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Biomedical subjects

R Xu

Publications and source records attributed to R Xu.

At least 235 records · Page 13Linked to original sources
PubMed1996

The quantitative anatomy of the cervical nerve root groove and the intervertebral foramen.

STUDY DESIGN: The present study evaluated the cervical nerve groove and intervertebral foramen using dried vertebrae and cadaveric cervical spine. OBJECTIVES: To measure the cervical nerve groove in eight linear and one angular dimensions and the intervertebral foramen in two linear diameters. SUMMARY OF BACKGROUND DATA: Several anatomic studies of the cervical spine exist, but very little quantitative data have been reported on the cervical nerve groove. METHODS: Dried cervical vertebrae, C3-C7, from 41 complete vertebral sets (205 vertebrae) and 14 cadaveric cervical spine were obtained for the present study. Anatomic evaluation focused on the cervical nerve groove for dry specimens and intervertebral foramen for cadaveric specimens. Ten linear and one angular measurements were made bilaterally. The mean, range, and standard deviation were calculated for all of the specimens and for male and female specimens separately. RESULTS: Differences in dimensions of male and female specimens were not found to be statistically significant. The average lengths of the medial zone and distances from the midline of the vertebral body to the anterior border of the medial zone for male and female specimens consistently increased from C3 to C7. The width of the medial zone was larger in C3 than that of C4, C5, and C6 in male and female specimens. The minimum width for all levels ranged 1-2 mm. The medial zone depths gradually increased from C3 (3.2 mm for male and 2.3 mm for female specimens) to C7 (4.9 mm for male and 4.4 mm for female specimens). The smallest anteroposterior distances from the posterior midpoint of the lateral mass to the posterior border of the nerve groove were found in C7 (6.7 mm for male and 6.1 mm for female specimens). The general trend of the foraminal height and width increased from the cephalad to caudal except at C2-C3. CONCLUSIONS: These data may enhance understanding of the important bony elements associated with the cervical spinal nerves and roots as they pass through the cervical nerve groove and the intervertebral foramen.

Adult↗
PubMed1996

The location of the vertebral artery foramen and its relation to posterior lateral mass screw fixation.

STUDY DESIGN: This study evaluated the anatomic relationship between the vertebral artery foramen and the posterior midpoint of the cervical lateral mass using cervical spine specimens. OBJECTIVES: To determine quantitatively the location of the vertebral artery foramens from C3 to C6 and their relationship to the posterior midpoints of the lateral masses. SUMMARY OF BACKGROUND DATA: Anatomic studies of the cervical nerve root and facet relative to lateral mass screw placement have been addressed. It is necessary to know the correct location of the vertebral artery foramen during lateral mass screw placement to minimize the risk of injury to the vertebral artery. METHODS: Forty-three cervical spines from C3 to C6 were directly evaluated for this study. Anatomic evaluation included the dimension of the vertebral artery foramen and its projection on the posterior aspect of the lateral mass. The vertical distance from the posterior midpoint of the lateral mass to the posterior border of the vertebral artery foramen, and the angle between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, were also measured. RESULTS: The vertical distances from the posterior midpoint of the lateral mass to the vertebral artery foramens at C3-C6 averaged from 9.3 to 12.2 mm for male and female specimens. The average angles medial to the sagittal plane, between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, from C3 to C5, were found to range from 6.0 degrees to 6.3 degrees for male specimens and from 5.3 degrees to 5.5 degrees for female specimens. At C6, the average angles lateral to the sagittal plane, between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, were 6.4 degrees for male specimens and 5.4 degrees for female specimens. CONCLUSIONS: The present study indicated that there is no risk of damaging the vertebral artery if a screw is directed perpendicular to the posterior aspect of the lateral mass at C3-C5 and 10 degrees lateral to the sagittal plane at C6 starting at the midpoint of the lateral mass.

Adult↗
PubMed1996

Projection of the lumbar pedicle and its morphometric analysis.

