NUMERICAL ANALYSIS OF BULLET IMPACT ONTO ARAMID LAYERS PLACED ON SUBSTRATA SIMULATING HUMAN BODY

Essential aspects of numerical analysis for bullet hitting elastic layers of aramid fabric placed on a plastic substratum imitating the human body are presented in the paper. A review of results for bullet-proof vests tested on various substrata is included in the paper with justification of their use. It is explained why the ballistic plasticine is used as a substructure imitating the human body in most standards binding in the world for testing individual protections. Methods for modelling the fabrics with results of own numerical analyses are presented. As mutual reaction of yarns creating the interweaving of the fabric has an essential impact on its deformation then it is represented in simulations by a model that directly describes its mezzo-structure. Simulations were carried out by using an explicit procedure for integration of motion equations in program ANSYS AUTODYN v.16. The results of hitting by 9 mm bullet Parabellum FMJ (Full Metal Jacket) into the layers of Twaron® T750 fabric placed on ballistic plasticine are presented. Results of simulation and bulletproof resistance tests are compared.

Cytoskeletal architecture and components involved in the attachment of Trypanosoma congolense epimastigotes

Scanning and transmission electron microscopy of Trypanosoma congolense epimastigotes attached to a plastic substratum shows them to elaborate a complex flagellum filament system and plaque with a highly organized structure. Non-ionic detergent extraction of these cells shows that the resulting cytoskeletons remain attached to the plaque. The subpellicular corset of microtubules can be removed by salt or Ca+2 treatment leaving the axoneme, paraflagellar rod, associated filaments and the plaque. Neither of these treatments therefore removed the plaque-associated material from the substratum. Analysis of these fractions by SDS–polyacrylamide gel electrophoresis reveals an abundant 70 kDa protein that is highly enriched in the salt extracted ‘minimal plaque’ structures and appears likely to be a major constituent of this structure. These studies reveal that the complex filament and microtubule systems of the cytoskeleton involved the attachment of trypanosomes to substrata and have established a method of biochemical fractionation of the structures and components involved.

Extracellular matrix stimulates production and breakdown of inositol phospholipids

Adhesion of rat glomerular epithelial cells (GEC) to collagen stimulates production of D-myo-inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol. This process is mediated via beta 1-integrins, and it modulates GEC proliferation. In this study, we address the changes in inositol-lipid turnover induced by GEC adhesion to extracellular matrix (ECM). The masses of both phosphatidylinositol 4,5-bisphosphate (PIP2) and IP3, as well as [3H]inositol phosphates, were increased in GEC adherent to collagen, compared with plastic substratum. Phosphatidylinositol-4-phosphate (PIP) 5-kinase activity was predominantly membrane associated and was enhanced in GEC on collagen. Phospholipase C (PLC) activity and PLC-gamma 1 protein were increased in membrane fractions of GEC adherent to collagen, compared with plastic. Stable overexpression of PLC-gamma 1 in GEC amplified the effect of ECM on the production of [3H]inositol phosphates. In addition, the PLC-gamma 1 that was membrane associated in collagen-adherent GEC was tyrosine phosphorylated. Thus production of IP3 in GEC adherent to ECM is associated with increased production of PIP2. Moreover, adhesion to ECM increases tyrosine phosphorylation and membrane association of PLC-gamma 1, which may facilitate PIP2 hydrolysis by increasing the catalytic activity of PLC-gamma 1 and the proximity of PLC-gamma 1 and its substrate. Understanding the process of ECM-induced inositol lipid production and breakdown in GEC may provide insights into the regulation of GEC proliferation and differentiated functions in normal conditions and during glomerular injury.

Binding of hexabrachion (tenascin) to the extracellular matrix and substratum and its effect on cell adhesion

Hexabrachion is a large glycoprotein of the extracellular matrix (ECM) that is prominent in embryogenesis, wound healing and tumorigenesis. Because of the role of extracellular matrix proteins in the regulation of cell differentiation and migration, the interaction of hexabrachion with cells as well as with other components of the ECM is of great interest. Early reports suggested that hexabrachion does not bind to fibronectin or gelatin but does bind to chondroitin sulfate proteoglycans. However, more recent reports have suggested that hexabrachion binds to fibronectin and inhibits cell adhesion as well as cell migration on fibronectin. We have found no evidence of strong hexabrachion-fibronectin binding on either a solid-phase ELISA assay or in a fluid-phase sedimentation assay in which the reactants were allowed to dissociate. However, hexabrachion sedimentation was accelerated in a gradient containing fibronectin throughout. This demonstrates an association between hexabrachions and fibronectin, but the complex is apparently weak and readily reversible. The solid-phase ELISA also shows no evidence of hexabrachion binding to gelatin, laminin or types I, III, IV or V collagen. Hexabrachion does not support strong cell attachment of the cell lines tested. Moreover, hexabrachion can inhibit cell attachment to fibronectin. We demonstrate here that this inhibition requires the hexabrachion to be able to bind to the plastic substratum. The results suggest that hexabrachion inhibition is via a steric inhibition. When the hexabrachion molecules bind to the plastic, they cover up a significant fraction of the underlying fibronectin molecules. Antibody studies are presented that show that hexabrachion can nonspecifically block access of immunoglobulin G molecules to the underlying matrix. This steric blocking is not unique to hexabrachion.

