Biomedical subjects

L F Zhang

Publications and source records attributed to L F Zhang.

At least 19 recordsLinked to original sources

PubMed2006

FK506 in the treatment of children with nephrotic syndrome of different pathological types.

OBJECTIVE: To evaluate the efficacy of FK506 in the treatment of children with nephrotic syndrome of different underlying pathology. METHODS: 12 patients were treated with FK506 with a dosage of 0.1 - 0.15 mg/kg/d while corticosteroid dose was tapered stepwise. This therapeutic course lasted 3 - 6 months during which the plasma concentration ofFK506 was monitored. RESULTS: 12 children with different pathological types nephrotic syndrome were treated with FK506, including 4 cases of MCN, 6 cases of MsPGN, and 1 case of MPGN and 1 case of FSGS. After 2-month duration, 8 patients got complete remission including 4 cases of MCN and 4 cases of MsPGN and 3 children including 1 case of MsPGN, 1 case of MPGN, and 1 case of FSGS got partial remission. Only 1 child with MsPGN was considered to be a treatment failure. The overall response rate was 91.67% with the plasma concentration of FK506 maintained at 5 approximately 12 ng/ml, and the response time was 10 - 38 days. After 1-month duration, all patients except one experienced a reduction in proteinuria to normal levels or a partial response (50% reduction in protein excretion), significant increase in serum albumin, decrease in serum cholesterol and triglyceride and disappearance of edema. 2 months later, in 11 patients, blood biochemical values had returned to normal levels. The drug was generally well-tolerated. 3 patients had anorexia, nausea, vomiting. 2 patients experienced transient elevated serum creatinine which was reversible after the adjustment of dosage. 3 patients had minor changes in urine NAG. Only 2 of all patients relapsed. CONCLUSION: FK506 is one of the effective immunosuppressants. In this study, FK506 in combination with a small doses of steroid while decreasing FK506 dosage plays a role in consolidating the curative effect and preventing relapse. In conclusion, FK506 may be effective in the treatment of nephrotic syndrome.

Adolescent↗

PubMed2003

Simulation study of the effects of hypovolaemia on cardiovascular response to orthostatic stress.

To investigate the role played by hypovolaemia in the mechanism of orthostatic intolerance, a mathematical model was developed. The model consisted of seven sub-models that describe: the redistribution of blood induced by lower body negative pressure (LBNP); filling of the left ventricle; contracting of the left ventricle; interaction between the left ventricle and peripheral circulation; and baroreflex regulation. The model was evaluated using experimental data. Using the model, computer simulations were performed to investigate the effects of hypovolaemia on the cardiovascular response to LBNP. The simulation results indicated that, first, when the blood loss is less than 5%, blood pressure can be maintained in the normal range by the baroreflex regulatory mechanism, even with high LBNP application; secondly, when the blood loss is between 15 and 20%, heart rate and blood pressure can be kept in the normal range if LBNP is not applied, but blood pressure falls sharply with LBNP application; and, thirdly, when the blood loss is 25%, the cardiovascular system is in an unstable state (heart rate: 116 beat min (-1), systolic blood pressure: 97 mmHg; diastolic blood pressure: 77 mmHg), even without any LBNP, and becomes more unstable with LBNP. The simulation results support the hypothesis that hypovolaemia is a cause of orthostatic intolerance.

Adult↗

PubMed2001

Quantitative analysis of synaptic contacts made between functionally identified oralis neurons and trigeminal motoneurons in cats.

