Chromium (VI) promotes lung cancer initiation by activating EGF/ALDH1A1 signalling

Lung cancer is the leading cause of cancer-related death worldwide and is strongly associated with tobacco smoke exposure. Though smoking remains the most important and best studied risk factor, recent data suggests that several other carcinogens have a driving role in lung cancer development, particularly in select populations at risk of high or prolonged exposure. Hexavalent chromium [Cr(VI)] is a known carcinogen that is widely used in the manufacturing industry. While the link between Cr(VI) and lung cancer incidence is well-accepted, the mechanisms through which Cr(VI) promotes lung cancer development are poorly understood. In the present study by Ge and colleagues published in Clinical and Translational Medicine, the authors explored the effects of prolonged Cr(VI) on non-malignant lung epithelial cells. They determined that Cr(VI) initiates lung tumorigenesis by transforming a subpopulation of stem-like, tumor initiating cells with increased expression of Aldehyde dehydrogenase 1 family member A1 (ALDH1A1). The observed increase in ALDH1A1 was dependent on transcriptional upregulation via Krüppel-like factor 4 (KLF4), and associated with enhanced Epidermal Growth Factor (EGF) biosynthesis. Cr(VI)-transformed tumor initiating cells accelerated tumor formation in vivo, which was ameliorated by therapeutic inhibition of ALDH1A1. Importantly, ALDH1A1 inhibition also sensitized Cr(VI)-driven tumors to Gemcitabine chemotherapy and extended overall survival in mice. This study not only offers novel insight into the mechanisms through which Cr(VI) exposure initiates lung tumorigenesis, but identifies a potential therapeutic target for patients with lung cancer secondary to Cr(VI) exposure. Additionally, this study underscores the importance of limiting exposure to Cr(VI) in the workplace and finding safer alternatives for use in the manufacturing industry.

Non-small cell lung carcinoma spheroid models in agarose microwells for drug response studies

There is a growing interest in developing personalized treatment strategies for each cancer patient, especially those with non-small cell lung carcinoma (NSCLC) which annually accounts for the majority of cancer related deaths in the US. Yet identifying the optimal NSCLC treatment strategy for each cancer patient is critical due to a multitude of mutations, some of which develop following initial therapy and can result in drug resistance. A key difficulty in developing personalized therapies in NSCLC is the lack of clinically relevant assay systems that are suitable to evaluate drug sensitivity using a minuscule amount of patient-derived material available following biopsies. Herein we leverage 3D printing to demonstrate a platform based on miniature microwells in agarose to culture cancer cell spheroids. The agarose wells were shaped by 3D printing molds with 1000 microwells with a U-shaped bottom. Three NSCLC cell lines (HCC4006, H1975 and A549) were used to demonstrate size uniformity, spheroid viability, biomarker expressions and drug response in 3D agarose microwells. Results show that our approach yielded spheroids of uniform size (coefficient of variation <22%) and high viability (>83% after 1 week-culture). Studies using epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKIs) drugs gefitinib and osimertinib showed clinically relevant responses. Based on the physical features, cell phenotypes, and responses to therapy of our spheroid models, we conclude that our platform is suitable for in vitro culture and drug evaluation, especially in cases when tumor sample is limited.

Endothelin-1-Mediated Drug Resistance in EGFR-Mutant Non-Small Cell Lung Carcinoma

Progression on therapy in non-small cell lung carcinoma (NSCLC) is often evaluated radiographically, however, image-based evaluation of said therapies may not distinguish disease progression due to intrinsic tumor drug resistance or inefficient tumor penetration of the drugs. Here we report that the inhibition of mutated EGFR promotes the secretion of a potent vasoconstrictor, endothelin-1 (EDN1), which continues to increase as the cells become resistant with a mesenchymal phenotype. As EDN1 and its receptor (EDNR) is linked to cancer progression, EDNR-antagonists have been evaluated in several clinical trials with disappointing results. These trials were based on a hypothesis that the EDN1-EDNR axis activates the MAPK-ERK signaling pathway that is vital to the cancer cell survival; the trials were not designed to evaluate the impact of tumor-derived EDN1 in modifying tumor microenvironment or contributing to drug resistance. Ectopic overexpression of EDN1 in cells with mutated EGFR resulted in poor drug delivery and retarded growth in vivo but not in vitro. Intratumoral injection of recombinant EDN significantly reduced blood flow and subsequent gefitinib accumulation in xenografted EGFR-mutant tumors. Furthermore, depletion of EDN1 or the use of endothelin receptor inhibitors bosentan and ambrisentan improved drug penetration into tumors and restored blood flow in tumor-associated vasculature. Correlatively, these results describe a simplistic endogenous yet previously unrealized resistance mechanism inherent to a subset of EGFR-mutant NSCLC to attenuate tyrosine kinase inhibitor delivery to the tumors by limiting drug-carrying blood flow and the drug concentration in tumors. SIGNIFICANCE: EDNR antagonists can be repurposed to improve drug delivery in VEGFA-secreting tumors, which normally respond to TKI treatment by secreting EDN1, promoting vasoconstriction, and limiting blood and drug delivery.

