Social media and use of electronic nicotine delivery systems among school-going adolescents in a rural distressed Appalachian community.

Electronic nicotine delivery systems (ENDS) are the most used tobacco products among middle and high schoolers in the United States (U.S.). Familial relations and access play a major role in uptake among adolescents; yet the role of social media in this phenomenon in the context of communities impacted by tobacco-related health disparities is understudied. In Spring 2019, data were collected from adolescents in 8th and 9th grades in a school located in a rural distressed county in Tennessee to assess social media's role in ENDS uptake. Descriptive and multivariable statistical analyses were performed to delineate factors associated with ENDS use. Of a total of 399 respondents, 12.5 % reported current ENDS use and 22.1 % indicated having ever discussed ENDS on social media. Closed messaging platforms (Snapchat) and video platforms (Facebook/Instagram/You Tube) were the most reported form of social media used (8.31 % and 8.31 % respectively). Social media use was positively associated with both ever ENDS use (odds ratio [OR] = 2.9) and current ENDS use (OR = 3.98). Parental advice against ENDS use was positively associated with ever ENDS use. In conclusion, social media use was positively associated with both ever and current ENDS use, and Snapchat was the most popular platform among this population of students. The results indicate that youth social media engagement may lead to exposure that can influence ENDS uptake. Future studies are needed to further examine these associations among distressed communities.

Massage or music for pain relief in labour: a pilot randomised placebo controlled trial.

Research on massage therapy for maternal pain and anxiety in labour is currently limited to four small trials. Each used different massage techniques, at different frequencies and durations, and relaxation techniques were included in three trials. Given the need to investigate massage interventions that complement maternal neurophysiological adaptations to labour and birth pain(s), we designed a pilot randomised controlled trial (RCT) to test the effects of a massage programme practised during physiological changes in pain threshold, from late pregnancy to birth, on women's reported pain, measured by a visual analogue scale (VAS) at 90 min following birth. To control for the potential bias of the possible effects of support offered within preparation for the intervention group, the study included 3 arms--intervention (massage programme with relaxation techniques), placebo (music with relaxation techniques) and control (usual care). The placebo offered a non-pharmacological coping strategy, to ensure that use of massage was the only difference between intervention and placebo groups. There was a trend towards slightly lower mean pain scores in the intervention group but these differences were not statistically significant. No differences were found in use of pharmacological analgesia, need for augmentation or mode of delivery. There was a trend towards more positive views of labour preparedness and sense of control in the intervention and placebo groups, compared with the control group. These findings suggest that regular massage with relaxation techniques from late pregnancy to birth is an acceptable coping strategy that merits a large trial with sufficient power to detect differences in reported pain as a primary outcome measure.

Molecular basis of passive stress relaxation in human soleus fibers: assessment of the role of immunoglobulin-like domain unfolding.

Titin (also known as connectin) is the main determinant of physiological levels of passive muscle force. This force is generated by the extensible I-band region of the molecule, which is constructed of the PEVK domain and tandem-immunoglobulin segments comprising serially linked immunoglobulin (Ig)-like domains. It is unresolved whether under physiological conditions Ig domains remain folded and act as "spacers" that set the sarcomere length at which the PEVK extends or whether they contribute to titin's extensibility by unfolding. Here we focused on whether Ig unfolding plays a prominent role in stress relaxation (decay of force at constant length after stretch) using mechanical and immunolabeling studies on relaxed human soleus muscle fibers and Monte Carlo simulations. Simulation experiments using Ig-domain unfolding parameters obtained in earlier single-molecule atomic force microscopy experiments recover the phenomenology of stress relaxation and predict large-scale unfolding in titin during an extended period (> approximately 20 min) of relaxation. By contrast, immunolabeling experiments failed to demonstrate large-scale unfolding. Thus, under physiological conditions in relaxed human soleus fibers, Ig domains are more stable than predicted by atomic force microscopy experiments. Ig-domain unfolding did not become more pronounced after gelsolin treatment, suggesting that the thin filament is unlikely to significantly contribute to the mechanical stability of the domains. We conclude that in human soleus fibers, Ig unfolding cannot solely explain stress relaxation.

