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L Wang

Publications and source records attributed to L Wang.

At least 1,477 records · Page 82Linked to original sources
PubMed1997

Growth factor-mediated K+ channel activity associated with human myeloblastic ML-1 cell proliferation.

ML-1 cell proliferation is dependent on the presence of serum growth factors. Removing serum from the culture medium results in growth arrest and promotes differentiation. In this study, we found that a 4-aminopyridine-sensitive K+ channel was highly expressed in proliferating ML-1 cells and significantly diminished in G1-arrested ML-1 cells induced by serum deprivation but was restored within 30 min in these cells with addition of 10% fetal bovine serum (FBS) or 5 ng/ml epidermal growth factor (EGF). Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels, but not guanosine 3',5'-cyclic monophosphate, were significantly increased in serum-deprived cells stimulated by FBS or EGF, and the effects of FBS and EGF on the channel activation were mimicked by exogenous cAMP. In inside-out patches, K+ channel activity was significantly increased by the cAMP-dependent protein kinase catalytic subunit, whereas the effect of EGF on K+ channel activation was blocked by Rp-8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphothioate. Together, our results demonstrate that serum growth factors stimulate K+ channel activity in proliferation of ML-1 cells through protein kinase-induced phosphorylation and suggest an important molecular mechanism for serum growth factor-stimulated mitogenesis in ML-1 cells.

4-Aminopyridine↗
PubMed1997

Bronchial vasodilatory response to ionic and nonionic contrast media.

It has recently been shown that bronchial arterial injection of conventional contrast medium causes a significant increase in bronchial blood flow (Qbr) and that this response is partially attenuated after infusion of N omega-nitro-L-arginine (L-NNA). However, the precise mechanism for this increase in Qbr is unknown. In this study we examined the effect of bronchial arterial injection of conventional ionic as well as nonionic contrast media. We measured Qbr in nine anesthetized, ventilated, open-chest sheep. Qbr was recorded before (baseline) and at the peak response to injection of 0.5 ml of either 0.9% saline (control; isosmolar with plasma), Omnipaque 300 (iohexol; nonionic), Conray 66 (sodium iothalamate; ionic), or 50% dextrose (viscous control). Measurements were made during a control period, after infusion of the alpha-agonist phenylephrine (5 x 10(-6) to 5 x 10(-7) M), and after bronchial arterial infusion of L-NNA (10(-2) M). The results were as follows: bronchial arterial injection of saline, Omnipaque, Conray, and dextrose caused an increase in Qbr (P < 0.05). During the control period, increases in peak Qbr on injection of saline, Omnipaque, Conray, and dextrose were 55 +/- 29, 112 +/- 62, 280 +/- 99, and 388 +/- 125% of baseline, respectively. Bronchial arterial infusion of L-NNA lowered baseline Qbr and partially attenuated the response to injection of saline, Omnipaque, and Conray (P < 0.05). Phenylephrine, in doses that decreased baseline Qbr to the same extent as did L-NNA, did not attenuate the bronchial vasodilation. There was a linear relationship between osmolality and the percentage increase in bronchial blood flow. We conclude that an osmolar stress is the trigger for the contrast-induced bronchial vasodilation and that the response is partially mediated by endothelial release of nitric oxide.

Animals↗
PubMed1997

Correlation of peripheral innervation density and dorsal horn map scale.

Dorsal horn map scale and peripheral innervation density were compared to test a hypothesized linear relationship. In anesthetized cats, low-threshold mechanoreceptive peripheral nerve innervation fields (IFs) were measured by outlining areas of skin from which action potentials could be elicited in cutaneous nerves. The same nerves were processed histologically and used to count myelinated axons. Innervation density for each nerve was calculated as number of axons divided by IF area. Single units were recorded throughout the hindlimb representation, in laminae III and IV. These data, combined with single-unit data from other animals and with cell counts in laminae III and IV, permitted estimation of numbers of cells whose receptive field centers fell in contiguous 1-cm bands from tips of toes to proximal thigh. A similar estimate was performed with the use of the nerve innervation data, so that peripheral innervation densities and map scales for the different 1-cm bands of skin could be compared. Correlation between the two was quite high (r = 0.8), and highly significant (P = 2.5 x 10(-7)). These results are consistent with a proposed developmental model in which map scale, peripheral innervation density, and reciprocal of dorsal horn cell receptive field size are mutually proportional, as a result of developmental mechanisms that produce constant divergence and convergence between primary afferent axons and dorsal horn cells.

