A study of native streptokinase and its polymeric derivative by means of small angle x-ray scattering

The gyration radius (R0) of native streptokinase (SK) was found to be R0 = (40 +/- ) A by small-angle X-ray scattering. Experimental hydrodynamic characteristics of SK were S0(20),W = (2.8 +/- 0.1)S; D0(20),W = (6.0 +/- 0.5) x 10(-7) cm2/s; [n] = 0.12 dl/g. The molecular weight of the enzyme was found to be 44,000. The values of the form factor R0/Rsphere = 2.1 and the frictional ratio f/f0 = 1.5 indicate considerable anisometry of the SK molecule. Basing on the curves of small-angle X-ray scattering of SK modified with a synthetic linear copolymer of N-vinylpyrrolidone (P) at a molar ratio SK less than P, a structural model of the conjugate was proposed. The modified form consisted of a dense nucleus covered with a diffuse polymeric membrane. In accordance with the model, R0 of modified SK and of the whole conjugate were found to be R0nucleus = (34 +/- 2) A and R0conjugate = (114 +/- 5)A.     

Characterization of four G0-type proteins purified from bovine brain membranes

Recently we reported there were at least four types of G0 or G0-like proteins in bovine brain membranes based on their elution profiles from Mono Q columns and their immunological reactivities; one of the proteins was purified as an alpha-monomeric form, and the others as alpha beta gamma-trimers. The four proteins, of which alpha-subunits were confirmed to be a family of G0-type by an immunoblot analysis, were thus referred to as alpha (0)1, G(0)2, G(0)3 and G(0)4, respectively, in order of their elutions from the column. Immunostained peptide mappings arising from proteolytic digestions of the four alpha-subunits, together with their fragmentation patterns containing radiolabeled ADP-ribose that had been incorporated by pertussis toxin-catalyzed ADP-ribosylation, suggested that the four G0-alpha were classified into either of two groups such as alpha (0)1 and G(0)2-alpha, or G(0)3-alpha and G(0)4-alpha. The kinetic parameters of their GTPase activities, however, revealed that there were different properties between alpha (0)1 and G(0)2-alpha or G(0)3-alpha and G(0)4-alpha. Thus, the four G0-type proteins appeared to be different entities from one another.     

Inclusion-induced bilayer deformations: effects of monolayer equilibrium curvature

The energetics of protein-induced bilayer deformation in systems with finite monolayer equilibrium curvature were investigated using an elastic membrane model. In this model the bilayer deformation energy delta G(def) has two major components: a compression-expansion component and a splay-distortion component, which includes the consequences of a bilayer curvature frustration due to a monolayer equilibrium curvature, c(0), that is different from zero. For any choice of bilayer material constants, the value of delta G(def) depends on global bilayer properties, as described by the bilayer material constants, as well as the energetics of local lipid packing adjacent to the protein. We introduce this dependence on lipid packing through the contact slope, s, at the protein-bilayer boundary. When c(0) = 0, delta G(def) can be approximated as a biquadratic function of s and the monolayer deformation at the protein/bilayer boundary, u(0): delta G(def) = a(1)u(0)(2) + a(2)u(0)s + a(3)s(2), where a(1), a(2), and a(3) are functions of the bilayer thickness, the bilayer compression-expansion and splay-distortion moduli, and the inclusion radius (this expression becomes exact when the Gaussian curvature component of delta G(def) is negligible). When c(0) not equal 0, the curvature frustration contribution is determined by the choice of boundary conditions at the protein-lipid boundary (by the value of s), and delta G(def) is the sum of the energy for c(0) = 0 plus the curvature frustration-dependent contribution. When the energetic penalty for the local lipid packing can be ignored, delta G(def) will be determined only by the global bilayer properties, and a c(0) > 0 will tend to promote a local inclusion-induced bilayer thinning. When the energetic penalty for local lipid packing is large, s will be constrained by the value of c(0). In a limiting case, where s is determined only by geometric constraints imposed by c(0), a c(0) > 0 will impede such local bilayer thinning. One cannot predict curvature effects without addressing the proper choice of boundary conditions at the protein-bilayer contact surface.     

