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Biomedical subjects

M Jiang

Publications and source records attributed to M Jiang.

At least 91 records · Page 5Linked to original sources
PubMed1999

[Mutations of the fibroblast growth factor receptor 3 gene in achondroplasia].

OBJECTIVE: To evaluate whether mutation in the exon 10 of the fibroblast growth factor receptor 3(FGFR3) gene in common in Chinese patients with achondroplasia. METHODS: Genomic DNA from seven sporadic cases of achondroplasia was studied by using PCR-SSCP and restriction enzymes. RESULTS: All patients carried the same glycine-to-arginine mutation at codon 380(G380R) of the transmembrane domain of FGFR3. CONCLUSION: The results suggest that the G380R mutation of FGFR3 is also a frequent mutation causing achondroplasia in Chinese. Detecting FGFR 3 gene mutation with PCR-SSCP and restriction enzymes analysis is a convenient, rapid and reliable molecular diagnostic assay for prenatal and early diagnosis of achondroplasia.

Achondroplasia↗
PubMed1999

Allosteric effects of mutations in the extracellular S5-P loop on the gating and ion permeation properties of the hERG potassium channel.

The hERG channel has an unusually long (39 amino acids) extracellular loop between the transmembrane S5 segment and the pore region that may play a role in channel function. We explored this possibility by mutating two histidine residues in this region (H578 and H587, referred to as H1 and H2) to various residues and examined the resulting changes in channel function. Both positions could tolerate drastic changes in side-chain properties (proline, cysteine, glutamate and lysine), indicating that they are solvent exposed. None of the H1 mutations affected hERG channel function. On the other hand, although replacing H2 with glutamate had little or no effect on hERG properties, putting a proline or lysine at this position disrupted the C-type inactivation process and the pore's K selectivity. There was also a hyperpolarizing shift in the voltage dependence of activation. The phenotype of the H2C mutant was similar to that of H2P or H2K. However, dithiothreitol (DTT, a thiol-reducing agent) treatment converted the H2C phenotype to that of the wild-type channel. These observations suggest that the peptide backbone conformation around position 587 in the extracellular S5-P loop of hERG channel can affect the channel's gating and ion selectivity functions.

Amino Acid Sequence↗
PubMed1999

Effects of outer mouth mutations on hERG channel function: a comparison with similar mutations in the Shaker channel.

The fast-inactivation process in the hERG channel can be affected by mutations in the pore or S6 domain, similar to the C-type inactivation in the Shaker channel. However, differences in the kinetics and voltage dependence of inactivation between these two channels suggest that different structural determinants may be involved. To explore this possibility, we mutated a serine in the outer mouth region of hERG (S631) to residues of different physicochemical properties and compared the resulting changes in the channel's inactivation process with those resulting from mutations of an equivalent position in the Shaker channel (T449). The most dramatic differences are seen when this position is occupied by a charged residue: S631K and S631E disrupted C-type inactivation in hERG, whereas T449K and T449E facilitate C-type inactivation in Shaker. S631K and S631E also disrupted the K selectivity of hERG pore, a change not seen in T449K or T449E of Shaker. To further study why there are such differences, we replaced S631 with cysteine. This allowed us to manipulate the properties of thiol groups at position 631 and correlate side-chain properties here with changes in channel function. S631C behaved like the wild-type channel when the thiol groups were in the reduced state. Oxidizing thiol groups with H2O2 or modifying them with MTSET or MTSES disrupted C-type inactivation and K selectivity, similar to the phenotype of S631K and S631E. The same thiol-modifying maneuvers did not affect the wild-type channel function. Our results suggest differences in the outer mouth structure between hERG and Shaker, and we propose a "molecular spring" hypothesis to explain these differences.

Amino Acid Sequence↗
PubMed1999

Heterogeneous changes in K currents in rat ventricles three days after myocardial infarction.

