Increased drug cytotoxicity at reduced pH counteracts cyclophosphamide resistance in cultured rat mammary carcinoma cells

The sensitivity of a cyclophosphamide (CP)-resistant MIR rat mammary carcinoma cell variant (MIRCPr) in monolayer culture towards the cytotoxic effect of mafosfamide (an analogue of "activated" CP) was measured as a function of extracellular pH (pHe). An inverse correlation was found between cell survival and the H+ ion concentration in the culture medium. At pHe 7.4, the fraction of clonogenic MIRCPr cells exposed to mafosfamide (7.5 micrograms/ml) for 24 hr was 1 X 10(-1) in relation to untreated control cells. At pHe 6.2, however, this value was reduced to 3 X 10(-4), i.e., a value equal to that for the CP-sensitive parental MIR cells exposed to the same concentration of mafosfamide at pHe 7.4. Our data indicate complete compensation of CP resistance in MIRCPr cells at pHe 6.2. MIRCPr cells were not resistant to the cytotoxic effect of nornitrogen mustard. This suggests that resistance to CP in MIRCPr cells is due to enzymatic inactivation of the primary intermediates in CP bioactivation. The alkylating activity of nornitrogen mustard (and less so that of phosphoramide mustard) is strongly enhanced at low pH. In MIRCPr cells shifted to an acidic environment, therefore, a (putative) decrease in the intracellular concentration of alkylating CP metabolites may be counteracted by an enhancement of their alkylating activity (on a molar basis). By parenteral administration of glucose, the pH in malignant tumors of both animal and human origin can be lowered to values between 5.6-6.6. Our data suggest that an upshift of H+ ion concentration in malignant tissues may at least partially counteract CP resistance in cancer cells in vivo.     

Rationale for clinical trials of opiate antagonists in treating patients with personality disorders and self-injurious behavior

A subgroup of patients with personality disorders from the DSM-III-R (American Psychiatric Association 1987) "flamboyant" cluster is characterized by repetitive self-injurious behavior (SIB) apparently not motivated by suicidal intent. After describing the clinical and demographic characteristics of these patients, the clinical and preclinical evidence suggesting the involvement of endogenous opiate systems in this behavior is reviewed. Patients with personality disorders and SIB have been found to have elevated levels of plasma beta-endorphin. However, the available evidence is not sufficient to show whether this is a cause of or a consequence of SIB. Behavioral stereotypies resulting in self-injury in animals and SIB in mentally retarded patients have been shown to be abolished by opiate antagonist administration in a significant proportion of both groups. The available evidence suggests that clinical trials of oral opiate antagonist drugs should be undertaken because of the promise such drugs have in the treatment of this sometimes life-threatening disorder.     

IL-18 induces the differentiation of Th1 or Th2 cells depending upon cytokine milieu and genetic background

The functional division of CD4(+) T cells into Th1 and Th2 subsets is generally accepted but the mechanisms leading to their preferential induction remain elusive. Cytokines are considered the main determining factors in the initial differentiation of precursor T cells into these distinct subsets. Thus, IL-12 drives Th1 cells whereas IL-4 drives Th2 cells. Recently IL-18, originally designated as IFN-gamma-inducing factor, has been reported to synergize with IL-12 in the induction of Th1 cells. We report here that IL-18 can also induce T cells to differentiate into Th2 cells, in the presence of TCR activation, either alone or together with IL-4. This effect of IL-18 is mediated primarily on CD4(+) T cells compared with CD8(+) T cells and is inhibited in the presence of IL-12. IL-18, however, has no effect on functionally committed Th2 cells.( )Moreover, the effect of IL-18 on Th2 cell development is differentially manifest in different mouse strains, suggesting profound underlying genetic influences. BALB/c mice infected with Leishmania major and treated with recombinant IL-18 developed exacerbated disease and enhanced Th2 response compared with untreated controls. These data therefore provide a novel mechanism for Th2 cell development. Thus, IL-18, a cytokine constitutively expressed by cells of the innate response, is capable of inducing Th2 cell differentiation in the absence of IL-4.     

Targeted disruption of hepatic frataxin expression causes impaired mitochondrial function, decreased life span and tumor growth in mice

We have disrupted expression of the mitochondrial Friedreich ataxia protein frataxin specifically in murine hepatocytes to generate mice with impaired mitochondrial function and decreased oxidative phosphorylation. These animals have a reduced life span and develop multiple hepatic tumors. Livers also show increased oxidative stress, impaired respiration and reduced ATP levels paralleled by reduced activity of iron-sulfur cluster (Fe/S) containing proteins (ISP), which all leads to increased hepatocyte turnover by promoting both apoptosis and proliferation. Accordingly, phosphorylation of the stress-inducible p38 MAP kinase was found to be specifically impaired following disruption of frataxin. Taken together, these findings indicate that frataxin may act as a mitochondrial tumor suppressor protein in mammals.     