Investigation of the cumulative tissue doses of naphthoquinones in human serum using protein adducts as biomarker of exposure

Both 1,2-naphthoquinone (1,2-NPQ) and 1,4-naphthoquinone (1,4-NPQ) are reactive metabolites of naphthalene that are thought to be responsible for the naphthalene-induced cytotoxicity and genotoxicity. The aim of this study was to investigate the cumulative tissue dose of 1,2-NPQ and 1,4-NPQ in human serum derived from blood donors in Taiwan via measurements of albumin adducts by a methodology, which employs trifluoroacetic acid anhydride and methanesulfonic acid to selectively cleave cysteinyl adducts on proteins. Both 1,2-NPQ and 1,4-NPQ adducts were detected in all male and female subjects (n = 22). The median levels of 1,2-NPQ adduct in human subjects were estimated to be 268 (range 139-857) and 203 (range 128-1352) (pmol/g) in male (n = 11) and female (n = 11) subjects, respectively. In contrast, the median levels of 1,4-NPQ adduct were estimated to be 45.0 (range 22.0-117) and 38.9 (range 21.5-172) (pmol/g) in male and female subjects, respectively. We noticed that levels of 1,2-NPQ adduct were significantly correlated with those of 1,4-NPQ adduct (correlation coefficient r = 0.643, p < 0.01). Results from in vitro experiments confirmed that the production of naphthoquinones-derived adducts on serum albumin increased with increased concentration of naphthoquinones (0-100 μM). Linear relationships were observed over the range of concentration. Time-course experiments suggested that both 1,2-NPQ and 1,4-NPQ-derived adducts rapidly reached maximum values at 10 min mark and remained constant thereafter. The reaction rate constant analyses indicated that the second-order rate constants, representing in vitro reactions between naphthoquinones and cysteine residues of serum albumin, were estimated to be 0.0044/0.0002 L(g protein)⁻¹ h⁻¹, respectively. Overall, the cumulative tissue doses of 1,4-NPQ (217-316 nM h) in male and female subjects were ∼3-fold greater than those of 1,2-NPQ (76-98 nM h) in the study population. The initial concentrations of serum 1,2-NPQ and 1,4-NPQ in the study population were estimated to be between 145-188 and 807-1175 nM, respectively. We conclude that the relatively large amounts of naphthoquinones present in human serum may point to toxicological consequences.     

Immobilization of catalase via adsorption onto metal-chelated affinity cryogels

A poly (acrylamide-allylglycidyl ether) [p(AAm-AGE)] cryogel was prepared by radical polymerization of acrylamide (AAm) and allylglycidyl ether (AGE). Cibacron Blue F3GA (CB) was covalently attached to the p(AAm-AGE) cryogel via the reaction between the chloride groups of the reactive dyes and the epoxide groups of the AGE. The CB-attached p(AAm-AGE) cryogel was chelated with Fe³⁺ ions. This immobilized metal ion affinity chromatography (IMAC) cryogel carrying 25.8 ± 2.0 μmol Fe³⁺ ions was used in adsorption studies to interrogate the effects of pH, protein initial concentration, flow rate, temperature and ionic strength on enzyme activity. Maximum adsorption capacities were found to be 75.7 ± 1.2 mg/g for p(AAm-AGE)-CB-Fe³⁺ cryogels and 60.6 ± 1.0 mg/g for p(AAm-AGE)-CB cryogels, respectively. The adsorbed amounts of catalase per unit mass of cryogel reached a plateau value at about 1.5 mg/mL at pH 6.0. The K_m values were found to be 0.73 ± 0.02 g/L for the free catalase and 0.18 ± 0.02 g/L for the immobilized catalase. The V_max value of free catalase (2.0 × 10³ U/mg enzyme) was found to be lower than that of the immobilized catalase (2.5 × 10³ U/mg enzyme). It was also observed that the enzyme could be repeatedly adsorbed and desorbed onto the p(AAm-AGE)-CB-Fe³⁺ cryogel.     

Developmental competence of frozen-thawed yak (Bos grunniens) oocytes followed by in vitro maturation and fertilization

In the present study, we examined the ability of immature germinal vesicle (GV) and subjected to in vitro matured (MII) yak oocytes to survive after cryopreservation as well as their subsequent development following in vitro maturation and fertilization. Both GV and MII oocytes were cryopreserved by using two different vitrification solutions (VS); VS-I contained 10% ethylene glycol (EG) and 10% dimethylsulfoxide (DMSO) in TCM-199 + 20% (v/v) fetal calf serum (FCS) whereas VS-II contained 40% EG + 18% Ficoll + 0.5 M sucrose in TCM-199 + 20% FCS. The percentage of oocytes found to be morphologically normal was greater (P < 0.01) in VS-I group than in VS-II group. Rates of cleavage (30.6–42.2%) and blastocyst formation (2.9–8.9%) did not differ among groups, but were lower than in unfrozen control (55.7% and 25.4%, P < 0.01). These results show that a combination of EG and DMSO or EG, Ficoll and sucrose can be used to cryopreserve yak oocytes in French straws.     