CXCR7 Reactivates ERK Signaling to Promote Resistance to EGFR Kinase Inhibitors in NSCLC

Although EGFR mutant-selective tyrosine kinase inhibitors (TKI) are clinically effective, acquired resistance can occur by reactivating ERK. We show using in vitro models of acquired EGFR TKI resistance with a mesenchymal phenotype that CXCR7, an atypical G protein-coupled receptor, activates the MAPK-ERK pathway via β-arrestin. Depletion of CXCR7 inhibited the MAPK pathway, significantly attenuated EGFR TKI resistance, and resulted in mesenchymal-to-epithelial transition. CXCR7 overexpression was essential in reactivation of ERK1/2 for the generation of EGFR TKI-resistant persister cells. Many patients with non-small cell lung cancer (NSCLC) harboring an EGFR kinase domain mutation, who progressed on EGFR inhibitors, demonstrated increased CXCR7 expression. These data suggest that CXCR7 inhibition could considerably delay and prevent the emergence of acquired EGFR TKI resistance in EGFR-mutant NSCLC. SIGNIFICANCE: Increased expression of the chemokine receptor CXCR7 constitutes a mechanism of resistance to EGFR TKI in patients with non-small cell lung cancer through reactivation of ERK signaling.

Abstract LB-085: A new role for LKB1 to regulate Heat Shock Protein 90 activity

Approximately 30% of human non-small cell lung cancer (NSCLC) patients harbor a somatic KRAS mutation resulting, in aberrant activation of downstream signaling pathways that control cell proliferation, cell growth, and cell survival. Importantly, alleles of LKB1, a serine/threonine kinase that functions as a tumor suppressor, are somatically inactivated in ~30% of NSCLCs within KRAS-mutant NSCLC. The loss of LKB1 gives rise to aggressive, highly metastatic, and highly drug resistant tumors. We have previously demonstrated that the inactivation of the tumor suppressor lkb1 rendered mutant kras murine NSCLC resistant to targeted agents including BET bromodomain and kinase inhibitors. However, the mechanism by which LKB1 inactivation attenuates the efficacy of the therapies remains elusive. Consequently, investigation of the molecular-basis of drug resistance to formulate effective therapies for this KRAS-mutated and LKB1-inactivated (KRAS/LKB1) subset of patients is warranted. Using lung adenocarcinoma cells that lack LKB1 expression, we have established isogenic cells that express vector control, wild-type LKB1, or kinase-dead LKB1. Our preliminary data using these isogenic cell lines suggest the previously unrealized function of LKB1 to activate HSP90 to stabilize client signaling proteins. Furthermore, we have performed p23 immunoprecipitation (IP) followed by Western blot for HSP90 to assess the HSP90 ATPase activity. In the cells ectopically expressing wild-type LKB1, p23 co-immunoprecipitated with HSP90 showing that HSP90 is in active conformation. In contrast, few HSP90 co-immunoprecipitated with p23 in the cells that express the kinase-dead version of LKB1 or vector control, demonstrating that little HSP90 is in active conformation without LKB1 kinase activity. Using NetworKIN, a web-based bioinformatic analysis, we find putative LKB1 phosphorylation motifs on HSP90. These results suggest that LKB1 phosphorylates and activates HSP90. Consequently, the inactivation of LKB1 contributes to the destabilization of key HSP90 client signaling proteins and inadvertently promotes compensatory mechanisms to stabilize the select signaling molecules. Using our LKB1-isogenic cell lines, we demonstrated that LKB1 activates HSP90 to stabilize RAF1, resulting in MAPK pathway activation. In contrast, LKB1 inactivation led to reduced HSP90 activity, which reduced MAPK activity and elevated IGF-1R-mediated phosphatidylinositol 3-kinase (PI3-K) activity in vivo and in vitro models of mutant KRAS NSCLC. The aberrant activation of PI3-K pathway augments survival by the stabilization of the anti-apoptotic molecule, MCL1. The use of HSP90 inhibitors does not fully inhibit MAPK or PI3-K pathways due to the compensatory mechanisms chaperoning the IGF-1R axis. Importantly, we confirmed that canonical LKB1-AMPK-mTOR pathway does not fully control PI3K or MAPK signaling. Taken together, our data supports the presence of an HSP90-independent mechanism to stabilize kinases, including IGF-1R, to make KRAS/LKB1 NSCLC resistant to targeted therapies.

