A Metropolis Monte Carlo algorithm for merging single-particle diffraction intensities.

Single-particle imaging with X-ray free-electron lasers depends crucially on algorithms that merge large numbers of weak diffraction patterns despite missing measurements of parameters such as particle orientations. The expand-maximize-compress (EMC) algorithm is highly effective at merging single-particle diffraction patterns with missing orientation values, but most implementations exhaustively sample the space of missing parameters and may become computationally prohibitive as the number of degrees of freedom extends beyond orientation angles. This paper describes how the EMC algorithm can be modified to employ Metropolis Monte Carlo sampling rather than grid sampling, which may be favorable for reconstruction problems with more than three missing parameters. Using simulated data, this variant is compared with the standard EMC algorithm.

BRAF V600E mutation in Juvenile Xanthogranuloma family neoplasms of the central nervous system (CNS-JXG): a revised diagnostic algorithm to include pediatric Erdheim-Chester disease.

The family of juvenile xanthogranuloma family neoplasms (JXG) with ERK-pathway mutations are now classified within the "L" (Langerhans) group, which includes Langerhans cell histiocytosis (LCH) and Erdheim Chester disease (ECD). Although the BRAF V600E mutation constitutes the majority of molecular alterations in ECD and LCH, only three reported JXG neoplasms, all in male pediatric patients with localized central nervous system (CNS) involvement, are known to harbor the BRAF mutation. This retrospective case series seeks to redefine the clinicopathologic spectrum of pediatric CNS-JXG family neoplasms in the post-BRAF era, with a revised diagnostic algorithm to include pediatric ECD. Twenty-two CNS-JXG family lesions were retrieved from consult files with 64% (n = 14) having informative BRAF V600E mutational testing (molecular and/or VE1 immunohistochemistry). Of these, 71% (n = 10) were pediatric cases (≤18 years) and half (n = 5) harbored the BRAF V600E mutation. As compared to the BRAF wild-type cohort (WT), the BRAF V600E cohort had a similar mean age at diagnosis [BRAF V600E: 7 years (3-12 y), vs. WT: 7.6 years (1-18 y)] but demonstrated a stronger male/female ratio (BRAF V600E: 4 vs WT: 0.67), and had both more multifocal CNS disease ( BRAFV600E: 80% vs WT: 20%) and systemic disease (BRAF V600E: 40% vs WT: none). Radiographic features of CNS-JXG varied but typically included enhancing CNS mass lesion(s) with associated white matter changes in a subset of BRAF V600E neoplasms. After clinical-radiographic correlation, pediatric ECD was diagnosed in the BRAF V600E cohort. Treatment options varied, including surgical resection, chemotherapy, and targeted therapy with BRAF-inhibitor dabrafenib in one mutated case. BRAF V600E CNS-JXG neoplasms appear associated with male gender and aggressive disease presentation including pediatric ECD. We propose a revised diagnostic algorithm for CNS-JXG that includes an initial morphologic diagnosis with a final integrated diagnosis after clinical-radiographic and molecular correlation, in order to identify cases of pediatric ECD. Future studies with long-term follow-up are required to determine if pediatric BRAF V600E positive CNS-JXG neoplasms are a distinct entity in the L-group histiocytosis category or represent an expanded pediatric spectrum of ECD.

Diffusion-weighted MRI: distinction of skull base chordoma from chondrosarcoma.

BACKGROUND AND PURPOSE: Chordoma and chondrosarcoma of the skull base are rare tumors with overlapping presentations and anatomic imaging features but different prognoses. We hypothesized that these tumors might be distinguished by using diffusion-weighted MR imaging. MATERIALS AND METHODS: We retrospectively reviewed 19 patients with pathologically confirmed chordoma or chondrosarcoma who underwent both conventional and diffusion-weighted MR imaging. Differences in distributions of ADC were assessed by the Kruskal-Wallis test. Associations between histopathologic diagnosis and conventional MR imaging features (T2 signal intensity, contrast enhancement, and tumor location) were assessed with the Fisher exact test. RESULTS: Chondrosarcoma was associated with the highest mean ADC value (2051 ± 261 × 10(-6) mm(2)/s) and was significantly different from classic chordoma (1474 ± 117 × 10(-6) mm(2)/s) and poorly differentiated chordoma (875 ± 100 × 10(-6) mm(2)/s) (P < .001). Poorly differentiated chordoma was characterized by low T2 signal intensity (P = .001), but other conventional MR imaging features of enhancement and/or lesion location did not reliably distinguish these tumor types. CONCLUSIONS: Diffusion-weighted MR imaging may be useful in assessing clival tumors, particularly in differentiating chordoma from chondrosarcoma. A prospective study of a larger cohort will be required to determine the value of ADC in predicting histopathologic diagnosis.

