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Biomedical subjects

X M Wang

Publications and source records attributed to X M Wang.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Thermodynamic analysis of saturation degree of O2 in myoglobin and hemoglobin].

OBJECTIVE: To analyze the saturation degree of O2 in myoglobin and hemoglobin. METHOD: Analysis is based on thermodynamic concepts such as Gibbs free energy, entropy, internal energy and so on. RESULT: The analytical result were consistent with the results of experiments and analysis made by other authors. CONCLUSION: The thermodynamic method is feasible in analysing O2 saturation degree in myoglobin and hemoglobin.

Hemoglobins↗
PubMed1999

[Temperature environment and the heat exchange of astronaut in the emergency landing areas].

OBJECTIVE: To analyze the temperature environment of different emergency landing areas and discuss the heat exchange between astronaut and the temperature environment. In addition, countermeasures against the emergency temperature environment were discussed. METHOD: Heat exchange equation between man and environment was built using the law of energy conservation, and factors that affect the heat balance of human body were discussed. RESULT: It was found that temperature, humidity, air pressure, velocity of wind and solar radiation are factors affecting the thermal balance of the astronaut. CONCLUSION: It is important for an astronaut to act properly and use the living devices and the environment conditions correctly during the emergency landing.

Body Temperature Regulation↗
PubMed1998

Regeneration of supraspinal axons after transection of the thoracic spinal cord in the developing opossum, Didelphis virginiana.

When the thoracic spinal cord of the North American opossum is transected early in development, supraspinal axons grow through the lesion. In the experiments reported here, we asked whether regeneration of cut axons contributes to such growth. Fast Blue (FB) was injected into the lumbar cord on postnatal day (PD)5, 8, 15, or 20. Five days later, FB was removed by gentle suction, and the spinal cord was transected at thoracic levels. Fourteen days later, rhodamine B dextran was injected between the site of the FB injection and the lesion. The pups were maintained for an additional 7-10 days before killing and perfusion. We assumed that supraspinal neurons that contained FB survived axotomy and those that contained both FB and rhodamine B dextran supported regenerating axons. In the PD5 group (lesioned at PD10), regenerative growth was documented for axons originating in all of the supraspinal nuclei that innervate the lumbar cord by PD10. When the injections were made at the later ages, however, neurons that supported regenerative growth were fewer in number and regionally restricted. In some cases, they were limited primarily to the red nucleus, the medullary raphe, and the adjacent reticular formation. Our results show that regeneration of cut axons contributes to growth of supraspinal axons through the lesion after transection of the thoracic cord in developing opossums and that the critical period for regenerative growth is not the same for all axons.

Amidines↗
PubMed1998

Use of a photoactivatable lipid to probe the topology of PA63 of Bacillus anthracis in lipid membranes.

The protective antigen of Bacillus anthracis is a key protein that promotes the translocation of the enzymatic moieties of the two toxins of B. anthracis into the cell cytoplasm. The membrane topology of the active form of the protective antigen (PA63) was investigated by proteolysis of PA63 inserted into liposomes containing a photoactivatable, radioactive lipid, and characterization of the N-terminal moiety of the deeply-inserted (and therefore radiolabeled) peptides. A single sequence starting at residue Ala258 was identified. Fourier-transform infrared spectroscopy showed that the protected peptide was mainly adopting a beta-sheet structure whose orientation was compatible with a transmembrane organization.

Antigens, Bacterial↗
PubMed1998

Origin, course, and laterality of spinocerebellar axons in the North American opossum, Didelphis virginiana.