Citation Format: Jeffrey H. Becker, Michael P. Kahle, Margaret Soucheray, Ines Pulido, Fatima Al-Shahrour, Manuel Sanchez del Pino, Kwok-Kin Wong, Julian Carretero, Takeshi Shimamura. A new role for LKB1 to regulate Heat Shock Protein 90 activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-085.

Abstract LB-C21: CXCR7 expression is necessary for the maintenance of mesenchymal phenotype in acquired EGFR TKI resistance in NSCLC

Activating EGFR mutations in non-small lung cancer (NSCLC) confer sensitivity to reversible EGFR tyrosine kinase inhibitors (TKIs), including gefitinib and erlotinib. Despite promising initial response, acquired resistance develops mediated by the emergence of the secondary T790M mutation or by focal amplification of MET. An epithelial-to-mesenchymal transition (EMT) is clinically linked to NSCLCs with acquired EGFR TKI resistance. The exact mechanisms of EGFR TKI resistance with EMT phenotype remain elusive; therefore, we have engineered EGFR-mutated NSCLC cell lines with mesenchymal phenotype by stably depleting E-Cadherin or by overexpressing Snail or chronically exposing the cells to TGFβ1. The resulting mesenchymal cells are resistant to EGFR TKIs. We employed genomic analyses to identify that C-X-C chemokine receptor type 7 (CXCR7) is commonly overexpressed in the engineered cells with mesenchymal phenotype. We also discovered that CXCR7 is overexpressed in EGFR-mutated HCC4006 NSCLC cells grown resistant to gefitinib that developed a mesenchymal phenotype (HCC4006 Ge-R). To extend our findings to in vivo, we assessed if CXCR7 is overexpressed in mouse lung cancers driven by human EGFR exon19 deletion/T790M (TD) that initially respond to the EGFR mutant-specific irreversible TKI WZ4002 to promote tumor regression but later develops tumors with acquired resistance. We discovered that the murine tumors with acquired resistance to WZ4002 present mesenchymal phenotype and overexpress CXCR7. Stable depletion of CXCR7 in HCC4006Ge-R mesenchymal gefitinib resistant cells promoted gradual mesenchymal to epithelial transition. Sustained depletion of CXCR7 in HCC4006Ge-R cells resulted in inactivation of PI3K and MAPK pathways upon gefitinib treatment and greatly restored the sensitivity to gefitinib. Furthermore, the depletion of CXCR7 in HCC4006GeR cells resulted in the downregulation of mesenchymal transcription factors essential including TWIST, ZEB1 and ZEB2, suggesting but not proving that CXCR7 maintains mesenchymal phenotype. To determine if the resistance mechanisms to gefitinib with mesenchymal cells expressing CXCR7 evolve under the selective pressure of gefitinib or pre-exist prior to treatment, we sorted EGFR-mutated NSCLC cells with CXCR7 and mesenchymal markers to find less than 5% of the cells express CXCR7 with mesenchymal phenotype.

Interestingly, ectopic expression of CXCR7 in EGFR-mutated cells was not sufficient to confer resistance to EGFR TKIs or to promote EMT. Taken together, we discovered that CXCR7 is necessary for the maintenance of EGFR TKI resistance with mesenchymal phenotype and the population of mesenchymal cells that overexpress CXCR7 pre-exists and is selected upon chronic EGFR TKI treatment.

Citation Format: Jeffrey H. Becker, Yandi Gao, Ines Pulido, Eiki Kikuchi, Margaret Soucheray, Rutu Gandhi, Camilla L. Christensen, Fatima Al-shahrour, Kwok-Kin Wong, Julian Carretero, Takeshi Shimamura. CXCR7 expression is necessary for the maintenance of mesenchymal phenotype in acquired EGFR TKI resistance in NSCLC. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-C21.

