Showing papers by "Charles University in Prague published in 1989"

Castrated men exhibit bone loss: effect of calcitonin treatment on biochemical indices of bone remodeling.

Abstract: To test the hypothesis that the reduction in gonadal function can lead to bone mass loss, a group of 12 men who had undergone bilateral orchidectomy at the age of 282+−68 yr was evaluated A progressive loss of the lumbar bone density was observed as a function of time after orchidectomy Both the biochemical indices of bone resorption (urinary hydroxyproline/creatinine ratio and plasma tartrate-resistant acid phosphatase) and bone formation (serum osteocalcin and bone isoenzyme of alkaline phosphatase) were significantly increased in the patients compared with healthy controls A positive correlation was found between urinary hydroxyproline excretion and percent change in spinal bone mineral density per yr Because of this increase in the biochemically indicated bone resorption, nine of the patients were studied again after 1-3 yr and were thereafter treated with intranasal calcitonin Urinary hydroxyproline excretion normalized after 3 months of treatment, and a significant decrease, but not to normal

A general mountain pass principle for locating and classifying critical points

Abstract: A general “Mountain Pass” principle that extends the theorem of Ambrosetti-Rabinowitz and which gives more information about the location of critical points, is established. This theorem also covers the problem of the “limiting case”, i.e. when “the separating mountain range has zero altitude”. It is also shown how this principle yields localized versions of recent results of Hofer and Pucci-Serrin concerning the structure of the critical set.

Enhanced sensitivity to conformation in various proteins. Vibrational circular dichroism results.

Abstract: Vibrational circular dichroism (VCD) spectra of several globular proteins dissolved in D2O are presented and compared to conventional UV-CD results. It can be seen that, for the alpha, beta, and alpha + beta categories of Levitt and Chothia, VCD evidences much larger band shape variations, including sign alteration, than does UV-CD. A direct parallel is seen between the VCD of the alpha-helix found in model polypeptides and the amide I' VCD of myoglobin. Since all structural aspects of the protein contribute to the VCD on a roughly equal footing, a similar correlation of the chymotrypsin amide I' VCD with that of beta-sheet models is not as clear. In addition, the VCD of random-coil-type proteins is found to be clearly related to VCD results from random-coil polypeptides. Finally, simulations are presented to postulate the expected VCD for protein structures having conformations that lie between the limiting cases discussed here.

Non-negative autoregressive processes

Abstract: . Consider a stationary autoregressive process given by Xt=b1Xt-1+…+bpXt-p+Yt, where the Yt are independent identically distributed positive variables and b1,…,bp are non-negative parameters. Let the variables X1,…,Xn be given. If p= 1 then it is known that b1*= min(Xt/Xt-1) is a strongly consistent estimator for b1 under very general conditions. In this paper the case p= 2 is analysed in detail. It is proved that min(Xt/Xt-1)b1 almost surely (a.s.) and min(Xt/Xt-2)b2+b12 a.s. as n 8. The convergence is very slow. Denote by b1* and b2* values of b1 and b2 respectively which maximize b2+b2 under the conditions Xt-b1Xt-1-b2Xt-2≥ 0 for t= 3,…, n. We prove that b1*b1 and b2*b2 a.s. Simulations show that b1* and b2* are better than the least-squares estimators of the autoregressive coefficients when the distribution of Yt is exponential.

Ray tracing in factorized anisotropic inhomogeneous media

Abstract: SUMMARY A concept of a factorized anisotropic inhomogeneous (FAI) medium is introduced. In the FAI medium, the position dependent density normalized elastic parameters aijkl(Xi) can be factorized in the following sense: aijkl(Xi) =f2(xi)Aijkl, where Aijkl are constants, independent of Cartesian coordinates xi, and f(xi) is an arbitrary continuous function of xi. Thus, all the density normalized elastic parameters aijkl(xi) in the FAI medium depend on the coordinates xi in the same way, but the generality of anisotropy and of inhomogeneity is not restricted. The factorization of aijkl(xi) leads to a factorization of certain important ray theory expressions and equations (eikonal equation, etc.), and to particularly simple ray tracing and dynamic ray tracing. For certain types of FAI media, these equations may even be solved analytically or semianalytically.

