On the increasing threat of extermination of the unique Caspian sturgeon populations and the urgent measures required to save them.

Sturgeon populations in the Caspian Sea are now in serious danger of extinction. This is primarily a result of reduced natural recruitment following a deterioration in the quality of habitats in both the river and the sea, combined with irrational fishing activities. Within this context, the desire of the newly-arisen Republics bordering the Caspian to re-open the sturgeon fishery in the sea has absolutely no scientific foundation and will prove to be an ecological disaster. There is an urgent need to conclude the International Agreement between Russia, Kazakhstan, Azerbaijan, Turkmenistan and Iran on the conservation, reproduction and rational exploitation of the Caspian sturgeon. The bases for this agreement must be (1) recognition of the fact that sturgeon populations are sustained by an ecosystem that comprises the entire Caspian Sea and the rivers that flow into it (primarily the Volga); (2) an absolute ban on uncontrolled fishing for sturgeon in the sea, and (3) that national fishing quotas must reflect the real contribution of a particular state to overall sturgeon stocks. Without adequate measures to save them, it is to be expected that the unique runs of Caspian sturgeons will be exterminated within 5–1 years.     

Heterogeneity and Polymorphism of Functionally Specialized Blood Proteins in Migratory Fish: The Case Study of the North Caspian Population of the Russian Sturgeon during Sea and River Periods of Life. 1. Albumins

A comparative study of the levels of heterogeneity and polymorphism of albumins, the most important functionally specialized blood proteins, has been carried out. The albumin system of Russian sturgeon undergoes distinct changes while the fish change habitat during the spawning migration from sea to river. They are expressed as an increased level of heterogeneity, an increased content of serum albumins in fish during the river period of life as compared to the sea period, and an increased share of a slow component of albuminograms. These changes suggest a significant role of the blood albumin system in adaptation of the Caspian sturgeon migratory species to fresh water life conditions.     

Isolation of calcium-transporting lipid from the mitochondrial glycolipoprotein

Summary From the mitochondrial Ca²⁺-transporting glycolipoprotein (GLP) the lipid was isolated which induced Ca²⁺-translocation through bilayer lipid membranes. Electroconductivity of modified phospholipid membranes in the presence of CaCl₂ is increased 150-200 times. At 10-fold CaCl₂ gradient a generation of membrane potential is observed close to its theoretical value. It is shown that the lipid forms separate conductivity channels of 10 and 20 pS in the bilayer. The mode of action of GLP in the membrane is proposed It is assumed that the carbohydrate part of GLP is a selective receptor-accumulator for Ca²⁻, whereas the function of the lipid component consists in forming channels in the bilayer.     

A Molecular Genetic Study of Hybridization in Four Species of Ground Squirrels (Spermophilus: Rodentia,Sciuridae)

Four species of ground squirrel—yellow (Spermophilus fulvus), russet (S. major), small (S. pygmaeus), and spotted (S. suslicus)—occur in the Volga region. Between S. major and S. pigmaeus, S. major and S. fulvus, and S. major and S. suslicus, sporadic hybridization was reported. Using sequencing and restriction analysis, we have examined the mtDNA C region in 13 yellow, 60 russet, 61 small, 45 spotted ground squirrels, and 9 phenotypic hybrids between these species. It was shown that 43% of S. major individuals had alien mitotypes typical of S. fulvus and S. pygmaeus. Alien mitotypes occurred both within and outside sympatric zones. No alien mitotypes were found in 119 animals of the other three species, which suggests that only one parental species (S. major) predominantly participates in backcrosses. Phenotypic hybrids S. fulvus × S. major and S. major × S. pygmaeus) were reliably identified using RAPD–PCR of nuclear DNA. However, we could find no significant traces of hybridization in S. major with alien mitotypes. Analysis of p53 pseudogenes of S. major and S. fulvus that were for the first time described in the present study produced similar results: 59 out of 60 individuals of S. major (including S. major with S. fulvus mitotypes) had only the pseudogene variant specific for S. major. This situation is possible even at low hybridization frequencies (less than 1% according to field observations and 1.4 to 2.7% according to nuclear DNA analysis) if dispersal of S. major from the sympatric zones mainly involved animals that obtained alien mtDNA via backcrossing. The prevalence of animals with alien mitotypes in some S. major populations can be explained by the founder effect. Further studies based on large samples are required for clarifying the discrepancies between mitochondrial and nuclear DNA data.     

Heterogeneity and Polymorphism of Functionally Specialized Blood Proteins of Migratory Fish on the Example of the North Caspian Population of Russian Sturgeons during the Sea and River Periods of Life. 2. Hemoglobins

We carried out comparative studies of the heterogeneity and polymorphism of the most important functionally specialized blood proteins, hemoglobins. The fractional composition of hemoglobin proved to be identical during the sea and river periods of life for all main parameters (number of components, relative mobility, and protein content of each component). This puts the Russian sturgeon in a special position with reference to migratory teleostean fish, specifically salmonids, in which the specific weight of the protein of slow and fast hemoglobins undergoes changes upon change of the habitat.     

Voltage-dependent calcium currents in cultured frog skeletal myocytes

Voltage-dependent calcium currents (I _Ca) in cultured embryonic skeletal frog myocytes at the stages of development ranging from one to six days were studied using the whole-cell patch-clamp recording technique. Fast dihydropyridine (DHP)-nonsensitiveI _Ca and slow DHP-sensitiveI _Ca were recorded during the early stages of myogenesis. These currents do not differ in their kinetics from theI _Ca found in the adult frog muscle. Two slow voltage-dependent DHP-sensitiveI _Ca were found. In terms of its activation time, the first slow I_Ca is similar toI _Ca described in phasic skeletal muscle fibers. The second slowI _Ca observed in about 10% of cells examined is similar toI _Ca described in tonic skeletal muscle fibers of adult frog. In some cases, two slow currents with different kinetics were recorded in the same myocyte.Neirofiziologiya/Neurophysiology, Vol. 26, No. 1, pp. 44–48, January–February, 1994.     

Three Novel Mutations in Porphobilinogen Deaminase Gene Identified in Russian Patients with Acute Intermittent Porphyria

Porphobilinogen deaminase (PBGD) is a key enzyme of the heme biosynthetic pathway. Defects in the PBGD gene lead to an autosomal dominant disease, acute intermittent porphyria (AIP). Almost all AIP patients with rare exceptions are heterozygous for the defective gene. To date, at least 160 different mutations causing AIP are identified. Extensive investigations along this line are conducted in many countries of the world. In Russia these studies had not been hitherto performed. Here we report the results of molecular genetic examination of four Russian patients with AIP diagnosed from clinical symptoms. By direct sequencing of the PBGD gene or the corresponding cDNA, we have detected four mutations, three of which were not previously encountered in the world population. These are TAAG deletion in intron 7 between positions +2 and +5 (IVS7 2–5 delTAAG); T deletion in the initiation codon ATG of exon 3, and the G for C replacement at position –1 of intron 5 (IVS5 as –1 G–C), which disrupts splicing. In addition, in one female patient, a known deletion CT in codon 68 was revealed. In two patients, expression of PBGD gene alleles was significantly disproportional, so that normal mRNA prevailed in one case and mutant mRNA of nonerythroid type in the other. Deletion in intron 7 was easily detectable due to the formation of a heteroduplex fragment with abnormal electrophoretic mobility directly in PCR. This simple heteroduplex analysis allowed us to exclude AIP carriage in son and daughter of a female patient with the genetic defect.