Andreev bound states at spin-active interfaces

Andreev bound states are ubiquitous in superconducting hybrid structures. They are formed near impurities, in Josephson junctions, in vortex cores and at interfaces. At spin-active superconductor-ferromagnet interfaces, Andreev bound states are formed due to spin-dependent scattering phases. Spin-dependent phase shifts are an important ingredient for the generation of triplet Cooper pairs in superconductor-ferromagnet hybrid structures. Spectroscopy of Andreev bound states is a powerful probe of superconducting order parameter symmetry, as well as spin-dependent interface scattering and the triplet proximity effect.This article is part of the theme issue 'Andreev bound states'.

Why we should have seen that coming

In this paper we examine the case of Tay, the Microsoft AI chatbot that was launched in March, 2016. After less than 24 hours, Microsoft shut down the experiment because the chatbot was generating tweets that were judged to be inappropriate since they included racist, sexist, and anti-Semitic language. We contend that the case of Tay illustrates a problem with the very nature of learning software (LS is a term that describes any software that changes its program in response to its interactions) that interacts directly with the public, and the developer's role and responsibility associated with it. We make the case that when LS interacts directly with people or indirectly via social media, the developer has additional ethical responsibilities beyond those of standard software. There is an additional burden of care.

Engineering Polarons at a Metal Oxide Surface

Polarons in metal oxides are important in processes such as catalysis, high temperature superconductivity, and dielectric breakdown in nanoscale electronics. Here, we study the behavior of electron small polarons associated with oxygen vacancies at rutile TiO_{2}(110), using a combination of low temperature scanning tunneling microscopy (STM), density functional theory, and classical molecular dynamics calculations. We find that the electrons are symmetrically distributed around isolated vacancies at 78 K, but as the temperature is reduced, their distributions become increasingly asymmetric, confirming their polaronic nature. By manipulating isolated vacancies with the STM tip, we show that particular configurations of polarons are preferred for given locations of the vacancies, which we ascribe to small residual electric fields in the surface. We also form a series of vacancy complexes and manipulate the Ti ions surrounding them, both of which change the associated electronic distributions. Thus, we demonstrate that the configurations of polarons can be engineered, paving the way for the construction of conductive pathways relevant to resistive switching devices.

Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions

We report on the experimental observation of spin-dependent thermoelectric currents in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of the particle-hole symmetry, and are found to be in excellent agreement with recent theoretical predictions. The maximum Seebeck coefficient inferred from the data is about -100  μV/K, much larger than commonly found in metallic structures. Our results directly prove the coupling of spin and heat transport in high-field superconductors.

Oxygen vacancies versus fluorine at CeO2(111): a case of mistaken identity?

We propose a resolution to the puzzle presented by the surface defects observed with STM at the (111) surface facet of CeO 2 single crystals. In the seminal paper of Esch et al. [Science 309, 752 (2005)] they were identified with oxygen vacancies, but the observed behavior of these defects is inconsistent with the results of density functional theory (DFT) studies of oxygen vacancies in the literature. We resolve these inconsistencies via DFT calculations of the properties of both oxygen vacancies and fluorine impurities at CeO2(111), the latter having recently been shown to exist in high concentrations in single crystals from a widely used commercial source of such samples. We find that the simulated filled-state STM images of surface-layer oxygen vacancies and fluorine impurities are essentially identical, which would render problematic their experimental distinction by such images alone. However, we find that our theoretical results for the most stable location, mobility, and tendency to cluster, of fluorine impurities are consistent with experimental observations, in contrast to those for oxygen vacancies. Based on these results, we propose that the surface defects observed in STM experiments on CeO2 single crystals reported heretofore were not oxygen vacancies, but fluorine impurities. Since the similarity of the simulated STM images of the two defects is due primarily to the relative energies of the 2p states of oxygen and fluorine ions, this confusion might also occur for other oxides which have been either doped or contaminated with fluorine.

Charge and spin transport in mesoscopic superconductors

BACKGROUND

Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin.

RESULTS

We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models.

CONCLUSION

The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures.

Inflammatory chemokines and metastasis--tracing the accessory

The tumor microenvironment consists of stromal cells and leukocytes that contribute to cancer progression. Cross-talk between tumor cells and their microenvironment is facilitated by a variety of soluble factors, including growth factors and cytokines such as chemokines. Due to a wide expression of chemokine receptors on cells in the tumor microenvironment, including tumor cells, chemokines affect various processes such as leukocyte recruitment, angiogenesis, tumor cell survival, tumor cell adhesion, proliferation, vascular permeability, immune suppression, invasion and metastasis. Inflammatory chemokines are instrumental players in cancer-related inflammation and significantly contribute to numerous steps during metastasis. Recruitment of myeloid-derived cells to metastatic sites is mainly mediated by the inflammatory chemokines CCL2 and CCL5. Tumor cell homing and extravasation from the circulation to distant organs are also regulated by inflammatory chemokines. Recent experimental evidence demonstrated that besides leukocyte recruitment, tumor cell-derived CCL2 directly activated endothelial cells and together with monocytes facilitated tumor cell extravasation, in a CCL2- and CCL5-dependent manner. Furthermore, CX3CL1 expression in the bone facilitated metastasis of CX3CR1 expressing tumor cells to this site. Current findings in preclinical models strongly suggest that inflammatory chemokines have an important role during metastasis and targeting of the chemokine axis might have a therapeutic potential.

Long-range spin-polarized quasiparticle transport in mesoscopic Al superconductors with a Zeeman splitting

We report on nonlocal transport in multiterminal superconductor-ferromagnet structures, which were fabricated by means of e-beam lithography and shadow evaporation techniques. In the presence of a significant Zeeman splitting of the quasiparticle states, we find signatures of spin transport over distances of several μm, exceeding other length scales such as the coherence length, the normal-state spin-diffusion length, and the charge-imbalance length. The relaxation length of the spin signal shows a nearly linear increase with magnetic field, hinting at a freeze-out of relaxation by the Zeeman splitting. We propose that the relaxation length is given by the recombination length of the quasiparticles rather than a renormalized spin-diffusion length.

