Successive microsporogenesis affects pollen aperture pattern in the tam mutant of Arabidopsis thaliana

Background and Aims

The tam (tardy asynchronous meiosis) mutant of Arabidopsis thaliana, which exhibits a modified cytokinesis with a switch from simultaneous to successive cytokinesis, was used to perform a direct test of the implication of cytokinesis in aperture-pattern ontogeny of angiosperm pollen grains. The aperture pattern corresponds to the number and arrangement of apertures (areas of the pollen wall permitting pollen tube germination) on the surface of the pollen grain.

Methods

A comparative analysis of meiosis and aperture distribution was performed in two mutant strains of arabidopsis: quartet and quartet-tam.

Key Results

While the number of apertures is not affected in the quartet-tam mutant, the arrangement of the three apertures is modified compared with the quartet, resulting in a different aperture pattern.

Conclusions

These results directly demonstrate the relationship between the type of sporocytic cytokinesis and pollen aperture-pattern ontogeny.     

Short note on the distribution and abundance of Anguillicola in The Netherlands

This short note presents data on the distribution of Anguillicola in The Netherlands on the basis of a study performed in 1986.

Zusammenfassung

Kurze Mitteilung über die Verbreitung und Häufigkeit von Anguillicola in den Niederlanden
Diese Kurzmitteilung beschreibt die Verbreitung von Anguillicola in den Niederlanden aufgrund einer Untersuchung, die im Jahre 1986 durchgeführt wurde.

Résumé

Note sur la distribution et la fréquence de Anguillicola dans les Pays Bas
Ce note présente des données d'une relève de Anguillicola dans les Pays Bas.     

A note on the diffusion approximation for single neuron firing problems

Summary This paper presents a well-known stochastic model used to describe the firing or discharge pattern of a single neuron in terms of various input processes, and shows how the potential level of the neuron can be given by means of a diffusion equation approximation. There is a discussion of the adequacy of this approximation, and the paper concludes with a brief discussion of first passage time problems.Supported in part by a grant from the Alfred P. Sloan Foundation to the Committee on Mathematical Biology and by a grant of the Statistical Branch, Office of Naval Research to the Department of Statistics, University of Chicago.     

Short note Report of diurnal acid metabolism in two aquatic Australian species of Isoetes

Previous studies have demonstrated the presence of crassulacean acid metabolism in the North American submerged aquatic Isoetes howellii (Isoetaceae). Diurnal changes in titratable acidity and malic acid levels indicate the presence of this pathway in two Australian species of Isoetes.     

EMG-interference pattern analysis.

The EMG interference pattern, built up of single motor unit action potentials, may be analyzed subjectively, or objectively by computer aided, quantitative methods, like counting of zero-crossings, counting of spikes, amplitude measurements, integration of the area under the curve, decomposition techniques, power spectrum analysis and turn/amplitude analysis. Since the shape of the interference pattern of healthy muscles is dependent on age, sex, force, muscle, temperature, fatigue, fitness level, recording site and surrounding tissue, electrode type, sensitivity, filters, sampling frequency and threshold level, all methods of analyzing the IP have to be standardized. Quantitative methods of analyzing the EMG interference pattern may be used for monitoring botulinum toxin therapy of dystonia and spasticity, quantifying spontaneous activity, assessment of chronic muscle pain, neuro-urological and proctological function, and diagnosing neuromuscular disorders. For diagnostic purposes, the methods favored are those that use needle electrodes and do not require measurement or monitoring of muscle force. The most well-evaluated methods are those using turn/amplitude analysis, like the cloud methods and the peak-ratio analysis. Peak-ratio analysis has the advantage that reference limits are easy to obtain and that its utility is well established and confirmed by several investigations. Overall, automatic methods of EMG interference pattern analysis are powerful tools for diagnostic and non-diagnostic purposes.     

Short Tandem Repeat loci analysis in forensic casework

The development of polymerase chain reaction typing method has enhanced the possibilities of genetic identification of biological evidence samples for forensic caseworks. The authors report the use of multiplex amplification reactions associating several short tandem repeat loci. These amplification systems produce reliable results and a sufficient incrimination power to send the cases before the court.     

Successive analysis of antigen trapping and enzymatic digestion on membrane-immobilized avidin

Avidin from egg white was migrated toward a cathode of nondenaturing electrophoresis and then immobilized on a polyvinylidene difluoride membrane. Adrenocorticotropic hormone (ACTH) was specifically captured after the biotinylated anti-ACTH antibody was bound to the membrane-immobilized avidin, and the captured ACTH was digested by the biotinylated trypsin on the membrane after extraction. The digested polypeptides from the ACTH were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). These results indicate that target substances can be specifically trapped and digested on membrane-immobilized avidin.     

A note on key factor analysis

Various aspects of a model for key factor analysis (Manly , 1977a) are discussed. Equations for estimating the parameters of the model are given. The jackknife method is suggested for obtaining standard errors for estimators. The case of circular populations (where the adults in one generation produce all the individuals alive at the start of the next, generation) is considered. A computer program is described. Varley et al.'s (1973) data on the winter moth is used for illustrative purposes.     

Mosaic pattern and lineage analysis in chimeras

Mammalian chimeras have been used in a number of developmental studies over the years. A major limitation in these studies has been the lack of in situ procedures for establishing mosaic pattern in the tissues of these animals. Recently, a number of procedures have become available for the histochemical demonstration of mosaicism in chimeras. These include the elucidation of various enzymes, receptors, or surface antigens, which have variant expression between strains. The observation of pattern in organs of mosaic animals can suggest possible modes of organogenesis and organ maintenance. Experimentation with such animals can be used to establish some mechanisms of pathogenesis as well.     

功能性脑成像的多维模式分析方法

利用非侵入式的功能性脑成像记录大脑活动极大地提升了我们对人类认知功能的理解.与此同时,分析成像数据的手段也逐渐从传统的一元方式向更加有效的多元分析转变.在本综述中,特别针对在认知神经科学领域占主导地位的功能性磁共振成像技术,介绍其多元数据分析方法的发展以及这种分析方法的生理学基础和未来发展方向.     

Spectral analysis of breathing pattern in man

The periodic oscillations of breathing pattern parameters were studied in 34 healthy subjects. In a three minutes' resting spirometric recording we determined the duration of inspiration, expiration and tidal volume in successive breaths and computed autocorrelation functions and power spectral density. Ten of the subjects were re-examined 2 years later. Pulmonary functions were examined in all of them. Rhythmic changes lasting several respiratory cycles were found in the breathing pattern. Rhythmic changes in the duration of inspiration, expiration and tidal volume differed from one another in the same individual. The spectrograms of the individual breathing pattern parameters in the same individual changed during a 2-year period. Despite individual differences, the power spectral density correlations in the same subject and between different subjects two years later, and the mean curves for power spectral densities, show that in all the subjects the power fell at values of 0 to 0.05 Hz and was then maintained at a roughly constant level. Differences in the spectrograms of the various parameters in the same subject can hardly be attributed to a feedback between peripheral receptors and respiratory centres. Rhythmic changes are probably of central origin.