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Biomedical subjects

T Xu

Publications and source records attributed to T Xu.

At least 109 records · Page 6Linked to original sources
PubMed1997

Exploring the basis for Tai Chi Chuan as a therapeutic exercise approach.

For many centuries Tai Chi has been a martial art form, practiced primarily in Oriental cultures. For the past 300 years this movement approach has been used as an exercise form, practiced by millions of Chinese elderly people. To date, virtually no information exists about the therapeutic elements of this intriguing movement sequence. This article provides a historical review of existing documentation of reputed Tai Chi benefits. The 108 "forms" of Tai Chi Chuan are reduced to 10 composite forms for ease of application of these forms to older individuals within a reasonable time frame. An effort is set forth to identify the potential therapeutic elements within these forms.

Age Factors↗
PubMed1997

Kinetic studies of Ca2+ binding and Ca2+ clearance in the cytosol of adrenal chromaffin cells.

The Ca2+ binding kinetics of fura-2, DM-nitrophen, and the endogenous Ca2+ buffer, which determine the time course of Ca2+ changes after photolysis of DM-nitrophen, were studied in bovine chromaffin cells. The in vivo Ca2+ association rate constants of fura-2, DM-nitrophen, and the endogenous Ca2+ buffer were measured to be 5.17 x 10(8) M-1 s-1, 3.5 x 10(7) M-1 s-1, and 1.07 x 10(8) M-1 s-1, respectively. The endogenous Ca2+ buffer appeared to have a low affinity for Ca2+ with a dissociation constant around 100 microM. A fast Ca2+ uptake mechanism was also found to play a dominant role in the clearance of Ca2+ after flashes at high intracellular free Ca2+ concentrations ([Ca2+]), causing a fast [Ca2+]i decay within seconds. This Ca2+ clearance was identified as mitochondrial Ca2+ uptake. Its uptake kinetics were studied by analyzing the Ca2+ decay at high [Ca2+]i after flash photolysis of DM-nitrophen. The capacity of the mitochondrial uptake corresponds to a total cytosolic Ca2+ load of approximately 1 mM.

Acetates↗
PubMed1997

Self-report benefits of Tai Chi practice by older adults.

Older persons who are willing to begin exercise programs are often not willing to continue them. At the Atlanta FICSIT (Frailty and Injuries: Cooperative Studies of Intervention Techniques) site, individuals aged 70+ were randomized to Tai Chi (TC), individualized balance training (BT), and exercise control education (ED) groups for 15 weeks. In a follow-up assessment 4 months post-intervention, 130 subjects responded to exit interview questions asking about perceived benefits of participation. Both TC and BT subjects reported increased confidence in balance and movement, but only TC subjects reported that their daily activities and their overall life had been affected; many of these subjects had changed their normal physical activity to incorporate ongoing TC practice. The data suggest that when mental as well as physical control is perceived to be enhanced, with a generalized sense of improvement in overall well-being, older persons' motivation to continue exercising also increases.

Activities of Daily Living↗
PubMed1997

Status of the eradication of indigenous wild poliomyelitis in the People's Republic of China.

A large nationwide outbreak occurred in 1989-1990 in China, in which nearly 10,000 poliomyelitis cases were reported. After two rounds of oral poliovirus vaccine (OPV) supplemental activity in nearly every province in the 1992-1993 winter season, no wild poliovirus was detected in 1993 in 22 provinces in the middle of China that contained 86% of the population. During the first national immunization days (NIDs) conducted in December 1993 and January 1994, 83 million children 0-47 months of age were immunized. In 1994, wild poliovirus was identified in only 6 of 2397 children with stool specimens tested. After a second NID in December 1994 and January 1995, no wild poliovirus was detected in 1995 despite a very high level of virus surveillance. In summary, double-round mass supplemental OPV immunizations in children 0-3 years old in two consecutive winters eliminated wild poliovirus from 23% of the world's population (1.2 billion people).

Child, Preschool↗
PubMed1997

Evidence of increased cholecalciferol requirement in chicks with tibial dyschondroplasia.

