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Non-invasive visualisation of the expression of hypoxia-related proteins, such as carbonic anhydrase IX (CA IX), by positron emission tomography (PET) could provide important information on the oxygenation status of tumours. Since betulinic acid derivatives bind specifically to CA IX the aim of the study was the development betulinic acid-based

Extracellular acidosis is a characteristic of solid tumours, resulting from hypoxia-induced glycolytic metabolism as well as from the "Warburg effect" (aerobic glycolysis). The acidic environment has shown to affect functional tumour properties (proliferation, migration, invasion) and thus the aim of the study was to identify signalling mechanisms, mediating these pH-dependent effects. Therefore, the serum response factor (Srf) and the activation of the serum response element (SRE) by acidosis were analysed in AT-1 prostate carcinoma cells. Furthermore, the expression of downstream targets of this cascade, namely the early growth response 1 (Egr1), which seems to be involved in tumour proliferation, and the cellular communication network factor 1 (Ccn1), which both contain SRE in their promotor region were examined in two tumour cell lines. Extracellular acidification led to an upregulation of Srf and a functional activation of the SRE. Egr1 expression was increased by acidosis in AT-1 cells whereas hypoxia had a suppressive effect. In experimental tumours, in vivo Egr1 and Ccn1 were also found to be acidosis-dependent. Also, it turned out that pH regulated expression of Egr1 was followed by comparable changes of p21, which is an important regulator of the cell cycle.This study identifies the Srf-SRE signalling cascade and downstream Egr1 and Ccn1 to be acidosis-regulated in vitro and in vivo, potentially affecting tumour progression. Especially linked expression changes of Egr1 and p21 may mediate acidosis-induced effects on cell proliferation.

Signalling pathways such as ERK1/2, p38 or PI3K are activated in tumour cells by extracellular acidosis, which is a common phenomenon in human tumours. These signalling pathways can modulate the mitochondrial function and activity. The aim of the study was to evaluate the impact of extracellular acidosis on the mitochondrial O

The metabolic microenvironment of solid tumours is often dominated by extracellular acidosis which results from glycolytic metabolism. Acidosis can modulate gene expression and foster the malignant progression. The aim of the study was to analyse the effects of extracellular acidosis on the mTOR signalling pathway, an important regulator of anabolic and catabolic processes like cell proliferation and autophagy. The study was performed in two tumour cell lines, AT-1 prostate and Walker-256 mammary carcinoma cells. Cells were incubated at pH 7.4 or 6.6 for 3 h and 24 h. Then RNA and protein were extracted and analysed by qPCR and western blot. mTOR and P70-S6 kinase (P70-S6K), an important downstream target of mTOR, as well as the autophagic flux were studied. The effect of acidosis on P70S6K phosphorylation was compared to pharmacological mTOR inhibition with LY294002 and rapamycin. In both cell lines the total mTOR expression was not altered by acidosis, however, the mTOR phosphorylation was reduced after 3 h but not after 24 h. The P70S6K phosphorylation was reduced at both time points comparable to changes by pharmacological mTOR inhibitors. The autophagic flux, also a target of mTOR and measured by LC3-II expression, was increased in both cell lines after 24 h of acidosis. The results of this study indicate that mTOR signalling is inhibited by extracellular acidosis which then lead to a reduced activity of the P70-S6 kinase (modulating gene expression) and increased autophagy possibly mediated by ULK1/2 activity. These finding may offer new perspectives for therapeutic interventions in acidic tumours.

Epithelial-mesenchymal transition (EMT), which is involved in metastasis formation, requires reprogramming of gene expression mediated by key EMT transcription factors. However, signals from the cellular microenvironment, including hypoxia, can also modulate the process of EMT. Hypoxia is often associated with a reduction in the extracellular pH of the tumor microenvironment (acidosis). Whether acidosis alone has an impact on the expression of the EMT markers E-cadherin, N-cadherin, and vimentin was studied in NCI-H358 lung cancer cells. Reducing extracellular pH decreased E-cadherin mRNA, while vimentin and N-cadherin mRNA were doubled. However, at the protein level, E-cadherin and N-cadherin were both reduced, and only vimentin was upregulated. E-cadherin and N-cadherin expression at the cell surface, which is the relevant parameter for cell-cell and cell-matrix interaction, decreased too. The reduction of cell surface proteins was due to diminished protein expression and not changes in cellular localization, since localization of EMT markers in general was not affected by acidosis. Acidosis also affected NCI-H358 cells functionally. Adhesion was decreased when the cells were primed in an acidic medium before measuring cell adherence, which is in line with the reduced expression of cadherins at the cell surface. Additionally, migration was decreased after acidic priming. A possible mechanism for the regulation of EMT markers involves the action of microRNA-203a (miR-203a). In NCI-H358 lung cancer cells, miR-203a expression was repressed by acidosis. Since a decrease in the level of miR-203a has been shown to induce EMT, it might be involved in the modulation of EMT marker expression, adhesion, and migration by the acidic tumor microenvironment in NCI-H358 lung cancer cells.

