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J Du

Publications and source records attributed to J Du.

At least 163 records · Page 9Linked to original sources
PubMed1998

Key peptide processing enzymes are expressed by a variant form of small-cell carcinoma of the lung.

Small-cell carcinoma of the lung (SCCL) is a neuroendocrine tumor characterized by having the capacity to produce and secrete a number of small neuropeptides. These peptides serve the tumor as autocrine growth factors. SCCL is known to undergo a process of dedifferentiation to a variant (drug-resistant) form, and this process is associated with loss of marker enzymes such as neuron-specific enolase (NSE) and dopa decarboxylase (DDC). The current study was designed to discover if variant SCCL, represented by cell line NCI H82, retains some capacity to generate active neuropeptides (like vasopressin) from their precursors by continuing to express the three key classes of enzymes necessary for such conversions, namely prohormone convertases (PCs), carboxypeptidases (CPs), and peptidylglycine a-amidating monooxygenase (PAM). RT-PCR for mRNAs representing PC1, PC2, CPE, and PAM was performed on total RNA extracted from NCI H82. The primers selected for PCR and partial sequencing were synthetic 20, 21, 22, and 24 oligomers designed to yield products of 533, 880, 405, and 560 base pairs (bp) for PC1, PC2, CPE, and PAM, respectively. For the conditions used, we were able to demonstrate products for all four enzymes. Each of the four products generated were of the expected size. Cloning and sequencing of these products revealed that each had a structure identical to that published for the human form of the respective enzyme. Western analysis with antibodies against PC1, PC2, CPE, and PAM, provided evidence that mRNAs for the four enzymes are translated into proteins that could represent functional forms. Our findings therefore demonstrate that key enzymes involved in the generation of active neuropeptides, unlike the marker enzymes NSE and DDC, continue to be expressed by variant SCCL.

Blotting, Western↗
PubMed1998

The K+ channel, Kv2.1, is apposed to astrocytic processes and is associated with inhibitory postsynaptic membranes in hippocampal and cortical principal neurons and inhibitory interneurons.

A variety of voltage-gated ion channels are expressed on principal cell dendrites and have been proposed to play a pivotal role in the regulation of dendritic excitability. Previous studies at the light microscopic level demonstrated that the K+ channel subunit Kv2.1 expression was polarized to the cell soma and dendrites of principal neurons throughout the central nervous system. Here, using double immunostaining we now show that Kv2.1 protein is similarly expressed in the majority of cortical and hippocampal parvalbumin, calbindin and somatostatin-containing inhibitory interneurons. At the electron microscopic level Kv2.1 immunoreactivity was primarily observed on the plasma membrane of the somata and proximal dendrites of both principal neurons and inhibitory interneurons; expression was low on smaller dendritic branches, and absent on axons and presynaptic terminals. Kv2.1 subunit expression was highly concentrated on the cell surface membrane immediately facing astrocytic processes. Kv2.1 expression was also concentrated in specific cytoplasmic compartments and on the subsurface cisterns underlying the plasma membrane facing astrocytes. In addition, Kv2.1 subunit immunoreactivity was associated with postsynaptic densities of a fraction of inhibitory symmetric synapses; while expression at asymmetric synapses was rare. These data demonstrate that channels formed by Kv2.1 subunits are uniquely positioned on the soma and principal dendrites of both pyramidal cells and inhibitory interneurons at sites immediately adjacent to astrocytic processes. This close apposition to astrocytes will ensure a rapid removal and limit the influence of K+ released into the extracellular space. This expression pattern suggests that channels formed by Kv2.1 are poised to provide a role in the regulation of neuronal dendritic excitability.

Animals↗
PubMed1998

Effects of GABA on acutely isolated neurons from the gustatory zone of the rat nucleus of the solitary tract.

