Non-CG DNA methylation and MeCP2 stabilize repeated tuning of long genes that distinguish closely related neuron types

The extraordinary diversity of neuron types in the mammalian brain is delineated at the highest resolution by subtle gene expression differences that may require specialized molecular mechanisms to be maintained. Neurons uniquely express the longest genes in the genome and utilize neuron-enriched non-CG DNA methylation (mCA) together with the Rett syndrome protein, MeCP2, to control gene expression, but the function of these unique gene structures and machinery in regulating finely resolved neuron type-specific gene programs has not been explored. Here, we employ epigenomic and spatial transcriptomic analyses to discover a major role for mCA and MeCP2 in maintaining neuron type-specific gene programs at the finest scale of cellular resolution. We uncover differential susceptibility to MeCP2 loss in neuronal populations depending on global mCA levels and dissect methylation patterns and intragenic enhancer repression that drive overlapping and distinct gene regulation between neuron types. Strikingly, we show that mCA and MeCP2 regulate genes that are repeatedly tuned to differentiate neuron types at the highest cellular resolution, including spatially resolved, vision-dependent gene programs in the visual cortex. These repeatedly tuned genes display genomic characteristics, including long length, numerous intragenic enhancers, and enrichment for mCA, that predispose them to regulation by MeCP2. Thus, long gene regulation by the MeCP2 pathway maintains differential gene expression between closely-related neurons to facilitate the exceptional cellular diversity in the complex mammalian brain.

DNMT3A Haploinsufficiency Results in Behavioral Deficits and Global Epigenomic Dysregulation Shared across Neurodevelopmental Disorders

Mutations in DNA methyltransferase 3A (DNMT3A) have been detected in autism and related disorders, but how these mutations disrupt nervous system function is unknown. Here, we define the effects of DNMT3A mutations associated with neurodevelopmental disease. We show that diverse mutations affect different aspects of protein activity but lead to shared deficiencies in neuronal DNA methylation. Heterozygous DNMT3A knockout mice mimicking DNMT3A disruption in disease display growth and behavioral alterations consistent with human phenotypes. Strikingly, in these mice, we detect global disruption of neuron-enriched non-CG DNA methylation, a binding site for the Rett syndrome protein MeCP2. Loss of this methylation leads to enhancer and gene dysregulation that overlaps with models of Rett syndrome and autism. These findings define the effects of DNMT3A haploinsufficiency in the brain and uncover disruption of the non-CG methylation pathway as a convergence point across neurodevelopmental disorders.

MeCP2 Represses Enhancers through Chromosome Topology-Associated DNA Methylation

The genomes of mammalian neurons contain uniquely high levels of non-CG DNA methylation that can be bound by the Rett syndrome protein, MeCP2, to regulate gene expression. How patterns of non-CG methylation are established in neurons and the mechanism by which this methylation works with MeCP2 to control gene expression is unclear. Here, we find that genes repressed by MeCP2 are often located within megabase-scale regions of high non-CG methylation that correspond with topologically associating domains of chromatin folding. MeCP2 represses enhancers found in these domains that are enriched for non-CG and CG methylation, with the strongest repression occurring for enhancers located within MeCP2-repressed genes. These alterations in enhancer activity provide a mechanism for how MeCP2 disruption in disease can lead to widespread changes in gene expression. Hence, we find that DNA topology can shape non-CG DNA methylation across the genome to dictate MeCP2-mediated enhancer regulation in the brain.

Oral administration of the flavanol (-)-epicatechin bolsters endogenous protection against focal ischemia through the Nrf2 cytoprotective pathway

Consumption of flavan-3-ols, notably (-)-epicatechin (EC), has been highly recommended in complementary and alternative medicine (CAM) due to reports that flavan-3-ols boost antioxidant activity, support vascular function, and prevent cardiovascular disease. To date, in vivo efficacy and mechanisms of action for many CAM therapies, including EC, remain elusive in brain ischemia. In contrast to its purported direct antioxidant role, we hypothesized protection through activation of the endogenous transcriptional factor Nrf2. To screen cellular protection and investigate Nrf2 activation, we adopted a pretreatment paradigm using enriched primary neuronal cultures from mice and washed out EC prior to oxygen glucose deprivation to attenuate direct antioxidant effects. EC protected primary neurons from oxygen glucose deprivation by increasing neuronal viability (40.2 ± 14.1%) and reducing protein oxidation, effects that occurred concomitantly with increased Nrf2-responsive antioxidant protein expression. We also utilized wildtype and Nrf2 C57BL/6 knockout mice in a permanent model of focal brain ischemia to evaluate glial cell regulation and complex sensorimotor functioning. EC-treated wildtype mice displayed a reduction or absence of forelimb motor coordination impairments that were evident in vehicle-treated mice. This protection was associated with reduced anatomical injury (54.5 ± 8.3%) and microglia/macrophage activation/recruitment (56.4 ± 13.0%). The protective effects elicited by EC in both model systems were abolished in tissues and neuronal cultures from Nrf2 knockout mice. Together, these data demonstrate EC protection through Nrf2 and extend the benefits to improved performance on a complex sensorimotor task, highlighting the potential of flavan-3-ols in CAM approaches in minimizing subsequent stroke injury.