STUDY DESIGN: This study defined the projection point of the lumbar pedicle on its posterior aspect and its relation to a reliable landmark and reported pedicle dimensions based on 50 lumbar spines. OBJECTIVES: To establish the best starting point for a pedicle screw for passing the screw down the center (axis) of the pedicle; to describe quantitatively the relations of the pedicle projection point to a reliable landmark; and to evaluate the linear and angular dimensions of the lumbar pedicle. SUMMARY OF BACKGROUND DATA: Posterior transpedicular screw fixation has been most widely used for management of the unstable lumbar spine. Several studies of pedicular anatomy exist, but little quantitative data regarding the location of the lumbar pedicle axis for each level have been reported. METHODS: Fifty dry lumbar specimens (250 lumbar vertebrae) were obtained for study of the lumbar pedicle. Anatomic evaluation focused on determination of the projection point of the lumbar pedicle axis on the junction of the superior facet and the transverse process and measured the distance from the projection point to the midline of the transverse process for each level of the lumbar vertebrae. Pedicle dimensions, including linear and angular, also were measured. RESULTS: Differences in dimensions between men and women were not found to be statistically significant. The average distance from the projection point to the midline of the transverse process consistently changed from L1 to L5. Above L4, the projection point for men and women averaged 3.9 mm for L1, 2.8 mm for L2, and 1.4 mm for L3 superior to the midline of the transverse process, respectively. At L4, the projection point was close to the midline of the transverse process (0.5 mm inferior). At L5, the projection point was an average of 1.5 mm inferior to the midline of the transverse process. CONCLUSIONS: The average distance from the projection point of the lumbar pedicle axis to the midline of the transverse process consistently varied at different levels. This information may prove helpful in the placement of screws into the lumbar pedicle.

Adult↗
PubMed1996

Characterization of products from the reactions of N-acetyldopamine quinone with N-acetylhistidine.

When insects harden or sclerotize their exoskeletons, quinones of N-acetylated catecholamines such as N-acetyldopamine (NADA) undergo nucleophilic addition reactions with amino acids such as histidine in cuticular proteins. To determine the products that might form when this type of reaction occurs during cuticle sclerotization, the reactions between electrochemically prepared NADA quinone and N-acetylistidine (NAcH), a protein model nucleophile, have been investigated at pH 7. Two major products, 6-[N-(N-acetylhistidyl)]-N-acetyldopamine and 2-[N-(N-acetylhistidyl)]-N-acetyldopamine, were purified by semipreparative reversed-phase liquid chromatography and identified by mass spectrometry and nuclear magnetic resonance spectroscopy. The relative molar ratio of the C(6) mono-addition adduct to the C(2) mono-addition adduct is 87:13. UV/vis spectroscopic analysis shows that both products have an absorption maximum at 284 nm. Cyclic voltammetry shows that these adducts are oxidized less readily than NADA.

Benzoquinones↗
PubMed1996

Anatomic considerations for posterior iliac bone harvesting.

STUDY DESIGN: This study analyzed bony features of the posterior ilium and relevant vital structures using cadavers and dry ilium specimens. OBJECTIVES: To determine quantitatively the safely zone of the posterior ilium and relevant vital structures with regard to bone graft harvesting. SUMMARY OF BACKGROUND DATA: The most frequently used site for bone graft harvesting is the posterior ilium. However, complications related to posterior iliac bone harvesting, such as donor site pain, neurovascular injury, instability of the sacroiliac joint, and herniation of abdominal contents, are still major concerns. Very little research with regard to the quantitative study of the posterior ilium has been reported. METHODS: Six cadavers (four male, two female) were used for the first part of this study. The posterior superior iliac spine was determined as a reference landmark. The distances from the posterior superior iliac spine to the superior cluneal nerves, the gluteal line, and the superior gluteal vessels were measured. The second part of the study involved 30 adult, dry iliac bony specimens. The posterior iliac region (extra-articular portion) was divided into three zones, and the corresponding dimensions of these zones were measured. RESULTS: The average distances from the posterior superior iliac spine to the superior cluneal nerves, gluteal line, and superior gluteal vessels were 68.8, 26.6, and 62.4 mm, respectively. The average width, height, and maximum thickness for Zone 1 were 34, 27.8, and 17.1 mm, respectively; the measurements for Zone 2 were 16.5, 31.8, and 14.2 mm, respectively. The average height for Zone 3 was 20.4 mm, and the average maximum thickness was 16.8mm. CONCLUSION: The ideal area of the posterior ilium for bone graft harvesting was found in Zone 1. Zones 2 or 3 may be considered it a greater quantity of cancellous bone graft is required; however, the risk of injury to the sacroiliac joint and superior gluteal vessels in these zones is increased.

