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X Hua

Publications and source records attributed to X Hua.

48 records · Page 3Linked to original sources
PubMed1994

Detection of point mutations in exon 2 of the G6PD gene in Chinese G6PD variants.

In the past few years, a total of 6 different mutations of the G6PD gene have been reported in China. One of these, the C6 mutation (A95-->G), accounted for about 15.4% of the Chinese G6PD variants. In order to develop a strategy for rapid detection of mutation-containing exons of the G6PD gene, we applied the single-strand conformation polymorphism (SSCP) technique to the detection of mutations in exon 2 of this gene. We observed four patients with abnormal migration patterns of the exon 2 band among 20 cases of G6PD variants. Direct PCR sequencing confirmed a T to C substitution in exon 2 that has previously been reported. This procedure is therefore of particular importance for the rapid detection of mutation-containing exons in the G6PD gene.

Base Sequence↗
PubMed1993

SREBP-2, a second basic-helix-loop-helix-leucine zipper protein that stimulates transcription by binding to a sterol regulatory element.

We report the cDNA cloning of SREBP-2, the second member of a family of basic-helix-loop-helix-leucine zipper (bHLH-Zip) transcription factors that recognize sterol regulatory element 1 (SRE-1). SRE-1, a conditional enhancer in the promoters for the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A synthase genes, increases transcription in the absence of sterols and is inactivated when sterols accumulate. Human SREBP-2 contains 1141 amino acids and is 47% identical to human SREBP-1a, the first recognized member of this family. The resemblance includes an acidic NH2 terminus, a highly conserved bHLH-Zip motif (71% identical), and an unusually long extension of 740 amino acids on the COOH-terminal side of the bHLH-Zip region. SREBP-2 possesses one feature lacking in SREBP-1a--namely, a glutamine-rich region (27% glutamine over 121 residues). In vitro SREBP-2 bound SRE-1 with the same specificity as SREBP-1a. In vivo it mimicked SREBP-1a in activating transcription of reporter genes containing SRE-1. As with SREBP-1a, activation by SREBP-2 occurred in the absence and presence of sterols, abolishing regulation. Cotransfection of low amounts of pSREBP-1a and pSREBP-2 into human embryonic kidney 293 cells stimulated transcription of promoters containing SRE-1 in an additive fashion. At high levels transcription reached a maximum, and the effects were no longer additive. The reason for the existence of two SREBPs and the mechanism by which they are regulated by sterols remain to be determined.

Amino Acid Sequence↗
PubMed1993

SREBP-1, a basic-helix-loop-helix-leucine zipper protein that controls transcription of the low density lipoprotein receptor gene.

Sterol regulatory element 1 (SRE-1), a decamer (5'-ATC-ACCCCAC-3') flanking the low density lipoprotein (LDL) receptor gene, activates transcription in sterol-depleted cells and is silenced by sterols. We report the cDNA cloning of human SREBP-1, a protein that binds SRE-1, activates transcription, and thereby mediates the final regulatory step in LDL metabolism. SREBP-1 contains a basic-helix-loop-helix-leucine zipper (bHLH-ZIP) motif, but it differs from other bHLH-ZIP proteins in its larger size (1147 amino acids) and target sequence. Instead of an inverted repeat (CANNTG), the target for all known bHLH-ZIP proteins, SRE-1 contains a direct repeat of CAC. Overexpression of SREBP-1 activates transcription of reporter genes containing SRE-1 in the absence (15-fold) and presence (90-fold) of sterols, abolishing sterol regulation. We suggest that SREBP-1 is regulated by an unknown factor that is overwhelmed when SREBP-1 is overexpressed. Understanding the regulation of SREBP-1 may be crucial for understanding the control of plasma cholesterol in humans.

Amino Acid Sequence↗
PubMed1993

Nuclear protein that binds sterol regulatory element of low density lipoprotein receptor promoter. II. Purification and characterization.