In comparison to normal tissue, solid tumors show an acidic extracellular pH, which results from hypoxia-induced glycolytic metabolism and the Warburg effect. Since acidosis modulates the expression of different microRNAs (e.g., miR-7, miR-183, miR-203, miR-215), microRNAs and their targets might be mediators between tumor acidosis and malignant behavior. The aim of this study was to investigate how modulation of these microRNAs affects the expression of their targets (Crem, cAMP-responsive element modulator; Gls2, glutaminase 2; Txnip, thioredoxin-interacting protein) in experimental tumors in vivo and whether these changes are acidosis dependent. The study was performed in two experimental tumor lines of the rat (AT-1 prostate carcinoma, Walker-256 mammary carcinoma). The results showed that all three targets were regulated by acidosis in vivo, Crem and Gls2 being downregulated and Txnip upregulated in both models. In AT-1 tumors at normal tumor pH, miR-203 overexpression increased Txnip expression by about 75%, whereas in Walker-256 tumors, miR-7 reduced protein expression. In more acidic tumors, no impact of microRNAs on Txnip expression was seen. On the other hand, Gls2 was significantly increased in acidic tumors by miR-183 or miR-7 overexpression (cell line dependent). As this increase was not present under control conditions, an acidosis-dependent effect can be assumed. These results indicate that tumor acidosis modulates the expression of targets of pH-sensitive microRNAs in experimental tumors. Especially the protein expression of Gls2 might be regulated via changes of microRNAs, which then affects the malignant progression of tumors.

The metabolic microenvironment in tumors is characterized by hypoxia and acidosis. Extracellular pH sometimes decreases to even below 6.0. Previous experiments showed that tissue pH has an impact on tumor cell proliferation and apoptosis. However, the mechanism of how cell cycle progression is affected by decreased pH is not fully understood yet. One possible mechanism includes changes in the expression of miRNAs. The aim of this study was to analyze the impact of pH-regulated miRNAs (miR-183 and miR-215) on proliferation, apoptosis, and necrosis of tumor cells. Therefore, AT1 prostate and Walker-256 mammary carcinoma cells were transfected with the miRNAs or with the respective antagomirs and incubated at pH 7.4 and 6.6 for 24 h. AT1 cells underwent a G0/G1 cell cycle arrest under acidic conditions and showed a marked reduction of the number of actively DNA-synthesizing cells. In Walker-256 cells, acidosis induced a reduction of apoptosis and additionally a significant increase in necrotic cell death. Transfection of tumor cells with miR-183 or miR-215, which were significantly downregulated under acidic conditions, had no impact on cell death of AT1 or Walker-256 cells. Overexpression of miR-183, which is also downregulated by acidosis, intensified G0/G1 cell cycle arrest in AT1 cells. Previous studies revealed that hypoxia-related tumor acidosis affects the expression of different small noncoding RNAs. However, not all of these acidosis-regulated miRNAs seem to have an impact on proliferation, apoptosis, and necrosis of tumor cells. While miR-215 had no influence, miR-183 seems to be an interesting candidate that could amplify the impact of extracellular acidosis on malignant behavior of tumor cells.

Tumor tissue shows special features in metabolism in contrast to healthy tissue. Besides a distinctive oxygen deficiency, tumors often show a reduced extracellular pH (acidosis) resulting from an intensified glycolysis not only under hypoxic but also under normoxic conditions (Warburg effect). As shown in previous studies, cell migration is increased in AT1 prostate carcinoma cells after incubation at pH 6.6, and this leads to an increased number of lung metastases in vivo. However, the signaling pathway causing these functional changes is still unknown. Possible mediators could be acidosis-regulated microRNAs (miR-7, miR-183, miR-203, miR-215). The aim of the study was therefore to analyze whether a change in the expression of these microRNAs has an impact on the tumor cell migration and adhesion. Studies were performed with AT1 rat prostate cancer cells which were incubated for 24 h at pH 7.4 or 6.6. Keeping AT1 tumor cells at low pH increased the migratory capacity by about 100%. But also the decrease of miR-203 and miR-215 expression (at normal pH) led to an increase in migration velocity by 50%. In contrast, cell adhesion was increased by about 75% at low pH. However, an increase in miR-215 expression at pH 6.6 reduced the adhesion by trend. These results clearly indicated that the extracellular pH has an impact on migration and adhesion of tumor cells. In this mechanism, pH-regulated microRNAs could play a role since changes in the expression of these microRNAs (especially miR-203) are also able to modulate the migratory behavior.

Acidification of the cellular microenvironment is found in different pathological states such as inflammation, ischemia and in solid tumors. It can affect cell function and phenotype, and by this aggravate the pathological process. Epithelial cells are a relevant functional part in several normal organs as well as in tumors and will thus be challenged by the acidic extracellular pH (acidosis). Therefore, the impact of acidosis on the expression of different inflammatory mediators (MCP-1, IL-6, osteopontin, iNOS, TNF-α, and COX-2), as well as the role of different signaling pathways regulating the expression, was studied in epithelial normal rat kidney cells (NRK-52E). Acidosis led to an increase in TNF-α expression but a down-regulation of MCP-1, iNOS and COX-2. Expression of IL-6 was only slightly modulated, while osteopontin was not regulated at all. Since acidosis activates ERK1/2 and p38 signaling in NRK-52E cells, the impact of MAP kinase signaling pathways on the expression of the inflammatory markers was analyzed. At normal pH, blocking ERK1/2 or p38 decreased the level of MCP-1, iNOS and partly TNF-α. However, the effect of acidosis on the expression of inflammatory mediators was not affected by inhibition of the MAP kinase pathways. In conclusion, our results show that an acidic microenvironment affects the transcriptional program of epithelial cells. Low pH mostly reduced the expression of pathological relevant genes and might thus repress inflammatory processes induced by epithelial cells.