Serotoninbestimmungen an Thrombocyten und an Fraktionen von Thrombocyten

Zusammenfassung Aus Suspensionen zerstörter Thrombocyten des Menschen wurden reine Fraktionen von Hyalomer und Granulomer hergestellt. Von den Fraktionen wurde jeweils ein Teil für die elektronenmikroskopische Untersuchung, ein anderer Teil für die Bestimmung des Serotonins verwandt. Durch die elektronenmikroskopische Untersuchung jeder einzelnen Fraktion wurde die Reinheit der Fraktionen überprüft. Die Bestimmung des Serotoningehaltes erfolgte am isolierten Rattenmagen. In Kontrollversuchen wurde ferner der Serotoningehalt intakter Thrombocyten bestimmt.Intakte Thrombocyten besitzen im Mittel einen Serotonin-Gehalt von 52 ng/10⁸ Thrombocyten. In den Fraktionierungsversuchen fanden wir 95% des Serotonins in den Hyalomer-Fraktionen und nur 5% des Serotonins in den Granulomer-Fraktionen. In vivo findet sich also der hohe Serotoningehalt fast ausschließlich im Hyalomer der Thrombocyten.

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Summary Pure fractions of hyalomer and granulomer were prepared from suspensions of destroyed human thrombocytes. One portion of the fractions was used for the electron microscopic studies, and the other part for the determination of serotonin (5-hydroxytryptamine). The electron microscopic investigation allowed to check the purity of each single fraction. On the isolated rat stomach the determination of the concentration of serotonin was performed. In control preparations we studied the serotonin concentration of intact thrombocytes. These thrombocytes have a mean serotonin concentration of 52 ng/10⁸ platelets. In fractioning experiments we found 95% of the serotonin in the hyalomer fractions and only 5% of the serotonin in the granulomer fractions. In vivo therefore, the high concentration of the serotonin is found almost exclusively in the hyalomer of the thrombocytes.

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Die Ergebniss wurden vor der Medizinischen Gesellschaft Düsseldorf am 23. 1. 1963 mitgeteilt. Herrn Prof. Dr.Meessen danken wir für die Anregung und Förderung der Arbeit, Herrn Prof. Dr.Greeff für die Hilfe bei den Serotoninbestimmungen.     

Localization of corticotropin-releasing activity in the rat hypothalamus

Hypothalamic nuclei were removed from frozen sections of rat brain and examined for their corticotropin-releasing activity. The highest concentration was measured in the median eminence. In addition there was significantly more activity detected in the nuclei paraventricularis, supraopticus, suprachiasmaticus and arcuatus than in the other nuclei.     

CXCR4 and Gab1 cooperate to control the development of migrating muscle progenitor cells

Long-range migrating progenitor cells generate hypaxial muscle, for instance the muscle of the limbs, hypoglossal cord, and diaphragm. We show here that migrating muscle progenitors express the chemokine receptor CXCR4. The corresponding ligand, SDF1, is expressed in limb and branchial arch mesenchyme; i.e., along the routes and at the targets of the migratory cells. Ectopic application of SDF1 in the chick limb attracts muscle progenitor cells. In CXCR4 mutant mice, the number of muscle progenitors that colonize the anlage of the tongue and the dorsal limb was reduced. Changes in the distribution of the muscle progenitor cells were accompanied by increased apoptosis, indicating that CXCR4 signals provide not only attractive cues but also control survival. Gab1 encodes an adaptor protein that transduces signals elicited by tyrosine kinase receptors, for instance the c-Met receptor, and plays a role in the migration of muscle progenitor cells. We found that CXCR4 and Gab1 interact genetically. For instance, muscle progenitors do not reach the anlage of the tongue in CXCR4;Gab1 double mutants; this target is colonized in either of the single mutants. Our analysis reveals a role of SDF1/CXCR4 signaling in the development of migrating muscle progenitors and shows that a threshold number of progenitor cells is required to generate muscle of appropriate size.     

Histopathological studies on the local reactions induced by complete Freund's adjuvant (CFA), bacterial lipopolysaccharide (LPS), and synthetic lipopeptide (P3C) conjugates

The inflammatory reactions following subcutaneous application of adjuvants revealed characteristic pathological patterns. The injection of complete Freund's adjuvant (CFA) resulted in the formation of large lipid deposits encircled by an inflammatory reaction and concentrically arranged collagen bundles. Bacterial lipopolysaccharide (LPS) caused granulomatous aggregations of mononuclear cells with thrombotic vessel occlusions. Inoculation of the lipopeptide adjuvants induced accumulation of mononuclear cells with only minimal fibrotic changes which were resolved after day 28. Lipopeptide conjugates based on the head group tripalmitoyl-S-glyceryl-cysteinyl-serin (P3CS) can thus be used as effective immunogens and adjuvants without long-term tissue damage.