Biomedical subjects

J F Yang

Publications and source records attributed to J F Yang.

At least 19 recordsLinked to original sources

PubMed2001

Schwann cells express active agrin and enhance aggregation of acetylcholine receptors on muscle fibers.

To explore novel roles of glial cells in synaptic function and formation, we examined the expression of agrin in frog Schwann cells and tested their role in the aggregation of acetylcholine receptors (AChRs). Using reverse transcription-PCR, we found that Schwann cells along nerve fibers in tadpoles expressed only the inactive agrin isoform B0 but began to also express active agrin isoforms B11 and B19 at approximately metamorphosis. During nerve regeneration in the adult, the expression of these active agrin isoforms in Schwann cells was upregulated, including the appearance of the most potent isoform, B8. This upregulation was induced by regenerating axons but not by nerve injury per se. In muscle cultures, the presence of adult Schwann cells enhanced the number and the total area of AChR aggregates 2.2- and 4.5-fold, respectively, and this enhancement was eliminated by heparin treatment. Furthermore, adult Schwann cells in culture expressed active agrin isoforms and produced agrin protein. Using a novel technique to selectively ablate perisynaptic Schwann cells (PSCs) at the neuromuscular junction, we found that PSCs also expressed active agrin isoforms B11 and B19, and these active isoforms were upregulated, including the appearance of B8, during reinnervation. Observation in vivo showed that extrajunctional AChR aggregates were associated with PSC sprouts after nerve injury and subsequent reinnervation. These results suggest that, contrary to the prevailing view that only neurons express active agrin, glial cells also express active agrin and play a role in the aggregation of AChRs both in vitro and in vivo.

Agrin↗

PubMed2001

[Statistical analysis of 47 cases with Holt-Qram syndrome].

By statistical analysis of 47 cases with Holt-Qram syndrome(HOS), we found that the severity of the upper limb abnormalities and cardiac defects in HOS varied significantly with different individuals. The variations of appearance were related with the types and positions of mutatons of TBX5 gene which could damage the gene function and cause HOS. It is suggested that the genetic heterogeneity in HOS may be caused by the mutations of different genes.

Abnormalities, Multiple↗

PubMed2001

[Syndrome differentiation and typing of traditional Chinese medicine and the clinical efficacy in 148 cases of acne vulgaris].

To differentiate and type the acne vulgaris patients and to treat them with our own recipes for dissipating heat and detoxifying in traditional Chinese medicine 148 cases were typed and trated as: carbuncles and stasis (84 cases), carbuncles and damp 'toxins' (16) and damp 'toxins' and stasis (48) as well as the contrast groups of 60 patients that treated with chemical medicines. The results were: cured 86 cases (58%); significantly effective 38 cases (26%); effective 18 cases (12%); and ineffective 6 cases (4%). The contrast groups had the results of: cured 10 (17%), significantly effective 14(23%), effective 21(35%) and ineffective 15(25%). The total effective rates of both groups were 96 and 75% (P < 0.01). Following the principles of traditional Chinese medicine in differentiating and typing the acne vulgaris patients and treating them accordingly with recipes of dissipating heat and detoxifying, dissipating heat and drying the dram, eliminating the stagnant and detoxifying is an effective treatment for clinic application.

Acne Vulgaris↗

PubMed2001

Interlimb co-ordination in human infant stepping.

1. We held infants (aged 4-12 months) over a treadmill to study how they co-ordinated the two limbs during stepping. We disturbed one limb during the stance or swing phase and recorded the responses (muscle activity and movement) from both lower limbs. Manual disturbances were applied during the stance phase by sliding the foot backward, forcing the limb into the swing phase. Disturbances were also applied in the swing phase by manually extending the hip, interfering with the forward motion of the limb. Additional disturbances were applied to see if both limbs could perform the stance and swing phase synchronously. 2. When the limb was forced to initiate the swing phase on one side, the contralateral limb either prolonged its contact with the ground or quickly established ground contact. When the forward motion of the limb was interrupted in the swing phase, the swing phase was prolonged on the disturbed side and the stance phase prolonged on the contralateral side. In most cases, one leg maintained ground contact. Moreover, it was easy to elicit bilateral, simultaneous stance phase, whereas it was difficult to elicit simultaneous swing phase. In cases where swing phase in the two limbs was initiated close in time, rhythmic alternate stepping was immediately restored in the following step. 3. We conclude that human infants can generate co-ordinated motor responses bilaterally in response to unilateral perturbations, well before the onset of independent walking.

