Tissue transglutaminase triggers oligomerization and activation of dual leucine zipper-bearing kinase in calphostin C-treated cells to facilitate apoptosis

Although tissue transglutaminase (tTG) has been recognized as a mediator of apoptosis in various experimental models, little is currently known about the molecular mechanisms by which this protein modulates cell death. Recent work from our laboratory has shown that activation of tTG in cells exposed to the apoptotic inducer calphostin C triggers the crosslinking of dual leucine zipper-bearing kinase (DLK), a proapoptotic kinase acting as an essential component of the c-Jun amino-terminal kinase (JNK) signaling pathway. As a consequence of this observation, we have undertaken experiments to investigate the functional relevance of DLK oligomerization in tTG-mediated apoptosis. Our results indicate that, in cells undergoing calphostin C-induced apoptosis, tTG-dependent DLK oligomerization occurs early in the apoptotic response. Both immunocomplex kinase assays and immunoblotting with phosphospecific antibodies revealed that oligomer formation by tTG-mediated crosslinking reactions significantly enhanced the kinase activity of DLK and its ability to activate the JNK pathway. Moreover, functional studies demonstrate that tTG-mediated oligomerization of wild-type DLK sensitizes cells to calphostin C-induced apoptosis, while crosslinking of a kinase-inactive variant of DLK does not. Collectively, these data strongly suggest that tTG facilitates apoptosis, at least partly, by oligomerization and activation of the proapoptotic kinase DLK.

The mixed lineage kinase leucine-zipper protein kinase exhibits a differentiation-associated localization in normal human skin and induces keratinocyte differentiation upon overexpression

Leucine-zipper protein kinase/dual leucine zipper bearing kinase/mitogen-activated protein kinase-upstream kinase is a recently described protein serine/threonine kinase which belongs to the mixed lineage kinase family. The overall pattern of expression of the leucine-zipper protein kinase/dual leucine zipper bearing kinase/mitogen-activated protein kinase-upstream kinase gene in embryonic and adult mouse tissues suggested that this kinase could be involved in the regulation of epithelial cell proliferation and differentiation. In order to get more insights into the potential role of leucine-zipper protein kinase in these cellular processes, we characterized its expression in normal human skin, both at the mRNA and protein levels. In situ hybridization, western blotting, and indirect immunofluorescence studies were conducted to localize leucine-zipper protein kinase on various human skin tissues. This is one of the first reports that leucine-zipper protein kinase has a very precise pattern of expression in human skin epithelia, as both mRNA and protein are restricted to the granular layer of the epidermis and inner root sheath of hair follicles. Detection of leucine-zipper protein kinase protein on skin from various body sites, donors of different ages as well as on reconstructed human skin always reveals that leucine-zipper protein kinase is present only in the very differentiated keratinocytes of epidermis and hair follicles. To determine directly whether leucine-zipper protein kinase exhibits any effect on cell growth and differentiation, keratinocytes were transfected with an expression vector harboring the leucine-zipper protein kinase cDNA. The presence of this construct in keratinocytes results in growth arrest together with a concomitant increase in filaggrin expression. Collectively, our results indicate that leucine-zipper protein kinase plays an active part in cellular processes related to terminal differentiation of epidermal keratinocytes.

The mixed lineage kinase DLK is oligomerized by tissue transglutaminase during apoptosis

Current evidence suggests that the mixed lineage kinase family member dual leucine zipper-bearing kinase (DLK) might play a significant role in the regulation of cell growth and differentiation, particularly during the process of tissue remodeling. To further explore this working model, we have investigated the regulation of host and recombinant DLK in NIH3T3 and COS-1 cells undergoing apoptosis. Using calphostin C, a potent and selective inhibitor of protein kinase C and a recognized apoptosis inducer for various cell types, we demonstrate, by immunoblot analysis, that DLK protein levels are rapidly and dramatically down-regulated during the early phases of apoptosis. Down-regulation in calphostin C-treated cells was also accompanied by the appearance of SDS- and mercaptoethanol-resistant high molecular weight DLK immunoreactive oligomers. Experiments aimed at elucidating the mechanism(s) underlying DLK oligomerization revealed that the tissue transglutaminase (tTG) inhibitor monodansylcadaverine antagonized the effects of calphostin C almost completely, thereby suggesting the involvement of a tTG-catalyzed reaction as the root cause of DLK down-regulation and accumulation as high molecular weight species. In support of this notion, we also show that DLK can serve as a substrate for tTG-dependent cross-linking in vitro and that this covalent post-translational modification leads to the functional inactivation of DLK. Taken together, these observations suggest that transglutamination and oligomerization may constitute a relevant physiological mechanism for the regulation of DLK activity.

