Saprophytic colonization of citrus twigs by Diaporthe citri and factors affecting pycnidial production and conidial survival

Melanose, caused by Diaporthe citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28 degrees C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. citri was high in rainy season, moderate in spring and early fall, and minimal in late fall and winter. Twig colonization was positively related to the number of rain days and average temperature, but not to total rainfall. In another experiment, inoculated twigs placed in the tree canopy developed pycnidia and then produced conidial masses for about 200 days. D. citri is a serious pathogen, but a weak parasite, that survives primarily by colonization and reproduction on dead twigs.

Valorização do diagnóstico laboratorial, na identificação de Rhodococcus equi isolado do escarro de pacientes suspeitos de tuberculose

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetics of the Brazilian Bolitoglossa paraensis (Unterstein, 1930) salamanders (Caudata, Plethodontidae)

Plethodontid salamanders of genus Bolitoglossa constitute the largest and most diverse group of salamanders, including around 20% of living caudate species. Recent studies have indicated the occurrence of five recognized species in the Brazilian Amazon Rainforest. We present here the first cytogenetic data of a Brazilian salamander, which may prove to be a useful by contribution to the cytotaxonomy of the genus. Specimens were collected near the “type” locality (Utinga, Belém, PA, Brazil). Chromosomal preparations from duodenal epithelial cells and testes were subjected to Giemsa staining, C-banding and DAPI/CMA₃ fluorochrome staining. All specimens showed a karyotype with 13 bi-armed chromosome pairs (2n = 26). Nucleolar Organizer Regions, evidenced by CMA₃, were located distally on the long arm of pair 7 (7q). DAPI₊ heterochromatin was predominantly centromeric, with some small pericentromeric bands. Although the C-banding patterns of other Bolitoglossa species are so far unknown, cytogenetic studies conducted in other Plethodontid salamanders have demonstrated that pericentromeric heterochromatin is a useful cytological marker for identifying interspecific homeologies. Species diversification is usually accompanied by chromosomal changes. Therefore, the cytogenetic characterization of Bolitoglossa populations from the middle and western Brazilian Amazon Basin could identify differences which may lead to the identification of new species.

Protocylindrocorpus brasiliensis n. sp. (Diplogastroidea: Cylindrocorporidae) associated with the ambrosia beetle, Euplatypus parallelus (f.) (Curculionidae: Platypodinae) in para rubber trees (Hevea brasiliensis)

Protocylindrocorpus brasiliensis n. sp. (Diplogastroidea: Cylindrocorporidae) is described from reproductive stages removed from galleries of the ambrosia beetle, Euplatypus parallelus (F.) (Curculionidae: Platypodinae) in Para rubber trees (Hevea brasiliensis) in Brazil. This is the first record of the genus Protocylindrocorpus from the Neotropics. Males of P. brasiliensis are quite striking because their long spicules extend up to 72% of their total body length. The adults exhibit conspecific agglutination where they congregate in a slimy substance that serves to maintain them in a coherent group for mating. Some of the adults were infected by fungal and protozoan pathogens, implying that disease plays a role in regulating natural populations. The discovery of P. brasiliensis provides new information on nematode structure, behavior, and ecology.

Morphological Homogeneity of Neurons: Searching for Outlier Neuronal Cells

We report a morphology-based approach for the automatic identification of outlier neurons, as well as its application to the NeuroMorpho.org database, with more than 5,000 neurons. Each neuron in a given analysis is represented by a feature vector composed of 20 measurements, which are then projected into a two-dimensional space by applying principal component analysis. Bivariate kernel density estimation is then used to obtain the probability distribution for the group of cells, so that the cells with highest probabilities are understood as archetypes while those with the smallest probabilities are classified as outliers. The potential of the methodology is illustrated in several cases involving uniform cell types as well as cell types for specific animal species. The results provide insights regarding the distribution of cells, yielding single and multi-variate clusters, and they suggest that outlier cells tend to be more planar and tortuous. The proposed methodology can be used in several situations involving one or more categories of cells, as well as for detection of new categories and possible artifacts.