The effects of spinal cord injury and exercise on bone mass: a literature review

INTRODUCTION

Bone loss is a common and often debilitating condition that accompanies spinal cord injury. Because bone loss after spinal cord injury is multifactorial, it can be difficult to assess and treat. This process becomes even more complex as secondary conditions associated with aging are introduced.

PURPOSE

There are two purposes of this literature review. The first is to summarize information concerning the mechanisms of bone loss and osteoporosis after spinal cord injury. The second is to summarize existing data concerning the effects of exercise on bone loss after spinal cord injury.

METHOD

Literature was reviewed concerning the bone loss process and the non-pharmacological treatment options for ameliorating bone loss after spinal cord injury.

RESULTS

(Part One) Osteoporosis is universal in persons with chronic complete spinal cord injury, which increases the risk of bone fracture. Bone loss after spinal cord injury is both sublesional and regional with the greatest areas of bone demineralization being in the sublesional trabecular laden areas of the distal and proximal epiphyses of the femur and tibia. (Part Two) While passive weight bearing of paralyzed lower extremities appears to be ineffective, stressing the bones through muscular contractions initiated by electrical stimulation (FES) have yielded positive results in some cases. The intensity, frequency, and duration of stress to the bones appear to be important determinants of improved bone parameters. Although further quantification of these components is needed, some generalized guidelines can be deduced from completed research. Intensities showing positive results have been loads of one to one and a half times body weight for FES exercise or having participants FES cycle at their highest power output. Safety precautions must be used to decrease risk of bone fracture. Generally, the frequency is effective with three or more weekly exercise sessions. Studies of duration suggest that several months to one or more years of FES are necessary.

DISCUSSION

In order to promote healthy and independent aging in patients with spinal cord injury, it is important to understand the processes, consequences and effective treatments involved with bone loss.

Distal humerus nonunion after failed internal fixation: reconstruction with total elbow arthroplasty

In nonunion after distal humerus fracture, osteoporosis, devascularized fracture fragments, and periarticular fibrosis limit potential reconstructive options. We assessed pain relief, functional gains, and complications in 12 patients whose long-standing, painful nonunions after previous treatment with rigid internal fixation were reconstructed with a semiconstrained total elbow arthroplasty, frequently with a triceps-sparing approach and anterior ulnar nerve transposition. At mean follow-up of 63 months, 11 patients had good pain relief and a good or excellent functional result: mean flexion/extension, 134 degrees to 18 degrees; mean total arc of motion, 117 degrees ; mean pronation/supination, 74 degrees to 69 degrees. Despite the 75% rate of complications (8), semiconstrained total elbow arthroplasty provides a viable treatment for this difficult problem.

Modulation of actin mechanics by caldesmon and tropomyosin

The ability of cells to sense and respond to physiological forces relies on the actin cytoskeleton, a dynamic structure that can directly convert forces into biochemical signals. Because of the association of muscle actin-binding proteins (ABPs) may affect F-actin and hence cytoskeleton mechanics, we investigated the effects of several ABPs on the mechanical properties of the actin filaments. The structural interactions between ABPs and helical actin filaments can vary between interstrand interactions that bridge azimuthally adjacent actin monomers between filament strands (i.e. by molecular stapling as proposed for caldesmon) or, intrastrand interactions that reinforce axially adjacent actin monomers along strands (i.e. as in the interaction of tropomyosin with actin). Here, we analyzed thermally driven fluctuations in actin's shape to measure the flexural rigidity of actin filaments with different ABPs bound. We show that the binding of phalloidin increases the persistence length of actin by 1.9-fold. Similarly, the intrastrand reinforcement by smooth and skeletal muscle tropomyosins increases the persistence length 1.5- and 2- fold respectively. We also show that the interstrand crosslinking by the C-terminal actin-binding fragment of caldesmon, H32K, increases persistence length by 1.6-fold. While still remaining bound to actin, phosphorylation of H32K by ERK abolishes the molecular staple (Foster et al. 2004. J Biol Chem 279;53387-53394) and reduces filament rigidity to that of actin with no ABPs bound. Lastly, we show that the effect of binding both smooth muscle tropomyosin and H32K is not additive. The combination of structural and mechanical studies on ABP-actin interactions will help provide information about the biophysical mechanism of force transduction in cells.

Hypertrophic and dilated cardiomyopathy mutations differentially affect the molecular force generation of mouse α-cardiac myosin in the laser trap assay

Point mutations in cardiac myosin, the heart's molecular motor, produce distinct clinical phenotypes: hypertrophic (HCM) and dilated (DCM) cardiomyopathy. Do mutations alter myosin's molecular mechanics in a manner that is predictive of the clinical outcome? We have directly characterized the maximal force-generating capacity (Fmax) of two HCM (R403Q, R453C) and two DCM (S532P, F764L) mutant myosins isolated from homozygous mouse models using a novel load-clamped laser trap assay. Fmaxwas 50% (R403Q) and 80% (R453C) greater for the HCM mutants compared with the wild type, whereas Fmaxwas severely depressed for one of the DCM mutants (65% S532P). Although Fmaxwas normal for the F764L DCM mutant, its actin-activated ATPase activity and actin filament velocity ( Vactin) in a motility assay were significantly reduced (Schmitt JP, Debold EP, Ahmad F, Armstrong A, Frederico A, Conner DA, Mende U, Lohse MJ, Warshaw D, Seidman CE, Seidman JG. Proc Natl Acad Sci USA 103: 14525–14530, 2006.). These Fmaxdata combined with previous Vactinmeasurements suggest that HCM and DCM result from alterations to one or more of myosin's fundamental mechanical properties, with HCM-causing mutations leading to enhanced but DCM-causing mutations leading to depressed function. These mutation-specific changes in mechanical properties must initiate distinct signaling cascades that ultimately lead to the disparate phenotypic responses observed in HCM and DCM.

