Kritische Phasen der Musterbildung in der Frühentwicklung des Menschen

Ohne ZusammenfassungVortrag anläßlich der Schlußsitzung der 103. Versammlung Deutscher Naturforscher und Ärzte in Weimar am 9. 10.64.Frau Prof.Paula Hertwig zum 75. Geburtstag zugeignet.     

Late Aspergillus fumigatus endomyocarditis with brain abscess as a lethal complication after heart transplantation.

We report the case of a 65-year-old male patient who died from lethal Aspergillus fumigatus endomyocarditis and multiple cerebral septic emboli 6 months after cardiac transplantation. This complication developed 4 weeks after diagnosis of bilateral pulmonary aspergillosis, which was immediately treated by surgical removal and intravenous amphotericin B. Preceding colonization with Aspergillus spp was not identified. Primary cytomegalovirus infection (donor+/recipient-) and toxoplasmosis reactivation (donor+/recipient+) occurring at 1 and 2 months post-transplantation were successfully treated.     

Impact of acute and chronic sodium loading on atrial natriuretic peptide and renin in man

The relationship between the renin-angiotensin system and the atrial natriuretic peptide and its contributions to the control of sodium balance is not clarified. We therefore studied plasma renin concentration (PRC) and plasma levels of atrial natriuretic peptide (ANP) in normal subjects during acute and chronic salt loading. Acute intravascular volume expansion by iv infusion of 2000 ml of normal saline resulted in sharp rise in plasma ANP from 122 +/- 24 to 405 +/- 141 pg/ml (p less than 0.05). This increase was only transient with plasma ANP returning to control levels after 240 min. In contrast, reduction in plasma renin concentration was less pronounced, however it was persistent for up to 240 min paralleled by a reduction in plasma protein. Reciprocal changes in ANP plasma levels and PRC were observed during dietary modification in sodium intake. At the end of low sodium diet over 4 days, supine plasma ANP averaged 49 +/- 7 pg/ml and levels increased to 128 +/- 38 pg/ml after 6 days of high sodium intake in 11 healthy subjects (p less than 0.05). In contrast, PRC values averaged 69.8 +/- 19.8 microU/ml and 14.4 +/- 6.5 microU/ml during low and high sodium diet respectively (p less than 0.01). The inverse relation between PRC and ANP was seen after prolonged dietary sodium loading over 15 days in 8 additional subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Different mechanisms of l-arginine induced dilation of brain arterioles in normotensive and hypertensive rats

We evaluated the response of pial arterioles to l-arginine in anesthetized normotensive rats and spontaneously hypertensive rats equipped with a closed cranial window. Topical application of 10⁻⁶ − 10⁻⁴ mol/l l-arginine, which is known to be the endogenous substrate for the synthesis of nitric oxide, induced dose-dependent arteriolar vasodilation. The response was more pronounced in hypertensive than in normotensive rats (at the concentration of 10⁻⁴ mol/l l-arginine: 18.3 ± 3.3% vs. 6.7 ± 1.7%, respectively, means ± S.E.). The stereoisomer d-arginine had no effect in hypertensive rats. Topical application of the nitric oxide synthase inhibitor N-nitro-l-arginine converted l-arginine-induced dilation to constriction in normotensive and hypertensive rats. The cyclooxygenase inhibitor indomethacin (5 μg/ml cerebrospinal fluid) also blocked the dilation in both strains. Photochemical endothelial injury blocked l-arginine-induced dilation in normotensive rats, but only partly antagonized the response in hypertensive animals. Intravenous or topical pretreatment with the free radical scavenger superoxide dismutase significantly reduced the dilating response to 10⁻⁴ mol/l l-arginine in hypertensive rats. Superoxide dismutase did not significantly change the response to l-arginine in normotensive animals. It is concluded that nitric oxid formation in the endothelium and liberation of cyclooxygenase products cause l-arginine-induced dilation in normotensive rats. While nitric oxide and cyclooxygenase products are also involved in l-arginine-induced dilation in spontaneously hypertensive rats, superoxide radicals contribute to the enhanced response in this strain. This mechanism appears to be specific for the hypertensive animals and is only partly dependent on an intact endothelium.     