A series of experiments was conducted to test the hypothesis that vitamin D utilization may not be as efficient in chicks with tibial dyschondroplasia (TD). The basal diet contained 1.0% Ca and 0.45% available P with no supplemental cholecalciferol (D3). Chicks from low TD (LTD) and high TD (HTD) selected lines were fed diets supplemented with various levels of vitamin D compounds and examined for rickets and TD. When chicks were fed a D3-deficient diet containing only 1.25 micrograms/kg added D3, HTD chicks had a greater incidence of severe rickets than LTD chicks (P < 0.05). The LTD chicks did not exhibit TD when fed a diet containing adequate (20 micrograms/kg) D3. The LTD chicks fed a diet supplemented with 5 micrograms/kg D3, however, had 22% incidence of TD. When HTD chicks were fed diets supplemented with 5 micrograms/kg D3 [control diet that meets NRC (1994) requirement for D3], 20 micrograms/kg D3, 5 micrograms/kg 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] or the combination of both D3 (20 micrograms/kg) and 1,25-(OH)2D3 (5 micrograms/ kg), TD incidence was highest in HTD chicks fed the control diet. When HTD chicks were fed diets with an increased dietary level of 1,25-(OH)2D3 (10 micrograms/kg) further reduction of TD incidence (P < 0.05) occurred. A potentially toxic level (Soares et al., 1983) of 1,25-(OH)2D3 (15 micrograms/kg) fed to HTD chicks resulted in still greater suppression of incidence of TD even though growth and feed intake in HTD chicks was greater than those of LTD chicks. It is concluded that the development of TD in HTD chicks is associated with subnormal ability to metabolize vitamin D.

Animals↗
PubMed1997

[Pharmacological studies of luohanguo yanhou tablet].

Luohanguo Yanhou Tablet possesses the action of cotton ball granuloma of mice and the auricular edema induced by xylol, and also inhibiting the swelling of rat hind paw induced by carrageenin. The tests of mice writhing induced by acetic acid showed that the preparation had obvious analgesic action. It also possesses the obvious bacteriostatic action in vitro on five kinds of strains.

Analgesics↗
PubMed1996

Transfer of a gene encoding the anticandidal protein histatin 3 to salivary glands.

Mucosal candidiasis, the most common opportunistic fungal infection in human immunodeficiency virus (HIV)-infected patients, is an early sign of clinically overt acquired immunodeficiency syndrome (AIDS) and an important cause of morbidity, particularly in HIV-infected children. The appearance of azole-resistant strains of Candida albicans had made clinical management of candidiasis increasingly difficult. We propose a novel approach to the management of candidal infections that involves the use of naturally occurring antifungal proteins, such as the histatins. Histatins are a family of small proteins that are secreted in human saliva. We have constructed recombinant adenovirus vectors that contain the histatin 3 cDNA. These vectors are capable of directing the expression of histatin 3 in the saliva of rats at up to 1,045 micrograms/ml, well above the levels found in normal human saliva. The adenovirus-directed histatin demonstrated a 90% candidacidal effect in the timed-kill assay against both fluconazole-susceptible and fluconazole-resistant strains of C. albicans and inhibited germination by 45% in the same strains. These studies suggest that a gene transfer approach to overexpress naturally occurring antifungal proteins may be useful in the management of mucosal candidiasis.

Adenoviridae↗
PubMed1996

The effect of mild trypsin digestion of F1 on energy coupling in the mitochondrial ATP synthase.

Mild trypsin digestion of isolated bovine-heart mitochondrial F1-ATPase removed the first 15 residues from the N-terminus of subunit alpha under conditions in which other F1 subunits were apparently untouched. When the trypsinized F1 (TF1) was reconstituted with the F0 sector in the mitochondrial membrane (USMP), the ATP hydrolase activity acquired oligomycin sensitivity but ATP hydrolysis was decoupled from proton pumping. TF1 added to USMP did not block the proton channel in F0 as the native F1 did. AMP-PNP inhibited proton conductivity in reconstituted F1-USMP but this effect was lost in reconstituted TF1-USMP. These results indicate that the N-terminus of the F1 alpha subunit plays a critical role in the conformational communication between F1 and F0.

Adenosine Triphosphate↗
PubMed1996

Candidacidal activity of human salivary histatin recombinant variants produced by site-directed mutagenesis.

Histatin 5 (Hst5) is a 24-amino acid (aa) member of the Hst family that is found in human salivary secretions and exhibits candidacidal activity. Hst5 contains a 13-aa region that alone is capable of killing fungal pathogens and is referred to as the functional domain. To investigate the role of specific aa located within the functional domain, the pRSET bacterial expression system was used to produce recombinant Hst5 (re-Hst5) and several re-variants that were generated by site-directed mutagenesis. The vector pRSETC expresses genes of interest as fusion proteins attached to the carboxy end of an N-terminal His6 tag that binds to nickel (Ni2+). The re-variants were generated using the polymerase chain reaction (PCR) and had Gly substituted for either the His, Glu or Lys/Arg within the functional domain. PCR products that encoded either the wild-type or variant forms of re-Hst5 were inserted into pRSETC and produced as fusion proteins which were affinity purified from cell lysates by Ni(2+)-Sepharose chromatography. Fusion proteins were digested with CNBr and re-Hsts were purified by reversed-phase high performance liquid chromatography (RP-HPLC). Re-Hsts were tested in bioassays to measure the ability to kill both Candida albicans (C. albicans) blastoconidia and spheroplasts which were generated by removal of the cell wall. In both assays, re-Hst5 displayed dose-dependent candidacidal activity that was nearly identical to that of native Hst5 purified from human salivary secretions. Re-Hst5 variants with either Glu or Lys/Arg substitutions demonstrated significantly lower candidacidal activity in both assays, while the variant with His mutated showed essentially no activity at physiological concentrations. These results indicate that acidic and basic aa within the functional domain contribute to candidacidal activity and that the His are essential for candidacidal activity. Additionally, since C. albicans spheroplasts were also susceptible to Hsts, the cell wall is not an essential component in the Hst mechanism of candidacidal action.

