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Background Context: The oblique lateral interbody fusion (OLIF) procedure is aimed at mitigating some of the challenges seen with traditional anterior lumbar interbody fusion (ALIF) and transpsoas lateral lumbar interbody fusion (LLIF), and allows for interbody fusion at L1-S1., Purpose: The study aimed to describe the OLIF technique and assess the complication and fusion rates., Study Design: This is a retrospective cohort study., Patient Sample: The sample is composed of 137 patients who underwent OLIF procedure., Outcome Measures: The outcome measures were adverse events within 6 months of surgery: infection, symptomatic pseudarthrosis, hardware failure, vascular injury, perioperative blood transfusion, ureteral injury, bowel injury, renal injury, prolonged postoperative ileus (more than 3 days), incisional hernia, pseudohernia, reoperation, neurologic deficits (weakness, numbness, paresthesia), hip flexion pain, retrograde ejaculation, sympathectomy affecting lower extremities, deep vein thrombosis, pulmonary embolism, myocardial infarction, pneumonia, and cerebrovascular accident. The outcome measures also include fusion and subsidence rates based on computed tomography (CT) done at 6 months postoperatively., Methods: Retrospective chart review of 150 consecutive patients was performed to examine the complications associated with OLIF at L1-L5 (OLIF25), OLIF at L5-S1 (OLIF51), and OLIF at L1-L5 combined with OLIF at L5-S1 (OLIF25+OLIF51). Only patients who had at least 6 months of postoperative follow-up, including CT scan at 6 months after surgery, were included. Independent radiology review of CT data was performed to assess fusion and subsidence rates at 6 months., Results: A total of 137 patients underwent fusion at 340 levels. An overall complication rate of 11.7% was seen. The most common complications were subsidence (4.4%), postoperative ileus (2.9%), and vascular injury (2.9%). Ileus and vascular injuries were only seen in cases including OLIF51. No patient suffered neurologic injury. No cases of ureteral injury, sympathectomy affecting the lower extremities, or visceral injury were seen. Successful fusion was seen at 97.9% of surgical levels., Conclusions: Oblique lateral interbody fusion is a safe procedure at L1-L5 as well as L5-S1. The complication profile appears acceptable when compared with LLIF and ALIF. The oblique trajectory mitigates psoas muscle and lumbosacral plexus-related complications seen with the lateral transpsoas approach. Furthermore, there is a high fusion rate based on CT data at 6 months., (Copyright © 2016. Published by Elsevier Inc.)

An understanding of the kinematics of posterior cruciate ligament (PCL) deficiency is important for the diagnosis and management of patients with isolated PCL injury. The kinematics of PCL injury has been analysed through cadaveric and in vivo imaging studies. Cadaveric studies have detailed the anatomy of the PCL. It consists of two functional bundles, anterolateral and posteromedial, which exhibit different tensioning patterns through the arc of knee flexion. Isolated sectioning of the PCL and its related structures in cadaveric specimens has defined its primary and secondary restraining functions. The PCL is the primary restraint to posterior tibia translation above 30° and is a secondary restraint below 30° of knee flexion. Furthermore, sectioning of the PCL produces increased chondral deformation forces in the medial compartment as the knee flexes. However, the drawback of cadaveric studies is that they can not replicate the contribution of surrounding neuromuscular structures to joint stability that occurs in the clinical setting. To address this, there have been in vivo studies that have examined the kinematics of the PCL deficient knee using imaging modalities whilst subjects perform dynamic manoeuvres. These studies demonstrate significant posterior subluxation of the medial tibia as the knee flexes. The results of these experimental studies are in line with clinical consequences of PCL deficiency. In particular, arthroscopic evaluation of subjects with isolated PCL injuries demonstrate an increased incidence of chondral lesions in the medial compartment. Yet despite the altered kinematics with PCL injury only a minority of patients require surgery for persistent instability and the majority of athletes are able to return to sport following a period of non-operative rehabilitation. Specifically, non-operative management centres on a programme of quadriceps strengthening and hamstring inhibition to minimise posterior tibial load. The mechanism behind the neuromuscular adaptation that allows the majority of athletes to return to sport has been investigated but not clearly elucidated. The purpose of this review paper is to draw together the findings of experimental studies on the anatomical and kinematic effects of PCL injury and summarise their relevance with respect to non-operative management and functional outcome in patients with isolated PCL deficiency., (Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.)

