Modulation of myosin function by isoform-specific properties of Saccharomyces cerevisiae and muscle tropomyosins

Tropomyosin is an extended coiled-coil protein that influences actin function by binding longitudinally along thin filaments. The present work compares cardiac tropomyosin and the two tropomyosins from Saccharomyces cerevisiae, TPM1 and TPM2, that are much shorter than vertebrate tropomyosins. Unlike cardiac tropomyosin, the phase of the coiled-coil-forming heptad repeat of TPM2 is discontinuous; it is interrupted by a 4-residue deletion. TPM1 has two such deletions, which flank the 38-residue partial gene duplication that causes TPM1 to span five actins instead of the four of TPM2. Each of the three tropomyosin isoforms modulates actin-myosin interactions, with isoform-specific effects on cooperativity and strength of myosin binding. These different properties can be explained by a model that combines opposite effects, steric hindrance between myosin and tropomyosin when the latter is bound to a subset of its sites on actin, and also indirect, favorable interactions between tropomyosin and myosin, mediated by mutually promoted changes in actin. Both of these effects are influenced by which tropomyosin isoform is present. Finally, the tropomyosins have isoform-specific effects on in vitro sliding speed and on the myosin concentration dependence of this movement, suggesting that non-muscle tropomyosin isoforms exist, at least in part, to modulate myosin function.

Two-dimensional noise-robust blind deconvolution of ultrasound images

This paper presents a new method for 2-D blind homomorphic deconvolution of medical B-scan ultrasound images. The method is based on noise-robust 2-D phase unwrapping and a noise-robust procedure to estimate the pulse in the complex cepstrum domain. Ordinary Wiener filtering is used in the subsequent deconvolution. The resulting images became much sharper with better defined tissue structures compared with the ordinary images. The deconvolved images had a resolution gain along the order of 3 to 7, and the signal-to-noise ratio (SNR) doubled for many of the images used in our experiments. The method gave stable results with respect to noise and grey levels through several image sequences.

Hypertrophic cardiomyopathy caused by a novel alpha-tropomyosin mutation (V95A) is associated with mild cardiac phenotype, abnormal calcium binding to troponin, abnormal myosin cycling, and poor prognosis

BACKGROUND

We report hypertrophic cardiomyopathy (HCM) in a Spanish-American family caused by a novel alpha-tropomyosin (TPM1) mutation and examine the pathogenesis of the clinical disease by characterizing functional defects in the purified mutant protein.

METHODS AND RESULTS

HCM was linked to the TPM1 gene (logarithm of the odds [LOD] score 3.17). Sequencing and restriction digestion analysis demonstrated a TPM1 mutation V95A that cosegregated with HCM. The mutation has been associated with 13 deaths in 26 affected members (11 sudden deaths and 2 related to heart failure), with a cumulative survival rate of 73+/-10% at the age of 40 years. Left ventricular wall thickness (mean 16+/-6 mm) and disease penetrance (53%) were similar to those for the ss-myosin mutations L908V and G256E previously associated with a benign prognosis. Left ventricular hypertrophy was milder than with the ss-myosin mutation R403Q, but the prognosis was similarly poor. With the use of recombinant tropomyosins, we identified several functional alterations at the protein level. The mutation caused a 40% to 50% increase in calcium affinity in regulated thin filament-myosin subfragment-1 (S1) MgATPase assays, a 20% decrease in MgATPase rates in the presence of saturating calcium, a 5% decrease in unloaded shortening velocity in in vitro motility assays, and no change in cooperative myosin S1 binding to regulated thin filaments.

CONCLUSIONS

In contrast to other reported TPM1 mutations, V95A-associated HCM exhibits unusual features of mild phenotype but poor prognosis. Both myosin cycling and calcium binding to troponin are abnormal in the presence of the mutant tropomyosin. The genetic diagnosis afforded by this mutation will be valuable in the management of HCM.

The effect of tailoring a model HIV prevention program for local adolescent target audiences

In five U.S. sites (Nashville, Tennessee; Newark, New Jersey; northern Virginia; Phoenix, Arizona; and Sacramento, California), HIV risk-reduction workshops were mounted as a part of the Prevention Marketing Initiative (PMI). In four of the five sites, the workshop curriculum was a version of Be Proud! Be Responsible! (Jemmott, Jemmott, & McCaffree, 1996) that had been tailored to fit the needs of local target audiences. This article describes the evaluation of the PMI workshops. Protective effects on several behavioral determinants and behavioral outcome measures were observed 1 month after the workshops. Based on the overall pattern of results, it was concluded that the PMI workshops reduced the likelihood of unprotected sex among participants. The intervention developed by Jemmott and colleagues appears to have retained its effectiveness after it was tailored to meet perceived local needs.

Performance evaluation of two-dimensional phase unwrapping algorithms

We present a performance evaluation of eight two-dimensional phase unwrapping methods with respect to correct phase unwrapping and execution times. The evaluated methods are block least squares (BLS), adaptive integration (AI), quality guided path following (QUAL), mask cut (MCUT), multigrid (MGRID), preconditioned conjugate gradient (PCG), Flynn's (FLYNN), and Liang's (LIANG). This set included integration- (path following), least-squares-, L(1)-, and model-based methods. The methods were tested on several synthetic images, on two magnetic resonance images, and on two interferometry images. The synthetic images were designed to demonstrate different aspects of the phase unwrapping problem. To test the noise robustness of the methods, independent noise was added to the synthetic images to yield different signal-to-noise ratios. Each experiment was performed 50 times with different noise realizations to test the stability of the methods. The results of the experiments showed that the congruent minimum L(1) norm FLYNN method was best overall and the most noise robust of the methods, but it was also one of the slowest methods. The integration-based QUAL method was the only method that correctly unwrapped the two interferometry images. The least-squares-based methods (MGRID, PCG) gave worse results on average than did the integration- (or path following) based methods (BLS, AI, QUAL, MCUT) and were also slower. The model-based LIANG method was sensitive to noise and resulted in large errors for the magnetic resonance images and the interferometry images. In conclusion, for a particular application there is a trade-off between the quality of the unwrapping and the execution time when we attempt to select the most appropriate method.