Responses of acutely isolated neurons from the rostral nucleus of the solitary tract (rNST) to GABA receptor agonists and antagonists were investigated using whole-cell recording in current clamp mode. The isolated neurons retain their morphology and can be divided into multipolar, elongate and ovoid cell types. Most rNST neurons (97%), including all three cell types, respond to GABA with membrane hyperpolarization and a reduction in input resistance. The GABA(A) receptor agonist muscimol reduces neuronal input resistance in a concentration-dependent manner, whereas the GABA(B) receptor agonist baclofen had no effect on any of the neurons tested. The GABA and muscimol reversal potentials were both found to be -75 mV Both the GABA competitive antagonist picrotoxin and the GABA(A) receptor antagonist bicuculline block the effect of GABA in a concentration-dependent manner. These results suggest that GABA activates all neurons in the rNST and that inhibitory synaptic activity is important in brainstem processing of gustatory and somatosensory information.

Animals↗
PubMed1998

Sth1p, a Saccharomyces cerevisiae Snf2p/Swi2p homolog, is an essential ATPase in RSC and differs from Snf/Swi in its interactions with histones and chromatin-associated proteins.

The essential Sth1p is the protein most closely related to the conserved Snf2p/Swi2p in Saccharomyces cerevisiae. Sth1p purified from yeast has a DNA-stimulated ATPase activity required for its function in vivo. The finding that Sth1p is a component of a multiprotein complex capable of ATP-dependent remodeling of the structure of chromatin (RSC) in vitro, suggests that it provides RSC with ATP hydrolysis activity. Three sth1 temperature-sensitive mutations map to the highly conserved ATPase/helicase domain and have cell cycle and non-cell cycle phenotypes, suggesting multiple essential roles for Sth1p. The Sth1p bromodomain is required for wild-type function; deletion mutants lacking portions of this region are thermosensitive and arrest with highly elongated buds and 2C DNA content, indicating perturbation of a unique function. The pleiotropic growth defects of sth1-ts mutants imply a requirement for Sth1p in a general cellular process that affects several metabolic pathways. Significantly, an sth1-ts allele is synthetically sick or lethal with previously identified mutations in histones and chromatin assembly genes that suppress snf/swi, suggesting that RSC interacts differently with chromatin than Snf/Swi. These results provide a framework for understanding the ATP-dependent RSC function in modeling chromatin and its connection to the cell cycle.

Adenosine Triphosphatases↗
PubMed1998

Induction of apoptosis and tyrosine phosphorylation of cellular proteins in T cells and non-T cells by stimulation with concanavalin A.

A high concentration (30 microg/ml or more) of Con A caused the death of not only thymocytes but also splenic cells of BALB/c mice, whereas a moderate concentration (3 microg/ml) of Con A induced proliferation of these cells. A high concentration of Con A also induced the death of splenic cells of athymic BALB/c-nu/nu mice and the bone marrow cells of BALB/c mice which mainly consist of non-T cells. However, any concentration (1-30 microg/ml) of Con A failed to induce the proliferation of these cells. Specific binding of tetrameric Con A to mannose-containing receptors was required for the induction of cell death. DNA fragmentation was observed by both laser flow cytometry and electrophoresis in Con A-stimulated T cells and non-T cells. This indicated that the mechanism of induction of apoptosis with Con A is not necessarily TCR-dependent. Con A induced tyrosine phosphorylation of a number of proteins in various types of cells. Interestingly, phosphorylation of the 40 kDa protein developed only in the thymocytes and spleen cells that contain T cells, whereas phosphorylation of the 80 and 120 kDa proteins appeared in both T cells and non-T cells. These results suggested that the Con A-induced apoptosis of T cells and non-T cells involves different but possibly mutually related protein tyrosine phosphorylation-linked signals.

Animals↗
PubMed1998

Egr-1 and Sp1 interact functionally with the 5-lipoxygenase promoter and its naturally occurring mutants.

