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At least 1,747 records · Page 97Linked to original sources
PubMed2005

Comparison of 3D segmented gradient-echo and steady-state free precession coronary MRI sequences in patients with coronary artery disease.

OBJECTIVE: Our objective was to compare two state-of-the-art coronary MRI (CMRI) sequences with regard to image quality and diagnostic accuracy for the detection of coronary artery disease (CAD). SUBJECTS AND METHODS: Twenty patients with known CAD were examined with a navigator-gated and corrected free-breathing 3D segmented gradient-echo (turbo field-echo) CMRI sequence and a steady-state free precession sequence (balanced turbo field-echo). CMRI was performed in a transverse plane for the left coronary artery and a double-oblique plane for the right coronary artery system. Subjective image quality (1- to 4-point scale, with 1 indicating excellent quality) and objective image quality parameters were independently determined for both sequences. Sensitivity, specificity, and accuracy for the detection of significant (> or = 50% diameter) coronary artery stenoses were determined as defined in invasive catheter X-ray coronary angiography. RESULTS: Subjective image quality was superior for the balanced turbo field-echo approach (1.8 +/- 0.9 vs 2.3 +/- 1.0 for turbo field-echo; p < 0.001). Vessel sharpness, signal-to-noise ratio, and contrast-to-noise ratio were all superior for the balanced turbo field-echo approach (p < 0.01 for signal-to-noise ratio and contrast-to-noise ratio). Of the 103 segments, 18% of turbo field-echo segments and 9% of balanced turbo field-echo segments had to be excluded from disease evaluation because of insufficient image quality. Sensitivity, specificity, and accuracy for the detection of significant coronary artery stenoses in the evaluated segments were 92%, 67%, 85%, respectively, for turbo field-echo and 82%, 82%, 81%, respectively, for balanced turbo field-echo. CONCLUSION: Balanced turbo field-echo offers improved image quality with significantly fewer nondiagnostic segments when compared with turbo field-echo. For the detection of CAD, both sequences showed comparable accuracy for the visualized segments.

Aged↗
PubMed1999

Risk factors for adjacent-segment failure following lumbar fixation with rigid instrumentation for degenerative instability.

OBJECT: The authors performed a retrospective analysis of 125 consecutive patients in whom instrumentation was placed to promote lumbar fusion for the treatment of degenerative instability. All procedures were performed by a single surgeon. The authors sought to determine the risk factors for next-segment degeneration after lumbar spinal fusion with rigid instrumentation. METHODS: Thirty-one of 125 fusion procedures were performed in women who were postmenopausal. A total of 18 of 125 patients developed symptomatic next-segment degeneration at a previously asymptomatic level; 15 were postmenopausal women. Data were obtained in patients with next-segment failure based on radiographic studies, neurological assessment, demographic factors, and sequential follow-up examinations. The mean follow-up period for this group was 44.8 months. All women were postmenopausal, and 53% received biphosphonate drugs and calcium supplementation preoperatively for osteopenia. Twenty percent of all patients with next-segment failure were cigarette smokers. Next-segment diseases included spondylolisthesis (39%), spinal canal stenosis due to disc herniation and/or facet hypertrophy (33%), stress fracture of the adjacent vertebral body (28%), and scoliosis (17%). Patients frequently had more than one degenerative process at the next segment. CONCLUSIONS: The risk of adjacent-segment failure is clearly higher for patients in whom lumbar fusion with rigid instrumentation is performed to treat degenerative instability. This risk appears to be especially high in postmenopausal women.

Aged↗
PubMed2006

Intracorneal asymmetrical rings for keratoconus: where should the thicker segment be implanted?