Anatomic considerations regarding the posterior interosseous nerve at the elbow

The relationship of the posterior interosseous nerve (PIN) to the radius was studied to determine the change in position associated with forearm motion because of the risk of injury during surgical exposure of the lateral elbow. The distance from the PIN to the radiocapitellar joint (RCJ) was measured in 24 cadaveric specimens in pronation, neutral rotation, and supination. The mean distance from the PIN to the RCJ was 4.6 +/- 0.5 cm, 5.3 +/- 0.6 cm, and 5.7 +/- 0.7 cm in supination, neutral rotation, and pronation, respectively. In pronation, there was substantial variation of this distance, with a minimum distance of 4.3 cm. In supination, the minimum distance was 4.0 cm. On the basis of limited PIN distal translation, noted with pronation, as well as the variation between individuals, we recommend limiting dissection to 4.0 cm from the RCJ during a lateral approach without formal identification of the PIN. This safe zone is recommended regardless of forearm rotation, in contrast to the recommendation of prior authors, as pronation does not reliably increase the distance of the PIN to the RCJ.

Myosin V exhibits a high duty cycle and large unitary displacement

Myosin V is a double-headed unconventional myosin that has been implicated in organelle transport. To perform this role, myosin V may have a high duty cycle. To test this hypothesis and understand the properties of this molecule at the molecular level, we used the laser trap and in vitro motility assay to characterize the mechanics of heavy meromyosin-like fragments of myosin V (M5(HMM)) expressed in the Baculovirus system. The relationship between actin filament velocity and the number of interacting M5(HMM) molecules indicates a duty cycle of > or =50%. This high duty cycle would allow actin filament translocation and thus organelle transport by a few M5(HMM) molecules. Single molecule displacement data showed predominantly single step events of 20 nm and an occasional second step to 37 nm. The 20-nm unitary step represents the myosin V working stroke and is independent of the mode of M5(HMM) attachment to the motility surface or light chain content. The large M5(HMM) working stroke is consistent with the myosin V neck acting as a mechanical lever. The second step is characterized by an increased displacement variance, suggesting a model for how the two heads of myosin V function in processive motion.

The value of diffusion-weighted imaging for prediction of lasting deficit in acute stroke: an analysis of 134 patients with acute neurologic deficits

Acute stroke is one of the three major causes of death and disability in the United States. Now that new, and possibly effective therapy is becoming available, accurate, rapid diagnosis is important to provide timely treatment, while avoiding the risk of complications from unnecessary intervention. Our objective was to test the hypothesis that use of echo-planar (EPI) diffusion-weighted imaging (DWI) is more accurate than conventional T2 weighted MRI in predicting progression to stroke in patients with acute ischemic neurologic deficits. We studied 134 patients presenting with acute neurologic deficits to a community hospital emergency room with both conventional MRI and DWI within 72 h of the onset of the acute deficit. We found DWI significantly more sensitive to permanent neurologic deficit at discharge (sensitivity 0.81) than conventional MRI (sensitivity 0.41). When available, DWI should be considered for routine use in patients being imaged for acute stroke.

Role of the elastic protein projectin in stretch activation and work output of Drosophila flight muscles

We examine how the stretch activation response of the Drosophila indirect flight muscles (IFM) is affected by the projectin mutation bentDominant. IFM from flies heterozygous for this mutation (bentD/+) produce approximately 85% full length projectin and approximately 15% truncated projectin lacking the kinase domain and more C-terminal sequences. Passive stiffness and power output of mutant fibers is similar to that of wild-type (+/+) fibers, but the amplitude of the stretch activation response (delayed tension rise) was significantly reduced. Measurement of actomyosin kinetics by sinusoidal analysis revealed that the apparent rate constant of the delayed tension rise (2 pi b) increased in proportion to the decrease in amplitude, accounting for the near wild-type levels of power output and nearly normal flight ability. These results suggest that projectin plays a crucial role in stretch activation, possibly through its protein kinase activity, by modulating crossbridge recruitment and kinetics.

Expression of c-kit (CD117) in benign and malignant human endometrial epithelium

BACKGROUND

The proto-oncogene c-kit encodes a tyrosine kinase receptor (CD117) with a molecular weight of 145 kd. Previous studies, predominantly utilizing immunohistochemistry, have led to contradictory findings regarding the expression of CD117 in the endometrium. To help resolve this issue, we analyzed a series of benign and malignant endometrial tissues using both immunohistochemistry and Western blot analysis.

OBJECTIVE

To examine the expression of CD117 in benign and malignant human endometrial tissues.

METHODS

The expression of CD117 in 35 benign endometrial tissues (7 hyperplastic, 14 proliferative, 14 secretory) and 10 endometrioid carcinomas was investigated by immunohistochemistry (clone K45 monoclonal antibody). Immunoprecipitation (clone K69 monoclonal antibody) followed by Western blotting (clone K45 monoclonal antibody and clone 1.D9.3D6 monoclonal antibody) was performed to confirm CD117 expression.