Overexpression of the reg gene in non-obese diabetic mouse pancreas during active diabetogenesis is restricted to exocrine tissue

We demonstrated pancreatic reg gene overexpression in non-obese diabetic (NOD) mice during active diabetogenesis. The aim of this study was to determine in which part of the pancreas (endocrine and/or exocrine) the gene(s) and the protein(s) were expressed and if their localization changed with progression of the disease. In situ hybridization analysis and immunocytochemical studies were carried out on pancreas of female and male NOD mice. Both develop insulitis but diabetes develops only in females and in males only when treated by cyclophosphamide. Our results show that whatever the age, sex, and presence of insulitis and/or diabetes, the expression of reg mRNAs and of the corresponding protein(s) was restricted to exocrine tissue. Moreover, reg remains localized in acinar cells in the two opposite situations of (a) cyclophosphamide-treated males in a prediabetic stage presenting a high level of both insulin and reg mRNAs, and (b) the overtly diabetic females with no insulin but a high level of reg mRNA. These findings suggest that overexpression of the reg gene(s) might represent a defense of the acinar cell against pancreatic aggression.

Localization of the mixed-lineage kinase DLK/MUK/ZPK to the Golgi apparatus in NIH 3T3 cells

DLK/MUK/ZPK is a serine/threonine kinase that belongs to the mixed-lineage (MLK) subfamily of protein kinases. As is the case for most members of this family, relatively little is known about the physiological role of DLK/MUK/ZPK in mammalian cells. Because analysis of subcellular distribution may provide important clues concerning the potential in vivo function of a protein, an antiserum was generated against the amino terminal region of murine DLK/MUK/ZPK and used for localization studies in wild-type NIH 3T3 cells. Light microscopic immunocytochemistry experiments performed with the antiserum revealed that DLK/MUK/ZPK was specifically localized in a juxtanuclear structure characteristic of the Golgi complex. In support of this, treatment of cells with brefeldin A, a drug known to disintegrate the Golgi apparatus, caused disruption of DLK/MUK/ZPK perinuclear staining. Ultrastructural observation of NIH 3T3 cells also confirmed this localization, showing that most of the immunoreactivity was detected on membranes of the stacked Golgi cisternae. Consistent with localization studies, biochemical analyses revealed that DLK/MUK/ZPK was predominantly associated with Golgi membranes on fractionation of cellular extracts and was entirely partitioned into the aqueous phase when membranes were subjected to Triton X-114 extraction. On the basis of these findings, we suggest that DLK/MUK/ZPK is a peripheral membrane protein tightly associated with the cytoplasmic face of the Golgi apparatus. (J Histochem Cytochem 47:1287-1296, 1999)

Effect of the acute-phase response on the pharmacokinetics of chlorzoxazone and cytochrome P-450 2E1 in vitro activity in rats