Electromyography↗

PubMed2001

Molecular characterization of Bacillus anthracis using multiplex PCR, ERIC-PCR and RAPD.

AIMS: To investigate the molecular characterization of Bacillus anthracis strains by multiplex PCR, enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) and random amplification of polymorphic DNA (RAPD). METHODS AND RESULTS: Three primers were used to amplify the cya, cap and cereolysinAB genes in the multiplex PCR. Two distinct ERIC-PCR and RAPD fragments, which separated B. anthracis into two groups, were used as probes in Southern hybridization experiments. The probes hybridized only to the cya+ B. anthracis strains identified by the multiplex PCR. Nucleotide sequence analysis of the two cloned fragments showed they were from the pXO1 plasmid of B. anthracis. CONCLUSION: Multiplex PCR simultaneously identified isolates of the Bacillus cereus group and the B. anthracis virulence factors. ERIC-PCR and RAPD, combined with the Southern hybridization analyses, differentiated B. anthracis strains and separated them from the closely related B. cereus group bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: ERIC-PCR and RAPD assay could be effective in differentiating virulent from avirulent B. anthracis. Our results also show that the amplification of the large plasmids was allowed in the ERIC-PCR and RAPD assay.

Bacillus anthracis↗

PubMed2000

The initiation of the swing phase in human infant stepping: importance of hip position and leg loading.

Hip extension and low load in the extensor muscles are important sensory signals that allow a decerebrate or spinal cat to advance from the stance phase to the swing phase during walking. We tested whether the same sensory information controlled the phases of stepping in human infants. Twenty-two infants between the ages of 5 and 12 months were studied during supported stepping on a treadmill. Forces exerted by the lower limbs, surface electromyography (EMG) from muscles, and the right hip angle were recorded. The whole experimental session was videotaped. The hip position and the amount of load experienced by the right limb were manipulated during stepping by changing the position of the foot during the stance phase or by applying manual pressure on the pelvic crest. Disturbances with different combinations of hip position and load were used. The stance phase was prolonged and the swing phase delayed when the hip was flexed and the load on the limb was high. In contrast, stance phase was shortened and swing advanced when the hip was extended and the load was low. The results were remarkably similar to those in reduced preparations of the cat. They thus suggest that the behaviour of the brainstem and spinal circuitry for walking may be similar between human infants and cats. There was an inverse relationship between hip position and load at the time of swing initiation, indicating the two factors combine to regulate the transition.

Animals↗

PubMed2000

Early corrective reactions of the leg to perturbations at the torso during walking in humans.

The contribution of afferent feedback to the regulation of locomotion in humans is not well understood. Animal experiments have suggested that loading of the leg during the stance phase may enhance the magnitude of extensor burst activity and delay the onset of swing phase. The aim of the present study was to determine whether transient loading of the leg at the end of stance would enhance extensor-muscle activity and delay the onset of swing in walking humans. To test this hypothesis, we applied loads to the hips of subjects so that the load was applied along the long axis of the leg at the end of stance (down-back unsupported, DBU). This resulted in an unexpectedly complex reaction characterised by rapid co-contraction of antagonist pairs of muscles around the ankle and knee and a prolongation of the stance phase. We speculated that the complexity of the reaction was, in part, due to a disturbance in equilibrium. To address this possibility, two additional perturbation paradigms were tested: (1) subjects held a rail during the loading paradigm (down-back supported, DBS), or (2) subjects received only a posteriorly directed perturbation of the hips, which added no additional load to the leg (backward unsupported, BU). As predicted, the DBS perturbation resulted in an enhancement of the ongoing soleus-muscle activity, and the unexpected tibialis anterior burst that was observed during the DBU paradigm was absent. Allowing the subjects to hold a rail substantially reduced the change in the timing of the step cycle observed in the DBU paradigm. The BU perturbation prolonged the stance phase duration and, as expected, resulted in a burst of activity in tibialis activity. This was usually accompanied by a reduction in the ongoing soleus activity. Two important conclusions are drawn from the present study. First, loading of the leg at the end of stance phase enhances the ongoing extensor-muscle activity. We suggest that afferent feedback responding to the increase load supported by the leg leads to rapid enhancement of the active extensor muscles to compensate for the increased load and prevent collapse of the leg. Interestingly, the duration of the stance phase was only marginally increased when loading was applied without a postural disturbance (DBS). Second, posterior perturbation of the centre of mass at the end of stance phase evokes an "automatic postural response" in tibialis anterior. Of particular interest, this evoked postural response can occur simultaneously with an enhanced activation of soleus. This indicates that the DBU perturbation employed in this study elicited two responses, one to prevent the collapse of the leg and the other to stabilise the centre of mass.

