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J Chin

Publications and source records attributed to J Chin.

At least 73 records · Page 4Linked to original sources
PubMed1995

The interleukin-1 beta-converting enzyme (ICE) is localized on the external cell surface membranes and in the cytoplasmic ground substance of human monocytes by immuno-electron microscopy.

Interleukin-1 beta (IL-1 beta)-converting enzyme (ICE) is a novel cysteine protease that cleaves the 31-kD inactive cytoplasmic IL-1 beta precursor into active extracellular 17-kD IL-1 beta. The ICE gene product is a 45-kD proenzyme that requires proteolytic processing to activate ICE. Active ICE is a heterodimer consisting of equal amounts of p20 and p10 subunits. Generation of active ICE is affected by the removal of an 11-kD NH2-terminal precursor domain (p11) and an internal 19-amino acid sequence that separates the 20- and 10-kD subunits. Immuno-electron microscopy was performed on human monocytes with immunoglobulins recognizing the active (p20) or precursor (p11) domains of ICE. Elutriated monocytes were stimulated with 50 pM lipopolysaccharide followed by heat-killed Staphylococcus aureus under conditions that induce maximal rates of IL-1 beta secretion. Ultrathin cryosections were cut from fixed frozen pellets of these monocytes and were immunogold labeled with either antibody. Active and precursor domain ICE epitopes were localized in the cytoplasmic ground substance, but they were not detected within the endoplasmic reticulum, the Golgi apparatus, and secretory granules of activated or inactive monocytes. Importantly, numerous ICE p20 epitopes were also observed on the extracellular surfaces of the cell membrane, and were concentrated on the microvilli. Very similar patterns of ICE localization were obtained with unstimulated blood monocytes. In contrast, ICE p11 epitopes were not detected on the surfaces of these monocytes. Likewise, labeling of fixed ultrathin cryosections of monocytes with a biotinylated irreversible ICE inhibitor [Ac-Tyr-Val-Lys(biotin)-Asp-(acyloxy)-methyl-ketone] showed that the compound localized on the outer cell surface as well, and to a lesser extent, within the cytoplasmic ground substance. Furthermore, antipeptide antibodies specific for either the mature or precursor domains of IL-1 beta were both localized upon the cell membrane after stimulation of IL-1 beta secretion. Lipopolysaccaride-primed monocytes that synthesized, but did not secrete IL-1 beta, exhibited only cytoplasmic staining. The data suggests that mature IL-1 beta is generated via cleavage of the 31-kD inactive cytoplasmic IL-1 beta precursor by ICE after association with the plasma membrane during secretion.

Amino Acid Sequence↗
PubMed1995

Involvement of the cell-cycle inhibitor Cip1/WAF1 and the E1A-associated p300 protein in terminal differentiation.

The mechanism of cell cycle withdrawal during terminal differentiation is poorly understood. We report here that the cyclin-dependent kinase (CDK) inhibitor p21Cip1/WAF1 is induced at early times of both keratinocyte and myoblast differentiation. p21Cip1/WAF1 induction is accompanied by a drastic inhibition of total Cdk2, as well as p21Cip1/WAF1-associated CDK kinase activities. p21Cip1/WAF1 has been implicated in p53-mediated G1 arrest and apoptosis. In keratinocyte differentiation, Cip1/WAF1 induction is observed even in cells derived from p53-null mice. Similarly, keratinocyte differentiation is associated with induction of Cip1/WAF1 promoter activity in both wild-type and p53-negative keratinocytes. Induction of the Cip1/WAF1 promoter upon differentiation is abolished by expression of an adenovirus E1A oncoprotein (d1922/947), which is unable to bind p105-Rb, p107, or cyclin A but which still binds the nuclear phosphoprotein p300. Overexpression of p300 can suppress the E1A effect, independent of its direct binding to E1A. Thus, terminal differentiation-induced growth arrest in both keratinocyte and myoblast systems is associated with induction of Cip1/WAF1 expression. During keratinocyte differentiation, Cip1/WAF1 induction does not require p53 but depends on the transcriptional modulator p300.

Animals↗
PubMed1995

Arrest of stomatal initials in Tradescantia is linked to the proximity of neighboring stomata and results in the arrested initials acquiring properties of epidermal cells.

