[Hepatic ultrasonographic imaging and serum amino acid levels in cured schistosomiasis cases]

Ultrasonography (B mode) of liver and serum amino-acid levels were studied in 15 cases of schistosomiasis japonica who had been cured for more than 5-15 years. Typical B-ultrasonic images of hepatic fibrosis due to schistosomiasis were found in all patients which could be classified into three types, namely, the spotty type (I), the tortoise-shell type (II) and the net-patchy type (III) according to the patterns of echogenic bands. Moderate to marked echogenic thickening of portal vein wall, and dilation of portal and splenic veins were revealed in patients with type II and III images. Free amino acids in sera were determined by using HPLC-AAAS. The result revealed that the concentration of 8 nonessential and 3 essential amino acids (threonine, valine, tryptophan) were significantly decreased in the 15 patients. The ratio of aromatic to aliphatic amino acid was markedly elevated in 3 patients of type III. The serum amino acid imbalance was attributed to the severe hepatic damage and impaired liver function.

Emulsification and fatty acid chain length affect the kinetics of [14C]-medium-chain triacylglycerol utilization by neonatal piglets

In vivo oxidation kinetics of medium-chain triglycerides (MCT) composed of [1-14C]hexanoate (tri-6:0) or [1-14C]octanoate (tri-8:0) were compared after being fed to day-old piglets (1.4 kg; n = 4/treatment). Animals were fitted with arterial and oro-gastric catheters and placed into respiration chambers held at 35 degrees C. The radiolabeled MCT were fed in equimolar amounts (6.5 mmol/kg0.75), in either nonemulsified form or as 30% (v/v) emulsions, using polyoxyethylene sorbitan monooleate as an emulsifier. Expired CO2 was quantified and specific radioactivity (Bq/mumol) determined at 20-min intervals over 24 h, and serial blood samples were drawn for measurement of plasma hexanoate and octanoate by HPLC. The rate [mumol/(h.kg0.75)] and extent (mmol/kg0.75) of MCT oxidative utilization (i.e., composite of digestion, absorption and oxidation) were calculated from the kinetics of 14CO2 expiration. Emulsification increased both the rate and extent of MCT oxidative utilization by > 20% regardless of fatty acid chain length (P < 0.05). Maximal MCT oxidation rates occurred at 3.5 h after feeding and were sufficient to meet up to 48% of the piglets' energy expenditure. The maximal rate of tri-6:0 oxidative utilization exceeded that of tri-8:0 by 37% (P < 0.05), but the extent of utilization was not affected by fatty acid chain length. Plasma medium-chain fatty acid concentrations were in agreement with these observations, being higher in pigs fed emulsified MCT than in pigs fed nonemulsified MCT (P < 0.05) and being higher in pigs fed tri-6:0 than in animals fed tri-8:0 (P < 0.05). Collectively, these data demonstrate that newborn piglets can effectively digest, absorb and oxidize MCT, that utilization is improved with emulsification, and that tri-6:0 is utilized more rapidly than tri-8:0.

Use of k0-NAA in the life sciences

The applicability and usefulness of k0-based reactor neutron activation analysis (NAA) in the life sciences is evaluated from the following examples: 1. Instrumental NAA of NIST SRM 1633a coal fly ash, as a quality assessment; 2. Radiochemical NAA of Versieck's reference human serum, and--herewith associated--the development of practical correction procedures for neutron-induced reaction interferences and of improved methods to evaluate the detection efficiency and the correction for true coincidence; and 3. Determination of the lanthanides in plant leaves and lichens near a Portuguese coal-fired power station, which led to the introduction of the Westcott formalism and to the use of a low-energy photon detector. As concluded, k0-based NAA is at present capable of tackling a large variety of analytical problems when it comes to the multielement determination in environmental and biological matrices.

An epidemiological model for HIV/AIDS with proportional recruitment

A model for HIV transmission is formulated for a homosexual population of varying size, with recruitment into the susceptible class proportional to the active population size and with stages of progression to AIDS. Analysis of this model includes identifying the threshold that determines whether the disease dies out or proportions remain endemic and establishing criteria that determine whether the population size decays asymptotically exponentially to zero or grows asymptotically exponentially to infinity. In an analogous heterosexual model, the conservation of heterosexual contacts is shown to imply that this two-sex model reduces to the one-sex model.

[Clinical analysis of 160 cases with the magnetic foreign bodies in the posterior segment of the eye]

One hundred and sixty cases of magnetic foreign bodies in the posterior segment of the eye are reported. Most of the foreign bodies are small (61.2% are less than 2mm) and near the wall of the eye (73.7% are less than 2mm). 110 cases were successfully operated in conventional way and just 20 cases needed to have vitrectomy. The result of the operation depends on the damage of the eye, location of the foreign body and the complication of the operation. In 77.6% of the cases, the wound was on the cornea or limbus. That is one of the important factors to affect the patients' postoperation vision.

