A10 OVEREXPRESSION OF ASCL2 ALTERS DIFFERENTIATION, CELL CYCLE AND RESISTANCE TO ANTI-CANCER TREATMENT IN ESOPHAGEAL ORGANOIDS

Background

The esophagus is in constant contact with the austere environment caused by food and gastric reflux. It is protected by a squamous epithelium which maintenance is provided by a rare subpopulation of basal cells: Keratin 15+ (Krt15+) stem cells. However, little is known about the mechanisms underlying the expansion and the function of these stem cells. It was shown that the transcription factor ASCL2 is strongly upregulated in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is a gene target of the Wnt/β-catenin pathway, which acts as a regulator of proliferation and maintenance of the stemness state.

Purpose

The ultimate goal of my research project is to determine the role of ASCL2 in the maintenance of esophageal stem cells. To do so, I will investigate the role of ASCL2 in esophageal epithelial biology.

Method

Lentiviral infection approach was used to obtain mouse esophageal organoids overexpressing ASCL2 (ASCL2^OE). Organoid culture, immunostaining (such as IF and H&E), qPCR, WB, mass spectrometry and proliferation assay were used to characterize the effect of ASCL2^OE on morphology, differentiation, proliferation, self-renewal, and gene expression.

Result(s)

ASCL2^OE severely altered the morphology of organoids, which were smaller and less differentiated. Defects in differentiation was investigated by IF which showed that some cells expressed both p63 and K13, respectively basal and suprabasal markers. Thus, cells seem to be blocked in an intermediate state of differentiation suggesting a default in cell fate decision. Mass spectrometry analysis confirmed a change in biological processes related to differentiation of keratinocytes and of epithelial cells. We also investigated the role of ASCL2 in self-renewal and observed that organoid formation rate (OFR) was reduced in ASCL2^OE organoids. Furthermore, proliferation was also reduced in WST-1 and EdU assays. We then observed significant changes in the cell cycle by flow cytometry: there is an increased in the number of cells in G0/G1 and a major decrease in G2/M cells, suggesting a blockade in G1. Interestingly, CDNK2a (p16INK4a), an inhibitor of cell cycle progression, was increased in our mass spectrometry results. Finally, ASCL2 could also play a role in radio and chemoresistance of Krt15+ stem cells, as ASCL2^OE organoids are less sensitive to radiation and chemotherapy agents than control.

Conclusion(s)

ASCL2 could play a role in orchestrating cell fate decision in the esophageal epithelium as ASCL2^OE organoids showed alteration in differentiation, proliferation, and cell cycle.

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Other

Please indicate your source of funding;

NSERC, Canada Research Chairs and CRCHUS scolarship

Disclosure of Interest

None Declared

A16 ESOPHAGEAL ORGANOID PROLIFERATION AND DIFFERENTIATION ARE ALTERED BY LOSS OF MSH2

Background

The stratified epithelium of the esophagus includes Krt15+ basal stem cells that display self-renewing and regenerative capacity, and multipotency. However, the mechanisms that specifically control their functions remain unknown. Interestingly, RNA sequencing and GSEA revealed an enrichment of a gene set associated with DNA repair in Krt15+ cells vs Krt15- cells. We also observed that Msh2 (DNA mismatch repair pathway) is the most significantly upregulated gene in Krt15+ stem cells.

Aims

To determine the effect of Msh2 loss on self-renewal and differentiation of esophageal organoids.

Methods

Esophageal epithelial cells were isolated from a wild-type mouse. Using flow cytometry, esophageal Krt15+ (GFP+) and Krt15- (GFP-) cells were sorted from Krt15-CrePR1 (R26^mT/mG) mice. All cell populations were grown as organoids and Msh2 was depleted using a CRISPR/Cas9 approach. Impact of Msh2 loss on self-renewal and differentiation in esophageal epithelial organoids was evaluated through organoid formation assays, WST-1 proliferation assays and histological analysis.

Results

At baseline, organoids depleted for Msh2 formed more poorly differentiated and less well-differentiated organoids than controls. Lower expression of differentiation gene Krt13 was also observed in Msh2-depleted organoids, confirming an altered differentiation pattern. Furthermore, these organoids showed a higher organoid formation rate and proliferation by WST-1 assay, suggesting that self-renewal capacity and viability are increased when Msh2 is depleted. Interestingly, following radiation, organoids depleted for Msh2 showed higher residual levels of p-H2AX (DNA damage marker), suggesting that their capacity to cope with DNA damages is altered. As mentioned above, we previously reported that Msh2 is the most upregulated gene in Krt15+ vs Krt15- cells. Therefore, to determine if Msh2 role is distinct in both populations, we depleted Msh2 in Krt15+ and Krt15- cells-derived organoids. Interestingly, our preliminary results suggest that Msh2 deletion led to increased p-H2AX and decreased Krt13 levels in Krt15+ organoids but not in Krt15- organoids.

Conclusions

Our results show that Msh2 is potentially a key contributor of esophageal stemness in homeostatic and injured conditions.

Funding Agencies

CIHRCanada Research Chair

A21 OVEREXPRESSION OF ASCL2 ALTERS DIFFERENTIATION IN ESOPHAGEAL ORGANOIDS

Background

The first population of stem cells in the esophageal epithelium was recently identified with the marker Keratin 15 ( Krt15). However, little is known about the mechanisms underlying the expansion and the function of these stem cells. It was shown that the transcription factor ASCL2 is upregulated in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is a gene target of the Wnt/β-catenin pathway, which acts as a regulator of proliferation and maintenance of the stemness state. The ultimate goal of my research project is to determine the role of ASCL2 in the maintenance of esophageal stem cells and to identify its binding partners.

Aims

Investigate the role of ASCL2 in esophageal epithelial biology.

Methods

Lentiviral infection approach was used to obtain mouse esophageal organoids overexpressing ASCL2. Organoid culture, immunostaining (such as IF and H&E), qPCR, WB and proliferation assay were used to characterize the effect of ASCL2 overexpression on morphology, differentiation, proliferation, self-renewal and gene expression.

Results

First, ASCL2 overexpression was confirmed by WB. Interestingly, the morphology of organoid overexpressing ASCL2 was severely altered: organoids were smaller and less differentiated. Defect in differentiation was investigated by qPCR and IF using relevant markers such as p63, Krt13, Wnt5a and NT5E. Indeed, we observed an increase in basal marker ( p63), a decrease in suprabasal markers ( Krt13, Wnt5a) and in a stem cell marker ( NT5E). We also investigated the role of ASCL2 in self-renewal and observed that organoid formation capacity was reduced in ASCL2-overexpressing organoids. Furthermore, proliferation was also reduced in WST-1 assays. We also observed lower expression of the gene Top2a, a recently identified marker of the proliferative basal cell population in the human esophagus. Finally, we observed significant changes in the expression of genes associated with quiescent stem cells (Clu, ZFP36L2 and Anxa1).