Validation comparing the effectiveness of a lactic acid dip with a lactic acid spray for reducing Escherichia coli O157:H7, Salmonella, and non-O157 Shiga toxigenic Escherichia coli on beef trim and ground beef

The objective of this research was to compare the effectiveness of two application methods (dip versus spray) of 4.4% lactic acid for reducing pathogens on inoculated beef trim and in ground beef. Beef trim inoculated with cocktail mixtures of E. coli O157:H7, non-O157 Shiga toxigenic E. coli (STEC), or Salmonella (10(5) to 10(6) CFU/g) at separate times was subjected to five treatments: lactic acid spray (LS), lactic acid dip (LD), water spray (WS), water dip (WD), and untreated control (CTL). Intervention effectiveness for pathogen reduction was measured at 1 and 20 h after treatment on beef trim. Trim was then ground and intervention effectiveness was measured 1 h, 24 h, 72 h, and 7 days after grinding. The LD treatment reduced all pathogens significantly (P < 0.05); E. coli O157:H7 was reduced by 0.91 to 1.41 log CFU/g on beef trim and ground beef, non-O157 STEC by 0.48 to 0.82 log CFU/g, and Salmonella by 0.51 to 0.81 log CFU/g. No other treatment significantly reduced any pathogen, although the WD treatment noticeably reduced (P > 0.05) both E. coli O157:H7 and non-O157 STEC populations compared with the CTL. The LS treatment reduced E. coli O157:H7 and Salmonella by up to 0.5 log CFU/g on beef trim, but these reduced counts did not significantly differ (P > 0.05) from the CTL counts. Overall, the LD treatment was most effective for reducing all pathogens and is the best of these options for improving the safety of beef trim and subsequently produced ground beef.

Observation of Andreev bound states at spin-active interfaces

We report on high-resolution differential conductance experiments on nanoscale superconductor-ferromagnet tunnel junctions with ultrathin oxide tunnel barriers. We observe subgap conductance features that are symmetric with respect to bias and shift according to the Zeeman energy with an applied magnetic field. These features can be explained by resonant transport via Andreev bound states induced by spin-active scattering at the interface. From the energy and Zeeman shift of the bound states, both the magnitude and sign of the spin-dependent interfacial phase shifts between spin-up and spin-down electrons can be determined. These results contribute to the microscopic insight into the triplet proximity effect at spin-active interfaces.

Parenting stress in mothers after very preterm birth and the effect of the Infant Behavioural Assessment and Intervention Program

OBJECTIVE

Purpose of this study was to examine maternal parenting stress as a secondary outcome of the Infant Behavioural Assessment and Intervention Program (IBAIP).

METHODS

In a randomized controlled trial 86 very preterm infants and their parents were assigned to the intervention group and 90 to the control group. Maternal parenting stress was assessed with the Dutch version of the Parenting Stress Index at 12 and 24 months post term.

RESULTS

Mothers in the intervention group mothers assessed their infants as happier and less hyperactive/distractible compared with the control group mothers. However, mothers in the intervention group reported more feelings of social isolation.

CONCLUSIONS

The IBAIP appears to have made mothers more satisfied about their infants' mood and distractibility, but also may have evoked more feelings of social isolation. Next to long-term evaluation of the development in very preterm born children, follow-up on functioning of their parents is important.

Development and growth in very preterm infants in relation to NIDCAP in a Dutch NICU: two years of follow-up

AIM

To study development and growth in relation to newborn individualized developmental and assessment program (NIDCAP) for infants born with a gestational age of less than 30 weeks.

METHODS

Developmental outcome of surviving infants, 25 in the NIDCAP group and 24 in the conventional care group, in a prospective phase-lag cohort study performed in a Dutch level III neonatal intensive care unit (NICU) was compared. Main outcome measure was the Bayley scales of infant development-II (BSID-II) at 24 months corrected age. Secondary outcomes were neurobehavioral and developmental outcome and growth at term, 6, 12 and 24 months.

RESULTS

Accounting for group differences and known outcome predictors no significant differences were seen between both care groups in BSID-II at 24 months. At term age NIDCAP infants scored statistically significant lower on neurobehavioral competence; motor system (median [IQR] 4.8 [2.9-5.0] vs. 5.2 [4.3-5.7], p = 0.021) and autonomic stability (median [IQR] 5.7 [4.8-6.7] vs. 7.0 [6.0-7.7], p = 0.001). No differences were seen in other developmental outcomes. After adjustment for background differences, growth parameters were comparable between groups during the first 24 months of life.

CONCLUSION

At present, the strength of conclusions to be drawn about the effect of NIDCAP on developmental outcome or growth at 24 months of age is restricted. Further studies employing standardized assessment approaches including choice of measurement instruments and time points are needed.

Influences on and incentives for increasing software reliability

We contend that software developers have an ethical responsibility to strive for reliable software. We base that obligation on long standing engineering traditions that place the public good as a central tenant and on the professional relationship between a software developer and the users of the software developed.

Neurobehavioral and developmental profile of very low birthweight preterm infants in early infancy

AIM

To describe the neurobehavioral and developmental profile of very low birthweight (VLBW) preterm infants in early infancy.

METHODS

Twenty VLBW infants and 10 term control infants were assessed at term, 3 and 6 mo of age. Neurobehavioral assessments included the Neonatal Behavioral Assessment Scale (NBAS) at term; the Infant Behavioral Assessment at term, 3 and 6 mo of age and the Behavioral Rating Scale of the Bayley Scales of Infant Development-II (BSID-II) at 3 and 6 mo of age. Development was evaluated with the Bayley Motor and Mental Scale at 3 and 6 mo.

