Adaptive reactions of the endocrine system of children living under conditions of contrasting photoperiods

Age-related changes in the levels of pituitary, thyroid, and sex hormones and their dependence on the day length were studied in 242 healthy 10-to 16-year-old boys born and permanently living in the southern part of Arkhangel’sk oblast. It was found that the serum levels of thyroid hormones, gonadotropins, and sex steroids underwent circannual changes. The minimum concentrations of thyroxine, testosterone, and estradiol and the maximum concentrations of triiodothyronine, lutcinizing and follicle-stimulating hormones, and progesterone were associated with the shortest days. In contrast, the longest days were associated with the maximum concentrations of thyroxine, testosterone, and estradiol and the minimum concentrations of triiodothyronine, luteinizing and follicle-stimulating hormones, and progesterone. A factor dependence of the thyroxine, triiodothyronine, testosterone, estradiol, and prolactin concentrations on the day length was found in the group examined. This dependence was more pronounced during the second half of adolescence.     

Evaluation of the number of agonist molecules needed to activate a ligand-gated channel from the current rising phase

We propose a new method for calculating the number of agonist binding sites (n) in ligand-gated receptor channels from the initial phase of the current. This method is based on the fact that the relation between the current (I) and its first-time derivative (I') at the beginning of the current reflects the number of transitions that lead to channel opening. We show that, for constant agonist concentration, the above relationship at t --> 0 provides the number of steps leading to channel opening. When the agonist concentration is not constant but rather increases linearly with time, the corresponding value can be obtained using a slightly modified procedure. The analytical results were compared with computer simulations and a good match between the two was obtained. The theoretical procedure was then validated experimentally using the nicotinic receptor, because, for this receptor, the number of binding sites is well established. Indeed, the expected number of two binding sites was obtained. The method was then tested for the quisqualate-type glutamate receptor channel from the opener muscle of crayfish. The number of this receptor's binding sites is not fully resolved. Our results suggest that, for this glutamate receptor as well, two binding sites must be occupied to open the channel.     

Age-dependent heart rate variability in preschool children living under the conditions of the European Arctic region

The results of analysis of specific characteristics of the heart rate variability (HRV) regulation in preschool children living under the Arctic high-latitude conditions are presented. The principal ageand gender-specific differences in the HRV regulation have been inferred from the intergroup evaluations of the HRV indicators in boys and girls. A functional developmental delay has been shown in 2.5-year-old girls compared with boys of the same age group. The applied orthostatic test has shown lower reserve capacities in children of the senior group compared with the junior group. It has been shown that the mechanisms of the regulation of cardiac rhythm in girls experience higher strain during orthostasis as compared with boys. The division of children into age groups with an age difference of one year has allowed the detection of the tendency towards basically different responses to functional loads during orthostasis. The mean HRV values characteristic of four- to six-year-old children living in the Arctic are presented. It has been shown that the children living at middle latitudes have a higher adaptive potential compared with the children living in high-latitude Arctic areas.     

Expression of genomic instability in lymphocytes from children living under conditions of long term exposure to radioactive factors

An experimental study of expression of genomic instability was carried out with the use of testing irradiation in peripheral blood lymphocytes of 15 children (born in 1986-1998) living on territories with radionuclide contaminations (over 15 Ci/km2, 137Cs, Novozybkov district, Bryansk region). In 5 children exposed to intrauterine irradiation in 1986 this phenomenon was studied in 3 successive cell generations (mitoses). The data obtained suggest the reality of expression of induced genomic instability in the offsprings of repeatedly divided cells of a growing organism exposed to prolonged action of low radiation levels.     

Pore-forming proteins and adaptation of living organisms to environmental conditions

Pore-forming proteins are powerful “tools” for adaptation of living organisms to environmental conditions. A wide range of these proteins isolated from various sources, from viruses to mammals, has been used for the analysis of their role in the processes of intra- and inter-species competition, defense, attack, and signaling. Here we review a large number of pore-forming proteins from the perspective of their functions, structures, and mechanisms of membrane penetration. Various mechanisms of cell damage, executed by these proteins in the course of formation of a pore and after its passing to conducting state, have been considered: endo- and exocytosis, lysis, necrosis, apoptosis, etc. The role of pore-forming proteins in evolution is discussed. The relevance of practical application of pore formers has been shown, including application in nanotechnological constructions.     