Animals↗
PubMed1997

Thrombomodulin expression in bovine brain capillaries. Anticoagulant function of the blood-brain barrier, regional differences, and regulatory mechanisms.

Thrombomodulin (TM), a key cofactor of the TM-protein C pathway, is of major biologic significance for the antithrombotic properties of endothelial cells. Yet, there is uncertainty whether TM is expressed in brain and what mechanisms govern brain endothelial anticoagulant activity. In this study, bovine brain capillaries were used as an in vitro model of the blood-brain barrier to determine factors involved in the regulation of TM expression in cerebral vasculature. Quantitative competitive-polymerase chain reaction assay revealed significant regional differences in the amount of brain capillary TM mRNA, i.e., cortical > cerebellar > pontine, consistent with the reverse transcription-polymerase chain reaction findings in which the abundance of TM mRNA was analyzed relative to beta-actin mRNA. Regional differences in TM mRNA brain capillary level correlated well with differences in protein C activation. The TM mRNA and activity were not detectable in brain parenchyma. Pathogenic mediators of ischemic stroke, interleukin 1 beta (10 U/mL), and tumor necrosis factor alpha (10 U/mL), produced a time-dependent decrease in brain capillary TM mRNA (t1/2 of 2.1 and 3.9 hours, respectively) and reduced endothelial TM activity. Incubation of brain capillaries with retinoic acid (10 mumol/L) and dibutyryl cAMP (3 mmol/L) resulted in a 4-fold increase in TM mRNA at 4 and 8 hours, respectively, followed by an increase in protein C activation. We conclude that TM at the blood-brain barrier is likely to be an important physiologic anticoagulant in brain microcirculation. Its downregulation by cytokines may contribute to ischemic brain damage and potentially could be counteracted by retinoic acid and cAMP.

Animals↗
PubMed1997

Developmental changes in transient outward current in mouse ventricle.

Developmental changes in the transient outward K+ current (Ito) in mouse ventricular myocytes were assessed by the whole-cell patch-clamp technique. The density of Ito in mouse ventricular myocytes was significantly increased from the day-1 neonate to the adult. At +50 mV, the density of Ito was 3 +/- 1 pA/pF in the day-1 neonate, 15 +/- 3 pA/pF in the day-14 neonate, and 19 +/- 4 pA/pF in the adult (P < .01). Unlike other species, the rate of Ito inactivation significantly slowed in mouse ventricular cells during development. Moreover, the time courses of inactivation and recovery from inactivation of Ito were well described by a monoexponential function in day-1 neonatal cells, whereas they were best fitted by a biexponential function in day-14 neonatal and adult cells. The characteristics of steady state inactivation were also significantly different in day-1 neonatal cells (half-inactivation potential [Vh] = -66 +/- 4 mV, slope factor [k] = 12 +/- 2 mV), in day-14 neonatal cells (Vh = -40 +/- 3 mV, k = 13 +/- 1 mV), and in adult cells (Vh = -34 +/- 4 mV, k = 6 +/- 1 mV). Microelectrode studies revealed that action potential duration progressively decreased in mouse ventricles during normal postnatal development. In addition, 4-aminopyridine (1 mmol/L) prolonged action potential duration more in adult than in neonatal mouse ventricles, suggesting that the developmental increase in the density of Ito contributes to the age-related shortening of action potential duration in mouse ventricles. In conclusion, Ito in adult mouse ventricular myocytes exhibits a higher density, slower inactivation kinetics, and a relatively more positive half-inactivation potential. All these characteristics result in Ito being a physiologically more important repolarizing K+ current in adult than in neonatal mouse hearts.

Action Potentials↗
PubMed1997

Electrophysiological characterization of an alternatively processed ERG K+ channel in mouse and human hearts.

