Separation and quantitation of linoleic acid oxidation products in mammary gland tissue from mice fed low- and high-fat diets

We have developed an assay for the isolation and quantitation by gas chromatography-mass spectrometry (GC-MS) of free 9- and 13-hydroxyoctadecadienoic acid (9-HODE, 13-HODE) in the mammary glands of female mice. Internal standards consisting of 18O2-labeled analogs of 9- and 13-HODE are added to pulverized frozen tissue prior to extraction with ethanol. Nonlipid materials are removed in a chloroform/methanol/water step. The remaining lipid material is methylated with ethereal diazomethane, and much of the nonoxygenated fatty acid methyl esters are removed via silica solid-phase extraction. Samples are either further derivatized with bis(trimethylsilyl)trifluoroacetamide to form the trimethylsilyl ethers for quantitative analysis by GC-MS or are analyzed as the methyl esters by chiral high-performance liquid chromatography to determine the enantiomeric distribution of the 9- and 13-HODE. The extraction and quantitation protocol was applied to the analysis of mammary glands for free 9- and 13-HODE from mice fed isocaloric diets containing 20% corn oil, 5% corn oil, or 20% beef tallow. Chiral analysis of the products showed higher production of 13(S)-HODE relative to 13(R)-HODE; the enantiomeric excess is most likely due to enzymatic production of 13-HODE superimposed on a background of autoxidative production of 13(R)- plus 9(S)- and 9(R)-HODE. In addition, the effect of sample handling and storage conditions on the formation of 9- and 13-HODE in the samples was assessed by exposing aliquots of a common pool of rat mammary gland tissue to specified conditions prior to analysis. This methodology will be important during investigations of the contribution of linoleate oxidation products to the enhancement of mammary tumorigenesis by dietary fat.

Intramedullary nailing of unstable diaphyseal fractures of the tibia with distal intraarticular involvement

OBJECTIVE

To evaluate the efficacy of intramedullary nailing in diaphyseal tibia fractures with distal intraarticular involvement.

DESIGN

Retrospective.

SETTING

Henry Ford Hospital, a level I trauma center.

PATIENTS/PARTICIPANTS

Twenty patients with twenty fractures at an average of twenty-two months of follow-up were evaluated. There were fifteen closed and five open fractures.

INTERVENTION

All fractures were stabilized with lag screw fixation (with or without supplemental plates) of the intraarticular-fracture extension or ankle fracture, and intramedullary nailing of the diaphyseal tibia fracture.

MAIN OUTCOME MEASUREMENTS

Time to bony union, malunion, knee and ankle range of motion, early arthrosis, and any complications of treatment were assessed.

RESULTS

Nineteen fractures healed, with an average time to bony union of seventeen weeks. One nonunion after a grade IIIB open fracture required exchange nailing and healed after sixty-two weeks. Nineteen fractures had excellent alignment after healing. There were no infections.

CONCLUSIONS

The indications for intramedullary nailing of unstable diaphyseal tibia fractures may be extended to include certain fractures with distal extension into the ankle joint, as well in a tibial shaft fracture occurring in combination with a noncontiguous ipsilateral ankle fracture.

Early complications in the operative treatment of patella fractures

OBJECTIVE

To identify and review early complications in the operative treatment of patella fractures.

DESIGN

Retrospective review.

SETTING

Single tertiary care institution with multiple surgeons, including generalists and fellowship trained subspecialists.

PATIENTS

A consecutive series of eighty-seven patella fractures over a five year period was reviewed. Patients treated nonoperatively or with partial or total patellectomy were excluded. Minimum follow-up to fracture healing (four months) was available in fifty-one fractures.

INTERVENTION

Modified tension band wire fixation was used in forty-nine fractures, whereas two fractures were treated with tension band wires threaded through cannulated screws.

OUTCOME MEASURES

Early complications such as loss of reduction or fixation, infection, or soft-tissue problems were evaluated.

RESULTS

Displacement of > or = 2 mm before healing was noted in eleven fractures. The displacement could be attributed to technical errors in five cases, and to patient noncompliance with postoperative activity restrictions in another five cases. Two cases of superficial infection were documented. Nine patients with symptomatic hardware required hardware removal.

