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Background: The diagnosis of diffuse hepatic lesions in early stage is a tough task at any time for clinical conventional imaging. Magnetic resonance diffusion-weighted imaging (MR DWI) can detect the changes of tissue structure at molecular level. This study was designed to determine the value of DWI in the diagnosis of diffuse liver lesions in early stage., Methods: Diffuse liver lesions were induced by diethylnitrosamine in 42 rats of test group. Fourteen rats in control group were fed with pure water. Dynamic changes of MR DWI were observed every week in both groups during the early stage of diffuse liver lesions (1 to 12 weeks after drug administration in the test group). Apparent diffusion coefficient (ADC) values of liver parenchyma in different stages and pathologic changes were analyzed., Results: The process of diffuse hepatic lesions in the test group was classified into three stages according to pathological changes, namely hepatitis, hepatic fibrosis and cirrhosis. No obvious morphological changes were shown by conventional imaging in both groups during this stage. But MR DWI demonstrated heterogeneous signal changes in early stage of hepatic cirrhosis in the test group. No significant change of ADC values was found in the control group between different weeks (P > 0.05). The ADC values of the test group declined from the fifth week, and after the tenth week the ADC values were significantly different between the test and control groups at gradient factor (b) value 300 sec/mm(2) (P < 0.05). At b value 600 and 1000 sec/mm(2), significant difference was seen between the two groups from the sixth week onward. The range of ADC value of the groups was (1.7 - 0.9) +/- (0.40 - 0.04) mm(2)/sec (b = 600) and (1.38 - 0.75) +/- (0.07 - 0.35) mm(2)/sec (b = 1000), respectively. Dominant pathological changes included swelled hepatocytes within 1 to 4 weeks after the administration of diethylnitrosamine in the test group, hyperplasia of fibrous tissues in 5 - 8 weeks and formation of cirrhotic nodules in 9 - 12 weeks., Conclusions: MR functional DWI could detect diffuse liver lesions earlier than conventional morphological imaging. ADC value as a marker for early diagnosis of diffuse liver lesions could also be used to inspect changes of the lesions.

Objective: To study the effect of disc degeneration on the structural property distributions in the cervical vertebral endplates., Methods: A 2 mm-diameter hemispherical indenter was used to perform indentation tests at 0.03 mm/s to the depth of 2 mm at 20 normalized locations in 50 bony endplates of intact human cervical vertebrae (C2 approximately C7). The resulting load-displacement curves were used to extract the failure load and stiffness of each test site. Grade of disc degeneration was determined using Nachemson's grading scale. One-way ANOVA, factorial analyses, SNK tests and correlate analyses were used to analyze the result data., Results: Both the failure load and stiffness decreased with disc degeneration in the cervical endplates (P <0.001, both), and correlated significantly with the disc degeneration (rs=-0.429 and rs=-0.244, respectively). Only the distribution of superior cervical endplate changed with disc degeneration, but that of inferior cervical endplate changed little., Conclusions: The structural property distributions in the cervical vertebral endplates change significantly in the degenerated discs. It suggests that disc degeneration is an important factor to evaluate the intervertebral implant subsidence in anterior cervical fusion.

Objective: To construct a three-dimensional (3D) mandibular model using a 3D laser scanner, and explore a new method for reconstructing the finite element geometry model., Methods: A mandible specimen was scanned with the 3D laser scanner to form the point clouds of the mandibular surface, which were subsequently aligned for reconstruction of the mandibular model., Result: A 3D model of the mandible surface was reconstructed, which could be used for finite element simulation., Conclusion: The 3D laser scanning system can be used to reconstruct the 3D model with irregular geometry for finite element simulation.

