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Recent findings revealed a correlation between vertebral bone quality based on T1-weighted (VBQThe aims of the study were to confirm the correlation between VBQThis was a retrospective cross-sectional study.The sample consisted of patients older than 18 years, who received treatment at a level-one university spine center of the German Spine Society for degenerative or traumatic reasons in 2017-2021.The outcome measures were the correlation of VBQs from different MRI sequences with vBMD and the association of VBQs with osteopenia/osteoporosis.Patients' VBQ was calculated based on the signal intensities of the vertebral bodies L1-4 in T1-, T2-, and STIR-weighted MRI. The VBQ was standardized according to the signal intensity of the cerebrospinal fluid. The vBMD was determined using data from a calibrated scanner (SOMATOM Definition AS+) and processed with CliniQCT (Mindways Software, Inc., USA). Groups were divided according to vBMD into the following groups: (I) osteoporosis/osteopenia (120 mg/mWe included 136 patients (women: 56.6%) in the study (69.7 ± 15.0 years). According to vBMD, 108 patients (79.4%) had osteoporosis/osteopenia. Women were affected significantly more often than men (p = .045) and had significantly higher VBQThis study confirms a significant correlation between VBQ

Osteosynthesis of the acetabulum is complex and requires very careful planning and preoperative preparation. The goal is to achieve anatomical reduction without steps or gaps in the articular surface. If it has not been possible to achieve an optimal reconstruction, one has to consider whether it makes sense to carry out reosteosynthesis or revise the fixation. The risk of infection, heterotopic ossification, avascular necrosis of the femur and cartilage damage is much higher than with the primary procedure. Often, especially in older patients, it may make more sense to achieve fracture union and to implant a total hip prosthesis in due course. In younger patients, every attempt should be made to achieve optimum anatomical reduction and this may mean consideration of reosteosynthesis after careful planning and counselling of the patient. If reosteosynthesis is considered adequate imaging including a postoperative CT is essential as part of the planning. This article looks at the possible solutions for failed osteosynthesis of the acetabulum.

The impact of the pandemic on the UK labour market has been extremely heterogeneous across occupations and industries. Using novel data on job search, we document how individuals adjust their job search in response to changing employment patterns across occupations and industries in the UK. We observe that workers changed their search direction in favour of expanding occupations and industries as the pandemic developed. However, non-employed workers are more attached to their previous occupations and workers with low education are more likely to target declining occupations. We also observe workers from declining occupations making fewer transitions to expanding occupations than those who start in expanding occupations, despite targeting these jobs relatively frequently. This suggests those at the margins of the labour market may be least able to escape occupations that declined during the pandemic.

Purpose: To evaluate the feasibility and accuracy of a radiation-free implantation of a thoracic aortic stent graft employing fiberoptic and electromagnetic tracking in an anthropomorphic phantom. Materials and Methods: An anthropomorphic phantom was manufactured based on computed tomography (CT) angiography data from a patient. An aortic stent graft application system was equipped with a fiber Bragg gratings and 3 electromagnetic sensors. The stent graft was navigated in the phantom by 3 interventionalists using the tracking data generated by both technologies. One implantation procedure was performed. The technical success of the procedure was evaluated using digital subtraction angiography and CT angiography (before and after the intervention). Tracking accuracy was determined at various anatomical landmarks based on separately acquired fluoroscopic images. The mean/maximum errors were measured for the stent graft application system and the tip/end of the stent graft. Results: The procedure resulted in technical success with a mean error below 3 mm for the entire application system and

In spite of the strong relevance of electrochemical energy conversion and storage, the atomistic modeling of structures and processes in electrochemical systems from first principles is hampered by severe problems. Among others, these problems are associated with the theoretical description of the electrode potential, the characterization of interfaces, the proper treatment of liquid electrolytes, changes in the bulk structure of battery electrodes, and limitations of the functionals used in first-principles electronic structure calculations. We will illustrate these obstacles, but also indicate strategies to overcome them.

