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Biomedical subjects

X L Hu

Publications and source records attributed to X L Hu.

At least 19 recordsLinked to original sources
PubMed2006

The mechanomyography of persons after stroke during isometric voluntary contractions.

This study was to investigate the properties of mechanomyography (MMG), or muscle sound, of the paretic muscle in the affected side of hemiplegic subjects after stroke during isometric voluntary contractions, in comparison with those from the muscle in the unaffected side of the hemiplegic subjects and from the healthy muscle of unimpaired subjects. MMG and electromyography (EMG) signals were recorded simultaneously from the biceps brachii muscles of the dominant arm of unimpaired subjects (n=5) and the unaffected and affected arms of subjects after stroke (n=8), when performing a fatiguing maximal voluntary contraction (MVC) associated with the decrease in elbow flexion torque, and then submaximal elbow flexions at 20%, 40%, 60% and 80% MVCs. The root mean squared (RMS) values, the mean power frequencies (MPF, in the power density spectrum, PDS) of the EMG and MMG, and the high frequency rate (HF-rate, the ratio of the power above 15Hz in the MMG PDS) were used for the analysis. The MMG RMS decreased more slowly during the MVC in the affected muscle compared to the healthy and unaffected muscles. A transient increase could be observed in the MMG MPFs from the unaffected and healthy muscles during the MVC, associated with the decrease in their simultaneous EMG MPFs due to the muscular fatigue. No significant variation could be seen in the EMG and MMG MPFs in the affected muscles during the MVC. The values in the MPF and HF-rate of MMG from the affected muscles were significantly lower than those from the healthy and unaffected muscles (P<0.05) at the high contraction level (80% MVC). Both the MMG and EMG RMS values in the healthy and unaffected groups were found to be significantly higher than the affected group (P<0.05) at 60% and 80% MVCs. These observations were related to an atrophy of the fast-twitch fibers and a reduction of the neural input in the affected muscles of the hemiplegic subjects. The results in this study suggested MMG could be used as a complementary to EMG for the analysis on muscular characteristics in subjects after stroke.

Adult↗
PubMed2005

Firing properties of motor units during fatigue in subjects after stroke.

The purpose of this work was to investigate the electromyographic (EMG) fatigue representations in muscles of subjects after stroke at the level of motor unit, based on the analysis of mean power frequency (MPF) in the power density spectrum (PDS) for intramuscular EMG and our previous modeling and experiment studies on the neuromuscular transmission failure (NTF). NTF due to the local muscular fatigue had been captured in motor unit signals from healthy subjects during a submaximal fatigue contraction previously. In this study, the EMG signals for the biceps brachii muscles were collected by needle electrodes from the affected and unaffected arms of six hemiplegic subjects after stroke, and from the dominated arm of six healthy subjects during a full maximum voluntary contraction (MVC) and a subsequent 20% MVC. The MPF of EMG trials detected intramuscularly during the full and 20% MVCs, and the parameters of motor unit action potential trains (MUAPTs) during 20% MVC were analyzed in three groups: the normal (from healthy subjects), unaffected (from subjects after stroke), and affected (from subjects after stroke). It was found that during the full MVC the MPFs of the normal and unaffected groups decreased more than the affected when monitored by a moving time window of 2 s. The comparison on the overall MPF during the full MVC for these three groups over the whole time course of the EMG signal (18 s) were: the affected overall MPF was higher than the unaffected (P < 0.05); and the unaffected overall MPF was larger than the normal (P < 0.05). However, no significant decrease in MPF was found for these three groups during 20% MVC. The NTF was captured in most MUAPTs in the groups of the normal and unaffected rather than in the affected group, symbolized by the lowered rates of change (RCs) of firing rate (FR) (P < 0.05), more MUAPTs with positive RCs of maximum oscillation (MO) in MUAPT power density spectra (P < 0.05), and the significant higher RCs of minimum inter-pulse interval (MINI) (P < 0.05) in the normal and unaffected compared to the affected group. Enhanced neural drives to the motor units of the unaffected and affected groups were observed during 20% MVC, which possibly came from the bilateral neural inputs due to the disinhibition of the ipsilateral projections in subjects after stroke. For identifying the fatigue associated with NTF, the motor unit firing parameters, FR, MINI, and MO, were more sensitive than the MPF. The results obtained in this work provided a further understanding on the EMG of the fatigue processes in paretic and non-paretic muscles during voluntary contractions.

Action Potentials↗
PubMed2004

Oscillations in the power spectra of motor unit signals caused by refractoriness variations.