Spinocerebellar axons have been studied extensively in placental mammals, but there have been no full reports on their origin, laterality, or spinal course in any marsupial. We have used the North American opossum (Didelphis virginiana) to obtain such information and to ask whether any spinocerebellar neurons innervate both the anterior and posterior lobes of the cerebellum through axonal collaterals. To identify spinal neurons that project to the cerebellum, we employed the retrograde transport of Fluoro-Gold (FG) from the anterior lobe, the main target of spinocerebellar axons. In some cases, cerebellar injections of FG were combined with hemisections of the rostral cervical or midthoracic spinal cord, so that laterality of spinocerebellar connections could be established. To determine whether single neurons project to both the anterior lobe and the posterior lobe, injections of Fast Blue (FB) into the anterior lobe were combined with injections of Diamidino yellow (DY) or rhodamine B dextran (RBD) into the posterior lobe, or vice versa. Following injections of FG into the anterior lobe, neurons were labeled throughout the length of the spinal cord, which differed in laminar distribution and laterality of their projections. Among other areas, neurons were labeled in the central cervical nucleus, the nucleus centrobasalis, Clarke's nucleus, the dorsal horn dorsal spinocerebellar tract area, the spinal border region, and Stilling's nucleus. When anterior lobe injections of FB were combined with injections of RBD or DY into the posterior lobe, or vice versa, some double-labeled neurons were present in all major spinocerebellar groups. Cerebellar injections of FG also retrogradely labeled spinocerebellar axons, allowing us to document their locations in the gray matter as well as within the periphery of the lateral and ventral funiculi at all spinal levels. A few spinocerebellar axons also were found in the dorsal funiculus (a dorsal column-spinocerebellar tract), which appeared to originate from neurons in the dorsal part of Clarke's nucleus from the ninth thoracic segment to the first lumbar segment. Our results indicate that spinocerebellar axons in the marsupial opossum are generally comparable in origin, course, and laterality to the same axons in the placental mammals studied to date.

Animals↗
PubMed1998

Adult opossums (Didelphis virginiana) demonstrate near normal locomotion after spinal cord transection as neonates.

When the thoracic spinal cord of the North American opossum (Didelphis virginiana) is transected on postnatal day (PD) 5, the site of injury becomes bridged by histologically recognizable spinal cord and axons which form major long tracts grow through the lesion. In the present study we asked whether opossums lesioned on PD5 have normal use of the hindlimbs as adults and, if so, whether that use is dependent upon axons which grow through the lesion site. The thoracic spinal cord was transected on PD5 and 6 months later, hindlimb function was evaluated using the Basso, Beattie, and Bresnahan (BBB) locomotor scale. All animals supported their weight with the hindlimbs and used their hindlimbs normally during overground locomotion. In some cases, the spinal cord was retransected at the original lesion site or just caudal to it 6 months after the original transection and paralysis of the hindlimbs ensued. Surprisingly, however, these animals gradually recovered some ability to support their weight and to step with the hindlimbs. Similar recovery was not seen in animals transected only as adults. In order to verify that descending axons which grew through the lesion during development were still present in the adult animal, opossums subjected to transection of the thoracic cord on PD5 were reoperated and Fast blue was injected several segments caudal to the lesion. In all cases, neurons were labeled rostral to the lesion in each of the spinal and supraspinal nuclei labeled by comparable injections in unlesioned, age-matched controls. The results of orthograde tracing studies indicated that axons which grew through the lesion innervated areas that were appropriate for them.

Age Factors↗
PubMed1998

Demonstration of identical strains of mutans streptococci within Chinese families by genotyping.

The aim of this study was to investigate the intra-familial distribution of mutans streptococci in some Chinese families. Eighteen families consisting of mother, father and a 3-yr-old child without any older siblings participated. Clinical examination and interview were performed to obtain information about level of mutans streptococci in saliva, caries prevalence scored by DMFT or deft, general health, diet regimens, breast-feeding time, principal caretaker of the child and the parents' profession. At the same appointment, two pooled plaque samples from each subject were collected with the tips of sterile tooth picks. From these plaque samples, mutans streptococci were isolated on MSB-agar plates and identified by serotyping. Pure isolates were obtained from all subjects of 11 families. These isolates were genotyped using restriction endonuclease HaeIII. The results showed that in 4 families the mothers shared genotype with the child, and in 3 families it was the father and the child who harboured a similar genotype. In 2 families, all subjects harboured an identical genotype. Further, the spouses in one parental pair showed an identical genotype, and, finally, in one family all subjects harboured their unique genotypes. None of the investigated factors could explain the differences in the intra-familial distribution of mutans streptococci. The pattern of similar genotypes in these Chinese families differs from that reported for western families.

Adult↗
PubMed1998

Effects of 5-azacytidine and butyrate on differentiation and apoptosis of hepatic cancer cell lines.

