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F Huang

Publications and source records attributed to F Huang.

At least 145 records · Page 8Linked to original sources
PubMed1995

Boron-containing oligodeoxyribonucleotide 14mer duplexes: enzymatic synthesis and melting studies.

A set of three 14mer oligodeoxyribonucleotides of sequence d(5'-CTATGGCCTCAG*CT-3'/3'-GATACCGGAGTCGA-5') containing G* variants either as 2'-deoxyguanosine phosphate (unmodified), N7-cyanoborane 2'-deoxyguanosine phosphate (base-modified) or 2'-deoxyguanosine boranophosphate (backbone-modified) were synthesized by template-directed primer extension. Both the N7-cyanoborane 2'-deoxyguanosine triphosphate and 2'-deoxyguanosine alpha-boranotriphosphate nucleotides are good substrates for Sequenase. We infer that a single Sp boranophosphate linkage (which has a stereochemistry equivalent to the corresponding Rp thiophosphate analog) is formed in the backbone-modified 14mer. Thermally induced helix-coil transitions were monitored for the hybridized duplexes using UV and circular dichroism (CD) spectroscopy. The CD spectra of the two types of boron-modified hybrids closely resemble the unmodified parent duplex, forming B-type helices in 150 mM NaCl, 1 mM EDTA, 10 mM phosphate, pH 7.4, buffer. UV melting results indicate that both hybrids have stabilities comparable with the parent duplex as measured by Tm or delta G degree 25. These studies indicate that singly modified base- or backbone-boronated DNA are good analogs of normal DNA.

Base Sequence↗
PubMed1995

N7-cyanoborane-2'-deoxyguanosine 5'-triphosphate is a good substrate for DNA polymerase.

The 5'-triphosphate of the boronated nucleoside analog N7-cyanoborane-2'-deoxyguanosine (7bdGTP) was synthesized, and a series of experiments was initiated to assess the potential of the compound to serve as a substrate for DNA polymerases. We show here that 7bdGTP can be incorporated into DNA by Sequenase. The resulting hemiboronated extension products are resistant to cleavage by treatment with either DMS and heat or a number of restriction enzymes. Further, in the polymerase chain reaction, 7bdGTP can be utilized as a substrate for Taq polymerase. Finally, by kinetic analysis, we have found that 7bdGTP is a more efficient substrate for exonuclease-free Klenow than normal dGTP. Thus, the introduction of a cyanoborane moiety to the N7 position of dGTP results in a nucleotide that is accepted in lieu of normal dGTP by a number of DNA polymerases.

Base Sequence↗
PubMed1995

Colon goblet cells lose proliferative response to TGF alpha as they differentiate.

Two cell line models for colon goblet cells expressed 6- to 14-fold elevated levels of the EGF receptor, 3- to 5-fold levels of TGF alpha and 11- to 15-fold levels of amphiregulin compared with 2 cell lines which model colon enterocytic differentiation, suggesting a role for the EGF receptor and its ligands in goblet cell growth control. Two HT29 colon carcinoma sublines were used to model normal goblet cells at different stages of maturation. TGF alpha induced a 2-fold increase in growth of the HD8 subline but inhibited the growth of the more differentiated HD6 subline by 40%. EGF receptors were activated in each line by ligand, but signal transduction varied sharply. Both MAP kinase isoforms, p44 and p42, were markedly activated in HD8 cells for at least 20 min, while only a marginal activation was seen in HD6 cells. In contrast, the more differentiated HD6 cells showed an increase in 105 kDa MBP kinase activity with EGF treatment, while HD8 cells displayed constitutively elevated levels of this kinase. Thus, activated EGF receptors initiated different signalling pathways in model cell lines for colon goblet cells at different stages of maturation. TGF alpha protein levels have been shown by other investigators to be restricted to the top of the cylinder-like colonic crypt, where cells terminally differentiate and cease division, an unexpected location for an epithelial cell mitogen. Our data with model cell lines imply that normal colon goblet cells lose proliferative response to TGF alpha as they differentiate and the elevated levels of TGF alpha at the top of the colonic crypt in vivo serve to inhibit goblet cell growth.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1995

Platelet-derived growth factor-B increases colon cancer cell growth in vivo by a paracrine effect.

