Dependence of the Composition of the Avermectin Complex of Streptomyces avermitilis on the Glucose Content in the Medium

The effects of the glucose concentration in the medium and O-methyl-L-threonine resistance on the ratio of components of the avermectin complex produced by Streptomyces avermitilishave been studied. Glucose deficiency increases the ratio of components A and ain the complex, while decreasing that of components 1. A mutation that renders the microorganisms resistant to O-methyl-L-threonine (an analogue of isoleucine) increases the ratio of components a in the complex, while decreasing that of components 1. The distribution of aand b in fractions 1and 2 remains constant: the values of the ratio a/b in the fractions amount, respectively, to 1 : 1 and 2 : 1. The relation of the variations in the composition of the avermectin complex to changes in the carbohydrate metabolism of the producer stain, underlain by availability of the source of carbon, is discussed.     

Seasonal study of the fungal biota of the fur of dogs

During a one year period, 944 dogs from the Municipal kennel of Barcelona were examined to detect animals with suspected dermatophytosis. Only a few animals (1.8%) presented skin lesions but none of them had dermatophytosis. A representative number of dogs without visible skin lesions (n=172), selected at random, were used to carry out a seasonal study of the mycobiota of their fur. Fifteen isolates belonging to the genera Microsporum and Trichophyton were isolated from 14 of the 172 (8.1%) dogs without lesions. The identity of these fungi was Microsporum gypseum (6/15), Trichophyton terrestre (4/15), M. canis (2/15), M. cookei (2/15) and Trichophyton ajelloi (1/15) (one strain each of M. gypseum and T. ajelloi were isolated from one dog). Species of Penicillium (% prevalence=89.5%), Alternaria (86.6%), Cladosporium (84.9%), Aspergillus (77.3%), Scopulariopsis (65.7%) and Chrysosporium (64.5%) were the most prevalent. No significant differences in the fungal biota were observed with respect to age, gender, hair length or between mixed and pure breed dogs. A large number of isolates, including species belonging to the genera Beauveria, Chrysosporium, Malbranchea and Scopulariopsis, that macroscopically and/or microscopically resemble dermatophytes and may be mistaken for them, produced a red color change in Dermatophyte Test Medium. No significant seasonal difference was detected among the isolates belonging to the the most frequently encountered genera, with the exception of Scopulariopsis (higher in summer and autumn) and Chrysosporium (higher in summer). Species from other genera, with lower occurrence also presented significant differences in their seasonal distribution. Arthrinium, Aureobasidium, Chaetomium and Phoma spp. presented maximum prevalence peaks in spring, Fusarium, Paecilomyces, Phoma and Rhizopus spp. in summer and Geotrichum and Mucor spp. in autumn. The Microsporum and Trichophyton species were more frequently isolated in summer.     

On the generalization of the logistic law of growth

This communication presents a discussion of some extensions of the formalism of Verhulst's simple logistics, which may constitute an autonomous growth model of a more general scope.For that purpose, the basis concept of growth diagram or trajectory is called upon, as it affords the graphic representation of the change in the growth variable y, using two relevant kinetic parameters: the instantaneous rate and the instantaneous acceleration. The two possible kinds of trajectories are in relation to the use of absolute (V = dyldt; = dV/dt) or relative (or specific) values (R = (1/y)(dy/dt); _R = dR/dt).In the case of simple logistics, the trajectory (V, ) allows 4 growth phases or states to be distinguished. The diagram (R, _R ) shows that the deceleration of the specific rate is not monotonous.In the case of Richards - Nelder's generalized logistics, the qualitative variation of the growth trajectory depends on the value of the dissymmetry parameter (occurrence of a critical value which determines the number of growth states).Blumberg's model is characterized by an analogous property and, moreover, can account for a non monotonous variation of the specific growth rate.     