OBJECTIVE: To determine the cellular effects of 5-azacytidine (5-azaC) and sodium butyrate on two human liver cancers, HepG2 and Hep3B. SUMMARY BACKGROUND DATA: Primary liver cancer is a significant health problem; treatment options are limited and prognosis is poor. Recent studies have focused on the role that programmed cell death (i.e., apoptosis) plays in both normal and neoplastic growth: certain genes can either suppress (e.g., Bcl-2, Bcl-xL) or promote (e.g., Bik, Bax, Bak) apoptosis. The identification of novel agents targeted to specific molecular pathways may be beneficial in the treatment of this disease. METHODS: Human liver cancer cell lines HepG2 and Hep3B were treated with 5-azaC alone, butyrate alone, or 5-azaC and butyrate. Morphologic and proliferative changes were assessed by light microscopy and 5-bromo-2'-deoxyuridine staining; flow cytometry was used to determine cell cycle characteristics. Apoptosis was assessed by DNA laddering and the in situ apoptosis detection assay using the TdT-mediated dUTP nick end labeling method. In addition, total RNA and protein were analyzed by ribonuclease protection and Western blot, respectively, to assess changes in the expression of apoptosis-related genes. RESULTS: Treatment with either 5-azaC or butyrate inhibited cell growth and induced apoptosis in both HepG2 and Hep3B cells; the combination of 5-azaC and butyrate was not more effective than either agent alone. 5-azaC alone resulted in a more differentiated-appearing morphology and G2 cell cycle arrest in both cell lines. Treatment with 5-azaC or butyrate affected the expression levels of proteins of the Bcl-2 family. CONCLUSIONS: Both 5-azaC and butyrate induced apoptosis in the HepG2 and Hep3B liver cancer cells; 5-azaC treatment alone produced G2 arrest in both cell lines. Proteins of the Bcl-2 family may play a role in the cellular changes that occur with treatment, but further studies are required to define this potential role. Products of the apoptotic pathway may prove to be useful therapeutic targets in the treatment of hepatic cancers.

Antimetabolites, Antineoplastic↗
PubMed1998

alpha2-adrenoceptors modulate NMDA-evoked responses of neurons in superficial and deeper dorsal horn of the medulla.

Extracellular single unit recordings were made from neurons in the superficial and deeper dorsal horn of the medulla (trigeminal nucleus caudalis) in 21 male rats anesthetized with urethan. NMDA produced an antagonist-reversible excitation of 46 nociceptive as well as nonnociceptive neurons. Microiontophoretic application of a preferential alpha2-adrenoceptor (alpha2AR) agonist, (2-[2, 6-dichloroaniline]-2-imidazoline) hydrochloride (clonidine), reduced the NMDA-evoked responses of 86% (6/7) of nociceptive-specific (NS) neurons, 82% (9/11) of wide dynamic range (WDR) neurons, and 67% (4/6) of low-threshold (LT) neurons in the superficial dorsal horn. In the deeper dorsal horn, clonidine inhibited the NMDA-evoked responses of 94% (16/17) of NS and WDR neurons and 60% (3/5) of LT neurons. Clonidine facilitated the NMDA-evoked responses in 14% (1/17) of NS, 9% (1/11) of WDR, and 33% (2/6) of LT neurons in the superficial dorsal horn. Idazoxan, an alpha2AR antagonist, reversed the inhibitory effect of clonidine in 90% (9/10) of neurons, whereas prazosin, an alpha1-adrenoceptor antagonist with affinity for alpha2BAR, and alpha2CAR, were ineffective. We suggest that activation of alpha2ARs produces a predominantly inhibitory modulation of the NMDA-evoked responses of nociceptive neurons in the medullary dorsal horn.

Adrenergic alpha-Agonists↗
PubMed1998

[Inhibition of the expression of delta opioid receptor mRNA by long-term exposure of NG-108-15 cell line to delta opioid agonists].

We used the method of reverse transcription-polymerase chain reaction (RT-PCR) to observe the effects of long-term administration of peptide delta opioid receptor agonist DPDPE and non-peptide delta agonist BW373U86 on the mRNA expression of delta receptor and the possible difference between the two agonists. The results showed: (1) the level of delta receptor mRNA decreased significantly 24-48 h after administration of DPDPE; the effect of BW373U86 lasted only 24 h; and (2) DPDPE produced a significant decrease of delta-receptor mRNA at 10(-6) mol/L, whereas BW373U86 was effective only at 10(-5) mol/L. These results suggest that long-term administration of both peptide delta opioid receptor agonist (24, 48 h) and non-peptide delta opioid agonist (24 h) significantly decreased mRNA expression of delta opioid receptor and the effect of peptide agonist DPDPE seems to be stronger and last longer than that of non-peptide agonist BW373U86.

Analgesics, Opioid↗
PubMed1998

[Changes in the binding characteristics of central kappa-opioid receptor during the development of 100 Hz electroacupuncture (EA) tolerance in rats].

