Biomedical subjects

R Xu

Publications and source records attributed to R Xu.

At least 199 records · Page 11Linked to original sources

PubMed1997

Mixed blockade of K+ and Na+ currents in rat ventricular myocytes by the tedisamil analogue, KC8851.

The whole-cell voltage clamp method has been used to study the actions of KC8851, a structural analogue of tedisamil (KC8857), on the transient outward K+ current (Ito) and the Na+ current (INa) in rat ventricular myocytes. KC8851 diminished the inactivation time course of Ito with an EC50 value of 2.2 microM. Kinetic analysis of the time-dependent effects of KC8851 on the decay of Ito was consistent with open channel blockade with respective blocking and unblocking rate constants of 9.3 X 10(6) M(-1) s(-1) and 19.3 s(-1). KC8851 was also found to be a potent inhibitor of peak Na+ current with an EC50 value of 5.1 microM. The inhibition of INa was primarily use-dependent with some contribution from tonic block. The results show KC8851 exhibits potent and selective mixed blockade of Ito and INa a result different from that previously documented for the analogue, tedisamil, which was found to be a potent blocker of Ito, but not INa, in rat ventricular cells.

Animals↗

PubMed1997

Acetylcholine receptors in innervated muscles of dystrophic mdx mice degrade as after denervation.

Acetylcholine receptors (AChRs) are present at the top of the postsynaptic membrane of the neuromuscular junction (NMJ) at very high density, possibly anchored to cytoskeletal elements. The present study investigated whether AChR degradation is affected in animals lacking dystrophin, a protein that is an integral part of the cytoskeletal complex and is missing in Duchenne muscular dystrophy. The animal model for Duchenne muscular dystrophy, the mutant mdx mouse, was used to determine whether disruption of the cytoskeleton, caused by the absence of dystrophin, affects AChR degradation. Of the two populations of junctional AChRs, Rs (expressed in innervated adult muscles) and Rr (expressed in embryonic or denervated muscles), only Rs are affected in mdx animals. In innervated mdx soleus, diaphragm, and sternomastoid muscles, the AChRs have an accelerated degradation rate (t1/2 of approximately 3-5 d), similar to that acquired by Rs in control muscles after denervation. The Rs in mdx NMJs do not accelerate further when the muscles are denervated. The absence of dystrophin does not affect the degradation rate of the Rr AChRs (t1/2 of 1 d), which are expressed after denervation in mdx as in control muscles. These results suggest that dystrophin or an intact cytoskeletal complex may be required for neuronal stabilization of Rs receptors at the adult neuromuscular junctions.

Animals↗

PubMed1997

Anatomic relations between the lumbar pedicle and the adjacent neural structures.

STUDY DESIGN: The authors analyzed anatomic parameters between the lumbar pedicles and the dural sac as well as the spinal nerve roots. OBJECTIVES: To determine quantitatively the anatomic relations between the lumbar pedicle and adjacent dural sac and nerve roots. SUMMARY OF BACKGROUND DATA: Posterior transpedicular screw fixation is the most commonly used method of instrumentation for stabilization of the unstable lumbar spine. A thorough knowledge of the unique anatomy of the lumbar pedicle and adjacent neural structures may avoid or minimize neurologic complications with pedicular screw placement. METHODS: Fifteen adult cadavers were obtained to evaluate quantitatively the anatomic relations of the lumbar pedicle to the adjacent neural structures. After removal of the laminas and facets, the lumbar pedicles, dural sac, and nerve roots were exposed. Direct measurements were taken from the pedicle to the dural sac medially, to the nerve roots superiorly and inferiorly, and between the pedicles. Also, the superoinferior diameter of the nerve root and the frontal angle of the nerve root were measured. Symmetric structures were measured bilaterally. RESULTS: No consistent changes from L1 to L5 were found in all parameters. The mean distances from the lumbar pedicle to the dural sac medially and to the adjacent nerve roots superiorly and inferiorly for all levels were 1.5 mm, 5.3 mm, and 1.5 mm, respectively. The mean interpedicular distance ranged from 23.2 to 24.4 mm. The mean superoinferior diameter of the nerve root ranged from 3.8 to 4.6 mm. The mean nerve root angle ranged from 33.7 degrees to 39.2 degrees. CONCLUSIONS: On the basis of this study, improper placement of the pedicle screw medially or caudally in the lumbar spine should be avoided.

