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.     

Complementary and alternative medical therapy utilization by people with chronic fatiguing illnesses in the United States

Background  

Chronic fatiguing illnesses, including chronic fatigue syndrome (CFS), pose a diagnostic and therapeutic challenge. Previous clinical reports addressed the utilization of health care provided to patients with CFS by a variety of practitioners with other than allopathic training, but did not examine the spectrum of complementary and alternative medicine (CAM) therapies used. This study was designed to measure CAM therapy use by persons with fatiguing illnesses in the United States population.     

Folate-related genes and omphalocele

Women who take folic acid in the periconceptional period greatly reduce their chances of having a child with a neural tube defect (NTD). Using multivitamins may also reduce the risk of having a child with an omphalocele. In this study, we tested single nucleotide polymorphisms in folate-related enzyme genes for association with omphalocele. Polymorphisms in methylenetetrahydrofolate reductase (MTHFR), methylenetetrahydrofolate dehydrogenase (MTHFD1), the reduced folate carrier (SLC19A1), and transcobalamin II (TCN2) were examined in 25 children with euploid omphalocele and 59 matched controls. Omphalocele cases were significantly more likely to carry the T allele of MTHFR 677C-->T, a known risk factor for NTDs (odds ratio 3.50, 95% confidence interval 1.07-11.47, P=0.035). The MTHFD1 R653Q, SLC19A1 R27H, and TCN2 P259R polymorphisms showed no significant association with omphalocele. In this small study, the thermolabile variant of MTHFR, 677C-->T, was associated with an increased risk for omphalocele. This variant causes reduced enzyme activity, thus suggesting a mechanism by which multivitamins with folic acid might prevent omphalocele. Additional investigation is required.     

Oral food challenge failures among foods restricted because of atopic dermatitis

Background

Recent studies have suggested that removing foods from the diet to manage atopic dermatitis (AD), based on positive allergy test results, may lead to immediate allergic reactions on reintroduction of that food.

Composite carcinoma-carcinoid tumors of the gastrointestinal tract. A morphologic, histochemical, and immunocytochemical study

A morphologic, histochemical, and immunocytochemical study of 20 cases of pure gastrointestinal carcinoids, adenocarcinomas, and mixed neoplasms composed of both elements, so-called composite carcinoma-carcinoid tumors (CCC), was undertaken in order to correlate the morphologic patterns with the immunocytochemical localization of carcinoembryonic antigen (CEA), serotonin, and a battery of polypeptide hormones (calcitonin, glucagon, insulin, gastrin, somatostatin, and adrenocorticotropin [ACTH]). Paraffin sections from five pure carcinoids, seven pure adenocarcinomas, and eight CCC from the stomach, small bowel, appendix, and colon were studied with mucicarmine, silver impregnation stains, and a peroxidase-anti-peroxidase technic. Of the eight CCC, all were mucin positive, four were argyrophilic, and three were argentaffin positive. CEA was present in all eight, serotonin in seven, and calcitonin in one. No other neurohormonal peptides were demonstrated. The distribution of serotonin and CEA generally corresponded to the morphologic pattern, but discordance was observed in two cases, i.e., serotonin was not always localized to areas of carcinoid and CEA not always confined to areas of carcinoma. All five pure carcinoids demonstrated intracytoplasmic localization of serotonin, whereas none contained intracytoplasmic CEA. In two cases, CEA was present within acinar lumens only. The seven colonic adenocarcinomas were argyrophil and argentaffin negative. All contained CEA within the cytoplasm and in gland lumens. None contained serotonin. None of the neurohormonal peptides was localized in either pure adenocarcinomas or carcinoids. This study reveals that among gastrointestinal neoplasms displaying morphologic patterns of adenocarcinoma and carcinoid, immunocytochemical localization of CEA and serotonin confirms their bidirectional differentiation and justifies the designation "composite carcinoma-carcinoid."