Bei der Lungenatmung wird die Luft der Alveolen (Lungenblaschen) zum Teil gegen Frischluft ausgetauscht. In Ruhe atmet der Erwachsene pro Minute 14 Atemzuge mit jeweils einem Volumen von 0,5 l (Atemzugvolumen). Hiervon gelangt aber nur 2/3 in den Alveolarraum und wird dort fur den Gasaustausch genutzt, wohingegen 1/3 in den Atemwegen verbleibt. Das Atemzugvolumen kann durch maximale Ein- und Ausatmung auf etwa 5 l gesteigert werden, jedoch verbleibt auch bei maximaler Exspiration ein Luftrest in der Lunge. Bei Einatmung wird durch die Brustkorb- und Zwerchfellbewegung ein Unterdruck (relativ zur Umgebung) erzeugt, wodurch die Luft in den Alveolarraum gesogen wird. Bei Exspiration entsteht ein Uberdruck in den Alveolen. Im Pleuraspalt zwischen Lunge und Brustkorb herrscht ein Unterdruck, der die Lunge im entfalteten Zustand halt. Wahrend der Atembewegung mussen verschiedene Atmungswiderstande uberwunden werden, da das Lungengewebe und der Brustkorb gedehnt werden und die Luft durch das starre Rohrsystem der Atemwege stromen muss. Die Messung dieser Widerstande liefert diagnostische Informationen fur verschiedene Lungenerkrankungen.

Nachdem uber die Ventilation O2-reiches Gas in die Alveolen transportiert wurde, findet dort der eigentliche Gasaustausch mit dem Blut statt. Hierbei wird O2 in das Blut aufgenommen und CO2 aus dem Blut abgegeben. Dieser Austausch erfolgt passiv uber den Vorgang der Diffusion. Wenn das Blut die Lungenkapillaren verlasst, herrschen dort die gleichen Gaspartialdrucke wie in der Alveole. Eine Storung der Diffusion verschlechtert die Sauerstoffanreicherung des Blutes. Wie gut das arterielle Blut mit Sauerstoff angereichert wird, hangt somit davon ab, wie gut die Atemgase durch die Alveolarwand diffundieren konnen, aber auch, wie viel Frischluft in die Alveolen gelangt (Ventilation) und wie viel Blut zur Verfugung steht, um den Sauerstoff aufzunehmen (Perfusion). Sowohl Ventilation als auch Perfusion sind in der Lunge ungleichmasig verteilt, wobei im Stehen die Lungenspitze schlechter beluftet und durchblutet wird als die unteren Lungenabschnitte. Diese Ungleichverteilung der relevanten Parameter bewirkt eine Verschlechterung der O2-Aufnahme. Je gleichmasiger die Verteilung ist, desto effektiver ist die Arterialisierung des Blutes in der Lunge.

Under pathological conditions like inflammation, ischemia or in solid tumors, parameters of the microenvironment like local oxygenation and extracellular pH show marked changes when compared to healthy tissue. The altered microenvironment affects cellular phenotype of omnipresent fibroblasts and immune cells. Recently, the impact of the microenvironment on the expression patterns of microRNAs, small non-coding RNAs that regulate gene expression on a post-transcriptional level, was discussed. Therefore, microRNAs might be the link between altered microenvironmental parameters and changes in cellular phenotype. In this study, the effect of hypoxia-induced extracellular acidosis (24 h pH 6.6) on microRNA expression in fibroblasts and macrophages was analyzed. MicroRNAs in rat fibroblasts (NRK-49F) were examined with the miScript miRNA PCR Array and changes in the expression validated by TaqMan qPCR. Subsequently, the identified microRNAs were analyzed in RAW 264.7 mouse macrophages. Nine out of 84 tested microRNAs were found to be acidosis-regulated in fibroblasts by miRNA PCR array, most of them up-regulated. Of those, the pH dependency could be validated by TaqMan qPCR for five of these nine microRNAs. When comparing these microRNAs in terms of their expression in macrophages, profound differences were observed. Thus, acidosis-induced alterations in the expression of microRNAs seem to be cell-type specific. Only the up-regulation of the miR-133b by low pH was seen in all normal cells, but not in tumor cells. As the identified microRNAs are involved in the regulation of proliferation, cell death and migration (amongst others), acidosis-induced changes in their expression might affect cellular behavior of fibroblasts and macrophages under pathological conditions. For instance the proto-oncogene c-Jun, which is a target of the miR-133b, was shown to be acidosis-regulated. Acidosis could regulate the biological behavior via miRNA-133b and c-Jun.

MicroRNAs (miRNAs) are small non-coding RNA sequences which are able to modulate the expression of many functional proteins. The expression level of miRNAs can be modulated by parameters of the tumor microenvironment like hypoxia, nutrient deprivation or oxidative stress. Since miRNAs can act either as oncogenes or tumor suppressors, this may affect malignant progression or therapy resistance. In the present study it was analyzed whether extracellular acidosis can impact on miRNA expression. Therefore, tumor cells (R3327-AT-1 prostate and Walker-256 mammary carcinoma cells) were incubated at pH 6.6 (acidosis) or pH 7.4 (control) for 24 h and changes in miRNA expression were analyzed by PCR array for 84 cancer-associated miRNAs and Next-Generation Sequencing (NGS) with a panel of 765 miRNAs.In the cancer-related PCR array an acidosis-induced reduction of 5 miRNAs in AT-1 and 6 miRNAs in Walker-256 cells was seen. The miR-203a was consensually down-regulated in both cell lines. Using NGS, 19 miRNAs were found to be upregulated and 14 miRNAS were downregulated in AT-1 prostate cancer cells. In Walker-256 cells the expression of 21 miRNAs was increased and decreased for 17 miRNAs. Eleven miRNAs were regulated by acidosis in both tumor cell lines in the same direction.Acidosis induced changes in the miRNA expression of prostate and breast carcinoma cells. However, miRNA profiles differed strongly between the tumor cell lines (and between the experimental methods used), indicating that cells can react individually to microenvironmental stress. However, some miRNAs were consensually regulated in both cell lines and thus might represent a general cellular response to an extracellular acidosis.