Adult↗

PubMed2000

Comparison of PCR-RFLP, ribotyping and ERIC-PCR for typing Bacillus anthracis and Bacillus cereus strains.

PCR-RFLP analysis of the vrrA gene and cerAB gene was used to investigate the genomic diversity in 21 strains of Bacillus anthracis and 28 strains of Bacillus cereus, and was compared with results obtained by ribotyping and enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) analysis. VrrA-typing divided the B. anthracis into four groups. Except for one Pasteur vaccine strain, the vrrA PCR-RFLP profiles of the B. anthracis were separated into three groups, which were different from those of the B. cereus strains. Ribotyping separated the B. anthracis isolates into seven ribotypes, and a common fragment of an approximately 850 bp band from the ERIC-PCR fingerprints separated most B. anthracis strains into two groups. VrrA/cerAB PCR-RFLP, ribotyping and ERIC-PCR generated 18, 22 and 23 types, respectively, from B. cereus strains. The results suggest that a combination of all three methods provides a high resolution typing method for B. anthracis and B. cereus. Compared with ribotyping and ERIC-PCR, PCR-RFLP is simple to perform and has potential as a rapid method for typing and discriminating B. anthracis strains from other B. cereus group bacteria.

Bacillus anthracis↗

PubMed2000

Could different directions of infant stepping be controlled by the same locomotor central pattern generator?

This study examined the idea of whether the same central pattern generator (CPG) for locomotion can control different directions of walking in humans. Fifty-two infants, aged 2-11 mo, were tested. Infants were supported to walk on a treadmill at a variety of speeds. If forward stepping was elicited, stepping in the other directions (primarily sideways and backward) was attempted. The orientation of the infant on the treadmill belt determined the direction of stepping. In some infants, we also attempted to obtain a smooth transition from one direction to another by gradually changing the orientation of the infant during a stepping sequence. Limb segment motion and surface electromyography from the muscles of the lower limb were recorded. Most infants who showed sustained forward walking also could walk in all other directions. Thirty-three of 34 infants tested could step sideways. The success of eliciting backward stepping was 69%. Most of the infants who did not meet our backward stepping criteria did, however, make stepping movements. The different directions of stepping had similar responses to changes in treadmill speed. The relationship between stance and swing phase durations and cycle duration were the same regardless of the direction of stepping across a range of speeds. Some differences were noted in the muscle activation patterns during different directions of walking. For example, the hamstrings were much more active during the swing phase of backward walking compared with forward walking. The quadriceps was more active in the trailing leg during sideways walking. In some infants, we were able to elicit stepping along a continuum of directions. We found no discrete differences in either the electromyographic patterns or the temporal parameters of stepping as the direction of stepping was gradually changed. The results support the idea that the same locomotor CPG controls different directions of stepping in human infants. The fact that most infants were able to step in all directions, the similarity in the response to speed changes, and the absence of any discrete changes as the direction of stepping was changed gradually are all consistent with this hypothesis.

Brain Stem↗

PubMed2000

Changes in the lifestyle of Mongolian pastoralists in China in connection with urbanization.