This paper describes the purification and characterization of a sterol regulatory element binding protein (SREBP) that recognizes the SRE-1 sequence in the 5' flanking region of the gene for the low density lipoprotein (LDL) receptor. The protein was purified more than 38,000-fold from nuclear extracts of human HeLa cells by ion exchange, gel filtration, and DNA-affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified preparation revealed a cluster of bands at 59-68 kDa, each of which bound to the SRE-1 element as revealed by cross-linking experiments. Binding of SREBP correlated perfectly with transcriptional activity in a series of 16 sterol regulatory elements with point mutations. In the LDL receptor promoter, the 10-base pair SRE-1 is embedded in a 16-base pair sequence designated Repeat 2, which is adjacent to Repeat 3, a binding site for nuclear factor Sp1. Oligonucleotides containing Repeat 2 + 3 bound SREBP and Sp1 as revealed by mobility shift assays. SREBP produced a DNase I footprint over the SRE-1 sequence, which was immediately adjacent to the footprint produced by Sp1. The current data are consistent with the concept that SREBP acts in concert with Sp1 to achieve high level, sterol-suppressible transcription of the gene for the LDL receptor.

Base Sequence↗
PubMed1992

Adipogenesis in a myeloid supporting bone marrow stromal cell line.

The bone marrow stroma contains pre-adipocyte cells which are part of the hemopoietic microenvironment. Cloned stromal cell lines differ both in their ability to support myeloid and lymphoid development and in their ability to undergo adipocyte differentiation in vitro. These processes have been examined in the +/+2.4 murine stromal cell line and compared to other stromal and pre-adipocyte cell lines. In long-term cultures, the +/+2.4 stromal cells support myeloid cell growth, consistent with their expression of macrophage-colony stimulating factor mRNA. However, despite the presence of mRNA for the lymphoid supportive cytokines interleukins 6 and 7, +/+2.4 cells failed to support stromal cell dependent B lineage lymphoid cells in vitro, suggesting that these stromal cells exhibit only a myelopoietic support function. The +/+2.4 cells differentiate into adipocytes spontaneously when cultured in 10% fetal bovine serum. The process of adipogenesis can be accelerated by a number of agonists based on morphologic and gene marker criteria. Following induction with hydrocortisone, methylisobutylxanthine, indomethacin, and insulin in combination, a time dependent increase in the steady state mRNA and enzyme activity levels of the following adipocyte specific genes was observed: adipocyte P2, adipsin, CAAT/enhancer binding protein, and lipoprotein lipase. In contrast, adipogenesis was accompanied by a slight decrease in the signal intensity of the macrophage-colony stimulating factor mRNA level, similar to that which has been reported in other bone marrow stromal cell lines. These data demonstrate that although the lympho-hematopoietic support function of pre-adipocyte bone marrow stromal cell lines is heterogeneous, they share a common mechanism of adipogenesis.

Adipose Tissue↗
PubMed1992

[Molecular cloning and identification of 130kd mosquitocidal protein gene of Bacillus thuringiensis var. israelensis (Bti)].

The location of 130kd mosquitocidal protein gene of Bti 4Q5 strain on its 75Md plasmid was confirmed by southern hybridization using a 18-base oligonucleotide probe. The crystal protein containing the component of 130kd toxic protein was purified. The crystal protein exhibiting the mosquitocidal activity against larvae of Aedes aegypti was shown by bioassay. The purified 75Md plasmid DNA of Bti 4Q5 strain was completely digested with HindIII restriction enzyme, ligated with the vector pUC18 and transformed into the recipient cells of E. coli TG1. From Apr transformants, four clones with HindIII restriction fragment inserts highly homologous to the 18-base oligonucleotide probe were obtained by in situ hybridization and southern hybridization. The 5.2kb HindIII restriction fragment insert was obtained in clone pFH2 and clone pFH4, and 2.3kb HindIII restriction fragment insert in clone pFH1 and pFH3. For pFH2 and pFH4, the 5.2kb fragment was inserted in pUC18 in opposite orientation. It contained 130kd mosquitocidal protein gene (type I) identified by restriction enzyme map analysis. The 2.3kb HindIII fragment insert in other two clones (pFH1 and pFH3) harbored a part of the type II mosquitocidal protein gene which can be used as a probe for cloning of the type II mosquitocidal protein gene.

