Low Molecular Weight Moieties Research Articles

Effects of atmospheric plasma treatment on adhesion and tribology of aromatic thermoplastic polymers

After cold plasma treatment of poly(ethylene terephthalate) and poly(ether‐ether ketone) surfaces by dielectric barrier discharge (DBD) under atmospheric (air) conditions, variations in surface chemistry, and morphology were investigated in relation with adhesion and tribological properties. According to XPS measurements, surface oxidation caused the formation of low molecular weight moieties of carboxylic acids. The latter resulted in more hydrophilic surfaces according to water contact angle measurements, with mainly a higher polar surface energy component. In parallel, the surface roughness of originally polished surfaces reduced due to flattening of local surface asperities after DBD. The DBD significantly improved the adhesive shear strength for different glue types in polymer/polymer and polymer/steel joints, while the best adhesion was observed for a two‐component epoxy type adhesive. Under dry sliding conditions, the coefficients of friction were lower after DBD compared to pristine samples only under mild sliding conditions (v = 0.05 m/s; p < 1 MPa.m/s), while the higher normal loads caused an increase in coefficients of friction likely due to the higher contributions of surface deformation. Most interestingly, the lower coefficients of friction after DBD were observed under oil lubrication and after cleaning the sliding track (“run‐out” condition), due to the better retention of oil at the sliding surface for plasma‐treated polymers. POLYM. ENG. SCI., 58:E93–E103, 2018. © 2017 Society of Plastics Engineers

Migration of low molecular weight moiety at rubber–polyurethane interface: An ATR-IR spectroscopy study

In this study, a novel approach based on ATR-IR spectroscopy consisting in the combined use of two prisms of different nature and refraction index (germanium—about 1 μm depth and zinc selenide—about 3 μm depth) was proposed to study the polyurethane–rubber interface. More precisely, the migration of paraffin wax additive in as-received and MEK cleaned vulcanized styrene–butadiene rubber (SBR)–polyurethane coating interface was monitored. Polyurethane coating with thickness of about 2 μm was applied on the SBR rubber surface and the ATR-IR spectra were recorded in the polyurethane coating. Thus, the ATR-IR spectrum obtained with Ge prism analyzed only the polyurethane coating whereas the ATR-IR spectrum obtained with ZnSe analyzed both the polyurethane coating and the near surface SBR. The results obtained showed that the paraffin wax migrated from the SBR rubber bulk to the rubber–polyurethane interface, then diffused into the polyurethane and finally migrated to the polyurethane surface.

Effect of temperature on the extent of migration of low molecular weight moieties to rubber surface

Vulcanized rubbers contain different low molecular weight additives in their formulation, including antiozonants, plasticizers, oils, etc. These moieties – mostly paraffin wax – often migrate to the surface causing a weak boundary layer of non-rubber contaminants which is deleterious for adhesion of rubber to adhesives (such as polyurethane and polychloroprene adhesives). One of the key steps in the manufacturing of rubber/adhesive joints is the reactivation, i.e. sudden heating of the thin adhesive layers on the substrates to be joined under infrared (IR) radiation to 80–90 °C for a few seconds to allow diffusion of the polymeric chains under pressure. This reactivation may cause the migration of low molecular weight additives to the rubber surface causing a lack of adhesion. The main aim of this study was to .identify the influence of the reactivation temperature (40 to 170 °C) on the surface properties of sulphur vulcanized styrene–butadiene rubber and determine the extent of the diffusion of paraffin wax and zinc stearate to the rubber surface. The changes produced on the rubber surface were measured immediately after reactivation treatment by ethylene glycol contact angle measurements, attenuated total reflectance infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM). Additionally, the weight loss of the rubber after reactivation at different temperatures was recorded. The reactivation of the rubber at different temperatures produced changes in the morphology and thickness of the paraffin wax layer on the surface. By heating at temperature close to that of the paraffin wax melting point, the paraffin wax migration was favoured and at the same time the crystals of paraffin wax on the rubber surface were melted. As a consequence a thicker and smoother film of melting paraffin wax was formed. By increasing the reactivation temperature, a partial removal of paraffin wax was produced and the thickness of the paraffin wax film on the rubber surface was reduced. For reactivation temperatures below 90 °C, the higher the temperature, the lower the weight loss of the rubber, because the increase in the surface area of the melted paraffin wax layer that prevented migration from the rubber bulk. However, for reactivation temperature higher than 90 °C, the weight loss of the rubber increased with the reactivation temperature and this was likely due to sublimation of the paraffin wax on the rubber surface. Besides, even after reactivation at 170 °C, a thin film of paraffin wax always remained on the rubber surface as was evidenced by contact angle measurements. On the other hand, a critical reactivation temperature at 90–100 °C existed at which the migration of zinc stearate to the paraffin wax layer on the rubber surface was favoured.