RESULTS

At term age VLBW infants differed from term infants on all the clusters and supplementary items of the NBAS. VLBW infants also showed more stress and less approach behavior at term and 6 mo of age and more problems with self-regulation in all subsystems at 6 mo of age. Moreover, VLBW infants performed lower on the Bayley Motor, Mental and Behavioral Rating Scale: 12 VLBW infants scored questionable or non-optimal on the Psychomotor Development Index and 18 questionable or non-optimal on the Behavioral Rating Scale. These results support the need for neurobehavioral intervention of VLBW infants in the first 6 mo of life.

CONCLUSION

Almost all VLBW infants showed non-optimal motor quality behavior at 6 mo and encountered far more problems with self-regulation compared with term infants.

Identification of the calmodulin-binding domain of recombinant calcium-independent phospholipase A2beta. implications for structure and function

Calcium-independent phospholipase A(2) (iPLA(2)) is the major phospholipase A(2) activity in many cell types, and at least one isoform of this enzyme class is physically and functionally coupled to calmodulin (CaM) in a reversible calcium-dependent fashion. To identify the domain in recombinant iPLA(2)beta (riPLA(2)beta) underlying this interaction, multiple techniques were employed. First, we identified calcium-activated CaM induced alterations in the kinetics of proteolytic fragment generation during limited trypsinolysis (i.e. CaM footprinting). Tryptic digests of riPLA(2)beta (83 kDa) in the presence of EGTA alone, Ca(+2) alone, or EGTA and CaM together resulted in the production of a major 68-kDa protein whose kinetic rate of formation was specifically attenuated in incubations containing CaM and Ca(+2) together. Western blotting utilizing antibodies directed against either the N- or C-terminal regions of riPLA(2)beta indicated the specific protection of riPLA(2)beta by calcium-activated CaM at a cleavage site approximately 15 kDa from the C terminus. Moreover, calcium-activated calmodulin increased the kinetic rate of tryptic cleavage near the active site of riPLA(2)beta. Second, functional characterization of products from these partial tryptic digests demonstrated that approximately 90% of the 68-kDa riPLA(2)beta tryptic product (i.e. lacking the 15-kDa C-terminus) did not bind to a CaM affinity matrix in the presence of Ca(2+), although >95% of the noncleaved riPLA(2)beta as well as a 40-kDa C-terminal peptide bound tightly under these conditions. Third, when purified riPLA(2)beta was subjected to exhaustive trypsinolysis followed by ternary complex CaM affinity chromatography, a unique tryptic peptide ((694)AWSEMVGIQYFR(705)) within the 15-kDa C-terminal fragment was identified by RP-HPLC, which bound to CaM-agarose in the presence but not the absence of calcium ion. Fourth, fluorescence energy transfer experiments demonstrated that this peptide (694) bound to dansyl-calmodulin in a calcium-dependent fashion. Collectively, these results identify multiple contact points in the 15-kDa C terminus as being the major but not necessarily the only binding site responsible for the calcium-dependent regulation of iPLA(2)beta by CaM.

TrExML: a maximum-likelihood approach for extensive tree-space exploration

MOTIVATION

Maximum-likelihood analysis of nucleotide and amino acid sequences is a powerful approach for inferring phylogenetic relationships and for comparing evolutionary hypotheses. Because it is a computationally demanding and time-consuming process, most algorithms explore only a minute portion of tree-space, with the emphasis on finding the most likely tree while ignoring the less likely, but not significantly worse, trees. However, when such trees exist, it is equally important to identify them to give due consideration to the phylogenetic uncertainty. Consequently, it is necessary to change the focus of these algorithms such that near optimal trees are also identified.

RESULTS

This paper presents the Advanced Stepwise Addition Algorithm for exploring tree-space and two algorithms for generating all binary trees on a set of sequences. The Advanced Stepwise Addition Algorithm has been implemented in TrExML, a phylogenetic program for maximum-likelihood analysis of nucleotide sequences. TrExML is shown to be more effective at finding near optimal trees than a similar program, fastDNAml, implying that TrExML offers a better approach to account for phylogenetic uncertainty than has previously been possible. A program, TreeGen, is also described; it generates binary trees on a set of sequences allowing for extensive exploration of tree-space using other programs.

AVAILABILITY

TreeGen, TrExML, and the sequence data used to test the programs are available from the following two WWW sites: http://whitetail.bemidji.msus. edu/trexml/and http://jcsmr.anu.edu.au/dmm/humgen.+ ++html.

Acquired microcephaly after low Apgar score in Zimbabwe

Serial head circumference measurements were made on 165 African babies born with a 5 min Apgar score of 5 or less. Measurements were taken at birth and at 4, 9, and 12 months of age. In the majority of infants the onset of microcephaly could be diagnosed as early as 4 months of age. Twenty-five of the 142 infants were microcephalic at 1 year. Neurological development was impaired in 19 of the 25 (76 per cent) microcephalic infants and in 18 of the 117 (15 per cent) normocephalic infants. Fourteen of the 16 (88 per cent) infants with severe quadriplegia developed microcephaly before the age of 4 months. A decreased rate of head growth during the first 4 months of life in African infants born with a low Apgar score correlates closely with the development of microcephaly. Infants with an acquired microcephaly have a high probability of developing neurologic impairment by the age of 1 year. Serial head circumference measurement in low Apgar score babies in developing countries is an easy, simple, and inexpensive method to detect microcephaly.

Neurodevelopmental outcome at 1 year in Zimbabwean neonates with extreme hyperbilirubinaemia

The study concentrates on estimating the magnitude of the effect of a single risk factor, maximum total serum bilirubin (TSB) in excess of 400 micromol/l (23.4 mg/dl), on the neurodevelopmental outcome of 50, singleton, Zimbabwean neonates at 1 year of age. At 1 year corrected age the Bayley Scales of Infant Development (BSID) was administered. Two infants died and five were lost to follow up. TSB was neither associated with birth weight nor with gestational age. Of 43 infants with a TSB > 400 micromol/l (23.4 mg/dl),11(26%) scored abnormal on the BSID at 1 year of age and 5 (12%) infants developed the choreoathetoid type of cerebral palsy.