The effect of repetitive 100 Hz EA stimulation on the characteristics of binding of kappa opioid receptors in discrete brain regions and the spinal cord of rats was investigated by radioligand binding assay. 100 Hz EA was administered once a day (30 min) for 7 d. Changes in Bmax and Kd of kappa opioid receptors of 4 discrete brain regions (cortex, midbrain, pons-medulla and striatum) and spinal cord were observed at d 1, 3, 5 and 7, respectively. It was found that the numbers (Bmax) of kappa opioid receptors of all the brain regions observed were decreased during the development of 100 Hz EA tolerance with a differential time course. In rat cortex and pons-medulla, a marked down regulation of kappa opioid receptors occurred within 24 h and remained at a low level throughout the observation. The Bmax of kappa receptor in spinal cord showed a bell-shaped curve, i.e., up regulation in the first 5 days and down regulation at d 7. In contrast a slow and steady down regulation was found in the midbrain and striatum, matching the course of development of 100 Hz EA tolerance. No significant changes in Kd of [3H]-U69593 were found except for a decrease of Kd in midbrain. In conclusion, administration of 100 Hz EA 30 min per day for 7 consecutive days resulted in a significant down regulation of kappa opioid receptor in CNS, especially in midbrain and striatum.

Animals↗
PubMed1998

[A primary study on the relationship between the weight of newborn and sucking pressure]

OBJECTIVE:In this study, the main aim is to investigate the relationship between the weight of newborn and sucking pressure.the relationship between the weight of 26 cases health newborn and sucking pressure was analyzed with "oral air manometers computer analysis system".The result showed that the relationship of both corelated positively.It showed that sucking pressure is one of the indication which reflects the condition of growth and development of newborn.

Journal Article↗
PubMed1998

Psoralen photochemotherapy, clinical efficacy, and photomutagenicity: the role of molecular epidemiology in minimizing risks.

Photochemotherapy employing 8-methoxypsoralen and ultraviolet radiation (PUVA) is widely used in the treatment of psoriasis. The photoactivation of psoralens in skin cells leads to DNA photoadduct formation which may be responsible for the efficacy of PUVA. Subsequent mutations may lead to the increased incidence of squamous cell carcinoma (SCC). Mutations in the p53 tumor suppressor gene have been detected in many human cancers. In this review, p53 mutation spectra in murine and human SCC are compared to those obtained from murine cells and skin treated with PUVA as well as to the p53 mutation spectrum in human solar SCC. While the expected psoralen-type mutations at alternating AT sites were detected in the treated cells and murine SCC (average frequency > 40%), such mutations were not commonly detected in the human SCC (< 10%). Other common mutations in the human SCC included: CG-->TA transitions (18%) and CG-->AT and TA-->GC transversions (17 and 25%, respectively). In addition, the frequency of UVB-type mutations at dipyrimidine sites (CC-->TT) in the SCC PUVA-treated psoriasis patients was comparable to that in patients with SCC from only solar exposure. A review of therapeutic history of these patients showed that many had also received UVB phototherapy. Furthermore, because sunlight is thought to be beneficial for psoriasis, nontherapeutic, casual UVB exposure cannot be excluded. Thus, the PUVA SCC may have arisen from the solar mutations and PUVA may enhance tumor progression by other epigenetic effects.

Ficusin↗
PubMed1998

The inhibitory effects of pravastatin on natural killer cell activity in vivo and on cytotoxic T lymphocyte activity in vitro.

BACKGROUND: We have reported that heart transplant recipients treated with pravastatin demonstrate decreases in the incidence of clinically severe acute rejection episodes, the incidence and progression of transplant coronary vasculopathy, and natural killer cytotoxicity. These patients also exhibited a significant improvement in 1-year allograft survival. Because of these clinical findings suggesting an immunosuppressive effect of pravastatin unique to transplant recipients and the unclear role of natural killer cells in allograft rejection, we postulated that pravastatin may exert its immunomodulatory effect by acting with cyclosporine to alter T lymphocyte function. METHODS: Twenty patients randomized into an ongoing trial of pravastatin after heart transplantation were monitored serially for natural killer cell cytotoxicity. In a separate experiment, lymphocytes isolated from normal volunteers were treated with various combinations of pravastatin and cyclosporine and tested for cytotoxic T lymphocyte toxicity in a one-way mixed lymphocyte reaction. RESULTS: Pravastatin-treated heart transplant recipients exhibited a decrease in natural killer cell cytotoxicity (9.8% mean natural killer cell cytotoxicity vs 22.1% in the control group, p < 0.01). In the one-way mixed lymphocyte reaction with blood obtained from control subjects, there was a synergistic inhibition of cytotoxic T lymphocyte activity when the cells were cultured in a combination of pravastatin and cyclosporine (20.3% mean cytotoxicity of target cells vs 41.4% in the control group, p < 0.01). CONCLUSIONS: Pravastatin exerts an immunosuppressive effect in heart transplant recipients as expressed by a reduction in rejection and natural killer cell cytotoxicity. Pravastatin and cyclosporine act synergistically to reduce cytotoxic T lymphocyte activity. This synergistic effect of pravastatin and cyclosporine may explain why this immunosuppressive effect is unique to transplant recipients.