Conclusions

ASCL2 overexpression alters differentiation and proliferation in organoids. ASCL2 could play a role in orchestrating cell fate decision in the esophageal epithelium.

Funding Agencies

NSERC, Canada Research Chair

A53 STUDYING THE ROLE OF ASCL2 IN THE ESOPHAGEAL EPITHELIUM USING ORGANOIDS

Background

The esophagus is lined with a stratified squamous epithelium that assure protection against the austere environment found in the esophageal lumen. The maintenance of this epithelium is ensured by a rare population of cells: stem cells. Those cells have increased capacity of self-renewal and multipotency, which is the capacity to give rise to every cell types of a tissue. The marker Krt15 was used to identify the first stem cell population in the esophagus. Krt15+ cells display an extended lifespan and they are radioresistant, multipotent and capable of self-renewal. Moreover, it was observed by RNA sequencing that the expression of the transcription factor ASCL2 is strongly increased in Krt15+ cells compared to Krt15- cells. Interestingly, ASCL2 is necessary to maintain the stemness of Lgr5+ intestinal stem cells. It is also a target of the Wnt/β-catenin pathway. The overall goal of this project is to determine the role of ACSL2 in the maintenance of esophageal stem cells and to identify its binding partners since ASCL2 needs to dimerize to efficiently bind DNA.

Aims

Confirm that esophageal organoids are adapted to study ASCL2 in the esophagus.

Methods

Esophageal organoids were established from esophageal epithelial cells from wildtype mice. Following this, organoids were treated with an inhibitor of the Notch pathway (DAPT) to induce hyperplasia or infected with lentiviruses to invalidate Ascl2 (CRISPR/Cas9 approach).

Results

To validate that Ascl2 plays an important role in esophageal cell proliferation, Notch pathway was inhibited through DAPT treatment in esophageal organoids to induce hyperplasia, which was confirmed by increased number of proliferative cells (Ki-67+). ASCL2 protein expression was also increased in DAPT-treated organoids supporting its role in proliferation and confirming that organoid is a good model to study ASCL2 role in esophageal epithelial cells. In this optic, organoids lines invalidated for Ascl2 (CRISPR/Cas9 approach) were established. Our preliminary results suggest that Ascl2 loss affects cell proliferation and organoid size under normal conditions.

Conclusions

The expression of ASCL2 correlates with hyperplasia which supports its role in esophageal epithelium homeostasis.

Funding Agencies

Canada research chair et NSERC

A27 MSH2 CONTRIBUTES TO SELF-RENEWAL OF ESOPHAGEAL ORGANOIDS

Background

The esophagus is lined by a stratified epithelium in which basal cells can proliferate and undergo differentiation while migrating towards the lumen. In the basal layer, we also find Krt15+ stem cells that are multipotent, self-renewing and that have regenerative capacity. However, mechanisms that specifically control their functions remain unknown. Interestingly, RNA sequencing and gene set enrichment analysis (GSEA) revealed an enrichment of a gene set associated with DNA repair in Krt15+ cells in comparison to Krt15- cells. We also observed that Msh2 (MutS homolog 2), a gene associated with the DNA mismatch repair (MMR) mechanism, is the most significantly upregulated gene in Krt15+ stem cells.

Aims

To determine the impact of Msh2 loss on self-renewal of esophageal organoids under normal and stress conditions.

Methods

Esophageal epithelial cells were isolated from a wild type mouse and grown as organoids, a 3D culture model that supports stem cell growth and morphologically reproduces the tissue of origin. To determine Msh2 role in esophageal epithelium, this gene was deleted through a CRISPR/Cas9 approach in mouse esophageal organoids. Invalidation was confirmed by Western Blot and immunofluorescence. Impact of Msh2 loss on self-renewal was measured under normal condition and following radiation.

Results

At baseline, loss of Msh2 decreases the organoid formation rate of esophageal organoids. Furthermore, following high-dose radiation, Msh2 deficient cells form less organoids than control cells. These results suggest that self-renewal capacity is reduced when Msh2 is depleted. Interestingly, following radiation, organoids depleted for Msh2 show higher residual levels of p-H2AX, a DNA damage marker, and p-ATM, a key kinase in DNA damage response, suggesting that their capacity to cope with DNA damages is reduced.

Conclusions

Our results suggest that Msh2 contributes to maintaining genomic integrity in esophageal cells and that contributes to maintaining self-renewal capacity of basal cells and possibly esophageal stem cells.

Funding Agencies

Canada Research Chair.

Respiratory and metabolic effects of massive administration of isotonic saline solution in heaves-affected and control horses

REASONS FOR PERFORMING STUDY

It has been suggested that rapid administration of isotonic saline solution relieves airway obstruction in heaves-affected horses, but the efficacy and tolerability of this treatment is poorly documented.

OBJECTIVES

To determine the respiratory and metabolic effects of a rapid administration of isotonic saline solution in control horses and those with heaves.

METHODS

Thirty litres isotonic saline solution were administered i.v. to 5 control (Group C) and 9 heaves-affected horses (Group H). Pulmonary function testing and arterial blood gas analysis were performed prior to saline infusion, at 90 and 180 mins after starting the infusion, and 1, 3, 6 and 10 days later. PCV, plasma total solids, plasma electrolytes (Na+, Cl- and K+) and venous blood gas analysis were performed prior, during and after saline infusion.

RESULTS

Rapid saline administration was shown to have no beneficial effects on lung function during infusion in Group H. On the contrary, they had significantly increased pulmonary resistance (RL) at 180 mins following the initiation of saline administration compared to baseline. In Group C, saline administration resulted in a significant increase in RL at 180 mins and a significant decrease in PaO2 at 90 mins. These results suggest a transient decrement in lung function caused by rapid saline administration. Group H had a metabolic alkalosis with hypochloraemia at baseline compared to control horses. This resolved following i.v. saline administration and returned to baseline within 6 h after treatment had been discontinued.

CONCLUSION

The administration of saline to Group H did not improve airway function significantly, but resulted in mild and transient side effects.

POTENTIAL RELEVANCE

Rapid administration of isotonic saline alone is not an effective therapy for heaves in horses.

Detection of rib trauma in newborn foals in an equine critical care unit: a comparison of ultrasonography, radiography and physical examination

REASONS FOR PERFORMING STUDY

Previous studies have shown that in man ultrasonography is more accurate than radiography for detecting rib fractures.