Objective: This study was to introduce the method for obtaining accurate 3D data of soft tissues using a 3D scanner under non-contact condition and the standard 3D measurement of the nasal orbit fossa for plastic surgery., Methods: A 3D laser scanner and the Geomagic software were used to obtain the standard facial contour of 30 Chinese people. The nasal orbit fossa, as the feature of beauty, was measured and the data were analyzed., Results: 3D measurement exhibited the three-dimensional facial shape at every meaningful angle, with the advantages of high precision of 0.01 mm. We determined the lowest point and described the 3D feature of the nasal orbit fossa., Conclusions: This method can illustrate the relation of the nasal orbit fossa and the surrounding structure. It is a new approach to facilitate preoperative plans, operation simulation and postoperative evaluation.

Objective: To research biomechanical mechanism of overuse injuries of second metatarsal and plantar aponeurosis of flat foot and normal foot, to contrast injury risk of flat foot with that of normal foot in gait cycle, and to offer quantitative academic base for clinical therapeutic and preventive measures., Methods: Biomechanical MTS test, computational medicine means, finite element method and fatigue injury theory were adopted, fatigue behavior of flat foot and normal foot in gait cycle was simulated quantificationally by computer, their models successfully validated by test of stress concentration of foot bones and X-ray measurement of arch deformation., Results: The finite element model of elastic arch of flat foot was established, peak values of fatigue stresses of second metatarsal and plantar aponeurosis in flat foot were individually 28.77 MPa and 12.53 MPa, these stresses of flat foot increased individually 8% approximately 21% and 21% approximately 51% than those of normal foot. Transfer of tension stresses of both flat foot and normal foot took place when plantar aponeurosis got infected or released partially, relative maximum of stress transfer occurred in plantar ligament, absolute maximum of stress transfer occurred in base of second metatarsal, the final stress of flat foot always overrun 0.26 approximately 5.32 MPa than normal foot., Conclusion: Von Mises stresses of both flat foot and normal foot are concentrated on second metatarsal and plantar aponeurosis, but peak values of fatigue stresses of flat foot are higher than normal foot. Tension stress of plantar aponeurosis is maximum in all plantar soft tissues, plantar fasciitis or surgical partial release of plantar fascia leads to transfer of tension stresses, and can aggravate overuse injury of plantar muscles and plantar ligament, also can add risk of fatigue fracture of second metatarsal. Internal rotation of flat foot, arch collapse, and hammer toe of second ray caused by bunions all can increase incidence rate of overuse injury in flat foot.

Comprehensive and structured annotations for all genes on a microarray chip are essential for the interpretation of its expression data. Currently, most chip gene annotations are one-line free text descriptions that are often partial, outdated and unsuitable for large-scale data analysis. Therefore the interpretation of microarray gene expression clusters is often limited. Although researchers can manually navigate a collection of databases for better annotations, it is only practical for limited number of genes. Existing meta-databases fail to provide comprehensive categorized annotations for hundreds of genes simultaneously. We have developed an automatic system to address this issue. GeneView system monitors various data sources, extracts gene information from a source whenever it is updated, comprehensively matches genes, and integrates them into a central database by categories, such as pathway, genetic mapping, phenotype, expression profile, domain structure, protein interaction, disease association, and references. The system consists of four major components: (1) relational database; (2) data processing; (3) user curation; (4) data query. We evaluated it by analyzing genes on cDNA and Affymetrix Oligo chips. In both cases, the system provided more accurate and comprehensive information than those provided by the vendors or the chip users, and helped identify new common functions among genes in the same expression clusters.

Objective: To study the biomechanical response and the role of articular surface on the femur-tibia model under impact loading of the body weight., Methods: A three-dimensional finite element (FE) model of the femur-tibia composite was reconstructed using the image data of the knee joint of Virtual Chinese Human No.1 Male, and FE calculation was performed to simulate the impact of the body weight on the knee joint while walking., Results: The femur-tibia composite was compressed during the impact with obvious protrusive movement. Diffusion and attenuation of the stress occurred during its conduction to the articular surface., Conclusion: The femur-tibia composite is unstable under the vertical impact loading of the body weight, with obvious protraction movement, and the articular surface may serve as the buffer of the impact.