Resveratrol Potentiates Growth Inhibitory Effects of Rapamycin in PTEN-deficient Lipoma Cells by Suppressing p70S6 Kinase Activity

Patients with phosphatase and tensin homolog (PTEN) hamartoma tumor syndrome and germline mutations in PTEN frequently develop lipomatosis, for which there is no standard treatment. Rapamycin was shown to reduce the growth of lipoma cells with heterozygous PTEN deficiency in vitro, but concomitantly induced an upregulation of AKT phosphorylation. Since it was shown that resveratrol stabilizes PTEN, we asked whether co-incubation with resveratrol could suppress the rapamycin-induced AKT phosphorylation in PTEN-deficient lipoma cells.

Resveratrol incubation resulted in decreased lipoma cell viability by inducing G1-phase cell cycle arrest and apoptosis. PTEN expression and AKT phosphorylation were not significantly changed, whereas p70S6 kinase (p70S6K) phosphorylation was reduced in PTEN-deficient lipoma cells after resveratrol incubation. Rapamycin/resveratrol co-incubation significantly decreased viability further at lower doses of resveratrol and resulted in decreased p70S6K phosphorylation compared to rapamycin incubation alone, suggesting that resveratrol potentiated the growth inhibitory effects of rapamycin by reducing p70S6K activation. Both viability and p70S6K phosphorylation of primary PTEN wild-type preadipocytes were less affected compared to PTEN-deficient lipoma cells by equimolar concentrations of resveratrol. These results support the concept of combining chemopreventive natural compounds with mammalian target of rapamycin (mTOR) inhibitors to increase the efficacy of chemotherapeutic drugs for patients suffering from overgrowth syndromes.     

Neuronal profilins in health and disease: Relevance for spine plasticity and Fragile X syndrome

Learning and memory, to a large extent, depend on functional changes at synapses. Actin dynamics orchestrate the formation of synapses, as well as their stabilization, and the ability to undergo plastic changes. Hence, profilins are of key interest as they bind to G-actin and enhance actin polymerization. However, profilins also compete with actin nucleators, thereby restricting filament formation. Here, we provide evidence that the two brain isoforms, profilin1 (PFN1) and PFN2a, regulate spine actin dynamics in an opposing fashion, and that whereas both profilins are needed during synaptogenesis, only PFN2a is crucial for adult spine plasticity. This finding suggests that PFN1 is the juvenile isoform important during development, whereas PFN2a is mandatory for spine stability and plasticity in mature neurons. In line with this finding, only PFN1 levels are altered in the mouse model of the developmental neurological disorder Fragile X syndrome. This finding is of high relevance because Fragile X syndrome is the most common monogenetic cause for autism spectrum disorder. Indeed, the expression of recombinant profilins rescued the impairment in spinogenesis, a hallmark in Fragile X syndrome, thereby linking the regulation of actin dynamics to synapse development and possible dysfunction.The immense computational power of the central nervous system depends on the formation of functional neuronal networks, which are further refined and adapted to environmental changes by processes of neuronal plasticity throughout the entire life span of an individual. The majority of synapses in highly plastic regions, such as the neocortex and hippocampus, are located at dendritic spines, tiny protoplasmatic membrane protrusions that build the postsynaptic compartment. Changes in spine shape are directly associated with the dynamic actin cytoskeleton, which is highly enriched in dendritic spines (1–6). In fact, up to 80% of actin filaments turn over in less than 2 min in the spine head (7). Hence, an understanding of the detailed molecular machinery and identification of key molecules that control actin polymerization in space and time will help to reveal details of spine function and plasticity, and might eventually also provide a better understanding of neurological disorders characterized by defects in spinogenesis and spine maintenance (8, 9).The small actin-binding protein profilin—present in the mammalian CNS in two different isoforms, profilin1 (PFN1) and profilin2a (PFN2a) (10)—has been described as such a promising candidate because its activity-dependent translocation into dendritic spines could be shown both in vitro and in vivo (11–13). However, recent studies exploiting knockout animals for either PFN1 or PFN2a demonstrated a surprising lack of a spine phenotype for both isoforms (14, 15). One explanation might reside in the crucial importance of tightly restricted actin dynamics for virtually all aspects of neuronal function that might be preserved in knockout animals by means of compensational effects acting on the expression or regulation of other actin-binding molecules. This theory is supported by work from our group showing that an acute knockdown of PFN2a actually revealed an important function in dendritic spines (16).In this study, we took advantage of an acute interference RNA (RNAi)-mediated loss-of-function approach, which allowed us to provide evidence that despite the fact that profilins are biochemically very similar, the two brain isoforms perform astonishingly diverse functions. Our results indicate that the ubiquitous isoform PFN1 is of great importance for spine formation. Furthermore, we can show that the expression of PFN1 is developmentally down-regulated in the hippocampus. In contrast to this, we found the evolutionary most-recent and brain-specific isoform PFN2a to be involved in synapse function, spine stabilization, and activity-dependent structural plasticity. Most notably, both isoforms were differentially engaged in regulating actin dynamics in dendritic spines. In line with a role of PFN1 for spine formation during development, we provide evidence that, of the brain profilin isoforms, only the mRNA of PFN1, comparable to the Drosophila homolog chickadee (17), is bound by the Fragile X mental retardation protein (FMRP). Similarly, PFN1 but not PFN2a levels were altered in the mouse model of the neurodevelopmental disorder Fragile X syndrome (FXS), a hallmark of which is an apparent defect in spine formation and maturation (18–20).Our results therefore point toward intriguingly different functions of profilin isoforms in the brain with a juvenile expression profile, indicating a major role of PFN1 during spinogenesis and a mature expression profile favoring PFN2a as the predominant isoform crucial for spine stabilization, synaptic function, and spine plasticity.     