Proliferative behaviour of fibroblasts in plasma-rich culture medium

We examined the proliferative behaviour in tertiary culture cells of human skin fibroblasts (HSF) as well as cells of the rat 3Y1 diploid fibroblast line placed on a plastic substratum in a nutrient-rich medium containing high concentrations of platelet-poor plasma (PPP). Autochthonous human PPP was used for the HSF cells and heat-treated (at 56 degrees C for 30 min) bovine PPP was used for the 3Y1 cells. In both types of cells, the saturation cell density rose with increasing PPP concentration and reached a plateau at 30–90% PPP. When the cells were cultivated in serum, the saturation densities were the same as those with the same concentrations of corresponding PPP in both the HSF and 3Y1 cells. When the cells were arrested at a saturation cell density in a medium containing 10% PPP and then were refed with a fresh medium containing 90% PPP, DNA synthesis and cell division occurred in both types of fibroblasts. This effect was either reduced in the HSF cells or enhanced in the 3Y1 cells by the addition of platelet lysate. TGF-beta 1 added to the fresh medium containing 90% PPP also inhibited the induction of DNA synthesis in the HSF cells but not in the 3Y1 cells. The inhibitory effect of the platelet lysate was neutralized by anti-TGF-beta 1 IgG. On the other hand, PDGF added to the fresh medium had no effect on either type of cells. These results suggest that cultured fibroblasts are capable of proliferating on a plastic substratum under fluid conditions that essentially reflect the fluid environment of the body, as long as sufficient nutrients are supplied. Platelet lysate represses the proliferation of HSF cells, possibly through the inhibitory effect of TGF-beta 1, and promotes the proliferation of 3Y1 cells by growth factor(s) other than PDGF and TGF-beta 1.

Influence of collagen gel substratum on response to low-density lipoprotein by cultured human skin fibroblasts

The effect of low-density lipoprotein (LDL) on accumulation of glycosaminoglycans (GAG) was compared in cultures of human skin fibroblasts on a conventional plastic substratum and in a native type I collagen gel. The 24-h incorporation of [3H]glucosamine and Na235SO4 into GAG secreted into the medium or associated with the substratum and cell surface (SCA) was measured in cells at subconfluent densities. When cells were grown on plastic, 13–25% of the labeled GAG was in the SCA pool. Cells cultured within a collagen gel matrix incorporated three times more [3H]glucosamine and up to five times more [35S]sulfate into this pool. The addition of LDL (300 μg protein/mL) to the medium increased the level of total GAG incorporation of [3H]glucosamine by 40–50% and of [35S]sulfate by 15–20% on both substrata. For cells on plastic the relative increase in the medium and SCA pool was similar, whereas for cells in collagen gel the response to LDL was twice as great in the SCA pool as in the medium. The distribution of GAG types was unaffected by LDL; hyaluronic acid remained the principal GAG in the media pools of both substrata, heparan sulfate remained the main SCA GAG in cultures on plastic, and dermatan sulfate remained the dominant GAG in the SCA pool of collagen gel cultures. LDL degradation was measured at intervals up to 48 h after the addition of 125I-labeled LDL. The rate of accumulation of degraded LDL products was lower in collagen gel cultures, but the final levels achieved were the same in the two substrata. Concentrations of total cell cholesterol were similar, although the increases in free cholesterol induced by LDL were 26% greater in cells within collagen gel than in those on plastic. We conclude that fibroblasts grown within a collagen gel, as compared with those on a plastic substratum, (i) accumulate more GAG that remain attached to the substratum and cell surface; (ii) respond to LDL with a similar degree of increase in GAG accumulation, but more of the increase is found in the substratum and cell surface compartment; and (iii) accumulate more intracellular free cholesterol in response to LDL.

Type I collagen reduces the degradation of basal lamina proteoglycan by mammary epithelial cells.