In Situ Hybridisation Analysis of the X-Linked Genes in the Species of the Virilis Group of Drosophila

When estimating the level of DNA sequence variation within and between populations or when planning QTL analysis, it is essential to know the location of the genes under study. In the present work, five X chromosomal genes, earlier localised in Drosophila virilis and D. littoralis, were mapped by in situ hybridisation on the larval polytene chromosomes of four other virilis group species, D. a. americana, D. flavomontana, D. lacicola and D. montana. Conjugation of X chromosomes of the most interesting species pairs was studied in interspecific hybrids. Three of the marker genes were used as RFLP markers to examine the occurrence of recombination in D. flavomontana and D. montana hybrid females. The gene arrangement of all species studied, appeared to be different at the proximal end of the X chromosome, which prevented normal conjugation along the most part of the X chromosome. The data illustrating the locations of five X chromosomal marker genes are presented for D. a. americana, D. flavomontana, D. lacicola and D. montana.     

Analysis of the expression of the Rhodobacter sphaeroides lexA gene

The regulation of the Rhodobacter sphaeroides lexA gene has been analyzed using both gel-mobility experiments and lacZ gene fusions. PCR-mediated mutagenesis demonstrated that the second GAAC motif in the sequence GAACN₇GAACN₇GAAC located upstream of the R. sphaeroides lexA gene is absolutely necessary for its DNA damage-mediated induction. Moreover, mutagenesis of either the first or the third GAAC motif in this sequence reduced, but did not abolish, the inducibility of the R. sphaeroides lexA gene. A R. sphaeroides lexA-defective (Def) mutant has also been constructed by replacing the active lexA gene with an inactivated gene copy constructed in vitro. Crude extracts of the R. sphaeroides lexA(Def) strain are unable to form any protein-DNA complex when added to the wild-type lexA promoter of R. sphaeroides. Likewise, the R. sphaeroides lexA(Def) cells constitutively express the recA and lexA genes. All these data clearly indicate that the lexA gene product is the negative regulator of the R. sphaeroides SOS response. Furthermore, the morphology, growth and viability of R. sphaeroides lexA(Def) cultures do not show any significant change relative to those of the wild-type strain. Hence, R. sphaeroides is so far the only bacterial species whose viability is known not to be affected by the presence of a lexA(Def) mutation. Received: 31 January 2000 / Accepted: 3 April 2000     

A new plesiosaur of the family aristonectidae from the early cretaceous of the center of the Russian platform

A new plesiosaur, Abyssosaurus nataliae gen. et sp. nov. from the Upper Hauterivian Substage (Lower Cretaceous) of Chuvashia, is described based on a postcranial skeleton. The new taxon is assigned to the family Aristonectidae where it presumably occupies an intermediate position between Late Jurassic Tatenectes and Kimmerosaurus and Late Cretaceous Aristonectes and Kaiwhekea. This is the first reliable record of this family in Russia.     

Evaluation of the Effect of Light Intensity on the Measurement of the Photosynthetic Rate in Plankton Microalgae by the Chlorophyll Fluorescence Method

The use of relative variable fluorescence (RVF) of chlorophyll, as measured in the presence of Diuron, an inhibitor of electron transfer, for the estimation of the photosynthetic activity of plankton microalgae was analyzed under a wide range of light intensities in the PAR region. Oxygen evolution rates (estimated by the method of light and dark bottles and the amperometric method), RVF, and chlorophyll a concentration were measured in parallel in natural algal cenoses and microecosystems. When the previously used regression equation, in the form A = b(F/F _d)C _chl I, where A is O₂ evolution rate (g/(m³ h), F/F _d is RVF (relative units), C _chl is chlorophyll a concentration (mg/m³), and I is light intensity (W/m²), was verified in the PAR region, we observed a nonlinear dependence of the correction coefficient b on I, which can be described by the formula b = 6.227 × 10³I. This result agrees with the hypothesis that chlorophyll a fluorescence quenching comprises photochemical (qQ) and energy (qE) components. On the basis of the energy model, we determined the upper limit b _max = 0.003 for light intensity range I< 4.4 W/m² and the lower limit b _min = 0.0003 for I = 400 W/m².     