Amino Acid Sequence↗
PubMed1996

KUZ, a conserved metalloprotease-disintegrin protein with two roles in Drosophila neurogenesis.

During neurogenesis in Drosophila both neurons and nonneuronal cells are produced from a population of initially equivalent cells. The kuzbanian (kuz) gene described here is essential for the partitioning of neural and nonneuronal cells during development of both the central and peripheral nervous systems in Drosophila. Mosaic analyses indicated that kuz is required for cells to receive signals inhibiting the neural fate. These analyses further revealed that the development of a neuron requires a kuz-mediated positive signal from neighboring cells. The kuz gene encodes a metalloprotease-disintegrin protein with a highly conserved bovine homolog, raising the possibility that kuz homologs may act in similar processes during mammalian neurogenesis.

Amino Acid Sequence↗
PubMed1996

Cholecystokinin octapeptide reverses the kappa-opioid-receptor-mediated depression of calcium current in rat dorsal root ganglion neurons.

Although the cholecystokinin octapeptide (CCK-8) is reported to antagonize the kappa-opioid-receptor-mediated analgesic effect in spinal cord, its mechanism and sites of action remain obscure. In the present study, the whole-cell patch-clamp recording technique was employed to examine the effect of kappa-opioid agonist U50488H on voltage-gated calcium channels and the interaction between the CCK-8 and U50488H in acutely isolated rat dorsal root ganglion neurons. The results indicate that the calcium currents elicited in dorsal root ganglion neurons can be depressed by U50488H, an effect readily reversed by the kappa-opioid receptor antagonist Nor-BNI or by the antiopioid peptide CCK-8. The effect of the CCK-8 can be abolished by the CCK-B receptor antagonist, L365,260. While CCK-8 showed a potent opioid-reversal effect, it by itself exerted a slight inhibitory effect on calcium current. This novel observation in the dorsal root ganglion neurons indicates that CCK-8 can antagonize the kappa-opioid-receptor-mediated depressant effect on voltage-gated calcium current, and this antagonizing effect appears to be mediated via CCK-B receptor.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1996

Reducing frailty and falls in older persons: an investigation of Tai Chi and computerized balance training. Atlanta FICSIT Group. Frailty and Injuries: Cooperative Studies of Intervention Techniques.

OBJECTIVE: To evaluate the effects of two exercise approaches, Tai Chi (TC) and computerized balance training (BT), on specified primary outcomes (biomedical, functional, and psychosocial indicators of frailty) and secondary outcomes (occurrence of falls). DESIGN: The Atlanta FICSIT (Frailty and Injuries: Cooperative Studies of Intervention Techniques), a prospective, randomized, controlled clinical trial with three arms (TC, BT, and education [ED]. Intervention length was 15 weeks, with primary outcomes measured before and after intervention and at 4-month follow-up. Falls were monitored continuously throughout the study. SETTING: Persons aged 70 and older living in the community. PARTICIPANTS: A total of 200 participants, 162 women and 38 men; mean age was 76.2. MEASUREMENTS: Biomedical (strength, flexibility, cardiovascular endurance, body composition), functional (IADL), and psychosocial well-being (CES-D scale, fear of falling questionnaire, self-perception of present and future health, mastery index, perceived quality of sleep, and intrusiveness) variables. RESULTS: Grip strength declined in all groups, and lower extremity range of motion showed limited but statistically significant changes. Lowered blood pressure before and after a 12-minute walk was seen following TC participation. Fear of falling responses and intrusiveness responses were reduced after the TC intervention compared with the ED group (P = .046 and P = .058, respectively). After adjusting for fall risk factors, TC was found to reduce the risk of multiple falls by 47.5%. CONCLUSIONS: A moderate TC intervention can impact favorably on defined biomedical and psychosocial indices of frailty. This intervention can also have favorable effects upon the occurrence of falls. Tai Chi warrants further study as an exercise treatment to improve the health of older people.

Accidental Falls↗
PubMed1996

ATP-sensitive potassium channels regulate stimulated ANF secretion in isolated rat heart.

