Analysis of birth intervals in a non-contracepting Indian population: an evolutionary ecological approach

Reproductive strategies are related to ecological constraints. This paper examines data on early birth spacing in a scheduled caste, Bengali-speaking, non-contracepting population of the Karimganj district of southern Assam, India, taking an evolutionary ecological perspective. It is found that on average birth intervals closed by boy-boy are longer than those closed by girl-girl. Birth spacing tends to be longer among upper-income and Craftsman sub-caste mothers. The presence of a 'grandmother' in the household shortens spacing. These findings are compatible with an evolutionary-based reproductive decision-making process.     

Oocyte development in Hydra involves selection from competent precursor cells

We have investigated oocyte development in Hydra vulgaris, a member of one of the oldest metazoan phyla. We show that oocyte determination involves a mechanism that establishes a subset of precursor interstitial cells competent to differentiate into oocytes. The oocyte is singled out from this subset and the competence of the remaining cells to become oocytes dramatically decreases as they adopt the alternative nurse cell fate. Progression through the nurse cell differentiation program requires the presence of the oocyte. When the oocyte is removed from the egg field, nurse cells abort their differentiation program, undergo apoptosis, and are phagocytosed and degraded by somatic epithelial cells. However, in the presence of the oocyte, nurse cells differentiate and enter an unusual apoptosis program where they are phagocytosed by the oocyte, but are not degraded. We show that the oocyte is able to induce this unusual apoptosis program in immature nurse cells that have not completed differentiation. A new model for oocyte development in Hydra is discussed.     

Expression, characterization and structure determination of an active site mutant (Glu202-Gln) of mini-stromelysin-1

Human stromelysin-1 is a member of the matrix metalloproteinase (MMP) family of enzymes. The active site glutamic acid of the MMPs is conserved throughout the family and plays a pivotal role in the catalytic mechanism. The structural and functional consequences of a glutamate to glutamine substitution in the active site of stromelysin-1 were investigated in this study. In contrast to the wild-type enzyme, the glutamine-substituted mutant was not active in a zymogram assay where gelatin was the substrate, was not activated by organomercurials and showed no activity against a peptide substrate. The glutamine-substituted mutant did, however, bind to TIMP-1, the tissue inhibitor of metalloproteinases, after cleavage of the propeptide with trypsin. A second construct containing the glutamine substitution but lacking the propeptide was also inactive in the proteolysis assays and capable of TIMP-1 binding. X-ray structures of the wild-type and mutant proteins complexed with the propeptide-based inhibitor Ro-26-2812 were solved and in both structures the inhibitor binds in an orientation the reverse of that of the propeptide in the pro-form of the enzyme. The inhibitor makes no specific interactions with the active site glutamate and a comparison of the wild-type and mutant structures revealed no major structural changes resulting from the glutamate to glutamine substitution.     

Characteristics of phosphate-induced Ca(2+) efflux from the SR in mechanically skinned rat skeletal muscle fibers

ATP is a candidate enteric inhibitory neurotransmitterin visceral smooth muscles. ATP hyperpolarizes visceral muscles via activation of small-conductance, Ca²⁺-activatedK⁺ (SK) channels. Coupling between ATP stimulation and SKchannels may be mediated by localized Ca²⁺ release.Isolated myocytes of the murine colon produced spontaneous, localizedCa²⁺ release events. These events corresponded tospontaneous transient outward currents (STOCs) consisting ofcharybdotoxin (ChTX)-sensitive and -insensitive events.ChTX-insensitive STOCs were inhibited by apamin. LocalizedCa²⁺ transients were not blocked by ryanodine, but theseevents were reduced in magnitude and frequency by xestospongin C(Xe-C), a blocker of inositol 1,4,5-trisphosphate receptors. Thus wehave termed the localized Ca²⁺ events in colonic myocytes"Ca²⁺ puffs." The P_2Y receptor agonist2-methylthio-ATP (2-MeS-ATP) increased the intensity and frequency ofCa²⁺ puffs. 2-MeS-ATP also increased STOCs in associationwith the increase in Ca²⁺ puffs.Pyridoxal-phospate-6-azophenyl-2',4'-disculfonic acid tetrasodium, aP₂ receptor inhibitor, blocked responses to 2-MeS-ATP. Spontaneous Ca²⁺ transients and the effects of 2-MeS-ATP onCa²⁺ puffs and STOCs were blocked by U-73122, an inhibitorof phospholipase C. Xe-C and ryanodine also blocked responses to2-MeS-ATP, suggesting that, in addition to release from IP₃receptor-operated stores, ryanodine receptors may be recruited duringagonist stimulation to amplify release of Ca²⁺. These datasuggest that localized Ca²⁺ release modulatesCa²⁺-dependent ionic conductances in the plasma membrane.Localized Ca²⁺ release may contribute to the electricalresponses resulting from purinergic stimulation.

     

Nucleocytoplasmic distribution of the ovalbumin serpin PI-9 requires a nonconventional nuclear import pathway and the export factor Crm1.