Background: The aim of the present study was to compare the in vivo articulation of the healthy knee to the contralateral knee of subjects with acute and chronic PCL injuries., Methods: Magnetic resonance was used to generate sagittal images of 10 healthy knees and 10 knees with isolated PCL injuries (5 acute and 5 chronic). The subjects performed a supine leg press against a 150 N load. Images were generated at 15 degree intervals as the knee flexed from 0 to 90 degrees. The tibiofemoral contact (TFC), and the centre of the femoral condyle (as defined by the flexion facet centre (FFC)), were measured from the posterior tibial cortex., Results: There was no significant difference in the TFC and FFC between the healthy knee and contralateral knee of subjects with acute and chronic PCL injuries in the medial and lateral compartments of the knee., Conclusions: The findings of this study suggest there is no predisposing articulation abnormality to PCL injury, in the setting of chronic injury the contralateral knee does not modify its articulation profile and the contralateral knee can be used as a valid control when evaluating the articulation of the PCL deficient knee.

Object: Tethered cord syndrome (TCS) is being diagnosed in an increasing number of adults and late teens. Before referral to neurosurgeons, however, the majority of patients in this group suffers back and leg pain for a long period without a definitive diagnosis. The diagnostic difficulty derives from 2 factors: the signs and symptoms are subtle and easily overlooked, and the combination of an elongated cord and a thickened filum is lacking in 65% of patients. When a patient presents with signs and symptoms typical for TCS but demonstrates no elongated cord or thickened filum on MR imaging, one must search for a more reliable finding to establish a diagnosis of TCS. Based on the authors' earlier surgical experiences, posterior displacement of the terminal filum is consistently found at surgery in all patients with TCS. In previous publications they interpreted this finding as the lower cord and filum traveling along the concave side of the lumbosacral spinal canal to minimize cord tension. In the present prospective study, the authors attempt to confirm posterior displacement of the filum terminale by using intrathecal endoscopy prior to wide exposure of the spinal cord and filum. Further, the stretch test was applied to the terminal filum to evaluate its elasticity., Methods: Sixty-eight patients with signs and symptoms as well as MR imaging studies indicative of TCS underwent endoscopic examination of the filum and cauda equina. After lumbar or sacral laminectomy, a flexible endoscope was inserted through a small dural and arachnoid incision into the subarachnoid space. The filum and cauda equina fibers were identified. Once the dura mater and arachnoid were opened widely, a stretch test was done to confirm filum inelasticity. In 3 patients, percutaneous endoscopy was also performed before open surgery to determine its applicability as compared with the open method., Results: On inserting the endoscope into the intrathecal space, the filum was immediately identified medioposterior to the cauda equina fibers in all 68 patients. The stretch test revealed a lack of filum elasticity in all patients. Preoperative percutaneous endoscopy was equally effective in identifying the position of the filum., Conclusions: Currently, endoscopic identification of the posteriorly displaced filum, which was confirmed at open surgery, is the essential diagnostic study for TCS or the tethered spinal cord. Furthermore, the stretch test of the filum proves its inelasticity, and filum sectioning leads to ascension and relaxation of the caudal spinal cord. These results can be linked to the impaired oxidative metabolism of the lumbosacral cord under excessive tension and to the metabolic and neurological improvements seen after filum sectioning.

The surgical treatment of chronic acromioclavicular injuries remains controversial. There is increasing use of autogenous tendon grafts to perform these reconstructions. This study examined the mechanical properties of differing configurations of these grafts. Mechanical testing of acromioclavicular joint reconstructions was performed with a screw and soft tissue washer for tendon fixation, a simple loop of tendon tied to itself, and a bio-interference screw for tendon fixation, with and without a loop of nonabsorbable suture for reinforcement. The bio-interference screw fixation, with reinforcement by a loop of nonabsorbable suture, gave the highest load to failure among the group (502N +/- 177), which was not significantly different from the intact ligaments (705 N +/- 132), although it was significantly less stiff than the intact group (57.2 N/mm +/- 12.6 and 109.7 N/mm +/- 32.6, respectively). All other reconstructions had an ultimate load and stiffness which were significantly less than that of the intact specimens.

