Comparative cytogenetic variability of polytene chromosomes from salivary glands of Chironomus riparius Mg., 1804 (Diptera, Chironomidae) from two polluted biotopes in Bulgaria and Russia

The structural-functional variation of Chironomus riparius salivary gland polytene chromosomes was studied in two geographically isolated Palearctic regions, Bulgaria (village Pancharevo) and Russia (St. Petersburg). The two biotopes, where larvae were collected, were polluted with various heavy metals from anthropogenic sources. Hereditary paracentric heterozygous inversions were characteristic of the Russian population, whereas somatic paracentric or pericentric heterozygous inversions were more common in the Bulgarian one. All inversions occurred at low frequencies. Other aberrations found in the two populations included somatic deletions resulting in a pompon structure of chromosome IVG, heterozygous translocation between chromosomes IVG and IIIF, enlargement of individual disks, and the appearance of a heterozygous block close to the centromere of chromosome IVG. In addition, changes in functional activity of the nucleolus organizer and Balbiani rings (BRc/BRb) were observed. Several aberration breakpoints proved to coincide with satellites of the Alu and Hinf families.     

Interaction of Oxoferrylmyoglobin and Dinitrosyl-Iron Complexes

It is shown that dinitrosyl-iron complexes (DNIC) with glutathione can reduce oxoferrylmyoglobin forming on interaction of tert-butyl hydroperoxide and metmyoglobin. A rapid decrease in the DNIC concentration was observed under the conditions of production of tert-butyl free radicals; however, destruction of DNIC in the presence of oxoferrylmyoglobin alone was negligible. It is demonstrated that DNIC reduces oxoferrylmyoglobin more than an order more efficiently than S-nitrosoglutathione and glutathione. DNIC also inhibits formation of the thiyl radicals of glutathione in a medium containing metmyoglobin and tert-butyl hydroperoxide. A mechanism of the antioxidant action of DNIC based on regeneration of the nitrosyl complexes from the products of their interaction with oxoferrylheme is proposed.     

Changes in the Nitrocellulose Molecule Induced by Sulfate-Reducing Bacteria Desulfovibrio desulfuricans 1388. The Enzymes Participating in This Process

The appearance of unsubstituted glucopyranose residues in nitrocellulose (NC) induced by Desulfovibrio desulfuricans was established by (13)C-NMR spectroscopy. After contact with bacterial cells, the degree of substitution by nitro groups in NC decreased from 2.59 to 2.40. The bacteria possess intra- and extracellular nitroesterase activities, which are responsible for denitration of the polymer. The presence of NC in the growth medium influences the extracellular nitroesterase activity. It is shown that inhibition of enzymatic activity in the presence of NC is caused by appearance of nitrates in the culture medium. Nitrate and nitrite reductases of dissimilatory type reduce nitrates. The data suggest consideration of bacteria belonging to the Desulfovibrio genus as the initial agent in utilization of an unnatural polymer--nitrocellulose--in a microbial consortium.     

Differentiation of embryonic stem cells into cardiomyocytes induced by leukemia inhibitory factor (LIF)

An experimental model of mouse embryonic stem cell (ESC) differentiation into cells with contractile activity (similar to that of cardiomyocytes) without embryoid body formation has been obtained. The main factor inducing ESC differentiation along the cardiomyocyte pathway is recombinant cytokine LIF added in the course of long-term culturing. The contractile cells respond positively to treatment with isoproterenol, a cardioactive drug, which is evidence for the presence in these cells of β-adrenoreceptors characteristic of terminally differentiated mammalian cardiomyocytes.     

Catalytically important amino acid residues in endoglucanases from a mutant strain Trichoderma sp. M7

Two endoglucanases, EG-III (49.7 kD) and EG-IV (47.5 kD), from a mutant strain Trichoderma sp. M7 were modified with several specific reagents. Water-soluble carbodiimide completely inactivated only one of the purified endoglucanases and kinetic analysis indicated that at least two molecules of carbodiimide bind to EG-IV for inactivation. The reaction followed pseudo-first-order kinetics with a second-order rate constant of 3.57 x 10(-5) mM(-1) x in(-1). Both endoglucanases were inhibited by iodoacetamide, but the absence of substrate protection excluded direct involvement of cysteine residues in the catalysis. N-Bromosuccinimide (NBS) showed a strong inhibitory effect on both endoglucanases, suggesting that tryptophan residues are essential for the activity and binding to the substrate, since the presence of substrates or analogs prior to NBS modification protected the enzymes against inactivation.     