The acute-phase response is known to produce alterations in hepatic cytochrome P-450 (CYP) expression. Lipopolysaccharide (LPS), a well known inducer of acute-phase response decreases hepatic CYP2E1 in vitro activity in rats. This study was designed to determine if LPS administration produced alterations in the pharmacokinetics of chlorzoxazone (CZN), a marker for CYP2E1 expression. Sprague-Dawley rats were administered a single i.p. injection of LPS (5 mg/kg) or saline control approximately 24 h before a single i.v. bolus dose of CZN (15 mg/kg). Serial blood samples were collected over a 120-min period to quantitate CZN plasma concentrations and protein binding. In addition, livers were removed and processed for evaluating in vitro CYP2E1 protein concentrations and activity. Systemic clearance decreased by 35% in LPS-treated rats, whereas half-life and steady-state volume of distribution increased by 167 and 66%, respectively. The plasma free-fraction of CZN increased 2-fold after LPS treatment. The CZN intrinsic clearance decreased in LPS rats by 71% compared with control values. The CYP2E1 liver microsomal activity decreased between 55 and 75% along with a 41% decrease in CYP2E1 protein concentration. The CZN intrinsic clearance was significantly correlated with both the CZN and p-nitrophenol liver microsomal activity (r = 0.97 and r = 0.91, respectively). This study demonstrated that LPS administration produced expected reductions in the in vivo intrinsic clearance of CZN, and these changes were highly correlated with in vitro activity studies. In addition, LPS produced significant increases in the steady-state volume of distribution of CZN secondary to reductions in its plasma protein binding.

Patient-controlled analgesia: optimizing the experience

A patient-controlled analgesia (PCA) program was established on a surgical unit with children age 7 years and older. The primary objectives for the PCA program were safety and efficacy. A retrospective evaluation of the first 30 patients enrolled in the program suggested in the program suggested that it was safe and adequately controlled pain for all but 4 patients. A chart review of these patients indicated that the relation between the number of failed administration attempts, the total hourly analgesic intake, and the pain intensity score was key to optimizing the use of PCA. Recommendations to strengthen the PCA program were implemented based on information gained from these 4 patients with poorly controlled pain.

Characterization of cytochrome P450 and glutathione S-transferase activity and expression in male and female ob/ob mice

OBJECTIVE

To characterize the effect(s) of gender, age (glycemic status) and obese state, on hepatic biotransformation activities, expression of cytochrome P450 (CYP450) mRNAs and glutathione transferase activity in the ob/ob mouse.

DESIGN

Male and female, ob/ob or ob/+ mice were killed at 3-4 months or 7-8 months of age. Hepatic microsomes, cytosol and RNA were prepared from each animal.

ANIMALS

Male and female ob/ob and ob/+ mice, 3-4 or 7-8 months of age.

MEASUREMENTS

CYP450 form-specific activities of CYP1A1/1A2, CYP3A and CYP2B were estimated by determining the 0-dealkylation of alkoxyresorufin substrates (ethoxy-EROD, benzoxy-BROD and pentoxy-resorufin, PROD, respectively). CYP2E1-dependent, 4-nitrophenol hydroxylase (PNP-OH) and CYP3A-dependent erythromycin N-demethylase (ERY-DM) were also measured in hepatic microsomes. CYP1A2, CYP2E1 and CYP3A protein in microsomal fractions was determined by ELISA. Glutathione transferase activity (GST) was determined in hepatic cytosol and CYP1A2 and CYP2E1 mRNA was estimated by Northern blot analysis.

RESULTS

Female mice, regardless of glycemic status, showed an obesity enhanced level of CYP2E1-dependent PNP-OH activity and CYP2E1 protein as shown by ELISA. These increases were observed to be independent of the diabetic state, since 7-8 month-old mice had blood glucose levels identical to lean mice. The mRNA level of CYP2E1 in female mice also exhibited age-and obesity-influenced decreases in expression. No significant differences in CYP2E1 activity or expression were observed in male mice. CYP3A-dependent ERY-DM activity was significantly higher in young males, regardless of phenotype. CYP3A and CYP2B activities did not differ among any animals; however, CYP1A activity, while depressed in obese animals of both genders, was significantly different in old animals. Glutathione S-transferase activity was lower in obese male mice, whereas no difference was observed between lean and obese females

CONCLUSION

This study supports earlier observations in man and rats that the obese state produces alterations in the expression of important oxidation and conjugation pathways. In addition, this report more thoroughly examines the role of gender and glycemic status on biotransformation activities in the ob/ob mouse as demonstrated by increased CYP2E1 protein and CYP2E1-dependent activity in obese females, decreased CYP1A2 protein and CYP1A2-dependent activity in obese animals, and obesity had no effect of glutathione transferase in female mice, in contrast with the previously reported obesity-dependent decrease of this activity in male mice.