Objectives: To investigate the natural stroke patterns of wheelchair users pushing on a level surface, to determine if users adapt their stroke patterns for pushing uphill, and to assess whether there are biomechanic advantages to one or more of the stroke patterns., Design: Case series., Setting: Biomechanics laboratory., Participants: Twenty-six manual wheelchair users with a spinal cord injury., Intervention: Subjects pushed their own wheelchairs at self-selected speeds on a research treadmill set to level, 3 degrees , and 6 degrees grades. Stroke patterns were measured using a motion capture system. Handrim biomechanics were measured using an instrumented wheel., Main Outcome Measures: Stroke patterns were classified for both level and uphill propulsion according to 1 of 4 common classifications: arcing, semi-circular, single-looping (SLOP), and double-looping (DLOP). Biomechanic outcomes of speed, peak handrim force, cadence, and push angle were all compared across stroke classifications using an analysis of variance., Results: Only 3 of the 4 stroke patterns were observed. None of the subjects used the semi-circular pattern. For level propulsion, the stroke patterns were fairly balanced between arcing (42%), SLOP (31%), and DLOP (27%). Subjects tended to change their stroke pattern for pushing uphill, with 73% of the subjects choosing the arcing pattern by the 6 degrees grade. No statistically significant differences were found in handrim biomechanics or subject characteristics across stroke pattern groups., Conclusions: Wheelchair users likely adapt their stroke pattern to accommodate their propulsion environment. Based on the large percentage of subjects who adopted the arcing pattern for pushing uphill, there may be benefits to the arcing pattern for pushing uphill. In light of this and other recent work, it is recommended that clinicians not instruct users to utilize a single stroke pattern in their everyday propulsion environments.

Objective: To test the hypothesis that pushing on a cross slope leads to increased handrim loading compared with that found on a level surface., Design: Case series., Setting: Biomechanics laboratory., Participants: Twenty-six manual wheelchair users., Intervention: Subjects pushed their own wheelchairs on a research treadmill set to level, 3 degrees , and 6 degrees cross slopes. Propulsion speed was self-selected for each cross-slope condition. Handrim biomechanics were measured for the downhill wheel, using an instrumented wheelchair wheel and a motion capture system., Main Outcome Measures: Speed, peak kinetics (force, rate of loading, torque), push angle, cadence, push distance, and power output were averaged over a 20-push set for each subject and each cross-slope condition. Outcomes were compared across cross slopes using a repeated-measures analysis of variance., Results: Push angle and cadence were unaffected by cross slope. A trend of decreasing self-selected speeds with increasing cross slope was not significant. There were considerable increases in the peak kinetic measures, with the axial moment increasing by a factor of 1.8 on the 6 degrees cross slope (P=.000). More pushes were required to cover the same distance when on a cross slope (P<.034). The power required for propulsion increased by a factor of 2.3 on the 6 degrees cross slope (P=.000)., Conclusions: Users must push harder when on a cross slope. This increased loading is borne by the users' arms, which are at risk for overuse injuries. Exposure to biomechanic loading can be reduced by avoiding cross slopes when possible.

Objective: To test the hypothesis that finger and wrist flexor activity is lower when pushing with a high-friction flexible handrim than with a standard uncoated handrim., Design: Case series., Setting: Biomechanics laboratory., Participants: Twenty-four manual wheelchair users., Intervention: Subjects pushed their own wheelchairs on a research treadmill set to level, 3 degrees , and 6 degrees grades using both a standard uncoated handrim and a high friction flexible handrim. Propulsion speed was self-selected and held constant between handrim trials. Handrim order was randomized. Finger and wrist flexor muscle activity was measured at the forearm using surface electromyography., Main Outcome Measures: Electromyographic data were rectified and normalized by each subject's maximum voluntary contraction. Total muscle exertion was determined by integrating the rectified signal over each push. Peak and total muscle exertion for each push were averaged across grade conditions and compared across handrims using a repeated measures t test., Results: The flexible handrim resulted in statistically significant reductions in both peak and total forearm muscle activation. Averaging across all subjects and grade conditions, peak muscle activation was reduced by 11.8% (P=.026) and overall muscle exertion was reduced by 14.5% (P=.016)., Conclusions: The flexible handrim was shown to require less finger and wrist flexor activity than a standard uncoated handrim for the same propulsion conditions.