Purification and properties of individual collagenases fromStreptomyces sp. strain 3B

Streptomyces strain 3B constitutively secreted collagenolytic enzymes during the post-exponential growth phase. Purification is described here leading to two collagenases (I and II) with specific activity of 3350 and 3600 U/mg, respectively, the highest activity obtained as yet for any streptomycete collagenase. Analysis of the purified enzymes by the method of zymography revealed that both I and II were homogeneous, with molar mass 116 and 97 kDa, respectively. Both collagenases were identical in their pH (7.5) and temperature optimum (37 degrees C). The inhibition profile of the enzymes by EDTA and 1,10-phenanthroline confirmed these enzymes to be metalloproteinases. By testing the activity with insoluble collagen, acid soluble collagen, gelatin, casein, elastin and Pz-PLGPR it was established that I and II are very specific for insoluble collagen and gelatin, showing a high activity toward acid soluble collagen and Pz-PLGPR. However, collagenases I and II failed to hydrolyze casein and elastin; they belong to true collagenases and resemble the clostridial enzymes.     

ADP ribosylation adapts an ER chaperone response to short-term fluctuations in unfolded protein load

Gene expression programs that regulate the abundance of the chaperone BiP adapt the endoplasmic reticulum (ER) to unfolded protein load. However, such programs are slow compared with physiological fluctuations in secreted protein synthesis. While searching for mechanisms that fill this temporal gap in coping with ER stress, we found elevated levels of adenosine diphosphate (ADP)-ribosylated BiP in the inactive pancreas of fasted mice and a rapid decline in this modification in the active fed state. ADP ribosylation mapped to Arg470 and Arg492 in the substrate-binding domain of hamster BiP. Mutations that mimic the negative charge of ADP-ribose destabilized substrate binding and interfered with interdomain allosteric coupling, marking ADP ribosylation as a rapid posttranslational mechanism for reversible inactivation of BiP. A kinetic model showed that buffering fluctuations in unfolded protein load with a recruitable pool of inactive chaperone is an efficient strategy to minimize both aggregation and costly degradation of unfolded proteins.     

Transmembrane electric potential difference in the protein-pigment complex of photosystem 2

The protein-pigment complex of photosystem 2 (PS2) localized in the thylakoid membranes of higher plants, algae, and cyanobacteria is the main source of oxygen on Earth. The light-induced functioning of PS2 is directly linked to electron and proton transfer across the membrane, which results in the formation of transmembrane electric potential difference (ΔΨ). The major contribution to ΔΨ of the PS2 reaction center is due to charge separation between the primary chlorophyll donor P₆₈₀ and the quinone acceptor Q_A, accompanied by re-reduction of P ₆₈₀ ⁺ by the redox-active tyrosine residue Y_Z. The processes associated with the uptake and release of protons on the acceptor and donor sides of the enzyme, respectively, are also coupled with ΔΨ generation. The objective of this work was to describe the mechanisms of ΔΨ generation associated with the S-state transitions of the water-oxidizing complex in intact PS2 complex and in PS2 preparation depleted of Mn₄Ca cluster in the presence of artificial electron donors. The findings elucidate the mechanisms of electrogenic reactions on the PS2 donor side and may be a basis for development of an effective solar energy conversion system.     

Absence of foramen spinosum and abnormal middle meningeal artery in cranial series

In comparative and evolutionary aspects in humans, the middle meningeal artery enters the cranium through the foramen spinosum, whereas in great apes the middle meningeal artery can enter the cranium through foramen spinosum, through foramen ovale or through petrosphenoid fissure. Generally, in nonhuman primates the anterior meningeal system is associated with the ophthalmic branch of the internal carotid artery. The vessels joining the two systems pass through the additional channels: the superior orbital fissure or through the cranio-orbital foramen. In anatomically modern humans, the absence of foramen spinosum involves abnormal development and course of the middle meningeal artery and it is usually accompanied with replacement of the conventional middle meningeal artery with such, arising from the ophthalmic artery system. In these cases the middle meningeal artery most often enters the middle cranial fossa through the superior orbital fissure and rarely through the meningo-orbital foramen. All skulls, investigated in the present study, belonged to adult individuals of both sexes, conditionally grouped into three cranial series--contemporary male, medieval male, and medieval female series. The absence of foramen spinosum was established only among the medieval male and female series--in 1 (0.70%) male and in 1 (0.72%) female skull on the right side and in 3 (2.13%) female skulls on the left side. In 1 (0.72%) female skull, a small atypically located foramen spinosum was established on the right side. In all of the described cases, the intracranial meningeal grooves started from the lateral edge of the superior orbital fissure and probably reflect the ophthalmic origin of the middle meningeal artery.