OBJECTIVES

To describe clinical, radiographic and ultrasonographic findings related with rib fractures in newborn foals in an equine critical care unit; and to compare diagnostic accuracy of ultrasonography to radiography.

METHODS

A prospective ultrasonographic study was performed on 29 foals presented to the emergency unit. This study was performed at the Centre Hospitalier Universitaire Vétérinaire (CHUV), University of Montreal. Physical examination as well as radiographic and ultrasonographic examinations were performed.

RESULTS

Thoracic radiographs revealed 10 rib fractures in 5 of 26 (19%) foals. Ultrasonography revealed 49 fractures in 19 of 29 (65%) foals of which fillies (n = 13; 68%) were significantly over represented as were fractures to the left thorax (n = 15; 78%). Seventeen of 19 foals (90%) had rib fractures located 3 cm or less from the costochondral junction, the distal part of the rib being displaced laterally in all cases. In 2 foals, where both thoracic radiographs and ultrasonography detected rib fractures, the site of fractures was located on the mid portion of the rib. Rib fractures were detected only by thoracic radiographs in one foal. Sixty-five percent (32/49) of fractured ribs had a moderate displacement (1-4 mm).

CONCLUSIONS

Rib fractures are seen frequently in newborn foals in equine critical care units. Ultrasonography is more accurate than radiography and reveals fractures in most patients presented in emergency. The position (costochondral junction) of rib fractures and of the fragments suggest that most thoracic trauma probably occurs during parturition.

POTENTIAL RELEVANCE

Ultrasound imaging increases awareness and improves the diagnosis of rib fractures in newborn foals.

Pharmacological activity of three commercialHypericum perforatum preparations in mice

St John's Wort (Hypericum perforatum) is the main herbal species used to treat depression. The products available on the pharmaceutical and dietary supplement markets are obtained by a variety of preparation processes and their pharmacological effects may differ significantly. The purpose of this study therefore was to investigate the effect of different St John's Wort commercial preparations available on the French market. Only one preparation gave significant results in the forced swimming test.

Expression of cathepsin L in human tumor cells is under the control of distinct regulatory mechanisms

Cathepsin L, a cysteine protease, is overexpressed in human tumor cells and plays a major role in melanoma progression. Our aim was herein to identify molecular mechanisms, which contribute to its overexpression. We found that cathepsin L protein expression correlated with mRNA level in tumor cells. Therefore, we focused on mechanisms involved in cathepsin L mRNA regulation. CpG island was localized in the 5' region of cathepsin L gene that encompassed regulatory regions identified as essential for promoter activity. CpG dinucleotides, not methylated in any melanoma cells analysed, were methylated in a B lymphoma cell line, which poorly express cathepsin L. Our data demonstrate that in lymphoma cells, cathepsin L silencing was methylation-dependent. Furthermore, gene amplification was involved in cathepsin L overexpression in one melanoma cell line, while transcriptional mechanisms but not mRNA stability are responsible of cathepsin L overexpression in others melanoma cells. In addition, NF-Y, Sp1, Sp2 and Sp3 transcription factors, essential to basal cathepsin L transcription, are not directly involved in overexpression. Thus, our data provides the first demonstration that cathepsin L expression in tumor cells is under the control of distinct molecular mechanisms.

Targeting the ATF-1/CREB transcription factors by single chain Fv fragment in human melanoma: potential modality for cancer therapy

Activating transcription factor-1 (ATF-1) and cAMP-responsive element (CRE)-binding protein (CREB) have been implicated in cAMP and Ca2+-induced transcriptional activation. The expression of the transcription factors ATF-1 and CREB is upregulated in metastatic melanoma cells. However, how overexpression of ATF-1/CREB contributes to the acquisition of the metastatic phenotype is unclear. Previously we demonstrated that quenching of CREB activity in metastatic melanoma cells by means of a dominant-negative form of CREB (KCREB) led to a decrease in their tumorigenicity and metastatic potential in nude mice. We identified two mechanisms that explain how overexpression of CREB/ATF-1 contributes to the metastatic phenotype. The first is one in which CREB/ATF-1 play an essential role in invasion by regulating the CRE-dependent expression of the metalloproteinase MMP-2 and the adhesion molecule MCAM/MUC18 genes. In the second mechanism, CREB and ATF-1 act as survival factors for human melanoma cells. Here, the effect of disrupting ATF-1 activity was investigated using intracellular expression of an inhibitory anti-ATF-1 single chain antibody fragment (ScFv). Intracellular expression of ScFv anti-ATF-1 in MeWo melanoma cells caused significant reduction in CRE-dependent promoter activation. In addition, expression of ScFv anti-ATF-1 in melanoma cells suppressed their tumorigenicity and metastatic potential in nude mice. ScFv anti-ATF-1 rendered the melanoma cells susceptible to thapsigargin-induced apoptosis in vitro and caused massive apoptosis in tumors transplanted subcutaneously into nude mice, confirming that AFT-1/CREB act as survival factors for human melanoma cells. These studies demonstrate the potential usage of ScFv anti-ATF-1 as an inhibitor of tumor growth and metastasis of solid tumors in vivo.

Vascular endothelial growth factor synthesis in the acute phase of experimental and clinical lung injury

Vascular endothelial growth factor (VEGF) is a potent angiogenic and endothelial survival factor, which is abundantly expressed in the normal lung. Conceivably, VEGF may be released by numerous cell types found around the airspaces, including alveolar type 2 cells, alveolar macrophages, and polymorphonuclear neutrophils. Using a bacteria-induced lung injury model in rats, VEGF expression in lung was investigated. Both VEGF protein and VEGF messenger ribonucleic acid (mRNA), 4 and 24 h after bacterial challenge (Pseudomonas aeruginosa), were decreased compared with sham rats. VEGF protein was also investigated in bronchoalveolar lavage (BAL) from patients studied within 7 days of acute respiratory distress syndrome (ARDS) onset and in patients without ARDS. VEGF protein levels in BAL were decreased in patients with ARDS versus those without (14.3 +/- 11.1 pg x mL(-1) versus 76.8 +/- 51.1 pg x mL(-1), p = 0.03). In aggregate, these findings show that the initial phase of acute lung injury is associated with a decrease in vascular endothelial growth factor in the lung. This downregulation may represent a protective mechanism aimed at limiting endothelial permeability, and may participate in the decrease in capillary number that is observed during early acute respiratory distress syndrome.