Potentially active copies of the gypsy retroelement are confined to the y chromosome of some strains of drosophila melanogaster possibly as the result of the female-specific effect of the flamenco gene

Gypsy is an endogenous retrovirus present in the genome of Drosophila melanogaster. This element is mobilized only in the progeny of females which contain active gypsy elements and which are homozygous for permissive alleles of a host gene called flamenco (flam). Some data strongly suggest that gypsy elements bearing a diagnostic HindIII site in the central region of the retrovirus body represent a subfamily that appears to be much more active than elements devoid of this site. We have taken advantage of this structural difference to assess by the Southern blotting technique the genomic distribution of active gypsy elements. In some of the laboratory Drosophila stocks tested, active gypsy elements were found to be restricted to the Y chromosome. Further analyses of 14 strains tested for the permissive vs. restrictive status of their flamenco alleles suggest that the presence of permissive alleles of flam in a stock tends to be associated with the confinement of active gypsy elements to the Y chromosome. This might be the result of the female-specific effect of flamenco on gypsy activity. Received: 13 June 1997 / Accepted: 27 August 1997     

A comparative study of the epidermis of the common carp and the three Indian major carp

A comparative study has been made of the mucogenic epidermis of the common carp, Cyprinus carpio var. communis, and the three Indian major carps, Catla catla, Labeo rohita and Cirrhina mrigala: on the basis of epidermis structural organization, these species are easily differentiated. The epithelial cells in the superficial layer, as in most fishes, show secretory activity, evidenced by positive histochemical reactions, which is high in C. carpio var. communis, moderate in C. catla and low in L. rohita and C. mrigala. The epithelial cells in the underlying two or three layers also give positive reactions, though their intensity is relatively weak. The mucous cells in C. carpio var. communis are distributed in large numbers arranged in several superimposed layers in the outer regions of the epidermis, whereas in C. catla they are fewer in number and are widely separated in the surface layers as well as in the deeper layers of the epidermis; in both species the mucous cells appear rounded, large, and open on the surface by wide pores. In contrast, in L. rohita and C. mrigala the mucous cells are smaller, restricted mainly to the superficial layer, close together in a single row, and open on the surface by narrow pores. The overall density of mucous cells in L. rohita and C. mrigala, as in C. catla, is much lower than in C. carpio var. communis. In the epidermis of C. carpio var. communis there are a large number of mucous cells, and the few club cells are restricted to the deeper layers. In contrast, in the epidermis of the three Indian major carp the overall density of the mucous cells is much lower and the club cells are very numerous. It is suggested that the high density of club cells compensates an overall low density of mucous cells as an adaptation for an effective defence mechanism. Increased mucus production in the epidermis of C. carpio var. communis, as evidenced by a large number of mucous cells in outer regions and high secretory activity of superficial layer epithelial cells, is associated with increased precipitation of mud held in suspension, needed as an adaptation to the species’peculiar bottom-scooping habits. The varied density of the taste buds in the epidermis of the four carp is associated with their feeding habits.     

Metabolomic analyses of the haemolymph of the Asian citrus psyllid Diaphorina citri,the vector of huanglongbing

The Asian citrus psyllid Diaphorina citri Kuwayama is currently threatening the citrus industry by transmitting the causative agent Candidatus Liberibacter asiaticus (CLas) of huanglongbing. Multiplication of CLas in haemolymph of D. citri indicates that it contains the necessary nutrients for CLas. Although many studies examine D. citri, the haemolymph composition of this dangerous pest remains to be investigated. In the present study, the haemolymph of D. citri is collected using a nanolitre syringe after the removal of one of its forelegs. The haemolymph is either derivatized with methyl chloroformate (MCF) or trimethylsilyl (TMS) derivatizing reagent and analyzed with gas chromatography–mass spectrometry. Nineteen amino acids, two organic acids and seven fatty acids are detected in the haemolymph after MCF derivatization. More metabolites are detected after TMS derivatization. Sugars are the most abundant metabolites in the haemolymph. Glucose and fructose are the main monosaccharides. Trehalose and sucrose are the major disaccharides. Furthermore, three inositol isomers (myo‐inositol, scyllo‐inositol and chiro‐inositol) are detected in the haemolymph. Organic acids are found in low amounts, whereas phosphoric acid is found at a higher concentration. Twenty‐four nucleotides and sugar nucleotides, including ATP, ADP and AMP, are detected using high‐performance anion‐exchange chromatography. Adenine nucleotides are the most abundant nucleotides followed by uridine and guanosine. The adenylate energy charge for the haemolymph is 0.77. Our results show that many metabolites found in the citrus phloem sap are also found in the haemolymph of D. citri.     