PDGF-B released from colon tumor cells regulated tumor growth in athymic mice in a paracrine manner by inducing blood vessel formation. A positive correlation was found between expression of PDGF B-chain in cells grown in vitro and the number of factor VIII-positive blood vessels in tumors induced by three classes of colon carcinoma cell lines. Elevated expression of PDGF-B was also correlated with tumor size. Each cell line had the same mutations in the colon cancer genes APC, DCC, and p53 and had wild type c-K-ras genes (Huang et al. [1994] Oncogene, 9:3701-3706.) eliminating the possibility that any differences in tumor blood vessel formation were due to mutations and/or deletions in these genes. Colon carcinoma cells released biologically active PDGF capable of stimulating the growth of NIH3T3 cells, which was inhibited by neutralizing antisera to PDGF-AB chains. An inverse correlation was found between induction of factor VIII-positive blood vessels and expression of vascular endothelial growth factor (VEGF), while no correlation was seen with expression of either TGF alpha or k-FGF. Basic fibroblast growth factor (FGF) expression was not detected in these tumor cells. TGF beta 1 was capable of inducing PDGF-B expression in the undifferentiated U9 colon carcinoma cell line, but this sensitivity was not seen in differentiated cells. In contrast, TGF beta 1 inhibited VEGF expression in both undifferentiated cells and differentiated colon cancer cells. Thus, TGF beta 1 has two roles in the growth of undifferentiated U9 colon carcinoma cells in vivo: direct stimulation of cell proliferation as we have showed in earlier studies, and an increase in angiogenesis by inducing PDGF-B.

Animals↗
PubMed1995

Colon absorptive epithelial cells lose proliferative response to TGF alpha as they differentiate.

As colon epithelial cells migrate up the cylindrical colonic crypt, they terminally differentiate and lose their ability to divide. Elevated levels of the epithelial cell mitogen TGF alpha have been found at the top of the crypt by other investigators, causing us to speculate that colon epithelial cells lose mitogenic response to TGF alpha as they differentiate. We tested this hypothesis by using the HT29 colon carcinoma sublines U4 and U4H as models of one colonocyte lineage, fluid-transporting enterocytes. TGF alpha was mitogenic for the U4 cells, but inhibited the growth of the more differentiated U4H cells. However, p44 MAP kinase was activated by TGF alpha in both U4 and U4H cells, as well as in two control undifferentiated HT29 sublines which showed no change in proliferation in response to TGF alpha. In addition, TGF alpha activated the EGF receptor in each line by increasing its tyrosine phosphorylation. No relationship was found in these four lines between response to TGF alpha and level of expression of either the EGF receptor or two EGF receptor ligands, TGF alpha and amphiregulin. Activated EGF receptors initiate both growth-inhibitory and mitogenic signals in these cells since blocking some of the EGF receptors on TGF alpha-growth-inhibited U4H cells and TGF alpha-unresponsive U9 cells overrode the inhibitory signals and made both U9 and U4H cells sensitive to mitogenesis by added TGF alpha. These data imply that upon reaching stages of greater maturation, colon enterocytes lose proliferative response to TGF alpha because of changes in signaling by their EGF receptors.

Amphiregulin↗
PubMed1995

Composite valve graft replacement of the ascending aorta and the aortic valve by a modified button technique: the influence of aortic pathology on early mortality and late survival.