SummaryTo unravel the evolutionarily conserved genetic network underlying energy homeostasis, we performed a systematic in vivo gene knockdown screen in Drosophila. We used a transgenic RNAi library enriched for fly orthologs of human genes to functionally impair about half of all Drosophila genes specifically in adult fat storage tissue. This approach identified 77 genes, which affect the body fat content of the fly, including 58 previously unknown obesity-associated genes. These genes function in diverse biological processes such as lipid metabolism, vesicle-mediated trafficking, and the universal store-operated calcium entry (SOCE). Impairment of the SOCE core component Stromal interaction molecule (Stim), as well as other components of the pathway, causes adiposity in flies. Acute Stim dysfunction in the fat storage tissue triggers hyperphagia via remote control of the orexigenic short neuropeptide F in the brain, which in turn affects the coordinated lipogenic and lipolytic gene regulation, resulting in adipose tissue hypertrophy.

Objectives The aim of this study was to assess the outcomes of patients at prohibitive surgical risk undergoing MitraClip therapy (Abbott Vascular, Redwood City, California) for severe mitral regurgitation (MR). Background The safety of percutaneous mitral valve repair has been documented. However, midterm development of mitral valve function, ventricular remodeling, and clinical outcomes in patients not amenable to surgery are unknown. Methods A total of 104 consecutive patients (mean age 74 ± 9 years; 64 men; 49 and 54 with MR 3+ and 4+, respectively; 69 with functional MR; 59 and 45 in New York Heart Association classes III and IV, respectively) were followed for a median of 359 days. Results Device success was achieved in 96 patients (92%). In patients with successful index procedures, MR grade ≤2+ was present at follow-up in 82.5%, left ventricular end-diastolic and -systolic volumes were reduced, and forward stroke volumes were significantly increased. Improvements in New York Heart Association functional class were observed in 80% of patients, with 69% in class I or II; 75% improved in the 6-min walk test; and 74% reported improvements in quality of life. One-year estimates of mortality and rehospitalization were 22% and 31%, respectively. Forward stroke volume at discharge emerged as a predictor of event-free survival. Conclusions MitraClip therapy improves clinical and echocardiographic outcomes at 1 year in about three-quarters of critically ill, elderly patients with moderate to severe MR not amenable to surgery.

SummaryLipid droplets are intracellular organelles enriched in adipose tissue that govern the body fat stores of animals. In mammals, members of the evolutionarily conserved PERILIPIN protein family are associated with the lipid droplet surface and participate in lipid homeostasis. Here, we show that Drosophila mutants lacking the PERILIPIN PLIN1 are hyperphagic and suffer from adult-onset obesity. PLIN1 is a central and Janus-faced component of fat metabolism. It provides barrier function to storage lipid breakdown and acts as a key factor of stimulated lipolysis by modulating the access of proteins to the lipid droplet surface. It also shapes lipid droplet structure, transforming unilocular into multilocular fat cells. We generated flies devoid of all PERILIPIN family members and show that they exhibit impaired yet functional body fat regulation. Our data reveal the existence of a basal and possibly ancient lipid homeostasis system.

Human mitogen-activated protein kinases (MAPK)-interacting kinases 1 and 2 (Mnk1 and Mnk2) target the translational machinery by phosphorylation of the eukaryotic initiation factor 4E (eIF4E). Here, we present the 2.1 A crystal structure of a nonphosphorylated Mnk2 fragment that encompasses the kinase domain. The results show Mnk-specific features such as a zinc binding motif and an atypical open conformation of the activation segment. In addition, the ATP binding pocket contains an Asp-Phe-Asp (DFD) in place of the canonical magnesium binding Asp-Phe-Gly (DFG) motif. The phenylalanine of this motif sticks into the ATP binding pocket and blocks ATP binding as observed with inhibitor bound and, thus, inactive p38 kinase. Replacement of the DFD by the canonical DFG motif affects the conformation of Mnk2, but not ATP binding and kinase activity. The results suggest that the ATP binding pocket and the activation segment of Mnk2 require conformational switches to provide kinase activity.

