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S Frank

Publications and source records attributed to S Frank.

At least 109 records · Page 6Linked to original sources
PubMed1996

Combined detection of CD44 isoforms by exon-specific RT-PCR and immunohistochemistry in primary human brain tumors and brain metastases.

Expression of CD44 has been implicated in tumor growth and metastasis. Here we demonstrate CD44 expression in primary human brain tumors (n = 44) and brain metastases (n = 7) by RT-PCR and immunohistochemistry. Standard CD44 was found to be expressed by the majority of primary brain tumors and brain metastases. For the first time to our knowledge, CD44 expression is demonstrated for acoustic neurinomas and pituitary adenomas. Exon-specific analysis by RT-PCR and indirect immunofluorescence revealed expression of alternatively spliced CD44 isoforms in the group of brain metastases only. However, in one glioblastoma multiforme, expression of CD44v5 and CD44v6 was found immunohistochemically. This tumor took an unusual clinical course giving rise to multiple intrahepatic and lymph node metastases. Quantitatively different expression of standard CD44 in gliomas versus meningiomas is reported (p < 0.01).

Alternative Splicing↗
PubMed1996

Transforming growth factors beta1, beta2, and beta3 and their receptors are differentially regulated during normal and impaired wound healing.

A series of studies has shown that application of transforming growth factor beta (TGF-beta) to a wound has a beneficial effect, especially in animals with wound healing disorders. In this study we have investigated the regulation of TGF-beta1, beta2, and beta3 and their receptors during the repair process. We found a large induction of all three TGF-beta isoforms and also of TGF-beta types I and II receptors, although the time course of induction and the absolute expression levels were different for these genes. Furthermore, each TGF-beta isoform had distinct sites of expression in the wound. Systemic treatment with glucocorticoids significantly altered the expression levels of TGF-betas and TGF-beta receptors. Whereas expression of TGF-beta1, TGF-beta2, and TGF-beta type II receptor was suppressed by glucocorticoids in normal and wounded skin, expression of TGF-beta3 and TGF-beta receptor type I mRNA was stimulated. These findings provide an explanation for the beneficial effect of exogenous TGF-beta in the treatment of impaired wound healing in glucocorticoid-treated animals. Furthermore, they suggest that a disturbed balance between the levels of the three TGF- beta isoforms and their receptors might underlie the wound healing defect seen in glucocorticoid-treated animals.

Animals↗
PubMed1996

Autocrine growth stimulation of SW403 colon carcinoma cell line is caused by transforming-growth-factor-alpha-mediated epidermal growth factor receptor activation.

Results of recent studies indicate that some cultured human carcinoma cell lines are capable of proliferating autonomously in serum-free medium as a result of the synthesis and secretion of transforming growth factor alpha (TGF alpha). TGF alpha interacts with epidermal growth factor receptor (EGFR) and induces its activation. In an attempt to extend these observations, we evaluated TGF alpha-mediated autonomous growth and constitutive EGFR activation in the human adenocarcinoma cell line SW403. The cell line shows synthesis of EGF receptors and TGF alpha but not EGF, and exhibits constitutive phosphorylation of the 170-kDa EGFR. Use of blocking anti-EGFR monoclonal antibodies (mAb) inhibits autonomous growth of SW403 cells and leads to a significant reduction of receptor phosphorylation. The inhibitory effect of the blocking anti-EGFR mAb is reversible upon addition of TGF alpha. In contrast, autonomous proliferation of SW403 cells is not inhibited by addition of neutralizing anti-EGF mAb. Our findings suggest that the proliferation of cells of the human SW403 adenocarcinoma cell line is regulated by an autocrine TGF alpha loop and that this regulatory pathway can be interrupted by using anti-EGFR mAb.

Adenocarcinoma↗
PubMed1996

Does this treatment work? Validation of an outcomes module for alcohol dependence.

The purpose of this study was to evaluate the outcomes of routine care administered to alcohol-dependent inpatients. The authors sought to validate a self-administered instrument that measures the types and extent of care delivered, the outcomes of that care, and casemix characteristics that influence the outcomes of care. Seventy-eight patients who were beginning inpatient treatment for alcohol dependence were recruited; 85% were followed 5 months later to examine cross-sectional and longitudinal relationships to gold standard assessments. The self-administered module demonstrated excellent agreement with structured interview assessments of diagnosis (kappa = .81), remission (kappa = .83), and change in severity of alcohol-related problems (r = .66 to .87). Casemix variables, particularly baseline severity, predicted change in alcohol consumption and functional status. The baseline module required 20 minutes for the average patient and 5 minutes for the average clinician to complete, with less than 2% missing data. Results indicated that the module measures key constructs with sufficient precision to assist clinicians and researchers in characterizing the degree to which routine inpatient care for alcohol dependence "works" in their patient population. The entire module is in the public domain and available free of charge to interested users.

