PubMed Health⌕ Search

Biomedical subjects

F Marks

Publications and source records attributed to F Marks.

At least 109 records · Page 6Linked to original sources
PubMed1991

TGF-beta 1 and skin carcinogenesis: antiproliferative effect in vitro and TGF-beta 1 mRNA expression during epidermal hyperproliferation and multistage tumorigenesis.

The role of transforming growth factor-beta 1 (TGF-beta 1) in multisage carcinogenesis in mouse skin was assessed by studying its growth inhibitory effects on nontumorigenic and tumorigenic keratinocytes and by examining its mRNA expression in vitro and during epidermal hyperproliferation and multistage carcinogenesis. While growth of primary basal keratinocytes was inhibited by TGF-beta 1 in doses as low as 0.1 ng/mL, the immortal keratinocyte line MCA/3D ("putatively initiated" cells) responded to TGF-beta 1 with slightly reduced sensitivity, and the papilloma-producing keratinocyte line 308 was considerably less sensitive. In contrast, the squamous carcinoma cell line Carc B was completely nonresponsive, and two other tumorigenic cell lines (PDV and PDVC57) were sensitive to growth inhibition by TGF-beta 1. Steady-state levels of TGF-beta 1 mRNA were high in all the malignant cell lines and in line 308 papilloma cells, but low in primary basal cells and in the nontumorigenic keratinocyte lines V2, Reb1, and MCA/3D. Our in vivo studies showed that tumor promoters, but not mitogenic or weak hyperplasiogenic agents, were able to induce transient expression of TGF-beta 1 mRNA in mouse epidermis. A constitutive overexpression of TGF-beta 1 mRNA was observed in malignant carcinomas but not in the benign premalignant lesions, indicating that overexpression may be associated with malignant progression.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Protein kinase C activation by phorbol esters: do cysteine-rich regions and pseudosubstrate motifs play a role?

A model for the binding of two activators of protein kinase C (PKC), the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and diacylglycerol, to the enzyme is proposed. It is suggested that each activator is hydrogen-bonded to sulfhydryl groups of cysteine residues and to the carbonyl of an asparagine within the cysteine-rich regions of PKC. This might induce a conformational change that would disrupt the association of the inhibitory pseudosubstrate sequence with the active center of PKC.

Amino Acid Sequence↗
PubMed1991

Stimulatory effect of thapsigargin, a non-TPA-type tumor promoter, on arachidonic acid metabolism in the murine keratinocyte line HEL30 and on epidermal cell proliferation in vivo as compared to the effects of phorbol ester TPA.

The effect of thapsigargin (Tg), a non-12-O-tetradecanoylphorbol-13-acetate (TPA) type skin tumor promoter, on arachidonic acid and prostaglandin E2 (PGE2) formation in HEL30 keratinocytes and on epidermal DNA synthesis in vitro and in vivo (mouse skin) was investigated and compared with that of the phorbol ester TPA. On a molar basis Tg was 30-fold more potent in inducing the arachidonic acid/PGE2 release than TPA. Applied together, the two agents showed a strong synergistic action. The response critically depended on the presence of Ca2+ in the extracellular medium. While the TPA-induced release was mediated by protein kinase C (PKC) the Tg-induced release was not. In contrast to TPA (1 microM), which is a stimulator of HEL30 DNA synthesis, Tg (0.1-1 microM) inhibited DNA labeling in vitro due to a pronounced cytotoxic effect. TPA did not exhibit such an effect. In vivo both agents were practically equipotent in inducing epidermal DNA synthesis and hyperplasia with TPA having an approximately 10-fold higher irritating potential than Tg. It is concluded that the hyperplasiogenic and tumor-promoting effect of Tg in vivo is due to cytotoxicity causing cell death and regenerative hyperproliferation. Thus, Tg-induced skin tumor promotion seems to resemble tumor promotion by mechanical skin wounding, whereas TPA evokes a more specific, i.e. PKC-mediated response. Since despite these mechanistic differences both agents induce an immediate release of arachidonic acid/PGE2 in keratinocytes, this response may be considered to provide an in vitro parameter for irritancy and tumor promotion.

Animals↗
PubMed1991

Pancreatic enzyme activity in pregnancy.