This prospective study used magnetic resonance imaging to record sagittal plane tibiofemoral kinematics before and after anterior cruciate ligament reconstruction using autologous hamstring graft. Twenty patients with anterior cruciate ligament injuries, performed a closed-chain leg-press while relaxed and against a 150 N load. The tibiofemoral contact patterns between 0 degrees to 90 degrees of knee flexion were recorded by magnetic resonance scans. All measurements were performed pre-operatively and repeated at 12 weeks and two years. Following reconstruction there was a mean passive anterior laxity of 2.1 mm (sd 2.3), as measured using a KT 1000 arthrometer, and the mean Cincinnati score was 90 (sd 11) of 100. Pre-operatively, the medial and lateral contact patterns of the injured knees were located posteriorly on the tibial plateau compared with the healthy contralateral knees (p=0.014), but were no longer different at 12 weeks (p=0.117) or two years postoperatively (p=0.909). However, both reconstructed and healthy contralateral knees showed altered kinematics over time. At two years, the contact pattern showed less posterior translation of the lateral femoral condyle during flexion (p<0.01).

Progressive degeneration of the anterior cruciate ligament (ACL) deficient knee may be partly due to chondral trauma at the time of ACL rupture and repeat episodes of subluxation, but also due to aberrant kinematics altering the wear pattern at the tibiofemoral interface. The hypothesis that altered kinematics, represented by the tibiofemoral contact pattern, would be associated with articular cartilage degeneration in ACL-deficient knees was tested in a cross-sectional study of 23 subjects with a history of > 10 years ACL deficiency without knee reconstruction. Subjects were aged 31 to 67 years. Eleven were male, 12 were female. Sagittal magnetic resonance imaging (MRI) scans enabled tibiofemoral contact mapping as subjects performed a closed-chain leg-press. Images were acquired at 15 degree intervals from 0 degrees to 90 degrees knee flexion. Articular cartilage degeneration was assessed by diagnostic MRI and where possible, arthroscopy. The ACL-deficient knees had a posterior tibiofemoral contact pattern on the tibial plateau compared to the healthy knees (F((1,171)) = 9.2, p = 0.003). The difference appeared to be seen in the medial compartment (F((1,171)) = 3.2, p = 0.07), though this failed to reach significance. Articular cartilage degeneration in the medial compartment was related to the variation of the tibiofemoral contact pattern (r = -0.53, p = 0.01). Articular cartilage degeneration was not related to time since injury (r = -0.16, p = 0.65). The association between aberrant kinematics and degenerative change may stimulate thinking on the role of dynamic stability and neuromuscular co-ordination in joint protection.

Two methods of analysis of knee kinematics from magnetic resonance images (MRI) in vivo have been developed independently: mapping the tibiofemoral contact, and tracking the femoral condylar centre. These two methods are compared for the assessment of kinematics in the healthy and the anterior cruciate ligament injured knee. Sagittal images of both knees of 20 subjects with unilateral anterior cruciate ligament injury were analysed. The subjects had performed a supine leg press against a 150 N load. Images were generated at 15 degrees intervals from 0 degrees to 90 degrees knee flexion. The tibiofemoral contact, and the centre of the femoral condyle (defined by the flexion facet centre (FFC)), were measured from the posterior tibial cortex. The pattern of contact in the healthy knee showed the femoral roll back from 0 degrees to 30 degrees, then from 30 degrees to 90 degrees the medial condyle rolled back little, while the lateral condyle continued to roll back on the tibial plateau. The contact pattern was more posterior in the injured knee (p=0.012), particularly in the lateral compartment. The medial FFC moved back very little during knee flexion, while the lateral FFC moved back throughout the flexion arc. The FFC was not significantly different in the injured knee (p=0.17). The contact and movement of the FFC both demonstrated kinematic events at the knee, such as longitudinal rotation. Both methods are relevant to design of total knee arthroplasty: movement of the FFC for consideration of axis alignment, and contact pattern for issues of interface wear and arthritic change in ligament injury.

A technique using magnetic resonance imaging (MRI) is proposed for analysis of knee motion that is practical in the clinical situation. T1 weighted fast spin echo (FSE) and spoiled gradient echo (GE) sequences were compared to image both knees at 15 degrees intervals from 0 degrees to 90 degrees flexion, while unloaded and loaded. The medial and lateral tibiofemoral contact points were mapped reliably using both FSE sequences and GE sequences with intra-class correlation((2,1)) of 0.96 (CI 99%=0.94-0.97) and 0.94 (CI 99%=0.91-0.97), respectively. Results were consistent with the current literature on knee motion: the medial and lateral tibiofemoral contact pathways were different (F(1,80) = 253.9, p < 0.0001) reflecting the longitudinal rotation of the knee, the loaded and unloaded knees were not different in the healthy knee (F(1,80) = 0.007, p = 0.935), and the left and right knee were consistent for each individual (F(1,80) = 0.005, p = 0.943). Therefore, right to left differences may be attributed to pathology. MRI analysis of knee kinematics as described by this technique of tibiofemoral contact point mapping provides a robust and reliable method of recording the tibiofemoral contact pattern of the knee.

