Crystallization and preliminary X-ray analysis of cardiotoxic phospholipase A2 from Ophiophagus hannah (king cobra)

An acidic phospholipase A2 exhibiting cardiotoxicity, myotoxicity and anti-platelet activity was isolated from Ophiophagus hannah (king cobra) from Guangxi, China. It contains an unusual 'pancreatic loop'. The enzyme was purified to homogeneity and crystallized using polyethylene glycol and ethylene glycol as precipitants. The crystal belongs to space group C2, with unit-cell parameters a = 117.92, b = 62.94, c = 57.16 A, beta = 100.93 degrees. Diffraction data were collected to 2.6 A.

Interindividual variations in levels and activities of cytochrome P-450 in liver microsomes of Chinese subjects

AIM

To compare the level and/or activity of several important cytochrome P-450 (CYP) enzymes in liver microsomes prepared from different Chinese subjects.

METHODS

Individual CYP contents, including CYP1A2, CYP2C9, and CYP3A4, in liver microsomes of 17 Han, 17 Zhuang, and 8 Miao subjects were determined by using Western blot analysis and densitometric scanning. The substrates for measuring the activity of individual CYP in vitro included phenacetin, tolbutamide, debrisoquine, and omeprazole.

RESULTS

There was a large interindividual variability in the content and activity of CYP1A2, 2C9 and 3A4. And the activity of CYP2D6 also varied greatly between individual samples. CYP3A4 (32 %) is the most abundant CYP in Chinese liver microsomes, and the levels of CYP2C9 (19 %) and CYP1A2 (16 %) were also considerable. No clear ethnic, sex- and age-related differences in individual CYP content and catalytic activity were detected in 42 Chinese liver samples, except that there were somewhat ethnic and sex-related differences in the content and activity of CYP1A2. Good correlation between enzyme protein content and activity was found for CYP1A2, 2C9 and 3A4.

CONCLUSION

Our results may provide useful information for the study of drug metabolism by liver microsomes in Chinese.

Role of cytochrome P450 in estradiol metabolism in vitro

AIM

Catechol estrogens and 16alpha-hydroxy estrogen are important metabolites that cause carcinogenesis. This study was aimed to stud y the role of cytochrome P450 in estradiol metabolism.

METHODS

The estradiol metabolites were determined with HPLC-ECD. Correlation of estradiol metabolites production between cytochrome P450 activity, the inhibitory effect of specific inhibitors and enzyme catalyzing kinetics were studied in cDNA-expressed P450 or human liver microsomes.

RESULT

CYP1A2, CYP3A4, and CYP2C9 catalyze the estradiol 2-hydroxylation. CYP2C9, CYP2C19, and CYP2C8 have high activity in catalyzing 17beta-hydroxy dehydrogenation in cDNA expressed P450, but CYP1A2 is the most important enzyme in catalyzing estradiol 2-hydroxylation. Using furafyllin and troleandomycin to inhibit CYP1A2 and CYP3A4 in liver microsomes, it was found that the 2-hydroxylation had been inhibited about the same amount. This result suggests that in human liver microsomes CYP1A2 and CYP3A4 play an important role in 2-hydroxy estradiol formation. At low substrate concentration, 17beta -hydroxy dehydrogenation dominated the estradiol metabolism, but at high substrate concentration, 2-hydroxylation exceeded 17beta-hydroxy dehydrogenation to become the important mechanism.

CONCLUSION

CYP1A2 and CYP3A4 are two important enzymes catalyzing the main estradiol 2-hydroxylation metabolism pathway at high substrate concentrations. 17beta-hydroxy dehydrogenation is the main metabolism pathway at low concentrations, and CYP2C9, CYP2C19, and CYP2C8 may have high catalyzing activity.

Effects of CYP2C19 genotype and CYP2C9 on fluoxetine N-demethylation in human liver microsomes

AIM

The present study was designed to define the kinetic behavior of fluoxetine N-demethylation in human liver microsomes and to identify the isoforms of cytochrome P-450 (CYP) involved in this metabolic pathway.

METHODS

The kinetics of Ne formation of norfluoxetine was determined in human liver microsomes from six genotyped CYP2C19 extensive metabolizers (EM). The correlation studies between the fluoxetine N-demethylase activity and various CYP enzyme activities were performed. Selective inhibitors or chemical probes of various cytochrome P-450 isoforms were also employed.

RESULTS

The kinetics of norfluoxetine formation in all liver microsomes were fitted by a single-enzyme Michaelis-Menten equation (mean Km=32 micromol/L+/-7 micromol/L). Significant correlations were found between N-demethylation of fluoxetine at both 25 micromol/L and 100 micromol/L and 3-hydroxylation of tolbutamide at 250 micromol/L (r1=0.821, P1=0.001; r2=0.668, P2=0.013), respectively, and S-mephenytoin 4'-hydroxylase activity (r=0.717, P=0.006) at high substrate concentration of 100 micromol/L. S-mephenytoin (SMP) (a CYP2C19 substrate) at high concentration and sulfaphenazole (SUL) (a selective inhibitor of CYP2C9) substantially inhibited norfluoxetine formation. The reaction was minimally inhibited by coincubation with chemical probe, inhibitor of CYP3A4 (triacetyloleandomycin, TAO). The inhibition of fluoxetine N-demethylation at high substrate concentration (100 micromol/L) was greater in PM livers than in EM livers (73 % vs 45 %, P < 0.01) when the microsomes were precoincubated with SUL plus TAO.

CONCLUSION

Cytochrome P-450 CYP2C9 is likely to be a major CYP isoform catalyzing fluoxetine N-demethylation in human liver microsomes at a substrate concentration close to the therapeutic level, while polymorphic CYP2C19 may play a more important role in this metabolic pathway at high substrate concentration.

5-hydroxylation of omeprazole by human liver microsomal fractions from Chinese populations related to CYP2C19 gene dose and individual ethnicity

It has been previously reported that omeprazole (OP) oxidation is mediated by CYP2C19 and CYP3A4 in human livers. In this study, we assessed their relative contributions with human liver microsomal fractions from Chinese populations that were genotyped by CYP2C19 and recruited from two ethnic groups, Han and Zhuang. The kinetics of 5-hydroxyomeprazole (5-OH-OP) formation was best described by the two-enzyme and single-enzyme Michaelis-Menten equations for liver microsomes from CYP2C19 extensive (EMs) and poor metabolizers, respectively. At a low substrate concentration that may be encountered in vivo, the monoclonal antibody to CYP2C8/9/19 strongly inhibited 5-OH-OP formation in EM microsomes, whereas troleandomycin (TAO) eliminated most of the formation at a high substrate concentration. In poor metabolizer microsomes, either TAO or anti-CYP3A4 could alone abolish 5-OH-OP formation. Furthermore, there were differences between homozygous and heterozygous EMs in the percentage of inhibition by TAO and the antibodies. At the low substrate concentration, OP 5-hydroxyaltion was correlated well with S-mephenytoin 4'-hydroxylation and CYP2C19 contents in liver microsomes of 34 Chinese individuals. Moreover, in these individuals, obviously genetic and somewhat ethnic differences in OP 5-hydroxylation were observed between different CYP2C19 genotypes (wt/wt > wt/m1 > m1/m1) and between Han and Zhuang (Han > Zhuang), respectively. The results indicate that CYP2C19 is a high-affinity enzyme for OP 5-hydroxylation by liver microsomes from Chinese individuals and that its contribution is CYP2C19 gene dependent and ethnically related. Similar studies indicate that OP sulfoxidation is mediated mainly by CYP3A4 and independent of CYP2C19 genotype status.