We examined spatial relations of arrested stomatal initials and their differentiated state on leaves of the monocotyledon Tradescantia. The placement and proximity of stomata and arrested stomatal initials to the five nearest stomata were studied to test the hypothesis that if developing stomatal initials occur too close to one another, initials will arrest. The results showed that arrested stomatal initials were not randomly placed, but were closely associated with another stoma, most often in an adjacent cell file. The distance to their nearest stomatal neighbors was less than the equivalent distance between stomata that mature. After stomatal initials form, their position within or across cell files was not adjusted by cell division or expansion. Synergistic effects from several neighboring stomata could not be linked to stomatal arrest; rather, arrest was associated only with the nearest stomatal neighbor. Since the arrest of stomatal initials was distance dependent, a failure intrinsic to the arrested initials is not solely responsible for halting stomatal development. These data show that an inhibitory mechanism adjusts stomatal development to influence the final distribution of Tradescantia stomata. The pigmentation and expansion characteristics of arrested stomatal initials were like those of epidermal cells, indicating that the initials did not remain halted at a specific point in their development. The capacity of arrested initials to differentiate in the epidermal cell pathway indicates that they remain pluripotent after their initial specification and that the opportunity for patterning is long enough to permit their entry into the epidermal cell pathway.

Cell Division↗
PubMed1995

Linear aggregations of stomata and epidermal cells in Tradescantia leaves: evidence for their group patterning as a function of the cell cycle.

We tested Charlton's hypothesis (1990) that stomata are present and patterned in linear cell aggregations using the monocot Tradescantia. We examined the following features of the leaf epidermis in support of this theory: linear groups (strings) of stomatal complexes and of epidermal cells were sought in immature and mature regions of entire leaves; the lengths (in cell number) and incidences (numerical occurrence) of both string types were determined; the uniformity and progression of stomatal differentiation within strings were studied; physical characteristics of differentiating strings within cell files were measured. Undifferentiated epidermal cells from the leaf base were stained with DAPI to reveal precursors of stomatal strings immediately proximal to the stomatal initial region. The results indicated that the Tradescantia epidermis in the leaf blade consists of linear groups of stomata and epidermal cells, which did not change in cell number nor incidence during development. The incidence of stomata by length was nonrandom. Although incidence decreased with string length, the decline was not linear nor exponential. Stomatal strings show cell cycle synchrony in DAPI staining of stomatal precursors and synchrony of stomatal differentiation within a string. The irregularity in the length of the stomatal development region, and each differentiation stage in it, by cell file was consistent with the variation in string length and unity in string development. The evidence supports Charlton's hypothesis that cells are patterned based on their position in the cell cycle and that linear groups of stomata reflect cell lineages, which maintain a degree of cell cycle synchrony.

Cell Aggregation↗
PubMed1995

Postprandial sympatho-adrenal activity: its relation to metabolic and cardiovascular events and to changes in meal frequency.

1. Sympatho-adrenal activity was measured after the consumption of a 3.15 MJ mixed meal. Whole-body noradrenaline spillover rates, forearm plasma noradrenaline spillover and adrenaline secretion rates were derived using isotope dilution methodology. Heart rate and blood pressure spectral analysis measurements were also made. The relation of sympathoadrenal activity to thermogenic and cardiovascular events was studied. Sympathetic nervous and thermogenic responses were measured for 120 min after the single 3.15 MJ meal and compared with those after three 1.05 MJ meals, given 30 min apart. 2. Whole-body and forearm plasma noradrenaline spillover, and the 0.1 Hz component of systolic pressure power all increased significantly postprandially, while the 0.1 Hz component of heart rate variability, an indirect index of cardiac sympathetic nervous activity, remained unaltered. Adrenaline secretion was unaltered postprandially. Whole-body plasma noradrenaline spillover and thermogenesis during the 120 min postprandial period were 37% and 36% higher after the single meal as compared with the multiple meals, although this was not statistically significant. 3. The sympathetic neural responses were delayed in relation to peak plasma insulin levels and sustained in the face of declining insulin levels. Energy expenditure increased significantly postprandially, but there was no direct quantitative relationship to plasma noradrenaline spillover. Forearm oxygen consumption did not increase postprandially despite significant increases in regional noradrenaline spillover. Thus, no close relation was demonstrated between postprandial sympathetic nervous activation and either insulin secretion or thermogenesis.

