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Biomedical subjects

J Ge

Publications and source records attributed to J Ge.

At least 145 records · Page 8Linked to original sources
PubMed1996

Autoradiographic distribution of [3H]-(S)-zacopride-labelled 5-HT3 receptors in human brain.

Autoradiographic binding studies using the 5-HT3 (5-hydroxytryptamine3) receptor radioligand, [3H]-(S)-zacopride (0.5 nM), identified a heterogeneous distribution of specific binding sites (defined by granisetron, 1 microM) throughout the human brain. Highest radiolabelled 5-HT3 receptor densities were detected in discrete nuclei within the brainstem (nucleus tractus solitarius, area postrema, spinal trigeminal nerve nucleus; 50-200 fmol/mg tissue equivalent) with more modest levels of expression in the forebrain (e.g. hippocampus, nucleus accumbens, putamen, caudate; 4-17 fmol/mg tissue equivalent). Within the hippocampal formation, radiolabelled 5-HT3 receptors were differentially distributed with highest levels in the granule cell layer of the dentate gyrus. Saturation studies with [3H]-(S)-zacopride (0.05-16 nM; non-specific binding defined by granisetron, 10 microM) binding to homogenates of human putamen indicated that [3H]-(S)-zacopride (0.05-16 nM; non-specific binding defined by granisetron, 10 microM) binding to homogenates of human putamen indicated that [3H]-(S)-zacopride labelled an apparently homogenous population of binding sites (Bmax = 72 + 7 fmol mg-1 protein, pKd = 8.69 +/- 0.09, Hill coefficient = 0.99 +/- 0.06, mean +/- SEM, n = 4). The pharmacological profile of [3H]-(S)-zacopride binding to homogenates of putamen indicated the selective labelling of the human variant of the 5-HT3 receptor. The marked differences, however, in the pharmacology (e.g. low affinity for D-tubocurarine) and relative distribution (e.g. presence of 5-HT3 receptors in the human extrapyramidal system) of 5-HT3 receptors in the human forebrain when compared with other species further necessitates caution in predicting clinical responses based on data generated in animal models of disease.

Adult↗
PubMed1996

Differences in the morphology of unstable and stable coronary lesions and their impact on the mechanisms of angioplasty. An in vivo study with intravascular ultrasound.

The aim of this study was to compare the morphology of stable and unstable coronary lesions using intravascular ultrasound in patients undergoing coronary balloon angioplasty and to determine whether lesion morphology had any influence on the mechanism of balloon angioplasty. Thirty three (15 stable and 18 unstable) patients undergoing single lesion percutaneous transluminal coronary angioplasty were studied with intravascular ultrasound before and after intervention. All examinations, recorded on S-VHS video tape, were studied off-line and matched sites from the point of minimum lumen area after the procedure and the corresponding site prior to intervention were compared. The morphology of lesions before intervention was noted and the mechanisms of angioplasty (vessel stretch, lesion remodelling and lesion tears) were determined by comparing pre- and post-interventional morphology and dimensions. The only significant morphological difference between stable and unstable lesions was the presence of a demarcated inner layer in unstable lesions, delimited by a fine circumferential line. This pattern was noted in 77% (14/18) of unstable lesions and in 7% (1/15) of stable lesions (P < 0.01). Unstable lesions tended to have more echolucent zones than stable lesions (72% (13/18) vs 46% (7/15), P = 0.13). The mechanisms of angioplasty were also found to differ. Whereas lesion remodelling (or 'compression') was seen in 77% (14/18) of unstable lesions, it occurred in only 13% (2/15) of stable lesions and mean lesion cross-sectional area reduction was greater in unstable lesions, - 14.8 +/- 8.3% (2.1 +/- 1.3 mm2) compared to stable lesions, - 4.1 +/- 8.4% (0.42 +/- 0.9 mm2), P < 0.01. In contrast, vessel stretch was seen more frequently in stable lesions (73%, 11/15) compared to unstable lesions (22%, 4/18) P < 0.01 and the mean increase in vessel cross-sectional area was + 13.5 +/- 6.8 (1.6 +/- 0.9 mm2) in stable lesions compared to + 5.5 +/- 5.6% (0.8 +/- 0.9 mm2) in unstable lesions, P < 0.01. Lesion tear was present to a similar degree in both groups of patients. In this observational study we found a set of echographic markers that distinguished unstable lesions. The mechanisms of angioplasty differed between stable and unstable angina, with greater lesion remodelling seen in unstable lesions and vessel stretch in stable lesions. Taken together, these findings suggest that the markers we describe may be echographic indicators of mural thrombus.