Intestinal epithelial cell differentiation involves activation of p38 mitogen-activated protein kinase that regulates the homeobox transcription factor CDX2

The intracellular signaling pathways responsible for cell cycle arrest and differentiation along the crypt-villus axis of the human small intestine remain largely unknown. p38 mitogen-activated protein kinases (MAPKs) have recently emerged as key modulators of various vertebrate cell differentiation processes. In order to elucidate further the mechanism(s) responsible for the loss of proliferative potential once committed intestinal cells begin to differentiate, the role and regulation of p38 MAPK with regard to differentiation were analyzed in both intact epithelium as well as in well established intestinal cell models recapitulating the crypt-villus axis in vitro. Results show that phosphorylated and active forms of p38 were detected primarily in the nuclei of differentiated villus cells. Inhibition of p38 MAPK signaling by 2-20 microm SB203580 did not affect E2F-dependent transcriptional activity in subconfluent Caco-2/15 or HIEC cells. p38 MAPK activity dramatically increased as soon as Caco-2/15 cells reached confluence, whereas addition of SB203580 during differentiation of Caco-2/15 cells strongly attenuated sucrase-isomaltase gene and protein expression as well as protein expression of villin and alkaline phosphatase. The binding of CDX2 to the sucrase-isomaltase promoter and its transcriptional activity were significantly reduced by SB203580. Pull-down glutathione S-transferase and immunoprecipitation experiments demonstrated a direct interaction of CDX3 with p38. Finally, p38-dependent phosphorylation of CDX3 was observed in differentiating Caco-2/15 cells. Taken together, our results indicate that p38 MAPK may be involved in the regulation of CDX2/3 function and intestinal cell differentiation.

Regulation of tumor growth and metastasis of human melanoma by the CREB transcription factor family

The purpose of this study was to determine the role of CREB and its associated proteins in melanoma progression. We used MeWo human melanoma cells transfected with a dominant negative construct of CREB, KCREB. KCREB has a mutation in its DNA-binding domain and can not bind the CRE element. Expression of KCREB yields proper heterodimerization with CREB and its associated proteins, but the proteins associated with KCREB do not confer the same degree of transcriptional activity as they would in the case of wild-type CREB. Here, we demonstrate that expression of KCREB in MeWo melanoma cells leads to a decrease in their tumorigenicity and metastatic potential in nude mice. We identified two mechanisms that explain at least partially this effect of KCREB. The first, is one in which CREB and its associated proteins play an essential role in invasion. We showed that the invasive properties of KCREB-transfected MeWo cells were reduced due to the downregulation of the CRE-dependent expression of the type IV collagenase MMP-2 and the adhesion molecule MCAM/MUC18. In the second mechanism, CREB and its associated proteins act as survival factors for human melanoma cells. Here we demonstrated that expression of KCREB in MeWo cells rendered them susceptible to apoptosis induced by thapsigargin, which in turn increased the intracellular level of Ca2+. Thapsigargin induced CREB and ATF-1 phosphorylation and activated CRE-dependent transcription in MeWo cells. Collectively, our data demonstrate that CREB and its associated proteins play an important role in tumor growth and metastasis of human melanoma.

Inhibition of tumor growth and metastasis of human melanoma by intracellular anti-ATF-1 single chain Fv fragment

Activating transcription factor-1 (ATF-1) and cAMP-responsive element (CRE)-binding protein (CREB) have been implicated in cAMP and Ca2+-induced transcriptional activation. The expression of the transcription factors CREB and ATF-1 is upregulated in metastatic melanoma cells. However, how overexpression of ATF-1/CREB contributes to the acquisition of the metastatic phenotype remains unclear. Here, the effect of disrupting ATF-1 activity was investigated using intracellular expression of an inhibitory anti-ATF-1 single chain antibody fragment (ScFv). Intracellular expression of ScFv anti-ATF-1 in MeWo melanoma cells caused significant reduction in CRE-dependent promoter activation. In addition, expression of ScFv anti-ATF-1 in melanoma cells suppressed their tumorigenicity and metastatic potential in nude mice. ScFv anti-ATF-1 rendered the melanoma cells susceptible to thapsigargin-induced apoptosis in vitro and caused massive apoptosis in tumors transplanted subcutaneously into nude mice, suggesting that ATF-1 and its associated proteins act as survival factor for human melanoma cells. This is the first report to demonstrate the potential of ScFv anti-ATF-1 as an inhibitor of tumor growth and metastasis of solid tumor in vivo. Oncogene (2000).

Factors predictive of oxygen consumption during the immediate postoperative period in open heart surgery

BACKGROUND

Postoperative oxygen consumption (VO2) is critical during the recovery period that follows open heart surgery and depends on patient characteristics and surgical factors.

OBJECTIVE

To explore the surgical and patient-related factors that may influence VO2 during the early postoperative period.

DESIGN

Prospective study.

SETTING

Postoperative intensive care unit.

PATIENTS

Study participants were 50 consecutive patients undergoing elective open heart surgery. There were 39 men and 11 women, with a mean age of 58+/-10 years.

MEASUREMENTS AND MAIN RESULTS

VO2, oxygen extraction and arterial lactate were measured 1, 4, 12 and 24 h postoperatively. VO2 increased significantly during the first 12 h and stabilized thereafter. Oxygen extraction remained stable through the first 24 h. Covariance analysis on repeated measures showed that the extracorporeal circulatory period (P<0.01), age (P<0.01), body temperature (P<0.05) and use of noradrenalin (P<0.05) were predictive factors influencing postoperative VO2. Although arterial lactate increased significantly during the first 12 h period, no correlation with VO2 was found. However, covariance analysis showed that female sex, patient age (older than 65 years) and bypass period were positive correlating factors for the increase in arterial lactate.

CONCLUSIONS

Patient VO2 need is decreased early after open heart surgery and returns to normal after 12 h. Surgical and patient-specific factors are responsible for these changes. Arterial lactate measurements were not found to be reliable indexes of VO2 need during this period.

Regulatory science: a special update from the United States Food and Drug Administration: Preclinical issues and status of investigation of botanical drug products in the United States

A recent survey was conducted across the therapeutic divisions within the CDER, U.S. FDA regarding the number of submissions related to botanical drug products over the past ten years. The overall number of botanical submissions as expressed in the parenthesis are as follows: 1990 (1), 1991 (4), 1992 (4), 1993 (5), 1994 (6), 1995 (5), 1996 (13), 1997 (16), 1998 (10). In the total of 64 counted, 50 of them are submitted in original IND and the rest (14) in pre-IND format. The therapeutic categories are focused on dermatological and topical (19), anti AIDS/antiviral (12), oncologic (13), neuropharmacologic (8), endocrine and metabolic (3), urologic (2), tobacco (2), and cardio-renal products (1). The regulatory actions taken on these submissions showed that 68% of them are evaluated as safe to proceed for the human trials, while the rest (32%) of submissions required agency's regulatory guidance. Among the submissions that required further guidance, 81% were deficient in preclinical pharmacology/toxicology information and the rest (19%) lacks information in other areas (chemistry, clinical protocols). Following agency's guidance, 93% of the submissions that were put on hold were allowed to proceed. In summary, a total of 94% of all the botanical INDs submitted to the agency were allowed to proceed without additional animal toxicity studies conducted. In conclusion, this survey indicates that the growing public interest in botanical supplements has prompted more formal evaluation of the efficacy/safety claims of these products.

