Sexual transmission of Borrelia garinii by male Ixodes persulcatus ticks (Acari, Ixodidae)

We investigated the transmission of Borrelia garinii and Borrelia afzelii between male and female Ixodes persulcatus ticks. For this purpose the infection rate of partners from tick couples was determined by polymerase chain reaction and reverse line blot. In couples, where the male tick was infected with B. garinii, four out of nine female partners carried B. garinii. In eight couples, male ticks had a dual infection of B. afzelii and B. garinii and three female partners were infected by Borrelia spirochetes. Two female ticks carried B. garinii, and one female tick had a dual infection. No evidence for transmission of B. afzelii from male to female ticks was found among seven couples. In 45 couples where the female tick was infected, not one male tick carried spirochetes. The difference in the B. garinii infection rate between male and female ticks among these couples is highly significant. Our data suggest that transmission of B. garinii from male ticks to female ticks does occur. Sexual transmission of this pathogen may play an important role in the maintenance of B. garinii in I. persulcatus. © Rapid Science Ltd. 1998     

Comparative analysis of the kinetic characteristics of L-type calcium channels in cardiac cells of hibernators.

An undefined property of L-type Ca2+ channels is believed to underlie the unique phenotype of hibernating hearts. Therefore, L-type Ca2+ channels in single cardiomyocytes isolated from hibernating versus awake ground-squirrels (Citellus undulatus) were compared using the perforated mode of the patch-clamp technique, and interpreted by way of a kinetic model of Ca2+ channel behavior based upon the concept of independence of the activation and inactivation processes. We find that, in hibernating ground-squirrels, the cardiac L-type Ca2+ current is lower in magnitude when compared to awake animals. Both in the awake or hibernating states, kinetics of L-type Ca2+ channels could be described by a d2f1(2)f2 model with an activation and two inactivation processes. The activation (or d) process relates to the movement of the gating charge. The slow (or f1) inactivation is associated with movement of gating charge and is current-dependent. The rapid (or f2) inactivation is a complex process which cannot be represented as a single-step conformational transition induced by the gating charge movement, and is regulated by beta-adrenoceptor stimulation. When compared to awake animals, the kinetic properties of Ca2+ channels from hibernating ground-squirrels differed in the following parameters: (1) pronounced shift (15-20 mV) toward depolarization in the normalized conductance of both inactivation components, and moderate shift in the activation component; (2) 1.5-2-fold greater time constants; and (3) two-fold greater activation gating charge. Thus, L-type Ca2+ channels apparently switch their phenotype during the hibernating transition. Stimulation of beta-adrenoceptors by isoproterenol, reversed the hibernating kinetic- (but not amplitude-) phenotype toward the awake type. Therefore, an aberrance in the beta-adrenergic system can not fully explain the observed changes in the L-type Ca2+ current. This suggests that during hibernation additional mechanisms may reduce the single Ca2+ channel-conductance and/or keep a fraction of the cardiac L-type Ca2+ channel population in a non-active state.     

Embryogenesis of the human tongue]

Developmental peculiarities of the tongue as a whole and its main structural elements (muscles, membranes, glands, lingual tonsil) have been studied in 120 human embryos and fetuses 5-week-old--9-month-old. Transmissive electron microscopy, electron histochemistry (for estimation of 5'-nucleotidase activity), staining of semithin slices with toluidine blue and aniline++ pink have been applied. Problems on migration of myogenic elements in the developing tongue have been discussed. Ultrastructure of gustatory bulbs of the human fetus tongues has been investigated. A complete formation of the tongue takes place by the 8th-9th months of the prenatal development.     

Ultrastructure of the digestive tract of Diacyclops thomasi (Cyclopoida, Copepoda) during different stages of encystment during a summer diapause

Baud, A., Cuoc, C. and Alekseev, V. 222_. Ultrastructure of the digestive tract of Diacyclops thomasi (Cyclopoida, Copepoda) during different stages of encystment during a summer diapause. — Acta Zoologica (Stockholm) 85 : 181–189 Diacyclops thomasi ( Forbes, 1882 ) has a life cycle comprising a summer diapause with whole‐body encystment at the copepodid IV stage. Formed progressively, the cyst can indicate the extent of entry into diapause. In this study the ultrastructure of the midgut epithelium during encystment of CIV was compared with that of active CIV and females. In active individuals two well‐differentiated epithelial cell types were observed: vacuolar cells (B‐cells), and cells without vacuoles but with more densely packed microvilli and abundant rough endoplasmic reticulum and mitochondria (F/R cells). In encysted specimens a striking transformation of the midgut epithelial layer was noted. Only inactive nuclei with highly concentrated euchromatin and encircled by a thin rim of hyaloplasm were observed. Compartments of both urosome and especially cephalothorax displayed large lipid‐rich lacunae. At the beginning of encystment, the midgut epithelium showed an intermediate state. Changes in ultrastructure observed in the midgut epithelium of D. thomasi clearly reflect different stages of diapause, and represent clear evidence of profound reorganization, which is progressively induced by diapause in the organism.     