Effects of maternal dietary n-3 and n-6 fatty acids (pre- and post-delta 6 desaturation) on tissue glycerophospholipid fatty acid compositions in dams and suckling mice

The present study examined the effects of supplementation of either 18:3n-3 or a mixture of its post-delta 6-desaturation metabolites, 20:5n-3/22:6n-3, in combination with either 18:2n-6 or its immediate delta 6-desaturation product, 18:3n-6, in the maternal diet (n-3 to n-6 ratio at 0.25) on brain, liver, heart, and kidney glycerophospholipid fatty acid composition in dams (B6D2F1 mice) and their 12-day-old suckling pups. As expected, n-3 and n-6 fatty acids competed for incorporation into tissue glycerophospholipids in both dams and their suckling pups. Feeding a 20:5n-3/22:6n-3 as compared with an 18:3n-3 rich diet increased the tissue levels of 20:5n-3 and 22:5n-3, whereas it decreased those of 20:3n-6 and 20:4n-6. Replacing 18:2n-6 with 18:3n-6 in the maternal diet increased significantly the levels of 18:3n-6, 20:3n-6, and 20:4n-6, whereas it reduced those of 20:5n-3. However, the effects of maternal dietary fats on tissue fatty acid compositions in pups were qualitatively similar to but quantitatively smaller than those in dams. The discrepancy might be due to differences in the composition of fatty acids taken up and synthesized by the dams and that transferred to the pups.

Voltage-dependent block by neomycin of the ATP-induced whole cell current of guinea-pig outer hair cells

1. The effects of externally applied ATP and neomycin on whole cell currents of isolated guinea pig cochlear outer hair cells (OHCs) were studied using the whole cell voltage-clamp technique. In OCHs held at -70 mV, ATP activated a large inward current. In the presence of neomycin, the ATP-induced whole cell current activated along a relatively unaltered time course, but the current then decreased to a reduced steady level. The neomycin inhibition of the ATP-induced current was dose dependent. The half-inhibitory concentration (IC50) of neomycin measured at steady state was estimated to be 90 microM. 2. Neomycin inhibition of the ATP response could not be reversed by increasing the concentration of ATP, indicating that the effect was noncompetitive. The inhibition was voltage dependent and was greatly reduced when OHCs were held at positive potentials. 3. Cells treated with 100 microM ATP gave maximal current responses. Addition of neomycin substantially increased membrane current noise of the 100 microM ATP responses. When neomycin concentration was varied from 10 to 500 microM, the current noise level peaked between 50 and 100 microM. The noise increase was observed at negative holding potentials but not at positive potentials. 4. The neomycin-induced whole cell current noise was used to estimate the size of the underlying elementary current. The ATP-induced single channel current of OHCs at -70 mV was estimated to be approximately 0.3 pA. The number of ATP-activated channels in a single OHC was estimated to be in the range of a few thousand. 5. The characteristics of the neomycin inhibition of ATP-induced currents were consistent with an open channel blocking mechanism. Analysis of the voltage dependence of the steady state neomycin inhibition suggested a neomycin binding site at an electrical distance of 0.3 from the extracellular side.

Recombinant canditropsin, an extracellular aspartic protease from yeast Candida tropicalis. Escherichia coli expression, purification, zymogen activation, and enzymic properties

A cDNA fragment which encodes the zymogen of canditropsin, the extracellular aspartic protease from the yeast Candida tropicalis (Togni,G., Sanglard, D., Falchetto, R., and Monod, M. (1991) FEBS Lett. 286, 181-185) was cloned into a T7 expression vector for the synthesis of the recombinant zymogen in Escherichia coli. Recombinant canditropsinogen (Ctg), which was expressed as inclusion bodies in the cytosol of E. coli, was refolded by dialysis from an 8 M urea solution and purified to homogeneity using chromatographies on Sephacryl S-300 and on MonoQ columns. The purified Ctg was converted into canditropsin by either acid activation or trypsin conversion. The specificity of the resulting recombinant canditropsin toward polypeptide substrates is significantly different from other aspartic proteases. Canditropsin hydrolyzes oxidized insulin B chain between Ala-Leu and many other minor cleavage sites. Canditropsin also hydrolyzes keratin and collagen, which are components of connective tissues known to be hydrolyzed by canditropsin during Candida infections. Canditropsin was strongly inhibited by the universal aspartic protease inhibitor pepstatin (Ki = 1.75 x 10(-8) M) and inactivated by two aspartic protease inactivators, DAN and EPNP. Canditropsin is weakly inhibited by leupeptin and antipain, with an apparent Ki of 1.74 x 10(-4)M and 1.5 x 10(-5) M, respectively.