Proteinase inhibitor 9 (PI-9) is a human serpin present in the cytoplasm of cytotoxic lymphocytes and epithelial cells. It inhibits the cytotoxic lymphocyte granule proteinase granzyme B (graB) and is thought to protect cytotoxic lymphocytes and bystander cells from graB-mediated apoptosis. Following uptake into cells, graB promotes DNA degradation, rapidly translocating to the nucleus, where it binds a nuclear component. PI-9 should therefore be found in cytotoxic lymphocyte and bystander cell nuclei to ensure complete protection against graB. Here we demonstrate by microscopy and subcellular fractionation experiments that PI-9 is present in the nuclei of human cytotoxic cells, endothelial cells, and epithelial cells. We also show that the related serpins, PI-6, monocyte neutrophil elastase inhibitor (MNEI), PI-8, plasminogen activator inhibitor 2 (PAI-2), and the viral serpin CrmA exhibit similar nucleocytoplasmic distributions. Because these serpins lack classical nuclear localization signals and are small enough to diffuse through nuclear pores, we investigated whether import occurs actively or passively. Large (approximately 70 kDa) chimeric proteins comprising PI-9, PI-6, PI-8, MNEI, or PAI-2 fused to green fluorescent protein (GFP) show similar nucleocytoplasmic distributions to the parent proteins, indicating that nuclear import is active. By contrast, CrmA-GFP is excluded from nuclei, indicating that CrmA is not actively imported. In vitro nuclear transport assays show that PI-9 accumulates at a rate above that of passive diffusion, that it requires cytosolic factors but not ATP, and that it does not bind an intranuclear component. Furthermore, PI-9 is exported from nuclei via a leptomycin B-sensitive pathway, implying involvement of the export factor Crm1p. We conclude that the nucleocytoplasmic distribution of PI-9 and related serpins involves a nonconventional nuclear import pathway and Crm1p.     

Characterization of an arylesterase from Lactobacillus helveticus CNRZ32

An esterase gene (estA) was isolated from a previously constructed genomic library of Lactobacillus helveticus CNRZ32. The estA gene consisted of a 558 bp open reading frame encoding a putative peptide of 21.3 kDa. Protein sequence homology searches using BLAST revealed that EstA had low amino acid sequence identity with the serine-dependent arylesterases TesI (24%) and EtpA (26%) from Escherichia coli and Vibrio mimicus, respectively. A recombinant EstA fusion protein containing a C-terminal six-histidine tag was constructed and purified to electrophoretic homogeneity. Characterization of EstA revealed that it was a serine-dependent enzyme having a monomeric Mr of 22.6-25.1 kDa. Optimum temperature, NaCl concentration and pH for EstA activity were determined to be 35-40 degrees C, 3.5% NaCl and 7.5-8.0, respectively. EstA had significant activity under conditions simulating those of ripening cheese (10 degrees C, 4% NaCl, pH 5.1). EstA hydrolysed a variety of ester compounds and preferred those with substituted phenyl alcohol and short-chain fatty acid groups. Site-directed mutagenesis suggested that the S10 and H164 residues were essential for EstA activity.     

Ontogeny and localization of TGF-beta type I receptor expression during lung development

Transforming growth factor (TGF)-beta is a family of multifunctional cytokines controlling cell growth, differentiation, and extracellular matrix deposition in the lung. The biological effects of TGF-beta are mediated by type I (TbetaR-I) and II (TbetaR-II) receptors. Our previous studies show that the expression of TbetaR-II is highly regulated in a spatial and temporal fashion during lung development. In the present studies, we investigated the temporal-spatial pattern and cellular expression of TbetaR-I during lung development. The expression level of TbetaR-I mRNA in rat lung at different embryonic and postnatal stages was analyzed by Northern blotting. TbetaR-I mRNA was expressed in fetal rat lungs in early development and then decreased as development proceeded. The localization of TbetaR-I in fetal and postnatal rat lung tissues was investigated by using in situ hybridization performed with an antisense RNA probe. TbetaR-I mRNA was present in the mesenchyme and epithelium of gestational day 14 rat lungs. An intense TbetaR-I signal was observed in the epithelial lining of the developing bronchi. In gestational day 16 lungs, the expression of TbetaR-I mRNA was increased in the mesenchymal tissue. The epithelium in both the distal and proximal bronchioles showed a similar level of TbetaR-I expression. In postnatal lungs, TbetaR-I mRNA was detected in parenchymal tissues and blood vessels. We further studied the expression of TbetaR-I in cultured rat lung cells. TbetaR-I was expressed by cultured rat lung fibroblasts, microvascular endothelial cells, and alveolar epithelial cells. These studies demonstrate a differential regulation and localization of TbetaR-I that is different from that of TbetaR-II during lung development. TbetaR-I, TbetaR-II, and TGF-beta isoforms exhibit distinct but overlapping patterns of expression during lung development. This implies a distinct role for TbetaR-I in mediating TGF-beta signal transduction during lung development.