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Biomedical subjects

L Butterfield

Publications and source records attributed to L Butterfield.

12 recordsLinked to original sources
PubMed2001

Induction of cytosolic phospholipase A2 by oncogenic Ras is mediated through the JNK and ERK pathways in rat epithelial cells.

Mutations in ras genes have been detected with high frequency in nonsmall cell lung cancer cells (NSCLC) and contribute to transformed growth of these cells. It has previously been shown that expression of oncogenic forms of Ras in these cells is associated with elevated expression of cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase-2 (COX-2), resulting in high constitutive levels of prostaglandin production. To determine whether expression of constitutively active Ras is sufficient to induce expression of these enzymes in nontransformed cells, normal lung epithelial cells were transfected with H-Ras. Stable expression of H-Ras increased expression of cPLA(2) and COX-2 protein. Transient transfection with H-Ras increased promoter activity for both enzymes. H-Ras expression also activated all three families of MAP kinase: ERKs, JNKs, and p38 MAP kinase. Expression of constitutively active Raf did not increase either cPLA(2) or COX-2 promoter activity, but inhibition of the ERK pathway with pharmacological agents or expression of dominant negative ERK partially blocked the H-Ras-mediated induction of cPLA(2) promoter activity. Expression of dominant negative JNK kinases decreased cPLA(2) promoter activity in NSCLC cell lines and inhibited H-Ras-mediated induction in normal epithelial cells, whereas expression of constructs encoding constitutively active JNKs increased promoter activity. Inhibition of p38 MAP kinase or NF-kappaB had no effect on cPLA(2) expression. Truncational analysis revealed that the region of the cPLA(2) promoter from -58 to +12 contained sufficient elements to mediate H-Ras induction. We conclude that expression of oncogenic forms of Ras directly increases cPLA(2) expression in normal epithelial cells through activation of the JNK and ERK pathways.

Animals↗
PubMed2001

Leptin in children with newly diagnosed type 1 diabetes: effect of insulin therapy.

Leptin, the gene product of adipose tissue that signals caloric plentitude via central nervous system receptors, may also have diverse peripheral metabolic actions. Of paramount interest has been the potential interaction(s) between leptin and insulin. Insofar as insulin alters leptin secretion/action (or vice versa), dysregulation of this system could contribute to disease states such as diabetes. The purpose of this study was to examine the effect of exogenous insulin on serum leptin in children with newly-diagnosed Type 1 diabetes. Since these patients are hypoinsulinemic (insulin-depleted) at diagnosis, they present an ideal opportunity to examine the effect of insulin repletion on serum leptin. Seventeen patients were enrolled. At baseline (prior to insulin therapy), leptin levels were 4.3 +/- 1.1 ng/ml; they were not statistically related to the baseline serum insulin or illness severity. There was no significant change in serum leptin before, shortly (1-6 days) or several weeks (3-26 weeks) after insulin treatment even when the data was corrected for changes in BMI, hemoglobin A1C, and daily insulin dose. Since repletion of the insulin deficiency that is present in non-acidotic, ambulatory patients with new onset Type 1 diabetes did not alter serum leptin, these results argue against an effect of insulin on serum leptin in the absence of the acute diabetic ketoacidosis. Because as the recuperative months following the diagnosis of new onset Type 1 diabetes are marked by weight gain, the absence of a rise in serum leptin might also indicate either an adaptive (weight permissive) or pathologic (impaired secretory) deficit.

Adolescent↗
PubMed2000

Akt negatively regulates the cJun N-terminal kinase pathway in PC12 cells.

The protein serine/threonine kinase Akt is a target of phosphatidylinositol 3-kinase that mediates many of the trophic actions of growth factors on cells. In PC12 cells, complete removal of serum leads to rapid stimulation of the cJun N-terminal kinase (JNK) pathway. Inclusion of insulin-like growth factor-1, a stimulator of Akt in PC12 cells, inhibits JNK activation in this setting, whereas addition of wortmannin to PC12 cells in the presence of serum stimulates JNK activity, suggesting that growth factor-mediated signaling through the phosphatidylinositol 3-kinase/Akt pathway chronically inhibits the JNK pathway in PC12 cells. To explore the possible role of Akt as a negative regulator of JNK activity in PC12 cells, a myristoylated, gain-of-function Akt polypeptide (Myr-Akt) was expressed by retrovirus-mediated gene transfer. Stimulation of JNK activity by serum withdrawal or UV irradiation in PC12 cell clones stably expressing Myr-Akt was inhibited approximately 95% or 50%, respectively, relative to control transfected PC12 cells. Phosphorylation of both JNKs and a proximal activator, MAP kinase kinase 4 (MKK4), in response to UV irradiation was inhibited in Myr-Akt-expressing PC12 cells. Furthermore, transient expression of Myr-Akt strongly inhibited cJun transactivation mediated by MEKK1 or MKK7-JNK3, a gain-of-function MKK7-JNK fusion protein. Interestingly, inhibited JNK activation in the Myr-Akt-expressing PC12 cells is associated with marked induction of JNK-interacting protein-1 (JIP-1). We propose that negative regulation of the JNK pathway through Akt-dependent induction of specfic JIP proteins contributes to the antiapoptotic actions of Akt in neuronal cell types.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Stress- and cell type-dependent regulation of transfected c-Jun N-terminal kinase and mitogen-activated protein kinase kinase isoforms.

