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D Tzvetkov

Publications and source records attributed to D Tzvetkov.

At least 19 recordsLinked to original sources
PubMed2003

Current pathophysiological views on vibration-induced Raynaud's phenomenon.

This review attempts to summarize and discuss contemporary pathogenetic views on vibration-induced Raynaud's phenomenon assuming its multifactorial etiology. An increase in central and peripheral sympathetic nervous activity is discussed based on different physiological indicators of autonomic dysfunction and sympathetic hyperactivity. Local acral vasodysregulation is considered. Receptor and nerve endings dysfunction presented with predominance of alpha(2)-receptor function in the digital arteries and neuronal loss in those digital cutaneous perivascular nerves containing calcitonin gene-related peptide result in deficiency of endogenous release of this powerful vasodilator. Endothelial damage and dysregulation induced by vibration and increased shear stresses are demonstrated by the elevated plasma level of thrombomodulin and of von Willebrand factor and reduced endothelium-dependent vasodilator responses. The concentrations of endothelin-1 are high, the highest being in most advanced stages. Decreased plasma thiol level, indicating increased production and activity of free radicals, contribute to vasospastic paroxysms in vibration white finger patients. Dysbalance of local vasoactive factors with opposing effects on vascular smooth muscle like endothelin and nitric oxide, endothelin and calcitonin gene-related peptide, nitric oxide and superoxide anion are discussed. Disturbed smooth muscle response is supposed. Changes in hemostasis, fibrinolysis and hemorrheology, activation of blood cells with erythrocyte hyperaggregation and red cell hypodeformability, platelet aggregation with increased release of vasoconstricting thromboxane A(2) and serotonin as well as leukocyte activation, entrapment within capillaries and post-capillary venules and increased reactive oxygen species and lysosomal lytic enzymes release might also contribute to digital vasospasms and tissue damage. Elevated soluble intercellular adhesion molecule-1 levels involved in the adherence of leukocytes to endothelium and to other leukocytes have been found in patients with hand-arm vibration syndrome.

Autonomic Nervous System Diseases↗
PubMed2002

Pathophysiology of vibration-induced white fingers--current opinion: a review.

Vibration-induced white finger (VWF) is secondary Raynaud's phenomenon caused by vibrating hand tools. Initially described in 1911 by Loriga, the pathophysiology of VWF remains unclear. This review attempts to summarize the current common and the most modern theories of the pathogenesis of VWF and propose a model of multifactorial etiology. The role of vasoregulatory abnormalities--autonomic dysfunction, local vasoregulatory abnormalities, of the endothelial cell control, of hemostasis, fibrinolysis and hemorrheology, of the leukocyte activation and the levels cell adhesion molecules and pro-inflammatory cytokines have been reviewed.

Endothelium, Vascular↗
PubMed2001

Opportunities for integration into ordinary school of students with emotional and behavioral disorders and students with chronic cardiovascular diseases (representative study for Republic of Bulgaria).

This article reviews the results of a representative study on the opportunities for integration into mainstream school of students with emotional and behavioral disorders and students with chronic cardiovascular disease. The aim of the study is to clarify some important personal characteristics as well as some factors, related to the school and family environment of students with EBD and those with chronic CVD in order to assess their capacities for integration. Altogether 192 students aged 8-15 years with psychic disorders and 337 aged 15-18 years with cardiovascular diseases were followed for two and four years respectively. Results show that students with EBD are with limited cognitive capacities, emotionally unstable, introverts, with high level of psychotisicm and higher level of personal anxiety compared to their healthy coavals. Students with EBD, studying with the healthy children, compared to their coevals with the same diagnoses, but studying separately in recovery school "pure model of special school" are with better short-term memory, lower level of situation anxiety, better mental work capacity and as whole more successfully socialized. In the end of the second year of investigation their psychic health improves as well. All this allow us to draw the conclusion that the integrated education of pupils with EBD has a better effect on the psychic health and improves as a whole their learning potentialities. Beside some significant differences between the students with CVD and the healthy referents, in terms of social and family status, school performance, school relationships, personal and cognitive characteristics, they could successfully be integrated into the public school in the presence of a well organized and individualized health, social and pedagogic support.

Adaptation, Psychological↗
PubMed1999

Effect of vibrations on male reproductive system and function.

From data in the literature, the potential risk of mechanical vibrations on reproduction in experimental, clinical and epidemiological studies (in experimental animals, men occupied in transport and industry), as well as the influence on sexuality are summarised. Results of the authors own experimental and clinical studies on the influence of the vibration on the male reproductive system are also presented. In male rats, decreased sperm counts, spermatogenesis index and size of testes, changed character of their motion, chronic venous stagnation and dystrophic alterations in tubuli contorti, changed ScDH, ATP-ase, LDH and GL-6-PDH activity, germ cells structural damages were observed. Workers exposed to vibrations had an increased prevalence of oligozoospermia, asthenozoospermia and teratozoospermia. Sexual disorders are also observed. The authors suggest that reproductive disorders should be included in the list of non-specific effects of vibrations. The detected changes justify further investigations and development of mathematical models for early detection and prognosis of the unfavourable effect on male reproductive function.