OBJECTIVE: After coronary artery occlusion, surviving myocardium in and around the infarct zone plays an important role in arrhythmogenesis. Understanding the mechanisms for derangements in cardiac electrical activity at the cellular and molecular levels is important for the design of effective therapeutic strategies. METHODS: To provide part of that understanding, we studied changes in K channel function and expression in rat ventricular myocardium three days after occluding the left major coronary artery. The epicardium and endocardium of infarcted region in the left ventricle and the free wall of right ventricle were separated for myocyte isolation, followed by whole-cell voltage clamp studies. Myocytes were also isolated from corresponding regions of control and sham-operated hearts and studied under the same conditions. RESULTS: We found that the transient outward (Ito), delayed rectifier (IK) and inward rectifier (IKI) currents have different distribution patterns in normal rat ventricular myocardium. Sham-operation did not affect any of these K currents in left ventricular myocytes, but coronary artery occlusion caused a reduction of all three. For Ito and IKI the reduction was greater in epicardial than in endocardial myocytes, but IK was reduced equally in these two cell groups. Unexpectedly, Ito and IK as well as cell capacitance were increased in right ventricular myocytes from infarcted as well as sham-operated hearts. Western blot analysis indicated that the level of Kv4 channel proteins (Kv4.2 + Kv4.3) was reduced in infarcted left ventricular myocardium, consistent with the reduction in Ito. CONCLUSION: Our data suggest that the distribution of K channels and changes in them induced by coronary artery occlusion are heterogeneous in ventricular myocardium. Understanding the molecular mechanisms for this heterogeneity and its implications in arrhythmogenesis poses a challenge in designing effective antiarrhythmic therapy for myocardial infarction patients.

Animals↗
PubMed1999

Real-time monitoring of enzymatic cleavage of nucleic acids using a quartz crystal microbalance.

The use of quartz crystal microbalance (QCM) for monitoring in situ the enzymatic cleavage of surface-confined nucleic acids by nucleases is described. Such real-time monitoring of mass changes associated with the enzymatic digestion indicates that the activity and specificity of nucleases is preserved at the gold surface, and can be used for manipulating surface-confined DNAs and RNAs. These observations indicate great promise for using QCM for elucidating the interactions of nucleic acids with enzymes, and for enhancing the power of hybridization biosensors.

Crystallization↗
PubMed1999

Prognostic role of p27Kip1 and apoptosis in human breast cancer.

Human breast carcinoma is biologically heterogeneous, and its clinical course may vary from an indolent slowly progressive one to a course associated with rapid progression and metastatic spread. It is important to establish prognostic factors which will define subgroups of patients with low vs high risk of recurrence so as to better define the need for additional therapy. Additional characterization of the molecular make-up of breast cancer phenotypes should provide important insights into the biology of breast cancer. In the present study, we investigated apoptosis, expression of p27Kip1 and p53 retrospectively in 181 human breast cancer specimens. In addition, their relevance to the biological behaviour of breast cancer was examined. Our studies found a significant association among high histological grade, high p53, low apoptosis and low p27. Our results also demonstrated that, in human breast cancer, low levels of p27 and apoptotic index (AI) strongly correlated with the presence of lymph node metastasis and decreased patient survival. In node-negative patients, however, p27 also had prognostic value for relapse-free and overall survival in multivariate analysis. Furthermore p27 and AI had predictive value for the benefits of chemotherapy. These latter observations should prompt prospective randomized studies designed to investigate the predictive role of p27 and AI in determining who should receive chemotherapy in node-negative patients.

Analysis of Variance↗
PubMed1999

Alanine mutants of the Spo0F response regulator modifying specificity for sensor kinases in sporulation initiation.