Intratumoral Heterogeneity in EGFR-Mutant NSCLC Results in Divergent Resistance Mechanisms in Response to EGFR Tyrosine Kinase Inhibition

Non-small cell lung cancers (NSCLC) that have developed resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI), including gefitinib and erlotinib, are clinically linked to an epithelial-to-mesenchymal transition (EMT) phenotype. Here, we examined whether modulating EMT maintains the responsiveness of EGFR-mutated NSCLCs to EGFR TKI therapy. Using human NSCLC cell lines harboring mutated EGFR and a transgenic mouse model of lung cancer driven by mutant EGFR (EGFR-Del19-T790M), we demonstrate that EGFR inhibition induces TGFβ secretion followed by SMAD pathway activation, an event that promotes EMT. Chronic exposure of EGFR-mutated NSCLC cells to TGFβ was sufficient to induce EMT and resistance to EGFR TKI treatment. Furthermore, NSCLC HCC4006 cells with acquired resistance to gefitinib were characterized by a mesenchymal phenotype and displayed a higher prevalence of the EGFR T790M mutated allele. Notably, combined inhibition of EGFR and the TGFβ receptor in HCC4006 cells prevented EMT but was not sufficient to prevent acquired gefitinib resistance because of an increased emergence of the EGFR T790M allele compared with cells treated with gefitinib alone. Conversely, another independent NSCLC cell line, PC9, reproducibly developed EGFR T790M mutations as the primary mechanism underlying EGFR TKI resistance, even though the prevalence of the mutant allele was lower than that in HCC4006 cells. Thus, our findings underscore heterogeneity within NSCLC cells lines harboring EGFR kinase domain mutations that give rise to divergent resistance mechanisms in response to treatment and anticipate the complexity of EMT suppression as a therapeutic strategy.

Abstract 766: Suppression of gefitinib-induced EMT in EGFR mutant NSCLC preferentially selects for acquired T790M

Activating EGFR mutations in non-small lung cancer (NSCLC) confer sensitivity to reversible EGFR tyrosine kinase inhibitors (TKIs), including gefitinib and erlotinib. Despite promising initial response acquired resistance develops mediated by the emergence of the secondary T790M mutation or by focal amplification of MET. An epithelial-to-mesenchymal transition (EMT) is clinically linked to NSCLCs with acquired EGFR TKI resistance. The exact mechanisms of EGFR TKI resistance with EMT phenotype remain elusive; therefore, we attempted to develop a strategy to prevent the emergence of EGFR TKI resistance with EMT phenotype. In order to mimic the development of acquired EGFR TKI resistance in NSCLC patients, TKI-sensitive HCC4006 cells harboring mutated-EGFR were exposed to increasing concentrations of gefitinib to generate resistant cells with mesenchymal phenotype. After 6 months, the cells became resistant to gefitinib (HCC4006GeR) with no MET copy number increase and with no apparent gain of secondary T790M mutation. Subsequent genomics and proteomics analyses of HCC4006GeR confirmed enrichment of genes distinctive to mesenchymal cells. Multiplex Luminex growth factor assays identified increased secretion of TGFβ1 from HCC4006Ge-R cells. We discovered that the depletion of EGFR by shRNA or inactivation of mutated EGFR activity by EGFR TKI promoted TGFβ1 secretion and subsequent induction of EMT, which modulate signaling and apoptosis pathways contributing to the development of the resistance. Consequently, we hypothesized that concurrent inhibition of EGFR and TGFβ receptor in HCC4006 cells should prevent the emergence of gefitinib resistance with mesenchymal phenotype. After culturing HCC4006 cells in EGFR (gefitinib) and TGFβ receptor (SB431542) inhibitors, we successfully prevented EMT, although those cells were still resistant to gefitinib (HCC4006GeSB-R). Interestingly, the cells remain sensitive to irreversible EGFR TKI AZD9291 and CO-1686, suggesting the presence of T790M mutation. DNA sequencing of EGFR expressed in HCC4006GeSB-R detected secondary T790M mutation. Droplet digital PCR analysis detected that the frequencies of EGFR allele coding for T790M in HCC4006Ge-R and HCC4006GeSB-R cells are 1.2% and 18.3%, respectively, which were increased from 0.015% in HCC4006 cells harboring heterozygous Del L747-E749+A750P/T790M mutation. The frequency of T790M allele in HCC4006 was higher than the frequency in PC9 cells (0.001%) which reproducibly develop EGFR T790M as a mechanism of EGFR TKI resistance. Taken together, we discovered that suppression of gefitinib-induced EMT in EGFR mutant HCC4006 NSCLC cells preferentially selects for the previously unreported and rare subpopulation of HCC4006 harboring T790M. These results also underscore heterogeneity within HCC4006 cells that give rise to the divergent resistance mechanisms according to treatment.

