Establishment and characterization of models of chemotherapy resistance in colorectal cancer: Towards a predictive signature of chemoresistance

Current standard treatments for metastatic colorectal cancer (CRC) are based on combination regimens with one of the two chemotherapeutic drugs, irinotecan or oxaliplatin. However, drug resistance frequently limits the clinical efficacy of these therapies. In order to gain new insights into mechanisms associated with chemoresistance, and departing from three distinct CRC cell models, we generated a panel of human colorectal cancer cell lines with acquired resistance to either oxaliplatin or irinotecan. We characterized the resistant cell line variants with regards to their drug resistance profile and transcriptome, and matched our results with datasets generated from relevant clinical material to derive putative resistance biomarkers. We found that the chemoresistant cell line variants had distinctive irinotecan- or oxaliplatin-specific resistance profiles, with non-reciprocal cross-resistance. Furthermore, we could identify several new, as well as some previously described, drug resistance-associated genes for each resistant cell line variant. Each chemoresistant cell line variant acquired a unique set of changes that may represent distinct functional subtypes of chemotherapy resistance. In addition, and given the potential implications for selection of subsequent treatment, we also performed an exploratory analysis, in relevant patient cohorts, of the predictive value of each of the specific genes identified in our cellular models.

Abstract 1157: MicroRNA-625-3p is associated with response to first-line oxaliplatin-based treatment of metastatic colorectal cancer

The backbone of current oncologic treatment of metastatic colorectal cancer (mCRC) consists of fluoropyrimidine together with either oxaliplatin (XELOX/FOLFOX) or irinotecan (XELIRI/FOLFIRI). With an overall objective response rate of approximately 50% for either treatment combination, a major unsolved problem is that no predictors of response to these treatments currently are available. To address this issue, we profiled 742 microRNAs in laser-capture microdissected cancer cells from responding and non-responding patients receiving XELOX/FOLFOX as first-line treatment for mCRC, and identified, among others, high expression of miR-625-3p, miR-181b and miR-27b to be associated with poor clinical response. In a validation cohort of 98 mCRC patients treated first-line with XELOX, high expression of miR-625-3p was confirmed to be associated with poor response (OR 6.25, 95%CIOR [1.8; 21.0]). Independent analyses showed that miR-625-3p was not dysregulated between normal and cancer samples, nor was its expression associated with recurrence of stage II or III disease, indicating that miR-625-3p solely is a response marker. Finally, we also found that these miRNAs are up-regulated in oxaliplatin resistant HCT116/oxPt (miR-625-3p, miR-181b and miR-27b) and LoVo/oxPt (miR-181b) CRC cell lines as compared with their isogenic parental cells. Altogether, our results suggest an association between miR-625-3p and response to first-line oxaliplatin based chemotherapy of mCRC.

Citation Format: Mads H. Rasmussen, Niels F. Jensen, Line S. Tarpgaard, Camilla Qvortrup, Maria U. Rømer, Jan Stenvang, Tine P. Hansen, Lise-Lotte Christensen, Jan Lindebjerg, Flemming Hansen, Benny V. Jensen, Torben F. Hansen, Anders M. Jakobsen, Per Pfeiffer, Nils Brünner, Torben F. Ørntoft, Claus L. Andersen. MicroRNA-625-3p is associated with response to first-line oxaliplatin-based treatment of metastatic colorectal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1157. doi:10.1158/1538-7445.AM2013-1157

Abstract 1912: An explorative analysis of ERCC1/ERCC4 copy number alterations in a chemonaive stage III colorectal cancer patient cohort

Background: Platinum-based chemotherapy is widely used in the treatment of cancer. Oxaliplatin, used in combination with 5-Fluorouracil in colorectal cancer (CRC), induces DNA damage which leads to death of the cancer cell. Oxaliplatin DNA damage can be removed by the nucleotide excision repair system. Two components of this system, ERCC1 and ERCC4, have previously been implicated in sensitivity/resistance to platinum-based treatment. The present study explores the mechanism, frequency and prognostic impact of ERCC1 and ERCC4 gene alterations in advanced CRC.