SummaryEnergy homeostasis, a fundamental property of all organisms, depends on the ability to control the storage and mobilization of fat, mainly triacylglycerols (TAG), in special organs such as mammalian adipose tissue or the fat body of flies. Malregulation of energy homeostasis underlies the pathogenesis of obesity in mammals including human. We performed a screen to identify nutritionally regulated genes that control energy storage in the model organism Drosophila. The brummer (bmm) gene encodes the lipid storage droplet-associated TAG lipase Brummer, a homolog of human adipocyte triglyceride lipase (ATGL). Food deprivation or chronic bmm overexpression depletes organismal fat stores in vivo, whereas loss of bmm activity causes obesity in flies. Our study identifies a key factor of insect energy homeostasis control. Their evolutionary conservation suggests Brummer/ATGL family members to be implicated in human obesity and establishes a basis for modeling mechanistic and therapeutic aspects of this disease in the fly.

We report the identification of Ima, a novel Drosophila MAGUK-like protein, which contains two WW and four PDZ protein interaction domains and interacts with the small GTPase dRal in the yeast two-hybrid system and pull-down assays. The gene is expressed in distinct spatiotemporal patterns throughout embryonic development. Overexpression of Ima interferes with normal Drosophila development, indicating that the gene functions in a tissue specific manner.

Three cDNAs encoding inwardly rectifying potassium (Kir) channels were isolated from Drosophila melanogaster. The protein sequences of DrosophilaKirI (dKirI) and dKirII are moderately (

Defense against oxidative stress in mammals includes the regeneration of the major thiol reductants glutathione and thioredoxin by glutathione reductase and thioredoxin reductase (TrxR), respectively. In contrast, Drosophila, and possibly insects in general, lacks glutathione reductase and must rely solely on the TrxR system. The mammalian TrxRs described so far are selenoproteins that utilize NADPH to reduce protein as well as nonprotein substrates in mitochondria and cytoplasm of cells. We show that a single Drosophila gene, Trxr-1, encodes non-selenocysteine-containing cytoplasmic and mitochondrial TrxR isoforms that differ with respect to their N termini. We generated transcript-specific mutants and used in vivo approaches to explore the biological functions of the two enzyme variants by introducing the corresponding transgenes into different Trxr-1 mutants. The results show that, although the two TrxR isoforms have similar biochemical properties, their biological functions are not interchangeable.

Annexins are a family of calcium-dependent phospholipid-binding proteins, which have been implicated in a variety of biological processes including membrane trafficking. The annexin 6/lgp120 prelysosomal compartment of NRK cells was loaded with low-density lipoprotein (LDL) and then its transport from this endocytic compartment and its degradation in lysosomes were studied. NRK cells were microinjected with the mutated annexin 6 (anx6(1-175)), to assess the possible involvement of annexin 6 in the transport of LDL from the prelysosomal compartment. The results indicated that microinjection of mutated annexin 6, in NRK cells, showed the accumulation of LDL in larger endocytic structures, denoting retention of LDL in the prelysosomal compartment. To confirm the involvement of annexin 6 in the trafficking and the degradation of LDL we used CHO cells transfected with mutated annexin 6(1-175). Thus, in agreement with NRK cells the results obtained in CHO cells demonstrated a significant inhibition of LDL degradation in CHO cells expressing the mutated form of annexin 6 compared to controls overexpressing wild-type annexin 6. Therefore, we conclude that annexin 6 is involved in the trafficking events leading to LDL degradation.