Aged↗
PubMed1996

The reactions catalyzed by the inducible bifunctional enzyme of rat liver peroxisomes cannot lead to the formation of bile acids.

The ability of the bifunctional 2-enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase from rat liver peroxisomes to metabolize (24E)-3alpha, 7alpha, 12alpha-trihydroxy-5beta-cholest-24-enoyl-CoA, a presumed intermediate during the beta-oxidative degradation of the steroid side chain in the formation of cholic acid, was investigated. The bifunctional enzyme efficiently hydrated the above compound specifically to (24S,25S)-3alpha, 7alpha, 12alpha, 24-tetrahydroxy-5beta-cholestanoyl-CoA, but the dehydrogenase component of the enzyme was virtually inactive toward this product. In contrast, the bifunctional enzyme efficiently catalyzed the dehydrogenation of the (24S,25R) diastereomer of the above hydroxy intermediate to two products whose uv absorbance and chemical properties were consistent with those of alpha-methyl-beta-ketoacyl-CoAs. These results suggest that the bifunctional enzyme is not sufficient for the formation of a 24-keto intermediate in bile acid biosynthesis.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1996

The projection of the lateral sacral mass on the outer table of the posterior ilium.

STUDY DESIGN: This study was designed to construct the projection of the lateral sacral mass on the posterior ilium using cadaveric pelves and to measure the dimensions of the projection. OBJECTIVES: The present study was undertaken to determine quantitatively the location of the lateral sacral mass on the outer table of the ilium. SUMMARY OF BACKGROUND DATA: Anatomic studies relative to instrumentation of the posterior iliosacral region are few. No previous anatomic studies with regard to the projection of the lateral sacral mass have been reported. METHODS: Twelve cadaveric pelves were used for this study. To determine the projection of the lateral sacral mass on the outer table of the posterior ilium, several Kirschner wires were drilled along the outermost peripheral edge of the lateral sacral mass from the inner table of the ilium through the outer table. A triangle projection on the outer table of the posterior ilium was then constructed according to the placed Kirschner wires. The widths and height of the projection, and the distances from the axis of the projection to posterior superior iliac spine and posterior inferior iliac spine were measured bilaterally. RESULTS: The average height of the projection of the lateral sacral mass was 61.4 mm. The average base width of the projection was 56.8 mm. The average distances from posterior superior iliac spine and posterior interior iliac spine to the longitudinal axis of the projection of the lateral mass were 30 mm and 27.4 mm, respectively. CONCLUSIONS: This study reported the average location of the lateral sacral mass on the outer table of the ilium. The superior area of the projection may be an ideal zone for transiliosacral screw placement.

Adult↗
PubMed1996

Local tissue of the lumbar spine response to titanium plate--screw system. Case reports.