Adjuvants, Immunologic↗
PubMed1997

Structure and interaction of PA63 and EF (edema toxin) of Bacillus anthracis with lipid membrane.

The secondary structures of the two components of the Bacillus anthracis edema toxin, protective antigen (PA63) and edema factor (EF), as well as the two EF mutants: CYA30 (containing the N-terminal PA63-binding domain) and CYA62 (containing the C-terminal catalytic domain) were investigated as a function of pH in the absence and in the presence of phospholipid vesicles using attenuated total reflection Fourier transform infrared spectroscopy. Secondary structures were independent of pH, whereas, in all cases, structural modifications were observed upon lipid binding. The ability of PA63 and EF to undergo hydrogen/deuterium exchange was evaluated. The binding of these proteins and the mutants to the lipid membrane was also characterized and it was demonstrated that the association of PA63 to the lipid bilayer was pH-dependent, while the binding of EF to the lipid membrane took place at both neutral and acidic pH. Interestingly, the two EF mutants are showing different lipid binding properties in response to pH: CYA30 has a strong pH-dependence whereas CYA62, as EF, binds to the lipid vesicles at all pHs. For the two proteins characterized by a pH-dependent lipid binding, the reversibility of binding upon neutralization was tested and binding of PA63 to the membrane was found to be irreversible whereas that of CYA30 was reversible.

Antigens, Bacterial↗
PubMed1997

Developmental plasticity of selected spinocerebellar axons. Studies using the North American opossum, Didelphis virginiana.

When the thoracic spinal cord of the opossum is hemisected at postnatal day 5 or 8, but not at day 12 or later ages, spinocerebellar axons which originate from spinal border cells, the sacral/coccygeal ventrolateral nucleus, and Stilling's nucleus grow through the lesion and reach the cerebellum. The critical period for such growth is comparable to that reported previously for spinocerebellar axons originating within Clarke's nucleus and for axons of the fasciculus gracilis, but shorter than that for most descending spinal axons. It appears, therefore, that differences exist in the ability of ascending and descending axons to traverse a lesion of their spinal pathway during development.

Animals↗
PubMed1997

Function of disintegrin-like/cysteine-rich domains of atrolysin A. Inhibition of platelet aggregation by recombinant protein and peptide antagonists.

Snake venom hemorrhagic metalloproteinase toxins that have metalloproteinase, disintegrin-like and cysteine-rich domains are significantly more potent than toxins with only a metalloproteinase domain. The disintegrin-like domains of these toxins differ from the disintegrin peptides found in crotalid and viperid venoms by the nature of their different disulfide bond structure and, in lieu of the disintegrins' signature Arg-Gly-Asp (RGD) integrin binding sequence, there is an XXCD disulfide-bonded cysteinyl sequence in that region. Due to these apparent differences, the contribution to the overall function of the hemorrhagic metalloproteinases by the disintegrin-like domain has been unknown. In this investigation we have expressed in insect cells the disintegrin-like/cysteine-rich (DC) domains of the Crotalus atrox hemorrhagic metalloproteinase atrolysin A and demonstrated that the recombinant protein (A/DC) can inhibit collagen- and ADP-stimulated platelet aggregation. Using synthetic peptides, we have evidence that the region of the disintegrin-like domain that is positionally analogous to the RGD loop of the disintegrins is the site responsible for inhibition of platelet aggregation. For these synthetic peptides to have significant inhibitory activity, the -RSECD- cysteinyl residue must be constrained by participation in a disulfide bond with another cysteinyl residue. The two acidic amino acids adjacent to the middle cysteinyl residue in these peptides are also important for biological activity. These studies emphasize a functional role for the disintegrin-like domain in toxins and suggest structural possibilities for the design of antagonists of platelet aggregation.

Amino Acid Sequence↗