The dependence on system size of self-diffusion in a dense binary liquid of hard spheres was studied by molecular dynamics simulation of two systems with 216 and 5832 particles. The ratio of particle radii is α=0.85. The relative difference between the self-diffusion coefficients Ds for both system sizes increases from 11% to 18% as the packing fraction φ is increased from 0.533 to 0.563. The relation between the size dependence of Ds and the underlying size dependence of the velocity-autocorrelation function (VAF) was studied in detail for φ=0.548. For intermediate and long times the difference Δψ(t) of the VAFs for the two sizes is well reproduced by the mode-coupling formula expressing the coupling of self-diffusion to modes of collective flow. However, the short-time part of Δψ(t) is equally important. A simpler relation was found between the size dependence of Ds and that of the memory function M(t) associated with the VAF. M(t) is larger and decays more slowly for the smaller systems, which leads to the observed size dependence of Ds.

The molecular mechanisms underlying axonal pathfinding are not well understood. In a genetic screen for mutations affecting the projection of the larval optic nerve we isolated the abstrakt locus. abstrakt is required for pathfinding of the larval optic nerve, and it also affects development in both the adult visual system and the embryonic CNS. Here we report the molecular characterization of abstrakt. It encodes a putative ATP-dependent RNA helicase of the DEAD box protein family, with two rare substitutions in the PTRELA and the RG-D motifs, thought to be involved in oligonucleotide binding: serine for threonine, and lysine for arginine, respectively. Two mutant alleles of abstrakt show amino acid exchanges in highly conserved positions. A glycine to serine exchange in the HRIGR motif, which is involved in RNA binding and ATP hydrolysis, results in a complete loss of protein function; and a proline to leucine exchange located between the highly conserved ATPase A and PTRELA motifs results in temperature-sensitive protein function. Both the broad requirement for abstrakt gene function and its ubiquitous expression are consistent with a molecular function of the abstrakt protein in mRNA splicing or translational control.

Bicoid (BCD), the anterior determinant of Drosophila , controls embryonic gene expression by transcriptional activation and translational repression. Both functions require the homeodomain (HD), which recognizes DNA motifs at target gene enhancers and a specific sequence interval in the 3′ untranslated region of caudal ( cad ) mRNA. Here we show that the BCD HD is a nucleic acid–binding unit. Its helix III contains an arginine-rich motif (ARM), similar to the RNA-binding domain of the HIV-1 protein REV, needed for both RNA and DNA recognition. Replacement of arginine 54, within this motif, alters the RNA but not the DNA binding properties of the HD. Corresponding BCD mutants fail to repress cad mRNA translation, whereas the transcriptional target genes are still activated.

Members of the conserved nop5/sik1 gene family encode components of small nucleolar ribonucleoprotein (snoRNP) complexes, which have an essential function in rRNA-processing. We describe a novel Drosophila member of this family, termed Dnop5. The gene is expressed in nurse cells during oogenesis and transcripts are deposited into the growing oocyte. Maternal transcripts become evenly distributed in the egg and remain in a ubiquitous pattern during early embryogenesis. Zygotic Dnop5 expression is initiated during the extended germband stage. Transcripts accumulate in mesoderm and midgut primordia, and in the developing imaginal discs of the larvae. Consistent with a function in rRNA processing, Dnop5 protein (DNop5) accumulates in a nuclear substructure, likely to be the nucleolus. Maternal protein accumulates in the nucleolus of all cells in the early embryo, whereas DNop5 that is derived from zygotic mRNA, is restricted to the nuclei of muscles and midgut.

