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Biomedical subjects

H M Liu

Publications and source records attributed to H M Liu.

At least 109 records · Page 6Linked to original sources
PubMed1994

The use of collagen polymer tube and fibrin clot in peripheral nerve repair.

Following extensive or multiple nerve injury, repair by nerve graft is the treatment of choice. In recent years, nerve repair using tubes made of synthetic material has yielded satisfactory results in experimental animals. Previously we have demonstrated that fibrin clot formed within an impermeable silicone tube promoted nerve regeneration. In the present study, we evaluated the applicability of a nerve graft fabricated out of autologous collagen and agarose. The copolymer collagen tube, 1 cm long and filled with autologous fibrin clot was implanted between transected rat right sciatic nerve and the left sciatic nerve was similarly transected and repaired with silicone tube. After 1, 2, and 4 months the regenerated nerves were removed and processed for light microscopic and morphometric analysis. We demonstrated that both types of tubes supported extensive nerve regeneration across the gap to reach the distal segment. The collagen tubes provoked a slow foreign body response with infiltration by macrophages and foreign body giant cells which became abated after 2 months. After 4 months, the nerve regenerate was encapsulated and separated from the collagen tube by a fluid exudate. The number of myelinated axons at midpoint in the nerve regenerate in the silicone tube was 9117 +/- 282 while that in the collagen tube was 8589 +/- 137. This preliminary study has demonstrated that collagen polymer tube may have potential use in peripheral nerve repair.

Animals↗
PubMed1994

The value of duplex and continuous wave Doppler sonography for evaluation of the extracranial vertebral arteries: a prospective comparison with angiography.

BACKGROUND: The role of duplex sonography in the detection of the extracranial vertebral arteries is not well established. The purpose of this study was to determine the practical possibilities of vascular sonography for non-invasive investigation of the vertebral arteries. METHODS: The extracranial vertebral artery was divided into the pretransverse segment, the intertransverse segment C6-C2, and the atlas loop. The first two segments were examined by duplex probe and the third segment, by continuous-wave probe. Sixty vertebral arteries were studied for detecting vessel diameter, peak systolic as well as diastolic frequency shifts, flow direction and Doppler flow characteristics. A blind angiographic comparison was also performed for the sake of confirming morphological findings and flow direction. RESULTS: Duplex imaging could detect more than 90% of the vertebral arteries. The mean value of vessel diameter was 3.3 +/- 0.6 mm for the right vertebral artery and 3.5 +/- 0.5 mm for the left. Peak systolic as well as diastolic frequency shifts expressed in KHz was 1.4 +/- 0.4 versus 1.6 +/- 0.5 and 0.5 +/- 0.2 versus 0.5 +/- 0.2 in the right and the left vertebral arteries respectively. A 74% agreement in vessel size was obtained by both duplex scanning and angiography. A 100% accuracy was obtained for blood flow direction through means of a Doppler signal. Abnormal findings included stenosis or occlusion (four arteries), hypoplasia or aplasia (two arteries), and subclavian steal phenomenon (two arteries); Six of these eight were correctly predicted by confirmation of the angiographic findings. CONCLUSIONS: A combination of duplex and continuous wave Doppler sonography was affirmed in this study as a relatively accurate screening technique for detection of vertebral artery abnormalities.

Adult↗
PubMed1993

Alpha 1-acid glycoprotein and peripheral nerve injury, studied with a wound chamber.

