THE INTERACTION PHENOTYPE IN THE DROSOPHILA WILLISTONI–SPIROPLASMA SYMBIOSIS

Both the population and coevolutionary dynamics of hereditary male-lethal endosymbionts, found in a wide range of insect species, depend on host fitness and endosymbiont transmission rates. This paper reports on fitness effects and transmission rates in three lines of Drosophila willistoni infected with either male-lethal spiroplasmas or a spontaneous nonmale-lethal mutant. Overall fitness measures were reduced or unaffected by the infection; however, some infected females produced more offspring in early broods. Maternal transmission rates were high, but imperfect, and varied with a female's age, host line, and spiroplasma type. No evidence for paternal or horizontal transmission was found. If an altered temporal pattern of reproduction is not a factor in countering the loss of spiroplasma hosts through imperfect maternal transmission, persistence of this endoparasitism remains unexplained. Tolerance of the infection and ability to transmit bacteria varied with both host and spiroplasma line. Analysis of the interaction between the spontaneous nonmale-lethal mutant and its host suggests this symbiosis has undergone coevolution under laboratory culture.     

幼年蝙蝠下丘神经元的听空间特性

实验分别在出生后４周龄的幼年和成年鲁氏菊头蝠（Ｒｈｉｎｏｌｏｐｈｕｓｒｏｕｘｉ）上进行。使用移动声刺激装置,高频喇叭可在动物头部前方水平方向１８０度、垂直方向６０度的范围内移动。玻璃微电极记录单个神经元的听反应。实验考察了幼年和成年动物下丘神经元的听空间特性,共观察了３０１个神经元,其中幼年动物１４８个,成年动物１５３个。结果表明,４周龄的幼年动物下丘听神经元已表现出方向敏感性,即每个听神经元均有一个特定的最佳反应中心和反应域。但神经元听反应中心在听空间的分布相当弥散,大多数位于对侧水平方向２０—８０度、垂直方向上下１５度范围内。而成年动物听神经元反应中心的分布则相当集中,局限地分布于对侧水平方向２８－５０度,垂直方向０—１０度范围内,两者构成明显差异。     

Combined genetic and physiological analysis of a locus contributing to quantitative variation

The natural variation of many traits is controlled by multiple genes, individually referred to as quantitative trait loci (QTL), that interact with the environment to determine the ultimate phenotype of any individual. A QTL has yet to be described molecularly, in part because strategies to systematically identify them are underdeveloped and because the subtle nature of QTLs prevents the application of standard methods of gene identification. Therefore, it will be necessary to develop a systematic approach(es) for the identification of QTLs based upon the numerous positional data now being accumulated through molecular marker analyses. We have characterized a QTL by the following three-step approach: (1) identification of a QTL in complex populations, (2) isolation and genetic mapping of this QTL in near-isogenic lines, and (3) identification of a candidate gene using map position and physiological criteria. Using this approach we have characterized a plant height QTL in maize that maps to chromosome 9 near the centromere. Both map position and physiological criteria suggest the gibberillin biosynthesis gene dwarf3 as a candidate gene for this QTL.     

Bioprocessing in space: Human cells attach to beads in microgravity

Attachment to a substrate and survival of human embryonic kidney (HEK) cells have been tested in an incubator installed in the flight-deck of the Space Shuttle ‘Challenger’ during its eighth mission.HEK cells are producing the enzyme urokinase and are presently investigated as candidates for electrophoretic separation in an apparatus developed and manufactured by McDonnell Douglas.Attachment of HEK cells to a substrate is mandatory for survival and production of urokinase after electrophoretic separation.Analysis of the samples shows that cells adhere, spread and survive in microgravity (< 10⁻³ ×g) conditions as well as the ground controls at 1 × g. This result represents an important step towards further bioprocessing in space.     

Activation of microcarrier-attached lymphocytes in microgravity

A technology has been developed to achieve optimal attachment of adhesion-independent lymphocytes to microcarrier beads. The activation of T-lymphocytes by concanavalin A was tested under microgravity conditions in an experiment carried out in space during the first Spacelab Life Science Mission. Activation, measured as the synthesis of deoxyribonucleic acid (DNA) and the production of interferon-gamma, more than doubled in attached lymphocytes in microgravity. The depression of the activation discovered in previous space experiments is due to an impairment not of the lymphocyte but of the macrophage function. The system described here may be useful for radiobiological investigations on the effect of high-energy particles and for testing the efficiency of the immune system in humans during the long-duration space flight planned in the future. The biotechnological significance of the increased lymphokine production in space remains to be assessed.     