Adult↗

PubMed1997

The quantitative anatomy of the thoracic facet and the posterior projection of its inferior facet.

STUDY DESIGN: This study evaluated the dimensions of the thoracic facet from T1 to T12 and determined the posterior projection of the inferior facet using thoracic spine specimens. OBJECTIVES: To evaluate quantitatively the thoracic facet and determine the projection of the inferior facet on the posterior aspect of the lamina relative to facet hook placement in the thoracic spine. SUMMARY OF BACKGROUND DATA: Anatomic evaluation of the thoracic facet has not been extensively addressed. No detailed studies of the thoracic facet relative to posterior facet hook fixation exist. METHODS: Forty-three thoracic spines from T1 to T12 were directly evaluated for this study. Anatomic evaluation of the thoracic superior and inferior facets included the facet width, height, and angulation relative to sagittal plane. The projection of the inferior facet on the posterior aspect of the lamina was constructed and measured. RESULTS: In general, the male linear and angular parameters were larger than the female ones. The average transverse angle of the facets at T1-T12 for both men and women ranged approximately from 74 degrees to 88 degrees for the superior facet and 74 degrees to 108 degrees for the inferior facet. The average inferior thickness from T1 to T12 for both sexes ranged from 3 to 5 mm. The posterior projection height of the inferior facet was found to be 9 to 12 mm from T1 to T12 for both men and women. The distance between the posterior midline and the inferior facet projection ranged from 7 to 11 mm at T1-T12 for both sexes. CONCLUSIONS: This study may aid in the understanding of the location, angulation, and dimensions of the facet and proper placement of hooks into the thoracic facet joint.

Adult↗

PubMed1997

Anatomic relations of the thoracic pedicle to the adjacent neural structures.

STUDY DESIGN: This study analyzed anatomic parameters between the thoracic pedicles and the spinal nerve roots. OBJECTIVES: To quantitatively determine the anatomic relations of the thoracic pedicle to the adjacent neural structures. SUMMARY OF BACKGROUND DATA: Pedicular screw placement carries with it potential hazard to the surrounding neural structures, especially in the thoracic spine. No studies exist regarding the anatomic relations of the thoracic pedicle to the adjacent nerve roots. METHODS: Fifteen cadavers were obtained for study of the thoracic spine. All soft tissue was dissected off the thoracic spine. Laminectomy and total removal of the superior and inferior articular facets was then performed on C7-T1 through T12-L1 to expose the pedicles, nerve roots, and dura. Measurements were taken from the pedicle to the nerve root superiorly and inferiorly as well as between the pedicles. Also, the superoinferior diameter of the nerve root and the frontal angle of the nerve root were measured. Symmetrical structures were measured bilaterally. RESULTS: The results showed that no epidural space could be found between the dural sac and the pedicle in all 15 cadavers. The average distances from the thoracic pedicle to the adjacent nerve roots superiorly or inferiorly at all levels ranged from 1.9 to 3.9 mm and from 1.7 to 2.8 mm, with a minimum of 1.3 mm, respectively. The interpedicular distance increased from T1 (13.8 mm) to T3, slightly decreased in T4-T5, then gradually increased to T12 (16.6 mm). The superoinferior diameter of the nerve root increased consistently from 2.9 mm at T1 to 4.6 mm at T11. The frontal nerve root angle decreased consistently from T1 (120.1 degrees) to T12 (57.1 degrees), except at T4-T5. CONCLUSIONS: This study suggested that more care be taken into consideration in placing a transpedicular screw in the transverse plane than in placing a screw in the sagittal plane in the thoracic spine.

Adult↗

PubMed1997

Morphologic considerations of the first sacral pedicle for iliosacral screw placement.

