A. A. Ukhtomskiĭ's ideas in studies on the cognitive activity

Experimental data on spatial and temporal organisation of the human EEG from birth to maturity, at resting and during cognitive activity, is presented. The data obtained is interpreted in light of a confirmation of the Ukhtomsky's ideas on the "functional working organ" appearing in the brain for realising cognitive processes. Role of the alpha-rhythm in formation of plastic intracortical neuronal network is elucidated. A hypothesis is advanced stating that the gradually developing brain system exerting a local regulated activating effects upon the cortical level, is a significant factor of the functional intercentre integration.     

A1 toxicity in yeast. A role for Mg?

We have established conditions in which soluble Al is toxic to the yeast Saccharomyces cerevisiae. The major modifications to a standard synthetic medium were lowering the pH and the concentration of Mg ions. Alterations to the PO4, Ca, or K concentration had little effect on toxicity. Organic acids known to chelate Al reduced its toxicity, suggesting that Al3+ is the toxic Al species. The unique ability of Mg ions to ameliorate Al toxicity led us to investigate the hypothesis that Al inhibits Mg uptake by yeast. Yeast cells accumulate Mg, Co, Zn, Ni, and Mn ions via the same transport system (G.F. Fuhrmann, A. Rothstein [1968] Biochim Biophys Acta 163: 325-330). Al3+ inhibited the accumulation of 57Co2+ by yeast cells more effectively than Ga, La, or Mg. In addition, a mutant yeast strain with a defect in divalent cation uptake proved to be more sensitive to Al than a wild-type strain. Taken together, these results suggest that Al may cause Mg deficiency in yeast by blocking Mg transport. We discuss the relevance of yeast as a model for the study of Al toxicity in plant systems.     

Predator-prey relationships in the southeastern Ozarks–A.D. 1300

Archeological findings provide the basis for analyzing the exploitation of deer by Powers Phase Indian hunters in the southeastern Ozarks circaA.D. 1300. Predatory patterns of wolves have been documented. It is hypothesized that men and wolves were complementary, noncompetitive predators and that their predation functioned to keep the deer population within the carrying capacity of the southeastern Ozarks. A model is developed to illustrate the predator-prey relationships in the area.Powers Phase Research Project is financed by National Science Foundation Grant GS-3215 to James B. Griffin, University of Michigan.The term Powers Phase has been applied to a pre-Columbian American Indian population of Middle Mississippian cultural affiliation which occupied an area in southeast Missouri for a relatively short period of timecirca A.D. 1300.     

Hemorheology and oxygen transport in vertebrates. A role in thermoregulation?

We studied the effect of temperature on blood rheology in three vertebrate species with different thermoregulation and erythrocyte characteristics. Higher fibrinogen proportion to total plasma protein was found in turtles (20%) than in pigeons (5.6%) and rats (4.2%). Higher plasma viscosity at room temperature than at homeotherm body temperature was observed in rats (1.69 mPa x s at 20 degrees C vs. 1.33 mPa x s at 37 degrees C), pigeons (3.40 mPa x s at 20 degrees C vs. 1.75 mPa x s at 40 degrees C), and turtles (1.74 mPa x s at 20 degrees C vs. 1.32 mPa x s at 37 degrees C). This fact allow us to hypothesize that thermal changes in protein structure may account for an adjustment of the plasma viscosity. Blood viscosity was dependent on shear rate, temperature and hematocrit in the three species. A different behaviour in apparent and relative viscosities between rat and pigeon at environmental temperature was found. Moreover, the blood oxygen transport capacity seems more affected by a reduction of temperature in rats than in pigeons. Both findings indicate a greater influence of temperature on mammalian erythrocyte than on nucleated red cells, possibly as a consequence of differences in thermal sensitivity and mechanical stability between them. A comparison between the three species revealed that apparent blood viscosity measured at homeotherm physiological temperature was linearly related to the hematocrit level of each species. However, when measured at environmental temperature, rat blood showed a higher apparent viscosity than those found in species with non-nucleated red cells, thus indicating a higher impact of temperature decrease on blood viscosity in mammals. This suggest that regional hypothermia caused by cold exposure may affect mammalian blood rheological behaviour in a higher extent than in other vertebrate species having nucleated red cells and, consequently, influencing circulatory function and oxygen transport.     

Cytogenetical studies in the bridge cross Allium cepa× (A. fistulosum×A. roylei)