CONCLUSION

Infants with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) who scored abnormal or suspect on the Bayley Scales of Infant Development were preterm or had haemolytic disease. All term infants without haemolysis and with bilirubin levels between 400 and 500 micromol/l (23.4 mg/dl-29.2 mg/dl) were normal at 1 year of age.

Neurological status in severely jaundiced Zimbabwean neonates

Neurological status was studied in 50 jaundiced infants with a total serum bilirubin of > 400 mumol/l (23.4 mg/dl). Infants were assessed in the neonatal period with the Neonatal Neurological Examination and 4 months of age with the Infant Motor Screen. Twenty-six (52 per cent) infants were premature. Analysis of variance did not show a significant difference between gestational age, birth weight, and maximum total serum bilirubin or between gestational age, birth weight, and neurological optimality score. Based on the presence of abnormal neurological syndromes the infants were classified as normal (n = 27), suspect (n = 11), or abnormal (n = 12). Serum bilirubin levels were higher (p < 0.0001) and the neonatal neurological examination scores lower (p < 0.0001) in the seven (14 per cent) infants who received an exchange transfusion. In the transfused group four out of seven infants and in the non-transfused group seven out of 43 infants were classified as abnormal (p < 0.03). The Neonatal Neurological Examination was shown to be sensitive in detecting neurodevelopmental abnormalities in the neonatal period, with a sensitivity of 83 per cent, specificity of 88 per cent, positive predictive value of 62 per cent, and negative predictive value of 96 per cent.

The predictive value of developmental testing of extremely jaundiced African infants

The predictive value of the Neonatal Neurological Examination (NNE) adapted from Prechtl (1977) and the Infant Motor Screen (IMS) from Nickel (1989) at 4 months was studied in severely jaundiced infants in Zimbabwe. Fifty infants were examined with the NNE, 41 with the IMS and 43 with the Bayley Scales of Infant Development (BSID) (Bayley 1969). Five infants had choreoathetosis and six had a motor delay at age 1 year. The NNE and IMS proved to be sensitive instruments particularly when two infants who became malnourished after the neonatal period were excluded. Logistic regression was used to investigate the relation between the BSID and five selected predictors from the NNE. This resulted in a correct classification of 93%. By using only the predictors acoustic blink and traction response, 80% of the infants were correctly classified but the number of false negatives was reduced from three to one.

Neonatal neurological examination as a predictor of neuromotor outcome at 4 months in term low-Apgar-score babies in Zimbabwe

The predictive value of the neonatal neurological examination (NNE) adapted from Prechtl, was investigated in 139 term Zimbabwean infants born with an Apgar score of five or less at 5 min. At 4 months, seven infants had died and 13 were lost to follow-up, leaving 119 infants to undergo the Infant Motor Screen (IMS). Eighty-eight infants were diagnosed as normal, six as suspect and 25 as abnormal at screening. The sensitivity, specificity, positive predictive value and negative predictive value of the NNE were 94%, 55%, 42% and 96%, respectively. Seventeen (14%) infants had developed microcephaly at 4 months and 13 (77%) of them scored abnormal on the IMS. Twenty-three of the 48 (48%) infants who had convulsions within 48 h of birth, were diagnosed as abnormal (P < 0.0001). The NNE proved to be very sensitive in detecting neurodevelopmental abnormalities in the neonatal period and the five abnormal syndromes derived from the NNE were able to correctly identify 94% of the abnormal infants.

Neurodevelopmental outcome in babies with a low Apgar score from Zimbabwe

The early identification of neurological dysfunction in the neonatal period, the predictive value of single items of the neonatal neurological examination (NNE) adapted from Prechtl and the developmental outcome at 1 year of age in infants with a low Apgar score in Zimbabwe were studied. One hundred and sixty-five infants were examined with the NNE and 142 with the Bayley Scale of Infant Development (BSID) at 1 year of age. Twenty-three infants had cerebral palsy, ten had a motor delay or developmental delay, and four were mentally retarded. The NNE proved to be a sensitive instrument for detecting neurodevelopmental abnormality. Logistic regression analysis was used to investigate the relationship between the BSID and nine selected predictors from the NNE. This resulted in a correct classification of 94%. However, the number of false negatives was high. By using only the variability of movements and fixation as predictors the number of false negatives was reduced to one.

Extreme hyperbilirubinaemia in Zimbabwean neonates: neurodevelopmental outcome at 4 months

As part of a prospective study of severely jaundiced Zimbabwean infants, the relationship between maximum total serum bilirubin (TSB) concentration in the neonatal period and neurodevelopmental outcome at the corrected age of 4 months was studied. Fifty infants with a TSB of > 400 micromol/l (23.4 mg/dl) were enrolled and screened with a neonatal neurological examination (NNE). The cause of jaundice was low birth weight in 22 (44%), ABO incompatability in 8 (16%), sepsis in 8 (16%) and congenital syphilis (6%) in 3 infants. In 9 infants a cause could not be determined. At 4 months, 2 infants had died and 3 were lost to follow up, leaving 45 infants for the infant motor screen (IMS) at 4 months of age. Mean TSB in the neonatal period was 485 micromol/l (28.2 mg/dl), and 7 infants received an exchange transfusion. Mean TSB of the infants with an exchange transfusion was 637 micromol/l (37.2 mg/dl) (range 429-865 micromol/l (25-50.3 mg/dl)) and of the infants without transfusion 459 micromol/l (26.8 mg/dl) (range 400 740 micromol/l (23.4-43 mg/dl)) (P < 0.0001). The TSB was not associated with birth weight, gestational age, gender or head circumference of the baby. On the IMS, 6 of 45 (13.3%) infants scored abnormal, 6 (13.3%) suspect and 33 (73%) scored normal. Three of the six (50%) remaining infants who received an exchange transfusion scored abnormal on the IMS while only 3 of the 39 (8%) infants without exchange transfusion were abnormal.

