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Biomedical subjects

F Liu

Publications and source records attributed to F Liu.

At least 631 records · Page 35Linked to original sources
PubMed1993

Interleukin-10 production by human carcinoma cell lines and its relationship to interleukin-6 expression.

Recent data indicate a major role for IL-10 in suppressing immune and inflammatory reactions. To date, expression of human IL-10 has been attributed primarily to helper T lymphocytes, activated monocytes, and neoplastic B cells, and was often found to be associated with IL-6 expression. In this study we sought to determine whether non-hematopoietic human tumor cell lines produce IL-10 and, if so, what is the relationship between IL-10 and IL-6. Using ELISA, we determined IL-10 and IL-6 levels in culture supernatants of 48 cell lines established from carcinomas of the kidney, colon, breast and pancreas, malignant melanomas and neuroblastomas. IL-6 protein was secreted by 28 of the tumor cell lines; IL-10 was measurable in 15 cell lines. IL-6 secretion was maximal and most frequent in renal-cancer cell lines, while IL-10 production was found to be highest and most common among cell lines derived from colon carcinomas. IL-10 in conditioned medium of one of the colon carcinoma cell lines (CCL222) was bio-active, as demonstrated in the mouse MC/9 mast-cell-line assay and in human mixed-lymphocyte reactions. In both assays, IL-10 bio-activity was neutralized by an anti-IL-10 monoclonal antibody. Expression of IL-6 and IL-10 was confirmed by RNA analysis using message amplification by PCR and sequencing of amplified cDNA. LPS, IL-1 alpha, and TNF-alpha strongly enhanced the release of IL-6 by RCC cells, but only marginally affected IL-10 production in colon-carcinoma cells. IL-10 secretion by colon-carcinoma cells was moderately stimulated by IFN-gamma and IL-4. Dexamethasone suppressed the release of IL-6, but had no inhibitory effect on IL-10 secretion. Our results demonstrate that tumor cell lines established from certain types of human carcinomas are capable of expressing and releasing IL-6 and/or IL-10, suggesting a role of these cytokines in solid-tumor development and anti-tumor immunity.

Animals↗
PubMed1993

Activating transcription factor-1 can mediate Ca(2+)- and cAMP-inducible transcriptional activation.

Increased intracellular cAMP and Ca2+ levels can activate transcription of a number of eukaryotic genes through a common promoter element, the cAMP/Ca2+ response element. This element is the binding site for activating transcription factor (ATF)/CREB proteins, an extensive transcription factor family. Here we report that one member of this family, ATF-1, can mediate both Ca2+ and cAMP transcriptional responses, but that the responses to the two pathways differ in magnitude. In contrast, another family member, CREB, has been shown to mediate Ca2+ and cAMP responses to similar levels. Taken together, these results suggest a mechanism that allows cells to integrate and differentiate gene regulation by cAMP and Ca2+.

Activating Transcription Factor 1↗
PubMed1993

Identification of the herpes simplex virus-1 protease cleavage sites by direct sequence analysis of autoproteolytic cleavage products.

Herpes simplex virus type-1 (HSV-1) encodes a protease responsible for proteolytic processing of the virus assembly protein, ICP35 (infected cell protein 35). The coding region of ICP35 is contained within the gene that encodes the protease, and ICP35 shares amino acid identity with the carboxyl-terminal 329 amino acids of the protease. The HSV-1 protease was expressed in Escherichia coli as a fusion protein containing a unique epitope and the protein A Fc binding domain at its carboxyl terminus. The fusion protease underwent autoproteolytic cleavage at two distinct sites. The size of the cleavage products containing the carboxyl-terminal epitope mapped one cleavage site near the carboxyl terminus of the protease corresponding to the proteolytic processing site of ICP35, and the second site proximal to the amino terminus consistent with previous data. The carboxyl-terminal autoproteolytic cleavage products were partially purified on an IgG affinity column by virtue of the protein A Fc binding domain and subjected to direct amino-terminal sequence analysis. Protein sequencing revealed that cleavage occurs between the Ala and Ser residues at amino acids 610/611 and 247/248 of the HSV-1 protease. The flanking sequences share homology with each other and are highly conserved in homologous proteases of other herpes viruses.