Comparative studies on the effects of pH and Ca2+ on bilayers of various negatively charged phospholipids and their mixtures with phosphatidylcholine.

(1) The thermotropic behaviour of dimyristoyl phosphatidylglycerol, phosphatidylserine, phosphatidic acid and phosphatidylcholine was investigated by differential scanning calorimetry and freeze-fracture electron microscopy as a function of pH and of Ca2+ concentration. (2) From the thermotropic behaviour as a function of pH, profiles could be constructed from which apparent pK values of the charged groups of the lipids could be determined. (3) Excess Ca2+ induced a shift of the total phase transition in 14 : 0/14 : 0-glycerophosphocholine and 14 : 0/14 : 0-glycerophosphoglycerol mixtures. In 14 : 0/14 : 0-glycerophosphocholine bilayers containing 16 : 0/16 : 0-glycerophosphoglycerol lateral phase separation was induced by Ca2+. (4) Up to molar ratios of 1 : 2 of 14 : 0/14 : 0-glycerophosphoserine to 14 : 0/14: 0-glycerophosphocholine, excess Ca2+ induced lateral phase separation. Addition to mixtures of higher molar ratios caused segregation into different structures: the liposome organization and the stacked lamellae/cylindrical organization. (5) Addition of excess Ca2+ to mixtures of 14 : 0/14 : 0-glycerophosphocholine and 14 : 0/14 : 0-phosphatidic acid caused, independent of the molar ratio, separation into two structural different organizations. (6) The nature of Ca2+-induced changes in bilayers containing negatively charged phospholipids is strongly dependent on the character of the polar headgroup of the negatively charged phospholipid involved.     

The carboxyl-terminal domain of murine H1(0). Immunochemical and partial amino acid sequence comparisons with other H1(0)/H1/H5 histones

The carboxyl-terminal domain of murine H1(0) histone was compared with that of human H1(0), bovine H1(0) and other H1 and H5 histones. Two sets of antibodies were induced by murine H1(0). One set reacted with only the carboxyl-terminal domain of murine H1(0) and preferred the murine over the bovine and human proteins. The second set of antibodies reacted with the globular domain of murine H1(0) and did not distinguish among murine, bovine and human H1(0) species. There were five positions in the first 60 residues of the carboxyl-terminal domain in which the murine H1(0) differed from the human H1(0). In this region, the murine H1(0) had no more than 49% overall homology with other H1 and H5 histones; however, short sequences in the domain were very similar to short sequences that occur in rabbit H1.3, trout H1 and goose or chicken H5. In comparisons based on these and other published data, the carboxyl-terminal domain of H1(0) is found to be more variable among species than is the globular domain; the first two-thirds of the H1(0) carboxyl-terminal domain is largely unique and does not show great overall homology with H1 or H5, whereas the last third is again more conserved. As the first two-thirds of the domain is the only portion where the homology with H5 is less than 50%, it may be responsible for functional differences between H1(0) and H5.     

A model of the role of natural killer cells in immune surveillance — II

The functioning of natural killer (NK) cells as immune surveillance effector cells against tumors is explored. In part I (J. Math. Biol. 12, 363-373 (1981], it was predicted that susceptible tumors would be eliminated if they have parameter lambda 0 value negative. They would not be eliminated if lambda 0 greater than 0. As the lambda 0 less than 0 result was local, one expected either that tumors of all sizes with lambda 0 less than 0 will be eliminated (global stability) or that tumor population will go to zero if in a domain of attraction of the critical point which is not all of the positive orthant. In this paper, the second is shown to be true. The general results are illustrated by a specific model.     

