An unusual bandlike web in an infant with lethal multiple pterygium syndrome

We report on a patient with a lethal multiple pterygium syndrome who also had an unusual, bandlike web across one axilla and partial intestinal atresia. Umbilical cord wrapping with subsequent vascular compromise appears to be the most likely pathogenetic mechanism for the additional anomalies.     

Asymmetric Infectivity of Pseudorecombinants of Cabbage Leaf Curl Virus and Squash Leaf Curl Virus: Implications for Bipartite Geminivirus Evolution and Movement

The bipartite geminiviruses squash leaf curl virus (SqLCV) and cabbage leaf curl virus (CLCV) have distinct host ranges. SqLCV infects a broad range of plants within the Cucurbitaceae, including pumpkin and squash, and CLCV has a broad host range within Brassicaceae that includes cabbage andArabidopsis thaliana.Despite this, the genomic A components of these viruses share a high degree of sequence identity, particularly in the gene encoding the replication protein AL1, and their common regions are 77% identical. However, there is unexpected sequence diversity in the common regions of the two CLCV genomic A and B components, these being only 80% identical. Based on these sequence similarities, we investigated the host range properties of pseudorecombinants of SqLCV and CLCV. We found that in a pseudorecombinant virus consisting of the A component of CLCV and the B component of SqLCV, both components replicated in tobacco protoplasts, and this pseudorecombinant was infectious and caused systemic disease inNicotiana benthamiana, a common host to all bipartite geminiviruses. However, this pseudorecombinant did not move systemically in pumpkin orArabidopsis, despite the demonstrated replication compatibility of the genome components. As a result of the greater sequence differences between the common regions, the pseudorecombinant of SqLCV A and CLCV B components neither replicated the CLCV B component nor systemically infected any of the hosts tested. These findings demonstrate that for different geminiviruses with distinct host ranges, the replication origins and AL1 proteins can be sufficiently similar to permit infectious pseudorecombinants, but replication alone is not sufficient to cause systemic disease, and host range may ultimately be limited at the level of movement. The results of this study further suggest that CLCV is an evolving virus that can provide insights into how new bipartite geminiviruses arise from mixed infections.     

CD28-dependent killing by human YT cells requires phosphatidylinositol 3-kinase activation

CD28/B7 interactions have been demonstrated to provide a co-stimulatory signal for the generation of CD8⁺ cytotoxic T lymphocytes in the absence of CD4⁺ T helper cells. The CD28 signals required for induction of cytotoxicity have yet to be described. To investigate further the biochemical signaling pathways associated with CD28-dependent cytotoxicity, we have studied the human thymic leukemia cell line, YT. YT cells kill B7⁺ targets in a non-major histocompatibility complex (MHC)-restricted, CD28-dependent manner. CD28 ligation on the surface of YT cells caused a rapid increase in the tyrosine phosphorylation of four major cellular substrates with masses estimated to be 110, 95, 85, and 44 kDa. The 110 and 85 kDa substrates were identified as the catalytic and regulatory subunits, respectively, of phosphatidylinositol 3-kinase (PI3-K). Engagement of CD28 caused the rapid receptor association and activation of PI3-K but did not activate phospholipase C_γ. CD28-induced tyrosine phosphorylation and PI3-K activation was independent of p56^lck protein tyrosine kinase (PTK) activity (previously reported to be associated with CD28) and was insensitive to inhibition by the PTK inhibitor herbimycin A. Two structurally and mechanistically dissimilar inhibitors of PI3-K, wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) also failed to block CD28-dependent tyrosine phosphorylation events or the association of PI3-K with the CD28 receptor. However, both drugs inhibited CD28-dependent cytotoxicity and CD28 receptor associated PI3-K activity with IC₅₀ values similar to the reported IC₅₀ values for PI3-K inhibition. Although herbimycin A did not significantly block the observed CD28-dependent tyrosine phosphorylation or PI3-K activation, herbimycin did block CD28-dependent cytotoxicity in a dose-dependent manner. These data support a role for PI3-K activation in the CD28-dependent initiation of cytotoxic effector function and suggest that a herbimycin sensitive step(s) is either CD28-independent, resides within a PI3-K-independent CD28 signaling pathway, or is downstream of CD28-dependent PI3-K activation.     

