Muscle Derived Stem Cells Stimulate Muscle Myofiber Repair and Counteract Fat Infiltration in a Diabetic Mouse Model of Critical Limb Ischemia

Background

Critical Limb Ischemia (CLI) affects patients with Type 2 Diabetes (T2D) and obesity, with high risk of amputation and post-surgical mortality, and no effective medical treatment. Stem cell therapy, mainly with bone marrow mesenchymal, adipose derived, endothelial, hematopoietic, and umbilical cord stem cells, is promising in CLI mouse and rat models and is in clinical trials. Their general focus is on angiogenic repair, with no reports on the alleviation of necrosis, lipofibrosis, and myofiber regeneration in the ischemic muscle, or the use of Muscle Derived Stem Cells (MDSC) alone or in combination with pharmacological adjuvants, in the context of CLI in T2D.

Methods

Using a T2D mouse model of CLI induced by severe unilateral femoral artery ligation, we tested: a) the repair efficacy of MDSC implanted into the ischemic muscle and the effects of concurrent intraperitoneal administration of a nitric oxide generator, molsidomine; and b) whether MDSC may partially counteract their own repair effects by stimulating the expression of myostatin, the main lipofibrotic agent in the muscle and inhibitor of muscle mass.

Results

MDSC: a) reduced mortality, and b) in the ischemic muscle, increased stem cell number and myofiber central nuclei, reduced fat infiltration, myofibroblast number, and myofiber apoptosis, and increased smooth muscle and endothelial cells, as well as neurotrophic factors. The content of myosin heavy chain 2 (MHC-2) myofibers was not restored and collagen was increased, in association with myostatin overexpression. Supplementation of MDSC with molsidomine failed to stimulate the beneficial effects of MDSC, except for some reduction in myostatin overexpression. Molsidomine given alone was rather ineffective, except for inhibiting apoptosis and myostatin overexpression.

Conclusions

MDSC improved CLI muscle repair, but molsidomine did not stimulate this process. The combination of MDSC with anti-myostatin approaches should be explored to restore myofiber MHC composition.

A new method to derive fetal heart rate from maternal abdominal electrocardiogram: monitoring fetal heart rate during cesarean section

Background

Monitoring of fetal heart rate (FHR) is important during labor since it is a sensitive marker to obtain significant information about fetal condition. To take immediate response during cesarean section (CS), we noninvasively derive FHR from maternal abdominal ECG.

Methods

We recruited 17 pregnant women delivered by elective cesarean section, with abdominal ECG obtained before and during the entire CS. First, a QRS-template is created by averaging all the maternal ECG heart beats. Then, Hilbert transform was applied to QRS-template to generate the other basis which is orthogonal to the QRS-template. Second, maternal QRS, P and T waves were adaptively subtracted from the composited ECG. Third, Gabor transformation was applied to obtain time-frequency spectrogram of FHR. Heart rate variability (HRV) parameters including standard deviation of normal-to-normal intervals (SDNN), 0V, 1V, 2V derived from symbolic dynamics of HRV and SD1, SD2 derived from Poincareé plot. Three emphasized stages includes: (1) before anesthesia, (2) 5 minutes after anesthesia and (3) 5 minutes before CS delivery.

Results

FHRs were successfully derived from all maternal abdominal ECGs. FHR increased 5 minutes after anesthesia and 5 minutes before delivery. As for HRV parameters, SDNN increased both 5 minutes after anesthesia and 5 minutes before delivery (21.30±9.05 vs. 13.01±6.89, P < 0.001 and 22.88±12.01 vs. 13.01±6.89, P < 0.05). SD1 did not change during anesthesia, while SD2 increased significantly 5 minutes after anesthesia (27.92±12.28 vs. 16.18±10.01, P < 0.001) and both SD2 and 0V percentage increased significantly 5 minutes before delivery (30.54±15.88 vs. 16.18±10.01, P < 0.05; 0.39±0.14 vs. 0.30±0.13, P < 0.05).

Conclusions

We developed a novel method to automatically derive FHR from maternal abdominal ECGs and proved that it is feasible during CS.

Synchronized imaging and acoustic analysis of the upper airway in patients with sleep-disordered breathing

Progressive narrowing of the upper airway increases airflow resistance and can produce snoring sounds and apnea/hypopnea events associated with sleep-disordered breathing due to airway collapse. Recent studies have shown that acoustic properties during snoring can be altered with anatomic changes at the site of obstruction. To evaluate the instantaneous association between acoustic features of snoring and the anatomic sites of obstruction, a novel method was developed and applied in nine patients to extract the snoring sounds during sleep while performing dynamic magnetic resonance imaging (MRI). The degree of airway narrowing during the snoring events was then quantified by the collapse index (ratio of airway diameter preceding and during the events) and correlated with the synchronized acoustic features. A total of 201 snoring events (102 pure retropalatal and 99 combined retropalatal and retroglossal events) were recorded, and the collapse index as well as the soft tissue vibration time were significantly different between pure retropalatal (collapse index, 2 ± 11%; vibration time, 0.2 ± 0.3 s) and combined (retropalatal and retroglossal) snores (collapse index, 13 ± 7% [P ≤ 0.0001]; vibration time, 1.2 ± 0.7 s [P ≤ 0.0001]). The synchronized dynamic MRI and acoustic recordings successfully characterized the sites of obstruction and established the dynamic relationship between the anatomic site of obstruction and snoring acoustics.