A previous study revealed that rostrodorsomedial oralis (Vo.r) neurons synapsing on trigeminal motoneurons use GABA and/or glycine as neurotransmitters. To determine the number and spatial distribution of contacts, injections of biotinamide and horseradish peroxidase were made into a Vo.r neuron and an alpha-motoneuron in the jaw-closing (JC) and jaw-opening (JO) motor nucleus, respectively, in 39 cats. All Vo.r neurons responded to low-threshold mechanical stimulation of the oral tissues. Single Vo.r neurons terminating in the JC nucleus (Vo.r-dl neurons; n = 5) issued, on average, 10 times more boutons than Vo.r neurons terminating in the JO nucleus (Vo.r-vm neurons; n = 5; 4437 vs 445). The Vo.r-dl neuron-JC alpha-motoneuron pairs (n = 4) made contacts on either the soma-dendritic compartment or dendrites, and the Vo.r-vm neuron-JO motoneuron pairs (n = 2) made contacts on dendrites, with a range of two to seven contacts. In five of the six pairs, individual or groups of two to three terminals contacted different dendritic branches of a postsynaptic cell. The Vo.r-dl neurons innervated a greater number of counter-stained motoneuronal somata than did the Vo.r-vm neurons (216 vs 26). Total number of contacts per Vo.r neuron was higher for the Vo.r-dl than Vo.r-vm neurons (786 vs 72). The present study demonstrates that axonal branches of Vo.r neurons are divided into two types with different innervation domains on the postsynaptic neuron and that they are highly divergent. The overall effect exerted by these neurons is predicted to be much greater within the JC than JO motoneuron pool.

Action Potentials↗

PubMed2001

A proteolytic NH2-terminal truncation of cardiac troponin I that is up-regulated in simulated microgravity.

In a tail suspension rat model, we investigated changes in myofilament protein during cardiac adaptation in simulated microgravity. Contractile force and velocity of cardiac muscle were decreased in the tail suspension rats as compared with the control. Ca(2+)-dependent actomyosin ATPase activity was also decreased; however, sensitivity of cardiac muscle to Ca(2+) activation was unchanged. There was no change in expression of myosin heavy chain, tropomyosin, troponin T, or troponin I isoforms in hearts of tail suspension rats. A novel finding is a fragment of cardiac troponin I (cTnI) that had increased amounts in the heart of tail suspension rats. Binding of this cTnI fragment by a monoclonal antibody that specifically recognizes the COOH terminus indicates an intact COOH terminus. NH(2)-terminal sequence analysis of the cTnI fragment revealed truncations primarily of amino acids 1-26 and 1-27 and smaller amounts of 1-30, including Ser(23) and Ser(24), which are substrates of protein kinase A phosphorylation. This cTnI fragment is present in normal cardiac muscle and incorporated into myofibrils, indicating a role in regulating contractility. This proteolytic modification of cTnI up-regulated during simulated microgravity suggests a potential role of the NH(2)-terminal segment of cTnI in functional adaptations of cardiac muscle.

Actins↗

PubMed2001

Quantitative ultrastructure of slowly adapting lingual afferent terminals in the principal and oral nuclei in the cat.

Previous studies provide evidence that a structure/function correlation exists in the cytoarchitectonically different zones of the trigeminal sensory nuclei. To extend this relationship, we examined the ultrastructural features of trigeminal primary afferent neurons in the cat dorsal principal nucleus (Vpd) and the rostrodorsomedial oral nucleus (Vo.r) using intra-axonal labeling with horseradish peroxidase and morphometric analyses. All labeled boutons contained round synaptic vesicles. Eighty-two percent of the boutons in the Vo.r and 99% of the boutons in the Vpd were presynaptic to nonprimary dendrites. The remaining boutons in the Vo.r were presynaptic to somata (8%) or primary dendrites (10%). The average number of postsynaptic profiles per labeled bouton did not differ in the Vpd and Vo.r. Most labeled boutons in the two nuclei were postsynaptic to unlabeled axon terminals with pleomorphic vesicles (p-ending). The number of p-endings per labeled bouton was higher in the Vpd than Vo.r A morphometric analysis indicated that labeled bouton volume and apposed surface area were larger in the Vpd than Vo.r while active zone area and vesicle number did not differ. All these parameters were larger than those of p-endings in each nucleus. In both labeled boutons and p-endings, the parameters were positively correlated with bouton size. These results suggest that sensory information conveyed through trigeminal afferents is more strongly controlled at the level of the first synapse by presynaptic mechanisms in the Vpd than in the Vo.r, while the efficacy of transmission at primary afferent synapses does not differ.

Animals↗

PubMed2001

Quantitative ultrastructure of synapses on functionally identified primary afferent neurons in the cat trigeminal mesencephalic nucleus.