Mutants of HERG, the human form of ERG (the ether-a-go-go-related K+ channel gene), are responsible for some forms of the long-QT syndrome, an abnormality of cardiac repolarization. HERG was cloned from brain and has properties similar but not identical to the rapidly activating component of the native cardiac K+ channel current (Ikr). We identified in the mouse an alternatively processed form of ERG (MERG B) that is expressed abundantly in heart but only in trace amounts in brain. MERG B has a unique 36-amino acid NH2-terminal domain that is strongly basic and considerably shorter than the 376-amino acid NH2-terminal domain of HERG. When expressed in Xenopus oocytes, the kinetics of activation and deactivation of the MERG B current were best fit by a biexponential function, with the fast components dominant over the slow components. The fast component of activation had a mean tau value of 163 +/- 16 ms at -20 mV and 8 +/- 4 ms at +20 mV (n = 4). The fast component of deactivation had a mean tau value of 145 +/- 29 ms at -20 mV and 12 +/- 4 ms at -90 mV (n = 4). The MERG B current was blocked by the selective IKr blocker, dofetilide, with an IC50 of 54 nmol/L. In addition, we isolated HERG B, the human homologue of MERG B, which has electrophysiological characteristics qualitatively similar to those of MERG B. We have identified ERG B, an alternatively processed isoform of the ERG gene, expressed selectively in heart and with electrophysiological characteristics similar to those of native cardiac IKr.

Amino Acid Sequence↗
PubMed1997

T-type calcium channels facilitate insulin secretion by enhancing general excitability in the insulin-secreting beta-cell line, INS-1.

The present study addresses the function of T-type voltage-gated calcium channels in insulin-secreting cells. We used whole-cell voltage and current recordings, capacitance measurements, and RIA techniques to determine the contribution of T-type calcium channels in modulation of electrical activity and in stimulus-secretion coupling in a rat insulin secreting cell line, INS-1. By employing a double pulse protocol in the current-clamp mode, we found that activation of T-type calcium channels provided a low threshold depolarizing potential that decreased the latency of onset of action potentials and furthermore increased the frequency of action potentials, both of which are abolished by administration of nickel chloride (NiCl2), a selective T-type calcium channel blocker. Moreover application of high frequency stimulation, as compared with low frequency stimulation, caused a greater change in membrane capacitance (deltaCm), suggesting higher insulin secretion. We demonstrated that glucose stimulated insulin secretion in INS-1 is reduced dose dependently by NiCl2. We conclude that T-type calcium channels facilitate insulin secretion by enhancing the general excitability of these cells. In light of the pathological effects of both hypo and hyperinsulinemia, the T-type calcium channel may be a therapeutic target.

Action Potentials↗
PubMed1997

Angiotensin II-induced pulmonary edema in a rabbit model.

We conducted the present study to propose a rabbit model of pulmonary edema (PE) induced by angiotensin II (AII) and to test the preventive effect of losartan on this form of PE. AII was administered to rabbits intravenously at 50, 100, 150 or 300 microg/kg, either by continuous infusion (10 min) or by bolus injection (30 sec). Continuously administered AII (150 microg/kg) induced PE in most cases, while a bolus injection of the same dosage did not. Additionally, the incidence of PE increased with higher dosages of AII when it was infused continuously. A newly established parameter, the area under the systolic blood pressure-time curve corrected by baseline (cAUC), was prone to rise as the incidence of PE increased. Moreover, cAUC signficantly correlated with the wet-dry lung weight ratio (r=0.66, P<0.05). Subsequently, 0.5 or 3.0 mg/kg of losartan was given before continuous infusion of 150 microg/kg of AII. The higher dosage of losartan prevented PE completely, while the lower one did so moderately. We concluded that intravenous administration of AII induces PE, probably as a result of increasing afterload. Furthermore, an adequate dosage of losartan can prevent PE because it reduces the pressor effect of AII.

Angiotensin II↗
PubMed1997

Short report: identification of B-cell epitopes in the serine-rich Entamoeba histolytica protein.