Serum amylase activity and the amylase:creatinine clearance ratio (Cam:Ccr%) are two of the most commonly used indicators for the diagnosis of pancreatitis. However, published data on the effect of pregnancy on these indicators are conflicting. Furthermore, there are no published data on the effect of pregnancy on serum lipase activity, which is considered one of the most sensitive and specific indicators of pancreatitis. A study was undertaken to determine the effect of pregnancy and gestational age on serum amylase, serum lipase and Cam:Ccr% levels and to establish a baseline of normal values for use in the diagnosis of pancreatitis in pregnant women. Serum amylase, serum lipase and Cam:Ccr% levels were determined on a sample population consisting of 175 pregnant women with gestational ages ranging from 5 to 40 weeks and on a control group of 44 reproductive-age, nonpregnant women. The study results indicated that there is no significant difference in serum amylase, serum lipase and Cam:Ccr% levels between pregnant and nonpregnant women. Cam:Ccr% showed a small but statistically significant increase in the third trimester of pregnancy.

Amylases↗
PubMed1991

The effect of the New York State restrictions on resident work hours.

New York state has recently restricted the hours that residents may work to an average of 80 hours per week. We have complied with these regulations through the addition of nonresident personnel, including attending physicians, a physician assistant, and nurse midwives. This study was designed to assess the effect of these changes on our residents. A questionnaire covering the effects of our new system was distributed to both attending and resident staff. Surgical case load and Council on Resident Education in Obstetrics and Gynecology (CREOG) scores since the change were compared with those of previous years. A marked improvement in resident life-style was noted. Although residents commented that they had increased time for reading, this was not reflected in an improvement in the CREOG scores. The quality of patient care was not felt to be improved, and the continuity of care was considered to be adversely affected. Resident surgical case load was unchanged. The assignment of emergency room coverage to attending physicians and gynecologic floor coverage to a physician assistant was seen as having a detrimental effect on resident experience. We conclude that the new restrictions on resident work hours in New York have improved resident quality of life. However, there does not appear to be an improvement in patient care, which was the original intent of the statute. Concerns are discussed about the effect of this decrease in hours worked on resident experience and education. Further research is needed to assess the long-term effects of reduced resident work hours on both patient care and resident education.

Attitude of Health Personnel↗
PubMed1990

Purification and characterization of a calcium-unresponsive, phorbol ester/phospholipid-activated protein kinase from porcine spleen.

A calcium-unresponsive, phorbol ester/phospholipid-activated protein kinase was purified to apparent homogeneity from a Triton X-100 extract of an EGTA/EDTA-preextracted particulate fraction of porcine spleen by chromatography on S-Sepharose Fast Flow, phenyl-Sepharose Fast Flow, protamine-agarose, and Superdex 200. The enzyme had a Mr of 76,000, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (p76-kinase). A similar value (78,000) was obtained by gel filtration. The purified p76-kinase proved to be much more stable than the enzyme in crude preparations. Storage in a buffer containing 50 mM mercaptoethanol and 20% glycerol at -20 degrees C for at least 4 months caused less than 20% loss in enzyme activity. The enzyme exhibited a pH optimum of 8.3. The affinity of the novel enzyme for substrates and cofactors differed to some extent from that of conventional alpha, beta, gamma protein kinase C (PKC). p76-kinase did not respond to calcium, had a lower requirement for magnesium, and a higher affinity for histone III-S than PKC. Both the p76-kinase-catalyzed phosphorylation of histone III-S and the autophosphorylation of the enzyme could be activated by the phorbol ester TPA (or diacylglycerol) plus phosphatidyl serine, but not by calcium plus phosphatidyl serine. The stoichiometry of autophosphorylation suggested that fully phosphorylated p76-kinase contained two phosphoserine residues and one phosphothreonine residue. Like PKC, p76-kinase bound TPA with high affinity (KD = 9.6 nM). In the absence of TPA, various unsaturated fatty acids, particularly arachidonic acid, were more potent as activators of the enzyme than phosphatidyl serine. The p76-kinase was recognized by an antiserum raised against a delta PKC-specific peptide, but not by an alpha, beta, gamma PKC-specific antiserum. The previously described p82-kinase of mouse epidermis and spleen exhibiting the same properties as the p76-kinase did also react with the p76-kinase-specific antiserum.