When mouse mammary epithelial cells are cultured on a plastic substratum, no basal lamina forms. When cultured on a type I collagen gel, the rate of glycosaminoglycan (GAG) synthesis is unchanged, but the rate of GAG degradation is markedly reduced and a GAG-rich, basal lamina-like structure accumulates. This effect of collagen was investigated by comparing the culture distribution, nature, and metabolic stability of the 35S-GAG-containing molecules produced by cells on plastic and collagen. During 48 h of labeling with 35SO4, cultures on collagen accumulate 1.4-fold more 35S-GAG per microgram of DNA. In these cultures, most of the extracellular 35S-GAG is immobilized with the lamina and collagen gel, whereas in cultures on plastic all extracellular 35S-GAG is soluble. On both substrata, the cells produce several heparan sulfate-rich 35S-proteoglycan fractions that are distinct by Sepharose CL-4B chromatography. The culture types contain similar amounts of each fraction, except that collagen cultures contain nearly four times more of a fraction that is found largely bound to the lamina and collagen gel. During a chase this proteoglycan fraction is stable in cultures on collagen, but is extensively degraded in cultures on plastic. Thus, collagen-induced formation of a basal lamina correlates with reduced degradation and enhanced accumulation of a specific heparan sulfate-rich proteoglycan fraction. Immobilization and stabilization of basal laminar proteoglycan(s) by interstitial collagen may be a physiological mechanism of basal lamina maintenance and assembly.

Latent effects on in vitro development following cytochalasin B treatment of 8-cell mouse embryos

Eight-cell mouse embryos when treated with 4·0 μg/ml cytochalasin B (CB) in vitro undergo a reversible developmental arrest. Upon rinsing of embryos and subsequent culture in control medium, normal morphogenetic processes such as compaction of 8-cell embryos, cavitation, and post-blastocyst attachment and outgrowth are restored. However, the effects of CB on mouse embryos are not completely reversible; latent post-blastocyst defects become increasingly more prevalent as CB treatment duration increases. The present study was conducted to quantitatively determine latent effects of CB on post-blastocyst embryos by comparing their ability to attach and to sustain the growth and differentiation of ICM and trophoblast tissues. Groups of 8-cell embryos were cultured in Brinster's BMOC-3 medium containing 40 μg/ml cytochalasin B for 6, 12, 18, and 24h. Following treatment, embryos were rinsed and cultured until 190 h post coitun (h.p.c.) in Eagle's MEM/10% fetal calf serum modified to contain optimal levels of essential amino acids. Blastocysts generally attached to the surface of the plastic substratum by 120 h.p.c. At selected time periods after attachment (130, 160, and 190 h.p.c), embryos were scored for outgrowth size, ICM size, extent of peripheral hyaloplasmic fan, and number of trophoblast nuclei per outgrowth. Analyses of variance (ANOVAs) were conducted for each of the four parameters listed above. Rates of attachment were analyzed by χ2 test. Results show that the treatments affect (P < 0·01) embryo attachment, number of trophoblast nuclei per outgrowth, hyaloplasmic fan production, and ICM growth in a durationdependent manner. Interestingly, since treatment effects on outgrowth areas are nonsignificant apparently CB does not significantly change total outgrowth area. But CB tieatment does cause abnormal fan production and decreased trophoblast nuclei numbers. However, trophoblast cells are apparently more resistant than ICM to CB as is evident by the high incidence of tiophoblast outgrowths devoid of ICM. CB (4·0 μg/ml) treatments at 8-cell stages for relatively short durations (6 and 12 h) induce latent effects on post-blastocyst embryos. Finally, there exists a definite 4·0 μg/ml CB duration response over the 68–190 h.p.c. observation interval.

Outgrowth of human fibroblast aggregates on a substratum triggers a wide variety of morphogenetic properties in the cells

Twenty-four-hour-old aggregates of human diploid skin fibroblasts are allowed to attach to a glass or plastic substratum. As a result of this attachment the cells in the aggregate demonstrate rapid and generalized changes in cell shape, cell surface and cytoplasm ultrastructure and in their ability to incorporate [3H]thymidine. Within 24 h they grow out on the substratum to attain the regular monolayer configuration. During the process of leaving the aggregate for the substratum a great number of different morphogenetic properties are displayed by the cells, resembling the properties of embryonic or epithelial cells. The simultaneous occurrence of this great variety of cell shape and cell surface changes, many of them unusual for fibroblasts, as well as the concurrent formation of organized cytoplasmic structures - microfilaments, microtubules - at localized areas of the cells, makes this system a potentially useful tool in the study of cell behaviour.