Biomedical subjects

V Belkin

Publications and source records attributed to V Belkin.

8 recordsLinked to original sources

PubMed2001

Occurrence and distribution of atrial natriuretic peptide-containing cells in the left ventricle of hypertensive rats. Effect of antihypertensive treatment.

In the ventricles of adult mammalian hearts, production of atrial natriuretic peptide (ANP) is negligible, restricted to the impulse-conducting cells, the papillary muscles, and a minority of subendocardial myocytes. ANP expression is reinduced in the ventricles of pressure-overloaded and failing hearts and is frequently used as a marker for myocyte hypertrophy. Using an immunohistochemical approach, we have characterized the size distribution of ANP-containing myocytes in the left ventricle of the spontaneously hypertensive rat (SHR) before and after chronic antihypertensive therapy and compared the results to age-matched normotensive Wistar rats (WR). Our findings show that in SHR the frequency of cells presenting ANP granularity is positively correlated with myocyte size (r=0.746, P<0.02). The highest proportion of ANP-positive myocytes (55-57%) was measured among cells of diameters 30-34 microm. In any corresponding cell size, the proportion of ANP-presenting myocytes was five- to tenfold higher in SHR than in the normotensive WR. We studied the effects of the antihypertensive drugs captopril, hydralazine, and nifedipine and found that, regardless of their effect on blood pressure or hypertrophy, all three eliminated ANP immunoproducts from the majority of the left ventricular myocytes and reduced the level of ANP mRNA, captopril being the most effective. The positive correlation between myocyte size and ANP expression was not maintained in the hearts of drug-treated SHR. Myocytes on the border of fibrotic areas or in regions of ANP presentation within the normal heart resisted the suppressive effect of the antihypertensive therapy, indicating that blood pressure or hypertrophy are not the sole correlates for ANP expression.

Animals↗

PubMed2001

The effect of season, occupation and repeated winterings on anthropologic and physiological characteristics in Russian antarctic staff.

UNLABELLED: Thirty anthropometric and ten physiological parameters were examined over a 10-month-period in 1985-86, in 66 male polar explorers, aged 25-61 years, at an Antarctic station (Mirny observatory). For 30 of these persons this was their first wintering in Antarctic while the remaining 36 had wintered there at least once before. The mentioned measurements were taken on 3 different occasions in April, September and January corresponding in the Antarctic to the beginning of the polar night and interim season period and the beginning of the polar day. Subjects of the investigation belonged to 3 occupational groups: administrative personnel, scientific staff, and manual laborers. Extended statistical analysis of the data was carried out in an attempt to distinguish the dynamics of the studied parameters in relation to the season of wintering (Climate), the number of previous winterings (Frequency), the type of occupation (Work), and their interactions. Multifactorial statistical analyses were also performed, so as to adjust for age of subjects, which is a requisite for evaluating the factor of repeating winterings, obviously age-related. Changes in a number of characteristics were clearly recognized as connected with the factor of repeating winterings, to wit: 1) Anthropometric parameters such as or subcutaneous fat and relative muscle mass; 2) Parameters pertaining to speed of neuromuscular response such as wrist muscle effort, or time of simple motor response; and 3) Physiological parameters encompassing vascular--blood pressure and respiratory--spirometric measurements. CONCLUSION: Our findings suggest that frequency of repeated winterings is not a leading factor influencing physical status of examinees. Occupational status of examinees alone or in interaction with repeated winterings and seasonal climatic factors have more prominent impact on the well-being of polar explorers.

Acclimatization↗

PubMed1999

Anthropometric characteristics of men in Antarctica.