PURPOSE: To report a 20-year-old man who presented with monocular diplopia in the right eye with uncorrected visual acuity (UCVA) of 0.3 and best spectacle-corrected visual acuity (BSCVA) of 1.0 with -0.50 -3.00 x 45 degrees. METHODS: Clinical examination and corneal topography revealed grade I keratoconus in the right eye. Intracorneal ring segments (INTACS; Addition Technology, Des Plaines, III) were implanted in May 2004 without surgical complications at 415 microm (70% of the corneal thickness), with the 450-microm segment implanted superiorly and the 250-microm segment inferiorly. RESULTS: For 2 months postoperatively, BSCVA remained at 0.4 with +1.50 -4.50 x 25 degrees. The segments were reversed, implanting the 450-microm (thick) segment inferiorly and the 250-microm (thin) segment superiorly. One week later, UCVA was 1.0 and remained stable for 3 months after reimplantation. CONCLUSIONS: This report shows that implanting the thicker segment inferiorly provides better visual results.

Adult↗
PubMed1996

Coronary segmental responses to acetylcholine in patients with hypercholesterolemia.

We investigated coronary segmental response to intracoronary acetylcholine (ACh) in 19 patients with hypercholesterolemia and 18 patients with normal cholesterol levels. All patients had atypical and chest pain and angiographically normal coronary arteries. After baseline angiography, ACh (3 and 30 micrograms/min) was infused into the left coronary artery, followed by infusion of nitroglycerin. Percent changes in diameter of the proximal, middle, and distal segments of the left coronary arteries were measured by quantitative angiography. In the normocholesterolemic group, 3 micrograms/min of ACh produced significant coronary vasodilation in the distal segments (+8.2 +/- 2.6%, p < 0.005), while 30 micrograms/min did not cause any changes. In the hypercholesterolemic group, 30 micrograms/min of ACh caused significant coronary vasoconstriction in the middle and distal segments (-7.2 +/- 1.9% and -6.2 +/- 1.9%, p < 0.001 and p < 0.01, respectively), while 3 micrograms/min caused no changes. In each group, vasodilator responses to nitroglycerin in the middle and distal segments were significantly greater than those in the proximal segments (p < 0.001). Our results suggest that impaired endothelial function may be evaluated more effectively in the distal coronary segments in patients in the early stage of epicardial coronary atherosclerosis attributable to hypercholesterolemia.

Acetylcholine↗
PubMed2006

Thin basement membrane nephropathy: diffuse and segmental types.

CONTEXT: Diffuse thinning of the glomerular basement membrane (GBM) is the ultrastructural diagnostic criterion of thin basement membrane nephropathy (TBMN). However, there is no consensus regarding what diagnosis should be made if the attenuation is segmental. OBJECTIVE: To develop a diagnostic approach to TBMN in cases with segmental GBM thinning. DESIGN: We compared the diagnostic sensitivities of 2 methods used for the quantitative expression of GBM width in a consecutive series of renal biopsies from 26 patients (median age, 36 years; range, 15 to 59 years) with dysmorphic hematuria (a variable degree of proteinuria in 19 patients), a thin GBM, and absence of other renal disease. The harmonic GBM width was determined from orthogonal intercepts, and the actual width in the thinnest loops was obtained by direct measurement. The GBM attenuation was categorized into diffuse or segmental types by conventional inspection. RESULTS: Segmental TBMN accounted for one third of the series. In neither type did the male patients have a higher harmonic mean GBM width than the female patients. Focal-global glomerulosclerosis was more common in diffuse TBMN. The laborious orthogonal intercept method proved insensitive for the verification of segmental TBMN, whereas the much simpler direct measurement technique captured all the cases. CONCLUSIONS: A considerable number of patients with TBMN display segmental GBM attenuation. Because the routine criterion excludes these cases from the diagnosis, we propose to define TBMN as a clinicopathologic entity of dysmorphic hematuria and a diffusely or segmentally thinned GBM confirmed by the direct measurement technique.

Adolescent↗
PubMed2003

[Gastric phantom for training beginners in gastric segment (Stomap) recognition].