Zonal induction of mixed lineage kinase ZPK/DLK/MUK gene expression in regenerating mouse liver

ZPK/DLK/MUK is a serine/theronine kinase believed to be involved in the regulation of cell growth and differentiation. To further explore the suggested participation of ZPK/DLK/MUK in this process, we examined the expression and cellular localization of ZPK/DLK/MUK mRNA in regenerating mouse liver following partial hepatectomy by ribonuclease protection assay and in situ hybridization. The steady-state level of APK/DLKMUK mRNA was very low in normal and sham-operated mouse livers, whereas a marked and transient increase was observed in the regenerating liver. While ZPK/DLK/MUK mRNAs were rarely detected in hepatocytes from all zones of the normal liver, hepatocytes of regenerating liver exhibit a gradient of expression ranging from low in the periportal zone, to intermediate in the mid-zone, to high in the pericentral zone. These findings demonstrate a transient stimulation of ZPK/DLK/MUK gene expression that correlates with the growth response of hepatocyte subpopulations in regenerating liver.

Establishment and immunocharacterization of an immortalized pancreatic cell line derived from the H-2Kb-tsA58 transgenic mouse

This study describes the establishment and characterization of an immortalized cell line derived from the pancreas of an adult H-2Kb-tsA58 transgenic mouse. These cells, designated IMPAN for IMmortalized PANcreatic cells, displayed a cobblestone appearance typical of confluent epithelial cells and a distinct polarity in the organization of their cytoplasmic organelles. Immunocytochemical studies revealed that all IMPAN cells stained positively for a wide range of markers characteristic of pancreatic acinar cells, namely the secretory products alpha-amylase, chymotrypsinogen, DNAse, the lectinlike secretory protein PAP (pancreatitis associated protein), and the zymogen granule membrane proteins GP-2 and gp300. They also stained positively for carbonic anhydrase II and cytokeratin 19, two proteins characteristic of pancreatic duct cells, as well as for rab3A, a small GTP-binding protein specifically localized in pancreatic islet cells. No reactivity was ever obtained with insulin antibodies. Taken together, these results show that the IMPAN cells exhibit a phenotype comparable to exocrine pancreatic acinar cells. However the expression of some proteins more specific to duct and islet cells make them similar to in vivo or in vitro growing acinar cells. The cell line should be a valuable model to study the mechanisms of growth, differentiation, and transformation of the exocrine pancreatic acinar cell.

Inhibition of cell growth by overexpression of the ZPK gene

ZPK is a recently described serine/threonine protein kinase that is thought to be involved in the regulation of cell proliferation and differentiation. To directly determine whether ZPK exhibits any effect on cell growth, NIH 3T3 fibroblasts were transfected with an expression vector harboring the murine ZPK cDNA. Stable expression of this construct led to a dramatic reduction in the proliferative capacity of these cells as measured by a colony formation assay in monolayer culture. By contrast, overexpression of a ZPK cDNA with a mutation in the ATP-binding domain did not affect clonal expansion of the transfected cells. These findings suggest that the ZPK gene may act as a negative regulator of cell growth and that this function may be mediated in part by the intrinsic kinase activity of the ZPK protein.

In situ hybridization analysis of ZPK gene expression during murine embryogenesis

ZPK is a recently described protein serine/threonine kinase that has been originally identified from a human teratocarcinoma cell line by the polymerase chain reaction and whose function in signal transduction has not yet been elucidated. To investigate the potential role of this protein kinase in developmental processes, we have analyzed the spatial and temporal patterns of expression of the ZPK gene in mouse embryos of different gestational ages. Northern blot analysis revealed a single mRNA species of about 3.5 KB from Day 11 of gestation onwards. In situ hybridization studies demonstrated strong expression of ZPK mRNA in brain and in a variety of embryonic organs that rely on epitheliomesenchymal interactions for their development, including skin, intestine, pancreas, and kidney. In these tissues, the ZPK mRNA was localized primarily in areas composed of specific types of differentiating cells, and this expression appeared to be upregulated at a time concomitant with the onset of terminal differentiation. Taken together, these observations raise the possibility that the ZPK gene product is involved in the establishment and/or maintenance of a fully cytodifferentiated state in a variety of cell lineages.