STUDY DESIGN: This study reported the histopathologic findings of peri-implant tissue harvested from two patients with titanium plate-screw fixation in the lumbar spine. OBJECTIVES: To describe and discuss the histopathologic findings with regard to local tissue response to the titanium plate-screw system in the lumbar spine. SUMMARY OF BACKGROUND DATA: There are no reports about local tissue of the lumbar spine response to titanium plate-screw system in the literature. METHODS: Two patients who underwent titanium plate-screw fixation in the lumbar spine were evaluated for this study. Histopathologic evaluation of the specimens from these cases included soft tissue, bone, and cartilage from the areas around the screws and plates. RESULTS: The primary histopathologic changes of the two cases included fibrous scarring, accumulation of metallic debris, both free in the fibrous tissue and within macrophages, and mild histiocytic and epithelioid changes. CONCLUSIONS: The histopathologic findings of the two cases presented resulted in local tissue response of the lumbar spine to titanium similar to tissue response in other previously reported cases.

Aged↗
PubMed1996

Anatomic consideration of C2 pedicle screw placement.

STUDY DESIGN: This anatomic study tested placement of C2 pedicle screws using cadaver specimens. OBJECTIVES: To further assess the safety of transpedicular screw placement in the axis by comparing two surgical techniques. SUMMARY OF BACKGROUND DATA: Transpedicular screw fixation of traumatic spondylolisthesis of the axis has been described in the literature. Recently, anatomic studies and clinical applications of transpedicular screw fixation for traumatic lesions of middle and lower cervical spine have been described. No previous study assessing the safety of C2 pedicle screw placement is available. METHODS: Sixteen embalmed cadaveric specimens were used for this study. In the first eight specimens (Method A), the point of entry for screw placement was chosen to be about 5 mm inferior to the superior border of C2 lamina and 7 mm lateral to the lateral border of the spinal canal. The screw direction was chosen to be about 30 degrees medial to the sagittal plane and 20 degrees cephalad to the transverse plane. A 3.5-mm cortical screw of appropriate length, determined with depth gauge, was placed bilaterally into the C2 pedicle. In the next eight specimens (Method B), the direction of the drill bit was guided directly by the medial and superior aspect of the individual C2 pedicle. Gross dissection was done to view violation of dura, nerve roots, vertebral artery, and penetration of medial, lateral, superior, and inferior cortex of the C2 pedicle. Radiographs and computed tomography scans were obtained to evaluate screw placement in the C2 pedicle. RESULTS: In Method A, four screws had lateral violations into the vertebral artery. In Method B, only two cases of minimal penetration of pedicle cortex were found. No medial, superior, or inferior violation of the pedicle cortex was found in the present study. CONCLUSIONS: The present anatomic study suggests that transpedicular screw fixation may be performed safely in the C2 pedicle by using the second technique. Using the first technique is not safe.

Bone Screws↗
PubMed1996

Evaluation of cervical posterior lateral mass screw placement by oblique radiographs.

STUDY DESIGN: The present study analyzed the two-dimensional representation of cervical lateral mass screws by oblique radiographs compared with cadaveric placement. This was accomplished by posterior and lateral cervical dissection of the lateral masses and intervertebral foramina, keeping the emerging nerve roots intact. The intervertebral foramina were divided into two zones for the study. OBJECTIVES: To identify and describe the value of oblique radiographs in evaluating posterior lateral mass screw placement in the cervical spine. SUMMARY OF BACKGROUND DATA: Posterior plate-screw fixation is an effective method of stabilizing the traumatized cervical spine. Because of the surrounding anatomy, precise placement of screws must be attained to avoid iatrogenic injury to the nerve roots, and incorrectly placed screws must be identified quickly to minimize the neurologic complication. No previous radiologic study regarding evaluation of the lateral mass screw placement has been reported. METHODS: Six cervical spines were removed from embalmed cadavers. Posterior and lateral removal of soft tissue ensued until the lateral masses and spinal nerves were clearly and completely exposed. Two specimens and 20 screws were used for each of the following methods: Roy-Camille, zone 1 placement, and zone 2 placement. Zone 1 was defined as the area between pedicles of adjacent vertebrae. Zone 2 was defined as the area between transverse processes of adjacent vertebrae. Forty-five degrees oblique left and right, anteroposterior, and lateral radiographs were taken. RESULTS: All screws placed by the Roy-Camille technique and 19 of 20 screws intentionally placed in zone 1 were represented accurately by oblique radiographs. Nineteen of 20 screws placed in zone 1 were well appreciated in the foramen in oblique view. However, 13 of 20 screws placed in zone 2 and approximating the nerve root were inaccurately represented or ambiguous in oblique radiographs. CONCLUSIONS: Oblique radiographs are valuable to view the relationship between screw placement and foramina. Screws crossing the line connecting the posterior borders of the intervertebral foramina and appearing in the pedicle actually exit the bone and may risk damaging the nerve root.

