The virus was not serologically related to the morphologically similar tenuiviruses, citrus psorosis-ringspot virus and tulip mild mottle mosaic virus. A major 43 kDa protein was present in purified preparations and in infected plant tissue, as also was a minor 28 kDa protein, serologically related to the major one. Nucleic acids extracted from purified particles consisted of at least three RNAs, of approximately 7.5, 1.8 and 1.5 kb, which appeared partly in single- and partly in double-stranded form. Purified preparations, but not viral RNAs, when mechanically inoculated, were infectious. Host range, tissue tropism, particle morphology and coat protein size place the virus closest to citrus psorosis-ringspot and tulip mild mottle mosaic viruses. These three viruses in turn show similarities with the Tenuiviruses and Bunyaviridae.

Cases of severe acute carbon tetrachloride poisoning are sporadically described in Spain. We report the cases of three patients that inhaled toxic vapour of carbon tetrachloride that they used as a solvent during their working activity. They developed hepatic disfunction and one of them acute renal failure. The interval between the labour exposure and the medical care was higher than 24 hours. All the patients received N-acetylcysteine treatment (300 mg/kg) and oxygen. The patient ith renal failure recurred hemodialysis. The basic aspects of diagnosis and treatment are commented.

Nicotiana benthamiana was transformed with the nucleoprotein (N) gene of an Italian isolate of tomato spotted wilt virus (TSWV). Forty-five T1 primary transformant lines were analyzed for the expression of N protein and for resistance to TSWV and three other tospoviruses: impatiens necrotic spot virus (INSV), groundnut bud necrosis virus (GBNV), and groundnut ringspot virus (GRSV). Thirteen of these lines were further characterized. Resistance to all TSWV isolates tested was found in two lines. The expression of the transgene (N mRNA) was lower in these resistant lines than in any of the susceptible lines, and the transgene N protein was either absent or present below detectable levels. These lines were susceptible to the other tospoviruses tested, but they developed symptoms milder than controls when inoculated with GRSV. Some of the lines producing high levels of N protein showed delays (of 2-3 weeks) in symptom expression with at least one of the TSWV isolates tested and symptom delay or attenuation with INSV or GRSV (or both). From our results it appears that high expression of TSWV N protein retards, in some cases, disease development by TSWV and INSV. In contrast, the lack of detectable expression of the transgenic N protein, accompanied by limited production of N transcripts, conferred TSWV-specific resistance.

Each of three patients with thyroid medullary carcinoma (TMC) presents the tumor as a family feature. Most of them have other associated endocrinous neoplasias. Through the study of baseline plasmatic calcitonin and after stimulus with calcium and pentagastrin, patients with silent TMC can be detected. We present the results of the study of a family including 70 members and with hereditary TMC, between 1988 and 1992. Six new cases of TMC were diagnosed starting from the case index. Their average age was 31.7 years. Five of them underwent surgery. None of them had other associated endocrinous neoplasias, which is extremely rare. In addition, we present data on the postoperative follow-up of the patients, two of which had high calcitonin and CEA levels.

White clover cryptic viruses (WCCV) 1, 2, and 3 were purified from apparently healthy plants with yields of about 200 mug of virus/kg of tissue. After isopycnic centrifugation in CsCl, WCCV 1 and 2 formed homogeneous bands at densities of 1.392 and 1.375 g/ml, respectively, whereas WCCV 3 was not recovered. Particles of WCCV 1 and 3 were 34 nm in diameter, without obvious morphological subunits, whereas WCCV 2 particles were 38 nm in diameter, with prominent morphological subunits. Antisera with titers up to 1:2048 were obtained against WCCV 1 and 2. Each of the three viruses contained two segments of linear dsRNA (Mr from 1.03 to 1.49 X 10(-6). Virus-like particles, probably those of WCCV 1 and 2 were detected in low numbers in the cytoplasm of about 1/10 of the parenchyma cells of carrier plants examined by thin sectioning. The particles of WCCV 1 and 2 were not transmitted by grafting or mechanical inoculation, but were seed transmitted. Evidence is given that WCCV 1 and 2 multiply in their carrier plants, and are not viruses of associated parasitic or commensal organisms.

The nucleic acid of carnation cryptic virus has been identified as double-stranded RNA on the basis of (i) susceptibility to RNase in 0.1 x SSC (SSC = 0.15 M NaCl-0.015 M sodium citrate buffer, pH 7.0) and resistance to RNase in 2 x SSC and to DNase, (ii) reaction with an antiserum containing antibodies to dsRNA, and (iii) electron microscopic appearance in nondenaturing media similar to that of the dsRNA of maize rough dwarf virus. Upon electrophoresis in 5% polyacrylamide gels carnation cryptic virus RNA separated into three major segments plus a fourth minor component, and had a total molecular weight of about 4 x 10(6).

Single stages of histiotypic formation from dissociated embryonic brain cells are described. The first stage, i.e. primary adhesion, is a phenomenon depending mainly on physicochemical features of the adhesive system. The composition of the membrane glycoprotein coat was studied during membrane regeneration and formation of cellular contacts. At the beginning single terminal sugar components and negative sialic acid residues are distributed non-homogeneously over the membrane according to the ligation of lectins. During the formation of cellular contacts this non-homogeneity progressively disappears, the thickness of the layer is reduced, however, the density of single markers increases. The highest increase of both density and layer thickness during the phase of membranes reparation occurs when the negative surface groups are labelled with cationized ferritin. The sorting out process was studied in mixed cultures as a stage of final specific recognition. It is assumed that the reaggregation of cells is a multistep process depending on maturation of the glycoprotein coat, characterized by multiple cellular adhesion and deadhesion, completed by specific recognition and fixation of recognized cells.