Though a number of studies have reported the presence of synapses on neurons in the trigeminal mesencephalic nucleus (Vmes), there have been no quantitative studies of either the density of innervation, or the ultrastructure, of the synapses on single, physiologically identified neurons in this nucleus. In this study we recorded from single neurons in the Vmes, identified them as being either muscle spindle afferents (MS) or periodontal ligament mechanoreceptor afferents (PL), and then labeled the neurons by intra-axonal injection of horseradish peroxidase (HRP). The material was first processed to reveal the HRP activity, following which ultrathin sections through the labeled somata were cut and examined under the electron microscope. Complete serial reconstructions were made through the soma of one MS neuron and one PL neuron, and the contacts on the neurons reconstructed. Boutons were found on the soma, spines, appendages and the axon hillock and the initial segment of the axon. The numbers of boutons terminating on the two neurons were 198 (PL) and 424 (MS), giving a packing density of 4.4 and 10.7 boutons respectively (i.e., number of boutons/100 micron 2 of the postsynaptic membrane). Boutons could be separated into two types on the basis of their vesicles: those containing clear, round vesicles (i.e., S-type) and those containing a mixture of round, oval and flattened vesicles (P-type). Ninety-five (PL neuron) and 99% (MS neuron) of terminals on the two neurons were P-type. All the S-type boutons and 80% of the P-type boutons formed asymmetric synaptic contacts while 10% of the P-type boutons made symmetric contacts. Quantitative measurements of the P-type boutons on the labeled neurons, in which the data of MS and PL neurons were pooled, revealed that bouton volume was highly correlated with bouton surface area, active zone number, total active zone area, vesicle number, and mitochondrial volume. However, comparing the quantitative measurements of the P-type boutons with those of previously reported vibrissa afferent terminals and their associated axon terminals revealed that all the parameters were smaller for the P-type boutons (on Vmes neurons) than those of the vibrissa afferent terminals but similar to those of axon terminals presynaptic to the vibrissa afferents. Taken together, our results emphasize the wide scope for synaptic interactions in the Vmes and suggest that it may be more fruitful to view the Vmes as an integrating center.

Action Potentials↗

PubMed2001

Approaches and thinking styles in teaching.

In this study, the author examined the relationship between teaching approaches and thinking styles in teaching. The study parallels previous investigations (Zhang, 2000a, 2000b; Zhang & Sternberg, 2000) of students' learning approaches and thinking styles in learning. Seventy-six in-service teachers from Hong Kong responded to the Approaches to Teaching Inventory (K. Trigwell & M. Prosser, 1996) and the Thinking Styles Inventory in Teaching (E. L. Grigorenko & R. J. Sternberg, 1993) as well as to a range of questions designed to assess the participants' perceptions about their work environment. It was concluded that approach and style are two overlapping constructs with different labels. The differences between approach and style are in degree, but not in kind.

Adult↗

PubMed2001

Do thinking styles contribute to academic achievement beyond self-rated abilities?

This research identifies individual differences in academic achievement attributable to thinking styles over and above what can be explained by self-rated abilities. Participants were 209 university students from Hong Kong and 215 university students from mainland China. Participants responded to the Thinking Styles Inventory (Chinese version) that is based on Sternberg's theory of mental self-government (R. J. Sternberg, 1988). They also rated their own analytical, creative, and practical abilities on a 10-point scale based on R. J. Sternberg's (1985) triarchic theory of human intelligence. Participants' academic achievement scores were also used. The prediction that thinking styles statistically predict academic achievement was supported by data from both Hong Kong and mainland China. Academic achievement and thinking styles are related differently in the two groups. Implications of these findings for both teaching and research are discussed.

Achievement↗

PubMed2001

Simulated microgravity enhances vasoconstrictor responsiveness of rat basilar artery.