Time-resolved chemical ionization mass spectrometry (CIMS) has been used to investigate the variations of the mixing ratios of benzene, toluene and the C 2 -benzenes (xylenes and ethyl benzene) in automotive exhaust during transient engine operation. A significant increase of the benzene/toluene ratios from 0.35 to 1.31 (median) was found upon introduction of a catalytic converter system. A preliminary emission model was developed from these test stand measurements to simulate benzene/toluene ratios of passenger car fleets with variable proportions of three-way catalyst vehicles. Although only the emissions of gasoline-driven passenger cars have been considered so far, the predicted increase of the benzene/toluene ratios during the introduction period of the three-way catalyst from 1980 to 2000 is in good agreement with the observed increase of the atmospheric benzene/toluene ratio measured at a suburban monitoring site (Dubendorf, Switzerland) which is strongly influenced by road traffic emissions. At this site, the atmospheric concentrations of benzene and alkyl benzenes have been detected at hourly intervals since 1993. A steady decrease of the yearly mean from 3.54 to 2.00 ppb for toluene and from 2.87 to 1.33 ppb for the sum of C 2 -benzenes was found from 1994 to 1998, respectively, when the proportion of three-way catalyst passenger cars increased from 60 to 82%. Nevertheless, the mean benzene concentration was only affected to a small degree (from 1.10 to 0.97 ppb) within the same period of time. Thus, the observed increase of the atmospheric benzene/toluene-mixing ratios from 0.32 to 0.58 (mean) is in good agreement with the predicted values from the presented emission model. Reduced catalyst conversion efficiency for benzene with respect to alkylated benzenes can explain most of the observed increase of the benzene/toluene and benzene/C 2 -benzenes mixing rations. In addition, benzene emissions e.g. from the class of light duty vehicles, which are operated more frequently at sub-optimal combustion conditions, may also contribute to the unexpectedly stable atmospheric benzene concentration at the investigated suburban monitoring site.

A review is given on the multiconfiguration time-dependent Hartree (MCTDH) method, which is an algorithm for propagating wavepackets. The formal derivation, numerical implementation, and performance of the method are detailed. As demonstrated by example applications, MCTDH may perform very efficiently, especially when there are many (typically four to twelve, say) degrees of freedom. The largest system treated with MCTDH to date is the pyrazine molecule, where all 24 (!) vibrational modes were accounted for. The particular representation of the MCTDH wavefunction requires special techniques for generating an initial wavepacket and for analysing the propagated wavefunction. These techniques are discussed. The full efficiency of the MCTDH method is only realised if the Hamiltonian can be written as a sum of products of one-dimensional operators. The kinetic energy operator and many model potential functions already have this required structure. For other potential functions, we describe an efficient algorithm for determining optimal fits of product form. An alternative to the product representation, the correlation discrete variable representation (CDVR) method, is also briefly discussed.

The Drosophila gap gene Krüppel (Kr) encodes a zinc finger-type transcription factor required for controlling the spatial expression of other segmentation genes during early blastoderm stage. Here we show that two independent and transferable repressor domains of Krüppel act to control expression of the pair-rule gene hairy, and that the minimal cis-acting element of hairy stripe7 (h7) mediates either Krüppel-dependent activation or repression in different regions of the blastoderm embryo. The C-terminal region of Krüppel which encompasses the predominant repressor domain is not essential for activation, but is required to fully suppress h7-mediated transcription in response to high levels of Krüppel activity. This domain contains an interaction motif for dCtBP, a homologue of the human co-repressor CtBP. dCtBP activity is, however, dispensable for Krüppel-mediated repression in the embryo since Krüppel-mediated repression functions in the absence of dCtBP. Possible modes of h7-mediated gene regulation in response to the different domains and levels of Krüppel are discussed.

The Drosophila gene buttonhead (btd) is required for the formation of the mandibular, the intercalary and the antennal head segments of the embryo. The btd protein (BTD) is functionally and structurally related to the human C2H2 zinc finger transcription factor Sp1. A second Sp1-like Drosophila gene, termed Drosophila Sp1 (D-Sp1), had been identified on the basis of a partial sequence showing that the gene encodes a characteristic zinc finger domain, composed of three finger motifs similar to both Sp1 and btd. D-Sp1 is located in the same cytological location as btd in chromosome band 9A on the X-chromosome. It had been proposed that D-Sp1 and btd are likely to act as a gene pair and function in a at least partially redundant manner. Here we report the molecular analysis of D-Sp1 and its expression pattern during embryonic and larval development. We show that D-Sp1 acts as a transcriptional regulator. Lack-of-function analysis combined with rescue and gain-of-function studies indicates that btd and D-Sp1 play essential and redundant roles for mechanosensory organ development. However, D-Sp1 lacks the specific features of BTD required for embryonic intercalary and antennal segment formation.

