scholarly journals Experimental study of mechanisms of disturbances of hypothalamic regulation of reproduction

2005 ◽  
Vol 54 (1) ◽  
pp. 57-63
Author(s):  
A. V. Arutjunyan ◽  
G. О. Kerkeshko ◽  
М. G. Stepanov ◽  
А. V. Korenevsky ◽  
Е. К. Ailamazyan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Sex Steroids ◽  
Circadian Oscillator ◽  
Diurnal Rhythms ◽  
Regulation Of Reproduction ◽  
Hypothalamic Regulation ◽  
Negative Effect ◽  
Rfbr Grant ◽  
Reproductive Cycles

Summary: Diurnal rhythms of the activity of a number of monoaminergic systems of the hypothalamus (norepinephrine and serotonin in PA and ME-ArN, as well as dopamine in ME-ArN) have been shown to depend on the functioning of an endogenous circadian oscillator in SCN of the hypothalamus. Light modifies the diurnal rhythms of the neurotransmitters. Enhancement of the activity of the noradrenergic systems with sex steroids in proestrus is an important mechanism of the forming of the preovulatory surge of GnRH and gonadotropines secretion, which initiates ovulation. Consideration of our own experimental data and literature allow the supposition that the change of diurnal rhythms of norepinephrine in PA and ME-ArN could result in profound disturbances of hypothalamic regulation of reproductive cycles and be one of key reasons for negative effect of xenobiotics on reproduction. Supported by RFBR grant 04-04-49204.

scholarly journals Role of bio-genic amines for the hypothalamic regulation of reproductive function

2004 ◽  
Vol 53 (1) ◽  
pp. 98-106
Author(s):  
A. V. Arutiunian ◽  
G. О. Kerkeshko ◽  
М. G. Stepanov ◽  
А. V. Korenevskiy ◽  
Е. К. Aylamazian
Keyword(s):  
Reproductive Function ◽  
Diurnal Rhythms ◽  
Central Regulation ◽  
Suprachiasmatic Nuclei ◽  
Regulation Of Reproduction ◽  
Secretion Regulation ◽  
Hypothalamic Regulation ◽  
Reproductive Cycles ◽  
Central Oscillator

The present review is dedicated to monoaminergic systems involved in hypothalamic regulation of reproduction, as well as to the role of the systems in GnRH synthesis and secretion regulation. Data are presented on the ovarian steroid hormones, the suprachiasmatic nuclei of the hypothalamus, in which the central oscillator of a mammalian organism's diurnal rhythms is located, and on the pineal hormone melatonin involved in formation of reproductive cycles. Both own results and literature data referring to the role of diurnal rhythms of the activity of monoaminergic systems of the hypothalamus in the central regulation of reproduction are discussed.

scholarly journals Impaired hypothalamic regulation of reproductive function when exposed to neurotoxic compounds and melatonin

2003 ◽  
Vol 52 (2) ◽  
pp. 77-85
Author(s):  
A. V. Arutjunyan ◽  
М. G. Stepanov ◽  
G O. Kerkeshko ◽  
Е. K. Ailamazyan
Keyword(s):  
Pineal Gland ◽  
Biogenic Amines ◽  
Blood Level ◽  
Female Rats ◽  
Diurnal Rhythms ◽  
Central Regulation ◽  
Exogenous Melatonin ◽  
Diurnal Dynamics ◽  
Regulation Of Reproduction ◽  
Hypothalamic Regulation