Correlations between the signal complexity of cerebral and cardiac electrical activity: a multiscale entropy analysis

The heart begins to beat before the brain is formed. Whether conventional hierarchical central commands sent by the brain to the heart alone explain all the interplay between these two organs should be reconsidered. Here, we demonstrate correlations between the signal complexity of brain and cardiac activity. Eighty-seven geriatric outpatients with healthy hearts and varied cognitive abilities each provided a 24-hour electrocardiography (ECG) and a 19-channel eye-closed routine electroencephalography (EEG). Multiscale entropy (MSE) analysis was applied to three epochs (resting-awake state, photic stimulation of fast frequencies (fast-PS), and photic stimulation of slow frequencies (slow-PS)) of EEG in the 1–58 Hz frequency range, and three RR interval (RRI) time series (awake-state, sleep and that concomitant with the EEG) for each subject. The low-to-high frequency power (LF/HF) ratio of RRI was calculated to represent sympatho-vagal balance. With statistics after Bonferroni corrections, we found that: (a) the summed MSE value on coarse scales of the awake RRI (scales 11–20, RRI-MSE-coarse) were inversely correlated with the summed MSE value on coarse scales of the resting-awake EEG (scales 6–20, EEG-MSE-coarse) at Fp2, C4, T6 and T4; (b) the awake RRI-MSE-coarse was inversely correlated with the fast-PS EEG-MSE-coarse at O1, O2 and C4; (c) the sleep RRI-MSE-coarse was inversely correlated with the slow-PS EEG-MSE-coarse at Fp2; (d) the RRI-MSE-coarse and LF/HF ratio of the awake RRI were correlated positively to each other; (e) the EEG-MSE-coarse at F8 was proportional to the cognitive test score; (f) the results conform to the cholinergic hypothesis which states that cognitive impairment causes reduction in vagal cardiac modulation; (g) fast-PS significantly lowered the EEG-MSE-coarse globally. Whether these heart-brain correlations could be fully explained by the central autonomic network is unknown and needs further exploration.

A consistent tissue attenuation coefficient estimator using bubble harmonic echoes

The ultrasonic property of soft tissue can be quantified by its attenuation coefficient α. Traditionally the backscattering signal of tissue is used to estimate α. To improve precision, a large number of spatially independent samples of tissue echoes are required for averaging. In this paper, we propose a new estimation method, which makes use of microbubbles to provide temporally independent samples for averaging. It is easier for temporal sampling to maintain ergodicity and provide a large number of independent samples for statistical averaging. A stochastic model for the harmonic signals of an ideal bubble attenuated by tissue is derived based on Kuc's and Miller's works. An estimator of α is then presented. This estimator is consistent and could be biased because of the unknown squarelaw relation between the second and fundamental harmonics for non-ideal bubble oscillation. In experimental works, we design a simplified phantom for demonstrating the performance of the proposed estimator. It is shown that both first and second harmonics can estimate α consistently. However, the interference of the tissue backscattering signal may cause additional estimation error using the first harmonic.

Ultrasonic renal-stone tracking with mesh regularization

The efficacy of Extracorporeal Shock Wave Lithotripsy (ESWL) depends greatly on the capability to focus shock waves on renal stone. To achieve automatic focusing on moving target, the target must be under tracking. A mesh-based block matching algorithm is proposed for renal stone tracking using ultrasound image sequence. Since multiple targets are tracked together, the mesh-based tracking algorithm can provide a function of contextual regularization for solving the target missing and image degradation problems in renal stone tracking. Recorded ultrasound images of kidney during ESWL treatment are modified for demonstrating the capability of this algorithm.

The effects of sampling rate on the texture separability of ultrasound images

Ultrasound machine has been a useful diagnosis tool for several decades, and many researches tried to use computerized algorithms to help physicians diagnose diseases according to the ultrasound texture patterns. However, the effects of sampling format and the sampling rate on the texture feature were not treated properly. In this paper, the authors try to evaluate the effects of the scan conversion done at imaging stage and the sampling rate used at the texture feature extraction stage. They demonstrate the indispensability of considering sampling format and sampling rate according to the feature used, and their proposed method would improve the separability of texture feature for coarse and homogeneous ultrasound images.

Design of broadband RF pulses with polynomial-phase response

The achievable bandwidth of common linear-phase RF pulses is limited by the maximum feasible B1 amplitude of the MR system. It has been shown previously, that this limitation can be circumvented by overlaying a quadratic phase in the frequency domain, which spreads the power across the pulse duration. Quadratic-phase RF pulses are near optimal in terms of achieving minimal B1max. In this work, it is demonstrated that further B1max reduction can be achieved by combining quadratic with higher-order polynomial-phase functions. RF pulses with a phase response up to tenth order were designed using the Shinnar-Le Roux transformation, yielding considerable increases in bandwidth and selectivity as compared to pure quadratic-phase pulses. These benefits are studied for a range of pulse specifications and demonstrated experimentally. For B1max = 20 microT and a pulse duration of 2.1 ms, it was possible to increase the bandwidth from 3.1 kHz for linear and 3.8 kHz for a quadratic to 9.9 kHz for a polynomial-phase pulse.

The effect of back-scan conversion on the texture features of ultrasound image

Ultrasound is an important way of physical examination nowadays. Many literatures tried to find a quantified standard for diagnosing ultrasonic images; however, they neglected the effect of scan-conversion on image textures. This paper provides a preprocessing method, which practically conforms to the ultrasound image formats, and then compares the effect of the preprocessing method. Several images of sponges were used to evaluate the effect of the preprocessing because of their nearly homogeneous texture. It was found that the spread of standard deviations of the extracted features got narrower, at best 4 times, with preprocessing than that without preprocessing. The back-scan conversion is indispensable for the analysis of ultrasound images using features sensitive to depth and orientation.

Ultrasonic renal-stone detection and identification for extracorporeal lithotripsy

The efficacy of extracorporeal shock wave lithotripsy (ESWL) depends greatly on the capability to focus shock waves on renal stone in real time. To achieve automatic focusing on moving targets, target detection, identification and tracking are required functions. An algorithm for renal stone detection and identification based on ultrasound images is proposed. Two types of image features (contrast and target shape) are selected for stone detection and identification. A feature extraction algorithm is proposed and tested. Statistical characteristics of these features are studied based on the images of kidney recorded during ESWL treatment. The results demonstrate the feasibility of automatic detection and identification of renal stone based on ultrasound images.