Animals↗
PubMed1998

Family and social determinants of school maladjustment in students with emotional disturbances and behavioral disorders from recovery schools in Bulgaria.

This inquiry study is part of a comprehensive investigation on the organization and the effect of the education of students with emotional disturbances and behavioral disorders in special recovery schools. The aim for conducting the inquiry is to reveal the characteristics of the family and social background which may affect the school adaptation. The investigated group includes 254 students--192 with emotional disturbances and behavioral disorders and 62 healthy children of the same age from the settlements where the recovery schools are based. Two types of questionnaires developed by the team are used for investigating the students' family and social status--one designed for the pupils and one--for the teachers and supervisors in the schools. The inquiry for the students contains 15 questions revealing family and school environment (family relations and problems; number of children and sequential number of the problem child; parents' education and employment; school training and curriculum; social contacts in the school; school results). The inquiry, engaging the class teachers, day and night supervisors in recovery schools, contains 19 questions. There are additional questions concerning students' specific learning difficulties as well. The results made it clear that parents' divorce is the most unfavorable family determinant for school maladjustment of students with emotional disturbances and behavioral disorders. Many other factors such as the poor educational qualification and social-professional status of the parents, children number, the sequential number of the problematic child additionally impedes the relationship with the parents, thus increasing the risk of school failure and the manifestations of school maladjustment. The determined peculiarities of the family environment of students with emotional disturbances and behavioral disorders suggest targeted psychocorrective work of the school psychologist individually with the student as well as with his/her family.

Adaptation, Psychological↗
PubMed1996

Male reproductive function in workers exposed to vibration.

Male infertility is a significant health problem. Increasing attention has been paid to the use of semen analysis as an indicator of exposure to potential reproductive hazards. The aim of the current paper was to study the effects of vibrations on the spermatogenesis in workers of different occupational groups (professional drivers, miners, engine drivers, etc.). Semen samples were analyzed for pH, volume, turbidity, sperm density sperm count and sperm morphology. Workers had an increased prevalence of oligospermia and azoospermia. The semen volume and percentage of motile spermatozoa decreased significantly and the incidence of sperm malformation increased in exposed workers.

Adult↗
PubMed1995

Detection of antibodies toward epididymal sperm antigens--an obligatory step in evaluation of human immunologic infertility?

PROBLEM: To test the relative impact of epididymal versus ejaculated sperm in immunologic infertility. METHOD: Human antibody binding to epididymal and ejaculated spermatozoa was compared by flow cytometry (FCM) since it allows quantitative analysis of viable sperm while ignoring nonsperm cells. To select sera for FCM, GAT, TAT, and ELISA were applied on 145 sera from fertile men, idiopathically infertile and varicocele patients. RESULTS: All GAT/TAT-positive infertile patients, a representative group of varicocele patients and the fertile control, were assessed by FCM. Higher reactivity toward epididymal sperm revealed 18/22 sera while only four out of them bound to ejaculated sperm stronger than the control. All varicocele sera were positive against epididymal while negative against ejaculated spermatozoa. CONCLUSIONS: Epididymal sperm antigens may play a predominant role in some cases of immunologic infertility. Such patients might not be adequately diagnosed and respectively treated due to the limitations of diagnostic procedures applying only ejaculated spermatozoa.

Antigens, Surface↗
PubMed1993

Effect of vibrations on the organism--possibilities for development of non-specific diseases and their prognostication.

Changes in the lipid metabolism, electrolytes, trace elements, acid-base balance in experimental animals and in workers exposed to vibrations, as well in patients suffering from vibration disease were investigated. The role of vibrations as a modifier of chemically induced cancerogenesis, and in implanted tumour cells was studied under laboratory conditions. A study was carried out on the morbidity with temporal work incapacity and total morbidity according to the turnover of the investigated groups (workers and patients suffering from vibration disease) in industrial branches with exposure to vibrations. Using statistical and mathematical methods of dispersion, correlation, factor and discriminant analysis, we detected interrelations between the investigated non-specific and specific indices of vibration exposure on the one hand, and possibilities for the development and the prognostication of cardiovascular, osteo-arthritic and other diseases and pathologic states, non-specific for vibration exposure, on the other hand.

Acid-Base Equilibrium↗
PubMed1992

Vibrations--discriminant models and possibilities for prognosticating specific and non-specific effects on the organism.

The present study involved 290 workers from branches of industry in which they were exposed to intense vibration and 102 patients suffering from disease due to vibration. Some specific (physiological) indices for exposure to vibration, such as the sensation of vibration, cold provocation test, Doppler-ultrasound, etc., and some non-specific (biochemical) indices, such as blood lipids, electrolytes and trace elements were studied. A discriminant analysis was made and 17 discriminant models (including different numbers of physiological and biochemical indices, age, and length of service) were elaborated. These models were used to predict the presence or absence of concomitant diseases, such as hypertension, coronary heart disease and arthritic lesions in persons exposed to vibrations; the stage of the vibration disease; the occurrence of exposure to vibration or of vibration disease. It was shown that physiological (specific) and biochemical (non-specific) indices affected by the exposure to vibration were interrelated, and that their estimation by means of the discriminant analysis revealed the distinction between the states mentioned above.