STUDY DESIGN: Morphometric, radiographic, and computed tomographic evaluation of the pedicle of the first sacral vertebra was performed, and the pedicle's spatial relation with the posterior surface of the ilium was defined. OBJECTIVES: To facilitate accurate localization of the entry site of the iliosacral pedicular screw on the posterior surface of the ilium, to provide optimal length and direction of iliosacral screw placement, and to investigate the feasibility of inserting two screws through the first sacral vertebral pedicle for unstable posterior pelvic fixation. METHODS: Anterior and posterior pedicular height, pedicular depth, alar depth, and posterior alar height of S1 vertebrae were measured in 11 body pelves bilaterally. Sacral pedicular height was also measured on the outlet view radiograph as visualized during intraoperative fluoroscopy, and compared with actual anatomic pedicular height. The distance from the posterior limit of the ilium to the S1 ala, pedicle, and pedicle axis, and the distance between the outer table of the ilium and anterior cortex of the sacrum were measured on axial computed tomography scans. Finally, parasagittal sections of the sacral were made to assess the safety zone for placement of two pedicular screws into the vertebral body. RESULTS: The mean anterior and posterior pedicular heights were 30.2 and 26.1 mm, respectively. The depths of the pedicle and ala were 27.8 and 45.8 mm, respectively. The mean posterior alar height was 28.7 mm. The mean first sacral pedicular height measured on the outlet-view radiographs was 20 mm, which was significantly less (P < 0.0001) than the actual gross anatomic pedicular height. The mean distance from the posterior limit of the ilium to the pedicle axis projection point on axial computed tomography scans was 32.5 mm, and the mean distance from this point to the greater sciatic notch was 38.6 mm. The mean distance between the outer table of the ilium and the anterior cortex of the sacrum was 105.2 mm. The safety margin for two closely inserted pedicular screws was only 4 to 6 mm. CONCLUSIONS: This study suggests that placement of one screw through the S1 pedicle into the vertebral body is safer, and routine placement of two sacral pedicular screws may be difficult. The optimal starting point for placement of single iliosacral screw is 3 to 3.5 cm anterior to the posterior border of the iliac bone in the sagittal plans, and 3.5 to 4 cm cephalad to the greater sciatic notch. The screw should be directed perpendicular to the outer surface of the table from this entry point. The safe length of the iliosacral pedicular screw is up to 80 mm.

Adult↗

PubMed1997

HCAR and MCAR: the human and mouse cellular receptors for subgroup C adenoviruses and group B coxsackieviruses.

The subgroup C of the adenoviruses (Ad) and the group B coxsackieviruses (CVB) are structurally unrelated viruses that are known to compete for an unidentified cell surface receptor. We now describe the isolation of cDNAs from human and mouse that encode the human CVB and Ad2 and 5 receptor (HCAR) and the mouse CVB Ad2 and 5 receptor (MCAR). Both are 46-kDa glycoproteins whose primary amino acid sequences are highly homologous. Structurally, HCAR and MCAR appear to be transmembrane proteins that contain two extracellular immunoglobulin-like domains and therefore belong to this superfamily. Transfection of either of these cDNA molecules into receptor-negative NIH 3T3 cells conferred susceptibility to CVB infection and permitted the expression of beta-galactosidase from a recombinant Ad5 vector. In addition, HCAR and MCAR mRNAs could be detected on Northern blots of oligo(dT)-selected RNA from receptor-positive HeLa cells and TCMK-1 as well as several tissues of human and mouse origin that are known to be targets for Ad and CVB infections. Finally, Western blots using antibodies that inhibit virus binding to either the human or mouse CVB receptors detected 46-kDa proteins in HCAR- and MCAR-transfected cells, respectively. Taken together, these results confirm that the isolated cDNAs encode the receptors for the subgroup C Ad and CVB.

3T3 Cells↗

PubMed1997

Projection of the thoracic pedicle and its morphometric analysis.