Protein kinase A phosphorylates titin's cardiac-specific N2B domain and reduces passive tension in rat cardiac myocytes.

beta-Adrenergic stimulation of cardiac muscle activates protein kinase A (PKA), which is known to phosphorylate proteins on the thin and thick filaments of the sarcomere. Cardiac muscle sarcomeres contain a third filament system composed of titin, and here we demonstrate that titin is also phosphorylated by the beta-adrenergic pathway. Titin phosphorylation was observed after beta-receptor stimulation of intact cardiac myocytes and incubation of skinned cardiac myocytes with PKA. Mechanical experiments with isolated myocytes revealed that PKA significantly reduces passive tension. In vitro phosphorylation of recombinant titin fragments and immunoelectron microscopy suggest that PKA targets a subdomain of the elastic segment of titin, referred to as the N2B spring element. The N2B spring element is expressed only in cardiac titins, in which it plays an important role in determining the level of passive tension. Because titin-based passive tension is a determinant of diastolic function, these results suggest that titin phosphorylation may modulate cardiac function in vivo.

The complete gene sequence of titin, expression of an unusual approximately 700-kDa titin isoform, and its interaction with obscurin identify a novel Z-line to I-band linking system.

Titin is a giant vertebrate striated muscle protein with critical importance for myofibril elasticity and structural integrity. We show here that the complete sequence of the human titin gene contains 363 exons, which together code for 38 138 residues (4200 kDa). In its central I-band region, 47 novel PEVK exons were found, which contribute to titin's extensible spring properties. Additionally, 3 unique I-band titin exons were identified (named novex-1 to -3). Novex-3 functions as an alternative titin C-terminus. The novex-3 titin isoform is approximately 700 kDa in size and spans from Z1-Z2 (titin's N-terminus) to novex-3 (C-terminal exon). Novex-3 titin specifically interacts with obscurin, a 721-kDa myofibrillar protein composed of 57 Ig/FN3 domains, followed by one IQ, SH3, DH, and a PH domain at its C-terminus. The obscurin domains Ig48/Ig49 bind to novex-3 titin and target to the Z-line region when expressed as a GFP fusion protein in live cardiac myocytes. Immunoelectron microscopy detected the C-terminal Ig48/Ig49 obscurin epitope near the Z-line edge. The distance from the Z-line varied with sarcomere length, suggesting that the novex-3 titin/obscurin complex forms an elastic Z-disc to I-band linking system. This system could link together calcium-dependent, SH3-, and GTPase-regulated signaling pathways in close proximity to the Z-disc, a structure increasingly implicated in the restructuring of sarcomeres during cardiomyopathies.

Titin-actin interaction in mouse myocardium: passive tension modulation and its regulation by calcium/S100A1.

Passive tension in striated muscles derives primarily from the extension of the giant protein titin. However, several studies have suggested that, in cardiac muscle, interactions between titin and actin might also contribute to passive tension. We expressed recombinant fragments representing the subdomains of the extensible region of cardiac N2B titin (tandem-Ig segments, the N2B splice element, and the PEVK domain), and assayed them for binding to F-actin. The PEVK fragment bound F-actin, but no binding was detected for the other fragments. Comparison with a skeletal muscle PEVK fragment revealed that only the cardiac PEVK binds actin at physiological ionic strengths. The significance of PEVK-actin interaction was investigated using in vitro motility and single-myocyte mechanics. As F-actin slid relative to titin in the motility assay, a dynamic interaction between the PEVK domain and F-actin retarded filament sliding. Myocyte results suggest that a similar interaction makes a significant contribution to the passive tension. We also investigated the effect of calcium on PEVK-actin interaction. Although calcium alone had no effect, S100A1, a soluble calcium-binding protein found at high concentrations in the myocardium, inhibited PEVK-actin interaction in a calcium-dependent manner. Gel overlay analysis revealed that S100A1 bound the PEVK region in vitro in a calcium-dependent manner, and S100A1 binding was observed at several sites along titin's extensible region in situ, including the PEVK domain. In vitro motility results indicate that S100A1-PEVK interaction reduces the force that arises as F-actin slides relative to the PEVK domain, and we speculate that S100A1 may provide a mechanism to free the thin filament from titin and reduce titin-based tension before active contraction.