Untersuchung zum Beitrag des ON-Kanals zu zeitlichen und chromatischen Verarbeitungsmechanismen in der Retina

Ziel der vorliegenden Arbeit war es, mithilfe von Dressurexperimenten in Kombination mit dem Einsatz von Neuropharmaka die Bedeutung des retinalen ON-Kanals für zwei visuelle Leistungen des Goldfisches – das kontrastabhängige zeitliche Auflösungsvermögen sowie die Wellenlängenunterscheidungsfähigkeit - zu untersuchen. Da die Tiere nach der pharmakologischen Blockade keinerlei verändertes Verhalten zeigten, kann davon ausgegangen werden, dass der retinale ON-Kanal weder für die Prozessierung des kontrastabhängigen zeitlichen Auflösungsvermögens noch für die Wellenlängenunterscheidungsfähigkeit eine maßgebliche Rolle spielt. Aus den Versuchen zur Wellenlängenunterscheidungsfähigkeit kann des Weiteren abgeleitet werden, dass der ON-Kanal auch für die spektrale Empfindlichkeit der Tiere bei der gegebenen Beleuchtungs- und Dressurbedingungen (L+-Dressur) keine Bedeutung zu haben scheint. Nach den Versuchen zum kontrastabhängigen zeitlichen Auflösungsvermögen kann festgehalten werden, dass das zeitliche Auflösungsvermögen des Goldfisches sich mit abnehmendem Stimuluskontrast verändert: Der für die Tiere wahrnehmbare Flickerfrequenzbereich wird mit abnehmendem Kontrast geringer. Die Flimmerfusionsfrequenz wird im oberen Frequenzbereich früher erreicht; im unteren Flickerfrequenzbereich tritt mit abnehmendem Kontrast auch eine untere Grenze des zeitlichen Auflösungsvermögens auf. Des Weiteren zeigen die Ergebnisse aus den Verhaltensversuchen zu den kontrastabhängigen zeitlichen Übertragungseigenschaften eine gute Vergleichbarkeit zu elektrophysiologisch gewonnenen Antworten von ON bzw. OFF-Bipolarzellen. Ebenso ähneln sich die Kurvenverläufe zum kontrastabhängigen zeitlichen Auflösungsvermögen und die aus den Versuchen zur kontrastabhängigen Ganzfeldbewegungswahrnehmung – einer visuellen Leistung, deren Prozessierung eines ON-Kanal-Beitrages bedarf. Diese Ergebnisse deuten darauf hin, dass das zeitliche Auflösungsvermögen wie auch die Ganzfeldbewegungswahrnehmung hauptsächlich von retinalen Verarbeitungsprozessen abhängen.

[Pneumatosis cystoides intestinalis: a rare illness in adults]

Pneumatosis cystoides intestinalis (PCI) is a rare illness in adults with gas filled blebs found in the submucosa or subserosa of the bowel wall. The main localization is the terminal ileum although all parts of the intestine can be affected. Clinical symptoms can vary from aqueous-slimy, bloody diarrhea to constipation and/or vague abdominal pain. Patients can also be completely asymptomatic. In symptomatic patients the therapy of PI is based on the assumed pathogenesis, so that a combined treatment of metronidazole 1500 mg daily during a period of 6-8 weeks additionally and oxygen application (PaO2 of 200-350 mmHg) for 7 days is suggested. In addition, elemental diets are recommended. Complications are indicated in the literature with 3%. In particular mechanical ileus, invagination and perforation as well as substantial intestinal bleeding up to the volvolus lead to further diagnostic and therapeutic steps. A surgical intervention is reserved for rare cases.

Amphibian Biodiversity Survey - Wetland Area Southwest of Montana Tech

The primary goal of this project was to launch a pilot population study in the spring-fed wetland area southwest of Montana Tech to establish baseline data on density, distribution, abundance, and diversity of amphibians in the area. The current confirmed species at the select site is the Columbia spotted frog (Rana luteiventris). Based on preliminary habitat assessment and existing literature, other species possibilities included the long-toed salamander (Ambrystoma macrodactylum) boreal chorus frog (Pseudacris maculata), the Rocky Mountain tailed frog (Ascaphus montanus), and the leopard frog (Rana pipiens), (Werner et al. 2004) though the latter species is considered unlikely based on the specie’s declining status (Werner 2003; Werner et al. 2004). The project’s secondary goal was to collect basic habitat and environmental data: vegetation, precipitation, temperature. The third goal was to explore correlations between species prevalence and environmental data to expand the scientific understanding of population dynamics in the field of amphibian studies (see: Ferner, 2007; Dodd, 2010).