Five single alanine substitution mutations in the Spo0F response regulator gave rise to mutant strains of Bacillus subtilis with seemingly normal sporulation that nevertheless rapidly segregated variants blocked in sporulation. The basis for this deregulated phenotype was postulated to be increased phosphorylation of the Spo0A transcription factor, resulting from enhanced phosphate input or decreased dephosphorylation of the phosphorelay. Strains bearing two of these Spo0F mutant proteins, Y13A and I17A, retained a requirement for KinA and KinB kinases in sporulation, whereas the remaining three, L66A, I90A and H101A, gave strains that sporulated well in the absence of both KinA and KinB. Sporulation of strains bearing L66A and H101A mutations was decreased in a mutant lacking KinA, KinB and KinC, but the strain bearing the I90A mutation required the further deletion of KinD to lower its sporulation frequency. The affected residues, L-66, I-90 and H-101, are involved in crucial hydrophobic contacts stabilizing the orientation of helix alpha4 of Spo0F. The data are consistent with the notion that these three mutations alter the conformation of the beta4-alpha4 loop of Spo0F that is known to contain residues critical for KinA:Spo0F recognition. As this loop has a propensity for multiple conformations, the spatial arrangement of this loop may play a critical role in kinase selection by Spo0F and might be altered by regulatory molecules interacting with Spo0F.

Alanine↗
PubMed1999

A common polymorphic allele of the human luteinizing hormone beta-subunit gene: additional mutations and differential function of the promoter sequence.

A common genetic variant (V) of the human luteinizing hormone (LH) beta-subunit gene was recently discovered. The V-LH molecules have higher bioactivity in vitro, but shorter half-life in circulation, which apparently is related to the alterations of LH function observed in individuals homo- and heterozygous for the V-LHbeta allele. We have now studied whether additional mutations in the V-LHbeta promoter sequence could contribute to the altered physiology of the LH variant molecules. The 661 bp 5'-flanking region of the V-LHbeta gene, retrieved from human genomic DNA by PCR, contained eight single-nucleotide changes, as compared with the wild-type (wt) LHbeta promoter. The finding was consistent in DNA samples of different ethnic groups. Reporter constructs with various lengths of the wt- and V-LH promoter sequences, driving the firefly luciferase reporter gene, were transfected into an immortalized mouse pituitary cell line, LbetaT(2), known to express the endogenous LHbeta gene, and into a non-endocrine human embryonic kidney cell line, HEK 293. Basal expression levels of the V-LHbeta promoter constructs were on average 36% higher in LbetaT(2)cells ( P < 0.001; n = 29), and 40% higher in HEK 293 cells ( P < 0.001; n = 16), as compared with the respective wt sequences. Numerous qualitative and quantitative differences were found between the two cell lines in responses of the two promoter sequences to stimulation with 12- O -tetradecanoylphorbol-13-acetate, forskolin, 8-bromo-cAMP, progesterone and gonado- tropin-releasing hormone. In conclusion, the V-LHbeta promoter has higher basal activity, and differs in response to hormonal stimulation, as compared with the wt-LHbeta promoter. The altered promoter function of the V-LHbeta gene provides evidence for differences in regulation of the wt- and V-LHbeta genes, which may contribute to the differences observed in pituitary-gonadal function between carriers of the two LHbeta alleles. The findings also suggest a novel evolutionary mechanism whereby polymorphic changes resulting in altered bioactivity of a gene product may be compensated for by additional mutations in the cognate promoter sequence, changing transcription of the same gene.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Coupling between a first-order gas-liquid phase transition and a second-order orientational transition in Langmuir monolayers.

The Ginzburg-Landau theory is developed to investigate coupling between a gas-liquid first-order phase transition (FOPT) and an orientational second-order phase transition (SOPT) in Langmuir monolayers. It is found that the coupled SOPT and FOPT takes place simultaneously if the uncoupled FOPT occurs prior to the SOPT with compression, and that in the opposite case, the coupling makes the FOPT take place at a lower pressure, but still behind the SOPT. Gas-liquid phase separation always leads to a decrease in the averaged order parameter of the orientational phase transition, which is qualitatively consistent with experimental data.

Journal Article↗
PubMed1999

Mechanism for the effects of extracellular acidification on HERG-channel function.