Bone Screws↗
PubMed1996

Radiologic evaluation of iliosacral screw placement.

STUDY DESIGN: This study analyzed anteroposterior, lateral, inlet, and outlet radiographic representations of different iliosacral screw orientations and evaluated anatomic features of the superior aspects of the sacral alae. OBJECTIVES: The purpose of this anatomical and radiologic study was to assess the value of anteroposterior, inlet, outlet, and lateral views with regard to the planning of iliosacral screw placement, to determine if screws penetrating the sacral surfaces and foramina can be detected during or after operation, and to evaluate the anatomy of the superior aspects of the sacral ala quantitatively. SUMMARY OF BACKGROUND DATA: Direct iliosacral screw fixation has recently become popular because it provides stable fixation using reasonably small implants and is biomechanically equal or superior to other techniques of internal fixation. However, misinterpretation of the relationship of pelvic radiographs and the position of a screw may result in incorrect screw placement during surgery or misdiagnosis of postoperative neurologic complications. The morphology of the sacrum is complex. No previous data relative to the superior aspect of the sacral alae are available. METHODS: Four bony pelves were used to model the different iliosacral screw orientations possible during iliosacral reconstruction. A drill bit was inserted laterally from the posterior ilium through the sacroiliac joint and into the S1 vertebra. Radiographs were taken from anteroposterior, lateral, inlet, and outlet views for evaluation of placement. Twenty-two dry sacra were obtained for anatomic evaluation of the superior aspects of the sacral alae. All symmetrical structures were measured bilaterally. Measurements included three angular and two linear parameters. RESULTS: The results showed that a misdirected drill bit penetrating the anterior aspect of the ala is best appreciated by the inlet view. A misdirected drill bit penetrating the superior aspect of the ala or the S1 foramen is best represented in the outlet view. The average angle between the coronal plane of the S1 vertebra and the anterior aspect of the ala was 27.1 degrees; between the superior aspect of the S1 vertebral body and superior edge of the ala, 36.9 degrees; and between the superior aspect of the S1 vertebral body and posterosuperior edge of the ala, 24.5 degrees. CONCLUSIONS: The inlet view shows the orientation of screws relative to the coronal plane and extraosseus screws extending anterior to the ala, whereas the outlet view elucidates the placement of screws relative to the transverse plane and extraosseus screw tips extending into the sacral foramina or superior to the ala. Evaluation of preoperative pelvic computed tomography scans may be helpful in understanding the unique morphology of each individual patient and enhancing the safety of iliosacral screw placement.

Bone Screws↗
PubMed1996

Radiologic and anatomic evaluation of the anterior sacral foramens and nerve grooves.

