Optimal filtering of nerve singnals

Recording from multiple electrodes at different sites along a peripheral nerve permits the application of powerful filtering methods to extract the activity of populations of fibres within the nerve which differ in temporal or spectral characteristics. The design of optimal linear filters is initially treated as a general problem in the calculus of variations in which the signals from one population of nerve fibres are extracted so as to minimize those from a second population of nerve fibres or from other sources (noise). A particularly important application arises when the signals at two electrodes are related by weighting functions. In the simplest example the weighting function represents the time delay for nerve impulses to conduct from one electrode to the other, but explicit results are also derivable when there are a range of conduction delays with probabilities distributed according to well-known functions such as the sinc² function.This work was partially supported by the National Research Council of Canada and Medical Research Council of Canada by Grant NRC A-4345 to MNO and Grant MRC MA-3307 to RBS through the University of Alberta     

Fetal cells in the maternal blood

Summary In an attempt to stimulate fetal cells in the maternal blood to mitotic division, peripheral blood lymphocytes were cultured from ten primiparous women and six multiparous women. In the case of the ten primiparous women, PWM was used to stimulate lymphocytes in 3- and 7-day cultures made at the 16th, 20th, 24th, and 28th week of gestation. Altogether, 10565 mitoses were analyzed after quinacrine staining of cells from five mothers who each subsequently gave birth to a male infant, and not a single XY mitosis was found.In the case of the multiparous women, lymphocyte cultures, with PHA or LPS as mitogen and MLC, were initiated between the 13th and 20th week of pregnancy. Four of the mothers were pregnant with a male child, and two with a female child. From cultures of each of the four mothers expecting a boy, a total of 9721 mitoses were analyzed after quinacrine staining, and not a single XY mitosis was found. However, one XY cell was found in the culture from one of the two women who delivered a girl. The XY mitosis probably originated from a pregnancy 8 months earlier which terminated in a male infant.In an attempt to culture and obtain good chromosome preparations from small numbers of cells, it was shown that a good mitotic response and good chromosome preparations could be obtained from as few as 6000 lymphocytes.     

The flagellar root apparatus,the microtubular system and associated organelles in the chrysophycean flagellate,Poterioochromonas malhamensis Peterfi (syn.Poteriochromonas stipitata Scherffel andOchromonas malhamensis pringsheim)

Summary The two flagella ofPoterioochromonas are inserted in an apical platform which is shaped by six long flagellar root fibres. The arrangement and structure of these root fibres are described in detail. One of these fibres is the single nucleating site for cytoplasmic interphase microtubules which extend peripherally down to the cytoplasmic tail. Another fibre proceeds toward the centre of the cell and passes the nucleus but is different in structure, position and function from the striated rhizoplast found in many chrysophycean flagellates which is observed but vestigial inPoterioochromonas.A specific kinetosomal mitochondrion has a threefold attachment to the flagellar root apparatus. The chloroplast is also bound to the root system. It has no stigma, but a special continuation of the periplastidial cisterna is developed instead. Another cisterna extends from the nuclear envelope-dictyosome interspace to the kinetosome of the long flagellum. The functional and taxonomic meanings of these structures and of their mutual arrangement are discussed. It is concluded that the present strain (no. 933-1 a of the Collection of Algal Cultures at the Institute of Plant Physiology, Göttingen) has to be excluded from the genusOchromonas.     

Book reviews

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Book reviews

     

The energy balance of leaves of the evergreen desert shrub Atriplex hymenelytra

Summary Atriplex hymenelytra is an evergreen shrub distributed in the hot deserts of parts of Mexico and the southwestern United States. The leaves of the species have a number of characteristics that are adaptive in a hot, dry environment, some of which change seasonally. Steeply angled leaves reduce midday solar interception, yet result in relatively high interception when solar angles are low and vapor pressure deficits are at a minimum. The leaves substantially reduce their absorptance of incident radiation during the hot periods of the year by changing their moisture and hence dissolved salt contents. At these times the light intensity required for saturation of photosynthesis is low and a reduction in the radiation absorbed by the leaves therefore results in a greater water-use efficiency.     

A new favreine coprolite (Crustacea,Decapoda) from the Jurassic of Iran and the Cretaceous of the Dinarids,Jugoslavia

Favreina tabasensis n. sp., a Crustacean (Decapoda) coprolite with numerous longitudinal canals is described from the Upper Jurassic of the Tabas area, east-central Iran. The same favreine form-species is also recorded and figured from the Neocomian of the Dinarids, Bata, Montenegro, Jugoslavia. Further, a lectotype is proposed forFavreina prusensis (Paréjas) from the Upper Portlandian of the region of Lake Apolyont, Turkey.Favreina montana Elliott from the Albian Qamchuqa formation, Gund-i-Shikavt, Erbil Liwa, northern Iraq, is considered as a nomen dubium non conservandum.     

Canarion,ein neues naphthochinon aus Usnea canariensis

The structure of canarione, a new naphthoquinone from the lichens Usnea canariensis and U. hookeri was elucidated by UV, ¹H-NMR, ¹³C-NMR, mass spectrometry, and chemical degradation as 5,8-dihydroxy-2-methyl-4H-naphtho [2,3b]-pyran-4,6,9 (6H, 9H)- trione.     

Initial phases of indoleacetic acid induced growth in coleoptile segments of Avena sativa L.

The intial phases of auxin-induced growth in coleoptile segments of Avena sativa L. were investigated using a high resolution growth recording technique, based on an angular position sensing transducer. The first response to the hormone is a slight, transient reduction of the growth rate lasting about 5 min. After this phase growth rate increases to a maximum. The duration of the increase and the maximum clearly depend on the concentration of the hormone. With increasing auxin concentration the duration of the growth rate increase is reduced from about 80 min in 10^-9 M indoleacetic acid (IAA) to about 14 min in 10^-4 M IAA. After the maximum the growth rate declines. Looking at the maximum of the growth rate, we obtained a dose-response curve with a sharp increase between 10^-9 M and 10^-6 M IAA and a slight decline between 10^-6 M and 10^-4 M IAA. This result is confirmed by growth rates measured one and two hours after the application of the hormone.Abbreviations IAA indoleacetic acid     

Cytophotometric investigation of DNA and RNA content in nuclei of active Strasburger cells in Pinus nigra var. austriaca (Hoess) Badoux

The nuclei of active, sieve cell-associated Strasburger cells in the secondary phloem of Pinus nigra var. austriaca (Hoess) Badoux have been studied for their structure and DNA and RNA content. No difference in size compared to those of ordinary ray cells was found. The nuclear surface is often increased by an ameboid or lobed shape. The amount of highly decondensed chromatin is greatly increased. Cytophotometric measurements of DNA content of both Feulgen and gallocyanine chromalum-stained nuclei showed normal DNA levels and proved absence of endomitotic polyploidization. RNA content, however, was significantly increased as compared to nuclei of young Strasburger cells and of ordinary ray parenchyma cells.Abbreviations StC₁ Strasburger cells in contact with young and immature sieve cells - StC₂ Srasburger cells in contact with mature and functionally active sieve cells - StC₃ dead Strasburger cells - eRPC pRPC erect and procumbent ray parenohyma cells, respectively - GCCA gallocyanine chromalum - T transmission - A absorbance Dedicated to Professor Dr. Wilhelm Halbsguth, Kiel, on the occation of his 65th birthday