Animals↗
PubMed1990

Epidermal G1-chalone and transforming growth factor-beta are two different endogenous inhibitors of epidermal cell proliferation.

Epidermal G1-chalone and transforming growth factor-beta (TGF beta), two endogenous inhibitors of epidermal cell proliferation, were compared with regard to several effects on epidermis in vivo and in vitro. Both factors inhibited DNA labeling in a rat tongue epithelial cell line, with similar kinetics and half-maximal effects at approximately 1 pg/ml (enriched chalone) and 1 ng/ml (TGF beta). For primary neonatal mouse keratinocytes, TGF beta was found to be a rather strong inhibitor of cell proliferation, whereas chalone showed only a weak effect on cells grown in medium containing 1.2 mM Ca2+ and no effect at all in the presence of 0.06 mM Ca2+. Vice versa, upon i.p. injection, only chalone was able to inhibit mouse epidermal DNA synthesis in vivo, whereas TGF beta had no effect at all. A moderate increase of transglutaminase activity in neonatal primary mouse keratinocytes was induced by both factors at concentrations of about 300 pg TGF beta/ml and 10 pg chalone fraction/ml. Chalone did not compete with [125I]TGF beta for specific binding sites on primary murine keratinocytes. A polyclonal "chalone antiserum" did not interact with TGF beta, and a neutralizing TGF beta antibody that inhibited the effect of TGF beta on cell proliferation could not block the inhibitory effect of chalone on RTE2 cells. In contrast to TGF beta, epidermal G1-chalone did not induce proliferation of NIH-3T3 cells. These results indicate that epidermal G1-chalone and TGF beta are two different inhibitors of epidermal cell proliferation.

Animals↗
PubMed1990

Mitochondrial myopathy and preeclampsia associated with pregnancy.

Mitochondrial myopathy is characterized by weakness, exercise intolerance, and acidosis. Pregnancy has been reported to accelerate the disease process. This report discusses pregnancy and management of labor complicated by mitochondrial myopathy and the therapeutic dilemmas that arise when preeclampsia is diagnosed.

Female↗
PubMed1990

Leukocyte esterase activity in amniotic fluid: normal values during pregnancy.

Chorioamnionitis during pregnancy is a common diagnostic dilemma for the obstetrician. Fast and accurate diagnosis poses the most significant problem. Since leukocytes are known to be released in response to infections, examination of amniotic fluid for their presence is an important part of the evaluation for chorioamnionitis. These neutrophils contain several esterases that are not present in serum, urine, or vaginal secretions. The esterases are not influenced by bacteria or by commonly used drugs. We have previously described the reliability of leukocyte esterase (LE) activity for the detection of chorioamnionitis in term pregnancies uncomplicated by other diseases. A prospective study was performed to assess the presence or absence of LE activity to establish normal values in amniotic fluid at various gestational ages prior to term before its use as a possible predictor for chorioamnionitis. Sterile amniotic fluid specimens were obtained from 13 patients undergoing second trimester genetic amniocentesis (with gestational ages varying from 15 to 19 weeks) and from 11 patients with a wide variety of medical problems, undergoing amniocentesis for Rh sensitization or lung maturation studies (with gestational ages ranging from 25 to 27 weeks). All patients with ruptured membranes or preterm labor were excluded. Each amniotic fluid sample was divided into two parts, one of which was transported to the laboratory for aerobic and anaerobic cultures and the other used for LE activity detection as measured by dipstick. The LE results were retrospectively compared with the results of the cultures. LE activity was always found to be negative when the culture results were negative. negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1989

Differentiative action of K252a on protein kinase C and a calcium-unresponsive, phorbol ester/phospholipid-activated protein kinase.

The Triton X-100 extract of the particulate fraction of porcine spleen contains a protein kinase which can be activated by phospholipid and the phorbol ester TPA but does not respond to phospholipid and calcium. The partially purified kinase has a molecular weight of 76 kDa (p76-kinase) and hence is somewhat smaller than the similarly behaving p82-kinase from mouse epidermis and spleen. The p76-kinase shows strong autophosphorylation. The protein kinase inhibitor K252a clearly differentiates between the Ca2+-unresponsive p76-kinase and Ca2+-responsive PKC. At concentrations of up to 5 x 10(-7)M it fails to suppress p76-kinase-catalyzed autophosphorylation and histone phosphorylation, but it inhibits PKC-catalyzed phosphorylation up to 50%. The IC50 values of K252a regarding PKC and the p76-kinase differ by two orders of magnitude. At low concentrations, K252a appears to slightly activate further TPA-activated p76-kinase. It is not able, however, to replace TPA and to stimulate the p76-kinase in the presence of phospholipid alone.