The refractory period of a motor unit is an important mechanism that regulates the motor unit firing, and its variation has been found in many physiological cases. In this study, a new observation that an increase in the motor unit refractoriness results in an enhancement of oscillations, or ripple effects, in the motor unit output power density spectra (PDS) has been identified and studied. The effects of the refractoriness variation on the PDS of motor unit firing were investigated on three levels: theoretical modeling, simulation and electromyographic (EMG) experimentation on human subjects. Both theoretical modeling and simulation showed the enhanced oscillations, ripple effects, in MUAPT PDS, given the increase in the refractoriness. It was also found that the extent of the increment in output PDS oscillation could be related to the motor unit size and the mean firing rate of the stimulation. A needle EMG experiment on biceps brachii muscles of five healthy human subjects was carried out during isometric contraction at 20% maximum voluntary contraction (MVC) for 20 s with a fatigue effort proceeded by MVC. The increased oscillations in the PDS of the real MUAPTs were observed with the rising of the motor unit refractoriness due to fatigue. The study gives new information for EMG spectra interpretation, and also provides a potential method for accessing neuromuscular transmission failure (NTF) due to fatigue during voluntary contraction.

Action Potentials↗
PubMed2004

The genetic epidemiology of alopecia areata in China.

BACKGROUND: Alopecia areata (AA) is hypothesized to be an organ-specific autoimmune disease with genetic predisposition and an environmental trigger. There are few clinical data in Asians. OBJECTIVES: To describe the genetic epidemiological features of AA patients in China and to determine the possible genetic model for AA. METHODS: Data for 1032 patients with AA were obtained by questionnaire in the Institute of Dermatology of Anhui Medical University in China from 2001 to 2003. Complex segregation analysis and heritability analysis were performed using Falconer's method, EPI INFO 6.0 and SAGE-REGTL programs. RESULTS: In total, 1032 AA patients (male/female ratio 1.1 : 1) were enrolled, representing 0.94% of the total number of cases seen in our outpatient clinic during that time. The mean +/- SD age of onset was 28.98 +/- 13.43 years. The difference between the mean age of onset in males and females was not significant. Most patients (82.6%) experienced their first episode of AA within the first four decades of life. A positive family history of AA was obtained in 87 patients (8.4%). The prevalence of AA in first-, second- and third-degree relatives of the proband with AA was 1.6%, 0.19% and 0.03%, respectively. These figures were higher than those in controls. A greater severity and longer duration of AA were seen in the early onset group than in the late-onset group. The early onset group also had more affected first- and second-degree relatives. The heritability of AA in first-, second- and third-degree relatives was 47.16%, 42.53% and 22.29%, respectively. Based on the REGTL results, the best model was a polygenic additive model for AA. CONCLUSIONS: The effect of genetic factors is strong in AA, but environmental factors such as infection and psychological stress may still play an important role. Our findings on the genetics of AA are consistent with a polygenic additive mode of inheritance.

Adolescent↗
PubMed2002

Neuroengineering modeling of single neuron and neural interface.

The single neuron has attracted widespread attention as an elementary unit for understanding the electrophysiological mechanisms of nervous systems and for exploring the functions of biological neural networks. Over the past decades, much modeling work on neural interface has been presented in support of experimental findings in neural engineering. This article reviews the recent research results on modeling electrical activities of the single neuron, electrical synapse, neuromuscular junction, and neural interfaces at cochlea. Single neuron models vary form to illustrate how neurons fire and what the firing patterns mean. Focusing on these two questions, recent modeling work on single neurons is discussed. The modeling of neural receptors at inner and outer hair cells is examined to explain the transforming procedure from sounds to electrical signals. The low-pass characteristics of electrical synapse and neuromuscular junction are also discussed in an attempt to understand the mechanism of electrical transmission across the interfaces.

Action Potentials↗
PubMed2001

A sequence-ready map of the human chromosome 1q telomere.

A 260-kb half-YAC clone derived from human chromosome 1q was mapped at high resolution using cosmid subclone fingerprint analysis and was integrated with overlapping clones from the telomeric end of a separately derived 1q44 BAC contig to create a sequence-ready map extending to the molecular telomere of 1q. Analysis of 100 kb of sample sequences from across the 260-kb region encompassed by the half-YAC revealed the presence of EST sequence matches corresponding to 12 separate Unigene clusters and to 12 separate unclustered EST sequences. Low-copy subtelomeric repeats typical of many human telomere regions are present within the distal-most 30 kb of 1q. The previously isolated and radiation hybrid-mapped markers Bda84F03, 1QTEL019, and WI11861 localized at distances approximately 32, 88, and 99 kb, respectively, from the 1q terminus. This sequence-ready map permits high-resolution integration of genetic maps with the DNA sequences directly adjacent to the tip of human chromosome 1q and will enable telomeric closure of the human chromosome 1q DNA reference sequence by connecting the molecular 1q telomere to an internal BAC contig.