Probing CYP2C19 and CYP3A4 activities in Chinese liver microsomes by quantification of 5-hydroxyomeprazole and omeprazole sulphone

AIM

To develop an analytical method for simultaneous quantification of 5-hydroxyomeprazole (5-OH-OP) and omeprazole sulfone (OPS), and explore whether omeprazole (OP) is an appropriate phenotypic probe for CYP2C19 and CYP3A4 in Chinese liver microsomes.

METHODS

OP metabolism in vitro was conducted in Chinese liver microsomes, and the major metabolites 5-OH-OP and OPS were determined using high pressure liquid chromatography (HPLC). Monoclonal antibodies anti-CYP2C8/9/19 and anti-CYP3A4 were employed to conduct inhibition experiments. The protein contents of CYP2C19 and CYP3A4 were quantified using Western blot analysis and densitometric scanning.

RESULTS

5-OH-OP and OPS gave a baseline resolution in the HPLC analysis. The detection limits for both compounds were 0.01 nmol and the recovery (98%-102%) had good precision with relative standard deviation of < 9.5%. Both anti-CYP2C8/9/19 and anti-CYP3A4 had a significant inhibitory effect (P < 0.05) on the 5-OH-OP formation in a substrate concentration-dependent manner, and anti-CYP3A4 alone could almost abolish the formation of OPS (> 87%). At a substrate concentration of 2 mumol/L OP, good correlations were found between OP 5-hydroxylation and S-mephenytoin 4'-hydroxylation activities (r = 0.72, P < 0.01), OP 5-hydroxylation activities and CYP2C19 contents (r = 0.82, P < 0.01), and OP sulfoxidation activities and CYP3A4 contents (r = 0.78, P < 0.01) in Chinese liver microsomes.

CONCLUSION

OP metabolism is mediated mainly by CYP2C19 and CYP3A4, and OP can be used to probe CYP2C19 and CYP3A4 activities in Chinese liver microsomes at appropriate substrate concentrations with the HPLC method presently developed.

In vitro proguanil activation to cycloguanil is mediated by CYP2C19 and CYP3A4 in adult Chinese liver microsomes

AIM

To identify the cytochrome P450 isoforms involved in proguanil (PG) activation to cycloguanil (CG) in Chinese liver microsomes.

METHODS

The kinetics of the CG formation from PG was determined in the liver microsomes of 6 Chinese subjects. Selective chemical inhibitors to various cytochrome P450 isoforms were employed to conduct inhibition experiments. The relationship between the CG formation and S-mephenytoin 4'-hydroxylation was analyzed.

RESULTS

The kinetic behaviors of CG formation were described well by a single-enzyme Michaelis-Menten equation in five livers. The apparent Km and Vmax were (82 +/- 47) mumol.L-1 and (8 +/- 6) pmol.min-1.mg-1 protein, respectively. However, the remaining one displayed a two-enzyme kinetic behavior. Inhibition experiments showed that troleandomycin (100 mumol.L-1) and diethyldithiocarbamate (100 mumol.L-1), as potent CYP3A4 and CYP2E1 inhibitors, respectively, reduced the formation rate of CG by 81.1% and 47.23%, while quinidine (10 mumol.L-1), furafylline (20 mumol.L-1), and sulfaphenazole (10 mumol.L-1), which were inhibitors towards CYP2D6, 1A2 and 2C9/10, respectively, did not display significant inhibition. At a low PG concentration of 5 mumol.L-1, the CG formation correlated well with S-mephenytoin 4'-hydroxylation (r = 0.805, P < 0.05). Nevertheless, when a high substrate concentration (500 mumol.L-1) was used, the correlation coefficient decreased (r = 0.581, P < 0.05).

CONCLUSION

The present study indicates that CYP3A4 and CYP2C19 are involved in PG activation to CG in adult Chinese liver microsomes. CYP2C19 played an important role in the clearance of PG at a substrate concentration close to in vivo therapeutic concentrations, while CYP3A4 gradually made a dominant contribution with the increase of PG concentration.

[Preliminary analysis of chromosome mosaicism in preimplantation embryos]

OBJECTIVE

Using fluorescence in situ hybridization to analyze chromosome mosaicism in human preimplantation embryos and access the influence of mosaicism on in vitro fertilization-embryo transfer (IVF-ET) and preimplantation genetic diagnosis.

METHODS

Normal fertilized embryos, which were not suitable for embryo transfer and cryopreservation, and male embryos in preimplantation gender diagnosis were analyzed by fluorescence in situ hybridization.

RESULTS

Two hundred and ninety three nucleuses were found among 38 embryos. The hybridization rate was 96.2%. Twelve embryos (31.6%) were normal. Twenty-eight embryos (73.7%) were diploid embryos, which included normal diploid embryos and embryos with diploid moscaicism. In addition, 19 (50.0%) embryos were considered to be chromosomal mosaics due to diploid mosaicism and abnormal mosaicsm. The frequency of mosaicism increased from 18.2% in < or = 4 cell-stage embryos to 68.4% and 50.0% in 5-8 cell-stage and > or = 9 cell-stage embryos respectively.

CONCLUSION

The frequency of Mosaicism increases with successive cleavage divisions. Moscaicism may be one of the important factors affecting the success rates in IVF-ET. Identification of sex by analysis of a single cleavage cell is accurate; however, it would be better to biopsy 2 cells to reduce errors in preimplantation genetic diagnosis of single gene diseases.

[Changes of lipoprotein lipase and hepatic lipase and their significance in gallstone formation in rabbit model]

This experiment was made to investigate the changes of lipoprotein lipase(LPL) and hepatic lipase (HL) activity and their effects on gallstone formation in rabbit model in which the stones were induced by high cholesterol diet. Activities of plasma LPL and HL were determined; other data including concentration of plasma lipoprotein cholesterol, concentration of bile cholesterol and bile acids were also obtained. The results showed that with the rabbits continuously fed on high cholesterol diet, LPL activity heightened markedly (P < 0.05), and HL activity increased gradually (3 and 4 weeks groups vs control group, P < 0.05). The changes of concentration of plasma VLDL-C and LDL-C were the same as that of LPL activity, but the concentration of plasma HDL-C, HDL2-C, HDL3-C and bile acids showed no significant changes (P > 0.05). These results suggest that the heightened activities of LPL and HL might make the liver take up more cholesterol, secrete it into the bile duct and hence accelerate gallstone formation.

