A Comparative Study of Internal Light Environment in Bifacial Leaves of Different Plants

Parameters of light propagation in plant leaves — absorption and scattering coefficients, asymmetry of scattering — have been estimated on the basis of measured transmission and emission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4-flux radiative transfer — a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiple scattering sample. Using the gained parameters, light flux gradients in a two-layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two-flux (Kubelka-Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for three different plants: Catalpa bignonioides, Tilia americana and Vitis riparia.     

Differential Impact of Tumor Suppressor Pathways on DNA Damage Response and Therapy-Induced Transformation in a Mouse Primary Cell Model

The RB and p53 tumor suppressors are mediators of DNA damage response, and compound inactivation of RB and p53 is a common occurrence in human cancers. Surprisingly, their cooperation in DNA damage signaling in relation to tumorigenesis and therapeutic response remains enigmatic. In the context of individuals with heritable retinoblastoma, there is a predilection for secondary tumor development, which has been associated with the use of radiation-therapy to treat the primary tumor. Furthermore, while germline mutations of the p53 gene are critical drivers for cancer predisposition syndromes, it is postulated that extrinsic stresses play a major role in promoting varying tumor spectrums and disease severities. In light of these studies, we examined the tumor suppressor functions of these proteins when challenged by exposure to therapeutic stress. To examine the cooperation of RB and p53 in tumorigenesis, and in response to therapy-induced DNA damage, a combination of genetic deletion and dominant negative strategies was employed. Results indicate that loss/inactivation of RB and p53 is not sufficient for cellular transformation. However, these proteins played distinct roles in response to therapy-induced DNA damage and subsequent tumorigenesis. Specifically, RB status was critical for cellular response to damage and senescence, irrespective of p53 function. Loss of RB resulted in a dramatic evolution of gene expression as a result of alterations in epigenetic programming. Critically, the observed changes in gene expression have been specifically associated with tumorigenesis, and RB-deficient, recurred cells displayed oncogenic characteristics, as well as increased resistance to subsequent challenge with discrete therapeutic agents. Taken together, these findings indicate that tumor suppressor functions of RB and p53 are particularly manifest when challenged by cellular stress. In the face of such challenge, RB is a critical suppressor of tumorigenesis beyond p53, and RB-deficiency could promote significant cellular evolution, ultimately contributing to a more aggressive disease.     

Mapping quantitative trait loci (QTLs) for fatty acid composition in an interspecific cross of oil palm

Background  

Marker Assisted Selection (MAS) is well suited to a perennial crop like oil palm, in which the economic products are not produced until several years after planting. The use of DNA markers for selection in such crops can greatly reduce the number of breeding cycles needed. With the use of DNA markers, informed decisions can be made at the nursery stage, regarding which individuals should be retained as breeding stock, which are satisfactory for agricultural production, and which should be culled. The trait associated with oil quality, measured in terms of its fatty acid composition, is an important agronomic trait that can eventually be tracked using molecular markers. This will speed up the production of new and improved oil palm planting materials.     

Ecdysteroids and meiotic reinitiation in Palaemon serratus (Crustacea Decapoda Natantia) and in Locusta migratoria (Insecta orthoptera). A comparative study

Summary

Meiotic reinitiation has been studied in Locusta migratoria and Palaemon serratus in relation to the titre of free ecdysteroids present in the maturing oocyte. In both species meiotic reinitiation is characterized by two meiotic arrests, in prophase I and in metaphase I, and the first meiotic resumption which leads to germinal vesicle breakdown (GVBD) is correlated with increasing titres of ecdysteroids in the oocyte. Meiotic reinitiation has been successfully triggered in the oocytes of both species by incubation with physiological doses of ecdysteroids.     

The laws of surface tension and their applicability to living cells and cell division

Summary If a drop of liquid is suspended in a liquid medium, any area whose surface tension is reduced, spreads and protrudes, causing vortical currents, whereas any area whose surface tension is increased, contracts and becomes more flattened, causing a vortex in the opposite direction.Division of a similar drop may be brought about by a condition in which an equatorial band has a higher surface tension than the remainder of the surface. Robertson came to opposite conclusions, but five fallacies in his argument are pointed out above.

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Zusammenfassung Wird ein FlÜssigkeitstropfen in einem flÜssigen Medium suspendiert, so breitet sich jeder Bezirk mit verminderter Oberflächenspannung aus und treibt sich vor, indem er vortikale Strömungen hervorbringt. Dagegen zieht sich jeder Bezirk mit vermehrter Oberflächenspannung zusammen und flacht sich ab, unter Veranlassung eines Wirbels in der entgegengesetzten Richtung.Teilung eines ähnlichen Tropfens kann durch Verhältnisse zustande kommen, bei denen ein äquatorial gelegener Streifen höhere Oberflächenspannung besitzt, als die Übrige Oberfläche. Robertson kam zu entgegengesetzten Folgerungen — im Vorstehenden sind aber fÜnf unrichtige Punkte in seiner BeweisfÜhrung aufgewiesen worden.