Two-dimensional phase unwrapping using a block least-squares method

We present a block least-squares (BLS) method for two-dimensional (2-D) phase unwrapping. The method works by tessellating the input image into small square blocks with only one phase wrap. These blocks are unwrapped using a simple procedure, and the unwrapped blocks are merged together using one of two proposed block merging algorithms. By specifying a suitable mask, the method can easily handle objects of any shape. This approach is compared with the Ghiglia-Romero method and the Marroquin-Rivera method. On synthetic images with different noise levels, the BLS method is shown to be superior, both with respect to the resulting gray values in the unwrapped image as well as visual inspection. The method is also shown to successfully unwrap synthetic and real images with shears, fiber-optic interferometry images, and medical magnetic resonance images. We believe the new method has the potential to improve the present quality of phase unwrapped images of several different image modalities.

DSM-III-R Axis I and II disorders in agoraphobic patients with and without panic disorder

Patients attending an inpatient phobia treatment program were diagnosed for DSM-III-R Axis I and II disorders, using the Structured Clinical Interview for DSM-III-R Disorders, and completed a set of self-report instruments. They were divided into 3 groups: (a) those who met the criteria for panic disorder with agoraphobia (n = 57), (b) those who met the criteria for agoraphobia without a history of panic disorder (n = 21), and (c) those who met criteria for other anxiety disorders, but not for panic/agoraphobia (n = 14). On Axis I, more of the panic with agoraphobia than of the agoraphobia without panic patients had obsessive-compulsive disorder. On Axis II, no significant differences between the agoraphobic patients with and without panic occurred. However, the number of hysterical traits was related to the presence of panic disorder among the agoraphobic patients. Avoidant and dependent traits were related to symptom severity.

Strategies for improving patient compliance

Achieving patient compliance in taking prescribed medications is a formidable challenge for all clinicians. As PAs, we have daily opportunities to communicate with patients and improve their compliance. An office-based compliance program, combining patient education and behavior-modification components, can be beneficial in this regard. Strategies for improving compliance include giving clear, concise, and logical instructions in familiar language, adapting drug regimens to daily routines, eliciting patient participation through self-monitoring, and providing educational materials that promote overall good health in connection with medical treatment.

Use of resectoscope for colon cancer

Urologic endoscopic resectoscopes greatly simplify electrofulguration and resection of rectal tumors. The most important advantage is the enhanced visibility that allows determination of the depth of resection and good hemostasis. The indications for this procedure are otherwise-poor surgical candidates, palliation, excision of locally aggressive tumors such as villous adenomas, and bowel diversion prior to definitive therapy. Bleeding, peritoneal perforation requiring colostomy, and postoperative infection have all been reported, but the complication rate appears to be acceptable. Further clinical studies are necessary to determine if, indeed, this can be considered a curative procedure. Finally, because the practicing urologist is intimately aware of the technical aspects of the urologic resectoscope, he will probably be called on to perform, and should be aware of, this procedure.

Physical fitness level in patients with anxiety and depressive disorders

Physical work capacity (PWC) and pulmonary function were measured shortly after admission in 90 inpatients with anxiety and depressive disorders. PWC was dramatically reduced while pulmonary function was slightly increased compared with predicted normal values. This indicates that the low fitness levels were caused by physical inactivity, and it is a strong argument for integrating physical fitness training into psychiatric treatment programs. Values obtained by direct measurement and indirect calculations of PWC were highly correlated (R = 0.67). The mean differences between the two tests were 21% on an individual level and 5% on a group level.

Renin release selectively stimulated by prostaglandin I2 in isolated rat glomeruli

Renal glomeruli were isolated from rat kidneys using a passive mechanical sieving technique. Glomerular microsomal fraction, glomerular homogenate, or intact glomeruli were incubated with [1-14C]arachidonic acid, and the profile of prostaglandin (PG) synthesis was determined by thin-layer chromatography. The three incubation systems produced 15.3, 20.8, and 40.4% 6-keto-PGF1 alpha; 19.1, 23.5, and 15.3 PGF2 alpha; 5.7, 9.1, and 3.9% thromboxane (TX) B2; 36.0, 35.1, and 37.0% PGE2; and 23.9, 11.3, and 3.4% PGD2, respectively. Glomeruli were placed in suspension within glass chambers and superfused with Krebs solution. Superfusion with 1.6 x 10(-4) M arachidonic acid stimulated a significant release of renin from glomeruli, whereas 2.7 x 10(-6) M PGE1, PGE2, PGF2 alpha, TXB2, PGD2, or a stable analog of PGH2 had no effect on renin. When the rapid breakdown of PGI2 was counteracted by either increasing the concentration to 1.7 x 10(-4) M or stabilizing in Krebs at pH 9.4, it stimulated a significant increase in renin release. Reducing the arachidonic acid concentration to 1.6 x 10(-5) M eliminated both renin release and PGI2 synthesis, while increased PGE2 synthesis persisted. Finally, using an inhibitor of PGI2 synthesis, azo analog 1 (2.8 x 10(-6) M), 6-keto-PGF1 alpha produced in response to arachidonic acid was eliminated, as was the concurrent release of renin, but PGE2 synthesis was not affected. These results suggest that the mechanism of direct interaction between renal PG and renin in isolated glomeruli is selectively due to the action of PGI2.