Electrostatic Interactions Control the Functionality of Bacterial Ice Nucleators.

Bacterial ice-nucleating proteins (INPs) promote heterogeneous ice nucleation more efficiently than any other material. The details of their working mechanism remain elusive, but their high activity has been shown to involve the formation of functional INP aggregates. Here we reveal the importance of electrostatic interactions for the activity of INPs from the bacterium Pseudomonas syringae by combining a high-throughput ice nucleation assay with surface-specific sum-frequency generation spectroscopy. We determined the charge state of nonviable P. syringae as a function of pH by monitoring the degree of alignment of the interfacial water molecules and the corresponding ice nucleation activity. The net charge correlates with the ice nucleation activity of the INP aggregates, which is minimal at the isoelectric point. In contrast, the activity of INP monomers is less affected by pH changes. We conclude that electrostatic interactions play an essential role in the formation of the highly efficient functionally aligned INP aggregates, providing a mechanism for promoting aggregation under conditions of stress that prompt the bacteria to nucleate ice.

Molecular structure of a hyperactive antifreeze protein adsorbed to ice.

Antifreeze proteins (AFPs) are a unique class of proteins that bind to ice crystal surfaces and arrest their growth. The working mechanism of AFPs is not well understood because, as of yet, it was not possible to perform molecular-scale studies of AFPs adsorbed to the surface of ice. Here, we study the structural properties of an AFP from the insect Rhagium mordax (RmAFP) adsorbed to ice with surface specific heterodyne-detected vibrational sum-frequency generation spectroscopy and molecular dynamic simulations. We find that RmAFP, unlike other proteins, retains its hydrating water molecules upon adsorption to the ice surface. This hydration water has an orientation and hydrogen-bond structure different from the ice surface, thereby inhibiting the insertion of water layers in between the protein and the ice surface.

[Yoga for mental disorders]. / Yoga bei psychischen Störungen.

BACKGROUND: The demand for complementary clinically efficacious, safe, patient acceptable, and cost-effective forms of treatment for mental illness is growing. Yoga has beneficial effects on somatic and mental health factors; therefore, yoga has preventive and therapeutic capabilities to improve mental dysfunction. OBJECTIVE: In this overview of the current literature, the evidence of the effects of yoga on selected major psychiatric disorders is summarized. RESULTS: The strongest evidence base for yoga exists in reducing depressive symptoms but its use in major depressive disorders is less clear. The evidence for the efficacy of yoga for anxiety disorders, and posttraumatic stress disorder (PTSD) is encouraging, but not definitive due to only a few randomized controlled trials and methodological problems. CONCLUSION: There is preliminary evidence that meditation-based yoga interventions may be helpful for depression, anxiety and PTSD; however, there may also be the risk of engaging in extreme yoga practices. The value of integrating yoga into a treatment plan for patients with psychiatric disorders needs to be evaluated on an individual basis. Healthcare providers can motivate and help patients evaluate whether a given yoga class is helpful and safe for them. Methodological problems and the unclear risk-benefit ratio preclude definitive recommendations for yoga as an adjunct treatment.

Identification of the response of protein N-H vibrations in vibrational sum-frequency generation spectroscopy of aqueous protein films.

The N-H stretching vibration is an important probe for investigating structural and functional properties of proteins but is often difficult to analyze as it overlaps with the O-H stretching vibration of water molecules. In this work we investigate the N-H signals of hydrophobins using conventional (VSFG) and heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSDG). Hydrophobins represent a group of surface active proteins that form highly-ordered protein films at the water-air interface and that give rise to prominent vibrational modes. We find that in conventional VSFG spectra N-H specific signals show significant changes in shape and intensity upon altering the pH values. These changes can easily be misinterpreted for conformational changes of the protein. Using HD-VSFG experiments, we demonstrate, that for hydrophobin films the change of the N-H response with pH can be well explained from the interference of the N-H response with the broad interfacial water O-H stretch band.

Membranes Are Decisive for Maximum Freezing Efficiency of Bacterial Ice Nucleators.