Conjugation of genetically engineered protein phosphatases to magnetic particles for okadaic acid detection

This work presents the functional characterisation of a protein phosphatase 2A (PP2A) catalytic subunit obtained by genetic engineering and its conjugation to magnetic particles (MPs) via metal coordination chemistry for the subsequent development of assays for diarrheic lipophilic marine toxins. Colorimetric assays with free enzyme have allowed the determination of the best enzyme activity stabiliser, which is glycerol at 10%. They have also demonstrated that the recombinant enzyme can be as sensitive towards okadaic acid (OA) (LOD = 2.3 μg/L) and dinophysistoxin-1 (DTX-1) (LOD = 15.2 μg/L) as a commercial PP2A and, moreover, it has a higher operational stability, which makes possible to perform the protein phosphatase inhibition assay (PPIA) with a lower enzyme amount. Once conjugated to MPs, the PP2A catalytic subunit still retains its enzyme activity and it can also be inhibited by OA (LOD = 30.1 μg/L).     

Unusually slow denaturation and refolding processes of pyrrolidone carboxyl peptidase from a hyperthermophile are highly cooperative: real-time NMR studies

The refolding rate of heat-denatured cysteine-free pyrrolidone carboxyl peptidase (PCP-0SH) from Pyrococcus furiosus has been reported to be unusually slow under some conditions. To elucidate the structural basis of the unusually slow kinetics of the protein, the denaturation and refolding processes of the PCP-0SH were investigated using a real-time 2D (1)H-(15)N HSQC and CD experiments. At 2 M urea denaturation of the PCP-0SH in the acidic region, all of the native peaks in the 2D HSQC spectrum completely disappeared. The conformation of the PCP-0SH just after removal of 6 M GuHCl could be observed as a stable intermediate (D(1) state) in 2D HSQC and CD experiments, which is similar to a molten globule structure. The D(1) state of the PCP-0SH, which is the initial state of refolding, corresponded to the state at 2 M urea and seemed to be the denatured state in equilibrium with the native state under the physiological conditions. The refolding of PCP-0SH from the D(1) state to the native state could be observed to be highly cooperative without any intermediates between them, even if the refolding rate was quite slow. In the higher concentration of denaturants, PCP-0SH showed HSQC and CD spectra characteristic of completely unfolded proteins called the D(2) state. The unusually slow refolding rate was discussed as originating in the conformations in the transition state and/or the retardation of reorganization in an ensemble of nonrandom denatured structures in the D(1) state.     

Immunochemical identification of coenzyme Q0-dihydrolipoamide adducts in the E2 components of the alpha-ketoglutarate and pyruvate dehydrogenase complexes partially explains the cellular toxicity of coenzyme Q0

Coenzyme Q(0) (Q(0)), a strong electrophile, is toxic to insulin-producing cells. Q(0) was incubated with rat and human pancreatic islets and INS-1 insulinoma cells, and its attachment to cellular proteins was studied with Western analysis using antiserum raised against the benzoquinone ring structure of ubiquinone (anti-Q). Q(0) covalently bonded to two proteins, one of 50 kDa and another of 70 kDa. Both proteins were found to be mitochondrial in human and rat islet cells and in many rat organs. Mitochondria were incubated with Q(0), and affinity-purified anti-Q was used to immunoprecipitate the 50-kDa protein. Amino acid sequencing identified it as dihydrolipoamide succinyltransferase, the E2 component of the alpha-ketoglutarate dehydrogenase complex (KDC). Western analysis also showed that Q bonds to the E2 components of the purified KDC and (0)the pyruvate dehydrogenase complex (PDC). Dihydrolipoamide acetyltransferase, the E2 of the PDC, has a molecular mass of 70 kDa, and the 70-kDa protein was inferred to be this enzyme. Q(0) was found to bond only to proteins containing dihydrolipoate, and in preparations of mitochondria, thiol reducing agents facilitated the attachment of Q(0), but oxidizing agents prevented it, suggesting that Q(0) bonds to thiols of dihydrolipoamide. Incubation of human or pig PDC with Q(0) followed by matrix-assisted laser desorption ionization time-of-flight and liquid chromatography/electrospray ionization mass spectrometry analyses of chymotrypsin-digested peptides of PDC E2 confirmed that Q(0) bonds to the dihydrolipoamide in these proteins. In mitochondria, coenzymes Q(1) and Q(2) did not bond to the 50-kDa protein but competed with the bonding of Q(0) to this protein. The prevention by Q(1) of characteristics the bonding of Q(0) to KDC E2, as well as other of the Q(0) effect, are reminiscent of the action of Q(0) on the mitochondrial permeability transition pore described previously (Fontaine, E., Ichas, F., and Bernardi, P. (1998) J. Biol. Chem. 273, 25734-25740).     