Improved Adhesion of RF Plasma Treated Rubbers by Isocyanate Incorporation to Polyurethane Adhesive

AbstractThe effect of addition of isocyanate to a polyurethane adhesive has been investigated. Polyurethane adhesive was used for bonding a thermoplastic (TR) and a vulcanized (VR) synthetic butadiene‐styrene rubber. CO2 plasma treatment has oxidized the rubber surfaces, increasing surface energy (wettability), roughness, and favoring mechanical interlocking of rubber surface with the adhesive. Adhesion of TR rubber towards PU polyurethane adhesive was enhanced by these mechanisms; however, migration of antiadherent low molecular weight moieties to the VR rubber/polyurethane adhesive interface produced a lack of adhesion. In this case, it was necessary to produce the crosslinking with isocyanate of the polyurethane adhesive and of the VR rubber surface.magnified image

Strategies to improve the adhesion of rubbers to adhesives by means of plasma surface modification

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N2 plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C–O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.

Fractionation and characterisation of arabinoxylans from brewers' spent grain and wheat bran

Two agro-industrial co-products, brewers' spent grain and wheat bran, were fractionated by sequentially extracting with alkali of increasing strength. Over 60% of the brewers' grain biomass was solubilised by these treatments, compared with only 25% for wheat bran. The carbohydrate and phenolic composition of the solubilised fractions were determined, highlighting two compositionally different sets of fractions. In both co-products arabinoxylan was the main polysaccharide released. The degree of arabinose substitution of the extracted arabinoxylan diminished as the alkali strength increased. Insoluble residues contained both cellulose and non-cellulosic polysaccharides. In spent grain, the composition of the arabinoxylan in the residue was similar to that of the starting material. In wheat bran, the residual xylan was very highly substituted with arabinose. Both ferulic acid and three forms of diferulic acid (5,5′, 8- O-4′ and 8,5′) were present in the solubilised material, even after treatment with 4 M KOH. Esterified acetate was also present on polymers solubilised with KOH at concentrations up to 1 M. The more soluble fractions of spent grain represented a heterogeneous aggregation of feruloylated arabinoxylans with a broad molecular mass range, but the fractions extracted with stronger base were separated into low molecular weight moieties, presumably due to cleavage of covalent cross-links. Potential food and non-food uses for the isolated fractions from the cereal co-products are discussed.

Fractionation of UV and VUV Pretreated Natural Organic Matter from Drinking Water

Recent studies have examined the potential of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm + 254 nm) irradiation as either a pretreatment for a biological process or as a sole treatment for the removal of natural organic matter as dissolved organic carbon from drinking water. To understand the potential of UV and VUV irradiation followed by subsequent biological treatment, treated water was fractionated into four components: very hydrophobic acid (VHA), slightly hydrophobic acid (SHA), hydrophilic charged (CHA), and hydrophilic neutral (NEU). The VHA fraction was found to be very susceptible to both UV and VUV irradiation, and the fragmentation products of the high molecular weight VHA and SHA molecules contributed to the CHA and NEU fractions to form a pool of biodegradable, non-UV-absorbing, low molecular weight moieties. The NEU fraction was the most difficult to remove, as most of the components in this fraction were refractory to both the biological and photo-oxidative processes. Therefore, enhanced removal of the NEU fraction is required to increase the effectiveness and potential of the treatment process.