Objective: To study the effects of iodine supplementation (in different kinds and doses) on the antioxidative ability of retina in iodine deficient rats., Methods: One hundred and twenty eight iodine deficient Wistar rats were randomly divided into four groups, normal dose of iodate, normal dose of iodide, high dose of iodate and high dose of iodide. Concentration of serum thyroid hormones, including total TT(3) and total TT(4), were estimated by radioimmunoassay. GSH-Px, SOD, TAOC activities and MDA content in the retina were determined using biochemical methods in the 22nd week of iodine supplementation., Results: Statistical analysis showed that a significant difference in TT(3) level of serum was observed between animals treated with different doses. Serum TT(3) level in the groups treated with high doses was significantly higher than those with normal doses. However, no statistical difference could be detected at TT(4) level between animals treated with different doses. Different kind of iodine did not affect the level of thyroid hormones. Statistical analysis showed that a difference in SOD activity of retina was observed between animals treated with different doses. SOD activity in the groups with normal doses was significantly higher than that in groups with larger doses. Retina TAOC activity was significantly higher in groups treated with iodide than that in groups of iodate. Although there was no statistical difference in GSH-Px activity between different groups, it showed the same tendency as the SOD and TAOC activities, i.e. GSH-Px activity in the groups of normal doses was higher than that in the groups of high doses. GSH-Px activity in groups of iodide was higher than that in the groups of iodate. There was no significant difference in MDA content among these four groups., Conclusions: Different iodine and doses have certain effects on the antioxidative ability of retina in iodine deficient rat. The rats supplemented potassium iodide at normal dose showed higher antioxidative ability of the retina than those of the others.

Objective: To evaluate the biomechanical stability of Shen's instrumentation in the management of thoracolumbar fractures., Methods: The ranges of movement (ROM) in three dimensions of twelve T(12) - S(3) specimen of fresh adult cadavers were measured sequentially in the states of normal, injured, GSS and SOCON fixation, fatigued GSS and SOCON fixation. Data were then compared., Results: For the L(2 - 3) segment, the average normal ROM in flexion was 8.3 degrees. In the established spondylolisthesis models, the ROM was 14.7 degrees. After fixation with SOCON, the ROM was decreased to 3.0 degrees, indicating that SOCON fixation can produce good stability. The ROM after fatigue test was 3.6 degrees, significantly lower than that of the normal state, indicating that SOCON still produces good stability after fatigue. For the L(4 - 5) segment, the average normal ROM in flexion was 8.6 degrees. In the established spondylolisthesis models, the ROM was 13.7 degrees. After GSS fixation, the ROM was decreased to 3.2 degrees, significantly lower than that in the normal state, indicating that GSS fixation can produce good stability. ROM after fatigue test was 3.7 degrees, significantly lower than that of the normal state, indicating that GSS can produce good stability after fatigue. The ROM measurements in the other five directions were similar to those for flexion described above., Conclusion: GSS produces good stability for spondylolisthesis, good fatigue resistance, and can be used in pedicle screw revision surgery. There were no significant differences between GSS and SOCON.

To establish an Internet-based database for the dataset of Virtual Chinese Human that is accessible to the interested researchers, modifications and compression of the original VCH-format dataset of Virtual Chinese Human were performed before it was uploaded to the server, and RAID0+1 storage technology was adopted with specific download accesses designed for different users. After dataset modification and compression, the data size was considerably reduced to allow convenient data storage and transfer. The RAID0+1 storage technology guarantees the security and high-speed download of data through different means established. Internet-based database provides important accesses for sharing the achievement in virtual human study between world-wide researchers, which has been imperative in the present situation of science development.

To provide a three-dimensional (3D) model of the knee joint of digitized Virtual Chinese Male No.1 for finite element simulation, the digitized image data of the serial sections of the virtual human knee joint were imported to a computer for 3D reconstruction using Mimics software after image segmentation and registration. Surface smoothing of the reconstructed model was performed with FreeForm system and transformation to IGES format executed. Following these procedures, the 3D model of IGES format of knee point was reconstructed, which can be used for finite element simulation.