Diurnal rhythms of the contents of biogenic amines in the hypothalamus are considered to play an important role in regulation of many functions such as motor activity, feeding behaviour, sleep-awake cycle formation as well as hormonal and immune statuses. Mechanisms of regulation of reproduction that participate in a circadian signal transmission from the suprachiasmatic nuclei (SCN) of the hypothalamus to hypothalamic structures responsible for gonadoliberin (GnRH) synthesis and secretion (the preoptic area - PA, and the medial eminence - ME) are at present being intensively studied. It has been shown that the aging caused disturbances of estrous cycles in female rats are accompanied by a disappearance of diurnal rhythms of activity of monoaminergic and opioid hypothalamic systems playing a key role in regulation of GnRH synthesis and secretion. The experiments carried out have revealed diurnal rhythms of the contents of the studied biogenic amines in the PA, ME and SCN of the hypothalamus. The rhythms are due to the amines increasing in the morning hours when compared to their evening and night levels. The neurotoxic compounds used disturbed the rhythms of the amines. Chronic inhalation of toluene caused a disappearance of the dynamics of all the studied neurotransmitters that was typical of the control group. Meanwhile, a single administration of 1,2-dimethylhydrazine resulted in either a complete disappearance of the diurnal rhythms of the biogenic amines contents found in control, or their phase shifts. Severe disturbances of the GnRH content and of the ROS diurnal dynamics were also observed in the studied hypothalamic areas. The literature allowed supposition that melatonin possessing entraining and antioxidant properties can be used as a protector of disturbances of central mechanisms of regulation of reproduction. However, our experiments have shown that exogenous melatonin does not only eliminate the neurotoxic compounds caused disturbances of diurnal rhythms of the studied indices, but it itself causes deep changes in their dynamics. The effect of melatonin has been found to result in a significant decrease of the catecholamines contents in all the studied hypothalamic structures, particularly of the norepinephrine content, that is accompanied by a profound decrease of the GnRH content and by a disturbance of the diurnal dynamics of reactive oxygen species (ROS) in the PA and ME. The effect of 1,2-dimethylhydrazine on the studied indices was less pronounced when compared to that of melatonin, whereas an injection of the xenobiotic on the background of the pineal gland hormone administration resulted in a predominant effect of the latter. Both the data obtained and the literature review allow to offer a hypothesis for a possible mechanism of involvement of diurnal rhythms of biogenic amines in central regulation of reproduction. It is known that synthesis and secretion of endogenous opioid peptides in the mediobasal hypothalamus undergo diurnal oscillations with minimum in the morning and maximum in the evening and/or at night. The revealed diurnal rhythms of the biogenic amines contents had opposite oscillations. This fact allows a supposition that these rhythms are due to the opioid system activity changing. Both decreased endogenous opioids contents and simultaneously increased morning biogenic amines levels in proestrus can create a neurotransmitter background that is necessary for GnRH surge formation. An evaluation of diurnal rhythms of the biogenic amines contents, GnRH and ROS in the studied hypothalamic structures can be used for an assessment of disturbances of central mechanisms of regulation of reproduction that are caused by other neurotoxic compounds or developed in some diseases and in aging when the functional activity of the pineal gland is altered. The data obtained testify to possible negative side effects of melatonin on hypothalamic regulation of reproduction in therapeutic use of the hormone. The effects of melatonin realized via its receptors are known to highly depend on amplitude of its nocturnal surge and on duration of its increased blood level during a day. Therefore administration of melatonin on the background of its normal synthesis can lead to a number of negative effects due to its increased blood level when compared to its physiological level. Elucidation of the exogenous melatonin caused disturbance of the studied diurnal rhythms of central regulation of reproduction is of great practical use in development of prophylactics helping to eliminate or decrease an effect of damaging factors in unfavourable environmental conditions.

EXPERIMENTAL STUDY OF THE KINEMATIC PARAMETERS OF MOVEMENT OF CARS FORCED IDLE MOTION

2018 ◽  
pp. 52-57
Author(s):  
Ivelin Kostov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Experimental Research ◽  
Kinematic Parameters ◽  
Research Results ◽  
Software Product

In the work brought some experimental data of kinematic parameters of movement of cars forced idle, as the software product was used to diagnose 900 ATS, which recorded kinematic parameters of vehicle. On the basis of the conducted experimental research results are shown tabulated and analysed.

Effects of ball properties on throwing in young team-handball beginners

2021 ◽  
pp. 174795412110236
Author(s):  
Frowin Fasold ◽  
Benjamin Noël ◽  
André Nicklas ◽  
Fabian Lukac ◽  
Stefanie Klatt
Keyword(s):  
Experimental Study ◽  
Movement Patterns ◽  
Team Handball ◽  
Throwing Accuracy ◽  
Different Types ◽  
Negative Effect ◽  
Study Participants

Throwing a ball is a primary skill in team-handball and can be directly influenced by the properties of different types of balls. Therefore, the use of different balls (i.e., methodic ball) recommended by the handball federations (e.g., IHF) and the education guidelines, are important in teaching throwing. Previous studies have shown that movement patterns and throwing velocity can be influenced by different ball types and sizes. However, the influence of these factors on throwing accuracy has not been investigated in detail yet. This study aims to replicate the findings of previous studies on increasing throwing velocity in children by comparing the use of a soft methodic ball with a size 0 handball. Furthermore, this study investigates the influence of these balls on throwing accuracy. In an experimental study, participants (10-years of age) threw a soft methodic ball and a size 0 ball at target areas in a handball goal. For all the throws, throwing velocity and accuracy were measured. Commensurate with previous research, throwing velocity was higher for the soft methodic ball compared to a size 0 ball. No difference was found in accuracy, although, it is worth mentioning that the participants were only experienced in throwing using the size 0 ball. Moreover, only one-third of the children favored throwing with a size 0 ball, which is what they are used to in training and competition. The results of our study, therefore, confirm that using soft methodic balls additionally, positively influences the throwing velocity and has no negative effect on the accuracy in throwing among young handball beginners.