5-Lipoxygenase (5-LO), an enzyme essential for the formation of leukotrienes, is functionally modulated by a number of mechanisms, including transcriptional controls. The 5-LO promoter has a unique G+C-rich sequence, located between 176 and 147 base pairs upstream of the ATG translation start site, which contains five tandem Sp1 (a zinc-finger transcription factor) consensus binding sites overlapping five tandem early growth response protein 1 (Egr-1), a zinc-finger transcription factor, consensus binding sites. A family of naturally occurring mutations has been identified that consists of additions or deletions of these binding sites. The role of these overlapping Sp1/Egr-1 sites in the regulation of 5-LO transcription and the effects of these mutations on transcriptional regulatory mechanisms are unknown. We now show that Sp1 and Egr-1 bind specifically to the G+C-rich promoter sequence using in vitro deoxyribonuclease I footprinting. Both Sp1 and Egr-1 activate 5-LO promoter-reporter constructs in a minimally active drosophila SL2 cotransfection system, and the G+C-rich sequence is involved in this process. Moreover, studies comparing mutant promoter function indicate that both Sp1 and Egr-1 trans-activation are proportional to the number of Sp1/Egr-1 consensus binding sites within the G+C-rich sequence. It is possible that basal and inducible 5-LO gene transcriptions are mediated by an interplay of Sp1, Egr-1, and other transcription factors within the G+C-rich promoter region, and the naturally occurring mutations alter transcription by modifying their trans-activation potential.

Animals↗
PubMed1998

Molecular cloning and characterization of a mouse gene with homology to the Duffy-antigen receptor for chemokines.

The Duffy antigen receptor for chemokines (DARC) is a receptor for both CXC and CC chemokines. We have cloned a mouse gene with a predicted amino acid sequence homology of approximately 63% to human DARC and localized this gene to mouse chromosome 1 between the Xmv41 and D1Mit166 loci. We further demonstrated that, like the human gene, the mouse gene exhibits a single intron of 462 bp which interrupts the open reading frame between the codons for the seventh and eighth amino acid residues. Northern blot analyses revealed that putative mDARC mRNA is highly expressed in adult mouse spleen and skeletal muscle and in whole embryos between embryonic days 8.5 to 12. Northern blot analysis of hemangiosarcomas which develop spontaneously in the spleen of the Eker rat reveal expression of mRNAs which hybridize with both DARC and CXCR2 probes, suggesting a potential role of these receptors in the angiogenesis associated with tumor formation.

Amino Acid Sequence↗
PubMed1998

[Effect of captopril on platelet cytosolic [Ca2+]i and plasma TXA2/PGI2 in renovascular hypertensive rats].

AIM: To study the effect of captopril (Cap) on platelet cytosolic free calcium concentration ([Ca2+]i), platelet aggregation (PAg), and plasma TXA2/PGI2 ratio in the renovascular hypertensive rats. METHODS: Blood pressure was measured once a week by tail-cuff microphonic manometer. Platelet [Ca2+]i was measured by Fura 2-AM. Plasma angiotensin II (Ang), thromboxane A2 (TXA2), and prostacycline (PGI2) were measured by radioimmunoassay. RESULTS: Platelet [Ca2+]i and PAg increased (P < 0.01), while plasma Ang and TXA2/PGI2 ratio elevated (P < 0.05) in the renovascular hypertensive rats; platelet [Ca2+]i and plasma TXA2/PGI2 ratio reduced markedly after i.g. Cap 100 mg.kg-1.d-1 compared with saline for 2 wk. CONCLUSION: The altered TXA2/PGI2 after Cap treatment contributed to the improvement of the platelet [Ca2+]i and PAg.

Angiotensin II↗
PubMed1998

[Free jejunal grafts for reconstruction of pharynx and cervical esophasgus].

Eleven patients with hypopharyngeal carcinoma were treated surgically and the pharynx and cervical esophagus were reconstructed with free jejunal grafts through the technique of microvascular anastomosis. The microvascular anastomosis were all successful and the patients all survived the operations. The operations were performed at one time with only a few complications. There were 2 cases of pharyngeal fistula and 1 case of bleeding from the anastomotic site. The patients could eat by their mouths and swallow very well just 15 days after the operation. The 3-year suvival rate was 36%. The main causes of death were the recurrence and the metastasis to the cervical lymph nodes. We came to the conclusion that the operation is safe with high success rate and no mortality during operation, and it is less injurious than the gastropharyngeal anastomosis. The key point of the operation is the surgeon's mastery of the microvascular anastomosis technique.

Aged↗
PubMed1998

[Hypoxia impacts expression of nitric oxide synthase mRNA of different segments of intrapulmonary arteries].

