Photoperiodic time measurement in the spider mite Tetranychus urticae: A novel concept

To explain photoperiodic induction of diapause in the spider mite Tetranychus urticae a new theoretical model was developed which took into account both the hourglass and rhythmic elements shown to be present in the photoperiodic reaction of these mites. It is emphasized that photoperiodic induction is the result of time measurement as well as the summation and integration of a number of successive photoperiodic cycles: the model, therefore, consists of separate ‘clock’ and ‘counter’ mechanisms. In current views involvement of the circadian system in photoperiodism is interpreted in terms of the hypothesis that the photoperiodic clock itself is based on one or more circadian oscillators. Here a different approach has been chosen as regards the role of the circadian system in photoperiodism: the possibility, previously put forward by other authors, that some aspect of the photoperiodic induction mechanism other than the clock is controlled by the circadian system was investigated by assuming a circadian influence on the photoperiodic counter mechanism. The derivation of this ‘hourglass timer oscillator counter’ model of photoperiodic induction in T. urticae is described and its operation demonstrated on the basis of a number of diel and nondiel photoperiods, with and without light interruptions.     

Bone marrow transplantation: current results in leukemia

Bone marrow transplantation offers two potential therapeutic advantages over more conventional therapy of leukemia. It allows more intensive treatment to be given without regard to marrow toxicity and allows in the case of allogeneic marrow an additional immunotherapeutic effect through graft-versus-host disease (GVHD). Initially, allogeneic transplants in HLA matched sibling donors were only employed in end-stage patients. Although there were encouraging results in terms of long-term therapeutic effects, the overall mortality was prohibitive. Subsequently, patients were transplanted in remission with a marked improvement in overall survival in both acute lymphocytic leukemia and acute non-lymphocytic leukemia. The major obstacles to further improvement in the therapeutic effects of this procedure have been identified (i.e., GVHD, viral infection, and relapse in ALL) and are subject to intensive investigations that already show encouraging results. Syngeneic marrow transplantation is limited for obvious reasons, but early results have shown significant therapeutic effects, in particular, in chronic myelogenous leukemia. These results have encouraged others to use autologous bone marrow. Marrow contamination with unseen tumor cells is being approached by pharmacologic and immunologic techniques designed to "purge" marrow of tumor cells. Animal and initial clinical studies have been encouraging.     

Dihydroisocoumarins and phthalide from wood samples infested by fungi

Wood samples, infested by fungi during storage, were shown to contain, besides the known 5-methyl-mellein, additional (3R)-8-hydroxy-3-methyl-3,4-dihydroisocoumarins substituted by 7-methyl, 5-formyl, 5-carboxy, 5-hydroxy, 5-methoxy, 6-methoxy-5-methyl and 6,7-dimethoxy-5-methyl groups, as well as 6-formyl-7-hydroxy-5-methoxy-4-methylphthalide. Several 2-methylchromanones were synthesized in order to show that this class of compounds can be distinguished from 3-methyl-3,4-dihydroisocoumarins by MS.     

The phosphorus efficiency of three annual legumes

Summary Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus were grown in soil and solution culture at varying P concentrations. Efficiency of P utilization was determined using the following criteria: (1) The ability to produce tops dry matter with a given amount of applied P, (2) Tops dry matter produced per unit of P taken up, (3) Tops dry matter produced at a constant plant P level and (4) Phosphorus uptake per unit root weight. The order of efficiency varied according to the crieteria used. Using the agronomic definition (1), Serradella was the most efficient species at 70 days. The need to clearly define what is meant by an efficient species is demonstrated.     