The objective of this study was to elucidate changes in the health-related lifestyle of Mongolian pastoralists in China in connection with their urbanization. A total of 592 people participated in a survey that included a medical examination and an interview questionnaire. Files of 72 pastoral Mongolians, 78 urban Mongolians, 380 urban Han/Man and 21 urban Hui were used for this analysis. Urban Mongolians consumed meat and milk products less frequently than did pastoral populations (p < 0.001), and consumed fish and vegetables more frequently than did pastoral populations (p < 0.001). Urban Mongolian consumed mutton, beef, rengyo fish, milk, milk tea, curd, butter, yogurt, and sheep milk less frequently (p < 0.05) and pork, sword fish, and dried milk more frequently (p < 0.05) than pastoral Mongolian. Male pastoral Mongolians were more likely to drink and smoke than were urban Mongolians (p < 0.01), urban Han/Man (p < 0.01), or urban Hui (p < 0.01). The lifestyles of pastoral Mongolians in Inner Mongolia, China have changed in connection with urbanization. Understanding of the traditional pastoral lifestyle and the urban-living acculturation process will contribute to maximizing the positive impacts of urbanization on people's health in Inner Mongolia.

Acculturation↗

PubMed2000

[Investigation on antibacterial activity of Forsythia suspense Vahl in vitro with Mueller-Hinton agar].

OBJECTIVE: To evaluate the antibacterial activity of Forsythia suspensa in vitro with different media. METHOD: MIC determination of Forsythia suspensa against Staphylococci was performed by the agar dilution method. RESULT: MIC90 of decoction of Forsythia suspensa against Staphylococcus epidermidis in M-H agar was 1:640, but in nutrient agar 1:40, the antibacterial activity with M-H agar being 16 fold higher than nutrient agar. CONCLUSION: The M-H agar should be recommended to replace nutrient agar as medium in the antibacterial experiment of Traditional Chinese medicine, and it is better to use multipoint inoculating device in the sensitivity test.

Agar↗

PubMed1999

A cysteine-rich form of Xenopus neuregulin induces the expression of acetylcholine receptors in cultured myotubes.

Neuregulin-1 (NRG-1) has diverse functions in neural development, and one of them is to up regulate the expression of acetylcholine receptors (AChRs) at muscle fibers during the formation of neuromuscular junctions. NRG-1 has two prominent alternative splicing sites at the N-terminus; it could be an immunoglobulin (Ig)-like domain named Ig-NRG-1 or an apolar cysteine-rich domain (CRD) named CRD-NRG-1. cDNAs encoding Xenopus CRD-NRG-1 were isolated by cross-hybridization with Xenopus Ig-NRG-1 cDNA fragment. The amino acid sequence of Xenopus CRD-NRG-1 is 45 to 70% identical to the human, rat, and chick homologs. Similar to Ig-NRG-1, two variation sites within CRD-NRG-1 were identified at the spacer domain with 0 or 43 amino acids inserted and at the C-terminus of the EGF-like domain to derive either alpha or beta isoform. Two transcripts encoding CRD-NRG-1, approximately 7.5 and approximately 9.0 kb, were revealed in adult brain and spinal cord, but the expression in muscle was below the detectable level. The recombinant Xenopus CRD-NRG-1 when applied onto cultured myotubes was able to induce the tyrosine phosphorylation of ErbB receptors and the expression of AChR. The AChR-inducing activity of CRD-NRG-1 was precipitated by anti-NRG-1 antibody but not by heparin. In situ hybridization showed a strong expression of CRD-NRG-1 mRNA in developing brain, spinal cord, and myotomal muscles of Xenopus embryo. Similar to the results in other species, both CRD-NRG-1 and Ig-NRG-1 may play a role in the developing Xenopus neuromuscular junctions.

Amino Acid Sequence↗

PubMed1999

Loading during the stance phase of walking in humans increases the extensor EMG amplitude but does not change the duration of the step cycle.