Objective: To study the mechanic response of children's pelvis to lateral impact., Methods: Twelve 2-to 12 year-old children's cadavers were donated by their relatives for this impact test, dividing into younger group (2 to 4 years old, n=6) and elder group (5 to 12 years old, n=6). CT scan and X-ray examination were performed before the impact test, and after the test, X-ray examination and autopsy were conducted. All the pelvises were impacted at a speed of 7.5+/-0.5 m/s but for one at 9.1m/s., Results: All tests showed similar behavior of the pelvis with similar timing and peak viscous criterion (V*C) values. Statistical significance was noted in the maximum V*C and degree of stiffness of the pelvis between the 2 groups (P<0.05). No injuries occurred in the 2 groups after the impact., Conclusion: The pelvic test yields very repeatable pelvic response among each group tested.

Objective: To test the mechanical strength and observe the in vivo degradation of self-made human hair keratin-polylactic acid (HHK-PLA) composite rods designed for use in internal fixation., Methods: Twenty such HHK-PLA composite rods were tested for shear strength, bending strength and bending modulus using the material testing system MTS-858 Mini Bionix. A total of 36 samples of HHK-PLA composite rods designed for internal fixation of bone fracture were randomly implanted in dorsal subcutaneous tissue of 18 SD rats, and weight losses of these rods were measured 1, 2, 4, 8, 12, 16, 20, 24 and 28 weeks after the implantation to evaluate the in vivo degradation of the material., Results: The initial shear strength of HHK-PLA rod was 241 MPa, bending strength 358 MPa, and bending modulus 13 GPa. The test demonstrated a slower rate of degradation in SD rats in earlier period following implantation than in later period., Conclusion: HHK-PLA composite rods have good initial mechanical strength and tolerable degradation in vivo, and may be used potentially for internal fixation of the weigh-bearing bones of the limbs.

Objective: To study the distribution of the biomechanical properties in the cervical vertebrae with or without the endplate, so as to evaluate the importance of the endplate in cervical anterior fusion., Methods: Indentation tests were performed at 20 standardized testing points chosen on each surface of the endplate with the impact adjusted perpendicular to the endplate surface using a hemispherical indenter 2 mm in diameter. The failure load and rigidity at each test site were determined from the load-displacement curves. Independent sample t test and factorial analyses were used to analyze the results., Results: On either superior or inferior endplate surface, both the failure load and rigidity differed significantly between the endplate-intact and endplate-removed groups (P < 0.001). The posterior region of the superior endplate and the lateral regions of the inferior endplate were stronger and more rigid than any other region across the endplate surface in the endplate-intact group, while for enplate-removed group, the posterior region of the superior endplate and the posterolateral regions of the inferior endplate were the stronger and more rigid., Conclusion: The endplate plays an important role in deciding the success of anterior cervical fusion, and due attention should be paid to the endplate in the intervertebral implant device designing and the surgical approach modification.

Objective: To investigate the impact of dorsally angulated malunited distal radius fractures on the stability of the radiocarpal joint., Methods: Eight fresh upper limb specimens from 4 human cadavers were obtained, in which radial osteotomy was performed to prepare models of Frykman I distal radius fracture. Pressure-sensitive film was applied to study the changes in the contact area distribution and the pressure load across the radiocarpal joint in response to palmar tilt variation, and the lateral radiograph of the wrist was taken at the end of pressure loading., Results: When the dorsal tilt exceeded 10 degrees, the radioscaphoid and radiolunate articular contact areas were markedly decreased (P<0.01) and shifted to the dorsal aspect of the radiocarpal joint, where the pressure load was significantly increased (P<0.01). A dorsal radiocarpal subluxation was liable to occur on the sagittal plane when the dorsal tilt exceeded 40 degrees., Conclusion: A dorsal tilt over 10 degrees is the most primary cause of radiocarpal instability after a dorsal deformity due to distal radius fractures.