The multigene family encoding the five classes of replication-dependent histones has been identified from the human and mouse genome sequence. The large cluster of histone genes, HIST1, on human chromosome 6 (6p21-p22) contains 55 histone genes, and Hist1 on mouse chromosome 13 contains 51 histone genes. There are two smaller clusters on human chromosome 1: HIST2 (at 1q21), which contains six genes, and HIST3 (at 1q42), which contains three histone genes. Orthologous Hist2 and Hist3 clusters are present on mouse chromosomes 3 and 11, respectively. The organization of the human and mouse histone genes in the HIST1 cluster is essentially identical. All of the histone H1 genes are in HIST1, which is spread over about 2 Mb. There are two large gaps (>250 kb each) within this cluster where there are no histone genes, but many other genes. Each of the histone genes encodes an mRNA that ends in a stemloop followed by a purine-rich region that is complementary to the 5' end of U7 snRNA. In addition to the histone genes on these clusters, only two other genes containing the stem-loop sequence were identified, a histone H4 gene on human chromosome 12 (mouse chromosome 6) and the previously described H2a.X gene located on human chromosome 11. Each of the 14 histone H4 genes encodes the same protein, and there are only three histone H3 proteins encoded by the 12 histone H3 genes in each species. In contrast, both the mouse and human H2a and H2b proteins consist of at least 10 non-allelic variants, making the complexity of the histone protein complement significantly greater than previously thought.

Myocardial preservation demands the precise and accurate delivery of cardioplegic solutions to provide nutritive delivery and metabolic waste removal. The purpose of this study was to evaluate the performance characteristics of the Medtronic CSS Cardioplegia Safety System in an in vitro setting. The CSS was evaluated under the following conditions: blood to crystalloid ratios of 1:0, 1:1, 4:1, 8:1, 0:1; potassium concentrations of 10, 20, and 40 mEq L-1; volumetric delivery collection at 100, 250, 500, 750, and 990 mL/min; pressure accuracy at 100 and 300 mmHg; and system safety mechanisms. Measured and predicted values from the CSS were compared using one way ANOVA, with statistical significance accepted at p < or = 0.05. The measured values for the tested ratios and volume collections were all within the manufacturer's technical parameters. Potassium concentration results were all within expected values except at 100 mL/min, where the measured value of 17.1 +/- 2.1 mmol was lower than the expected 20.0 +/- 0.2 mmol (p < .034). As flow rates changed, the CSS line pressure error was constant (0.5 to 3.7%), and the only significant difference was observed at 100 mmHg, 500 mL/min (102.3 +/- 1.7 vs. 100.0 +/- 0.0 mmHg, P < .003). The device performed accurately and reliably under all simulated safety conditions, including bubble detection, over pressurization and battery backup. In conclusion, the performance of the CSS was within the manufacturer's specifications for the majority of the tested conditions and operated safely when challenged under varying conditions.

Previous studies on human autologous antiidiotypes have been based largely upon analyses of autoimmune disease. We have previously described polyclonal, naturally occurring human autoantibodies directed against antibodies with specificity toward bovine casein in the sera of IgA-deficient humans. In order to define this system more exactly we have not produced two murine monoclonal antibodies directed against bovine milk kappa-casein to use as clonal tools to identify specific antiidiotypes in these human sera. Kappa-casein is an important part of the casein micelle in milk and cheese; in addition to being an important immunogen for man, kappa-casein is known to have conserved amino acid sequence and two antigenic epitopes. Data presented here show that the serum of up to 74% of IgA-deficient and 10% of normal humans have specific autologous antiidiotypes in their serum which bind to monoclonal antibodies directed to bovine kappa-casein. These human antibodies [intact or F(ab)'2] can be blocked from binding to the monoclonal anti-kappa-caseins by pure bovine kappa-casein or the kappa-casein peptide fragment. In contrast to previous studies in autoimmune disease, serum levels of the autoantiidiotypes were directly proportional to the level of IgG antibody to bovine kappa-casein. These observations suggest that continual exposure to a ubiquitous dietary antigen may produce an antigen driven system in which stimulation of both Ab1 and Ab2 occurs in concert.