It is usually difficult for a beginner to understand precisely and quickly the three-dimensional (3D) construction of gastric lesions in a gastric X-ray examination with barium meal. In this study, a training-use stomach phantom was developed using the stomach segment to provide beginners with an understanding of 3D stomach construction. The hook-shaped phantom (the shape of the stomach when a patient is in the supine position) was formed by using styrene, wire, and clay. It was then coated with dental stiffening agent, and wires were attached along the stomach segment. After drying, the stomach phantom was cut off and the oil clay was removed. The phantom then was immersed in water and the oil clay was dried. After that, the phantom again was glued together with a dental stiffening agent. The usefulness of the phantom was determined by an evaluation experiment. Ten students, as observers, were selected randomly for evaluation from 40 students of the Department of Radiological Technology, College of Medical Technology, Hokkaido University. Eight films were shown to the observers, 4 films with segment and 4 films without segment. The observers checked 5 markers in different positions of the phantom and recorded the results on an answer sheet with segment picture. The significance of position recognition was identified by Wilcoxon's sign rank sum test (p=0.021) between the segment film and non-segment film.

Humans↗
PubMed1998

Collective adaptation: the exchange of coding segments.

Coding segments are those subsegments of the chromosome that contribute positively to the fitness evaluation of the chromosome. Clique detection is a NP-complete problem in which we can detect such coding segments. We extract coding segments from chromosomes, and we investigate the duplication of coding segments inside the chromosome and the collection of coding segments outside of the chromosome. We find that duplication of coding segments inside the chromosomes provides a back-up mechanism for the search heuristics. We further find local search in a collective memory of coding segments outside of the chromosome, collective adaptation, enables the search heuristic to represent partial solutions that are larger than realistic chromosomes lengths and to express the solution outside of the chromosome.

Algorithms↗
PubMed1999

Segmental spinal dysgenesis: neuroradiologic findings with clinical and embryologic correlation.

BACKGROUND AND PURPOSE: Segmental spinal dysgenesis (SSD) is a rare congenital abnormality in which a segment of the spine and spinal cord fails to develop properly. Our goal was to investigate the neuroradiologic features of this condition in order to correlate our findings with the degree of residual spinal cord function, and to provide insight into the embryologic origin of this disorder. We also aimed to clarify the relationship between SSD and other entities, such as multiple vertebral segmentation defects, congenital vertebral displacement, and caudal regression syndrome (CRS). METHODS: The records of patients treated at our institutions for congenital spinal anomalies were reviewed, and 10 cases were found to satisfy the inclusion criteria for SSD. Plain radiographs were available for review in all cases. MR imaging was performed in eight patients, one of whom also underwent conventional myelography. Two other patients underwent only conventional myelography. RESULTS: Segmental vertebral anomalies involved the thoracolumbar, lumbar, or lumbosacral spine. The spinal cord at the level of the abnormality was thinned or even indiscernible, and a bulky, low-lying cord segment was present caudad to the focal abnormality in most cases. Closed spinal dysraphisms were associated in five cases, and partial sacrococcygeal agenesis in three. Renal anomalies were detected in four cases, and dextrocardia in one; all patients had a neurogenic bladder. CONCLUSION: SSD is an autonomous entity with characteristic clinical and neuroradiologic features; however, SSD and CRS probably represent two faces of a single spectrum of segmental malformations of the spine and spinal cord. The neuroradiologic picture depends on the severity of the malformation and on its segmental level along the longitudinal embryonic axis. The severity of the morphologic derangement correlates with residual spinal cord function and with severity of the clinical deficit.

Coccyx↗
PubMed1999

Segmentation by color influences responses of motion-sensitive neurons in the cortical middle temporal visual area.