Phenotypic characteristics and cyclin-dependent kinase inhibitors repression in hyperplastic epithelial pathology in idiopathic focal segmental glomerulosclerosis

Hyperplastic glomerular epithelial lesion is an important determinant of the progression of idiopathic focal segmental glomerulosclerosis (FGS). The proliferation and differentiation of glomerular epithelial cells and parietal epithelial cells (PECs) are regulated differently by cyclin and cyclin-dependent kinase inhibitors (CKIs) during nephrogenesis. To access the cellular mechanism underlying epithelial hyperplasia in the development of FGS, the present study applied immunohistochemistry to 21 cases of FGS to demonstrate expression of cell-cycle molecules and phenotypic characterization in proliferative epithelial lesions in FGS. The materials included segmental sclerosis (18.1%), which was divided into monolayer epithelial lesions (64.6%) and cellular lesions (35.4%). All of the cellular lesions expressed cytokeratin, frequently with Ki-67 (82.4%) and less frequently with cyclin A (17.7%), but were invariably negative for podocyte markers (PHM-5 and synaptopodin) and CKIs (p27kip1 and p57kip2). Podocytes in nonsclerotic tuft in the same glomeruli with cellular lesions strongly expressed CKIs and podocyte markers. Moreover, electron microscopy showed that some large proliferating cells with prominent nucleoli have a broad cell base attached to Bowman's capsule. These cells have cilia and a junctional complex with neighboring hyperplastic cells, some of which directly cover the glomerular basement membrane. This suggests that cellular lesions are of PEC origin. Monolayer epithelial lesions also exclusively exhibited a PEC phenotype with reciprocal expression of podocyte markers and cytokeratin. In addition, CKIs are weakly expressed in monolayer epithelial lesions, suggesting a re-entry of cell-cycle quiescent. In conclusion, proliferation of PEC, sustained by repression of CKIs in nature and simultaneous activation of cyclin A, is the actual molecular background to the cellular lesions in FGS. Cellular lesions may result in monolayer epithelial lesions that retain the PEC phenotype and enter a common pathway to glomerulosclerosis.

Summary curves for patients transplanted for chronic myeloid leukaemia salvaged by a donor lymphocyte infusion: the current leukaemia-free survival curve

A significant number of patients who relapse after allogeneic stem cell transplantation (SCT) for chronic myeloid leukaemia (CML) will achieve sustained molecular remissions after treatment with donor lymphocyte infusions (DLI) from the original stem cell donor. Leukaemia-free survival, defined as survival without evidence of relapse at any time after transplant does not account for patients who are successfully treated with DLI. To summarize adequately the response to treatment, a new summary probability, called the current leukaemia-free survival (CLFS), is proposed. This quantity is defined as the probability that a patient is alive and in remission at a given time after transplant. We discuss two statistical methods for estimating CLFS. The first is based on a multistate modelling approach. The second is based on an estimate constructed by looking at appropriate differences between Kaplan-Meier estimates. We compare these estimates using data on 189 consecutive patients who underwent SCT over a 7-year period.

Phenotypic polymorphism and gender-related differences of CYP1A2 activity in a Chinese population

AIMS

To investigate the distribution characteristics of CYP1A2 in a Chinese population, and to examine gender-related differences in CYP1A2 activity.

METHODS

Two hundred and twenty-nine healthy subjects, 120 men and 109 women, were enrolled in this study. CYP1A2 activity was measured by plasma paraxanthine/caffeine (1,7X/1,3,7X) ratio 6 h after administration of 300 mg caffeine. The concentrations of paraxanthine and caffeine in plasma were detected by h.p.l.c.

RESULTS

A 16-fold variation of CYP1A2 activity (range 0. 09 to 1.46) was shown in this study. The coefficient of variation (CV %) of CYP1A2 activity was 62.9%. Non-normal distribution of CYP1A2 activity was indicated by the Shapiro-Wilk test (P<0.001). Probit plots of CYP1A2 activity revealed a bimodal distribution with breakpoint of 1,7X/1,3,7X ratio of 0.12. The percentage of poor metabolizers (PMs) was 5.24% (95% CI: 2.35% approximately 8.13%) in this Chinese population. Residual analysis of the data also supported bimodality (P<0.01). The CYP1A2 activity of men was higher than that of women (median: 0.33 vs 0.23, P<0.001). A probit plot of CYP1A2 activity in men was shifted to the left compared with that in women. Based on phenotype, the gender-related difference was observed in extensive metabolizers (EMs) (P<0.001), but not in PMs (P >0.1). In addition, there was no sex-related difference in the incidence of PMs (P >0.1).

CONCLUSIONS

There is a phenotypic polymorphism in CYP1A2 activity in this Chinese population, and CYP1A2 activity is higher in men than that in women.

Linkage and association analyses of alcoholism using a regression-based transmission/disequilibrium test

Recently, George et al. proposed a regression-based transmission/disequilibrium test for linkage using information on the parent-to-offspring transmission status of an allele at a marker locus. We extended this test by simultaneously testing for any population association by incorporating the presence/absence status of the associated allele as a covariate in the model. We used this method to analyze markers on chromosomes 1 through 21 of the Collaborative Study on the Genetics of Alcoholism data on alcoholism for possible association and linkage. We found nominal significance (at the 0.02 level) at eight different regions for linkage, though statistical significance may not be concluded due to multiple testing. The strongest evidence of linkage was observed for markers D4S2639 and D12S397 with p-values less than 0.005. We also found strong association between the trait and alleles 149 of D7S691 and 131 of D21S1437.

Association and linkage analysis of ICD-10 diagnosis for alcoholism

We analyzed the GAW11 data on alcoholism provided by the Collaborative Study on the Genetics of Alcoholism (COGA) using an extension of a new test of linkage and association for quantitative traits developed by George et al. [1999]. This method determines linkage between marker loci and quantitative traits, when allelic association is present between the trait and marker loci, by regressing the disease trait on the parental transmission of the allele of interest. We found no strong evidence of linkage to any markers. However, we found several markers suggestive of possible linkage that may deserve further investigation.

A novel recombinant adeno-associated virus vector packaging system with HSV-1 amplicon providing helper functions

A novel packaging system for producing recombinant adeno-associated virus (rAAV) vector was described. Instead of the conventional method for rAAV production by two-plasmid co-transfection followed by superinfection with adenovirus 5, an HSV-1 amplicon system expressing AAV-2 rep and cap genes from their native promoters was used to provide complete helper functions for rAAV replicating and packaging. This HSV-1 amplicon stock consisted of two kinds of infectious HSV-1 virions, a replicating-defective HSV-I amplicon pseudovirus harboring multi-copies of AAV-2 rep and cap gene and a temperature-sensitive HSV-1 mutant strain ts-KOS. High-titer rAAV was generated with this new packaging system. This packaging system gives a simple and scaleable process for rAAV production.

