Role of the carboxy-termini of tubulin on its chaperone-like activity.

Mutational analysis and the enzymatic digestion of many chaperones indicate the importance of both hydrophobic and hydrophilic residues for their unique property. Thus, the chaperone activity of alpha-crystallin is lost due to the substitution of hydrophobic residues or upon enzymatic digestion of the negatively charged residues. Tubulin, an eukaryotic cytoskeletal protein, exhibits chaperone-like activity as demonstrated by prevention of DTT-induced aggregation of insulin, thermal aggregation of alcohol dehydrogenase, betagamma-crystallin, and other proteins. We have shown that the tubulin lost its chaperone-like activity upon digestion of its negatively charged C-termini. In this article, the role of the C-terminus of individual subunits has been investigated. We observe that the digestion of C-terminus of beta-subunit with subtilisin causes loss of chaperone-like activity of tubulin. The contribution of C-terminus of alpha-subunit is difficult to establish directly as subtilisin cleaves C-terminus of beta-subunit first. This has been ascertained indirectly using a 14-residue peptide P2 having the sequence corresponding to a conserved region of MHC class I molecules and that binds tightly to the C-terminus of alpha-subunit. We have shown that the binding of P2 peptide to alphabeta-tubulin causes complete loss of its chaperone-like activity. NMR and gel-electrophoresis studies indicate that the P2 peptide has a significant higher binding affinity for the C-terminus of alpha-subunit compared to that of beta-subunit. Thus, we conclude that both the C-termini are necessary for the chaperone-like activity of tubulin. Implications for the chaperone functions in vivo have been discussed.     

Longevity and population age structure of the arroyo southwestern toad (Anaxyrus californicus) with drought implications

The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to estimate the ages of adult arroyo toads in seven occupied drainages with varying surface water hydrology in southern California. We processed 179 adult toads with age estimates between 1 and 6 years. Comparisons between skeletochronological ages and known ages of PIT tagged toads showed that skeletochronology likely underestimated toad age by up to 2 years, indicating they may live to 7 or 8 years, but nonetheless major patterns were evident. Arroyo toads showed sexual size dimorphism with adult females reaching a maximum size of 12 mm greater than males. Population age structure varied among the sites. Age structure at sites with seasonally predictable surface water was biased toward younger individuals, which indicated stable recruitment for these populations. Age structures at the ephemeral sites were biased toward older individuals with cohorts roughly corresponding to higher rainfall years. These populations are driven by surface water availability, a stochastic process, and thus more unstable. Based on our estimates of toad ages, climate predictions of extreme and prolonged drought events could mean that the number of consecutive dry years could surpass the maximum life span of toads making them vulnerable to extirpation, especially in ephemeral freshwater systems. Understanding the relationship between population demographics and hydrology is essential for predicting species resilience to projected changes in weather and rainfall patterns. The arroyo toad serves as a model for understanding potential responses to climatic and hydrologic changes in Mediterranean stream systems. We recommend development of adaptive management strategies to address these threats.     

A New Genus of the Tetraphyllidean Cestodes from <Emphasis Type="Italic">Dasyatis sephen</Emphasis> Forsskal, 1775 Captured from Digha Coastal Water,Bay of Bengal,India

Aloculibothrium dasyatii n. gen. n. sp. is described from the spiral intestine of Dasyatis sephen Forsskal, 1775 captured at Digha coastal waters, Bay of Bengal, India. This species is placed under the famil Onchobothriidae (Braun, 1900) and erected a new genus Aloculibothrium to accommodate this specimen. The body is 24.22–36.58 mm long and with 310–325 proglottids; scolex rectangular with two parts; anterior bearing four bothridia with paired bifurcated hooks, divided into inner and outer prong and posterior with fleshy collar. The cestode has been compared with all the existing twelve different valid genera under the family Onchobothriidae but to accommodate the present specimens a new genera Aloculibothrium is erected.     

TheAzotobacter vinelandii chromosome

The chromosome ofAzotobacter vinelandii was digested with the restriction endonucleasesSpeI (5’-ACTAGT),DraI (5’-TTTAAA) andAsel (5’-ATTAAT) and the products were separated by pulsed-field gel electrophoresis. The sum of the sizes of the restriction fragments comes to around 4.5 megabasepairs. Our earlier studies had revealed the presence of about 80 copies ofnifH, nifD, nifK andleuB genes in a log-phase cell ofA. vinelandii. To determine whether there are multiple identical chromosomes inA. vinelandii or one large chromosome with identical segments joined in tandem, we have subjected gamma-irradiated DNA ofA. vinelandii andEscherichia coli to pulsed-field gel electrophoresis. The results suggest thatA. vinelandii chromosomes contain multiple identical chromosomes of about the same size as that ofE. coli.     

Cerium levels are elevated in the serum of patients with endomyocardial fibrosis (EMF)

The geochemical hypothesis on endomyocardial fibrosis (EMF) links causation of the disease to increased levels of cerium in the heart. Since cardiac tissues are not easily accessible from patients, we explored whether cerium can be detected in the serum using neutron activation analysis (NAA). Cerium levels in serum of EMF patients were significantly elevated (p < 0.05) compared to controls.