Methods: Fluorescent In Situ Hybridization (FISH) probes directed at ERCC1 (location: 19q13.32) and ERCC4 (location: 16p13.12) were constructed. Nine CRC cell line metaphase spreads were analyzed with an ERCC1 probe in combination with a reference probe covering the centromeric region of chromosome 2 (CEN-2) and with an ERCC4 probe combined with CEN-16. FFPE tissue sections from 152 stage III CRC (81 colon, 71 rectum) chemonaive patients were analyzed. Relationships between biomarker status and overall survival (OS) and time to recurrence (TTR) were analyzed using multivariate statistics.

Results: ERCC1 alterations were observed in a single cell line metaphase (HT29), whereas no alterations were observed with ERCC4. Among the 152 patient tumor sections which were successfully analyzed with ERCC1/CEN-2, 43 (28.3%) patients harbored an ERCC1 aberration, specifically: 2 (1.3%) deletions (ERCC1/CEN-2 < 0.8) and 41 (27.0%) gains (ERCC1/CEN-2 ≥ 1.5). ERCC1 gains were detected in 17 (21.0%) and 24 (33.8%) colon and rectum tumor specimens, respectively; whereas ERCC1 deletions were only detected in colonic tumors. Increased ERCC1 gene copy numbers, when analyzed as a continuous variable, were significantly associated with longer survival (HR: 0.32, 95% CI: 0.14-0.75, p=0.01) and TTR (HR: 0.34, 95% CI: 0.12-1.00, p=0.0498) in tumors of the colon, but not with rectal tumors (OS HR: 1.01, p=0.66; TTR HR: 0.87, p=0.77). Similarly, ERCC1 gains (ERCC1/CEN-2 ≥ 1.5) showed a trend towards longer OS (HR: 0.46, 95% CI: 0.20-1.02, p=0.06) and TTR (HR: 0.44, 95% CI: 0.17-1.14, p=0.09) for patients with tumors of colonic origin, but not for those with rectal tumors. The impact of ERCC1 deletions were not analyzed due to the low number of patients, and were excluded from survival analysis. No ERCC4 aberrations were detected and scoring was discontinued after 50 patients.

Conclusions: ERCC1 gene gain occurs frequently in stage III CRC, whereas ERCC1 loss occurs infrequently. Higher ERCC1 counts and ERCC1/CEN-2 ratios were significantly associated longer OS and TTR in patients with colonic tumors. Accordingly, ERCC1 gain (ERCC1/CEN-2 ≥ 1.5) showed a similar tendency towards longer OS and TTR for colonic tumors. Future studies will investigate the effect of ERCC1 aberrations in a platinum-treated CRC patient population.

Citation Format: David H. Smith, Niels F. Jensen, Ib J. Christensen, Sven Müller, Hans J. Nielsen, Nils Brünner, Kirsten V. Nielsen. An explorative analysis of ERCC1/ERCC4 copy number alterations in a chemonaive stage III colorectal cancer patient cohort. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1912. doi:10.1158/1538-7445.AM2013-1912

High expression of microRNA-625-3p is associated with poor response to first-line oxaliplatin based treatment of metastatic colorectal cancer

The backbone of current cytotoxic treatment of metastatic colorectal cancer (mCRC) consists of a fluoropyrimidine together with either oxaliplatin (XELOX/FOLFOX) or irinotecan (XELIRI/FOLFIRI). With an overall objective response rate of approximately 50% for either treatment combination, a major unsolved problem is that no predictors of response to these treatments are available. To address this issue, we profiled 742 microRNAs in laser-capture microdissected cancer cells from responding and non-responding patients receiving XELOX/FOLFOX as first-line treatment for mCRC, and identified, among others, high expression of miR-625-3p, miR-181b and miR-27b to be associated with poor clinical response. In a validation cohort of 94 mCRC patients treated first-line with XELOX, high expression of miR-625-3p was confirmed to be associated with poor response (OR = 6.25, 95%CI [1.8; 21.0]). Independent analyses showed that miR-625-3p was not dysregulated between normal and cancer samples, nor was its expression associated with recurrence of stage II or III disease, indicating that miR-625-3p solely is a response marker. Finally, we also found that these miRNAs were up-regulated in oxaliplatin resistant HCT116/oxPt (miR-625-3p, miR-181b and miR-27b) and LoVo/oxPt (miR-181b) colon cancer cell lines as compared with their isogenic parental cells. Altogether, our results suggest an association between miR-625-3p and response to first-line oxaliplatin based chemotherapy of mCRC.

