Ribosomal DNA non-transcribed spacer polymorphism in subterranean mole rats: genetic differentiation,environmental correlates and phylogenetic relationships

Summary An analysis is presented of genetic differentiation in the non-transcribed spacers of ribosomal DNA (NTS rDNA). Diversity, environmental correlates and the phylogenetic relationships are examined within and between species of the actively speciating subterranean mole rat, superspeciesSpalax ehrenbergi (2n=52, 54, 58, 60) in Israel. This analysis is based on a previous study of the geographic distribution of restriction fragment length polymorphisms of NTS rDNA. Here we present results indicating that NTS rDNA diversity exists mostly (66%) within populations, while 20% is between populations within species, and 14% between species. Multivariate discriminant analysis succeeded in separating 10 of the 13 populations (77%) into their correct chromosomal species, on the basis of the combination of three NTS rDNA repetypes. The phylogenetic relationships suggest that the complex involves two pairs of closely related species (2n=52–54 and 2n=58–60). NTS rDNA diversity, as well as the decrease southward in frequency of repetype C, are correlated with climatic factors of humidity and temperature. These data are discussed in terms of the evolutionary forces of migration and selection which may cause NTS rDNA differentiation. Climatic selection appears to be the major differentiating factor of NTS rDNA.     

Measurement of chlorophyll fluorescence within leaves using a fibreoptic microprobe

Abstract. The distribution of chlorophyll fluorescence was measured within leaves of Medicago saliva with a fibre optic microprobe. Leaves were irradiated with broad band blue light (1000 μmol m⁻²s⁻¹) and chlorophyll fluorescence was measured at 688 nm. The amount of fluorescence measured within the leaf depended upon the direction in which the probe was inserted. When the probe was advanced directly through the leaf from the shaded towards the irradiated surface, the maximum amount of detected fluorescence occurred near the boundary between the palisade and spongy mesophyll. When the probe was advanced through the leaf from the opposite direction maximum detected fluorescence was at the boundary between the epidermis and palisade. These results appear to be a consequence of the blue light gradient, which declined exponentially within the palisade but was counterbalanced by increasing chlorophyll content within the leaf. Modelling indicates that the measured distribution of chlorophyll fluorescence can be explained by relatively uniform emission of fluorescence throughout the palisade layer, indicating that the chloroplasts may be photosynthetically specialized to their light environment within the leaf.     

Rapid acquisition of three-dimensional triple-resonance experiments using pulsed field gradient techniques

Summary A rapid method for recording three-dimensional triple-resonance experiments utilising pulsed field gradient techniques is proposed, and applied to the HNCO experiment. In order to optimise the sensitivity of the method, a short phase cycle is used in conjunction with the pulsed field gradients to select the desired coherence transfer pathway. The method is demonstrated for the HU protein.     

Enucleation of protoplasts derived from suspension cultures of winged bean and from a crown gall cell line ofParthenocissus tricuspidata

Protoplasts derived from suspension cultures of the winged bean and a crown gall lineof Parthenocissus tricuspidata were enucleated by centrifugation on iso-osmotic discontinuous Percoli gradients and on discontinuous sucrose-mannitol density gradients. Enucleation was achieved according to the buoyant density of the protoplasts and preparations of both cytoplasts and miniprotoplasts were recovered. The Percoll gradients gave more satisfactory results than the sucrose-mannitol gradients. Enucleation was increased by raising the centrifugal force from 20 kg to 60 kg. The presence of nuclei was determined by the DNA specific probe 4′6-diamidino-2-phenylindole (DAPI). Membrane integrity, as measured by staining with fluorescein diacetate, showed that some 85 % of the cytoplasts were bounded by an intact plasma membrane.     

The selection mutation equation

Fisher's Fundamental Theorem of Natural Selection is extended to the selection mutation model with mutation rates _ij=_ii.e. depending only on the target gene, by constructing a simple Lyapunov function. For other mutation rates stable limit cycles are possible.     

Models of localized energy coupling

It is proven that any model of localized protonmotive energy coupling that relies upon properties of a homogeneous surface phase must, when operated in the steady state, lead to bulk phase electrochemical potentials for protons that are as large as those required by the delocalized chemiosmotic theory. To obtain models consistent with experiments supporting localized energy coupling requires some kind of surface heterogeneity for the proton conducting pathways. Two general classes of heterogeneous surface models are mentioned. One class involves phase-separated lipid domains. The second class involves hydrogen-bonded chains in proteins that traverse the membrane laterally.     

Ethylene biosynthesis in isolated vacuoles of Vicia faba L. — requirement for membrane integrity

The ability of vacuoles prepared from V. faba leaves to convert 1-aminocyclopropane-1-carboxylic acid to C₂H₄ was destroyed when vacuoles were lysed by passage through a hypodermic needle, freezing and thawing, osmotic shock, treatment with ethanol or with a detergent. Ethylene synthesis in the vacuolar fraction was also inhibited by the uncouplers carbonyl cyanide m-chlorophenyl hydrazone and dinitrophenol and by the ionophores valinomycin, nigericin, and A23187. Ethylene formation increased with increasing pH of the incubation medium over the pH range of 5.0–7.5. These observations support the hypothesis that C₂H₄ biosynthesis in vacuolar preparations is dependent on membrane integrity, possibly because of the requirement for a transmembrane ion gradient.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - CCCP carbonyl cyanide m-chlorophenyl hydrazone     

Observations on the separation of Theileria sporozoites from ticks

Hyalomma anatolicum anatolicum ticks infected with Theileria annulata were partially fed on rabbits and then ground up with tissue culture medium. The ground up ticks were treated by centrifugation at 100 g, filtration through membranes of 8 μm pore diameter and centrifugation on a discontinuous density gradient of Percoll. Counts of sporozoites and tick debris were made from Giemsa stained slides of samples at each stage of the separation. Debris was removed during light centrifugation and filtration at a greater rate than sporozoites. After filtration approximately 41% of the original sporozoites remained in the suspension. After density gradient centrifugation most sporozoites were found in a distinct zone, at approx. 1·08 g/cm³ density, separate from most dense debris and light debris and soluble contaminants. After this final centrifugation approximately 24% of the original sporozoites remained in the recovered suspension.     

Climate and vegetation in China II. Distribution of main vegetation types and thermal climate

The authors examined relationships between Kira's warmth index (WI) and four other important thermal indices: the sums of daily mean temperatures above 5°C and 10°C, Thornthwaite's potential evapotranspiration (PE) and Holdridge's annual biotemperature. The thermal records of 671 meteorological stations evenly located all over China were used to make these comparisons. Close correlations were found within the four relationships, and accordingly WI was used to analyse the thermal distributions of the main vegetation types. Vegetation types around the 671 stations were read from a vegetation map with a scale of 1/4000000. Vegetation types at 269 stations corresponded to the natural or seminatural vegetation, and 29 vegetation types were distinguished by arranging the 269 data into the same or similar types. The geographical distribution of these 29 types and the corresponding main climatic features were described. The relations between WI and distribution of these vegetation types were discussed in detail. As a result, WI values (°C month) corresponding to the vegetation zones could be summarized as follows: (1) arctic or alpine vegetation zone: 0–15; (2) boreal or subalpine vegetation zone: 15-(50–55); (3) cool-temperate vegetation zone: (50–55)–(80–90); (4) warm-temperate vegetation zone: (80–90)–(170–180). These values almost coincided with Kira's values. Chinese postgraduate student in Japan sent by the Chinese Government.