Monthly, daily, and circadian variations of measurements of pulmonary mechanics in horses with chronic obstructive pulmonary disease

OBJECTIVES

To determine temporal variations of pulmonary function in horses without respiratory tract disease (controls) and horses with chronic obstructive pulmonary disease (COPD) and determine whether reversibility of airway obstruction after environmental control can be predicted by response to atropine administration.

ANIMALS

7 COPD-affected and 5 control horses.

PROCEDURES

Pulmonary function testing was performed monthly during 3 consecutive months, daily for 5 consecutive days, and at 6-hour intervals for 24 hours before and after administration of atropine (0.02 mg/kg of body weight, i.v.) and after 5 consecutive months at pasture. Respiratory rate, tidal volume (VT), minute ventilation (VE), maximal change in transpulmonary pressure (deltaP(L)), pulmonary resistance (R(L)), and pulmonary elastance (E(L)) were calculated.

RESULTS

COPD-affected horses had a significantly higher expiratory to inspiratory time ratio (T(E)/T(I)) and deltaP(L), E(L), and R(L) than horses without respiratory tract diseases during all periods and higher V(E) during monthly and daily evaluations. Daily variation in VT and monthly and circadian variation in E(L) were significant in COPD-affected horses. In control horses, significant changes were apparent only in T(E)/T(I) during daily recordings. In COPD-affected horses, reduction in deltaP(L), R(L), and E(L) was significant after atropine administration and after maintenance on pasture.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite variations in measurements of respiratory mechanics in both groups of horses, values remained significantly different between groups over time. Despite individual variation, measurements were repeatable during short and long periods. Response to administration of atropine to COPD-affected horses underestimated improvement in respiratory tract function that resulted from maintenance on pasture.

Six6 (Optx2) is a novel murine Six3-related homeobox gene that demarcates the presumptive pituitary/hypothalamic axis and the ventral optic stalk

We report on the isolation of a murine homeobox-containing gene, Six6 (Optx2), that shows extended identity in its coding region with Six3, the only member of the mammalian Six gene family known to be expressed in the optic primordium. Phylogenetic analysis demonstrates that Six6 and Six3 belong to a separate group of homeobox-genes that are closely related to the recently identified Drosophila optix. Earliest Six6 expression was detected in the floor of the diencephalic portion of the primitive forebrain, a region predicted to give rise to the neurohypophysis and to the hypothalamus. Later on, Six6 mRNA was found in the primordial tissues giving rise to the mature pituitary: the Rathke's pouch and the infundibular recess. In the optic primordium, Six6 demarcates the presumptive ventral optic stalk and the ventral portion of the future neural retina. In the developing eye. Six6 expression was detected in the neural retina, the optic chiasma and optic stalk, but not in the lens. When compared to Six6, Six3 expression pattern was highly similar, but with a generally broader transcripts distribution in the brain and in the visual system. We finally show that Six6 does not require Pax6 for its expression in the optic primordium, suggesting that Six6 acts on a parallel and/or independent pathway with Pax6 in the genetic cascade governing early development of the eye.

Thoracic trauma in newborn foals

In a report describing life ending fractures (255 horses) from the Livestock Disease Diagnostic Center, Kentucky (1993 and 1994), 32 foals had rib fractures. The purpose of our study was to examine the incidence of rib fractures in newborn foals on a Thoroughbred studfarm by physical and radiographic examination, to determine factors which may contribute to the problem and to document any clinical consequences. All foals (263) included were examined within 3 days of birth. The thoracic cage was palpated externally for abnormalities and all foals were placed in dorsal recumbency to evaluate thoracic cage symmetry. Radiographs were used to diagnose foals with thoracic cage asymmetry (TCA) and rib fracture (RF). A diagnosis of costochondral dislocation (CD) was made when no radiographic evidence of fracture was present but there was severe TCA. Fifty-five foals (20.1%) had TCA (9 RF). One to 5 ribs were fractured on 9 of 40 radiographic studies. No consequences of the thoracic trauma was detected clinically, radiographically or ultrasonographically in this group of foals or at a 2- and 4-week follow-up examination. The percentage of foals with a history of abnormal parturition was higher in the TCA foals (15%) compared to the normal foals (6.8%). There were more primiparous dams in the TCA group than in the normal foal group. Fillies (56.6%) had a higher incidence of birth trauma than colts (43.4%). This study demonstrates that thoracic trauma is often present in newborn foals and may not always be of clinical significance. Dystocia foals and foals from primiparous mares should be considered high risk for thoracic trauma.

Interactions between the class II transactivator and CREB binding protein increase transcription of major histocompatibility complex class II genes

Class II major histocompatibility (class II) genes are regulated in a B-cell-specific and gamma interferon-inducible fashion. The master switch for the expression of these genes is the class II transactivator (CIITA). In this report, we demonstrate that one of the functions of CIITA is to recruit the CREB binding protein (CBP) to class II promoters. Not only functional but also specific binding interactions between CIITA and CBP were demonstrated. Moreover, a dominant negative form of CBP decreased the activity of class II promoters and levels of class II determinants on the surface of cells. Finally, the inhibition of class II gene expression by the glucocorticoid hormone could be attributed to the squelching of CBP by the glucocorticoid receptor. We conclude that CBP, a histone acetyltransferase, plays an important role in the transcription of class II genes.