The risk factors for in-hospital mortality and mid-term survival in patients undergoing composite graft replacement of the aortic root with reimplant or coronary arteries by a modified button technique were evaluated with special emphasis on the underlying aortic pathology. Between 1985 and 1993 74 patients underwent replacement of the ascending aorta and the aortic valve following a modified button technique. The patients were divided into three groups according to aortic pathology: annuloaortic ectasia (43.58%), type A dissection (18.24%), and miscellaneous (13.18%). In-hospital mortality rates were 4.7%, 33.3% and 23.1%, respectively (P = 0.011). Univariate analysis showed that aortic pathology, NYHA class, emergency operation, redo operation, acute aortic dissection, preoperative cardiogenic shock, preoperative cardiac tamponade, longer cardiopulmonary bypass (CPB) and aortic cross-clamp times, and the need of femoral vein or femoral artery cannulation at intervention had univariate influence on in-hospital mortality. Multivariable stepwise logistic regression analysis identified CPB time odds ratio (OR) = 1.021/min, P = 0.007), the need of femoral vein cannulation at intervention (OR= 4.85, P = 0.008) and preoperative cardiac tamponade (OR = 3.11, P = 0.07) as independent predictors of in-hospital death. Follow-up ranged from 1 to 98 months (mean 39 +/- 30 months) with an actuarial survival rate of 75 +/- 9%, 52 +/- 13% and 67 +/- 14% at 5 years in annuloaortic ectasia, type A dissection, and miscellaneous patients, respectively (P = 0.18); when survival was evaluated in hospital survivors only, Kaplan-Meier survival rates were 77 +/- 9%, 79 +/- 14% and 89 +/- 10% at 5 years (P = 0.87). Comparing survival of annuloaortic ectasia patients (5-year survival 75 +/- 9%) versus survival of all other patients pooled together (5-year survival 55 +/- 11%), there was a statistically significant difference (P < 0.05); such a difference was no longer significant when comparing hospital survivors alone (5-year survival rate 77 +/- 9% annuloaortic ectasia patients vs 79 +/- 12% all other patients P = 0.61). Although aortic root replacement carries higher in-hospital mortality in some high-risk subgroups of patients, mid-term survival seems to be less affected by aortic pathology; high-risk patients are expected to have an out-hospital outcome comparable to the low-risk ones.

Aortic Dissection↗
PubMed1995

Colon carcinoma cells with inactive nm23 show increased motility and response to motility factors.

nm23H1 has properties of a metastasis suppressor gene. Although its mechanism of action is unknown, nm23 has been implicated in transforming growth factor beta 1 (TGF beta 1) signal transduction. In an earlier study we decreased nm23 mRNA levels 2- to 8-fold by antisense phosphorothiolated oligonucleotides in two HT29 colon carcinoma sublines at different stages in tumor progression with different responses to TGF beta 1: the HD3 subline, which shows TGF beta 1-induced growth arrest and differentiation; and the more tumorigenic U9 subline, whose growth and invasion are stimulated by TGF beta 1. Only TGF beta 1-mediated responses in HD3 cells were inhibited by nm23 antisense oligos, suggesting that nm23 functions in only one TGF beta 1 signaling pathway. In the current report we have extended this study to cell motility. HD3 motility was increased by nm23 phosphorothiolated antisense oligos which decrease nm23 mRNA levels, while HD3 cell motility was conversely decreased by TGF beta 1 which increases nm23 mRNA levels. HD3 motility was not increased by basic FGF, TGF beta 1 or TGF alpha, while the 13-fold higher basal motility of U9 cells was stimulated 3-fold by basic FGF, 4-fold by TGF beta 1 and 5-fold by TGF alpha, but not by scatter factor. Differences in motility and response to motility factors could not be ascribed to differences in either basal levels of proteases or modulation of their levels by TGF beta 1. Both HD3 and U9 cells displayed equal levels of urokinase activity and mRNA, equal expression of the metalloproteinase inhibitor TIMP-1, and no detectable collagenases by zymography. No differential response to TGF beta 1 was seen in any of these assays. Thus limited cell motility and lack of response to motility factors in HD3 colon cancer cells could be correlated with expression of nm23 active in signal transduction.

Base Sequence↗
PubMed1995

The effect of multiple blood conservation techniques on donor blood exposure in adult coronary and valve surgery performed with a membrane oxygenator: a multivariate analysis on 1310 patients.