Cell-specific expression of the ZPK gene in adult mouse tissues

ZPK is a recently identified human putative protein kinase gene that encodes an unusual serine/threonine kinase containing two potential leucine zipper motifs similar to those found in transcription factors as well as in members of the newly discovered mixed-lineage family of protein kinases. To study the normal biological function of ZPK, we have isolated a mouse ZPK cDNA and examined the pattern of ZPK mRNA expression in adult mouse tissues by Northern blot and in situ hybridization analyses. The predicted open reading frame of this cDNA encodes an 888-amino-acid protein that shares 95% overall identity with its human counterpart. By Northern blot analysis, we detected expression of ZPK mRNA in the brain of adult mice, but not in any other tissue tested. In situ hybridization analysis of mouse brain sections revealed specific association of ZPK mRNA with neuronal cell populations, primarily in the hippocampus, the cerebral cortex, and the Purkinje cell layer of the cerebellum. Interestingly, a remarkable pattern of cell-type-specific expression was also found in the epithelial compartment of various organ systems, including stomach, small intestine, liver, and pancreas, as well as in the seminiferous tubules of mature testes. Taken together, these observations suggest that ZPK could play a role in development, function, and maintenance of a variety of specialized cells.

A randomized, controlled trial of radiograph ordering for extremity trauma in a pediatric emergency department

STUDY OBJECTIVES

The objectives of this study were to determine whether triage nurses using the Brand protocol would order fewer radiographs than would physicians carrying out standard practice procedures, without missing an increased number of joint or bone injuries; the test characteristics and the interobserver reliability of the Brand protocol; and whether having triage nurses order radiographs could reduce total patient waiting time in the emergency department.

DESIGN

Randomized, controlled trial.

SETTING

The ED of a free-standing children's hospital with approximately 55,000 visits annually.

TYPE OF PARTICIPANTS

Children less than 18 years of age who had a history of extremity trauma in the preceding seven days.

INTERVENTIONS

Triage nurses applied the Brand protocol to determine the need for a radiograph.

MEASUREMENTS AND RESULTS

Of the Brand protocol group, 81.9% had radiographs ordered compared with 87.1% of the control group (P = .03). The percent of positive radiographs was 40.8% in the Brand protocol group compared with 42.6% in the control group (P = .21). There were 3.2% (16) missed radiographic findings in the Brand protocol group compared with none in the control group (P < .001). Patients randomized to the Brand protocol group spent 3.3 hours in the ED compared with 3.6 hours for the control group (P < .001).

CONCLUSION

Having triage nurses use the Brand protocol reduced the number of radiographs ordered but at the same time increased the number of missed radiographic findings. However, having triage nurses order radiographs also significantly shortened waiting time in the ED.

The effects of liver and renal disease on stereoselective serum binding of flurbiprofen

Stereoselectivity in the serum binding of flurbiprofen, a non-steroidal anti-inflammatory drug which is highly bound to albumin, was studied in patients with liver and renal disease. Subjects with renal disease or liver disease with ascites had significantly lower serum albumin concentrations than normals, resulting in higher free fractions of both the R(-) and S(+) enantiomers of flurbiprofen as determined by equilibrium dialysis. The ratio (+/- s.d.) of R/S-flurbiprofen free fractions was lower in the subjects with ascites (0.714 +/- 0.298) than in those without ascites (0.796 +/- 0.090) (P < 0.05).

