Inverted pyramidal neurons and their axons in the neocortex of reeler mutant mice

Summary Inverted pyramidal neurons are very abundant in the cerebral cortex of the adult reeler mutant mouse. Two types of inverted pyramid are found in rapid Golgi impregnations. In the first type the axon starts from the base of the cell body and bends towards the white matter. In the second type, which is more common, the axon emerges from the apical dendritic tree and descends directly towards the white matter.Despite its abnormal topography, the site of origin of the axon in pyramids of the second type displays a normal differentiation, when analysed with the electron microscopic Golgi technique, suggesting that the ectopic initial axon segment is able to fulfil its normal functions.     

Improvements in immunostaining samples embedded in methacrylate: localization of microtubules and other antigens throughout developing organs in plants of diverse taxa

Microtubules are important in plant growth and development. Localizing microtubules in sectioned material is advantageous because it allows any tissue of interest to be studied and it permits the positional relations of the cells within the organ to be known. We describe here a method that uses semi-thin (0.5–2 m) sections of material embedded in butyl-methylmethacrylate, to which 10 mM dithiothreitol was added. After removing the embedding material and using indirect immunofluorescence staining, we obtain clear images of microtubules, actin microfilaments, callose and pulse-fed bromodeoxyuridine. This method works on the root tissues of Arabidopsis thaliana(L.) Heynh, Pinus radiataD. Don, Zamia furfuraceaAit., Azolla pinnataR. Br. and on sporophytic tissues of Funaria hygrometricaHedw. In general, most of the cells in the organs studied are successfully stained. Using this method, we find that interphase meristematic cells in all of these species have microtubules not only in the usual cortical array but also throughout their cytoplasm. The presence of the calcium chelator ethylene glycol-bis(-aminoethyl ether)N,N,N,N-tetraacetic acid EGTA in fixation buffers led to some tissue damage, and did not enhance the preservation of microtubules. The common assumption that EGTA-containing buffers stabilize plant microtubules during fixation appears unwarranted.Abbreviations BrdU 5-bromodeoxyuridine - DTT dithiothreitol - EGTA ethylene glycol-bis(-aminoethyl ether) - N,N,N,N tetraacetic acid We thank Ann Cork for technical assistance, Professor B.E.S. Gunning (Australian National University) and Drs. A.R. Hardham (A.N.U.) and R.E. Williamson (A.N.U.) for intellectual and material support, Dr D. McCurdy (A.N.U.) for the purified anti-actin antibody, and Professor B. Stone (La Trobe University, Melbourne, Australia) for generously providing the anti-callose antibody. We also thank the Electron Microscopy Unit of A.N.U. for the use of facilities. L.C.F. gratefully acknowledges financial support from the National Sciences and Engineering Research Council of Canada.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Observations on Schizothrix mexicana Gomont (Cyanophyta) under culture conditions

Using agar gel électrophoresis, the number and relative mobility of seric protein fractions has been determined for twelve species of fishes belonging to the Elasmobranchii, Dipnoi and Actinopterygii.The study of relative mobilities has shown both similitudes and divergences between some of the proteinograms. Immunoelectrophoretic cross tests using the twelve sera and five antisera have shown that these similitudes did not result from protein homology and thus agar gel electrophoresis could not be used to determine phylogenetic relationships between the species considered.

Laboratoire d'Hydrobiologie et de Pisci culture, Université de Kinshasa (Zaïre)     

Parameter identification of the calvin photosynthesis cycle

Summary This article is concerned with the determination of kinetic parameters of the Calvin photosynthesis cycle which is described by seventeen nonlinear ordinary differential equations. It is shown that the task requires dynamic data for several sets of initial conditions. The numerical technique is based upon an algorithm for non-linear optimization and Gear's numerical integration scheme for stiff systems of differential equations. The sensitivity of the parameters to noise in the data is tested with a method adapted from Rosenbrook and Storey. A preliminary set of parameters has been obtained from a preliminary set of experimental data. The numerical methods are then tested with synthetic data derived from these parameters. The mathematical model and the results obtained in the simulation are used as an aid in designing new experiments.     

Stereological investigation on the increase in surface area due to the microtriches of the hydatid cyst in different organs and in different hosts

Bortoletti G. and Diaz G. 1978. Stereological investigation on the increase in surface area due to the microtriches of the hydatid cyst in different organs and in different hosts. International Journal for Parasitology8: 433–436. The increase in surface area of the germinal membrane due to the microtriches has been morphometrically investigated in Echinococcus granulosus cysts developed in three different intermediate hosts. The results, achieved by Stereological methods, indicate that the development of the microtriches: (a) is more or less homogeneous all over the germinal membrane of the cysts; (b) is greater in human than in pig and sheep cysts; (c) is also greater in lung than in liver cysts within the same host and it is not related to the fertility or sterility of the parasite.     

Strategies for rapid assessment of fungal diversity

The problems of estimating fungal diversity are considerable, due especially to the large numbers of species even in small study sites, only a small proportion of which are adequately characterized, and the lack of trained staff and appropriate identification manuals. These difficulties are multiplied in the tropics. Strategies for providing preliminary assessments of fungal diversity which can be carried out within short time-frames are discussed, which will allow initial site valuations to be made for conservation purposes. The necessity of identifying all species discovered is considered, and the need emphasized for strictly defined sampling protocols which allow proper comparison between sites. The advantages and disadvantages of preliminary diversity analyses involving different taxonomic and ecological groups, fungus/plant associations, spatial sampling, soil and litter analysis, molecular methods and indirect assessment are considered.     

Review: Recent advances in bovine in vitro embryo production: reproductive biotechnology history and methods

In vitro production (IVP) of embryos and associated technologies in cattle have shown significant progress in recent years, in part driven by a better understanding of the full potential of these tools by end users. The combination of IVP with sexed semen (SS) and genomic selection (GS) is being successfully and widely used in North America, South America and Europe. The main advantages offered by these technologies include a higher number of embryos and pregnancies per unit of time, and a wider range of potential female donors from which to retrieve oocytes (including open cyclic females and ones up to 3 months pregnant), including high index genomic calves, a reduced number of sperm required to produce embryos and increased chances of obtaining the desired sex of offspring. However, there are still unresolved aspects of IVP of embryos that limit a wider implementation of the technology, including potentially reduced fertility from the use of SS, reduced oocyte quality after in vitro oocyte maturation and lower embryo cryotolerance, resulting in reduced pregnancy rates compared to in vivo–produced embryos. Nevertheless, promising research results have been reported, and work is in progress to address current deficiencies. The combination of GS, IVP and SS has proven successful in the commercial field in several countries assisting practitioners and cattle producers to improve reproductive performance, efficiency and genetic gain.     

Synthesis of gold nanoparticles using Crinum macowanii bulb extracts and the application of these materials in blood detections at crime scenes

We here in report the synthesis of gold nanoparticles (AuNPs) using a Crinum macowanii bulb water extract. The as‐synthesized AuNPs were characterized using ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and a zeta potential‐sizer. The results showed that the as‐synthesized AuNPs were crystalline and mostly spherical in shape with a small mixture of triangular, tetrahedral, hexagonal, octagonal, and diamond shapes. The as‐synthesized AuNPs together with those synthesized by conventional methods were subsequently used as enhancers for the luminol signal in blood detection. It was noted that the AuNPs synthesized from the Crinum macowanii bulb water extract could enhance the chemiluminescence signal for blood detection by luminol to the same extent as AuNPs prepared by conventional methods. Furthermore, both types of AuNPs served as fluorescence enhancers for blood detection when luminol was replaced with the bulb water extract.