STUDY DESIGN: This study defined the projection point of the thoracic pedicles on their posterior aspect and its relation to a reliable landmark. It also reported pedicle dimensions based on 43 thoracic spines. OBJECTIVES: To determine the projection point of the pedicle axis on the posterior aspect of the thoracic spine, quantitatively describe relations of the projection point to some reliable landmarks, and evaluate linear and angular dimensions of the thoracic pedicle. SUMMARY OF BACKGROUND DATA: Posterior segmental screw fixation is the current standard of internal fixation at the level of the second lumbar vertebrae or below. However, pedicular screw fixation in the thoracic spine, especially in the middle and upper thoracic region, is not common because the small dimensions of the pedicle in this region make screw insertion difficult. More information about pedicle axis projection (not pedicle zone) and its quantitative relationship to some reliable landmarks is essential. METHODS: Forty-three dry thoracic specimens (516 vertebrae) were obtained for study of the thoracic pedicle. Anatomic evaluation focused on the determination of the projection point of the thoracic pedicle axis on its posterior aspect and the anatomic relationship of this point to the lateral edge of superior facet and the midline of the transverse process. Also, pedicle dimensions, including linear and angular, were measured. The mean, range, and standard deviation were calculated for all of the specimens and for male and female specimens separately. RESULTS: Sexual difference was found to be significant statistically in more than half of parameters. For T1-T2, the projection point of the pedicle axis was approximately 7-8 mm medial to the lateral edge of the superior facet and 3-4 mm superior to the midline of the transverse process. For T3-T12, this point was 4-5 mm medial to the lateral margin of the facet and 5-8 mm superior to the midline of the transverse process. The transverse angle of the pedicle axis was found to be 30-40 degrees at T1-T2, 20-25 degrees at T3-T11, and 10 degrees at T12. CONCLUSIONS: This information, in conjunction with preoperative computed tomography evaluation, may enhance our knowledge of transpedicular screw fixation in the thoracic pedicle.

Adult↗

PubMed1997

Morphometric evaluation of lower cervical pedicle and its projection.

STUDY DESIGN: This study evaluated the lower cervical pedicle from C3 to C6 to provide information for accurate transpedicular screw fixation in this region. OBJECTIVES: To measure the dimensions of the lower cervical pedicle and to determine the correct location of the pedicle axis on the posterior aspect of the lateral mass. SUMMARY OF BACKGROUND DATA: Several anatomic studies and clinical applications of transpedicular screw fixation in the cervical spine have been documented, but little quantitative data concerning the lower cervical pedicle and its projection are available. METHODS: Forty dry cervical specimens from C3 to C6 (160 cervical vertebrae) were used for this study. Anatomic evaluation included pedicle height, width, effective length, and anguli. The distances from the projection point of the pedicle axis to reference lines related to the lateral edge of the lateral mass (vertical) and the inferior edge of the superior facet (horizontal) also were measured. The means, ranges, and standard deviations were calculated for all of the specimens and separately for male and female spines. RESULTS: Statistically significant differences in dimensions of males and females were found in one linear and one angular measurement, which included the pedicle height of C6 and the pedicle sagittal angle of C4. The greatest variation for males and females was found in the pedicle sagittal angle, with a range of 4.3-9.8 degrees. The distances from the projection point to the horizontal line did not show any real pattern of change from C3 to C6, whereas the distances from the projection point to the vertical line consistently increased from cephalad to caudad. CONCLUSIONS: Taking into consideration some variations between individuals, this information, combined with evaluation of results of preoperative axial computed tomography and conventional radiography, may enhance the safety of transpedicular screw fixation in the lower cervical spine.

Adult↗

PubMed1997

The effect of changes in hepatocyte membrane potential on immediate-early proto-oncogene expression following partial hepatectomy in rats.

