Ultrasonographic assessment of bone maturity in newborns

BACKGROUND: Traditionally, the bone maturity at birth has been estimated from the radiological presence and size of the ossified distal femoral epiphysis. This study was conducted in a search for a sonographic tool for the evaluation of neonatal bone maturity. METHODS: We examined sonographically 256 neonates within 24 h of birth. Gestational ages ranged from 36 to 42 weeks (mean: 39.4; median: 40). Birth weights ranged from 1,945 to 5,000 g (mean: 3,175; median: 3,180). The distal femoral epiphysis was imaged on the coronal plane sonogram of the distal femur with the knee at 90 degrees flexion and the distal femoral epiphysis maximal height was recorded. The acetabulum was imaged using Graf's method in the coronal plane image and the acetabular diameter recorded. RESULTS: It was found that plotting the distal femoral epiphysis against neonatal birth weight and gestational age provided a simple method for assessing the bone maturity. According to our study, a neonate can be regarded as bone maturity percentile X when plotting distal femoral epiphysis height or acetabulum diameter against birth weight and gestational age or when averaging the four readings. CONCLUSIONS: We suggest performing sonography of the distal femoral epiphysis as a bedside tool for the assessment of skeletal maturity in newborns.     

SCAR is a primary regulator of Arp2/3-dependent morphological events in Drosophila

The Arp2/3 complex and its activators, Scar/WAVE and Wiskott-Aldrich Syndrome protein (WASp), promote actin polymerization in vitro and have been proposed to influence cell shape and motility in vivo. We demonstrate that the Drosophila Scar homologue, SCAR, localizes to actin-rich structures and is required for normal cell morphology in multiple cell types throughout development. In particular, SCAR function is essential for cytoplasmic organization in the blastoderm, axon development in the central nervous system, egg chamber structure during oogenesis, and adult eye morphology. Highly similar developmental requirements are found for subunits of the Arp2/3 complex. In the blastoderm, SCAR and Arp2/3 mutations result in a reduction in the amount of cortical filamentous actin and the disruption of dynamically regulated actin structures. Remarkably, the single Drosophila WASp homologue, Wasp, is largely dispensable for these numerous Arp2/3-dependent functions, whereas SCAR does not contribute to cell fate decisions in which Wasp and Arp2/3 play an essential role. These results identify SCAR as a major component of Arp2/3-dependent cell morphology during Drosophila development and demonstrate that the Arp2/3 complex can govern distinct cell biological events in response to SCAR and Wasp regulation.     

Role of M3 protein in the adherence and internalization of an invasive Streptococcus pyogenes strain by epithelial cells

Streptococcus pyogenes utilizes multiple mechanisms for adherence to and internalization by epithelial cells. One of the molecules suggested of being involved in adherence and internalization is the M protein. Although strains of the M3 serotype form the second largest group isolated from patients with severe invasive diseases and fatal infections, not much information is known regarding the interactions of M3 protein with mammalian cells. In this study we have constructed an emm3 mutant of an invasive M3 serotype (SP268), and demonstrated that the M3 protein is involved in both adherence to and internalization by HEp-2 cells. Fibronectin promoted both adherence and internalization of SP268 in an M3-independent pathway. Utilizing speB and speB/emm3 double mutants, it was found that M3 protein is not essential for the maturation of SpeB, as was reported for the M1 protein. Increased internalization efficiency observed in both the speB and emm3/speB mutants suggested that inhibition of S. pyogenes internalization by SpeB is not related to the presence of an intact M3 protein. Thus, other proteins in SP268, which serve as targets for SpeB activity, have a prominent role in the internalization process.     

Cloning and functional expression of alkaline alpha-galactosidase from melon fruit: similarity to plant SIP proteins uncovers a novel family of plant glycosyl hydrolases

Raffinose and stachyose are ubiquitous galactosyl-sucrose oligosaccharides in the plant kingdom which play major roles, second only to sucrose, in photoassimilate translocation and seed carbohydrate storage. These sugars are initially metabolised by alpha-galactosidases (alpha-gal). We report the cloning and functional expression of the first genes, CmAGA1 and CmAGA2, encoding for plant alpha-gals with alkaline pH optima from melon fruit (Cucumis melo L.), a raffinose and stachyose translocating species. The alkaline alpha-gal genes show very high sequence homology with a family of undefined 'seed imbibition proteins' (SIPs) which are present in a wide range of plant families. In order to confirm the function of SIP proteins, a representative SIP gene, from tomato, was expressed and shown to have alkaline alpha-gal activity. Phylogenetic analysis based on amino acid sequences shows that the family of alkaline alpha-gals shares little homology with the known prokaryotic and eukaryotic alpha-gals of glycosyl hydrolase families 27 and 36, with the exception of two cross-family conserved sequences containing aspartates which probably function in the catalytic step. This previously uncharacterised, plant-specific alpha-gal family of glycosyl hydrolases, with optimal activity at neutral-alkaline pH likely functions in key processes of galactosyl-oligosaccharide metabolism, such as during seed germination and translocation of RFO photosynthate.     

Delayed Wound Healing in Heat Stable Antigen (HSA/CD24)-Deficient Mice

Background

Healthy individuals rarely have problems with wound healing. Most skin lesions heal rapidly and efficiently within one to two weeks. However, many medical and surgical complications can be attributed to deficiencies in wound repair. Open wounds have lost the barrier that protects tissues from bacterial invasion and allows the escape of vital fluids. Without expeditious healing, infections become more frequent. The CD24 gene encodes a heavily-glycosylated cell surface protein anchored to the membrane by phosphatidylinositol. CD24 plays an important role in the adaptive immune response and controls an important genetic checkpoint for homeostasis and autoimmune diseases in both mice and humans. We have previously shown that overexpression of CD24 results in increased proliferation and migration rates.

