Analogue of aspartate and glutamate active at synapses are attractants forEscherichia coli

Summary 1. This research was carried out to compareEscherichia coli bacteria with animals in their response tol-aspartate andl-glutamate and their analogues.2. Various analogues of aspartate and glutamate known to be neurotransmitters at synapses were shown to be attractants forE. coli.3. The amino acid sequences of the animal receptors and the bacterial receptor, however, have no detectable relationship. Based on the amino acid sequence, evolutionarily the two systems appear not to be related.     

Nucleocytoplasmic Recycling of the Nuclear Localization Signal Receptor α Subunit In Vivo Is Dependent on a Nuclear Export Signal, Energy, and RCC1

Nuclear protein import requires a nuclear localization signal (NLS) receptor and at least three other cytoplasmic factors. The α subunit of the NLS receptor, Rag cohort 1 (Rch1), enters the nucleus, probably in a complex with the β subunit of the receptor, as well as other import factors and the import substrate. To learn more about which factors and/or events end the import reaction and how the import factors return to the cytoplasm, we have studied nucleocytoplasmic shuttling of Rch1 in vivo. Recombinant Rch1 microinjected into Vero or tsBN2 cells was found primarily in the cytoplasm. Rch1 injected into the nucleus was rapidly exported in a temperature-dependent manner. In contrast, a mutant of Rch1 lacking the first 243 residues accumulated in the nuclei of Vero cells after cytoplasmic injection. After nuclear injection, the truncated Rch1 was retained in the nucleus, but either Rch1 residues 207–217 or a heterologous nuclear export signal, but not a mutant form of residues 207–217, restored nuclear export. Loss of the nuclear transport factor RCC1 (regulator of chromosome condensation) at the nonpermissive temperature in the thermosensitive mutant cell line tsBN2 caused nuclear accumulation of wild-type Rch1 injected into the cytoplasm. However, free Rch1 injected into nuclei of tsBN2 cells at the nonpermissive temperature was exported. These results suggested that RCC1 acts at an earlier step in Rch1 recycling, possibly the disassembly of an import complex that contains Rch1 and the import substrate. Consistent with this possibility, incubation of purified RanGTP and RCC1 with NLS receptor and import substrate prevented assembly of receptor/substrate complexes or stimulated their disassembly.     

Activation of G-Proteins with AlF4Induces LFA-1-Mediated Adhesion of T-Cell Hybridoma Cells to ICAM-1 by Signal Pathways That Differ from Phorbol Ester- and Manganese-Induced Adhesion

T-cell hybridomas metastasize widely, and the extent of dissemination correlates with invasiveness in fibroblast cultures. Previously, we provided evidence that both metastasis andin vitroinvasion require activation of LFA-1, induced by G-protein-transduced signals triggered by as yet unidentified factors. We show here that LFA-1-mediated adhesion of TAM2D2 T-cell hybridoma cells to ICAM-1 can in fact be induced by direct activation of G-proteins using AlF⁻₄, to the same extent as by using PMA or Mn²⁺. We assessed effects of protein kinase C (PKC), tyrosine kinase (TK), PI3-kinase (PI3K), and phospholipase C (PLC) inhibitors. Both AlF⁻₄-induced adhesion and invasion were completely blocked by the TK inhibitor genistein and partially blocked by the PI3K inhibitor wortmannin, but not influenced by PKC inhibitor GF109203X. Downregulation of PKC did not affect invasion or adhesion induced by AlF⁻₄either. In contrast, GF109203X and PKC downregulation blocked PMA-induced adhesion, but genistein and wortmannin had no effect. Invasion and both AlF⁻₄- and PMA-induced adhesion were completely blocked by the PLC inhibitor U73122. Mn²⁺-induced adhesion, which was not or was only partially blocked by the other inhibitors, was delayed by U73122, and spreading of Mn²⁺-treated cells was completely prevented by U73122. However, PLC activity during adhesion was not detected. We conclude that signals required for invasion and G-protein-induced adhesion are similar and are distinct from PKC-induced adhesion, and that in all cases PLC is likely to be activated, but is probably too local and/or transient to be detected.     

Male-female differences in effects of parental absence on glucocorticoid stress response

This study examines the family environments and hormone profiles of 316 individuals aged 2 months-58 years residing in a rural village on the east coast of Dominica, a former British colony in the West Indies. Fieldwork was conducted over an eight-year period (1988–1995). Research methods and techniques include radioimmunoassay of cortisol and testosterone from saliva samples (N=22,340), residence histories, behavioral observations of family interactions, extensive ethnographic interview and participant observation, psychological questionnaires, and medical examinations. Analyses of data indicate complex, sex-specific effects of family environment on endocrine function. Male endocrine profiles exhibit greater sensitivity to presence of father than do female endocrine profiles. Father-absent males tend to have (a) low cortisol levels during infancy, (b) high or abnormal cortisol profiles during childhood and adolescence, and (c) high cortisol and low testosterone levels during adulthood compared with those of males raised with a resident father. These results indicate that early family environment has significant effects on endocrine response throughout male life histories. Mark V. Flinn is an Associate Professor of Anthropology at the University of Missouri, Columbia. He studies family relationships, endocrine stress response, and child health from a mix of evolutionary and developmental psychology perspectives. Robert J. Quinlan is a graduate student in the Department of Anthropology at the University of Missouri, Columbia. His interests include time allocation, family relationships, and medical anthropology. He is planning a long-term ethnographic study of cross-cousin marriage among the E’nyepa of Venezuela. Mark T. Turner is a graduate student in the Department of Anthropology at Northwestern University. He studies covariance of mother and infant hormone and immune function in naturalistic settings using assays from saliva and breast milk samples and ethnographic observations. Seamus A. Decker is a graduate student in the Department of Anthropology at Emory University. He has studied social factors associated with daily variations of salivary cortisol and testosterone levels among males in a Caribbean village. He is currently investigating levels of stress in rural and urban populations in Botswana. Barry G. England is an Associate Professor of Pathology and director of the ligand assay laboratories of the University of Michigan Hospitals. His primary interests concern reproductive endocrinology.     