Adult↗
PubMed1995

A synthetic inhibitor of interleukin-1 beta converting enzyme prevents endotoxin-induced interleukin-1 beta production in vitro and in vivo.

A potent, reversible, tetrapeptide inhibitor of interleukin-1 beta converting enzyme (ICE), L-709,049, has been shown to suppress the in vitro production of mature IL-1 beta. We now report that this inhibitor also effectively suppresses the production of mature IL-1 beta in a murine model of endotoxic shock. Intraperitoneal administration of L-709,049 reduced the elevations of IL-1 beta in the plasma and peritoneal fluid of mice treated with LPS in a dose-related manner (ED50 = 2 +/- 0.9 mg/kg). LPS-induced elevations in IL-1 alpha and IL-6 in these mice were unaffected, indicating that the inhibitor specifically affected IL-1 beta production. Immunoblot analysis of plasma and peritoneal fluid indicated that L-709,049 suppressed the formation of mature IL-1 beta production in vivo. When mouse blood was incubated in vitro with LPS, IL-1 beta was released into the plasma. This assay was used to determine ex vivo the activity of an ICE inhibitor in the blood following its administration to mice. Blood obtained 15 minutes after ip administration of 10 mg/kg of L-709,049 to mice produced 80% less IL-1 beta than control blood, and IL-1 beta production returned to control levels in blood obtained 30 minutes after injection of this inhibitor. In addition, the capacity of the blood plasma obtained from these animals to prevent the cleavage of a synthetic substrate by ICE disappeared within 1 h of ip administration of 50 mg/kg of inhibitor.

Animals↗
PubMed1995

Endoscopic detection of ischaemia with a new probe indicates low oxygenation of gastric epithelium in portal hypertensive gastropathy.

Changes in mucosal blood flow may be important in the pathogenesis of many conditions. Study of mucosal blood perfusion is difficult, and available methods have significant technical limitations. This study describes the development of an instrument for endoscopy, which indicates blood flow indirectly, by measuring the quantity of tissue oxygen that can diffuse from the mucosa to a luminal surface electrode. The instrument was used through an endoscope in patients with portal hypertension (n = 14), scleroderma (n = 3), disease controls (n = 7), and normal controls (n = 11). In portal hypertension readings were one quarter that in normal controls in both antrum (geometric mean (SEM) 35 (1.1)), nanoamps v 137 (1.1), and upper corpus 34 (1.1) v 125 (1.1)). Scleroderma patients showed greatly reduced oxygen readings in both antrum (18 (1.2)) and corpus (24 (1.2)), an expected but hitherto undiscovered result. These differences are highly significant (p = 0.0001), and the findings suggest that tissue hypoxia may contribute to mucosal changes in portal hypertensive gastropathy and in scleroderma.

Epithelium↗
PubMed1995

Cardiovascular effects of octreotide in patients with hepatic cirrhosis.

Octreotide is thought to reduce splanchnic and variceal blood flow with minimal effects on the systemic circulation in cirrhotic patients with portal hypertension. However, we noticed significant bradycardia in some patients immediately after administration of bolus doses of octreotide. Therefore, we investigated the effect of intravenous octreotide on systemic hemodynamics in 59 patients with cirrhosis. In two double-blind, placebo-controlled protocols, 32 patients received a 25-micrograms bolus and 20 patients received an infusion of 50-micrograms/hr of octreotide/placebo. Immediately after the bolus dose of octreotide was administered, there were significant reductions in pulse rate (77 +/- 3 vs. 65 +/- 3 beats per minute, P < .01) and cardiac output (9.2 +/- 0.8 vs. 7.9 +/- 0.8 L/min; P < .01) and significant increases in mean arterial pressure (81 +/- 3 vs. 87 +/- 3 mm Hg; P < .05), mean pulmonary artery pressure (9.1 +/- 1.0 vs. 16.6 +/- 1.5 mm Hg; P < .01), right atrial pressure (3.8 +/- 0.8 vs. 6.6 +/- 1.0 mm Hg; P < .01), right ventricular pressure (7.1 +/- 0.6 vs. 12.5 +/- 1.3 mm Hg; P < .01), pulmonary capillary wedge pressure (4.8 +/- 0.8 vs. 11.2 +/- 1.4 mm Hg; P < .01), systemic vascular resistance, and pulmonary vascular resistance. Thirty minutes after the start of the infusion, there were significant increases in mean right atrial pressure, right ventricular pressure, pulmonary artery pressure, and pulmonary capillary wedge pressure. This study suggests that intravenous octreotide has significant effects on the systemic circulation in patients with cirrhosis and that these effects appear to be more marked after administration of bolus doses.