Prior work from mammals suggests that load experienced by extensor muscles of the hindlimbs (i.e. Duysens and Pearson 1980; Pearson and Collins 1993; Fouad and Pearson 1997) or cutaneous afferents from the plantar surface of the foot (Duysens and Pearson 1976; Guertin et al. 1995) enhances activity in extensor muscles during the stance phase, and delays the onset of flexor activity associated with the swing phase. The presumed functional significance of this phenomenon is that extensor activity of the supporting limb during walking can: (a) reinforce the supporting function in proportion to the load experienced, and (b) prolong the stance phase until unloading of the limb has occurred. Whether a similar functional role exists for load-sensitive afferents during walking in the human is unknown. In this study, the effect of adding or removing a substantial load (30% of body weight) at the centre of mass was studied in healthy adult human subjects. Loads were applied near the centre of mass to avoid the need for postural adjustments which might confound the interpretation of the results. Subjects walked on a treadmill with either: (a) a sustained increase or decrease in load, or (b) a sudden unexpected increase or decrease in load. In general, subjects responded to the changes in load by changing the amplitude of the extensor electromyographic (EMG) bursts. For example, with sudden unexpected additions in load, the average increase in amplitude was 40% for the soleus across the stance phase, and 134% for the quadriceps during the early part of the stance phase. Extensor EMGs increased with both sustained and sudden increases in load. Extensor EMG durations also increased (average increase in duration of 4% for soleus with sudden loading, and 7% for sustained loading). Cycle duration hardly changed (average increase of 0.5% with both sudden and sustained loading). These results differ from those of infants subjected to a similar perturbation during supported walking. A large change in timing (i.e. an increase in the duration of the stance phase by 30% and the step cycle by 28%) was seen in the infants, with no change in the amplitude of the EMG burst (Yang et al. 1998). These results suggest that the central nervous system can control the timing and amplitude of extensor EMG activity in response to loading independently. Maturation of the two components most likely occurs independently. In the adult, independent control of the two components may provide greater flexibility of the response.

Adult↗

PubMed1998

Cloning of cDNAs encoding xenopus neuregulin: expression in myotomal muscle during embryo development.

Neuregulin has diverse functions in neural development, and one of them is the up regulation of acetylcholine receptors (AChRs) at the muscle fiber during the formation of neuromuscular junctions. Although the primary source of neuregulin is derived from motor neuron, the expression in muscle has also been demonstrated. The precise role of neuron-derived and muscle-derived neuregulin during the early stages of development is not known. In order to study the role of neuregulin during early embryo development, we isolated the cDNAs encoding Xenopus neuregulin by cross-hybridization with its chick homologue. The amino acid sequence of Xenopus protein is 50 to 70% identical to members of the neuregulin family. The cDNAs encoding different isoforms of Xenopus neuregulin were identified, and these isoforms have two variation sites: (i) the spacer domain with either 0 or 43 amino acid insertion; and (ii) the C-terminus of EGF-like domain to derive either alpha or beta isoform. When the EGF-like domain of Xenopus neuregulin was expressed in mammalian cells, the recombinant protein was able to induce the expression of AChR and the tyrosine phosphorylation of erbB receptors in cultured myotubes. An approximately 6.5 kb transcript corresponding to neuregulin was detected in RNA isolated from brain and muscle. Various splicing variants were expressed in different Xenopus tissues. In situ hybridization showed a strong expression of neuregulin in developing brain and spinal cord of Xenopus embryo. In addition, it was also prominently expressed in the myotomal muscle. These data suggest that in addition to motor neurons, the postsynaptic muscle cells can also contribute neuregulin for synaptogenesis.

Amino Acid Sequence↗

PubMed1998

Self-sustained firing of human motor units.

Motoneurons of invertebrates and vertebrates can continue to fire repetitively after being activated by a brief, excitatory synaptic input (self-sustained firing). This firing behavior is due to the activation of intrinsic, voltage-gated currents which produce sustained regenerative depolarizations (plateau potentials) of the cell. Examination of these intrinsic cellular properties has been performed in reduced animal preparations and it is unknown if such self-sustained firing occurs in motoneurons of the intact human. In this paper, we present evidence of this in the human by using a technique of dual motor unit recordings. Subjects were instructed to maintain a constant dorsiflexion effort, and the common synaptic input (e.g. descending drive) onto the tibialis anterior (TA) motoneuron pool was monitored by recording the firing frequency of a low threshold 'control' unit. Once the firing rate of the control unit was constant, vibration of the TA tendon recruited a second 'test' unit which continued to fire after the vibration (i.e. synaptic input) was removed, even though the firing rate of the control unit (and thus, the common drive) remained the same or decreased. Self-sustained firing of motoneurons such as this may reduce the need for prolonged synaptic input when constant muscle activation is required (e.g. for postural tone).

Evoked Potentials, Motor↗

PubMed1998

Infant stepping: a method to study the sensory control of human walking.