Aim

To examine the role of CD24 in the wound healing process.

Methods

An excisional model of wound healing was used and delayed wound healing was studied in genetically modified heat stable antigen (HSA/CD24)-deficient mice (HSA ^-/-) compared to wild-type (WT) mice.

Results

Large full-thickness skin wounds, excised on the back of mice, exhibited a significant delay in the formation of granulation tissue, and in wound closure when compared to their WTHSA ^+/+ littermates. Wounds were histologically analyzed and scored, based on the degree of cellular invasion, granulation tissue formation, vascularity, and re-epithelialization. Additionally, in stitched wounds, the HSA ^-/- mice failed to maintain their stitches; they did not hold and fell already 24 hours, revealing erythematous wound fields. Re-expression of HSA, delivered by lentivirus, restored the normal healing phenotype, within 24 hours post-injury, and even improved the healing in WT, and in BalbC mice.

Conclusions

Delayed wound-healing in the absence of HSA/CD24 suggests that CD24 plays an important role in this process. Increased expression of CD24, even in the normal state, may be used to enhance wound repair.     

Mitochondrial translation in absence of local tRNA aminoacylation and methionyl tRNAMet formylation in Apicomplexa

Apicomplexans possess three translationally active compartments: the cytosol, a single tubular mitochondrion, and a vestigial plastid organelle called apicoplast. Mitochondrion and apicoplast are of bacterial evolutionary origin and therefore depend on a bacterial‐like translation machinery. The minimal mitochondrial genome contains only three ORFs, and in Toxoplasma gondii the absence of mitochondrial tRNA genes is compensated for by the import of cytosolic eukaryotic tRNAs. Although all compartments require a complete set of charged tRNAs, the apicomplexan nuclear genomes do not hold sufficient aminoacyl‐tRNA synthetase (aaRSs) genes to be targeted individually to each compartment. This study reveals that aaRSs are either cytosolic, apicoplastic or shared between the two compartments by dual targeting but are absent from the mitochondrion. Consequently, tRNAs are very likely imported in their aminoacylated form. Furthermore, the unexpected absence of tRNA^Met formyltransferase and peptide deformylase implies that the requirement for a specialized formylmethionyl‐tRNA^Met for translation initiation is bypassed in the mitochondrion of Apicomplexa.     

Mutations in IMPG2, Encoding Interphotoreceptor Matrix Proteoglycan 2, Cause Autosomal-Recessive Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal diseases caused by progressive degeneration of the photoreceptor cells. Using autozygosity mapping, we identified two families, each with three affected siblings sharing large overlapping homozygous regions that harbored the IMPG2 gene on chromosome 3. Sequence analysis of IMPG2 in the two index cases revealed homozygous mutations cosegregating with the disease in the respective families: three affected siblings of Iraqi Jewish ancestry displayed a nonsense mutation, and a Dutch family displayed a 1.8 kb genomic deletion that removes exon 9 and results in the absence of seven amino acids in a conserved SEA domain of the IMPG2 protein. Transient transfection of COS-1 cells showed that a construct expressing the wild-type SEA domain is properly targeted to the plasma membrane, whereas the mutant lacking the seven amino acids appears to be retained in the endoplasmic reticulum. Mutation analysis in ten additional index cases that were of Dutch, Israeli, Italian, and Pakistani origin and had homozygous regions encompassing IMPG2 revealed five additional mutations; four nonsense mutations and one missense mutation affecting a highly conserved phenylalanine residue. Most patients with IMPG2 mutations showed an early-onset form of RP with progressive visual-field loss and deterioration of visual acuity. The patient with the missense mutation, however, was diagnosed with maculopathy. The IMPG2 gene encodes the interphotoreceptor matrix proteoglycan IMPG2, which is a constituent of the interphotoreceptor matrix. Our data therefore show that mutations in a structural component of the interphotoreceptor matrix can cause arRP.     

Tools for the study of protein quality control systems: use of truncated homoserine trans-succinylase as a model substrate for ATP-dependent proteolysis in Escherichia coli

Protein quality control, mediated by chaperones and ATP-dependent proteases, is essential for maintaining balanced growth and for regulating critical processes. To study these systems it is necessary to have model substrate proteins. However, most cellular proteins are stable and the few unstable proteins are usually regulatory and present in low concentrations, making them unsuitable for studies, especially in vivo. We present HTS(Delta1-6), a truncated homoserine trans-succinylase (HTS) which is unstable, can be expressed at high levels and has an enzymatic, measurable, activity. This protein can serve as a good model substrate for Escherichia coli ATP-dependent proteolysis.     

Living in the city: resource availability, predation, and bird population dynamics in urban areas

This article explores factors that shape population structure in novel environments that have received scant theoretical attention: cities. Urban bird populations exhibit higher densities and lower diversity. Some work suggests this may result from lower predation pressure and more predictable and abundant resources. These factors may lead to populations with few winners and many losers regarding access to food, body condition, and reproductive success. We explore these hypotheses with an individual-energy-based competition model with two phenotypes of differing foraging ability. We show that low frequency resource fluctuations favor strong competitors and vice versa. We show that low predation skews equilibrium populations in favor of weak competitors and vice versa. Increasing the time between resource pulses can thus shift population structure from weak to strong competitor dominance. Given recent evidence for more constant resource input and lower predation in urban areas, the model helps understand observed urban bird population structure.