Effect of freezing and freeze-drying on the viability and storage of Lilium longiflorum L. and Zea mays L. pollen

The freeze-preservation of pollen is dependent on the interaction of several factors such as freezing rate, thawing rate, freeze-drying temperature and duration, storage temperature and environment and rehydration rates. Changes in any of these variables affects the others directly or indirectly.Rapid freezing of pollen at rates of approximately 200 °C/min maintains the highest degree of viable pollen in combination with rapid thawing rates of 218 °C/min. Rapid cooling and slow rewarming resulted in a substantial loss of pollen viability. This might indicate that intracellular ice crystals formed during rapid cooling perhaps grow into larger ice masses during slow rewarming or storage at temperatures above ?50 °C.The germinability of pollen freeze-dried at temperatures below ?50 °C was also prolonged over that of the controls. Germination values for unfrozen pollen stored for 30 days at 0–5 °C averaged 50% for lily and 20% for corn. Freeze-dried pollen stored for 30 days at the same temperature yielded considerably higher viability percentages for both lily and corn pollen. Drying time is an important factor, perhaps indicating that residual moisture is critical. Freeze-dried pollen can be stored at higher temperatures than frozen and control pollen. Freeze-dried material stored for five months at 0–5 °C, upon slow rehydration yielded intact grains which has average germination percentages of 25 for lily and 15 for corn. The same pollen upon rapid rehydration showed rupturing of 20–40% of the cells and practically no germination.     

Augmentation of sickling process due to turbulent blood flow.

The purpose of this study was to determine if the fluid mechanical stresses associated with turbulent blood flow can contribute to the sickling process. Blood from seven patients with sickle cell disease was subjected to intermediate and high levels of turbulent flow in vitro. Turbulence was quantitated by hot film anemometry. Control samples showed 20 +/- 3% sickled cells. Cells subjected to intermediate levels of turbulent flow showed 26 +/- 4% sickling (P less than 0.01); and blood subjected to high intensities of turbulence showed 31 +/- 4% sickling (P less than 0.01). A quantitative count by electronmicroscopy, performed in one patient, showed polymerization of the hemoglobin indicative of sickling in more cells subjected to turbulence than in the control sample. A turbulence-reducing agent, polyethylene oxide, diminished the augmentation of the sickling process as it reduced turbulence at comparable Reynolds numbers. These results support the hypothesis that a deleterious effect upon hemoglobin SS erythrocytes may occur due to the mechanical stresses of turbulent flow. The agitation associated with turbulent flow presumably modifies the stabilizing factors of the intracellular colloidal solution of hemoglobin, thereby contributing to sol-gel transformation. Such hydrodynamic stresses may supplement the previously described factors which contribute to sickle cell crises.     

Detection and identification of phytoplasma associated with witches’ broom and little leaf disease in Arundo donax: first report from India

During the survey of two successive years 2012–2013, in nearby places of Gorakhpur districts, Uttar Pradesh, India, Arundo donax plants were found to be exhibiting witches’ broom, excessive branching accompanied with little leaf symptoms with considerable disease incidence. Nested PCR carried out with universal primers pair R16F2n/R16R2 employing the PCR (P1/P7) product as a template DNA (1:20) resulted in expected size positive amplification ~1.2 kb in all symptom-bearing plants suggested the association of phytoplasma with witches’ broom disease of Narkat plants. BLASTn analysis of the 16S rRNA gene sequence showed the highest (99%) sequence identity with Candidatus phytoplasma asteris (16SrI group). In phylogenetic analysis, the sequence data showed close relationships with the members of 16SrI phytoplasma and clustered within a single clade of 16SrI group and closed to B subgroup representatives. This is a first report of 16Sr I-B group phytoplasma associated with witches’ broom accompanied with little leaf disease of Narkat in India.     

Wrinkling instabilities for biologically relevant fiber-reinforced composite materials with a case study of Neo-Hookean/Ogden–Gasser–Holzapfel bilayer

Biomechanics and Modeling in Mechanobiology - Wrinkling is a ubiquitous surface phenomenon in many biological tissues and is believed to play an important role in arterial health. As arteries are...     

De‐ubiquitinases on the move: an emerging field in plant biology

A balance between the synthesis and degradation of active proteins governs diverse cellular processes in plants, spanning from cell‐cycle progression and circadian rhythm to the outcome of several hormone signalling pathways. Ubiquitin‐mediated post‐translational modification determines the degradative fate of the target proteins, thereby altering the output of cellular processes. An equally important, and perhaps under‐appreciated, aspect of this pathway is the antagonistic process of de‐ubiquitination. De‐ubiquitinases (DUBs), a group of processing enzymes, play an important role in maintaining cellular ubiquitin homeostasis by hydrolyzing ubiquitin poly‐proteins and free poly‐ubiquitin chains into mono‐ubiquitin. Further, DUBs rescue the cellular proteins from 26S proteasome‐mediated degradation to their active form by cleaving the poly‐ubiquitin chain from the target protein. Any perturbation in DUB activity is likely to affect proteostasis and downstream cellular processes. This review illustrates recent findings on the biological significance and mechanisms of action of the DUBs in Arabidopsis thaliana, with an emphasis on ubiquitin‐specific proteases (UBPs), the largest family among the DUBs. We focus on the putative roles of various protein–protein interaction interfaces in DUBs and their generalized function in ubiquitin recycling, along with their pre‐eminent role in plant development.     

Identification of chironomid species as natural reservoirs of toxigenic Vibrio cholerae strains with pandemic potential

Vibrio cholerae causes the fatal cholera diarrhea. Chironomids (Diptera; Chironomidae) are abundant in freshwater aquatic habitats and estuaries and are natural reservoirs of V. cholerae. Until now, only the non-O1/O139 serogroups of V. cholerae were identified in chironomids. Here, we explored whether chironomids are natural reservoirs of V. cholerae O1/O139 serogroups, which are associated with cholera endemics and pandemics. All four life stages of chironomids were sampled from two rivers, and a laboratory culture in Pune, India, and from a pond in Israel. In total, we analyzed 223 chironomid samples. The presence of V. cholerae O1/O139 serogroups was verified using molecular tools. Nine chironomid species were identified; of them, Chironomus circumdatus was the most abundant. The presence of V. cholerae serogroup O1 and the cholera toxin genes were detected in samples from all chironomid species. However, serogroup O139 was detected in only two chironomid species. Besides PCR to detect specific genes, a metagenomic analysis that was performed in three selected C. ramosus larvae, identified a list of virulence genes associated with V. cholerae. The findings provide evidence that chironomids are natural reservoirs of toxigenic V. cholerae O1/O139. Chironomid populations and V. cholerae show biannual peak patterns. A similar pattern is found for cholera epidemics in the Bengal Delta region. Thus, we hypothesize that monitoring chironomids in endemic areas of the disease may provide a novel tool for predicting and preventing cholera epidemics. Moreover, serogroup O139 was detected only in two chironomid species that have a restricted distribution in the Indian subcontinent, possibly explaining why the distribution of the O139 serogroup is limited.