Motor and electrocorticographic epileptic activity induced by bicuculline in developing rats.

Abstract: Summary: Motor seizures were induced by intraperito-neally (i.p.) injected bicuculline in 270 rats aged 7,12,18, 25, or 90 days. Bicuculline was able to elicit both minimal (clonic) and major (tonic-clonic) seizures in all age groups, but in 7-day-old rats minimal seizures were only noted exceptionally. CD50s (for major seizures) ranged from 2.48 to 2.85 mg/kg in the three younger groups and increased to 7mg/kg in 25- and 90-day-old rats. An intravenous (i.v.) administration of bicuculline in 67 rats, 18 and 25 days old, caused identical CD50s in these groups, indicating that the difference that occurs with an i.p. administration is due to pharmacokinetic reasons. Electrocorticographic (ECoG) studies in acute experiments as well as in young rats with implanted electrodes demonstrated general principles of the development of EEG: an increase in frequency of individual elements, in generalization of the epileptic activity, in synchronization of activity among various cortical regions, and in the correlation between ECoG and motor phenomena. An exception occurred as an age-related phenomenon: rhythmic activity of the spike-and-wave type. This activity appeared in 18-day-old and older rats and was invariably accompanied by “freezing” of the animals. RESUME Des crises motrices ont ete induites par injection intraperitoneale de Bicuculline chez 270 rats âges de 7,12, 18,25, ou 90 jours. La Bicuculline a provoque des crises mineures (cloniques) et majeures (tonico-cloniques) dans tous les groupes âges, mais chez les ratons de 7 jours, les crises mineures n'ont ete vues qu'exceptionnellement. Les CD 50 (pour les crises majeures) variaient de 2.48 a 2.85 mg/kg dans les 3 groupes âges inferieurs et augmentaient a 7 mg/kg chex les rats âges de 25 et 90 jours. administration intravetneuse de Bicuculline effectuee chez 67 rats âges de 18 et 25 jours a mis en evidence des CD 50 identiques dans ces groupes, ce qui montre que la difference trouvee avec administration intraperitoneale n'est due qu'a des raisons pharmacocinetiques. Les etudes electrocortico-graphiques effectuees en aigu chez les jeune rats porteurs e-lectrodes implantees ont mis en evidence des principes generaux du developpement de EEG: augmentation de frequence des grapho-elements individuels, generalisation de activiteepileptique, synchronisation de activite entre diverses regions corticales, et correlation entre electrocorticogramme et les phenomenes moteurs. Une exception etait representee par un phenomene lie a âge: activite rythmique de type Pointe-Onde. Cette activite est apparue chez les rats âges de 18 jours ou plus, elle etait constamment accompagnee une immobilisation de animal. RESUMEN Mediante la inyeccion intraperitoneal de bicuculina se han inducido ataques motores en 270 ratas de 7,12,18,25, o 90 dias de edad. La bicuculina produjo ataques minimos (clonicos) y ma-yores (clonico-tonicos) en todos los grupos de edades pero, en las ratas de 7 dias, los ataques minimos se observaron excepcionalmente. El CD s (para ataques mayores) oscilo entre 2.48 y 2.85 mg/kg en los ties grupos de animates mas jovenes y aumento hasta, aproximadamente, 7 mg/kg en las ratas de 25 y 90 dias de edad. La administracion intravenosa de bicuculina en 67 ratas (de 18 y 25 dias de edad) demostro identicos CD s en estos grupos de animales, lo que indica que la diferencia encontrada tras la inyeccion intraperitoneal es debida a razones farmacocineticas. Los estudios electrocorticograficos practicados en experimentos agudos con electrodos implantados demostraron los principios generates del desarrollo del EEG: un incremento de la frecuencia de los grafo-elementos individuates, de la generalization de la actividad epileptica, de la sincronizacion de la actividad entre diversas regiones corticales y de la correlacion entre el ECoG y los fenomenos motores. Aparecio una excepcion consistente en actividad ritmica (fenomeno ligado a la edad) del tipo de los complejos punta-onda lenta. ZUSAMMENFASSUNG Bei 270 Ratten im Alter von 7,12,18,25, and 90 Tagen wurden motorische Anfalle durch intraperitoneale Gabe von Bicuculin ausgelost. Durch Bicuculin konnten sowohl kleine (klonische) als auch grose (tonisch-klonische) Anfalle in alien Altersgruppen ausgelost werden; allerdings boten die 7 Tage alten Raten nur ausnahmsweise mimimale kleine Anfalle. Die CD 50 (fur grose Anfalle) lag bei den 3 jungen Gruppen bei 2.48-2.85 mg/kg und stieg auf 7 mg/kg bei 25–90 Tage alten Tieren an. Die IV-Gabe von Bicuculin bei 67 Ratten im Alter von 18 und 25 Tagen, ergab iden-tische CD 50 in dieser Gruppe. Die encephalographischen Studien im akuten Experiment Oder bei Tieren mit implantierten Elektroden zeigten die allgemeinen Prinzipien der EEG-Entwicklung: eine Zunahme der Frequenz der individuellen Graphoelemente, der Gerneralisierung epileptischer Aktivitat, der Synchronisierung von Aktivitat der verschiedenen Kortexregionen und der Korrelation zwischen ECoG und motorischen Phanomen. Eine Ausnahme bildete eine altersgebundene rhythmische Aktivitat vom spike-wave Typ. Diese Aktivitat erschien ab 18. Tag und war unverandert von “Frieren” der Tiere begleitet.