Comparative genet survival after fire in woody Mediterranean species

Summary Using data from three fires in northeastern Spain, we tested a condition necessary to support the idea that fire has been a factor in the evolution of the resprouting habit: populations of all resprouting species within a community should show high levels of genet survival after fires and show a low coefficient of variation. Species with high mean survival values were:Quercus ilex L.,Phillyrea latifolia L., andViburnum tinus L., with 88, 86 and 83% survival respectively; these groups had resprouts emerging from rootcrowns. Then followedArbutus unedo L. (75%),Pistacia lentiscus L. (73%),Erica arborea L. (77%),Erica multiflora L. (57%) andJuniperus oxycedrus L. (55%). This last group had resprouts from lignotubers or burls. These two groups also differed in the variability around the mean: the first showed a lower coefficient of variation, 6–12, and the second ranged from 19 to 26. Slope exposure had no significant influence on the process of resprouting, but soil depth did, with precipitation as a covariate. In the shallow soil category, the difference in genet survival between southern and northern exposures was 14% (71% vs. 57%); while the difference in the deep soil category was low, 5% (87% vs. 82%). There was no significant interaction. The component of variance for soils was larger than that for species-specific effects; substantial overlap of the within-species variance indicated that species responded as if they were a single hypothetical population, in which most of the variation in chances of survival was due to the soil conditions. The possession of the resprouting habit did not ensure a high performance. Hence, we find weak support for fire as a factor in the evolution of the resprouting habit.     

Calcaneus secundarius: description and frequency in six skeletal samples

The calcaneus secundarius (CS) is a small accessory ossicle of the anterior calcaneal facet. A sample of 1,367 calcanei including early 20th century U.S. blacks and whites, XIIth Dynasty Egyptians, Islamic Period Bahrainis, and protohistoric American Indians from two states were examined to determine the frequency of this nonmetric trait. Statistical testing of the correlation of the trait with sex could only be performed on the blacks and whites, a documented cadaver collection. Tests of chi 2 indicated that, although sex differences were insignificant, significant group (not necessarily racial or geographical) differences existed at the .05 level. There was no correlation of side dominance in the overall sample, although significant population differences existed. The trait frequencies of the black and white samples were more similar to one another than to the nonindustrial groups who, in turn, were more similar to each other than to the Terry sample. The findings suggest that a CS is of genetic or congenital origin resulting in a secondary center of ossification in the anterior calcaneal facet.     

Separation of metabolic and non-metabolic steps of Rb+ uptake in spring wheat roots with different K+ status

Uptake of Rb⁺ from a complete nutrient solution with 2.0 mM Rb⁺ was studied in roots of spring wheat seedlings ( Triticum aestivum L. cv. Svenno) with different K⁺ levels. The relationship between Rb⁺ uptake and concentration of K⁺ in the roots indicated a negative feedback mechanism operating through allosteric control. The Rb⁺ uptake process in root cells was divided into two steps: (1) binding of the ion in the free space, and (ii) transmembrane transport into the cytoplasm. Metabolic and non-metabolic components of uptake were separated by addition of the metabolic inhibitor 2,4-dinitrophenol (DNP) to the nutrient solution. It is suggested that metabolic Rb⁺ uptake requires energy in two uptake steps (for binding to the carrier entity in the free space and for transmembrane transport) or in one step only (for transmembrane transport), dependent on the K⁺ status of the roots. The change from metabolic to non-metabolic binding in the free space is accomplished by changing the conformational state of the carrier (slow/fast transitions). There may be a hysteretic effect on metabolic Rb⁺ uptake through a slow transition between carrier states. This is superimposed on the negative cooperativity, strengthening further cooperativity at intermediate K⁺ levels in the roots. Non-metabolic Rb⁺ uptake probably consists of two components, a carrier-mediated (facilitated diffusion) and a parallel diffusive component.     

Organization and development of the perivascular space system in the neurohypophysis of the laboratory mouse

Summary The organization of the system of perivascular space around the capillaries in the neurohypophysis was studied in the adult and developing laboratory mouse by the use of histological silver impregnation and electron microscopical techniques.In the median eminence short and long extensions, arising mainly from the shallow space around capillary loops of the primary plexus of the portal system, formed radiations into the adjacent neural tissue of the external zone. The tissue of the neural lobe was separable into non-vascular regions dominated by undilated portions of neurosecretory nerve fibres and pituicytes, and neurovascular regions with perivascular space extensions forming an extensive system of connections between neighbouring capillaries.In the median eminence, the system of extensions of the perivascular space was estimated to increase the neurovascular contact surface area by at least 50%, implying an increased efficiency of the organ without a notable increase of its volume. The possibility that the ramifications of the perivascular space imply an enhanced uptake rate into the bloodstream and a subsequent increased concentration of the neurohormones in the portal blood, was discussed.During development of the median eminence, differentiation of perivascular space extensions of the adult type started in the juvenile of about three weeks of age, when shallow capillary loops had been formed. In the neural lobe, perivascular space ramifications were already present when the internal capillaries were formed and were fairly frequent in ten-day young. At the age of three to four weeks the organization of the system was similar to that of the adult animal.     

Interpersonal relationships and personal space: Research review and theoretical model

This article reviews research concerning interpersonal distance as a function of interpersonal relationships, attraction, and reactions to spatial invasion. To integrate research findings, we propose a simple model, based on the idea that people seek an optimal distance from others that becomes smaller with friends and larger for individuals who do not expect to interact. The model describes comfort-discomfort as a function of interaction distance in three situations: interacting friends, interacting strangers, and strangers who do not expect interaction. These three personal space profiles are discussed in terms of qualifying variables, such as seated vs. standing interaction, sex composition of the dyad, intimacy of conversation topics, and situational variables.A version of the theoretical section of this article was presented at the 82nd annual convention of the American Psychological Association in a symposium entitled Getting Close: Personal Space and Privacy, New Orleans, 1974. An earlier version of the material appears in a book by Irwin Altman (1975).