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.     

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.     

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.     

Non-Circadian Periodicity in the Duration of the Cell Cycle and the G1 Phase in the Hindlimb Epidermis of the Anuran Tadpole,Rana Pipiens

Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-hr intervals over a 36-hr span in order to see if the cell cycle in the tadpole hindlimb epidermis varied with time or showed rhythmicity. There was a pattern of two long cell cycles followed by a shorter one. Total cell cycle length (Tc) and the length of the G₁ phase plus one-half of the mitotic time (TG₁+½M) fluctuated the most, although only TG₁+½M varied significantly with the Chi-square test. The proportion of TC spent in each phase was also calculated. Only TG₁+½M/Tc had statistically significant fluctuations with time.

Rhythmicity was analyzed by a computer program using the method of least squares for cosine curve fitting. Statistically significant ultradian rhythms of 18.4 hr in TC, 18.5 hr in TG₁+½M and 18.6 hr in TG₁+½M/TC and the length of the DNA synthetic phase/total cell cycle length (TS/TC) were found. Circadian rhythmicity was not observed. The acrophases of the ultradian rhythms of TC and TG₁+½M coincided, suggesting that the rhythm of TC was due mainly to variation in TG₁+½M. In the absence of significant variation in TS, the longest phase of the cell cycle, whenever G₁+½M was short, TS/TC increased, so that the 18.6 hr rhythm in TS/TC was also a result of the periodicity in TG₁+½M.     

Mesotocin and vasotocin in the brain of the lizard Gekko gecko

Summary The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.Abbreviations acc nucleus accumbens - bst bed nucleus of the stria terminalis - bv blood vessel - dB diagonal band of Broca - dc dorsal cortex - dth dorsolateral thalamic nucleus - lc lateral cortex - me median eminence - oc optic chiasma - ot optic tract - pag periaqueductal grey - pvn paraventricular nucleus - rc rhombencephalic cell group - sep septum - son supraoptic nucleus - tect mesencephalic tectum - vth ventrolateral thalamus     

Contributions to the cytotaxonomy of the Commelinaceae*

Further material of Gibasis geniculata (Jacq.) Rohw. (syn. Tradescantia geniculata Jacq.) and other Gibasis species collected in the field has been studied. The existence of several species in our earlier experimental material is confirmed. These include G. geniculata itself (2n= 32 or 48 small chromosomes), G. oaxacana D. R. Hunt (2n= 16 small chromosomes) and G. schiedeana (Kunth) D. R. Hunt, which has two chromosome forms, 2n= 10 and 2n= 16, both with large chromosomes. These forms are diploid and tetraploid based on x= 5 and x= 4 respectively and show a Robertsonian relationship with each other. The cytology of tetraploid (2n= 20) G. karwinskyana is confirmed and that of a diploid form (2n=10) described. The recently described G. consobrina D. R. Hunt (2n= 20) is shown to be cytologically comparable with G. karwinskyana, but to differ in significant details. Next, the cytology of G. pulchella (Kunth) Rafin., the type species of Gibasis, is described and also that of the allied G. matudae D. R. Hunt. Both G. pulchella (2n= 10, 15) and G. matudae (2n= 10) show interchange heterozygosity, with complete rings of ten chromosomes at meiosis in some plants of G. pulchella. Preliminary comments are made on the cytology of G. aguensis (Standl. & Steyerm.) Rohw. (2n= 10), another ally of G. pulchella, and on the G. linearis group, where the basic number appears to be x= 6 but two karyotype patterns have been found. A discussion of chromosome architecture in Gibasis in relation to the taxonomy of the genus concludes the paper.     

Circadian organization in the ruin lizard Podarcis sicula: the role of the suprachiasmatic nuclei of the hypothalamus

The effects of electrolytic lesions to the suprachiasmatic nuclei of the hypothalamus (SCN) on circadian rhythms of locomotor activity were examined in ruin lizards Podarcis sicula maintained in constant darkness and constant temperature (29°C). All lizards (N=15) in which the lesion damaged 80% or more of the SCN became behaviorally arrhythmic. On the contrary, locomotor rhythms persisted in all cases (N=11) when the SCN remained intact and lesions were confined to neighbouring regions of the preoptic area. Taken together with previous work which demonstrates that the pineal and the retinae are not essential for the persistence of circadian locomotor rhythmicity in Podarcis sicula and with recent evidence showing the homology between the SCN of lizards and those of mammals the present results strongly support the view that the SCN of Podarcis sicula contain the primary pacemaker(s) for locomotor rhythms.Abbreviations DD constant darkness - LL constant light - SCN suprachiasmatic nuclei of the hypothalamus - PH nucleus periventricularis hypothalami - OC optic chiasm - te length of circadian activity - freerunning circadian period     

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.     

Trypomastigotes and potential flea vectors of the endemic rodents and the introduced Rattus rattus in the rainforests of Madagascar

Transmission of parasites and diseases may be one of the mechanisms for the displacement of native and endemic rodents of Madagascar (subfamily Nesomyinae) by the introduced Rattus rattus (subfamily Murinae). We studied the occurrence of trypomastigotes in rodents at several rainforest sites on the island. Examination of blood smears showed Trypanosoma lewisi-like trypomastigotes in 11.5% of the R. rattus (n = 52). Trypomastigotes differing in morphology from those of T. lewisi were detected in 4% of the endemic rodent Nesomys rufus (n = 23). In contrast to the relatively heavy infections found in R. rattus, only a few trypomastigotes were found in the infected N. rufus. Trypomastigotes were not found in other nesomyine rodents including Eliurus minor (n = 18), E. tanala (n = 15), E. grandidieri (n = 12), E. majori (n = 9) or E. webbi (n = 9). Of potential vectors of trypomastigotes, six endemic species of fleas were identified from the rodents.     