Hypoxia and extracellular acidosis are common features of solid malignant tumors. The aim of the study was to analyze whether these pathophysiological parameters affect the expression of inflammatory mediators in tumor cells. Therefore the mRNA expression of MCP-1 (monocyte chemotactic protein 1), iNOS and osteopontin was measured under hypoxic (pO2 1 mmHg) and acidotic (pH 6.6) conditions by qPCR in AT1 R-3327 prostate cancer cells. In addition, the underlying signaling cascades were analyzed by using inhibitors of the p38 and ERK1/2 MAP kinase pathways.Hypoxia led to a significant decrease of the expression of MCP-1 and osteopontin over the complete observation period of 24 h, whereas the iNOS expression after an initial reduction slightly increased. Acidotic conditions for up to 6 h increased the iNOS expression significantly which was functional as indicated by an elevated level of nitrate/nitrite formation by 30 %. Acidosis had almost no impact on the MCP-1 expression of tumor cells, whereas the osteopontin level tended to increase leading to a significantly elevated level after 24 h at pH 6.6. Inhibiting the p38 and ERK1/2 under control conditions revealed that the MAPKs play a significant role for the regulation of the expression of inflammatory mediators. MCP-1 expression could be lowered by inhibiting ERK1/2 whereas iNOS expression was dependent on both p38 and ERK1/2 MAPK. These results indicate that the adverse tumor microenvironment affects the expression of inflammatory mediators by tumors cells and may therefore modulate the immune response within the tumor tissue.

The tumor microenvironment is characterized by hypoxia, acidosis as well as other metabolic and biochemical alterations. Its role in cancer progression is increasingly appreciated especially on invasive capacity and the formation of metastasis. The effect of acidosis on metastasis formation of two rat carcinoma cell lines was studied in the animal model. In order to analyze the pH dependency of different steps of metastasis formation, invasiveness, cell adhesion and migration of AT-1 prostate cancer cells as well as possible underlying cell signaling pathways were studied in vitro. Acidosis significantly increased the formation of lung metastases of both tumor cell lines in vivo. In vitro, extracellular acidosis neither enhanced invasiveness nor affected cell adhesion to a plastic or to an endothelial layer. However, cellular motility was markedly elevated at pH 6.6 and this effect was sustained even when extracellular pH was switched back to pH 7.4. When analyzing the underlying mechanism, a prominent role of ROS in the induction of migration was observed. Signaling through the MAP kinases ERK1/2 and p38 as well as Src family kinases was not involved. Thus, cancer cells in an acidic microenvironment can acquire enhanced motility, which is sustained even if the tumor cells leave their acidic microenvironment e.g. by entering the blood stream. This increase depended on elevated ROS production and may contribute to the augmented formation of metastases of acidosis-primed tumor cells in vivo.

BACKGROUND The cochlear aqueduct is a route for direct pressure transfer between intracranial and intracochlear fluids. In patients with Meniere's disease, intracochlear pressure is presumably disturbed. The "Tympanic Membrane Displacement Analyser (TDA)" is a new system which provides a useful noninvasive method of detecting intracranial and intracochlear pressure changes. PATIENTS In this study TDA measurements in combination with a glycerol test were performed in nine patients with Meniere's disease and in seven normal persons. RESULTS Before ingestion of glycerol, no significant difference in pressure was found between the two groups. After ingestion of glycerol a temporary decrease in intracochlear pressure was detected in both groups without any significant difference between the two groups. CONCLUSION These results show that the combination of glycerol testing and TDA measurements does not seem to be helpful for the differential diagnosis of Meniere's disease.

The data of a patient undergoing complex diagnostic and therapeutic procedures do not only form a simple chronology of events, but are closely related in many ways. Such data contexts include causal or temporal relationships, they express inconsistencies and revision processes, or describe patient-specific heuristics. The knowledge of data contexts supports the retrospective understanding of the medical decision-making process and is a valuable base for further treatment. Conventional data models usually neglect the problem of context knowledge, or simply use free text which is not processed by the program. In connection with the development of the knowledge-based system THEMPO (Therapy Management in Pediatric Oncology), which supports therapy and monitoring in pediatric oncology, a graph-grammar approach has been used to design and implement a graph-oriented patient model which allows the representation of non-trivial (causal, temporal, etc.) clinical contexts. For context acquisition a mouse-based tool has been developed allowing the physician to specify contexts in a comfortable graphical manner. Furthermore, the retrieval of contexts is realized with graphical tools as well.

