The circahoral rhythm of the functional activity of rat adrenocorticocytes]

Functional manifestations of biological ultradian rhythms in the adrenal cortex were first confirmed on the cytologic level. The cycle of the ultradian rhythm in the cells of the adrenal cortex fascicular zone consisted was determined to involve three phases: accumulation of lipids, delipoidization, and the rest period. A definite volume of cells and their nuclei, certain nuclear-cytoplasmic relations, the number of liposomes and mitochondria on the square unit are characteristic of each phase. The activity of cells is especially high during the second phase which is characterized by the increase in nuclear sizes and nuclear-cytoplasmatic relations, by the decrease in cell volume and in the number of liposomes in their cytoplasm; this is indicative of the rised synthesis and secretion of hormones. It is underlined that the cell volume increases when liposomes are accumulated in the cytoplasm to decrease upon their disappearance.     

Osmoregulatory reactions of frog erythrocytes under conditions of activation and blockade of Ca2+-channels

The kinetics of cell osmoregulatory reactions under conditions of activation and blockade of Ca2+-channels was studied on a model of frog polyfunctional nuclear erythrocyte. Both activation and blockade of Ca2+-channels has been established to promote swelling of nuclei and an increase of the nuclear-cytoplasmic ratios under conditions of hypotonic exposure. The osmoregulatory cell reactions after activation of Ca2+-channels are expressed as a decrease of the cell volume. The blockator of Ca2+-channels verapamil produces an alternated increase and decrease of the erythrocyte volume with time intervals of 30 and 60 s. The clearly expressed functional activity of the nuclear membrane in response to the hypotonic action under conditions of activation and blockade of Ca2+-channels indicates participation of Ca2+ ions in mechanisms of the nuclear-cytoplasmic transfer.     

Topography and parameters of the intertrabecular spaces of the heart ventricles in man and laboratory animals

The heart of the man, dog, cat and rabbit have been investigated using biometry and corrosive methods. In the horizontal sections the volume of the intertrabecular spaces (IS) of the ventricles has been estimated and the "coefficient of the myocardial sponginess" has been calculated as the ratio of the cavities volume to the myocardial volume. In the corrosive casts of the ventricular cavities the deviation angles of the IS casts from the axial line along the afferent and deferent tracts have been measured. Differences in manifestation of the IS in the hearts of the mammals studied have been revealed. The IS are best pronounced in the human heart, less in the dog heart and still less in the cat and rabbit hearts. For all the hearts studied predominance of the volume of the IS in the right ventricle is specific. The deviation angle of the IS casts from the axial line along the afferent tract increases from the cardiac basis towards its apex, while the deviation angle of the IS along the deferent tract decreases from the apex towards the basis. The functional predisposition of the IS is supposed to consist in providing systolic reserves of the cardiac ventricular cavities. The results of the mathematical analysis of the changes in the cast deviation angles of the IS along the afferent and deferent tracts demonstrate their role in twisting and acceleration of the blood stream in the systolic phase and slowing down of the blood stream in the diastolic phase.     

Role of interprotein interactions in the regulation of the sarcoplasmic reticulum Ca-pump

The data on the structural state of sarcoplasmic reticulum membranes in skeletal muscles of rabbit were obtained by EPR-spectroscopy, fluorescent analysis and flash-photolysis and discussed in the paper. Comparison of the functional state of Ca-pump and variations in hydrophobic volume and membrane microviscosity permits concluding that thermoinduced anomalies of the enzymic activity are due to changes in the phase state of lipids. It is shown that changes in the physiochemical state of lipids affect the interprotein interactions in the oligomeric Ca-pump structure. In this case ATP weakens the interaction between Ca-pump globules, while a decrease in the hydrophobic membrane volume intensifies it. An assumption is advanced that the modifying ATP effect on Ca-pump is based on an increase in the functional independence of Ca2+-ATPase monomers, and therefore it is under the control of the membrane lipid phase.     

Training-overtraining: influence of a defined increase in training volume vs training intensity on performance, catecholamines and some metabolic parameters in experienced middle- and long-distance runners.

