Taxonomy of the African giant pouched rats (Nesomyidae: Cricetomys): molecular and craniometric evidence support an unexpected high species diversity

Our study combined a mitochondrial cytochrome b phylogeny with cranial measurements from giant pouched rats collected across sub‐Saharan Africa. The mitochondrial phylogeny resolves two West African clades and a clade with east and central Africa representatives. This last clade can be further divided into four subclades. Altogether they represent six species (Cricetomys gambianus, Cricetomys ansorgei, Cricetomys emini, and three undescribed taxa) that can be distinguished on the basis of their mitochondrial DNA sequences and craniometry. In the absence of adequate craniometric data the existence of Cricetomys kivuensis cannot be confirmed by our data. Our combined molecular and craniometric data allowed us to broadly delineate the distribution ranges of the detected species. Cricetomys gambianus occurs in the savannah and forest clearings of West Africa. Cricetomys ansorgei is distributed in the savannah of East and southern Africa. Cricetomys emini, as currently recognized across the Guineo‐Congolian forest of Africa, is shown to be diphyletic. Cricetomys sp. 1, a separate operational taxonomic unit closely resembling C. emini, occurs in the forest zone of West Africa. An undescribed sister‐species of C. ansorgei, Cricetomys sp. 2, occurs in the forest of Central Africa along the left bank of the Congo River. Cricetomys sp. 3 occurs on the right bank of the Congo River from Cameroon to the Republic of Congo, whereas the true C. emini also occurs on the right bank of the Congo River but appears to be restricted to the Democratic Republic of Congo. Cranial phenotype within the genus tends to conform to ecological zonation (either forest or savannah) rather than to phylogenetic affiliation of the species concerned, suggesting that diversifying selection across environmental gradients could be responsible for biological diversification within the genus.     

Rhythmic Growth Rings of Wood and Their Relationship with the Foliage in Oak Seedlings Grown in a Favourable Environment

The anatomy of wood was studied inQuercus roburL. andQuercussuberL. seedlings exhibiting 3–8 units of extension, eachwith a tier of photosynthesizing leaves in their upper parts,generated as the result of rhythmic shoot growth under favourableconditions. At all the axis levels examined (i.e. the base ofeach of the different units of extension, four other equidistantlevels within the first unit of extension and the upper partof the taproot), the wood displayed rings when treated withWiesner reagents. This indicated cinnamaldehyde groups presentin lignins. No rings appeared when the Maüle reaction wasused for specific detection of syringyl subunits in lignins.A trend towards a periodical arrangement of xylem parenchymabands was also found when sections were treated with I₂/KI.The number of rings coincided with the number of leaf tiersabove the level of measurement, and did not vary inside thefirst unit of extension. Thus, the rings are called rhythmicgrowth rings. In sections of the first and the second unitsof extension, and in the taproot, the area and width of a givenrhythmic growth ring were highly correlated with the total areaof leaves present above the level of measurement at the presumedtime of growth ring formation. Moreover, stem diameter at thebase of the units of extension was highly correlated with theleaf area above. These results indicate that differentiationof xylem, particularly its lignification, varies rhythmicallyin oak seedlings. They imply that wood production is linkedto the photosynthesizing and/or transpiring area of the plant.Thus, during a growth cycle ofQ. roburandQ. suberseedlings,there appears to be integration of the primary metabolic activitieswith the laying down of rhythmic growth rings.Copyright 1998Annals of Botany Company Allometric relationship, juvenile wood, leaf area, lignification, oak seedling, periodic structure,Quercus roburL.,Quercus suberL., rhythmic growth ring, unit of extension.     

A PANEL PERFORMANCE PROCEDURE IMPLEMENTED IN R

Monitoring performance is essential for the efficient use of a sensory panel both during training and while carrying out product assessments. We present a concise procedure to monitor panel performance based on classical statistical methods. The program includes tests for the ability to discriminate between products, repeatability of assessments, scale use, agreement between panelists and a principal component analysis map of panelist means across attributes. The algorithm is implemented in R – a state‐of‐the‐art, freely available statistical software package. The program output is summarized in graphs and tables. This easily applicable panel performance procedure is aimed at improving sensory practice, especially in areas where the use of highly complex systems is not feasible.     