RESULTS

Fifty-seven percent of the hyperplasias, 93% of proliferative endometria, and 79% of secretory endometria immunostained positively for CD117. In benign endometria, epithelial staining tended to be more intense in the hyperplastic and proliferative endometria as compared to the secretory endometria, whereas endometrial stromal cells were not immunoreactive. Of the 10 frozen endometrial tissues analyzed by immunohistochemistry, 4 of 9 endometrioid carcinomas and a single case of an endometrioid polyp developing in association with a carcinoma expressed CD117. Immunoprecipitation followed by Western blot analysis confirmed expression of full-length CD117 in an endometrial polyp and carcinoma, and revealed a correlation between levels of immunoprecipitated CD117 and immunohistochemical staining intensity.

CONCLUSIONS

Benign and malignant endometrial tissues express CD117. Our data suggest (a) a possible relationship between estrogen and CD117 expression in benign endometrium and (b) potential involvement of this growth factor receptor in endometrial carcinogenesis.

High-resolution diffusion imaging using phase-corrected segmented echo-planar imaging

Diffusion magnetic resonance imaging (MRI) was performed with a high-resolution segmented echo-planar imaging technique, which provided images with substantially less susceptibility artifacts than images obtained with single-shot echo-planar imaging (EPI). Diffusion imaging performed with any multishot pulse sequence is inherently sensitive to motion artifacts and in order to reduce motion artifacts, the presented method utilizes navigator echo phase corrections, performed after a one-dimensional Fourier transform along the frequency-encoding direction. Navigator echo phases were fitted to a straight line prior to phase correction to avoid errors from internal motion. In vivo imaging was performed using electro cardiographic (ECG) triggering. Apparent diffusion coefficient (ADC) maps were calculated on a pixel-by-pixel basis using up to seven diffusion sensitivities, ranging from b = 0 to 1129 x 10(6) s/m(2).

The effect of removing the N-terminal extension of the Drosophila myosin regulatory light chain upon flight ability and the contractile dynamics of indirect flight muscle

The Drosophila myosin regulatory light chain (DMLC2) is homologous to MLC2s of vertebrate organisms, except for the presence of a unique 46-amino acid N-terminal extension. To study the role of the DMLC2 N-terminal extension in Drosophila flight muscle, we constructed a truncated form of the Dmlc2 gene lacking amino acids 2-46 (Dmlc2(Delta2-46)). The mutant gene was expressed in vivo, with no wild-type Dmlc2 gene expression, via P-element-mediated germline transformation. Expression of the truncated DMLC2 rescues the recessive lethality and dominant flightless phenotype of the Dmlc2 null, with no discernible effect on indirect flight muscle (IFM) sarcomere assembly. Homozygous Dmlc2(Delta2-46) flies have reduced IFM dynamic stiffness and elastic modulus at the frequency of maximum power output. The viscous modulus, a measure of the fly's ability to perform oscillatory work, was not significantly affected in Dmlc2(Delta2-46) IFM. In vivo flight performance measurements of Dmlc2(Delta2-46) flies using a visual closed-loop flight arena show deficits in maximum metabolic power (P(*)(CO(2))), mechanical power (P(*)(mech)), and flight force. However, mutant flies were capable of generating flight force levels comparable to body weight, thus enabling them to fly, albeit with diminished performance. The reduction in elastic modulus in Dmlc2(Delta2-46) skinned fibers is consistent with the N-terminal extension being a link between the thick and thin filaments that is parallel to the cross-bridges. Removal of this parallel link causes an unfavorable shift in the resonant properties of the flight system, thus leading to attenuated flight performance.

The Drosophila projectin mutant, bentD, has reduced stretch activation and altered indirect flight muscle kinetics

Projectin is a ca. 900 kDa protein that is a member of the titin protein superfamily. In skeletal muscle titins are involved in the longitudinal reinforcement of the sarcomere by connecting the Z-band to the M-line. In insect indirect flight muscle (IFM), projectin is believed to form the connecting filaments that link the Z-band to the thick filaments and is responsible for the high relaxed stiffness found in this muscle type. The Drosophila mutant bentD (btD) has been shown to have a breakpoint close to the carboxy-terminal kinase domain of the projectin sequence. Homozygotes for btD are embryonic lethal but heterozygotes (btD/+) are viable. Here we show that btD/+ flies have normal flight ability and a slightly elevated wing beat frequency (btD/+ 223+/-13 Hz; +/+ 203+/-5 Hz, mean +/- SD; P < 0.01). Electron microscopy of btD/+ IFM show normal ultrastructure but skinned fiber mechanics show reduced stretch activation and oscillatory work. Although btD/+ IFM power output was at wild-type levels, maximum power was achieved at a higher frequency of applied length perturbation (btD/+ 151+/-6 Hz; +/+ 102+/-14 Hz; P < 0.01). Results were interpreted in the context of a viscoelastic model of the sarcomere and indicate altered cross-bridge kinetics of the power-producing step. These results show that the btD mutation reduces oscillatory work in a way consistent with the proposed role of the connecting filaments in the stretch activation response of IFM.