P5-01-14: Phosphoproteomic Analysis of TIMP-1 Overexpressing MCF-7 Human Breast Cancer Cells Reveals Increased Expression and Phosphorylation of Topoisomerase Proteins

Background

Tissue inhibitor of metalloproteinase 1 (TIMP-1) is a protein with a potential biological role in drug resistance. Lack of TIMP-1 protein either alone (Willemoe et al., Eur J Cancer 2009) or in combination with Topoisomerase 2A gene aberrations has been shown to associate with increased benefit from adjuvant treatment with a Topoisomerase 2 inhibitor (epirubicin containing combination chemotherapy) while this association was not observed in patients treated with a non-Topoisomerase 2 inhibitor combination chemotherapy (Ejlertsen et al., JCO 2010).

Aim: To further investigate the molecular mechanisms underlying the association between TIMP-1 and epirubicin sensitivity by quantitative phosphoproteomics.

Methods: MCF-7 human breast cancer cells were transfected with pcDNA3.1(Hyg)-TIMP-1. Among 11 single cell clones, two TIMP-1 low expressing and two TIMP-1 high expressing clones were selected. The clones were labeled by SILAC (stable isotope labeling with amino acids in cell culture). Lysates were digested with trypsin and fractionated with SCX followed by subsequent enrichment of phosphopeptides by TiO2-based chromatography and desalting by C18 purification. Total peptides and phosphopeptides were analyzed by tandem mass spectrometry and quantified as described (JV Olsen et al., Science Signaling 2010). Selected proteins were confirmed on Western blots. The sensitivity of the four TIMP-1 cell clones was analyzed by treatment of the cells with the following drugs: The Topoisomerase 2 inhibitor epirubicin (an anthracycline). The Topoisomerase 1 inhibitor SN-38 (the active metabolite of irinotecan, a camptothecin analogue) and the combination of these. A specific Topoisomerase 2B inhibitor (XK 469, a quinoxaline analogue and the DNA crosslinker cisplatin. All experiments were determined with an endpoint MTT assay.

Results: The quantitative proteomic analyses confirmed the differences in TIMP-1 levels among the four clones. Several proteins were consistently found to be upregulated and/or had changed phosphorylation levels in the TIMP-1 high cells in two biological replicates. Of particular interest was the observation that the phosphorylation status and protein levels of Topoisomerase-1, -2A and -2B were increased in TIMP-1 high expressing cells compared to TIMP-1 low expressing cells. When the four clones were treated with specific Topoisomerase inhibitors, the TIMP-1 high expressing cells exhibited significantly more resistance to all three inhibitors compared to TIMP-1 low expressing cells. When cells were treated with a combination of SN-38 and epirubicin, we observed an additive but not a synergistic effect. At last, cells were treated with cisplatin with no different effect on TIMP-1 high and low expressing cells.

Conclusion and perspectives: The observed upregulation of both protein and phosphorylation levels of Topoisomerases in TIMP-1 high cells may be part of the mechanism by which TIMP-1 confers resistance to treatment with Topoisomerase inhibitors in primary breast cancer. Further work will include pathway analyses and hypothesis testing in clinical material.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-01-14.

A novel nonsense variant in Nav1.5 cofactor MOG1 eliminates its sodium current increasing effect and may increase the risk of arrhythmias

BACKGROUND

The protein MOG1 is a cofactor of the cardiac sodium channel, Nav1.5. Overexpression of MOG1 in Nav1.5-expressing cells increases sodium current markedly. Mutations in the genes encoding Nav1.5 and its accessory proteins have been associated with cardiac arrhythmias of significant clinical impact. We sought to investigate whether MOG1 is implicated in cardiac arrhythmias.

