Contractility parameters of human β-cardiac myosin with the hypertrophic cardiomyopathy mutation R403Q show loss of motor function

Hypertrophic cardiomyopathy (HCM) is the most frequently occurring inherited cardiovascular disease. It is caused by mutations in genes encoding the force-generating machinery of the cardiac sarcomere, including human β-cardiac myosin. We present a detailed characterization of the most debated HCM-causing mutation in human β-cardiac myosin, R403Q. Despite numerous studies, most performed with nonhuman or noncardiac myosin, there is no consensus about the mechanism of action of this mutation on the function of the enzyme. We use recombinant human β-cardiac myosin and new methodologies to characterize in vitro contractility parameters of the R403Q myosin compared to wild type. We extend our studies beyond pure actin filaments to include the interaction of myosin with regulated actin filaments containing tropomyosin and troponin. We find that, with pure actin, the intrinsic force generated by R403Q is ~15% lower than that generated by wild type. The unloaded velocity is, however, ~10% higher for R403Q myosin, resulting in a load-dependent velocity curve that has the characteristics of lower contractility at higher external loads compared to wild type. With regulated actin filaments, there is no increase in the unloaded velocity and the contractility of the R403Q myosin is lower than that of wild type at all loads. Unlike that with pure actin, the actin-activated adenosine triphosphatase activity for R403Q myosin with Ca(2+)-regulated actin filaments is ~30% lower than that for wild type, predicting a lower unloaded duty ratio of the motor. Overall, the contractility parameters studied fit with a loss of human β-cardiac myosin contractility as a result of the R403Q mutation.

A delicate subject: The impact of cultural factors on neonatal and perinatal decision making

The neonatal intensive care unit (NICU) is a high-stress environment for both families and health care providers that can sometimes make appropriate medical decisions challenging. We present a review article of non-medical barriers to effective decision making in the NICU, including: miscommunication, mixed messages, denial, comparative social and cultural influences, and the possible influence of perceived legal issues and family reliance on information from the Internet. As examples of these barriers, we describe and discuss two cases that occurred simultaneously in the same NICU where decisions were influenced by social and cultural differences that were misunderstood by both medical staff and patients' families. The resulting stress and emotional discomfort created an environment with sub-optimal relationships between patients' families and health care providers. We provide background on the sources of conflict in these particular cases. We also offer suggestions for possible amelioration of similar conflicts with the twin goals of facilitating compassionate decision making in NICU settings and promoting enhanced well-being of both families and providers.

The hypertrophic cardiomyopathy myosin mutation R453C alters ATP binding and hydrolysis of human cardiac β-myosin

The human hypertrophic cardiomyopathy mutation R453C results in one of the more severe forms of the myopathy. Arg-453 is found in a conserved surface loop of the upper 50-kDa domain of the myosin motor domain and lies between the nucleotide binding pocket and the actin binding site. It connects to the cardiomyopathy loop via a long α-helix, helix O, and to Switch-2 via the fifth strand of the central β-sheet. The mutation is, therefore, in a position to perturb a wide range of myosin molecular activities. We report here the first detailed biochemical kinetic analysis of the motor domain of the human β-cardiac myosin carrying the R453C mutation. A recent report of the same mutation (Sommese, R. F., Sung, J., Nag, S., Sutton, S., Deacon, J. C., Choe, E., Leinwand, L. A., Ruppel, K., and Spudich, J. A. (2013) Proc. Natl. Acad. Sci. U.S.A. 110, 12607-12612) found reduced ATPase and in vitro motility but increased force production using an optical trap. Surprisingly, our results show that the mutation alters few biochemical kinetic parameters significantly. The exceptions are the rate constants for ATP binding to the motor domain (reduced by 35%) and the ATP hydrolysis step/recovery stroke (slowed 3-fold), which could be the rate-limiting step for the ATPase cycle. Effects of the mutation on the recovery stroke are consistent with a perturbation of Switch-2 closure, which is required for the recovery stroke and the subsequent ATP hydrolysis.

Measurement of the refractive index of highly turbid media: reply to comment

Peiponen et al. [Opt. Lett.35, 4108 (2010)] have expressed concern that a theoretical model we proposed in Calhoun et al. [Opt. Lett.35, 1224 (2010)] for total internal reflection from a turbid medium may be inconsistent with the experimental data, in the sense that the model fails to take into account unexplained oscillations in our data. We show that their concern arises from misinterpretation of our data and theory, and is, therefore, unfounded. NOTE: Optics Letters apologizes to the authors for the delay in the publication of this Reply.