1. Stepping responses were studied in infants between the ages of 10 days and 10 months while they were supported to step on a slowly moving treadmill belt. Surface electromyography (EMG) from muscles in the lower limb, force exerted by the feet on the treadmill belt, and the motion of the lower limbs were recorded. 2. Two groups of infants were studied, those who had a small amount of daily practice in stepping and those who did not. Practice resulted in a dramatic increase in the incidence of stepping recorded in the laboratory, particularly for the periods between 1 and 6 months of age. 3. The majority of infants showed clear alternation between the flexor and extensor muscles during walking, regardless of age. Co-contraction between flexors and extensors, estimated by the overlap in area between rectified and smoothed EMG from a muscle pair, was greater for some muscle groups in the infant compared with the adult. 4. Practice resulted in a significantly lower co-contraction index for the tibialis anterior- quadriceps muscle pair. Practice did not affect the mean step cycle duration. 5. Infants of all ages could step at a range of treadmill speeds by adjusting their step cycle duration. The relationship between the treadmill speed and cycle duration was well fitted by a power function, similar to those reported for intact cats and adult humans. The change in step cycle duration resulted almost entirely from a change in the extensor burst duration, whereas the flexor burst duration remained constant. 6. Airstepping could be elicited in some infants. The cycle durations for airstepping were close to the shortest cycles recorded on the treadmill. 7. In conclusion, the system for generating rhythmic, alternating activity of the lower limbs for stepping is clearly developed by birth. The stepping is sustained and regular, particularly if stepping practice is incorporated briefly each day. The infant population provides a good subject pool for studying the afferent control of walking in the human, before cerebral influences are fully developed. The characteristics and maturity of the system remain to be determined.

Adult↗

PubMed1998

Physical association between the EBV protein EBNA-1 and P32/TAP/hyaluronectin.

Epstein-Barr virus (EBV) nuclear antigen-1 (EBNA-1) is a protein expressed constitutively during EBV latency. It is required to support the replication of the EBV genome once per cell cycle via the latent origin of replication, oriP. EBNA-1 also can activate transcription through binding to the family repeats of oriP. We wished to identify candidate cellular protein(s) that may interact with EBNA-1 and mediate these functions. A 32-kd protein was co-immunoprecipitated with EBNA-1 from 293 cells using a monoclonal antibody EBNA.OT1x. The regions of EBNA-1 which interact with this protein were studied using two deletion clones and mapped to EBNA-1 residues 1-102 and 325-357. Deletion of this region was shown previously in a mutant of EBNA-1 which had dominant-negative effects on both DNA replication and transactivation assays. The 32-kd protein was found to react with a polyclonal antiserum against P32/TAP (HIV Tat associated protein), which is known to interact with other RNA binding proteins and the RNA splicing factor SF2. The function of P32 was therefore proposed to involve RNA processing. In addition, this molecule was recently identified as hyaluronectin, which binds hyaluronic acid. Because several reports documented that intracellular hyaluronic acid can potentially affect cell proliferation, the association between EBNA-1 and P32/TAP/hyaluronectin may help the maintenance of episomal viral DNA within proliferating cells.

Animals↗

PubMed1998

Transient disturbances to one limb produce coordinated, bilateral responses during infant stepping.

Transient disturbances were applied to the lower limbs of infants (3-10 mo of age) while they were supported to stepped on a treadmill. The aim was to determine how stepping infants respond to novel disturbances that would disrupt equilibrium during independent walking. Their responses were also compared with those from lower mammals and adult humans. In the first series of experiments, the motion of the limb in the swing phase was transiently stopped by the experimenter grasping the limb for a short time (0.1-1.7 s). During such disturbances, the stance phase was prolonged in the contralateral limb, and the onset of the swing phase was delayed. The degree to which the stepping was modified in the contralateral limb depended on the amount of load experienced by that limb. If the contralateral limb was bearing very little weight at the time of the disturbance, its rhythm did not change appreciably. In the second series of experiments, load was added to the infant by pushing down on the pelvis during the stance phase. This greatly prolonged the stance phase and delayed the swing phase. It did not increase the amplitude of the extensor electromyogram (EMG) of the loaded limb. In conclusion, the neural circuitry controlling stepping in the infants responds to disturbances in an organized fashion that is conducive to maintaining equilibrium and forward progression.

Biomechanical Phenomena↗