BACKGROUND: The aim of the present study is to demonstrate the distribution and quantitative changes of alpha 1-acid glycoprotein (AGP) in rat sciatic nerve subsequent to mechanical injury. AGP is a serum protein, whose level rises after injury; hence the term "acute phase reactant." AGP is synthesized mainly by hepatocytes and the production is stimulated by cytokines released by inflammatory cells. The biologic role of AGP is not known except that it has in vitro nerve growth promoting property. EXPERIMENTAL DESIGN: Impermeable silicone tubes, 10 mm long and 1.4 mm in internal diameter, were sutured to the ends of transected rat sciatic nerve. On the 1st to 21st postoperative days, the wound fluid in the tube and the rat sera were collected for protein analysis and quantitative determination of AGP. The sciatic nerves were removed and immunostained with a monoclonal antibody against rat AGP. RESULTS: The protein content in the wound fluid was 1/5 that of the serum, the proteins of the wound fluid and the serum had similar electrophoretic patterns on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There was a parallel rise of AGP levels in serum and in wound fluid beginning 1 day after the operation reaching the highest level on the 5th day. Immunohistochemical study showed deposits of extravasated AGP in fibrin cable connecting the ends of the transected nerve, in endoneurium, perineurium, perivascular mononuclear, and mesenchymal cells of epineurium at the wound and diffusely in the entire distal nerve segment. CONCLUSIONS: Increased vascular permeability with exudation of leukocytes and plasma proteins are basic pathophysiologic reactions to injury. The wound chamber method employed in the present study may provide a useful model for investigations dealing with the roles of circulating plasma proteins and other molecules as well as local cellular products involved in wound healing and nerve regeneration.

Acute-Phase Proteins↗
PubMed1993

[New oxindole alkaloid glycosides from Uncaria sinensis].

Two 16-carboxy derivatives of pentacyclic oxindole alkaloids and its glucopyranosyl esters have been isolated from the ethanolic extract of the leaves of Uncaria sinensis (Olive.) Havil. These structures were deduced on the basis of spectroscopic evidences and chemical correlations, and named mitraphyllic acid (I), isomitraphyllic acid (II), isomitraphyllic acid (16-1)-beta-D-glucopyranosyl ester (III) and mitraphyllic acid (16-1)-beta-D-glucopyranosyl ester (IV).

Drugs, Chinese Herbal↗
PubMed1993

Modified method of vascular repair with autologous fascia and synthetic adhesive: an animal experiment.

Subsequent to arteriotomy of the common carotid artery on both sides in rats, the right common carotid was repaired by microvascular suture, and the left with autologous fascia and synthetic adhesive; the results of both types of repair were compared. The rats were sacrificed at weekly intervals for up to two months, and the arteries were examined for patency and histopathologic changes. The initial inflammation and wound healing were similar in both types of repair. Vessels repaired by fascia and adhesive had a prolonged period of perivascular inflammation and formation of a microcyst containing crystallized adhesive. After two months, the vessels were grossly normal showing only mild perivascular inflammation and residual microcysts. Microvascular suture was followed by medial displacement and fibrosis of the wall, resulting in marked narrowing of the lumen after two months. In our series, the results of repair with fascia and adhesive were considered satisfactory, and the pathologic changes were less severe than those reported in the literature. This could be ascribed to the use of a minimal amount of adhesive and of covering the vasculotomy opening with fascia before applying the adhesive so as to avoid contact between the adhesive and the cut edges of the vessel wall. This modified technique may be considered in the repair of intracranial vessels in emergency situations when microvascular suture is difficult or impossible.

Animals↗
PubMed1993

[Changes of blood dynamics measured by vein impedance blood stream charts in pregnant women].

The vein impedance blood stream charts were analysed in 32 pregnant women with gestational age between 38-42 weeks and in 31 healthy nonpregnant women as well. Measurement included maximal venous out flow (MVO), 3-sec venous outflow (VO), venous capacity (VC) and arterial blood flow (ABF). The results showed that all the parameters mentioned above were significantly lower in pregnant women either in 3rd trimester or at post partum when compared with nonpregnant women (P < 0.01). All parameters were increased after delivery. The significant change was only seen in VC. It suggested that the vein impedance blood stream chart might be used as an early diagnostic tool for thrombophlebitis occurred in lower extremities after delivery.

Adult↗
PubMed1992

The role of extracellular matrix in peripheral nerve regeneration: a wound chamber study.