Measurement of the refractive index of highly turbid media

We demonstrate a first simultaneous measurement of the real and imaginary parts of the refractive index of a highly turbid medium by observing the real-time reflectance profile of a divergent laser beam made incident on the surface of the turbid medium. We find that the reflectance data are well described by Fresnel theory that correctly includes the effect on total internal reflection of angle-dependent penetration into the turbid medium.

Screening guidelines for retinopathy of prematurity: the need for revision in extremely low birth weight infants

OBJECTIVE

To determine whether significant retinopathy of prematurity (ROP) can be detected before 31 to 33 weeks' postmenstrual age (PMA) in extremely low birth weight (ELBW) infants.

METHODS

Medical records of all ELBW infants (<1000 g at birth) admitted to our regional perinatal center between April 1995 and January 1999 were reviewed retrospectively. Screening examinations for ROP were routinely performed at 4 to 6 weeks' chronological age (CA) from birth and followed at least every other week. Data were collected for infants who developed ROP. We determined the PMA at which the first screening eye examination demonstrated prethreshold disease and the subsequent examination that showed threshold disease (if it occurred). The percentages of infants who developed prethreshold ROP diagnosed at </=31 weeks' PMA and of those who progressed to threshold ROP before 34 weeks' PMA were determined.

RESULTS

All 258 ELBW infants were screened for ROP. Seventy-eight infants (30%) were diagnosed with prethreshold ROP. Twenty-seven of these infants (35%) progressed to threshold ROP. Ten infants who progressed to threshold ROP were <34 weeks' PMA at the time of this diagnosis. Of these 10 infants, 3 were diagnosed at 31 weeks' PMA, 4 at 32 weeks', and 3 at 33 weeks'.

CONCLUSION

More than 80% of ELBW infants who developed prethreshold disease in this cohort were </=33 weeks' PMA. The joint statement screening option of independently using 31 to 33 weeks' PMA for the first eye examination would have led to a diagnosis of threshold ROP on first examination in as many as 13% (10/78) of our patients. Early identification of prethreshold ROP is important for providing timely intervention in this rapidly progressive disease. Therefore, ELBW infants should receive initial ROP screening using the CA guideline of 4 to 6 weeks rather than the 31- to 33-week postconceptional age guideline.

Characterization of heat-inducible expression and cloning of HtpG (Hsp90 homologue) of Porphyromonas gingivalis

Porphyromonas gingivalis is implicated in the etiology of periodontal disease. Associations between microbial virulence and stress protein expression have been identified in other infections. For example, Hsp90 homologues in several microbial species have been shown to contribute to virulence. We previously reported that P. gingivalis possessed an Hsp90 homologue (HtpG) which cross-reacts with human Hsp90. In addition, we found that elevated levels of serum antibody to Hsp90 stress protein in individuals colonized with this microorganism were associated with periodontal health. However, the role of HtpG in P. gingivalis has not been explored. Therefore, we cloned the htpG gene and investigated the characteristics of HtpG localization and expression in P. gingivalis. htpG exists as a single gene of 2,052 bp from which a single message encoding a mature protein of approximately 68 kDa is transcribed. Western blot analysis revealed that the 68-kDa polypeptide was stress inducible and that a major band at 44 kDa and a minor band at 40 kDa were present at constitutive levels. Cellular localization studies revealed that the 44- and 40-kDa species were associated with membrane and vesicle fractions, while the 68-kDa polypeptide was localized to the cytosolic fractions.

Cellular localization of a Hsp90 homologue in Porphyromonas gingivalis

We previously reported an association between elevated serum antibody titers to the 90-kDa human heat shock protein (Hsp90), periodontal health and colonization by Porphyromonas gingivalis. In this study, we examined the cellular localization of the Hsp90 homologue of P. gingivalis. Cultures of P. gingivalis were heat-stressed (45 degrees C) and examined for localization of the Hsp90 homologue. Heat stress induced a 4-5-fold increase in anti-Hsp90 antibody reactivity over that of the unstressed controls. Western blot analysis revealed two bands (44 and 68 kDa) that reacted with anti-Hsp90 antibodies. The 68-kDa band was heat-inducible, while the 44-kDa band was not. Immunogold staining revealed that the Hsp90 homologue localized principally to the membrane and extracellular vesicles. Subcellular fractionation confirmed that the Hsp90 homologue was primarily membrane-associated.