Mechanical properties of titin isoforms.

Titin is a giant filamentous polypeptide of multi-domain construction spanning between the Z- and M-lines of the sarcomere. As a result of differential splicing, length variants of titin are expressed in different skeletal and cardiac muscles. Here we first briefly review some of our previous work that has revealed that titin develops force in sarcomeres either stretched beyond their slack length (passive force) or shortened to below the slack length (restoring force) and that titin's force underlies a large fraction of the diastolic force of cardiac muscle. Next we present our mechanical and immunoelectron microscopical (IEM) studies of skeletal and cardiac muscles that express titin isoforms. The previously deduced molecular properties of titin were used to model titin's extensible region in the sarcomere as serially linked WLCs: rigid segments (containing folded Ig/Fn domains) and more flexible segments (PEVK segment). The model was tested on skeletal muscle fibers that express titin isoforms with tandem Ig and PEVK length variants. The model adequately predicts titin's behavior along a wide sarcomere length range in skeletal muscle, but at long sarcome lengths (SLs), predicted forces are much higher than those determined experimentally. IEM reveals that this may result from Ig domain unfolding. Experiments were also performed on cardiac myocytes from mouse and cow that express predominantly a small cardiac titin isoform (N2B titin) or a large isoform (N2BA titin), respectively. The passive tension-SL relation of myocytes was found to increase more steeply with SL in mouse than in cow. IEM revealed an additional source of extensibility within both of these cardiac titins: the unique N2B sequence (absent in skeletal muscle). Furthermore, the PEVK segment of the N2BA isoform extended to a maximal length of approximately 200 nm, as opposed to approximately 60 nm for the N2B isoform. We propose that, along the physiological SL range, the long PEVK segment found in N2BA titins results in a low PEVK fractional extension and that this underlies the lower passive tensions of N2BA-expressing cow myocytes.

Alterations in the determinants of diastolic suction during pacing tachycardia.

In cardiomyocytes, generation of restoring forces (RFs) responsible for elastic recoil involves deformation of the sarcomeric protein titin in conjunction with shortening below slack length. At the left ventricular (LV) level, recoil and filling by suction require contraction to an end-systolic volume (ESV) below equilibrium volume (Veq) as well as large-scale deformations, for example, torsion or twist. Little is known about RFs and suction in the failing ventricle. We undertook a comparison of determinants of suction in open-chest dogs previously subjected to 2 weeks of pacing tachycardia (PT) and controls. To assess the ability of the LV to contract below Veq, we used a servomotor to clamp left atrial pressure and produce nonfilling diastoles, allowing measurement of fully relaxed pressure at varying volumes. We quantified twist with sonomicrometry. We also assessed transmural ratios of N2B to N2BA titin isoforms and total titin to myosin heavy chain (MHC) protein. In PT, the LV did not contract below Veq, even with marked reduction of volume (end-diastolic pressure [EDP], 1 to 2 mm Hg), whereas in controls ESV was less than Veq when EDP was less than approximately 5 mm Hg. In PT, both systolic twist and diastolic untwisting rate were reduced, and there was exaggerated transmural variation in titin isoform and titin-to-MHC ratios, consistent with the more extensible N2BA being present in larger amounts in the subendocardium. Thus, in PT, determinants of suction at the level of the LV are markedly impaired. The altered transmural titin isoform gradient is consistent with a decrease in RFs and may contribute to these findings.

Differential expression of cardiac titin isoforms and modulation of cellular stiffness.