Chromosomes, Artificial, Bacterial↗
PubMed2001

Integration of telomere sequences with the draft human genome sequence.

Telomeres are the ends of linear eukaryotic chromosomes. To ensure that no large stretches of uncharacterized DNA remain between the ends of the human working draft sequence and the ends of each chromosome, we would need to connect the sequences of the telomeres to the working draft sequence. But telomeres have an unusual DNA sequence composition and organization that makes them particularly difficult to isolate and analyse. Here we use specialized linear yeast artificial chromosome clones, each carrying a large telomere-terminal fragment of human DNA, to integrate most human telomeres with the working draft sequence. Subtelomeric sequence structure appears to vary widely, mainly as a result of large differences in subtelomeric repeat sequence abundance and organization at individual telomeres. Many subtelomeric regions appear to be gene-rich, matching both known and unknown expressed genes. This indicates that human subtelomeric regions are not simply buffers of nonfunctional 'junk DNA' next to the molecular telomere, but are instead functional parts of the expressed genome.

Chromosomes, Artificial, Bacterial↗
PubMed2001

[Determination of thyroxine enantiomers in human plasma with normal high performance liquid chromatography-chiral complex exchange mobile phase].

An HPLC method was developed with normal HPLC-chiral complex mobile phase for the separation and determination of D- and L-thyroxine enantiomers (D- and L-T4) in human plasma. The method includes extraction of thyroxine from plasma and separation of thyroxine enantiomers on HPLC silica column with chiral eluent containing L-proline, cupric acetate and triethylamine (TEA). The sensitivity of the method was 0.1 mg/L. The precisions of inter-day and intra-day, linearity, extraction recovery, and stability of T4 enantiomers in plasma and in deproteinized plasma were determined for the validation of the method. Baseline enantioseparation of the compounds containing D- and L-T4 was achieved. Meantime we determined the concentrations of D-T4 and L-T4 in plasma of 15 volunteers with euthyroid, hypothyroid and hyperthyroid symptoms. Liquid chromatographic method based on the described procedure was useful for the determination of D- and L-thyroxine in patient plasma and for pharmacokinetics investigation.

Chromatography, High Pressure Liquid↗
PubMed2000

[Analysis of a suppressor element of mouse Nodal gene in its 5' flanking sequences].

Nodal gene is a member of the TGF-beta superfamily. It is required for the formation of the primitive streak during mouse gastrulation. Mice without Nodal gene will die due to the lack of mesoderm formation. F9 cells were transiently transfected with a series of luciferase reporter constructs containing the subcones of Nodal 5' filanking sequences and their deletions. By analyzing the luciferase activity of these constructs, a suppressor element was determined at about 1 kb up stream the transcription initiation site, around an EcoR I site. Its central part was located at about 100 bp downstream of that EcoR I site. It could almost totally, suppress the Nodal gene promoter activity, though it had no effect on SV40 promoter. It behaved differently in different cell lines. In CHO cells, it had an activation activity.

Animals↗
PubMed2000

[Analysis of an inhancer element of mouse Nodal gene in its 5' flanking sequence].

Nodal, a member of TGF-beta superfamily, plays a very important role in the mesoderm formation during mouse early development. Mice without the Nodal gene will die due to the lack of mesoderm. The flanking sequences of Nodal were dissected. By using lucifirase as reporter gene, F9 cells were transfected with a series of reporter constructs containing the subclones of the flanking sequences and their nested deletions. The effect of these subclones and deletions-2 kb up stream the Nodal gene and its cell type specificity was determined.

Animals↗
PubMed2000

Theoretical analysis of a rectifying gap junction model.

Based on the experimental observations, an electrical circuitry model for a rectifying gap junction was developed in previous work. In order to show the physiological function for each element in the model, a theoretical analysis is carried out in this report. The results indicate that the gap junctional capacitance Cj newly introduced into the model plays a major role in determining the duration increase, the peak attenuation, and the peak delay on the postmembrane action potential. Also, a comparison between the newly proposed model and the widely accepted kinetic model by Giaume is made. The results show that the electrical circuitry model can not only describe the characteristics of Giaume's model but also allow the interpretation of some experimental phenomena that were not reflected in other gap junctional models.

Animals↗
PubMed2000

[Studies on the recurrent attacks of acute adenolymphangitis due to Malayan filariasis].