Energy cost of running in similarly trained men and women.

Abstract: The energy demand of running on a treadmill was studied in different groups of trained athletes of both sexes. We have not found any significant differences in the net energy cost (C) during running (expressed in J·kg−1·m−1) between similarly trained groups of men and women. For men and women respectively in adult middle distance runnersC=3.57±0.15 and 3.65±0.20, in adult long-distance runnersC=3.63±0.18 and 3.70±0.21, in adult canoeistsC=3.82±0.34 and 3.80±0.24, in young middle-distance runnersC=3.84±0.18 and 3.78±0.26 and in young long-distance runnersC=3.85±0.12 and 3.80±0.24. This similarity may be explained by the similar training states of both sexes, resulting from the intense training which did not differ in its relative intensity and frequency between the groups of men and women. A negative relationship was found between the energy cost of running and maximal oxygen uptake\((\dot V_{O_{2max} } )\) expressed relative to body weight (for menr=−0.471,p<0.001; for womenr=−0.589,p<0.001). In contrast, no significant relationship was found in either sex between the energy cost of running and\(\dot V_{O_{2max} } \). We conclude therefore that differences in sports performance between similarly trained men and women are related to differences in\(\dot V_{O_{2max} } \cdot kg^{ - 1} \). The evaluation ofC as an additional characteristic during laboratory tests may help us to ascertain, along with other parameters, not only the effectiveness of the training procedure, but also to evaluate the technique performed.

Xenogeneic pericardium as a dural substitute in reconstruction of suboccipital dura mater in children.

Abstract: ✓ A 5-year experience with the glutaraldehyde-stabilized freeze-dried radiation-sterilized calf pericardium used as a dural substitute is reported. The structure of pericardium xenograft is compared with other collagenous materials used for duraplasty (allogeneic fascia lata and dura mater) by light and electron microscopy. The special neurosurgical techniques involved in using pericardium xenografts in the reconstruction of suboccipital dura mater in children are presented in detail.