The influence of an increase in training volume (ITV; February 1989) vs intensity (ITI; February 1990) on performance, catecholamines, energy metabolism and serum lipids was examined in two studies on eight, and nine experienced middle- or long-distance runners; seven participated in both studies. During ITV, mean training volume was doubled from 85.9 km.week-1 (pretrial phase) to 174.6 km within 3 weeks. Some 96%-98% of the training was performed at 67 (SD 8)% of maximal performance. During ITI, speed-endurance, high-speed and interval runs increased within 3 weeks from 9 km.week-1 (pretrial phase) to 22.7 km.week-1 and the total training distance from 61.6 to 84.7 km.week-1. The ITV resulted in stagnation of running velocity at 4 mmol lactate concentration and a decrease in total running distance in the increment test. Heart rate, energy metabolic parameters, nocturnal urinary catecholamine excretion, low density, very low density lipoprotein-cholesterol and triglyceride concentrations decreased significantly; the exercise-related catecholamine plasma concentrations increased at an identical exercise intensity. The ITI produced an improvement in running velocity at 4 mmol lactate concentration and in total running distance in the increment test; heart rate, energy metabolic parameters, nocturnal catecholamine excretion, and serum lipids remained nearly constant, and the exercise-related plasma catecholamine concentrations decreased at an identical exercise intensity. The ITV-related changes in metabolism and catecholamines may have indicated an exhaustion syndrome in the majority of the athletes examined but this hypothesis has to be proven by future experimental studies.     

Pushing the envelope: chromatin boundaries at the nuclear pore

In a novel genetic screen, the nuclear-cytoplasmic transport system was found to reposition DNA to the nuclear pore and establish a barrier to the spread of heterochromatin. These data provide a mechanism for movement and attachment of DNA to a functional nuclear compartment.     

CRM1-mediated nuclear export determines the cytoplasmic localization of the antiapoptotic protein Survivin

Survivin is a member of the inhibitor of apoptosis (IAP) family of negative regulators of programmed cell death that is frequently overexpressed in human tumors. Survivin is not only involved in the regulation of apoptosis, but is also known to play a role in the control of cell cycle progression at the G2/M phase. Survivin is a predominantly cytoplasmic protein expressed in a cell cycle-dependent manner, but the mechanism(s) that determine its nuclear-cytoplasmic localization have not been described. In this study, we report that Survivin is a nuclear shuttling protein that is actively exported from the nucleus via the CRM1-dependent pathway. Nuclear export of Survivin is independent of the export of other shuttling proteins that control the G2/M phase transition, such as cyclin B1 and cdc25. The carboxy-terminal domain of Survivin is both necessary and sufficient for its nuclear export, although this region does not contain a functional leucine-rich nuclear export signal. Differences in the amino acid sequence of this region determine the dramatically different localization of Survivin (in the cytoplasm) and its splicing variant Survivin-DeltaEx3 (in the nucleus). The carboxy-terminal end of Survivin-DeltaEx3 contains a bipartite nuclear localization signal, not present in Survivin, which mediates its strong nuclear accumulation. These data suggest that active transport between the nucleus and cytoplasm may constitute an important regulatory mechanism for Survivin function.     

Some functional consequences of partial hepatectomy in rainbow trout (Salmo gairdnerii)

A partial hepatectomy (an average of 36% of hepatic mass removed) was performed in rainbow trout. Thirty days after this partial hepatic removal, the liver had recovered its initial weight. During regeneration the remaining liver was unable to maintain normal blood levels of protein, cholesterol and, partially, lipids which decrease after surgery. The results obtained show that functional and liver weight regeneration proceed at different rates throughout a given time course, weight recovering faster than complete functional restoration.     

Ubiquitin-regulated nuclear-cytoplasmic trafficking of the Nipah virus matrix protein is important for viral budding

Paramyxoviruses are known to replicate in the cytoplasm and bud from the plasma membrane. Matrix is the major structural protein in paramyxoviruses that mediates viral assembly and budding. Curiously, the matrix proteins of a few paramyxoviruses have been found in the nucleus, although the biological function associated with this nuclear localization remains obscure. We report here that the nuclear-cytoplasmic trafficking of the Nipah virus matrix (NiV-M) protein and associated post-translational modification play a critical role in matrix-mediated virus budding. Nipah virus (NiV) is a highly pathogenic emerging paramyxovirus that causes fatal encephalitis in humans, and is classified as a Biosafety Level 4 (BSL4) pathogen. During live NiV infection, NiV-M was first detected in the nucleus at early stages of infection before subsequent localization to the cytoplasm and the plasma membrane. Mutations in the putative bipartite nuclear localization signal (NLS) and the leucine-rich nuclear export signal (NES) found in NiV-M impaired its nuclear-cytoplasmic trafficking and also abolished NiV-M budding. A highly conserved lysine residue in the NLS served dual functions: its positive charge was important for mediating nuclear import, and it was also a potential site for monoubiquitination which regulates nuclear export of the protein. Concordantly, overexpression of ubiquitin enhanced NiV-M budding whereas depletion of free ubiquitin in the cell (via proteasome inhibitors) resulted in nuclear retention of NiV-M and blocked viral budding. Live Nipah virus budding was exquisitely sensitive to proteasome inhibitors: bortezomib, an FDA-approved proteasome inhibitor for treating multiple myeloma, reduced viral titers with an IC(50) of 2.7 nM, which is 100-fold less than the peak plasma concentration that can be achieved in humans. This opens up the possibility of using an "off-the-shelf" therapeutic against acute NiV infection.     