The stimulus responsible for inducing hepatocytes to enter the cell cycle following partial hepatectomy (PHx) remains to be identified. One suggested candidate is the change in hepatocyte membrane potential (PD) that occurs immediately following PHx. To test this possibility, we monitored changes in hepatocyte PD and immediate-early proto-oncogene expression in rats pretreated with saline or gamma aminobutyric acid (GABA), an amino-acid neurotransmitter that hyperpolarizes isolated hepatocytes. Intraperitoneal injections of saline or GABA (500 microg/g body weight) were administered to adult, male Sprague-Dawley rats 1 hour prior to 70% PHx. Rats were sacrificed and the livers excised at various times until 180 minutes post-PHx for messenger RNA (mRNA) and protein analyses. In additional groups of saline- and GABA-treated rats, PD changes were recorded continuously from -260 to 180 minutes post-PHx. Serum GABA concentrations were determined by ion-exchange chromatography with orthopthaldehyde fluorescence detection. Hepatocyte PD's were recorded in situ by intracellular microelectrodes with an Axoprobe-1A amplifier. Steady-state levels of c-fos, c-jun, jun-B, and c-myc transcripts and proteins were documented by Northern blots of poly(A)-enriched RNA derived from resected livers and Western blots of total nuclear protein, respectively. Serum GABA concentrations remained unchanged in saline-treated controls but increased 10- to 20-fold above baseline values in GABA-treated rats. In saline-treated controls, hepatocyte depolarization occurred immediately and was maintained throughout the 180 minutes post-PHx period (PD pre-PHx, -36.8 +/- 5.1; 15 minutes post-PHx, -27.5 +/- 5.7; and 180 minutes post-PHx, -28.3 +/- 4.4 mV, mean +/- SD); whereas in GABA-treated rats, hepatocyte PD remained unchanged (-37.0 +/- 1.1; -36.4 +/- 3.1 and -39.2 +/- 2.7 mV, respectively). Despite abrogation of hepatocyte PD changes, proto-oncogene mRNA and protein levels in saline- and GABA-treated rats were either similar or, in the case of c-fos and c-jun, increased five- to sevenfold in GABA-treated rats. The results of this study indicate the following: 1) hepatocytes depolarize immediately post-PHx and remain depolarized throughout the priming phase of the cell cycle; 2) elevated serum GABA concentrations prevent PHx-induced hepatocyte depolarization; and 3) depolarization is not the stimulus responsible for priming hepatocytes into replicative competence.

Animals↗

PubMed1997

KC8851, a tedisamil analogue with mixed channel blockade, exhibits antiarrhythmic properties against ischemia- and electrically-induced arrhythmias.

KC8851, a structural analogue of tedisamil, has previously been found to exhibit mixed blockade of K+ and Na+ currents in isolated rat ventricular myocytes. We have now investigated the antiarrhythmic actions of this compound in the anaesthetized rat and isolated rat heart. In the rat, KC8851, at concentrations as low as 0.2 micromol kg(-1) min(-1), widened the QT intervals of the ECG and prolonged the effective refractory period in a dose-dependent manner. Such actions were consistent with blockade of repolarizing K+ currents. At relatively higher doses (above 0.5 micromol kg(-1) min(-1)), KC8851 increased RSh amplitude suggesting blockade of Na+ currents. The compound was found to be effective against occlusion-induced arrhythmias at doses of 0.5 to 2 micromol kg(-1) min(-1). In isolated hearts, the effects of KC8851 on PR and QRS intervals were potentiated by elevated concentrations of K+ and H+. Overall, KC8851 was found to exhibit antiarrhythmic actions consistent with inhibition of both K+ and Na+ currents.

Animals↗

PubMed1997

Telomerase activity in ordinary meningiomas predicts poor outcome.

