ACL microtrauma: healing through nutrition, modified sports training, and increased recovery time.

PURPOSE: Sports injuries among youth and adolescent athletes are a growing concern, particularly at the knee. Based on our current understanding of microtrauma and anterior cruciate ligament (ACL) healing characteristics, this clinical commentary describes a comprehensive plan to better manage ACL microtrauma and mitigate the likelihood of progression to a non-contact macrotraumatic ACL rupture. METHODS: Medical literature related to non-contact ACL injuries among youth and adolescent athletes, collagen and ACL extracellular matrix metabolism, ACL microtrauma and sudden failure, and concerns related to current sports training were reviewed and synthesized into a comprehensive intervention plan. RESULTS: With consideration for biopsychosocial model health factors, proper nutrition and modified sports training with increased recovery time, a comprehensive primary ACL injury prevention plan is described for the purpose of better managing ACL microtrauma, thereby reducing the incidence of non-contact macrotraumatic ACL rupture among youth and adolescent athletes. CONCLUSION: Preventing non-contact ACL injuries may require greater consideration for reducing accumulated ACL microtrauma. Proper nutrition including glycine-rich collagen peptides, or gelatin-vitamin C supplementation in combination with healthy sleep, and adjusted sports training periodization with increased recovery time may improve ACL extracellular matrix collagen deposition homeostasis, decreasing sudden non-contact ACL rupture incidence likelihood in youth and adolescent athletes. Successful implementation will require compliance from athletes, parents, coaches, the sports medicine healthcare team, and event organizers. Studies are needed to confirm the efficacy of these concepts. LEVEL OF EVIDENCE: V.

Return to sports bridge program improves outcomes, decreases ipsilateral knee re-injury and contralateral knee injury rates post-ACL reconstruction.

PURPOSE: To present the results of a return to sports bridge program designed to reduce knee injuries following ACL reconstruction and physical therapy. METHODS: One hundred and fifty (male = 83, female = 67) patients participated in a whole body neuromuscular control, progressive resistance strength and agility training program. Post-program testing included functional movement form, dynamic knee stability, lower extremity power, agility, and sports skill assessments. Participants completed the Knee Outcome Survey-Sports Activity Scale (KOS-SAS) before and after program initiation. Pre-participation scores were re-estimated following program completion. RESULTS: Global rating KOS-SAS score at program entry was 75 ± 13. Post-program global rating and calculated KOS-SAS were 91.0 ± 9.8 and 90.9 ± 9.7, respectively (p < 0.0001). Pre-participation KOS-SAS score re-estimates at program completion were 54.5 ± 23.3 and 57.3 ± 18.5, respectively. The approximately 20% lower pre-program KOS-SAS score re-estimates (p < 0.0001) observed at program completion suggests that subjects had inaccurately high sports readiness perceptions at program entry. Perceived overall sports activity knee function ratings improved from 2.9 ± 0.6 (abnormal) at program entry to 1.3 ± 0.5 (normal) at completion (p < 0.0001). Most subjects returned back to sports at or above their pre-injury performance skill/performance level (84%, 126/150). By 6.8 ± 3.2 years (range = 2-13 years) post-surgery, ten subjects had sustained an ipsilateral knee re-injury or contralateral knee injury (6.7%). The 2.7% non-contact contralateral and 1.3% non-contact ipsilateral knee injury rates observed were significantly lower than those cited in previous reports. CONCLUSION: Supplementing primary ACL reconstruction and standard physical therapy with a return to sports bridge program prior to release to unrestricted sports performance was effective at improving patient outcomes and decreasing ipsilateral knee re-injury and contralateral knee injury rates. LEVEL OF EVIDENCE: II.

Biomechanical comparison between CentraLoc and Intrafix fixation of quadrupled semitendinosus-gracilis allografts in cadaveric tibiae with low bone mineral density.

Supplementary or back-up tibial tunnel fixation of a quadruple semitendinosus-gracilis (STG) graft is often performed when the knee surgeon questions the integrity of intra-tunnel fixation. Back-up fixation devices such as staples however may contribute to increased knee pain and dysfunction. Both primary extra-tunnel and intra-tunnel fixation devices may provide sufficient quadruple STG graft fixation in a tibial tunnel to preclude the need for back-up fixation. This biomechanical study compared the fixation of quadruple STG allografts in standard drilled tunnels prepared in low apparent bone mineral density (BMD) cadaveric tibiae using either an Intrafix device with primary intra-tunnel fixation in a region of predominantly cancellous trabecular bone, or a CentraLoc device with primary extra-tunnel fixation in a region of predominantly cortical bone. The study hypothesis was that the CentraLoc device would display superior fixation in these low apparent BMD cadaveric tibiae. Matched pair tibiae and quadruple STG allografts were divided into two groups of seven specimens each. Extraction drilled tunnels matched allograft diameter. Constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles and isometric pretensioned at 50 N for 1 min prior to undergoing 500 loading cycles (50-250 N) and load to failure testing (20 mm/min). The CentraLoc group displayed superior load at failure (448.4+/-171 N vs. 338.4+/-119 N, P=0.04) and survived more loading cycles (410+/-154 cycles vs. 196+/-230 cycles, P=0.04) than the Intrafix group. Most CentraLoc group specimens (6/7, 85.7%) failed by device pullout with intact quadruple STG allograft strands while all Intrafix group specimens (7/7, 100%) failed by slippage of one or more strands (P=0.005).