Adult↗
PubMed1995

Expression of GM-CSF and a functional GM-CSF receptor in the human colon carcinoma cell line SW403.

Only little is known about the expression of a functional granulocyte-macrophage colony-stimulating factor receptor (GMR) and its ligands in human colon carcinoma cell lines. To obtain more information on this subject, we investigated the human colon carcinoma cell line SW403, and we were able to demonstrate the constitutive synthesis of a 85-kDa GMR in SW403 cells. After stimulation with 10% fetal calf serum, GM-CSF transcripts were expressed as well. The incubation of SW403 cells with GM-CSF resulted in an intensive down-regulation of the activity of the interferon-gamma-receptor gene, which could be reconstituted by simultaneous addition of an anti-GM-CSF antibody. GM-CSF induced an activation of tyrosine-phosphorylated protein kinases with molecular weights in the range of 30 to 210 kDa, but it had no effect on the DNA synthesis of SW403 cells.

Adenocarcinoma↗
PubMed1995

Regulation of vascular endothelial growth factor expression in cultured keratinocytes. Implications for normal and impaired wound healing.

Recent in situ hybridization studies had demonstrated a strong increase in vascular endothelial growth factor (VEGF) mRNA expression in the hyperproliferative epithelium during wound healing. To determine potential mediators of VEGF induction during this process, we analyzed the regulation of VEGF expression in cultured human keratinocytes. We found a large induction of VEGF expression upon treatment of quiescent cells with serum, epidermal growth factor, transforming growth factor-beta 1, keratinocyte growth factor, or the proinflammatory cytokine tumor necrosis factor alpha, respectively. Since all these factors are present at the wound site during the early phase of wound healing, they might also be responsible for VEGF induction after cutaneous injury. To determine the importance of increased VEGF production for wound repair, we compared the time course of VEGF mRNA expression during wound healing of healthy control mice with the kinetics of VEGF expression during skin repair of genetically diabetic db/db mice which are characterized by impaired wound healing. In normal mice we found elevated VEGF mRNA levels during the period when granulation tissue formation occurs. In contrast, VEGF mRNA levels even declined during this period in db/db mice, suggesting that a defect in VEGF regulation might be associated with wound healing disorders.

Animals↗
PubMed1995

Responses of antioxidant system to acute and trained exercise in rat heart subcellular fractions.

The effects of acute and trained exercise on antioxidant enzymes (AOE), glutathione (GSH), and malondialdehyde (MDA) were compared in rat heart subcellular fractions and red blood cells. Fischer-344 rats were exercised acutely to 100% VO2 max and another group of Fischer-344 rats were given trained exercise for 10 weeks. The AOE and MDA were measured by spectrophotometry and GSH and oxidized GSH (GSSG) by high pressure liquid chromatography. Trained exercise significantly increased cytosol GSH to 131% of sedentary control (SC). Acute exercise significantly increased mitochondrial superoxide dismutase, catalase, and glutathione peroxidase by 167%, 358%, and 129% of SC, respectively, whereas enzyme activities following trained exercise were increased by 133%, 166%, and 128% of SC. The mitochondria/cytosolic ratio for superoxide dismutase, catalase, and glutathione peroxidase after acute exercise increased to 1.9, 2.7, and 1.7, respectively, whereas the respective ratios of these enzymes after trained exercise were 1.3, 1.6, and 1.3. Acute exercise contributed to oxidative stress more than trained exercise. Acute exercise resulted in a larger increase in enzyme activities than trained exercise, possibly as a compensatory mechanism to cope with the enhanced production of superoxides and oxyradicals during exhaustive exercise.

Animals↗
PubMed1995

Inhibitors for the in vitro assembly of Lp(a).

