Search PubMed⌕ Search

Biomedical subjects

J Mao

Publications and source records attributed to J Mao.

At least 127 records · Page 7Linked to original sources
PubMed1994

Muscle atrophy and procedures for training after spinal cord injury.

Functional electrical stimulation (FES) of paralyzed muscles holds promise as a strategy to assist patients in executing functional movements after spinal cord injuries. Muscle atrophy is one of the major problems that must be addressed for this approach to be successful. Loss of muscle mass may occur as a result of lesions to motoneurons in either the spinal cord or the central command pathway, or a combination of the two. For injuries to spinal motoneurons, muscle fibers undergo denervation atrophy. Damage to the central command pathway, on the other hand, results in disuse atrophy. In association with atrophy, the low contractile forces and inability of the muscles to sustain contractions are of direct therapeutic concern. In this review, methods aimed at recovery of function of paralyzed limbs by reducing susceptibility to fatigue and atrophy of paralyzed muscles are discussed. One is related to promoting nerve sprouting in partially denervated muscles to reinnervate muscle fibers and reverse denervation atrophy. The other regards training of paralyzed muscles to increase strength (muscle force) and endurance (fatigue resistance) by means of FES. Most training regimens with low-frequency FES increase muscle endurance. Efforts to design optimal regimens for increasing both muscle strength and endurance must involve consideration of several factors that are still controversial. These factors, which include muscle properties (such as fiber type composition and physiological type) and conditions imposed on the muscle (such as loading) during contractions elicited by FES, are discussed in detail.

Electric Stimulation Therapy↗
PubMed1994

Paternal pericentric inversion of chromosome 4 as a cause of recurrent pregnancy loss.

A paternal pericentric inversion of chromosome 4 was ascertained through karyotype analysis of an abortus specimen proven to be 46,XX,rec(4),dup q, inv (4)(p13q28). The relationship of paternal pericentric inversion to pregnancy loss is discussed, and a recommendation for karyotype analysis of recurrent abortion specimens is made.

Abortion, Habitual↗
PubMed1994

Direction of a bite force determines the pattern of activity in jaw-closing muscles.

Human individuals were hypothesized to use the same pattern of jaw muscle activity to produce the same bite force. To test this hypothesis, we used a 2-mm-thick force transducer to monitor the magnitude and direction of a bite force between a single pair of occluding first molars. Five subjects performed standardized bite force tasks. Six different magnitudes were tested, each in five directions. The surface electromyographic (EMG) activity in the left and right masseter and temporalis muscles was recorded, integrated, and normalized. Ratios of the EMG activity of paired muscles (e.g., the ratio of working temporalis and working masseter) were calculated for each bite force task. Each ratio was roughly constant for each direction of bite force, regardless of its magnitude. In contrast, when the magnitude of bite force was the same but the directions were different, the ratio was not constant. We conclude that the direction of a bite force, not its magnitude, determines the pattern of activity of jaw-closing muscles. The shared patterns of muscle activation may be the result of a subconscious optimization of jaw muscle forces to improve efficiency.

Adult↗
PubMed1994

[Study on motilin and spleen-yin deficiency].

The Plasma motilin level in 44 cases patients with Spleen-Yin deficiency (SYD) was observed and compared with Spleen-Qi Insufficiency (SQI), the normal control group. SYD patients were treated using self-made Shen Rou Yang Zhen Tang oral liquor. The results showed that plasma motilin level was higher significantly than that of the control group (P < 0.01), but was remarkably lower than that of SQI. The difference was significant among the three groups (P < 0.01). The abnormal incidence of positive plasma motilin was 65.91% and 75.00% respectively. It is conjectured that the plasma motilin level in SYD was related to excitability of vagus nerve, disturbance of gastro-intestinal internal environment, indigestion and malabsorption of GI tract.

Adult↗
PubMed1994

[Effects of methylprednisolone pulse therapy on TNF alpha levels in chronic nephritis].