Plant smells---important determinants in the behavior and rate of development of ixodid disease vectors]

Experiments with nymphs of Ixodes persulcatus and Dermacentor marginatus have shown that the rate and degree of engorgement, dropping off from the mouse, metamorphosis longevity and weight of emerging imagoes change under plant odour influence. The influence of acetone extract vapours of pepper, poplar buds, linden and aspen was tested. Under the influence of the vapour, acting as an attractant for the adults, engorgement weight of their nymphs and the weight of imagoes emerging from them increased; attractants change the nymph-imago metamorphosis duration as well. Repellent acting odours, as a rule, produce an opposite reaction. The phenomenon of the inversion of the infected D. marginatus reaction to the odour is proved in nymphs. Attractant for naive adult ticks (poplar buds) increased the time of feeding and weight of nymphs in comparison with the control. Just the opposite: nymphs infected with tick-borne encephalitis (TBE) virus produce an opposite reaction--weight decrease under influence of poplar buds as the repellent. Importance of the above phenomena for the ticks distribution and TBE epizootiology is discussed.     

Comparative analysis of the structure and function of recA genes from Serratia marcescens Sb and Escherichia coli K-12

Nucleotide sequence of the 1276 bp fragment of Serratia marcescens DNA coding for the recASM gene has been determined. This structure was shown to contain an ORF corresponding to a protein with molecular weight of 37766 D. Comparative analysis of the regulatory part of recASM and recAEC (Escherichia coli) demonstrated identity of "-35" and "-10" boxes for these genes and similarity of the SOS box and the enhancer sequences. A comparison of the amino acids sequences of RecASM, RecAEC and RecAPA (Pseudomonas aeruginosa) proteins revealed a great conservatism in the N-terminus and in some structural patches (alpha-helices and beta-sheets) of the RecA proteins predicted by the model of Blanar et al. In contrast, a strong variability of the C-terminus (for the last 25 amino acids, in particular) was revealed. A necessity for definite amino acids composition of the carboxy-terminal end is discussed.     

Role of active ion transport in reception of the generator potential of the isolated frog muscle spindle

The effect of complete replacement of sodium ions by lithium ions in Ringer's solution and of 10⁻⁴ M ouabain on the receptor potential of the isolated frog muscle spindle was investigated. Initially, under the influence of lithium ions and ouabain, the hyperpolarization phase of this potential diminished and disappeared, and later the same fate befell the static and dynamic part of its depolarization phase. The rise time of the receptor potential was increased in a solution containing lithium ions but in the solution with ouabain it remained the same as initially. No appreciable changes were found in the rate of fall of the dynamic part of the depolarization phase. On rinsing the muscle spindle in normal Ringer's solution in the experiment with lithium ions recovery was incomplete, and in the experiments with ouabain the receptor responses were not restored.     

Effect of combined anesthetics on the activity of various myocardium enzymes

It is demonstrated by experiments with rabbits that the Ca2+-ATP-ase activity is stabilized when using combined anesthetics (diacetylcholine + halothane + N2O) as distinct from application of halothane. A decrease in the cholinesterase activity is less pronounced than under the halothane action but more than with the diacetylcholine application. A decrease in the Na+, K+-ATP-ase activity is observed with all types of anesthesia. A considerable inhibition of creatine kinase under the action of combined anesthesia and halothane and an increase of the lactate dehydrogenase activity under diacetylcholine application in mitochondria are shown. Reliable differences in the succinic dehydrogenase activity are not detected.     

Stability of glucose-6-phosphate dehydrogenase in human cells cultivated in vitro]

It was shown that the thermal stability of glucose-6-phosphate dehydrogenase in human diploid cells is much higher than in human heteroploid cell lines HeLa and T-9. The purified enzymes from human diploid cells and from HeLa and T-9 cells possess similar thermal stabilities. Mixing of T-9 extracts with the purified enzyme preparations revealed that the non-stability factors of the dehydrogenase are present in the T-9 extracts. An addition of NADP- and NADPH-containing buffers and crystalline NADP to the heteroploid cell extracts stabilizes the enzyme. The thermal stability of the enzyme from "in vitro" cultivated human cells depends on the concentration of the coenzyme. It was also demonstrated that glucose-6-phosphate dehydrogenase stability in HeLa and T-9 extracts is the same at low concentrations of the coenzyme and after addition of crystalline NADP. However, at NADP concentration of 10(-3) M the enzyme stability in HeLa and T-9 extracts is different. It is assumed that the destabilizing factors are the enzymes possessing the nucleotidases activity, which is different in various cell lines.