STUDY DESIGN: The present study evaluated the anterior sacral foramen using plain radiographs and projected the positions of S1-S3 anterior sacral foramen and corresponding nerve root groove on the posterior aspect of the sacrum. OBJECTIVES: To evaluate the plain radiographs of anteroposterior, inlet, and outlet views regarding the sacral foramen, and to determine quantitatively the location of the anterior sacral foramens on the posterior aspect of the sacrum. SUMMARY OF BACKGROUND DATA: Injury to the sacral nerve roots associated with posterior sacral screw placement remains a potential hazard. Few studies regarding the evaluation of the anterior sacral foramen and its projection on the posterior sacral surface are available. METHODS: Six bony pelves were harvested from preserved cadavers. The superior aspects of the sacral alae, the openings of the anterior and posterior foramens of S1-S2, were marked by outlining them with K-wires. Anteroposterior, inlet, and outlet plain radiographs were taken. The bony sacra were further disarticulated from the above six pelvic specimens. K-wires were drilled through the sacra to project the dimensions of the anterior foramens and nerve grooves of S1-S3 onto the posterior sacral surface. The dimensions between the perimeter of the projection and the corresponding posterior foramen were measured. RESULTS: The plain radiographs show that the shape and relative position between the anterior and posterior foramens vary with different projections. It was believed that outlet projection is the best view of plain and radiographs in the evaluation of the sacral foramens and corresponding pedicles. The approximate boundaries of the anterior sacral foramens' projections were 6 mm superior, 10 mm lateral, 3 mm inferior, and 3 mm medial to the corresponding margins of the posterior foramens. CONCLUSIONS: The outlet projection is the most useful view in plain radiographs for the evaluation of sacral foramens and pedicles. Quantitative data of the anterior sacral foramen's anatomic position on the dorsal aspect of the sacrum may be helpful in the sacral pedicle screw placement.

Aged↗
PubMed1996

Correlation of p53 immunoreactivity and sequencing in patients with glioma.

This study examines the relationship between p53 immunostaining and direct sequencing of polymerase chain reaction (PCR) products in 61 gliomas. Glioma tissues obtained from patients at surgery were analyzed immunohistochemically with the monoclonal antibody PAb1801 to detect p53 protein abnormalities. Amplified p53 cDNA from these samples was analyzed by direct sequencing. Four grades of p53 immunostaining were evaluated: grade 0 = no labeling, grade 1 = less than 5% labeled cells, grade 2 = 5-30% labeled cells, and grade 3 = more than 30% labeled cells. Twenty-six of 36 glioblastomas, 14 of 23 anaplastic gliomas, and none of two low-grade gliomas had positive p53 immunoreactivity. Direct sequencing of PCR-amplified p53 cDNA revealed that 10 glioblastomas, 11 anaplastic gliomas, and no low-grade gliomas had mutations. Comparison of p53 immunostaining and sequencing data revealed that among all the gliomas, mutations were found in three of 21 with p53 grade 0, one of 16 with p53 grade 1, seven of nine with p53 grade 2, and 10 of 15 with p53 grade 3. These results indicate a good correlation between the p53 immunostaining and sequencing data when the percentage of abnormal cells within the tumor was greater than 5% (p53 grades 2 and 3). However, the correlation was poor when the percentage of abnormal cells was less than 5% (p53 grade 1) because of the limited sensitivity of sequencing techniques. Thus, p53 immunostaining may be more accurate in detecting p53 alterations when the percentage of abnormal cells is small; however, in rare cases, p53 immunostaining may fail to detect mutations confirmed by sequencing.

Adult↗
PubMed1996

Studies on bioactive saponins from Chinese medicinal plants.