Telomerase, the enzyme that stabilizes telomere length, is reactivated with almost all cancer types, and it may be necessary for unlimited cell proliferation. Assessment of malignancy in ordinary meningiomas is inconclusive because no clear-cut correlation exists between aggressive clinical behavior and histological features or karyotypic abnormalities. We analyzed telomerase activity in 52 cases of meningioma by using the highly sensitive telomeric repeat amplification protocol and then compared clinical behavior in telomerase-positive and -negative ordinary meningiomas. Twenty-six of the 52 tumors (50%) had detectable telomerase activity. Twenty-one of the 22 neoplasms classified as malignant or atypical (95%) had detectable telomerase activity, and these tumors generally had a poor outcome. Interestingly, 5 of 30 ordinary (morphologically benign) meningiomas (17%) also showed detectable telomerase activity. Of the 5 patients with telomerase-positive ordinary meningiomas, 3 had rapid regrowth of the tumor despite gross total resection. The remaining 2 patients also had other primary malignancies. We observed a highly significant correlation in ordinary meningiomas between the presence of telomerase activity and a poor prognosis for the patient (P = .0002). Telomerase activity in benign meningiomas is clinically relevant because the presence of the enzyme suggests that these benign-appearing tumors may contain a population of immortal cells. The detection of telomerase activity may help to identify benign meningiomas that would be more likely to continue to grow and to recur clinically if surgical resection were incomplete.

Adolescent↗

PubMed1997

The location of the intervertebral lumbar disc on the posterior aspect of the spine.

BACKGROUND: Epidural fibrosis or scar formation is considered one cause of failed lumbar discectomy. Avoidance of unnecessary bony resection of the lamina may prevent or decrease postoperative scar formation. The knowledge of the precise location of the projection of the lumbar disc may also facilitate surgery and decrease patient morbidity. No studies exist regarding the projection of the lumbar disc on the posterior aspect of the lumbar spine. METHODS: Thirty-six whole lumbar spine specimens from L1 to L5 (180 lumbar vertebrae) and sacra were used for this study. Anatomic evaluation included the distance between the superior border of the vertebral body (inferior border of the intervertebral disc) and the superiormost margin of the lumbar lamina, and the distance between the inferior border of the vertebral body (superior border of the intervertebral disc) and the inferiormost margin of the lumbar lamina. The width of the interlaminar space was also measured. RESULTS: The data showed that the level of the superior margin of the lamina was consistently inferior to the superior border of the corresponding vertebral body from L1 to S1. This distance for both sexes ranged from 10 to 11 mm for L1-L5 and 14 mm for S1. The level of the inferior margin of the lamina varied from 3 mm inferior to 9 mm superior to the inferior border of the corresponding vertebral body for L1-L5. The width of the interlaminar space averaged from 16.8 mm for L1 to 31.0 mm for L5. CONCLUSIONS: This study suggests that the superior margin of the lamina represents a consistent, useful landmark in determining the location of the lumbar disc on the posterior aspect of the spine. The relationship between the inferior margins of the lamina and the vertebral body is not consistent.

Female↗

PubMed1997

Ion channels of human microglia in culture.

Macroscopic and microscopic currents have been recorded using human microglia isolated from fetal human brains (12-20 weeks gestation). Within a period of two days following plating of cells, inward K+ currents were small (mean amplitude of 0.3 nA at -100 mV) and outward K+ currents were not observed. For periods in excess of five days after adherence to substrate, an inactivating outward K+ current, sensitive to 4-aminopyridine, was expressed. A slowly rising current, blocked by tetraethylammonium, was also evident in a small population of human microglia. This current was activated with cell depolarization positive to +10 mV and had properties similar to those recently described for a proton current in mouse cells. In early adherent cells (days 1 or 2 after plating), treatment of microglia with interferon-gamma led to the expression of outward K+ current which was lacking in the absence of the treatment. In excised, inside-out patches, two high conductance channels were identified. A calcium-dependent K+ channel (unitary conductance of 106 pS with physiological levels of K+ across the patch) had an open probability of 0.5 with internal Ca2+ at 7 microM and the patch potential at 0 mV. In addition, an anion channel (unitary conductance of 280 pS) was transiently activated with depolarizing or hyperpolarizing steps applied from 0 mV. Characterization of the macroscopic and unitary properties of currents in microglia will have relevance to a description of putative cell functions in the human CNS. In particular, modification of cell electrophysiological properties by various activating stimuli may contribute to signalling processes in CNS pathology.

Anions↗

PubMed1997

A preliminary morphometric study on the endometrium from patients treated with indomethacin-releasing copper intrauterine device.