Human ether-à-go-go-related gene (HERG) encodes a K channel similar to the rapid delayed rectifier channel current (I(Kr)) in cardiac myocytes. Modulation of I(Kr) by extracellular acidosis under pathological conditions may impact on cardiac electrical activity. Therefore, we studied the effects of extracellular acidification on I(Kr) function and the underlying mechanism, using HERG expressed in Xenopus oocytes as a model. Acidification [extracellular pH (pH(o)) 8.5-6.5] accelerated HERG deactivation (at -80 mV, the time constant tau of the major component of deactivation was 253 +/- 17, 158 +/- 10, and 65 +/- 5 ms at pH(o) 8.5, 7.5, and 6.5, respectively; n = 7-10 each), with no effects on other gating kinetics except a modest acceleration of recovery from inactivation (at -80 mV, tau of recovery was 4.7 +/- 0.3, 3.8 +/- 0.3, and 1.3 +/- 0.2 ms at pH(o) 8. 5, 7.5, and 6.5, respectively; n = 4-7 each). The following were ruled out as the underlying mechanisms: 1) voltage shift in channel activation, 2) pore blockade by protons, 3) protonation of histidines on the extracellular domain of HERG, 4) acceleration of recovery from C-type inactivation, and 5) interaction between an external H(+) binding site and the cytoplasmic NH(2)-terminal domain (a key determinant of HERG deactivation rate). Extracellular application of diethylpyrocarbonate caused an irreversible acceleration of HERG deactivation and prevented further acceleration by external acidification. Our data suggest that side chains accessible to the extracellular solution mediated the effects of elevating extracellular H(+) concentration on channel deactivation.

Acids↗
PubMed1999

[Study of NAIP gene in spinal muscular atrophy].

OBJECTIVE: Investigating the correlation between the genotype and spinal muscular atrophy(SMA) clinical phenotype. METHODS: Neuronal apoptosis inhibitory protein(NAIP) gene analysis was performed by PCR amplification of exon 5 in 13 unrelated SMA patients with deletions of SMN gene. RESULTS: Two Type-I patients(2 M5, 40%) lacked the NAIP exon 5. CONCLUSION: The results suggest a possible correlation between NAIP gene deletion and the disease severity of SMA.

Child↗
PubMed1999

[Dynamic changes of nitric oxide and biochemistry in rats with intrahepatic cholestasis].

OBJECTIVE: To investigate the correlation between nitric oxide and biochemical changes of intrahepatic cholestasis. METHODS: Studies were made on endogenous NO, biochemical changes of cholestasis, liver mitochondrial function and renal excretion in a rat model at different time points after ANIT administration. RESULTS: In acute reactive phase, serum bilirubin, ALT, AKP, and bile acids significantly increased, accompanied by enhanced plasma NO and renal excretion. Liver NO increased and mitochondrial SDH activity decreased for 2-6 days after ANIT. There was a high negative correlation between liver NO and mitochondrial SDH activity (r = -0.92). CONCLUSION: These results show that higher liver NO may be an important mediator of intrahepatic cholestasis. However, plasma NO increase may play a role in rapidly decreasing serum bilirubin and restoring bile acids, ALT, and AKP to control levels by mediating enhanced renal excretion.

Alanine Transaminase↗
PubMed1999

Use-dependent 'agonist' effect of azimilide on the HERG channel.

Azimilide (AZ) is a class III antiarrhythmic drug that has voltage-dependent dual effects on the HERG channel: 1) increasing current amplitude at low-voltage depolarization (agonist effect), and 2) suppressing current at more depolarized voltages (antagonist effect). We examined the mechanism for the agonist effect of AZ on HERG expressed in Xenopus oocytes. The agonist effect resulted from an AZ-induced 'prepulse potentiation: a strong depolarization prepulse increased the rate and degree of channel activation induced by subsequent depolarization to -50 or -40 mV. The potentiated state decayed slowly in an exponential fashion (time constant, 60-80 s). Degrees of potentiation were proportional to degrees of channel activation during prepulses; hence, the agonist effect of AZ was use dependent. AZ exerted its agonist effect from outside the cell membrane, and the effect did not depend on intracellular G-protein or protein kinase activity. Mutations made in the outer mouth or an extracellular loop connecting the S5 and P regions of HERG, which could hinder or modify conformational changes in the pore region during membrane depolarization, reduced or abolished AZ-induced prepulse potentiation. Importantly, these same mutations also increased the rate and degree of channel activation in the negative voltage range, and the degree of change in the activation properties was inversely correlated with the degree of AZ-induced prepulse potentiation. We propose that conformational changes in the outer mouth and neighboring extracellular domain of HERG during membrane depolarization can affect the process of channel activation. In the presence of AZ, channel activation allowed drug modification of these conformational changes, which subsequently facilitated HERG activation by low-voltage depolarization.