OBJECTIVE: To investigate expression and localization of nitric oxide synthase (cNOS) mRNA of normoxic pulmonary arteries and the impact of hypoxia on its expression. METHODS: In situ hybridization was performed on each lung sections from rats in 1-week hypoxic group, 2-week hypoxic group, and control group to detect cNOS mRNA expression and localization by using cRNA probe for NOS. RESULTS: The positive score of cNOS mRNA expression by endothelial cells of pulmonary arteries associated with bronchioli was significantly higher than that of arteries associated with respiratory or terminal bronchioli (q = 8.13, 5.49, P < 0.01) in the control rats. In the 1-week hypoxic group or the 2-week hypoxic group, however, cNOS mRNA expression by endothelial cells of pulmonary arteries associated with either respiratory or terminal bronchioli was markedly decreased compared with that of the control group. No significant difference was found in cNOS mRNA expression by smooth muscle cells of each segments of pulmonary arteries (F = 2.26, P > 0.05). However, cNOS mRNA expression by smooth muscle cells of pulmonary arteries associated with respiratory bronchioli or terminal bronchioli was significantly decreased in the 1-week or the 2-week hypoxic group compared with the control group. CONCLUSION: These findings suggest that NOS mRNA expression by endothelial cells is greater in the larger, more proximal pulmonary arteries than at the periphery. Chronic hypoxia mainly impairs cNOS mRNA expression by proximal pulmonary artery endothelial cells and periphery pulmonary artery smooth muscle cells.

Animals↗
PubMed1998

Expression of type-I collagen and matrix metalloproteinase-9 mRNA in bone of castrated adult female rats: effects of estrogen.

OBJECTIVES: To elucidate the molecular changes of bone collagen during the development of postmenopausal osteoporosis and to investigate the molecular effects of estrogen replacement. METHODS: An adult ovariotomy rat model was used. Type-I collagen and matrix metalloproteinase-9 (MMP-9) expressions in bone tissues of rats treated by sham surgery (SH), bilateral ovariotomy (OVX) and OVX with estradiol (OVX-E2) were analysed at mRNA level by using dot blot technique. The distribution of mRNA of these two genes in bone tissues was studied by in situ hybridization. RESULTS: The expression levels of both type-I collagen and MMP-9 in bone tissues of OVX rats were higher than those of SH group, while treated with estradiol, the expression of both genes declined to some degree. In situ hybridization showed that type-I collagen mRNA located in osteoblasts, whereas MMP-9 was mainly expressed in osteoclasts, some lining cells on bone surface, and some mononuclear cells in bone marrow. CONCLUSIONS: The reduction of high bone turnover in osteoporotic bone tissues induced by estrogen replacement may result from alterations in gene expression related to bone formation and bone resorption. These alterations are consistent with the changes observed previously by histomorphometry and biochemical markers of bone metabolism on OVX animals and postmenopausal osteoporosis.

Animals↗
PubMed1998

[Detection of ET-1, TNF-alpha, oxidative radicals in sera of asthmatics and in sera and lung tissue of asthmatic guinea pigs].

OBJECTIVE: To investigate the role of the ET-1, TNF-alpha and oxidative radicals of MDA and SOD in the pathogenesis of asthma and the effect of the nitric oxide synthase inhibitor, L-NAME to above factors. METHOD: ET-1 was detected by the radio-immunoassay and TNF-alpha was detected by ELISA, SOD and MDA were detected by using thiobarbituric acid method. RESULT: The contents of ET-1, TNF(and MDA in the serum of the asthmatic patients and in the serum and lung tissue of asthma models of guinea pigs were significantly increased, in the contrast, the content of SOD was decreased compared with those in the controls(P < 0.01). All the changes in the serum and in the lung tissues of the asthma models of guinea pigs returned to the levels of the controls by dexamethasone inhalation or L-NAME by intraperitoneal injection. CONCLUSION: ET-1, TNF alpha and the oxidative radicals and NO may play important roles in the pathogenesis of asthma, L-NAME, which is similar to the dexathamethsone, may either decrease the content of NO or decrease the content of ET-1, TNF alpha and oxidative radicals in asthma.

Adult↗
PubMed1998

A biomechanical analysis of unilateral hooked-sulcated external fixator on osteomined tibia.