The serine-rich Entamoeba histolytica protein (SREHP) has been shown to be a protective antigen in animal models of amebic liver abscess when delivered by either parenteral or oral routes of immunization, and antibodies to SREHP can prevent amebic liver abscess in severe combined immunodeficient mice. To identify B cell epitopes of the SREHP molecule that could serve as the basis for a peptide-based vaccine, we synthesized overlapping peptides spanning the amino acid sequence of SREHP, and looked at the reactivity of serum samples from five individuals with amebic liver abscess to the overlapping peptides. We found that most of the epitopes recognized by serum samples from patients with amebic liver abscess map to the hydrophilic dodecapeptide or octapeptide repeats of SREHP, but there was no universal epitope recognized by all five serum samples. In addition, we show that synthetic peptides that include the epitopes of SREHP recognized in the mapping study are immunogenic in animals and can generate antibodies that recognize SREHP.

Amino Acid Sequence↗
PubMed1997

[Implementation of mid-term national tuberculosis control programme].

OBJECTIVE: To evaluate the implementation of mid-term National Tuberculosis Control Programme (NTP). METHOD: The construction of tuberculosis control organizations, implementation of tuberculosis control work, etc, were investigated retrospectively. RESULTS: Almost all the tuberculosis control indices had reached the mid-term NTP target except the case-finding index. CONCLUSIONS: Much more efforts are required to reach the NTP target of year 2000 that the prevalence of smear positive pulmonary tuberculosis decrease to 70 per 100,000 populations.

China↗
PubMed1997

[Effects of NPY microionophoresis on the units in nucleus tractus solitarius (NTS) responsive to baro- and chemoreceptor].

This experiment is designed to study the effects of NPY microionophoresis on the units in NTS responsive to baro- and chemoreceptor activiation at cellular level. In the experiment, it examined 62 units with spontaneous discharge in NTS. Among them, 34 were excited and 19 were inhibited by NPY microionophoresis. And other 9 units failed to respond to NPY microionophoresis. The units with the increase and decrease of discharge frequency to the activation of carotid baroreceptor showed excitation (16/21) and inhibition (7/11) respectively in response to NPY microionophoresis. The units with the increase (8/14) and decrease (5/9) of discharge frequency to the activation of carotid chemoreceptor mainly showed excitation.

Animals↗
PubMed1997

[Endoscopic reconstruction of 192 patients with traumatic urethral stenosis].

We treated traumatic urethral stenosis with endoscopic technique and observed effects. 192 men with traumatic urethral stenosis (47 with anterior urethral stenosis and 145 with posterior urethral stenosis) were treated with hydroelectric shock wave, cold knife, microwave and electroincission through transurethral endoscopy. We punched hole in the centre of the scar with hydroelectric shock waves for long segment urethral complete occlution. 43 patients were treated with obliteration and 50 with endoscopic operation again for 1-3 times. With a mean of 29. 3 months (range 3-60 months) of followup, 187 patients were treated successfully. Endoscopic operation has good effects on traumatic urethral stenosis with smaller trauma, and few complications.

Accidents, Traffic↗
PubMed1997

[Inclusion body myositis: clinical and myopathological features].

Inclusion body myositis has been recognized as a major form of idiopathic inflammatory myopathy. An old male patient with insidious onset and slowly progressive muscular weakness and artrophy has been reported in this article. The duration of symptom before biopsy was 23 years. The first symptom was dysphagia, and muscular weakness developed seven years later. Muscular atrophy was predominant symmetrically and proximally, particularly the quadriceps femoris muscles. Cervical and abdominal muscles were also affected. Myalgia was absent. Electromyogrophy showed myopathic alterations. Erythrocyte sedimentation rate, creatine kinase, immunoglobulins G increased slightly or moderately. Rheumatoid factor was positive, and he had been diagnosed as having rheumatoid arthritis for 23 years. Inclusion body myositis was ultimately diagnosed based on the muscle biopsy which showed mononuclear cell invasion of nonnecrotic muscle fibers, the characteristic rimmed vacuoles in cryostat sections and cytoplasmic inclusion bodies consisted of plenty of tubulofilaments by electron microscope.

Aged↗