SURFACE MODIFICATIONS AND ADHESION OF VULCANIZED SBR RUBBER TREATED WITH RF PLASMAS OF DIFFERENT GASES

The surface modifications produced by treatment of a synthetic vulcanized styrene-butadiene rubber (R1) with oxidizing (oxygen, air, carbon dioxide) and nonoxidizing (nitrogen, argon) RF plasmas have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the treatment depended on the gas atmosphere used to generate the RF plasma. In general, acceptable adhesion values of treated R1 rubber were obtained for all plasmas, except for the nitrogen plasma treatment during 15 min, due to the creation of weak layers of low molecular weight moieties on the outermost R1 rubber layer. A toluene wiping of the 15 min N2-plasma–treated R1 rubber surface removed those moieties, and increased adhesion was obtained. On the other hand, the air, carbon dioxide, and oxygen plasmas produced ablation of the R1 rubber surface, whereas mechanical degradation was not produced by treatment with the Ar plasma.

A metabonomic investigation of hepatotoxicity using diffusion-edited 1H NMR spectroscopy of blood serum.

It has been shown extensively, that chemometric investigations of 1H NMR spectra of rat urine taken from animals dosed with model toxins produce characteristic patterns of metabolic responses and that this permits the identification of biomarkers of toxic response and regeneration. To date, metabonomic methods have been mainly optimised for urine which contains mainly low molecular weight moieties, and thus a conventional 1-dimensional 1H NMR pulse sequence is an efficient means of obtaining information-rich data. In the case of biofluids such as blood plasma or serum, which contain a wide range of macromolecules the resonances of which can overlap with peaks from small molecule metabolites, the information giving rise to sample classification can be concealed in a conventional NMR spectrum andthis presents a different analytical challenge in terms of chemometric analysis of spectral profiles. Here, the use of other types of NMR data have been investigated and it is shown that by using spectra where the peak intensities are edited according to their molecular diffusion coefficients, it is possible to improve differentiation of control animals and those treated with the model hepatotoxin, alpha-naphthylisothiocyanate (ANIT). By using diffusion-edited spectroscopy, plasma lipid moieties are less attenuated than those from small endogenous metabolites and thus the toxin-induced changes to the lipoprotein profiles are more easily detectable.

Characterisation of humic substances by acid catalysed transesterification

The chemical composition of low molecular weight moieties linked to the core structures of humic substances (HS) are of substantial importance for the understanding of the chemical structures and mode of interactions of HS with other substances in the environment. In this study a novel approach to characterise certain low molecular weight compounds bound to HS is suggested. The method includes transesterification (TE) of ester and amide bound structures, and esterification (E) of free carboxylic groups using acid catalysed methanolysis followed by gas chromatography (GC)–mass spectrometry (MS) and GC-FID analysis. Methanolysis of five HS of different origin, demonstrated the presence of multifunctional hydroxy-substituted benzoic acids, hexoses, and long chain fatty acids. Based on GC-FID and addition of the internal standard before methanolysis, the total amounts of low molecular weight material could be estimated. In case of HS from the aqueous sources the yields were below 1%, whereas in case of the HS derived from lignite the yield was significantly higher. The hydrophobic long chain fatty acids constituted about one-third of this material. Principal component analysis (PCA), which was used for extended data evaluation, differentiated between the samples in terms of chemical composition.

The effect of solvent extraction and sterilization procedure on the tissue response to Dacron ® velour

The effects of solvent extraction and sterilization procedure on tissue response to Dacron ® velour were studied in a canine model, using histomorphometrical techniques. The solvents used for extraction of low molecular weight moieties were either ethanol or water; the sterilization techniques examined were ethylene oxide (ETO) treatment, steam sterilization, and radiofrequency glow discharge (RFGD) treatment. The effect of the sterilization procedure was most marked in the outermost regions (velour) of the implant; no sterilization effects were determined in the capsule or the knitted regions. Velour in the steam sterilized implants had the smallest blood vessel dimensions compared with those that were treated with ETO or RFGD. The effects of different extraction methodologies appeared to be more significant than sterilization effects and were detected further into the implant. That is, not only were extraction effects detected in the capsule and velour, they were also detected in the outer knitted region. Extraction with water resulted in histological responses considered more biologically desirable (thinner capsule, lower giant cell presence, and larger blood vessel diameters) than responses to extraction with ethanol. Neither extraction nor sterilization effects were detected in the inner layers of the knitted region, which were adjacent to the adhesive.