Ectopic purinergic sensitivity develops at sites of chronic nerve constriction injury in rat

The possibility that ectopic purinergic sensitivity develops following peripheral nerve injury was investigated in chronic constriction injury (CCI). Spontaneous firing of A-fibers originated from the injury site or from sensory endings of afferents in the contralateral sciatic nerve. ATP injected intravenously excited most of the injured fibers whereas none of the contralateral afferents responded to ATP. The ATP-induced effect was blocked by the P2 receptor antagonist reactive blue 2, but not the P1 receptor antagonist aminophylline. Neither the alpha-adrenoreceptor antagonist phentolamine nor the cyclooxygenase inhibitor indomethacin attenuated the ATP-evoked effect. We conclude that a novel ectopic purinergic sensitivity mediated by P2 receptors develops at sites of the CCI of nerves in the rat, which may contribute to neuropathic pain.

[Change of high density lipoprotein receptor of hepatocyte during cholesterol gallstone formation in rabbit model]

In order to study the formation of cholesterol gallstone through rabbit model which was induced by high cholesterol diet (HCD), we investigated the high density lipoprotein receptor (HDLr) activities of hepatocytes, total bile acids and cholesterol of common duct bile at 1 week(1 w), 2 weeks(2 w), 3 weeks (3 w) and 4 weeks(4 w) in comparison with those of a control group respectively. The results were as follows: 1. The HDLr Bmax decreased and the kd value increased significantly (1 w group vs control group, P < 0.05); In 2 w group the two variables recovered to the level of control group; and after that, the HDLr Bmax increased and Kd value decreased markedly (3 w and 4 w groups vs control group, P < 0.05). 2. Total bile acids in bile increased slightly in 1 w group (vs control group, P > 0.05), then decreased in 2 w, 3 w and 4 w groups (4 w group vs control group, P < 0.05). 3. The concentration of cholesterol in bile increased gradually as the time of feeding HCD went on (3 w and 4 w groups vs control group, P < 0.05). The results demonstrated that owing to the intake of HCD with the passage of time, the activity of HDLr was up at the beginning and down gradually in the rest period. The change in concentrations of bile acids was similar to that of HDLr, and the concentration of cholesterol in bile was foreign to the change of HDLr. These results suggest that the decrease of HDLr activity may cause the absence of material for bile acids synthesis and it may play an important role in the formation of gallstone.

Evidence for involvement of polymorphic CYP2C19 and 2C9 in the N-demethylation of sertraline in human liver microsomes

AIMS

The present study was designed to define the kinetic behaviour of sertraline N-demethylation in human liver microsomes and to identify the isoforms of cytochrome P450 involved in this metabolic pathway.

METHODS

The kinetics of the formation of N-demethylsertraline were determined in human liver microsomes from six genotyped CYP2C19 extensive (EM) and three poor metabolisers (PM). Selective inhibitors of and specific monoclonal antibodies to various cytochrome P450 isoforms were also employed.

RESULTS

The kinetics of N-demethylsertraline formation in all EM liver microsomes were fitted by a two-enzyme Michaelis-Menten equation, whereas the kinetics in all PM liver microsomes were best described by a single-enzyme Michaelis-Menten equation similar to the low-affinity component found in EM microsomes. Mean apparent Km values for the high-and low-affinity components were 1.9 and 88 microm and V max values were 33 and 554 pmol min-1 mg-1 protein, respectively, in the EM liver microsomes. Omeprazole (a CYP2C19 substrate) at high concentrations and sulphaphenazole (a selective inhibitor of CYP2C9) substantially inhibited N-demethylsertraline formation. Of five monoclonal antibodies to various cytochrome P450 forms tested, only anti-CYP2C8/9/19 had any inhibitory effect on this reaction. The inhibition of sertraline N-demethylation by anti-CYP2C8/9/19 was greater in EM livers than in PM livers at both low and high substrate concentrations. However, anti-CYP2C8/9/19 did not abolish the formation of N-demethylsertraline in the microsomes from any of the livers.

CONCLUSIONS

The polymorphic enzyme CYP2C19 catalyses the high-affinity N-demethylation of sertraline, while CYP2C9 is one of the low-affinity components of this metabolic pathway.

[Clinical study on effect of Chinese herbal medicine for supplementing kidney and qi and activating blood circulation in treating intrauterine growth retardation of fetus]

OBJECTIVE

To explore the therapeutic effect and its possible mechanism on using Chinese herbal medicine (CHM) for supplementing Kidney and Qi, and activating blood circulation in treating intrauterine growth retardation of fetus (IUGR).

METHODS

Fifty-five cases of IUGR were observed, 30 of them were treated with CHM and 25 treated with amino acid for control.

RESULTS

The neonatal birth weight in the CHM group was markedly greater than that in the control group. Not only the maternal fundal height and abdominal circumference, but also the fetal growth parameters, including biparietal diameter, head circumference, abdominal circumference, femur length in the CHM group increased much faster than those in the control group. After CHM treatment, the maternal serum levels of estriol (E3) and human placental lactogen (hPL) were close to the normal pregnancy group, but the levels in the control group were significantly different from the normal range. The umbilical venous plasma concentration of essential amino acids was markedly improved after treatment, however, the improvement in the CHM group was more significant than that in the control group. No adverse effect of CHM was found both in mother and fetus.

CONCLUSION

CHM for supplementing Kidney and Qi, and activating blood circulation was more effective in the improvement of placental function and amino acid transportation than those of amino acid.

Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (Isc). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 µM, and reversibly activated Isc in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 µg/mL) increased whole-cell current and Isc, whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.Key words: matrix metalloproteinases, Cl- current, Calu-3 cells, zymography, phenanthroline.

Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (I(sc)). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 microM, and reversibly activated I(sc) in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 microg/mL) increased whole-cell current and I(sc), whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.

[Clinical and experimental study on the treatment of endometriosis with dan'e mixture]

OBJECTIVE

To find a medicine to treat endometriosis effectively with less side-effect.

METHODS

Dan'e mixture (DEM, consists of Radix Salviae Miltiorrhizae and Rhizoma Zedoariae) was used to treat 189 cases of endometriosis and the change of symptom and sign, the B ultrasonograph, the anti-endometrium antibody and endometriosis quantitative diagnostic index were observed, another 160 cases were treated with Danazol as control, also using animal model to treat with DEM and Danazol.