Inhibition of the nuclear localization of [3H]estradiol in rat uterine tissue in vitro

The temperature coefficient (Q10) for the nuclear-cytoplasmic intracellular distribution of specifically-bound [3H]estradiol is approximately 1.0 over the interval 10-30 degrees C. However, this value increases to 3.19 for the temperature influence upon the nuclear-cytoplasmic localization of hormone between 30 degrees and 37 degrees C. A Q10 value of this magnitude is indicative of a biological, rather than physical, translocation event. In assessment of a biological basis for translocation, several antimicrotubular/antimicrofilamentous agents were used alone and in combination to ascertain their effects upon in vitro nuclear localization of labeled estradiol in the uterus. The incubation of uterine tissue in D2O-Locke-Ringer's solution containing 10(-4) M colchicine or vinblastine significantly reduced the nuclear localization of [3H]estradiol to nonspecific retention. Tissue uptake of the hormone, cytoplasmic binding and retention of estrogen, and the nucleophilic property of the receptor-estrogen complex (REC) were unaffected. Other drug treatments were without effect upon nuclear occupancy of the REC. The apparent inhibition of translocation by the above regimen could be due to an alteration in cellular architecture incompatible with hormone movement or the result of a direct effect upon cellular components which impede the dynamic interactions of REC in nuclei of whole tissue. Although these results do not necessarily imply that a functional cytoskeleton is required for translocation, we suggest that the estrogen-mediated nuclear occupancy of REC is a biological process susceptible to disruption.     

Regulation of PI4,5P2 synthesis by nuclear-cytoplasmic shuttling of the Mss4 lipid kinase

The essential phospholipid PI4,5P(2) is generated by a well conserved PI4P 5-kinase, Mss4, in yeast. Balanced production and turnover of PI4,5P(2) is important for normal organization of the actin cytoskeleton and cell viability. Previous studies have shown that multiple PI phosphatases can regulate PI4,5P(2) levels. We report a new, unexpected regulatory mechanism for PI4,5P(2) homeostasis, directed by nuclear-cytoplasmic shuttling of the lipid kinase. We show that Mss4 is a phosphoprotein, which contains a functional nuclear localization signal (NLS) and can shuttle between the cytoplasm and the nucleus. Temperature-conditional mss4 cells that accumulate Mss4 protein in the nucleus exhibit reduced levels of PI4,5P(2), depolarization of the actin cytoskeleton and a block in Mss4 phosphorylation, suggesting an essential role for phosphorylated Mss4 at the plasma membrane. Through the isolation of gene dosage-dependent suppressors of mss4 mutants, we identified Bcp1, a protein enriched in the nucleus, which is required for Mss4 nuclear export and is related to the mammalian BRCA2-interacting protein BCCIP. Together, these studies suggest a new mechanism for lipid kinase regulation through regulated nuclear-cytoplasmic shuttling.     

Gravity effects on regional lung ventilation determined by functional EIT during parabolic flights.

Gravity-dependent changes of regional lung function were studied during normogravity, hypergravity, and microgravity induced by parabolic flights. Seven healthy subjects were followed in the right lateral and supine postures during tidal breathing, forced vital capacity, and slow expiratory vital capacity maneuvers. Regional 1) lung ventilation, 2) lung volumes, and 3) lung emptying behavior were studied in a transverse thoracic plane by functional electrical impedance tomography (EIT). The results showed gravity-dependent changes of regional lung ventilation parameters. A significant effect of gravity on regional functional residual capacity with a rapid lung volume redistribution during the gravity transition phases was established. The most homogeneous functional residual capacity distribution was found at microgravity. During vital capacity and forced vital capacity in the right lateral posture, the decrease in lung volume on expiration was larger in the right lung region at all gravity phases. During tidal breathing, the differences in ventilation magnitudes between the right and left lung regions were not significant in either posture or gravity phase. A significant nonlinearity of lung emptying was determined at normogravity and hypergravity. The pattern of lung emptying was homogeneous during microgravity.     