Background: Objective tumor remissions are induced by a variety of immunomodulating agents in a minority of patients suffering from metastasizing renal cell carcinoma. The results of different clinical studies, however, varied greatly for each of these treatment modalities. In order to elucidate potential causes for this variability and to further study the long-term results of intermittent low-dose IFN gamma therapy in patients with advanced renal cell cancer (RCC) we retrospectively analyzed factors predicting clinical response and long-term survival of 121 patients. Material and Methods: We retrospectively analyzed the clinical results of 5 phase II studies treating 121 patients with intermittent low-dose IFN gamma as first-line treatment for metastatic RCC. Results: 15% complete and partial responses were observed in these patients. Intermittent low-dose IFN gamma was well-tolerated and treatment was performed largely on an outpatient basis. Clinical presentation of the disease was the only factor predicting both clinical response and survival. Whereas a 23% response rate was observed in patients suffering from limited disease RCC (disease limited to one site including adjacent lymph nodes), the response rate in patients with widespread disease was less than 5%. When the results of the 5 studies were compared, a statistically highly significant correlation between the proportion of treated patients with limited disease and response rate was observed. Conclusion: We conclude that intermittent low-dose IFN gamma is effective and induced long-term complete remissions in a proportion of patients with limited disease metastatic RCC.

A decision support system has been developed that determines the optimal dialysate bicarbonate concentration in hemodialysis therapy for each patient individually. The knowledge about the behavior of the acid-base state during treatment has been provided by a mathematical model for the description of dynamic exchange processes during hemodialysis. This model simulates the sodium and water distribution, the acid-base state as well as the ventilation. The decision support system uses the model for the prediction of the end-dialysis acid-base state and calculates by means of linear optimization the dialysate bicarbonate concentration which is necessary to reach a specified end-dialysis state. If the aspired acid-base state can not be reached, the system varies the dialysate sodium concentration and the treatment time. The whole program can be used on a PC and is easy to use. One decision making process lasts between 10 seconds and 5 minutes depending on the computer.

The effect of dialysis control parameters (dialysate composition, ultrafiltration rate, blood flow rate) on the patient's internal milieu were studied using a mathematical model for the description of the dynamic exchange processes during hemodialysis. This model simulates the electrolyte and water distribution, the acid-base and the oxygenation state as well as the ventilation. The dialysate sodium concentration affects mainly the intra-/ extracellular water and the potassium distribution. The dialysate bicarbonate and acetate concentrations control the acid-base state and the electrolyte distribution (sodium and potassium). In addition, the dialysate acetate concentration has a strong effect on arterial oxygenation and on ventilation. The ultrafiltration rate controls the water distribution between plasma and the interstitial space but also the sodium distribution and the arterial acid-base state. The blood flow rate through the dialyser influences the acid-base state and, by this, it affects the potassium and sodium distribution. The acid-base state is affected in opposite directions when acetate or bicarbonate is used as a buffer.

In an investigation of the antitumor effects of 2-methoxyestradiol (2-ME) in combination with other reactive oxygen generating treatments, 2-ME (0.5 microM) was found to completely inhibit cell proliferation of rat DS-sarcoma cells in vitro, with 71% of cells dying after exposure to 5 microM 2-ME. Concentration-dependent increases in ROS-formation, lipid peroxidation and mitochondrial changes were also observed, and an elevation in caspase-3 activity resulted in DNA fragmentation and apoptosis. Combination of 2-ME with hypoxanthine and xanthine oxidase enhanced in vitro cytotoxicity. In vivo, 2-ME caused a slight inhibition of tumor growth, with no tumors cured. Combination of 2-ME treatment with localized 44 degrees C hyperthermia, respiratory hyperoxia and xanthine oxidase caused a tumor growth delay with 51% of tumors cured. These results suggest that amplifying the levels of reactive oxygen species within tumor tissue with substances such as 2-ME may prove to be a promising strategy for adjuvant treatment of solid tumors.

Hypoxia is a characteristic property of locally advanced solid tumors, resulting from an imbalance between the supply and consumption of oxygen. Major pathogenetic mechanisms for the development of hypoxia are (1) structural and functional abnormalities of the tumor microvasculature, (2) increased diffusion distances, and (3) tumor-associated and therapy-induced anemia. The oxygenation status is independent of clinical tumor size, stage, grade, and histopathological type, but is affected by the hemoglobin level. Hypoxia is intensified in anemic patients, especially in tumors with low perfusion rates. Hypoxia and anemia (most probably via worsening of tumor hypoxia) can lead to therapeutic problems, as they make solid tumors resistant to sparsely ionizing radiation and some forms of chemotherapy. In addition to more direct mechanisms involved in the development of therapeutic resistance, there are also indirect machineries that can cause barriers to therapies. These include hypoxia-driven proteome and genome changes and clonal selection. These, in turn, can drive subsequent events that are known to further increase resistance to therapy (in addition to critically affecting long-term prognosis). Treatment resistance in anemic patients can be, at least partially, prevented or overcome by anemia correction, resulting in better locoregional tumor control and overall survival of patients.

The aim of this study was to examine the impact of anemia prevention by recombinant human erythropoietin (rHuEPO) treatment on the cytotoxicity of cyclophosphamide in solid experimental tumors. Anemia was induced using a single dose of carboplatin (50 mg/kg i.v.) resulting in a long-lasting reduction (30%) of the hemoglobin concentration. In a second group, the development of anemia was prevented by rHuEPO (1000 IU/kg) administered s.c. three times/week starting 7 days before carboplatin application. Four days after carboplatin treatment, tumors (DS-sarcoma of the rat) were implanted s.c. onto the hind food dorsum. Neither carboplatin nor rHuEPO treatment influenced tumor growth rate per se. When tumors were treated with a single dose of cyclophosphamide (60 mg/kg i.p.) 5 days after implantation, a growth delay with a subsequent regrowth of the tumors was observed. In the anemia group, the growth delay was significantly shorter compared with nonanemic controls (13.3 days versus 8.6 days). In the group where anemia was prevented by rHuEPO treatment, growth delay was comparable with that of nonanemic controls (13.3 days). These results suggest that chemotherapy-induced anemia reduces cytotoxicity of cyclophosphamide in tumors, whereas correction of anemia by rHuEPO treatment (epoetin alpha) increases the sensitivity, probably as a result of an improved oxygen supply to tumor tissue.