A review of the systematic position of the North American species of the genusGlyptotendipes

The systematic position of the North American species of the genusGlyptotendipes is reviewed using morphological characters from all life history stages. The cladistic analysis revealed adult characters which support the monophyly of the three species groups (A, B and C) of PINDER and REISS (1983, 1986) for pupae and larvae. These species groups are given formal subgeneric status, with Group A becomingGlytotendipes, s.s., placingPhytotendipes Goetghebuer, 1937 in synonymy, Group B is namedCaulochironomus (type-species,Tendipes caulicola Kieffer, 1913) and Group C is namedTrichotendipes (type-species,Tendipes signatus Kieffer, 1911).     

Regulation of the activity of alcohol dehydrogenase isozymes during the development of the maize kernel

Summary The relative activities of alcohol dehydrogenase isozymes have been studied during the development of the endosperm and scutellum of heterozygous Adh ₁ ^F /Adh ₁ ^S maize kernels. The products of the Adh ₁ ^F allele are found earlier than the products of the Adh ₁ ^S allele in both the scutellum and the endosperm. A second gene (Adh _r )which controlsthe activity level of ADH is active in the scutellum only. The Adh _r ^N allele specifies increase in the relative activity of the Adh ₁ ^S products from 26 to 38 days after pollination. This increase is prevented by the Adh _r ^L allele which is dominant. These results ar discussed on the basis of the limited factor hypothesis proposed recently by Schwartz (1971) for the regulation of the Adh ₁gene in maize.     

Analysis of the genetic diversity of wild Spanish populations of the genusHordeum through the study of their endosperm proteins

A study was made of the genetic variability of 101 barley populations belonging to the four, wild, Spanish species of the genusHordeum (the autogamousH. marinum subspp.marinum andgussoneanum, andH. murinum subspp.murinum andleporinum, plus the allogamous speciesH. bulbosum andH. secalinum). Electrophoresis of endosperm proteins was performed using a large number of individuals from each population sampled, in order to determine intra- and interpopulational variation. The distribution of variability observed by population and taxonomic unit, is closely related to the breeding system.Hordeum bulbosum showed the greatest intrapopulational variability andH. marinum subsp.gussoneanum the least. In contrast to the autogamous species, the allogamous species showed low levels of interpopulational variation.     

Dactylogyridean monogeneans of the siluriform fishes of the Old World

This is a catalogue and discussion of the known dactylogyridean monogenean genera of siluriform fishes of the Old World. Of a total of 38 nominal genera, only 19 are considered valid. Seventeen of these 19 genera are currently in the Ancyrocephalidae (containing the Ancyrocephalinae and Ancylodiscoidinae), whilst the other two (Neocalceostoma and Neocalceostomoides) are in the Neocalceostomatidae. The 17 genera are Anchylodiscus, Ancylodiscoides, Bagrobdella, Bifurcohaptor, Bychowskyella, Chauhanellus, Cornudiscoides, Hamatopeduncularia, Mizelleus, Paraquadriacanthus, Pseudancylodiscoides, Protoancylodiscoides, Quadriacanthus, Schilbetrema, Schilbetrematoides, Synodontella and Thaparocleidus. Clariotrema Long, 1981 and Neobychowskyella Ma, Wang & Li, 1983 are considered synonyms of Bychowskyella Akhmerov, 1952, Anacornuatus Dubey, Gupta & Agarwal, 1992 is considered a synonym of Quadriacanthus Paperna, 1961, Mizellebychowskia Gupta & Sachdeva, 1990 is considered a synonym of Neocalceostoma Tripathi, 1959 and Hargitrema Tripathi, 1959 is treated as a synonym of Hamatopeduncularia Yamaguti, 1953. It is proposed that the Ancylodiscoidinae be raised to family status within the order Dactylogyridea to accommodate these 17 `ancyrocephalid' genera from siluriforms, together with Malayanodiscoides and Notopterodiscoides from notopterids. A key and the diagnostic characteristics of the 19 recognised dactylogyridean genera from catfishes plus two from notopterids, together with a list of species and synonyms, are included. New combinations made in this work are Thaparocleidus avicularia (Chen, 1987) n. comb., T. calyciflorus (Chen, 1987) n. comb., T. choanovagina (Luo & Lang, 1981) n. comb., T. dissimilis (Chen, 1988) n. comb., T. leiocassis (Reichenbach-Klinke, 1959) n. comb., T. meticulosa (Chen, 1987) n. comb., T. parasoti (Zhao & Ma, 1999) n. comb., T. persculpus (Chen, 1987) n. comb., T. valga (Chen, 1987) n. comb. and T. wulingensis (Yao & Wang, 1997) n. comb. [all from Silurodiscoides] and Bychowskyella glyptothoraci (Ma, Wang & Li, 1983) n. comb. [from Neobychowskyella].     