A wound chamber model was used for the study of the interaction between axon, Schwann cell and extracellular matrix during peripheral nerve regeneration. Impermeable silicone tubes, 8 mm long and 1.4 mm in internal diameter were sutured to transected rat sciatic nerve and the contents of the tubes were removed at intervals for chemical, histological, immunocytochemical and electron microscopic studies. There was an initial phase of fluid accumulation and the formation of a fibrin/fibronectin clot or cable which connected the cut ends of the nerve. The chamber fluid was shown to have a protein profile similar to that of rat serum. Schwann cells, endothelial cells and fibroblasts migrated first into the cable, apparently mediated by cell-fibrin interaction. Axons buried within the Schwann cell cytoplasm were led into the cable but an axon-fibrin interaction was not observed. After 1 week, the fibrin matrix underwent dissolution, with replacement by collagen. This marked the onset of myelination and the organization of nerve fibers into fascicles. The findings from the present study suggest that the interactions between axon and Schwann cell and between Schwann cell and a changing extracellular matrix are the essential driving force in nerve growth and differentiation during peripheral nerve regeneration.

Animals↗
PubMed1992

Subclavian steal phenomenon: a correlation between duplex sonographic and angiographic findings.

Correlation of duplex sonography, angiography of the vertebral artery, and the degree of subclavian or innominate stenosis was carried out in ten patients with the subclavian steal phenomenon. Four successive stages of Doppler waveform were identified by duplex sonography. Three angiographic patterns of decreasing severity, permanent reversal, to-and-fro motion and delayed opacification, were found. Permanent reversal angiograms corresponded to complete reversal or late transient Doppler waveforms. To-and-fro motion and delayed opacification angiograms did not necessarily have a corresponding Doppler pattern. The different stages of subclavian steal phenomenon on duplex sonography correlated significantly with the degree of subclavian or innominate stenosis. Stenosis of at least 60% was found to produce abnormal vertebral artery Doppler sonography, except in one patient. Duplex sonography is considered to be a sensitive and convenient method for detecting abnormal vertebral artery haemodynamics and the subclavian steal phenomenon, but some other factors may be important in producing the Doppler waveforms.

Adult↗
PubMed1992

Interactions between bluetongue virus core and capsid proteins translated in vitro.

To determine whether the two major core proteins (VP3 and VP7) of bluetongue virus can interact in vitro to form morphological structures, linearized VP3 and VP7 cDNA clones were transcribed using SP6 polymerase and the resultant transcripts were co-translated using rabbit reticulocyte lysates. The structures derived were isolated by sedimentation through a sucrose gradient and found to resemble VP3-VP7 core-like particles (CLPs) expressed in vivo. Reacting CLPs synthesized in vivo with outer capsid proteins translated in vitro (VP2 or VP5) indicated that each outer capsid protein has the capacity to bind to a preformed CLP. This was confirmed by in vivo expression of the appropriate genes using baculovirus vectors. The interaction of VP2 or VP5 with the CLP was analysed by electron microscopy and by using immunogold-labelled monoclonal antibody.

Antigens, Viral↗
PubMed1992

Isolation and structure elucidation of gymnemic acids, antisweet principles of Gymnema sylvestre.

The structure of gymnemagenin (3 beta,16 beta,21 beta,22 alpha,23,28-hexahydroxy-olean-12-ene), the sapogenin of the antisweet principles of Gymnema sylvestre, was established by X-ray analysis of the 3 beta,23;21 beta,22 alpha-di-O-isopropylidene derivative. On the basis of this result, the structure of deacylgymnemic acid was elucidated as the 3-O-beta-glucuronide from the carbon-13 nuclear magnetic resonance spectra. Five antisweet principles, gymnemic acid-III, -IV, -V, -VIII, and -IX, were isolated in pure states from the hot water extract of leaves of Gymnema sylvestre. Of these, three (GA-III, -IV, and -V) were known, while two (GA-VIII and -IX) were new compounds. The structures of GA-VIII and -IX were elucidated as 3'-O-beta-D-arabino-2-hexulopyranosyl gymnemic acid-III and -IV, respectively.