METHODS

We performed a genetic screening of the MOG1-encoding gene (gene symbol RANGRF, alias MOG1) in 220 Danish patients with cardiac arrhythmia. Of the 220, 197 were young patients with lone atrial fibrillation and 23 were patients with Brugada syndrome. The effect of one variant was investigated functionally by patch-clamping CHO-K1 cells coexpressing Nav1.5 with MOG1.

RESULTS

We uncovered a novel heterozygous nonsense variant, c.181G>T (p.E61X), that, however, was also present in control subjects, albeit at a lower frequency (1.8% vs 0.4%, P = 0.078). Electrophysiological investigation showed that the p.E61X variant completely eliminates the sodium current-increasing effect of MOG1 and thereby causes loss of function in the sodium current. When mimicking heterozygosity by coexpression of Nav1.5 with wild-type MOG1 and p.E61X-MOG1, no current decrease was seen.

CONCLUSIONS

Our screening of Nav1.5 cofactor MOG1 uncovered a novel nonsense variant that appeared to be present at a higher frequency among patients than control subjects. This variant causes MOG1 loss of function and therefore might be disease causing or modifying under certain conditions.

Risk factors for pulmonary complications in the postoperative head and neck surgery patient

BACKGROUND

Pulmonary complications are a primary source of increased cost and morbidity in surgically treated head and neck cancer patients. This study investigates potential risk factors related to postoperative pulmonary complications (pneumonia, adult respiratory distress syndrome (ARDS), and prolonged mechanical ventilation) in head and neck cancer patients.

METHODS

Data from 144 major head and neck procedures performed at the University of Washington between 1985 and 1991 were retrospectively reviewed. Univariate and multivariate analysis were used to evaluate preoperative and perioperative variables identified as potential risk factors for postoperative pulmonary complications.

RESULTS

Fifteen percent of patients had a postoperative pulmonary complication, (n = 21: 18 postoperative pneumonia; 2 ARDS; and 4 prolonged ventilation). The most common pneumonia pathogen was Staphylococcus aureus (62%). Univariate analysis identified smoking and weight loss as significant factors associated with pulmonary complications. The variables preoperative blood urea nitrogen, white blood cell count, and operative chest flap closure all approached but did not reach significance. Multivariate analysis of a subgroup of patients identified smoking history and perioperative antibiotic choice as the only independently significant variables.

CONCLUSIONS

Patient smoking history was the primary variable related to postoperative pulmonary problems, with evidence of increasing risk with increased exposure. Other variables added only limited additional risk association information after multivariate analysis.

Vasopressin Levels in Major Head and Neck Surgery

In an effort to further understand the perioperative intravascular volume status of major head and neck surgery patients, serum antidiuretic hormone (ADH) and osmolality levels were assessed at four perioperative junctures. Thirty-five major head and neck surgical patients were randomly selected for examination with placement of a central venous pressure monitor. Serum osmolality and serum vasopressin levels were obtained at four junctures perioperatively. ADH levels were lower both after patients were anesthetized and five hours into the procedure than at either baseline or 24 hours after the end of the procedure. ADH levels after patients were anesthetized did not differ from those at five hours into the procedure, nor did ADH levels at baseline differ from those 24 hours after the end of the procedure. In addition, osmolality levels did not change over time. Additional analyses examining relationships between preoperative, intraoperative, and postoperative characteristics and ADH levels after patients were anesthetized and five hours into the procedure, as well as changes from baseline at these times and the baseline levels themselves, detected no significant relationships. This study provides information about the perioperative intravascular volume status of major head and neck surgery patients which may be important to intraoperative care, especially to decisions regarding invasive intraoperative fluid monitoring. Specifically, the data provide additional evidence against the need for the routine placement of central venous catheters to guide fluid administration during major head and neck surgery.