Librarians' use of HealthWeb for reference and instruction

HealthWeb is a selective Internet resource that links users to annotated, evaluated Internet resources in the health sciences. A collaborative effort of librarians from more than twenty academic institutions, it is a valuable tool for librarians at the Reference Desk and during instruction sessions. Contents of the Reference Resources section are highlighted, as well as an example of use of the Nursing page during a typical class.

Consciousness as a self-organizing process: an ecological perspective

The evolution of consciousness is seen in the context of energy-driven evolution in general, where energy and information are understood as two sides of the same coin. From this perspective consciousness is viewed as an ecological system in which streams of cognitive, perceptual, and emotional information form a rich complex of interactions, analogous to the interactive metabolism of a living cell. The result is an organic, self-generating, or 'autopoietic', system, continuously in the act of creating itself. Evidence suggests that this process is chaotic, or at least chaotic-like, and capable of assuming a number of distinct states best understood as chaotic attractors.

Periurethral collagen injection for the treatment of urinary incontinence in children

PURPOSE

We assessed the efficacy and safety of periurethral collagen injection for urinary incontinence in children with neurogenic bladder dysfunction.

MATERIALS AND METHODS

We treated 11 children (mean age 10.6 years) who had incontinence and neurogenic bladder dysfunction with periurethral injections of glutaraldehyde cross-linked collagen. All patients were on anticholinergics and all but 1 were on clean intermittent catheterization preoperatively. Four patients had previously undergone augmentation cystoplasty. All patients were assessed before and after injection with a subjective continence scale and multichannel urodynamics. Followup ranged from 4 to 20 months from the last injection.

RESULTS

Mean group Valsalva leak point pressure was 34.5 cm. water. Four of the 11 patients had an identifiable detrusor leak point pressure. Overall success rate was 55% with 4 patients dry and 2 improved. Success correlated with a minimum increase in Valsalva leak point pressure of 20 to 25 cm. water to greater than 60 cm. water. Three patients had no demonstrable Valsalva leak point pressure after injection. All 5 patients in whom treatment failed had no change in Valsalva leak point pressure, including 2 with small capacity, poorly compliant bladders preoperatively. Because they had a component of sphincteric insufficiency, they underwent injection in the hope of increasing capacity with increased continence. In 3 patients Valsalva leak point pressure was greater than 50 cm. water. Detrusor leak point pressure developed in 3 patients postoperatively, including 1 with significantly increased Valsalva leak point pressure. One patient with significantly increased Valsalva leak point pressure had urethral hypermobility postoperatively. Of the 3 patients who subsequently underwent augmentation cystoplasty 1 is now dry, 1 is wet and 1 died of complications unrelated to urological disease. Patients underwent 1 to 4 procedures (mean 2.5).

CONCLUSIONS

Periurethral collagen injection may be effective for urinary incontinence in patients who have adequate capacity with good compliance and low Valsalva leak point pressure. When there is no response to repeat injections or a transient response, one should consider the possibility of bladder decompensation.

Comparative urodynamic findings after primary valve ablation, vesicostomy or proximal diversion

PURPOSE

There is little known about the effect of urinary diversion on the bladder of children with posterior urethral valves. There is a fear that diversion may result in contracted noncompliant bladders. We wished to compare urodynamic parameters in patients who underwent primary ablation of posterior urethral valves and in those who underwent diversion in the form of vesicostomy or pyelostomy.

MATERIALS AND METHODS

Urodynamics were done in 32 boys with a history of posterior urethral valves divided into 3 groups based on initial treatment: 1) transurethral valve ablation; 2) cutaneous vesicostomy, subsequent closure and valve ablation, and 3) proximal cutaneous pyelostomy, subsequent reconstitution and valve ablation.

RESULTS

Patients who underwent initial diversion with vesicostomy or pyelostomy had bladders with larger functional capacity, better compliance and less instability. Chronic renal failure developed in 25% of the patients who underwent primary valve ablation and 33% of those who underwent diversion. Average period of diversion in vesicostomy and pyelostomy patients was 25 months.