We examined the tumor necrosis factor (TNF alpha) bioactivity in patients with chronic glomerulonephritis (CGN) treated with methylprednisolone (MP) pulse therapy (1 course of 1 g/day x 3 days). TNF alpha bioactivity in CGN, including 5 cases of membranoproliferative glomerulonephritis (MPGN), 8 lupus nephritis (LN) and 6 purpura nephritis, was determined by ELISA with TNF alpha monoclonal antibody. TNF alpha values in the serum, urine and cultured lymphocyte supernatant (CLS) of patients was significantly higher than in control. (serum: 131.6 +/- 20.2 vs 70.4 +/- 13.8, urine: 26.2 +/- 8.2 vs 11.2 +/- 2.0, P < 0.05, CLS: 97.4 +/- 9.8 vs 59.5 +/- 10.1, P < 0.05, pretreatment vs control), but it was markedly reduced after treated with MP therapy. (serum: 60.2 +/- 11.2 vs 131.6 +/- 20.2, P < 0.05, urine: 10.2 +/- 1.6 vs 26.2 +/- 8.2, P < 0.05, CLS: 54.1 +/- 11.2 vs 97.4 +/- 9.8, P < 0.05, posttreatment vs pretreatment). These results indicated that TNF alpha levels in serum, urine and supernatant of lymphocyte were markedly higher in chronic nephritis, the MP pulse therapy possessed a striking effect on inhibiting the production of TNF alpha in peripheral lymphocytes.

Adolescent↗
PubMed1994

Thermal hyperalgesia in association with the development of morphine tolerance in rats: roles of excitatory amino acid receptors and protein kinase C.

In a rat model of morphine tolerance, we examined the hypotheses that thermal hyperalgesia to radiant heat develops in association with the development of morphine tolerance and that both the development and expression of thermal hyperalgesia in morphine-tolerant rats are mediated by central NMDA and non-NMDA receptors and subsequent protein kinase C (PKC) activation. Tolerance to the analgesic effect of morphine was developed in rats utilizing an intrathecal repeated treatment regimen. The development of morphine tolerance and thermal hyperalgesia was examined by employing the tail-flick test and paw-withdrawal test, respectively. Intrathecal MK 801 (an NMDA receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; a non-NMDA receptor antagonist), or GM1 ganglioside (an intracellular PKC inhibitor) treatment was given to examine the effects of these agents on the development and expression of thermal hyperalgesia in morphine-tolerant rats. Tolerance to the analgesic effect of morphine was reliably developed in rats following once daily intrathecal (onto the lumbosacral spinal cord) injection of 10 micrograms of morphine sulfate for 8 consecutive days as demonstrated by the decreased analgesia following morphine administration on day 8 as compared to that on day 1. In association with the development of morphine tolerance, thermal hyperalgesia to radiant heat developed in these same rats. Paw-withdrawal latencies were reliably decreased in morphine-tolerant rats as compared to nontolerant (saline) controls when tested on day 8 before the last morphine treatment and on day 10 (i.e., 48 hr after the last morphine treatment). The coincident development of morphine tolerance and thermal hyperalgesia was potently prevented by intrathecal coadministration of morphine with MK 801 (10 nmol) or GM1 (160 nmol), and partially by CNQX (80 nmol). MK 801 (5, 10 nmol, not 2.5 nmol) and CNQX (80, 160 nmol, not 40 nmol), but not GM1 (160 nmol), also reliably reversed thermal hyperalgesia in rats rendered tolerant to morphine when tested 30 min after each drug treatment on day 10 (48 hr after the last morphine treatment). The data indicate that thermal hyperalgesia develops in association with the development of morphine tolerance and that the coactivation of central NMDA and non-NMDA receptors is crucial for both the development and expression of thermal hyperalgesia in morphine-tolerant rats. Furthermore, intracellular PKC activation plays a critical role in the development of thermal hyperalgesia in morphine-tolerant rats.(ABSTRACT TRUNCATED AT 400 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1994

Effects of muscle electrical activity on the transmission of developing neuromuscular junction.

