On the ovary development in queenless worker bees (Apis mellifica L.)

Zusammenfassung Gruppen von 50 Jungbienen wurden in kleinen Versuchskäfigen im Thermostaten bei 30°C gehalten und mit Zuckerteig + 15% Pollen gefüttert. Bei Anwesenheit einer Königin entwickelten sich ihre Ovarien nicht. Ohne Königin waren jedoch die Ovarien bei Tötung nach 3 Wochen deutlich entwickelt. Die hemmende Wirkung geht nicht nur von der lebenden Königin aus: auch bei Anwesenheit einer toten Königin unterbleibt die Ovarienentwicklung. Es genügte sogar bloss deren Kopf oder Abdomen; der Thorax hingegen war nicht deutlich wirksam. Für das Zustandekommen der hemmenden Wirkung ist direkter Kontakt jeder einzelnen Arbeiterin mit der Königin bzw. deren erwähnten Körperteilen erforderlich. Mit Alkohol oder Azeton extrahierte Königinnen waren unwirksam; nach Imprägnierung mit der Extraktflüssigkeit wirkten sie wieder hemmend.Aus den Versuchen scheint somit hervorzugehen, dass die Entwicklung der Arbeiterinnen-Ovarien normalerweise deshalb unterbleibt, weil jede einzelne Arbeiterin in direktem Kontakt vom Körper der Königin eine Substanz aufnimmt, welche die Ovarienentwicklung hemmt.     

The Fanconi anaemia gene FANCF encodes a novel protein with homology to ROM

Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder with locus heterogeneity. None of the 'responsible' genes have previously been identified. Some BBS cases (approximately 10%) remain unassigned to the five previously mapped loci. McKusick-Kaufma syndrome (MKS) includes hydrometrocolpos, postaxial polydactyly and congenital heart disease, and is also inherited in an autosomal recessive manner. We ascertained 34 unrelated probands with classic features of BBS including retinitis pigmentosa (RP), obesity and polydactyly. The probands were from families unsuitable for linkage because of family size. We found MKKS mutations in four typical BBS probands (Table 1). The first is a 13-year-old Hispanic girl with severe RP, PAP, mental retardation and obesity (BMI >40). She was a compound heterozygote for a missense (1042GA, G52D) and a nonsense (1679TA, Y264stop) mutation in exon 3. Cloning and sequencing of the separate alleles confirmed that the mutations were present in trans. A second BBS proband (from Newfoundland), born to consanguineous parents, was homozygous for two deletions (1316delC and 1324-1326delGTA) in exon 3, predicting a frameshift. An affected brother was also homozygous for the deletions, whereas an unaffected sibling had two normal copies of MKKS. Both the proband and her affected brother had RP, PAP, mild mental retardation, morbid obesity (BMI >50 and 37, respectively), lobulated kidneys with prominent calyces and diabetes mellitus (diagnosed at ages 33 and 30, respectively). A deceased sister (DNA unavailable) had similar phenotypic features (RP with blindness by age 13, BMI >45, abnormal glucose tolerance test and IQ=64, vaginal atresia and syndactyly of both feet). Both parents and the maternal grandfather were heterozygous for the deletions. Genotyping with markers from the MKKS region confirmed homozygosity at 20p12 in both affected individuals.     

Histidine-induced injury to cultured liver cells,effects of histidine derivatives and of iron chelators

The amino acid histidine is an excellent buffer and is therefore included in several organ preservation solutions used in transplantation medicine. However, when used at concentrations as in these solutions, histidine has a marked injurious potential. Therefore, we here assessed the mechanism of histidine-induced cell injury and searched for ways to use the buffering power of histidine but avoid histidine toxicity. When cultured hepatocytes were incubated in HTK solution or in modified Krebs-Henseleit buffer containing 198 mM L-histidine at 37°C, most cells lost viability within 3 h (LDH release 86 ± 7% and 89 ± 5%, respectively). This injury was accompanied by marked lipid peroxidation, and was strongly inhibited by hypoxia, by the antioxidants trolox, butylated hydroxytoluene and N-acetylcysteine and by the membrane-permeable iron chelators 2,2′-dipyridyl, 1,10-phenanthroline, LK 614, LK 616 and deferoxamine. Thus, histidine-induced cell injury appears to be mediated by an iron-dependent formation of reactive oxygen species. D-Histidine, imidazol and L-histidine methyl ester also elicited marked injury, while the N-substituted derivatives Nα-acetyl-L-histidine and tert-butyl-oxycarbonylhistidine and histidine-containing dipeptides showed almost no toxicity. Histidine toxicity, its iron dependence and the superiority of Nα-acetyl-L-histidine were also evident during/after cold (4°C) incubations. Therefore, we suggest the addition of iron chelators to histidine-containing solutions, and/or replacing histidine with Nα-acetyl-L-histidine in organ preservation solutions. Received 23 October 2006; accepted 21 November 2006     

Cardiovascular development: towards biomedical applicability

During cardiogenesis, the epicardium grows from the proepicardial organ to form the outermost layer of the early heart. Part of the epicardium undergoes epithelial-mesenchymal transformation, and migrates into the myocardium. These epicardium-derived cells differentiate into interstitial fibroblasts, coronary smooth muscle cells, and perivascular fibroblasts. Moreover, epicardium-derived cells are important regulators of formation of the compact myocardium, the coronary vasculature, and the Purkinje fiber network, thus being essential for proper cardiac development. The fibrous structures of the heart such as the fibrous heart skeleton and the semilunar and atrioventricular valves also depend on a contribution of these cells during development. We hypothesise that the essential properties of epicardium-derived cells can be recapitulated in adult diseased myocardium. These cells can therefore be considered as a novel source of adult stem cells useful in clinical cardiac regeneration therapy.     

Aspects of Aristotelian statics in Galileo's dynamics

This paper examines geometrical arguments from Galileo's Mechanics and Two New Sciences to discern the influence of the Aristotelian Mechanical Problems on Galileo's dynamics. A common scientific procedure is found in the Aristotelian author's treatment of the balance and lever and in Galileo's rules concerning motion along inclined planes. This scientific procedure is understood as a development of Eudoxan proportional reasoning, as it was used in Eudoxan astronomy rather than simply as it appears in Euclid's Elements. Topics treated include the significance of the circle in Galileo's demonstrations, the substitution of rectilinear elements for heterogeneous factors like weight and curvilinear distance, and the way in which elements of a motion are used to measure other elements of the same motion. The indirectness of Galileo's proofs, his conception of speed as relative and comparative, and the meaning of his concept of moment all come into clearer focus. Conclusions are drawn about Galilean idealization, and also about the contrast of literal versus figural modes of explanation in Galileo's science.