Detection of the Microtubule Cytoskeleton of the Coccidian Toxoplasma gondii and the Hemoflagellate Leishmania donovani by Monoclonal Antibodies Specific for β-Tubulin1

Seven monoclonal antibodies specific for mammalian β-tubulin demonstrate the microtubule cytoskeleton of Toxoplasma gondii and Leishmania donovani by indirect immunofluorescence microscopy. Immunoblots of T. gondii and L. donovani proteins separated by SDS polyacrylamide gel electrophoresis confirm the specificity of the monoclonal antibodies for tubulin. Differential staining of flagellar and subpellicular microtubule populations was not seen in L. donovani with these antibodies. All seven antibodies also detected the subpellicular microtubules of T. gondii, but the polar ring and conoid of this organism was not visualized by any of them. This technique provides a rapid and specific way to assess microtubular organization in whole organisms.     

Observations on the Endogenous Stages of Eimeria confusa Joseph, 1969 from the Grey Squirrel Sciurus carolinensis*

SYNOPSIS. Stages in the endogenous cycle of Eimeria confusa from the grey squirrel, Sciurus carolinensis, are described from mixed infections with another species, Eimeria lancasterensis. All corresponding stages were markedly different in the 2 species. In E. confusa infections, the parasites were located below the host cell nuclei of the epithelial cells of the villi of the jejunum and ileum. Mature schizonts were ellipsoidal, averaged 20.9 × 18.6 μm and had 18–30 merozoites. The mature microgamonts measured 34.3 × 24.7 μm and had hundreds of microgametes. Mature macrogametes were ovoid, averaged 31.3 × 25.6 μm, and contained 2 kinds of plastic granules.     

Aluminium Toxicity in Roots: An Investigation of Spatial Sensitivity and the Role of the Root Cap

The primary symptom of aluminium (Al) toxicity in higher plantsis inhibition of root growth. In this study, we investigatedthe spatial sensitivity of maize (Zea mays L.) roots to Al.A divided-chamber technique indicated that only exposure ofthe terminal 10 to 15 mm of the root to Al resulted in inhibitionof growth. Application of Al to all but this apical region ofthe root had little or no effect on growth for 24 h and causedminimal damage to the root tissue. Small agar blocks infusedwith Al were then applied to discrete areas of the apex of maizeroots to determine which section (root cap, meristem or elongationzone) was more important to Al-induced inhibition of growth.The terminal 20 to 30 mm of root (root cap and meristem) mustbe exposed to Al for inhibition. Application of Al to the 30mm of root proximal to this terminal zone (elongation zone)resulted in damage to the root tissue but no significant inhibitionof growth. Therefore, the visible injuries incurred by rootsduring Al-stress are not associated directly with the inhibitionof root growth. Furthermore, removal of the root cap had noeffect on the Al-induced inhibition of root growth in solutionexperiments and argues against the root cap providing protectionfrom Al stress or serving an essential role in the mechanismof toxicity. We suggest that the meristem is the primary siteof Al-toxicity. Key words: Aluminium, toxicity, root growth, root cap     

Evolution and Diversification of Antarctic Notothenioid Fishes

Antarctica supported fossil ichthyofaunas during the Devonian,Jurassic, Cretaceous and Eocene/Oligocene. These faunas arenot ancestral to each other, nor are they related to any componentof the modern fauna. About one hundred species of notothenioidsdominate a modern fauna of over 200 species of bottom fishes.This highly endemic perciform suborder is not representedinthe fossil record of Antarctica. Notothenioids may have evolvedin situ on the margins of the Antarctic continent while graduallyadapting to cooling conditions during the Tertiary. Cladisticstudies indicate that notothenioids are a monophyletic group,but a sister group has not been identified among perciform fishes.With relatively few non-notothenioid fishes in Antarctic waters,notothenioids fill ecological roles normally occupied by taxonomicallydiverse fishes in temperate waters. There are six notothenioidfamilies: Bovichtidae, Nototheniidae, Harpagiferidae, Artedidraconidae,Bathydraconidae and Channichthyidae. Aspects of theirbiologyare briefly considered with emphasis on the Nototheniidae, themost speciose family. Evolutionary diversification within thisfamily allows recognition of species which are pelagic, cryopelagic,benthopelagic and benthic.     

Stereological Analysis of Floral Development and Quantitative Histochemistry of Nucleic Acids in Fertile and Base-sterile Varieties of Wheat