A novel homozygous SCO2 mutation, p.G193S, causing fatal infantile cardioencephalomyopathy.

Cytochrome c oxidase (COX) deficiency is a frequent cause of mitochondrial disease in infants. Mutations in the COX assembly gene SCO2 cause fatal infantile cardioencephalomyopathy. All patients reported to date with SCO2 deficiency share a common p.E140K mutation in at least 1 allele. In order to further the understanding of the genotype-phenotype spectrum associated with fatal infantile cardioencephalomyopathy, we describe a novel homozygous SCO2 mutation p.G193S in a patient with fatal infantile cardioencephalomyopathy born to consanguineous parents of Indian ancestry.

Features of hemolysis due to Clostridium perfringens infection.

Infection by Clostridium perfringens can be an unsuspected cause of hemolysis in emergency room patients. Historically, this condition has been associated with wound contamination and other tissue infections. We report the case of an autistic patient who presented to our emergency department with a distended abdomen and hemolysis of unknown etiology. The patient had no history of recent surgery. Exploration of the abdomen revealed a hepatic abscess. Blood cultures tested culture positive for C. perfringens. We present images demonstrating the salient features of the peripheral blood smear in cases of this uncommon but deadly cause of hemolysis.

The polar T1 interface is linked to conformational changes that open the voltage-gated potassium channel.

Kv voltage-gated potassium channels share a cytoplasmic assembly domain, T1. Recent mutagenesis of two T1 C-terminal loop residues implicates T1 in channel gating. However, structural alterations of these mutants leave open the question concerning direct involvement of T1 in gating. We find in mammalian Kv1.2 that gating depends critically on residues at complementary T1 surfaces in an unusually polar interface. An isosteric mutation in this interface causes surprisingly little structural alteration while stabilizing the closed channel and increasing the stability of T1 tetramers. Replacing T1 with a tetrameric coiled-coil destabilizes the closed channel. Together, these data suggest that structural changes involving the buried polar T1 surfaces play a key role in the conformational changes leading to channel opening.

Early environmental regulation of glucocorticoid feedback sensitivity in young adult monkeys.

Variations in maternal care induce in neonatal rodents life-long changes in glucocorticoid feedback regulation of the hypothalamic-pituitary-adrenal axis. This aspect of plasticity in neuroendocrine development has not been established in primates. We assessed, in young adult squirrel monkeys, postnatal rearing effects on cortisol-induced suppression of corticotropin-releasing factor (CRF) stimulated secretion of adrenocorticotropic hormone (ACTH). Offspring of randomly bred monkeys were periodically removed from natal groups between 13 and 21 weeks of age. In two other postnatal rearing conditions, systematic differences in maternal availability were produced by manipulating the effort required of lactating mothers to successfully find food. All offspring were subsequently administered, 3-5 years later on two occasions, an intravenous ovine CRF injection preceded 60 min earlier by placebo or cortisol pretreatment. The difference between CRF-stimulated time-integrated secretion of ACTH following placebo vs cortisol pretreatment served as an index of glucocorticoid negative feedback. Difference scores were greatest in monkeys previously separated from natal groups. This finding was not attributable to significant rearing condition differences in plasma cortisol levels achieved following pretreatment with exogenous cortisol, nor plasma ACTH levels produced when the CRF injection was preceded by pretreatment with placebo. The results suggest that postnatal experiences altered glucocorticoid feedback in monkeys at least through early adulthood. This conclusion supports retrospective reports indicating that, for humans with major mood and anxiety disorders, systematic differences in glucocorticoid feedback may reflect neural mechanisms in development linking early life stress with psychopathology in adulthood.

Predictions of coronary artery stenosis by artificial neural network.