Phosphorylation-dependent power output of transgenic flies: an integrated study

We examine how the structure and function of indirect flight muscle (IFM) and the entire flight system of Drosophila melanogaster are affected by phosphorylation of the myosin regulatory light chain (MLC2). This integrated study uses site-directed mutagenesis to examine the relationship between removal of the myosin light chain kinase (MLCK) phosphorylation site, in vivo function of the flight system (flight tests, wing kinematics, metabolism, power output), isolated IFM fiber mechanics, MLC2 isoform pattern, and sarcomeric ultrastructure. The MLC2 mutants exhibit graded impairment of flight ability that correlates with a reduction in both IFM and flight system power output and a reduction in the constitutive level of MLC2 phosphorylation. The MLC2 mutants have wild-type IFM sarcomere and cross-bridge structures, ruling out obvious changes in the ultrastructure as the cause of the reduced performance. We describe a viscoelastic model of cross-bridge dynamics based on sinusoidal length perturbation analysis (Nyquist plots) of skinned IFM fibers. The sinusoidal analysis suggests the high power output of Drosophila IFM required for flight results from a phosphorylation-dependent recruitment of power-generating cross-bridges rather than a change in kinetics of the power generating step. The reduction in cross-bridge number appears to affect the way mutant flies generate flight forces of sufficient magnitude to keep them airborne. In two MLC2 mutant strains that exhibit a reduced IFM power output, flies appear to compensate by lowering wingbeat frequency and by elevating wingstroke amplitude (and presumably muscle strain). This behavioral alteration is not seen in another mutant strain in which the power output and estimated number of recruited cross-bridges is similar to that of wild type.

Nasal cartilage grafts: more than a decade of experience

From 1985 to 1995, a total of 311 patients underwent nasoplasties. During this time period, the number of patients receiving grafts increased from 94 percent in 1985-1989 to 100 percent in 1993-1995. The donor grafts averaged 72 percent nasal cartilage, 10 percent conchal cartilage, 9 percent fascia, and 9 percent rib allograft. Graft recipient sites averaged 41 percent in the tip, 31 percent in the dorsum, 17 percent in the columella, and 3 percent in the region of the lower lateral cartilage; 8 percent were spreader grafts. During this time frame, tip grafting increased from 34 percent in 1985-1989 to 54 percent in 1993-1995. Reoperation for complications decreased from 17 percent in 1985-1989 to 2 percent in 1993-1995. During the time span examined, the use of rib allografts declined, the use of autologous cartilage increased, the use of onlay tip grafts increased, and the incidence of reoperations declined. Early in the series, 80 percent of the malplaced tips were shield type grafts. With the use of the onlay tip graft, the complication of a malpositioned tip has been substantially diminished. The increased use of crushed cartilage has resulted in improvement in results and patient satisfaction, as it serves to camouflage slight irregularities in the tip and dorsum of the nose.

Correction for distortion of echo-planar images used to calculate the apparent diffusion coefficient

An algorithm for correcting the distortions that occur in diffusion-weighted echo-planar images due to the strong diffusion-sensitizing gradients is presented. The dominant distortions may be considered to be only changes of scale coupled with a shear and linear translation in the phase-encoding direction. It is then possible to correct for them by using an algorithm in which each line of the image in the phase-encoding direction is considered in turn, with only one parameter (the scale) to be found by searching.

Endoscopic transaxillary submuscular augmentation mammaplasty with textured saline breast implants

The utility of the endoscope was realized in a retrospective analysis of 92 consecutive patients undergoing augmentation mammaplasty with saline-filled textured implants. The transaxillary submuscular approach was used. All patients received preoperative antibiotics and instillation of methylprednisolone into the saline fill, with inflation to manufacturer-recommended levels. complications included seven implant deflations (3.8%), eight implant malpositions (4.3%), and one capsular contracture (0.6%). Of the eight malpositions, six were corrected using the endoscopic technique without removal of the implant and with early manipulation of the implant within the pocket. We conclude that endoscopic control in augmentation mammaplasty is beneficial in secondary operative procedures and we speculate that the endoscope will lessen the rate of implant malposition observed in this study.

Infant sleep position and the sudden infant death syndrome. A survey of pediatric recommendations

A questionnaire survey was conducted to assess the impact of the April 1992 American Academy of Pediatrics Task Force Statement, "Infant Positioning and SIDS," on the routine advice provided by pediatricians in Minnesota to families with newborn infants regarding sleep practices, including sleep position. There was a trend toward more discussion between all pediatric practice groups and families regarding infant sleep practices following the AAP Sleep Position Statement (P < 0.001-0.003). Prone sleep recommendations ranged from 9.2% for newborn infants to 21.4% for infants 6 months of age. Recommendations for the supine or lateral sleep positions predominated at all infant ages. Pediatricians in private practice were more likely to identify the AAP Statement as establishing a medicolegal standard (P < 0.05). We conclude that the 1992 AAP Statement has had a significant impact on the routine advice provided to families regarding infant sleep practices, including infant sleep position.

Solid state phosphorus-31 magnetic resonance imaging of bone mineral

Chemically selective solid state phosphorus-31 nuclear magnetic resonance (NMR) imaging of the mineral phase of bone and synthetic calcium phosphate models for bone mineral is demonstrated with microscopy-scale (about 5 mm field of view) apparatus at 6.0 T magnetic field strength. Pixel-by-pixel linear combination of image data from multiple radio frequency (RF) pulse sequences, chosen to develop contrast between chemical constituents of interest in the mineral, generates derived images showing the distribution of individual constituents. The technique combines the noninvasive character of magnetic resonance imaging (MRI) with the ability of solid state NMR spectroscopy to characterize subtle chemical variations in bone mineral, as well as to measure the amount of mineral. These methods are, in principle, extensible to larger dimensional scales suitable for live animal subjects or human limbs.