Studies were undertaken to enhance the sensitivity of a previously developed RPHA test for HBsAg. A net increase in sensitivity of approximately 3-fold was achieved by modifying the elution procedure used to purify chimpanzee anti-HBs by affinity chromatography. A further 3- or 4-fold sensitivity increase was achieved by increasing the volume of specimen tested. A concomitant increase in nonspecific agglutination usually observed with increased specimen size was avoided by incubating the reaction mixture at 37 or 45 degrees C. Evaluation of the test in detection of HBsAg in blood obtained from volunteer donors indicates that the materials produced at the New York Blood Center using the modified test protocol compare favorably with a commercial RPHA test. Modifications which did not contribute toward enhancing sensitivity are also reported.

Antibodies to three different samples of hepatitis B antigen-positive serum were found to be absent from a Cohn fraction II hepatitis B immune globulin preparation, but present in the whole plasma from which the immune globulin was made. Fractions containing the antibodies specific for the three antigen samples were isolated from the plasma by euglobulin precipitation, and the antibodies were characterized as to immunoglobulin class and precipitability in the Cohn fractionation procedure. They appear to be IgG antibodies which, however, were detectable only in Cohn fraction I, while the remainder of the HB specificity present in the original plasma was found, as expected, in fraction II.

Conditions favoring the coupling of antibody to human erythrocytes stabilized by a variety of reagents were studied with the use of antibody to hepatitis B surface antigen. Functional anti-HBs bound to erythrocytes was measured by radioimmune assay using 125 I-HBsAg. The attachment of anti-HBs to aldehyde-stabilized cells is favored by low pH and low ionic strength. The extent of antibody binding is both concentration and time dependent. Development of spontaneous agglutination of the coated erythrocytes occurs with the attachment of increasing quantities of anti-HBs. Although antibody was rapidly taken up by aldehyde-stabilized erythrocytes, it was initially readily dissociable, but after longer exposure became firmly bound. Experiments pertaining to the chemical nature of the more stable antibody-erythrocyte complex gave results consistent with covalent bond formation, though rigorous proof was not developed.

The red blood cells of blood stored in containers made of polyvinylchloride (PVC) film are osmotically more stable and lose on average about 1/3 less hemoglobin than when blood is stored in another plastic [poly-(ethylene-co-ethyl acrylate); EEA]. The stability of uniform volumes of stored red blood cells varies directly with PVC surface area, whereas changes in EEA surface area have comparatively little or no effect. PVC contains high concentrations of the plasticizer, diethylhexylphthalate (DEHP), known to migrate into blood and to have a high potential for toxicity. To determine if DEHP could be the red cell stabilizing agent in PVC, whole blood was stored in containers made from EEA into which was incorporated varying amounts of DEHP. Incorporation of DEHP into EEA significantly reduced erythrocyte osmotic fragility (p = 0.01). The degree of reduced fragility correlated with the level of DEHP in the cell phase implicating DEHP in PVC containers as the stabilizing agent for red cells.

Rabbit alpha-lactalbumin was purified from the milk of New Zealand White rabbits. It was found to exist predominantly as a glycoprotein, containing 5 mol of glucosamine per mol of protein, as well as other sugars. The amino acid sequence of the protein was determined by sequenator analysis and carboxypeptidase digestion. There are 122 amino acids in the protein and a single carbohydrate moiety, probably attached to an asparagine residue at position 45. The C terminus of rabbit alpha-lactalbumin is one residue shorter than that of the other alpha-lactalbumins. Sequence comparisons indicate that the alpha-lactalbumin gene has been undergoing more frequent mutation than had previously been thought. A new method of preparative peptide mapping using 2,5-diphenyloxazole (PPO) fluor to detect peptides is described.

A computerized method for predicting the locations of protein antigenic determinants is presented, which requires only the amino acid sequence of a protein, and no other information. This procedure has been used to predict the major antigenic determinant of the hepatitis B surface antigen, as well as antigenic sites on a series of test proteins of known antigenic structure [Hopp & Woods (1981) Proc. natn. Acad. Sci. U.S.A. 78, 3824-3828.] The method is suitable for use in smaller personal computers, and is written in the BASIC language, in order to make it available to investigators with limited computer experience and/or resources. A means of locating multiple antigenic sites on a homologous series of proteins is demonstrated using the influenza hemagglutinin as an example.

