Sexual development and the effects of active immunization against GnRH in Chinese Tanyang ram lambs

Tanyang is one of the most important sheep breeds in the northwest of China. However, there is no detailed data on sexual development and timing of puberty/sexual maturity of this breed. This experiment was designed to study the relationships between growth rate and sexual development by measuring body weight, testis diameter, and plasma testosterone concentrations, and observing sexual behavior through puberty from 3 to 8 months old of entire Tanyang ram lambs. At same time, to assess the potential efficacy and welfare benefits of non-surgical castration, the effect of active immunization against gonadotrophin-releasing hormone (GnRH) on sexual development and growth rate on ram lambs was evaluated, and compared with surgically castrated and entire lambs. The results showed that body weight increased at a constant rate from 3 to 8 months old of age. Testis diameter increased rapidly between 3 and 5 months, followed by a period of slow growth. Plasma testosterone concentrations increased sharply from 3 to 6 months of age (P<0.05), after which there were no significant changes from 6 to 8 months of age. Sexual behavior started from 5 months of age. After ram lambs were immunized against GnRH at 3 months of age, there was no increase in testis diameter in the first 4 months after immunization. Plasma testosterone concentrations remained at similar levels to surgically castrated lambs until 6 months of age, and the onset of sexual behavior was delayed, compared with entire ram lambs. GnRH immunization and surgical castration had no significant effect on the body weight by the end of this experiment. These results suggest that 4-5 months of age is a critical period for pubertal changes and testosterone plays an important role in the initiation of puberty and sexual maturity of Tanyang ram lambs in China. In addition, a single shot GnRH immunization at 3 months, acting as an alternative to surgical castration, is a practical method for Chinese Tanyang ram lambs, and provides animal welfare benefits.

Simultaneous improvement for four quality traits of Zhenshan 97, an elite parent of hybrid rice, by molecular marker-assisted selection

"Zhenshan 97" is the female parent of a number of widely used hybrids for rice production in China. However, this line is of poor quality because of a high amylose content (AC), a hard gel consistency (GC) and a low gelatinization temperature (GT), together with a chalky endosperm. It had been determined that the three traits for cooking and eating quality, AC, GC and GT, are controlled by the Waxy locus and/or the tightly linked genomic region. In this study we improved the eating and cooking quality of Zhenshan 97 by introgressing the Waxy gene region from Minghui 63 (wx-MH), a restorer line, that has medium AC, soft GC and high GT. The wx-MH fragment was transferred to Zhenshan 97B by three backcrosses and one selfing, then from Zhenshan 97B to Zhenshan 97A by a cross and a backcross. Molecular marker-assisted selection was applied in the series to select for individuals carrying wx-MH, to identify recombination between the Waxy and flanking markers, and also to recover the genetic background of the recurrent parent. According to the marker genotypes, the improved versions of Zhenshan 97B and Zhenshan 97A, or Zhenshan 97B(wx-MH) and Zhenshan 97A(wx-MH), were the same as the originals except for the Waxy region of less than 6.1 cM in length. The selected lines and their hybrids with Minghui 63, or Shanyou 63(wx-MH), showed a reduced AC and an increased GC and GT, coupled with a reduced grain opacity. Field examinations of agronomic performance revealed that Zhenshan 97B(wx-MH) and Shanyou 63(wx-MH) were essentially the same as the originals except for a significant decrease in grain weight. The simultaneous improvement of AC, GA, GT and opacity, indicated that the Waxy region had major effects on the four quality traits. The improved versions of Zhenshan 97 A and B should be immediately useful in hybrid rice production.

The genetic determinants of the CYP3A5 polymorphism

CYP3A proteins comprise a significant portion of the hepatic cytochrome P450 (CYP) protein and they metabolize around 50% of drugs currently in use. The dissection of the individual contributions of the four CYP3A genes identified in humans to overall hepatic CYP3A activity has been hampered by sequence and functional similarities. We have investigated the expression of CYP3A5 and its genetic determinants in a panel of 183 Caucasian liver samples. CYP3A5 expression is increased in 10% of livers in this ethnic group. Using a high density map of CYP3A5 variants, we searched for genetic markers of the increased CYP3A5 expression. In agreement with an independent, recent study, we report that a SNP within intron 3 (g.6986G>A) is the primary cause of the CYP3A5 protein polymorphism. The frequencies of the g.6986A variant which allow for normal splicing of CYP3A5 transcripts are 5% in Caucasians, 29% in Japanese, 27% in Chinese, 30% in Koreans and 73% in African-Americans. In the last ethnic group, the expression of CYP3A5 in some individuals who carry the g.6986A variant is affected adversely by a frame shift mutation (CYP3A5*7, D348., q = 0.10). In summary, these results should add to efforts to identify clinically relevant, CYP3A5-specific reactions and to further elucidate traits responsible for variable expression of the entire CYP3A family.