Elderly residents: perceptions of nurses' comforting touch

1. Elderly nursing home residents often feel unwanted or unloved because of a lack of physical contact with others or their caregivers' inability to communicate love and belonging. 2. In a study of 25 elderly nursing home residents, it was found that those who were subjected to comforting touch by their nurses perceived an increased feeling of affection and immediacy. 3. The conscious and intentional use of comforting touch by nurses and caregivers to elderly nursing home residents should be encouraged because of its beneficial effect of conveying love and belonging.

Steps in the evolution of extracranial time-of-flight MR angiography

Magnetic resonance (MR) angiography is not a set technique but is constantly evolving. This article illustrates changes in image quality in extracranial MR angiography that have been achieved over the past few years by the introduction of several technical developments. Images from patients examined at intervals of 12 months or more demonstrate the improvements in image quality that have resulted from these technical changes. These include bandwidth optimization for operation at 1.0 T and changes in flip angle section thickness, repetition time, and echo time. Improved image quality was assessed with objective measures of contrast-to-noise and signal-to-noise ratios. The cases illustrated show the use of MR angiography to evaluate the portal or systemic veins in patients being evaluated for liver transplantation, venous occlusion, and other venous disease. Improvements in image quality are subjectively apparent and emphasize the importance of keeping pace with technical improvements in MR angiography.

Antioxidant status of dairy cows supplemented prepartum with vitamin E and selenium

Possible relationships among dietary antioxidants, oxidative status, and placental retention were investigated in periparturient dairy cows. During 6 wk prepartum, 16 cows each were given daily by capsule 1000 IU of vitamin E, 3 mg of Se, both vitamin E and Se, or neither (control). alpha-Tocopherol in serum and fast-acting antioxidants in plasma increased, but, in red blood cells, thiobarbituric acid-reactive substances decreased during the last 6 wk before parturition in cows given vitamin E. These measurements were unaffected by supplementation of Se. Cows that had retained placenta > or = 12 h had lower fast-acting antioxidants in plasma and glutathione peroxidase in red blood cells up to 2 wk before calving than did cows that shed fetal membranes in < 12 h. Results suggest that inadequate dietary antioxidants may increase oxidative stress, production of lipid peroxides, and incidence of retained fetal membranes in dairy cows.

Hypertension secondary to chlorpropamide with amelioration by changing to insulin

A retrospective analysis of the records of 22 type II diabetics whose treatment had been changed from insulin to chlorpropamide was performed to investigate the relative effects of insulin and chlorpropamide on blood pressure. Although diastolic BP index was not significantly different between the treatments, systolic BP index was significantly higher on chlorpropamide than on insulin (141 +/- 3 v 135 +/- 3 mm Hg, P = .02). In 10 patients in whom insulin was reinstituted, systolic BP fell significantly (P < .005), suggesting that in type II diabetics chlorpropamide exerts a relative hypertensive effect in comparison to insulin.

Measurement of visceral blood flow with magnetic resonance imaging

With the increasing application of magnetic resonance imaging (MRI) and MR angiography in parenchymal liver disease, methods are becoming more widely available for noninvasive measurement of visceral blood flow. Amplitude-based (time-of-flight) and phase-based techniques have proved effective for measurement of portal blood flow, and phase-sensitive methods are applicable to arterial flow measurements. Because respiratory motion degrades the quality of examinations in the abdomen, it is desirable to use methods that can generate flow information in a breath-hold period. Although substantial technical difficulties persist for quantitative arterial flow measurements in the abdomen, the technical requirements for venous flow are less stringent, and important clinical information can be derived using straightforward techniques. The authors describe the principles of flow measurement using time-of-flight and phase methods in visceral arteries and veins, and discuss their practical implementation. Clinical applications are discussed, based on the experience of the authors and others working in the field.

The transverse carpal ligament. An important component of the digital flexor pulley system

The effect of release of the transverse carpal ligament on the mechanics of the flexor tendons was investigated with use of a fresh-frozen cadaver model. A 25 per cent increase in the amount of excursion of the tendons that was consumed by motion of the wrist was demonstrated for the digitorum profundus tendons after transection of the transverse carpal ligament, and a 20 per cent increase was noted for the digitorum superficialis tendons (p < 0.001). These values represent 5.4 +/- 1.2 and 5.5 +/- 1.3 millimeters of bow-stringing for each group of tendons.

Real-time NMR beam-directed velocity mapping. V-mode NMR

BACKGROUND

Currently available noninvasive techniques for measuring blood flow velocities are constrained by limited view orientations (Doppler ultrasound) or limited time resolution (magnetic resonance imaging, MRI). We describe an MRI technique for measuring flow velocities in real time at arbitrary orientations within a cylindrical volume or "beam": V-mode nuclear magnetic resonance (NMR).