Angina Pectoris↗
PubMed1996

Value of intracoronary ultrasound and Doppler in the differentiation of angiographically normal coronary arteries: a prospective study in patients with angina pectoris.

BACKGROUND: A substantial proportion of patients undergoing heart catheterization for suspected coronary artery disease have normal angiograms. Coronary morphology and blood flow velocity can be assessed very accurately with intracoronary ultrasound and Doppler. The purpose of this study was to use both methods to classify further patients with suspected coronary artery disease but with coronary angiograms adjudged normal at the time. METHODS AND RESULTS: In forty-four patients with suspected coronary artery disease and normal coronary angiograms, intracoronary ultrasound and intracoronary Doppler were performed in the left anterior descending and left main coronary arteries. Coronary flow reserve was obtained by calculating the ratio of the maximal coronary flow mean velocity after the intracoronary administration of 10 mg papaverine to the coronary flow mean velocity at rest. Of 44 patients, 16 (36%) (group I) were found to have normal coronary morphology by intracoronary ultrasound and normal (> 3.0) coronary flow reserve (5.3 +/- 1.8). In seven patients (16%) (group II) there were normal intracoronary ultrasonic findings but a reduced coronary flow reserve (2.1 +/- 0.4). Plaque formation was found in a total of 21 (48%) of the 44 patients; mean plaque sizes were 3.6 +/- 1.6 mm2 for those in group III (normal coronary flow reserve) and 5.0 +/- 2.3 mm2 for those in group IV (reduced coronary flow reserve). Vessel area in both of these groups (16.3 +/- 8.0 mm2 and 19.2 +/- 6.1 mm2) was significantly larger than that of group I (14.6 +/- 5.7 mm2, P < 0.01). Plaque calcification was found in 25% of those in group III and 44% of those in group IV. Thus, only 36% of the patients with normal angiograms were true normal, 48% exhibited early stage of coronary atherosclerosis, and the other 16% might be considered as syndrome X. CONCLUSION: Intracoronary ultrasound and Doppler can be used to differentiate further heart disease in patients with normal coronary angiograms. Only a minority were true normal. Early signs of atherosclerosis cannot be detected by coronary angiography. This may have important therapeutic and prognostic implications.

Adult↗
PubMed1996

A comparative biomechanical analysis of resorbable rigid fixation versus titanium rigid fixation of metacarpal fractures.

Linear (two-dimensional) and three-dimensional (3D) plating systems (Poly-Medics) composed of the resorbable copolymer of polyglycolic acid (PGA) and poly-l-lactic acid (PLLA) (Lactosorb) were studied in vitro. The plates were applied to osteotomized fresh frozen human cadaveric metacarpal bones that were then tested for torsional rigidity and three-point bending strength and rigidity. The results were compared to those from another study of two low-profile titanium plating systems (Leibinger and Synthes). Analysis of variance revealed that the linear-flat Lactosorb plate and screws had apex dorsal rigidity and force-to-displacement measurements equal to all but two of the titanium plates (3D). The 3D-flat Lactosorb plate had the highest torsional rigidity of the resorbable system, but it was only moderately rigid compared to the titanium plating systems. This in vitro biomechanical study of the copolymer PGA-PLLA plating system indicates that, in clinical applications, it may be better suited for metacarpal fractures rather than proximal phalangeal fractures due to the lower demands of torsional loading compared to apex bending.

Biomechanical Phenomena↗
PubMed1996

A biomechanical analysis of the stability of titanium bone fixation systems in proximal phalangeal fractures.