RESULTS

One hundred and eighty-nine cases were treated for 9 months. According to National Standards, 39 cases (20.6%) were cured, 67 cases (35.4%) were markedly effective, 67 cases (35.4%) were effective, and 16 cases (8.4%) were ineffective. Compared with 160 cases treated with Danazol for 9 months, the total effective rates were 95% and 91.5% respectively, the difference between them was insignificant. Animal experiments showed the similar results to the clinical ones.

CONCLUSION

SZM is a safe and effective medicine to treat endometriosis, which deserves further study and development. It is particularly helpful for diagnosis, treatment and prevention of endometriosis in the early stage.

[Changes of lipids metabolism during gallstone formation in rabbit model and the effects on these changes by high density lipoprotein preparation injection]

To study the changes of lipids metabolism during gallstone formation and the effects fo the exogenous high-density lipoprotein (HDL) preparation on the formation of gallbladder stone in rabbit model in which the stones were induced by high-cholesterol (HC) diet. The plasma lipids, the bile cholesterol, the activity of plasma lecithine cholesterol acyltransferase (LCAT), the bile acids in both bile and plasma, and the incidence of stone formation were investigated in the control group, HC group, and HC + HDL group (in this group the rabbits were given HDL preparation intravenously regularly). The results showed that the lipids metabolic disorder was characterized by a large amount of cholesterol accumulated in the rabbit's body and when the liver cleaned the accumulated cholesterol, the ratio of biliary cholesterol to bile acids was significantly increased. The latter could cause the production of lithogenic bile. Thought HDL preparation could decrease hepatic cholesterol and increase the level of plasma HDL2-C and the activity of LCAT, it could not lower the incidence of gallstone formation. The results suggest that the HDL preparation had some effects on lipids metabolism, but no significant effect on gallstone formation in rabbit model has been evidenced, so the problem awaits further studies.

[The feature of pancreatic microcirculatory impairment in caerulein induced acute pancreatitis]

OBJECTIVE

To study the feature of pancreatic microcirculatory impairment in caerulein-induced acute pancreatitis.

METHODS

The AP model of subcutaneous injection of caerulein was studied by intravital fluorescence microscopy of erythrocytes labeled by FITC (FITC-RBC) and by scanning electron microscopy of vascular corrosion casts and light microscopy of Chinese ink-injected/cleared tissues.

RESULTS

Animals treated with caerulein showed hyper-amylases. Contractions of intralobular arteriolar sphincter, presence of vacuoles in all the layers of sphincter, gross irregularity in capillary network of acini were observed in caerulein-induced groups. The decrease of pancreatic capillary blood flow (P < 0.01), reduction of functional capillary density, and irregular intermittent perfusion (P < 0.05) were found.

CONCLUSIONS

Impairment and contraction of pancreatic intralobular arteriolar sphincter are the initial microcirculatory lesions in the early phase of acute pancreatitis induced by Caerulein, and play a key role in the pancreatic ischemia and pancreatic microvascular failure in acute pancreatitis.

[Determination of germanium and selenium in malt powder by GFAAS]

A method for determination of germanium and selenium in malt powder has been developed by graphite furnace atomic absorption spectrometry with L'vov platform. While (Pd+Ni) and Pd were used as matrix modifiers,the ashing temperatures of Ge and Se were increased to 1400 and 1200 degrees C respectively,and the matrix inferences were removed. The characteristic masses are 31 pg Ge and 23pg Se(0.0044 A), the detection limits are 28pg Ge and 62pg Se (3 sigma), the precisions (n = 9) are 3. 7-5.6%(Ge) and 4.3-6.5% (Se) and the recoveries are among 90-105%.

Activation of bovine tracheal chloride channels by amino group-specific reagents

1. The predominant Cl- channel in bovine tracheal epithelial cells has a conductance of approximately 71 pS and accounts for more than 80 % of the total chloride conductance. We examined the effects of protein-modifying reagents on channel function and found that amino groups are critically involved in gating. 2. Patch clamp studies showed that lysine-specific reagents, such as dimethyl adipimidate (DMA), significantly increased the channel open probability, but not its conductance. This suggests that modified residues are involved in the gating mechanism, but are distant from the channel permeation pathway. 3. Kinetic analysis of channel activity showed that histograms of open and closed durations could be well fitted by double exponential distributions, suggesting that the channel has at least two open and two closed states. DMA did not change the number of open or closed states, but increased channel mean open time. 4. Since membrane impermeant reagents were effective only from the extracellular side, we conclude that lysine residues in the extracellular domain of the channel are critically involved in gating. These residues may present an important target for site-directed mutagenesis and pharmacological activation of Cl- channels in epithelial cells.

Determination of amitriptyline and nortriptyline in human liver microsomes with reversed-phase HPLC in vitro

AIM

To develop a method for simultaneous determinations of amitriptyline (Ami) and its metabolite nortriptyline (Nor) in human liver microsomes.

METHODS

An incubation buffer containing microsomes, NADPH-generating system, and Ami, after termination of enzyme reaction and desipramine (Des) as internal standard (IS), was extracted with diethy ether and separated on a reversed-phase ODS column. Detection was achieved at 242 nm by ultraviolet detector.

RESULTS

No potential interfering peaks were found. Ami and Nor gave rapid elution and baseline resolution. The linear curves of both analyses ranged 0.02-10 nmol and the limit of detection was 0.01 nmol. The recovery (94%-101%) had good precision with relative s of < 8.3%.

CONCLUSION

This method is rapid, sensitive, and simple for studying the metabolism of Ami and Nor.

[Effects of composite blood-activating decoction on bone marrow microenvironment in mice of immune-induced aplastic anemia]

OBJECTIVE

To explore the mechanism of elevating efficacy for aplastic anemia (AA) by using blood-activating and stasis-eliminating drugs.

METHODS

Immune-induced aplastic anemia model was established. Each mouse was gastrogavaged by 0.2 ml 100% composite blood-activating decoction (CBAD) twice a day. On the 10th day, the bone marrow histology, CFU-F, adhesive function of the cultured stromal cell layer, bone marrow PO2 were observed.

RESULTS

In CBAD group, the WBC count, bone marrow karyocytes, bone marrow hematopoietic tissue volume, CFU-F count were significantly higher than those in AA group (P < 0.01). Moreover, the adhesive function of stromal cells and bone marrow PO2 recovered to normal level.

CONCLUSION

The commonly used composite blood-activating decoction could promote the recovery and oxygen-supply of bone marrow microenvironment in AA mice, and improved the bone marrow hematopoiesis.

[Study on the improvement of bone marrow microenvironment by ligustrazine in immune-induced aplastic anemia mice]

OBJECTIVE

To explore the effects of ligustrazine on bone marrow microenvironment and its mechanism in aplastic anemia (AA).