Cytotoxicity of carbon nanohorns in different human cells of the respiratory system

ABSTRACT

One of the new synthetic carbon-based nanomaterials is carbon nanohorns (CNH). A potential risk for employees of production processes is an unintentional intake of these nanomaterials via inhalation. Once taken up, nanoparticles might interact with cells of different tissues as well as with intercellular substances. These interactions may have far-reaching consequences for human health. Currently, many gaps in available information on the CNH toxicological profile remain. The aim of this study was to determine the cytotoxicity of CNH particles on human epithelial cells of the respiratory system with special consideration given to different particle sizes. In all cell lines, cell viability was reduced after 24 h of exposure up to 60% and metabolic activity as evidenced by mitochondrial activity was lowered to 9% at a concentration of 1 g/L. The three respiratory cell lines differed in their sensitivity. The most robust cells were the bronchial epithelial cells. Further, particle size fractions induced different adverse effect strength, whereby no correlation between particle size fraction and toxicity was found. These findings demonstrate the need for further information regarding the behavior and effect strength of nanomaterial. To avoid the production of new harmful materials, a more comprehensive integration of results from toxicity studies in the development processes of engineered nanomaterials is recommended not only from an occupational viewpoint but also from an environmental perspective.     

Adenosine 5'-tetraphosphate is a highly potent purinergic endothelium-derived vasoconstrictor

Besides serving as a mechanical barrier, the endothelium has important regulatory functions. The discovery of nitric oxide revolutionized our understanding of vasoregulation. In contrast, the identity of endothelium-derived vasoconstrictive factors still remains uncertain. The supernatant from mechanically stimulated human microvascular endothelial cells elicited a potent vasoconstrictive response in the isolated perfused rat kidney. Whereas a nonselective purinoceptor blocker blocked this vasoactivity most potently, the inhibition of the endothelin receptor by BQ123 weakly affected that vasoconstrictive response. As a compound responsible for that vasoconstrictive effect, we have isolated from HMECs and identified the mononucleotide adenosine 5'-tetraphosphate (AP4). This nucleotide proved to be the most potent vasoactive purinergic mediator identified to date, exerting the vasoconstriction predominantly through activation of the P2X1 receptor. The intraarterial application of AP4 in a Wistar-Kyoto rat induced a strong increase of the mean arterial pressure. The plasma concentration of AP4 is in the nanomolar range, which, in vivo, induces a significant change in the mean arterial pressure. To our knowledge, AP4, which exerts vasoactive effects, is the most potent endogenous mononucleotide identified to date in mammals. The effects of AP4, the plasma concentration of AP4, and its release suggest that this compound functions as an important vasoregulator.