The role of cytochrome 2B1 substrate recognition site residues 115, 294, 297, 298, and 362 in the oxidation of steroids and 7-alkoxycoumarins

At least two substitutions were made at each of five amino acid residues in rat cytochrome P450 2B1 that align to residues of known importance in other P450s. The mutants were histidine tagged for purification from Escherichia coli, and the proteins were assessed for testosterone and 7-alkoxycoumarin oxidation. Alteration of each of the sites studied, Phe-115, Ser-294, Phe-297, Ala-298, and Leu-362, was found to affect overall enzyme activity or the metabolite profile. In particular, most of the mutants, excluding F297A, A298G, and L362F, exhibited significantly altered ratios of 16alpha-hydroxytestosterone:16beta-hydroxytestosterone, with the most dramatic alteration being displayed by A298V. Four 7-butoxycoumarin metabolites were produced by CYP2B1, of which two, 7-hydroxycoumarin and 7-(3-hydroxybutoxy)coumarin, were formed at nearly equal rates. Several mutants, F115A, F297A, F297I, and A298V, exhibited an increased predominance of one of the metabolites. The results from this study illustrate the conservation of functionally important residues across P450 subfamilies and families.

[Study on the genetic variations of the major neutralization antigen VP7 of group A rotavirus type G1 in China]

OBJECTIVE

To study the genetic variations of the major neutralization antigen VP7 of group A rotavirus, type G1 in China.

METHODS

Twenty-three isolates derived from seven cities (Beijing, Shenyang, Xinxiang, Shanghai, Shenzhen, Guangzhou and Chongqing) during the period of 1988-1998 were analyzed for the VP7 cDNA sequences.

RESULTS

An obvious homology was observed in amino acid sequences of VP7 in the 23 isolates. Compared with the standard strain Wa, the variations were found at the position of aa 41, 49, 57, 65, 68, 74, 94, 97, 147, 170, 217, 218, 268, 281 and 291, respectively, and all of these were located in the variable region(VR)3,4,5,7,8 as well as in the C-terminal of the peptide. There seemed to be no remarkable divergence among the samples collected from different cities and all of them shared the same genetic lineage with the strain Jpn-417, though there might be one or two amino acid substitutions as time passed. When detected simultaneously with ELISA using G1 serotype-specific monoclonal antibody, the location of amino acid 91 was found presumably related to the neutralization epitope in VP7 of the type G1. Variations at some position may be resulted in the change of electropherotype.

CONCLUSIONS

The results indicated that the recent isolates with representative genetic and antigenic features should be used to develop effective vaccines, and the antigenic variations should be monitored periodically.

Importance of amino acid residue 474 for substrate specificity of canine and human cytochrome p450 3A enzymes

Canine cytochromes P450 3A12 and 3A26 are identical in sequence at 481 of 503 amino-acid positions but exhibit different substrate specificities. A recent study utilizing chimeric enzymes and site-directed mutagenesis identified three residues (187, 368, and 369) that contribute to differences in steroid hydroxylation and also indicated the presence of additional determinants of specificity among the 44 carboxyl terminal residues. Therefore, three 3A26 multiple mutants (I187T-S368P-V369I-S467P, I187T-S368P-V369I-S474P, and I187T-S368P-V369I-R476K-I477L-T479A-R480Q) were constructed. Insertion of 3A12 residue Pro-474 into 3A26 I187T-S368P-V369I resulted in metabolite profiles with testosterone, androstenedione, and progesterone very similar to 3A12. Substitution of Pro-474 with Ser in P450 3A12 or human 3A4 significantly increased 2beta-hydroxylase activity with all three steroids. Residue 474 was also found to be an important contributor to diazepam metabolism by the canine and human enzymes. The results provide further evidence for the role of steric constraints exerted by the enzyme in P450 3A-mediated oxidations.

Amino acid residues critical for differential inhibition of CYP2B4, CYP2B5, and CYP2B1 by phenylimidazoles

The molecular basis for reversible inhibition of rabbit CYP2B4 and CYP2B5 and rat CYP2B1 by phenylimidazoles was assessed with active-site mutants and new three-dimensional models based on the crystal structure of CYP2C5. 4-Phenylimidazole was 17- to 32-fold more potent toward CYP2B4 and CYP2B1 than CYP2B5. The 3D models, along with site-directed mutagenesis data, revealed the importance of residue 114 for sensitivity to inhibition of all three CYP2B enzymes. Besides Ile 114, Val 367 was also found to be critical for inhibition of CYP2B4 and CYP2B1. The most interesting new insights were obtained from analysis of the CYP2B5 model and the CYP2B5 active-site mutants. Simultaneous substitution of residues 114, 294, 363, and 367 with the corresponding residues of CYP2B4 decreased the IC(50) value for inhibition by 4-phenylimidazole 12-fold. Docking 4-phenylimidazole into the models of CYP2B5 mutants demonstrated that the inhibitor-binding site is strongly influenced by residue-residue interactions, especially between residues 114 and 294. A chlorine substitution at position 4 of the phenyl moiety of 4- and 1-phenylimidazole resulted in IC(50) values 95- and 130-fold lower for CYP2B4 than for CYP2B5, respectively, suggesting that these compounds are selective inhibitors of CYP2B4. Overall, the study revealed that differences in the determinants of inhibition between CYP2B4 and CYP2B5 are caused not only by single residue inhibitor contacts but also by residue-residue interactions. This new generation of CYP2B models may provide valuable information for the design of selective inhibitors of human CYP2B6 and for the development of drugs that avoid drug interactions due to P450 inhibition.