Amino Acid Sequence↗
PubMed1993

Production of human cloned antibodies specific for hepatitis D virus-encoded small and large protein.

Cloned antibodies to specific epitopes of hepatitis D virus were produced by transformation with Epstein-Barr virus and subsequent cloning of peripheral blood B lymphocytes from a patient with chronic hepatitis D virus infection. Several stable cloned B cell lines, derived from two parent cultures, produced hepatitis D-virus-specific IgG antibodies. Some cloned IgG antibodies detected hepatitis D virus-associated antigen in hepatitis D virus-infected woodchuck liver tissue sections by indirect immunofluorescence staining and some reacted in an inhibition ELISA test detecting hepatitis D virus antibodies; most cloned IgG lines detected hepatitis D antigen both in immunofluorescence tests and in inhibition ELISA. Cloned antibodies to hepatitis D antigen detected by ELISA and/or immunofluorescence staining recognized the two major specific native and denatured polypeptides, p27 and p29, in Western blot analysis. Such cloned antibodies for hepatitis D virus are potentially useful for clinical diagnosis and research.

Antibodies, Viral↗
PubMed1993

Effect of metabolic acidosis on the expression of insulin-like growth factor and growth hormone receptor.

To further our understanding of the growth failure in metabolic acidosis, we examined the insulin-like growth factor (IGF-I and IGF-II), the IGF binding protein-3 (IGFBP-3), and the hepatic IGF mRNA and growth hormone receptor mRNA in control, pair-fed and acidotic rats. The rats in the last group were made acidotic by using ammonium chloride (1.5%) as their sole fluid intake for eight days. Metabolic acidosis was confirmed by a blood pH of 7.11 +/- 0.10 (mean +/- SD). The mean starting weights for all rats were 167.1 +/- 3.4 grams. Growth impairment was observed in the acidotic rats after one week of ammonium chloride intake. The body weights of the acidotic rats compared to those of the control rats were 155.5 +/- 18.9 g versus 222.8 +/- 9.7 g, P < 0.001; the pair-fed rats weighed 156.8 +/- 19.6 grams. All rats were bled and sacrificed on day 8. Sera and tissue were analyzed with the following results: compared to the ad libitum controls, the same IGF-I concentrations were significantly decreased in the acidotic animals (P < 0.02) as well as pair-fed controls (P < 0.005). The serum IGF-II and IGF-binding protein-3 concentrations were unchanged by acidosis or food restriction. The hepatic IGF-I mRNA was significantly reduced by acidosis (P < 0.01) and pair-feeding (P < 0.01). Compared to control, the mean hepatic IGF mRNA in acidosis was significantly lower (P < 0.01). However, there was no significant difference between the acidotic and the pair-fed groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1993

Brief physical inactivity prolongs colonic transit time in elderly active men.

The effects of two weeks of reduced activity on gastrointestinal transit time were studied in nine healthy elderly subjects, who had engaged in regular recreational exercise for ten years. Physical inactivity was achieved by a restriction of all kinds of physical exercise and by staying at home. Mouth-to-cecum transit time was measured by a breath hydrogen method and mean total and segmental colonic transit times by a radiopaque marker method. The mouth-to-cecum transit time did not change during the period of physical inactivity. The mean total colonic transit time (10.9 +/- 2.7 h) was significantly prolonged to 19.5 +/- 2.9 hours during the physical inactivity (p < 0.01). This prolongation was due to slowed transit through the right and the left segments of the colon. The transit time of the rectosigmoid segment of the colon was not affected. In conclusion, the period of physical inactivity prolonged the colonic transit time in active elderly subjects.

Aged↗
PubMed1993

Characterization of the protease and other products of amino-terminus-proximal cleavage of the herpes simplex virus 1 UL26 protein.