Recently, hypertrophy and increased myogenic tone of brain vessels have been observed in rats after simulated microgravity. It is expected that simulated microgravity may also induce hyperreactivity of brain vessels. To test this hypothesis, Sprague-Dawley rats were subjected to a 4-wk tail-suspended hindlimb unloading (TS) to simulate the cardiovascular deconditioning effect of microgravity. After 4 wk, the vasoreactivity of isolated basilar arterial rings from TS rats to both receptor- and non-receptor-mediated vasoconstrictors, such as KCl, arginine vasopressin, or 5-hydroxytryptamine (5-HT), and vasodilators such as ACh, thrombin, adenosine, or sodium nitroprusside were examined and compared with those from simultaneous control (Cn) rats. In the first part of this study, it was found that the maximal isometric contractile responsiveness evoked by vasoconstrictors such as KCl, arginine vasopressin, or 5-HT was enhanced in basilar arterial rings from TS rats, whereas vasodilatory responsiveness to vasodilators showed no significant difference between TS and Cn rats. In the second part of this study, it was found that removal of the endothelium had no effects on the contractile responsiveness to 5-HT in basilar arterial rings from TS rats but enhanced markedly the responsiveness in basilar arterial rings from Cn rats to an extent comparable with that of TS rats. Application of tetraethylammonium also had no effects on the contractile response to 5-HT in basilar arterial rings from TS but significantly increased the responsiveness of basilar arterial rings from Cn rats with endothelium intact. These results showed that 4-wk simulated microgravity enhanced the vascular contractile responsiveness of basilar arterial rings to both receptor- and non-receptor-mediated vasoconstrictors, and the enhancement of 5-HT-induced contraction in TS rat basilar arteries was due to an impairment of endothelium-dependent mechanism. These results suggest that endothelium-derived hyperpolarizing factors are responsible for this endothelium-dependent attenuating modulatory mechanism in contractile responsiveness of rat basilar arteries to 5-HT.

Animals↗

PubMed2001

Vascular adaptation to microgravity: what have we learned?

Findings from recent bed rest and spaceflight human studies have indicated that the inability to adequately elevate the peripheral resistance and the altered autoregulation of cerebral vasculature are important factors in postflight orthostatic intolerance. Animal studies with rat model have revealed that simulated microgravity may induce upward and downward regulations in the structure, function, and innervation of the cerebral and hindquarter vessels. These findings substantiate in general the hypothesis that microgravity-induced redistribution of transmural pressures and flows across and within the arterial vasculature may well initiate differential adaptations of vessels in different anatomic regions. Understanding of the mechanisms involved in vascular adaptation to microgravity is also important for the development of multisystem countermeasures. However, future studies will be required to further ascertain the peripheral effector mechanism of postflight cardiovascular dysfunction.

Animals↗

PubMed2001

Effect of repeated +Gz exposures on energy metabolism and some ion contents in brain tissues of rats.

BACKGROUND: It has been demonstrated that during +Gz exposure cerebral blood flow is significantly reduced, resulting in brain ischemia. In pilots, such conditions could recur several times during centrifuge training and combat maneuvers and could possibly cause reversible change in brain energy metabolism. HYPOTHESIS: In rats there is an association between +10 Gz exposure and the decreased brain metabolism, as indicated by decreased adenosine triphosphate (ATP) and ATPase activity, and increased adenosine diphosphate (ADP) and lactate, etc. The aim of the present study was to examine the time course and recovery of brain energy metabolism, lactate, ATPase activity, Na+, K+, Ca2+ and water contents after three +10 Gz exposures in rats. METHODS: There were 64 male Sprague-Dawley rats that were restrained and placed on an animal centrifuge. They were divided into groups of 16. Control rats were exposed to +1 Gz and experimental rats were exposed to +10 Gz three times each for 3 min at 30-min intervals. After being euthanized, rat brains were removed 0 h, 1 h, or 6 h after the last centrifuge run. Brain samples were analyzed for energy metabolism, lactate, Na+-K+-ATPase activity, water and electrolytes contents. RESULTS: The cortical ATP content, Na+-K+-ATPase and lactate dehydrogenase (LDH) activities decreased significantly, whereas the cortical ADP, adenosine monophosphate (AMP) and lactate contents increased significantly 0 h after three +10 Gz exposures, as compared with those of control. The ATP, ADP, and AMP contents returned to their control levels 1 h after the +10 Gz exposures, however, lactate content, Na+-K+-ATPase and LDH activities delayed recovery 6 h after +10 Gz exposures. The cortical K+ content increased significantly 0 h and 1 h after +10 Gz exposures, and returned to the control level 6 h after +Gz exposures. Na+ and water contents increased significantly 1 h and 6 h after the +10 Gz exposures. There was no significant change in Ca2+ content after +Gz exposures. CONCLUSIONS: Three +10 Gz (3 min each) exposures were associated with transient depression of brain metabolism as indicated by a decrease in ATP, Na+-K+-ATPase activity, and an accumulation of lactate, and disturbance of ion homeostasis. It is suggested that a causal relationship might exist between repeated high +Gz exposures and brain metabolism.