Carbon Isotopes↗
PubMed1992

Hypothalamic hamartoma and precocious puberty: report of a case.

Hypothalamic hamartoma is reported to be associated with precocious puberty. Here, the authors present a seven-year-old girl whose onset of puberty occurred at the age of two. Under the impression of idiopathic precocious puberty, cyproterone acetate was initially tried. Since the effect of her medication was not satisfactory, it was discontinued at the age of five years and 11 months. However, rapid advance of bone age and vaginal spotting recurred after the withdrawal of treatment. She was re-evaluated at the age of six, and a magnetic resonance image (MRI) study of the head revealed a hypothalamic hamartoma. At that time, a long-acting analog of luteinizing hormone-releasing hormone (LHRHa), leuprolide acetate, was prescribed. Her secondary sex characteristics regressed and her hypothalamic-pituitary-gonad axis was suppressed after treatment. The clinical presentation, mechanism and treatment of precocious puberty caused by hypothalamic hamartomas are fully discussed in this report.

Child↗
PubMed1992

Wound chamber study of nerve and blood vessel growth.

Recent experimental studies using wound chambers (silicone tubes) sutured to the transected rat sciatic nerve or thigh muscle have shown an accumulation of plasma-containing fluid and the formation of a fibrin/fibronectin clot within the chambers during the early phase. The plasma proteins leaked into the wound due to increased vascular permeability caused by the trauma. The fibrin/fibronectin clot in concert with neurotrophic factors play a key role in the promotion of growth and migration of endothelial cells, Schwann cells and axons during the early phase. Cessation of cell growth and migration coincided with removal of fibrin through fibrinolysis and collagen deposition in the extracellular space. The appearance of extracellular matrix was closely related to the morphological event of differentiation and formation of open capillaries and nerve fascicles. These findings suggest that in addition to hemostasis, fibrin polymerization (thrombosis) and fibrinolysis play vital pathophysiological roles in angiogenesis, nerve regeneration and other aspects of wound healing. These studies emphasize the importance of integrating information from many areas of research in order to understand some of the basic principles in Biology and Medicine.

Animals↗
PubMed1991

The effect of iohexol on brainstem auditory evoked potentials. A prospective study on 30 patients.

A prospective study was made to evaluate the effect of intrathecal injection of iohexol on brainstem auditory evoked potentials (BAEP) following myeloradiculography, in order to assess its neurotoxicity. Thirty patients who received contrast medium via the lumbar route for myeloradiculography (cervical level = 25 patients, lumbar level = 5 patients) had BAEP examinations before, 2 h and 24 h after myelography. No statistically significant prolongation of absolute and interpeak latencies was found between premyelographic and postmyelographic records. Low incidence (20%) of insignificant clinical adverse effect following myelography was also noted in the same group of patient.

Adolescent↗
PubMed1991

New Indole Alkaloids from Amsonia sinensis.

Fourteen indole alkaloids, Delta (14)-isoeburnamine ( 1), amsosinine ( 2), tabersonine, vincadifformine, lochnericine, tetrahydroalstonine, beta-yohimbine, isoeburnamine, minovicinine, picrinine, strictamine, rhazimine, vincanidine, and decarbomethoxytetrahydrosecamine, were isolated from AMSONIA SINENSIS. Delta (14)-isoeburnamine ( 1) and amsosinine ( 2) are new compounds, their structures have been established by spectral and chemical methods. A known sterol glycoside, daucosterol, has also been obtained. The structures of compounds 1 and 2 were finally confirmed by X-ray diffraction of single crystals.

Journal Article↗
PubMed1991

Computed tomography of the brain in patients with serum prolactin levels over 200 ng/ml.