The Challenge of Pneumocystis carinii Culture1

ABSTRACT. Published and unpublished data on the cultivation of P. carinii were reviewed by a panel of investigators convened by the National Institutes of Health. Although several cell culture systems allow propagation of P. carinii for a limited time with modest rates of replication, these have not proved adequate for isolation of P. carinii in sufficient quantity to explore important basic biological investigation. Attempts at cell-free culture have yielded only transient proliferation. Because much of the unsuccessful work on cultivation of the organism has been unpublished, the panel agreed that these data may be useful to other investigators in designing experimental strategies for cultivation. Therefore, the purpose of this report is to make available this information to researchers, lest others unknowingly repeat unsuccessful methods. It is hoped that by documenting the history and the complexities of Pneumocystis culture, renewed interest and efforts will be directed toward this fundamental scientific challenge.     

Ionic Diffusion Through the Nitella Cell Wall in the Presence of Calcium

Diffusion potentials (concentration and bi- or multi-ionic potentials)in KC1, NaCl, or LiCl solutions have been measured across anisolated cell wall of Nitella, with or without the same concentrationof CaCl² on either side of the cell wall. The absolute valueof the potentials decreases as the external Ca²⁺concentrationincreases and it may happen that an inversion of the sign ofthe concentration potentials results when the external Ca²⁺solution reaches 1 mM. Dosages of K⁺ and Ca²⁺ in the cell wallhave shown that Ca²⁺ easily displaces the monovalent ion fromthe exchange sites and tends to neutralize the cationic exchanger.However, in most cases, the measured potentials are still morenegative than the theoretical potentials which would be setup by a neutral-site membrane in the same conditions. Theseresults suggest that Ca²⁺ largely reduces the discriminationproperties of the cell wall between cations and anions.     

Action of Mono- and Difluorodinitrobenzene on Induced Electrical Modifications by External pH Changes in Nitella

The action of mono- (FNB) or difluorodinitrobenzene (DFNB) onion permeability is mainly attributed to its interactionwithamino groups of the membrane by dinitrophenylation. Nitella cells were dimtrophenylated at pH 7.3 and the membranepotential and electrical resistance were then measured in acidicor basic solutions. No matter what the pH value was, FNB andDFNB induced a depolarization of the membrane potential andcaused a diminution of resistance. However these effects ofFNB and DFNB were more drastic at alkaline pH and in the presenceof a weak concentration of potassium. Neither the addition of0.1 mM calcium nor the substitution of chlorides by nitratesmodified the DFNB effect. These results are compatible withthe assumption that the DFNB binding to the membrane leads toan augmentation of the negative charges of the membrane bringingabout an increased cation conductance and a modification ofthe affinity of a K⁺/H⁺exchange pump. The transient responseof the membrane potential at the time of dinitrophenylationwas used to roughly estimate the total density of amino groupsof the membrane of Nitella.     

A phylogenetic reconstruction of the Ichneumonoidea (Hymenoptera) based on the D2 variable region of 28S ribosomal RNA

The D2 variable region of 28S rRNA was sequenced in a wide range of Ichneumonoidea to provide the first comprehensive phylogenetic reconstruction of this superfamily. The two constituent families (Braconidae and Ichneumonidae) were each found to contain a single well-supported clade dominated by the more plesiomorphic life history strategies (idiobiosis, ectoparasitism and attacking endoephytic hosts). In the Braconidae this clade corresponds to the morphologically-defined group called the cyclostomes. In the Ichneumonidae the clade unites for the first time the pimpliformes ( sensu Wahl) with most of the phygadeuontoid subfamilies and several small taxa including Adelognathus and Euceros . Relationships among the remaining, more biologically-derived, subfamilies were less well resolved, but included among the Braconidae a well-supported microgastroid clade and strong evidence for a sister group relationship between the Agathidinae and Sigalphinae.     

Ultrastructure and Cytochemistry of the Cell-types in the Tumorous Hematopoietic Organs and the Hemolymph of the Mutant Lethal (1) Malignant Blood Neoplasm (l(1)mbn) of Drosophila Melanogaster

The fine structure and histochemistry of the neoplastic primordial blood cell-types in the larval hematopoietic organs and the mature cell-types in the hemolymph of the blood tumor mutant lethal (1) malignant blood neoplasm (l(1) mbn ) of Drosophila melanogaster were investigated. In this mutant the cell-types of the plasmatocyte-line are neoplastic while the cell-types of the crystal-cell-line are not and are much reduced in numbers (1, 2).
In contrast to the wild-type the mutant hematopoietic organs are enlarged and contain, in addition to primordial blood-cells, large numbers of mature plasmato-, podo-, and lamellocytes.
All cell-types of the plasmatocyte-line differ in their fine structure and behavior from their wild-type counterparts. The mutant blood cells show generally a numerical increase of cell organelles and acid phosphatase positive primary and secondary lysosomes. In the phenol oxidase test they showed a vigorous melanization reaction. Plasmato- and podocytes invade into the tissues of the larva and show high phagocytic activity.