The cJun N-terminal kinases (JNKs) are encoded by three genes generating ten protein kinase polypeptides and are activated in settings of cell stress, mitogenesis, differentiation and morphogenesis. The specific role of the JNK family members in these diverse cell programmes is largely undefined. In this study, we tested the hypothesis that individual JNK isoforms would exhibit distinct patterns of regulation within cells. The cDNAs encoding five haemagglutinin (HA)-tagged JNK isoforms (p46JNK1alpha, p54JNK2alpha, p54JNK2beta, p46JNK3 and p54JNK3) were expressed in cultured rat PC12 phaeochromocytoma cells and human small-cell lung cancer (SCLC) cells by retrovirus-mediated gene transfer. In addition, HA-tagged forms of the dual-specificity mitogen-activated protein kinase kinases (MKKs), MKK4 and MKK7, which are specific activators of the JNK enzymes, were similarly expressed. Reverse transcription and PCR revealed that JNK3 is endogenously expressed in SCLC cells, but not in either chromaffin or neuronally differentiated PC12 cells. MKK4 and MKK7 were endogenously expressed in both PC12 cells and SHP77 cells. Immunoprecipitation and analysis of the JNKs expressed in SCLC cells revealed strong stimulation of all five JNK isoforms by UV radiation. Hypertonic stress, elicited by mannitol, also significantly stimulated these same JNKs, although the JNK3 isoforms were most strongly activated. In PC12 cell transfectants, however, selective and equal activation of p54JNK2alpha and p54JNK3 by UV and osmotic stress was observed, with little or no activation of JNK1alpha or JNK2beta. In contrast with the broad activation of the JNK enzymes by UV in SCLC cells, only HA-MKK4 was stimulated by UV exposure in these cells, whereas osmotic stress stimulated both HA-MKK4 and HA-MKK7. These findings indicate selective activation of JNK and MKK isoforms in a manner that is dependent upon the specific cell stress and the cell type.

Animals↗
PubMed1999

Retinal detachment in Olmsted County, Minnesota, 1976 through 1995.

OBJECTIVE: To estimate the incidence of rhegmatogenous retinal detachment (RD) in a geographically defined population and to compare the probability of RD in residents after cataract extraction with the probability of RD in residents who did not have cataract extraction. DESIGN: Rochester Epidemiology Project databases were used to perform a retrospective population-based incidence study of RD diagnosed between 1976 and 1995 with cohort analyses of the influence of risk factors on the occurrence of RD. PARTICIPANTS: The population of Olmsted County, Minnesota, participated. MAIN OUTCOME MEASURE: Incidence rates of RD adjusted to the age and gender distribution of the 1990 U.S. white population were measured. RESULTS: Three hundred eleven incident cases of rhegmatogenous RD were identified. The mean annual age- and gender-adjusted incidence rate of rhegmatogenous RD was 17.9 per 100,000 persons (95% confidence interval [CI], 15.9-19.9). For idiopathic rhegmatogenous RD alone, the mean annual age- and gender-adjusted incidence rate was 12.6 (95% CI, 10.9-14.3) per 100,000 persons. Ten years after phacoemulsification and extracapsular cataract extraction, the estimated cumulative probability of RD was 5.5 (95% CI, 3.4-7.6) times as high as would have been expected in a similar group of county residents not undergoing cataract surgery. CONCLUSIONS: Cataract surgery is associated with a significantly elevated long-term cumulative probability of retinal detachment.

Adolescent↗
PubMed1998

Abnormal cervical cytology in pregnancy: experience of 811 cases.

This paper reviews our hospital's experience spanning 15 years and involving 811 women referred with abnormal cervical cytology in pregnancy. It supports the safety and accuracy of managing dysplasia in pregnancy with colposcopy, directed punch biopsy and deferral of treatment until the postpartum period. The histologically-proven progression in pregnancy to a higher grade of dysplasia postpartum was 7%. None of the women are known to have developed microinvasive or invasive cancer between antenatal assessment and postpartum review. Of these 811 women, 16% were lost to follow-up, 1 of whom subsequently represented 4 years later with invasive cervical cancer.

Adult↗
PubMed1998

Barriers to seeking care following school vision screening in Rochester, Minnesota.

School vision screening provides an effective way to identify children who require vision therapy, usually glasses. To benefit from screening, children with abnormal screening test results must receive follow-up eye care, but care may be delayed for months or years. This project used community focus groups in Rochester, Minn., to identify barriers that may delay seeking professional care following school vision screening. Major barriers identified included lack of community awareness about the frequency and potential effect of refractive errors in children, a parental perception of inadequate communication between schools and the parents and community, high cost of corrective lenses, limited availability of convenient eye care appointments, and adolescents reluctance to wear glasses. Program planners developed a community action plan to address the perceived barriers.

