ANALYSIS OF EXTENSION AND CURVATURE DURING THE GRAVIRESPONSE IN LEPIDIUM ROOTS

Intact roots of Lepidium sativum were photographed at 1.5- to 6-min intervals before and after being tilted from a vertical to a horizontal position. Relative extension rates were calculated for segments of the root by measuring the rate of movement of charcoal particles on the surface of the root. Curvature was measured at points separated by 0.8 mm, from the tip to the root hair zone. For the first hour after the root was tilted to a horizontal position, the relative extension rate for the side of the root producing the outer side of the curve is higher than that during straight growth. The relative rate for the inner side falls to near zero during the first hour in the horizontal position. There is thus a positive gradient in extension rate from the inner to the outer side of the curve. For most of the second hour, the two sides have approximately equal relative rates of extension. In the last 12 min of the second hour, as the root tip is moving the final distance to a vertical position, the rate on the inner side shows a high extension rate. The gradient in extension rate from the inner to the outer side of the curve has thus become negative during the second hour. This reversal in the extension gradient is necessary to prevent the root from continuing to grow in a circle past the point where the root tip is vertical. Curvature reaches maximal values of 0.7 mm^-1 to 1.2 mm^-1 for the inner side and 0.5 mm^-1 to 0.7 mm^-1 for the outer side. (Units express reciprocals of the radius of curvature in mm.) Two locations where curvature is highest are separated by a flatter region. The charcoal particles marking specific locations on the root surface move away from the tip at the same rate as the features of the curvature pattern.     

Visualization of NO3?/NO2? Dynamics in Living Cells by Fluorescence Resonance Energy Transfer (FRET) Imaging Employing a Rhizobial Two-component Regulatory System

Nitrate (NO₃⁻) and nitrite (NO₂⁻) are the physiological sources of nitric oxide (NO), a key biological messenger molecule. NO₃⁻/NO₂⁻ exerts a beneficial impact on NO homeostasis and its related cardiovascular functions. To visualize the physiological dynamics of NO₃⁻/NO₂⁻ for assessing the precise roles of these anions, we developed a genetically encoded intermolecular fluorescence resonance energy transfer (FRET)-based indicator, named sNOOOpy (sensor for NO₃⁻/NO₂⁻ in physiology), by employing NO₃⁻/NO₂⁻-induced dissociation of NasST involved in the denitrification system of rhizobia. The in vitro use of sNOOOpy shows high specificity for NO₃⁻ and NO₂⁻, and its FRET signal is changed in response to NO₃⁻/NO₂⁻ in the micromolar range. Furthermore, both an increase and decrease in cellular NO₃⁻ concentration can be detected. sNOOOpy is very simple and potentially applicable to a wide variety of living cells and is expected to provide insights into NO₃⁻/NO₂⁻ dynamics in various organisms, including plants and animals.     

Codetection of Respiratory Syncytial Virus in Habituated Wild Western Lowland Gorillas and Humans During a Respiratory Disease Outbreak

Pneumoviruses have been identified as causative agents in several respiratory disease outbreaks in habituated wild great apes. Based on phylogenetic evidence, transmission from humans is likely. However, the pathogens have never been detected in the local human population prior to or at the same time as an outbreak. Here, we report the first simultaneous detection of a human respiratory syncytial virus (HRSV) infection in western lowland gorillas (Gorilla gorilla gorilla) and in the local human population at a field program in the Central African Republic. A total of 15 gorilla and 15 human fecal samples and 80 human throat swabs were tested for HRSV, human metapneumovirus, and other respiratory viruses. We were able to obtain identical sequences for HRSV A from four gorillas and four humans. In contrast, we did not detect HRSV or any other classic human respiratory virus in gorilla fecal samples in two other outbreaks in the same field program. Enterovirus sequences were detected but the implication of these viruses in the etiology of these outbreaks remains speculative. Our findings of HRSV in wild but human-habituated gorillas underline, once again, the risk of interspecies transmission from humans to endangered great apes.     

The polarity of statocytes and the gravisensitivity of roots are dependent on the concentration of calcium in statocytes

In order to examine a possible role of calcium in graviperception, the calcium ionophore A23187 was used to elevate the concentration of free cytoplasmic calcium in statocytes of the roots of Lepidium sativum L. After a brief incubation (30 min) in a medium that contained 10 micromoles A23187 and 5.5 micromoles CaCl2, 50% of the roots bent gravitropically during a subsequent 2 h of horizontal exposure, with an angle of curvature that varied from 5 degrees to 70 degrees. The corresponding statocytes exhibited a polar arrangement of cell organelles as did the controls. However, in statocytes from 50% of the roots which were not curved after gravistimulation a portion of the distal endoplasmic reticulum (ER) complex was displaced in the direction of gravity within 30 min of horizontal exposure. After washing of the briefly treated roots for 24 h with 1% dimethylsulfoxide the percentage of gravitropically bending roots increased to approximately 80%, but the angle of curvature amounted to only 5 degrees-10 degrees. Longer treatment (2 h) with A23187 caused a complete loss of graviresponsiveness which was accompanied by disintegration of statocyte polarity. We concluded from these results that i) calcium is involved in graviperception and ii) gravisensitivity depends on the integrity of statocytes.     