Bacillus thuringiensis↗
PubMed1985

Co-existence of substance P and calcitonin gene-related peptide-like immunoreactivities in sensory nerves in relation to cardiovascular and bronchoconstrictor effects of capsaicin.

Immunohistochemical studies showed that substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity co-exist in capsaicin-sensitive primary sensory neurons. Varicose SP- and CGRP-immunoreactive nerve fibres with a similar distribution pattern were seen in the lower airways and heart. The functional analysis revealed that CGRP caused cardiac stimulation and had, together with SP and neurokinin A, potent hypotensive effects. Vascular permeability was increased by SP and neurokinin A, and the bronchial smooth muscle was particularly sensitive to neurokinin A. Thus, multiple peptides stored in an possible released from the same nerve endings by capsaicin may exert differential effects in various target tissues.

Animals↗
PubMed1984

Inhibition of compound 48/80--induced vascular protein leakage by pretreatment with capsaicin and a substance P antagonist.

Intravenous injection of compound 48/80 (1 mg X kg-1) induced an acute increase in vascular permeability to plasma proteins in various organs of rats. The compound 48/80 response was partly inhibited by histamine H1 and H2 receptor blockade in the urinary bladder and in the duodenum, but not in the trachea, the oesophagus, the ureter and the paw skin. Blockade of 5-hydroxytryptamine receptors with methysergide led to a reduction of the permeability response in the oesophagus and in the urinary bladder, leaving responses in other organs unchanged. Pretreatment of neonatal rats with capsaicin almost abolished the 48/80 response in all organs except in the duodenum. Pretreatment of rats with [D-Arg1, D-Trp7,9, Leu11]-substance P, a substance P antagonist, also caused a partial inhibition of the permeability response to compound 48/80 in several organs. Topical administration of compound 48/80 (1 mg X ml-1) onto the tracheal mucosa induced local Evans blue extravasation. This response was resistant to pretreatment with histamine receptor antagonists, but was largely inhibited after neonatal capsaicin pretreatment. Topical administration of compound 48/80 (1 mg X ml-1 or 10 mg X ml-1) into the eye did not cause visible Evans blue extravasation in the conjunctiva, nor any signs of pain reaction as indicated by the absence of the wiping response, usually seen upon noxious chemical stimuli in the eye. In guinea-pigs, 10 mg X kg-1 compound 48/80 i.v. were required to induce vascular protein leakage in different organs. This response was blocked by pretreatment with H1 and H2 receptor antagonists, but only slightly reduced after systemic capsaicin pretreatment of guinea-pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Comparison of cardiovascular and bronchoconstrictor effects of substance P, substance K and other tachykinins.

The effects of substance P (SP), substance K (SK), physalaemin, eledoisin, kassinin, neuromedin K and bombesin on blood pressure, heart rate, respiratory insufflation pressure and plasma extravasation were studied in the guinea-pig. All tachykinins except neuromedin K caused a fall in blood pressure with rather similar potency. The hypotensive response after physalaemin was comparatively more long-lasting. SK and eledoisin (2.5 nmol X kg-1 i.v.) caused an initial bradycardia which then changed into tachycardia. The other tachykinins induced a slowly developing tachycardia. Neuromedin K (up to 40 nmol X kg-1) did not influence heart rate. SK, kassinin and eledoisin were more potent than SP and physalaemin in increasing respiratory insufflation pressure. The effect of SK had a particularly long duration. Neuromedin K only induced a weak increase in insufflation pressure at a very high dose. All tachykinins except neuromedin K induced an increase in vascular permeability to plasma proteins in many visceral organs, as indicated by Evans blue extravasation. The trachea and ureter were the most sensitive organs with regard to this effect. Physalaemin and eledoisin were generally more potent in increasing vascular permeability in various organs than SP and SK. The maximal permeability-increasing effect of SK was smaller than that of SP, although the potency was similar. Bombesin increased insufflation pressure with no clearcut effects on vascular permeability. It is concluded that in the same species, i.e. guinea-pig, several tachykinins have rather similar hypotensive action, while the vascular permeability increase to plasma proteins is especially pronounced after physalaemin and eledoisin. SK, kassinin and eledoisin have prominent bronchoconstrictor effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Vascular permeability changes and smooth muscle contraction in relation to capsaicin-sensitive substance P afferents in the guinea-pig.