Adult↗
PubMed1991

Effect of orchiopexy on human testicular ultrastructure.

The effect of orchiopexy performed before puberty on the testicular ultrastructure in sexually mature infertile men have been levels, as well as an analysis of spermogram and karyotype was carried out. It was found an elevation of FSH and LH, while T levels were decreased. Disturbances in the ultrastructure of all testicular cell types-germ, Sertoli and Leydig cells are related with the smooth and rough endoplasmic reticulum and mitochondria as well. It is concluded that the application of orchiopexy in 8-10 years old cryptorchid boys have no curative effect on the descended testes.

Adult↗
PubMed1991

Electrolytic exchange in organism under the conditions of vibration. Experimental studies.

The study deals with a wide spectrum of indices of the electrolytic metabolism--sodium, potassium, calcium, chlorides, magnesium, iron, copper, zinc, cobalt and manganese--in blood, organs and tissues under the conditions of experimental chronic exposure of whole-body vibration frequency of 50 and 150 Hz and velocity of 85 mm.s-1 during a three months experiment (3 h daily) Reference methods were used for the determination of the indices--atom absorption spectrophotometry (variants with flame and without flame), coulometric chlorine titrator, flame photometry, etc. The indices were examined three times (1, 2 and 3rd months). Statistic analysis of the data showed significant changes in the number and the values of the indices and their character (increase or decrease) in comparison with the control values. The indices modifications occur early (at the end of the first month) and they proceed till the end of the experiment (till the end of the 3rd month) during the exposure to both frequencies, but are strongly expressed in the case of high frequency vibrations. The disorders in electrolytic metabolism established in the experiment testify that people exposed to vibrations are likely to suffer analogical changes and develop other pathologies--diseases of cardiovascular system, of blood and haematopoietic organs, etc. as well as an increase of specific disorders in connection with vibration exposure.

Animals↗
PubMed1989

Testicular ultrastructure in infertile men.

The review shows typical ultrastructural alterations of germ, Sertoli, and Leydig cells in infertile men. Regardless of the cause of infertility, the disruption of the spermatogenic process usually occurs in the pachytene stage of meiotic prophase and in the stages of early spermatid maturation. The disturbances affect the cytoplasm more than the nucleus, and the synaptonemal complexes have shown significant stability even in the severely injured testes. An acrosome formation is found to be open to injury in more advanced germ cells during spermatid maturation. The manner of reaction of the Sertoli cells under different pathological conditions depends on the presence and degree of maturation of the neighboring germ cells. The appearance of immature Sertoli cells is accompanied by the loss of germ cells more advanced in their differentiation. In most pathologically altered testes, mature Sertoli cells reveal a universal manner of reaction of cell organelles. Leydig cell ultrastructure fluctuates considerably, and the alterations predominantly affect the sites of steroid synthesis, in spite of disease specificity. It becomes clear that a complex estimation of a real testicular state requires the application of new techniques as well as recognition of local control mechanisms. This will provide evidence toward elucidation of male infertility.

Humans↗
PubMed1987

Cytogenetic analysis of men with cryptorchidism and reduced fertility.

A cytogenetic chromosomal analysis was performed in 140 infertile men with cryptorchidism--85 with unilateral and 55 with bilateral. The most frequent anomaly was sex chromosomal aneuploidy found in 7.1% of patients. This is significantly higher compared to a group of infertile men with normal descended testes. Other chromosomal anomalies were not more frequent than in infertile men without cryptorchidism.

Bulgaria↗
PubMed1986

Electron microscopic and enzyme investigations of the testicular tissue in infertile males.

The ultrastructural characteristics of the testicular tissue in male infertility and the isoenzyme spectrum of some enzymes in sperm cells have been studied. The testicular material was taken by Vilar's method from three healthy males with normospermia and eleven males with hypogonadism, azoospermia and infertility. The material was treated by the routine methods for electron investigation and the observations were done with an electron microscope Opton EM 109. Horizontal electrophoresis of the testicular homogenate was done according to Nance. Malate dehydrogenetic activity (MDX) was rendered according to the method of Shaw and Prasad, and diaphoresis (DP) was carried out according to Brewer. It was found that spermatogenesis was interrupted at the pachytene stage at an ultrastructural level. Biochemical investigations showed that in the infertile testis two other atypical fractions appeared on diaphoresis, while at the malate dehydrogenase, a second fraction had considerably lower intensity as compared to the controls. It is pointed out that some profound disorders developing in the infertile testis affect mainly the germinal cells, which was proved at the ultrastructural level and also by the analysis of the isoenzymes MDH and DF key enzymes of carbohydrate metabolism.

Humans↗