Response to disodium cromoglycate in children with chronic asthma

Twenty-three children with chronic severe perennial asthma received randomly-allocated disodium cromoglycate or placebo four times a day for 12 weeks, and the alternative regimen for the subsequent 12 weeks. More than half the patients improved while on DSCG according to clinical assessment. There was a significant increase in the mean FEV_{0·75 second} during the drug period, largely owing to dramatic improvement in nine patients. No reduction in the mean decrease of FEV after exercise was demonstrated. Response, when it occurred, was evident within four weeks. The effect of the medication was consistent in individual patients throughout the 12-week period. No evidence of toxicity was discovered during the period of study.     

Postvaccinal immunity to polio-viruses of children with chronic renal pathology

41 children with chronic renal diseases (with different forms of chronic glomerulonephritis or chronic renal failure) previously vaccinated with 5 to 9 doses of oral poliovaccine (OPV) were examined. Analysis of immunity to polioviruses revealed insufficient serologic protection against all three types of polioviruses compared with general population. Algorithm of yearly serologic examination as well as a schedule of additional vaccination against poliomyelitis depending on chronic renal pathology were developed.     

通过诱导剂作用于启动子的条件性基因表达(英文)

通过遗传工程技术获得的转基因动植物对分析某些生化过程和发育途径极为有用。通过化学诱导剂作用于启动子的条件性基因表达是分子生物学和生物技术应用研究中的强有力的手段。建立于目标基因激活和失活基础之上的几个化学分子诱导基因表达系统已有报道。将来自于原核生物、昆虫和其它动物的调节因子应用于新的物种有利于促进转基因技术的应用和有关基因的时空表达研究。本文综述了有关的基因表达调节系统 ,启动子激活的基因表达系统 ,启动子失活的基因表达系统 ,以及可诱导的基因过度表达和反义抑制系统     

Dissociation characteristic of the inclusion complex of cyclomaltohexaose (α-cyclodextrin) with 1-methylcyclopropene in response to stepwise rising relative humidity

The dissociation of a crystalline complex of cyclomaltohexaose (α-cyclodextrin) and 1-methylcyclopropene has been studied in response to stepwise rising relative humidity at 50 °C using a dynamic vapor sorption instrument. The dissociation of the inclusion complex was monitored with a proton transfer reaction mass spectrometer. The increase in relative humidity generally triggered the complex dissociation. However, the dissociation was greatly retarded at 80% relative humidity, presumably owing to collapse of the crystalline structure. Abrupt dissociation was observed at 90% relative humidity which corresponded to complex dissolution. The changes in powder X-ray diffraction pattern of the inclusion complex during the storage period were also investigated.     

On the number of experiments required to find the causal structure of complex systems

The need to capture the complexity of biological systems in a simpler formalism is the underlying impetus of biological sciences. Understanding the function of many biological complex systems, such as genetic networks or molecular signalling pathways, requires precise identification of the interactions between their individual components. A number of questions in the study of complex systems are then important-in particular, what can be inferred about the interactions in a complex system from an arbitrary set of experiments, and, what is the minimum number of experiments required to characterize the system? This paper shows that the problem of finding the minimal causal structure of a system based on a set of observations is computationally intractable for even moderately sized systems (it is NP-hard), but a reasonable approximation can be found in a relatively short (polynomial) time. Next, it is shown that the number of experiments required to characterize a complex system grows exponentially with the upper bound on the number of immediate upstream influences of each element, but only logarithmically with the number of elements in the system. This makes it possible to study biological systems with extremely large number of interacting elements and relatively sparse interconnections, such as gene regulatory and cell signalling networks. Finally, the construction of a randomized experimental sequence which achieves this bound is discussed.     