The occurrence of neurogenic inflammation as indicated by Evans blue extravasation was studied in various organs of the guinea-pig. Electrical stimulation of the trigeminal nerve caused Evans blue extravasation due to increased vascular permeability in the nasal mucosa and gingiva. Vagal stimulation induced extravasation in the epiglottis, larynx, trachea, bronchial tree and esophagus. Splanchnic stimulation induced Evans blue extravasation in the gall bladder, bile ducts and superior mesenteric artery. Stimulation of the inferior mesenteric ganglion caused a marked extravasation in the upper and middle part of both ureters, while pelvic activation induced a reaction in the lower ureter, urinary bladder, urethra and vagina. I.v. substance P (SP) (3 nmol X kg11) or capsaicin (1 mumol X kg-1) both induced extravasation in many tissues including those in which nerve stimulation produced a response. The extravasation responses to SP, capsaicin or nerve stimulation all had similar border-line zones, such as esophagus to stomach, bile ducts to duodenum, rectum to anal mucosa, pulmonary artery to heart and vagina to uterus. Quantitative determinations showed especially large permeability effects in the trachea, umbilical ligament and ureter. The permeability effect of capsaicin and nerve stimulation was abolished in capsaicin-pretreated animals, while the response to SP was still present. Capsaicin pretreatment caused an almost total loss of SP in several visceral organs including the respiratory and urinary tracts. The SP content in these tissues was correlated (r = 0.97) to the Evans blue extravasation following nerve stimulation or i.v. capsaicin. SP and capsaicin caused contractions in vitro of the esophagus, ureter, urinary bladder, trachea and gall bladder. The capsaicin-induced contraction of the trachea was resistant to tetrodotoxin pretreatment. The non-cholinergic, non-adrenergic contraction of the urinary bladder upon field stimulation was still present in capsaicin-pretreated animals. In conclusion, neurogenic inflammation occurs in several organs with a highly region-specific distribution, which is accompanied by the presence of capsaicin-sensitive SP neurons. Both parasympathetic and sympathetic pathways contain capsaicin-sensitive afferent fibres which mediate an increase in vascular permeability most likely by releasing SP. In addition, both capsaicin and SP cause smooth muscle contraction in several visceral organs.

Animals↗
PubMed1983

Capsaicin-induced substance P release and sensory control of vascular permeability in the guinea-pig ureter.

Substance P-immunoreactivity (SP-IR) in the guinea-pig ureter was found to be totally depleted after systemic capsaicin pretreatment. Removal of the inferior mesenteric ganglion (IMG) led to a total depletion of SP-IR from the rostral third of the ureter and to a partial depletion from the caudal third. Electrical stimulation of the IMG caused Evans blue extravasation mainly in the rostral third of both ureters, whereas stimulation of the right pelvic nerve caused Evans blue extravasation in the caudal third of the ureters on both sides. The responses to nerve stimulation were absent in capsaicin-pretreated animals. Furthermore, capsaicin caused release of SP-IR from ureter slices in vitro, this release was not inhibited by tetrodotoxin. Potassium (60 and 120 mM) also released SP-IR. It is concluded that SP-IR in the ureter is contained in capsaicin-sensitive sensory neurons reaching the ureter via both parasympathetic (caudal part) and sympathetic nerves (rostral part). Activation of these neurons by capsaicin leads to a peripheral release of SP-IR which most likely increases vascular permeability.

Animals↗