Experimental study of hypochloremia

1935 ◽  
Vol 31 (8-9) ◽  
pp. 1112-1112
Keyword(s):  
Experimental Data ◽  
Experimental Study

Analyzing clinical and experimental data on hypochloremia, the authors show that both during vomiting and when giving diuretica, it is not only about the loss of chlorine, but at the same time a large amount of water is lost.

Kinetics of hypso anhydrites dissolution in water. Experimental studies

2019 ◽  
pp. 93-96
Author(s):  
A. L. Lebedev ◽  
I. V. Avilina
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Riccati Equation ◽  
Balance Equation ◽  
Experimental Studies ◽  
Common Ion ◽  
The Common ◽  
Common Ion Effect ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Experimental study of kinetics of dissolution of hypso anhydrites at 25 ᵒC made it possible to formulate model of the process in the form of a balance equation for the kinetics of dissolution of gypsum, anhydrite (first and second orders, respectively) and kinetics of precipitation of gypsum (second order). The processing of the experimental data were carried out on the basis of the solution of the Riccati equation. When taking into account the common-ion effect on the solubility of gypsum and anhydrite, the calculated values turned out to be more comparable with the experimental ones.

Effect of Tightening Speed on the Torque-Tension and Wear Pattern in Bolted Connections

2006 ◽  
Author(s):  
Sayed A. Nassar ◽  
Ramanathan M. Ranganathan ◽  
Saravanan Ganeshmurthy ◽  
Gary C. Barber
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Surface Roughness ◽  
Initial Level ◽  
Zinc Coating ◽  
Optical Microscope ◽  
Wear Pattern ◽  
Highly Sensitive ◽  
Contact Surfaces ◽  
Scanning Electron

This experimental study investigates the effect of tightening speed and coating on both the torque – tension relationship and wear pattern in threaded fastener applications. The fastener torque – tension relationship is highly sensitive to normal variations in the coefficients of friction between threads and between the turning head and the surface of the joint. Hence, the initial level of the joint clamp load and the overall integrity and reliability of a bolted assembly is significantly influenced by the friction coefficients. The effect of repeated tightening and loosening is also investigated using M12, Class 8.8, fasteners with and without zinc coating. The torque – tension relationship is examined in terms of the non-dimensional nut factor K. The wear pattern is examined by monitoring the changes in surface roughness using a WYKO optical profiler and by using a LECO optical microscope. A Hitachi S-3200N Scanning Electron Microscope (SEM) is used to examine the contact surfaces, under the fastener head, after each tightening/loosening cycle. Experimental data on the effect of variables and the tightening speed, fastener coating and repeated tightening on the nut factor are presented and analyzed for M8 and M12, class 8.8, fasteners.

Experimental Study of Typical Graded Asphalt Mixture about Dynamic Stability at High Temperature

2016 ◽  
Vol 858 ◽  
pp. 300-304
Author(s):  
Zhen Fu Chen ◽  
Dan Wu ◽  
Qiu Wang Tao ◽  
Yuan Chu Gan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
High Temperature ◽  
Asphalt Mixture ◽  
Temperature Stability ◽  
Specimen Thickness ◽  
High Temperature Stability ◽  
Change Trend ◽  
Comparison And Analysis ◽  
The Stability

The high temperature stability of AC-16, AC-13, AC-20 under specimen thickness of 5cm and 6cm is studied through indoor asphalt mixture high rutting test, Through comparison and analysis about experimental data, it is found that the stability of AC-16, AC-13, AC-20 asphalt mixture at high- temperature decreases in turn. It is shown that thickness changes did not affect the change trend of the high temperature stability under gradation change, and the stability of AC-16 at high-temperature is the best, the AC-13 is second and the AC-20 is less.

Sign in / Sign up

Export Citation Format

Share Document