Ein Beitrag zur Morphologie der labellaren Marginalborste der Fliegen Calliphora und Phormia

Zusammenfassung Die Marginalborste auf der Marginalleiste der Rüsselscheibe von Calliphora und Phormia ist bei adulten Tieren und reifen Puppen lichtmikroskopisch untersucht worden. Sie besteht aus einer zweilumigen Borste, unter der sich ein Sack mit Sinneszellen und akzessorischen Zellen befindet. Der Sack baut sich aus zwei Hüllen auf, deren innere aus bindegewebigem Perilemm gebildet wird. Distal grenzt das Perilemm an die Basalmembran, proximal zieht es von der Basis des Sackes aus als Nervenscheide in das Labellum, wo es sich mit den Nervenscheiden anderer Marginalborsten vereinigt und an der Basis des Labellums in die Nervenscheide des Labialnerven mündet. Die äußere Hülle des Sackes besteht aus granuliertem Septum, das distal 2–25 unterhalb der Basalmembran endet und proximal die Nervenscheide etwa bis zur Mitte des Labellums eng anliegend überzieht. Dort löst es sich von der Nervenscheide und zieht unter die Basalmembran, unter der es auch im Haustellum und Rostrum vorkommt. Die trichogene Zelle der Marginalborste verschließt den Sack in Höhe der Basalmembran wie ein zugespitzter Korken. Die Membran ihrer Zelle im intrakutikulären Bereich wird beschrieben. Ein Scolops zieht als Fortsetzung vom engen Lumen der Borste durch die trichogene Zelle hindurch in den Sack hinein, wo sein freies Ende distale Nervenfortsätze aufnimmt. Zur Anzahl und Art der Zellen im Sack wird Stellung genommen. Ein Netz aus Fibrillen unbekannter Art um den Kern der Sinneszellen und der Verlauf einer mechanorezeptorischen Faser werden beschrieben. In den Nervenscheiden kommen biund tripolare Zellen mit kurzen Fasern vor, die für Perilemmzellen gehalten werden. Nach Berechnungen über die Anzahl der Sinneszellen je Labellum und nach Querschnitten durch den Labialnerven in Höhe des Haustellums besteht eine Reduktion der afferenten Axone von etwa 1000 Sinneszellen zu rund 250, was einer Reduktion von vier Axonen zu einem einzigen entspricht.Herrn Prof. Dr. R. Stämpfli danke ich sehr für sein großes Interesse und seine Anregungen, Herrn Prof. Dr. B. Hassenstein (Direktor des Instituts für Zoologie der Universität Freiburg) für die kritische Durchsicht des Manuskripts.     

Variegation patterns caused by excision of the maize transposable element Dissociation (Ds) are autonomously regulated by allele-specific Activator (Ac) elements and are not due to trans-acting modifier genes

The Ac elements present in the unstable wxm7 and wx-m9 alleles of maize trigger different patterns of Ds excision in trans. To determine whether this differential regulation is a feature of the Ac alleles themselves or is mediated by genetically distinct factors, maize plants heterozygous for the wx-m7 and wx-m9 alleles were crossed to tester strains homozygous for Ds reporter alleles. Kernels showing the variegation pattern characteristic for the Ac elements carried in the wx-m7 and wx-m9 alleles were found to be present in the ratios expected from the genetic constitution of the strains. The aleurone variegation caused by excision of the Ds reporter element and the endosperm variegation caused by excision of Ac from the wx-m7 and wx-m9 alleles themselves segregated with the original wx-m alleles. In addition, stable Wx and wx derivatives of wx-m9 that have lost Ac no longer exert any trans effect on the wx-m7 allele (and vice versa). Therefore it is concluded that the observed variegation patterns are autonomously determined by specific trans effects of the particular Ac element.     

Ventilation and metabolism among rat strains

Strohl, Kingman P., Agnes J. Thomas, Pamela St. Jean, EvelynH. Schlenker, Richard J. Koletsky, and Nicholas J. Schork. Ventilation and metabolism among rat strains. J. Appl. Physiol. 82(1): 317-323, 1997.We examinedventilation and metabolism in four rat strains with variation in traitsfor body weight and/or blood pressure regulation.Sprague-Dawley [SD; 8 males (M), 8 females (F)], BrownNorway (BN; 10 M, 11 F), and Zucker (Z; 11 M, 12 F) rats were comparedwith Koletsky (K; 11 M, 11 F) rats. With the use of noninvasiveplethysmography, frequency, tidal volume, minute ventilation(E),O₂ consumption, andCO₂ production were derived atrest during normoxia (room air) and during the 5th minute of exposureto each of the following: hyperoxia (100% O₂), hypoxia (10%O₂-balanceN₂), and hypercapnia (7%CO₂-balance O₂). Statistical methods probedfor strain and sex effects, with covariant analysis by body weight,length, and body mass. During resting breathing, strain effects werefound with respect to both frequency (BN, Z > K, SD) and tidal volume(SD > BN, Z) but not to E. Sexinfluenced frequency (F > M) alone. Z rats had higher values forO₂ consumption,CO₂ production, and respiratoryquotient than the other three strains, with no independent effect bysex. During hyperoxia, frequency was greater in BN and Z than in SD orK rats; SD rats had a larger tidal volume than BN or Z rats; Z rats hada greater E than K rats; and M had alarger tidal volume than F. Strain differences persisted duringhypercapnia, with Z rats exhibiting the highest frequency andE values. During hypoxic exposure,strain effects were found to influenceE (SD > K, Z), frequency (BN > K), and tidal volume (SD > BN, K, Z). Body mass was only amodest predictor of E during normoxia, of both E and tidal volume withhypoxia, hypercapnia, or hyperoxia, and of frequency duringhypercapnia. We conclude that strain of rats, more than their body massor sex, has major and different influences on metabolism, the patternand level of ventilation during air breathing, and ventilation duringacute exposure to hypercapnia or hypoxia.