Animals↗
PubMed1999

[Deep venous incompetence of legs: experimental studies].

OBJECTIVE: To seek best wrapping materials of valvular wrapping operation of deep veins in the lower limbs and to understand the value of diagnostic value of duplex scanning for incompetence of the deep veins and the function of the popliteal valve. METHODS: Strips of the autogenous saphenous vein, autogenous fascia lata and PEFE graft were used respectively as the material for valve constriction. The results were compared of duplex scanning and trans-popliteal venography. RESULTS: In the saphenous vein and fascia lata groups, diffuse fibrosis and marked narrowing of the femoral vein were found, whereas in the vascular graft group the graft was intact without prominent fibrosis and narrowing of the vein. The accurate rates of duplex scanning and trans-popliteal venography were 91.86%. at the same time the thigh and popliteal valve was closed when held breath. CONCLUSIONS: Vascular graft is the best constriction material. Duplex scanning is a important method. Popliteal valve is an important barrier for protecting the function of the deep vein.

Adult↗
PubMed1999

[Experimental research of Ephedra sinica's influence on lipid metabolism of lipocyte].

OBJECTIVE: To study the influence of Ephedra sinica on the lipid metabolism of lipocyte. METHOD: The rat's epididymal lipocytes were used to observe the effect of Ephedra sinica in lipogenesis from 14C-glucose and lipolysis promoted by norepinephrine (NE). RESULT: Ephedra sinica can promote lipogenesis from glucose, which is related with the pH value of matrix solution; and it also can inhibit the lipolysis promoted by NE. CONCLUSION: Ephedra sinica can promote the lipogenesis of lipocyte that is not induced by ephedrine, the mechanism being similar to that of insulin.

Adipocytes↗
PubMed1999

[Effects of Rg1 on calcium channel of guinea pig ventricular myocytes].

OBJECTIVE: To evaluate the effect of Rg1 (purified saponin of Panax notoginseng) on L-Ca2+ channel of guinea pig ventricular myocytes. METHOD: The whole-cell patch clamp recording technique. RESULT: When the holding potential was kept at -40 mV, and the cell was depolarized to +40 mV for 150 ms at a frequency of 0.5 Hz.Rg1 10 mumol.L-1 and 30 mumol.L-1 could not reduce Bay K 8644 and nifedipine-sensitive L-type Ca2+ inward current (P > 0.05, n = 5). CONCLUSION: Rg1 should not be a Ca2+ channel antagonist.

Animals↗
PubMed1999

[Applied anatomy of anterior ethmoid relevant to endoscopic transnasal dacryocystorhinostomy].

OBJECTIVE: This study provided clinical guidance for the endoscopic transnasal dacryocystorhinostomy. METHOD: 16 adult cadavers were studied on the applied anatomy of between anterior ethmoid and fossa of lacrimal sac and the anatomic relationship between uncinate process and medial wall of orbit. RESULT: According to the anatomic relationship between anterior ethmoid sinus and fossa of lacrimal sac, the cells of anterior ethmoid sinus were classified into three typies, The results was that type I accounted for 31.2%, type II 50.0% type III 18.8%. CONCLUSION: CT scans should be performed to determine the anatomic relationships between fossa of lacrimal sac and anterior ethmoid and between uncinate process and medial wall of orbit before operation for patients with different typies of obstruction of nasocrimal duct, thus the proper bony opening was located during dacryocystorhinostomy.

Adult↗