Acceleration↗

PubMed2001

Peripheral effector mechanism hypothesis of postflight cardiovascular dysfunction.

Studies on the mechanisms of cardiovascular dysfunction after space-flight are important to illustrate the cardiovascular effect of microgravity and develop appropriate multi-system countermeasures for future long-duration spaceflights. Over the past 10 yr, we have systematically studied the adaptational changes in structure and function of both the heart and vessels, using the tail-suspension rat model to simulate microgravity effects. Our results indicate that simulated microgravity induced atrophic changes and reduced contractility of the heart muscle, and upward- and downward-regulation in structure, function, and innervation state of vessels in the brain and hind body of the rat. In addition, more recent advances in relevant ground-based and space-flight studies from different laboratories have also been reviewed. Based on these studies, it has been speculated that, in addition to hypovolemia, the microgravity-induced adaptational changes in the structure and function of the two main effectors of the cardiovascular system, i.e., the arterial smooth muscle and the cardiac muscle, might be among the most important mechanisms responsible for postflight cardiovascular dysfunction and orthostatic intolerance. In this paper we will review the available evidence with comments.

Adaptation, Physiological↗

PubMed2001

[Heat stress-induced HSP70 expression in heart and vessels of simulated weightless rats].

To examine the effect of simulated weightlessness on inducible HSP70 expression in the heart and vessel tissues of rats, a tail-suspension rat model was used to simulate weightlessness. HSP72 mRNA and HSP70 expression in heart and vessel tissues of both simulated weightless and control rats exposed to heat stress (ambient temperature, Ta = 43 degrees C) and recovered at Ta of 25 degrees C for 1 h (CON-H1, SUS-H1) or 2 h (CON-H2, SUS-H2) were analyzed using Northern blot and Western blot. The expression of HSP72 mRNA in the myocardium significantly decreased in SUS-H2, as compared with that of CON-H2 rats. The amount of HSP72 in the myocardium tended to decrease in both SUS-H1 and SUS-H2 groups, as compared with the corresponding control groups, but the differences were not statistically significant. The levels of inducible HSP70 expression in the vessels were related with their anatomical locations, for that the expression of both HSP72 mRNA and HSP72 significantly increased in basilar arteries, whereas it showed a slight decline in femoral arteries. The blunted HSP70 expression in myocardium suggests that simulated weightlessness may induce myocardial changes similar to those in aging. However, the HSP70 expression changes in arteries are in accord with the trend of differential adaptation changes in vessels to simulated weightlessness.

Animals↗

PubMed2001

[Counteraction effect of intermittent -Gx on changes of responsiveness of basilar artery in tail-suspended rats].

OBJECTIVE: To investigate counteracting effects of intermittent -Gx exposure on changes of responsiveness of basilar artery in tall-suspended rats. METHOD: Rats tail-suspended for 3 wk were daily subjected to 1 h 1.5 G or 2.6 G centrifugation, simulating -Gx exposure of various G values. Responses of perfused isolated basilar arterial rings to KCl was examined. RESULT: Maximal isometric contractile response to KCl were significantly enhanced in arterial rings isolated from 3 wk tail-suspended rats as compared with that from simultaneous control rats (P < 0. 05). However, maximal isometric contractile responses to KCl of arterial rings isolated from 3 wk tail-suspended plus daily -Gx exposure rats were no difference as compared with that from simultaneous control rats, and were significantly decreased (P < 0.05) as compared with that from 3 wk tail-suspended rats. CONCLUSION: Daily intermittent -Gx exposure as a countermeasure to prevent the effects of simulated weightless on changes in responsiveness of basilar artery from tail-suspended rats was valid.