Linking number anomalies in DNA under conditions close to condensation

Changes in linking number and the apparent winding angle of pBR322 DNA have been evaluated in mixed ethanol-water solvents containing either Na or Mg as the major counterion contributing to the electrostatic shielding of the duplex. The average number of superhelical turns (tau) produced in the standard electrophoresis buffer (Tris-borate-EDTA, pH 8.0) by the transfer of DNA, relaxed in 200 mM NaCl, 10 mM NaH2PO4/Na2HPO4, and 2 mM EDTA, pH 7, by calf thymus topoisomerase or ligated in 6.6 mM MgCl2, 1 mM KCl, 1 mM ATP, 1 mM dithiothreitol, and 66 mM Tris, pH 7.6, by T4 ligase, was determined as a function of the EtOH concentration. At low enzyme concentrations, the tau values became increasingly more positive in the presence of both cations as the ethanol concentration increased, indicating that the duplex structure was overwound in the ethanol solvents. Winding angle changes between 0 and 20% ethanol, calculated from these values of tau, exhibited the same correlations with CD spectral properties as had been previously observed for 100% aqueous systems containing monovalent cations [Kilkuskie, R., Wood, N., Shinn, R., Ringquist, S., & Hanlon, S. (1988) Biochemistry 27, 4377-4386]. The results at higher concentrations of ethanol (25-30%), however, were anomalous for the Mg-ligase system. The anomalies increased with higher ethanol, ligase, or Mg concentration. Gel run under these conditions showed enhanced concentrations of slow-moving components, indicative of ligation of intermolecular associated DNA species. At a 10-fold higher level of ligase, ethanol appeared to unwind the duplex, confirming the results of Lee, Mizusawa, and Kakefuda [(1981) Proc. Natl. Acad. Sci. U.S.A. 78, 2838-2842]. All of these anomalies occur under solvent conditions which are close to conditions which produce a heterogeneous dispersion of sedimenting species in ultracentrifugal experiments and compact rodlike structures, visualized by electron microscopy. The circular dichroism spectra at the onset of the formation of these structures show the characteristics of a chirally packed array of DNA duplexes. The reversal of the trend of the ethanol effect on linking number at higher enzyme and Mg(II) concentrations can be most easily explained by the promotion of the condensation phenomenon by either the ligase or a contaminating factor in the preparation. We suggest that the anomalies in the linking number and winding angle values are due to either ligation of chirally bent DNA species or a change in the helical period as the linear DNA adapts to the conformation required for collapse.(ABSTRACT TRUNCATED AT 400 WORDS)     

Osteoporosis due to glucocorticoid use in children with chronic illness

Osteoporosis is increasingly recognized as a complication of chronic childhood illnesses, particularly when glucocorticoids (GCs) are necessary for treatment. Elucidation of the mechanisms leading to bone fragility in these settings requires disentanglement of the relative contributions of myriad risk factors, including disease activity, muscle weakness, immobilization, delayed growth and puberty, compromised nutrition, and osteotoxic medications. Over the years, bone mass and density evaluations by dual energy X-ray absorptiometry (DXA) have become popular for assessing bone health in children; however, such measurements are difficult to interpret because of the confounding effect of bone size and the lack of DXA-based densitometric criteria for defining osteoporosis in childhood. Recently, a new diagnostic approach for evaluation of densitometric data in children has been suggested, driven by Frost's mechanostat theory. A diagnostic algorithm based on the mechanostat theory of bone-muscle development is proposed for the characterization of bone disease in children with chronic illness. In addition to DXA-based assessments, techniques such as peripheral quantitative computerized tomography and ilial histomorphometry, for which there are pediatric reference data, are gaining ground in the characterization of skeletal changes due to chronic illness. Although these diagnostic techniques expand our understanding of osteoporosis in children, they do not replace clinical assessment. Concrete clinical evidence for GC-induced bone fragility can be seen in spinal changes due to vertebral compression, with spinal morphometry emerging as an essential, but frequently overlooked, tool in the evaluation of children's bone health. Presently, osteoporosis treatment in the chronic illness setting remains experimental and should be restricted to clinical studies. Following an understanding of the natural history of GC-induced osteoporosis in children, randomized, placebo-controlled prevention and intervention trials will be the next step toward the development of clinical practice guidelines.     

Adaptation of Camelus dromedarius pars nervosa of the hypophysis to winter and summer living conditions

The aim of this work is to study the characteristics of the dromedary nervous lobe and determine how the seasons condition its organization. To this end, electron microscopy was performed and examined quantitatively on animals from winter and summer periods. The results show a higher number of cells in the nervous lobe in summer than in winter. The most abundant glial elements in winter are light pituicytes engulfing neurosecretory nerve fibers making neuroglial contact, and dark pituicytes containing numerous heterogeneous light bodies. In summer, the most distinctive glial cells may be pituicytes in a phagocytic state making contact with characteristic large light bodies that could represent a degenerative process of large neuropeptide storage. Granular pituicytes were also observed in contact with glial and neuronal components. However, lipid droplets, described in pituicytes of other mammals, were not observed in our samples. Quantitative analysis of neurovascular contacts revealed that the number of nerve terminals contacting the basal lamina did not differ between summer and winter, but the mean number of glial processes increased in winter. Our data provides evidence that the storage of neuropeptides is very marked in summer and that, associated with an autophagic and phagocytic phenomenon, this suggests an adaptation to anticipate any situation that would cause dehydration of the dromedary. Thus, in its tough environment, the animal remains permanently prepared to avoid any large water loss.