The question of cosmopolitanism in the deep-sea ostracod fauna: the example of the genus Pedicythere

Deep-sea Pedicythere species which had been earlier considered as pan-abyssal in distribution are shown to be composite species including similar, but separate species in the Pacific, Indian and Atlantic oceans. Morphology and distribution of Pedicythere are analysed. A key to well-described Cenozoic species and forms in open nomenclature which are referred to Pedicythere is presented, together with an annotated checklist of species. Five new species of Pedicythere are described from the South China Sea: P. hirundo sp. nov., P. gibbera sp. nov., P. dentata sp. nov., P. arator sp. nov. and P. nivea sp. nov.     

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.     

Unravelling the structure and function of the petal appendages in the tribe Schwenckieae (Solanaceae)

• The tribe Schwenckieae (Solanaceae) is characterised by the presence of appendages on the corolla, a diagnostic trait for the group. These appendages constitute a median distal projection of the three‐lobed petal and occur in the genera Melananthus and Schwenckia but are absent in Heteranthia.
• We investigated the micromorphology and anatomical structure of the appendages and lateral petal lobes of Schwenckia americana (two varieties), S. angustifolia, S. curviflora and S. novaveneciana, and Melananthus fasciculatus. We also performed histochemical tests to determine if the appendages are involved in the production of volatiles, acting as a fragrance secretory structure (osmophore).
• The appendages have a uniseriate epidermis, whose cells store phenolics and lipids. The parenchyma is starch‐rich just prior to anthesis in all species studied. The sensory test and anatomical analyses identified scent‐secreting tissues, not only in the appendages, but also in the lateral petal lobes, whose cells are papillose with a sculptured surface. The α‐naphthol p‐phenylenediamine (NADI) reaction detected volatile (essential oils) compounds in S. americana var. americana and S. americana var. angustifolia.
• We demonstrated the secretory tissues and the production of lipids in the corolla appendages of Schwenckia and Melananthus, which indicate their osmogenic function and probable scent emission to attract pollinators.

     

Influence of rabbit cold adaptation on the depressor muscarinic cholinergic reaction of the arterial pressure of the hind limb vessels and the small intestine in situ and the systemic arterial pressure

Modification of the main parameters of cholinergic reactions in rabbits, i.e., of the specific sensitivity to agonists (EC ₅₀), maximal reaction values (P _m ) of arterial pressure in the hind limb vessels and small intestine in situ, and systemic arterial pressure after adaptation to cold for 1, 5, 10, and 30 days has been investigated. The depressor reaction to acetylcholine (muscarinic cholinergic receptors agonist) was established to correspond to the model p = (P _m A ⁿ )/(EC ₅₀ ⁿ + A ⁿ ) with n =1. In the control EC ₅₀ was equal to 0.85, 1.01, and 1.21 nmol/kg, while P _m equaled 100, 32.6, and 61.2 mm Hg for the hind limb vessels, small intestine in situ, and systemic arterial pressure, respectively.     

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.     

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.     

Distribution of the Transposable Element Minos in the Genus Drosophila

We analyzed 28 species of the genus Drosophilafor the presence of the Tc1-like transposable element Minosusing Southern blot hybridization under high stringency conditions. The Minostransposon was found in members of both the Drosophilaand the Sophophorasubgenus showing a distribution that is wider if compared to other well-studied Drosophilatransposons such as the Pelement, hoboand mariner. The presence of Minos-hybridizing sequences was discontinuous in the Sophophorasubgenus, especially in the melanogasterspecies group. Using the Polymerase Chain Reaction we amplified a portion corresponding to the putative Minostransposase from different Drosophilaspecies. Cloning and sequence analysis of randomly selected Minoscopies from D. mojavensisis, D. saltansand D. willistonisupports the idea that event(s) of horizontal transfer may have contributed to the spreading of this transposon in the Drosophilagenus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Correlation between the shoot-cutting behavior of the acorn weevil and the reproductive traits of host fagaceous trees

Many fagaceous species mature acorns during the second autumn after flowering and are called “2-year species.” In 2-year species of subgenus Cyclobalanopsis (genus Quercus), alternate bearing (2-year seed production cycle) is prominent, but this has not been reported for other 2-year species in the genera of Lithocarpus and Castanopsis. We tested the hypothesis that the difference in reproduction of 2-year species is linked to the weevil, Mechoris ursulus. After ovipositing on acorns, this insect cuts the shoots to which the acorns are attached. We examined the host preference of M. ursulus and reproductive traits of fagaceous 2-year species. Percentage infestation was remarkably high in the subgenus Cyclobalanopsis, whereas Lithocarpus and Castanopsis species suffered almost no damage. Furthermore, unlike Lithocarpus and Castanopsis, most of the acorn-producing shoots in subgenus Cyclobalanopsis had no current-year shoots. The clear relationship suggests that alternate bearing in subgenus Cyclobalanopsis is an adaptation to the shoot-cutting behavior of M. ursulus.