Three-dimensional mapping of temporo-limbic regions and the lateral ventricles in schizophrenia: gender effects.

BACKGROUND: Local alterations in morphological parameters are poorly characterized in several brain regions widely implicated in schizophrenia neuropathology. METHODS: Surface-based anatomical modeling was applied to magnetic resonance data to obtain three-dimensional (3D) average anatomical maps and measures of location, shape, asymmetry, and volume for the lateral ventricles, hippocampus, amygdala, and superior temporal gyrus in schizophrenic (n = 25; 15 male) and normal subjects (n = 28; 15 male) matched for demographic variables. For all regions, intra-group variability was visualized and group differences assessed statistically to discriminate local alterations in anatomy across sex and diagnosis. RESULTS: Posterior hippocampal volumes, lengths, and widths were reduced in patients. The right amygdala showed volume increases in schizophrenia patients versus controls. Ventricular enlargements, pronounced in the left hemisphere, occurred in the superior and lateral dimensions in patients, and these effects interacted with gender. Superior horn anterior extremes, inferior horn volumes, and hippocampal asymmetries exhibited gender effects. Significant group differences were absent in superior temporal gyrus parameters. Finally, regional variability profiles differed across groups. CONCLUSIONS: Clear morphometric differences of the lateral ventricles, hippocampus, and amygdala indicate regional displacements and shape distortions in several functional systems in schizophrenia. Alterations in these structures as mapped in 3D may provide the foundation for establishing brain abnormalities not previously defined at such a local level.

DsbD-catalyzed transport of electrons across the membrane of Escherichia coli.

Dsb proteins catalyze folding and oxidation of polypeptides in the periplasm of Escherichia coli. DsbC reduces wrongly paired disulfides by transferring electrons from its catalytic dithiol motif (98)CGYC. Genetic evidence suggests that recycling of this motif requires at least three proteins, the cytoplasmic thioredoxin reductase (TrxB) and thioredoxin (TrxA) as well as the DsbD membrane protein. We demonstrate here that electrons are transferred directly from thioredoxin to DsbD and from DsbD to DsbC. Three cysteine pairs within DsbD undergo reversible disulfide rearrangements. Our results suggest a novel mechanism for electron transport across membranes whereby electrons are transferred sequentially from cysteine pairs arranged in a thioredoxin-like motif (CXXC) to a cognate reactive disulfide.

Racial differences in ischemic cerebrovascular disease.

PURPOSE: To evaluate racial differences in extracranial carotid atherosclerosis and vascular risk factors in patients with symptomatic cerebrovascular disease. BACKGROUND: There are conflicting data on racial differences in certain vascular risk factors and prevalence of large-vessel versus small-vessel disease in patients with stroke. METHODS: We prospectively studied 211 consecutive patients admitted to our stroke service. There were 71 African-American, 114 Caucasian, 20 Hispanic, and 6 other patients. Extracranial vascular stenosis was assessed with a carotid duplex (CD) scan. Risk factors monitored included race, age, history of hypertension (HTN), diabetes mellitus (DM), prior stroke, hyperlipidemia, smoking, cardiac disease (congestive heart failure, atrial fibrillation), and family history of stroke. Cholesterol and triglyceride blood levels, and computed tomography/magnetic resonance imaging results were obtained in most cases. RESULTS: Significant differences were found between Caucasians and African-Americans in several variables. Caucasians had more frequent hypertriglyceridemia and a higher rate of cardiac disease. African-Americans had more frequent lacunar infarcts. There was a trend toward decreased risk of CD scan abnormality, and more HTN and prior stroke in African-Americans. There were no differences in the presence of DM, both HTN and DM, abnormal cholesterol (including high- and low-density lipoprotein) values, and smoking history. Except for the difference in lacunar infarction, there were no differences in the type of stroke. CONCLUSIONS: Our data indicate a greater risk of cardiac disease and hypertriglyceridemia in Caucasians with cerebrovascular disease. There was a trend for Caucasians to have more extracranial carotid disease, and a trend for African-Americans to have more hypertension and prior stroke, although the difference did not reach significance. Consistent with prior racial studies, we found African-Americans to have more lacunar strokes than Caucasians.