Down regulation of myocardial beta1-adrenoceptor signal transduction system in pacing-induced failure in dogs with aortic stenosis-induced left ventricular hypertrophy

We recently demonstrated that rapid ventricular pacing caused cardiac failure (Failure) in dogs with aortic stenosis-induced left ventricular hypertrophy (Hypertrophy) and isoproterenol caused no significant increases in function, O2 consumption and intracellular cyclic AMP level in the failing hypertrophied hearts. We tested the hypothesis that alterations in the beta1-adrenoceptor-signal transduction pathway would correlate with the reduced functional and metabolic responses to beta-adrenergic stimulation during the transition from the compensated hypertrophy to failure. Pressure overload-induced left ventricular hypertrophy was created using aortic valve plication in 10 dogs over a 6-month period. Five months after aortic valve plication, congestive heart failure was induced in 5 dogs by rapid ventricular pacing at 240 bpm for 4 weeks. The density of myocardial beta1-adrenoceptors (fmoles/mg membrane protein; fmoles/g wet tissue) was significantly reduced in the Failure dogs (176+/-19; 755+/-136) when compared to those of the Control (344+/-51; 1,551+/-203) and the Hypertrophy (298+/-33; 1,721+/-162) dogs. The receptor affinities were not significantly different among all groups. There was a small but significant decrease in the percentage of beta1-adrenoceptors of the failing hypertrophied hearts (62+/-3%) when compared to that of the hypertrophied hearts (77+/-5%). The basal myocardial adenylyl cyclase activity (pmoles/mg protein/min) was significantly lower in the Failure dogs (45+/-4) than in the Control (116+/-14) and Hypertrophy (86+/-6) dogs. The forskolin (0.1 mM)-stimulated adenylyl cyclase activity was also significantly lower in the Failure dogs (158+/-17) than in the Control dogs (296+/-35) and slightly lower than in the Hypertrophy dogs (215+/-10). There were no significant differences in low Km cyclic AMP-phosphodiesterase activities among all groups. We conclude that down regulation of beta1-adrenoceptors and reduced adenylyl cyclase activities contribute to the decreases in myocardial functions and beta-adrenergic responses in the failing hypertrophied hearts induced by rapid ventricular pacing.

Assessment of a new quantitative ultrasound calcaneus measurement: precision and discrimination of hip fractures in elderly women compared with dual X-ray absorptiometry

The incidence of osteoporotic hip fracture increases in postmenopausal women with low hip bone mineral density (BMD). Dual X-ray absorptiometry (DXA) is the most commonly used technique for the assessment of bone status and provides good measurement precision. However, DXA affords little information about bone architecture. Quantitative ultrasound (QUS) systems have been developed to evaluate bone status for assessment of fracture risk. Our study was designed to assess a new QUS system from Hologic, the Sahara; to compare it with a previous model, the Walker-Sonix UBA 575+; and to investigate whether it is able to discriminate between women with and without fracture. Using both ultrasound devices, the measurements were performed at the heels of 33 postmenopausal women who had recently sustained hip fracture. A control group of 35 age-matched postmenopausal women was recruited for comparison. The total, neck and trochanter femoral BMD values were assessed using DXA for both groups. QUS and DXA measurements were significantly lower in fractured patients (p < 0.005) than in the control group. The short-term, mid-term and standardized short-term precisions were used to evaluate the reproducibility of the two QUS systems. The Sahara showed a better standardized coefficient of variation for broadband ultrasound attenuation (BUA) than did the UBA 575+ (p < 0.001). The correlation of BUA and speed of sound (SOS) between the two QUS devices was highly significant, with an r value of 0.92 for BUA and 0.91 for SOS. However, the correlation between DXA and ultrasound parameters ranged from 0.28 to 0.44. We found that ultrasound measurements at the heel were significant discriminators of hip fractures with odds ratios (OR) ranging from 2.7 to 3.2. Even after adjusting the logistic regressions for total, neck or trochanter femoral BMD, QUS variables were still significant independent discriminators of hip fracture. The areas under the ROC curves of each ultrasound parameter ranged from 0.75 to 0.78, and compared very well with femoral neck BMD (p > 0.05). In conclusion, our study indicated that the calcaneal QUS variables, as measured by the Sahara system can discriminate hip fracture patients equally as well as hip DXA.