Dehydrochlorination of poly(sulfonyl-co-2-chloroethylene)

Poly(sulfonyl-co-2-chloroethylene)s were shown to have an enhanced tendency to undergo dehydrochlorination compared with poly(vinyl chloride). Dehydrochlorination was observed under the following conditions: (a) during preparation of the copolymers by γ-radiation initiated copolymerization of vinyl chloride and sulfur dioxide, (b) by γ-irradiation of the polymer, (c) during ageing, (d) on heating and (e) in solution in basic solvents, such as DMSO. The dehydrochlorination was studied by microanalysis, by IR and UV spectroscopy and by ¹H and ¹³C NMR. Hydrogen chloride was eliminated preferentially from chloroethylene units occurring between two sulfonyl units. The proportion chloroethylene units: sulfonyl units in poly(sulfonyl-2-chloroethylene) decreased from ≈ 2:1 at a copolymerization temperature of 0°C to ≈ 1:1 at a temperature of ?78°C. The results show, that dehydrochlorination of copolymers prepared at low temperatures is a serious problem, especially with initiation by γ-irradiation.     

Smooth muscle myosin filament assembly under control of a kinase-related protein (KRP) and caldesmon

Kinase-related protein (KRP) and caldesmon are abundant myosin-binding proteins of smooth muscle. KRP induces the assembly of unphosphorylated smooth muscle myosin filaments in the presence of ATP by promoting the unfolded state of myosin. Based upon electron microscopy data, it was suggested that caldesmon also possessed a KRP-like activity (Katayama et al., 1995, J Biol Chem 270: 3919–3925). However, the nature of its activity remains obscure since caldesmon does not affect the equilibrium between the folded and unfolded state of myosin. Therefore, to gain some insight into this problem we compared the effects of KRP and caldesmon, separately, and together on myosin filaments using turbidity measurements, protein sedimentation and electron microscopy. Turbidity assays demonstrated that KRP reduced myosin filament aggregation, while caldesmon had no effect. Additionally, neither caldesmon nor its N-terminal myosin binding domain (N152) induced myosin polymerization at subthreshold Mg²⁺ concentrations in the presence of ATP, whereas the filament promoting action of KRP was enhanced by Mg²⁺. Moreover, the amino-terminal myosin binding fragment of caldesmon, like the whole protein, antagonizes Mg²⁺-induced myosin filament formation. In electron microscopy experiments, caldesmon shortened myosin filaments in the presence of Mg²⁺ and KRP, but N152 failed to change their appearance from control. Therefore, the primary distinction between caldesmon and KRP appears to be that caldesmon interacts with myosin to limit filament extension, while KRP induces filament propagation into defined polymers. Transfection of tagged-KRP into fibroblasts and overlay of fibroblast cytoskeletons with Cy3KRP demonstrated that KRP colocalizes with myosin structures in vivo. We propose a new model that through their independent binding to myosin and differential effects on myosin dynamics, caldesmon and KRP can, in concert, control the length and polymerization state of myosin filaments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structure and evolution of the Smith-Magenis syndrome repeat gene clusters, SMS-REPs

An approximately 4-Mb genomic segment on chromosome 17p11.2, commonly deleted in patients with the Smith-Magenis syndrome (SMS) and duplicated in patients with dup(17)(p11.2p11.2) syndrome, is flanked by large, complex low-copy repeats (LCRs), termed proximal and distal SMS-REP. A third copy, the middle SMS-REP, is located between them. SMS-REPs are believed to mediate nonallelic homologous recombination, resulting in both SMS deletions and reciprocal duplications. To delineate the genomic structure and evolutionary origin of SMS-REPs, we constructed a bacterial artificial chromosome/P1 artificial chromosome contig spanning the entire SMS region, including the SMS-REPs, determined its genomic sequence, and used fluorescence in situ hybridization to study the evolution of SMS-REP in several primate species. Our analysis shows that both the proximal SMS-REP (approximately 256 kb) and the distal copy (approximately 176 kb) are located in the same orientation and derived from a progenitor copy, whereas the middle SMS-REP (approximately 241 kb) is inverted and appears to have been derived from the proximal copy. The SMS-REP LCRs are highly homologous (>98%) and contain at least 14 genes/pseudogenes each. SMS-REPs are not present in mice and were duplicated after the divergence of New World monkeys from pre-monkeys approximately 40-65 million years ago. Our findings potentially explain why the vast majority of SMS deletions and dup(17)(p11.2p11.2) occur at proximal and distal SMS-REPs and further support previous observations that higher-order genomic architecture involving LCRs arose recently during primate speciation and may predispose the human genome to both meiotic and mitotic rearrangements.     