DNA-strand exchange promoted by RecA protein in the absence of ATP: implications for the mechanism of energy transduction in protein-promoted nucleic acid transactions.

DNA-strand exchange promoted by Escherichia coli RecA protein normally requires the presence of ATP and is accompanied by ATP hydrolysis, thereby implying a need for ATP hydrolysis. Previously, ATP hydrolysis was shown not to be required; here we demonstrate furthermore that a nucleoside triphosphate cofactor is not required for DNA-strand exchange. A gratuitous allosteric effector consisting of the noncovalent complex of ADP and aluminum fluoride, ADP.AIF4-, can both induce the high-affinity DNA-binding state of RecA protein and support the homologous pairing and exchange of up to 800-900 bp of DNA. These results demonstrate that induction of the functionally active, high-affinity DNA-binding state of RecA protein is needed for RecA protein-promoted DNA-strand exchange and that there is no requirement for a high-energy nucleotide cofactor for the exchange of DNA strands. Consequently, the free energy needed to activate the DNA substrates for DNA-strand exchange is not derived from ATP hydrolysis. Instead, the needed free energy is derived from ligand binding and is transduced to the DNA via the associated ligand-induced structural transitions of the RecA protein-DNA complex; ATP hydrolysis simply destroys the effector ligand. This concept has general applicability to the mechanism of energy transduction by proteins.

Biochemical events essential to the recombination activity of Escherichia coli RecA protein. I. Properties of the mutant RecA142 protein.

We have characterized the biochemical properties of Escherichia coli RecA142 protein, the product of a recA allele that is phenotypically defective in genetic recombination. In vitro, this mutant RecA protein is totally defective in DNA heteroduplex formation. Despite this defect, RecA142 protein is not deficient in all other biochemical activities. RecA142 protein is proficient in single-strand (ss) DNA binding ability, ssDNA-dependent ATPase activity, and DNA-free self-association (although the first 2 properties show a greater sensitivity to NaCl concentration than does the wild-type protein). However, RecA142 protein is deficient in four properties: (1) its ssDNA-dependent ATPase activity is completely inhibited by ssDNA binding (SSB) protein, demonstrating that RecA142 protein is unable to compete effectively with SSB protein for ssDNA binding sites; (2) it is unable to promote the coaggregation of ssDNA and double-strand (ds) DNA; (3) its M13 dsDNA-dependent ATPase activity is attenuated to approximately 5% of the level of the wild-type protein; (4) it is unable fully to develop characteristics of the high-affinity ssDNA-binding state that is normally induced by ATP. The first three deficiencies correspond to defects in the presynaptic, synaptic and postsynaptic steps of the in vitro DNA strand exchange reaction, respectively; the fourth is the likely fundamental basis for defects 1 and 3. Therefore, one or more of these properties must be important to both the in vitro and in vivo processes.

Biochemical events essential to the recombination activity of Escherichia coli RecA protein. II. Co-dominant effects of RecA142 protein on wild-type RecA protein function.

In the accompanying paper, RecA142 protein was found to be completely defective in DNA heteroduplex formation. Here, we show that RecA142 protein not only is defective in this activity but also is inhibitory for certain activities of wild-type RecA protein. Under appropriate conditions, RecA142 protein substantially inhibits the DNA strand exchange reaction catalyzed by wild-type RecA protein; at equimolar concentrations of each protein, formation of full-length gapped duplex DNA product molecules is less than 7% of the amount produced by wild-type protein alone. Inhibition by RecA142 protein is also evident in S1 nuclease assays of DNA heteroduplex formation, although the extent of inhibition is less than is observed for the complete DNA strand exchange process; at equimolar concentrations of wild-type and mutant proteins, the extent of DNA heteroduplex formation is 36% of the wild-type protein level. This difference implies that RecA142 protein prevents, at minimum, the branch migration normally observed during DNA strand exchange. RecA142 protein does not inhibit either the single-strand (ss) DNA-dependent ATPase activity or the coaggregation activities of wild-type RecA protein. This suggests that these reactions are not responsible for the inhibition of wild-type protein DNA strand exchange activity by RecA142 protein. However, under conditions where RecA142 protein inhibits DNA strand exchange activity, RecA142 protein renders the M13 ssDNA-dependent ATPase activity of wild-type protein sensitive to inhibition by single-strand DNA-binding protein, and it inhibits the double-strand DNA-dependent ATPase activity of wild-type RecA protein. These results imply that these two activities are important components of the overall DNA strand exchange process. These experiments also demonstrate the applicability of using defective mutant RecA proteins as specific codominant inhibitors of wild-type protein activities in vitro and should be of general utility for mechanistic analysis of RecA protein function both in vitro and in vivo.