The intrauterine device (IUD) is an effective method of birth control. However, IUD-induced uterine bleeding is a major side-effect and always causes inconvenience, sometimes even anaemia. It has been reported that oral administration of indomethacin could can reduce IUD-induced uterine bleeding. In the present study, we investigated whether indomethacin-releasing copper IUD (IR-Cu-IUD) can prevent insertion-induced uterine bleeding and its mechanism. Nine healthy volunteers of reproductive age were selected for the study. Endometrial tissues were collected at same menstrual stage prior to and 3-6 months after IR-Cu-IUD insertion. Endometrial morphology, cell proliferation/differentiation, morphometry and activity of complement Factor VIII were examined. No significant difference was found in any of the parameters examined in the same patients, both prior to and after IR-Cu-IUD insertion. By comparison with data previously obtained from the patients who had Cu-IUD insertions, it is clear that IR-Cu-IUD markedly reduced IUD-induced uterine bleeding and this reduction is primarily contributed by the anti-inflammatory action of indomethacin.

Adult↗

PubMed1997

Multidrug-resistant gene expression in small-cell lung cancer.

The development of drug resistance can contribute to treatment failure in small-cell lung cancer (SCLC). In this report, we investigate p-glycoprotein-mediated multidrug resistance (MDR) in these patients. Tumor tissue was obtained prior to treatment and at relapse if possible, short-term culture was carried out, and these tumor cells were analyzed for MDR gene expression by slot blot and reverse transcriptase polymerase chain reaction (RT-PCR) and northern blot analysis. Three cell lines were also established from short-term cultures. Twenty-four patients with MDR(-) and seven with MDR +(++) were available for survival analysis. Median survival for MDR (-) patients was 10 months, whereas for MDR +(++) patients it was 2 months. This was statistically significance (p < 0.0007). The presence of MDR1 gene expression also correlated with the lack of response to chemotherapy (p < 0.001). Increased MDR1 gene expression is usually present in patients with more tumor burden at initial diagnosis. Furthermore, loss of MDR1 gene expression can occur in intrinsically MDR(+) SCLC cells after multiple passages in drug-free media. We concluded that increased MDR1 gene expression is present in a small number of SCLC both before and after chemotherapy and usually signifies poor survival and no response to chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Anatomic basis of lag screw placement in the anterior column of the acetabulum.

The projection point of the axis of the anterior column of the acetabulum on the outer table of the iliac wing was determined in 15 adult bony hemipelves. The optimal entry point for lag screw fixation in the anterior column was located 16 +/- 3.9 mm superior to the midpoint of the line connecting the apex of the sciatic notch with the notch between anterior superior iliac spine and anterior inferior iliac spine, and 46 +/- 5.9 mm superior to the acetabular rim. The mean inclination of the projected axis was 90.6 degrees +/- 5.0 degrees in the sagittal plane and 29.0 degrees +/- 4.4 degrees in the transverse plane. These data may facilitate insertion of a lag screw into the anterior acetabular column and minimize the risk of articular violation or cortical penetration because there is a narrow margin of safety. The lag screw placement also may be aided by palpating the anterior column with a finger and by intraoperative fluoroscopy for visualization of the hip joint and the anterior column in the obturator or pelvic outlet views.

Acetabulum↗

PubMed1997

Location of the extraforaminal lumbar nerve roots. An anatomic study.

Twelve cadavers were used to determine the anatomic location of the extraforaminal lumbar nerve root in the intertransverse space. After exposure of the transverse processes of the lumbar spine and the extraforaminal lumbar nerve roots, direct measurements, including the nerve root angle, nerve root diameter, distance to the superior facet, and the intertransverse space, were made bilaterally. The results showed that the extraforaminal nerve root angle and diameter and the distance between the superior facet and lateral limit of the nerve root consistently increased from cephalad to caudal. The largest dimension for height and width of the intertransverse space was found at the level of L3-4, and the smallest was found at the level of L5-S1. This information may be helpful in minimizing the incidence of injury to the lumbar nerve root during a posterolateral approach to lumbar disc.

Aged↗