Four tibiae removed from 30-40 years males, who died of accidents in less than 12 hours, were osteomized at medium part. Then these tibiae were fixed by an unilateral hooked-sulcated external fixator (UHSEF), and the bone-fixator system was used as a model of external fixation of tibial fracture. The axial compression, distraction, torsion, antero-posterior and lateral bending rigidity and the strain of the pins were determined in this system. Based on the results, we found that compared with the configuration of four paralleled pins, the rigidity of the fan-like configuration didn't decrease significantly if the angle between lateral and medium pins was less than 45 degrees. But the reverse was true when the frame separation increased from 5 to 8 cm. What' more, the pin strain decreased if the rigidity of the system was improved. These data provided a theoretical basis of biomechanics for the improvement of UHSEF.

Adult↗
PubMed1998

[Animal experiment and clinical application of self-made mechanically detachable coils].

OBJECTIVE: To evaluate the practical and thrombogenetic characteristics of self-made mechanically detachable coils by the animal experiment and primary clinical application. METHOD: The bifurcation type of aneurysm model was established on rabbit and embolized with self-made mechanically detachable coils 2 weeks after surgery. 24 coils were used in 5 experimental aneurysms. Control angiography was performed and the rabbits were sacrificed 2 - 3 weeks after the embolization. The embolized aneurysm samples were examined by pathologist. Ten patients were treated with self-made mechanically detachable coils in primary clinical application. They were divided into aneurysms (7 patients), traumatic carotid-carvenous fistulas (2), dural arterio-venous fistula in carvenous sinus region (1). 146 coils were used totally and all were delivered with mechanical detachable system (MDS Balt co. France). RESULT: Pathologically, the cavities of rabbit aneurysm models were occluded by tungsten coils (2 complete, 3 almost complete). The coils were trapped in granulation tissue which was covered by a thin layer of endothelium on the surface facing the blood flow. In the coils dense packing ones, the aneurysms were completely excluded from the parent circulation by neointimal layers. In the practice procedures, the coils fit MDS (Balt co. France) very well and can be delivered, withdrew and detached smoothly. CONCLUSION: The self-made mechanically detachable coils have practical reliability and evident thrombogenetic effects.

Adult↗
PubMed1998

[Pathological changes of viscera after brain death: an experimental study].

In order to study the viscera changes after brain death while the function of the heart and lung was sustained artificially, 34 cats were used and divided into three groups. The results showed that pathological changes of viscera (heart, lung, liver and kidney) developed, including 1. ischemic cardiomyopathy, endocardiac hemorrhage, focal necrosis, mitochondria and microfilament destruction. 2. pulmonary congestion, edema and parenchymal inflammation. 3. ischemic lesions in the central band of hepatic lobular and ischemic lesions in renal proximal convoluted tubule.

Animals↗
PubMed1998

[The fluorescence properties of DaYaWan soil humic acid].

The fluorescence properties of humic acid derived from DaYaWan soil were analyzed using the conventional fluorescence and synchronous scan fluorescence spectroscopy. The results show that synchronous technique applied to the study of humic acid can reduce the fluorescence spectrum of a compound to a single sharp peak, and decrease the signal overlapping. In addition, the effects of various deltalambda, concentration and pH values on synchronous fluorescence spectroscopy were investigated in detail.

China↗
PubMed1997

Ig Sgamma3 DNA-specifc double strand breaks are induced in mitogen-activated B cells and are implicated in switch recombination.

The looping-out and deletion model of switch recombination suggests that double strand breaks (DSBs) may occur in switch regions and participate in the recombination transaction. A DSB assay based on the ligation-mediated PCR method has been devised for the Sgamma3 region. Mitogen-inducible DSBs have been detected in Sgamma3 DNA of normal splenic B cells but not in splenic T cells or thymocytes. The breaks are restricted to the Sgamma3 region and are sequence specific. Examination of the sequence surrounding the DSBs has led to the derivation of a consensus sequence for DSB formation. Induction of Sgamma3-specific DSBs is correlated with the onset of switch recombination. The DSBs flank clusters of Sgamma3 recombination breakpoints, suggesting that processing of the broken ends may occur during the recombination reaction.

Animals↗