Citation Format: Margaret Soucheray, Marzia Capelletti, Ines Pulido, Yunan Kuang, Cloud P. Paweletz, Jeffrey H. Becker, Eiki Kikuchi, Chunxiao Xu, Tarun B. Patel, Fatima Al-shahrour, Julian Carretero, Kwok-Kin Wong, Pasi A. Janne, Geoffrey I. Shapiro, Takeshi Shimamura. Suppression of gefitinib-induced EMT in EGFR mutant NSCLC preferentially selects for acquired T790M. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 766. doi:10.1158/1538-7445.AM2015-766

Is intrapartum fever associated with ST-waveform changes of the fetal electrocardiogram? A retrospective cohort study

OBJECTIVE

To investigate the association between maternal intrapartum fever and ST-waveform changes of the fetal electrocardiogram.

DESIGN

Retrospective cohort study.

SETTING

Three academic and six non-academic teaching hospitals in the Netherlands.

POPULATION

Labouring women with a high-risk singleton pregnancy in cephalic position beyond 36 weeks of gestation.

METHODS

We studied 142 women with fever (≥38.0°C) during labour and 141 women with normal temperature who had been included in two previous studies. In both groups, we counted the number and type of ST-events and classified them as significant (intervention needed) or not significant, based on STAN(®) clinical guidelines.

MAIN OUTCOME MEASURES

Number and type of ST-events.

RESULTS

Both univariable and multivariable regression analysis showed no association between the presence of maternal intrapartum fever and the number or type of ST-events.

CONCLUSIONS

Maternal intrapartum fever is not associated with ST-segment changes of the fetal electrocardiogram. Interpretation of ST-changes in labouring women with fever should therefore not differ from other situations.

Rehabilitation after surgery for flexor tendon injuries in the hand

BACKGROUND

Postoperative rehabilitation of the flexor tendons in the hand consists of a short period of immobilisation while pain and swelling diminish, followed by progressive mobilisation to maximize the range of motion of the affected fingers. By altering the time of immobilisation and the manner of subsequent mobilisation different rehabilitation regimes are created.

OBJECTIVES

To determine, with evidence from randomised controlled trials, the optimal rehabilitation strategy after surgery for flexor tendon injuries in the hand.

SEARCH STRATEGY

We searched the Cochrane Musculoskeletal Injuries Group specialised register (November 2002), the Cochrane Central Register of Controlled Trials (The Cochrane Library, issue 4, 2002), MEDLINE (1966 to November 2002), EMBASE (1988 to November 2002), CINAHL (1982 to October 2002), CURRENT CONTENTS (1993 to October 2002), PEDro - The Physiotherapy Evidence Database (http://ptwww.cchs.usyd.edu.au/pedro/ accessed 30/10/2002) and reference lists of articles.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials of interventions for rehabilitation after surgery of flexor tendon injuries in the hand after surgery.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality, using a 10 item scale, and extracted data where possible. Additional information was sought from trialists when required. Due to the lack of extractable data and the variety of interventions used, pooling was not attempted. Where possible relative risks and 95 per cent confidence intervals were calculated for dichotomous outcomes, and mean differences and 95 per cent confidence intervals calculated for continuous outcomes.

MAIN RESULTS

Six trials, including three reported only in abstracts, with a total of 464 participants were included. Data were not pooled. One trial compared continuous passive motion (CPM) with controlled intermittent passive motion (CIPM) and found a significant difference in mean active motion favouring CPM (WMD 19.00 degrees, 95% CI 15.11 to 22.89). One trial compared a shortened passive flexion/active extension programme with a normal passive flexion/active extension mobilisation programme, and reported (without data) a significant reduction in absence from work of 2.1 weeks in favour of the shortened programme. Other trials compared active flexion with rubber band traction, early controlled active mobilisation with early controlled passive mobilisation and dynamic splintage versus static splintage. No trials found significant differences in overall functioning or complication rate.

REVIEWERS' CONCLUSIONS

Controlled mobilisation regimens are widely employed in rehabilitation after flexor tendon repair in the hand. This review found insufficient evidence from randomised controlled trials to define the best mobilisation strategy.