Data from angiography patient records comprised 14 input variables of a neural network. Outcomes (coronary artery stenosis or none) formed both supervisory and output variables. The network was trained by backpropagation on 332 records, optimized on 331 subsequent records, and tested on final 100 records. If 0.40 was chosen as the output distinguishing stenosis from no stenosis, 81 patients who had stenosis would have been identified, while 9 of 19 patients who did not have stenosis might have been spared angiography. The results demonstrated that artificial neural networks could identify some patients who do not need coronary angiography.

Artificial neural network predictions of lengths of stay on a post-coronary care unit.

OBJECTIVE: To create and validate a model that predicts length of hospital unit stay. DESIGN: Ex post facto. Seventy-four independent admission variables in 15 general categories were utilized to predict possible stays of 1 to 20 days. SETTING: Laboratory. SAMPLE: Records of patients discharged from a post-coronary care unit in early 1993. RESULTS: An artificial neural network was trained on 629 records and tested on an additional 127 records of patients. The absolute disparity between the actual lengths of stays in the test records and the predictions of the network averaged 1.4 days per record, and the actual length of stay was predicted within 1 day 72% of the time. CONCLUSIONS: The artificial neural network demonstrated the capacity to utilize common patient admission characteristics to predict lengths of stay. This technology shows promise in aiding timely initiation of treatment and effective resource planning and cost control.

A comparison of the differential diagnostic efficiency of three personality disorder inventories.

This study was a comparison of the relative diagnostic efficiency of the Millon Clinical Multiaxial Inventory-II, the MMPI Personality Disorder Scales, and the Personality Disorder Questionnaire-Revised. The Structured Clinical Interview for DSM-III-R, Axis II was used as the criterion measure. The operating characteristics of all three objective instruments revealed a high rate of false-positive diagnoses, but negative test results were generally valid. Each instrument was found to possess clinical utility in its ability to improve diagnostic efficiency over base rate predictions for most disorders. It is suggested that many of the psychometric limitations revealed in this study reflect the limitations of DSM-III-R, Axis II.

Myofibrillar and membrane-bound enzymes in skeletal muscle from myodystrophic mice.

1. Experiments were carried out to examine the biochemical changes, such as contractile protein biochemistry and membrane bound enzyme alterations associated with skeletal muscles of myd/myd. 2. Our studies demonstrate that there was a progressive decline in myofibrillar ATPase activity, and this decrease is greatest in 30 weeks old animals of myd/myd as compared to controls. 3. The proteolytic activity of myofibrils isolated from myd/myd was significantly higher than controls. 4. There was no significant difference in Ca2+ ATPase activity of myosin and actin-activated myosin ATPase activity of myd/myd and their controls. 5. Mg2+ ATPase and Na(+)+K(+)-ATPase of myodystrophic SL showed significant increase compared to controls. 6. Isoproterenol stimulated adenylate cyclase activity was significantly lower in the SL of dystrophic mice compared to controls. 7. GTP+isoproterenol stimulate adenylate cyclase was significantly higher in control SL and SR when compared to SL and SR isolated from myd/myd. 8. Guanylate cyclase activity was greater in myodystrophic mice both in the absence and presence of Triton X-100. cGMP and cAMP phosphodiesterase activities were greater in dystrophic mice as compared to controls. 9. These observations suggest that there are significant changes in myofibrillar ATPase, myofibrillar protease and membrane bound enzymes of myd/myd compared to control.

Additional force during stretch of single frog muscle fibres following tetanus.

Single fibres from the anterior tibialis muscles of frogs were used in paired difference experiments to investigate the long-term effect (up to 3.8 s) of tetanic stimulation on fibre stiffness during relaxation. The fibres were stretched from sarcomere lengths of 2.5 microns to 3.0 microns at constant velocities for periods ranging from 0.5 to 1.75 s. The first stretch of each pair took place when the fibres had not experienced a tetanus for at least 5 min. The second stretch took place 20-30 s after the first, but it was preceded by a tetanus (100 Hz stimulation applied for 190 ms; temperature, 23 degrees C). The force produced by the first stretch was subtracted from the force produced by the second to produce a paired difference. The fibres were held at the sarcomere length of 3.0 microns except for a brief period of time immediately prior to the stretches (1200 or 1450 ms). During those periods the fibres were shortened to 2.5 microns (250 ms) and then held at 2.5 microns, regardless of whether a tetanus was elicited, for either 950 or 1200 ms. The second stretch of each pair began either at the end of, or 250 ms after, the last stimulating pulse of the tetanus. At every velocity of stretch, the force produced by the fibres during the stretches was greater when the stretches were preceded by a tetanus than when they were not, and the additional force peaked at the conclusion of the stretches. The additional force, which was produced during the stretches following the tetani, declined for the remainder of the data acquisition period (up to 3 s) following the completion of stretches; it extrapolated to zero at 7-8 s after the completion of the stretches. The magnitude of the additional force was a non-linear direct function of the rate of stretch. Thixotropy or an increased stiffness to stretch was observed in all of the fibres following periods of quiescence.