[A study on P21(ras) in human lung cancer and body fluid of cancer patients]

The McAb of anti-P21(ras) has been used to screen 9 cases of human lung cancer tissues, 18 cases of samples and 2 cases of hydrothorax samples of lung cancer patients by means of PAGE-immunoblots. The expression of ras gene was found in 8 cases of human lung cancer among which the expression of 4 cases was higher than that of normal control. P21(ras) has not been detected in serum and hydrothorax samples of cancer patients. The present study indicated that there was P21(ras) in human lung cancer and normal control and the expression level of ras gene in lung cancer was related to the differentiation of cancer.

Conformational instability of the N- and C-terminal lobes of porcine pepsin in neutral and alkaline solutions

Pepsin contains, in a single chain, two conformationally homologous lobes that are thought to have been evolutionarily derived by gene duplication and fusion. We have demonstrated that the individual recombinant lobes are capable of independent folding and reconstitution into a two-chain pepsin or a two-chain pepsinogen (Lin, X., et al., 1992, J. Biol. Chem. 267, 17257-17263). Pepsin spontaneously inactivates in neutral or alkaline solutions. We have shown in this study that the enzymic activity of the alkaline-inactivated pepsin was regenerated by the addition of the recombinant N-terminal lobe but not by the C-terminal lobe. These results indicate that alkaline inactivation of pepsin is due to a selective denaturation of its N-terminal lobe. A complex between recombinant N-terminal lobe of pepsinogen and alkaline-denatured pepsin has been isolated. This complex is structurally similar to a two-chain pepsinogen, but it contains an extension of a denatured pepsin N-terminal lobe. Acidification of the complex is accompanied by a cleavage in the pro region and proteolysis of the denatured N-terminal lobe. The structural components that are responsible for the alkaline instability of the N-terminal lobe are likely to be carboxyl groups with abnormally high pKa values. The electrostatic potentials of 23 net carboxyl groups in the N-terminal domain (as compared to 19 in the C-terminal domain) of pepsin were calculated based on the energetics of interacting charges in the tertiary structure of the domain. The groups most probably causing the alkaline denaturation are Asp11, Asp159, Glu4, Glu13, and Asp118.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular diversion of glycoprotein GP160 of human immunodeficiency virus to lysosomes as a strategy of AIDS gene therapy

A potential gene therapy strategy against human immunodeficiency virus (HIV-1) is to disrupt the intracellular transport of viral proteins. We report here the binding and transporting of HIV-1 glycoprotein gp160 to lysosomes as a result of the expression of fusion genes consisting of soluble CD4 and lysosome targeting domains. The effective lysosome targeting domain tested includes a lysosomal protease zymogen, procathepsin D, and the COOH-terminal domains of three lysosome membrane proteins: lamp-1, lamp-2, and lysosomal acid phosphatase. We demonstrated that cell fusion (syncytium), caused by the transport of gp160 to the surface of HeLa-CD4+ cells, was completely abolished by the expression of these fusion genes. The lysosomal localization of gp160 in HeLa cells coexpressing CD4-fusion genes was also established. From pulse-chase experiments, we observed that gp160 and the fusion proteins were degraded, as expected of lysosomal activities. Additionally, T lymphoblastoid cells transiently and permanently expressing these fusion genes strongly retarded the propagation of human immunodeficiency virus type 1. Thus, these fusion genes can deprive HIV of newly synthesized envelope protein gp160 for the assembly of new virions and are potentially useful in gene therapy against AIDS.

Molecular analysis of HLA-DR beta and DQ beta polymorphism in Chinese with rheumatoid arthritis

OBJECTIVES

Several studies have suggested that genetic predisposition to rheumatoid arthritis may be related to the presence of specific polymorphic HLA sequences that are often associated with HLA-DR4 haplotypes. This study was performed to determine if an association exists between Chinese with rheumatoid arthritis and a particular HLA-DR beta or DQ beta subtype.

METHODS

This study used the polymerase chain reaction to amplify HLA-DR beta and DQ beta genes, and oligonucleotide probe hybridisation to examine the association of certain polymorphic sequences with rheumatoid arthritis in 23 Chinese patients from Shanghai.

RESULTS

An HLA-DR4 associated sequence was significantly increased in the Chinese patients (43%) compared with healthy controls (14%) from the same location (relative risk = 4.6, 95% confidence limits 1.1 to 19.3). Analysis of the third hyperpolymorphic region of DR4 positive samples was performed to detect polymorphic sequences associated with Dw4, Dw10, Dw13, Dw14, Dw15, and KT2 cellular specificities. Examination of this region showed that 91% of patients had sequences encoding amino acids QRRAA (associated with Dw14 and Dw15) or QKRAA (associated with Dw4) compared with 64% of the DR4 positive controls.

CONCLUSIONS

Rheumatoid arthritis in the Chinese is associated with HLA-DR4. There is a possible relationship between sequences within the third hyperpolymorphic region of the DRB allele and rheumatoid arthritis in the Chinese.

