Population structure in Chilean hake Merluccius gayi as revealed by mitochondrial DNA sequences.

Genetic variation and divergence among samples of Chilean hake Merluccius gayi, from three localities off the coast of Chile and one locality off the coast of northern Peru, were assessed using sequences from the control region of mitochondrial DNA. Homogeneity tests revealed occurrence of at least three distinct genetic stocks of M. gayi within the region sampled. Factors potentially contributing to genetic divergence among M. gayi probably include hydrodynamics and behaviour.

Environmental variation, hybridization, and phenotypic diversification in Cuatro Ciénegas pupfishes.

Hybridization can generate novel phenotypes, and in combination with divergent selection along environmental gradients, can play a driving role in phenotypic diversification. This study examined the influence of introgressive hybridization and environmental variation on the phenotypic diversity of two pupfish species (Cyprinodon atrorus and Cyprinodon bifasciatus) endemic to the Cuatro Ciénegas basin, Mexico. These species occupy opposite environmental extremes and are comprised of multiple, intraspecifically isolated populations. However, interspecific hybridization occurs to various degrees within connecting, intermediate environments. Using geometric morphometric analysis, extensive variation of body shape was observed between and within species, and phenotypic variation was strongly correlated with environmental conditions. Furthermore, some introgressed populations exhibited unique phenotypes not found in either of the parents, and overall morphospace occupation was significantly higher in introgressed populations when compared to the parentals. Overall, we find environmental variation and transgressive segregation both appear to have been important in shaping phenotypic variation in this system.

Analysis of peridural scar formation and its prevention after lumbar laminotomy and discectomy in dogs.

STUDY DESIGN: Peridural fibrosis after lumbar laminectomy and discectomy has been implicated (not proven) as one of the factors that contribute to continuing or recurrent radicular and/or low back pain. This animal experimental study was designed to unequivocally show the stages in the development of scar tissue and to what extent, if any, scar tissue development is influenced by interposing fat grafts and Na hyaluronate of different molecular weights. METHODS: A four-level unilateral lumbar laminotomy, anular fenestration, and nucleotomy was performed in 11 dogs. In each dog, levels were selected at random: one to serve as an empty control and three to insert the following: a fat graft, a viscous (1.9%) solution of Na hyaluronate, and a 1% high molecular weight solution of Na hyaluronate solution. The animals were killed at 1 day, 2 days, and 1, 2, 4, and 12 weeks postoperatively. Immediately after the dogs were killed, the lumbar spines were frozen in situ with dry ice, the lumbar spines were harvested and sectioned with a cryomicrotome. Close-up photographs taken at submillimeter intervals at each level were digitized and postprocessed with a computer. RESULTS: In the early postoperative period a hematoma was found in the pathway of the surgical dissection. During a 2-4 week period, this hematoma was replaced by a thick, white fibrotic tissue mass. Fibrosis was markedly less pronounced at the hyaluronate levels, especially the high molecular weight subset. Two-way statistical analysis of variance without replications revealed significantly less scar formation at the 0.05 level in the hyaluronate vs. the control segments. Dunnett's test, comparing each group individually with the control, revealed no difference between the fat groups and the control subjects. There was a significant difference between 1.9% Na hyaluronate and control. CONCLUSIONS: Viscous hyaluronate solution with its semifluid properties coats the nerve roots and dura anteriorly and posteriorly and reduces peridural fibrosis in the critical anterior region where adhesions form between the nerve root and anulus fibrosus.

Arthroscopic acromioplasty. Current status.

Impingment is a chronic syndrome characterized by microtrauma, which causes progressive injury to the rotator cuff tendon. In recent years, arthro- scopic subacromial decompression/acromioplasty has been frequently used for the treatment of impingement syndrome and is quickly becoming the preferred surgical treatment when conservative modalities fail. Arthroscopic acromioplasty offers many benefits over open acromioplasty, including better cosmesis, lessened preoperative morbidity, a more complete intraoperative examination, and a hastened, early rehabilitation program.

Revision anterior cruciate ligament surgery.