Ice-nucleating proteins (INPs) from Pseudomonas syringae are among the most active ice nucleators known, enabling ice formation at temperatures close to the melting point of water. The working mechanisms of INPs remain elusive, but their ice nucleation activity has been proposed to depend on the ability to form large INP aggregates. Here, we provide experimental evidence that INPs alone are not sufficient to achieve maximum freezing efficiency and that intact membranes are critical. Ice nucleation measurements of phospholipids and lipopolysaccharides show that these membrane components are not part of the active nucleation site but rather enable INP assembly. Substantially improved ice nucleation by INP assemblies is observed for deuterated water, indicating stabilization of assemblies by the stronger hydrogen bonds of D2O. Together, these results show that the degree of order/disorder and the assembly size are critically important in determining the extent to which bacterial INPs can facilitate ice nucleation.

[Dual diagnosis psychosis and substance use disorders in adolescents--part 1]. / Psychose und Sucht bei Jugendlichen und Jungerwachsenen[nl]Teil 1: Prävalenz und Erklärungsmodelle.

Epidemiological studies suggest that 20 % to 50 % of patients with schizophrenia have a lifetime comorbid substance use disorder (SUD). In first-episode psychosis this prevalence is even higher and varies between 20 % and 75 % with cannabis being the most widely used illicit drug. These difficult to treat patients usually have a worse prognosis as compared with non-substance abusing schizophrenic patients. Despite multiple theories proposed such as the self medication hypothesis, common or bidirectional factor models or genetic vulnerability, there is no consensus on the aetiology of increased rates of substance use in people with psychosis which is important to treat these patients. The dually diagnosed population is a heterogeneous group and it is likely that different models may explain comorbidity in different subgroups. The present review part one gives an overview on prevalence and explanation models for dual diagnosis psychosis and substance use with focus in adolescent and young adult populations, the second part reviews the clinical course for both disorders and current psychosocial treatment options.

[Dual diagnosis psychosis and substance use disorders in adolescents--part 2]. / Psychose und Sucht bei Jugendlichen und Jungerwachsenen [nl]Teil 2: Verlauf und Behandlung.

Despite the high prevalence of comorbid substance use disorders (SUD) in young schizophrenic patients and the association of persisting SUD and poor outcome, there are only few randomized controlled psychological treatment studies in this special dual diagnosis group available. According to therapeutic recommendations, efficient treatment models need to integrate traditional psychiatric therapy and therapy of addiction offered in one setting. Short-term interventions have adapted Motivational interviewing (MI) for dual diagnosis, which has been shown to be effective among other substance abuse disorders. However a recent Cochrane review showed that insufficient evidence exists to show that any psychosocial treatment method for dual diagnosis is superior to others. The aim of this review was to assess the current evidence for the efficacy of psychosocial interventions for reducing substance in young patients with psychosis. Five randomized-controlled studies were identified. This review did not find any specific psychosocial intervention that had been replicated and consistently showed clear advantages over comparison condition for substance-related and other psychiatric outcomes.

Winter mortality modifies the heat-mortality association the following summer.

The present study aimed to investigate how the heat-related increase in deaths in summer and the extent of mortality displacement depend on influenza and other categories of mortality in the previous winter, which when low leaves a greater pool of susceptible individuals. Mortality data from Stockholm, Sweden, from 1990-2002 were stratified into a summer period and a winter period. A Poisson regression model was established for the daily mortality in the summer, with temperature and confounders as explanatory variables. In addition, indicators of total, respiratory, cardiovascular and influenza mortality of the winter period were incorporated as effect modifiers in the summer model, and lagged effects in strata defined by indicators were studied. A high rate of respiratory as well as cardiovascular mortality in winter reduced the heat effect the following summer, and influenza mortality tended to do so as well. The cumulative effect per degrees C increase was 0.79% below and 0.88% [corrected] above a threshold (21.3 degrees C) after a winter with low cardiovascular and respiratory mortality, but modified with -0.29% [corrected] below and -0.04% [corrected] above the threshold after a winter with high cardiovascular and respiratory mortality. The current study shows that high respiratory, cardiovascular and influenza mortality in winter leads to lower temperature effects in the following summer. It also suggests that persons for whom influenza may be fatal are often also susceptible to heat and this subgroup might, therefore, not benefit as much as expected from influenza vaccinations.

Surface Structure of Solutions of Poly(vinyl alcohol) in Water.