     

Killer-toxin-resistantkre12 mutants ofSaccharomyces cerevisiae: genetic and biochemical evidence for a secondary K1 membrane receptor

TheSaccharomyces cerevisiae killer toxin K1 is a secreted α/β-heterodimeric protein toxin that kills sensitive yeast cells in a receptor-mediated two-stage process. The first step involves toxin binding to β-1,6-d-glucan-components of the outer yeast cell surface; this step is blocked in yeast mutants bearing nuclear mutations in any of theKRE genes whose products are involved in synthesis and/or assembly of cell wall β-d-glucans. After binding to the yeast cell wall, the killer toxin is transferred to the cytoplasmic membrane, subsequently leading to cell death by forming lethal ion channels. In an attempt to identify a secondary K1 toxin receptor at the plasma membrane level, we mutagenized sensitive yeast strains and isolated killer-resistant (kre) mutants that were resistant as spheroplasts. Classical yeast genetics and successive back-crossings to sensitive wild-type strain indicated that this toxin resistance is due to mutation(s) in a single chromosomal yeast gene (KRE12), renderingkrel2 mutants incapable of binding significant amounts of toxin to the membrane. Sincekrel2 mutants showed normal toxin binding to the cell wall, but markedly reduced membrane binding, we isolated and purified cytoplasmic membranes from akrel2 mutant and from an isogenicKre12+ strain and analyzed the membrane protein patterns by 2D-electrophoresis using a combination of isoelectric focusing and SDS-PAGE. Using this technique, three different proteins (or subunits of a single multimeric protein) were identified that were present in much lower amounts in thekre12 mutant. A model for K1 killer toxin action is presented in which the gene product ofKRE12 functions in vivo as a K1 docking protein, facilitating toxin binding to the membrane and subsequent ion channel formation.     

Direct molecular analysis of the fragile X syndrome in a sample of Egyptian and German patients using non-radioactive PCR and Southern blot followed by chemiluminescent detection

Molecular genetic analysis of individuals from 6 Egyptian and 33 German families with fragile X syndrome and 240 further patients with mental retardation was performed applying a completely non-radioactive system. The aim of our study was the development of a non-radioactive detection method and its implementation in molecular diagnosis of the fragile X syndrome. Furthermore, we wanted to assess differences in the mutation sizes between Egyptian and German patients and between Egyptian and German carriers of a premutation. Using non-radioactive polymerase chain reaction (PCR), agarose gel electrophoresis and blotting of the PCR products, followed by hybridisation with a digoxigenin-labelled oligonucleotide probe (CGG)₅ and chemiluminescent detection, we identified the fragile X full mutation (amplification of a CGG repeat in the FMR-1 gene ranging from several hundred to several thousand repeat units) in all patients. We observed no differences in the length of the CGG repeat between the Egyptian and German patients and carriers, respectively. However, in one prenatal diagnosis, we detected only one normal sized allele in a female fetus using the PCR-agarose assay, whereas Southern blot analysis with the digoxigenin labelled probe StB 12.3 revealed presence of a full mutation. Our newly established nonradioactive genomic blotting method is based on the conventional radioactive Southern blot analysis. Labelling of the probe StB 12.3 with digoxigenin via PCR allowed the detection of normal, premutated and fully mutated alleles. For exact sizing of small premutated or large normal alleles, we separated digoxigenin labelled PCR products through denaturing poly-acrylamide gelelectrophoresis (PAGE) and transfered them to a nylon membrane using a gel dryer. The blotted PCR-fragments can easily be detected with alkaline phosphate-labelled anti-digoxigenin antibody. The number of trinucleotide repeat units can be determined by scoring the detected bands against a digoxigenated M13 sequencing ladder. Our newly developed digoxigenin/chemiluminescence approach using PCR and Southern blot analysis provides reliable results for routine detection of full fragile X mutations and premutations.     

Muscle-specific enzyme activity patterns of the capillary bed of human oro-facial,masticatory and limb muscles

Enzyme-histochemical methods were used to analyse the activities of alkaline phosphatase (AP), dipeptidylpeptidase IV (DPP IV) and adenosine triphosphatase (ATPase) in capillaries of four different human oro-facial muscles, the major and minor zygomatic, the orbicularis oris and buccinator, one masticatory, the masseter and two limb muscles, the biceps brachii and first dorsal interosseus muscles. In all muscles, except for the orbicularis oris, the majority of the capillaries lacked enzyme activity. Therefore, none of these enzymes seems to be reliable as a general marker for human muscle capillaries. In general, the capillaries of the limb muscles and the major and minor zygomatic and the buccinator, were similar in their staining pattern for AP and ATPase, but differed in DPP IV staining. The orbicularis oris muscle differed from the other muscles by showing the largest proportion of capillaries with AP and ATPase activity. The masseter muscle had the largest proportion of capillaries stained for DPP IV. The muscle specific differences in enzyme activity of the capillaries are in agreement with our previous findings of specific differences between limb, oro-facial and masticatory muscles with respect to capillary supply and composition of fibre types and myosins. The results reflect functional specialization of the capillary bed of human muscles.