We previously showed that human subjects are better able to discriminate the direction of a motion signal in dynamic noise when the signal is distinguished (segmented) from the noise by color. This finding suggested a hitherto unexplored avenue of interaction between motion and color pathways in the primate visual system. To examine whether chromatic segmentation exerts a similar influence on cortical neurons that contribute to motion direction discrimination, we have now compared the discriminative capacity of single MT neurons and psychophysical observers viewing motion signals with and without chromatic segmentation. All data were obtained from rhesus monkeys trained to discriminate motion direction in dynamic stimuli containing varying proportions of coherently moving (signal) and randomly moving (noise) dots. We obtained psychophysical and neurophysiological data in the same animals, on the same trials, and using the same visual display. Chromatic segmentation of the signal from the noise enhanced both neuronal and psychophysical sensitivity to the motion signal but had a smaller influence on neuronal than on psychophysical sensitivity. Hence the ratio of neuronal to psychophysical thresholds, one measure of the relation between neuronal and psychophysical performance, depended on chromatic segmentation. Increased neuronal sensitivity to chromatically segmented displays stemmed from larger and less noisy responses to motion in the preferred directions of the neurons, suggesting that specialized mechanisms influence responses in the motion pathway when color segments motion signal in visual scenes. These findings lead us to reevaluate potential mechanisms for pooling of MT responses and the role of MT in motion perception.

Animals↗
PubMedDate not supplied

Angiographic correlates of anterior ST segment depression in acute inferior wall myocardial infarction.

This study was conducted prospectively to assess the correlation between the pattern of anterior ST segment depression on the admission electrocardiogram and the in-hospital morbidity and mortality in patients with acute inferior wall myocardial infarction. Coronary angiography was also done to assess its correlation, if any, with pattern of anterior ST segment depression. Our study cohort comprised of 165 consecutive patients with acute inferior wall myocardial infarction divided into four groups based on admission electrocardiogram. Group I (n = 33): patients with no anterior ST segment depression; group II (n = 16): patients with ST segment depression in leads V1-V3; group III (n = 71): patients with ST segment depression in leads V4-V6, I and aVF, and; group IV (n = 45): patients with ST segment depression in all anterior leads (V1-V6, I, aVL). The outcomes were analysed in terms of high grade atrioventricular block, Killip class II or higher failure, and in-hospital mortality. Coronary angiography was performed to analyse coronary anatomy. Group IV patients had increased incidence of complete heart block (37.8% vs 15.2% in the total group) (p < 0.001) and increased mortality (11.1% vs 4.2% in the total group) (p < 0.05). This group also had greater incidence of triple vessel disease (76.7%) (p < 0.001). Group II patients had greater incidence of double vessel disease (88.9%) (p < 0.05) and had no triple vessel disease. Group III patients had double vessel disease (76.5%) (p < 0.05) or triple vessel disease (23.5%) (p = NS) and no single vessel disease. Coronary angiography in group II showed greater incidence of involvement of left circumflex artery and right coronary artery while in group III there was left anterior descending artery and right coronary artery disease. We conclude that patients with anterior ST segment depression in group III and group IV categories are in high risk subset with acute inferior wall myocardial infarction.

Aged↗
PubMed2000

Initiating or blocking locomotion in spinal cats by applying noradrenergic drugs to restricted lumbar spinal segments.

After an acute low thoracic spinal transection (T13), cats can be made to walk with the hindlimbs on a treadmill with clonidine, an alpha2-noradrenergic agonist. Because previous studies of neonatal rat spinal cord in vitro suggest that the most important lumbar segments for rhythmogenesis are L1-L2, we investigated the role of various lumbar segments in the initiation of walking movements on a treadmill of adult cats spinalized (T13), 5-6 d earlier. The locomotor activities were evaluated from electromyographic and video recordings. The results show that: (1) localized topical application of clonidine in restricted baths over either the L3-L4 or the L5-L7 segments was sufficient to induce walking movements. Yohimbine, an alpha2-noradrenergic antagonist, could block this locomotion when applied over L3-L4 or L5-L7; (2) microinjections of clonidine in one or two lumbar segments from L3 to L5 could also induce locomotion; (3) after an intravenous injection of clonidine, locomotion was blocked by microinjections of yohimbine in segments L3, L4, or L5 but not if the injection was in L6; (4) locomotion was also blocked in all cases by additional spinal transections at L3 or L4. These results show that it is possible to initiate walking in the adult spinal cat with a pharmacological stimulation of a restricted number of lumbar segments and also that the integrity of the L3-L4 segments is necessary to sustain the locomotor activity.