We use surface-specific heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSFG) and surface tension measurements to investigate the molecular structure of the surface of aqueous solutions of poly(vinyl alcohol) (PVA) polymers with average molecular weights of 10000 and 125000 g/mol. We find that the interfacial water molecules have a preferred orientation with their hydrogen-bonded O-H groups pointing away from the bulk, for both PVA10000 and PVA125000. This observation is explained from the ongoing hydrolysis of the acetyl impurities on the PVA polymer chains. This hydrolysis yields negatively charged acetate ions that have a relatively high surface propensity. For both PVA10000 and PVA125000 the strong positive signal vanishes when the pH is decreased, due to the neutralization of the acetate ions. For solutions with a high concentration of PVA10000 the interfacial water signal becomes very small, indicating that the surface gets completely covered with a disordered PVA polymer film. In contrast, for high concentrations of PVA125000, the strong positive water signal persists at high pH, which shows that the water surface does not get completely covered. The HD-VSFG data combined with surface tension data indicate that concentrated PVA125000 solutions form a structured surface layer with pores containing a high density of interfacial water.

Molecular Structure of Hydrophobins Studied with Site-Directed Mutagenesis and Vibrational Sum-Frequency Generation Spectroscopy.

Hydrophobins are surface-active fungal proteins that adsorb to the water-air interface and self-assemble into amphiphilic, water-repelling films that have a surface elasticity that is an order of magnitude higher than other molecular films. Here we use surface-specific sum-frequency generation spectroscopy (VSFG) and site-directed mutagenesis to study the properties of class I hydrophobin (HFBI) films from Trichoderma reesei at the molecular level. We identify protein specific HFBI signals in the frequency region 1200-1700 cm-1 that have not been observed in previous VSFG studies on proteins. We find evidence that the aspartic acid residue (D30) next to the hydrophobic patch is involved in lateral intermolecular protein interactions, while the two aspartic acid residues (D40, D43) opposite to the hydrophobic patch are primarily interacting with the water solvent.

Common sports hand injuries. An overview of aetiology, management and prevention.

Injuries to the hand are among the most common in all of sports. Appropriate care should include prompt diagnosis and treatment. Dislocations of the digits should be reduced promptly, particularly the carpometacarpal joint of the thumb. Volar dislocations of the proximal interphalangeal joint need to be splinted in full extension, and the more common dorsal dislocations in slight flexion. Collateral ligament injuries of the fingers respond well to initial immobilisation followed by early motion. Although ligament injuries to the thumb metacarpophalangeal joint may be treated closed, they generally respond better to operative management. This is true particularly for those occurring on the ulnar side which are at risk for soft tissue interposition. Metacarpal shaft fractures can usually be treated closed with acceptance of more significant deformity in the ulnar 2 shafts. Open reduction is reserved for multiple shaft fractures and deformity in the second and third metacarpals. Near-perfect alignment should be the goal in extra-articular fractures of the phalanges as well as fractures involving the articular surface. Closed tendon injuries occurring on the extensor side, i.e. mallet finger, may be treated with prolonged splinting if a congruous reduction can be achieved with closed reduction. Flexor side avulsions occurring most commonly in the ring finger also require prompt attention with the level of retraction of the tendon dictating the need for the immediacy of repair. Although often not initially debilitating, lack of recognition of hand injuries and improper treatment can lead to debilitating sequelae. Therefore, early recognition and diagnosis can easily avoid many of the pitfalls of care resulting in a less than optimal outcome.

Injuries to the shoulder in the throwing athlete. Part two: evaluation/treatment.

In part one of this three-part series (March/April 2000), I concentrated on summarizing the biomechanics of the normal throwing shoulder and the pathophysiology of injury. A classification of injury was presented that was based on the principles contained in that article. Part two of this series will focus on the evaluation and treatment of injuries, expanded from an understanding of the principles learned in part one. The ability to perform a skillful examination, and thus develop an accurate diagnosis, is the foundation for treatment. Fortunately, many difficulties encountered in a thrower's shoulder can be treated with a nonoperative approach. However, in instances where conservative measures fail, an improved understanding of the pathophysiology of injury and the development of improved surgical techniques are leading to more accurate diagnoses and more successful rates of return of the athlete to a premorbid level of activity.

