Protective properties of IgM in experiments on animals]

On a model of intraperitoneal infection of albino mice the authors demonstrated a protective action of the fraction enriched with IgM and of gamma-globulin isolated from the normal human blood serum, against E. coli O111. The intensity of the protective action depended on the method, duration of administration of the preparation and also on the infective dose. Protective properties of the fraction enriched with IgM were more pronounced in comparison with the gamma-globulin preparation.     

Aquatic animals and use of centrifuge in space experiments]

There are some experiments which do not need a centrifuge apparatus in space, however, for other space experiments the use of centrifuge is indispensable as the control. The characteristics of these two types of space experiments are explained. Generally, the more quantitatively the phenomenon is analyzed, the greater the need of centrifuge apparatus becomes. The centrifuge in space can realize various gravity values ranging from 0 to 1 G, and this will extend the present biology to a more universal biology.     

Further experiments with digestive enzymes in freshly killed animals

A number of modifications of Freeland's method for the assay of enzymes by radial diffusion in agar are described. Amylase does not obey Fick's Law but methods for producing a standard curve are given. An alternative method of assay is to time the loss of colour in a standard solution of substrate.     

Effect of Age on Human Brain Serotonin (S-1) Binding Sites

The effect of age on the binding of [3H]5-hydroxytryptamine [( 3H]5-HT, serotonin) to postmortem human frontal cortex, hippocampus, and putamen from individuals between the ages of 19 and 100 years was studied. One high-affinity binding site was observed in adult brains, with a mean KD of 3.7 nM and 3.2 nM for frontal cortex and hippocampus, respectively, and 9.2 nM for putamen. Decreased binding capacities (Bmax) with age were detected in frontal cortex and hippocampus. In putamen a decrease in affinity was noted. Postmortem storage did not significantly contribute to the age-related changes. No significant sex differences were detected. [3H]5-HT binding was also studied in brains from human neonates. The specific binding was 1.5-3 times lower than in adult frontal cortex and putamen, and Scatchard analysis suggested more than one binding site. In infant hippocampus a single binding site was observed and except for a premature individual, the binding capacity approximated adult values.     

Serotonin 5-HT(3) receptors on mechanosensitive neurons with cardiac afferents

In rats, the mechanosensitive cardiorenal baroreflex influencing renal excretory function might be impaired by serotonin occurring in coronary arteries, e.g., in hypertension. Because the afferent limb of this reflex could be affected, we investigated the responses of nodose ganglion cells (one neuron of reflex) to osmotic, mechanical stress in presence or absence of the serotonin 5-HT(3) receptor agonist phenylbiguanide (PBG). Current-voltage relationships (from -100 to +50 mV) were obtained using cell patch recordings while the cells were exposed to control or hypoosmotic solutions to induce mechanical stress. This protocol was repeated after low doses of PBG (10 microM), angiotensin II (10 nM), or the stretch-activated channel blocker gadolinium (20 microM) were added to the extracellular medium (EM). Hypoosmotic EM induced significant changes in cellular conductance. The full-range current-voltage relationship allowed for the calculation of a mean reversal potential of -13 +/- 1.2 mV with respect to this change in cellular conductance (n = 44). This increase in conductance was impaired after addition of either PBG or gadolinium to the EM,which was statistically evaluated at a voltage of -80 mV, where influences of voltage-gated channels are not likely to interfere with the responses recorded. The serotonin 5-HT(3) receptor antagonist tropisetron (10 nM) prevented the PBG effect on conductance responses. Angiotensin II had no influence. Hence, serotonin might decrease the mechanical sensitivity of afferent cardiac nerves controlling renal sympathetic nerve activity.     

Origin of bilateral-symmetrical animals (Bilateria)

The paper is an attempt to attack the old problem of the origin of Bilateria by the methods of evolutionary tetrad (i.e. combination of comparative anatomy, comparative embryology, paleontology, and molecular biology). Three groups of theories of classical comparative anatomy (planulod-turbellarian, archicoelomate, and metameric) are discussed. Comparative embryology brings out clearly that the ventral side of embryo comes from the blastoporal region in all groups of Bilateria (except Chordata, where the blastoporal region corresponds to the dorsal side that is come out of the upside-down morphology of chordates) and mouth and anus comes from the anterior and posterior ends of elongated blastopore. From the point of view of paleontology, some of vendian metazoans demonstrate transitional conditions between the Radiata and Bilateria. Vendian bilaterians are metameric organisms with normal or asymmetric position of segments and could be pictured as "bilateral coelenterates" creeping on the oral surface. In Cnidaria, the expression of homologues of "Brachyury", "goosecoid", and "fork head" genes are revealed in the circular region around the mouth. In Bilateria, these genes are expressed along the elongated blastopore and around the mouth and anus. These results support the old conception on the amphistomic origin of mouth and anus as well as the homology between the oral disc of cnidarians and ventral side of Bilateria. The combination of four mentioned approaches enables us to propose the conception of the origin of Bilateria from vendian bilateral coelenterates with numerous metameric pouches of gastral cavity. Bilaterian ancestors crawled on the oral disc (= ventral side). These ancestors gave rise to both phanerosoic cnidarians and triploblastic bilaterians. Cnidarian ancestors attached to bottom by the aboral pole with the resulting degradation of aboral nerve ganglion. Bilateral symmetry of anthozoans is considered to be primitive feature for cnidarians. In case of triploblastic Bilateria, the elongated blastopore closed in the middle and subdivided into mouth and anus (amphistomy) and gastral pouches separated from the central part of gastral cavity and transformed to metameric coelomic chambers. The primary bilaterians are supposed to be complicated organisms having coelom and segmentation. The complexity of primary Bilateria provides an explanation for the abundance of highly organized organisms (arthropods, mollusks etc.) in Cambrian time. It is postulated that Ctenophora is the only group recent eumetazoans with primary axial symmetry.