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PubMed1990

[Hygienic evaluation of technological, design and sanitary-technical solutions for large-scale chemical plants].

Complexes of technologic solution for the construction of large-scale plants producing ammonia, nitric and sulfuric acids, ammonium nitrate, carbomide and caprolactam , are characterized by both positive and negative hygienic features. The hygienic shortcomings reveal themselves in sporadic increases of hazardous ingredients in concentrations up to the MAC and higher levels, as well as in unfavorable labour conditions when dealing with catalysts, storage operations, inter-enterprise transportation, dispatching of raw materials and finished products, in the contamination of the in-going ventilation air, and in the compound influence of low temperatures and toxic substances. The concentration of several large-capacity enterprises in the same area entails large-scale discharges in the atmosphere with subsequent contamination of the surrounding protection areas. The author proposes a set of major preventive measures.

Air Pollution↗
PubMedDate not supplied

[Determination of the enzymatic activity of lysine amidase].

A technique is proposed for determining lysinamidase and aminolactamase activities of lysinamidase (EC 3.5.1.n.). It is based on spectrophotometric measurement of the optical density decrease of the substrate solution at 227 nm. For cyclic lysinamide L-alpha-amino-epsilon-caprolactam epsilon 227 M = 151 M-1.cm-1, for linear lysinamide epsilon 227 M = 73 M-1.cm-1, and for lysine epsilon 227 M = 5 M-1.cm-1. The technique is simple and requires no additional reagents.

Amidohydrolases↗
PubMed1986

Identification of metabolites of the cell-differentiating agent hexamethylene bisacetamide in humans.

Hexamethylene bisacetamide, a compound which in vitro induces differentiation in a wide variety of human and animal cancer cell lines, is being investigated in phase I clinical trials. After i.v. administration of hexamethylene bisacetamide to humans, urine contained the parent compound and at least five metabolites formed by deacetylation and oxidation pathways. Identification of urinary metabolites was accomplished by gas chromatography-mass spectrometric analysis after isolation by ion exchange chromatography or extraction with ethyl acetate. Metabolites with amino or alcohol groups were trifluoroacetylated and acidic functional groups were esterified with 2,2,2-trifluoroethanol or methanol. The structure of each metabolite was confirmed by comparison with authentic standards. Metabolites identified included the major metabolite, 6-acetamidohexanoic acid; the monodeacetylated product, N-acetyl-1,6-diaminohexane; the bis-deacetylated diamine, 1,6-diaminohexane; and the amino acid, 6-aminohexanoic acid and its lactam, caprolactam.

Acetamides↗
PubMed1984

[Synthesis of N alpha-(tosyl-beta-alanyl)- and N alpha-(tosyl-epsilon-aminocapronyl)amidinophenylalanineamides as strongly effective inhibitors of thrombin].

The headline compounds were prepared for further determination of structure-activity-relationships. By conversion of cyanophenylalanines with the acidic chloride of tosyl-beta-alanine resp. tosyl-epsilon-aminocapronic acid and aminolysis of the following prepared p-nitrophenylic esters the cyano compounds would get the desired structure, which were converted over the thioamides and thioimidic esters in the amidines by the common way. At the preparation of epsilon-aminocapronic acid derivatives occurred difficulties because of simultaneous formation of the N-tosyl-epsilon-caprolactame. The preparation of corresponding aminobutyric acid derivatives wasn't possible. The prolongation of the C-chain of the branchless amino acid decreased the antithrombine effect.

Aminocaproates↗
PubMed1983

[Industrial hygiene studies in the production of various fibers and plastics].

The results from the labour-hygienic and clinical laboratory studies on working environment and workers engaged in production of polyamide (PAS) and polyacrylnitrile fibres (PAN) are summed up as well as in the production and processing of polyvinylchloride resin, polyurethan, polysterene and glass fibre laminates. The main deleterious factors in those productions are the chemical ones: caprolactam, acrylonitrile,tolyl diisocyanate, vinylchloride, styrene, etc. Noise and microclimate are the other unfavourable on-the-job factors. The concentrations of the toxic substances in the air of the working environment are pointed to be far over MAC, in spite of the new plants. Experiments are reported aiming at the determination of the real exposure of the workers - via individual sample collecting and elaboration of BMAC. The measures for the improvement of the conditions of the working environment in the production of synthetic fibres and plastics are summed up as well as the reduction of occupation risk of the workers.