Effects of organophosphorus agents on sarcoplasmic reticulum in skinned skeletal muscle fibers.

These experiments were designed to determine whether skinned skeletal muscle fibers could be useful in screening new antidotes to organophosphorus poisons. Isometric force and fiber diameter were measured in mechanically skinned fibers from mice and frogs. Fibers were depleted of calcium and placed in a calcium loading solution that contained 0.5 mM EGTA with pCa 6.25. The elapsed time (zero time) before a contracture began and the maximum rate of force development (slope) were measured and divided by the square of the diameter (normalized zero time, normalized slope). The zero time was assumed to be the time required for the sarcoplasmic reticulum to attain a threshold concentration for calcium-induced calcium release, and the slope was assumed to indicate primarily the rapidity of the release of calcium from the sarcoplasmic reticulum. Organophosphorus agents, sarin, soman, tabun, and VX were also placed in the loading solutions. Only sarin failed to shorten the normalized zero times of mouse fibers compared to controls, and all agents decreased the normalized slopes. The normalized zero times of frog fibers were not altered by the agents, but the normalized slopes were altered by some agents. Pralidoxime chloride (PAM) and 3-Cl-2,5,6-trimethylbenzoic acid (TBA) were also added to the loading solution for mouse fibers; PAM was marginally effective in moderating some actions of the organophosphates. Because the effects of the agents on the fibers were so definite, we concluded that the skinned muscle fiber might indeed be useful as a screening tool for developing and testing new antidotes to organophosphorus poisons.

Control of myofibrillar ATPase activity and force in myodystrophic muscle.

Myofibrillar ATPase activity was measured as a function of the free calcium concentration in skeletal muscles of control and myodystrophic mice. In addition, the force developed in skinned extensor digitorum longus (EDL) fibers of control and myodystrophic mice was measured as a function of the free calcium concentration, and a histomorphometric study was performed on soleus and EDL muscles of control and myodystrophic mice. The results showed that the myofibrillar ATPase activity and the force-generating mechanisms of control and myodystrophic muscles were controlled to the same relative degree by equivalent concentrations of calcium ions. Upon maximal activation of the ATPase activities, we measured 18% less activity in myodystrophic muscles than in control muscles. Maximal activation of the force-generating capacity in skinned fibers showed there was no significant difference in force produced in the control compared to myodystrophic fibers. The histomorphometric study revealed no alteration in the relative distribution of different fiber types in myodystrophic compared to control muscles. However, the histomorphometry did reveal a larger slow (type 1) relative cellular area compared to total cross-sectional area in myodystrophic muscle than in controls. We propose that the lower ATPase activity but equal force-generating capacity of myodystrophic muscles compared to control muscles is due to myodystrophic muscles being composed of a greater fraction of myofibrils from slow (type 1) fibers than control muscles.

Ca2+ capacity and uptake rate in skinned fibers of myodystrophic muscle.