Apex bending and torsional loading were utilized to study the effects of different plate design and thickness, and screw size and design on the rigidity and strength of seven different titanium mini- and microplates placed onto osteotomized proximal phalanges. One hundred forty-four fresh frozen human cadaveric proximal phalangeal bones underwent a mid shaft osteotomy followed by application of one of the following plates: (1) Synthes linear 1.5-mm five-hole plates, (2) Leibinger linear 1.2-mm five-hole or (3) 1.7-mm four-hole plates, or (4) Leibinger three-dimensional 1.2-mm four-hole, (5) 1.2-mm eight-hole, (6) 1.7-mm four-hole, or (7) 1.7-mm eight-hole plates. Three-point bending (apex dorsal or apex volar) and torsional loading were utilized for each plating configuration. Analysis of variance models of bone specimen width, depth, cortical thickness, and length revealed that increasing plate thickness was associated with increasing rigidity, but that the three-dimensional design yielded a higher relative rigidity except under apex volar loading.

Biomechanical Phenomena↗
PubMed1996

Ability of 5-HT4 receptor ligands to modulate rat striatal dopamine release in vitro and in vivo.

1. The ability of 5-HT4 (5-hydroxytryptamine4) receptor ligands to modify dopamine release from rat striatal slices in vitro and in the striatum of freely moving rats was assessed by the microdialysis technique. 2. The release of dopamine from slices of rat striatum continually perfused with Krebs buffer was enhanced by 5-HT4 receptor agonists; 5-HT (10 microM), 5-methoxytryptamine (5-MeOT; 10 microM), renzapride (10 microM) and (S)-zacopride (10 microM) maximally increased dopamine release by 133 +/- 5, 214 +/- 25, 232 +/- 29 and 264 +/- 69%, respectively (mean +/- s.e.mean, n = 3-8). The drug-induced responses were maximal within the first 2 min of drug application, and subsequently declined. The non-selective 5-HT3/5-HT4 receptor antagonist, SDZ205-557 (10 microM), failed to modify basal dopamine release from striatal slices but completely antagonized the (S)-zacopride (10 microM)-induced increase in dopamine release. 3. To allow faster drug application, the modulation of dopamine release from rat striatal slices in a static release preparation was also investigated. The 5-HT4 receptor agonist, renzapride (10 microM) also enhanced dopamine release in this preparation (maximal increase = 214 +/- 35%, mean +/- s.e.mean, n = 14), whilst a lower concentration of renzapride (3 microM) was less effective. The renzapride-induced response was maximal within the first 2 min of drug application, before declining. In this preparation, the stimulation of dopamine release by renzapride (10 microM), was completely antagonized by the selective 5-HT4 receptor antagonist, GR113808 (100 nM). In addition, both the Na+ channel blocker, tetrodotoxin (100 nM) and the non-selective protein kinase A inhibitor, H7 (100 nM) completely prevented the stimulation of dopamine release induced by renzapride (10 microM). 4. In vivo microdialysis studies demonstrated that the 5-HT4 receptor agonists, 5-MeOT (10 microM), renzapride (100 microM) and (S)-zacopride (100 microM) maximally elevated extracellular levels of dopamine in the striatum by 220 +/- 20, 161 +/- 10 and 189 +/- 53%, respectively (mean +/- s.e.mean, n = 5-9). A lower concentration of renzapride (10 microM) was less effective. The elevation of extracellular striatal dopamine levels induced by either renzapride (100 microM) or (S)-zacopride (100 microM) were completely antagonized by the non-selective 5-HT4 receptor antagonist, SDZ205-557 (100 microM). In addition, the elevation of extracellular levels of dopamine induced by either 5-MeOT (10 microM) or renzapride (100 microM) was completely prevented by the selective 5-HT4 receptor antagonist, GR113808 (1 microM) and the renzapride (100 microM)-induced response was also completely prevented by the non-selective protein kinase A inhibitor, H7 (1 microM). In this in vivo preparation, both GR113808 (1 microM) and H7 (1 microM), when perfused alone, reduced extracellular levels of dopamine. 5. In conclusion, the present study provides evidence that the 5-HT4 receptor facilitates rat striatal dopamine release in vitro and in vivo.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

5-HT4 receptor-mediated modulation of 5-HT release in the rat hippocampus in vivo.