Cytokeratin 14 expression in rat liver cells in culture and localization in vivo

Rat liver epithelial cells (LECs) are non-parenchymal proliferating cells that readily emerge in primary culture and can be established as cell lines, but their in vivo cell(s) of origin is unclear. We reported recently some evidence indicating that the LEC line, T51B, contains two cytokeratins (CKs) equivalent to human CK8 and CK14 respectively. T51B cells also contain vimentin assembled as a network of intermediate filaments distinct from that of the CKs. In the present study, we examined the expression of CK14 gene in various LEC preparations and a Triton-resistant rat skin cytoskeletal fraction, and then assessed its usefulness as an LEC specific marker in the liver. Northern and Western blot analyses with cDNAs and antibodies for CK8, CK14, CK18 and vimentin confirmed that rat hepatocytes express CK8 and CK18 genes only, whereas T51B cells express CK8, CK14 and vimentin genes in the absence of CK18. CK14 was also present in LECs derived as primary from embryonic-day 12 rat liver and secondary cultures from 4-day-old rat liver. Primary cultures of oval cells isolated from 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) treated rat liver (an enriched source of biliary epithelial cells) contained CK14 mRNAs which were slightly shorter than those in LECs. The analyses of CK5 (the usual partner of CK14) gene expression using specific cDNA and antibody clearly demonstrated its absence in LECs. In situ double immunolocalization analyses by laser scanning confocal microscopy showed that CK14 was not present in hepatocytes (HES6+ cells) and was expressed in some biliary epithelial (BDS7+ cells). CK14-positive cells were also found in the Glisson's capsule. However, CK14-positive cells of the portal region were vimentin negative, whereas those of the Glisson's capsule were vimentin positive. Our results suggest that CK14 gene expression is part of the differentiation program of two types of LECs and that this differential CK14 gene expression can be used as a new means to type LECs in culture and in vivo.

Down-regulation of cytokeratin 14 mRNA in polyoma virus middle T-transformed rat liver epithelial cells

We have recently shown that rat liver nonparenchymal epithelial cells, such as T51B cells, selectively express cytokeratin (CK) 14 as a partner of CK8 in their intermediate filaments, and we proposed CK14 as a unique cell lineage marker of the liver epithelial cell population (R. Blouin, M-J. Blouin, I. Royal, A. Grenier, A. Loranger, D. R. Roop, and N. Marceau, Differentiation, submitted for publication, 1992). In the present study, T51B-261A (spontaneously transformed) and T51B-261B (aflatoxin B1-treated) clones and clones derived from T51B cells transfected with SV40 large T (LT) and polyoma virus middle T (MT) were used to investigate CK gene expression in nontransformed and transformed liver epithelial cells. T51B-261A, T51B-261B, MT-T51B, and LT/MT-T51B clones all grew in calcium-deficient medium and formed colonies in soft agar, whereas LT-T51B clones did not grow at all in either one of these assays. T51B-261A and T51B-261B clones formed small, slow growing tumors when injected into newborn syngenic rats, whereas the MT-T51B and LT/MT-T51B clones produced rapidly forming, large tumors. There was no effect of cell transformation on CK expression, except in the clones expressing MT, where the CK intermediate filaments were completely lost. Analyses of [35S]methionine incorporation into the Triton-resistant cytoskeleton and of total proteins confirmed that CKs were absent. In contrast, vimentin intermediate filaments remained unaffected in all of the clones.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for post-transcriptional regulation of cytokeratin gene expression in a rat liver epithelial cell line

T51B, a cell line of the rat liver nonparenchymal cell compartment, contains a cytokeratin (CK) pair composed of CK8, a CK typical of simple epithelium, and CK14, a CK usually present in proliferative stratified epithelium. T51B-Ni, a subclone selected by prolonged exposure of the parental clone to nickel subsulfide contains CK8 and CK18 (its usual partner in simple epithelium), as well as CK14, at a lower level. The two clones have comparable levels of vimentin. Northern blot analyses of cytoplasmic mRNA demonstrated that the differences in the steady state mRNA levels of each CK paralleled those observed at the protein level, thus showing that the regulatory events occurred prior to translation. The most prominent difference was a 30-fold higher level of CK18 mRNA in T51B-Ni cells. Run-off assays of isolated nuclei revealed that the level of CK8, CK14, and vimentin was regulated primarily at the transcriptional level. However, the large increase in CK18 mRNA levels in T51B-Ni cells did not result from a corresponding increase in the relative level of CK18 gene transcription nor from a change in cytoplasmic CK18 mRNA stability. Comparative Northern blot analyses of nuclear and cytoplasmic mRNAs further suggested that the control of CK18 gene expression in T51B cells is post-transcriptionally mediated by nuclear events.