The speltoid series of mutations provides a genetic tool forinvestigating the control of flower development. In fertileGabo wheat and in St₂ and St₃ basal sterile speltoids, the changesin RNA staining patterns have been followed histochemicallyas a marker of cellular activity. Sterile floret sites are characterizedby a reduced RNA content. Use of dual-wavelength microspectrophotometryhas provided evidence that RNA content is similar in lemma primordiasubtending presumptive fertile and sterile primordia, but isstrikingly different in the floral meristems in the two types.The total nucleic acid content of the floral primordia has beenrelated to the number of epidermal cells in the subtending lemmaprimordium as a marker of development, using a linear modelanalysis of covariance. There is a linear increase in nucleicacid content during fertile floret development, but no significantincrease in RNA content in sterile St₃ primordia. The rate constantis only 1/10th to 1/20th of that of Gabo. A stereological analysisshows that cell number in the floral meristems of Gabo increasesexponentially during development. In contrast, in St₃, whilethere is a significant increase in cell number, it is at a drasticallyreduced rate. The intercept values are close to zero, indicatingthat only one or two cells initiate floral meristem development.The fertility-controlling alleles exert their effect prior tothe appearance of a visible floral primordium, and probablyafter initiation of the lemma. Triticum aestivum, wheat, floral development, histochemistry, nucleic acids, speltoids     

Effect of Low Relative Humidity on {delta}13C Value in Two C3 Grasses and in Panicum milioides, a C3-C4 Intermediate Species

When grown under conditions of low relative humidity, the C₃–C₄intermediate Panicum milioides, as well as the C₃ grasses Triticumaestivum and Poa pratense, exhibited ¹³C values which were upto 2–7%o less negative than the ¹³C values of the correspondingplants grown at high relative humidity. At both humidity levels,there was no evidence of a substantial contribution of phosphoenolpyruvatecarboxylase to carbon gain in Panicum milioides     

Shell-banding polymorphism of the land snail Xeropicta vestalis along the coastal plain of Israel

Along the coastal plain of Israel, shell darkness of the polymorphic land snail Xeropicta vestalis is positively related to the extent of perennial vegetation. It is not related to rain, temperature, geographic position or darkness of the ground.
White shells reflect more radiation than dark ones do, and therefore in Israel's coastal plain, where solar radiation is very strong, they are favoured. Perennial vegetation, where it occurs, shields the snails from the sun by absorbing radiation, so that snails amongst them can afford to be darker, and thus more cryptic. Hence, the more perennial vegetation in the habitat, the darker the shells.
Also during the Pleistocene, when temperatures were 5–10°C lower than today, the shells of the coastal plain were as pale as recent ones are. The distribution of a snail-predator, Gerbillus allenbyi , which is restricted to sandy biotopes where perennial bushes occur, and which was absent from Israel during the Pleistocene, could perhaps explain the distribution of X. vestalis morphs, both today and in the past.     

Ferredoxin–NADP+ Reductase from Tsuga canadensis. A Procedure for Isolation and Properties

Activity of ferredoxin-NADP⁺ reductase in leaf extracts of eastern hemlock [Tsuga canadensis (L.) Carr.] was relatively low, but could be markedly increased by use of protective agents. The best method employed polyvinylpolypyrrolidone (PVP) in the extraction medium plus removal of phenolic compounds by filtering the extracts through an insoluble PVP (Polyclar AT) column. Further purification of the enzyme was achieved by means of DEAE cellulose chromatography and DEAE Sephadex chromatography. A 94-fold purification of the enzyme with a total recovery of 43% was obtained. The eastern hemlock ferredoxin-NADP⁺ reductase was characterized by its diaphorase activity, i.e. the transfer of electrons from NADPH to an electron acceptor. 2,6-dichlorophenol indophenol. The pH optimum for the oxidation of NADPH is between 8.5 and 9.0. The enzyme is highly specific for its electron donor. NADPH, but shows low specificity for electron acceptors. The apparent Michaelis constant values of the enzyme for NADPH. NADH, and 2,6-dichlorophenol indophenol are 2.4 × 10^?5, 5.4 × 10^?3, and 4.7 × 10^?5M respectively. The molecular weight of the enzyme, as estimated by gel filtration, is about 45,000. The enzyme is inhibited by both organic and inorganic mercurials and certain cations. Comparison of properties of eastern hemlock ferredoxin-NADP⁺ reductase and spinach ferredoxin-NADP⁺ reductase shows that both enzymes are similar.     

Salinity and the Hydraulic Conductance of Roots

The effect of salinity on hydraulic conductance of intact roots of tomato (Lycopersicon esculentum Mill.) and sunflower (Helianthus annuus L.) was determined in split-root experiments using salinized nutrient solutions. Experiments were conducted in controlled climate chambers under two or three relative humidity levels and four solution osmotic potential levels. The relationship between water flux through roots (J_v) and total water potential difference between the leaves and the root medium (Δψ) was linear, usually with a small intercept. Thus, the root hydraulic conductance (L) was not affected by salinity within the range of fluxes obtained in these experiments, with L= 0.036 mm h^?1 bar^?1 for tomato and L= 0.0167 mm h^?1 bar^?1 for sunflower. Our results agreed with theoretical analysis of coupled water and ion uptake. From Cl^? and Na⁺ uptake data, the reflection coefficient (o) for tomato roots was calculated as 0.956, which was compatible with the near-zero intercept. A large intercept for sunflower could not be readily explained. Relative humidity strongly affected root growth, with more rapid growth under low humidity conditions. Transpiration of sunflower plants was reduced by 20% when the relative humidity was increased from 34% to 84%, whereas transpiration in tomato was reduced 50%.