Medianstipulierte Staubblätter

Zusammenfassung Es werden die sog. Ligulen an der Basis der Staubblätter vonReinwardtia, Simaruba, Zygophyllum und einigen Cruciferen-Gattungen (Alyssum, Aubrietia, Draba) beschrieben und auf ihren Stipularcharakter wird neuerlich hingewiesen. Der morphologische Vergleich mit einem diplophyllen und mit einer Medianstipel versehenen Stengelblatt vonBergenia zeigt deutlich, daß diese fraglichen Bildungen Medianstipeln darstellen. An verbildeten Kronblättern vonReinwardtia trigyna konnte überdies aufgezeigt werden, daß diese Bildung tatsächlich Ausgliederungen des echten Blattrandes darstellen.Es lassen sich demnach an günstig gebauten Staubblättern alle Teile eines typischen Blattes nachweisen: das Qberblatt, Anthere und Filament umfassend, und das Unter blatt, das gewöhnlich als Filamentbasis bezeichnet wird und deutlich in Blattgrund und Nebenblätter gegliedert ist. Diese Nebenblätter treten nun normalerweise in Gestalt einer Medianstipel auf, welche ihrerseits einen weiteren Beweis für den unifazialen Bau des darüber befindlichen Filamentabschnittes darstellt. Durch Hemmung des Querzonenwachstums kann die Medianstipel in laterale Stipeln zerteilt werden, die uns beiZygophyllum als freie Blättchen und bei den in Frage kommenden Cruciferen vielfach als Flügelungen des Filamentes entgegentreten. Das Vorhandensein und die Ausbildung dieser Nebenblätter läßt darüber hinaus erkennen, daß unter Umständen wesentliche Teile des Filamentes dem Unterblatt angehören.     

Mutation of the PAX6 gene in patients with autosomal dominant keratitis.

Autosomal dominant keratitis (ADK) is an eye disorder chiefly characterized by corneal opacification and vascularization and by foveal hypoplasia. Aniridia (shown recently to result from mutations in the PAX6 gene) has overlapping clinical findings and a similar pattern of inheritance with ADK. On the basis of these similarities, we used a candidate-gene approach to investigate whether mutations in the PAX6 gene also result in ADK. Significant linkage was found between two polymorphic loci in the PAX6 region and ADK in a family with 15 affected members in four generations (peak LOD score = 4.45; theta = .00 with D11S914), consistent with PAX6 mutations being responsible for ADK. SSCP analysis and direct sequencing revealed a mutation in the PAX6 exon 11 splice-acceptor site. The predicted consequent incorrect splicing results in truncation of the PAX6 proline-serine-threonine activation domain. The SeyNeu mouse results from a mutation in the Pax-6 exon 10 splice-donor site that produces a PAX6 protein truncated from the same point as occurs in our family with ADK. Therefore, the SeyNeu mouse is an excellent animal model of ADK. The finding that mutations in PAX6 underlie ADK, along with a recent report that mutations in PAX6 also underlie Peters anomaly, implicates PAX6 broadly in human anterior segment malformations.     

Deterministic Three-Half-Order Kinetic Model for Microbial Degradation of Added Carbon Substrates in Soil

The kinetics of mineralization of carbonaceous substrates has been explained by a deterministic model which is applicable to either growth or nongrowth conditions in soil. The mixed-order nature of the model does not require a priori decisions about reaction order, discontinuity period of lag or stationary phase, or correction for endogenous mineralization rates. The integrated equation is simpler than the integrated form of the Monod equation because of the following: (i) only two, rather than four, interdependent constants have to be determined by nonlinear regression analysis, (ii) substrate or product formation can be expressed explicitly as a function of time, (iii) biomass concentration does not have to be known, and (iv) the required initial estimate for the nonlinear regression analysis can be easily obtained from a linearized form rather than from an interval estimate of a differential equation. ¹⁴CO₂ evolution data from soil have been fitted to the model equation. All data except those from irradiated soil gave better fits by residual sum of squares (RSS) by assuming growth in soil was linear (RSS = 0.71) as opposed to exponential (RSS = 2.87). The underlying reasons for growth (exponential versus linear), no growth, and relative degradation rates of substrates are consistent with the basic mechanisms from which the model is derived.     

Separation and subfractionation of small numbers of cells (approximately 10(6)) by countercurrent distribution in dextran-poly(ethylene glycol) aqueous-phase systems

Separation and subfractionation of cells on the basis of subtle differences in surface properties by partitioning in dextran-poly(ethylene glycol) aqueous phase systems is an established method. We report here that the incorporation of fetal bovine serum into such systems permits countercurrent distribution of small quantities of cells (approximately 10(6]. In the absence of serum such small quantities of cells are lost (probably by adherence) and cannot be recovered after countercurrent distribution.     

Acoustic communication in spring peepers

Summary In the previous study (Wilczynski et al. 1984) we found that neurons in the auditory nerve of female spring peepers (Hyla crucifer) are tuned to frequencies in the male advertisement call, whereas auditory units in male peepers are mismatched in spectral sensitivity to their call. We investigated, in the present report, behavioral consequences of this sexual dimorphism in auditory sensitivity. Call amplitude, rate of call attenuation with environmental transmission, and the amplitude of ambient noise were measured and used to compute the active space of this signal for males and females. The effect of calling height upon active space was considered. Measurements of active space were compared with intermale distances within breeding choruses.Results indicate that active space of the advertisement call for females is as much as 6 times greater than that for males, and varies directly with the height above ground from which males call. Observed maximum intermale distances correspond closely to the active space of the call for this sex. This suggests that males space themselves so that the amplitude of a neighbor's calls approximates their auditory neural threshold to call frequencies. By this proximal mechanism, peepers maximize intermale distance but ensure that they remain within a chorus.Abbreviation dB SPL decibels sound pressure levelre: 20 Pa     

A simple liquid medium for chlamydospore formation in Candida albicans

A new, relatively simple and inexpensive liquid medium was devised to produce all structural forms ofC. albicans. Optimum conditions to induce the yeast cells, germ tubes, pseudohyphae and chlamydospores along with the methods to obtain them are described.Supported in part by Grant CA 20917, National Cancer Institute, National Institutes of Health and ALSAC.     

Molecular and cytological characteristics of nuclear DNA and chromatin for angiosperm systematics: DNA diversification in the evolution of four orchids

The species- and genus-specific DNA content, average base composition of nuclear DNA, presence or absence of satellite DNA, the percentage of heterochromatin and other characteristics of nuclear DNA and nuclear structure allow to deduce the molecular changes which accompanied, or more probably caused, cladogenesis in the orchids studied. It is suggested that saltatory replication (generative amplification) of certain DNA sequenes, diversification of reiterated DNA sequences, and loss of DNA play an important role in the evolution of orchids.—The relationship between changes of genome composition and of nuclear structure and ultrastructure is discussed on the basis of cot curves, heterochromatin staining with Giemsa (C banding), electron microscopy of nuclei, and molecular hybridization in situ.Some aspects of this paper have been presented at the Helsinki Chromosome Conference, August 1977 (Nagl & Capesius 1977).