Utilization of medium-chain triglycerides by neonatal pigs: effects of emulsification and dose delivered

Four trials were conducted using 86, 24-h-old pigs to evaluate the utilization of medium-chain triglycerides (MCT). Effects of emulsification and amount of MCT fed were examined. After a 4-h period during which feed was withheld, pigs were force-fed MCT (containing 75% octanoate and 25% decanoate), marking time 0 of the experiment. Blood samples were obtained at 1 and 2 h for subsequent medium-chain fatty acid (MCFA) analysis. In Trials 1 (six pigs/treatment) and 2 (four pigs/treatment) the response to three emulsifying agents was compared to a nonemulsified (NE) control. Twenty milliliters of a 30% (vol/vol) emulsion of MCT or 6 mL of NE MCT was administered. Concentrations of MCFA at 1 h in pigs receiving a Tween 80 (polyoxy-ethylene [20] sorbitan monooleate) emulsion were 3- to 19-fold higher than concentrations in animals administered a gum arabic/gum tragacanth emulsion, a lecithin emulsion, or NE MCT. Trials 3 (eight pigs/treatment) and 4 (six pigs/treatment) were conducted to determine the plasma MCFA concentrations resulting from feeding increasing levels of NE (3, 6, 9, or 12 mL of MCT) or emulsified MCT oil (2, 4, 6, or 8 mL in a 30% Tween 80 emulsion). Plasma octanoate concentrations measured at 1 h increased linearly (P < .05) with increasing MCT dosage through 9 mL of NE and 6 mL of emulsified MCT. A transient narcosis was observed in 8 of 12 animals that received 6 or 8 mL of emulsified MCT and was most pronounced 1 to 2 h after feeding, which roughly corresponded to peak plasma MCFA concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Emulsification and fatty-acid chain length affect the utilization of medium-chain triglycerides by neonatal pigs

Three experiments were conducted using 52 pigs between 22 and 35 h of birth to determine the effects of emulsification and fatty-acid chain length on utilization of medium-chain triglycerides (MCT). After a 4-h period during which feed was withheld, pigs were force-fed 6 mL of nonemulsified (NE) MCT or 20 mL of a 30% (vol/vol) Tween 80-(polyoxy-ethylene [20] sorbitan monooleate) MCT emulsion, marking time 0, and serial blood samples were drawn throughout 8 h for analysis of medium-chain fatty acid (MCFA) concentrations by HPLC. In Exp. 1, pigs received either NE or emulsified Tri-C4, -C5, -C6, or -C7. The emulsified treatments were discontinued due to deaths caused by coma resulting from high concentrations (up to 12 mM) of plasma MCFA. Concentrations in pigs fed emulsified MCT were 2.5-fold higher than those in pigs fed NE MCT. In pigs fed NE MCT, concentrations of even-chain-length MCFA were higher than those of odd-chain-length MCFA (P < .001), with a tendency for C6 to be higher than C4 (P < .1). In Exp. 2 and 3, pigs received an equimolar mixture of MCT in either emulsified or NE form. In Exp. 2, the mixture contained Tri-C4 through Tri-C7; whereas, in Exp. 3 the mixture contained Tri-C4, -C6, -C8, and -C10. A three-way interaction (emulsion x fatty acid x sample time; P < .05) was observed in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Superoxide production by neutrophils from diabetics and normal subjects in response to glucose and galactose

Glucose added to the medium was found to enhance superoxide production by isolated circulating neutrophils from both diabetic and normal subjects, but quantitatively the enhancement decreased from 4 to 50 mmole/liter. Galactose up to 50 mmole/liter had no effect on superoxide production in cells from the control subjects, but appeared to depress it in those from diabetics. No correlations were found between indices of the degree of hyperglycemia (plasma glucose and hemoglobin A1c) and the magnitude of the respiratory burst in cells from diabetics. When the isolated cells from normal and diabetic subjects were restored to a medium containing glucose at the original concentration in plasma at phlebotomy, the rate of superoxide production was approximately doubled in every case and there was no significant difference between diabetic and normal cells. Preincubation of cells for 1 hr in the presence of 0-50 mmole/liter glucose or galactose prior to activation had no significantly depressant effect on the respiratory burst except at 50 mmole/liter glucose in diabetic cells. It is concluded that circulating neutrophils from the diabetic population under the conditions studied are just as competent as control cells in their ability to sustain superoxide production over a wide range of energy availability.

[Studies on percutaneous absorption of ruyi jinhuang san patcher with radioisotope tracer]

Berberine is one of the active ingredients in Ruyi Jinhuang San Patcher. With 3H-berberine as the tracer, a radio-labelled method was used for determining percutaneous rate and drug concentration of berberine in plasma in vivo and in vitro. A study on the percutaneous rate of different technological plasters and various animal skins was also carried out.