Investigation of human erythrocyte ghost membranes with intramolecular excimer probes

Human erythrocyte ghost membranes have been investigated using two intramolecular excimer probes, di(1-pyrenyl)propane and di(1-pyrenylmethyl) ether. Values for the viscosity of the direct probe environment in the ghost membranes range from 76 cP at 37°C to 570 cP at 5°C, as reported for di(1-pyrenyl)propane, with liquid paraffin as the reference solvent. For the activation energy of the excimer formation process, determined here mainly by the viscosity of the medium, a value of 37 kJ/mol is obtained. The other probe molecule reports a higher local viscosity, 133 cP at 37°C, as well as a higher activation energy of excimer formation, 54 kJ/mol. Neither thermotropic phase transitions nor temperature hysteresis effects are observed within the temperature range (0 to 40°C) studied. From the vibrational structure of the fluorescence spectrum of di(1-pyrenylmethyl) ether, a polarity of the probe environment close to that of hexanol ($\text{? = 13.3}$) results for the erythrocyte ghost membranes. The polarity measured in egg phosphatidylcholine membranes and in multibilayers of dimyristoylphosphatidylcholine is slightly larger, comparable to that of butanol ($\text{? = 17.5}$), whereas a polarity comparable to that of methanol ($\text{? = 32.7}$) is observed for aqueous micellar solutions of sodium dodecyl sulphate. Further, from the wavelength shifts in the absorption spectrum of di(1-pyrenyl)propane and di(1-pyrenylmethyl) ether, the polarizability of the probe surroundings can be determined, leading to a surprisingly high value for the apparent refractive index. This is attributed to a high local density of the direct environment of the probe, for which a location between the membrane/water interface and the unpolar bilayer mid-plane is deduced.     

B-chromosome polymorphism and interchromosomal chiasma interference in Eyprepocnemis plorans (Acrididae; Orthoptera)

Using the C-banding technique, the morphology and meiotic behaviour of four different types of B-chromosomes present in several populations of Eyprepocnemis plorans have been studied. The possible relationship between these four types is discussed. The analysis of chiasma frequency in A and B-chromosomes suggests the existence of interchromosomal interference and demonstrates that the chiasma frequency of B-s depends on the genetic background of the individual carrying them.     

Size dependence of the translational diffusion of large integral membrane proteins in liquid-crystalline phase lipid bilayers. A study using fluorescence recovery after photobleaching

The translational diffusion of bovine rhodopsin, the Ca2+-activated adenosinetriphosphatase of rabbit muscle sarcoplasmic reticulum, and the acetylcholine receptor monomer of Torpedo marmorata has been examined at a high dilution (molar ratios of lipid/protein greater than or equal to 3000/1) in liquid-crystalline phase phospholipid bilayer membranes by using the fluorescence recovery after photobleaching technique. These integral membrane proteins having molecular weights of about 37 000 for rhodopsin, about 100 000 for the adenosinetriphosphatase, and about 250 000 for the acetylcholine receptor were reconstituted into membranes of dimyristoylphosphatidylcholine (rhodopsin and acetylcholine receptor), soybean lipids (acetylcholine receptor), and a total lipid extract of rabbit muscle sarcoplasmic reticulum (adenosinetriphosphatase). The translational diffusion coefficients of all the proteins at 310 K were found to be in the range (1-3) X 10(-8) cm2/s. In consideration of the sizes of the membrane-bound portions of these proteins, this result is in agreement with the weak dependence of the translational diffusion coefficient upon diffusing particle size predicted by continuum fluid hydrodynamic models for the diffusion in membranes [Saffman, P. G., & Delbrück, M. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 3111-3113]. Lipid diffusion was also examined in th same lipid bilayers with the fluorescent lipid derivative N-(7-nitro-2,1,3-benzoxadiazol-4-yl)dimyristoylphosphatidylethanolamine. The translational diffusion coefficient for this lipid derivative was found to be in the range (9-14) X 10(-8) cm2/s at 310 K. In consideration of the dimensions of the lipid molecule, this value for the lipid diffusion coefficient is in agreement with the continuum fluid hydrodynamic model only if a near-complete slip boundary condition is assumed at the bilayer midplane. Alternatively, kinetic diffusion models [Tr?uble, H., & Sackmann. E. (1972) J. Am. Chem. Soc. 94, 4499-4510] may have to be invoked to explain the lipid diffusion behavior.     