Comparison of six calcaneal quantitative ultrasound devices: precision and hip fracture discrimination

Quantitative ultrasound (QUS) is now accepted as a useful tool in the management of osteoporosis. There are a variety of QUS devices clinically available with a number of differences among them, including their coupling methods, parameter calculation algorithms and sites of measurement. This study evaluated the abilities of six calcaneal QUS devices to discriminate between normal and hip-fractured subjects compared with the established method of dual-energy X-ray absorptiometry (DXA). The short-term and mid-term precisions of these devices were also determined. Thirty-five women (mean age 74.5+/-7.9 years) who had sustained a hip fracture within the past 3 years, and 35 age-matched controls (75.8+/-5.6 years) were recruited. Ultrasound measurements were acquired using six ultrasound devices: three gel-coupled and three water-coupled devices. Bone mineral density was measured at the hip using DXA. Discrimination of fracture patients versus controls was assessed using logistic regression analysis (expressed as age- and BMI-adjusted odds ratios per standard deviation decrease with 95% confidence interval) and receiver operating characteristics (ROC) curve analysis. Measurement precision was standardized to the biological range (sCV). The sCV ranged from 3.14% to 5.5% for speed of sound (SOS) and from 2.45% to 6.01% for broadband ultrasound attenuation (BUA). The standardized medium-term precision ranged from 4.33% to 8.43% for SOS and from 2.77% to 6.91% for BUA. The pairwise Pearson correlation coefficients between different devices was highly significant (SOS, r = 0.79-0.93; BUA, r = 0.71-0.92). QUS variables correlated weakly, though significantly, with femoral BMD (SOS, r = 0.30-0.55; BUA, r = 0.35-0.61). The absolute BUA and SOS values varied among devices. The gel-coupled devices generally had a higher SOS than water-coupled devices. Bone mineral density (BMD) and BUA were weakly correlated with weight (r = 0.48-0.57 for BMD and r = 0.18-0.54 for BUA), whereas SOS was independent of weight. All the QUS devices gave similar, statistically significant hip fracture discrimination for both SOS and BUA measures. The odds ratios for SOS (2.1-2.8) and BUA (2.4-3.4) were comparable to those for femoral BMD (2.6-3.5), as were the area under the curve (SOS, 0.65-0.71; BUA, 0.62-0.71; BMD, 0.65-0.74) from ROC analysis. Within the limitation of the sample size all devices show similar diagnostic sensitivity.

2,2',3,3',6,6'-hexachlorobiphenyl hydroxylation by active site mutants of cytochrome P450 2B1 and 2B11

The structural basis of species differences in cytochrome P450 2B-mediated hydroxylation of 2,2',3,3',6,6'-hexachlorobiphenyl (236HCB) was evaluated by using 14 site-directed mutants of cytochrome P450 2B1 and three point mutants of 2B11 expressed in Escherichia coli. To facilitate metabolite identification, seven possible products, including three hydroxylated and four dihydroxylated hexachlorobiphenyls, were synthesized by direct functionalization of precursors and Ullmann and crossed Ullmann reactions. HPLC and GC/MS analysis and comparison with authentic standards revealed that 2B1, 2B11, and all their mutants produced 4, 5-dihydroxy-236HCB and 5-hydroxy-236HCB, while 2B11 L363V and 2B1 I114V mutants also catalyzed hydroxylation at the 4-position. The amount of products formed by 2B1 mutants I114V, F206L, L209A, T302S, V363A, V363L, V367A, I477A, I477L, G478S, I480A, and I480L was smaller than that of the wild type. I477V exhibited unaltered 236HCB metabolism, and I480V produced twice as much dihydroxy product as the wild type. For 2B11, substitution of Val-114 or Asp-290 with Ile decreased the product yields. Replacement of Leu-363 with Val dramatically altered the profile of 236HCB metabolites. In addition to an increase in the overall level of hydroxylation, the mutant mainly catalyzed hydroxylation at the 4-position. Incubation of P450 2B1 with 5-hydroxy-236HCB produced 4,5-dihydroxy-236HCB, which indicates that 4,5-dihydroxy-236HCB may be formed by a direct hydroxylation of 5-hydroxy-236HCB. The findings from this study demonstrate the importance of residues 114, 206, 209, 302, 363, 367, 477, 478, and 480 in 2B1 and 114, 290, and 363 in 2B11 for 236HCB metabolism.