Protective effect of endotoxin instillation on subsequent bacteria-induced acute lung injury in rats

The phagocytic capability afforded by neutrophil influx into the lungs is essential to ward off invading bacteria. The objective of this study was to evaluate the effect of prior neutrophil recruitment induced by alveolar instillation of endotoxin (LPS, 200 micrograms/kg) 16 h before a pulmonary infection caused by instillation of live Pseudomonas aeruginosa ([PYO]: 1.5 x 10(8) colony-forming units [cfu]/kg) in rats. A first series of experiments showed that lipopolysaccharide (LPS) instillation induced recruitment of alveolar neutrophils that were capable, ex vivo, of elastase exocytosis, reactive oxygen species secretion, and PYO killing. In a second set of experiments, LPS followed by PYO was compared with PYO alone (n = 11 surviving rats in each group). Parameters were studied 24 h after the bacterial challenge. As compared with PYO alone, pretreatment with LPS followed by PYO was associated with decreased mortality (0% versus 54%, p < 0.05), decreased protein leakage into bronchoalveolar lavage (BAL) fluid (1.8 +/- 0.4 versus 13.5 +/- 2.2 mg/ml, p < 0.001), and improved bacterial clearance from BAL (4.0 +/- 1.4 x 10(2) versus 1.2 +/- 0.5 x 10(4) cfu/ml, p < 0.05) and from pulmonary parenchyma (8.5 +/- 6.4 x 10(5) versus 1.9 +/- 0.8 x 10(7) cfu/ml, p < 0.05). We conclude that prior alveolar endotoxin instillation induces local recruitment of functionally active neutrophils, and that this is associated with resistance to subsequent experimental pneumonia.

CREB and its associated proteins act as survival factors for human melanoma cells

cAMP response element-binding protein (CREB) and activating transcription factor 1 (ATF-1), members of the CREB/ATF family, have been implicated in cAMP- and calcium-induced transcriptional activation. We have previously demonstrated that quenching of CREB-associated proteins in metastatic melanoma cells by a dominant-negative CREB (KCREB) that is mutated within its DNA-binding domain decreased their radiation resistance, and their tumorigenic and metastatic potential in nude mice. As the induction of apoptosis by diverse exogenous signals is dependent on the elevation of intracellular Ca2+, the purpose of this study was to determine the role of CREB and its associated proteins in apoptosis using KCREB. We used thapsigargin (Tg), which inhibits endoplasmic reticulum-dependent Ca2+-ATPase and thereby increases cytosolic Ca2+, to induce apoptosis. MeWo human melanoma cells were transfected with the KCREB expression vector and subsequently analyzed for their susceptibility to Tg-induced apoptosis. Here we demonstrate that expression of KCREB in MeWo cells rendered them susceptible to Tg-induced apoptosis. Tg treatment induced phosphorylation of CREB and possibly ATF-1 transcription factors. Treatment with Tg induced CRE-dependent transcription in parental cells, whereas this activation was reduced in the KCREB-transfected cells. In addition, CAT activity driven by the CRE-dependent promoter was inhibited in parental MeWo cells cotransfected with increasing concentrations of KCREB in a dose-dependent manner. We did not observe any changes in Bcl-2 or Bcl-2-related proteins (Bcl-x, Bax, and Bad) in control or KCREB-transfected cells before or after treatment with Tg. Collectively, these data indicate that CREB and its associated proteins act as survival factors for human melanoma cells, and hence contribute to the acquisition of the malignant phenotype.

Loss of AP-2 results in downregulation of c-KIT and enhancement of melanoma tumorigenicity and metastasis

Expression of the tyrosine kinase receptor, c-KIT, progressively decreases during local tumor growth and invasion of human melanomas. We have previously shown that enforced c-KIT expression in highly metastatic cells inhibited tumor growth and metastasis in nude mice. Furthermore, the ligand for c-KIT, SCF, induces apoptosis in human melanoma cells expressing c-KIT under both in vitro and in vivo conditions. Here we show that loss of c-KIT expression in highly metastatic cells correlates with loss of expression of the transcription factor AP-2. The c-KIT promoter contains three binding sites for AP-2 and EMSA gels demonstrated that AP-2 protein binds directly to the c-KIT promoter. Transfection of wild-type AP-2 into c-KIT-negative A375SM melanoma cells activated a c-KIT promoter-driven luciferase reporter gene, while expression of a dominant-negative AP-2B in c-KIT-positive Mel-501 cells inhibited its activation. Endogenous c-KIT mRNA and expression of proteins were upregulated in AP-2-transfected cells, but not in control cells. In addition, re-expression of AP-2 in A375SM cells suppressed their tumorigenicity and metastatic potential in nude mice. These results indicate that the expression of c-KIT is highly regulated by AP-2 and that enforced AP-2 expression suppresses tumorigenicity and metastatic potential of human melanoma cells, possibly through c-KIT transactivation and SCF-induced apoptosis. Therefore, loss of AP-2 expression might be a crucial event in the development of malignant melanoma.

Molecular regulators involved in vertebrate eye development

Development of the eye can be subdivided into three phases. The first phase is the formation of the major structures of the eye by the processes of induction and regional specification. The second is the maturation of these structures to form the functional eye, and the third phase is the formation of neuronal connections between retina and the optic tectum. These processes are tightly regulated by signalling cascades that direct axonal outgrowth, cellular proliferation and differentiation. Some members of these signalling cascades have been identified in recent studies. These include secreted factors which transmit signals extracellularly, and receptors and transcription factors which are members of intracellular signalling pathways that respond to extracellular signals. This review summarizes the recent research that has implicated these factors in playing a role in eye development on the basis of functional or expression criteria.

Loss of AP-2 results in up-regulation of MCAM/MUC18 and an increase in tumor growth and metastasis of human melanoma cells

MCAM/MUC18 is a cell-surface glycoprotein of 113 kDa, originally identified as a melanoma antigen, whose expression is associated with tumor progression and the development of metastatic potential. We have previously shown that enforced expression of MCAM/MUC18 in primary cutaneous melanoma led to increased tumor growth and metastatic potential in nude mice. The mechanism for up-regulation of MCAM/MUC18 during melanoma progression is unknown. Here we show that up-regulation of MCAM/MUC18 expression in highly metastatic cells correlates with loss of expression of the transcription factor AP-2. The MCAM/MUC18 promoter contains four binding sites for AP-2, and electrophoretic mobility shift assay gels demonstrated that the AP-2 protein bound directly to the MCAM/MUC18 promoter. Transfection of AP-2 into highly metastatic A375SM melanoma cells (AP-2-negative and MCAM/MUC18-positive) inhibited MCAM/MUC18 promoter-driven chloramphenicol acetyltransferase reporter gene in a dose-dependent manner. MCAM/MUC18 mRNA and protein expression were down-regulated in AP-2-transfected but not in control cells. In addition, re-expression of AP-2 in A375SM cells inhibited their tumorigenicity and metastatic potential in nude mice. These results indicate that the expression of MCAM/MUC18 is regulated by AP-2 and that enforced AP-2 expression suppresses tumorigenicity and metastatic potential of human melanoma cells, possibly by down-regulating MCAM/MUC18 gene expression. Since AP-2 also regulates other genes that are involved in the progression of human melanoma such as c-KIT, E-cadherin, MMP-2, and p21(WAF-1), we propose that loss of AP-2 is a crucial event in the development of malignant melanoma.