Air Pollutants, Occupational↗
PubMed1993

Alkylamides as inducers of human leukemia cell differentiation: a quantitative structure-activity relationship study using comparative molecular field analysis.

Computer assisted quantitative structure-activity studies using comparative molecular field analysis (CoMFA) were performed on a series of alkylamides that induce cell differentiation. The series included alkylformamides, alkylacetamides, alkylureas, and substituted hexyl analogues of acetamide. The biological activity studied for correlation with structure was the ability of each compound to induce differentiation of the human promyelocytic leukemia cell line, HL-60, to granulocyte-like cells. In the CoMFA study, both steric and electrostatic fields were used along with molecular weight to determine a correlation between biological activity of the compounds and their structural features. The CoMFA results indicated a linear structure-activity correlation with a high predictive value. There was almost an even contribution towards activity from steric interactions, electrostatic potential, and molecular weight. These findings confirm a previous report by Langdon and Hickman (S. P. Langdon and J. A. Hickman, Cancer Res., 47: 140-144, 1987) that the ability to induce cell differentiation is highly dependent on molecular weight. Additionally, CoMFA contour maps provided information about regions of the molecule that are favorable to increased steric bulk and electrostatic charge. CoMFA was used to predict the activities of six hexamethylene acetamide analogues: ethyl 6-acetamidohexanoate; 6-acetamidohexanol; 1,5-bis(acetamido)hexane; 6-acetamidohexanonitrile; 6-acetamidohexanoic acid; and caprolactam. Although the model incorrectly predicted high activity for 6-acetamidohexanoic acid, the predicted activities for the remaining compounds were 0.3 to 1.5 times that of the corresponding experimental activities, which is comparable to the results obtained from other published CoMFA studies.

Cell Differentiation↗
PubMed2004

Complex morphology of melt-spun nylon-6 fibres investigated by 1H double-quantum-filtered NMR spin-diffusion experiments.

The complex morphology of high-speed melt-spun nylon-6 fibres hydrated with D2O was investigated using 1H double-quantum-filtered spin-diffusion NMR experiments. The magnetisation exchange from selected crystalline domains along the fibrils and interfibrils was simulated with the help of a three-dimensional solution of a spin-diffusion equation approximated by a product of one-dimensional analytical NMR signals, which correspond to a lamellar morphology. This allows to measure the sizes of crystalline and less-mobile amorphous domains along the fibrils, as well as the diameter of the fibrils and interfibril distances. A series of nylon-6 fibres with extreme values of winding speed and draw ratio was investigated. The changes detected in the domain size along the fibrils and interfibrils show the same trend in the data obtained from wide-angle X-ray diffraction and small-angle X-ray scattering.

Caprolactam↗
PubMed1994

Apatite coated on organic polymers by biomimetic process: improvement in its adhesion to substrate by NaOH treatment.

A dense, uniform and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure. First, a substrate is set in contact with particles of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyleneterephthalate (PET), polymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone (PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed by the hydrolysis of an ester group on PET and PMMA and of an amide group on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, attached a large number of hydrated silica dissolved from the glass particles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing as well as soft tissue-repairing materials.

Adhesiveness↗
PubMed1976

A unified mathematical model for diffusion from drug-polymer composite tablets.

The derivation and experimental verification of a unified mathematical model for the estimation of drug release rate from drug-polymer composite tablets are presented. Cylindrical coordinates are utilized in the solution of the diffusion equation for a three-dimensional system. The model is applicable to tablets that range from the shape of a flat disk (radius greater than thickness) to that of a cylindrical rod (radius less than thickness). The general solution for the fraction of drug released at a time t is (see article). This approach to a three-dimensional system, utilizing cylindrical coordinates, presents a comprehensive method for the estimation of drug release rates from sustained release tablets with drug distributed homogeneously throughout a polymer matrix. The calculated and experimental drug diffusion rate of pyrimethamine from pyrimethamine-silicone rubber composite tablets that range in shape from that of a disk to a cylinder, and of hydrocortisone from EVA, polycaprolactone, and PVA terpolymer, are compared.