Genetic bases of instability of male sterility and fertility reversibility in photoperiod-sensitive genic male-sterile rice

Photoperiod-sensitive genetic male-sterile (PSGMS) rice, with its male fertility regulated by photoperiod length, is very useful for hybrid rice development. However, breeding for new PSGMS lines has faced two major difficulties - the stability of male sterility and the reversibility of male fertility. In this study we assessed the genetic bases of stability of sterility and fertility reversibility using a molecular marker-based approach. A cross was made between two newly bred PSGMS lines: Peiai 64S, which has a stable sterility but is difficult to reverse to fertility, and 8902S, which has a unstable sterility but is easy to reverse to fertility. The fertility of the parents and of the F(1) and F(2) populations was repeatedly examined under 11 different long-day and short-day conditions. The genetic effects were assayed by interval mapping and two-way analyses of variance using the F(2) data of 128 polymorphic loci representing all the 12 rice chromosomes. The analyses resolved a number of single-locus QTLs and two-locus interactions under both long-day and short day conditions. The interactions involved a large number of loci, most of which were not detectable on a single-locus basis. The results showed that the genetic bases of both stability of sterility and reversibility of fertility are the joint effects of the additive effects of the QTLs and additive-by-additive components of two-locus interactions. The implications of these findings in hybrid rice development are also discussed.

An evaluation of a new gel-coupled ultrasound device for the quantitative assessment of bone

Quantitative ultrasound (QUS) is now being accepted as a tool in the assessment of bone status. Most QUS devices measure broadband ultrasound attenuation (BUA) and speed of sound (SOS). A newly introduced device, the Acoustic Osteo-Screener (AOS-100), measures both SOS and an attenuation related parameter called the transmission index (TI) and provides a derived parameter called osteo sono-assessment index (OSI). The purpose of this study was to examine the reproducibility of this new device, compare the results with the UBA 575+ and evaluate the effect of using two platforms to compensate for different foot sizes on the measured values. 83 subjects aged 21-89 years, who gave informed consent, were recruited. Subjects were assigned to three different groups determined by age and health status. The short-term measurement precision (expressed as root mean square coefficient of variation) of SOS (0.13-0.16%) and TI (1.18-1.96%) was similar to and better than that obtained for the UBA 575+. Significant negative correlations were found between the differences in SOS measured with the two platforms (adaptors to adjust the position of the foot relative to the foot plate) and foot length (p < 0.0001). This implies that small feet are more influenced by the differences of measured location. All QUS parameters measured with the small platform were found to be significantly smaller than those with the large platform (p < 0.0001). The mean percentage differences were 0.6% in SOS, 2.8% in TI and 4.3% in OSI with the large foot platform giving larger value results. Proper use of the platforms resulted in more reproducible SOS and TI. This study demonstrated that the newly developed AOS-100 parameters TI and OSI were highly reproducible. This study also demonstrated that the use of an inappropriate platform can cause discrepancies in QUS readings and poor reproducibility.

Use of chimeric enzymes and site-directed mutagenesis for identification of three key residues responsible for differences in steroid hydroxylation between canine cytochromes P-450 3A12 and 3A26

Canine cytochromes P-450 3A12 and 3A26 differ by 22 out of 503 amino acid residues. Chimeric constructs and site-directed mutants were used to identify the residues responsible for the much higher rates of steroid hydroxylation by 3A12. Six initial 3A12/3A26 hybrids were generated using convenient restriction sites, and site-directed mutagenesis was used to restore full 3A12 activity to two of the hybrids. One pair of 3A12/3A26 chimeras indicated that the first four residue differences between 3A12 and 3A26 were at least partially responsible for the differences in progesterone hydroxylation. Conversion in one of the hybrids of the Ile-187 residue found in 3A26 to the Thr in 3A12 conferred 3A12 levels of progesterone 6beta-hydroxylase activity. Analysis of another chimera identified key residues within an internal PstI fragment (codons 331-459) containing six amino acid residue differences. Subsequent site-directed mutagenesis of 3A26 residues Ser-368 and Val-369 to Pro and Ile, respectively, restored the rate of formation of 6beta-hydroxyprogesterone by the hybrid to that of 3A12. The simultaneous conversion of 3A26 residues 187, 368, and 369 to those of 3A12 conferred greater than a third of the progesterone 6beta-hydroxylase activity and all of the testosterone and androstenedione 6beta-hydroxylase activity of 3A12. Addition of the carboxyl terminal 44 3A12 residues to the 3A26 triple mutant doubled progesterone 6beta-hydroxylase activity. This is the first study to use catalytically distinct cytochromes P-450 3A from the same species in the elucidation of structure-function relationships.

Osteoarthrosis of the temporomandibular joint induced by intra-articular injection of lactate dehydrogenase: an experimental study in adult rabbits

OBJECTIVE

The purpose of this study was to establish an animal model of osteoarthrosis in the temporomandibular joint (TMJOA) by injecting lactate dehydrogenase (LDH) into the maxillary compartments of TMJs in adult rabbits.