Patients with cystic fibrosis (CF) represent a special risk for commercial airlines. Even on ground conditions the oxygen partial pressure (paO subset2) of these patients is partially clearly reduced. The reduced air pressure on board of an airplane can cause a drop of the paO subset2 to a critical point (below 50 mmHg) during a flight. Therefore, medical assistance or at least oxygen-supply over a longer time period could be necessary. Aim of this study was to investigate reaction and clinical outcome of patients with CF during a hypobaric-chamber-flight at altitudes of 2. 000 and 3.000 m to appraise their risk for a flight-trip.10 CF-patients (age 19-35 years, mean age 30 y) were investigated in a hypobaric chamber prior to an already booked flight-trip to the Baleares (Spain). Lung-function, oxygen saturation (SO subset2) and paO subset2 by pressure adjusted blood gas analysis were measured on ground level, at 2.000 m and 3.000 m pressure-altitude.Forced expiratory vital capacity (FVC) over the entire group was 2. 9 l (range 1.4 to 4.0 l), forced expiratory 1-second volume (FEV subset1) 2.08 l/sec (range: 1.22 to 3.61 l/sec). Values dropped slightly at 3.000 m chamber altitude (VC=2.7 l, FEV subset1=1.95 l/sec). SO subset2 decreased from 95 % on ground to 89% at 2.000 m and 86 % at 3.000 m chamber altitude. paO2 decreased from 79.5 mmHg at ground level to 60 mmHg at 2000m and 45.5 mmHg at 3.000 m. Only one patient with a paO subset2 of 52 mmHg didn t fall below the critical flight limit of 50 mmHg. No patient felt below a paO subset2 of 40 mmHg. No patient experienced dyspnea during the chamber flight. Two patients without subjective symptoms before the chamber flight developed mild ear blocks during descent presumably due to swollen polyps. Complaints improved quickly by applying decongestant nose-spray. -The results of the chamber flights indicate that chronically adapted adult lung disease patients without accompanying heart disease and a paO subset2 of40 mmHg during flight can anticipate a safe flight trip. These results could be confirmed by the consecutive flight trip to Spain.

Tumor oxygenation is dependent on the cellular O2 consumption rate and on the O2 supply to the respiring cells. The latter is mainly determined by the convective transport via the blood and by the diffusional flux from the microvessels to the O2 consuming sites. Peculiarities of tumor tissue oxygenation can therefore mainly be attributed to characteristic structural and functional abnormalities of the tumor microcirculation (perfusion-limited O2 delivery), to a deterioration of the diffusion geometry (diffusion-limited O2 delivery), and--in some cases--to a reduced O2-carrying capacity of the blood due to tumor-associated anemia. As a result of a compromised and anisotropic microcirculation, the O2 availability to the cancer cells shows great variability, and many human malignancies reveal hypoxic tissue areas which are heterogeneously distributed within the tumor mass and which may be located next to well-perfused tumor areas (intra-tumor heterogeneity). As a rule, in most solid malignancies the tissue O2 status is poorer than in normal tissue at the site of tumor growth. Hypoxia in human tumors per se has been shown to contribute to resistance to standard radiotherapy, chemotherapy and photodynamic therapy with photosensitizing hematoporphyrins. In addition to conferring a direct resistance, hypoxia-induced inhibition of proliferation may also contribute to resistance since both modalities are primarily effective against rapidly dividing cells. Hypoxia in solid tumors, however, has further implications in the clinical setting: Recent data provide strong evidence suggesting that O2 deprived tumor cells are predisposed to a more malignant phenotype, i.e., tumor cells are more likely to be more metastatic and/or invasive. In addition, clonal heterogeneity is more pronounced in hypoxic tumors.

Tumor growth, oxygenation and radiosensitivity were investigated in a series of studies in which anemia was induced in rats either by the development of a hemorrhagic ascites or by a single dose of carboplatin, which resulted in reductions in the hemoglobin concentration of 30%. The development of both the tumor- and chemotherapy-induced forms of anemia could be prevented by the s. c. administration of recombinant human erythropoietin (rhEPO; 1000 IU/kg, 3 times per week over 14 days). Seven days before pO2 measurements, DS-sarcomas were implanted s. c. on the hind foot dorsum. With both anemia models, tumor growth did not differ between anemic animals and animals treated with rhEPO. Tumor oxygenation was measured polarographically using O2-sensitive needle electrodes and pO2 histography. In anemic animals, tumor oxygenation was poorer compared to untreated controls. The reduction could be partially reversed by rhEPO treatment, but not fully compensated. These findings suggested that rhEPO treatment can improve tumor oxygenation by increasing the O2 availability to tumor tissue. Further experiments therefore assessed the possibility of enhancing the efficacy of a single radiation dose (10 Gy) by rhEPO treatment of anemic animals. While anemic animals showed decreased radiosensitivity, prevention of anemia by rhEPO treatment resulted in a significant increase in tumor radiosensitivity, although again a full recovery to radiosensitivity levels found in non-anemic animals was not achieved.