6-OHDA-induced ectopia of external granule cells in the subarachnoid space covering the cerebellum

The present report describes the genesis, development and topographical distribution of ectopic cells of the external granular layer in the subarachnoid space covering the rat cerebellum. Following one intracisternal injection to newborn rats of 100 micrograms 6-hydroxydopamine (6-OHDA), the meningeal cells degenerate and are removed by phagocytosis within 24 h post injection (p.i.), leaving the cerebellar cortex without a pia-arachnoid cover. Defects appear in the basal lamina investing the cerebellar cortex 3 to 5 days p.i., and both external granule cells and 'sprouts' from Bergmann-glia endfeet grow into the subarachnoid space. The latter form large, flat glial lamellae and cover extensive areas of the denuded cerebellar surface, although they do not form a glial scar over the exposed neuropil of the cerebellar cortex. The numbers of ectopic external granule cells increase within the subarachnoid space both by proliferation and a continuous efflux of cells from the cerebellar cortex. They migrate, aggregate, and ultimately develop into granule, stellate and basket cells, the morphology of which is indistinguishable from their counterparts in situ; they make specific afferent and efferent connections, both among themselves and with the underlying cerebellar cortex and brainstem. The distribution of ectopic external granule cells and their derivatives is restricted to the anterior vermal fissures and the vermal-hemispheric junctions. The present results indicate that external granule cells and their derivatives are capable of both differentiating normally and surviving in the subarachnoid space if they become associated with glial cells and establish synaptic connections.     

Differential effects of propofol and ketamine on critical brain dynamics

Whether the brain operates at a critical “tipping” point is a long standing scientific question, with evidence from both cellular and systems-scale studies suggesting that the brain does sit in, or near, a critical regime. Neuroimaging studies of humans in altered states of consciousness have prompted the suggestion that maintenance of critical dynamics is necessary for the emergence of consciousness and complex cognition, and that reduced or disorganized consciousness may be associated with deviations from criticality. Unfortunately, many of the cellular-level studies reporting signs of criticality were performed in non-conscious systems (in vitro neuronal cultures) or unconscious animals (e.g. anaesthetized rats). Here we attempted to address this knowledge gap by exploring critical brain dynamics in invasive ECoG recordings from multiple sessions with a single macaque as the animal transitioned from consciousness to unconsciousness under different anaesthetics (ketamine and propofol). We use a previously-validated test of criticality: avalanche dynamics to assess the differences in brain dynamics between normal consciousness and both drug-states. Propofol and ketamine were selected due to their differential effects on consciousness (ketamine, but not propofol, is known to induce an unusual state known as “dissociative anaesthesia”). Our analyses indicate that propofol dramatically restricted the size and duration of avalanches, while ketamine allowed for more awake-like dynamics to persist. In addition, propofol, but not ketamine, triggered a large reduction in the complexity of brain dynamics. All states, however, showed some signs of persistent criticality when testing for exponent relations and universal shape-collapse. Further, maintenance of critical brain dynamics may be important for regulation and control of conscious awareness.     

A comparative study of the low-temperature magnetic circular dichroism spectra of horse heart metmyoglobin and bovine liver catalase derivatives

The magnetic circular dichroism (MCD) spectra of three horse heart metmyoglobin compounds, the cyanide, azide and hydroxide forms, have been measured in the visible and near infrared spectral regions at temperatures down to 1.5 K. The three compounds are all virtually completely low-spin at low temperatures with ground g factors of decreasing rhombicity in the order CN- greater than N3- greater than OH-. The MCD magnetization curves have been constructed at selected wavelengths throughout the visible and near infrared regions. The curves are independent of wavelength, showing that all the bands studied are x,y polarized and can, moreover, be satisfactorily fitted to the g factors determined by EPR spectroscopy with theoretical expressions (Thomson, A.J. and Johnson, M.K. (1980) Biochem. J. 191, 411-420). This confirms the assignment and polarizations of the near infrared region low-spin ferric haem charge-transfer bands. The energies of these transitions are markedly dependent upon the added axial ligand, ranging from 1595 to 1295, and 1050 nm for the compounds CN-, N3- and OH-. The MCD spectra of bovine liver catalase and its cyanide adduct have been recorded in the Soret, visible and near infrared regions. Catalase is know to have phenolate anion as the proximal ligand of the haem group. The forms of the spectra make an interesting comparison with those of the analogous metmyoglobin derivatives, in which histidine is the proximal ligand. The MCD spectra of catalase at 4.2 K is an example of a fully high-spin haemoprotein. The cyanide compound is completely low-spin at 4.2 K. The near infrared charge-transfer band is at 1300 nm, showing the effect on the energy of this band of changing from imidazole to phenolate ion as the proximal ligand to haem.     

Adenovirus in Rural Côte D`Ivoire: High Diversity and Cross-Species Detection

The Taï region in Western Côte d`Ivoire is characterized by extensive overlap of human and animal habitats. This could influence patterns of adenovirus transmission between humans and domestic animals. Fecal samples from humans and various domestic animals were tested for the presence of adenoviruses by PCR. Phylogenetic and species delineation analyses were performed to further characterize the adenoviruses circulating in the region and to identify potential cross-species transmission events. Among domestic animals, adenovirus shedding was frequent (21.6% of domestic mammals and 41.5% of chickens) and the detected strains were highly diverse, several of them representing novel types. Although no evidence for zoonotic transmission of animal adenovirus was obtained, the present study provides concordant evidence in favor of common cross-species transmission of adenoviruses between different animal species and first indications for adenovirus transmission from humans to animals. These findings underline the thus far underestimated importance of reverse zoonotic transmission of viruses and of the role of domestic animals as pathogen reservoirs, “bridge species,” or intermediate hosts.