METHODS

Each immune-induced AA mouse was gastric fed by 4 mg ligustrazine twice a day. On the 10th day, the ulnar bone marrow partial pressure of oxygen (PbO2) was determined in vivo by a PO2 sensory needle. Then the histological features, fibroblastic colony forming unit (CFU-F) yields and the adhesive function of stromal cells of the bone marrow were assayed in vitro.

RESULTS

The PbO2 in ligustrazine-treated group was 10.32 +/- 1.27 kPa, while in AA group was 4.32 +/- 2.86 kPa (P < 0.001). In AA group, the microvessels were expanded, broken and being stasis. The percentage of hematopoietic tissue volume was 24.9% +/- 9.6% and the CFU-F yields was 12.5 +/- 7.3/2 x 10(6) BMNC. The microvessels in ligustrazine group were more clear and intact, not being broken and had no stasis. The percentage of hematopoietic tissue volume was 52.8% +/- 15.6% and the CFU-F yields was 31.5 +/- 10.6/2 x 10(6) BMNC. In ligustrazine group, the adhesive function of stromal cell layer cultured with bone marrow nucleated cells from normal mice was 72.7% +/- 7.8%, which was not different from that in normal group (73.4% +/- 3.4%), but much higher than that in AA group (56.2% +/- 9.8%, P < 0.01).

CONCLUSION

Ligustrazine can promote the rehabilitation of bone marrow microvessels in AA mice, increasing the oxygen supply for bone marrow microenvironment, promoting the growth of stromal cells and strengthening their adhesive function. Ligustrazine enbances the bone marrow hematopoietic cells proliferation by improving their microenvironment.

[Chemical constituents of tissue cultures of Salvia miltiorrhiza Bunge]

Two compounds were isolated from the tissue cultures of Salvia miltiorrhiza for the first time, and identified as danshenxinkun B and Ro-09-0680 by spectroscopic methods.

[A novel gene delivery system targeting to epidermal growth factor receptor overexpressing cancer cells]

A polypeptide with 33 amino acid residues was designed and synthesized. Its C terminal was composed of multiple lysine residues, which played as a DNA condensing agent, whereas the N terminal was the receptor binding domain of Epidermal Growth Factor(N32-K48). Through a spontaneous self-assembly process with electrostatic interaction, the synthetic peptide combined with a luciferase expression vector, pEBluc, to form an EGF receptor targeting nucleic acid complex. Significant luciferase activity was detected 48 hours after adding this complex directly to the culture medium of the A431 cells. This synthetic peptide could be used to construct a gene transfer system mediated by the endocytosis via EGF receptor. It promoted a very possibility of the gene therapy for the cancers such as glioma, melanoma and squamous carcinoma which are known of epidermal growth factor receptor overexpression.

[Effect of ligustrazine on CD34 antigen expression of bone marrow cells in immune-mediated aplastic anemia mice]

OBJECTIVE

To explore the effect of ligustrazine on CD34 antigen expression of bone marrow cells in immune-mediated aplastic anemia (AA) mice.

METHODS

The model of immune aplastic anemia mice was induced by means of 6.0 Gy60Co gamma-ray irradiation and lymphocyte infusion through tail vein. The mice were divided into 3 groups: the normal group, the AA control group and the ligustrazine group. Mice of the ligustrazine group were fed by 4 mg of ligustrazine injection twice a day by gastrogavage. On the 10th day, CD34 antigen expression intensity of bone marrow cell membrane was measured by flow cytometer analysis system.

RESULTS

CD34 antigen expression intensity of ligustrazine group was 77.6 +/- 6.5, with no statistic difference from that in the normal group (80.0 +/- 2.6), while that of the control group was much higher (68.6 +/- 4.5, P < 0.05).

CONCLUSIONS

Ligustrazine could promote proliferation of stem and progenitor cell of AA mice through influencing on bone marrow micro-environment so as to increase the CD34 antigen expression of bone marrow cells.

Extractive L-lactic acid fermentation with immobilized Rhizopus oryzae in a three-phase fluidized bed

The Rhizopus oryzae was immobilized by the calcium alginate entrapment method. A three-phase fluidized-bed bioreactor was designed to perform the immobilized-cell L-lactic acid fermentation. A solvent extraction column was coupled with the bioreactor to remove L-lactic acid from the fermentation broth. The TRPO was selected as solvent and sulfonated kerosene as diluent. The results indicated that the pH value in the broth was regulated above pH 3.5 and the fermentation rate was as high as 11 g L-lactic acid per hour per liter of beads. A mathematical model was proposed to describe the concentration of L-lactic acid in the extractive fermentation.

Meta-analysis of phenotype and genotype of NAT2 deficiency in Chinese populations

Data on both the incidence of slow acetylator phenotype of probe drugs isoniazid, sulfadimidine or sulfamethazine, caffeine and dapsone in mainland or overseas Chinese, and the distribution of NAT2 genotypes and the frequency of NAT2 alleles in the Chinese populations were summarized and reanalysed using a meta-analysis method. Frequency of the slow acetylator phenotype in 3516 healthy Han Chinese gave an overall mean of approximately 19.9 +/- 4.0%, with the range of the combined data being between 15.8% and 25.5%. In addition, frequencies of the slow acetylator phenotype differ between the different minorities in Chinese populations and the range was between 3.2% and 50.6%, with a mean value of 20.6 +/- 12.9% in a total of 1842 individuals from 17 Chinese minorities. In addition, there was no significant heterogeneity in overseas Chinese between the probe drugs isoniazid and sulfadimidine or sulfamethazine (chi 2 = 5.97, df = 4; p > 0.05), and the mean value of slow acetylator phenotype incidence was 24.5% (119/485; 95% CI: 20.7-28.3%), consistent with that of the native Chinese. As expected, frequency of the slow acetylator genotypes in Chinese populations was 25.4% (112/441; 95% CI: 21.3-29.5%), which was in accordance with that of the slow acetylator phenotype in native or overseas Chinese. For all genotypes, *4/*4 (29.9%, 132/441), *4/*6A (27.4%, 121/441), *4/*7A (12%, 53/441) and *6A/*6A (11.3%, 50/441) occupied 80.6%, but *5A/*7A (0.2%, 1/441), *5A/*5A (1.1%, 5/441) and *7A/*7A (1.8%, 8/441) were not frequently found. From this report, the genotype frequencies of homozygous rapid acetylator, heterozygous rapid acetylator, and homozygous slow acetylator were found to be 0.299 (132/441), 0.447 (197/441) and 0.254 (112/441), respectively. Furthermore, both *4 (52.3%; 95% CI: 49-56%) and *6A (30.5%; 95% CI: 28-34%) were major NAT2 alleles, while *7A (11.2%; 95% CI: 9-13%) and *5A (6%; 95% CI: 4-8%) were uncommonly present. Frequency of the mutant alleles was observed at 0.477 (421/882 alleles). The *7A constituted 23.5% t(99/421) of slow acetylator alleles in Chinese populations, showing that this point mutation exists not only in Oriental or Asiatic, but also in Chinese populations. According to the Hardy-Weinberg equilibrium, in the phenotyped Chinese populations, the mean estimate of predicted allelic frequencies of the genotypes RR, Rr, and rr was 0.294, 0.496, and 0.210 for the Chinese, and the expected frequency of the deficient gene r was 0.458. By comparison, the predicted values are in complete agreement with the observed ones. In conclusion, this meta-analysis determined the accurate population frequencies of phenotype and genotype of the NAT2 genetic deficiency in healthy Chinese subjects.