Adrenergic alpha-Agonists↗
PubMed2000

Hepatic grooves and portal segmentation.

The aim of the present study was to examine the topographical relationship between the locations of the grooves and the borders of Couinaud's portal segments. We found 79 grooves on the diaphragmatic surfaces of 50 livers from 420 cadavers. Most grooves were located within segment VIII wholly (31/79) or partially (39/79). By contrast, only 11 grooves corresponded to the border between two segments (segments VIII/IV in 6 cases and segments VIII/VII in 5 cases). Diaphragmatic indentations (fold-like protrusions) into the groove were observed in 1 case. Our results suggest that the grooves did not form during the early embryonic period when intrahepatic vessels and ducts ramify, but that they formed during a later stage of diaphragmatic growth after establishment of the basic segmental configuration of the liver. The grooves do not seem to be critical landmarks for segmental borders of the liver.

Aged↗
PubMed1979

The membrane current of single rod outer segments.

1. Outer segments of individual rods in the retina of the toad, Bufo marinus, were drawn into a glass pipette to record the membrane current. 2. Light flashes evoked transient outward currents. The peak response amplitude was related to flash intensity by a Michaelis equation with half-saturating intensity about 1 photon mum-2. 3. The saturating response amplitude ranged up to 27 pA and corresponded closely to complete suppression of the steady inward current present in darkness. 4. For a given cell the saturating response amplitude varied linearly with the length of outer segment within the pipette. This is consistent with a uniform density of light-sensitive channels and negligible gradient of membrane potential along the outer segment. 5. Responses to bright flashes never showed the relaxation from an initial peak seen previously in intracellular voltage recordings, suggesting that the conductance change responsible for the relaxation does not occur in the outer segment. 6. Responses to local illumination of only the recorded outer segment were very similar to those obtained with diffuse light at the same intensity, indicating that peripheral rods made little contribution to the responses. 7. The spectral sensitivity of 'red' rods was consistent with a retinal1-based pigment with lambda max = 498 +/- 2 nm. 8. The kinetics of the response were consistent with four stages of delay affecting action of the internal transmitter. Responses were faster at the basal end of the outer segment than at the distal tip. 9. Background light reduced the sensitivity to a superposed dim test flash and shortened the time course of the response, indicating that adapting light modifies the kinetics and gain of the transduction mechanism within the outer segment. 10. Responses to dim lights exhibited pronounced fluctuations which are attributed in the succeeding paper (Baylor, Lamb & Yau, 1979) to the quantal nature of light.

Animals↗
PubMed2000

Postischemic reperfusion of the spinal cord: prolonged reperfusion alleviates the metabolic alterations induced by 25 min ischemia in the cervical and thoracolumbal segments.