Miniature endplate potentials (MEPPS) caused by the spontaneous release of ACh from the growth cone of cholinergic neurons, are recorded by the whole-cell patch-clamp technique on a large number of 1-day cultured myoballs which have contact neurites of co-cultured neurons. Both muscle cell and neuron are dissociated from the 1-day-old (about stage 20) Xenopus embryo. Frequency and/or amplitude of MEPPs can obviously increase after the repetitive high-level depolarization caused by the stimuli on muscle cells. No detectable changes of single ACh receptor channel property are observed by using the single-channel recording technique. These results suggest that the mechanism of the increase of MEPPs after electrical activity of postsynaptic muscle cells probably involve some alteration of presynaptic membrane.

Acetylcholine↗
PubMed1993

Rapid identification of overlapping YACs in the MEN2 region of human chromosome 10 by hybridization with Alu element-mediated PCR products.

An overlapping set of 21 yeast artificial chromosomes (YACs) spanning the RET proto-oncogene [Takahashi et al., Oncogene 3 (1988) 571-578] and D10S102 markers on human chromosome 10 was isolated in a series of hybridization-based chromosomal walks in a YAC library. Genetic linkage analyses implicate this chromosomal region as the location of the gene (MEN2A) responsible for multiple endocrine neoplasia type 2A. Four YACs carrying a RET sequence-tagged site (STS) and two YACs carrying a D10S102 STS were used to initiate chromosome walks. These were based on hybridization of Alu element-mediated polymerase chain reaction (Alu-PCR) products from YACs to dot blots of Alu-PCR products from complex pools of YAC clones. The hybridization anchor content of YACs identified in the walks was confirmed by probing blots of Alu-PCR products from individual YACs and by comparing Alu-PCR fingerprints of each YAC. Ten hybridization-based Alu-PCR anchors and three STS anchors were ordered within eleven intervals created by the 21 overlapping YACs. The order of anchors requiring the fewest gaps in the YACs is consistent with the walking results and establishes the STS anchor order as D10S102-D10S94-RET. The overlapping set of YACs represents about 1.55 Mb of the human genome according to restriction mapping of four representative YACs in the contig. These results demonstrate the power of Alu-PCR hybridization for chromosomal walking and provide a rich source of overlapping YACs which can be used to identify candidate MEN2A genes.

Base Sequence↗
PubMed1993

Intrathecal treatment with dextrorphan or ketamine potently reduces pain-related behaviors in a rat model of peripheral mononeuropathy.

The therapeutic effects of dextrorphan and ketamine, two non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists, on neuropathic pain-related behaviors were examined in rats with peripheral mononeuropathy induced by loose ligation of the common sciatic nerve (chronic constrictive injury, CCI). Four daily intrathecal treatments (beginning 1 h after nerve ligation) with dextrorphan or ketamine (12.5-100 nmol) reliably attenuated hyperalgesia to radiant heat and spontaneous pain-related behaviors in CCI rats. Thermal hyperalgesia also was reduced in CCI rats receiving a single intrathecal treatment with either dextrorphan or ketamine (50 and 100 nmol for each compound) on day 3 after nerve ligation when thermal hyperalgesia was well developed. Since both dextrorphan and ketamine are currently utilized in other clinical applications, the results suggest a new therapeutic utility of these 'old' compounds in treatment of neuropathic pain syndromes resulting from peripheral nerve injury.

Animals↗
PubMed1993

Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging.

OBJECTIVE: To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities. DESIGN: Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history. SETTINGS: Hospital pediatric neurology clinic and private reading clinic. PATIENTS AND OTHER PARTICIPANTS VOLUNTEERS: individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years). INTERVENTIONS: Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images. MAIN OUTCOME MEASURES: (1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum. RESULTS: All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12). CONCLUSIONS: Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.

Adolescent↗
PubMed1993

A thin bite-force transducer with three-dimensional capabilities reveals a consistent change in bite-force direction during human jaw-muscle endurance tests.