Contributions of bone density and geometry to the strength of the human second metatarsal

We investigated, at the whole bone level, the contribution of bone density and geometry to the fracture load of the second metatarsal, a bone that is prone to stress fracture. Dual-energy X-ray absorptiometry (DXA) was used to determine the areal bone mineral density (BMD), projected area of bone, and bone mineral content. Peripheral quantitative computed tomography (pQCT) was used to determine the volumetric cortical bone mineral density (vCtBMD) and cross-sectional moment of interia. Various metatarsal linear dimensions were also measured. The load at failure in cantilever bending was determined. The only linear dimension that had a significant correlation with load at failure was the height of the metatarsal base (r(2) = 0.30, p = 0.008). Utilizing all of the information provided by DXA gave no greater indication of whole bone strength than just BMD alone (adjusted r(2) = 0.40, p = 0.001). Using all of the information provided by pQCT gave no greater indication of whole bone strength than just vCtBMD alone (r(2) = 0. 46, p < 0.001). Volumetric cortical density and BMD were strongly correlated (r(2) = 0.81, p < 0.001). Our data suggest that, in the human second metatarsal, a variable such as material strength (as inferred from cortical density), and not geometry, may be the major factor in determining cantilever load to failure.

Osteogenic ability of free periosteal autografts in tibial fractures with severe soft tissue damage: an experimental study

OBJECTIVE

The present study was undertaken to assess whether free nonvascularized autologous periosteum transplants enhance bone healing in a rabbit fracture model designed to resemble a tibial fracture with severe soft tissue damage.

DESIGN

Transplantation of free autologous periosteal grafts on the anteromedial site of the tibia (experimental group) was compared with nontransplantation on the contralateral tibia (control group). We produced a standardized transverse osteotomy of both tibial diaphyses in white male adult New Zealand rabbits. The endomedullary cavity was reamed and nailed, and then a one-centimeter segment of periosteum was excised from either side of the osteotomy. To prevent periosteal and extraosseous ingrowth at the osteotomy site, a silastic sheet was wrapped around two-thirds of the circumference of the tibia. In the first group, on the silastic-free bone window, we then spanned the osteotomy with a free, nonvascularized, longitudinally oriented autologous periosteum and sewed it to the adjacent periosteum both proximally and distally. In the second group, the periosteum was placed transversely, leaving a gap between it and the adjacent periosteum proximally and distally. Revascularization of the graft was determined with the colored microsphere technique.

MAIN OUTCOME MEASUREMENTS

Histomorphometric analysis of the periosteal callus was done on a transparent grid superimposed on enlarged photographs of the histologic sections.

RESULTS

Free, nonvascularized, longitudinally placed autologous periosteum in contact with intact periosteum produced significantly more periosteal callus than was seen in the control group, in which no periosteal graft was used. However, when transversely placed periosteal grafts were set in the silastic-free bone window and there was no contact with surrounding remnants of intact periosteum, no significant difference in callus production was noted when compared with the control. Revascularization of these grafts was seen within one week after transplantation. Bone healing occurred mainly through endochondral ossification.

CONCLUSION

Our data suggest that orthotopically placed autologous nonvascularized periosteum retains its osteogenic potential in a poorly vascularized environment such as a tibial fracture with severe soft tissue damage. The effect is enhanced if the graft is in contact with intact periosteum. Histologically, callus formation after periosteal grafting resembles endochondral and intramembranous ossification.

Noma (Cancrum Oris) associated with Kwashiorkor: a case report and review of the literature

Noma (Cancrum Oris/Ulcerogingivostomstitis) is a rare devastating grangrenous orofacial disease. It may lead to severe facial mutilation and deformities with dysfunctional effects. This disease primarily affects malnourished children from underdeveloped countries. It has recently been associated with AIDS in North America and Western Europe. We will be reporting and discussing the pathogenesis, bacteriological complications and treatments according to the literature.

A complication of mesenteric lymphangioma: case report and brief review of literature

Mesenteric lymphangioma (ML) has only rarely been reported in the literature. These cases are rare enough to arouse interest when encountered. Usually, the cases are asymptomatic but may present with acute or chronic intestinal obstruction. We report an additional case of ML associated with intermittent intestinal volvulus in a 5 years old boy.