Calcium speciation and exchange between blood and extrapallial fluid of the quahog Mercenaria mercenaria (L.).

Calcium and small organic molecules (e.g., tyrosine, MW 181 Da) introduced into the extrapallial fluid (EPF) of the quahog Mercenaria mercenaria exhibit rapid fluxes across the outer mantle epithelium and are distributed throughout the circulatory system within 3 h. Larger molecules (e.g., bovine serum albumin, MW 66,000 Da) are less readily exchanged between EPF and blood. The protein compositions of blood plasma and EPF are different, with at least seven protein bands expressed more prominently in the EPF. Equilibrium dialysis experiments reveal that Ca2+ constitutes only 2% of the total Ca in plasma; most of the Ca (85%) is bound to macromolecules, and the remaining 13% is present as dialyzable low molecular weight moieties. This distribution cannot be explained by speciation of inorganic Ca alone, since the MINTEQA2 equilibrium speciation model predicts that 79%-86% of the Ca should be present as Ca2+, with the remainder as CaSO4 (20%-13%). However, inclusion of a weakly Ca-binding organic molecule (log10 Ka approximately 2 M-1) into MINTEQA2 could fully reconcile modeling with experimental measurements. Results suggest that calcium transport in blood plasma and EPF is mediated by a suite of proteins and small organic ligands with a low affinity for Ca.

Common and form-specific cell wall antigens of Candida albicans as released by chemical and enzymatic treatments.

In order to investigate the antigenic properties of the proteins and mannoproteins present in the cell surface of Candida albicans, and to identify individual antigenic moieties and their distribution, a number of polyclonal antisera were obtained by immunizing rabbits with chemical and enzymatic cell wall extracts obtained from intact cells from both growth forms (yeast and mycelium) of the fungus. Prior to injection, wall moieties present in the extracts were subjected to different treatments and/or purification procedures such as adsorption onto polystyrenelatex microbeads or electrophoretic separation. When used as probes in indirect immunofluorescence assays, the different antisera gave rise to different fluorescence patterns varying in intensity and topological localization of the reactivity in C. albicans cells. When the different antisera were used as probes in Western blots of wall proteinaceous materials solubilized from both blastospores and germ tubes, differences in reactivity and specificity were readily discernible, allowing to identify a number of common and form-specific cell wall components. Of special interest was the fact that one of the antisera raised, after adsorption onto heat-killed blastospores, specifically recognized medium to low molecular weight moieties present only in the cell wall extracts from germ tubes. When this antiserum was used as probe in immunofluorescence assays, reactivity was confined to the hyphal extensions. Together, these observations seem to indicate that the different antibody preparations described in this report could represent important tools in the study of different aspects of the cell wall biology in C. albicans, including the identification and study of the distribution of common and form-specific cell wall-bound antigens.

Flow defects in linear low density polyethylene processing: Instrumental detection and molecular weight dependence

AbstractAn elongational rheometer coupled with a primary extrusion device has been used for the detection of flow limitations in the extrusion of linear low density polyethylenes (LLDPE). The shear rate for the onset of flow defects (fd) was found to decrease with increasing branch length in the LLDPE copolymer, but the severity of fd was greater in butene‐ than in hexene‐ and octene‐copolymers. Studies of partially fractionated LLDPE showed that the critical shear rate for the onset of fd was closely related to the minimum molecular weight in the distribution of molecular weights. In addition, evaluations of bond strengths in LLDPE/metal joints showed that the same molecular weight parameter significantly affected that performance criterion. In combination, the experimental findings provided confirmation of sporadic adhesive failure (slip/stick effect) as the mechanism responsible for the occurrence of observed flow defects. Its manifestation is attributable to the thermodynamic drive that promotes the preferential localization of low molecular weight moieties at surfaces and at interfaces of polyolefins such as LLDPE.