The construction of a 2 mm-thick bite-force transducer, capable of measuring the magnitude and direction of a bite force in three dimensions, is described. The transducer is programmed to display the properties of a bite force on a computer monitor. A preliminary study was designed to test its performance. This took the form of endurance tests on three human subjects: the test was repeated on one subject. The direction of a sustained maximum incisal bite force was monitored while subjects clenched for as long as possible on the transducer. The initial bite force was directed about 10-15 degrees forward of the vertical. During the test the magnitude of the bite force was kept roughly constant but, for all four tests, its direction gradually changed until at the failure point it was nearly vertical. The consistency of the results suggests that the transducer is sufficiently accurate to be a useful tool for studying human jaw mechanics.

Acrylic Resins↗
PubMed1993

Fat tissue and fat suppression.

Fat tissues consist of fat cells, capillaries, and collagen fibers. In order to completely suppress the signals from fat tissues in clinical magnetic resonance imaging, the signal from capillaries and collagen fibers as well as from fat cells should all be suppressed. We have previously reported that fat signal can be uniformly suppressed by applying an optimized presaturation pulse. The inhomogeneously broadened fat peak of tissue spectrum is excited by the optimized pulse and dephased by a subsequent field gradient. The broadened water peak is not affected. In this paper we discuss a technique that suppresses signals from fat tissues completely as well as uniformly. This technique is based on the cancellation of fat and water signals in the same image voxel by combining the optimized selective excitation with the opposite phase imaging technique. Experimental and clinical images demonstrate that the new technique improves the delineation and depiction of anatomy in clinical fat suppression imaging.

Adipose Tissue↗
PubMed1993

Oxidant-scavenging activities of ampicillin and sulbactam and their effects on neutrophil functions.

Luminol-enhanced luminescence is a method used to measure formation of reactive oxygen intermediates important in the ability of neutrophils to kill microbes. Several studies have demonstrated that under some conditions of incubation, ampicillin can inhibit neutrophil-derived luminol-enhanced luminescence. We evaluated the mechanism(s) by which ampicillin inhibited the luminescent response of stimulated neutrophils. We also investigated sulbactam, a beta-lactamase inhibitor which has been given in combination with ampicillin and other beta-lactam antibiotics to increase their spectra, for possible similar effects. Both ampicillin and sulbactam attenuated luminol-enhanced luminescence by approximately 40%. Superoxide production was not prevented by added ampicillin, nor was superoxide scavenged by it. Myeloperoxidase reacts with H2O2 and Cl- to generate OCl-, which is believed to be the oxidizer of luminol that is primarily responsible for enhancement of neutrophil-derived luminescence. Hydroxyl radicals (HO.), which may also oxidize luminol, resulting in luminescence, can be formed from O2- and H2O2 via either myeloperoxidase-dependent (involving intermediate OCl-) or myeloperoxidase-independent (through a metal ion catalyst) reactions. Ampicillin scavenged H2O2 and OCl- and prevented 95% of Fenton reaction-generated HO. from reacting with 5,5-dimethyl-1-pyrroline-N-oxide. Sulbactam was found to scavenge OCl- and HO., but less avidly than ampicillin did. Neither ampicillin nor sulbactam inhibited myeloperoxidase activity. Sublethal concentrations of sulbactam had no significant effect on neutrophil killing of Staphylococcus aureus and Escherichia coli. Our results demonstrate a mechanism(s) by which ampicillin inhibits luminol-enhanced luminescence from stimulated neutrophils, namely, through scavenging of the oxidant(s) primarily responsible for the generation of luminescence.

Ampicillin↗
PubMed1993

Spatial patterns of increased spinal cord membrane-bound protein kinase C and their relation to increases in 14C-2-deoxyglucose metabolic activity in rats with painful peripheral mononeuropathy.