Adult↗
PubMed1994

Molecular characterization of a second iron-responsive element binding protein, iron regulatory protein 2. Structure, function, and post-translational regulation.

Several genes critical to the uptake, sequestration, and utilization of iron are regulated at the post-transcriptional level. The mRNAs encoded by these genes contain highly conserved stem-loop structures called iron-responsive elements (IREs). IREs function as the nucleic acid-binding sites for a cytosolic RNA-binding protein called the IRE-binding protein or IRE-BP. Binding of the IRE-BP to IREs is reversibly regulated by the iron status of the cell. The IRE-BP is highly conserved among human, rat, mouse, and rabbit, and it is identical to the cytosolic form of aconitase. In this study, we demonstrate that a distinct human gene encoding a protein which is 57% identical to the initially described IRE-BP, now referred to as iron regulatory protein 1 or IRP1, is also capable of binding to IREs with the same in vitro affinity and specificity the originally identified protein. This second gene product, which we call IRP2, is expressed in many tissues, but its mRNA abundance and tissue distribution are different from IRP1. In most cell lines tested, levels of IRP2 are inversely regulated by iron levels due to iron-dependent regulation of the half-life of the protein. In addition to changes in total amounts of IRP2, we demonstrate that the IRE binding activity of IRP2 can also vary up to 4-fold in the absence of any change in IRP2 protein levels. The possible reasons for the existence of a second IRP are discussed.

Amino Acid Sequence↗
PubMed1994

IL-1 beta-converting enzyme is present in monocytic cells as an inactive 45-kDa precursor.

The major form of IL-1 beta-converting enzyme (ICE) identified in THP.1 monocytic cells and human monocytes is the 45-kDa precursor protein (p45), which is found in the cytoplasm. Cytoplasmic extracts of these cells show no pIL-1 beta cleavage activity, indicating that the p45 has no detectable catalytic activity. pIL-1 beta cleavage activity can only be observed after incubation in vitro when p45 breaks down to the active p20 form of the enzyme. LPS stimulation of human monocytes or THP.1 monocytic cells results in no change in the amount of p45 or its activity and no detectable appearance of p20 ICE. Immunoprecipitation of [35S]Met-labeled LPS-stimulated monocyte extracts revealed only p45 with no other co-precipitating protein. The inability to identify active ICE in stimulated monocytic cells was probably a reflection of the very low levels of active ICE present.

Caspase 1↗
PubMed1994

Two patients with overlapping de novo duplications of the long arm of chromosome 9, including one case with Di George sequence.

Duplications of chromosome 9q are rare. We describe the cytogenetic and phenotypic findings in 2 patients, one with a large duplication covering most of 9q(q12-q33.2) and one with a smaller duplication (q21.12-q22.1) who had Di George sequence (DGS). The chromosome 9 origin of the extra material in the second case was confirmed by fluorescence in situ hybridization (FISH) analysis with a whole chromosome 9 paint. Microdeletions of chromosome 22 are common in DGS and have been reported in CHARGE association. This is the first report of an association of a chromosome 9 abnormality with DGS in the absence of a chromosome 22 abnormality and the seventh report of a patient with a duplication of a large portion of 9q (q11-q13 to q32-q33).

Abnormalities, Multiple↗
PubMed1994

The growing impact of the HIV/AIDS pandemic on children born to HIV-infected women.

The increasing numbers of children born to HIV-infected women poses formidable problems for maternal and child health programs throughout the world. Between 20% and 40% of these children will be infected with HIV and most are expected to die by the age of 5 years as a result. The vast majority of the uninfected children will be orphaned before age 15 years as their mothers and fathers die of AIDS. By the late 1990s, several hundred thousand children will be born annually to HIV-infected women in developing countries, with the majority in sub-Saharan Africa and Asia compared with a few thousand in North America.