The object of the study was to retrospectively evaluate protective and risk factors for receiving donor blood products and red cell transfusions after coronary and valve surgery performed with a hollow-fiber oxygenator and with multiple blood-saving techniques. During the period of January 1991 to June 1993, 1310 patients underwent primary coronary and valve surgery using a hollow-fiber oxygenator at our institution; the mean age of this population was 61 +/- 10 years; 977 patients were men (74.6%). Of these patients, 73.5% (963/1310) underwent coronary, 21.5% (281/1310) valve, and 5% (66/1310) combined surgery. Two hundred seventy-six (21.1%) needed donor blood product transfusions, while 153 (11.7%) patients underwent red cell transfusions. Significant risk factors for homologous blood product exposure after multivariate logistic regression analysis were, in order of importance: (1) postoperative blood loss (O.R. = 1.0009 per mL, p = 0.0000); (2) cardiopulmonary bypass (CPB) time (O.R. = 1.008 per min, p = 0.0001); (3) age at intervention (O.R. = 1.031 per calendar year, p = 0.0026); and (4) reoperation for bleeding (O.R. = 1.71, p = 0.0078). Protective factors were: (1) male gender (O.R. = 0.56, p = 0.0000); (2) preoperative withdrawal of autologous blood (O.R. = 0.66, p = 0.0018); and (3) a preoperative hematocrit greater than 34% (O.R. = 0.76, p = 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

[A preliminary study on the inhibitory action of target-primaqine on the exoerythrocytic forms of Plasmodium yoelii yoelii].

Target-primaquine (TPQ)--the primaquine entrapped by galactosylneoglycoalbumin (G-NGA), was given intravenously (iv) to Wistar rats 2 h after sporozoite inoculation. The sporozoite viability (SPV) of TPQ 20 mg/kg group was revealed to be 1.2% 42 h after inoculation, which showed a decline of about 6% as compared to the control; besides, degeneration or retardation of development was present in 90% of EEF. In TPQ 10 mg/kg and PQ 20 mg/kg groups, the SPV were 2.8% and 5.0%, respectively, showing drops by 15% and 26% as compared with that of the control. Degeneration or retardation in development was also visible in about half of the EEF. In mice which were treated iv with TPQ 10 mg/kg or PQ 20 mg/kg 2 h after sporozoite inoculation, the prepatent periods were delayed markedly as compared with that of the control. Parasitemia did not appear in 2 mice in 10 mg/kg TPQ group further indicated the effectiveness of the drug. The results suggest that the anti-EEF effect of TPQ is apparently more promising than that of PQ.

Albumins↗
PubMed1995

An extensive subfrontal approach to the lesions involving the skull base.

A modification of the transbasal approach of Dorome called extensive subfrontal approach and the surgical results with this approach in 22 cases are presented. Bilateral frontal craniotomies incorporated with the removal of orbital ridges and part of the orbital roofs were fashioned en bloc. It may give rise to good exposure of the midline lesions of the anterior, middle and posterior skull base, minimizing the need for the retraction of frontal lobes. There was no surgical mortality in this series of cases. Of the 20 cases with tumors, total resections were achieved in 11 cases, subtotal or large resections in 4 cases and partial resection in one case. Two patients with spontaneous rhinorrhea were successively treated surgically. 21 patients had a follow-up with a time ranging from 1-11 years (a mean of 3 years). 15 patients resumed their jobs with no evidence of recurrence of the original disease, and 5 patients able to live self-care. One patient with an olfactory neuroblastoma died 3 years after the operation owing to relapse of the tumor.

Adolescent↗
PubMed1995

[Detection of estrogen receptor messenger ribonucleic acid in normal and ovariectomized rat bone].

Using ovariectomized female SD rats (OVX) as animal osteoporosis models, RNA samples were extracted directly from rat bone. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to examine the estrogen receptor (ER) messenger RNA (mRNA) level of expression in normal and OVX rat bone tissue. Results demonstrated that the rat ER gene is expressed in normal rat bone. DNA sequencing showed 300 bases sequence. We found that the OVX rats showed a sharp decrease in ER mRNA level when estrogen was reduced after ovariectomy and the expression of bone ER mRNA increased during estradiol therapy, suggesting that the expression of bone ER mRNA relies upon the level of estrogen. In addition, ER plays a very important role in the pathogenesis by means of its gene regulatory functions.

Animals↗
PubMed1995

Transforming growth factor beta 1 (TGF beta 1) is an autocrine positive regulator of colon carcinoma U9 cells in vivo as shown by transfection of a TGF beta 1 antisense expression plasmid.