Parameters related to the capacity and the rate of uptake of calcium ions by the sarcoplasmic reticulum were measured in skinned extensor digitorum longus fibers of control and myodystrophic mice. Single fibers were isolated and skinned in a relaxing solution and mounted on a force transducer and apparatus for changing the bathing solution (T = 25 degrees C). To test the capacity of the sarcoplasmic reticulum, fibers were placed in a solution for maximal loading and then moved to a test solution in which the major anion in the relaxing solution, gluconate, was replaced by chloride. In the resulting contractures, the means of the forces produced by 10 control and myodystrophic fibers were not significantly different. The conclusion is that the capacities of sarcoplasmic reticulum for calcium in control and myodystrophic fibers are equivalent. To test the rate of loading of sarcoplasmic reticulum, 11 control and myodystrophic fibers were depleted of calcium with caffeine and EGTA. Then they were placed in a solution with pCa = 5.5, and the delay before a contracture began was recorded. The delay was the time required for the sarcoplasmic reticulum to load calcium and attain a threshold for calcium-induced calcium release. The mean delay for the control fibers was significantly less than the mean delay in myodystrophic for the control fibers was significantly less than the mean delay in myodystrophic fibers. The disparity of loading times probably reflected a difference in the activities of the calcium pumps or a difference in the number of pump sites; 5 microM valinomycin did not significantly alter the loading times of either type or fiber.

Transverse impedance of single frog skeletal muscle fibers.

The transverse electrical impedance of single frog skeletal muscle fibers was measured at 31 frequencies that ranged from 1 to 100,000 Hz. Each fiber was bathed entirely in Ringer's solution, but it was positioned so that a central length of 5 mm was in a hollow plastic disk and was electrically isolated from the ends of the fiber. The diameter of the segment of the fiber in the disk was measured and then the segment was pressed from opposite sides by two insulating wedges. Electrical current was passed transversely through the segment between two platinum-platinum black electrodes that were located in the pools of Ringer's solution within the disk. The results were corrected for stray parallel capacitance, series resistance of the Ringer's solution between the fiber and the electrodes, parallel shunt resistance around the fiber, and the phase shift of the measuring apparatus. A nonlinear least-squares routine was used to fit a lumped equivalent circuit to the data from six fibers. The equivalent circuit that was chosen for the fibers contained three parallel branches; each branch was composed of a resistor and a capacitor in series. The model also included a seventh adjustable parameter that was designed to account for the degree of compression of the fibers by the insulating wedges. The branches of the equivalent circuit were assumed to represent the electrical properties of: (a) the myoplasm in series with the membrane capacitance that was exposed directly to the pools of Ringer's solution; (b) the capacitance and series resistance of the transverse tubules that were exposed directly to the pools of Ringer's solution; (c) the membrane capacitance in series with the shunt resistance between the fibers and the insulating wedges. The results gave no indication that current entered the sarcoplasmic reticulum.

Calcium ionophores and tension production in skinned frog muscle fibers.

Antibiotics, X-537A and A23187, were added in micromolar concentrations to selected bathing solutions of skinned frog muscle fibers, and they were shown to affect the production of tension in the skinned fibers. Segments of skinned fibers were bathed in a buffered calcium solution with a pCa near the threshold for contraction. When a segment was moved to a lightly buffered calcium solution with a pCa higher than the threshold for contraction but one containing either antibiotic, a transient contracture of the segment resulted. if the procedure was repeated in the same segment, no contracture was produced. The results are consistent with the idea that the antibiotics function as calcium ionophores in the membrane of the sarcoplasmic reticulum of skinned fibers.

Sizes of components in frog skeletal muscle measured by methods of stereology.

Stereological techniques of point and intersection counting were used to measure morphological parameters from light and electron micrographs of frog skeletal muscle. Results for sartorius muscle are as follows: myofibrils comprise 83% of fiber volume; their surface to volume ratio is 3.8 mum-1. Mitochondria comprise 1.6% of fiber volume. Transverse tubules comprise 0.32% of fiber volume, and their surface area per volume of fiber is 0.22 mum-1. Terminal cisternae of the sarcoplasmic reticulum comprise 4.1% of fiber volume; their surface area per volume of fiber is 0.54 mum-1. Longitudinal sarcoplasmic reticullum comprises 5.0% of fiber volume, and its surface area per volume of fiber is 1.48 mum-1. Longitudinal bridges between terminal cisternae on either side of a Z disk were observed infrequently; they make up only 0.035% of fiber volume and their surface area per volume of fiber is 0.009 mum-1. T-SR junction occurs over 67% of the surface of transverse tubules and over 27% of the surface of terminal cisternae. The surface to volume ratio of the caveolae is 48 mum-1; caveolae may increase the sarcolemmal surface area by 47%. Essentially the same results were obtained from semitendinosus fibers.