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Biomedical subjects

H M Liu

Publications and source records attributed to H M Liu.

At least 19 recordsLinked to original sources
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

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↗
PubMed1990

Plasma electrolyte changes after ingestion of bile extract of the grass carp (Ctenopharyngodon idellus) in rats.

Some Chinese people believe that eating the gallbladder of the grass carp (Ctenopharyngodon idellus) may improve their visual acuity. However, ingestion of grass-carp bile, in severe cases, may kill human beings and experimental animals. The cause of death after eating grass-carp bile was studied in rats. The bile acid fraction was prepared from the n-hexane-insoluble and alcohol-soluble parts of grass-carp and hog bile. The bile extract (6 ml/kg, 15%) was administrated by gastric intubation to conscious female Long-Evans rats. Ingestion of grass-carp bile extract killed all the experimental rats in 2-8 h and was associated with a decrease in blood pressure and an increase in plasma potassium, hydrogen ions, blood urea nitrogen and hematocrit. However, rats that ingested hog bile or saline showed no significant changes in the measured parameters. If the rats were fed cholestyramine-treated grass-carp bile extract, they survived without significant change in the measured parameters. This report demonstrates that a drastic increase in plasma potassium and hydrogen ions probably caused the death of the rats, and also shows that bile acid (alcohol) in grass-carp bile is related to the toxicity.

Animals↗
PubMed1989

Molecular cloning, coding nucleotides and the deduced amino acid sequence of P-450BM-1 from Bacillus megaterium.

The gene encoding barbiturate-inducible cytochrome P-450BM-1 from Bacillus megaterium ATCC 14581 has been cloned and sequenced. An open reading frame in the 1.9 kb of cloned DNA correctly predicted the NH2-terminal sequence of P-450BM-1 previously determined by protein sequencing, and, in toto, predicted a polypeptide of 410 amino acid residues with an Mr of 47,439. The sequence is most, but less than 27%, similar to that of P-450CAM from Pseudomonas putida, so that P-450BM-1 clearly belongs to a new P-450-gene family, distinct especially from that of the P-450 domain of P-450BM-3, a barbiturate-inducible single polypeptide cytochrome P-450:NADPH-P-450 reductase from the same strain of B. megaterium (Ruettinger, R.T., Wen, L.-P. and Fulco, A.J. (1989) J. Biol. Chem. 264, 10987-10995).

Amino Acid Sequence↗
PubMed1989

Immunohistochemical localization of intracellular plasma proteins in the human central nervous system.

The regional distribution of plasma protein immunoreactivity was studied in the postmortem central nervous system (CNS) of normal subjects 18 to 78 years old. Samples taken from various areas of brain and spinal cord were processed for peroxidase-antiperoxidase immunocytochemistry using polyclonal antibodies against plasma albumin, prealbumin, alpha 1-acid glycoprotein, alpha 2-macroglobulin, IgG, transferrin, haptoglobin, hemopexin, fibrinogen, as well against the glial fibrillary acidic and S-100 proteins. Many neurons of the spinal cord, cranial nerve nuclei, pontine nuclei, cerebellar dentate nucleus, red nucleus, thalamus and hypothalamus showed strong immunostaining for albumin and moderate to strong staining for alpha 1-acid glycoprotein, IgG, transferrin, haptoglobin, as well as relatively weak immunoreactivity against other plasma proteins. Less intense staining was seen in the nucleus basalis, putamen and Purkinje cells. In contrast, most cerebral cortical neurons were negative except for a few positively stained pyramidal neurons in the hippocampus and in layers III and V of the association neocortex, although more positive pyramidal neurons were observed in the motor and sensory neocortices. Reaction products were also seen in axons of motor and sensory long tracts. These findings suggest that plasma proteins may be transported to spinal cord and brain stem neurons by peripherally projecting nerves and that a series of anterograde and retrograde transneuronal transfers are responsible for the accumulation of plasma proteins in relay nuclei and in other CNS neurons.

Adult↗
PubMed1988

In vitro nerve-growth-promoting activity of human plasma alpha 1-acid glycoprotein.