METHODS AND RESULTS

The technique was implemented on a standard 1.5-T clinical NMR imager with no special hardware and was tested on phantoms and human volunteers. The beam can be fired at rates up to 60 times per second, allowing measurements on a time scale that is appropriate for ungated cardiac studies. In phantoms, steady flow velocities were measured with the beam aligned along the direction of flow, and the measured velocities correlated well with the actual velocities (r > 0.99). The radial distribution of velocities in phantoms under constant flow conditions was also determined. In humans, flow of blood in the descending aortas of normal and aortic insufficiency subjects was measured. Distinctive backflow of blood because of aortic insufficiency was readily apparent.

CONCLUSIONS

The V-mode NMR technique is capable of acquiring clinically relevant real-time blood flow information from any desired angle of view with no attenuation at bone or air-tissue interfaces.

Neonatal compartment syndrome

Two cases of forearm compartment syndrome in neonates are presented. The compartment syndrome may be initiated before actual delivery and may appear in an advanced stage. In both children good clinical results were achieved when standard guidelines for managing compartment syndrome and established Volkmann's contracture were applied. Although uncommon, compartment syndrome should be considered in the differential diagnosis of the neonate who is unable to move an extremity.

Rapid NMR cardiography with a half-echo M-mode method

A real-time NMR cardiac profiling pulse sequence has been developed that incorporates two-dimensional (2D) selective excitation and a half-echo readout. The time resolution has been improved by a factor of two relative to the previous flow-compensated, full-echo version. The technique produces a 2D plot of "beam"-axis position versus time, analogous to M-mode echocardiography. In human subjects, details of valve leaflet motion, intracardiac flow, wall motion, and wall thickening may be observed along optimal lines of sight selected interactively. The pulse sequence uses a low-tip-angle 2D selective-excitation pulse derived from a spiral k-space trajectory to excite a narrow cylinder of magnetization, followed by a half-echo readout gradient oriented along the axis of the cylinder. One-dimensional Fourier transformation of the acquired signal results in a magnetization profile along the length of the cylinder, or beam. The pulse sequence is effectively flow compensated without any additional gradient lobes, because the rapid oscillation in the gradient wave forms of the 2D excitation pulse produces relatively small net gradient moments, and the shortened readout gradient has minimal first-order moment relative to center echo. The signal from moving blood can alternatively be velocity encoded by the addition of bipolar gradients along any of the three axes, producing Doppler-like traces of intracardiac blood flow.

Radial shortening for Kienböck disease

The cases of twenty-nine consecutive patients (thirty wrists) who had radial shortening for the treatment of stages I through IIIB Kienböck disease were reviewed to assess the results of this procedure. Thirteen patients (45 per cent) had a history of trauma, and all thirty wrists had a negative ulnar variance (average, 2.8 millimeters) on radiographs. All wrists were re-examined after an average follow-up of 3.8 years (minimum, two years). At that time, the pain had decreased in 87 per cent of the wrists. Extension of the wrist had improved an average of 32 per cent; flexion, 27 per cent; radial deviation, 30 per cent; ulnar deviation, 41 per cent; and grip strength on the affected side, 49 per cent. Analysis of the radiographs by computer digitization showed no significant changes in the amount of collapse of the lunate at the latest follow-up. In two wrists, there were complications at follow-up (excessive shortening of the radius and non-union of the radial osteotomy). Radial shortening is an effective treatment for Kienböck disease in wrists that do not have degenerative changes in adjacent carpal joints. Pain, range of motion, and strength can be expected to improve, but the radiographic appearance of the lunate changes little, if any.

Progress in efforts to prevent the spread of HIV infection among youth

The Human Immunodeficiency Virus (HIV) that causes AIDS will continue to threaten public health for years to come. Despite some popular misperceptions, adolescents are at risk of infection. Twenty percent of persons reported with AIDS have been ages 20 through 29. Given the long incubation period between HIV infection and AIDS, some of these young adults probably were infected while they were teenagers. Young people must develop the skills they will need to avoid HIV infection and other related health problems. In 1987, the Centers for Disease Control (CDC) launched a national program to help schools and other agencies that serve youth across the nation provide effective health education to prevent the spread of HIV. CDC supports and works closely with national health and education organizations, State and local education agencies, colleges and universities, and local health departments to establish HIV prevention policies and programs, training and demonstration centers, information development and dissemination activities. The impact of these efforts are assessed through applied surveillance and evaluation research. Through this system, CDC is attempting to institutionalize the means for continuously providing educational programs that will be effective in preventing HIV infection and other important health problems.

Unconstrained shoulder arthroplasty. A five-year average follow-up study

A series of 42 total shoulder arthroplasties and four humeral hemiarthroplasties were performed with either the English-McNab or Neer prosthesis. Retrospective follow-up study averaged five years with a three-year minimum. Preoperative diagnoses included rheumatoid arthritis, osteoarthritis, posttraumatic arthritis, rotator cuff arthropathy, avascular necrosis, failed prosthesis, and congenital dislocation. Postoperatively, pain improved in 94% of shoulders, and active range of motion improved an average of 42 degrees in abduction and 47 degrees in forward flexion. Rotator cuff lesions were correlated with poorer postoperative function. Complications developed in four shoulders (9%) and consisted of humeral component protrusions (two shoulders), loosened prosthesis (one shoulder), and unrecognized, preoperative tuberculous infection (one shoulder). Fifteen glenoid components (36%) and six humeral components (13%) developed lucent lines roentgenographically, but only one glenoid component developed migration.