Radiograph ordering: agreement between the triage nurse and the physician in a pediatric emergency department

We hypothesized that the triage nurse in a busy pediatric emergency department (ED) could accurately order radiographs, ultimately reducing patient waiting time. Protocols utilized to reduce patient waiting time are of importance in busy emergency departments. All patients registering at the ED of the Children's Hospital in a one-week period were entered into the study. The triage nurse documented whether they would send the patient for a radiograph, if allowed to, and were asked to designate a specific radiograph. The radiographs that were actually ordered by the physicians were subsequently obtained from radiology records. Data were analyzed for agreement beyond chance (kappa), positive (PPV) and negative predictive values. The results showed excellent agreement for extremity radiographs and poor agreement for nonextremity radiographs.

Selective accumulation of IF proteins at a focal juxtanuclear site in COS-1 cells transfected with mouse keratin 18 cDNA

COS-1 cells contain two keratins analogous to human keratins 8 (type II) and 18 (type I), and vimentin. Transfection of a plasmid, pSVK18, containing a mouse keratin 18 cDNA regulated by the SV40 early region promoter, was used to force the synthesis of exogenous (but homologous) type I keratin and to assess the effect of the oversynthesis of a keratin on endogenous keratins and vimentin intermediate filaments (IFs). Double immunofluorescence microscopy with monoclonal antimouse keratin 18 and monoclonal anti-human keratins 8 and 18 antibodies which cross-react with monkey keratins, showed that mouse keratin 18 formed typical IFs with the endogenous keratins but also accumulated in a focal area near the nucleus. Vimentin and its associated protein, p50, also colocalized at the juxtanuclear focal region, but the vimentin IFs of the outer cytoplasm vanished. Similar analyses with anti-tubulin and anti-actin antibodies indicated that the accumulated mouse keratin 18 colocalized with the centrosome but did not disturb the organization of microtubules or microfilaments. Anti-lamin and anti-SV40 large T antibodies showed that the oversynthesis of mouse keratin 18 had no effect on the distribution of these proteins. The accumulation was therefore selective for the cytoplasmic IF proteins. Electron microscopy and immunogold labeling of whole-mount detergent-extracted cells demonstrated that the accumulated IFs in the centrosomal region extended as a dense IF plexus-like network anchored to part of the nuclear surface.

Epidermal growth factor-induced selective phosphorylation of cultured rat hepatocyte 55-kD cytokeratin before filament reorganization and DNA synthesis

We have reported previously that the addition of dexamethasone to cultured quiescent suckling rat hepatocytes in the presence of insulin, a culture condition which does not cause growth activation, induces a selective increase in the synthesis of the 49-kD/55-kD cytokeratin (CK49/CK55) pair over a 24-h period. This increased synthesis coincides with the formation of dense filament networks reminiscent of those observed in situ at the cell periphery (Marceau, N., H. Baribault, and I. Leroux-Nicollet. 1985. Can. J. Biochem. Cell Biol. 63:448-457). We show here for the first time that when EGF is added 48 h after insulin and dexamethasone, there is an early preferential phosphorylation of the CK55 of the CK49/CK55 pair, an induced filament rearrangement from the cell periphery to the cytoplasm, and a subsequent entry into S phase and mitosis after a lag period of 8 h. Indirect immunofluorescence microscopy with monoclonal antibodies to CK49 and CK55 indicate that, while before EGF treatment the cytokeratin filaments were mainly distributed near the cell periphery, the addition of EGF resulted in their reorganization to a predominantly cytoplasmic localization within less than 3 h. Antitubulin and anti-actin antibodies showed no detectable alteration in the distribution of microtubules and microfilaments. Pulse-chase measurements with [35S]methionine showed no apparent change in the turnover of either CK49 or CK55 during the period that precedes the initiation of DNA synthesis. 32P-labeling in vivo followed by SDS-PAGE demonstrated that CK55 was phosphorylated at a much higher level than CK49 in nonstimulated hepatocytes, and that the addition of EGF resulted in a selective stimulation of 32P-CK55 labeling within less than 30 min. Comparative analyses by two-dimensional PAGE of [35S]methionine and 32P-labeled cytokeratins at various times after EGF stimulation demonstrated a rapid increase in a first phosphorylated form of CK55 and the appearance of a second phosphorylated form at 30 min poststimulation. The changes in the relative proportion of nonphosphorylated and phosphorylated forms were confirmed by immunoblotting with the anti-CK55 monoclonal antibody. Determinations of the 32P-labeled phosphoamino acids of CK55 extracted from the gels demonstrated that the radioactivity was mostly in serine residues. Labeling of Triton-permeabilized hepatocytes with gamma 32P-ATP after treatment with EGF for 30 min to 3 h at 37 degrees C, also demonstrated a phosphorylation of CK55 and CK49 as well, implying that the EGF-responsive serine protein kinase is detergent insoluble and probably part of the surface membrane skeleton.(ABSTRACT TRUNCATED AT 400 WORDS)