     

Modeling conformational ensembles of slow functional motions in Pin1-WW

Protein-protein interactions are often mediated by flexible loops that experience conformational dynamics on the microsecond to millisecond time scales. NMR relaxation studies can map these dynamics. However, defining the network of inter-converting conformers that underlie the relaxation data remains generally challenging. Here, we combine NMR relaxation experiments with simulation to visualize networks of inter-converting conformers. We demonstrate our approach with the apo Pin1-WW domain, for which NMR has revealed conformational dynamics of a flexible loop in the millisecond range. We sample and cluster the free energy landscape using Markov State Models (MSM) with major and minor exchange states with high correlation with the NMR relaxation data and low NOE violations. These MSM are hierarchical ensembles of slowly interconverting, metastable macrostates and rapidly interconverting microstates. We found a low population state that consists primarily of holo-like conformations and is a "hub" visited by most pathways between macrostates. These results suggest that conformational equilibria between holo-like and alternative conformers pre-exist in the intrinsic dynamics of apo Pin1-WW. Analysis using MutInf, a mutual information method for quantifying correlated motions, reveals that WW dynamics not only play a role in substrate recognition, but also may help couple the substrate binding site on the WW domain to the one on the catalytic domain. Our work represents an important step towards building networks of inter-converting conformational states and is generally applicable.     

Structural Transformations in the Dynamics of Michaelis Complex Formation in Lactate Dehydrogenase

The dynamical nature of the binding of a substrate surrogate to lactate dehydrogenase is examined on the nanoseconds to milliseconds timescale by laser-induced temperature-jump relaxation spectroscopy. Fluorescence emission of the nicotinamide group of bound NADH is used to define the pathway and kinetics of substrate binding. Assignment of specific kinetic states and elucidation of their structures are accomplished using isotope edited infrared absorption spectroscopy. Such studies are poised to yield a detailed picture of the coupling of protein dynamics to function.     

THE ENZYMATIC MACERATION OF PLANT TISSUES: OBSERVATIONS USING A NEW METHOD OF MEASUREMENT

Mc Clendon , J. H., and G. F. Somers . (U. Delaware, Newark.) The enzymatic maceration of plant tissues: observations using a new method of measurement. Amer. Jour. Bot. 47(1) :1-7. Illus. 1960.—An apparatus is described for measuring the breaking strength of tissue slices. The apparatus was used in the measurement of maceration of potato tuber slices by fungal and tomato enzymes. During the enzymatic maceration of the slices, the strength fell in an approximately logarithmic manner to a stable value less than 5% of the initial strength. Calcium ion did not prevent enzymatic maceration, although it increased the strength of the tissue. Chelating agents used alone did not macerate but facilitated the enzymatic maceration. There was a pH optimum at 3.0—3.5 with a commercial “Pectinase” and enzymes from Botryosphaeria ribis but near 4.7 for a preparation from tomato fruit. The reciprocal of the time for a set strength reduction was proportional to the square root of the enzyme concentration. The relative strength remaining [(initial strength/final strength)–1] after an arbitrary reaction time was proportional to the enzyme concentration raised to the 0.8 power. The temperature coefficient was about 2.5, but other evidence indicated some limitation by diffusion. Non-enzymatic maceration increased rapidly below pH 3 and was especially prominent after subsequent neutralization.     

Role of Recurrent Hypoxia-Ischemia in Preterm White Matter Injury Severity

Objective

Although the spectrum of white matter injury (WMI) in preterm infants is shifting from cystic necrotic lesions to milder forms, the factors that contribute to this changing spectrum are unclear. We hypothesized that recurrent hypoxia-ischemia (rHI) will exacerbate the spectrum of WMI defined by markers of inflammation and molecules related to the extracellular matrix (hyaluronan (HA) and the PH20 hyaluronidase) that regulate maturation of the oligodendrocyte (OL) lineage after WMI.

Methods

We employed a preterm fetal sheep model of in utero moderate hypoxemia and global severe but not complete cerebral ischemia that reproduces the spectrum of human WMI. The response to rHI was compared against corresponding early or later single episodes of HI. An ordinal rating scale of WMI was compared against an unbiased quantitative image analysis protocol that provided continuous histo-pathological outcome measures for astrogliosis and microglial activation. Late oligodendrocyte progenitors (preOLs) were quantified by stereology. Analysis of hyaluronan and the hyaluronidase PH20 defined the progressive response of the extracellular matrix to WMI.

Results

rHI resulted in a more severe spectrum of WMI with a greater burden of necrosis, but an expanded population of preOLs that displayed reduced susceptibility to cell death. WMI from single episodes of HI or rHI was accompanied by elevated HA levels and increased labeling for PH20. Expression of PH20 in fetal ovine WMI was confirmed by RT-PCR and RNA-sequencing.

Conclusions

rHI is associated with an increased risk for more severe WMI with necrosis, but reduced risk for preOL degeneration compared to single episodes of HI. Expansion of the preOL pool may be linked to elevated hyaluronan and PH20.