Lp(a) is composed of an LDL-like core and the glycoprotein apo(a). Current evidence strongly suggests that the assembly of this atherogenic lipoprotein proceeds outside the liver cells in a two-step fashion. In the first step, a loose complex is formed involving kringle-4 motifs in apo(a) and one or more Lys side chains in apoB-100. In the second step, this complex is stabilized by a disulfide bridge. Indications are that Lp(a) assembly is critical in the determination of plasma apo(a) concentrations. Therefore, we searched for substances that interfere with the first step of Lp(a) assembly. epsilon-Aminohexoic acid (epsilon-AHA), known as an inhibitor from earlier assembly studies, had an IC50 of 4.8 mmol/L. The IC50 of Pro, HO-p-aminobenzene sulfonamide, Lys, N-epsilon-acetyl-Lys, taurine, Glu, serotonin, and benzamidine were all > 20 mmol/L. gamma-Aminobutyric acid, spermine, and spermidine exhibited IC50 on the same order of magnitude as epsilon-AHA. The substances with the highest inhibitory action were tranexamic acid and delta-aminovaleric acid. Seven of eight patients treated in a pilot study with tranexamic acid (Cyclocapron) responded with a decrease of plasma apo(a) of 18.5 +/- 8.2%. We suggest that substances that interfere with the Lp(a) assembly are worth pursuing further for their usefulness as therapeutic agents in reducing high plasma Lp(a) concentrations.

Adult↗
PubMed1995

The influence of anesthetic method on infrainguinal bypass graft patency: a closer look.

Although several studies have demonstrated a reduced incidence of postoperative deep venous thrombosis among patients who receive regional anesthesia, the influence of anesthetic method on early arterial bypass graft patency has not been well studied. The records of 78 consecutive patients undergoing elective femoro-popliteal (FP) or femoro-tibial (FT) bypass grafts, and who were randomized to receive general anesthesia and postoperative patient-controlled intravenous narcotic analgesia (GEN, n = 41), or epidural anesthesia and postoperative continuous epidural analgesia (EPI, n = 37), were retrospectively reviewed. The two groups were evenly matched with respect to demographic characteristics, risk factors, and vascular variables. There was one death in each group, yielding an operative mortality of 2.6 per cent, and leaving 76 patients available for further analysis. Graft occlusion occurred in 11 (14.5%) cases within the first 7 postoperative days, including 9 (22.5%) GEN and 2 (5.6%) EPI patients (P < 0.05). There were two (4.4%) FP occlusions, including two (8.7%) GEN and 0(0%) EPI cases; there were nine FT occlusions, including seven (41.2%) GEN and two (14.3%) EPI cases. Graft occlusion occurred in 11 (17.1%) of the 64 limb salvage cases, including nine (27.3%) GEN and two (6.5%) EPI cases (P < 0.05), and in seven (12.7%) of 55 greater saphenous vein grafts, including six (22.2%) GEN and 1 (3.6%) EPI cases (P < 0.05). By multivariate analysis, FT grafts, preoperative plasminogen activator inhibitor-1 (PAI-1) levels, and GEN were predictive of early graft occlusion (P < 0.05). Furthermore, the levels of circulating PAI-1 were higher 24 hours postoperatively among patients in the GEN group (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Protein phosphatase 2A, a potential regulator of actin dynamics and actin-based organelle motility in the green alga Acetabularia.

The giant, unicellular alga Acetabularia is a well known experimental model for the study of actin-dependent intracellular organelle motility. In the cyst stage, however, which is equivalent to the gametophytic stage, organelles are immobile, even though an actin cytoskeleton is present. The reason for the lack of organelle motility at this stage has not been known. To test the hypothesis that organelle motility could be under the control of posttranslational modification by protein phosphorylation, we have treated cysts with submicromolar concentrations of okadaic acid or calyculin A, both potent inhibitors of serine/threonine protein phosphatases (ser/thr-PPases). The effects were dramatic: Instead of linear actin bundles typical for control cysts, circular arrays of actin bundles formed in the cortical cyst cytoplasm. Concomitant with the formation of these action rings, the cytoplasmic layers beneath the rings began to slowly rotate in a continuous and uniform counter-clockwise fashion. This effect suggests that protein phosphorylation acts on the actin cytoskeleton at two levels: (1) It changes the assembly properties of the actin filament system to the extent that novel cytoskeletal configurations are formed and (2) it raises the activity of putative motor proteins involved in the rotational movements to levels sufficiently high to support motility at a stage when organelle motility does not normally occur. Northern blot analysis of cyst stage-mRNA using probes specific to protein phosphatase type 1 (PP1) and type 2A (PP2A) reveals that PP2A is strongly expressed at this developmental stage whereas PP1 is not detectable, suggesting that PP2A is the likely target to the protein phosphatase inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabularia↗
PubMed1994

Decreased binding of apolipoprotein (a) to familial defective apolipoprotein B-100 (Arg3500-->Gln). A study of the assembly of recombinant apolipoprotein (a) with mutant low density lipoproteins.