Predator-Induced Plasticity in Spotted Salamanders (Ambystoma maculatum)

The ability to respond plastically to the environment has allowed amphibians to evolve adaptive responses to spatial and temporal variation in predation threat. However, animals exposed to predators may also show costs of plasticity or tradeoffs. This study examines predator-induced plasticity in larval development, behavior, and metamorphosis in the spotted salamander, Ambystoma maculatum. Salamanders were raised in two treatments: with predator cues (a fish predator, genus Lepomis, on the other side of a divided tank), or without predator cues. During the larval stage the predator treatment group experienced higher mortality rates than the no-predator treatment group. Behavioral trials revealed that predator treatment animals ate less than those not exposed, and that this feeding response was immediately inducible and had lasting effects. Animals in the predator treatment group had smaller tail areas during the mid-larval period. Feeding and body size effects may have contributed to increased mortality in the predator-treatment animals. The timing of metamorphic onset was not affected by the presence of predators, but predator-treatment salamanders had shorter snout/vent lengths at metamorphosis. The duration of metamorphosis showed a potentially adaptive plastic response to the presence of predator cues: metamorphosis was longest in the no-predator treatment group, reduced in the predator treatment group, and even further reduced for animals exposed to predator cues only during metamorphosis. Overall, we found a mix of potentially adaptive and costly plastic responses in spotted salamanders.

The role of thyroid hormone in zebrafish and axolotl development

Exogenous thyroid hormone (TH) induces premature differentiation of the zebrafish pectoral fins, which are analogous to the forelimbs of tetrapods. It accelerates the growth of the pelvic fins but not precociously. Goitrogens, which are chemical inhibitors of TH synthesis by the thyroid gland, inhibit the transition from larva to juvenile fish including the formation of scales, and pigment pattern; they stunt the growth of both pectoral and pelvic paired fins. Inhibition by goitrogens is rescued by the simultaneous addition of thyroxine. The effect of adding TH to the rearing water of the postembryonic Mexican axolotl was reinvestigated under conditions that permit continued growth and development. In addition to morphological changes that have been described, TH greatly stimulates axolotl limb growth causing the resulting larva to be proportioned as an adult in about two months. This study extends the known evolutionary relatedness of tetrapod limbs and fish fins to include the TH stimulation of salamander limb and zebrafish fin growth, and suggests that TH is required to complete the life cycle of a typical bony fish and a salamander at the same developmental stage that it controls anuran and flounder metamorphosis.

Cannabinoid CB1 receptors and ligands in vertebrate retina: Localization and function of an endogenous signaling system

CB1, a cannabinoid receptor enriched in neuronal tissue, was found in high concentration in retinas of rhesus monkey, mouse, rat, chick, goldfish, and tiger salamander by using a subtype-specific polyclonal antibody. Immunolabeling was detected in the two synaptic layers of the retina, the inner and outer plexiform layers, of all six species examined. In the outer plexiform layer, CB1 was located in and/or on cone pedicles and rod spherules. Labeling was detected in some amacrine cells of all species and in the ganglion cells and ganglion cell axons of all species except fish. In addition, sparse labeling was found in the inner and/or outer segments of the photoreceptors of monkey, mouse, rat, and chick. Using GC/MS to detect possible endogenous cannabinoids, we found 3 nmol of 2-arachidonylglycerol per g of tissue, but no anandamide was detectable. Cannabinoid receptor agonists induced a dramatic reduction in the amplitude of voltage-gated L-type calcium channel currents in identified retinal bipolar cells. The presence and distribution of the CB1 receptor, the large amounts of 2-arachidonylglycerol found, and the effects of cannabinoids on calcium channel activity in bipolar cells suggest a substantive role for an endogenous cannabinoid signaling system in retinal physiology, and perhaps vision in general.

The structure and precision of retinal spike trains

Assessing the reliability of neuronal spike trains is fundamental to an understanding of the neural code. We measured the reproducibility of retinal responses to repeated visual stimuli. In both tiger salamander and rabbit, the retinal ganglion cells responded to random flicker with discrete, brief periods of firing. For any given cell, these firing events covered only a small fraction of the total stimulus time, often less than 5%. Firing events were very reproducible from trial to trial: the timing jitter of individual spikes was as low as 1 msec, and the standard deviation in spike count was often less than 0.5 spikes. Comparing the precision of spike timing to that of the spike count showed that the timing of a firing event conveyed several times more visual information than its spike count. This sparseness and precision were general characteristics of ganglion cell responses, maintained over the broad ensemble of stimulus waveforms produced by random flicker, and over a range of contrasts. Thus, the responses of retinal ganglion cells are not properly described by a firing probability that varies continuously with the stimulus. Instead, these neurons elicit discrete firing events that may be the fundamental coding symbols in retinal spike trains.