Vasopressin levels in major head and neck surgery

In an effort to further understand the perioperative intravascular volume status of major head and neck surgery patients, serum antidiuretic hormone (ADH) and osmolality levels were assessed at four perioperative junctures. Thirty-five major head and neck surgical patients were randomly selected for examination with placement of a central venous pressure monitor. Serum osmolality and serum vasopressin levels were obtained at four junctures perioperatively. ADH levels were lower both after patients were anesthetized and five hours into the procedure than at either baseline or 24 hours after the end of the procedure. ADH levels after patients were anesthetized did not differ from those at five hours into the procedure, nor did ADH levels at baseline differ from those 24 hours after the end of the procedure. In addition, osmolality levels did not change over time. Additional analyses examining relationships between preoperative, intraoperative, and postoperative characteristics and ADH levels after patients were anesthetized and five hours into the procedure, as well as changes from baseline at these times and the baseline levels themselves, detected no significant relationships. This study provides information about the perioperative intravascular volume status of major head and neck surgery patients which may be important to intraoperative care, especially to decisions regarding invasive intraoperative fluid monitoring. Specifically, the data provide additional evidence against the need for the routine placement of central venous catheters to guide fluid administration during major head and neck surgery.

Defining the concentration-effect relationship of volatile anesthetics in vessels using an in vitro nonsteady-state technique

We compared traditional steady-state experiments with nonsteady-state experiments in defining the vasodilating potency of isoflurane in isolated cerebral vessels. The effects of volatile anesthetics on isolated arterial vessel wall tension are typically examined by means of steady-state methodology. This requires the prolonged administration of the agent under study until a stable wall tension is achieved. An alternative, non-steady-state approach to such experiments is proposed as an adjunct technique to help simplify and in some cases evaluate more fully vascular response. Cylindrical segments of the rabbit basilar artery were placed into a perfused tissue bath, stretched to a resting tension of approximately 2000 dynes and then constricted with 30 nM K+. Thirty minutes later, 2.0 MAC of isoflurane was introduced into the fluid reservoir supplying the chamber. This administration was continued for 10 min, at which time isoflurane was discontinued and vessel tension was monitored for another 10 min. During this 20-min washin-washout period, samples of bath fluid were obtained q 1 min and isoflurane concentrations were subsequently determined by gas chromatography. After completion of these "nonsteady-state" measurements, another 30-min waiting period was allowed, after which vessels were exposed to stable concentrations of 0.5, 1.0, 1.5 and 2.0 MAC of isoflurane in varied order. Each exposure was for 15 min, with a 30-min agent-free rest period between exposures. An effect compartment model was selected for analysis of the nonsteady-state data. Ke0, a first order rate constant linking the concentrations in the bath to a theoretical effect compartment, was estimated by using a hysteresis minimization technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetic considerations in porphyrias

Four hereditary types of porphyria are now classified as acute porphyrias. Enzymatic defects result in accumulation of porphyrin precursors (usually ALA and PGB). The quantity of these precursors may be normal or slightly increased in latent periods but increase to toxic levels during a porphyric crisis. Iatrogenic induction of ALA synthetase by administration of certain triggers (classically barbiturates) is only one of several factors which contribute to porphyric crisis. Signs and symptoms of acute porphyric attack consist primarily of neurologic dysfunction, which occurs secondary to neurotoxicity of ALA or diminished intraneuronal heme levels. Appropriate anesthetic management of porphyria requires knowledge of the type of porphyria (acute vs non-acute), assessment of latent versus active (crisis) phase, awareness of clinical features of porphyric attack, and knowledge of safe pharmacologic intervention.

The efficacy of routine central venous monitoring in major head and neck surgery: a retrospective review

STUDY OBJECTIVE

To further define the efficacy of routine central venous catheter placement for major head and neck surgery from the standpoint of fluid and blood administration, and various other parameters of perioperative management.

DESIGN

Randomized, retrospective chart review.

SETTING

University-affiliated medical center.