Effects of age and size in the ears of gekkonomorph lizards: middle-ear morphology with evolutionary implications

The function of the ear depends in part on its absolute size and internal proportions. Thus, in both young individuals and small species, the middle ear is expected to be allometrically enlarged despite its smaller absolute size. Here we aim to compare the ontogenetic allometry of relevant middle-ear structures as observed within gecko (gekkonomorph lizards) species, with the evolutionary allometry observed interspecifically. These observations also provide middle-ear data for future evaluation of variation in auditory sensitivity. The material comprised 84 museum specimens of geckos, representing nine species of three gekkonomorph subfamilies. The results of dissections and measurements show that different reports notwithstanding, the middle-ear ossicular chain is indeed structured as described for geckos by Werner and Wever. Some sexual dimorphism is indicated, but this requires further study. During postnatal ontogeny, the allometric growth in the ratio of the columellar footplate area to body length differed between the intraspecific and interspecific levels, hence species differences in the middle ear do not merely result from animal size. The ratio of the tympanic membrane area to the columellar footplate area increased during ontogeny. In this, geckos resemble birds and probably also mammals. Similarly, when the comparison was among adults representing different species, the ratio of the tympanic membrane area to the columellar footplate area increased with body size. In this, however, the geckos differed from birds and mammals, in which this ratio varied taxonomically, irrespective of body size. It would thus seem that middle-ear proportions have evolved among geckos to produce small interspecific differences, but among amniote tetrapods they have evolved according to different principles in the classes reptiles, birds, and mammals.     

Fingertip contact influences human postural control

Touch and pressure stimulation of the body surface can strongly influence apparent body orientation, as well as the maintenance of upright posture during quiet stance. In the present study, we investigated the relationship between postural sway and contact forces at the fingertip while subjects touched a rigid metal bar. Subjects were tested in the tandem Romberg stance with eyes open or closed under three conditions of fingertip contact: no contact, touch contact (<0.98 N of force), and force contact (as much force as desired). Touch contact was as effective as force contact or sight of the surroundings in reducing postural sway when compared to the no contact, eyes closed condition. Body sway and fingertip forces were essentially in phase with force contact, suggesting that fingertip contact forces are physically counteracting body sway. Time delays between body sway and fingertip forces were much larger with light touch contact, suggesting that the fingertip is providing information that allows anticipatory innervation of musculature to reduce body sway. The results are related to observations on precision grip as well as the somatosensory, proprioceptive, and motor mechanisms involved in the reduction of body sway.     

Numerical simulation of aerosol particle transport by oscillating flow in respiratory airways

Particle transport by oscillating flow in a tapered channel or in a tapered tube was computed from the complete equations of motion. These geometries represent a simplified model of the divergent flow field of the mammalian bronchial tree. The computed deformation profile of a line of particles, transported by the oscillatory motion, was compared with prior experimental results and analytical calculations. All three methods agree that there is transport in the divergent direction of the tube by an axial stream of steady drift in the core for moderately high frequency of oscillation (Womersley parameter in the range of 1 to 10). Bidirectional flow is established by an annular stream in the convergent direction, with no net flow on integral cycles of the oscillating fluid. At higher frequency, however, the steady stream transforms to a different shape in the tapered tube, with transport in the divergent direction nearer the walls of the tube, rather than in the core. Transport by the continuing streams with oscillatory ventilation of the respiratory tract should deliver medicinal aerosols of low intrinsic particle mobility to the peripheral regions of the lungs.