Predominance of High Molecular Weight Plasma Na+-K+-ATPase Inhibitor in Essential Hypertension

Circulating inhibitors of the transport enzyme, sodium-potassium-activated adenosine triphosphatase (Na(+)-K(+)-ATPase), have been shown to be of possible pathogenetic importance in the mechanism of essential hypertension. Although previous studies have demonstrated the presence of both high molecular weight (HMW) and low molecular weight (LMW) natriuretic plasma Na(+)-K(+)-ATPase inhibitors, no previous attempts have been made to ascertain whether HMW or LMW forms predominate in hypertension. In this study, plasma samples obtained from 26 patients with essential hypertension, 12 normotensive controls, and six normotensives with a family history of hypertension, were separated into HMW and LMW moieties by passage through a 1 kDa Amicon membrane. The LMW moiety was separated on C18 Sep-Pak cartridges, applying a 10% step-wise acetonitrile trifluoroacetic acid gradient. The HMW moiety was further separated on Sephadex G-75. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the fraction with inhibitory activity contained a distinct 12 kDa protein band, with staining intensity depending on the presence or absence of hypertension. Na(+)-K(+)-ATPase inhibitory activity was found in several LMW fractions, but differences between hypertensives and normotensives were observed in only one fraction (0.29 +/- 0.12 SD v 0.11 +/- .12 mumol/L ouabain equivalents, P < .01). Na(+)-K(+)-ATPase inhibitory activity in the HMW fraction was 38 x the inhibitory activity in the LMW fraction and was significantly increased in hypertensives as compared to normotensive controls (10.9 +/- 8.9 v 1.3 +/- 0.8 mumol/L ouabain equivalents, P < .01). Inhibitory activity in both HMW and LMW fractions correlated positively with mean blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Rheological properties of corona modified cellulose/polyethylene composites

AbstractThe rheological behavior of wood fiber/polyethylene composites made of corona treated constituents was investigated. Corona treatment of one or both of the constituents resulted in decreased melt viscosities relative to compounds containing untreated materials. The reduction of melt viscosity may originate from low molecular weight moieties formed on the surfaces of both polyethylene and cellulose during corona treatment. These may act as lubricants at interfaces. Also it was found that the corona treatment of fibers leads to higher packing volumes; this may result from a reduction in fiber length when treated fibers are processed under high shear conditions. As a result these fibers perturb the normal flow pattern in the melt to a lesser degree than the longer fibers of untreated cellulose.

Morphological responses in thermally conditioned linear low density polyethylene

AbstractAn octene‐modified linear low density polyethylene has been used to examine the mechanisms involved during thermal annealing. Annealing temperatures ranged from 60 to 100°C. Annealing results in crystallinity increments and these respond to two concurrent effects. One involves the segregation from crystalline regions of low molecular weight moieties in the polymer's molecular weight distribution; the other is lamellar thickening, leading to the formation of more highly perfected crystalline domains. In the present polymer, the two effects were found to be in balance at annealing temperatures near 80°C leading to the optimum distribution of crystalline regions in the amorphous portions of the polymer. The effect of thermal conditioning on mechanical properties of the polymer was illustrated in terms of the initial modulus and the polymer's yield strength. The twin mechanisms of molecular fractionation and lamellar thickening were found to influence both of the mechanical property parameters.