Buckytubes and Derivatives: Their Growth and Implications for Buckyball Formation

Transmission electron microscopy (TEM) observations of graphite tubules (buckytubes) and their derivatives have revealed not only the previously reported buckytube geometries but also additional shapes of the buckytube derivatives. Detailed cross-sectional TEM images reveal the cylindrical cross section of buckytubes and the growth pattern of buckytubes as well as their derivatives. These observations of frozen growth stages of buckytubes and derivatives suggest a helical growth mechanism analogous to that of crystal growth via screw dislocations. The helicacy of buckytubes is analyzed by electron diffraction whereas the anisotropy of electronic structure is revealed by momentum transfer resolved electron energy loss spectrometry. Based on the TEM observations, it is proposed that buckytubes act as precursors to closed-shell fullerene (buckyball) formation and the possible steps in buckyball formation are outlined. In arc evaporation experiments in which residue rods (containing various amounts of buckytubes) were used as the starting anode for fullerene production, the amount of buckytubes in the rod was correlated with fullerene yield.

Effect of salt-loading and spontaneous hypertension on in vitro metabolism of [1-14C]linoleic and [2-14C]dihomo-gamma-linolenic acids

The present study compared the effect of spontaneous hypertension and salt-loading on in vitro metabolism of 18:2n-6 (linoleic acid) and 20:3n-6 (dihomo-gamma-linolenic acid). Ten weanling spontaneously hypertensive rats (SHR) and 10 normotensive Wistar-Kyoto rats (WKY) maintained on a rodent lab chow were given tap water with (n = 5) or without (n = 5) addition of 1% NaCl for 4 weeks. Thereafter, animals were killed and liver microsomes were prepared. Aliquots of microsomes suspended in the phosphate-sucrose buffer containing MgCl2, ATP, CoA, and NADPH were incubated with 0.3 microCi of [1-14C]-18:2n-6 or [2-14C]-20:3n-6 at 37 degrees C for 15 min. The activity of delta 6- and delta 5-desaturases, and the distribution of radioactivity in different lipid fractions and in phospholipid fatty acids were determined. Results showed that both spontaneous hypertension and salt-loading suppressed the desaturation of radiolabeled 18:2n-6 and of 20:3n-6. Incubation of microsomes with [1-14C]-18:2n-6 resulted in 29% of radioactivity being associated with phospholipid fraction, of which 3% was associated with 18:3n-6. Incubation with radiolabeled 20:3n-6 resulted in 30% of the radioactivity being incorporated into phospholipids, of which 50% was associated with 20:4n-6 (arachidonic acid). Salt-loading suppressed the incorporation of radiolabeled fatty acids into phospholipids, more so in SHR than in WKY. Thus, salt-loading not only suppressed the desaturation of 18:2n-6 and 20:3n-6, but also interfered with the acylation of n-6 fatty acids into the phospholipid fraction.

Functional analysis of the human platelet-derived growth factor A-chain promoter region

The platelet-derived growth factor (PDGF) A-chain gene is a developmentally regulated gene that is expressed in high levels in a limited number of normal and transformed cell lines and in cells stimulated by cytokines, including PDGF itself. We have now analyzed potential regulatory elements in 3.6 kilobase pairs (kb) of the 5'-flanking sequences of the human PDGF A-chain gene using reporter gene constructs and transient transfection analyses. The region between base pairs (bp) -618 and +392 (relative to the transcription initiation site) is sufficient for optimal promoter activity. A highly G + C region containing three contiguous Sp1 binding sites between bp -150 and -33 contributes over 80% of promotor activity. DNase I footprinting analyses indicates that Sp1 binds to and protects over 57 bp of this G + C region. A functional serum response element is located within bp -477 and -468 and positively regulates induction of PDGF A by PDGF. A negative regulatory (silencer) element is located from -1.9 to -0.9 kb. The results suggest that the major constitutive expression of the PDGF A-chain gene requires a highly G + C-rich region containing three Sp1 binding sites and that induction of the PDGF A-chain gene by PDGF is mediated by a SRE located at bp -477 to -468.

Potentiation of sodium chromate(VI)-induced chromosomal aberrations and mutation by vitamin B2 in Chinese hamster V79 cells

The effect of vitamin B2, which is capable of reducing chromium(VI) to chromium(V), on chromosomal aberrations and mutation caused by Na2CrO4 was investigated in Chinese hamster V79 cells. Pretreatment with 200 microM vitamin B2 (riboflavin) for 24 h prior to exposure to Na2CrO4 (2.5-5 microM) resulted in an increase of metal-induced chromosomal aberrations and mutation at the HGPRT locus. These and other previous studies suggest that vitamin B2 enhances the clastogenic and mutagenic action of chromate compounds, through its ability to directly reduce chromium(VI) in cells.