CONCLUSIONS

Based on our findings temporary diversion does not seem to damage bladders. On the contrary, placing a damaged bladder at rest may help to improve bladder function. Bladder function following reconstitution correlated poorly with ultimate outcome and progression to renal failure. While we do not recommend temporary diversion as the treatment of choice for patients with posterior urethral valves, we believe that when chosen as treatment, it can be safely performed with little risk of further damage to the bladder.

A chaotic systems analysis of the nasal cycle

The nasal cycle is a chaotic ultradian rhythm with a period ranging from about 75 to 200 minutes. It has been shown to correlate highly with EEG amplitude in the contralateral hemisphere at virtually all frequencies, suggesting a connection between this rhythm and laterality of brain function. During a three-week period, five participants estimated airflow from both nostrils every 30 minutes during waking hours. Estimates were recorded on Likert scales and analyzed in three distinct phases: (1) reconstructing two-dimensional attractors by lagging and embedding; (2) computing Fourier frequency analyses; and (3) estimating fractal dimensions. Attractor reconstructions demonstrate noticeable order when compared to Monte Carlo reconstructions of the same data sets, and dimension estimates are in the fractal range. The attractor reconstructions, in combination with the frequency analyses, show distinct individual differences in the structure of the nasal cycle. The advantages of chaotic systems analyses over traditional behavioral statistics are discussed.

Light does not induce an increase in cyclic-GMP content of squid or Limulus photoreceptors

Both slices of squid (Loligo) retinas and Limulus ventral photoreceptors, with or without prior stimulation by flashes of bright light, were rapidly frozen and analysed for cyclic-GMP content by radioimmunoassay. Measurement of the freezing process indicated that freezing occurred at about 100 msec after the light flash. No significant changes in cyclic-GMP content were induced by light in either tissue. These data do not confirm previous reports that cyclic-GMP content of invertebrate photoreceptors is markedly increased by illumination.

Light-induced GTPase activity and GTP[gamma S] binding in squid retinal photoreceptors

Illumination greatly increases the GTPase activity in homogenates of squid (Loligo) whole retinas or rhabdomeric membranes. Adenylylimidodiphosphate inhibits the light-insensitive (but not the light-sensitive) GTPase activity in these homogenates. Illumination also greatly increases the binding of GTP[gamma S] to the rhabdomeric membranes. This binding at saturating illuminations indicates that there are approximately 10-100 times more rhodopsin molecules than G-protein molecules in squid photoreceptors. Each light-activated rhodopsin molecule activates about 10 G-protein molecules which might provide amplification for the first stage of the phototransduction cascade.

Pharmacokinetics of caffeine in breast milk and plasma after single oral administration of caffeine to lactating mothers

Six healthy lactating women ranging in age from 28 to 35 years were selected to participate in the study. The women had been nursing their infants from 3 1/2 weeks up to 17 weeks. On the morning of the study each participant received 100 mg dose of caffeine. The oral dose of caffeine was taken with a glass of water on an empty stomach. Blood samples were collected from zero time to 24 h after caffeine administration. Each subject aseptically collected breast milk from the right and left breasts by manual expression or using a mechanical breast pump, from zero time to 24 h after caffeine administration. Caffeine in plasma and breast milk was determined by gas liquid chromatography using nitrogen phosphorous detection. Caffeine was rapidly absorbed producing plasma time to peaks ranging from 0.50 to 1.00 h, with values for peak concentrations between 3.60 and 6.15 micrograms ml-1 in plasma. In breast milk, time to peak ranged from 0.75 to 2.00 h and concentration values between 1.98 and 4.30 micrograms ml-1. No significant differences were found between attainment of the time of the peak in plasma and breast milk, p greater than 0.05. In addition, peak concentration for the right and left breast were not statistically different, p greater than 0.05. However, significant differences, p less than 0.05, between plasma and both breasts in regards to the peak concentrations were found. The overall breast milk/plasma ratio obtained from the respective area under the curves were 0.815 +/- 0.0521 and 0.809 +/- 0.202 for the right and left breast, respectively, and no statistical differences were observed between the right and left breasts, p greater than 0.05. In summary, caffeine is rapidly transferred to breast milk. Multiple dose studies are needed to provide more information about caffeine concentration in breast milk of women who receive multiple doses of caffeine or who chronically consume caffeine.