Stereoselective binding of propranolol in the elderly

The influence of age on the stereoselective serum protein binding of propranolol was investigated. Serum was obtained from 10 young (mean age 23 +/- 2 years) and ten elderly (mean age 68 +/- 2 years) healthy male volunteers. The free fraction of propranolol (fu) was measured by equilibrium dialysis, using tritium labeled (+/-)- and (-)-propranolol. The fu values were 0.159 +/- 0.049 and 0.148 +/- 0.028 (+/-), 0.135 +/- 0.041 and 0.136 +/- 0.04 (-), 0.174 +/- 0.056 and 0.161 +/- 0.028 (+) in the young and elderly subjects, respectively. Serum alpha 1-acid glycoprotein (AAG) concentrations were 81.4 +/- 33.0 and 81.0 +/- 21.6 mg 100 ml-1 in young and elderly respectively (P greater than 0.05). Variability in AAG concentration accounted for most of the observed intersubject variability in the binding of both propranolol isomers. The stereoselective binding of propranolol does not appear to be affected by age.

Hemodialysis clearance of pentobarbital during continuous infusion

The hemodialysis clearance of pentobarbital during continuous infusion was determined in a 34-year-old man in acute renal failure. Pentobarbital specimens were obtained simultaneously from arterial blood entering and leaving the dialysis machine at five 1-h intervals. The mean hemodialysis clearance of pentobarbital was 22.3 ml/min. Pentobarbital concentration was relatively unaffected throughout the dialysis period, because of the high dose and continuous infusion of a drug with low hepatic intrinsic clearance and a short dialysis period. A large contribution to total body clearance was not evident, and dosage adjustment would have been unwarranted.

Adriamycin and cis-platinum in advanced ovarian cancer

Forty-eight patients with stage III and IV ovarian epithelial carcinoma were treated with single doses of adriamycin (ADM) 50 mg/m2 and cis-platinum (DDP) 50 mg/m2 every month for nine courses. The pathologically proven response rate was 52.2%, with 22.7% complete response and 29.5% partial response. Median survival was 22 months for all patients, 25 months in stage III and 15 months in stage IV. This study confirms that ADM-DDP is a valuable drug regimen in advanced ovarian carcinoma but further progress is needed to improve the cure rate, which remains low.

Dopamine-phenytoin interaction. A cause of hypotension in the critically ill

Five critically ill patients received dopamine hydrochloride intravenously to support their blood pressure. When seizures developed, intravenous phenytoin sodium therapy was begun. Coincident with the infusion of phenytoin, the blood pressure, which was stable on the dopamine infusion, declined rapidly. Analysis of these cases led to a hypothesis that the interaction of dopamine and phenytoin produced the hypotension. When this hypothesis was tested in the normovolemic dog, intravenous dopamine produced no change in the blood pressure, and the addition of a phenytoin infusion had little effect. In animals rendered hypovolemic and hypotensive by bleeding, intravenous dopamine returned the blood pressure to the prebleeding level. At this point, an infusion of phenytoin produced a sustained decrease in the blood pressure. The mechanism of this action may be related to a combination of catecholamine depletion and myocardial depression.