Sterols and sterol biosynthesis in the slugAplysia depilans

Zusammenfassung Aplysia depilans ist fähig, Lipide, einschliesslich der Sterinen, aus Azetat zu synthetisieren. Cholesterin ist das wichtigste Sterin (87%), aber auch andere Sterine, bisher bei Opisthobranchia unbekannt, wurden gefunden.     

A microscopic film of the movements of bull sperm cells in dark-field illumination

Zusammenfassung Eine Anordnung zur kinematographischen Aufnahme von Spermien von Musterbullen in Dunkelfeldbeleuchtung wird beschrieben. Die Bildfolge von 50 Aufnahmen je Sekunde erfordert eine Lichtquelle von etwa 0,8 kW, welche von einer Spezial-Elektronenblitzlampe geliefert wird.     

From parasympathomimetics to parasympatholytics by homologous substitution

Zusammenfassung Auf Grund der theoretischen Befunde war zu erwarten, dass Änderungen an der negativen und positiven Seite der Dioxolan-Verbindung 2249 F zu graduellen Übergängen von Parasympathikomimetika zu Parasympathikolytika führen würden. Die Experimente bestätigten die Erwartungen vollauf.Untersuchung homologer Reihen von Alkyltrialkylammonium-Verbindungen zeigte die negative Gruppe als nicht wesentlich für die parasympathische Wirkung und ergab ebenso einen graduellen Übergang von Mimetika zu Lytika.     

Genetically modified photosynthetic antenna complexes with blueshifted absorbance bands.

Light energy for photosynthesis is collected by the antenna system, creating an excited state which migrates energetically 'downhill'. To achieve efficient migration of energy the antenna is populated with a series of pigments absorbing at progressively redshifted wavelengths. This variety in absorbing species in vivo has been created in a biosynthetically economical fashion by modulating the absorbance behaviour of one kind of (bacterio)chlorophyll molecule. This modulation is poorly understood but has been ascribed to pigment-pigment and pigment-protein interactions. We have examined the relationship between aromatic residues in antenna polypeptides and pigment absorption, by studying the effects of site-directed mutagenesis on a bacterial antenna complex. A clear correlation was observed between the absorbance of bacteriochlorophyll a and the presence of two tyrosine residues, alpha Tyr44 and alpha Tyr45, in the alpha subunit of the peripheral light-harvesting complex of Rhodobacter sphaeroides, a purple photosynthetic bacterium that provides a well characterized system for site-specific mutagenesis. By constructing single (alpha Tyr44, alpha Tyr45----PheTyr) and then double (alpha Tyr44, alpha Tyr45----PheLeu) site-specific mutants, the absorbance of bacteriochlorophyll was blueshifted by 11 and 24 nm at 77 K, respectively. The results suggest that there is a close approach of tyrosine residues to bacteriochlorophyll, and that this proximity may promote redshifts in vivo.     

The peripheral myelin gene PMP-22/GAS-3 is duplicated in Charcot-Marie-Tooth disease type 1A.

Charcot-Marie-Tooth disease type 1A (CMT1A) is associated with a DNA duplication at chromosome 17p11.2. In view of the point mutation in the gene for peripheral myelin protein pmp-22/gas-3 in Trembler mice, a murine model for CMT1A, we have analysed whether this gene is altered in CMT1A. Here we show that the human homologue of the murine pmp-22 gene is located within the CMT1A DNA duplication, which is a direct repeat and does not interrupt the coding region of PMP-22. Expression of PMP-22 in CMT1A fibroblasts is similar to expression in control fibroblasts. Increased gene dosage or altered PMP-22 expression in the peripheral nervous system are therefore possible mechanisms by which PMP-22 is involved in CMT1A.     

Cumulative record of motor activity. (A new procedure and its use for the study of central stimulant drugs)

Zusammenfassung Eine Methode zur kumulativen Registrierung spontaner motorischer Aktivität kleiner Tiere wird beschrieben. Die Wirksamkeitsbestimmung aus dem kumulativen Rekord und die analytische Bedeutung der Methode für die Wirkungsweise zentralstimulierender Substanzen wird diskutiert.     

Prevalence of ras gene mutations in human colorectal cancers

A combination of DNA hybridization analyses and tissue sectioning techniques demonstrate that ras gene mutations occur in over a third of human colorectal cancers, that most of the mutations are at codon 12 of the c-Ki-ras gene and that the mutations usually precede the development of malignancy.