NMR redox studies of Desulfovibrio vulgaris Cytochrome c3. Electron transfer mechanisms

The 300-MHz proton NMR spectra of the tetrahaem cytochrome c3 from Desulfovibrio vulgaris were examined while varying the pH and the redox potential. The analysis of the complete NMR reoxidation pattern was done taking into account all the 16 redox states that can be present in the redox titration of a tetra-redox-center molecule. A network of saturation transfer experiments performed at different oxidation stages, between the fully reduced and the fully oxidized states, allowed the observation of different resonances for some of the haem methyl groups. In the present experimental conditions, some of the haems show a fast intramolecular electron exchange rate, but the intermolecular electron exchange is always slow. In intermediate reoxidation stages, large shifts of the resonances of some haem methyl groups were observed upon changing the pH. These shifts are discussed in terms of a pH dependence of the haem midpoint redox potentials. The physiological relevance of this pH dependence is discussed.     

Lysis of human keratinocytes by allogeneic HLA class I-specific cytotoxic T cells. Keratinocyte ICAM-1 (CD54) and T cell LFA-1 (CD11a/CD18) mediate enhanced lysis of IFN-gamma-treated keratinocytes.

Exposure of human KC to IFN-gamma increases their susceptibility to lysis by CTL. The mechanism of this enhanced lysis was investigated by analyzing interactions of IFN-gamma-treated and nontreated cultured KC with allogeneic class I-specific CTL clones. rIFN-gamma treatment augmented KC lysis in a time- and dose-dependent manner. Increased lysis of IFN-KC was detected after only 2 h of IFN-gamma treatment and was maximal by 12 h. Enhanced lysis of IFN-KC was Ag-specific, inasmuch as nonantigenic IFN-KC were not lysed either directly or as bystanders during the lysis of antigenic KC. Parallel immunofluorescence and cytotoxicity assays of KC treated with IFN-gamma for various intervals revealed a direct correlation between the degree of increased KC lysis and levels of cell surface ICAM-1 (CD54), but not of specific alloantigen or beta 2-microglobulin. Lysis of nontreated KC was blocked by mAb against class I or CD3, but not by mAb against ICAM-1 or LFA-1. In contrast, lysis of IFN-KC was partially inhibited by anti-ICAM-1 or anti-LFA-1 mAb, but resisted inhibition by anti-class I mAb except in the presence of anti-ICAM-1. These results indicate that both ICAM-1/LFA-1 and Ag/CD3-TcR interactions are important for Ag-specific lysis of IFN-KC, whereas lysis of nontreated KC depends on Ag/CD3-TcR but not ICAM-1/LFA-1 interactions. Equivalent inhibition of IFN-KC lysis by mAb against ICAM-1 or LFA-1 suggests that ICAM-1 is the only LFA-1 ligand involved in enhanced IFN-KC lysis. Furthermore, enhanced CTL lysis of KC after short-term IFN-gamma treatment can be explained solely on the basis of ICAM-1 induction, because all of the increase in specific lysis associated with IFN-gamma treatment could be blocked by mAb that block ICAM-1/LFA-1 interactions.     

Socioeconomic transition and physical growth of Tupí-Mondê Amerindian children of the Aripuan? Park, Brazilian Amazon

Anthropometric assessment of nutritional status is reported for three Tupí-Mondê-speaking groups from Rond?nia and Mato Grosso, Brazil. This region of the Amazon basin is experiencing rapid development through government-oriented colonization. The Gavi?o, Suruí, and Zoró had their first contacts with Brazilian national society at different times, and the nature and degree of their participation in regional markets varies. Height, weight, sitting height, subischial leg length, upper arm circumference, triceps skin-fold thickness, and upper arm muscle and fat areas are reported for children 0-10.9 years of age. Like other Amazonian Amerindians, Tupí-Mondê children are short for their age but normal or above normal in weight for height with respect to the National Center for Health Statistics reference. Hence stunting levels are high (55.4%) and wasting levels are low (0.8%). There are also deficits in body composition parameters, especially in upper arm circumference and estimated muscle and fat areas. We interpret the results as evidence of suboptimal nutritional status, reflecting the interaction between poor diet and infectious and parasitic diseases. The Gavi?o, with the longest period of contact, present the lowest level of stunting. This finding is attributed to the use of cash income from rubber tapping and nut gathering to purchase of food items and health care. Differences in height between the three groups are mostly due to leg length, instead of sitting height, reinforcing the idea that environmental conditions can alter body proportions.