Altered membrane fluidity in rat hepatocytes during endotoxic shock

Steady-state fluorescence anisotropy measurements of the fluorescent hydrocarbon probe 1,6-diphenyl-1,3,4-hexatriene (DPH) were carried out in isolated hepatocytes of saline control and Salmonella enteritidis endotoxin (20 mg/kg) injected rats. Statistically significant differences were observed in the fluorescent anisotropy (rs) and membrane microviscosity (eta) values of control (rs = 0.107 +/- 0.004 (SEM), eta = 0.98 +/- 0.08, n +/- 6) versus endotoxin injected rat hepatocytes (rs = 0.134 +/- 0.005, eta = 1.43 +/- 0.08, n = 6, p < 0.001) at 37 degrees C. Fluidity was similarly lower in the isolated plasma membrane preparations from endotoxin-injected rat livers relative to control livers. When endotoxin-injected rats were treated with the calcium channel-blocker diltiazem, the anisotropy and microviscosity values were comparable to those obtained from control rats (rs = 0.152 +/- 0.003, eta = 1.00 +/- 0.003, n = 6). These measurements were made in animals five hours after endotoxin had been injected, and thus represent the in vivo effects of bacterial endotoxins. Temperature scan studies of DPH from 5-40 degrees C revealed that the membrane fluidity of endotoxin-injected rat hepatocytes was significantly lower than control hepatocytes at all temperatures investigated. The data suggest that endotoxin alters the membrane fluidity of hepatocytes, and that calcium-channel blockers can prevent the alteration. Our previous studies have shown that calcium channel blocker prevented endotoxin induced alterations in hepatic cellular regulation of Ca2+. Thus, cellular calcium homeostasis may be important in the maintenance of membrane fluidity and other membrane-associated transport functions.

Curriculum at the Scholl College. Toward mainstream medical education

The Dr. William M. Scholl College of Podiatric Medicine in Chicago recently affiliated with a teaching hospital, the Illinois Masonic Medical Center, and used this alliance as a catalyst to effect a change in the clinical curriculum. The affiliation set up a joint venture to operate two clinics, one on Scholl College's traditional campus and one at the teaching hospital. At the hospital site, Scholl College students rotate through clinical externships in areas such as internal medicine, emergency medicine, and podiatric elective; podiatric and general medical residents assist in the tutelage of the students. At the Scholl College campus, beginning clinical students learn basic skills in a teaching clinic, then refine and further their skills in a comprehensive clinic under the guidance of faculty members. The faculty and administration at Scholl College have embraced the concept of mainstream medical education, and are striving to prepare podiatric physicians to practice 21st century medicine.

Juvenile gastrointestinal polyposis or the infantile Cronkhite-Canada syndrome

This is a report of a case of juvenile gastrointestinal polyposis consisting of widespread juvenile polyps encountered from the stomach into the rectum. Only few cases have been reported, and extra intestinal manifestations include clubbing of fingers, macrocephaly, hypotonia, hepatosplenomegaly, anemia, and protein-losing enteropathy. The outcome is usually dismal, the children barely becoming older than 2 years. Modern fibreoptic endoscopy with polypectomies performed via the upper and lower gastrointestinal intestinal tracts and via a midbowel ileostomy may offer a viable form of management.

Inhibition of Na+ flux in Chinese hamster ovary cells and Swiss 3T3 cells by a potent new derivative of amiloride, methylisopropyl-amiloride

Amiloride inhibits the mitogen-stimulated Na+ influx of cultured fibroblasts with very low affinity. We have therefore analyzed eight new derivatives of amiloride for their efficacies of inhibiting the Na+ flux in Chinese hamster ovary cells (CHO-K1). Four of these analogs demonstrate markedly enhanced potencies relative to amiloride. One of the derivatives, methylisopropyl-amiloride (MIA), is approximately 900-fold more potent (ID50 = 42 nM) than amiloride in inhibiting Na+ uptake of these cells. Inasmuch as external Na+ ions antagonize amiloride inhibition of Na+ influx competitively, we investigated the ability of MIA to inhibit Na+ flux in the absence of external Na+ ions. The ID50 value determined for MIA inhibition of CHO-K1 cell Na+ efflux from Na+-loaded cells into Na+-free media is 15 nM. We also examined the efficacy of MIA for Na+ efflux inhibition in a nontransformed fibroblast cell line, Swiss 3T3. The ID50 value for inhibition of Na+ efflux from 3T3 cells is comparable to that for CHO-K1 cells. Thus, we have identified a highly potent derivative of amiloride, MIA, that inhibits Na+ flux at nanomolar concentrations in both a transformed and a nontransformed cell line. It is possible that MIA may serve as a useful tool for biochemical characterization of the mitogen-stimulated Na+ transporter and for assessment of the role of this transporter in mitogenesis.

Localization of parathyroid adenomas by digital subtraction angiography. A report of 4 cases

Intravenous digital subtraction angiography provides an accurate but not specific method for localization of small vascular tumours. It is carried out on outpatients as an intravenous procedure and takes only 40 minutes. It appears to be eminently suited to the demonstration of parathyroid adenomas and shows that a hyperplastic parathyroid gland can produce a significant enough vascular blush to create a visible image.