Dosage prediction via estimation of shell thickness and concentration of drug carrier with microbubbles

For drug delivery applications, dosage prediction before release and estimation after release are required functions. In this study, we attempted to establish a method to evaluate liposome concentrations and liposome shell thickness for dosage prediction. We use the Trilling model with parameter of phospholipids bilayers to simulate the frequency responses under the different acoustic pressure and establish an experimental protocol to evaluate the liposome concentrations and the liposome shell thickness. Our results illustrate the changes on the signal strength for different concentrations and show that it is relatively stable to estimate the concentrations when the cycles are lower (15 cycles). Besides, it is verified that the second harmonic signal is more sensitive in analyzing different concentrations. On the other hand, it is proved that the liposome shell thickness affect signal strength and thinner thickness will increase the second harmonic response. Therefore, in accordance with the theoretical and experimental results, we would be able to estimate the concentration and the shell thickness of the liposomes. By numerical analysis methods, dosage prediction would be built.

Spatiotemporal patterns of host-seeking Ixodes scapularis nymphs (Acari: Ixodidae) in the United States

The risk of Lyme disease for humans in the eastern United States is dependent on the density of host-seeking Ixodes scapularis Say nymphal stage ticks infected with Borrelia burgdorferi. Although many local and regional studies have estimated Lyme disease risk using these parameters, this is the first large-scale study using a standardized methodology. Density of host-seeking I. scapularis nymphs was measured by drag sampling of closed canopy deciduous forest habitats in 95 locations spaced among 2 degrees quadrants covering the entire United States east of the 100th meridian. Sampling was done in five standardized transects at each site and repeated three to six times during the summer of 2004. The total number of adults and nymphs of the seven tick species collected was 17,972, with 1,405 nymphal I. scapularis collected in 31 of the 95 sites. Peak global spatial autocorrelation values were found at the smallest lag distance (300 km) and decreased significantly after 1,000 km. Local auto-correlation statistics identified two significant high-density clusters around endemic areas in the northeast and upper Midwest and a low-density cluster in sites south of the 39th parallel, where only 21 nymphs were collected. Peak nymphal host-seeking density occurred earlier in the southern than in the most northern sites. Spatiotemporal density patterns will be combined with Borrelia prevalence data as part of a 4-yr survey to generate a nationwide spatial risk model for I. scapularis-borne Borrelia, which will improve targeting of disease prevention efforts.

An ultrasonic microbubble semi-intermodulated imaging technique

The performance of contrast imaging technique is critically influenced by some factors, such as spatial resolution, agent-to-tissue ratio, lifetime of contrast agents and attenuation effect. By using a transducer with higher frequency and higher bandwidth of transmitted signals, the spatial resolution can be improved. Similarly, a better signal-to-interference ratio (SIR) can improve the agent-to-tissue ratio, a lower transmission pressure can prolong the lifetime of contrast agents and a lower center frequency can diminish the attenuation effect. We extend the two-frequency analytic solutions of to approximate the short-pulse responses of microbubbles in a low-amplitude field. Based on their results, there is an expected component near 0 Hz in the spectrum of bubble echoes excited by a short pulse of ultrasound. Here, this component is called the low-frequency response; and it is shown to have a special bandwidth-dependent property and to have potential applications in imaging. We have established the procedure of semi-intermodulated (low-frequency) imaging and the effects of the attenuation effect on imaging resolution, SIR, and signal-to-noise ratio are also analyzed. The obtained experimental images demonstrate that the SIR in semi-intermodulated imaging is better than that in fundamental imaging under various attenuation conditions.

Aperture size effect on ultrasonic wavefront distortion correction

The influences of aperture size on wavefront distortion correction are investigated both theoretically and numerically. A multilayer, phase-screen model is assumed to be the underlying, distorting medium. Numerical simulations were performed using three wavefront distortion correction methods: time-shift compensation (TSC), backpropagation followed by time-shift compensation (BP+TSC), and the previously proposed, multilayer, phase-screen compensation (MPSC) method. The distorted wavefronts were generated by propagating a planar wavefront through a multilayer, phase-screen model constructed with a two-dimensional (2-D) scanned map of a real abdominal slice. Performances were evaluated by L2 errors between the corrected wavefronts and the undistorted planar wavefront. Point spread functions also were calculated to evaluate the relative image quality. Theoretical analysis shows L2 error will decrease as aperture size grows when exact phase compensation (EPC) is applied, although finite errors will always exist along the edges of the corrected wavefront. Three different aperture sizes, 14.24 mm (64 elements), 28.48 mm (128 elements), and 56.96 mm (256 elements) are considered in this study. Numerical results show that the quality of wavefront with EPC is essentially limited by the aperture size, and the correction methods considered are relatively robust against the aperture size. It also shows that, for low aberration, results with MPSC and EPC are comparable. However, for high aberration, MPSC significantly outperforms EPC in suppression of L2 error and sidelobes. This study suggests that, for most medical ultrasound imaging systems, the exact structure of the distorting medium may not be necessary to be known a priori for optimal distortion correction because of the limitation imposed by finite aperture size.

Factor analysis in both spatial and temporal domains of color blooming artifacts in ultrasound investigations utilizing contrast agents

Color blooming artifacts can cause misinterpretations of normal and pathological structures during color Doppler flow imaging with ultrasound contrast agents (USCAs). These artifacts are characterized in both the spatial and temporal domains: in the spatial domain, artifacts result from wave propagation and the ultrasound system; and in the temporal domain, the color blooming time (CBT) is used to denote the duration of artifacts. In our experiments, CBT decreased from 86.7 to 46.8 s when the transmitting pressure was decreased from 370 to 180 kPa. From this, we conclude that an adaptive mechanical index can significantly shorten the CBT, which may in turn prolong the optimal viewing time during in vivo ultrasound investigations utilizing USCAs.