In familial defective apolipoprotein B-100 (FDB), glutamine is substituted for arginine at position 3500 of the amino acid sequence. This mutation alters the structure of low density lipoproteins (LDL) and reduces their binding to LDL receptors. We studied the assembly in vitro of FDB-LDL with two recombinant apo(a) (r-apo(a)) isoforms containing 17 or 18 kringle IV-type repeats, respectively. R-apo(a) complexed to LDL in a concentration- and time-dependent manner. When we mixed normal LDL at protein concentrations from 1 to 10 mg/liter with 200 micrograms/liter r-apo(a) and incubated for 20 h, 15-44% of r-apo(a) were bound to LDL, forming an artificial Lp(a)-like particle. With LDL from a homozygous FDB patient, only 2-16% of r-apo(a) were complexed; heterozygous FDB-LDL bound 2-30% of r-apo(a). We also studied the effect of r-apo(a) on the interaction of the monoclonal antibody MB47 with normal and mutant apoB-100. FDB-LDL displayed enhanced binding of MB47. Adducts generated from normal LDL and r-apo(a) had an increased affinity for MB47, when compared to LDL alone. In contrast, r-apo(a) did not change MB47 reactivity when incubated with FDB-LDL. Altogether, our findings suggest that domains in apolipoprotein B which are important for the interaction with the LDL receptor play a role in the assembly of Lp(a) as well. They provide, in addition, an explanation for the observation that in Lp(a) of heterozygous FDB patients, the ratio of defective to normal apoB-100 is significantly smaller than in LDL from the same patients.

Adult↗
PubMed1994

Structural requirements of apo-a for the lipoprotein-a assembly.

Lipoprotein-a [Lp(a)], one of the most atherogenic lipoproteins, is composed of a low-density lipoprotein (LDL) core in addition to an apo-a of variable size which is linked to apoB by a disulphide bridge. Lp(a) synthesized in vitro by incubation of recombinant apo-a (r-apo-a) with LDL is physico-chemically indistinguishable from native Lp(a). The synthesis of Lp(a) in vitro proceeds in two steps. In the first step, one of the unique kringle-IVs (K-IVs) in apo-a binds to a Lys residue of apoB; in the second step, Cys-4057 of K-IV type-9 (T-9) forms a disulphide bridge with Cys-3734 of LDL. Here we have produced r-apo-a with different combinations of unique K-IVs and shown that K-IV T-6 is required for the first step of Lp(a) assembly. For the second step not only is K-IV T-9 essential, but also the distance between T-6 and T-9 requires a length of two K-IVs. These findings give additional insight into the mode of Lp(a) assembly and are of relevance in the search for apo-a mutants influencing Lp(a) levels and for the development of Lp(a)-lowering medications.

Blotting, Western↗
PubMed1994

High-level expression of various apolipoprotein(a) isoforms by "transferrinfection": the role of kringle IV sequences in the extracellular association with low-density lipoprotein.

Characterization of the assembly of lipoprotein(a) [Lp(a)] is of fundamental importance to understanding the biosynthesis and metabolism of this atherogenic lipoprotein. Since no established cell lines exist that express Lp(a) or apolipoprotein(a) [apo(a)], a "transferrinfection" system for apo(a) was developed utilizing adenovirus receptor- and transferrin receptor-mediated DNA uptake into cells. Using this method, different apo(a) cDNA constructions of variable length, due to the presence of 3, 5, 7, 9, 15, or 18 internal kringle IV sequences, were expressed in cos-7 cells or CHO cells. All constructions contained kringle IV-36, which includes the only unpaired cysteine residue (Cys-4057) in apo(a). r-Apo(a) was synthesized as a precursor and secreted as mature apolipoprotein into the medium. When medium containing r-apo(a) with 9, 15, or 18 kringle IV repeats was mixed with normal human plasma LDL, stable complexes formed that had a bouyant density typical of Lp(a). Association was substantially decreased if Cys-4057 on r-apo(a) was replaced by Arg by site-directed mutagenesis or if Cys-4057 was chemically modified. Lack of association was also observed with r-apo(a) containing only 3, 5, or 7 kringle IV repeats without "unique kringle IV sequences", although Cys-4057 was present in all of these constructions. Synthesis and secretion of r-apo(a) was not dependent on its sialic acid content. r-Apo(a) was expressed even more efficiently in sialylation-defective CHO cells than in wild-type CHO cells. In transfected CHO cells defective in the addition of N-acetylglucosamine, apo(a) secretion was found to be decreased by 50%. Extracellular association with LDL was not affected by the carbohydrate moiety of r-apo(a), indicating a protein-protein interaction between r-apo(a) and apoB. These results show that, besides kringle IV-36, other kringle IV sequences are necessary for the extracellular association of r-apo(a) with LDL. Changes in the carbohydrate moiety of apo(a), however, do not affect complex formation.

Animals↗