Vascularized fibular grafts in the treatment of congenital pseudarthrosis of the tibia

Free vascularized fibular bone grafts were used in nineteen children, seen consecutively, who had congenital pseudarthrosis of the tibia. The average age was 5.1 years (range, 1.4 to 11.4 years). Sixteen of the patients had been treated with electrical stimulation for at least one year, and the tibia had not united. All but four patients had had at least one previous operative procedure. At an average follow-up of 6.3 years (range, 2.0 to 11.0 years), eighteen (95 per cent) of the nineteen pseudarthroses had healed. The leg-length discrepancy averaged 1.6 centimeters (range, 0 to 4.0 centimeters), but ten tibiae had residual or progressive valgus or anteroposterior malalignment despite bracing. There was minimum morbidity at the donor site.

Glomus tumor originating within a digital nerve

Glomus tumors are thought to arise from specialized cells normally found within the glomus apparatus of the dermal stratum reticularis. We report the unusual occurrence of a glomus tumor from within a peripheral nerve. Previous investigators have suggested that the rare occurrence of glomus tumors in tissue where the glomus apparatus has not been described arise from ectopic glomus cells or differentiate from nonglomus cell sources. Many of the "ectopic" glomus tumors have been found in regions of extensive arteriovenous shunting such as in the digestive system and lung suggesting the presence of glomera at these locations. The finding of a glomus tumor within a peripheral nerve, a region where extensive arteriovenous shunting and glomus bodies have not been described, supports the occasional origin of a glomus tumor from a nonglomus cell source.

Oxygen radical scavengers improve vascular patency and bone-muscle cell survival in an ischemic extremity replant model

We examined the use of oxygen radical scavengers in preventing the no-reflow phenomenon and improving bone-muscle cell survival in an ischemic extremity replant model. A total of 70 Lewis rat modified hindlimb replants were performed after specific periods of cold ischemia and intraarterial perfusion with either superoxide dismutase and catalase, specific oxygen free-radical scavengers, or a control solution. Ischemic hindlimbs treated with superoxide dismutase and catalase showed a statistically significant (p less than 0.05) improvement in vascular patency after prolonged cold ischemia when compared to controls. Histologically, experimental extremities demonstrated greater osteoblast, osteocyte, and muscle cell survival in replanted hindlimbs with patent vascular anastomoses. The perfusion of severed limbs and digits and free vascularized tissue transfers with superoxide dismutase and catalase after a period of ischemia has already occurred may prolong the ischemic "time window" tolerated for successful tissue survival.

Natural alteration of speaking rate: the effect on passage comprehension by listeners over 75 years of age

The purpose of the study was to assess the comprehension performance of "old-old" listeners for naturally rate-altered passages. Fourteen men and 14 women between 75 and 84 years of age responded to comprehension questions after hearing matched passages at four different rates. The listeners' performances were significantly worse under 60% time compression than at normal rate and two rates of time expansion. Comprehension differences between the sexes were not significant. The results are compared with prior findings for old-old listeners responding to electronically altered speech stimuli (Schmitt, 1983a) and for "young-old" listeners (65-74 years of age) who also responded to naturally rate-altered passages.

Nursing home employee attitudes towards AIDS

This article examines nursing home employee attitudes toward issues related to AIDS and is based on data collected from 343 employees from 13 nursing homes in rural, small towns in sourthern Illinois during the spring of 1988. Results suggested that a large majority of the employees had negative attitudes toward people with AIDS. For example, 67% of the sample indicated that it was more important to limit the spread of AIDS rather than to protect the rights of people with AIDS. Furthermore, 42% suggested that AIDS patients should be sent to sanitariums to protect others from AIDS. Greater than half of the sample (56%) responded that they would feel uncomfortable around people with AIDS. About one third (32%) felt that being around someone with AIDS would put their health in danger, and 21% would be afraid to even take care of a family member with AIDS. With regard to job-specific AIDS attitudes, 51% indicated that health-care workers should be able to refuse to work with AIDS patients, and another 46% felt that hospitals and nursing homes should be able to refuse to admit people with AIDS. In addition to these and other results, this article presents a brief discussion concerning possible educational strategies which might be implemented in this setting to reduce the negative attitudes of these employees. Considerations are also presented for nursing home administrators, who face the problem of developing effective policies for dealing with the rising number of AIDS patients who will be admitted to their facilities.

Capitellocondylar total elbow replacement. A long-term follow-up study

The results of forty total elbow replacements in which a capitellocondylar prosthesis was implanted in thirty-five patients (five of whom had a bilateral procedure) were reviewed retrospectively. The average length of follow-up was 7.2 years (range, four to twelve years). Pronation, supination, and flexion of the elbow improved considerably, but extension did not change a great deal. The average rating of the elbow, according to the scoring system of Ewald et al., improved from 30 to 88 points, but the functional score, as defined by the American Rheumatism Association, improved in only four patients. Malarticulation or dislocation of the prosthesis occurred in ten patients (29 per cent). In two other patients, a deep infection developed, necessitating removal of the prosthesis. Ten prostheses (ten patients) had radiolucent lines on follow-up radiographs, but these lines were not associated with pain or loosening. Seven patients (seven elbows) had a transient ulnar-nerve palsy. The incidence of this complication was reduced from 30 per cent (five of seventeen patients) to 15 per cent (four of twenty-eight patients) when the lateral Kocher approach to the elbow was adopted.