Pattern formation along the anterior-posterior (A/P) axis of the developing Drosophila wing depends on Decapentaplegic (Dpp), a member of the conserved transforming growth factor b (TGFb ) family of secreted proteins. Dpp is expressed in a stripe along the A/P compartment boundary of the wing imaginal disc and forms a long-range concentration gradient with morphogen-like properties which generates distinct cell fates along the A/P axis. We have monitored Dpp expression and Dpp signalling in endocytosis-mutant wing imaginal discs which develop severe pattern defects specifically along the A/P wing axis. The results show that the size of the Dpp expression domain is expanded in endocytosis-mutant wing discs. However, this expansion did not result in a concommittant expansion of the functional range of Dpp activity but rather its reduction as indicated by the reduced expression domain of the Dpp target gene spalt. The data suggest that clathrinmediated endocytosis, a cellular process necessary for membrane recycling and vesicular trafficking, participates in Dpp action during wing development. Genetic interaction studies suggest a link between the Dpp receptors and clathrin. Impaired endocytosis does not interfere with the reception of the Dpp signal or the intracellular processing of the mediation of the signal in the responder cells, but rather affects the secretion and/or the distribution of Dpp in the developing wing cells. q 1999 Elsevier Science Ireland Ltd. All rights reserved.

For a hierarchically constrained kinetic Ising chain it is shown that the process of spin-up propagation for small concentration c of facilitating up spins occurs recursively near the bottom of the configuration space, which has a self-similar structure. For chains with a finite number N of spins the spin autocorrelation function is calculated analytically for N =2 and 4 and numerically for N =4 and 8. From the conjectured behaviour for arbitrary N it is concluded that the mean spin relaxation time τ ∞ on the infinite chain for c →0 diverges more strongly than any positive power of (1/ c ).

It is shown that spinodal decomposition in thin films of mixtures of liquids of very different viscosity may exhibit an inversion of percolation of the low- or the high-mobility portions of the liquid. The condition is that the initial single phase lies in the low-mobility region. This result is derived from the non-linear Cahn-Hilliard equation with a stongly concentration-dependent mobility. Viscoelastic effects are neglected.

Drosophila pair-rule gene expression, in an array of seven evenly spaced stripes along the anterior–posterior axis of the blastoderm embryo, is controlled by distinct cis-acting stripe elements. In the anterior region, such elements mediate transcriptional activation in response to the maternal concentration gradient of the anterior determinant BICOID and repression by spatially distinct activities of zygotic gap genes. In the posterior region, activation of hairy stripe 6 has been shown to depend on the activity of the gap gene knirps , suggesting that posterior stripe expression is exclusively controlled by zygotic regulators. Here we show that the zygotic activation of hairy stripe 6 expression is preceded by activation in response to maternal caudal activity. Thus, transcriptional activation of posterior stripe expression is likely to be controlled by maternal and zygotic factors as has been observed for anterior stripes. The results suggest that activation and the expression level mediated by the hairy stripe 6-element depend on the number of activator binding sites, likely to involve additive rather than synergistic interactions. We found an identical transacting factor requirement for hairy stripe 6 and 7 expression. The arrangement of the corresponding binding sites for the common factors involved in the control of the two stripes share a high degree of similarity, but some of the factors exert opposite regulatory functions within the two enhancer elements.