Analysis of the factors related with mate choice and reproductive success in male three-spined sticklebacks

Territorial three-spined sticklebacks moved 5·3 times as far as non-territorial males in 2 min ( P < 0·001) and spent 11·1 times longer in aggression in the pools ( P < 0·001). Territorial males had slightly higher condition factors than non-territorial males. Condition factor was correlated positively with the gonad mass ( P < 0·006), carotenoid concentration ( P < 0·006) and the activity of CS in the axial muscle ( P < 0·05) and lactate dehydrogenase (LDH) in pectoral muscle ( P < 0·003). The male traits best correlated positively with female mate choice were courtship effort ( P < 0·001), coloration ( P < 0·003) and initial condition ( P < 0·025). Courtship behaviour was related to intestine mass ( P < 0·018), axial ( P < 0·028) and pectoral muscle citrate synthase (CS) activity ( P < 0·047); coloration was related to gonad mass ( P < 0·037). These muscle enzymes may be involved in ATP generation for sustained activities or in recuperation between bouts of burst activity. Females that choose to mate with assiduously courting males which bear higher CS levels may be choosing individuals that show honestly their good condition and capacity to accomplish reproductive tasks.     

Elemental sulphur as an induced antifungal substance in plant defence

Man's oldest fungicide has probably long functioned in this role in plants, as a natural component of induced antifungal defence. Elemental sulphur (S(0)) is the only inorganic phytoalexin and the only phytoalexin produced by so many different taxa. S(0) (detected by GC-MS as (32)S(8)) is produced in representative species of Sterculiaceae (cocoa), Solanaceae (tomato, tobacco), Malvaceae (cotton), and Leguminosae (French bean) in response to xylem-invading fungal and bacterial pathogens. Production was more rapid and intensive in disease-resistant genotypes. Gene expression for S(0) production may be xylem-specific as S(0) was not present in leaves of six species undergoing hypersensitivity to Pseudomonas syringae. Anomalously, high constitutive S(0) levels occurred in leaves of Arabidopsis and Brassica oleracea. S(0) was highly toxic (ED(50) 1-3 microg ml(-1)) to many fungal pathogens representing ascomycetes, basidiomycetes, and deuteromycetes, but not to an oomycete, Phytophthora, or to bacteria. Levels in cocoa and tomato xylem and Arabidopsis leaves were potentially inhibitory, but in other interactions were below theoretically toxic concentrations. However, S(0) accumulation is highly localized, suggesting that the element is produced in sufficient amounts, at the right time and place to be effective. SEM-EDX revealed S in tomato and cocoa xylem walls, xylem parenchyma, and vascular gels and tyloses, all sites appropriate to counter vascular pathogenic Verticillium dahliae. Transient increases in sulphate, glutathione and cysteine occurred in tomato xylem. The sulphate may reflect the over-expression of sulphate transporters, but the thiols might be possible precursors. Analysis of differential gene expression should reveal what may be a novel biosynthetic pathway of S(0) formation in eukaryotes.     

Differential response of cycling and noncycling cells to inducers of DNA synthesis and mitosis

The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment.     

Regulation of Triacylglucose Fatty Acid Composition (Uridine Diphosphate Glucose:Fatty Acid Glucosyltransferases with Overlapping Chain-Length Specificity)

UDP-glucose (UDP-Glc):fatty acid glucosyltransferases catalyze the UDP-Glc-dependent activation of fatty acids as 1-O-acyl-[beta]-glucoses. 1-O-Acyl-[beta]-glucoses act as acyl donors in the biosynthesis of 2,3,4-tri-O-acylglucoses secreted by wild tomato (Lycopersicon pennellii) glandular trichomes. The acyl composition of L. pennellii 2,3,4-tri-O-acylglucoses is dominated by branched short-chain acids (4:0 and 5:0; approximately 65%) and straight and branched medium-chain-length fatty acids (10:0 and 12:0; approximately 35%). Two operationally soluble UDP-Glc:fatty acid glucosyltransferases (I and II) were separated and partially purified from L. pennellii (LA1376) leaves by polyethylene glycol precipitation followed by DEAE-Sepharose and Cibacron Blue 3GA-agarose chromatography. Whereas both transferases possessed similar affinity for UDP-Glc, glucosyltransferase I showed higher specificity toward short-chain fatty acids (4:0) and glucosyltransferase II showed higher specificity toward medium-chain fatty acids (8:0 and 12:0). The overlapping specificity of UDP-Glc:fatty acid glucosyltransferases for 4:0 to 12:0 fatty acid chain lengths suggests that the mechanism of 6:0 to 9:0 exclusion from acyl substituents of 2,3,4-tri-O-acylglucoses is unlikely to be controlled at the level of fatty acid activation. UDP-Glc:fatty acid glucosyltransferases are also present in cultivated tomato (Lycopersicon esculentum), and activities toward 4:0, 8:0, and 12:0 fatty acids do not appear to be primarily epidermal when assayed in interspecific periclinal chimeras.     