Internal anatomy of Hypochthonius rufulus (acari: Oribatida)

Abstract: The internal anatomy of juveniles and adults of Hypochthonius rufulus selected as a model species representing the lower Oribatida was investigated histologically and compared with the published characteristics of higher oribatid internal anatomy. In this species, the cuticle is weak and flexible, consisting of epicuticle and endocuticle on the body, but including an exocuticle between the epicuticle and endocuticle of the legs. Walls of the mesenteron in the digestive tract are of uniform thickness and structure without any regional thickening, and there are no proventricular glands. The hindgut is apparently divided into five parts: colon 1 and 2, rectum 1 and 2, and anal atrium; food bolus exhibits a multilamellar structure in this section. The glandular system is less diversified than in some other oribatids. Tracheae are apparently lacking. Females possess only two relatively large eggs, filling one-half of opistosoma, and they lack ovipositors. Eggs are present in females during the whole year. Gonad buds appear first in the protonymph stage. Only one male was found among 146 adults studied. No male external organ (aedeagus or penis) is present.

The application of plasma tartrate-resistant acid phosphatase to assess changes in bone resorption in response to artificial menopause and its treatment with estrogen or norethisterone

Abstract: Plasma tartrate-resistant acid phosphatase (TR ACP), urinary hydroxyproline excretion (UH), serum osteocalcin, and bone alkaline phosphatase isoenzyme were determined in a prospective study in 31 women who had undergone bilateral ovariectomy (OOX). Nine patients were followed up for 1 year without treatment and for the following 3 years when on mestranol (M) substitution. On the basis of UH, 22 patients were identified as having increased bone resorption (BR) within 3 months of OOX. Subsequently, 11 patients were treated with transdermal estradiol (E2) and 11 patients with norethisterone (norethindrone, NE). In untreated patients, the biochemical indices of BR peaked 3–6 months following OOX and biochemical indices of bone formation (BF) continued to increase from 3 until 12 months. The substitution with both E2 or M resulted in normalization in serum and urinary calcium, serum phosphate, renal threshold phosphate concentration (TmPO 4/GRF), and biochemical indices of BR within 4 months of treatment. Biochemical indices of BF normalized within 6 months of treatment. In the M-treated group, these effects continued for 3 years of the follow-up. The hormonal substitution had a protective effect on cortical and lumbar spine bone mass. A significant decrease, but not to normal values, in biochemical indices of BR and a persistent elevation in indices of BF were found in NE-treated patients. Unlike E2, NE does not depress osteoblastic function. There is strong evidence supporting the utility of measurements of TR ACP in plasma in examination of women who had ovariectomies and in assessment of the efficacy of treatment.

Dynamics of the Golgi method: a time-lapse study of the early stages of impregnation in single sections.

Abstract: This paper describes the early stages of impregnation by the Golgi method. Sections of aldehyde-fixed and potassium dichromate-treated cerebral cortex were mounted on glass slides and cover slipped. The dichromate solution was replaced by silver nitrate solution and events in the section were followed and recorded by time lapse microphotography and video recording until stopped by replacement of silver nitrate solution by glycerol. The sections were subsequently prepared for electron microscopy (EM) study. In sections about 2×2 mm and 100 μm thick a fine, dark granular precipitate formed at the edges within the first minutes of exposure to silver nitrate and a wave of brownish colouration spread to a depth of about 0.3 mm. After approximately 7 min, shrub-like focal precipitates (nucleation centres) appeared in the sections. From these nucleation centres (but also from the section edges) thread-like ‘outgrowths’, usually identified as dendrites, spread into somata. Sometimes impregnation began within the soma and spread into dendrites. The rate of impregnation (i.e., of silver chromate deposition within dendrites) was typically 1–7 μm mins-1, faster in the earlier stages (up to 3 μm ss-1) and very slow after 30 min, by which time many neurons were more or less fully impregnated. The dimensions of the section, the width of an agar frame around the sections, and the frequency with which the silver nitrate in the sections was replenished all affected the extent and time course of the impregnation. By EM the earliest intracellular deposits consisted of tubulolamellar formations which did not cross plasma or endocellular membrane boundaries and which contained irregularly shaped and scattered granules, initially about 10 nm in diameter. The latter progressively enlarged and coalesced as the tubulolamellar formations extended, eventually to fill the cross-sectional area of neuronal processes and cell bodies. These observations shed light on why so few neurons become impregnated with the Golgi method. Impregnation occurred only in those cells a part of which was within a nucleation centre.