Effects of hypoxia on respiratory defence reflexes. Effects of thirty hours' oxygen deficiency on cough, the expiration reflex and sneezing in awake cats

The authors studied, in 11 awake adult cats, the parameters of the expiration reflex (ER), tracheobronchial (TB) and laryngopharyngeal (LPh) cough, the respiratory rate (f), tidal volume (VT), the end tidal fractional CO2 concentration (FETCO2), the pH, the blood gases and the heart rate during 30 hours' isobaric hypoxic hypoxia (FO2 = 0.11). During the whole 30 hours the cats developed hypocapnic hypoxemia, f remained unchanged and VT was markedly elevated. In the acute phase (15 min) of hypoxic hypoxia of the same intensity, changes in respiratory parameters were the same and the intensity of respiratory reflexes increased significantly (Tatár et al. 1984). During prolonged hypoxic hypoxia there were no statistically significant changes in the intensity of the ER and of TB and LPh cough. The authors assume that some adaptation of the central mechanisms regulating the defence reflexes of the airways took place; this hypothesis is warranted, because an increase in the susceptibility of the cough centre during constant conditions of the stimulation of cough receptors would not be biologically expedient. The different changes in the intensity of respiratory defense reflexes in the acute and the prolonged phase of hypoxic hypoxia in the presence of identical changes in respiratory parameters are further indirect evidence pointing to the existence of functional differences between the respiratory centre and the cough centre.     

A quantitative dynamic concept of the interphase partition of lipids: application to bile salt-lecithin-cholesterol mixed micelles

A system is proposed for a quantitative classification of lipids, based on interphase partition coefficients. This system enables calculation of exchanges of lipid molecules between phases. The mass/volume chemical unit mol X cm-3, strictly derived from the CGS system, is used, thus simplifying mathematical relations. Applied to bile salt-lecithin-cholesterol mixed micelles, this dynamic concept gives new insight into the variations of physico-chemical parameters. Experimental results obtained with the glycodesoxycholate and the taurocholate show a striking difference in partition coefficients between aqueous and mixed bile salt-lecithin interfacial phases. A new model applying triangular co-ordinates to a bile salt-lecithin-cholesterol mixed lipid phase is described.     

Compensatory-adaptive modifications of the C-cell apparatus of the thyroid in normal rats of various ages and in partial sympathectomy

Population of the thyroid C-cells, normal and at sympathectomy has been analyzed in 75 white male rats at the age of 1, 3 and 6 months by means of electron microscopical, morphometrical and radioimmunological methods. Partial sympathectomy has been performed using subcutaneous injection of guanethidine (15 mg/kg of body mass) during 14 days after birth. During the period from 1 up to 6 months of life in intact rats a decrease in C-cells functional activity is observed. Under conditions of sympathectomy in 30-day-old animals decreasing extrusion processes of the secretory material are observed. During successive periods of life (3 and 6 months) mechanisms of paracrinic evacuation of hormonal products enhance considerably, nuclear volume of the cells and number of C-cells in the field of vision increase. Their hyperplastic alterations in the sympathectomized thyroid gland are more pronounced in 3-month-old animals.     

Direct action of low-intensity laser irradiation on the morphofunctional status of the zona fasciculata of the adrenal cortex of white rats

Increase of capillaries blood volume, nuclear mass and nuclear cytoplasmic relationship and decrease of lipid content and adrenocortical sizes were determined in superficial adrenocortical layers on helium-neon LAZER irradiation of uncovered left adrenal glands in white female rats. It was confirmed by corticosteroid function increase. Similar morphometric changes were identified all over adrenocortical bundles on arsenate-helium irradiation of covered left adrenal gland from the back of the animal. According to obtained results LAZER irradiation may be recommended to use for functional stimulation of adrenal cortex.     

On the yolk sac of the cat

Summary The phase of primitive erythropoiesis in the feline yolk sac lasts from the 14th to the 20th day after mating. The globular nucleated primitive erythroblasts are formed extravascularly to some extent, but they can be clearly distinguished from the endoderm. They do not undergo a denucleation and are still present in the circulating blood on the 45th day. Aging primitive erythroblasts are characterized by a loss of polysomes, by the appearance of long intracytoplasmic electron-lucent channels, and by a nuclear pyknosis which can turn into a karyolysis. Definitive erythropoiesis begins around the 17th day but, even by the 19th day, it is not particularly prominent. It ends around the 45th day. It is almost exclusively intravascular. The distinction of immature primitive erythroblasts from erythroblasts of the definitive series is difficult, because it is based upon only slight differences in the heterochromatinization, in the nuclear-cytoplasmic ratio, and in the organelle content of the cells. In the definitive series, the nuclear divisions follows the law of the rhythmical halving of the nuclear volume. The cells exhibit more clearly identifiable maturation stages here, and the checkerboard nucleus is more distinct. The vascular endothelium is largely attenuated and moderately fenestrated; it lacks a distinct basement membrane. Organelle-rich adventitial cells are found in close apposition.