METHODS

Adult New Zealand white rabbits were randomly divided into four groups (A through D) of five animals each. The A and B groups were used as a control. The maxillary compartments of the C and D group (TMJs) were injected with 0.1 mL of LDH in two different concentrations. The TMJ samples were analyzed histologically and with a scanning electron microscope four different times after injection.

RESULTS

The animals that had been injected with LDH at two different concentrations showed similar results. The TMJs had changes typical of OA in early to moderate stages. No pathologic changes could be found in the TMJs of the control groups.

CONCLUSIONS

The results suggest that LDH may be of use in establishing an animal model of TMJOA.

Differentiation and classification of parental lines and favorable genic interactions affecting F1 fertility in distant crosses of rice (Oryza sativa L.)

This study was intended to investigate the extent of genetic differentiation in parental lines of rice hybrids and to analyze the genetic basis underlying the fertility phenomenon in distant crosses. Two subsets of rice material (111 entries in total) were used, including 81 doubled-haploid (DH) lines and 30 Indica and Japonica rice varieties or lines (as a control). The DH lines was derived from a heterotic Indica/Japonica cross (Gui630/02428) by anther culture. The materials in the control represent a broad spectrum of the Asian cultivated rice gene pool including landraces, primitive cultivars, historically important cultivars, modern elite cultivars, super rice and parents of superior hybrids. In accordance with the NC II design, 57 out of the DH lines were test-crossed to two important wide compatibility lines: photoperiod-sensitive genetic male sterile (PGMS) line N422s and thermo-sensitive genetic male sterile (TGMS) line Peiai64s. The F1s and their parents, 182 entries in total, were examined for the performance of seven traits in a replicated field trial. All the rice materials was surveyed for polymorphisms using 92 RFLP markers selected from two published molecular marker linkage maps. Genotypes of the F1 hybrids at the molecular-marker loci were deduced from the parental genotypes. The analysis showed that there were two types of genetic differentiation in the two subsets of rice material; that is, qualitative differentiation in the control and quantitative differentiation in the DH lines. In addition, favorable genic interactions (both intra- or inter-locus) contributed to better increase the fertility in hybrids of distant crosses through incorporation of a wide-compatibility line as the female parent. Favorable genic interactions can be applied in hybrid rice breeding programs by selecting parents with an appropriate extent of genetic differentiation.

Structural determinants of progesterone hydroxylation by cytochrome P450 2B5: the role of nonsubstrate recognition site residues

The highly related rabbit cytochromes P450 2B4 and 2B5 differ in only 12 amino acid positions, but only 2B5 has activity toward progesterone. Previously, simultaneous site-directed mutagenesis of four key substrate recognition site (SRS) residues (114, 294, 363, and 367) was shown to result in interconversion of the androstenedione hydroxylase specificities of cytochrome P450 2B4 and 2B5. However, the progesterone metabolite profiles of the 2B4 quadruple mutant or of a quintuple mutant in which residue 370 was also mutated to the 2B5 residue were not identical to that of P450 2B5. Therefore, single mutants of P450 2B5 at the remaining seven positions were constructed, expressed in Escherichia coli, and studied with progesterone as the substrate. The single mutants at positions 120 and 221, which are outside any known SRS, exhibited a significant alteration in progesterone hydroxylation. Based on these results, Ile-114, Arg-120, Ser-221, Ser-294, Ile-363, and Val-367 in cytochrome P450 2B4 were replaced simultaneously with Phe, His, Pro, Thr, Val, and Ala, respectively, from 2B5. This yielded a mutant with a very similar progesterone metabolite profile to that of 2B5, although the total activity was lower. An additional substitution at residue 370 produced a multiple mutant P450 2B4 I114F-R120H-S221P-S294T-I363V-V367A- T370M with very similar or identical substrate specificity, regio- and stereospecificity and kinetic properties to that of P450 2B5 wild type.

[Determination of sinomenine HCl in serum and urine by HPLC and its pharmacokinetics in normal volunteers]

A RP-HPLC method was developed to determine the concentrations of sinomenine HCl in serum and urine and its pharmacokinetics was studied in healthy volunteers. C18H37 column was eluted with the mobile phase of acetonitrile--0.01 mol.L-1 sodium phosphate monobasic--N, N, N', N'-tetramethylenediamine (46:54:0.22 v/v, pH 6.9) and the ultraviolet absorbance was monitored at 263 nm. Triazolan was used as internal standard. The calibration curves were linear in the range of 6-480 ng.ml-1 in serum and 0.06-3 micrograms.ml-1 in urine, with mean recoveries of 75.46% and 91.38% respectively. The lowest detectable limits were 4 ng.ml-1 in serum and 40 ng.ml-1 in urine and the RSD for the intra-day and inter-day were less than 5%. A single oral dose of 80 mg sinomenine HCl tablet was given to 8 healthy male volunteers. The concentrations of sinomenine HCl in serum and urine were determined. The serum concentration--time curve was found to fit a two-compartment open model with first order elimination. The pharmacokinetic parameters were: T1/2 alpha 0.791 +/- 0.491 h, T1/2 beta 9.397 +/- 2.425 h, Tmax 1.040 +/- 0.274 h, Cmax 246.604 +/- 71.165 ng.ml-1, AUC 2651.158 +/- 1039.050 ng.h.ml-1, CL 0.033 +/- 0.010 ng.ml-1.