Caprolactam↗
PubMed2005

Selective inhibition of type X collagen expression in human mesenchymal stem cell differentiation on polymer substrates surface-modified by glow discharge plasma.

Recent evidence indicates that a major drawback of current cartilage- and disc-tissue engineering is that human mesenchymal stem cells (MSCs) rapidly express type X collagen-a marker of chondrocyte hypertrophy associated with endochondral ossification. Some studies have attempted to use growth factors to inhibit type X collagen expression, but none to date has addressed the possible effect of the substratum on chondrocyte hypertrophy. Here, we sought to examine the growth and differentiation potential of human MSCs cultured on two polymer types, polypropylene and nylon-6, both of which have been surface-modified by glow discharge plasma treatment in ammonia gas. Cultures were performed for up to 14 days in Dulbecco's modified Eagle medium + 10% fetal bovine serum. Commercial polystyrene culture dishes were used as control. Reverse transcriptase-polymerase chain reaction was used to assess the expression of types I, II, and X collagens and aggrecan using gene-specific primers. Glyceraldehyde-3-phosphate dehydrogenase was used as a housekeeping gene. Types I and X collagens, as well as aggrecan, were found to be constitutively expressed by human MSCs on polystyrene culture dishes. Whereas both untreated and treated nylon-6 partially inhibited type X collagen expression, treated polypropylene almost completely inhibited its expression. These results indicate that plasma-treated polypropylene or nylon-6 may be a suitable surface for inducing MSCs to a disc-like phenotype for tissue engineering of intervertebral discs in which hypertrophy is suppressed.

Aged↗
PubMed2001

Electrospray and matrix-assisted laser desorption/ionization mass spectral characterization of linear single nylon-6 oligomers.

Synthetic nylon-6 single molecular mass oligomers were studied by matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry. These oligomers, considered as model compounds for the study of nylon-6 polymers, gave good mass spectrometric results using both MALDI and ESI. In spite of the gentle nature of both techniques, the MALDI and ESI spectra showed evidence of end-group cleavage from the oligomer chains. MALDI-MS was found to give similar fragmentation patterns for all of the oligomer samples. An increase in doubly charged ion signals with increasing oligomer mass was observed in the ESI mass spectra, as was end-group fragmentation. Signals from oligomer clusters were observed in ESI-MS for the dimer, tetramer and hexamer, most likely due to non-covalent bonding among the low-mass oligomer molecules.

Caprolactam↗
PubMed1986

Mechanical and biochemical effects of man-made fibres and metals in the human eye, a SEM-study.

Prolene, perlon, supramid and titanium, either used as sutures, 'Strampelli' sutures or artificial lens loops, were compared after remaining in the human eye for at least one year. For comparison, non-implanted samples of each of the materials were used as blanks. Prolene and Perlon in particular showed severe biodegradation after a given period; Supramid showed much less degradation of its surface. Titanium showed a rather rough outer surface (even in the non-implanted samples), particularly as bends in the lens loop, which facilitated the adherence of cells, fibres and microorganisms.

Azepines↗
PubMed2006

Comparison of glass vessels and plastic bags for enclosing living plant parts for headspace analysis.