Volume scattering of distributed microbubbles and its influence on blood flow estimation

In recent years, microbubble contrast agents have become a potential adjunct in Doppler ultrasound diagnosis. In this paper, we show that volume scattering makes the effective band in Doppler spectrum shift downward after injection of microbubbles. Because the insonified volume comprises a collection of distributed microbubbles, the statistical properties such as the autocorrelation function and ensemble average power spectrum of the echoes from a collection of distributed microbubbles were derived first. It can be observed that, beyond a critical frequency, the theoretical volume backscattering cross section derived from the ensemble average power spectrum of microbubbles decreases with frequency. On the contrary, the volume backscattering cross section of red cells increases with frequency. Using two-dimensional (2-D) Fourier transform, the variation in Doppler spectrum caused by different volume backscattering cross section can be demonstrated, and the consequential downward shifts of the estimated Doppler parameters (e.g., the mean and maximum Doppler shifts, and the variance of Doppler power spectrum) after microbubble injection are shown. In addition, it can be observed that the variation gets larger as the transmitted bandwidth increases. And, the variations in Doppler parameters estimated with experimental data are presented to verify the theoretical deviations.

The ultrasonic weak short-pulse responses of microbubbles based on a two-frequency approximation

The ultrasonic short-pulse responses of microbubbles are of interest in cavitation, transient responses, and contrast imaging. We extend the two-frequency analytic solutions of Newhouse and Shankar [J. Acoust. Soc. Am. 75, 1473-1477 (1984)] to approximate the short-pulse responses of microbubbles in a low-amplitude field. Based on their results, there is an expected component near dc in the spectrum of bubble echoes excited by a short pulse. Here this component is named the low-frequency response, and its theoretical properties are verified experimentally. Including the fundamental and second-harmonic components, the weak short-pulse responses of microbubbles include three types of response. Our work has determined the constraint conditions under which this approximated solution can be used to analyze these short-pulse responses. This paper also provides the amplitude and spectral properties of these responses. The low-frequency response has a special bandwidth-dependent property and has potential applications in imaging and bubble sizing.

OspA immunization decreases transmission of Borrelia burgdorferi spirochetes from infected Peromyscus leucopus mice to larval Ixodes scapularis ticks

Recombinant outer surface protein A (OspA) vaccination of wild animal reservoirs has potential application for reducing Borrelia burgdorferi transmission in nature and subsequent risk of human infection. As a major reservoir host, the white-footed mouse (Peromyscus leucopus) is a candidate for a vaccination program designed to reduce infection prevalence in vector ticks. In this study we characterized the effect of various levels of immunization with recombinant OspA-glutathione transferase fusion protein on transmission dynamics from infected P. leucopus to larval ticks. Control mice were vaccinated with glutathione transferase alone. All mice were experimentally infected with B. burgdorferi before vaccination. The immune responses of the immunized mice were assessed by enzyme-linked immunosorbent assay for antibodies to OspA. Transmission of B. burgdorferi from infected mice was determined by xenodiagnosis with uninfected larval ticks. Spirochetes in ticks were counted by direct immunofluorescence assay. The concentration of antibody to OspA increased with each OspA vaccination but most markedly after the first and second vaccinations. In comparison with control mice, there was reduced transmission by OspA-vaccinated mice to uninfected ticks. One, two, or three doses of OspA reduced infection prevalence in xenodiagnostic ticks by 48%, 92%, or 99% and the numbers of spirochetes per tick by 84%, 98%, or 99%, respectively. This study suggests that vaccination of P. leucopus with OspA could reduce transmission to the tick vector in nature despite prior infection of the reservoir host.

Analysis and correction of ultrasonic wavefront distortion based on a multilayer phase-screen model

A model is introduced that incorporates the cumulative wavefront distortion effects caused by spatial heterogeneities along the path of propagation, and a corresponding model-based wavefront distortion-correction method is presented. In the proposed model, a distributed heterogeneous medium is lumped into a series of parallel phase screens. The distortion effects can be compensated--without a priori knowledge of the distorting structure--by backpropagation of received wavefronts through hypothetical multiple phase screens located between the imaging system and targets, while each pointwise time shift is adjusted iteratively to maximize a specified image quality factor at the final layer. Theoretical analyses indicate that the mean speckle brightness decreases monotonically with the root-mean-square value of distributed phase distortions; therefore, the speckle brightness can be used as an image quality factor. Experimental one-dimensional (1-D) array data with simulated distortion effects based on a real 2-D abdominal-tissue map were used to evaluate the performance of the proposed method and existing aberration-correction techniques. The simulated characteristics of wavefront distortion and relative performance of existing correction techniques were similar to reports based on abdominal-wall data and breast data. This investigation shows that the proposed method provides better compensation for wavefront distortion.

Extension of finite-support extrapolation using the generalized series model for MR spectroscopic imaging

In magnetic resonance (MR) imaging, limited data sampling in k-space leads to the well-known Fourier truncation artifact, which includes ringing and blurring. This problem is particularly severe for MR spectroscopic imaging, where only 16-24 points are typically acquired along each spatial dimension. Several methods have been proposed to overcome this problem by incorporating prior information in the image reconstruction. These include the generalized series (GS) model and the finite-support extrapolation method. This paper shows the connection between finite-support extrapolation and the GS model. In particular, finite-support extrapolation is a limiting case of the GS model, when the only available prior information is the support region. The support region refers to those image portions with nonzero intensities, and it can be estimated in practice as the nonbackground region of an image. By itself, the support region constitutes a rather weak constraint that may not lead to considerable resolution gain. This situation can be improved by using additional prior information, which can be incorporated systematically with the GS model. Examples of such additional prior information include intensity estimates of anatomical structures inside the support region.

Unifying linear prior-information-driven methods for accelerated image acquisition

In the ongoing quest for faster imaging and higher spatial resolution, several methods have been developed to speed up data acquisition by incorporating prior information about the object being imaged. This study shows that many of these methods can be integrated into a single common equation. The unified framework provides a conceptual link that facilitates comparison among these methods to reveal their strengths and weaknesses. By considering the limitations of existing methods, a new member in this class of methods was developed. The broad-use linear acquisition speed-up technique (BLAST) uses the estimated amount of change within the FOV as prior information. BLAST has the flexibility of incorporating a variable amount of prior information to avoid the misleading appearance of "phantom features," which arise from overconstraining the reconstruction. Examples from dynamic imaging and MR thermometry are shown.