Thirty anthropometric and ten physiological parameters were evaluated over a 10-month period during 1985-86 in 66 polar explorers at an Antarctic station (Mirny observatory), all of them males aged 25-61 years. The evaluations were made in the months of April, September and January, which corresponded to the following Antarctic seasons: the beginning of the polar night, an intermediate period, and the beginning of the polar day; the necessary measurements were performed on subjects belonging to three occupational groups, namely: administrative, scientific, and manual workers. Significant changes in the pattern of skinfold thickness were observed using ANOVA with repeated measurements during the winter period (p < 0.05). Despite the fact that body weight and BMI of subjects remained unchanged, the mean sum of skinfold thickness and subcutaneous fat mass increased over the studied period at the expense of muscle mass. In participants engaged in high levels of outdoor physical activity (e.g. construction workers, drivers, technicians), an increase in fat mass, significant fall in muscle mass on wrist dynamometry, and protracted time of the simple motor response time was documented. Systolic blood pressure showed a downward trend during the winter in the group of manual workers, while significant rises in the diastolic pressure (p < 0.05) were found in the group of scientists at the end of the polar night. The present findings may be interpreted as evidence for destabilization in the studied individuals, and for an adaptation response to the Antarctic environment, which results in apparent increase in body fat and decrease in muscle mass.

Adaptation, Physiological↗

PubMed1998

Aging bone score and climatic factors.

Hand radiograms for osseographic assessment of bone aging status were taken from more than 7,500 individuals residing in 31 different localities and belonging to 20 ethnic groups. Multiple regression analysis was used to evaluate possible associations between bone aging parameters and several climatic factors, to wit: hours of daylight in January and July, average monthly humidity and partial vapor pressure in January and July, and one climatic index pertaining to comfort conditions in life, namely, the Bioclimatic Index of Severity of Climatic Regime. Multiple regression analysis clearly pointed to significant correlations between climatic characteristics and indices defining the relative rate of bone aging in humans; it also evinced an independent contribution of July's humidity and January's mean temperature to earliest age at which first signs of bone aging can be found. In sum, there are grounds for concluding that temperature and humidity are key factors in triggering initial bone changes in individuals within the human populations prone to environmental effects. The combination of humidity and temperature with other factors which reflect the sharpness of the interseasonal differences in climatic conditions predispose the populations to early onset of bone changes.

Adolescent↗

PubMed1998

Microcirculatory bed of the human trigeminal nerve.

BACKGROUND: The structure and topography of the microcirculatory bed of the human trigeminal nerve are described. Details of microvascular morphology in the epi-, peri-, and endoneurium in different parts of the nerve are emphasized. METHODS: The vascular bed of the trigeminal nerve was studied following injecting an aqueous solution of black ink and differentiating between microcirculatory components using silver nitrate impregnation. Morphometric parameters were statistically analyzed. RESULTS: Features of vascular organization that control blood flow are found within the pia mater of the trigeminal nerve root coverings, capsule and stroma of the trigeminal ganglion, and the epineurium and external layer of perineurium of extracranial branches. The precapillary arterioles, capillaries, postcapillary venules, and venules are situated in the internal layers of the perineurium. However, while the endoneurium contains only capillaries, the epineurium and external layers of the perineurium contain blood vessels whose features reflect a capability of adapting to a vascular change (transepineural arterioles, arteriolovenular anastomoses, and precapillary sphincters). The inner perineurium layer contains only precapillary sphincters. CONCLUSIONS: Results show that the make-up and topography of the microcirculatory bed throughout the trigeminal nerve are determined by features of the connective tissue components. Arteriolovenular anastomoses facilitate blood redistribution within the superficial layers of the trigeminal nerve, while precapillary sphincters and transepineural arterioles provide optimal regulation of blood flow in deeper layers of the nerve trunk.

Adolescent↗

PubMed1995

Metabolic adaptations for desert survival in the Bedouin goat.