The effects of respiratory hyperoxia (RH) and xanthine oxidase (XO) during localized hyperthermia (HT) were investigated by determining markers of oxidative damage to lipids and proteins and tumor growth. Anesthetized rats with s.c. DS-sarcomas underwent one of the following treatments: (a) localized saline-bath HT (60 min, 44 degrees C); (b) HT + RH (100% O2); and (c) HT + RH + XO (15 units/kg i.v.). Sham-treated animals served as controls. Tumors were investigated for: (a) thiobarbituric acid-reactive substance formation and protein-bound 4-hydroxynonenal, as indicators of lipid peroxidation; (b) reactive oxygen-mediated protein modifications; (c) apoptosis; and (d) tumor volume growth. Upon treatment, increases in thiobarbituric acid-reactive substances, protein-bound 4-hydroxynonenal, protein-associated carbonyl functions, and number of cells undergoing apoptosis were found in tumor tissue, together with an inhibition of tumor growth. When treatment groups were compared, effects in the group HT + RH + XO were generally most pronounced. These findings indicate that the antitumor effect of HT is at least partially mediated through the selective induction of lipid peroxidation and oxidative injury in tumor cells, leading to apoptosis. This effect was enhanced by adding RH or RH + XO, presumably due to enhanced tissue damage following an increased formation of reactive oxygen species, with higher levels of lipid peroxidation and protein oxidation.

Growth, blood flow, oxygenation, and bioenergetic status of experimental tumors were investigated in normal (control) and anemic animals after administration of recombinant human erythropoietin (rhEPO). DS sarcomas were implanted s.c. onto the hind foot dorsum of Sprague-Dawley rats. Tumor-associated anemia was induced by the development of an i.p. hemorrhagic ascites. rhEPO (1000 IU/kg) was administered s.c. three times per week over 14 days, after which it was found to have significantly increased hematocrit values in both normal and anemic animals. Tumor growth in anemic animals was slower than in normal animals, and rhEPO administration did not influence tumor growth in either group. Tumor blood flow in anemic animals was lower than in control animals and was only increased in larger tumors in animals in which anemia was prevented by prophylactic rhEPO application. Tumor oxygenation, determined using polarographic needle electrodes and oxygen partial pressure histography, was poorer in anemic animals than in normal animals. This reduction could be reversed partially, but not compensated fully by rhEPO treatment in smaller tumors (or = 1.4 ml). These changes suggest that rhEPO, by improving tumor oxygenation, may increase the efficacy of standard radiotherapy in anemic animals and may be of use in anemic tumor patients in whom the success of radiotherapy or O2-dependent chemotherapy might be limited by tumor hypoxia.

The cochlear aqueduct is a route for direct pressure transfer between intracranial and intracochlear fluids. In patients with Menière's disease, intracochlear pressure is presumably disturbed. The "Tympanic Membrane Displacement Analyser (TDA)" is a new system which provides a useful noninvasive method of detecting intracranial and intracochlear pressure changes.In this study TDA measurements in combination with a glycerol test were performed in nine patients with Menière's disease and in seven normal persons.Before ingestion of glycerol, no significant difference in pressure was found between the two groups. After ingestion of glycerol a temporary decrease in intracochlear pressure was detected in both groups without any significant difference between the two groups.These results show that the combination of glycerol testing and TDA measurements does not seem to be helpful for the differential diagnosis of Menière's disease.

Several studies using different methods of pO2 measurement have shown that in many tumor entities tissue oxygenation is quite heterogeneous and thus cannot be sufficiently described by a single value. This study presents those distribution parameters which are mandatory to describe the complete oxygenation status of a solid tumor.In determining the oxygenation status different aspects of relevancy have to be taken into account. First, several parameters are necessary to characterize the location, the spread, and the shape of the pO2 distribution from a statistical point of view (statistical parameters). In addition, parameters for the description of the biological relevance of the tumor oxygenation have to be considered (biological parameters). These parameters reflect the role of oxygenation for the metabolic microenvironment and the biological behavior of the tumor as well as the significance under therapeutic and diagnostic aspects. Finally, some parameters are necessary to assess the quality of pO2 measurement itself (quality parameters).By combining all pO2 readings from one tumor a statistical distribution is obtained, which is in many tumors asymmetrically shifted towards low pO2 values. In order to describe the location, spread, and shape of this distribution the following parameters should be stated: median, mean, 10% and 90% percentile, minimum, maximum and 10 to 90% interpercentile range. For data presentation these values can be combined in a box-whiskers plot. In order to reflect the importance of tumor oxygenation under diagnostic, therapeutic or cell-biological aspects the fraction of pO2 readingsor = 2.5 mm Hg,or = 5 mm Hg, andor = 10 mm Hg should be stated. Where negative pO2 readings occur in a study, the fraction of pO2 readings0 mm Hg as well as the most negative pO2 value should be presented in order to assess the quality of the pO2 measurement.For a comprehensive description of the oxygenation status of solid tumors the following distribution parameters should be stated: median, mean, 10% and 90% percentile, minimum, maximum, 10 to 90% interpercentile range, fraction of pO2 readings0 mm Hg,or = 2.5 mm Hg,or = 5 mm Hg, andor = 10 mm Hg as well as the most negative pO2 reading.