Developing BSN leaders for the future: the Fuld Leadership Initiative for Nursing Education (LINE)

The Helene Fuld Leadership Initiative in Nursing Education (LINE) program was designed to enhance beginning leadership competencies of baccalaureate nursing students. Given the increasing need for strong and effective leadership throughout the health care system, and the demands new graduates encounter as they move into practice, the LINE program is built on the premise that leadership skills must be instilled at the undergraduate level. The program achieves its goal through an intensive 5-day institute focused on assessing and developing the leadership competencies of nurse educators and their clinical partners to enable them to be effective agents of curriculum change in their home institutions. The institute also assists participants to redesign their baccalaureate nursing (BSN) curricula to ensure that students learn to: (1) work effectively within and across complex, integrated organizational and institutional boundaries; (2) think and act from the perspective of a system; and (3) communicate, negotiate, lead, and facilitate change within health care organizations. D. Goleman's (1998) framework of emotional intelligence, which addresses both personal competence (managing oneself) and social competence (handling one's relationships with others) provides the framework for operationalizing leadership in the BSN curriculum. To date, 26 BSN programs and their clinical partners have participated in the LINE program, which has the potential to influence the beginning leadership development of more than 2,400 BSN students. Program outcomes reveal that education-practice collaboration, professional networking, individual leadership development of nurse educators and their clinical partners as change agents, and the integration of leadership experiences at all levels of the BSN curriculum are important in developing beginning leadership competencies in BSN students.

Impaired steroidogenic factor 1 (NR5A1) activity in mutant Y1 mouse adrenocortical tumor cells

Mutants isolated from the Y1 mouse adrenocortical tumor cell line (clones 10r-9 and 10r-6) are resistant to ACTH because they fail to express the melanocortin-2 receptor (MC2R). In this study, we show that a luciferase reporter plasmid driven by 1,800 bp of the proximal promoter region of the MC2R was expressed poorly in the mutant cells compared with parent Y1 cells. The differential expression of the MC2R in parent and mutant cells resulted from impaired activity of the orphan nuclear receptor NR5A1 (SF1) on the promoter as determined by 5'-deletion analysis. Furthermore, the activity of an SF1 expression plasmid on an SF1-dependent reporter plasmid was compromised in mutant clones. The site-specific DNA binding properties of SF1 from parent and mutant cells did not differ as determined in electrophoretic mobility shift assays, and the addition of the activation domain of VP16 to the amino terminus of SF1 restored the transcriptional activity of the protein. In addition, the levels of SF1 and other cofactors including WT1, CBP/p300, and steroid receptor coactivator 1 did not differ appreciably between parent and mutant cells. Taken together, these results suggest that ACTH resistance in the mutant clones resulted from a defect that affected the activation properties of SF1 rather than its DNA binding activity. Consistent with the observed impairment in SF1 function, other SF1-dependent genes, including Cyp11b1 and steroidogenic acute regulatory protein (StAR), were poorly expressed and global steroidogenesis, as evidenced by the metabolism of 22(R)-hydroxycholesterol to steroid products, was impaired. Interestingly, MC2R, Cyp11a, Cyp11b1, and StAR transcripts were not affected to the same degree, suggesting that each of these genes may have a different absolute requirement for SF1. These mutants thus provide an experimental paradigm to identify factors that influence SF1 function and to evaluate the relative importance of SF1 in the expression of genes essential for adrenal steroidogenesis.

Sialylation of the host receptor may modulate entry of demyelinating persistent Theiler's virus

Theiler's murine encephalomyelitis virus (TMEV) is a picornavirus of the Cardiovirus genus. Certain strains of TMEV may cause a chronic demyelinating disease, which is very similar to multiple sclerosis in humans, associated with a persistent viral infection in the mouse central nervous system (CNS). Other strains of TMEV only cause an acute infection without persistence in the CNS. It has been shown that sialic acid is a receptor moiety only for the persistent TMEV strains and not for the nonpersistent strains. We report the effect of sialylation on cell surface on entry and the complex structure of DA virus, a persistent TMEV, and the receptor moiety mimic, sialyllactose, refined to a resolution of 3.0 A. The ligand binds to a pocket on the viral surface, composed mainly of the amino acid residues from capsid protein VP2 puff B, in the vicinity of the VP1 loop and VP3 C terminus. The interaction of the receptor moiety with the persistent DA strain provides new understanding for the demyelinating persistent infection in the mouse CNS by TMEV.

The preterm prediction study: failure of midtrimester cervical sialidase level elevation to predict subsequent spontaneous preterm birth

OBJECTIVE

Our objective was to determine any associations among midtrimester cervical fluid sialidase activity, bacterial vaginosis, and subsequent spontaneous preterm birth.

STUDY DESIGN

In this nested case-control study all patients (n = 126) with spontaneous preterm birth at <35 weeks' gestation and selected control subjects delivered at >/=37 weeks' gestation (n = 126, matched for race, parity, and center) were derived from women enrolled in the multicenter National Institute of Child Health and Human Development Preterm Prediction Study. Sialidase activity and presence of bacterial vaginosis according to Gram stain were determined in cervical swabs and vaginal smears, respectively, obtained at 22 weeks' to 24 weeks 6 days' gestation.

RESULTS

The mean +/- SD sialidase activities were similar in case patients and control subjects (0.64 +/- 1.60 vs 0.41 +/- 0.94 nmol. mL-1. min-1, P =.21). Neither sialidase activity above the 90th percentile (10.3% vs 9.5%, P =.8) nor sialidase activity above the 95th percentile (7.9% vs 4. 8%, P =.3) of control specimens (>1.43 and >2.23 nmol. mL-1. min-1, respectively) was associated with spontaneous preterm birth. The frequency of combinations of bacterial vaginosis and elevated sialidase activity was similar (P >/=.63 with either cutoff) in case patients and control subjects. Sialidase activity was significantly higher among women with bacterial vaginosis than among those without bacterial vaginosis (1.35 +/- 1.87 vs 0.03 +/- 0.14 nmol. mL-1. min-1, P <.0001).