PATIENTS

104 patients who had undergone major head and neck surgery (defined as surgery lasting longer than 4 hours with a predicted blood loss of 500 ml or greater) at the University of Iowa Hospitals and Clinics between 1985 and 1992.

MEASUREMENTS AND MAIN RESULTS

Central venous monitoring was used in 51 of the 104 (49%) procedures. Patients with and without central monitors did not differ in age, weight, preoperative laboratory values [i.e., hemoglobin (Hb), blood urea nitrogen (BUN), creatinine), incidence of significant cardiac or renal disease, or a smoking history exceeding 30 pack years. In addition, these patients did not differ with respect to the following intraoperative characteristics: general type of anesthetic; duration of surgery; estimate of blood loss; Hb values; lowest urine output per hour; development of oliguria; total urine output; amount of replacement of blood, colloid, or crystalloid; development of systolic blood pressure less than 70 mmHg; or use of a myocutaneous flap. Patients also did not differ with respect to the following postoperative characteristics: duration of stay in the surgical intensive care unit or hospital, BUN or creatinine values on days 1 and 2, total urine output or the development of oliguria on days 1 through 3, incidence of reintubation, fever on days 1 through 5, wound dehiscence, death, myocardial infarction, or the development of pneumonia, pulmonary edema, or sepsis. Patients with central monitors had a greater incidence of having a tracheostomy performed and a slightly lower Hb level on the first postoperative day than those without central monitors.

CONCLUSIONS

The study raises doubt about the efficacy of routine central venous catheter placement as a necessary guide for fluid and blood administration for these procedures, or as a necessary adjunct for several other parameters of perioperative management. It suggests the need for a randomized, prospective evaluation.

Quality in anesthesia care: lessons from industry and a proposal for valid measurement and improvement

Quality anesthetic care is a goal fundamental to our tradition and our training, but defining and measuring quality in anesthesia presents special challenges. Industrial models of quality, especially those so fundamental to the re-emergence of post-war Japan, deserve careful study and are discussed at some length, but they clearly have limitations in understanding quality in anesthesiology. We suggest that most current quality efforts are inherently flawed. Whether or not they rigorously attempt to define quality, they are hampered by lack of data concerning outcomes and alternatives, as well as lack of distinction between quality and efficacy. Quality efforts in American medicine and anesthesiology seem mired in a "criterion of potential benefit," which is still central to many of our prescriptions for individual medical care. Current quality improvement efforts do not seem well suited to correct these flaws. Anesthetic care, and that of American medicine in general, is fragmented, enormously costly, and sometimes inappropriate or poor. Anesthesiologists are suspicious of current quality efforts to improve this care. The system often seems more geared to eliminate bad apples than to improve patient care. Because anesthesia is a specialty that facilitates care but seldom "cures," we face greater challenges in studying and defining quality than do other specialties. Because of this, it is imperative that several principles govern future quality improvement efforts in anesthesiology. First, a reasonable balance must be attained between study of outcomes and processes of anesthesia care. Second, anesthesia-specific severity of illness indexing must be developed. Third, and perhaps most important, anesthetic processes and outcomes must be reported on a national level. Fundamental to future quality efforts in our specialty, we believe, is the establishment of a protected National Anesthesia Outcome Registry. This article reviews the industrial and medical history of quality, its measurement and improvement, and attempts to apply principles learned over many decades to anesthesiology.

A comparison of the vasodilating effects of halothane and isoflurane on the isolated rabbit basilar artery with and without intact endothelium