The content of Rhodium in extraction solution of the catalyst from HNBR was determined by FAAS. The results showed that this method was simple, rapid, accurate and convenient. Furthermore, this method was used as a means to investigate the optimum process conditions for removing catalyst from HNBR by ligation-extraction technology. When sulfocarbmide was used as a ligation agent and 88% formic acid as an extraction agent, the removal rate of Rh was greater than 98% under the condition of 100 degrees C and two hours of reaction time.

Objective: To evaluate the effect of a new internal fixation system utilizing vertebral pedicle screw in fixing unstable lumbar spine in vitro., Methods: Twelve lumbar spine specimens (L(2 to 5)) obtained from fresh human cadavers were randomly divided into 2 equal groups, namely groups A and B. All intact specimens were subjected to nondestructive testing in 6 loading modalities on a universal testing machine, before complete L(2 to 5) instability was produced by means of a wedge fracture induced by resection of the posterior ligamentous structures. Specimens in group A were fixed with the new internal fixation system, and group B with SOCON pedicle screw. The same nondestructive testing was repeated to determine the structural stability of the spine after fixation in both groups., Results: The injured spines fixed with implants in both groups were significantly more stable than the intact specimens in all modes of tests (P < 0.05), especially in flexion and extension tests, in which a stability increase by 62.8% for flexion and 63.9% for extension was recorded in group A, and 54.9% for flexion and 51.0% for extension in group B. The two fixation systems exhibited similar effect in stabilizing the injured lumbar in all the 6 loading modalities (P < 0.05)., Conclusion: This internal fixation system with vertebral pedicle screw is capable of providing biomechanical stability for unstable lumbar spine.

Objective: To explore effects of prednisone on the bone mineral density (BMD) and biomechanics of the femora and lumbar vertebras in rats., Methods: Twenty one 3-month-old male Sprague-Dawley rats weighing 226+/-12 g were randomly divided into basal control, age-matched and hormone groups. The rats in basal control group were killed at the beginning of the experiment without any treatment, and those in age-matched group were given oral normal saline (5 ml x kg(-1) x d(-1)) while the rats in hormone group received oral prednisone acetate (4.5 ml x kg(-1) x d(-1) twice a week) to establish osteoporotic models. The treatment for the latter 2 groups of rats lasted for 90 days, after which the BMD and mechanical measurements of the femurs and L5 vertebra were carried out by way of torsion, three-point bending and compression tests. The measurements were also conducted in the basal control group at the time indicated above., Results: In hormone group, the total BMD of the femora and L5 vertebra was decreased by 14.64%(P<0.01), and the BMD in the right and left distal femoral segments and the vertebra decreased by 21.42% (P<0.01), 19.62% (P<0.05) and 23.48%(P<0.01), respectively, in comparison with the control group. In the meantime, the loads of three-point bending test in hormone group was decreased by 17.1%(P<0.05), whereas the rest parameters tended to decrease as compared with the control group., Conclusions: Chronic use of corticosteroid is more liable to cause bone mass loss in rat cancellous bone than in the cortical bone, and mechanical properties of the cortical and cancellous bone, especially those of the latter, will also decline, to give rise to easy bone fracture at the trabecular bone in osteoporotic conditions.

Objective: To evaluate the effect of bending and rotation on the lumbar facet joints under load-bearing conditions., Methods: Eight lumbar-sacral spines (L1-S1) taken from fresh young adult cadavers were placed on the MTS system. The forces of the two facet joints of the L4-5 motion segments were measured using pressure sensitive films. The specimens were measured in erection, bending and rotation postures., Results: In erection posture the L4-5 facet joints could support 31.16+/-7.15 N of 400 N which was axial compressing load. In bending 15 degree posture the forces of each side of the L4-5 facet joints were equal, and were found to have no marked effect on the force in erection. Yeat only opposite facet joints could endure force in rotation, but the force was 7 times that in erection., Conclusion: Both sides of lumbar facet joints could support load in bending position but only the opposite could endure load in rotation.