In our recent studies on bioactive saponins, two Chinese medicinal plants: Mussaenda pubescens Ait.f (Rubiaceae) and Clematis chinensis Osbeck (Ranunculaceae), were investigated. Of the two medicinal plants, M. pubescens is a Chinese folk medicine which has been used as a diuretic, antiphlogistic, diaphoretic and antipyretic agent, and has also been used to detoxify mushroom poisons and to terminate early pregnancy. Clematis chinensis is a Chinese traditional medicine which has been used as an analgesic, diuretic, antitumor, antiinflammatory and insecticidal agent for ages. As a result of our studies, eighteen saponins were identified from M. pubescens, among which seventeen were new compounds, while eleven saponins were isolated from C. chinensis, three of which were new compounds. In the course of our structural studies, mass fragment analysis in FAB-mass spectra and 1H- and 13C-NMR spectra were used to determine the structures of the sapogenin and oligosaccharide moieties. In those more complicated and minor saponins, various 2D-NMR experiments were carried out on 400-, 500- or 600-MHz NMR instruments, which permitted the identification of new sapogenins in glycoside form. In addition, it was also possible to assign all the proton and carbon signals of the sugar units on the basis of 1H-1H DQF COSY, TOCSY and HMQC spectra, which further permitted the establishment of linkage sites and sequences among the sugar units and aglycones by means of NOESY, ROESY and HMBC spectra. When the proton signals of sugar units are overlapped seriously in 1H-NMR spectra, peracetylation is a very helpful technique which can spread proton signals in wider range, thus simplifying their assignment by means of 2D-NMR spectra. When some of the sugar proton signals of a peracetylate are also overlapped coincidentally, alternation of deuterated solvents for measuring NMR spectra can circumvent the difficulties. Pharmacological tests indicated that mussaendoside O, the most abundant saponin from M. pubescens, can inhibit significantly the secretions of the lachrymal and salivary glands induced by galanthamine, and can also inhibit the contraction of the isolated longitudinal muscle strip from guinea pig ileum evoked by an M-Ach receptor agonist (carbachol, 10(-6) M) at concentrations of 10(-4) and 10(-5) M. From these results, the saponin should be an antagonist of the M-Ach receptor, and was presumed to be responsible for its antitoxicity activity toward some mushroom poisons of medicinal plant origin. In addition, mussaendoside O also showed immunopromotive and hemolytic activities.

Animals↗
PubMed1996

Ethylene control of E4 transcription during tomato fruit ripening involves two cooperative cis elements.

E4 gene transcription is controlled by ethylene during tomato fruit ripening. To define the ethylene-responsive promoter elements, we have tested the activity of mutations of the E4 promoter, and of chimeric genes in transient assay. Using a set of linker scan mutations of the region from -160 to -91, we determined that sequences located between -150 and -121 bp from the transcription start site are required for normal levels of ethylene-regulated transcription. However, E4 sequences from -193 to -40 were not able to confer ethylene-responsiveness to the minimal (-46) 35S promoter. The E4/E8 binding protein (E4/E8 BP) interacts with sequences in the 5'-flanking regions of both E4 and the coordinately regulated E8 gene, and its role in regulation of E4 transcription was investigated. The E4 binding site spans the E4 TATA box, and so mutations of this site were limited to those that did not disrupt the E4 TATA box. Mutations of this site which reduced affinity for the E4/E8 BP also resulted in reduced activity in transient assay, supporting a role for this element in normal regulation of the gene. Fusion of the 35S enhancer to E4 sequences from -85 to +65 did not result in an ethylene-responsive promoter, indicating that the E4/E8 BP-binding site is not sufficient for ethylene response. We conclude that at least two cis elements are required for ethylene-responsive transcription of the E4 gene during fruit ripening, one between -150 and -121 and the other between -40 and +65.

Base Sequence↗
PubMed1996

Saponins from Mussaenda pubescens.

From the hydrophilic fractions of aerial parts of Mussaenda pubescens, three new saponins named mussaendosides D, E and H, along with a known saponin, mussaendoside S, were isolated. Their structures were elucidated on the basis of chemical and spectral evidence.

Carbohydrate Sequence↗
PubMed1996

Saponins from Clematis chinensis.

From ethanol extracts of the roots of Clematis chinensis, a new saponin, named clematichinenoside C, was isolated and its structure was established as 3-O-beta-D-glucopyranosyl-(1-4)-beta-D-ribopyranosyl-(1-3)-alpha-L - rhamnopyranosyl-(1-2)-alpha-L-arabinopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-4)-beta-D-glucopyranosyl- (1-6)-beta-D-glucopyranosyl ester by spectroscopic and chemical means. In addition, one known saponin, huzhongoside B, was identified in the plant.

Carbohydrate Sequence↗