Identification of three key residues in substrate recognition site 5 of human cytochrome P450 3A4 by cassette and site-directed mutagenesis

Cassette mutagenesis and site-directed mutagenesis were used to investigate the importance of individual amino acid residues at positions 364-377 of cytochrome P450 3A4 in determining steroid hydroxylation or stimulation by alpha-naphthoflavone. The mutants were expressed in an Escherichia coli system, and solubilized membranes were prepared. All mutants except R365G and R365K exhibited anti-3A immunoreactivity on Western blotting, although R372S and R375K were not detected as the Fe2+-CO complex. Replacement of Arg-372 by Lys yielded a typical P450 spectrum. The results indicate that the highly conserved Arg residues at positions 365 and 375 may play a role in stabilizing the tertiary structure or in heme binding. Catalytic activities of 12 mutants were examined using progesterone and testosterone as substrates, and residues 369, 370, and 373 were found to play an important role in determining substrate specificity. Although the three mutants hydroxylated progesterone and testosterone primarily at the 6beta-position like the wild-type, replacement of Ile-369 by Val suppressed progesterone 16alpha-hydroxylase activity, whereas substitution of Ala-370 with Val enhanced progesterone 16alpha-hydroxylation. Interestingly, substitution of Leu-373 with His resulted in production of a new metabolite from both steroids. Moreover, the mutants at positions 369 and 373 were more and less responsive, respectively, than the wild-type to alpha-naphthoflavone stimulation. Alterations in activities or expression of several mutants were interpreted using a three-dimensional model of P450 3A4. The results suggest that analogy with mammalian family 2 and bacterial cytochromes P450 can be used to predict P450 3A residues that contribute to regiospecific steroid hydroxylation.

Interconversion of the androstenedione hydroxylase specificities of cytochromes P450 2B4 and 2B5 upon simultaneous site-directed mutagenesis of four key substrate recognition residues

Based on recent studies of single reciprocal mutants of cytochrome P450 2B4 and the highly related P450 2B5 at positions 114, 294, 363, and 367 [G. D. Szklarz, Y. Q. He, K. M. Kedzie, J. R. Halpert, and V. L. Burnett (1996) Arch. Biochem. Biophys. 327,308-318], a number of multiple mutants were constructed, expressed in Escherichia coli, and assayed with androstenedione, progesterone, and benzyloxyresorufin. Simultaneous substitutions of Ile-114, Ser-294, Ile-363, and Val-367 in cytochrome P450 2B4 with Phe, Thr, Val, and Ala, respectively from 2B5, resulted in a marked increase in androstenedione 15alpha- and 16alpha-hydroxylation compared with the wild-type enzyme and yielded a metabolite profile indistinguishable from that of cytochrome P450 2B5. Likewise, the reciprocal P450 2B5 quadruple mutant exhibited the specificity for 16beta-hydroxylation characteristic of the 2B4 wild type. The two reciprocal quadruple mutants of P450 2B4 and 2B5 also displayed benzyloxyresorufin dealkylase activities similar to those of the wild-type P450 2B5 and 2B4, respectively. However, the progesterone metabolite profile of P450 2B5 was not identical to that of the 2B4 quadruple mutant or of a quintuple mutant in which residue 370 was also mutated to the 2B5 residue. Therefore, the 17beta-acetyl group on progesterone as opposed to the oxo group on androstenedione may lead to interaction with additional amino acid residues.

Elucidation of amino acid residues critical for unique activities of rabbit cytochrome P450 2B5 using hybrid enzymes and reciprocal site-directed mutagenesis with rabbit cytochrome P450 2B4