An increasing number of revision ACL reconstructions are being performed each year. Revision ACL surgery is challenging and cannot be approached in the same manner as primary ACL surgery. Successful revision ACL surgery requires a detailed history, a comprehensive physical examination, appropriate radiologic studies, and careful preoperative planning. The results of revision ACL surgery do not equal the results of primary ACL surgery, and this should be explained to the patient prior to surgery. In order to avoid repeating errors that led to failure of the primary reconstruction, the etiology of the primary failure must be clearly understood before proceeding with the revision procedure. Although graft failure is the most common reason for failure of the original reconstruction and revision surgery, other non-graft-related problems, such as loss of motion, extensor mechanism dysfunction, and degenerative arthritis, can also result in an unsatisfactory outcome and residual complaints. Errors in surgical technique, specifically nonanatomic graft placement and failure to address associated ligamentous injuries at the time of the original procedure, are responsible for graft failures in most reported series. Preoperative planning must address the issues of graft selection, skin incisions, hardware removal, tunnel placement, graft fixation, and associated ligamentous injuries. Loss of motion and in some cases enlarged bone tunnels may require a staged approach. Because of the weaker initial graft fixation, laxity of secondary restraints, the potential need to address associated ligamentous injuries, and the presence of more significant articular cartilage changes, an accelerated rehabilitation program is inappropriate in most revision cases. Successful revision ACL surgery requires a motivated and compliant patient, a well thought out plan, and an experienced surgeon who is knowledgeable and proficient with a variety of different surgical techniques, graft sources, and graft fixation techniques.

The use of hamstring tendons for anterior cruciate ligament reconstruction. Technique and results.

We feel that some of the current prejudice against use of hamstring tendon grafts for ACL reconstruction has not been justified if one critically reviews the literature. In this article, we have tried to provide the reader with our current indications, present our current surgical technique, and review some of the outcome studies involving use of the hamstring tendons for ACL reconstruction. We also feel that some of the poor results of hamstring tendon ACL reconstructions previously reported resulted from the use of inadequate strength grafts (single-stranded grafts) and lack of rigid fixation on both ends of the graft (usually secondary to inadequate graft length). We feel that the technique described in this article addresses both of these issues. It is our clinical impression that, in appropriately selected patients, this technique produces stability and functional outcome similar to that obtained with patellar tendon grafts but results in less postoperative pain, a quicker return of quadriceps muscle function, and less donor site morbidity.

Performance of 18S rDNA helix E23 for phylogenetic relationships within and between the Rotifera-Acanthocephala clades.

The species diversity of the phylum Rotifera has been largely studied on the basis of morphological characters. However, cladistic relationships within this group are poorly resolved due to extensive homoplasy in morphological traits, substantial phenotypic plasticity and a poor fossil record. We undertook this study to determine if a phylogeny based on partial 18S rDNA, which included the helix E23 of 18S rDNA sequence, was concordant with established taxonomic relationships within the order Ploimida (class: Monogononta). We also estimated the level of polymorphism within clones and populations of Ploimida 'species'. Finally, we included the Cycliophora Symbion pandora as outgroup and the variable helix E23 region to examine the influence of their signal on the evolutionary relationships among Acanthocephala, Bdelloidea and Ploimida. Phylogenetic reconstruction was performed using maximum parsimony, neighbour joining and maximum likelihood methods. We found 1) that morphologically similar Ploimida 'species' show vastly different 18S E23 rDNA sequences; 2) inclusion of the helix E23 of 18S rDNA and its secondary structure analysis results in better resolution of family level relationships within the Ploimida; 3) an impact of Symbion pandora as an outgroup with inclusion of the helix E23 on the relationships between the Rotifera and the Acanthocephala; and 4) partial incongruence and differential substitution rate between conserved region and helix E23 region of the 18S rDNA gene depending on the taxomic group studied.

Reliability of the quadriceps angle measurement.

The quadriceps angle (Q-angle) is used to determine patellofemoral alignment. Although this measurement has been used to evaluate and treat patellofemoral joint pathology, few studies have examined its reliability. This study evaluated the interobserver and intraobserver reliability of the Q-angle measurement. To investigate the interobserver reliability of the Q-angle, 25 individuals of varying levels of training served as observers and participants as each measured the other 24 participants. To investigate the intraobserver reliability of the Q-angle, 3 of the observers measured 13 of the participants an additional 2 times. Additionally, clinically derived Q-angle measurements were compared with radiographically derived measurements. The reliability analysis was performed using intraclass correlation coefficients. For interobserver measurements, the intraclass correlation coefficients ranged from 0.17-0.29 for the four variables evaluated (right and left, extension and flexion). For intraobserver measurements, the intraclass correlation coefficients ranged from 0.14-0.37. The average intraclass correlation coefficient between the clinically and radiographically derived measurements ranged from 0.13-0.32. This study demonstrates poor interobserver and intraobserver reliability of Q-angle measurement and poor correlation between clinically and radiographically derived Q-angles.