A transforming growth factor beta1 (TGF beta1) antisense expression plasmid under constitutive control of the Rous sarcoma virus promoter was introduced into the highly tumorigenic and invasive colon carcinoma U9A cell line, which uses its autocrine TGF beta1 as a growth-stimulating factor. Stable transfectants were infrequent, and only the K6 transfectant exhibited 39 and 33%, respectively, of the levels of TGF beta1 mRNA and active, secreted TGF beta1 protein of the parental line. K6 exhibited no change in TGF beta2 expression, and TGF beta3 expression was not detected in either parental or transfectant cells. Compared to the parental line, the K6 antisense transfectant exhibited a 3-fold increase in lag time in anchorage-dependent colony formation. The parental line was 44 times as invasive through a collagen l-coated polycarbonate membrane in vitro as K6 cells and, after s.c. injection at low-cell inocula, U9A cells induced tumors 75 times as large in vivo as did the K6 antisense transfectant. The decreases in in vitro invasion and anchorage-dependent colony formation seen in K6 cells were largely reversed by the addition of TGF beta1. Tumors that did arise from the K6 antisense transfectant cells had lost antisense TGF beta1 expression and expressed the same TGF beta1 mRNA levels as controls. U9A cells were more metastatic to the liver after intrasplenic injection than K6 cells. These findings demonstrate a role for autocrine TGE beta1 in colon cancer tumorigenicity and invasion. They also show that a relatively small decrease in TGF beta1 levels was enough to markedly decrease colon carcinoma cell aggressiveness. This is not unprecedented, as we had found in an earlier study that a small, 2-4-fold increase in TGF beta1 protein levels in human colon cancers correlated with disease progression to metastases (E. Friedman et al., Cancer Epidemiol, Biomarkers & Prev., 4:549-554, 1995).

Animals↗
PubMed1994

The effect of mutant beta 2-microglobulins on the conformation of HLA-B27 detected by antibody and by CTL.

The arthritis-predisposing HLA-B27 consists of a heavy chain, a small peptide, and the monomorphic beta 2-microglobulin (beta 2-m). CTLs and a mAb, Ye-2, which recognize the complex with specificities both for the heavy chain and for the peptide, are available. The beta 2-m is in noncovalent association with the heavy chain at multiple points and is exchangeable with free beta 2-m outside of the complex. The purpose of our experiments was to test whether mutant beta 2-m capable of modulating HLA-B27 activity could be created. Eighteen recombinant mutants of the human beta 2-m were experimentally generated. In 14 of these, mutations were at or near residues that are either contact residues or interface residues with the heavy chain. Relative to the parent beta 2-m, two-thirds of the mutants showed reduced ability to exchange into HLA-B27 complexes. However, at least four of them induced more than 80% decrease in Ye-2 Ab reactivity. Two mutants were able to induce a minor decrease in susceptibility to lysis by four CTL clones. One of the CTL clones was autoreactive. Two of the CTL clones were specific for HLA-B27 cells experimentally infected with arthritis-causing Yersinia enterocolitica. These results indicate that certain beta 2-m residues play an indirect role in peptide presentation, although they are not directly associated with the peptide residues.

Amino Acid Sequence↗
PubMed1994

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies.

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

Amino Acid Sequence↗
PubMed1994

Position-reading and the emergence of sense organ precursors in Drosophila.

Genetic analysis of development in Drosophila melanogaster has advanced our understanding of "position reading", where the expression of particular genes informs a cell of its position in the developing animal. The first step in localization of fly sense organs is the local expression of a gene conferring neural competence on epidermal cells. The four genes of the achaete-scute (AS-C) complex play crucial roles in the localization of sense organs. The resolution of local expression of AS-C genes along one dimension is about 10%; accuracy is improved by the balancing local expression of AS-C antagonist genes such as extramacrochaete. Position reading seems to depend primarily on such patterns of gene expression, and not upon the compartmental identity of the cells. No evidence has been found for differing roles of the four AS-C genes in the generation of sense organ progenitor cells or in the specification of neuronal properties of innervating neurons. The formation of each sense organ may be a unique case where the different proneural and neurogenic gene products have varying importance, and fortuitous local effects acting on this complex combination of factors have come to be important. The fly may be evolving from a flexible regular pattern to an inflexible irregular pattern strongly dependent on local factors, turning the fly into a crystallized system. (Written by R. Wayne Davies.).

Animals↗