1. In the present study, the ability of the 5-hydroxytryptamine, receptor (5-HT4 receptor) to modulate the release of 5-HT in the hippocampus of freely-moving rats was investigated by the in vivo microdialysis technique. 2. The 5-HT4 receptor agonist, renzapride (1.0-100 microM, administered via the microdialysis probe) increased extracellular hippocampal levels of 5-HT in concentration-dependent manner (approximately 200% maximal increase). The ability of renzapride (100 microM, administered via the microdialysis probe) to elevate extracellular levels of 5-HT remained in the presence of the selective 5-HT reuptake blocker, paroxetine (1.0 microM, administered via the microdialysis probe). Furthermore, another 5-HT4 receptor agonist 5-methoxytryptamine (5-MeOT; 10 microM, administered via the microdialysis probe, in the presence of the non-5-HT4 5-HT receptor antagonists pindolol (10 microM) and methysergide (10 microM)) maximally elevated extracellular levels of 5-HT by approximately 450% in the rat hippocampus. The elevation of extracellular 5-HT levels induced by either renzapride (100 microM) or 5-MeOT (10 microM) was completely prevented by combined administration of the selective 5-HT4 receptor antagonist, GR113808 (100 nM, administered via the microdialysis probe). GR113808 (100 nM, administered via the microdialysis probe) administered alone, however, reduced extracellular hippocampal 5-HT levels by some 60%. 3. Systemic administration of the 5-HT1A receptor agonist, 8-OH-DPAT (0.1 mg kg-1, s.c.) reduced extracellular levels of 5-HT in the rat hippocampus by approximately 40%. Prior administration of 8-OH-DPAT (0.1 mg kg-1, s.c.), with an associated reduction of extracellular hippocampal 5-HT levels by approximately 40-50%, however, failed to prevent a subsequent elevation of extracellular levels of 5-HT induced by renzapride (100 microM, administered via the microdialysis probe). 4. Systemic administration of the 5-HT4 receptor agonist, renzapride (0.25 and 1.0 mg kg-1, i.p.) increased extracellular levels of 5-HT in the hippocampus in a dose-dependent manner. The higher dose of renzapride increasing extracellular 5-HT levels by some 200%. The selective 5-HT4 receptor antagonist, GR125487D (1.0-100 micrograms kg-1, i.p.) caused a dose-dependent reduction in extracellular levels of 5-HT in the hippocampus (maximally approximately 80% reduction). Prior administration of GR125487D (10 micrograms kg-1, i.p.) prevented the elevation of extracellular levels of 5-HT induced by renzapride (1.0 mg kg-1, i.p.). 5. In conclusion, the present study provides evidence that activation of the 5-HT4 receptor facilitates 5-HT release in the rat hippocampus in vivo.

Animals↗
PubMed1996

Ability of angiotensin II to modulate striatal dopamine release via the AT1 receptor in vitro and in vivo.

1. The ability of angiotensin II to modulate dopamine release from rat striatal slices in vitro and in the intact rat striatum in vivo was assessed by the microdialysis technique. 2. In slices of rat striatum, angiotensin II (0.1-1.0 microM) induced a concentration-related increase in endogenous dopamine release which was maximal (approximately 250% above basal levels) within the first 2-4 min of agonist application and subsequently declined to near basal values. The angiotensin II-induced increase in dopamine release was Ca(2+)-dependent and was completely antagonized by the selective AT1 receptor antagonist, losartan (1.0 microM). In contrast, the AT2 receptor antagonist, PD123177 (1.0 microM) failed to modify the angiotensin II-induced response. Neither antagonist alone modified basal dopamine release from striatal slices. 3. In freely moving rats, angiotensin II (1.0-10 microM; administered via the microdialysis probe) induced a concentration-related increase in extracellular levels of dopamine which was maximal (approximately 150% above basal levels) within 20-40 min of agonist application and subsequently declined. The angiotensin II (10 microM)-induced increase in extracellular levels of dopamine was completely antagonized by the AT1 receptor antagonist, losartan (0.1-1.0 microM; administered via the microdialysis probe) but not by the AT2 receptor antagonist, PD123177 (1.0 microM; administered via the microdialysis probe). Neither antagonist alone modified basal extracellular levels of dopamine. 4. Homogenate radioligand binding studies with [125I]-angiotensin II (0.1 nm) identified relatively low levels of specific binding sites in rat striatal homogenates compared to homogenates of pyriform cortex (51.3 +/- 9.2 and 651.3 +/- 55.1 fmol g-1 wet weight, respectively, mean +/- s.e.mean, n = 3; non-specific binding defined by unlabelled angiotensin II). The majority of the specific [125I]-angiotensin II (0.1 nM) binding in the striatal and pyriform cortex homogenates was sensitive to the selective AT1 receptor antagonist, losartan (1.0 microM). 5. In conclusions the present study provides direct evidence that angiotensin II acting via the AT1 receptor subtype facilitates the release of dopamine in the rat striatum in vitro and in vivo. This receptor-mediated response may account for the modulation of dopamine-mediated behavioural responses by antagonists of the AT1 receptor and inhibitors of angiotensin converting enzyme.

