Stimulation of Ca efflux from fura-2-loaded platelets activated by thrombin or phorbol myristate acetate

We investigated the restoration of [Ca²⁺]_i in fura-2-loaded human platelets following discharge of internal Ca²⁺ stores in the absence of external Ca²⁺. After stimulation by thrombin [Ca²⁺]_i returned from a peak level of 0.6 μM to resting levels within 4 min. When ionomycin discharged the internal stores the recovery was slower with [Ca²⁺]_i still elevated at around 0.5 μM after 5 min. Thrombin added shortly after ionomycin could accelerate the recovery of [Ca²⁺]_i and restore resting levels within 5 min, an effect that was mimicked by phorbol-12-myristate-13-acetate (PMA). Since the continued presence of ionomycin precluded reuptake into the internal stores we conclude that thrombin and PMA stimulate Ca²⁺ efflux, perhaps via protein kinase C actions on a plasma membrane Ca²⁺ pump.     

2,3-Bisphosphoglycerate inhibits ATP-stimulated proteolysis

Intracellular protein breakdown could be regulated at the substrate level by changes in the environment. Under in vitro conditions, ATP increases the proteolytic susceptibility of several mitochondrial and cytosolic proteins, while 2,3-bisphosphoglycerate not only has the opposite effect but also prevents the ATP-stimulated proteolysis. ATP and 2,3-bisphosphoglycerate, present at relatively high levels in many tissues, provide a good model of environmental components that may influence intracellular proteolysis.     

Role of nucleoside components and internucleotide phosphate groups of oligodeoxyribonucleotide template in its binding to human DNA polymerase alpha

Affinity labelling of human placenta DNA polymerase alpha (EC 2.7.7.7) with the reactive oligodeoxyribonucleotide d(pT)2pC[Pt2+(NH3)2OH](pT)7 was used for quantitative analysis of enzyme interaction with oligodeoxyribonucleotides as templates. Dissociation constants and Gibb's energy values for different oligothymidylates d(pT)nT where n = 1-14 have been evaluated by competitive experiments of these ligands with Pt2+ reagent. The data obtained prove the formation of one Me2+-dependent electrostatic contact and a hydrogen bond between the enzyme and one phosphate of these templates. One may suppose that the hydrophobic interaction of any other monomeric link of oligodeoxyribonucleotides with the enzyme template site takes place.     

The NH2-terminal cleavage of Escherichia coli translational initiation factor IF3. A mechanism to control the intracellular level of the factor?

A short form of Escherichia coli translational initiation factor IF3, repeatedly found both in vivo and in vitro, lacking the positively charged N-terminal hexapeptide has been produced by mild trypsinization. The properties of this short form of IF3 have been studied. Compared to the long native form of the factor, the shortened IF3 displays a markedly decreased thermal stability and affinity for the 30 S ribosomal subunit, as well as a reduced biological activity in protein synthesis. Following the loss of the N-terminal hexapeptide, a second peptide bond (Lys-90-Val-91) becomes easily accessible to proteolytic attack suggesting that formation of the short IF3 may be the first step in the physiological degradation of the factor.     

Characterization of the nucleotide tight-binding sites of the isolated mitochondrial F1-ATPase

The properties of the nucleotides tightly bound with mitochondrial F1-ATPase were examined. One of three bound nucleotide molecules is localized at the site with Kd approximately 10(-7) M and released with koff approximately 0.1 s-1. The second nucleotide molecule is bound with the enzyme with Kd approximately 10(-8) M and koff for its dissociation is 3 X 10(-4) s-1. The third is never released even in the presence of 1 mM ATP or ADP. The last two nucleotides are believed to be bound at the noncatalytic sites of F1-ATPase. Pyrophosphate promotes liberation of two releasable nucleotide molecules, decreasing the affinity of the enzyme to AD(T)P. From the results obtained it follows that the only suitable criterion for localization of the nucleotide at the F1-ATPase catalytic site is the high rate (koff greater than or equal to 0.1 s-1) of its spontaneous release.     

On secondary hyperparathyroidism in orang-utans, Pongo satyrus (Linnaeus, 1758)

Orang-utan crania with alterations in bone structure which could be determined morphologically were studied and evaluated. The alterations in bone structure were referred to in the literature up to about 1939 as "rickets"; when vitamin D was given to the animals, the alterations diminished, until they were almost unnoticeable. From about 1941/52, the alterations were diagnosed as "Morbus Paget". Research on orang-utan crania has become possible through comparison of a larger number of single symptoms, occurring in a number of individuals. Out of a larger sample, the study was carried out on 5 individuals, showing these alterations in varying degrees. The individuals also covered various age groups, both sexes and both subspecies of orang-utans. The findings permit a diagnosis of secondary (or tertiary) hyperparathyroidism (= Morbus Engel-von Recklinghausen = fibrous cystic osteitis). The study also showed that orang-utans fall prey to Morbus Engel-von Recklinghausen in a shorter period and suffer more severely than humans. The frequency of orang-utans suffering from this disease, which are kept captive in zoos, is statistically far higher than the occurrence in humans. Orang-utans living under natural conditions do not suffer from the disease at all; according to the study of 500 animals. The authors also believe that there is a psychogenic basis for the occurrence of Morbus Engel-von Recklinghausen in zoo animals; psychological conditions such as apathy, disinterest, etc. are part of the illness, and these symptoms are also shown by animals having no outward signs of fibrous cystic osteitis. The authors believe that improved prophylaxis of orang-utans in zoos would lead to discovery of Morbus Engel-von Recklinghausen in early stages, and allow early therapy to arrest the disease. This is necessary for preservation of the species.     

Degradation dynamics of lignocellulose materials by wood-rottingPleurotus fungi

When grown on wheat straw,Pleurotus decomposes both the lignin and the cellulose components of the substrate. The course of degradation differs during growth and fructification. The losses of dry mass during growth were about 20 %. The absolute amount of hemicelluloses, cellulose and lignin was decreasing. Hemicelluloses and lignin were degraded at a higher rate than cellulose. The total mass losses of the substrate after fructification were 32 to 45 %. Cellulose was consumed at a higher rate than lignin.     

Selective regeneration ofBacillus subtilis protoplasts transformed to kanamycin resistance

An HTY medium osmotically stabilized with 0.5 M D-glucitol was used for regeneration ofBacillus subtilis protoplasts. The application of glucitol as osmotic stabilizer allows simultaneous selection of cells resistant to kanamycin to be made since this antibiotic is not inactivated by glucitol when added to the regeneration medium.     

Antimicrobial effects of some mono- and bishydrazones

Antibacterial, antifungal and antiprotozoal effects of nine mono- and bishydrazones of glycolaldehyde, glyoxal, methoxyacetaldehyde and glutaraldehyde were studied using eight model organisms. It was found that bishydrazones are much more efficient antimicrobial agents than monohydrazones in the case of all model microorganisms.