Extension of the I-band segment of titin gives rise to part of the diastolic force of cardiac muscle. Previous studies of human cardiac titin transcripts suggested a series of differential splicing events in the I-band segment of titin leading to the so-called N2A and N2B isoform transcripts. Here we investigated titin expression at the protein level in a wide range of mammalian species. Results indicate that the myocardium coexpresses 2 distinct titin isoforms: a smaller isoform containing the N2B element only (N2B titin) and a larger isoform with both the N2B and N2A elements (N2BA titin). The expression ratio of large N2BA to small N2B titin isoforms was found to vary greatly in different species; eg, in the left ventricle the ratio is approximately 0.05 in mouse and approximately 1.5 in pig. Differences in the expression ratio were also found between atria and ventricles and between different layers of the ventricular wall. Immunofluorescence experiments with isoform-specific antibodies suggest that coexpression of these isoforms takes place at the single-myocyte level. The diastolic properties of single cardiac myocytes isolated from various species expressing high levels of the small (rat and mouse) or large (pig) titin isoform were studied. On average, pig myocytes are significantly less stiff than mouse and rat myocytes. Gel analysis indicates that this result cannot be explained by varying amounts of titin in mouse and pig myocardium. Rather, low stiffness of pig myocytes can be explained by its high expression level of the large isoform: the longer extensible region of this isoform results in a lower fractional extension for a given sarcomere length and hence a lower force. Implications of our findings to cardiac function are discussed.

A six-year retrospective analysis of shoulder dystocia and delivery of the shoulders.

OBJECTIVE: To investigate the diagnosis, incidence and management of shoulder dystocia. DESIGN: Retrospective review of all the deliveries between 1988 and 1993 which were coded on the computer data base as 'moderate difficulty with the shoulders' or 'shoulder dystocia'. SETTING: A teaching hospital in the south of England. PARTICIPANTS: The study population consisted of 15,658 women who had cephalic vaginal deliveries of babies weighing > 2.5 kg. The sample consisted of the 257 women reported to have moderate difficulty with the shoulders or shoulder dystocia at delivery. FINDINGS: There was a significant fall in the reported incidence of shoulder dystocia during the period under investigation. Eighty-six (1.1%) of the deliveries between 1988 and 1990 were reported to have been complicated by shoulder dystocia. In 1991 a second option was introduced to allow both shoulder dystocia or moderate difficulties with the shoulders to be coded after delivery. Following this change in categorisation, the incidence of shoulder dystocia was reduced to 30 (0.6%) reported cases in 1992-1993. Over the same period the reported incidence of moderate difficulty rose significantly from 29 (1.1%) in 1992 to 60 (2.4%) in 1993 (P < 0.001). Disparity was noted between the experience of practitioners and contemporary definitions of shoulder dystocia and this was highlighted by the number of reported cases of moderate difficulty. In this study practitioners used the term shoulder dystocia in a general sense to describe a range of difficulties encountered with the delivery of the shoulders and they identified many varied manifestations. In comparison, contemporary literature describes shoulder dystocia as a discrete entity. KEY CONCLUSIONS: Shoulder dystocia is a complex clinical scenario and perceptions of the incidence may be influenced by alterations in the delivery technique and changes in the diagnosis and documentation. IMPLICATIONS FOR PRACTICE: The application of traction may interfere with the normal mechanisms of labour and the spontaneous birth of the shoulders, whilst increasing the risk of trauma to the baby. It may be unnecessary to use such interventions routinely in the care of normal labouring women.

Constitutive nitric oxide synthase in Saccharomyces cerevisiae.

After removing nonspecific immunoreactivities from crude extract by immunoaffinity chromatography, an immunoreactive-band at 60 kDa of constitutive nitric oxide synthase (cNOS) from Saccharomyces cerevisiae was detected by Western blot using mouse monoclonal anti-neuronal NOS (cNOS). The activity of yeast cNOS, which was prepared by either histone-agarose chromatography or anti-neuronal NOS immunoprecipitation, was monitored by the formation of citrulline. Yeast cNOS was activated in the presence of calmodulin and arginine, whereas it was inhibited by L-NAME, a mammalian NOS inhibitor. Moreover, actinomycin-D decreased the extracellular and the intracellular levels of nitrate and nitrite which had been converted from NO. The results suggest that cNOS occurs in unicellular eukaryotes and the enzyme activity can be regulated.

Soluble guanylate cyclase in Saccharomyces cerevisiae.

