Longer Gestation among Children Born Full Term Influences Cognitive and Motor Development

Children born preterm show persisting impairments in cognitive functioning, school achievement, and brain development. Most research has focused on implications of birth prior to 37 gestational weeks; however, the fetal central nervous system continues to make fundamental changes throughout gestation. Longer gestation is associated with reduced morbidity and mortality even among infants born during the period clinically defined as full term (37–41 gestational weeks). The implications of shortened gestation among term infants for neurodevelopment are poorly understood. The present study prospectively evaluates 232 mothers and their full term infants (50.4% male infants) at three time points across the first postnatal year. We evaluate the association between gestational length and cognitive and motor development. Infants included in the study were full term (born between 37 and 41 weeks gestation). The present study uses the combination of Last Menstrual Period (LMP) and early ultrasound for accurate gestational dating. Hierarchical Linear Regression analyses revealed that longer gestational length is associated with higher scores on the Bayley scales of mental and motor development at 3, 6 and 12 months of age after considering socio-demographic, pregnancy, and infant-level covariates. Findings were identical using revised categories of early, term, and late term proposed by the Working Group for Defining Term Pregnancy. Our findings indicate that longer gestation, even among term infants, benefits both cognitive and motor development.     

Fatty acids increase paracellular absorption of aluminium across Caco-2 cell monolayers

Passive paracellular absorption, regulated by tight junctions (TJs), is the main route for absorption of poorly absorbed hydrophilic substances. Surface active substances, such as fatty acids, may enhance absorption of these substances by affecting the integrity of TJ and increasing the permeability. It has been suggested that aluminium (Al) absorption occurs mainly by the paracellular route. Herein, we investigated if physiologically relevant exposures of fully differentiated Caco-2 cell monolayers to oleic acid and docosahexaenoic acid (DHA), which are fatty acids common in food, increase absorption of Al and the paracellular marker mannitol. In an Al toxicity test, mannitol and Al absorption through Caco-2 cell monolayers were similarly modulated by Al concentrations between 1 and 30 mM, suggesting that absorption of the two compounds occurred via the same pathways. Exposure of Caco-2 cell monolayers to non-toxic concentrations of Al (2 mM) and ¹⁴C-mannitol in fatty acid emulsions (15 and 30 mM oleic acid, 5 and 10 mM DHA) caused a decreased transepithelial electrical resistance (TEER). Concomitantly, fractional absorption of Al and mannitol, expressed as percentage of apical Al and mannitol retrieved at the basolateral side, increased with increasing dose of fatty acids. Transmission electron microscopy was applied to assess the effect of oleic acid on the morphology of TJ. It was shown that oleic acid caused a less structured morphology of TJ in Caco-2 cell monolayers. Taken together our findings indicate that fatty acids common in food increase the paracellular intestinal absorption of Al. These findings may influence future risk assessment of human Al exposure.     

Zinc Ions Stabilise the Association of Basic Protein with Brain Myelin Membranes

Myelin basic protein (MBP) dissociated from brain myelin membranes when they were incubated (37 degrees C; pH 7.4) at physiological ionic strength. Zinc ions inhibited, and calcium promoted, this process. Protease activity in the membrane preparations cleaved the dissociated MBP into both small (less than 4 kilodaltons) and large (greater than 8 kilodaltons) fragments. The latter were detected, together with intact MBP, by gel electrophoresis of incubation media. Zinc ions appeared to act in two distinct processes. In the presence or absence of added CaCl2, zinc ions in the range 0.1-1 mM inhibited MBP-membrane dissociation. This process was relatively insensitive to heat and Zn2+ could be substituted by either copper (II) or cobalt (II) ions. A second effect was evident only in the presence of added calcium ions, when lower concentrations of Zn2+ (less than 0.1 mM) inhibited MBP-membrane dissociation and the accumulation of intact MBP in incubation media. This process was heat sensitive and only copper (II), but not cobalt (II), ions could replace Zn2+. To determine whether endogenous zinc in myelin membranes is bound to MBP, preparations were solubilised in buffers containing Triton X-100/2 mM CaCl2 and subjected to gel filtration. Endogenous zinc, as indicated by a dithizone-binding method, eluted with fractions containing both MBP and proteolipid protein (PLP). Thus, one means whereby zinc stabilises association of MBP with brain myelin membranes may be by promoting its binding to PLP.     

Intraspecific host discrimination and larval competition inMicroplitis croceipes,Microplitis demolitor,Cotesia kazak (Hym.: Braconidae) andHyposoter didymator (Hym.: Ichneumonidae), parasitoids ofHeliothis virescens (Lep.: Noctuidae)

Intraspecific host discrimination and larval competition were studied forMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga), andHyposoter didymator (Thunberg), solitary endoparasitoids of the tobacco budworm,Heliothis virescens (F.). In ovipositional choice tests between unparasitized and parasitized hosts, the mean number of ovipositions for unparasitized hosts was significantly higher than the mean number of ovipositions for hosts parasitized once by a conspecific female forC. kazak andH. didymator, demonstrating that females of these 2 species discriminate against hosts recently (within a few seconds) parasitized by a conspecific female. No significant difference in oviposition occurred between these 2 kinds of hosts forM. croceipes andM. demolitor. Mean percent parasitization by a 2^nd conspecific female was determined at 24, 48, and 72-h delays in time between the 1^rst and 2^nd female attack, and with no delay. Except for the 0 h time delay forC. kazak andH. didymator, percent parasitization by a 2^nd conspecific female generally decreased as the delay in time between the 1^rst and 2^nd female attack increased. When the 2^nd parasitization immediately followed the 1^rst, one parasitoid larva always eliminated the other by physical combat. With a 24 or 48 h delay between the 1^rst and 2^nd parasitization, the younger larva was the victor over the older larva forM. croceipes, M. demolitor andC. kazak in at least 50% of the cases. Elimination of older larvae by younger larvae was by physical attack. However, forH. didymator, the older instar was the victor, and elimination of younger larvae by older larvae was probably through physiological processes. Further, older larvae ofH. didymator apparently killed the eggs of the 2^nd female by physiological processes.      