  Allium fistulosum harbours a number of desirable agronomical traits for the breeding of onions. However exploitation of A. fistulosum for onion breeding via direct sexual hybridization is problematic. Therefore, we examined if a bridge cross, using A. roylei as a bridging species, might provide an alternative. By means of genomic in situ hybridization (GISH) we showed that each of the three parental genomes can be distinguished from the others in interspecific hybrids, suggesting that these genomes contain sufficiently different repetitive DNA families. We succeeded in carrying out multi-colour GISH to metaphase spreads of a first-generation bridge-cross individual [A. cepa× (A. fistulosum×A. roylei], which is composed of three parental genomes. Recombination between the genomes of A. fistulosum and A. roylei took place to a large extent: 7 recombined chromosomes were observed, and it could be shown that the proximal regions of the recombined A. fistulosum/A. roylei chromosomes belonged to the former, whereas the distal parts belonged to the latter. The high percentage of bound bivalent arms in metaphase I of pollen mother cells of a fertile bridge-cross individual suggests the introgression of A. fistulosum genes, mediated by A. roylei, into the genome of A. cepa. However, the presence of univalents reflects decreased pairing and recombination between the three genomes. Pollen fertility and pollen-tube growth of the first-generation bridge-cross individual seem to be sufficient to produce a second generation bridge-cross (A. cepa×first-generation bridge cross) progeny. Received: 27 May 1997 / Accepted: 30 June 1997     

A.A.Khan教授将来华讲学

美国康乃尔大学种子生理学家A.A.Khan教授,将于今年十月中旬来华,到广州及杭州访问,并在广州举办讲习班,做以下五方面的报告:①应用种子预措施改善幼苗生长与产     

Innatism in the Anthropology of A. L. Kroeber: A Critique of ‘the Boasian Paradigm’

Basing his analysis on Kroeber's ‘The superorganic’ (1917 Kroeber, A. L. 1917. The superorganic.. American Anthropologist, 19: 163–213. [Crossref] [Google Scholar]) and ‘Eighteen professions’ (1915 Kroeber, A. L. 1915. Eighteen professions.. American Anthropologist, 17: 283–88. [Crossref] [Google Scholar]), Derek Freeman has put forward the notion of a ‘Boasian paradigm’, whereby Kroeber is alleged to have perpetuated the biology/culture split suggested by Boas. I argue, instead, that there is a strong innatist element in Kroeber's writings throughout his long career; and that the articles noted above need to be placed in the social and intellectual contexts of their time, particularly the encroachment of the eugenics movement on social theory and its application to immigration restriction.     

Neurofilament phosphorylation in development. A sign of axonal maturation?

Monoclonal antibodies to the 200K neurofilament (NF) protein selectively decorated axons in tissue sections. Dilution of the antibodies in phosphate buffer and digestion with phosphatase abolished the stain. With conventional monoclonal and polyclonal NF antibodies, i.e. antibodies decorating NF regardless of their location (axons, perikarya and dendrites), the staining was not affected by this treatment. With all antibodies, axon-specific and conventional, the staining was abolished by trypsin digestion. Subsequent digestion with phosphatase did not restore the staining. Compared with conventional NF antibodies, staining with axon-specific anti-NF 200K was a late phenomenon in chick embryo development. NF 200K immunoreactivity was first observed in peripheral nerves and in the anterior columns of the spinal cord on day 10. Sensory ganglia and optic nerve fibers were negative. With conventional NF antibodies these structures were stained on days 4 and 5, respectively. In the following days of development the study was confined to the retina, optic nerves, cranial peripheral nerves and sensory ganglia. Up to day 16, bundles of thin peripheral nerve fibers, strongly decorated by conventional NF antibodies, did not stain with anti-NF 200K in double labelling experiments. Nerve bundles emerging from the ganglia were also negative, although some thick nerve fibers within the ganglia were stained. NF 200K immunoreactivity was first observed on day 17 in the optic nerve and in the layer of optic nerve fibers. At this time, staining was confined to the bundle emerging from the temporal side of the retina. In newborn chicken, only few fibers stained with anti-NF 200K in the nasal bundle, while the temporal bundle was well stained. It is suggested that the NF 200K antibodies reacted with a phosphorylated epitope in the axon, and that NF phosphorylation is a late event in ontogenesis probably related to axonal maturation.     

Molybdenum sequestration in Brassica species. A role for anthocyanins?

To elucidate plant mechanisms involved in molybdenum (Mo) sequestration and tolerance, Brassica spp. seedlings were supplied with molybdate, and the effects on plant physiology, morphology, and biochemistry were analyzed. When supplied with (colorless) molybdate Indian mustard (Brassica juncea) seedlings accumulated water-soluble blue crystals in their peripheral cell layers. Energy dispersive x-ray analysis showed that Mo accumulated predominantly in the vacuoles of the epidermal cells. Therefore, the blue crystals are likely to be a Mo compound. The x-ray absorption spectrum of the plant-accumulated Mo was different than that for molybdate, indicating complexation with a plant molecule. Because the blue compound was water soluble and showed a pH-dependent color change, possible involvement of anthocyanins was investigated. An anthocyanin-less mutant of Brassica rapa ("fast plants") was compared with varieties containing normal or high anthocyanin levels. The anthocyanin-less mutant did not show accumulation of a blue compound when supplied with molybdate. In the anthocyanin-containing varieties, the blue compound colocalized with anthocyanins in the peripheral cell layers. Mo accumulation by the three B. rapa varieties was positively correlated with anthocyanin content. Addition of molybdate to purified B. rapa anthocyanin resulted in an in vitro color change from pink to blue. Therefore, Mo appears to be sequestered in vacuoles of the peripheral cell layers of Brassica spp. as a blue compound, probably a Mo-anthocyanin complex.