Biodiversity of Costa Rican salamanders: Implications of high levels of genetic differentiation and phylogeographic structure for species formation

Although salamanders are characteristic amphibians in Holarctic temperate habitats, in tropical regions they have diversified evolutionarily only in tropical America. An adaptive radiation centered in Middle America occurred late in the history of a single clade, the supergenus Bolitoglossa (Plethodontidae), and large numbers of species now occur in diverse habitats. Sublineages within this clade decrease in number from the northern to southern parts of Middle America, and in Costa Rica, there are but three. Despite this phylogenetic constraint, Costa Rica has many species; the number of salamander species on one local elevational transect in the Cordillera de Talamanca may be the largest for any such transect in the world. Extraordinary variation in sequences of the mitochondrial gene cytochrome b within a clade of the genus Bolitoglossa in Costa Rica reveals strong phylogeographic structure within a single species, Bolitoglossa pesrubra. Allozymic variation in 19 proteins reveals a pattern largely concordant with the mitochondrial DNA phylogeography. More species exist than are currently recognized. Diversification occurs in restricted geographic areas and involves sharp geographic and elevational differentiation and zonation. In their degree of genetic differentiation at a local scale, these species of the deep tropics exceed the known variation of extratropical salamanders, which also differ in being less restricted in elevational range. Salamanders display “tropicality” in that although speciose, they are usually local in distribution and rare. They display strong ecological and physiological differentiation that may contribute importantly to morphological divergence and species formation.

The effect of recombinant recoverin on the photoresponse of truncated rod photoreceptors

Recoverin is a heterogeneously acylated calcium-binding protein thought to regulate visual transduction. Its effect on the photoresponse was investigated by dialyzing the recombinant protein into truncated salamander rod outer segments. At high Ca2+ (Ca), myristoylated recoverin (Ca-recoverin) prolonged the recovery phase of the bright flash response but had less effect on the dim flash response. The prolongation of recovery had an apparent Kd for Ca of 13 μM and a Hill coefficient of 2. The prolongation was shown to be mediated by inhibition of rhodopsin deactivation. After a sudden imposed drop in Ca concentration, the effect of recoverin switched off with little lag. The myristoyl (C14:0) modification of recoverin increased its activity 12-fold, and the C12:0 or C14:2 acyl group gave similar effects. These experiments support the notion that recoverin mediates Ca-dependent inhibition of rhodopsin phosphorylation and thereby controls light-triggered phosphodiesterase activity, particularly at high light levels.

On the origin of and phylogenetic relationships among living amphibians

The phylogenetic relationships among the three orders of modern amphibians (Caudata, Gymnophiona, and Anura) have been estimated based on both morphological and molecular evidence. Most morphological and paleontological studies of living and fossil amphibians support the hypothesis that salamanders and frogs are sister lineages (the Batrachia hypothesis) and that caecilians are more distantly related. Previous interpretations of molecular data based on nuclear and mitochondrial rRNA sequences suggested that salamanders and caecilians are sister groups to the exclusion of frogs. In an attempt to resolve this apparent conflict, the complete mitochondrial genomes of a salamander (Mertensiella luschani) and a caecilian (Typhlonectes natans) were determined (16,656 and 17,005 bp, respectively) and compared with previously published sequences from a frog (Xenopus laevis) and several other groups of vertebrates. Phylogenetic analyses of the mitochondrial data supported with high bootstrap values the monophyly of living amphibians with respect to other living groups of tetrapods, and a sister group relationship of salamanders and frogs. The lack of phylogenetically informative sites in the previous rRNA data sets (because of its shorter size and higher among-site rate variation) likely explains the discrepancy between our results and those based on previous molecular data. Strong support of the Batrachia hypothesis from both molecule- and morphology-based studies provides a robust phylogenetic framework that will be helpful to comparative studies among the three living orders of amphibians and will permit better understanding of the considerably divergent vertebral, brain, and digit developmental patterns found in frogs and salamanders.