High lung inflation increases mRNA levels of ECM components and growth factors in lung parenchyma

Berg, John T., Zhenxing Fu, Ellen C. Breen, Hung-Cuong Tran,Odile Mathieu-Costello, and John B. West. High lung inflation increases mRNA levels of ECM components and growth factors in lungparenchyma. J. Appl. Physiol. 83(1):120-128, 1997.Remodeling of pulmonary capillaries occurs afterchronic increases in capillary pressure (e.g., mitral stenosis). Also,remodeling of pulmonary arteries begins within 4 h of increased wallstress and is endothelium dependent. We have previously shown that highlung inflation increases wall stress in pulmonary capillaries. Thisstudy was designed to determine whether high lung inflation inducesremodeling of the extracellular matrix (ECM) in lung parenchyma.Open-chest rabbits were ventilated for 4 h with9-cmH₂O positive end-expiratory pressure (PEEP) on one lung and1-cmH₂O PEEP on the other(High-PEEP group), or with 2-cmH₂OPEEP on both lungs (Low-PEEP group). An additional untreated controlgroup was also included. We found increased levels of mRNA in bothlungs of High-PEEP rabbits (compared with both the Low-PEEP anduntreated groups) for ₁(III)and ₂(IV) procollagen,fibronectin, basic fibroblast growth factor, and transforming growthfactor-₁. In contrast,₂(I) procollagen and vascularendothelial growth factor mRNA levels were not changed. We concludethat high lung inflation for 4 h increases mRNA levels of ECMcomponents and growth factors in lung parenchyma.

     

In vivo validation of whole body composition estimates from dual-energy X-ray absorptiometry

Prior, Barry M., Kirk J. Cureton, Christopher M. Modlesky,Ellen M. Evans, Mark A. Sloniger, Michael Saunders, and Richard D. Lewis. In vivo validation of whole body composition estimates fromdual-energy X-ray absorptiometry. J. Appl.Physiol. 83(2): 623-630, 1997.We validated wholebody composition estimates from dual-energy X-ray absorptiometry (DEXA)against estimates from a four-component model to determine whetheraccuracy is affected by gender, race, athletic status, ormusculoskeletal development in young adults. Measurements of bodydensity by hydrostatic weighing, body water by deuterium dilution, andbone mineral by whole body DEXA were obtained in 172 young men(n = 91) and women(n = 81). Estimates of body fat(%Fat) from DEXA (%Fat_DEXA)were highly correlated with estimates of body fat from thefour-component model [body density, total body water, and totalbody mineral (%Fat_d,w,m);r = 0.94, standard error of theestimante (SEE) = 2.8% body mass (BM)] with no significantdifference between methods [mean of the difference ± SD ofthe difference = 0.4 ± 2.9 (SD) % BM,P = 0.10] in women and men. Onthe basis of the comparison with%Fat_d,w,m, estimates of%Fat_DEXA were slightly moreaccurate than those from body density(r = 0.91, SEE = 3.4%; mean of the difference ± SD of the difference = 1.2 ± 3.4% BM).Differences between %Fat_DEXA and%Fat_d,w,m were weakly related tobody thickness, as reflected by BMI (r = 0.34), and to the percentage of water in the fat-free mass(r = 0.51), but were notaffected by race, athletic status, or musculoskeletal development. Weconclude that body composition estimates from DEXA are accuratecompared with those from a four-component model in young adults whovary in gender, race, athletic status, body size, musculoskeletaldevelopment, and body fatness.

     

Individual constancy of local search strategies in the giant tropical ant,Paraponera clavata (Hymenoptera: Formicidae)

Paraponera clavata workers engage in a period of local search after encountering a small amount of artificial nectar. Giving-up times from local search are not distributed normally; there is a strong skew to longer times. There is no statistically significant relationship between the amount of time required to collect the food and the subsequent search time. Giving-up time in response to the first reward presented to an ant is positively correlated with that ant's response to a second such reward. However, giving-up times diminish when an ant is presented with a series of rewards. Local search is a function of individual strategies, which remain relatively constant in the short term.     

Bifurcations in haploid and diploid sequence space models

 Deterministic models of mutation and selection in the space of (binary) nucleotide-type sequences have been investigated for haploid populations during the past 25 years, and, recently, for diploid populations as well. These models, in particular their ‘error thresholds’, have mainly been analyzed by numerical methods and perturbation techniques. We consider them here by means of bifurcation theory, which improves our understanding of both equilibrium and dynamical properties. In a caricature obtained from the original model by neglecting back mutation to the favourable allele, the familiar error threshold of the haploid two-class model turns out to be a simple transcritical bifurcation, whereas its diploid counterpart exhibits an additional saddle node. This corresponds to a second error threshold. Three-class models with neutral spaces of unequal size introduce further features. Such are a global bifurcation in haploid populations, and simple examples of Hopf bifurcations (as predicted by Akin’s theorem) in the diploid case. Received 13 June 1995; received in revised form 26 July 1996