CONCLUSIONS

Elevated cervical fluid sialidase activity at 22 to 24 weeks' gestation did not distinguish women at increased risk for spontaneous preterm birth, nor did it discriminate a subgroup of patients who had bacterial vaginosis associated with spontaneous preterm birth.

Computer-assisted quantification of periaxial bone rotation from X-ray CT

PURPOSE

Numerous orthopedic disorders involve periaxial rotation of long bones. We have developed and evaluated a computer-assisted method that segments a bone from X-ray CT, graphically unwraps the bone around its long axis into a surface plot (signature landscape), and measures periaxial rotation as the translation shift of the landscape. Bones in known rotations and partially segmented surfaces were used, respectively, to test accuracy and problematic situations in bone segmentation.

METHOD

CT images of three chicken femora at known rotations were analyzed to determine their relative periaxial rotations, which were compared with the known rotations.

RESULTS

The regression slope between measured and expected periaxial rotations was 1.005 +/- 0.003, with a maximum discrepancy of 2 degrees for same-bone and 3 degrees for interbone comparisons. Rasterization artifacts and the use of partial surfaces (with < 40% surface omission) resulted in a < 3 and < 1 degree error, respectively.

CONCLUSION

The current method provides accurate and objective periaxial rotation measurements of a long bone.

Fully automated establishment of stereotaxic image orientation in six degrees of freedom for technetium-99m-ECD brain SPECT

Anatomical localization requires establishing an anatomical space within the image matrix. We developed a fast, fully automated method to establish the image orientation for 99mTc-ethylcysteinate dimer (ECD) brain SPECT images.

METHODS

The image orientation of ECD brain SPECT images was established in four stages. First, the brain surface was edge-detected as an isosurface at an adaptive threshold. Second, a "convex hull" was determined for the isosurface to minimize regional variability in brain shape. A principal axis transformation and a symmetry vector analysis were applied to the convex hull to resolve the craniocaudal direction and to estimate the midsagittal plane. Third, the brain orientation was refined from this estimate by location of the interhemispheric fissure, the tentorial groove and the frontotemporal groove on the isosurface. Last, the intercommissural (anterior commissure-posterior commissure, or AC-PC) line was detected on the midsagittal slice, and the Talairach grid was scaled to fit the maximal brain dimensions from the AC-PC line.

RESULTS

The average absolute errors were 2.3 degrees +/- 1.5 degrees and 1.08 mm +/- 1.11 mm for the midsagittal plane (n = 24) and 2.04 degrees +/- 0.80 degrees, 2.0% +/- 1.8% of the brain length and 2.3% +/- 2.2% of the brain height for the AC-PC line (n = 8). In addition, this program successfully established the image orientation in 94 of 100 clinical ECD brain SPECT studies. Processing time was <40 sec for 128 x 128 x 50 matrices on a DEC Alpha workstation.

CONCLUSION

We have developed a fast, robust and fully automated method that determines the orientation of ECD brain SPECT images. This objective method of standardizing the image orientation should be useful for anatomical localization and clinical interpretation of these images.

Minimally invasive management of low-grade and benign gastric tumors

BACKGROUND

Benign gastric tumors and tumors of low-grade malignancy can be safely removed laparoscopically.

METHODS

Seven patients were considered candidates for laparoscopic resection of gastric tumors. Inclusion criteria included small tumor size (less than 6 cm), exophytic or endophytic tumor morphology, and benign characteristics. Indications for surgical intervention included bleeding, weight loss, and need for tissue diagnosis. Patients ranged in age from 38 to 70. There were five female and two male patients. All patients underwent preoperative upper GI endoscopy. The procedures were performed using a four- or five-port technique. An Endo-GIA (US Surgical Company, Norwalk, Connecticut) was used to amputate those tumors located on the serosal surface of the stomach. Tumors on the mucosal surface were exposed via a gastrotomy, then likewise amputated using an Endo-GIA. The gastrotomy closure was then either hand sewn or stapled. Operating time ranged from 95 to 225 min.

RESULTS

Final pathologic diagnoses included lipoma, lymphoma, leiomyoma, and leiomyosarcoma. There was a 28% conversion rate. There were no complications. Length of postoperative stay ranged from 4 to 7 days. There have been no tumor recurrences in 6-38-month follow-up.

CONCLUSIONS

Minimally invasive management of benign and low-grade gastric tumors can be performed safely with excellent short- and long-term results.

Consequences of lost gallstone

Laparoscopic cholecystectomy has become the treatment of choice in the management of calculus gallbladder disease. Intraperitoneal gallstone loss is not uncommon; it occurs in up to 40% of cases. Often, the stones are left unretrieved and are thought to be inconsequential. We present a series of patients who have had serious sequela from gallstones in the peritoneal cavity. We performed a retrospective study of the management of six patients with complications from intraperitoneal gallstones. The patients presented with a variety of complaints, from fevers to pneumonia to a colo-cutaneous fistula. Presentation ranged from immediately postoperatively to 18 months after surgery. Diagnosis included perihepatic abscesses and colo-biliary fistula. General anesthesia was usually necessary for removal of the stones. All patients have resolved following the removal of the gallstones. Our recommendation is to attempt to avoid spillage through careful dissection and retrieve any lost stones. The defect in the gallbladder can be closed with a clip. Whether the procedure should be converted to an open one to retrieve all the stones remains open to debate. The surgeon should be aware of the possible consequences of the lost gallstone.