New condition numbers for matrices and linear systems

Abstract: New condition numbers for matrices and linear systems are proposed, based on the dependence of the relative errors in the result upon the relative errors of the data.

On the use of Diagonally Nonrecursive Functions

Abstract: Publisher Summary This chapter describes the functions that diagonalize all partial recursive functions possess important properties and the study of these functions gives a new view on some results in recursion theory as well as new methods to prove them. The chapter explains a function f , which is called a “diagonally nonrecursive function” (a DNR function) and the function g is called a fixed-point free function (an FPF function). A degree containing an FPF function is called an “FPF degree.” DNR functions differ from FPF functions, FPF degrees coincide with degrees of DNR functions. It is more convenient to work with the class of DNR functions instead of the class of FPF functions. A degree containing a 0-1 valued DNR function is called a “PA degree.” The chapter reviews some known facts about FPF degrees and PA degrees. From a global point of view, the class of FPF degrees has (Lebesgue) measure 1, while the class of PA degrees has measure 0.

Physiological Considerations in Training Young Athletes

Abstract: Healthy children evidence smaller values of cardiorespiratory function than adults, but these are in proportion to the smaller body size. At birth, the distribution of muscle fibres and the activity of enzymes in muscle are different from in adults, but these differences disappear at about age 6. On the other hand, muscle fibre thickness increases from birth to about 18 years of age and this is concurrent with increases in muscular strength. The increase in maximal oxygen consumption (VO2max) that accompanies growth and maturation in the human has been attributed in the main to appreciating muscle mass. During exercise, heart rate and cardiac output increase in the child as in the adult, but the heart rate in the child is greater and the stroke volume smaller. Furthermore, the arteriovenous difference in oxygen is greater in the exercising child than in the adult. Children also evidence a diminished blood pressure response to exercise. It seems that control of ventilation at exercise is the same in children as in adults, but exercise ventilation has been reported to be less efficient in the child. The young are less capable of regulating core temperature at exercise than adults and are more readily dehydrated. Very limited data suggest that muscle energy substrate storage and utilisation in children are such that they are less capable of anaerobic metabolism than adults. Generally, children respond to aerobic training as do adults, but such training in the first decade of life has been reported to have negligible effects. Blood lipid levels in children seem to be favourably influenced by persistent endurance activity. Ventilatory efficiency of children at exercise is augmented by aerobic training. Maximal values of ventilation and breathing frequency are increased in children and youth by endurance training. Conflicting data exist regarding the influence of training upon the child's vital capacity. Pulmonary diffusion capacity in well trained children has been seen to be greater than in untrained youngsters and many workers have reported increased VO2max as an outcome of endurance training. Limited data indicate that the nature of training may alter muscle fibre distribution in youthful athletes, and that muscle fibre hypertrophy can be induced in the young by means of strength and power training.(ABSTRACT TRUNCATED AT 400 WORDS)

Nonlinear nonnegative AR(1) processes

Abstract: Let {et} be a nonnegative strict white noise and Xtan independent nonnegative random variable. For t ≧ 2 define where g is a nonnegative function and b ≧ 0. Then is an estimator for b . Under some general conditions, which do not include stationarity, it is proved that is strongly consistent.