Although volatile anesthetics result in cerebral arterial dilation, the precise mechanisms underlying this effect are not known. In vitro tension recordings were used to study the vasodilating potencies of halothane and isoflurane in isolated cerebral vessels and to examine the possible role of the endothelium in modulating any effects observed. Cylindrical segments of the rabbit basilar artery and midline ear artery from the same animal were placed in a flow-through bath of 37 degrees C oxygenated (95% O2/5% CO2) physiologic salt solution and stretched to a resting tension of approximately 2,000 dynes. They were then constricted with 3.0 x 10(-2) M K+, 1.0 x 10(-3) M norepinephrine, or 5.0 x 10(-6) M serotonin and exposed to either halothane or isoflurane at concentrations of approximately 0.5, 1.0, 1.5, and 2.0 MAC in varied order for 15 min at each concentration. A 30-min period of perfusion with anesthetic-free, vasoconstrictor-containing perfusate separated successive exposures to an anesthetic. Vessels prepared in this fashion retained their responsiveness to both vasoconstrictors and volatile anesthetics for as long as 4 h. They also relaxed appropriately to acetylcholine, indicating that the endothelium was intact. Concentrations of volatile anesthetic in the tissue perfusate were directly measured using gas chromatography, and the relationship between bath concentrations (expressed as MAC fractions) and the degree of relaxation were determined. The data were analyzed by parallel line regression. Halothane was found to be a significantly more potent vasodilator of the isolated basilar artery than was isoflurane. For example, in K(+)-constricted vessels, the concentration of halothane needed to produce a 50% reduction in tension was 1.32 MAC, compared with 1.66 MAC for isoflurane. Comparable differences were found in the basilar artery in the presence of other constrictors. However, there was no significant difference between the two agents in their effects upon the ear artery. In a separate series of experiments, the endothelium of basilar artery segments was removed by drying. Removal was confirmed by observing a diminished dilator response to acetylcholine. These vessels were subsequently constricted with K+, and relaxation dose-response curves were obtained for both halothane and isoflurane. There were no differences in the dose-response curves for deendothelialized versus intact vessels, with halothane still the more potent relaxant after endothelial removal. These data demonstrate that halothane and isoflurane cause a dose-dependent relaxation of rabbit cerebral vessels, regardless of the vasoconstrictor used. Halothane was a more potent relaxant of the basilar artery when expressed on a MAC-fraction basis.(ABSTRACT TRUNCATED AT 400 WORDS)

The influence of inhalational anesthetics on in vivo and in vitro benzodiazepine receptor binding in the rat cerebral cortex

The effect of volatile anesthetics on benzodiazepine receptor binding was examined autoradiographically in the rat brain both in vivo and in vitro with the use of [3H]-Ro-15-1788, a benzodiazepine antagonist. For in vitro studies, slide-mounted brain sections were incubated at 37 degrees C in Tris buffer (50 mM, pH 7.4) with [3H]-Ro-15-1788 (flumazenil, 0.5-12.0 nM) in the presence of air (control) or 1 MAC concentrations of halothane or isoflurane. Brain sections were exposed to x-ray film and their images digitized, and specific cortical [3H]-Ro-15-1788 binding was determined. A Scatchard plot of specific cortical binding was constructed, and the dissociation constant (KD) and maximum bound ligand per milligram tissue (Bmax) were determined for each experimental group. In the in vivo trials, rats were anesthetized with 1 MAC halothane or isoflurane; 0.5 microCi/g [3H]-Ro-15-1788 was given intravenously, and the animals were killed 15 min later. Seven standardized sagittal brain sections were examined from autoradiographs. Mean specific cortical binding was determined for each group and was compared with binding in unanesthetized control rats. A third experimental trial analyzed the timed arterial blood history of [3H]-Ro-15-1788 in animals prepared exactly as in the in vivo study. The [3H]-Ro-15-1788 blood clearance over 20 min and plasma [3H]-Ro-15-1788 levels at 15 min after injection of isotope were evaluated. In vitro Scatchard analysis showed no difference in experimental groups in KD or Bmax at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Omeprazole and cimetidine versus pentagastrin in canine ex vivo gastric chamber