The female mice of DDK strain are almost infertile when mated with males from other strains. This phenomenon is caused by the early death of F1 embryos owing to the incompatibility system attributed to the ovum mutant (Om) locus on Chromosome (Chr) 11 and known as DDK syndrome. In the present study, DDK females were found to be fully fertile in the intersubspecific matings with the males of two wild mouse-derived strains, MOM (originated from Japanese wild mice, Mus musculus molossinus) and Cas (originated from Philippine wild mice, M. m. castaneus), indicating that no incompatibility exists between DDK oocytes and spermatozoa of MOM and Cas strains. Furthermore, this compatibility has been confirmed by the following two findings: (1) Normal fertility was shown by the two types of backcrosses, DDK females x F(1) (DDK female x MOM male) males and DDK females x F(1) (DDK female x Cas male) males; and (2) the offspring from these backcrosses segregated equally into the homozygotes and heterozygotes as genotyped by the microsatellite markers closely linked to Om locus. MOM and Cas strains would be useful for further investigations on the Om locus. On the other hand, the litter size of F(1) [C57BL/6Cr (B6) female x Cas male] females mated with B6 males was about half that of the mating with DDK males. It would be interesting to investigate whether this reduction in fertility is related to the Om locus or not.

The recent release of the first draft of the human genome provides an unprecedented opportunity to integrate human genes and their functions in a complete positional context. However, at least three significant technical hurdles remain: first, to assemble a complete and nonredundant human transcript index; second, to accurately place the individual transcript indices on the human genome; and third, to functionally annotate all human genes. Here, we report the extension of the UNIGENE database through the assembly of its sequence clusters into nonredundant sequence contigs. Each resulting consensus was aligned to the human genome draft. A unique location for each transcript within the human genome was determined by the integration of the restriction fingerprint, assembled genomic contig, and radiation hybrid (RH) maps. A total of 59,500 UNIGENE clusters were mapped on the basis of at least three independent criteria as compared with the 30,000 human genes/ESTs currently mapped in Genemap'99. Finally, the extension of the human transcript consensus in this study enabled a greater number of putative functional assignments than the 11,000 annotated entries in UNIGENE. This study reports a draft physical map with annotations for a majority of the human transcripts, called the Human Index of Nonredundant Transcripts (HINT). Such information can be immediately applied to the discovery of new genes and the identification of candidate genes for positional cloning.

Factors which regulate transcription in immature myeloid cells are of great current interest for the light they may shed upon myeloid differentiation. In the course of screening for transcription factors which interact with the human myeloperoxidase (MPO) promoter we, for the first time, identified and cloned the cDNA and genomic DNA for human HBP1 (HMG-Box containing protein 1), a member of the high mobility group of non-histone chromosomal proteins. HBP1 cDNA was initially cloned from rat brain in 1994, but its presence in human cells or in myeloid tissue had not been described previously. The sequence of human HBP1 cDNA shows 84% overall homology with the rat HBP1 cDNA sequence. We have subsequently cloned the gene, which is present as a single copy, 25 kbp in length. Northern blotting reveals a single 2.6 kb mRNA transcript which is expressed at higher levels in human myeloid and B lymphoid cell lines than in T cell lines tested and is present in several non-myeloid human cell lines. Comparison of the mRNA and genomic sequences reveals the gene to contain 10 exons and 9 introns. The sequence of human HBP1 mRNA contains a single open reading frame, which codes for a protein 514 amino acids in length. The amino acid sequence specified by the coding region shows 95% homology with the rat HBP1 protein. The human protein sequence exhibits a putative DNA-binding domain similar to that seen in rat HBP1 and shows homology with the activation and repressor domains previously demonstrated in the rat protein. We have expressed human HBP1 protein both in vitro and in prokaryotic and eukaryotic cells. The expressed fusion protein binds to a sequence in a functionally important region within the basal human MPO promoter. In transient co-transfection experiments HBP1 enhances MPO promoter activity. Human HBP1 appears to be a novel transcription factor which is likely to play an important role in regulating transcription in developing myeloid cells.