CONCLUSION

More than 25% of infants with a TSB of > 400 micromol/l (23.4 mg/dl) scored abnormal or suspect at 4 months of age and half of these infants already showed irreversible neurological symptoms. All infants who scored abnormal or suspect on the IMS with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) had haemolytic disease or were premature.

Neurological findings in neonates with low Apgar in Zimbabwe

OBJECTIVES

Document neurological condition of African neonates with a low apgar score.

SETTING

Mpilo Hospital, Bulawayo, Zimbabwe.

SUBJECTS

165 babies with an Apgar score of 5 or less at 5 min.

METHODS

Neurological examination at term age according to Prechtl. Babies were classified as normal, suspect or abnormal and compared with two reference groups, one from Groningen, the Netherlands and one from Grenada in the Caribbean.

RESULTS

A higher number of Zimbabwean babies were delivered by Caesarean section compared to the Groningen group (P < 0.001). Babies delivered by vacuum extraction scored significantly lower compared to babies delivered by Caesarean section (P < 0.003). Twenty abnormal signs derived from the neonatal neurological examination proved to be predictive on the total optimality score (P < 0.001). The number of infants who were classified as abnormal was higher in the Zimbabwean population (P < 0.01).

CONCLUSION

The selected abnormal signs derived from the neonatal neurological examination proved to be highly predictive on the neurological condition. The neonatal morbidity in Zimbabwean neonates with a low Apgar score was higher when compared with two reference groups from Groningen and Grenada.

Glucose-responsitivity and expression of an ATP-stimulatable, Ca(2+)-independent phospholipase A2 enzyme in clonal insulinoma cell lines

We have previously reported that pancreatic islet beta-cells and clonal HIT insulinoma cells express an ATP-stimulatable Ca(2+)-independent phospholipase A2 (ASCI-PLA2) enzyme and that activation of this enzyme appears to participate in glucose-stimulated insulin secretion. To further examine this hypothesis, glucose-responsitivity and expression of ASCI-PLA2 activity in various insulinoma cell lines were examined. Secretagogue-stimulated insulin secretion was observed with beta TC6-f7 and early passage (EP)-beta TC6 cells. In contrast, RIN-m5f, beta TC3, and late passage (LP)-beta TC6 cells exhibited little secretagogue-induced secretion. A haloenollactone suicide substrate (HELSS) which inhibits ASCI-PLA2 activity ablated secretagogue-induced insulin secretion from beta TC6-f7 and EP-beta TC6 cells. All insulinoma cell lines studied expressed both cytosolic and membrane-associated Ca(2+)-independent PLA2 activities which were inhibited by HELSS. The cytosolic enzymatic activity in the glucose-responsive beta TC6-f7 and EP-beta TC6 cells was activated by ATP and protected against thermal denaturation by ATP, but this was not the case in the glucose-unresponsive RIN-m5f, beta TC3, or LP-beta TC6 cells. Comparison of the distribution of Ca(2+)-independent PLA2 activity revealed that membrane-associated activity was higher than cytosolic activity in beta TC6-f7 and EP-beta TC6 cells but not in RIN-m5f, beta TC3, or LP-beta TC6 cells. Insensitivity of cytosolic activity to ATP may prevent association of the PLA2 activity with membrane substrates and contribute to attenuated glucose-responsitivity in the RIN-m5f, beta TC3, or LP-beta TC6 cells. HIT insulinoma cells were also found to undergo a decline in both glucose-responsitivity and membrane-associated Ca(2+)-independent PLA2 activity upon serial passage in culture, and this was associated with a reduction in membrane content of arachidonate-containing phospholipids. These and previous results suggest that the ATP-stimulatable PLA2 enzyme may participate in glucose-induced insulin secretion.

Depletion of intracellular calcium stores activates smooth muscle cell calcium-independent phospholipase A2. A novel mechanism underlying arachidonic acid mobilization

Herein we present multiple lines of evidence which demonstrate that depletion of internal calcium stores is both necessary and sufficient for the activation of calcium-independent phospholipase A2 during arginine vasopressin (AVP)-mediated mobilization of arachidonic acid in A-10 smooth muscle cells. First, AVP-induced [3H]arachidonic acid release was independent of increases in cytosolic calcium yet was decreased by pharmacological inhibition of the release of calcium ion from internal stores. Second, thapsigargin induced the dramatic release of [3H]arachidonic acid from A-10 cells at a similar rate as the AVP-induced release of arachidonic acid, and the release of arachidonic acid by either AVP or thapsigargin was entirely inhibited by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one (BEL). Third, the magnitude of thapsigargin-induced [3H]arachidonic acid release was entirely independent of alterations in cytosolic calcium concentration. Fourth, A23187 resulted in the BEL-inhibitable release of [3H]arachidonic acid from A-10 cells even when ionophore-induced increases in cytosolic calcium were completely prevented by calcium chelators. Fifth, pretreatment of A-10 cells with a calmodulin antagonist (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, HCl) resulted in the time-dependent decrease of subsequent thapsigargin-induced [3H]arachidonic acid release. Collectively, these results identify a novel paradigm which links alterations in calcium homeostasis to the calmodulin-mediated regulation of calcium-independent phospholipase A2 through the depletion of internal calcium stores.

Expression, purification, and kinetic characterization of a recombinant 80-kDa intracellular calcium-independent phospholipase A2

A CHO cell-derived 80-kDa recombinant polypeptide (GenBank number I15470I15470) putatively encoding a calcium-independent phospholipase A2 was expressed in S. frugiperda cells resulting in over a 15-fold increase in a calcium-independent phospholipase A1/A2 activity which was entirely inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. The recombinant polypeptide was purified from cytosol by sequential tandem affinity chromatographies employing ATP-agarose and calmodulin-Sepharose stationary phases. This strategy resulted in the rapid purification (36 h) of recombinant phospholipase A2 activity in 56% overall yield to a single intense 80-kDa protein band on SDS-polyacrylamide gel electrophoresis after silver staining. The purified protein possessed phospholipase A1, phospholipase A2, and lysophospholipase activities. Microbore anion exchange chromatography demonstrated that the 80-kDa protein band was comprised of multiple distinct isoforms including an anionic isoform which possessed over a 5-fold higher specific activity (5 micromol/mg.min) than earlier eluting isoforms. Collectively, these results unambiguously demonstrate that: 1) the 80-kDa polypeptide catalyzes phospholipase A1/A2 and lysophospholipase activities with distinct kinetic parameters; 2) calmodulin and ATP both interact with the catalytic polypeptide independent of regulatory proteins; and 3) distinct isoforms of this polypeptide exist which possess markedly different specific activities.