Aspartate modulates the circadian patterns of a few biochemical variables in Wistar rats

D-aspartate was used to demonstrate possible sources of excitatory input to the suprachiasmatic nucleus (SCN) in rats. Aspartate (50 mg/kg bodyweight) was orally administrated chronically for 60 days to Wistar rats and 24 h rhythmic patterns of glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under light - dark (LD 12:12 h) cycle. Our results showed acrophase advances in glucose and delays in cholesterol and AST rhythms. Increased mesor and altered amplitude values were found in all rhythms; aspartate levels in the brain were found to be significantly increased in aspartate treated animals. We hypothesised that the altered biochemical rhythms in aspartate treated rats could be due to (1) modulation of neurotransmission in SCN, (2) behavioural rhythms and (3) feeding rhythms.     

Polysaccharides as potential antioxidative compounds for extended-release matrix tablets

The objective of this study was to identify polysaccharides with antioxidant properties for use as potential antioxidative compounds for extended-release matrix tablets. The antioxidant properties of five different polysaccharides, high molecular weight alginate (H-ALG), low molecular weight alginate (L-ALG), high molecular weight chitosan (H-chitosan), low molecular weight chitosan (L-chitosan), and pectic acid (PA) were examined using N-centered radicals from 1,1′-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and reducing power, based on their ability to reduce Cu²⁺. L-chitosan and PA had acceptable scavenging abilities and were good radical scavengers, with good reducing power, but the H-chitosan and alginate derivatives were much less effective. The results suggest that L-chitosan and PA could be useful in combating oxidative stress. A PA and L-chitosan interpolymer complex (IPC) tablet was prepared and evaluated as an extended-release tablet matrix using theophylline (TPH) as a model drug. The release of TPH from the matrix tablet (TPH/PA/L-chitosan = 200 mg:150 mg:50 mg) was slower than that from PA only (TPH/PA/chitosans = 200 mg:200 mg:0 mg) or L-chitosan only (TPH/PA/L-chitosan = 200 mg:0 mg:200 mg) tablet. Turbidity measurements also indicated the optimum complexation ratio for IPC between PA/L-chitosan to be 1/3, indicating an acceptable relationship between the turbidity of the complex and the release ratio of TPH. These results suggest that an L-chitosan/PA complex would be potentially useful in an extended-release IPC tablet with high antioxidant activity.     

Relationship of H1(0) histone to differentiation and cancer

The H1(0) histone was first described by Panyim and Chalkley in 1969 as a new electrophoretic band found with histones of non-replicating tissues. Tissues which are active in DNA replication such as ascites tumor cells or thymus cells were reported to lack this band. In this respect the H1(0) histone differs from the bulk of histones which are generally maintained in a constant ratio with respect to each other and to DNA. An inverse relationship between H1(0) histone levels and growth rate was suggested by the decrease in H1(0) histone concentration during regeneration of the pancreas and liver. The synthesis of H1(0) is unusual but not unique in that, unlike the major histone species, it is not restricted to the S phase of the cell cycle. Although there is a general trend for the levels of H1(0) histone to be lower in neoplastic than normal tissues, exceptions have been observed. Compounds such as sodium butyrate and dimethylsulfoxide, which can induce differentiated properties in neoplastic cells, can bring about the accumulation of increased amounts of H1(0) histones. The relative magnitude of these effects exhibits cell-type specificity. There are two H1(0) histone subtypes (a and b) with ratios which differ according to the tissue examined and whose relative importance is not known. The levels of H1(0) histone appear to be more closely related to the degree of differentiation than to the proliferative activity of cells.