The effects of acid inhibitory doses of omeprazole were compared with equieffective doses of cimetidine in the canine ex vivo stomach model (n = 30). Systemic blood pressure, temperature, stomach fluid and ion fluxes, potential difference, blood flow rates, and arterial and venous blood gases were monitored during each of nine 30-min periods. Two resting periods preceded seven periods of pentagastrin stimulation. During the last four of these, the drug effect was recorded (cimetidine 1.2 or 4.8 mumol.kg-1.h-1; omeprazole 0.3, 0.6, or 1.2 mumol/kg). Omeprazole (1.2 mumol/kg) produced 100% inhibition of stimulated acid efflux, no significant decrease in total gastric blood flow (venous outflow), 90% return of potential difference (PD) toward resting values, and a 55% reduction in stimulated oxygen consumption. Omeprazole also showed a dose-dependent K+ efflux at the two lower doses. Cimetidine (4.8 mumol.kg-1.h-1) given during pentagastrin stimulation showed a 70% decrease in total gastric blood flow, a 40% return of PD toward resting, and a 77% reduction in stimulated oxygen consumption. Neither drug showed significant changes in mucosal blood flow from resting values, thus supporting the principle that changes in gastric acid secretion and changes in blood flow are not necessarily correlated.

A system for trochanteric osteotomy and reattachment for total hip arthroplasty with a ninety-nine percent union rate

In certain circumstances osteotomy of the greater trochanter in total hip arthroplasty is of benefit. To attack the problem of nonunion following trochanteric osteotomy, the authors apply several different wiring techniques. To quantify the efficacy of these approaches, they have reviewed 804 consecutive total hip arthroplasties in which the greater trochanter was osteotomized, including 725 primary total hip arthroplasties. Ninety-nine percent of the trochanters united. Among the 79 revision cases, the trochanter united in every case. The use of two independent vertical wires with one transverse wire was the preferred technique.

The cytoprotective effects of (+/-)-15-deoxy-16-alpha, beta-hydroxy-16-methyl PGE1 methyl ester (sc-29333) versus aspirin-shock gastric ulcerogenesis in the dog

SC-29333 (SC) has been reported to protect the gastric mucosa from the effects of topical aspirin. We compared SC and 16,16-dimethyl PGE2 (16-dm) in 20 chambered canine stomachs (6 controls and 7 of each PG). Prostaglandin was added to an acid solution (100 mM HCl; 54 mM NaCl) at 0, .001, .01, 0.1, and 1.0 microgram/ml (two periods each). Then aspirin (20 mM) and PG (1.0 microgram/ml) (two periods) were followed by hemorrhagic shock (near 60 mm Hg mean arterial pressure). 16-dm caused a significant efflux of fluid (-6.5 +/- 5.3 to 17.3 +/- 6.7 microliters/min), Na+ (2.1 +/- 0.5 to 6.8 +/- 1.6 muEq/min), and Cl- (-0.9 +/- 2.4 to 5.3 +/- 1.3 muEq/min), but did not affect K+ or H+. 16-dm also caused a slight drop in potential difference (PD) (67.6 +/- 1.7 to 60.3 +/- 2.0 mV). 16-dm did not significantly affect total blood flow. Percent lesion formation was more severe than controls (20.2 +/- 3.5 vs 11.6 +/- 1.7 percent) but not statistically significant. SC had no significant effect on fluid, H+, Na+, K+, or Cl-. It caused an increase in blood flow (6.85 +/- 1.46 to 26.20 +/- 2.74 ml/min, p less than .001). SC significantly reduced percent lesion formation (1.9 +/- 0.9% p less than .001). We conclude: 1) SC causes an increase in mucosal blood flow and protects from aspirin-shock ulcerogenesis. 2) 16-dm stimulates an efflux of non-parietal extracellular fluid and fails to protect against aspirin injury during mucosal ischemia. 3) SC cytoprotection may be mediated by increased mucosal blood flow. 4) The mechanism of cytoprotection with 16-dm may require sufficient mucosal blood flow for filtration of non-acid fluid from blood to gastric lumen.

Limits to growth in world food production

The dramatic increases in wheat yields that began in the mid-1930's in the United States will soon begin to level off. The favorable mix of genetics and technology that has characterized this era must build upon an ever higher yield base for the future. At the same time the residue of factors that can lower wheat yields includes a larger proportion of forces not easily shaped or controlled by man. An example is weather. The result is a natural yield ceiling that is already visible and that will impose a limit on future productivity growth.