1. Three-dimensional spatial patterns of changes in membrane-bound protein kinase C (PKC) were examined in the lumbar spinal cords (L1-L5) of rats with an experimental painful peripheral mononeuropathy. Painful peripheral mononeuropathy was produced by loosely ligating the rat's common sciatic nerve, resulting in chronic constrictive nerve injury (CCI). Changes in spinal cord membrane-bound PKC distribution were assayed by employing an established quantitative [3H]-phorbol-12,13-dibutyrate ([3H]PDBu) autoradiographic assay, which includes spinal cord sectioning, incubation of spinal cord sections with [3H]PDBu, production of autoradiographs, and computer-assisted image processing. 2. Sciatic nerve ligation induced demonstrable thermal hyperalgesia in response to radiant heat stimulation and spontaneous pain-related behaviors (such as lifting of the nerve-ligated hind paw) in CCI rats 3, 7, and 10 days after unilateral sciatic nerve ligation. 3. Consistent with behavioral changes, CCI rats examined 3 or 10 days after sciatic nerve ligation displayed a three-dimensional pattern of increased membrane-bound PKC in the lumbar spinal cord (L1-L5) strikingly different from that of sham-operated rats: in the dorsoventral dimension, reliable increases in membrane-bound PKC occurred mainly within spinal cord laminae I-IV and V-VI in CCI rats; in the ipsilateral-contralateral dimension, changes in membrane-bound PKC were seen on both sides of the spinal cord in CCI rats with reliably higher levels of membrane-bound PKC on the side ipsilateral than on the side contralateral to sciatic nerve ligation; in the rostrocaudal dimension, increases in membrane-bound PKC in the spinal cord dorsal horns of CCI rats extended from spinal segments L2-L5. 4. Both three-dimensional increases in spinal cord membrane-bound PKC and nociceptive behaviors (thermal hyperalgesia and spontaneous pain behaviors) in CCI rats were reliably reduced after three daily intrathecal treatments with 80 nmol GM1 ganglioside (a glycosphingolipid shown to prevent PKC translocation/activation), the first of which was given 1 h after sciatic nerve ligation. This reduction was seen 24 h but not 7 days after the last GM1 ganglioside treatment. 5. This three-dimensional increase in membrane-bound PKC in the spinal cord dorsal horn of CCI rats displayed high correlations with thermal hyperalgesia and with spontaneous pain-related behaviors in CCI rats observed both 3 and 10 days after sciatic nerve ligation. Similar correlations were observed between decreases in levels of membrane-bound PKC in the spinal cord dorsal horn and the attenuation of nociceptive behaviors in CCI rats after three daily intrathecal treatments with GM1 ganglioside.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Combination of DNA single strand synthesis with PCR to construct mung bean trypsin inhibitor gene.

This paper using the synthesis of mung bean trypsin inhibitor gene as an example, presented a new method for gene synthesis. The principle of the method was based on the combination of the single strand strategy and the PCR technique. The synthesis was very simple, convenient and rapid. The mung bean trypsin inhibitor is a protein composed of 72 amino acid residues. Its amino acid sequence has been determined, but the DNA sequence of gene still unknown. The synthetic mung bean trypsin inhibitor gene was 248 bp in length. It contains the encoded sequence, the start and stop codons, the restriction sites of EcoRI and BamHI at both ends, The codon selection of the synthetic gene was carried out according to the codon usage of other plant protease inhibitor gene or plant gene. The synthetic double-stranded DNA was digested with EcoRI and BamHI or PstI first, then cloned into plasmid pUC19. The synthetic gene was proved to be correct by the restriction map and the sequence analysis using the dideoxy-mediated chain termination method.

Amino Acid Sequence↗
PubMed1993

The effects of glutamate and GABA (gamma-amino-butyric-acid) on spontaneous acetylcholine release at the neuromuscular junction in Xenopus laevis embryo cell cultures.

The miniature endplate currents (MEPC's) were recorded at the neuromuscular junction of Xenopus laevis embryo neuron-muscle co-cultured cells. These MEPC's were due to the spontaneous release of acetylcholine from the nerve terminal. After perfusion with glutamate (10 mumol/L), both frequency and amplitude of the MEPC's increased. After washing away of glutamate, this effect persisted. We named this phenomena "Long-Term Facilitation". GABA (20 mumol/L) on the other hand had an inhibitory effect on both frequency and amplitude of the MEPC's. After washing away of GABA, the MEPC frequency and amplitude increased. We named this effect "Post-Potentiation". Local perfusion experiments furthermore indicated that the effect of glutamate was restricted to the neuromuscular junction, the effect of GABA was restricted to the soma.

Acetylcholine↗