The calcium-dependent association and functional coupling of calmodulin with myocardial phospholipase A2. Implications for cardiac cycle-dependent alterations in phospholipolysis

Herein we demonstrate the calcium-dependent regulation of myocardial phospholipase A2 activity, which is mediated by a cytosolic protein constituent that can be chromatographically resolved from, and subsequently reconstituted with, purified myocardial phospholipase A2. Purification of this protein by sequential column chromatographies revealed an 18-kDa doublet, which was identified as calmodulin by Western blotting, calcium-dependent precipitation with W-7 agarose beads, and reconstitution of calcium-mediated phospholipase A2 inhibition with authentic homogeneous calmodulin. Calcium-induced calmodulin-mediated inhibition of myocardial phospholipase A2 was titrated by physiologic increments of calcium ion (Kd approximately 200 nM). Moreover, ternary complex affinity chromatography with calmodulin-Sepharose demonstrated that inhibition of myocardial phospholipase A2 activity by calmodulin resulted from the direct interaction of calmodulin with the myocardial phospholipase A2 catalytic complex. Exposure of cultured A-10 muscle cells to three structurally disparate calmodulin antagonists (W-7, trifluoperazine, and calmidazolium) resulted in the robust release of arachidonic acid, which was entirely ablated by pretreatment of cells with (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2-H-tetrahydropyran-2-one. Collectively, this study identifies a novel mechanism whereby latent phospholipase A2 activity can be released from tonic inhibition by alterations in the interactions between the phospholipase A2 catalytic complex, calcium ion, and the intracellular calcium transducer, calmodulin.

Evidence for association of an ATP-stimulatable Ca(2+)-independent phospholipase A2 from pancreatic islets and HIT insulinoma cells with a phosphofructokinase-like protein

Glucose-induced insulin secretion from pancreatic islets requires metabolism of glucose within islet beta-cells, and ATP has attracted interest as a messenger of glucose metabolism within beta-cells. Glucose-induced insulin secretion from islets and HIT insulinoma cells is accompanied by activation of an ATP-stimulatable Ca(2+)-independent phospholipase A2 (ASCI-PLA2) enzyme, the catalytic activity of which resides in a 40 kDa protein. An analogous PLA2 enzyme in myocardium was recently found to consist of a complex of a 40 kDa catalytic protein with a tetramer of an isoform of the glycolytic enzyme phosphofructokinase (PFK). Association of the PFK isoform with the myocardial PLA2 catalytic protein was found to confer ATP sensitivity onto the enzyme complex. Here we demonstrate that the majority of HIT cell and islet ASCI-PLA2 catalytic activity elutes from a gel filtration column in a region corresponding to 400 kDa, suggesting that the 40 kDa beta-cell ASCI-PLA2 catalytic protein exists as part of a larger molecular mass complex. Islet and HIT cell ASCI-PLA2 activities were immunoprecipitated by antibodies directed against PFK, and the immunoprecipitates contained 40 and 85 kDa proteins which correspond to the molecular masses of the PLA2 catalytic protein and of a PFK monomer, respectively. Islet and HIT cell ASCI-PLA2 activities were selectively and reversibly adsorbed to affinity matrices containing immobilized PFK but not to similar matrices containing immobilized transferrin or bovine serum albumin. Addition of free PFK prevented binding of HIT cell ASCI-PLA2 activity to immobilized PFK matrices and promoted desorption of activity previously bound to such matrices. These results suggest that beta-cell ASCI-PLA2, like the myocardial enzyme, exists as a complex comprised of a catalytic protein and a PFK-like protein and raise the possibility that the ASCI-PLA2 complex may represent a component of the beta-cell glucose sensor, which links glycolysis, phospholipid hydrolysis, and membrane electrochemical events involved in glucose-induced insulin secretion.

Long-term potentiation requires activation of calcium-independent phospholipase A2

The predominant phospholipase activity present in rat hippocampus is a calcium-independent phospholipase A2 (302.9 +/- 19.8 pmol/mg.min for calcium-independent phospholipase A2 activity vs. 14.6 +/- 1.0 pmol/mg.min for calcium-dependent phospholipase A2 activity). This calcium-independent phospholipase A2 is exquisitely sensitive to inhibition by the mechanism-based inhibitor, (E)-6-(bromomethylene)-tetrahydro-3-(1-naphthalenyl)-2H-pyran -2-one (BEL). Moreover, treatment of hippocampal slices with BEL prior to tetanic stimulation prevents the induction of LTP (40.8 +/- 5.6% increase in excitatory post-synaptic potential (EPSP) slope for control slices (n = 6) vs. 5.8 +/- 8.5% increase in EPSP slope for BEL-treated slices (n = 8)). Importantly, LTP can be induced following mechanism-based inhibition of phospholipase A2 by providing the end product of the phospholipase A2 reaction, arachidonic acid, during the application of tetanic stimulation. Furthermore, the induction of LTP after treatment with BEL is dependent on the stereoelectronic configuration of the fatty acid provided since eicosa-5,8,11-trienoic acid, but not eicosa-8,11,14-trienoic acid, rescues LTP after BEL treatment (37.6 +/- 16.1% increase in EPSP slope for eicosa-5,8,11-trienoic acid vs. -3.7 +/- 5.2% increase in EPSP slope for eicosa-8,11,14-trienoic acid). Collectively, these results provide the first demonstration of the essential role of calcium-independent phospholipase A2 in synaptic plasticity.