Internal ribosomal entry sites (IRESs) of certain plus-strand RNA viruses direct cap-independent initiation of protein synthesis both in vitro and in vivo, as can be shown with artificial dicistronic mRNAs or with chimeric viral genomes in which IRES elements were exchanged from one virus to another. Whereas IRESs of picornaviruses can be readily analyzed in the context of their cognate genome by genetics, the IRES of hepatitis C virus (HCV), a Hepacivirus belonging to Flaviviridae, cannot as yet be subjected to such analyses because of difficulties in propagating HCV in tissue culture or in experimental animals. This enigma has been overcome by constructing a poliovirus (PV) whose translation is controled by the HCV IRES. Within the PV/HCV chimera, the HCV IRES has been subjected to systematic 5' deletion analyses to yield a virus (P/H710-d40) whose replication kinetics match that of the parental poliovirus type 1 (Mahoney). Genetic analyses of the HCV IRES in P/H710-d40 have confirmed that the 5' border maps to domain II, thereby supporting the validity of the experimental approach applied here. Additional genetic experiments have provided evidence for a novel structural region within domain II. Arguments that the phenotypes observed with the mutant chimera relate solely to impaired genome replication rather than deficiencies in translation have been dispelled by constructing novel dicistronic poliovirus replicons with the gene order [PV]cloverleaf-[HCV]IRES-Deltacore-R-Luc-[PV]IRES-F-Luc-P2,3-3'NTR, which have allowed the measurement of HCV IRES-dependent translation independently from the replication of the replicon RNA.

Background: The recent draft assembly of the human genome provides a unified basis for describing genomic structure and function. The draft is sufficiently accurate to provide useful annotation, enabling direct observations of previously inferred biological phenomena., Results: We report here a functionally annotated human gene index placed directly on the genome. The index is based on the integration of public transcript, protein, and mapping information, supplemented with computational prediction. We describe numerous global features of the genome and examine the relationship of various genetic maps with the assembly. In addition, initial sequence analysis reveals highly ordered chromosomal landscapes associated with paralogous gene clusters and distinct functional compartments. Finally, these annotation data were synthesized to produce observations of gene density and number that accord well with historical estimates. Such a global approach had previously been described only for chromosomes 21 and 22, which together account for 2.2% of the genome., Conclusions: We estimate that the genome contains 65,000-75,000 transcriptional units, with exon sequences comprising 4%. The creation of a comprehensive gene index requires the synthesis of all available computational and experimental evidence.

Internal ribosomal entry sites (IRESs) can function in foreign viral genomes or in artificial dicistronic mRNAs. We describe an interaction between the wild-type hepatitis C virus (HCV)-specific sequence and the poliovirus (PV) 5'-terminal cloverleaf in a PV/HCV chimeric virus (containing the HCV IRES), resulting in a replication phenotype. Either a point mutation at nucleotide (nt) 29 or a deletion up to nt 40 in the HCV 5' nontranslated region relieved the replication block, yielding PV/HCV variants replicating to high titers. Fortuitous yet crippling interactions between an IRES and surrounding heterologous RNA must be considered when IRES-based dicistronic expression vectors are being constructed.