We present a computer simulation study of spinodal decomposition with one of the two phases freezing in a glassy state during phase separation. As a model we used the Cahn-Hilliard equation with a concentration-dependent mobility coefficient which decreases rapidly with increasing concentration of the glass-forming component. We solved the Cahn-Hilliard equation numerically for two dimensions. The domain growth depends crucially on the volume fraction of the glassy phase. For high volume fractions, when the glassy phase forms a percolating matrix, a novel coarsening mechanism is discovered, which arises from the migration and coalescence of liquid droplets within the glassy matrix. Various quantities characterizing the time-dependent domain pattern, like droplet size distribution, one- and two-point distribution function and structure factor of the concentration field, are computed. We checked the validity of the dynamic scaling hypothesis.

Pattern formation along the anterior-posterior axis of the Drosophila embryo is organized by asymmetrically distributed maternal transcription factors. They initiate a cascade of spatially restricted and interacting zygotic gene activities that provide a molecular blueprint of the larval body at blasioderm stage. The key players in the pattern forming process have been identified. Recent progress has begun to reveal the mechanisms by which coherent positional information of maternal origin becomes transferred into serially repeated zygotic gene expression domains reflecting the metameric body plan of the larva.

In this work, the usefulness of modulated DSC (MDSC) for measuring the heat capacity of commercial hydrocarbon fuels is illustrated. Specifically, the reliability of the method is outlined by testing five liquid fuels of diverse composition and origin over a temperature range between − 70°C and 70°C. The experiments were carried out using a DSC 2910 module from TA Instruments Inc., upgraded with the MDSC option. The samples were exposed to a cyclic heating profile which was generated by a linear heating rate of 2°C min−1 while simultaneously superimposing a sinusoidally varying time-temperature wave with an amplitude of ± 0.5°C and a period of 100 s. On the basis of these measurements, MDSC proved to be a valuable technique with which to measure directly the heat capacity of hydrocarbon fuels. Moreover, the ability of MDSC to measure heat capacity with great accuracy and precision offers a powerful approach for studying the effects of compositional differences on heat capacity.

We have isolated two fractions of very low density lipoprotein particles in human plasma that lack apolipoprotein (apo) E by combined anti-apoE and heparin affinity chromatography of whole plasma followed by ultracentrifugation. The two fractions are distinguished by their ability to bind to heparin. Each of these fractions, designated “B” particles to distinguish them from very low density lipoproteins that contain apoE (“B,E” particles), comprises an appreciable fraction of total particles in very low density lipoproteins of normolipidemic and hypertriglyceridemic subjects. The heparin-unbound B particles, which have been reported previously by others, are larger and have negligible affinity for low density lipoprotein receptors. The heparin-bound B particles are smaller and do bind to low density lipoprotein receptors, albeit with much lower affinity than B,E particles. No differences in accessibility to limited protease digestion were found between apoB-100 in the two types of B particles. Our data indicate that a substantial fraction of human very low density lipoproteins lacks apoE, the principal ligand for lipoprotein receptors that mediate the terminal catabolism of these lipoproteins. Whereas the B particles that fail to bind to heparin are likely to represent a form of nascent lipoprotein, the origin of those B particles that bind to heparin remains to be determined.

The Drosophila gene buttonhead ( btd ) is a gap-like head segmentation gene which encodes a triple zinc finger protein structurally and functionally related to the human transcription factor Spl. Here we report the pattern of btd expression during embryogenesis. btd is not only expressed and required in the blastoderm anlagen of the antennal, intercalary and mandibular segments as reported previously, but both expression and requirement extend into the anlage of the maxillary segment. From gastrulation onwards, btd is expressed in distinct spatial and temporal patterns, suggesting that btd might be required for a number of developmental processes beyond head segmentation. In fact, analysis of btd mutant embryos revealed that btd participates in the formation of the peripheral nervous system. However, no other morphologically apparent phenotype was observed. We identified a btd -related gene, termed D-Spl , which is expressed in temporal and spatial patterns similar to btd during postblastodermal development. No localized expression domains of D-Spl , which is located in the same X-chromosomal band as btd , were seen during the blastoderm state. The results suggest that D-Spl and btd represent a novel gene pair with partially redundant edundant functions after the blastoderm stage.