The effects of glucagon-like peptide-I (GLP-I) on hormone secretion from isolated human pancreatic islets

Glucagon-like peptide-I (GLP-I) is a potent incretin hormone that is now considered as a new therapeutic tool in the treatment of diabetes mellitus. In this study we characterized the effects of GLP-I on peptide hormone release from isolated human pancreatic islets. GLP-I stimulated insulin release in the presence of 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 166%; 10 mM glucose + 10 nM GLP-I, 222%) but had only a weak insulinotropic effect (128%) at 2.8 mM glucose. Glucagon release was inhibited by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 72%) and by 10 nM GLP-I at 2.8 mM glucose (67%). Somatostatin secretion was increased by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 166%). GLP-I stimulated somatostatin release in the presence of 2.8 mM glucose (172%). Pancreatic polypeptide (PP) secretion was enhanced by 10 mM glucose (2.8 mM glucose, 100%; 10 mM glucose, 236%). GLP-I induced PP release only in the presence of 2.8 mM glucose (184%).

Nitric oxide activates the glucose-dependent mobilization of arachidonic acid in a macrophage-like cell line (RAW 264.7) that is largely mediated by calcium-independent phospholipase A2

Herein, we demonstrate that nitric oxide is a potent (> 20% release) and highly selective inducer of [3H]arachidonic acid mobilization in the macrophage-like cell line RAW 264.7. Treatment of RAW 264.7 cells with (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one resulted in the inhibition of the large majority (86%) of nitric oxide-induced [3H]arachidonic acid release into the medium (IC50 < 0.5 microM) and the concomitant inhibition of in vitro measurable calcium-independent phospholipase A2 activity (92% inhibition) without demonstrable effects on calcium-dependent phospholipase A2 activity. Since nitric oxide is a potent stimulator of glycolysis (and therefore glycolytically derived ATP) and since cytosolic calcium-independent phospholipase A2 exists as a catalytic complex comprised of ATP-modulated phosphofructokinase-like regulatory polypeptides and a catalytic subunit, we examined the role of glucose in facilitating nitric oxide-mediated arachidonic acid release. Nitric oxide-induced release of [3H]arachidonic acid possessed an obligatory requirement for glucose, was highly correlated with the concentration of glucose in the medium, and was dependent on the metabolism of glucose. Thus, [3H]arachidonic acid release is coupled to cellular glucose metabolism through alterations in the activity of calcium-independent phospholipase A2. Collectively, these results identify a unifying metabolic paradigm in which the generation of lipid second messengers is coordinately linked to the signalstimulated acceleration of glycolytic flux, thereby facilitating integrated metabolic responses to cellular stimuli.

Characterization of an ATP-stimulatable Ca(2+)-independent phospholipase A2 from clonal insulin-secreting HIT cells and rat pancreatic islets: a possible molecular component of the beta-cell fuel sensor

Isolated pancreatic islets from rats and humans express a plasmalogen-preferring ATP-stimulatable, Ca(2+)-independent phospholipase A2 (ASCI-PLA2) enzyme which participates in the glucose-stimulated hydrolysis of arachidonate from membrane phospholipids and in insulin secretion. Here we report that clonal insulin-secreting HIT beta-cells contain substantial amounts of endogenous plasmalogens and express a similar ASCI-PLA2 activity with the following properties: (1) Enzymatic activity as well as glucose-induced eicosanoid release and insulin secretion are inhibited by a mechanism-based suicide substrate directed towards ASCI-PLA2. (2) HIT cell ASCI-PLA2 is selectively activated and protected against thermal denaturation by ATP. (3) The magnitude of ASCI-PLA2 activation by the nonhydrolyzable ATP analog AMP-PCP is similar to that by ATP. (4) The ATP concentrations required to activate ASCI-PLA2 fall within physiologic ranges in the presence of Mg2+. (5) ADP induces a concentration-dependent attenuation of the activation of ASCI-PLA2 by ATP. HIT cell ASCI-PLA2 exhibited an apparent isoelectric point of 7.5 on chromatofocusing analysis and was quantitatively adsorbed to an ATP-agarose matrix and selectively desorbed from this column by ATP. Mono-Q anion-exchange analysis of the active ATP-agarose eluant yielded a peak of ASCI-PLA2 activity associated with a single protein band with an apparent molecular mass of 40 kDa. Similar chromatographic behavior of the rat pancreatic islet ASCI-PLA2 activity was observed during sequential ATP-agarose and Mono-Q anion-exchange steps. These results indicate that HIT cells express an ASCI-PLA2 similar to the analogous islet enzyme and suggest that expression of this enzyme and of its preferred plasmalogen substrates may be a general property of insulin-secreting beta-cells.

The rapid and reversible association of phosphofructokinase with myocardial membranes during myocardial ischemia

Myocardial calcium-independent phospholipase A2 (PLA2) activity is mediated by a 400 kDa catalytic complex comprised of a tetramer of phosphofructokinase (PFK) and a 40 kDa catalytic subunit [1,2]. During myocardial ischemia, calcium-independent PLA2 activity rapidly and reversibly translocates from the cytosol to a membrane-associated compartment where it has been implicated as a mediator of ischemic damage [3,4]. Herein we demonstrate that the majority of both PFK mass and activity is translocated from the cytosol to a membrane-associated compartment prior to the onset of irreversible myocytic injury and that translocated PFK is catalytically inactive while membrane-associated. Furthermore, reperfusion of ischemic myocardium, or treatment of membranes derived from ischemic myocardium with ATP results in the conversion of both PFK mass and activity from its membrane-associated state to a soluble, catalytically-competent form. Collectively, these studies demonstrate that the concomitant changes in glycolysis and phospholipid hydrolysis during early myocardial ischemia result, at least in part, from the translocation of a common regulatory polypeptide critical in both processes.