Alpha 1-proteinase inhibitor is the serum regulator of the activity of p57, a C3-cleaving proteinase present in human erythrocyte membranes

Human erythrocytes express at the membrane level a p57 serine proteinase which cleaves C3, the third component of complement. We demonstrated herein that human serum carries an inhibitory activity against this p57 membrane proteinase. Purification allowed to identify this inhibitor as the alpha 1-proteinase inhibitor (alpha 1-PI) on the basis of its molecular weight, antigenicity and amino acid sequence identity. Data demonstrated that alpha 1-PI is the unique and strong serum inhibitor of the p57 proteinase activity: inhibition studies showed that alpha 1-PI inhibited p57 proteinase activity with a kass value of 10(5) M-1 s-1. Inhibition of p57 proteinase by alpha 1-PI was due to formation of a SDS-stable complex between both components. We suggest that inhibition of the membrane p57 proteinase activity by serum alpha 1-PI may be involved in the regulation of C3 fragment generation and/or in clearance in liver of C3b bearing immune complexes by erythrocyte-CR1.

[Cytomegalovirus infection in pregnant women. Seroepidemiological prospective study in 1,018 women in Isere]

Cytomegalovirus (CMV) is the leading cause of viral congenital infections. In children, the consequences may be severe, especially in case of maternal primary infection during pregnancy. A prospective study was carried out in the department of Isère, in 1,018 pregnant women, in order to establish the seroprevalence of CMV, the frequency of primary infections during pregnancy and the associated risk factors. The overall seroprevalence was 51.5%; it increased significantly with age, parity, and low socioeconomic status. It was higher in women born in the South of France (51.6%) than in those born in the North (37.4%). Among a total of 878 women with serological follow-up, 7 primary infection cases (0.8%) were observed. Seventeen women (1.9%) presented border IgM values in the first serum, and these values were not related to recent infection. Extrapolation of the results to the whole department of Isère, suggests that each year about 100 pregnant women would be concerned by CMV primary infection, with 2 or 3 cases of death or severe sequelae in children. In light of these results, the interest of serological screening is discussed.

[The effect of the formulation of a skin cream with a procyanidin polymer base and its effect on skin lesions caused by herpesviruses]

Procyanidin polymers are reported to be virostatic and virucidal in vitro. In this experiment we showed, on a hairless mouse model, biological effects of these agents, already demonstrated in vitro on cell cultures. Several dermic cream compositions have been tested and compared for reduction of HSV1 cutaneous lesions. In this study, it appeared clearly that active principle dosage form is as important as the biological effect of the agent. Composition and water content influence permeation speed, contact time with surface skin layers and consequently the pharmacological effect on herpetic skin injuries.

Dominant-negative CREB inhibits tumor growth and metastasis of human melanoma cells

The ATF/CREB family of eukaryotic transcription factors contain the bZIP structural motif and mediate their transcriptional activities via heterodimerization with ATF and AP-1 family members. Quenching of CREB-associated proteins by a dominant-negative CREB (KCREB) that is mutated within its DNA-binding domain decreases radiation resistance of human melanoma cells. The purpose of this study was to determine the role of CREB in tumor growth and metastasis of human melanoma using KCREB. Highly metastatic MeWo human melanoma cells were transfected with the KCREB expression vector and subsequently analysed for changes in their tumorigenic and metastatic potential. Expression of KCREB in MeWo human cells decreased their tumorigenic and metastatic potential in nude mice compared with parental and control transfected cells. The KCREB-transfected cells displayed downregulation of 72 kDa collagenase type IV (MMP-2) mRNA expression and activity and decreased invasiveness through Matrigel-coated filters. Moreover, transcriptional activities mediated by the CAT gene driven by the MMP-2 promoter were decreased by 14-45-fold in KCREB-transfected cells. In addition, the cell-surface adhesion molecule MCAM/MUC18 that is involved in metastasis of human melanoma was downregulated in the KCREB-transfected cells. These data indicate that, through their transcriptional activities, CREB and its associated proteins play an important role in the acquisition of the metastatic phenotype of human melanoma cells.

p53-mediated DNA renaturation can mimic strand exchange

The process of strand exchange is considered to be the hallmark of DNA recombination. Proteins known to carry out such exchange are believed to operate via one or the other of two mechanisms. RecA-like proteins promote the formation of a three-stranded or triplex synaptic intermediate in which strand exchange occurs, whereas other proteins would allow the coordinated exonucleolytic degradation of one strand in the duplex DNA and its replacement by an invading strand of similar sequence and polarity. In view of properties ascribed to it, we have attempted to determine whether p53 belongs to one or the other of these groups of proteins. The in vitro assay used relies on a double-stranded (ds) oligonucleotide (oligo 1+2) and a single-stranded (ss) oligonucleotide (oligo 3), part of which is complementary to oligo 1. The data collected suggest that, under the conditions of the assay, oligo 1+2 undergoes partial denaturation; p53 then catalyzes renaturation of oligo 1 with oligo 3, rather than true strand exchange. Since p53 is not known for being able to 'melt' DNA, it would seem unlikely that this protein would effect strand exchange in vivo without assistance from another, denaturing, protein.

Co-expression and secretion of C3, the third component of complement and a C3-cleaving cysteine proteinase in a highly metastatic human melanoma cell line

We recently demonstrated that DM-4, a human melanoma cell line highly metastatic in nude mice, expressed a p41 C3-cleaving proteinase. This p41 proteinase is a cysteine proteinase, associated to cell surface and involved in tumorigenicity and metastatic properties of these tumor cells. We demonstrate herein that DM-4 cells also secrete the p41 proteinase. In addition, analysis of cellular components which reacted with the p41 proteinase led us to demonstrate that DM-4 cells synthesized and secreted human C3. Secreted C3 is cleaved by the secreted p41 proteinase and a C3dg-like fragment is generated. This is the first demonstration that a human melanoma cell line co-expresses and co-secretes human C3 and a C3-cleaving cysteine proteinase, antigenically related to procathepsin L.

A cysteine proteinase, which cleaves human C3, the third component of complement, is involved in tumorigenicity and metastasis of human melanoma

The DM-4 human melanoma cell line, which is highly metastatic in nude mice, expresses a C3-cleaving activity that proteolyzes labeled as well as unlabeled human C3. This C3-cleaving activity is a cysteine proteinase characterized by a M(r) 41,000. The p41 proteinase shares antigenic determinants with murine p39 procathepsin-L and human procathepsin-L. Preincubation of DM-4 cells with anti-p39 F(ab')2 induced up to 45% decrease in their complement resistance. Pretreatment of DM-4 cells with anti-p39 Ab strongly inhibited their tumorigenicity and significantly decreased their metastatic potential in nude mice. Thus, the p41 C3-cleaving proteinase contributes to tumorigenicity and metastasis of human melanoma DM-4 cells.