Mutations to forskolin resistance result in loss of adrenocorticotropin receptors and consequent reductions in levels of G protein alpha-subunits

A family of mutants isolated from the Y1 mouse adrenal cell line on the basis of their resistance to the growth inhibitory effects of forskolin have an underlying mutation that affects the activity of adenylyl cyclase. As part of the mutant phenotype, adenylyl cyclase is partially resistant to activation by forskolin, completely insensitive to ACTH, and fully responsive to NaF; the levels of Gs alpha and G1 alpha in plasma membrane fractions are decreased; and the activity of G beta/gamma is impaired. In the present study, we examine the basis for the complex phenotype associated with forskolin resistance to better understand the factors that contribute to the regulation of adenylyl cyclase activity. We demonstrate that the resistance of these mutants to ACTH results from the failure to express ACTH receptor transcripts. Transfection of these mutants with a gene encoding the mouse beta 2-adrenergic receptor led to the recovery of transformants with normal receptor-G protein coupling and with increased levels of Gs alpha and G1 alpha that approached those in parental Y1 cells. These beta 2-adrenergic receptor transformants, nonetheless, remained resistant to forskolin and ACTH. Two spontaneous Y1 mutants, Y6 and OS3, previously characterized as ACTH-resistant clones that failed to accumulate ACTH receptor transcripts, were shown to be forskolin resistant and to contain less Gs alpha in membrane fractions, indicating that forskolin resistance, failure to express the ACTH receptor, and the consequent reduction in Gs alpha are closely linked. Expression of the human ACTH receptor in Y6 and OS3 cells restored ACTH-responsive adenylyl cyclase activity and increased the level of Gs alpha, but did not otherwise reverse the forskolin-resistant phenotype. Together, these results demonstrate that mutations to forskolin resistance have downstream consequences that result in the loss of ACTH receptor expression and the consequent reduction in levels of membrane-associated G alpha subunits. The results further suggest that G protein-coupled receptors may have a stabilizing influence on G alpha subunits associated with the cell membrane. According to current models, forskolin activates adenylyl cyclase by forming a ternary complex with adenylyl cyclase and Gs alpha. Our results suggest that this model may be incomplete and that an additional component, acting directly or indirectly, is required for optimal activation of adenylyl cyclase by forskolin.

Amplification of the transketolase gene in desensitization-resistant mutant Y1 mouse adrenocortical tumor cells

As shown previously, mutants of the Y1 mouse adrenocortical tumor cell line that resist agonist-induced desensitization of adenylyl cyclase have elevated levels of a 68-kDa protein (designated p68), suggesting a possible relationship between p68 and the regulation of adenylyl cyclase activity. In the present study, cDNA cloning and sequencing were used to identify p68 as mouse transketolase. Cells overexpressing p68 exhibited a 17.4-fold increase in transketolase enzymatic activity relative to parental Y1 cells and a 28-fold amplification of the transketolase gene as determined by Southern blot hybridization analysis. Using fluorescent in situ hybridization analysis, the transketolase gene was mapped to mouse chromosome 16B1 and to human chromosome 3p21.2. Transketolase gene amplification was associated with telomeric fusion of the chromosome 16 pair together with the appearance of multiple copies of the transketolase gene throughout a different chromosome. The relationship between overexpression of transketolase and desensitization resistance was evaluated in somatic cell hybrids formed between a desensitization-resistant adrenal cell line and a desensitization-sensitive rat glial cell line. In these hybrids, transketolase overexpression behaved dominantly, whereas desensitization resistance behaved recessively. These results dissociate the desensitization resistance phenotype from overexpression of transketolase and suggest that desensitization resistance may have resulted from disruption of an essential regulatory gene in conjunction with the amplification event.

Biliary tract complications of laparoscopic cholecystectomy are detected more frequently with routine intraoperative cholangiography

Controversy over whether intraoperative cholangiography (IOC) should be done routinely has intensified since the advent of laparoscopic cholecystectomy (LC). As yet, no study has demonstrated a clear benefit to its use, although their have been suggestions in the literature that routine use may confer an advantage to detection of injuries. One-hundred seventy-seven biliary tract complications occurring secondary to LC were identified from the combined data of seven institutions. The goal of this retrospective study was to examine the impact of IOC on the occurrence, recognition, and correction of such complications. The complications identified include 39 cystic duct leaks, 69 major ductal leaks or strictures, and 69 major ductal transection or excision injuries. Whether IOC was performed was known in 157 (88%) patients with 53 patients definitely having and 104 not having an IOC. Data concerning IOC were unavailable in 20 cases. More injuries were detected intraoperatively in the group having IOC (P < 0.001). Conversion of the LC to a laparotomy, often for repair of the injury, occurred more commonly in the group having a correctly interpreted IOC (P < 0.001). Conversion resulted in detection of injuries sooner, resulting in fewer operative procedures to correct the injury (P < 0.001). A transecting injury was prevented in at least seven patients when no visualization of the proximal biliary tree was documented by IOC. These partial ductal incisions were treated by t-tube placement. Incorrect interpretation of the IOC occurred in at least eight patients, with no identification of the proximal biliary tree in six.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropin-resistant mutants of the Y1 adrenal cell line fail to express the adrenocorticotropin receptor

This report examines the basis for adrenocorticotropin (ACTH) resistance in two mutant clones (Y6 and OS3) derived from the ACTH-responsive Y1 mouse adrenocortical tumor cell line. These two mutants were originally characterized by their failure to respond to ACTH with increased adenylyl cyclase activity and as a consequence were resistant to the steroidogenic effects of the hormone. We now demonstrate that ACTH resistance in the Y6 and OS3 mutants results from the failure to express the gene encoding the ACTH receptor. Whereas parental Y1 cells express ACTH receptor transcripts at low levels and are stimulated by ACTH or 8-bromo-cAMP to increase the accumulation of ACTH receptor transcripts approximately twofold, the Y6 and OS3 mutants do not express receptor transcripts either in the presence or absence of 8-bromo-cAMP. The gene encoding the ACTH receptor appears to be present in the Y6 and OS3 mutants, as determined by Southern blot hybridization analysis. Moreover, in the Y6 mutant the ACTH receptor gene appears to be silenced by a modification that is reversed following the growth of the cells as tumors in mice. Clonal isolates of Y6 cells grown as tumors recover the ability to express ACTH receptor transcripts at low but detectable levels and acquire the ability to respond to ACTH with increased adenylyl cyclase activity. Finally, Y6 and OS3 cells transformed with a gene encoding the mouse beta 2-adrenergic receptor respond to the beta-adrenergic agonist, isoproterenol, in a manner that is indistinguishable from the similarly transformed parent Y1 cell line. These latter results demonstrate the functional integrity of the adenylyl cyclase system in the ACTH-resistant mutants and indicate that the failure to express ACTH receptor transcripts limits the responsiveness of these clones.