After removing nonspecific immunoreactivities from crude extract by immunoaffinity chromatography, an immunoreactive-band at 40kDa of soluble guanylate cyclase (SGC) from Saccharomyces cerevisiae was detected by Western blot using rabbit anti-beta 1 subunit of SGC. Cyclic GMP level and SGC activity was measured by ELISA. Immunoprecipitated yeast SGC was activated by sodium nitroprusside, whereas inhibited by 1H-(1,2,4)oxadiazolo(4,3-A)quinoxalin-1-one. Increased cyclic GMP level was also noted when intact yeast cells were incubated with s-nitrosoglutathione, a NO donor. The result implies that NO can be utilized intracellularly and extracellularly. Moreover, the presence of SGC suggests the significance of NO/cyclic GMP signaling in unicellular eukaryotes.

The presence/absence of Bcl-2, Ca2+/calmodulin-dependent protein kinase IV, calretinin and p53 in baker's yeast and wheat germ.

After removing the nonspecific immunoreactivities from crude extracts of Saccharomyces cerevisiae and wheat germ by immunoaffinity chromatography, the presence of Ca(2+)-related proteins was tested by Western blot analysis. Immunoreactivity for Bcl-2 was absent in the yeast, whereas the immunoreactivity was evident in wheat germ and remained unchanged after incubation for 4 h with or without actinomycin D. Such incubation caused the degradation of immunoreactive-peptides of Ca2+/calmodulin-dependent protein kinase IV (CaMPK IV) in the yeast and wheat germ. Calretinin and p53 were absent in the yeast and wheat germ. The level of cyclic AMP in the yeast increased 100% after incubation for 30 min with actinomycin D. These results suggest that actinomycin D may not affect intracellular levels of these calcium-related proteins in the yeast and wheat germ, and that Bcl-2 occurs in multicellular eukaryotes. Moreover, the cellular level of CaMPK IV may vary during the onset of cell division and differentiation.

HMO case management and the surgical patient.

A nurse serving as a case manager in an HMO describes the major aspects of the role at present and also identifies and explains areas that are expanding. This role is vital to the quality outcomes and cost effectiveness of surgical procedures for HMO members. The case manager is a central member of the health care team of the HMO.

Popliteal pterygium syndrome: an orthopaedic perspective.

Popliteal pterygium syndrome (PPS) is a rare autosomal dominant disorder consisting of popliteal webs and craniofacial, genitourinary, and extremity anomalies. The popliteal webs make this syndrome particularly important to the orthopaedic surgeon. The resultant fixed flexion deformity can be severe, at times approximating the ischium to the calcaneus. The neurovascular bundle is contained in the web's posterior subcutaneous (S.C.) margin, which makes surgery precarious and difficult. We reviewed four patients between 1964 and 1986, three of whom were severely affected with fixed flexion deformities at the knee. Distal femoral shortening and extension osteotomies provided good results, and this procedure should be considered earlier rather than later in treatment of this problem.

Nicotine tolerance questionnaire scores and plasma nicotine: no correlation.

A questionnaire has been proposed to estimate degree of nicotine tolerance and thereby to rate the physical dependence of cigarette smokers. To examine its validity, 97 persons entering a smoking cessation clinic completed the Tolerance Questionnaire and gave late afternoon blood specimens for nicotine determination. There was no correlation between questionnaire scores and plasma nicotine levels. None of the questions had discriminatory value. A simple, nonchemical method of indicating degree of nicotine tolerance has not yet been validated.

Chewing nicotine gum for 3 months: what happens to plasma nicotine levels?

Techniques that help patients stop smoking should also reduce their exposure to agents such as nicotine. The mean plasma nicotine levels in 50 subjects while they were still smoking and then while they were chewing pieces of gum containing either 2 or 4 mg of nicotine over a 12-week period of abstinence were 35, 9 and 23 ng/mL (217, 56 and 143 nmol/L) respectively. A small number of subjects given an unlimited supply of gum used 14 to 24 pieces of 4-mg gum daily and had plasma nicotine levels exceeding the levels achieved while smoking. There were no acute symptoms necessitating medical intervention associated with these excessive levels. Side effects were uncommon and usually controllable. When simple dosage rules are followed people who chew nicotine gum for a few months to stop smoking lower their exposure to nicotine.