The molecular basis for the unique activities of rabbit cytochrome P450 2B5, compared with the highly related rabbit 2B4, was investigated using hybrid enzymes and site-directed mutagenesis. Alterations in androstenedione hydroxylase profiles observed with 2B4-2B5 hybrids expressed in COS cells showed that key amino acids are present in both the N-terminal ApaI fragment (codons 1-122) and an internal SstI fragment (codons 220-393). Based on these results, data obtained with other cytochromes P450 2B, and correlation to the six substrate recognition sites proposed by Gotoh (1992, J. Biol. Chem. 267, 83-90), reciprocal 2B4-2B5 mutants were constructed at positions 114, 294, 363, and 367. Wild-type and mutant enzymes were expressed in Escherichia coli, and the oxidation of a number of substrates was analyzed. All residues studied were found to be important for regio- and stereospecificity of androstenedione hydroxylation. Mutations at these positions also caused alterations in the oxidation of progesterone, benzyloxyresorufin, pentoxyresorufin, ethoxycoumarin, and benzphetamine, with the magnitude and direction of the changes dependent upon the enzyme, residue, and substrate. Major changes in activity were consistently observed upon mutation of residues 114 and 294 in both enzymes, and some of these alterations were interpreted with the help of a 3-D model of P450 2B4. For example, in the 2B4 Ile-114--> Phe mutant, Phe prevents androstenedione from assuming a 16 beta-binding orientation and also hinders binding of benzyloxyresorufin, leading to a loss of activity. Conversely, the presence of Phe-114 stabilizes a 16 alpha-binding orientation of androstenedione, resulting in an increase in this activity.

Escherichia coli expression of site-directed mutants of cytochrome P450 2B1 from six substrate recognition sites: substrate specificity and inhibitor selectivity studies

Cytochrome P450 2B1 wild-type and eight site-directed mutations at positions 114, 206, 236, 302, 363, 367, and 478 have been expressed in an Escherichia coli system. Solubilized membrane preparations yielded 100-180 nmol of P450/L of culture. The metabolism of a number of substrates including androstenedione, progesterone, (benzyloxy)resorufin, pentoxyresorufin, and benzphetamine was analyzed. The E. coli-expressed enzymes displayed the same androstenedione metabolite profiles previously observed with a COS cell expression system. Several of the mutants exhibited an increased rate of progesterone hydroxylation, possibly as the result of an enlarged substrate binding pocket and increased D-ring alpha-face binding. (Benzyloxy)resorufin and pentoxyresorufin O-dealkylation by the P450 2B1 mutants exhibited activities ranging from 10% to 99% and 3% to 71% of wild-type, respectively. Interestingly, the Val-363-->Leu mutant showed markedly suppressed pentoxyresorufin but unaltered (benzyloxy)resorufin dealkylase activity. Benzphetamine N-demethylase activities ranged from 28% to 110% of wild-type. Mechanism-based inactivation of the P450 2B1 mutants showed that susceptibility to inactivation by chloramphenicol and D-erythro- and L-threo-chloramphenicol was abolished in the Val-367-->Ala mutant. The Val-363-->Leu mutant was refractory to L-threo-chloramphenicol. Studies of chloramphenicol covalent binding and metabolism by the Val-367-->Ala mutant showed that its resistance to inactivation is largely attributable to an inability to bioactivate the inhibitor. The expression of P450 2B1 wild-type and mutants in E. coli provides an excellent opportunity to study structure/function relationships by site-directed mutagenesis.

[Trans-corneal trabeculectomy]

One of the main causes in failure of fistulizing operations for glaucoma is related to conjunctival and subconjunctival cicatrization. Trans-corneal trabeculectomy is different from conventional fistulizing operations and the conjunctival incision is avoided. Passing through the cornea, partial thickness sclera and trabecula are removed. The conjunctiva is least violated during the procedures. Trans-corneal trabeculectomy was completed in 15 eyes with glaucoma. Most of filtering blebs revealed diffuse. The conjunctival inflammatory reaction was minimal with only mild hyperemia even at the first postoperative day. Intraocular pressure of 14 eyes was normal without any medication postoperatively.

Effects of exogenous gamma-aminobutyric acid on experimental arrhythmias

The effects of exogenous gamma-aminobutyric acid (GABA) 10 mg.kg-1 iv in preventing arrhythmias induced by drugs and ischemia were studied in mice, rats, and guinea pigs. It was found that the threshold dose of aconitine inducing arrhythmia in mice and the recovery rate to normal sinus rhythm increased significantly, ED50 of GABA was 5.4-5.8 mg.kg-1. The duration of ventricular tachycardia (VT) induced by aconitine in rats was shortened (P < 0.01). The incidence and the mortality of ventricular fibrillation (VF) in GABA group were decreased to 0/10 vs 6/10 and 5/10 in control, respectively (P < 0.05). The doses of ouabain to induce ectopic beats (EB), VT, VF, and cardiac arrest (CA) in guinea pigs were increased (P < 0.01). The incidence of VF induced by coronary artery ligation in rats was decreased to 0/5 in GABA group vs 4/5 in control group (P < 0.01). The total amount of EB, total time of VT, and VF were 66%, 41%, and 0% of the control group, respectively. The anti-arrhythmic effects of GABA were dose-dependent and as potent as procainamide (10 or 5 mg.kg-1, iv). The results suggest GABA (10 mg.kg-1, iv) may be useful for the prevention of VT and VF.