Energy conservation is a key adaptation for desert survival in the Bedouin goat. When food is scarce, metabolism is reduced and body weight can be maintained indefinitely on less than one-half of normal intake. We hypothesized that metabolism would be turned down during both rest and exercise, but it was not. It was low when animals rested and returned to normal during exercise. We expected catecholamines and thyroid hormones would modulate metabolism, but they did not. The reduction in metabolism preceded any change in thyroid hormone concentrations, and infusions of epinephrine did not restore reduced metabolism to normal levels. Finally, we expected the gut would be the major organ system involved in the metabolic reduction because less food is eaten, processed, and absorbed. Contrary to our expectations, we found that muscle is the primary organ system responsible for the reduction. It appears that the adaptations of the Bedouin goat for surviving on limited food supplies involve different organ systems and different modulators to reduce metabolism from those known for other mammals.

Adaptation, Physiological↗

PubMed1994

Enhancement of angiogenesis in regenerating gastrocnemius muscle of the toad (Bufo viridis) by low-energy laser irradiation.

The effect of low-energy laser (He-Ne) irradiation on the process of neoformation of blood capillaries during regeneration in the toad (Bufo viridis) gastrocnemius muscle was studied using histomorphometric methods. The injured zones of the experimental toads were subjected to four direct He-Ne laser irradiations (632.8 nm wavelength; 6.0 mW for 2.3 min) every alternate day, commencing on the second day after injury. Muscles that were injured as above and subjected to red light irradiation served as control. The volume density (cm3/cm3) of the capillaries in the injured zone at 9 days after injury was significantly (P < 0.01) higher (0.09 +/- 0.006) than in the control muscles (0.048 +/- 0.007). At 14 days after injury, the volume density in the injured zone of the control muscles further increased, while the value in the laser-irradiated muscles remained unchanged. The surface density (m2/cm3) of the capillaries in the injured zone was 2.3-fold higher in the laser-irradiated muscles than in the control muscles at 9 days after injury. The surface density further increased in the control muscles between 9 and 14 days after injury, while in the laser-irradiated muscles there was a decrease in this value during the above period. The surface-to-volume ratios of the capillaries in the injured zone of control and laser-irradiated muscles indicate a straighter, rather than a convoluted appearance between 9 and 14 days after injury. It is concluded that He-Ne laser irradiation during skeletal muscle regeneration in the toad markedly promotes the process of neoformation of blood vessels in the injured zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Bone ageing: genetics versus environment.

Bone ageing results from a complex interaction between genetic and environmental factors (such as diet, climate and physical exercise) throughout human life. According to current literature, the most popular measures of bone ageing are osseometric measurements (OSM), bone mineral density (BMD) and osseographic scores (OSS), based on descriptive criteria of bone age. Plain roentgenography allows simultaneous assessment of all three measures. Ethnic differences with regard to these bone ageing characteristics have prompted us to study to the process anew, with the aim of elucidation the nature of the genetic and environmental components involved, and the possible interaction(s) between them. Despite abundant data on ethnic differences regarding these measures, modern knowledge on the genetics of these processes has derived primarily from the family studies of BMD, which pointed to strong involvement of the familial factors on bone mass. Segregation analysis performed by us in two ethnically different samples of pedigrees revealed a significant effect of the putative major gene on BMD of both compact and cancellous bone. The major finding of our bivariate segregation analysis was that it lead to the acceptance of the hypothesis predicating a single major locus with pleiotropy to both cancellous and compact BMD, but clearly rejecting the polygenic hypotheses. Our study of cortical index (CI) provided evidence that a single potential major gene controls not only the baseline trait level, but also the age at onset of the involutive bone changes, and the rate of the CI change with age. When we examined the environmental vs genetic influences on OSS variation in 32 human populations, we found very little environmental effect on the rate of bone change (r2 = 0.107), but a substantial effect on this rate of the genetic differences between populations (r = 0.480). Clarification of the genetic basis of bone ageing could have wide-ranging applications in the prevention and treatment of bone degenerative diseases such as osteoporosis and osteoarthritis, before irreversible damage takes place. There is thus a need to target the genetic analysis of BMD and the biochemical regulating factors of bone turnover through the use of molecular genetic techniques.

Aging↗