Golgi-enriched membrane fractions from rat brain and liver contain long-chain polyisoprenyl pyrophosphate phosphatase activity

The subcellular distribution of polyisoprenyl pyrophosphate phosphatase activity has been examined in rat brain by assaying the release of 32Pi from [beta-32P]dolichyl pyrophosphate (Dol-P-P) as described previously (Scher,M.G. and Waechter, C.J. (1984) J. Biol. Chem., 259, 14580-14585). The highest specific activities of Dol-P-P phosphatase in rat brain were found in the Golgi-enriched light microsomal, synaptic plasma membrane and heavy microsomal fractions. A comparative analysis of the distribution of galactosyltransferase and dolichol kinase reveals that Dol-P-P phosphatase activity co-fractionates with galactosyltransferase activity, and that the high level found in the Golgi-enriched fraction is not due to cross-contamination with heavy microsomes. When beta-labelled C95 Dol-P-P and the C95 allylic polyisoprenyl pyrophosphate (Poly-P-P) were compared as substrates for the Golgi-enriched light microsomal and heavy microsomal fractions, similar Km values were calculated for the two pyrophosphorylated substrates for each membrane fraction. Based on these kinetic analyses, the enzyme(s) catalysing this reaction do not distinguish between substrates containing saturated or allylic alpha-isoprene units. When Dol-P-P phosphatase activity was assessed in submicrosomal fractions obtained from rat liver by two separate procedures, the highest specific activity was also detected in the Golgi-enriched fraction. While the specific activities for Dol-P-P phosphatase and sialyltransferase were in the relative order of Golgi greater than smooth endoplasmic reticulum (ER) greater than rough ER, the relative order of dolichol kinase was rough ER greater than smooth ER greater than Golgi.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes in enzymes involved in dolichyl phosphate metabolism in cultured embryonic rat brain cells

The rates of synthesis of dolichol-linked oligosaccharide intermediates and protein N-glycosylation increased substantially during a developmental period corresponding to glial differentiation in primary cultures of embryonic rat brain. In this study developmental changes in three enzymes involved in dolichyl phosphate (Dol-P) metabolism have been examined by in vitro assays and correlated with the induction pattern for lipid intermediate synthesis and protein N-glycosylation. Dolichyl pyrophosphate (Dol-P-P) phosphatase activity was relatively low during the first 9 days in culture, but it increased significantly between days 9 and 25. Dol-P-P phosphatase did not change appreciably between days 22 and 30 in culture. A kinetic analysis of the developmental change in Dol-P-P phosphatase activity revealed that the Vmax increased 10-fold between days 4 and 22, and there was also a significant change in the apparent Km for Dol-P-P. Dolichol kinase activity increased during the period (9-15 days) when there was a significant induction in oligosaccharide-lipid synthesis and protein N-glycosylation, and then declined in parallel with lipid intermediate synthesis and protein N-glycosylation. Dol-P phosphatase activity was present at relatively low levels for the first 9 days in culture, but it increased steadily between days 9 and 30. A kinetic comparison of the activity in membrane fractions from brain cells cultured for 9 and 25 days indicated that there was a 10-fold increase in enzyme protein with unaltered affinity for Dol-P.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship marketing: positioning for the future

This year, almost 4 million expectant mothers will receive personalized letters about infant care from a disposable diaper manufacturer. A leading manufacturer of hair coloring products will send trial samples to regular users of competing brands. And at supermarkets across the country, shoppers will watch personalized advertisements for cookies, toothpaste, and coffee at checkout counters equipped with video screens. In these instances and countless others, advertisers are finding new ways to communicate with their customers that capitalize on and leverage the long‐term relationship between the advertiser and consumer.

Synthesis and properties of 5-azido-UDP-glucose. Development of photoaffinity probes for nucleotide diphosphate sugar binding sites

A new active site directed photoaffinity probe, which is a model compound for studying nucleotide diphosphate sugar binding proteins, has been synthesized by coupling 5-azido-UTP and [32P]Glc-1-P using yeast UDP-glucose pyrophosphorylase to produce [beta-32P]5-azidouridine 5'-diphosphoglucose (5N3UDP-Glc). This probe has photochemical properties similar to that of 5-azidoUTP (Evans, R. K., and Haley, B. E. (1987) Biochemistry 26, 269-276). The efficacy of 5N3UDP-Glc as an active site directed probe was demonstrated using yeast UDP-Glc pyrophosphorylase. Saturation effects of photoinsertion were observed with an apparent Kd of 51 microM and the natural substrate, UDP-Glc, prevented photoinsertion of [beta-32P]5N3UDP-Glc with an apparent Kd of 87 microM. Prevention of photoinsertion was also seen with UTP and pyrophosphate with apparent Kd values less than 200 microM. UMP, UDP, ATP, and GTP were much less effective competitors. Selective photoinsertion was observed with several partially purified enzymes including UDP-Glc dehydrogenase, UDP-Gal-4-epimerase, Gal-1-P uridyltransferase, and phosphorylase a. The absence of nonselective photoinsertion into bulk proteins was demonstrated with crude homogenates of rabbit liver as well as with several UDP-Glc binding proteins. Of the six purified enzymes tested, only phosphoglucomutase has been shown to incorporate radiolabel from the photoprobe in the absence of UV irradiation. These results and a discussion of the utility of 5N3UDP-Glc for detecting UDP-Glc binding proteins and isolating active site peptides are presented.

Subcellular Structure of Endosperm Protein in High-Lysine and Normal Corn

Optical microscopy shows that the protein network in endosperm cells of normal corn is composed of an amorphous matrix in which granules averaging about 2 microns in diameter are embedded. That these granules are rich in zein is demonstrated by their solubility in 80 percent ethanol. High-lysine corn, with submicroscopic granules clearly resolved only in the electron microscope, has a much lower content of zein than normal corn. The small size of subcellular protein granules in high-lysine maize as compared with normal corn correlates with the reported difference in zein content of the two types of corn.