Animals↗
PubMed1989

A type 2A protein phosphatase dephosphorylates the elongation factor 2 and is stimulated by the phorbol ester TPA in mouse epidermis in vivo.

Mouse epidermal cytosol contains a protein phosphatase with Mr 38,000, which dephosphorylates the elongation factor 2 (EF-2) of protein biosynthesis and is stimulated after topical application of TPA to mouse skin [(1988) Biochem. Biophys. Res. Commun. 153, 1129-1135]. Dephosphorylation of EF-2 by this phosphatase is inhibited by okadaic acid at concentrations as low as 10(-8) M, but not by heparin up to concentrations of 600.micrograms/ml. The catalytic subunit of protein phosphatase 2A (PP2Ac) with EF-2 as a substrate exhibits the same sensitivity towards okadaic acid and insensitivity towards heparin as the EF-2 phosphatase of epidermal cytosol. The catalytic subunit of protein phosphatase 1 (PP1c) is strongly suppressed by heparin and less sensitive towards okadaic acid than PP2Ac. PP2Ac is around 50 times more efficient in dephosphorylating EF-2 than PP1c. These data indicate that the TPA-stimulated EF-2 phosphatase in epidermal cytosol is a type 2A protein phosphatase.

Animals↗
PubMed1989

Cyclosporine A suppresses an early process in phorbol ester action.

Simultaneous application of cyclosporine A (CsA) and the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on mouse skin strongly inhibits various biological responses to TPA. Delayed application of CsA is less effective. CsA given 1-2 h after TPA is unable to suppress TPA effects. Thus, the process that can be inhibited by CsA and that appears to be crucial for the response to TPA occurs rather early in TPA action.

Animals↗
PubMed1989

Stimulatory role of transforming growth factors in multistage skin carcinogenesis: possible explanation for the tumor-inducing effect of wounding in initiated NMRI mouse skin.

Mechanical wounding provides a convertogenic ("stage I tumor-promoting") stimulus in initiated NMRI mouse skin, indicating that this stage of carcinogenesis can be entirely controlled by endogenous factors. A search for such factors led to the finding that both platelet-derived Epstein-Barr-virus-inducing factor (EIF), alias human TGF beta 1 and porcine TGF beta, exhibited--upon intracutaneous injection--convertogenic efficacy in initiated NMRI-mouse skin in vivo provided that their injection was combined with a single topical application of the non-convertogenic tumor promoter 12-O-retinolyphorbol-13-acetate (RPA). Since TGF beta inhibits epidermal cell proliferation, the RPA treatment is thought to provide a mitogenic stimulus required for conversion. The RPA treatment can be replaced by intracutaneous injection of transforming growth factor alpha (TGF alpha). These results indicate that the stage of conversion consists of two components, one of which is related to mitogenesis (RPA or TGF alpha), the other to a still unknown activity exhibited by TGF beta-like factors. Thus, endogenous factors with the quality of "wound hormones" may be involved in multistage skin carcinogenesis. This finding could explain the convertogenic effect of skin wounding.

Animals↗
PubMed1989

Tumor prevention by a xanthate compound in experimental mouse-skin tumorigenesis.

The antiviral and antitumoral compound tricyclodecan-9-yl-xanthogenate (D609), which is an inhibitor of protein kinase C activation, has been used for tumor prevention in vivo. When applied chronically together with 12-O-tetradecanoylphorbol-13-acetate (TPA) in the classic initiation-promotion mouse-skin model, D609 prevented tumor induction in a dose-dependent manner. At the concentration that inhibited tumor formation by 97%, no toxic effects were detected and the TPA-induced hyperplasia remained unaffected. As D609 failed to prevent the activity of a chronically applied carcinogen, it is concluded that the observed tumor prevention achieved with D609 is tumor-promotion-specific and is not due to killing of tumor cells.

9,10-Dimethyl-1,2-benzanthracene↗