Aluminum, altered transcription, and the pathogenesis of Alzheimer's disease

The etiology of some, if not all, cases of Alzheimer's disease is linked to a mutation in the proximal portion of the long arm of chromosome 21∶21q11.2 → 21q22.2. While the functional consequences of the mutation are unknown, we speculate that one consequence of the mutation is loss of the natural barriers and intracellular ligands for aluminum. As a result, aluminum gains access to several brain sites including the nuclear compartment in certain neurons of the central nervous system.Both sporadic and familial Alzheimer's disease are associated with an increased compaction of DNA within chromatin as measured by physical shearing and resistance to digestion by micrococcal nuclease and DNase I. There is also an increase in linker histone Hl(o) content on dinucleosomes released by light (3-5% ASN) micrococcal nuclease digestion, and an increase in the affinity of histone Hl(o) for DNA as measured by a salt elution technique. The change in enzyme accessibility to chromatin also involves the 5' promoter region of at least one physiologically important gene: the gene which codes for the low molecular weight moiety of neurofilament (NF-L). The conformation change involving the 5' regulator region probably reduces transcription because the pool size of the mRNA coding for NF-L is reduced to 14% of age matched control in cerebral grey matter. Reduced transcription may account for many disorders in cellular metabolic processes including the regulation of phosphorylation, calcium homeostasis, free radical metabolism, proteolysis and neurotransmitter metabolism.The experimental evidence indicates that one important toxic action of aluminum in Alzheimer's disease neocortex is to increase the binding of histones, particularly Hl(o), to DNA which results in increased compaction of chromatin and reduced transcription. The supporting evidence includes: (1) A statistically reliable correlation between the aluminum to DNA ratio on intermediate euchromatin and the amount of highly condensed heterochromatin found in a given preparation from Alzheimer affected neocortex (Crapperet al., 1980). (2) A nine-fold increase in aluminum content in Alzheimer's disease in the di- and tri- nucleosome fraction released by light micrococcal nuclease digestion of nuclei from cerebral grey matter compared to age matched controls. Compared to age matched control dinucleosomes, the Alzheimer affected dinucleosomes contain an increased abundance of the linker histone Hl(o) and an increased proportion of DNA containing the promoter region of the gene coding for NF-L. (3) A reduction in abundance to 14% of control mRNA coding for NF-L in Alzheimer affected neocortex (Crapper McLachlanet al., 1988). (4) In vitro evidence that Alzheimer linker histones bind more tightly to DNA than control and that aluminum added to nuclei,in vitro, extracted from normal control brain, enhances DNA-protein binding of Hl and Hl(o) at concentrations found in the Alzheimer affected chromatin (Lukiwet al., 1987). (5) Application of a band retardation assay indicates that aluminum,in vitro, selectively binds human Hl(o) to a 300 bp human ALU DNA fragment from a crude extract of 5% per chloric acid soluble proteins. (6) Aluminum experimentally applied to rabbit CNS induces a marked reduction in NF-L mRNA in anterior horn cells (Mumaet al., 1988). We therefore conclude that aluminum plays a major role in the pathogenesis of Alzheimer's disease. Further understanding of the role of aluminum in Alzheimer's disease requires a detailed investigation of the precise sites of co-ordination of this trivalent metal within chromatin.

Enzymatic modification of Novikoff hepatoma lamins A and C.

A significant increase in the molecular weights of lamin A and more so of lamin C was observed when isolated Novikoff hepatoma chromatin was incubated in the presence of Ca2+. This increase did not occur to any significant degree in similar preparations of normal rat liver nuclei. Although detectable in Coomassie Brilliant Blue stained gels, this increase to a higher molecular weight (by approximately 2000 Mr) was much more visible when the electrophoretically separated lamins were transferred to nitrocellulose sheets and stained (using peroxidase-antiperoxidase) with polyclonal antiserum to the three major lamin proteins. This modification could also be induced when whole Novikoff hepatoma cell lysates were incubated in the presence of calcium. Again, this change did not occur in normal rat liver cells treated in the same manner. Further analysis has provided evidence that this modification is most likely mediated by the transaminating activity of an intrinsic nuclear transglutaminase forming a cross-link between the affected lamins and an unknown low molecular weight (approximately equal to 2000 Mr) moiety.

Hemodialysis of the rat.

A technique is described for hemodialysis of either anesthetized or non-restrained rats. In the apparatus the dialysis plates of an autoanalyzer system are used with only minor modification. The efficiency of this method has been evaluated with regard to the clearance of saccharides, both in vitro and in vivo, as well as the extraction of nitrogenous low molecular weight moieties from circulating blood. Approximately 50% of the dialyzable material was obtained in a 1-hour dialysis. Further fractionation of the dialyzate was accomplished by gel filtration (Sephadex G-25).