The herpes simplex virus 1 UL26 open reading frame encodes a protease which cleaves a small carboxyl-terminal peptide of itself and its substrate encoded by an overlapping, 3'-coterminal transcriptional unit, designated UL26.5. The translational product of UL26.5 is infected-cell protein 35c,d (ICP35c,d) (F. Liu and B. Roizman, J. Virol. 65:206-212, 1991; F. Liu and B. Roizman, J. Virol. 65:5149-5156, 1991). The protease activity maps at the amino terminus of UL26 translation product designated Pra. Cleavage of Pra to remove the carboxyl-terminal 25 amino acids converts the protein to Prb (F. Liu and B. Roizman, Proc. Natl. Acad. Sci. USA 89:2076-2080, 1992). Other studies reported a second, amino-terminus-proximal cleavage in UL26 gene products made in Escherichia coli (I. C. Deckman, M. Hagen, and P. J. McCann III, J. Virol 66:7362-7367, 1992; C. L. DiIanni, D. A. Drier, I. C. Deckman, P.J. McCann III, F. Liu, B. Roizman, R. J. Colonno, and M. G. Cordingley, J. Biol. Chem., 368:2048-2051, 1993). We report the following results. (i) The amino-terminus-proximal cleavage of UL26 protein in eukaryotic cells generates two polypeptides, an apparent M(r)-25,000 amino-terminal polypeptide designated Prn and a carboxyl-terminal polypeptide which corresponds in electrophoretic mobility to ICP35a. Cleavage of the carboxyl-terminal 25 amino acids by the UL26 protease converted ICP35a to ICP35b. (ii) Replacement of Ala-247-Ser-248 with Arg-Pro precluded the amino-terminus-proximal cleavage. (iii) Prn, the amino-terminal product of the cleavage reaction at amino acid 247 functions as a protease. (iv) Additional amino acid substitutions in the putative domain of the protease yielded results consistent with the hypothesis that UL26 encodes a serine protease. (v) The domain of the UL26 protein whose modification confers the formation of double bands for all products (Pra, Prb, ICP35a, ICP35b, ICP35c,d, and ICP35e,f) except Prn maps in the domain shared by UL26 and UL26.5, between codons 307 and 417.

Amino Acid Sequence↗
PubMed1993

Characterization of insulin-like growth factor binding protein-3 in chronic renal failure serum.

IGF-binding protein-3 (IGFBP-3), usually found as glycosylated 41- and 38-kD forms, is the major serum IGFBP during extrauterine life. In normal serum IGFBP-3 binds one IGF peptide and one acid-labile (alpha) subunit in a high-molecular-weight (MW) complex of 150 kD. By RIA, an excess of IGFBP-3 is present in chronic renal failure (CRF) serum, where it reportedly accumulates at low MW (25-55 kD) rather than as part of the 150-kD complex. To further evaluate IGFBP-3 forms in CRF, sera were obtained from seven healthy adolescents and seven adolescents with CRF. By RIA, IGFBP-3 levels were higher in CRF than normal sera (15.4 +/- 2.2 versus 10.1 +/- 2.1 micrograms/mL). High-MW (150-kD) fractions of CRF and normal sera, obtained by neutral size-exclusion chromatography, had equal amounts of IGFBP-3 by RIA. However, a second RIA peak of IGFBP-3, present in low-MW (35-kD) fractions of CRF but not normal sera, could account for the higher IGFBP-3 levels of CRF serum. [125I]IGF ligand blots of whole serum and serum fractions, either with or without prior precipitation by IGFBP-3 antiserum, found levels of 41- and 38-kD IGFBP-3 forms to be similar between CRF and normal whole sera and located these forms in the high-MW (150-kD) fractions of CRF and normal sera.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Characterization of proinsulin-like growth factor-II E-region immunoreactivity in serum and other biological fluids.