Pharyngeal injuries. A report on 2 cases

Two patients incurred barotrauma to the pharynx by the explosion of soft-drink bottles into their mouths. The resultant effects on the pharynx (and in one case on the right lung) are described and guidelines are laid down for the approach to and treatment of these injuries. Both patients recovered, with an acceptable cosmetic and functional result.

The effect of harmaline on unidirectional potassium fluxes and ouabain binding in renal cell cultures

Harmaline inhibits K+ influx into primary cell cultures of ground squirrel kidneys to a greater extent than either ouabain or furosemide. A concentration of 200 microM harmaline was required to inhibit half of the total K+ influx; this effect was also seen at low temperature (5 degrees C), and in another species (hamster). Although kinetic analysis of K+ influx indicates that harmaline does not compete with extracellular K+, harmaline did reduce the binding of [3H]ouabain to the cells. K+ efflux was also reduced. Therefore, harmaline may inhibit the furosemide-sensitive Na+/K+ cotransport system as well as the ouabain-sensitive Na+/K+ pump.

Effect of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate on alpha-aminoisobutyrate uptake in friend Erythroleukemic cells

In Friend erythroleukemic cells, the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) increases the rate of influx as well as the steady-state accumulation of the amino acid transport probe alpha-aminoisobutyric acid (AIB). This nonmetabolizable analog is concentrated in these cells by utilizing the energy of the Na+ electrochemical gradient. The effect of TPA is to increase the ouabain-sensitive component of uptake of AIB (and of the K+ analog 86Rb+). Transport changes are not observed until 30 min after application of the promoter and reach a maximum in about 6 hr. The effects are blocked by cycloheximide. The flux results are consistent with a model in which the membrane potential is increased and, with it, the driving force on the coupled Na+-AIB movement. The effect is possibly mediated by a change in electrogenicity of the Na:K pump. TPA raises the steady-state accumulation levels of AIB. By altering external K+ in the presence of valinomycin, the membrane potential may be adjusted and, with it, the accumulation of AIB. Over a wide range of membrane potentials, TPA-treated cells accumulate more AIB than do controls, suggesting a possible change in the internal Na+ activity.

Properties of Na-K pump in primary cultures of kidney cells

Activities related to Na-K transport were measured in cell cultures of ground squirrel kidney cortex in order to compare these cells with those of intact kidney and of continuous cell lines. A microsomal preparation containing plasma membrane Na,K-ATPase from fresh kidney showed twice the activity of a similar preparation from 72-hour cultured cells. Na,K-ATPase of homogenates of 72-hour cells showed one-third to one-fourth the specific activity of that from 6-hour cultured cells. The associated K-dependent phosphatase activity also declined as a function of time in culture. The ouabain-sensitive influx of K into 6-hour cultured cells was twice as great as the K influx into 72-hour cells. The number of sites binding 3H-ouabain in intact cultured cells declined 81% on a cell protein basis between 6 and 72 hours in culture. This decline in ouabain binding sites was relatively greater than that of K influx, so that the K turnover number increased over this same time period. The decline in ouabain-sensitive K influx during culture was complementary to an increase in furosemide-sensitive K influx. Measurements of unidirectional and net K fluxes showed that there were three components of K influx into 3-day cultured cells: ouabain-sensitive Na:K exchange, furosemide-sensitive K:K exchange, and K diffusion. In the 6-hour cultures, however, there was no furosemide-sensitive K:K exchange. Thus, after three days in culture ground squirrel kidney cells lose a feature characteristic of the original parent cells (high Na,K-ATPase activity), and gain a feature common to many undifferentiated cultured cells (furosemide-sensitive K:K exchange).

Na-K pump and Na-K-ATPase: disparity of their temperature sensitivity

As previously observed in red blood cells, ouabain-sensitive K influx of kidney cells grown in culture for 3 days was much less inhibited by cooling that Na-K-ATPase of the same cells. (At 5 degrees C K influx was 9.7% of that at 38 degrees C, Na-K-ATPase, 1--2%.) Resealed ghosts of erythrocytes of ground squirrels were made containing 24Na and ATP, and the Na efflux and ATP hydrolysis were measured simultaneously. Under these conditions there was no difference in the reduction of activity with cooling, and the amount of reduction was close to that of active K transport in intact cells. The high sensitivity to temperature, characteristic of broken membranes, could not be induced in intact cells or resealed ghosts by eliminating either the Na/K gradient or the ATP gradient nor by chelation of cellular and extracellular Ca. It could not be eliminated in broken membranes by protection with ATP or Mg. Structural reorganization of membrane during lysis may cause the increase in temperature sensitivity of Na-K-ATPase.