In recent years, increasing amount of information has indicated that in some tissues the main damage due to oxidative stress does not occur during reperfusion but during the ischemic episode of the ischemia/reperfusion event. In this respect, serious doubts were also expressed about the origin of the increased amounts of free radicals which were believed to form and reported to appear in the perfusate during the first minutes of reperfusion. Moreover, speculative explanations were only available for a second increase in lipid peroxidation which was reported to occur after postischemic reperfusions exceeding 60 min. For this reasons, the present paper reports the results of investigation of ischemia/reperfusion injury to the cervical (CE) and thoracolumbal (ThL) segments of the spinal cord (SP) after an acute 25 min occlusion of the abdominal aorta, followed by 60-120 min reperfusion of the ischemic areas in rabbits. In CE and ThL segments of the SP, the ischemia induced: 1) a decrease in activities of superoxide dismutase (SOD), from 57.35+/-6.36 to 45.27+/-5.45 U x mg(-1) x min(-1) (S.E.M., 20.92%), p < 0.01, and from 58.36+/-5.45 to 33.00+/-4.55 U x mg(-1) x min(-1) (S.E.M., 43.46%), p < 0.001; 2) a significant decrease in gamma-glutamyl transpeptidase (gamma-GTP), from 114.66+/-1.45 to 99.88+/-4.4 micromol p-nitroaniline x mg(-1) x h(-1) (S.E.M. 12.89 %), p < 0.05 and from 112.24+/-1.20 to 95.09+/-2.40 micromol p-nitroaniline x mg(-1) x h(-1) (S.E.M., 16.26%), p < 0.05; 3) a considerable depression in Na,K-ATPase activity, from 7.14+/-0.58 to 5.08+/-0.32 micromol Pi x mg(-1) x h(-1) (S.E.M., 28.86%), p < 0.01, and from 7.23+/-0.11 to 5.09+/-0.31 micromol Pi x mg(-1) x h(-1) (S.E.M., 30.00%), p < 0.01. The Na,K-ATPase activity became decreased by ischemia and remained depressed significantly (all p < 0.01) throughout the experiment. After 60 min of reperfusion, SOD activity in the CE segment and that of gamma-GTP in the CE as well as ThL segments recovered, even slightly surpassing the control values, wheras SOD activity in the ThL segment became stabilized again close to its post-ischemic value. Prolonged, reperfusion for 120 min resulted in a further increase in gamma-GTP activity in the CE and ThL segments (to 132.79 and 132.30%, p < 0.01), and this was accompanied by a slight (p > 0.05) elevation in the content of conjugated dienes as well as by a new wave of depression of the SOD activity (p < 0.05) in both the CE and the ThL segment. From our results it could be concluded that all considerable damage to the spinal cord occurred during the ischemic period. In the period of reperfusion reparative changes started to predominate. This is in accordance with the recent discoveries indicating that, when coupled with an increase in tissue gamma-GTP activity, the post-ischemic reparative changes comprise a replenishment of the cell glutathione pool. This process is accompanied with a gradual increase in H2O2 production that results in repeatead inhibition of the SOD activity and a tendency to conjugated dienes formation.

Animals↗
PubMed2001

Reconstruction of ureter with transverse retubularized colon segments.

PURPOSE: We present a technique in which colon segments are reconfigured as substitutes for ureteral defects. MATERIALS AND METHODS: Via a flank incision a 3 cm. segment was obtained from the ascending or descending colon and reconfigured into a well vascularized tube. In 2 patients a single retubularized colon segment was interposed into an extensive defect of the upper and mid ureter, respectively. In an additional 2 patients 2 combined anastomosed reconfigured colon segments were used for pyelo-colo-cutaneostomy. RESULTS: At a followup of 9 to 27 months (mean 15), no complications related to the reconfigured colon segments were noted. One patient died of progressive disease 9 months postoperatively but with no evidence of ureteral substitute malfunction. CONCLUSIONS: Reconfigured colon segments may be used successfully to reconstruct extensive ureteral defects. Access is via a flank or pararectal incision and intraperitoneal surgery is minimal. The colon segments are obtained immediately proximal to the ureteral defect, necessitating little mobilization of the mesenteric pedicle. Metabolic consequences should be absent or low since only minimal amounts of intestine are isolated. In patients with renal insufficiency or a history of irradiation this technique may be superior to the use of ileum.

Adult↗
PubMed2000

[The partial nucleotide sequence of L segment of Hantavirus strain].