DQB1-0602 (DQw1) is not present in most nonDR2 Caucasian narcoleptics

Human narcolepsy is a genetically determined disorder of sleep strongly associated with the human leucocyte antigens (HLA) DR2 and DQw1. In black narcoleptic patients, susceptibility for narcolepsy is more closely related to a specific gene subtype of DQw1, DQB1-0602, than to DR2. About 30% of black narcoleptic patients are nonDR2, but all carry the HLA DQB1-0602 gene. In the present study, we have tested caucasian nonDR2 cataplectic patients (6 sporadic cases and 7 familial cases from 3 multiplex families) for the presence of the HLA DQB1-0602 and DQA1-0102 (DQw1) using a specific polymerase chain reaction (PCR)-oligotyping technique. None of the patients was DQB1-0602 or DQA1-0102 positive, thus proving that, in caucasians, DQB1-0602 and DQA1-0102 (DQw1) are not prerequisites for the diagnosis of narcolepsy. Further studies with more patients are warranted to exclude the possibility that a few caucasian patients carry rare haplotypes with DQB1-0602 independently of DR2.

Analysis of residual amino acid--DNA crosslinks induced in intact cells by nickel and chromium compounds

Chinese hamster ovary cells were incubated with radioactive amino acids, the DNA was isolated by standard proteinase K/phenol/chloroform extraction and residual amino acids complexed to the DNA were examined as an index of metal induced DNA-protein crosslinks. Using this method, both chromate and nickel caused residual histidine and cysteine to be complexed with the DNA isolated from metal-treated cells. In the case of chromate, a number of amino acids were studied and Tyr, Thr and Cys were found to be complexed to DNA at a level (above the untreated control) that was statistically significant. Stability studies indicated that some of the chromate-induced DNA-protein complexes were mediated by direct participation of chromium(III), whereas others that were resistant to dissociation by EDTA and mercaptoethanol did not seem to involve direct chromium(III) participation. A significant portion of the cysteine complexed to DNA by chromate was believed to involve glutathione since treatment of cells with cycloheximide did not decrease chromate-induced cysteine-DNA crosslinks. In the case of nickel, most of the stable DNA-protein crosslinks did not involve direct metal participation and were probably oxidatively mediated by Ni(II)/Ni(III) redox cycling. These findings present new methodology for analysis of DNA-protein crosslinks by examination of residual amino acids associated with the DNA. This method should be highly sensitive and will yield important information about the mechanism of metal-induced DNA-protein crosslinks.

pH dependence of kinetic parameters of pepsin, rhizopuspepsin, and their active-site hydrogen bond mutants

The pH dependence of the kinetic parameters of pepsin, rhizopuspepsin, and their active-site hydrogen bond mutants has been determined. These data have permitted the calculation of two active-site ionization constants in the free enzymes (pKe1 and pK32) and in the enzyme-substrate complexes (pKes1 and pKes2). The pKe1 of rhizopuspepsin (2.8) is near that of a normal carboxyl group and near the pKe1 of human immunodeficiency virus type 1 (HIV-1) protease (3.32) (Ido, E., Han, H. P., Kezdy, F. J., and Tang, J. (1991) J. Biol. Chem. 266, 24359-24366). The pKe1 of pepsin (1.57) is thus abnormally low. The pKe2 of rhizopuspepsin (4.44) is lower than that of pepsin (5.02) and HIV protease (6.80). The binding of substrate to rhizopuspepsin causes the lowering of pKes1 to 1.8 and the elevating of pKes2 to above 6. The pK alpha shifts due to substrate binding are much less pronounced in pepsin. Thus, the two enzyme-substrate complexes have similar pK alpha values. For both pepsin and rhizopuspepsin, the removal of hydrogen bonds to the active-site carboxyls by mutagenesis results in negligible changes in the four pK alpha values. The major alteration caused by these mutations is the decrease in kcat values, while there is little change in Km. These observations suggest that these hydrogen bonds to the active-site aspartyls contribute little to the pH-activity relationships of the aspartic proteases. The role of the active-site hydrogen bonds may well be to preserve the conformational rigidity of the catalytic apparatus.