ACTH-receptor deficient mutants of the Y1 mouse adrenocortical tumor cell line

Two mutant clones (Y6 and OS3) derived from the ACTH-responsive Y1 mouse adrenocortical tumor cell line fail to respond to ACTH with increased adenylyl cyclase activity and, as a consequence, are resistant to the steroidogenic effects of the hormone. As determined from Northern blot and RNase protection assays, ACTH resistance in these mutants results from the failure to accumulate ACTH receptor transcripts. The ACTH receptor gene appears to be present in these mutants as determined by Southern blot hybridization analysis and can be activated following the growth of the mutant cells as tumors in mice, suggesting that the ACTH receptor gene is modified in a reversible manner. When mutant cells are transformed with a gene encoding the mouse beta 2-adrenergic receptor they respond to beta-adrenergic agonists with increased adenylyl cyclase activity in a manner that is indistinguishable from a similarly transformed parent Y1 cell line. These results suggest that the adenylyl cyclase system in the mutants is otherwise intact and that the failure to express ACTH receptor transcripts limits the responsiveness of these clones to the hormone.

In vitro proteolytic activity and active-site identification of the human cytomegalovirus protease

Human cytomegalovirus (HCMV) encodes a protease that cleaves itself and the HCMV assembly protein. Two proteolytic processing sites within the protease were identified at Ala 256-Ser 257 (release site) and Ala 643-Ser 644 (maturation site). Identification of rP5-P4' and mP4-P6' as the minimal peptide substrates spanning the release and maturation cleavage sites, respectively, demonstrated a requirement for residues flanking the conserved core in substrate recognition and hydrolysis, which are unique to HCMV. Kinetic parameters determined for release-site-derived and maturation-site-derived peptides revealed a 10-fold increase in kcat/Km for a maturational peptide (mP4-P8') over release-site peptide (rP5-P5'). Experimental results with a panel of class-specific protease inhibitors were consistent with the protease being a member of the serine or cysteine family of proteases. Further investigation revealed that the HCMV protease activity decreased with incorporation of [14C]iodoacetic acid, but when approximately 4.5 mol 14C were incorporated/mol enzyme, the enzyme retained approximately 20% of its original activity, indicating that hydrolysis does not require a cysteine nucleophile. Analysis of diisopropyl-fluorophosphate-inactivated protease by mass spectrometry indicated a stoichiometry of 1 diisopropyl phosphate/protease molecule, suggesting that hydrolysis requires a single serine nucleophile. The residue modified by diisopropyl fluorophosphate was identified as Ser132 by modification with 3H-labeled diisopropyl fluorophosphate, peptide mapping and Edman degradation. This residue and the region in which it is found is highly conserved among the herpes virus proteases. These data demonstrates that HCMV protease is a serine protease and that Ser132 is the active-site nucleophile.

Orientation of peptide fragments from Sos proteins bound to the N-terminal SH3 domain of Grb2 determined by NMR spectroscopy

NMR spectroscopy has been used to characterize the protein-protein interactions between the mouse Grb2 (mGrb2) N-terminal SH3 domain complexed with a 15-residue peptide (SPLLPKLPP-KTYKRE) corresponding to residues 1264-1278 of the mouse Sos-2 (mSos-2) protein. Intermolecular interactions between the peptide and 13C-15N-labeled SH3 domain were identified in half-reverse-filtered 2D and 3D NOESY experiments. Assignments for the protons involved in interactions between the peptide and the SH3 domain were confirmed in a series of NOESY experiments using a set of peptides in which different leucine positions were fully deuterated. The peptide ligand-binding site of the mGrb2 N-terminal SH3 domain is defined by the side chains of specific aromatic residues (Tyr7, Phe9, Trp36, Tyr52) that form two hydrophobic subsites contacting the side chains of the peptide Leu4 and Leu7 residues. An adjacent negatively charged subsite on the SH3 surface is likely to interact with the side chain of a basic residue at peptide position 10 that we show to be involved in binding. The peptide-binding site of the SH3 is characterized by large perturbations of amide chemical shifts when the peptide is added to the SH3 domain. The mGrb2 N-terminal SH3 domain structure in the complex is well-defined (backbone RMSD of 0.56 +/- 0.21 calculated over the backbone N, C alpha, and C atoms of residues 1-54). The structure of the peptide in the complex is less well-defined but displays a distinct orientation.(ABSTRACT TRUNCATED AT 250 WORDS)

Further evidence that one of the earliest alterations in colorectal carcinogenesis involves APC

Colorectal cancer is hypothesized to arise after the accumulation of multiple mutations in critical oncogenes or tumor suppressor genes. The relative timing of each mutation is unknown because the exact number and types of mutations differ between tumors. However, for every mutation except the first, tumor heterogeneity must exist until clonal dominance is reestablished. This principle was applied to mutant APC genes in eight colorectal adenomas. The APC mutations were homogeneously present throughout the adenomas, including those less than 1 cm in size, but absent from the normal polyp stalks. In one adenoma with APC and c-K-ras mutations, both mutations were simultaneously present in only a small discrete portion, suggesting that the c-K-ras mutation was acquired after the APC mutation. These findings suggest that when mutations in APC occur, they are usually one of the first events in colorectal carcinogenesis or provide such a strong selective advantage that intratumor heterogeneity is seldom observed.