Human plasma alpha 1-acid glycoprotein or orosomucoid (OR), and its derivatives, prepared by sequential enzymatic cleavage of the carbohydrate units, were tested for their nerve-growth-promoting activities with explants of whole dorsal root ganglia from chick embryos. The results showed that the OR derivatives with terminal galactose, N-acetylglucosamine, or mannose have marked neurite-promoting activities. These preparations at a concentration of 100 micrograms/ml are equivalent to 5% fetal bovine serum (protein concentration 3,000 micrograms/ml) in their ability to elicit extensive neurite outgrowth and collateral branching. The asialo-OR, or ASOR, is the most potent form: its activity is estimated to be 20 times higher than that of transferrin and 100 times over that of fibronectin; it is approximately 1/1,500 that of NGF. The neurite-promoting activity of OR is independent of the non-neuronal cells and their products and can be blocked by a specific antiserum against OR. The mode of action of OR on the in vitro nerve growth is discussed and the pathophysiological significance of this plasma glycoprotein is considered in light of data from recent clinical and pathological studies.

Animals↗
PubMed1988

Neovasculature and blood-brain barrier in ischemic brain infarct.

The cellular events occurring in ischemic brain infarcts of 1 day to 8 weeks duration were investigated. The material consisted of 17 human postmortem brains with anemic infarcts caused by occlusive vascular diseases. Using antiserum against human plasma albumin as a marker for the breakdown of blood-brain barrier and ammoniacal silver nitrate stain to demonstrate the vasculature, the onset and distribution of the extravasated plasma protein was compared with histological changes in the blood vessels. It was observed that extravasation occurred in several separate regions of the infarct during different time periods. During the first few days, plasma proteins exudated from the vessels located at the marginal zone surrounding the infarct. This was followed by a prolonged phase of intense extravasation that coincided with the production of new capillaries originating from the blood vessels at the margin of the infarct and from pial vessels. It is postulated that the actively proliferative and migratory activities of the endothelial cells and pericytes in the neovasculature may be responsible for the extravasation which is reflected in the contrast enhancement of the infarct observed clinically during the recovery phase.

Blood-Brain Barrier↗
PubMed1988

A method for the quantitative analysis of nerve growth in vitro.

A method is described for the quantitative analysis of the nerve-growth-promoting activity of biological molecules in tissue culture. The criteria used for the evaluation of this activity is based on the neurite length as well as the total number of neurites produced by the explant of whole dorsal root ganglia from 12-d-old chick embryos. A nerve growth index (NGI) is given to each ganglion during each of a 5-d culture period. The NGI is defined as the product of average neurite length in millimeters and the total number of neurites. We report that with increasing concentrations of fetal bovine serum, there was a proportional increase in NGI due to increased neurite density while the neurite length was not greatly affected. The NGI of several proteins with known nerve growth promoting activity, namely nerve growth factor, insulin, transferrin, and fibronectin were investigated for their activity and compared with that of fetal bovine serum.

Animals↗
PubMed1988

Extravasation of plasma proteins in brain trauma.

The cellular distribution of extravasated plasma proteins in cortical contusions was studied with an immunoperoxidase method using polyclonal antibodies against human plasma albumin, alpha 1-acid glycoprotein, alpha 2-macroglobulin, alpha 1-antitrypsin, transferrin, hemopexin, haptoglobin, fibrinogen, fibronectin and immunoglobulin G. The material consisted of 24 human autopsy brains with a primary diagnosis of cerebral contusion due to blunt trauma. The time interval between injury and death ranged between minutes and 7 years. Immediately after the trauma, a complete breakdown of the blood-brain barrier (BBB) occurred with hemorrhage and extravasation of all types of plasma proteins. This was followed by spreading of edema fluid within the extracellular space in and around the wound. Uptake of extravasated protein by glial cells began on the 3rd day followed by proliferation of reactive astrocytes whose ample cytoplasm appeared to serve as a reservior for the extravasated plasma proteins. Within the reactive astrocytes, plasma proteins and S-100 protein had a similar and diffuse distribution in the immunostained sections. The plasma proteins once incorporated into the glial cells remained unchanged for several years with little sign of degradation. It is suggested that the extravasated plasma proteins subsequent to uptake and processing by the glial cells, may serve some important physiological function in wound healing.

Adolescent↗