Perfused hearts (n = 127) were exposed to acute hypoxia (10% O2 for 12 or 20 min) or left atrial stretch (increase in atrial pressure) in the presence or absence of 100 mumol/l ATP-sensitive potassium channel blocker (tolbutamide) or openers (pinacidil and diazoxide). Hypoxia alone elicited a prolonged atrial natriuretic factor (ANF) release, peaking at 74% over baseline (P < 0.01); with tolbutamide, ANF secretion peaked at 132% over baseline (P < 0.01). Pinacidil and diazoxide abolished the ANF response to hypoxia (P < 0.01). Atrial stretch alone (1 mmHg) transiently (2 min) increased ANF by 56% (P < 0.05); with tolbutamide, ANF increased transiently by 124% and showed a prolonged increase of 52% (P < 0.05). With tolbutamide, graded stretch (0.5-2.3 mmHg) induced a bell-shaped transient (2-min) increase of ANF release [-3% at 0.5 mmHg, 124% (P < 0.05) at 1.0 mmHg, 80% (P < 0.05) at 1.48 mmHg, and 14% at 2.22 mmHg] and a saturating prolonged ANF response. Tolbutamide increased the ANF response nonsignificantly at lower doses (30 mumol/l) and had no effect at 1 mumol/l. Pinacidil abolished the stretch-induced ANF release. These results suggest that ATP-sensitive potassium channels are extremely potent modulators of stimulated ANF secretion.

Adenosine Triphosphate↗
PubMed1996

[Effect of acupuncture on the restrained state of stomach after injecting TFP in zusanli point].

A model of the reducible movement of stomach in a big mouse was set up by injecting solution of 654-2. At first, the state of stomach movement was proved to be improved by acupuncture. After that, the activity of CaM in Zusanli point was lost by injecting TFP and effect of acupuncture on the stomach movement was studied. The result showed that the effect of acupuncture was abolished during manipulating the needles for 5 minutes. But retaining the needle for 25 minutes, the effect of acupuncture was recovered gradually. It indicates that the activity of Ca-CaM compounds may be of the key factor of acupuncture effect and one of the important links of the functional activity of meridians and collaterals.

Acupuncture Points↗
PubMed1995

The 10-Hz rhythm in the sympathetic nerve activity of cats, rats and rabbits.

Since the 10-Hz rhythmic activity in the sympathetic nerves was reported only in cats, we examined whether the activity of the same frequency could be observed in rats and rabbits as well as in the cats. Histograms of inter-burst-peak intervals of discharges of the renal nerves revealed that the 100 ms interval activity, the reverse of the 10-Hz, was observed in all the three mammals, of which the baroreceptor afferents were intact or inactivated. Further, the same frequency activity could be evoked by intermittent electrical stimulation of the dorsolateral funiculus of the cervical cord in spinal animals. It was suggested that the 10-Hz rhythmic activity in the sympathetic nerves was a common phenomenon throughout mammals and this activity was produced in the spinal cord. The physiological significance of the 10-Hz activity in the sympathetic nerves was discussed.

Afferent Pathways↗
PubMed1995

Recombinant histatins: functional domain duplication enhances candidacidal activity.

Histatin 3 (Hst3) is a 32-amino-acid (aa) His-rich protein with antimicrobial activity found in human salivary secretions. To explore further the structure/function relationship of Hst, we utilized a bacterial system for the efficient production of recombinant Hst3 (re-Hst3) and Hst variants. Previously, we demonstrated that the middle portion of Hst3 (aa 13-24) contains the functional domain responsible for killing Candida albicans. Using PCR and splice overlap extension, a Hst variant (re-Hst3rep) was made in which the functional domain was repeated in tandem. Using the pRSET bacterial expression system, re-Hst3 and the variant re-Hst3rep were produced as chimeric fusions and were isolated from bacterial sonicates by affinity chromatography. Affinity purified fusion proteins were digested with CNBr and re-Hst were separated from their fusion partners by reverse-phase high-performance liquid chromatography. The activity of re-Hst3 and re-Hst3rep was compared to that of native Hst3 from human salivary secretions in the C. albicans killing assay. The LD50 values for candidacidal activity of native Hst3, re-Hst3 and re-Hst3rep were 7.2, 6.8 and 4.1 nmol/ml, respectively. At lower concentrations re-Hst3rep was five times more active than native Hst3 or re-Hst3 and at even lower concentrations re-Hst3rep exhibited significant candidacidal activity while native Hst3 and re-Hst3 were inactive. These results demonstrate an expression system for production of biologically active functional Hst and Hst variants and shows that repetition of the functional domain of Hst3 enhances candidacidal activity.

Amino Acid Sequence↗