OBJECTIVE: To study the nucleotide sequence of L segment of Hantavirus strain A9. METHODS: The partial L segment cDNA of A9 strain was amplified by PCR, the PCR product was sequenced. RESULTS: The nucleotide sequence of partial L segment of A9 strain was provided, the sequence was A, T rich, similar to other Hantaviruses, and similar to both M, S segments. Compared with nucleotide sequences from other Hantaviruses, it revealed a higher homology to HTN virus strain 76-118,83.5% at nucleotide level and 96.7% at deduced amino level. SNV, PUU and Tula viruses shared the lower homology. A9 and 76-118 were at same cluster in phylogenetic analysis, close to SEO virus but not to PUU, SNV, Tula viruses. Comparing of partial nucleotide sequence of strain A9 with 76-118, some conserved regions were found, but also some regions of A9 were more conserved to other viruses not 76-118. It suggested that when design the primers for L segments amplification, more than one type of Hantavirus sequence should he concerned. Like the homology from M and S segments of Hantaviruses, the viruses isolated from same host animal showed high homology. CONCLUSIONS: Nucleotide sequence of L segment of Hantavirus strain A9 revealed homology between 85.2% -70.8% to different types of Hantavirus and shared a higher homology of 85.2% to strain 76-118.

Animals↗
PubMed2001

Segmentation of medical ultrasonic image using hybrid neural network.

Objective. To solve one of the most difficult problems in multi-dimensional reconstruction of medical ultrasonic images: image segmentation. Method. A new segmental method based on hybrid neural network was presented in this paper. The hybrid neural network comprised two phases. The first phase was Kohonens self-organization neural network, which was used to segment and label the image coarsely. The feature vectors of those pixels within a specified distance from the cluster centers were employed to train the second phase--a three-layer perception network using back-propagation (BP) technique. Then the trained BP network was used to label every pixel of the image. In the end, a post-processing stage was used to remove the small isolated points and smooth out the contours of the segmented image. Result. The segmented image had smooth continuous edges, few noises or speckles, and the contour of ventricle was clear and accurate. Conclusion. Our method could segment the ultrasonic images accurately and effectively, and had a lot of advantages compared to traditional methods. The unsupervised segmentation problems could be solved using supervised methods.

Cardiovascular Physiological Phenomena↗
PubMed2000

[The attractive effects of nerve regeneration chamber fluid and degenerated nerve segments on the growth and the migration of the cocultured dorsal root ganglion neuron].

OBJECTIVES: We intended in this study to investigate the neurotropic effects of regeneration chamber fluid (RCF) and the degenerated nerve segments from distal of the regeneration chamber on the dorsal root ganglion (DRG). METHODS: The capillary model was first tested for its reliability to form concentration gradient with a dye being contained in the capillaries. The tissue culture in RCF test was divided into two groups each with 8 DRGs implanted in 8 dishes. RCF was contained in capillaries inserted down to the bottom of the dishes with their lower ends at a distance of about 1 mm to the DRGs in the experimental group, and DMEM media was contained in the control group. Segments of degenerated sciatic nerve from distal of the regeneration chamber were implanted with DRGs at a distance of about 0.5 - 1 mm in the coculturing experiment. DRGs were observed for the direction of the growth of the cells and the fibres. RESULTS: While the capillary containing the dye was put down to the bottom of the culture dish coated with a piece of nylon pad, the red color slowly disseminated with heavier staining in the center and lighter staining in the peripheral portion. We believe this pattern of shade could simulate the concentration gradient of tropic factors in this model. There were significantly more nerve fibres growing from the DRGs towards the capillaries in 6 of the 8 dishes in the experimental group after 72 hours of culture. The tissue and nerve fibers grew evenly in the control group. 76.5% of all the nerve fibres were growing in the direction facing the degenerated nerve segments after 12 hours of coculturing, and only 33.3% of the nerve fibres growing in that direction in the control group. Cells from the DRGs migrated towards the degenerated nerve segments, yet they tended to avoid the normal nerve segments. The migration index of the cells was 0.98 in average in the coculturing experiment with the degenerated nerve segments, but only 0.43 in average with the normal nerve coculturing. CONCLUSION: The capillary model was effective in studying the chemotactic growth of nerve tissue. RCF and the degenerated nerve segments had definite neurotropic effects on DRGs tissue.

Animals↗