Adolescent↗
PubMed1993

Dissociation of IL-1 beta synthesis and secretion in human blood monocytes stimulated with bacterial cell wall products.

Human blood monocytes synthesize but do not secrete IL-1 beta in response to low doses of bacterial cell-wall products. With this observation, we have developed a two-step staged release assay that separates IL-1 beta synthesis from secretion. This assay can be used to identify secretagogues or inhibitors of IL-1 beta secretion as well as the biochemical events leading to IL-1 beta release. Human blood monocytes are first treated with low (< 50 pg/ml) doses of LPS, which causes the synthesis of intracellular proIL-1 beta. Release of intracellular IL-1 beta can be induced by further treatment with 100 ng/ml of LPS or 1 x 10(6) CFU/ml of heat-killed Staphylococcus aureus. The amount and the efficiency of IL-1 beta secretion in the staged release assay was comparable with that of a standard method of treating blood monocytes with a single dose of 100 ng/ml LPS. Ongoing protein synthesis was not required for IL-1 beta secretion because mature IL-1 beta release occurred in the presence of the protein synthesis inhibitor cycloheximide. We have compared the effects of four different inhibitors of cytokine synthesis on IL-1 beta production in the standard and staged release assays. We find that dexamethasone or IL-10, when added together with 100 ng/ml LPS, inhibits IL-1 beta production with IC50 levels of 0.2 microM and 2.0 ng/ml, respectively. The IC50 levels increase greater than 50-fold when tested against monocytes pretreated with 50 pg/ml of LPS. These data suggest that dexamethasone and IL-10 have little effect on IL-1 beta secretion. Conversely, the IL-1 beta converting enzyme inhibitor, Ac-Tyr-Val-Ala-Asp-CHO (L-709,049) and the anti-inflammatory agent [5-(4-pyridyl)6(4-fluorophenyl)-2,3-dihydroimidazo(2,1-b)thiazole] (SK&F 86002) inhibited IL-1 beta release in both the standard and staged release assays with IC50 of 1 microM. The data suggest that L-709,049 and SK&F 86002 interfere with steps involved in IL-1 beta secretion, as opposed to synthesis. The results also document a novel method for delineating separate events in the pathway required for IL-1 beta biosynthesis and further distinguish two classes of compounds capable of modulating IL-1 beta secretion.

Amino Acid Sequence↗
PubMed1993

An anti-okadaic acid-anti-idiotypic antibody bearing an internal image of okadaic acid inhibits protein phosphatase PP1 and PP2A catalytic activity.

Okadaic acid (OA), produced by marine phytoplankton, is the parent compound of a family of marine toxins responsible for diarrheic shellfish poisoning (DSP). A monoclonal antibody to OA (6/50) (Ab1) has been raised and in turn used for immunization of syngeneic animals. Mice inoculated with the 6/50 idiotype produced both anti-idiotypic antibodies (Ab2) and OA binding antibodies (Ab3). The selected anti-idiotypic antibody 1/59 bound to the immunizing 6/50 idiotype but not to F(ab')2 fragments of pooled normal mouse Ig. It inhibited the binding of OA to solid-phase attached F(ab')2 of 6/50 IgG as well as the binding of 6/50 IgG to a solid-phase bound OA. Like OA, 1/59 anti-idiotypic antibody inhibited protein phosphatase 1 and 2A catalytic subunits in a 32P-phosphorylase a phosphatase radioassay. Thus, 1/59 IgG is a novel internal image anti-idiotypic antibody (Ab2 beta) and can serve as a surrogate of OA in biological assays.

Animals↗
PubMed1993

Interleukin 1 beta (IL-1 beta) processing in murine macrophages requires a structurally conserved homologue of human IL-1 beta converting enzyme.