Effect of dietary linoleic acid content on the distribution of triacylglycerol molecular species in rat adipose tissue

The present study examined the effect of varying dietary linoleate intake (0.01, 0.24, 2.4, 24, 80 or 160 g/kg diet) for 24 weeks on the distribution of triacylglycerol (TG) molecular species in rat epididymal adipose tissue. Adipose TG fractions were purified by thin-layer chromatography and separated into different molecular species by reverse-phase high-performance liquid chromatography. The identification of TG species was based on fatty acid composition, retention time and the theoretical carbon number. When the dietary 18:2n-6 content was equal to or less than 24 g/kg, no significant amounts of n-6 fatty acids (mainly 18:2n-6) were observed in adipose tissue TG despite the fact that the levels of 20:4n-6 in liver phospholipids increased significantly. There were 12 major molecular species in adipose tissue when the dietary 18:2n-6 content was less than 2.4 g/kg. When the dietary 18:2n-6 content reached 24 g/kg, an additional six TG species containing one, two or three molecules of 18:2n-6 were observed. The levels of TG molecules containing two or three 18:2n-6 residues were further increased when the diet contained very large amounts of linoleic acid (160 g/kg). Conversely, those TG species containing only one 18:2n-6 residue became less abundant. It is suggested that the accumulation of these linoleate-rich TG molecular species in adipose tissue, particularly di- and trilinoleoyl containing TG, is the result of an adequate or an excessive intake of linoleic acid.

[Biochemical and immunological characterization of desmosomal proteins]

Desmosmoes were dissolved by incubation at 100 degrees C for 30 minutes in lysis buffer containing 9.5 M urea. SDS-PAGE revealed seven high molecular weight (> 67 kd) bands and some keratins. Seven of these were considered to be major bands. Bands 1 and 2 with M(r) values of 250 kd and 215 kd, called desmoplakins I and II. Polypeptide bands 3, 4a 4b, 5 and 6 had M(r) values of 165kd, 130kd, 115kd, 83kd and 75kd, respectively. 2-2.5mg of Desmoplakin I was obtained by a preparative electrophoresis; the purity reached 93.1%. The isoelectric pH range was between 6.8 and 7.2, and the amino acid compositions displayed a relatively high content of glycine. It was found that McAb Desmoplakin I recognized specifically the 250kd antigenic band by immunoblotting.

Heterologous expression of thermopsin, a heat-stable acid proteinase

We have previously reported the isolation, characterization, and gene sequence of a new thermostable acid protease, thermopsin, from Sulfolobus acidocaldarius, a thermophilic archaebacterium. Thermopsin is similar to aspartic protease pepsin in specificity and pH dependence. However, it optimally catalyzes in the temperature range of 85 to 90 degrees C and it is not structurally related to pepsin. The current report describes the synthesis of recombinant thermopsin in E. coli and in insect cells. Several recombinant thermopsin fusion proteins were expressed as "inclusion bodies" in the cytosol of E. coli. Active thermopsin preparations were obtained by refolding from urea solutions. Recombinant thermopsin was also expressed in insect cells using a baculovirus expression system. The thermostability of recombinant thermopsin is similar to that of the native enzyme.

[The effects of dachengqi decoction, shaogan decoction, emodin and sennoside on the histamine level of intestinal mucosa in intestinally obstructed rats]

The experimental intestinal obstruction model was made by partly ligating the ileum in rat. The histamine levels of obstruction groups (8.14 +/- 2.28 micrograms/g) were obviously lower than those of control groups (P < 0.01). After administration of Dachengqi decoction, Shaogan decoction, emodin and sennoside, the levels of histamine were significantly higher than those of obstruction groups, but there were no significant differences as compared with control groups.

A conserved region in human and Chinese hamster X chromosomes can induce cellular senescence of nickel-transformed Chinese hamster cell lines

Cellular senescence is the genetically programmed cessation of cellular proliferation. We have recently mapped a putative senescence gene(s) on the X chromosome of Chinese hamster embryo (CHE) cells. In the present study, we have utilized microcell-mediated chromosome transfer (microcell fusion) to test whether: (i) the human X chromosome exhibits similar genetic potential to induce senescence and (ii) the deletion or inactivation of the X-linked senescence gene(s) in CHE cells is associated with nickel-induced immortalization. A normal CHE or human X chromosome was first introduced into mouse-cell hybrids, then transferred by microcell fusion into a nickel-transformed, immortal male CHE cell line (Ni-2/TGR) with an X deletion (Xq1). Microcell fusion of the normal CHE X chromosome into tumorigenic Ni-2/TGR cells yielded senescence of all X recipient clones. The normal human X chromosome induced dominant senescence of tumorigenic Ni-2/TGR cells in only 17% of the resulting microcell hybrids (14/81). Karyotypic analyses of 13 non-senescing human X chromosome-derived microcell hybrid clones revealed that none of these clones retained the complete X. A normal CHE X chromosome induced senescence of 75% of hybrids obtained with another immortal and tumorigenic nickel-transformed male CHE cell line (Ni-6/TGR), which exhibited no visible deletion of the X chromosome, while the normal human X chromosome, only induced senescence in 19% of these hybrids. Transfer of the normal CHE or human X chromosome into spontaneously transformed and tumorigenic cell lines, CHO/TGR or V79/TGR, had little or no effect on their growth. These data suggest that both human and CHE cells possess similar X-linked genetic activities that regulate the process of cellular senescence, and that in Chinese hamster cells nickel-induced immortalization but not that of CHO or V79 cells is associated with inactivation of an X-linked senescence gene.