gamma-Glutamyltransferase from Marthasterias glacialis: purification procedures and enzyme characterisation

gamma-Glutamyl transferase has been purified 239-fold from the pyloric caeca of Marthasterias glacialis. It has a mol. wt. of 229,000. The pH optima for the hydrolysis and transfer reactions are 5.0 and 9.2. Novel purification procedures using hydroxyhexyl and aminohexyl derivatives of Sepharose 4B are described. The enzyme was bound by immobilised m-aminophenylboronic acid but not by immobilized concanavalin A.     

Environmental influences on skeletal banding in eastern Pacific (Panama) corals

The timing of skeletal band formation and concomitant changes in calcification rates and linear skeletal extension were investigated in Pavona corals growing under two distinct thermal regimes along the Pacific coast of Panama: fluctuating, marked by seasonal upwelling (Gulf of Panama) and stable, nonupwelling (Gulf of Chiriqui). The purpose of this study was to test the hypothesis that banding in corals is largely mediated by seasonal variations in temperature (Highsmith 1979). Our results indicate that the timing of band formation is synchronous at these two environmentally distinct locations. The low density (LD) portion of the annual band is accreted over a five month period (January–June) and represents an increase in linear skeletal extension (mm/mo.) as well as a marked increase in calcification rate (g CaCO₃ · cm^-2 · mo^-1) relative to the high density portion which forms over the remaining seven month period (July through December). In contrast to the predictions of the Highsmith model these findings indicate that variations in light levels rather than fluctuation in temperature is a better correlate to changes in skeletal density. Qualitatively, banding patterns were similar at the two sites; however, higher growth rates (particularly with respect to the LD band) for Pavona clavus in the Gulf of Panama indicate that lower water temperatures and higher productivity, or both, may be responsible for quantitative differences in banding between sites. We found that formation of the HD band corresponds to lower light levels and the production of gametes. We propose that banding in corals is a complex phenomenon governed by endogenous processes (e.g. reallocation of energy from growth to reproduction) which may be mediated by exogenous factors (e.g light and productivity).     

Basic Protein Dissociating from Myelin Membranes at Physiological Ionic Strength and pH Is Cleaved into Three Major Fragments

Experiments were performed with isolated human myelin membrane preparations to analyse factors that may modulate association of myelin basic protein (MBP) with the membranes and could contribute to demyelinating processes. Transfer of membranes (5 mg protein ml-1) at 37 degrees C and pH 7.4 from a hypotonic medium, in which they were relatively stable, to one of physiological ionic strength produced three major effects: (1) initial dissociation of MBP from the membranes by a nonenzymatic process that was doubled in the presence of millimolar Ca2+/Mg2+; (2) within 10 min, the appearance in the medium of three major MBP fragments (14.4, 10.3, and 8.4 kilodaltons); and (3) progressive acidification of dissociated MBP and its fragments, probably due to deamidation. Between 1 and 6 h a steady state was apparent in which protein equivalent to 15% of the MBP originally bound to the membranes was found in the medium. The three major MBP fragments formed two-thirds of this solubilised material and appeared metabolically stable for 24 h. The kinetics of peptide formation suggested that dissociated, rather than membrane-bound, MBP was cleaved by myelin-associated neutral proteases. Two-dimensional electrophoresis and immunoblotting using two monoclonal antibodies indicated that proteolysis occurred in the vicinity of residues 35 and 75. Evidence was also obtained for removal of C-terminal arginines and relatively rapid deamidation in the C-terminal half of MBP. These modifications of MBP might also occur if extracellular fluid gained access to the compacted cytoplasmic space of the myelin sheath.     

A novel metalloproteinase associated with brain myelin membranes. Isolation and characterization

Brain myelin membrane preparations contain a metalloproteinase activity which degrades myelin basic protein (MBP). The activity was associated with lentil lectin-binding glycoproteins solubilized from myelin and could be detected in the presence of the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS). The metalloproteinase represented about 5% of this glycoprotein fraction and was isolated from it by chromatography on DEAE-Sephacel, CM-Sepharose, and Superose 6. The proteinase had an apparent relative molecular weight (Mr) of approximately 58,000 both by gel filtration and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Mr value was unaffected by the presence of reducing agents but was diminished to about 52,000 by treating the proteinase with endoglycosidase F. The purified proteinase cleaved many bonds in MBP but did not generate trichloroacetic acid-soluble products. Two major polypeptides, putatively MBP1-73 and MBP74-170, were prominent in digests of MBP by either the purified enzyme or myelin membranes. The proteinase was active between pH 7 and 9 and was inhibited by phenanthroline and dithiothreitol but not phosphoramidon or inhibitors of serine or cysteine proteinases. Histones, but not azocasein, also served as substrates for the proteinase. From its enzymic and molecular characteristics the myelin-derived metalloproteinase appears distinct from previously described enzymes.