The DDK syndrome (polar infertility) is caused by an incompatibility system due to the ovum mutant (Om) locus. For brevity, the following gene symbols are used in the present report: DDK allele, Om; C57BL/6Cr allele, +. In this investigation, we first attempted to introduce the Om allele of DDK strain into the genetic background of C57BL/6Cr strain. The attempt resulted in the production of no young at the third generation of successive backcrosses. Secondly, mating experiments were performed with heterozygous (Om/+) females having background genes of C57BL/6Cr and DDK strains in the ratios 1:1(B1D), 3:1(B3D), 7:1(B7D), and 15:1(B15D). The survival rate of the embryos as judged by the percentage number of live fetuses/number of corpora lutea at Day 12 of pregnancy was 41.3 +/- 3.2%, 27.3 +/- 3. 2%, 16.4 +/- 3.3%, and 11.3 +/- 3.2% (mean +/- SEM) in the B1D, B3D, B7D, and B15D females, respectively, when they were mated with C57BL/6Cr males. Furthermore, the increased embryonic mortality in the heterozygous (Om/+) females with more background genes of C57BL/6Cr strain was found to be due to a failure in blastocyst formation, as in the DDK syndrome. The parallelism between the proportion of C57BL/6Cr background genes and embryonic mortality has led to a hypothesis proposing the participation of a modifier gene, namely that a mechanism similar to allelic exclusion may be working in the synthesis of cytoplasmic factor of eggs and that only the Om allele is activated during oogenesis to produce DDK-type cytoplasmic factor in heterozygous (Om/+) females having a modifier gene in the homozygous state.

A method for the determination of aflatoxin B1, B2, G1 and G2 in peanut by high performance liquid chromatography using immunoaffinity column clean-up and on-line electrochemical derivatization was developed. Sample was extracted with 80% methanol and the extract was passed through the IAC. Aflatoxins were retained by the monoclonal in the IAC and eluted with actonitrile. AFT B1 and G1 were derivatized with on-line electrochemical equipment Kobra Cell. The four toxins can be separated in 13 minutes and the detection limit was 0.1 microgram/kg for each toxin. The method has been applied to the determination of peanut sample. The relative standard deviation was 9.2%-15% and the average recovery of AFT spiked at 0.5-9.0 micrograms/kg levels was in the range of 74.8%-97.3%.

H.-H. Lu and E. Wimmer (Proc. Natl. Acad. Sci. USA 93:1412-1417, 1996) have demonstrated that the internal ribosomal entry site (IRES) of poliovirus (PV) can be functionally replaced by the related genetic element from hepatitis C virus (HCV). One important finding of this study was that open reading frame sequences 3' of the initiating AUG, corresponding to the open reading frame of the HCV core polypeptide, are required to create a viable chimeric virus. This made necessary the inclusion of a PV 3C protease (3Cpro) cleavage site for proper polyprotein processing to create the authentic N terminus of the PV capsid precursor. Chimeric PV/HCV (P/H) viruses, however, grew poorly relative to PV. The goal of this study was to determine the molecular basis of impaired replication and enhance the growth properties of this chimeric virus. Genetic modifications leading to a different proteinase (PV 2Apro) cleavage site between the HCV core sequence and the PV polyprotein (P/H701-2A) proved far superior with respect to viral protein expression, core-PV fusion polyprotein processing, plaque phenotype, and viral titer than the original prototype PV/HCV chimera containing the PV 3Cpro-specific cleavage site (P/H701). We have used this new virus model to answer two questions concerning the role of the HCV core protein in P/H chimeric viral proliferation. First, a derivative of P/H701-2A with frameshifts in the core-encoding sequence was used to demonstrate that production of the core protein was not necessary for the translation and replication of the P/H chimera. Second, a viral construct with a C-terminal truncation of 23 amino acids of the core gene was used to show that a signal sequence for signal peptidase processing, when present in the viral construct, is detrimental to P/H virus growth. The novel P/H chimera described here are suitable models for analyzing the function(s) of the HCV elements by genetic analyses in vivo and for antiviral drug discovery.

83 kinds of main food on the market in Tianjin were determined using alklin ashing method. The iodine intake of adult in Tianjin was found to be 113.76 mg/day which is below the recommended daily intake. It is not adequate for pregnant and lactational women. Its deficiency may possibly affect the intellectual development of infants. Hence sufficient attention should be paid by public health authorities.