The effect of inhibiting DNA synthesis on the cellular O2 consumption rate of tumor cells (DS sarcoma) in vivo was analyzed using a photometric technique. Five days after DS-sarcoma ascites was induced in SD rats, animals were treated either with fludarabine (400 mg/kg i.p., 6 h prior to measurements) or lovastatin (3 x 20 mg/kg i.p., 24, 15, and 3 h prior to measurements), drugs that can inhibit tumor cell proliferation. In addition to cellular O2 consumption, the cell cycle distribution and the fraction of DNA-synthesizing cells in the tumor ascites were measured. Both drugs lowered DNA synthesis significantly, an effect that was more pronounced with fludarabine. The cellular O2 consumption rate following lovastatin application was significantly impaired (approximately 33%), whereas fludarabine had practically no effect on the respiration rate of tumor cells. From these data, it is concluded that a reduction in DNA synthesis does not necessarily result in a decrease in the O2 consumption rate of tumor cells in vivo.

Intracranial pressure is transmitted to the perilymph of the cochlea via the cochlear aquaeduct and via Reissner's membrane to the endolymph. The "Tympanic Membrane Displacement Analyser (TDA)" is a new device that may be a useful non-invasive method to show intracranial and intracochlear pressure changes indirectly measured by tympanic membrane displacement during stapedial reflex contraction. The TDA was utilised in 20 normal persons and in 29 patients with unilateral diseases of the inner ear. No significant differences in the tympanic membrane displacement were found between patients with sensorineural hearing loss, patients with Ménière's disease, and normal persons.

Arterial oxygen partial pressure decreases during hemodialysis if acetate as buffer is used or if certain types of bioincompatible dialyzer membranes are used. Several hypotheses considering the main cause of this hypoxemia have been proposed. To gain more insight into the mechanisms leading to this hypoxemia, a mathematical model for the computerized simulation of exchange processes during hemodialysis has been used. To simulate the ventilation-perfusion ratio (VA/Q), a simplified two-compartment model of the lung has been applied. The simulation results reveal that hypoxemia during hemodialysis has two reasons. In acetate hemodialysis, the main cause is a shift of the CO2-bicarbonate equilibrium caused by "consumption" of hydrogen ions during acetate metabolization resulting in hypoventilation due to a decrease in CO2 partial pressure. During hemodialysis with bioincompatible dialyzer membranes, the hypoxemia may be explained by an increase in inhomogeneity of the VA/Q ratio in the lung. The loss of CO2 and bicarbonate into the dialysate during acetate hemodialysis has only a minor effect on arterial PO2 and cannot explain the observed hypoxemia. The decrease of O2 diffusing capacity during hemodialysis with bioincompatible membranes has only a negligible effect on the arterial PO2. The simulation results show also that the venous PO2 in the brain may fall below a critical level of less than 25 mm Hg, thereby possibly causing oxygen deficiency in the cortex.

The present model for the mathematical description of exchange processes during hemodialysis includes submodels for potassium, sodium, chloride, acetate, acid-base status (with CO2, bicarbonate and H(+)-ions), water distribution, oxygen, ventilation, and the uremic catabolites urea, creatinine, and vitamin B12. For potassium, sodium and urea a 2-compartment model is used consisting of the extra- and the intracellular space. For chloride, creatinine and vitamin B12 a 3-compartment model is necessary. For the description of acetate kinetics a 1-compartment model consisting of the extracellular space is sufficient. For description of the acid-base balance the model includes three submodels for CO2, bicarbonate, and hydrogen ions. All submodels are made of eight compartments, namely the intracellular and the interstitial space as well as six spaces for the blood. The three submodels are coupled to each other by the chemical reaction of CO2 to HCO3- and a H(+)-ion. Besides this reaction the diffusive exchange between the compartments, the convective transport with the blood and the elimination through the dialyzer and the lung for the molecules and ions are considered. Because of the strong buffer capacity of plasma and intracellular proteins, the functional compartments for hydrogen ions are larger than the anatomical spaces. Also the influence of extracellular pH on the electrolyte distribution at the cell membrane has been considered. With this model, which will be adapted to the patient by more than 45 individual parameters, the mass transfer and the course of concentrations during hemodialysis therapy can be reproduced adequately. Further on the values of some unknown parameters, such as the metabolic rate for acetate in the organism, can be estimated by varying the parameters systematically for several runs of the computer simulation until the simulation results are optimally fitted to measured data.

Tumor hypoxia is an important factor limiting the efficacy of sparsely ionizing radiation and O2-dependent chemotherapy.Because the tumor pO2 is the result of a dynamic steady state between oxygen supply and O2 consumption of the tumor cells,hypoxia could be reduced by improving the O2 supply for instance by breathing hyperoxic gas mixtures to increase the arterial oxygen partial pressure. This technique seems to be the most effective method to improve tumor oxygenation, and thus to enhance the efficacy of standard radiotherapy and chemotherapy in experimental malignancies, as well as in human tumors. However, the role of varying inspiratory pCO2 on tumor oxygenation has been discussed controversially. Although carbogen (95% O2 + 5% CO2) is used in the clinical setting, it remains unclear whether the beneficial therapeutic effects are more pronounced than with pure oxygen. Because insome tumor entities oxygenation is inadequate and anisotropic, normobaric hyperoxia is often not sufficient to completely eradicate tumor hypoxia. In these cases, breathing of hyperoxic gases under hyperbaric conditions (2-3 atm) may be sufficient to lead to therapeutic results. However, studies on experimental tumors in animals as well as clinical trials in patients showed nonuniform results concerning the therapeutic benefit of hyperbaric hyperoxia, depending on the tumor entity, site of growth, or tumor vascularization. Especially, squamous cell carcinomas of the head and neck region seem to benefit from additional HBO therapy during radiotherapy, although several technical problems of irradiation during hyperbaric conditions are presently not satisfactorily resolved.