Identification on melanoma cells of p39, a cysteine proteinase that cleaves C3, the third component of complement: amino-acid-sequence identities with procathepsin L

We previously identified, on normal or tumour cells, two membrane proteinases, p57 and p65, that cleave human C3, the third component of complement, thus regulating C3's biological properties. Whereas p57 was purified from human erythrocytes, p65 was identified using polyclonal anti-p57 antibodies on a human melanoma cell line resistant to complement lysis. Analysis of cell distribution of C3-cleaving proteinases established that DSm, a murine melanoma cell line, expressed a C3-cleaving proteinase distinct from p57 and p65 proteinases. Thus we purified the C3-cleaving proteinase solubilized from membranes of DSm cells. The purified proteinase, termed 'p39' on the basis of its molecular mass of 39 kDa, was identified, using specific proteinase inhibitors, as a cysteine proteinase. Anti-p39 antibodies, prepared against highly purified p39, localized the p39 C3-cleaving proteinase mainly at the cell surface and demonstrated that p39 is also secreted. Anti-p39 antibodies inhibited solubilized C3-cleaving activity. Preincubation of DSm cells with anti-p39 F(ab')2 fragments increased up to 60% complement cell susceptibility. Amino acid analysis of N-terminal and three other regions of p39 demonstrated that this C3-cleaving proteinase carries 100% identity within four regions of procathepsin L. This is the first demonstration that a melanoma cell line expresses on its surface and secretes a p39 C3-cleaving cysteine proteinase that shares sequence identities with procathepsin L. Thus the p39 cysteine proteinase represents a new member of the C3-cleaving proteinase family associated with, and/or expressed on, the cell surface.

Cutaneous hemangiosarcoma with pulmonary metastasis in a horse

A 6-year-old Thoroughbred mare had a 7-cm ulcerated mass on the cranial aspect of the left cervical area. Ultrasonography revealed the mass to be < 1 cm thick and composed of small lobules that were filled by material hypoechoic to the surrounding muscle tissues. Fine-needle aspiration of the mass yielded blood, and cytologic examination revealed a few epithelial cells with neoplastic changes. Thoracic radiography revealed an interstitial pattern with several disseminated nodules. A diagnosis of cutaneous hemangiosarcoma with pulmonary metastases was made. The diagnosis was confirmed at necropsy.

Genetic analysis of Cln/Cdc28 regulation of cell morphogenesis in budding yeast

The CLN1, CLN2 and CLN3 gene family of G1-acting cyclin homologs of Saccharomyces cerevisiae is functionally redundant: any one of the three Cln proteins is sufficient for activation of Cdc28p protein kinase activity for cell cycle START. The START event leads to multiple processes (including DNA replication and bud emergence); how Cln/Cdc28 activity activates these processes remains unclear. CLN3 is substantially different in structure and regulation from CLN1 and CLN2, so its functional redundancy with CLN1 and CLN2 is also poorly understood. We have isolated mutations that alter this redundancy, making CLN3 insufficient for cell viability in the absence of CLN1 and CLN2 expression. Mutations causing phenotypes specific for the cell division cycle were analyzed in detail. Mutations in one gene result in complete failure of bud formation, leading to depolarized cell growth. This gene was identified as BUD2, previously described as a non-essential gene required for proper bud site selection but not required for budding and viability. Bud2p is probably the GTPase-activating protein for Rsr1p/Bud1p [Park, H., Chant, I. and Herskowitz, I. (1993) Nature, 365, 269-274]; we find that Rsr1p is required for the bud2 lethal phenotype. Mutations in two other genes (ERC10 and ERC19) result in a different morphogenetic defect: failure of cytokinesis resulting in the formation of long multinucleate tubes. These results suggest direct regulation of diverse aspects of bud morphogenesis by Cln/Cdc28p activity.

Pressurization and acute mountain sickness

Numerous cases of acute mountain sickness (AMS) during trekking were reported to have been successfully treated with portable pressure chambers. The effect of early pressurization during acute altitude exposure in the Alps had not been previously studied. In order to test the hypothesis that an early pressurization of unacclimatized subjects for 3 h could prevent or delay the appearance of symptoms of AMS, 51 previously healthy subjects climbed from 1,030 to 4,360 m within 12 h. Upon arrival at 4,360 m, AMS scores (Lake Louise Consensus Questionnaire '91), oxygen saturation (SaO2), and heart rate (HR) were determined at rest. The subjects were then randomly divided in two groups; one group was pressurized to 200 mBar for 3 h while the other rested. AMS score, HR, and SaO2 were similar in both groups before treatment. AMS score had decreased (from 2.44 +/- 0.41 (S.E.) to 0.89 +/- 0.26, p < 0.05) and SaO2 had increased (from 75.22 +/- 1.32% to 79.07 +/- 1.27%, p < 0.05) in the treatment group 15 min after leaving the pressure chamber whereas the control group had unchanged AMS score (2.50 +/- 0.40 vs. 2.40 +/- 0.40, N.S.) and SaO2 (77.83 +/- 1.41 vs. 76.67 +/- 1.24, N.S.). The next morning, however, AMS score, HR, and SaO2 were similar for both groups. It is concluded that during acute ascent in the Alps, an early 3-h pressurization of unacclimatized subjects does slightly delay the onset of AMS but does not prevent the illness nor does it attenuate its severity upon appearance.

Topoisomerase activity associated with SV40 large tumor antigen

Purified preparations of simian virus 40 (SV40) large tumor antigen (LT) from three different sources, including LT expressed from a recombinant baculovirus, were found to relax negatively supercoiled cyclic DNA molecules, whether or not they contained SV40 sequences. Relaxation was stimulated by MgCl2 but not by ATP, and inhibited by camptothecin, suggesting the involvement of an enzymatic activity similar to that of topoisomerase I (topo I). However, the pH requirements for relaxation by respectively LT and topo I are different. Also, antibodies reacting with LT inhibited relaxation by preparations of LT but not topo I, whereas antibodies inhibiting relaxation by topo I had no effect on relaxation by LT. Reconstruction experiments suggested that both procedures used to purify LT, immunoaffinity chromatography and DEAE-Sepharose chromatography, separate topo I from LT. Finally, relaxing activity was found in over 40 preparations of LT, and in the few instances where activity could not be found, it probably had been lost during storage, rather than absent from the start. Whereas these results seem to exclude that the activity being detected is that of a contaminant of LT, they would be consistent with this activity being that of a stable topo-LT complex, or else intrinsic to LT itself.