OBJECTIVE: To explore the role of filarial and bacterial infections in the recurrent attacks of acute adenolymphangitis due to malayan fialriasis. METHODS: 1. To observe the seasonal fluctuation of acute attacks by performing monthly follow-up on patients with history of acute attacks in recent years. 2. To study the relationship between bacterial infection and filarial adenolymphangitis by performing bacteria culture and anti-streptolysin O test. 3. To investigate the variation of acute attacks by controlling filariasis transmission or by treating patients with a history of recurrent acute attacks. RESULTS: 1. The peak of acute attacks in patients coincided with the peak of vector transmission season. 2. Of the 97 cases examined by bacteria culture, 90 cases were negative; of the 255 cases examined by anti-streptolysin O test, the titres in 94.1% (143/152) of the cases with first attack and simple adenolymphangitis were within normal limits, however, the titres in 27.2% (28/103) of the cases complicated with elephantiasis were increased. 3. The acute attack rate of adenolymphangitis per year reduced significantly in cases with first attack and simple adenolymphangitis after effective control of filariasis transmission. 4. There was no evidence of the reduction of acute attacks by treating patients with DEC alone. CONCLUSION: In malayan filariasis endemic areas, the main causes of recurrent attacks of acute adenolymphangitis might be the repeated filarial infections due to the persistence of filariasis transmission.

Acute Disease↗
PubMed1999

A sequence-ready map of the human chromosome 17p telomere.

A half-YAC clone derived from human chromosome 17p was mapped at high resolution using cosmid subclone fingerprint analysis. Colinearity of the half-YAC with the telomeric human genomic DNA fragment was ascertained by RecA-assisted restriction endonuclease cleavage mapping. Previously isolated and radiation hybrid-mapped markers TEL17P37, TEL17P49, and TEL17P80 mapped 30-60 kb from the 17p terminus. This sequence-ready map permits high-resolution integration of genetic maps with the DNA sequences directly adjacent to the tip of human chromosome 17p, and will provide the cloned DNA required for ascertaining the nucleotide sequence of this subtelomeric region.

Chromosome Mapping↗
PubMed1999

Expression of RET proto-oncogene and GDNF deficit in Hirschsprung's disease.

PURPOSE: The aim of this study was to investigate GDNF (glial cell line-derived neurotrophic factor) protein expression and RNA expression level of the RET proto-oncogene in human aganglionic (AG) bowel in Hirschsprung's disease (HD) and to further understand the pathophysiology of HD. METHODS: To evaluate the possible implication of the RET gene and GDNF for the development of HD, mRNA expression level of the RETgene was examined by using the reverse transcription-polymerase chain reaction (RT-PCR) technique and protein expression level of the GDNF using an immunohistochemical technique in the bowel specimens of 15 HD patients. RESULTS: A significantly less intense signal for RETmRNA was found in the AG bowel compared with the ganglionic bowel. In different age groups of patients, the intensities of RET level had similar results. In the same patients, there was strong GDNF immunoreactivity in the myenteric plexuse in ganglionic bowel. In the myenteron in AG bowel, the number of GDNF immunoreactive neuron cells was reduced significantly compared with normal ganglionic bowel. CONCLUSIONS: From these preliminary data we conclude that the decreased RET expression in the AG bowel may suggest mal development of neural crest-derived cells in HD. The reduced level of GDNF in AG bowel may suggest a GDNF expression deficit interrupting the faithful signaling via RET, and both are implicated in the pathogenesis of HD.

Base Sequence↗
PubMed1999

[Delineation of the cis-regulatory sequences of the nodal gene].

In mouse embryo development, nodal is expressed in the node during the gastrulation. It is involved in mesoderm formation and left-right axis determination. The expression of the nodal gene has a restricted spatial and temporal specificity. Studies on the function of the nodal first intron in the gene expression regulation have shown that a 220 bp fragment at the 5' end of the first intron has an enhancer activity. Rather unexpectedly, the transient transfection assays in F9 cells indicate that this fragment also displayed a promoter activity when it is cloned upstream of basic luciferase reporter gene only in sense orientation. We present here the nucleotide sequence of this 220 bp fragment, and discuss its possible role in the nodal gene regulation.

Animals↗
PubMed1999

[The experimental study of repairing bone defects with allogeneic bone matrix gelatin and plaster].

OBJECTIVE: To study the function of the composite of bone matrix gelatin(BMG) and plaster in the repairing process of bone defects. METHODS: Sixteen New Zealand rabbits which were defected in corpus radii were made as implant zone of bone. Sixteen sides of radii were implanted with the composite of BMG and plaster as experimental group. Others were implanted with BMG(8 sides) and bone stored in alcohol(8 sides) as control groups. The repairing process in bone defects were observed by X-ray and histological examination. RESULTS: There was an obvious osteogenesis in experimental group. The defects of radii were almost healed at 12th week after operation. There were osteogenesis in both control groups, but the repairing process was slower than that of the experimental group. CONCLUSION: The composite of BMG and plaster is a good material for bone transplantation.

Animals↗