Animals↗

PubMed2001

[A simulation study of effects of depressed myocardial contractility on cardiovascular response to lower body negative pressure].

OBJECTIVE: To study the effects of depressed myocardial contractility induced by microgravity on cardiovascular response to orthostatic stress, and to investigate the role played by the changes of myocardial contractility in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness. METHOD: On the basis of our previous model used to simulate the cardiovascular response to lower body negative pressure (LBNP), the factor of changes of myocardial contractility was incorporated into the model by multiplying a coefficient to the maximum elastance of the heart working sub-model. By decreasing the coefficient progressively, then the changes of heart rate (HR), blood pressure (BP), and cardiac output (CO) during LBNP after 0 - 30% of myocardial contractility depression combined with 12% decrease of total blood volume were simulated. RESULT: Simulation results indicated that depressed myocardial contractility induces more augment of HR, and more decrease of BP and CO during LBNP. CONCLUSION: The depression of myocardial contractility degenerated cardiovascular response to orthostatic stress.

Blood Pressure↗

PubMed2001

[Changes of human recombination bone morphogenetic protein-2 in bone and marrow in tail suspended rats].

OBJECTIVE: To study human recombination bone morphogenetic protein-2 (rhBMP-2) change in bone and marrow under simulated weightlessness. METHOD: 5 SD rats were tail suspended for 14, 28 d with another 5 freely active rats as control. Histological samples were in situ hybridized. RESULT: rhBMP-2 expression of bone and marrow were lower in tail suspended rats than control levels (P < 0.05). rhBMP-2 expression tail suspended rats in 14 day were higher than that in 28 day suspended group (P < 0.05). CONCLUSION: rhBMP-2 levels in rats bone and marrow were lower after tail suspension.

Animals↗

PubMed2001

[Biomedical problems of artificial gravity: overview and challenge].

The limitations of the currently used exercise-based countermeasures and the scientific rationale for the gravity-based countermeasures are addressed. Then, an overview of the physiological effects and requirements for the two types of artificial gravity (AG), i.e., the continuous AG provided by full-time spinning of the entire space system/habitat and the intermittent AG by incorporating a short-arm centrifuge into the spacecraft, is presented. Finally, significance and challenge faced in future research on biochemical problems of artificial gravity are discussed.

Adaptation, Physiological↗

PubMed2001

Inhibition by nociceptin on excitatory non-adrenergic non-cholinergic response in guinea pig airways.

AIM: To study the effect of nociceptin (NC), a newly discovered heptadecapeptide, and U-50488H, a kappa-opioid receptor agonist, on excitatory non-adrenergic non-cholinergic (eNANC) constriction responses in guinea pig isolated bronchus. METHODS: An eNANC response was induced by electric field stimulation (EFS) in the preparation via activation of the sensory nerve terminals. The effect of NC and U-50488H was analyzed on the response. RESULTS: Nociceptin 0.001 - 0.1 micromol/L inhibited the eNANC constriction which was induced by EFS but not by capsaicin in guinea pig bronchus. The constriction inhibited by NC 0.01 micromol/L was (43 +/- 31) % compared with the control. After pretreatment with naloxone 0.1 micromol/L, the constriction was inhibited by (46 +/- 28) %, without marked change compared with the above figure. IC50 (95 % of confidence limits) was 6.12 (3.8 - 9.9) nmol/L. U-50488H also inhibited the EFS-evoked eNANC constriction and the effect was abolished after pretreatment with naloxone. IC50 (95 % of confidence limits) was 1.08 (0.5 - 2.2) micromol/L. Capsaicin 0.01 - 1 micromol/L caused a cumulative constriction response in the preparation. Moreover, the effect of capsaicin was not affected by pretreatment with NC 0.01 micromol/L or U-50488H 0.1 micromol/L. The constriction induced by exogenous neurokinin A, were also unaffected by treatment with NC 0.01 micromol/L or U-50488H 0.1 micromol/L in isolated bronchus. CONCLUSION: Nociceptin inhibits EFS-induced eNANC constriction, which is not reversed by naloxone, while U-50488H inhibits EFS-induced eNANC response via activation of opioid receptor in guinea pig airways.

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