Properties of the duplex DNA-dependent ATPase activity of Escherichia coli RecA protein and its role in branch migration.

We have investigated the double-stranded DNA (dsDNA)-dependent ATPase activity of recA protein. This activity is distinguished from the single-stranded DNA (ssDNA)-dependent ATPase activity by the presence of a pronounced lag time before the onset of steady-state ATP hydrolysis. During the lag phase there is little ATP hydrolysis. The duration of the lag phase, referred to as the lag time, is found to increase with the thermal stability of the dsDNA substrate. Increasing either the MgCl2 or NaCl concentration increases the lag time, whereas increasing the temperature decreases the lag time. The lag time shows little dependence on recA protein concentration but is strongly dependent on ATP concentration. After the lag phase, a steady-state ATP hydrolysis rate is achieved that approaches the rate observed with ssDNA. The steady-state phase of the reaction is proportional to the concentration of recA protein-DNA complex and shows saturation behavior at approximately equal to 5 +/- 1 base pairs per recA protein monomer. These results suggest that the lag phase represents a rate-limiting step in the dsDNA-dependent ATP hydrolysis reaction that requires a structural transition in the dsDNA and that involves a ternary complex of ATP, recA protein, and DNA. We propose that this transition involves the transient denaturation of the dsDNA to form regions of ssDNA. Elsewhere we demonstrate that the dsDNA-dependent ATPase activity is proportional to the rate of recA protein-catalyzed branch migration. We suggest that this activity is responsible for a polar polymerization that drives the branch migration reaction.

Effects of Escherichia coli SSB protein on the single-stranded DNA-dependent ATPase activity of Escherichia coli RecA protein. Evidence that SSB protein facilitates the binding of RecA protein to regions of secondary structure within single-stranded DNA.

The effect that Escherichia coli single-stranded DNA binding (SSB) protein has on the single-stranded DNA-dependent ATPase activity of RecA protein is shown to depend upon a number of variables such as order of addition, magnesium concentration, temperature and the type of single-stranded DNA substrate used. When SSB protein is added to the DNA solution prior to the addition of RecA protein, a significant inhibition of ATPase activity is observed. Also, when SSB protein is added after the formation of a RecA protein-single-stranded DNA complex using either etheno M13 DNA, poly(dA) or poly(dT), or using single-stranded phage M13 DNA at lower temperature (25 degrees C) and magnesium chloride concentrations of 1 mM or 4 mM, a time-dependent inhibition of activity is observed. These results are consistent with the conclusion that SSB protein displaces the RecA protein from these DNA substrates, as described in the accompanying paper. However, if SSB protein is added last to complexes of RecA protein and single-stranded M13 DNA at elevated temperature (37 degrees C) and magnesium chloride concentrations of 4 mM or 10 mM, or to poly(dA) and poly(dT) that was renatured in the presence of RecA protein, no inhibition of ATPase activity is observed; in fact, a marked stimulation is observed for single-stranded M13 DNA. A similar effect is observed if the bacteriophage T4-coded gene 32 protein is substituted for SSB protein. The apparent stoichiometry of DNA (nucleotides) to RecA protein at the optimal ATPase activity for etheno M13 DNA, poly(dA) and poly(dT) is 6(+/- 1) nucleotides per RecA protein monomer at 4 mM-MgCl2 and 37 degrees C. Under the same conditions, the apparent stoichiometry obtained using single-stranded M13 DNA is 12 nucleotides per RecA protein monomer; however, the stoichiometry changes to 4.5 nucleotides per RecA protein monomer when SSB protein is added last. In addition, a stoichiometry of four nucleotides per RecA protein can be obtained with single-stranded M13 DNA in the absence of SSB protein if the reactions are carried out in 1 mM-MgCl2. These data are consistent with the interpretation that secondary structure within the natural DNA substrate limits the accessibility of RecA protein to these regions. The role of SSB protein is to eliminate this secondary structure and allow RecA protein to bind to these previously inaccessible regions of the DNA.(ABSTRACT TRUNCATED AT 400 WORDS)

[The seat belt: effect on the consequences of traffic accidents (author's transl)]. / Bisherige Erfahrungen mit dem Sicherheitsgurt in seiner Auswirkung auf die Unfallfolgen im Strassenverkehr.

At the present time, more than 90% of the motor vehicles in the Federal Republic of Germany are equipped with seat belts. On the average, however, only one out of two drivers uses his belt. It has been established that the seat belt, considering the present rate of use, annually protects about 1700 car occupants from fatality and about 30,000 from injuries (resulting in economic savings of approx. DM 1.8 X 10(9)). If all car occupants were to observe seat-belt regulations, this gain in safety might be doubled. Experience of other countries indicates that the introduction of the fine would result in much better compliance with the regulation than has been observed thus far.