Adolescent↗
PubMed1997

c-Jun NH2-terminal kinase regulation of the apoptotic response of small cell lung cancer cells to ultraviolet radiation.

Exposure of cultured small cell lung cancer (SCLC) cells to UV radiation induces apoptosis. We observed that the UV sensitivity of a panel of SCLC lines and the activation of c-Jun NH2-terminal kinases (JNKs) by UV in the individual SCLC lines, assessed by binding and phosphorylation of glutathione S-transferase (GST)-c-Jun fusion proteins, ranged widely. In fact, increased JNK activity in this assay was closely correlated with decreased sensitivity to apoptosis following UV irradiation. Increased JNK activity was also detected in anti-JNK1 immune complexes collected from UV-irradiated SCLC cells, although the level of activity was similar among the various SCLC lines and correlated poorly with UV sensitivity. Immunoblot analysis of JNK polypeptides that bound to GST-c-Jun revealed at least two JNK polypeptides, one of which appeared only in extracts from UV-irradiated SCLC. To test the role of JNKs in UV-induced apoptosis, nonphosphorylatable mutants of JNK1 or JNK2 in which the phosphorylation site Thr-Pro-Tyr is changed to Ala-Pro-Phe (JNK-APF) and are predicted to behave as competitive inhibitors were stably expressed in SCLC. Expression of JNK1-APF or JNK2-APF significantly reduced UV-stimulated JNK activity. However, JNK1-APF markedly increased the resistance of the cells to UV-induced apoptosis, while JNK2-APF did not influence SCLC sensitivity to UV. The findings suggest that UV-stimulated JNK1 activation promotes UV-induced SCLC apoptosis, while a JNK isoform that is variably activated among the SCLC lines may signal a UV-protective response. We hypothesize that integration of distinct JNK activities dictates the relative responsiveness of SCLC to UV and ionizing radiation.

Apoptosis↗
PubMed1996

GTPase-deficient G alpha 16 and G alpha q induce PC12 cell differentiation and persistent activation of cJun NH2-terminal kinases.

Persistent stimulation of specific protein kinase pathways has been proposed as a key feature of receptor tyrosine kinases and intracellular oncoproteins that signal neuronal differentiation of rat pheochromocytoma (PC12) cells. Among the protein serine/threonine kinases identified to date, the p42/44 mitogen-activated protein (MAP) kinases have been highlighted for their potential role in signalling PC12 cell differentiation. We report here that retrovirus-mediated expression of GTPase-deficient, constitutively active forms of the heterotrimeric Gq family members, G alpha qQ209L and G alpha 16Q212L, in PC12 cells induces neuronal differentiation as indicated by neurite outgrowth and the increased expression of voltage-dependent sodium channels. Differentiation was not observed after cellular expression of GTPase-deficient forms of alpha i2 or alpha 0, indicating selectivity for the Gq family of G proteins. As predicted, overexpression of alpha qQ209L and alpha 16Q212L constitutively elevated basal phospholipase C activity approximately 10-fold in PC12 cells. Significantly, little or no p42/44 MAP kinase activity was detected in PC12 cells differentiated with alpha 16Q212L or alpha qQ209L, although these proteins were strongly activated following expression of constitutively active cRaf-1. Rather, a persistent threefold activation of the cJun NH2-terminal kinases (JNKs) was observed in PC12 cells expressing alpha qQ209L and alpha 16Q212L. This level of JNK activation was similar to that achieved with nerve growth factor, a strong inducer of PC12 cell differentiation. Supportive of a role for JNK activation in PC12 cell differentiation, retrovirus-mediated overexpression of cJun, a JNK target, in PC12 cells induced neurite outgrowth. The results define a p42/44 MAP kinase-independent mechanism for differentiation of PC12 cells and suggest that persistent activation of the JNK members of the proline-directed protein kinase family by GTPase-deficient G alpha q and G alpha 16 subunits is sufficient to induce differentiation of PC12 cells.

Animals↗
PubMed1995

Antioxidant function of recombinant human natural killer enhancing factor.

Natural killer enhancing factor (NKEF) is a member of a new class of highly conserved antioxidant proteins. Members of this family have been described as thiol-specific antioxidants. In this study, we show that recombinant proteins encoded by the two human NKEF genes (nkef-A and B) possess antioxidant function in the protection of protein and DNA from oxidative damage. The production of separate proteins from each of the genes encoding NKEF is an important step in the elucidation of its function.

Antioxidants↗
PubMed1984

Beyond the therapeutic window: a case presentation.

The relationship of haloperidol dose and plasma concentration to psychotic symptoms of schizophrenia is described. The authors present evidence supporting a therapeutic window hypothesis, in which an individual patient's course follows an inverted U curve. The clinical implications for dosage strategies are discussed.

Adult↗