Multivalued stimulus-response relation in isolated elasmobranch utricles

The relation between a maintained spatial orientation and the corresponding fully adapted discharge rate was multivalued in all the afferents tonically sensitive to maintained spatial orientation observed in isolated utricles of Rhinobates productus. The spread of rate values was of the order of changes produced by natural tilts. The occurrence of multivaluedness in isolated receptors indicated that peripheral issues are sufficient. Two factors contributed: firstly, the side from which the orientation had been reached (i.e. hysteresis): higher adapted rates occurred when the preceding orientation was characterized by lower rates and when the corresponding transition caused acceleration; secondly, spontaneous rate variations, some of which resembled markedly, and interacted with, the effects of tilts. It was not possible to identify the basic mechanisms underlying these factors. The multivaluedness in the coding of maintained position, because of its constancy and magnitude, cannot be ignored. It, as well as the sensitivity to fast transients, must be taken into account in utricular models, in evaluations of information transmission, and in psychophysical explorations.Supported by grants (to J.P.S.) from NIH and NSF, and by NIH fellowships (to G.E.W. and R.B.) The tilting equipment was built with funds from the United Cerebral Palsy Foundation     

Substructural features of pulmonary endothelial caveolae

Substructural specializations of the endothelial caveolae of rat lung capillaries are described. Dense knobs occur at the place where caveola membrane, diaphragm and plasma membrane fuse. Similar structures are seen where caveolae fuse to form complex groups and in preparations of isolated caveolae. The appearance of these knobs in transverse sections may represent a circular skeletal structure, possibly functioning to maintain the patency of the stoma and the integrity of the diaphragm. In addition, the inner concave surface of the caveola membrane contains regularly spaced globular structures, possibly enzyme clusters or binding sites. This interpretation is supported by the finding that the distribution of lead phosphate deposits (formed on reaction of caveolar 5'-nucleotidase with AMP in the presence of Pb(N0(3))(2)) corresponds with the spacing of globular structures. These substructural features of caveolae are considered with reference to the ability of caveolae to metabolize circulating vasoactive substances.     

Substructural studies on sporulation of Saccharomycopsis lipolytica

During sporulation of diploids from crosses between different strains of the yeast Saccharomycopsis (Candida) lipolytica irregular numbers of ascospores per ascus have been observed. Using the serial section method it could be shown now by means of electron microscopy that in one-, two-, and three-spored asci unenclosed "naked" nuclei occur additionally to nuclei incorporated in mature spores. It was demonstrated that the production of less than four spores per ascus in this yeast is not the result of a lack of meiotic products but of the nonutilization of nuclei from meiosis. In 2--4 spored asci usually four products of meiosis in form of enclosed and free nuclei could be demonstrated which indicate a normal meiotic division. All ascospores derived from asci with different spore numbers are uninuclear. It is assumed that a defect in spore formation caused by structural changes of chromosomes or aneuploidy should give rise to the occurrence of non incorporated nuclei and spore irregularity. It was concluded that meiosis and spore formation in Saccharomycopsis lipolytica seem to represent parallel and coordinated processes which generally resemble those recorded for Saccharomyces cerevisiae and Hansenula species.     

A Remeasurement of the Molecular Weights of T-Even Bacteriophage Substructural Proteins

T-even bacteriophage substructural proteins were studied by using discontinuous sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was found that tail fibers are composed of two major proteins of 155,000 and 120,000 daltons molecular weight and four minor proteins of 51,000, 38,000, 27,000, and 23,000 daltons. Tail tubes were composed of one predominant protein of 18,500 daltons and one minor protein of 35,000 daltons molecular weight. Tubular polyheads obtained from a T4D amber mutant and by treatment of T4B-infected cells with L-canavanine were also examined, and no significant differences were noted in the molecular weight of the P23 protein.     

Types of biological reactions to the gravitation loads

The nature of adaptation to gravitational loads is reviewed. Topics include an organism's antigravitation function, exposure to gravitational loads, types of physiological reactions, and results of adaptation.     

Substructural morphogenesis of the spindle apparatus in meiotic basidia ofCoprinus micaceus (Agaricales)

The spindle apparatus ofCoprinus micaceus begins to develop from the diglobular polar body outside the nucleus. During both meiotic divisions it operates inside the nuclear envelope and consists of two amorphous poles, a central bundle of interpolar microtubules, and chromosomal microtubules. A metaphase plate cannot exist because the interpolar strand of fibers is persistent throughout the division process. Within the spindle axis more than 100 microtubules can be estimated. They are encircled by a ring of chromatic structures. During the telophase the former spindle pole is evaginated from the nuclear envelope and contacts the plasmalemma near the cell wall.     