Insulin-like growth factor-II (IGF-II) purified from human serum consists of 67 amino acids. However, mRNA sequence predicts a long carboxy-terminal extension (E-region), which on translation would yield a bigger IGF-II prohormone than the peptide isolated from serum. A peptide containing the predicted IGF-II prohormone sequence extending from Asp69 to Tyr84 (E-II) was synthesized by the solid state method and used to generate a polyclonal antiserum. Using this E-II antiserum, a specific RIA for IGF-II prohormone forms was developed. [125I]E-II was used as tracer, and synthetic E-II was used for the standard curve. The antiserum was highly sensitive and specific for E-II. It also recognized pro-IGF-II-E21, a 9.8-kilodalton (kDa) synthetic peptide which consisted of IGF-II plus the first 21-amino acid sequence of the IGF-II E-peptide region. Human biological fluids assayed included serum and amniotic, seminal, and cerebral spinal fluids. Sera from patients with chronic renal failure (CRF) and nonislet cell tumor hypoglycemia (NICTH) had the highest levels of E-II immunoreactivity. Amniotic and seminal fluids and acromegalic plasma had intermediate levels. E-II levels in normal, cord, and pregnancy sera were low, but measurable. To further characterize the molecular forms of the apparent E-II immunoreactivity, sera pooled from five normal subjects, five CRF patients, and one patient with NICTH were chromatographed separately over a Sephadex G-50 column in formic acid. With all samples, there was a major peak of E-II immunoreactivity at about 15 kDa, consistent with the predicted size of the IGF-II prohormone. There was a second smaller peak at about 10 kDa in NICTH serum. With CRF serum, there was a prominent peak at 3 kDa, which probably consisted of breakdown products of the IGF-II E-peptide region. The 15-kDa peak was highest in NICTH serum. With all three samples, IGF-I eluted in a single peak at about 7 kDa and was low in NICTH serum. There were two peaks of IGF-II. The first coincided with the peak of E-II at 15 kDa, while the second comigrated with IGF-I. By Western immunoblot analysis, the E-II antiserum detected pro-IGF-II-E21 as a band at 10 kDa, but it did not recognize 7.5-kDa recombinant IGF-II, which did not have the E-peptide region.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1993

Possibility of signal transduction through microfilaments below the membrane following ligand-receptor interaction.

In this paper, we describe the changes of microfilament assembly and 3H-TdR incorporation in mouse ascites liver cancer cells under the action of concanavalin A (ConA) and laminin (LN). We have also studied the variation of 3H-TdR incorporation induced by destroying microfilaments with cytochalasin B (CB) following ConA and LN binding with their membrane receptors. It was found that ConA and LN interactions with their membrane receptors could induce the assembly of microfilaments below the membrane and promote DNA synthesis in these cells, but this effect was inhibited when microfilaments were destroyed by CB treatment. These results suggest that microfilaments might play a role in transferring signals from the membrane to the nucleus.

Actin Cytoskeleton↗
PubMed1993

Detection of the HPV16 E6 transforming gene by PCR in tissue samples from normal cervix and from cervix with precancerous lesions and carcinomas.

A study of 130 biopsies from cases of histologically confirmed normal cervix (30), cervicitis (28), cervical intraepithelial neoplasia (CINI-CIN III, 29), and cervical cancer (43) was performed to determine the presence of human papillomavirus (HPV) type 16 DNA sequences. The polymerase chain reaction technique was adopted using two oligonucleotides as primer pairs in the HPV16 early 6 (E6) gene open reading frame (ORF). The rates of HPV16 infection in normal tissues, cervicitis, CINI-CIN III and cervical cancer were found to be 16.67% (5/30), 25.00% (7/28), 41.38% (12/29) and 69.77% (30/43), respectively. Statistical analysis showed that the relative risk (RR) of association between HPV16 infection and the development of cervicitis, CINs and cervical carcinomas was increased with the severity of cervical lesions, from 1.0 (normal) to 1.67, 4.62 (P < 0.05; 95% CI 0.28-8.95) and 11.54 (P < 0.001; 95% CI 3.94-33.81), respectively. Our results strongly support the idea that the development of cervical precancerous lesions and cervical carcinomas is closely associated with HPV16 infection.

Adult↗