Angiotensin I↗
PubMed1996

Intravascular ultrasound for evaluation of coronary arteries.

Intravascular ultrasound (IVUS) has emerged form a research tool to an intrinsic part of modern invasive cardiology. The main reason is the capability to obtain "in vivo" histology. For the first time it is possible to base decisions not only on lumenograms but also on vessel wall assessment. The capabilities of IVUS can be divided in its (a) diagnostic and (b) intervention associated potentials. Diagnostic strength of IVUS is the ability to monitor compensatory coronary artery enlargement as a response to arteriosclerosis, to assess intermediate lesions, to reveal occult left main stem disease, and angiographycally "silent" arteriosclerosis. The intervention associated potentials of IVUS are the ability to allow optimal device selection, i.e. rotablators in calcified lesions or atherectomy devices in large plaque burden. The effects of PTCA on vessel wall morphology can be studied in great detail and the effect on luminal gain can be assessed almost on-line. Several groups showed, that the residual plaque area even after angiographycally successful PTCA lies still in the range of 60%. A significant reduction of this number may influence longterm outcome after PTCA. Minimal luminal areas and residual plaque area after PTCA seem to be an indicator of restenosis, while the presence or absence of dissections seem to be less predictive. Intravascular monitoring of stent expansion led to high-pressure stent deployment with significant increase in post-procedural luminal diameters and finally the ability to withhold anticoagulation in patients with optimal stent deployment. In the future, integrated devices, like balloons on intravascular ultrasound catheters, steerable catheters, integrated flow and pressure transducers, tissue characterization, and 0.018 "intravascular ultrasound guide-wires will further enhance the usefulness of IVUS.

Angioplasty, Balloon, Coronary↗
PubMed1996

[High frequency rotational angioplasty].

High-speed rotational coronary atherectomy is an alternative method to treat complex, especially calcified coronary stenoses. A rotating burr tip removes the occlusive plaque tissue. The applied rotating frequency is between 160 000 to 190 000 rpm. The primary technical success-rate for high frequency rotational atherectomy alone yields between 50 to 60% on average. Associated with consecutive additional balloon angioplasty, the success rate is between 80 and 95% when treating complex type B II or C stenoses. Today, the usage of a single burr tip size with adjunctive balloon angioplasty has become a standard procedure. The occurrence of serious complications such as extensive dissections or thrombotic vessel occlusion is a rare phenomenon after high-speed rotational atherectomy compared to coronary balloon angioplasty, whereas coronary spasm is more common after high-speed rotational atherectomy. According to the actual results, high-speed rotational angioplasty did not lower the rate of long-term restenosis, compared to the results achieved by balloon angioplasty alone. The rate of long-term restenosis is reported to be between 40 to 50% after highspeed rotational angioplasty with or without adjunctive balloon angioplasty.

Atherectomy, Coronary↗
PubMed1996

[The significance of intravascular ultrasound in differential diagnosis and therapy of coronary stenoses].