Murine interleukin 1 beta (IL-1 beta) convertase (mICE) was identified in cytosolic extracts of peritoneal exudate cells (PECs) and macrophage cell lines. mICE cleaves both the human and mouse IL-1 beta precursors (pIL-1 beta) at sites 1 and 2 but fails to cleave a human pIL-1 beta (Asp116 to Ala) mutant at site 2, indicating that Asp is required to the left of the scissile bond. Ac-Tyr-Val-Ala-Asp-amino-4-methyl coumarin, patterned after site 2 of human pIL-1 beta, is a fluorogenic substrate for mICE, while the tetrapeptide aldehyde Ac-Tyr-Val-Ala-Asp-CHO is a potent inhibitor (Ki = 3 nM) that prevents generation and release of mature IL-1 beta by PECs (IC50 = 7 microM). Cloning of a full-length 1.4-kb cDNA shows that mICE is encoded as a 402-aa proenzyme (p45) that can be divided into a prodomain (Met1-Asp122), followed by a p20 subunit (Gly123-Asp296), a connecting peptide (Ser297-Asp314), and a p10 subunit (Gly315-His402). At the amino acid level, p45, p20, and p10 are 62%, 60%, and 81% identical with human IL-1 beta convertase (hICE). The active site Cys284 lies within a completely conserved stretch of 18 residues; however, Ser289 in hICE, which aligns with the catalytic region of serine and viral cysteinyl proteases, is absent from mICE. Expression in Escherichia coli of a truncated cDNA encoding Asn119-His402 generated active enzyme, which was autocatalytically processed at three internal Asp-Xaa bonds to generate a p20 subunit (Asn119-Asp296) complexed with either p11 (Ala309-His402) or p10. Recombinant mICE cleaves murine pIL-1 beta accurately at the Asp117-Val118 bond. The striking similarities of the human and murine enzymes will make it possible to assess the therapeutic potential of hICE inhibitors in murine models of disease.

Amino Acid Sequence↗
PubMed1993

Superior mesenteric artery blood flow in man measured with intra-arterial Doppler catheters: effect of octreotide.

Changes in splanchnic blood flow are important in the pathogenesis of portal hypertension, but research in this area is hampered by the difficulty in measuring splanchnic arterial blood flow in man. We therefore investigated the use of intra-arterial Doppler catheters in measuring superior mesenteric artery blood flow in man and assessed the effect of intravenous octreotide on superior mesenteric artery blood flow in a placebo-controlled double-blind study. Nine experiments were performed in a flow model using vessels with internal diameters of 6.5, 4.5 and 3.0 mm, with flow rates ranging from 50 to 700 ml/min. In this model the catheters gave instantaneous, reproducible measurements of blood flow in vessels of 6.5 mm internal diameter with a mean error ranging from +5.3% to +36.4%, compared to electromagnetic flowmetry, but were less accurate in smaller vessels. When used in patients, the catheters provided stable, reproducible measurements of superior mesenteric blood flow, in 16 out of 20 patients studied. In a double-blind placebo-controlled study, including 12 subjects, superior mesenteric artery blood flow was significantly reduced in patients receiving octreotide. We suggest that measurement of splanchnic arterial blood flow using intra-arterial Doppler catheters may be a useful additional investigation in the assessment of splanchnic vascular pathophysiology and pharmacology in man.

Adenoma↗
PubMed1993

A comparison of transjugular and plugged-percutaneous liver biopsy in patients with impaired coagulation.

Patients with liver disease frequently have impaired blood coagulation. The optimal method for liver biopsy in this situation is not established. To investigate this issue we randomised 117 patients with impaired blood coagulation, in whom liver biopsy was required, to receive either transjugular or plugged-percutaneous biopsy. Seventeen patients were excluded prior to biopsy and a protocol biopsy was performed in 100 patients (44 transjugular, 56 plugged-percutaneous). Liver tissue was obtained in 97 (42 transjugular, 55 plugged-percutaneous). Plugged-percutaneous liver biopsy was quicker and easier than transjugular liver biopsy and the biopsies obtained were significantly larger (12 +/- 5 mm vs. 6 +/- 4 mm; p < 0.001). However, 2 of 56 (3.5%) patients who received plugged-percutaneous biopsy had haemorrhage which required transfusion, while none of the 44 patients who received transjugular biopsy had haemorrhage (not significant). Both methods of liver biopsy were associated with a high success rate and a low incidence of complications. Plugged-percutaneous liver biopsy provides larger biopsies but may be associated with an increased risk of haemorrhage.

Biopsy↗