[Isolation of desmosomes: a marker for epithelial tumors]

A simple method is reported for the isolation of desmosomes. The fresh noncornified layers of cow nose epidermis were immersed in 0.1 mol/L citric acid-sodium citrate buffer (pH 2.3, containing 0.5 mmol/L PMSF), and then treated with homogenization and discontinuous sucrose density gradient centrifugation. Desmosomes were located at the 50-56% sucrose interface. Electron microscopy revealed that the characteristic desmosome structure was well preserved, and that a few intermediate filament bundles attached to desmosome plaque were removed by the solubilizing action of the buffer. Approximate 100 mg desmosomes (dry weight) were got from 20g wet noncornified layers of epidermic tissue.

Internally standardized amino acid analysis for determining peptide/carrier protein coupling ratio

A method based on amino acid analysis has been developed for monitoring the covalent conjugation of synthetic peptide haptens to carrier proteins. The marker amino acid, alpha-aminobutyric acid, is included in the sequence during peptide synthesis. Following reaction, the carrier protein-conjugate is freed of excess peptide by two successive rounds of gel filtration chromatography. Amino acid analysis of a hydrolysate of the conjugate allows the calculation of the coupling ratio of the peptide to the carrier protein. Two typical procedures for conjugation, carbodiimide cross-linking and cysteine-thiol reaction with maleimidyl-proteins, have been evaluated.

Differential accumulation of transcripts encoding protein kinase homologs in greening pea seedlings

Degenerate oligonucleotides, corresponding to conserved regions within the catalytic domain of known protein-serine/threonine kinases, were used as primers for the polymerase chain reaction to amplify cDNA synthesized from poly(A)+ RNA purified from the apical buds of 7-day-old pea seedlings. Five partial cDNAs were obtained and designated PsPK1 through PsPK5 (for Pisum sativum protein kinase) in order of decreasing length. The deduced amino acid sequences show that each member of the PsPK series is different in length, and, although their sequences are quite similar overall, each has a unique sequence. Moreover, each member of the PsPK series has structural features typical of members of the protein-serine/threonine kinase family of protein kinases. All are equally similar to cyclic nucleotide-dependent protein kinase and protein kinase C, suggesting that the pea homologs may be involved in signal transduction. DNA gel blots show that each PsPK cDNA is likely to be encoded by a single gene within the pea genome. RNA blot analyses show that the PsPK transcripts accumulate differentially during greening of etiolated seedlings. PsPK3 and PsPK5 transcripts show a large and rapid decline during deetiolation. In contrast, the level of PsPK4 RNA increases steadily during deetiolation whereas PsPK1 and PsPK2 transcripts show little change during the greening period. Thus light regulates changes in the levels of transcripts encoding putative protein kinases in plants.

A receptor that is highly specific for extracellular ATP in developing chick skeletal muscle in vitro

1. Extracellular adenosine 5'-triphosphate (ATP) activated an early excitatory conductance followed by a late potassium conductance in developing chick skeletal muscle. A series of ATP analogues were tested for their ability to activate these two conductances. All compounds tested were either agonists for both responses or for neither. Furthermore, the potency of agonists was similar for the two responses. 2. The order of potency for agonists was ATP approximately adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma-S) approximately 2-methylthio-ATP (2-CH3S-ATP) greater than 2'-deoxy-ATP approximately 3'-deoxy-ATP greater than adenosine 5'-tetraphosphate (ATP-OPO3) approximately adenosine 5'-diphosphate (ADP). Many other ATP analogues were not agonists. 3. Activation of the excitatory response did not require divalent cations. Furthermore, the concentration-response relation of the excitatory response was similar when ATP was applied as the free anion of ATP (ATP4-) or complexed with a divalent cation (M.ATP2-). 4. Three antagonists of the ATP response were characterized. 8-Br-ATP was a weak antagonist, while 2',3'-dialdehyde-ATP and DIDS (4,4'-diisocyanatostilbene-2,2'-disulphonic acid) were potent irreversible inhibitors. The two conductances were equally affected by these antagonists. 5. These results suggest that both ATP responses are activated through the same receptor type, or two very similar receptors.

Qualitative analysis of an HIV transmission model

In 1988, a multiple-group model for HIV transmission with preferred mixing was proposed by Jacquez and coworkers. In the present paper, the work done by Jacquez et al. is extended. It is shown that the stability modulus of the Jacobian matrix at the no-disease equilibrium is a threshold for this model. Furthermore, if the no-disease equilibrium is unstable, the number of infected individuals will remain above a certain positive level regardless of initial levels; that is, the disease will persist uniformly. The stability of the endemic equilibrium in the case of restricted mixing is also studied. A series of sufficient conditions for local and global asymptotic stability of the endemic equilibrium are stated.