On the Structure of the Avian Maculae

The maculae of the labyrinths of several avian species were examined. The striola of the macula utriculi and lagenae is tri-zonal, consisting of two zones of hair cells type I (HC I) located on each side of a middle zone of hair cells type II (HC II). An exception is the mute swan, in which the macula utriculi has a striola consisting of one broad zone of HC I. The macula sacculi is, in its central part, mainly consisting of HC I, and the striola does not have a tri-zonal structure. The hair cells in the macula utriculi are polarized with their kinociliar end oriented towards the striola, while in the macula sacculi and lagenae they are oriented away from this dividing line. A varying number, from 1 to 12, of HC I are enclosed within the same nerve chalice. The macula sacculi seems to contain chalices with slightly more HC I than the two other maculae do.     

Asymmetries of the long bones of the limbs and of the clavicles in Indian Lorises

Eighteen adult skeletons ofLoris tardigradus lydekkerianus (4 males and 4 females) andNycticebus coucang (6 males and 4 females) have been studied for the asymmetries in the long bones of the limbs and of the clavicles. The bones of the upper extremity are longer in the right inLoris andNycticebus. Asymmetry favours the right side more inLoris than inNycticebus regarding the thigh bone and the total length of the lower extremity. Lorises do not essentially differ from the other primates including man, regarding the asymmetries of the lower extremities as they do in regard to the asymmetries of the upper extremities.Averages of the percentage asymmetries are higher in females than in males. Cases of symmetry are rarer in clavicles (0%) than in the other bones of the upper and lower extremities ofLoris andNycticebus but they do favour radius inNycticebus (45%) alone. There are no significant sex differences in the 2 series in the distribution of the asymmetries.The average of the degrees in which the lengths of the corresponding limb bones are unequal on the 2 sides of the body are approximately the same inLoris (0.78),Hylobatidae (0.70) and the great apes (0.72) with regard to the upper extremities. In the lower extremities, however, these degrees including those in man (0.63) and the macaque (0.61), excepting inHylobatidae (0.86) are practically the same as inNycticebus (0.61) while much higher than those inLoris (0.43).This investigation forms a part of the main research programme based on the anatomical and metrical data, on the Indian Lorises, conducted under the aegis of the Council of Scientific and Industrial Research, New Delhi, during the years 1962–65.This paper was presented before the section of Anthropology and Archaeology of the Indian Science Congress Association at its 54th annual session held at Hyderabad in January 3–9, 1967.     

Phragmoplastins,the Trentepohliales,and the Evolution of the Cytokinesis in Green Plants

Representatives of the monophyletic Trentepohliales are widely distributed in the tropics, subtropics, and temperate regions worldwide. They grow in soil, or are epilithic, epiphytic or endophytic. The family comprises approximately 70 species placed in at least four genera (Trentepohlia, Cephaleuros, Phycopeltis and Stomatochroon), with Trentepohlia sensu lato (including Printzina and Physolinum) accounting for half of the species in this family. PCR amplification and sequencing of the 18 SSU rDNA of 18 isolates of the Trentepohliaceae were used to assess the monophyly of the genus Cephaleuros and to determine the phylogenetic relationships among species of Trentepohlia sensu lato. Distance, Parsimony, and Maximum Likelihood analyses indicate that Trentepohlia sensu lato is basal and includes two species recently transferred to Phycopeltis (P. umbrina) and Printzina (P. lagenifera). In contrast, Cephaleuros is a derived monophyletic clade. Analysis of isolates of C. virescens, from the USA, Taiwan, and South Africa indicate that this taxon may consist of different species sharing a convergent morphology. The results of this study have implications for the taxonomy of the genera.