We reviewed the computed tomographic (CT) findings of the sella turcica in 26 patients with a serum prolactin level of over 200 ng/ml. The interval between the dates of CT examination and checking of the serum prolactin level were within 2 months. There were 24 nonpregnant women with a mean age of 30 years and 2 men with a mean age of 28.5 years. None of them were taking medication known to cause an elevation in serum prolactin levels. Surgery was performed on 8 patients with chromophobe adenomas of the pituitary gland: 6 of them were proven to have prolactin-secreting tumors (prolactinomas) after performing a special stain, and the remaining 2 patients, clinically diagnosed as prolactinomas, showed extremely high serum prolactin levels (3,200 and 2,251 ng/ml, respectively). CT studies showed that the height of the pituitary gland in the coronal sections were more than 7 mm in 15 cases (58%) and more than 10 mm in 13 cases (50%); focal bulging of the diaphragma sellae in 16 cases (62%); erosion of the sellar floor in 20 cases (77%); deviation of the pituitary stalk in 19 cases (73%); and abnormal attenuation or enhancement of the pituitary gland in 18 cases (69%). Three patients (12%) showed no evidence of any abnormal CT finding despite a hyperprolactinemic state of over 200 ng/ml. Six histologically proven cases (23%) of prolactinomas and chromophobe adenomas showed radiologic evidence of cavernous sinus invasion. We conclude that patients with a serum prolactin level higher than 200 ng/ml generally show significant changes in the sella turcica in CT.

Adenoma, Chromophobe↗
PubMed1991

CT myelography for differential diagnosis between intramedullary and intradural-extramedullary spinal tumors in the region of the conus medullaris.

We reviewed the myelograms and computed tomographic myelograms of 12 cases of intraspinal tumor with a "cupping sign" on the myelogram in the region of the conus medullaris from 1986 to 1988. There were 5 intramedullary tumors, 4 of them having an exophytic component, and 7 intradural-extramedullary tumors. The myelograms revealed that 4 of the 5 intramedullary tumors showed expansion and the outline of the conus medullaris was irregular, whereas 1 of the tumors showed smooth compression (crescent-shaped) and displacement of the conus medullaris. Six of the 7 intradural-extramedullary tumors showed smooth compression and displacement of the conus medullaris, while 1 of the tumors had caused expansion of the conus medullaris. Complete blockage of the passage of the contrast medium was noted in 3 of the 5 intramedullary tumors, while a partial block was noted in 3 of the 7 intradural-extramedullary tumors. Two of the 7 intradural-extramedulllary tumors showed an extradural tumor component, such as a dumb-bell tumor and a enlarged intervertebral neural foramen. Tumor calcification was noted in 1 of the 7 intradural-extramedullary tumors. Dural ectasia was noted in 2 of the 7 intradural-extramedullary tumors which were later proven to be neurofibromatosis. We conclude that smooth compression (crescent-shaped) and displacement of the conus medullaris, existence of an extradural tumor component, and eroded intervertebral neural foramina favor intradural-extramedullary tumors, while expansion and a conus medullaris with an irregular outline favors intramedullary tumors.

Adolescent↗
PubMed1990

Interactions between fibrin, collagen and endothelial cells in angiogenesis.

The role of fibrin in the generation of new blood vessels was examined in this study. Using a wound chamber model, we investigated the sequential interactions between endothelial cells and the extracellular matrix during angiogenesis. Silicone tubes 5 mm long and 1.4 mm in internal diameter were sutured to the cut ends of thigh muscles in the rats. The contents of the chamber were removed at intervals for histological, immunohistochemical and electron microscopic studies. We observed an initial phase of fluid accumulation in the wound chamber followed by formation of a fibrin/fibronectin clot. Migration of endothelial cells, macrophages and fibroblasts into the clot occurred after the 1st week. The subsequent phase of fibrinolysis was accompanied by deposition of collagen and organization of endothelial cells into capillary tubes. These findings support the view that angiogenesis is the product of interactions between endothelial cells and a changing extracellular matrix (ECM) and requires the participation of soluble and immobilized plasma proteins and local ECM factors. Our findings indicate that fibrin is intimately involved in both hemostasis and angiogenesis; these are sequential steps in the initial phase of wound healing. Thus, fibrin/fibrinogen occupies a central position and provides a vital link in the initiation of the cascade event of wound healing.

Animals↗