Injuries to the shoulder in the throwing athlete. Part one: Biomechanics/pathophysiology/classification of injury.

Over the last decade, significant advances have been made in the study and understanding of shoulder mechanics. Much of this may be attributed to the use of more sophisticated technology to improve our ability to assess the shoulder in real-time athletics. As a consequence of these advances, our understanding of the pathophysiology of injury has also increased. Our manual examination skills have improved and our noninvasive diagnostic techniques have advanced greatly. New insight into forces at play during actions as complex as the throwing motion has allowed us to develop better protocols for the prevention and treatment of the most common injuries. Additionally, paralleling improvements in the understanding of shoulder kinematics and the pathophysiology of injury, advances in surgical techniques, particularly arthroscopy, have aided in the diagnosis of and the development of less invasive surgical treatments for injuries that do not respond to nonoperative measures. Undoubtedly, an up-to-date understanding of the developments in shoulder biomechanics, pathophysiology of injury, diagnostic techniques, and surgical management is necessary for the clinician who wishes to continue to apply proper skills in the sports medicine setting.

Comparison of an optical catheter office arthroscope with a standard rigid rod-lens arthroscope in the evaluation of the knee.

In a prospective, randomized study, 47 patients underwent arthroscopic evaluation of the knee in an operating room setting with both a standard rod-lens arthroscope and a newer flexible optical catheter fiberoptic system. The goal of the study was to assess the diagnostic accuracy of the newer catheter system, which is recommended for use in the office setting. Forty-four patients were included in the data analysis, three were eliminated because we were unable to perform an adequate examination with the catheter scope secondary to intraarticular adhesions or excessive bleeding. A comparison of the two systems revealed an overall underestimation and underrecognition of intraarticular knee pathologic changes. Anterior cruciate ligament tears were missed in 3 of 21 knees; no posterior cruciate ligament tears were detected by the rod-lens arthroscope in 44 knees, but one false-positive result was "seen" using the optical catheter device. Similar trends in diagnosis (sensitivity, 25% to 67%; specificity, 96% to 99%) were seen for tears of the medial and lateral menisci, chondral lesions, and the identification of loose bodies. We conclude from the results of this study that the use of the optical catheter system for arthroscopic evaluation and treatment of the knee in the office setting may result in a significant compromise in visual acuity, resulting in missed and incorrect diagnoses.

Biomechanical analysis of the effect of varying suture pitch in tendon graft fixation.

The purpose of this study was to biomechanically assess the effect of varying suture pitch on the holding power of the Krackow suture technique for tendon graft fixation. Seven pairs of rabbit Achilles tendons were sutured with single No. 5 Ti-Cron suture using the Krackow technique. One tendon from each pair was sutured using a 0.5-cm suture pitch (half-pitch group) while the contralateral tendon from each pair was sutured with a 1.0-cm suture pitch (one-pitch group). The tendons were loaded to failure using a servohydraulic materials test system at a loading rate of 0.5 mm/sec. There were no statistically significant differences noted in suture slippage at failure (1.58 cm for half pitch versus 1.45 cm for one pitch) or maximal force to failure (158.5 N for half pitch versus 168.2 N one pitch) between the two treatment groups. However, the construct with the 1-cm suture pitch was significantly stiffer than the construct with the 0.5-cm suture pitch, with stiffness values of 106.2 N/cm and 91.4 N/cm, respectively. The most common mechanism of failure was slippage of the suture at the first suture throw and tearing of the first knot through the most distal portion of the tendon. Four constructs failed by suture rupture, two from each experimental group.

Symptomatic thrower's exostosis. Arthroscopic evaluation and treatment.

A long-term follow-up was performed on 22 patients treated for a posterior glenoid osteophyte and symptomatic posterior shoulder pain during either the late cocking, acceleration, or follow-through phases of throwing. Arthroscopic evaluation of these patients revealed undersurface tearing of the rotator cuff in all but one. Fifteen patients also had tearing of the posterior labrum. Anterior labral fraying was noted in four patients. Treatment consisted of debridement of the rotator cuff and labral tears. The posterior glenoid osteophyte was removed arthroscopically in 11 patients. Eighteen of 22 throwers treated were available for long-term follow-up at a mean of 6.3 years (range, 1 to 12). Only 10 of 18 (55%) throwers evaluated had returned to their premorbid level of throwing. All 10 were asymptomatic and had maintained a high level of performance for a mean of 3.6 years (range, 1 to 8). At the time of latest follow-up, five players were still participating at the major league level and five had retired. One patient had recurrence of the exostosis 8 years after surgery. Among our patients a trend existed toward a poorer result and failure of return to activity with a posterior osteophyte greater than 100 mm2. A posterior glenoid exostosis, when identified in the symptomatic shoulder of the throwing athlete, can be considered a definite marker of internal impingement.