Plants release volatile chemicals into their surrounding air space that can affect the physiology of neighboring plants and influence the behavior of insects. In studying these interactions, it is desirable to collect volatiles from plants that have not been excised and are growing under as natural conditions as possible. We compared a vessel of borosilicate glass and Nylon-6 or polyester [poly(ethyleneterephthalate) or PET] cooking bags for enclosing plants during collection of volatiles. A push-pull airflow system was used, and volatiles were trapped on Tenax TA and analyzed by gas chromatography after thermal desorption. Low levels of impurities were found for the glass vessel and polyester bags. Nylon bags contained higher levels and more impurities. Recoveries of standards of 10 plant volatiles were measured in static and dynamic systems. In a static air system, there was good recovery only from the glass vessel. In a dynamic system, there was generally good recovery from both the glass vessel and polyester bags. Recoveries of alpha-pinene and (Z)-jasmone were poor throughout. The former was shown to have a very low breakthrough volume on the Tenax TA adsorbent, and the latter may be strongly adsorbed on glass. All three materials were essentially transparent in the IR and visible (photosynthetic) range but with significantly different absorptions in the UV range. In a simulated dynamic entrainment in full sunlight, internal vessel temperatures were higher than ambient by up to 9.5 degrees C in the glass vessel and 7.5 degrees C in the polyester bag. Lower increases in temperature relative to ambient (<1 degrees C) were recorded when entrainments were conducted in the shade. In a field trial, the profiles of volatiles collected from an apple tree infested with rosy apple aphid using a glass vessel and a polyester bag were similar. Polyester bags are recommended as more convenient than glass vessels for the enclosure of plants during the collection of volatiles.

Adsorption↗
PubMed1985

New matrices for the purification of pectinases by affinity chromatography.

Polygalacturonic acid was used as a ligand in the affinity technique for pectinases purification from the filtrate of Aspergillus niger 71 culture. For this purpose four matrices were examined, namely, alkylamine controlled porous glass (CPG), alkylamine silica gel as well as keratin or polyamide coated silica gel. Good results of pectinase purification was obtained on silanized CPG or keratin coated silica gel supports.

Amines↗
PubMed1980

Polycaproamide degradation in rabbits and in several model media.

The nets of polycaproamide removed from rabbits after implantation for times up to 400 days showed a significant change in mass and in molecular weight. The degradation of polycaproamide filaments takes place both on the surface (change of mass) and in the bulk of the polymer implant (change in the molecular weight). The role of phosphates and the enzymes in the polymer degradation are discussed.

Animals↗
PubMed1985

Reversibility of granulocyte adhesion using polyamine-grafted nylon-6 as a new column substrate for granulocyte separation.

Reversibility of leucocytes adhered onto the surface of polyamine-grafted nylon-6 was investigated to estimate its feasibility as a new column substrate for granulocyte separation from whole blood. Polyamine-grafted nylon-6 was synthesized by a radical polymerization of 2-diethylaminoethyl methacrylate monomer onto nylon-6. The surfaces of these graft copolymers were found to show a microphase-separated structure composed of island-like phases of cationic polyamine and continuous phases of nonionic nylon-6. Interaction between leucocytes and these copolymer surfaces was studied by passing rabbit heparinized blood through a column packed with glass beads precoated with these copolymers. Columns of these copolymers showed a selective adhesion of granulocytes among leucocyte populations. Also, the adhering granulocytes were able to be recovered from the column by a gentle elution procedure. From these results, it was concluded that polyamine-grafted nylon-6 having a microphase-separated structure is suitable for use as a column substrate in granulocyte separation from whole blood.

Animals↗
PubMed1995

High-impact poly(L/D-lactide) for fracture fixation: in vitro degradation and animal pilot study.

The impact strength of amorphous lactide copolymers can be significantly improved by blending with biodegradable rubbers. Rubber toughening of amorphous poly(85L/15D -lactide) with the copolymer poly (50/50-trimethylenecarbonate-co-epsilon-caprolactone) results in a high-impact polymer (PDLLA/P(TMC-CL)). In vitro, the PDLLA/P(TMC-CL) blend retained its tensile and impact strength for a long period of time. Up to 45 weeks, the amount of water absorbed by the blend remained very low and no significant mass loss was observed. To test the suitability for fracture fixation, in a dog study mandibular fractures were fixated with PDLLA/P(TMC-CL) bone plates and screws. Bone healing was uneventful without premature failure of the implants. Although long-term degradation studies have to be carried out, PDLLA/P(TMC-CL) seems to be promising for application in fracture fixation.

Animals↗