The antigenic structural features of alpha-lactalbumin have been investigated using a radioimmunoassay, peptide inhibition of the quantitative precipitin reaction, and by immunodiffusion analysis after chemical modification of the molecule. Antigenic activity (in rabbits) was localized to several peptic fragments and the single arginine residue of bovine alpha-lactalbumin. Antigenic activity was also found to be associated with the single methionine residue. A peptic fragment containing a disulfide loop was found to possess antigenic activity in both bovine and goat alpha-lactalbumin. Radioimmunoassay cross-reactivity between the alpha-lactalbumins is correlated with amino acid sequence similarities; bovine alpha-lactalbumin antiserum cross-reacts with goat alpha-lactalbumin more extensively than with human alpha-lactalbumin, while the more distantly homologous protein, chicken lysozyme, does not cross-react at all. Nevertheless our data indicate that the alpha-lactalbumins and lysozyme share a similar distribution of antigenic determinants on their surfaces.

A method is presented for locating protein antigenic determinants by analyzing amino acid sequences in order to find the point of greatest local hydrophilicity. This is accomplished by assigning each amino acid a numerical value (hydrophilicity value) and then repetitively averaging these values along the peptide chain. The point of highest local average hydrophilicity is invariably located in, or immediately adjacent to, an antigenic determinant. It was found that the prediction success rate depended on averaging group length, with hexapeptide averages yielding optimal results. The method was developed using 12 proteins for which extensive immunochemical analysis has been carried out and subsequently was used to predict antigenic determinants for the following proteins: hepatitis B surface antigen, influenza hemagglutinins, fowl plague virus hemagglutinin, human histocompatibility antigen HLA-B7, human interferons, Escherichia coli and cholera enterotoxins, ragweed allergens Ra3 and Ra5, and streptococcal M protein. The hepatitis B surface antigen sequence was synthesized by chemical means and was shown to have antigenic activity by radioimmunoassay.

The biochemical status of whole blood stored in containers fabricated of ethylene ethylacrylate (EEA) film was monitored at several times during 4 weeks of storage at 4 degrees C. Fifteen biochemical indicators were studied to reflect on erythrocyte integrity, cellular metabolism, plasma protein stability, and microaggregate formation. Comparison to storage in polyvinyl chloride (PVC) containers was made by distributing aliquots from each unit of blood among the containers being compared. Whole blood in EEA developed significantly higher levels of plasma hemoglobin, erythrocyte osmotic fragility, and D-glycerate-2,3-diphosphate (2,3-DPG), and somewhat greater glucose utilization, lactate production, and pH. These biochemical differences were not of great magnitude and the data suggest that EEA containers are compatible with the storage of whole blood.

Preparations of hypertensin II, obtained from the treatment of hypertensin I by the action of the hypertensin converting enzyme of plasma and purified by countercurrent distribution, were quantitatively analyzed for their amino acid content. Chromatography on ion exchange columns showed the presence of equimolar amounts of aspartic acid, proline, valine, isoleucine, tyrosine, phenylalanine, histidine, and arginine. Hypertensin I was found to contain one mole of leucine and one mole of histidine in addition to the amino acids of hypertensin II. These two amino acids were isolated from the conversion products of hypertensin I and identified as the peptide histidylleucine. Carboxypeptidase digestion of hypertensin I showed the carboxyl terminal sequence of amino acids to be residue-phenylalanyl-histidylleucine. Similar studies of hypertensin II demonstrated residue-phenylalanine. It was concluded that the conversion of hypertensin I by the plasma hypertensin converting enzyme involved hydrolysis of the phenylalanyl-histidine bond to form hypertensin II and histidylleucine. The further removal by carboxypeptidase of phenylalanine from hypertensin II destroyed all of the vasoconstrictor activity.

The amino acid sequence of horse hypertensin II has been determined by the use of chymotrypsin, the fluorodinitrobenzene method, and stepwise phenylisothiocyanate degradation. The results indicate that the amino acids of hypertensin II are arranged in the following order: asp-arg-val-tyr-iso-hist-pro-phe.