[Change of serum lipid, apolipoprotein during cholesterol gallstone formation in rabbit model]

In order to study the formation of cholesterol gallstone through rabbit model which was induced by high cholesterol diet (HCD), we investigated the rabbits' serum lipoprotein cholesterols and apolipoprotein (apo) at 1 week (1w), 2 weeks (2w), 3 weeks (3w) and 4 weeks (4w) in comparison with those of a control group respectively. The results were as follows: (1) of 10 rabbits subjected to experiment, 4, 6, and 7 rabbits were found to have induced-cholesterol gallstones in the 2w, 3w and 4w groups respectively. (2) The serum concentrations of total cholesterol (TC), triglyceride (TG), phospholipid (PL), low density lipoprotein cholesterol (LDL-C) and very low density lipoprotein chloesterol (VLDL) increased significantly (1w, 2w, 3w and 4w groups vs control group, P < 0.05), especially in the 3w and 4w groups; the surum concentrations of high density lipoprotein cholesterol and its subfractions (HDL-C, HDL2-C, HDL3-C) decreased slightly (vs control group, P > 0.05). (3) The serum contents of apoB100, apoC II and apoC III increased significantly (vs control group, P < 0.05), especially in the 3w and 4w groups; the serum apoA I reduced gradually in 1w, 2w and 3w groups, and decreased greatly in 4w group (vs control group, P < 0.05). The results demonstrated that owing to the intake of high cholestrol diet with the passage of time, the increased concentrations of serum VLDL-C, apoB, apoC II and apoC III possibly caused an enhanced secretion of biliary cholesterol into bile; that the decreased serum apoA I level might reduce the secretion of anti-nucleating factor into bile. All of these factors and changes may play important roles during the formation of cholesterol gallstones.

Molecular genetic analysis of Rts1p, a B' regulatory subunit of Saccharomyces cerevisiae protein phosphatase 2A

The Saccharomyces cerevisiae gene RTS1 encodes a protein homologous to a variable B-type regulatory subunit of the mammalian heterotrimeric serine/threonine protein phosphatase 2A (PP2A). We present evidence showing that Rts1p assembles into similar heterotrimeric complexes in yeast. Strains in which RTS1 has been disrupted are temperature sensitive (ts) for growth, are hypersensitive to ethanol, are unable to grow with glycerol as their only carbon source, and accumulate at nonpermissive temperatures predominantly as large-budded cells with a 2N DNA content and a nondivided nucleus. This cell cycle arrest can be overcome and partial suppression of the ts phenotype of rts1-null cells occurs if the gene CLB2, encoding a Cdc28 kinase-associated B-type cyclin, is expressed on a high-copy-number plasmid. However, CLB2 overexpression has no suppressive effects on other aspects of the rts1-null phenotype. Expression of truncated forms of Rts1p can also partially suppress the ts phenotype and can fully suppress the inability of cells to grow on glycerol and the hypersensitivity of cells to ethanol. By contrast, the truncated forms do not suppress the accumulation of large-budded cells at high temperatures. Coexpression of truncated Rts1p and high levels of Clb2p fully suppresses the ts phenotype, indicating that the inhibition of growth of rts1-null cells at high temperatures is due to both stress-related and cell cycle-related defects. Genetic analyses show that the role played by Rts1p in PP2A regulation is distinctly different from that played by the other known variable B regulatory subunit, Cdc55p, a protein recently implicated in checkpoint control regulation.

[Characterization of immunoblots of hydrophobic outer membrane proteins Leptospira interrogans serovar lai strain 017]

Outer membrane proteins (OMP) of Leptospira interrogans serovar lai strain 017 were extracted by using Triton X-114 (TX-114). The OMP were solubilized and phase partitioned into both the hydrophilic, aqueous phase and hydrophobic, detergent phase. TX-114 did not solubilize the protoplasmic cylinder in intact organisms. The protoplasmic cylinders contained a lot of protein bands and most of the TX-114 solubilized proteins partitioned into the aqueous phase, whereas only 14 protein bands entered the detergent phase with SDS-PAGE. Detergent phase proteins were of 5 major protein bands such as 66 kd, 39 kd, 35 kd, 27 kd, and 16 kd. Immunoblotting of the material extracted with TX-114 showed that detergent phase proteins of alone 39 kd was apparently immunoblotting with antiserum against such as whole cell of 017 strain the outer envelope of 017 strain and the immunoprotective anti-017 Mb E4B7G5. The results showed that we could separate and purify the 39 kd protein to analyse the amino acid sequence for the cloning, expression and development of genetic engineering vaccines.

Drug leads from the Kallawaya herbalists of Bolivia. 1. Background, rationale, protocol and anti-HIV activity

Aqueous, organic and alcoholic extracts of over 100 samples of 60 species of Kallawaya medicinal herbs representing 30 plant families were assayed to compare their toxicity and ability to protect MT-2 T-lymphoblastoid cells from the cytopathic effect of human immunodeficiency virus (HIV). The results are reported as a therapeutic index (TI) which was > 25 for eighteen species, including seven > 50 and one > 100. The anti-HIV activity resided primarily in the aqueous rather than in the organic extracts and was concentrated in plants used in ethnomedicine to treat lung and liver diseases.

[The changes in mucus components of intestine after burn and their relationship with bacterial translocation]

A dynamic observation at 0.5 hr, 1 hr, 6 hr, 12 hr and 24 hr after 25% third degree burn in 363 rats: 1) The lesions of mucous membrane of ileum. 2) Assessment of the depth of mucus layer and the contents of protein, hexose and sialic acid. 3) Estimation of the content of mucus IgA, serum IgA and the number of plasma cell producing IgA in mucous membrane. 4) Bacterial culture of mesentery lymph node. The following results were achieved: 1) Serious lesions were discovered in ileal mucous membrane. 2) Mucus IgA content was reduced markedly and the reduction was related to bacterial translocation.