Intravascular ultrasound (IVUS) has emerged from being a research tool to becoming an important aspect in invasive cardiology, because it offers the possibility to obtain "in vivo" histology, including the vessel wall, while angiography allows for lumenograms only. The reasons for performing IVUS can be divided into either diagnostic or intervention associated indications. Diagnostic strength of IVUS is the ability to monitor compensatory coronary artery enlargement as a response to arteriosclerosis, to reveal occult left main stem disease, and angiographically "silent" arteriosclerosis. The peri-interventional potentials of IVUS are the ability to allow optimal device selection, i.e., rotablators in calcified lesions or atherectomy devices in large plaque burden. The effects of PTCA on vessel wall morphology can be studied in great detail and the effect on true luminal gain assessed almost on-line. Several groups showed that the residual plaque area after angiographically successful PTCA lies in the range of 60%. A significant reduction of this number may influence long-term outcome after PTCA. Minimal luminal areas after PTCA seem to be an indicator of restenosis, while the morphological appearance alone seems to be less predictive. Intravascular monitoring of stent implantation led to high-pressure stent deployment with significant increase in postprocedural luminal diameters and, finally, the ability to withold anticoagulation in patients with optimal stent deployment. Furthermore, integrated devices, like balloons on IVUS catheters, steerable catheters, integrated flow measurements and pressure transducers will further increase the usefulness of IVUS.

Angioplasty, Balloon, Coronary↗
PubMed1996

[Superoxide dismutase and malonyl dialdehyde in human pulp tissue].

A total of 21 pulps were collected from 12 inflamed and 9 normal cases. SOD activity and MDA content were identified in the normal and inflamed pulpal tissues. In the inflamed pulpal tissues, SOD activity and MDA content were significantly increased than those in the normal tissues. The results demonstrated that the inflammation of pulpal tissues resulted in the increasing of the reactivity of superoxide radical and lipid peroxide (LPO). The results also indicated that human dental pulp possessed an endogenous defense mechanism to protect the tissue components from the toxic effects of the reactive oxygen intermediates.

Adult↗
PubMed1996

[The study of the biological character on the culture of human trabecular meshwork cells in vitro].

PURPOSE: To establish the culture of human trabecular cells in vitro and to study their biological character. METHOD: The trabecular specimens from human eyes were cultured. The morphologic features of cultured cells were examined by light and electron microscopy, the immunohistochemical characteristics and the proliferative curve of the cultured cells were also investigated. RESULTS: The primary cells in culture are multiangular or irregular, and the confluent trabecular cells grow as a single cell layer. The junctions between trabecular cells observed most frequently are puncta adherens and gap junction. Trabecular cells showed apical villons projections and had a high density of various organelles. The trabecular cells were stained intensely with monoclone antibodies to fibronection and laminin and NSE. And it had negative reaction to monocolone antibodies to VIII factor. The cultured cells showed a longer doubling time. CONCLUSION: The culture of human trabecular cells in vitro was established. This was a key step to dissect the trabecular specimen accurately and carefully. According to the different cellular growth patterns and speed, morphologic and immunohistochemical characteristics from that of the near cells, the cultured human trabecular cells can been identified.

Cell Division↗
PubMed1996

[The comparative study of the macular light threshold in the normal and low visual acuity people].

PURPOSE: To test the macular light threshold (MLT) and the change of macular light sensitivity (MLS) in the normal and low visual acuity people. METHODS: MLT of 93 eyes of the normal and 76 eyes of low visual acuity people was measured with macular threshold test of Humphrey Field Analyzer-640. RESULTS: 1. MLT increases with age, there is a negative correlation between MLS and age 2. MLT of low visual acuity people is significantly higher than that of the normal visual acuity people in the same age group; 3. No significant difference of MLT was found in the four quadrants of visual field in the same age group; 4. No significant difference of MLT was found between male and female. CONCLUSIONS: MLS of the normal visual acuity people is superior to that of the low visual acuity people; MLS decreases with age.

Adult↗
PubMed1995

Acute coronary artery closure following intracoronary ultrasound examination.

Two patients undergoing intracoronary ultrasound examination were complicated by acute coronary artery closure. One of the complications was thought to be caused by intimal dissection and thrombus formation and the other was thought to be caused by intimal dissection and subsequent embolization. The complications were successfully managed conservatively in both cases.

Acute Disease↗