Treatment of painful articular cartilage defects of the patella by carbon-fibre implants.

Between 1989 and 1993 we implanted a matrix support prosthesis made of carbon fibre for the treatment of chronic painful articular defects of the patella in 27 patients. The mean period of follow-up was 33 months (11 to 54) with clinical and arthroscopic evaluation of the implant. Overall, there were four excellent, three good, seven fair and 13 poor results. Nine patients subsequently had a patellectomy for persistent pain at a mean of 27 months after surgery (14 to 47). The mean visual analogue pain scores in those who retained their patella were 7.6 before operation and 5.5 at the time of the latest follow-up. Patient satisfaction for the entire group was 41%. There appeared to be good incorporation of the prosthesis and a satisfactory ingrowth of fibrocartilage, but the poor results in 48% and low patient satisfaction discourage us from recommending the procedure for lesions of the articular cartilage of the patella. The consistent seeding of the joint with carbon-fibre debris and a histiocytic giant-cell reaction in the synovium are also a cause for concern.

Classification and treatment of rotator cuff injuries in the overhand athlete.

Rotator cuff injury in athletes results from accumulation of microtrauma to both the static and dynamic stabilizers of the shoulder. Our classification of these injuries and treatment protocol is based on knowledge of the pathophysiology of events leading to rotator cuff failure. Rotator cuff disease is attributed to one of five different modes of failure: primary compressive disease, secondary compressive disease, primary tensile overload, secondary tensile overload, and macrotraumatic injuries. Although disease is categorized based on a single failure mode, there is often significant overlap between the mechanisms of injury leading to the disease. Categorization and, consequently, treatment of the injury rely upon proper identification of the primary pathology and an understanding of the causative factors leading to rotator cuff failure. In most cases conservative management is successful, but, in the refractory cases, minimally invasive surgical techniques have also been successful in returning most athletes to a premorbid level of function.

Internal impingement in the shoulder of the overhand athlete: pathophysiology, diagnosis, and treatment.

The etiology of rotator cuff disease is multifactorial in nature. The process by which the articular surface of the rotator cuff can become diseased secondary to direct abutment against the glenoid rim and labrum has been termed internal impingement. Damage to the undersurface of the rotator cuff can occur from contact at the extremes of shoulder motion and can increase secondary to adaptive changes in bone and soft tissue. Diagnosis is achieved in most instances by a thorough physical examination. Adjunctive tests, particularly magnetic resonance imaging, can increase the accuracy of the diagnosis. If this disease is recognized early, nonoperative intervention may be successful. When nonoperative treatment fails, the use of arthroscopy for the treatment of torn rotator cuff and labral tissue and capsular laxity may be indicated to resolve symptoms and restore the premorbid level of function.

Proximal tibial derotation osteotomy for anterior knee pain in the miserably malaligned extremity.

In an 18-year review period, 10 patients were identified with debilitating anterior knee pain and severe rotational malalignment of the lower extremity. Eight of the most symptomatic knees in 7 of these patients were treated with a rotational osteotomy of the tibia performed proximal to the tibial tubercle. Six of the 7 patients who fit a previously described spectrum of rotational deformity consisting of mild femoral anteversion, severe external tibial torsion, mild tibia vara, and pes planovalgus deformity, underwent unilateral procedures for external tibial torsion. Duration of preoperative symptoms averaged 6.3 years. Intraoperative torsional correction obtained with internal rotation of the tibia averaged 19.7 degrees. Subjectively, 1 excellent, 5 good, and 1 fair result were obtained. Functionally, 3 excellent and 4 good results were obtained. Follow-up evaluation averaging 10 years revealed no deterioration of the results, proving the success of the procedure in this group of select individuals over the long term.