SCS1, a multicopy suppressor of hsp60-ts mutant alleles, does not encode a mitochondrially targeted protein

We identified and isolated a Saccharomyces cerevisiae gene which, when overexpressed, suppressed the temperature-sensitive phenotype of cells expressing a mutant allele of the gene encoding the mitochondrial chaperonin, Hsp60. This gene, SCS1 (suppressor of chaperonin sixty-1), encodes a 757-amino-acid protein of as yet unknown function which, nonetheless, has human, rice, and Caenorhabditis elegans homologs with high degrees (ca. 60%) of amino acid sequence identity. SCS1 is not an essential gene, but SCS1-null strains do not grow above 37 degrees C and show some growth-related defects at 30 degrees C as well. This gene is expressed at both 30 and 38 degrees C, producing little or no differences in mRNA levels at these two temperatures. Overexpression of SCS1 could not complement an HSP60-null allele, indicating that suppression was not due to the bypassing of Hsp60 activity. Of 10 other hsp60-ts alleles tested, five could also be suppressed by SCS1 overexpression. There were no common mutant phenotypes of the strains expressing these alleles that give any clue as to why they were suppressible while others were not. An epitope (influenza virus hemagglutinin)-tagged form of SCS1 in single copy complemented an SCS1-null allele. The Scs1-hemagglutinin protein was found to be at comparable levels and in similar multiply modified forms in cells growing at both 30 and 38 degrees C. Surprisingly, when localized either by cell fractionation procedures or by immunocytochemistry, these proteins were found not in mitochondria but in the cytosol. The overexpression of SCS1 had significant effects on the cellular levels of mRNAs encoding the proteins Cpn10 and Mgel, two other mitochondrial protein cochaperones, but not on mRNAs encoding a number of other mitochondrial or cytosolic proteins analyzed. The implications of these findings are discussed.

Limitations to in vivo import of hydrophobic proteins into yeast mitochondria. The case of a cytoplasmically synthesized apocytochrome b

The apocytochrome b gene, exclusively encoded by the mitochondrial genome, was engineered so that it could be expressed in the yeast cytoplasm. Different combinations of the apocytochrome b transmembrane domains were produced in the form of hybrid proteins fused to both the N-terminal mitochondrial targeting sequence of the ATPase subunit 9 from Neurospora crassa and to a cytoplasmic version of the bI4 RNA maturase, localised on the N-terminal and C-terminal sides, respectively, of the hydrophobic stretches. The bI4 RNA maturase, which can complement mitochondrial mutations, was used as an in vivo reporter to assess the mitochondrial import of the different groups of transmembrane helices. This new, reliable and sensitive reporter activity allowed us to experimentally determine the limitations to the mitochondrial import of hydrophobic proteins. All eight transmembrane helices of apocytochrome b could be imported into mitochondria, either alone or in combination, but no more than three to four transmembrane helices could be imported together at one time. This limit is close to that observed in the population of nuclear-encoded mitochondrial proteins. The hydrophobic characteristics of engineered and natural proteins targeted to the mitochondrial inner membrane revealed two factors important in the import process. These were (a) the local hydrophobicity of a transmembrane segment, and (b) the average regional hydrophobicity of the protein over an extended length of 60-80 residues. Such features may have played a major role in the evolution of mitochondrial genomes.

Influence of exercise training on myocardial beta-adrenergic signal transduction: differential regulation with age

Exercise training is known to increase cardiovascular performance and decrease heart rate. Because activation of adenylyl cyclase is an important factor in beta-adrenergic signal transduction and in the decline in signal transduction with age, we hypothesized that some of the effects of exercise training may be mediated by changes in postreceptor activation of adenylyl cyclase. To this end, we assessed isoproterenol-, G protein-, and forskolin-mediated activation of adenylyl cyclase as well as G protein immunoreactivity in the myocardium from young and senescent F-344 rats with and without prior exercise training by treadmill running. Isoproterenol, beta-gamma-imidoguanosine 5'-triphosphate, and forskolin stimulation of adenylyl cyclase activity declined by approximately 50% with age. Training increased the stimulation in the senescent rats and decreased the stimulation in the young rats such that the age-related decline in signal transduction was no longer significant. Gs alpha protein immunoreactivity was unchanged by age or training. These data suggest that in young rats exercise training decreases beta-adrenergic signal transduction, whereas in older rats training increases signal transduction, partially offsetting the decline in signal transduction with age.

Forskolin binding sites and G-protein immunoreactivity in rat hearts during aging

Although the number of beta-adrenoceptors is unchanged with age in rat heart, both beta-adrenoceptor and postreceptor activation of adenylyl cyclase decreases with age. Pharmacologic data suggest that it is the amount of adenylyl cyclase enzyme units that limit activation of adenylyl cyclase with senescence, but direct quantitation of either G protein or adenylyl cyclase in rat heart with age is lacking. To quantitate the amount of adenylyl cyclase and G proteins with age directly, we assessed forskolin-stimulated adenylyl cyclase activity, the number of [3H] forskolin binding sites, and stimulatory G protein (Gs alpha) and inhibitory G protein (Gi alpha) immunoreactivity in the ventricles from 6- and 24-month-old F-344 rats. The amount of Gs alpha and Gi alpha was unchanged with age in both crude membranes and partially purified membranes from ventricles. In contrast, there was a 32% decrease in the ability of forskolin to stimulate adenylyl cyclase maximally and a 41% decrease in the number of forskolin binding sites with age. Sensitivity for forskolin activation was unchanged with age, but there was a slight increase in affinity for [3H]forskolin binding. The decrease in the amount of adenylyl cyclase with age correlates with the diminished capacity to activate adenylyl cyclase with age and may account for the reduced beta-adrenergic signal transduction observed in senescent rat heart.

Loss of mitochondrial hsp60 function: nonequivalent effects on matrix-targeted and intermembrane-targeted proteins

We have created yeast strains in which the mitochondrial chaperonin, hsp60, can be either physically depleted or functionally inactivated. Cells completely depleted of hsp60 stop growing but retain for awhile the capacity to reaccumulate hsp60. While this newly made hsp60 is targeted to and processed correctly within the mitochondrion, assembly of a functional hsp60 complex does not occur. Rather, the hsp60 monomers are localized in different-size soluble complexes containing another mitochondrial chaperone, the mitochondrial form of hsp70. A number of other mitochondrial matrix-targeted proteins synthesized in the absence of functional hsp60 are imported into mitochondria but often show some buildup of precursor forms and, unlike hsp60, accumulate as insoluble aggregates. By contrast, several mitochondrial proteins normally targeted to the intermembrane space show normal processing in the complete absence of a functional hsp60 complex. Similar and complementary results were obtained when we examined the metabolism of matrix- and intermembrane space-localized proteins in cells expressing three different temperature-sensitive alleles of HSP60. In all cases, matrix-targeted proteins synthesized at nonpermissive (i.e., hsp60-inactivating) temperatures were correctly targeted to and processed within mitochondria but accumulated predominantly or totally as insoluble aggregates. The metabolism of two intermembrane space proteins, cytochrome b2 and cytochrome c1, was unaffected at the nonpermissive temperature, as judged by the correct processing and complete solubility of newly synthesized forms of both proteins. These findings are discussed with regard to current models of intermembrane targeting.