Morphological variability of Carex spicata Huds. utricles among plant communities

Differentiation in the size and number of seeds among populations or particular individuals of a given species may depend on genetic features and environmental conditions. The objective of our study was to answer two questions: whether any differences exist in the size and shape of utricles among Carex spicata populations growing in several plant communities and whether the hypothesized differences remain constant in ‘common garden’ conditions (i.e. if the sedges grown in different plant communities are evolving distinctly separate ecotypes). We studied utricle morphological traits (projected area, width, length, W/L ratio and projected perimeter) and number of utricles per spike collected from plants grown in five different plant communities (natural sites) and from plants transferred to common garden conditions. C. spicata utricles showed significant variability of morphological traits that depended on the plant community of origin. Among five plant communities, the largest utricles were found in Agropyron repens–Urtica dioica and Convolvulo arvensis–Agropyretum repentis communities, while the smallest ones were in plants from the Lolio-Plantaginetum community. The similarity of the analyzed populations regarding sedge utricle traits corresponded to the similarity of plant communities where the populations had grown. Moreover, the differences in utricle traits collected from natural conditions remained stable in common garden conditions. This indicated that differences in traits among utricles had a physiological dependence on different biotope conditions or different interspecific interactions prevailing in the particular plant communities. The relationship between the similarities in the diaspores of the populations studied and the similarities in the ecological conditions of the communities may also indicate that the variability of utricles is important for evolution and adaptation.The results support the hypothesis that C. spicata populations in different communities are producing separate ecotypes, i.e. specific species forms with genetically fixed traits adapted to narrowly determined habitat conditions.     

Study of skeleton gravitation physiology and problem of osteoporosis

Main osteoporosis definitions and some results of bone tissue research in Russian astronauts, patients, and healthy subjects, using modern osteodensitometry, are presented. Bone mineral density (BMD) was regularly decreased at lower segments of skeleton. In the skull bone and some other sites of upper part of skeleton, a tendency was revealed for an increase of the bone mineral content (BMC). The mean value of bone loss was within the normal range and not correlated with duration of space flight; it revealed a high individual variability and in some cases was clinically qualified as local osteopenia. On the ground of analysis of own results and animal and bone cultural experiments data in microgravity conditions, the described changes seem to be reflecting a deceleration of bone formation as an adaptive response of bone tissue to the mechanical unloading. The response is realized mainly on the tissue level. It does not exclude bone resorption activity as a result of changes in hierarchy of water and electrolytes metabolism as reflected by body fluid redistribution in cranial direction. The results obtained broaden our notions on pathogenesis of some types of osteoporosis in clinic.     

A computer-assisted study of the effect of gravitation on the functional state of the lungs

Gravitation influence on lung function was investigated in 115 patients and 21 healthy persons. Changing of an examinee's position from vertical into a horizontal one causes changes in lung function in health and disease. Characteristic features of lung function were determined for each group of examinees in order to improve the diagnosis and differential diagnosis of bronchial cancer and nonspecific chronic pulmonary diseases with a similar x-ray picture. A study of pulmonary ventilation and blood supply of the lungs in vertical and horizontal postures in Hodgkin's disease patients led to a conclusion that irradiation of patients seemed more effective in a phase of deep breath. It made it possible to reduce radiation exposure of healthy parts in a zone to be irradiated.     

Recovery of motor function after partial decortication under the effects of double gravitation

The motor function recovery was studied after surgical damage of the left motor cortex in albino rats in control and under double gravitation action for 20 and 40 min a day. Distance between the 1st and 5th finger was measured. The positive influence was shown on post-lesional recovery.     

Role of gravitation in solving a haptic comparison problem

The effect of haptic perception-reproduction task performed by means of a force feedback handle was studied under ground-based conditions and on board an orbital station. In contrast to visual perception, which exhibits a pronounced domination of vertically and horizontally oriented stimuli in such experiments, haptic perception did not display a dependence of responses on the tilt of the reference stimulus in the presence or absence of gravity. Thus, when solving a purely haptic problem, the CNS uses only proprioception, even in the presence of gravitation.