CONCLUSIONS

Twenty-two percent of fractures treated with tension band wiring and early motion displaced > or = 2 mm within the early postoperative period. Technical errors or patient noncompliance were identified as factors. The incidence of early complications in operatively treated patella fractures is higher than previously reported.

A novel methodology for assignment of disulfide bond pairings in proteins

A novel methodology is described for the assignment of disulfide bonds in proteins of known sequence. The denatured protein is subjected to limited reduction by tris(2-carboxyethyl)phosphine (TCEP) in pH 3.0 citrate buffer to produce a mixture of partially reduced protein isomers; the nascent sulfhydryls are immediately cyanylated by 1-cyano-4-dimethylamino-pyridinium tetrafluoroborate (CDAP) under the same buffered conditions. The cyanylated protein isomers, separated by and collected from reversed-phase HPLC, are subjected to cleavage of the peptide bonds on the N-terminal side of cyanylated cysteines in aqueous ammonia to form truncated peptides that are still linked by residual disulfide bonds. The remaining disulfide bonds are then completely reduced to give a mixture of peptides that can be mass mapped by MALDI-MS. The masses of the resulting peptide fragments are related to the location of the paired cysteines that had undergone reduction, cyanylation, and cleavage. A side reaction, beta-elimination, often accompanies cleavage and produces overlapped peptides that provide complementary confirmation for the assignment. This strategy minimizes disulfide bond scrambling and is simple, fast, and sensitive. The feasibility of the new approach is demonstrated in the analysis of model proteins that contain various disulfide bond linkages, including adjacent cysteines. Experimental conditions are optimized for protein partial reduction, sulfhydryl cyanylation, and chemical cleavage reactions.

A picomole-scale method for charge derivatization of peptides for sequence analysis by mass spectrometry

A highly activated ester containing a fixed positive charge, S-pentafluorophenyl [tris(2,4,6-trimethoxyphenyl)phosphonium]acetate bromide (TMPP-AcSC6F5 bromide), has been synthesized as a reagent for N-terminal modification of peptides. Stable in aqueous acetonitrile solution during extended storage, TMPP-AcSC6F5 bromide reacts with unprotected peptides through p-(dimethylamino)pyridine (DMAP)-promoted amidation in aqueous acetonitrile (15 min, ambient temperature) to form N-TMPP-Ac derivatives of peptides. These peptide derivatives are readily amenable to analysis by fast atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Greater than 90% conversion has been observed in transforming low-nanomole quantities of analyte using molar ratios of 1:5:10 (peptide/reagent/ DMAP). For reactions at the picomole level a slightly modified stoichiometry, with molar ratios of 1:10:500, is employed. Owing to the high reaction efficiency and the tolerance to moderate excess reagent and base during analysis by FAB- and MALDI-MS, the reaction mixture containing the modified peptides can be analyzed directly in most cases, without sample cleanup. Examples of the preparation and analysis of a variety of N-TMPP-acetyl-peptides (TMPP-Ac-peptides) ranging from hexamers to 15-mers are given. Collisionally activated dissociation tandem mass spectrometry of TMPP-Ac-derivatives showed dominant a-type ions, accompanied by d- and c-type ions in some cases, allowing sequence determination to be made in a straightforward manner.

Orthopedic implants: a guide to radiographic analysis

Orthopedic technology is growing at a rapid rate. New implants reflect this technology whether it pertains to fracture fixation, joint replacement, spine stabilization, or soft-tissue reconstruction. This monograph is designed to assist both the radiologist and the orthopedist in accurately assessing plain radiographs of commonly used orthopedic implants. We discuss the biologic response of the surrounding bone to these devices; herein lies the key to understanding the radiographic presentation of these devices.

Composition-selective detection of polychlorinated biphenyls (PCBs) by oxygen-chlorine exchange reaction in a tandem mass spectrometer (MS/MS)

The exchange reaction of chlorine by oxygen with polychlorinated biphenyl (PCB) anions was explored as a method for composition-selective detection of PCB congeners in a gas chromatograph/tandem mass spectrometer (GC/MS/MS) experiment. The odd-electron molecular anions of PCBs react with molecular oxygen introduced into the collision cell of a triple-quadrupole mass spectrometer to form a product ion that has 19 mass units less (35Cl - 16O) than the precursor. The even-electron anions which also form in the source do not react when allowed to pass through the precursor analyzer. Multiple reaction monitoring allows the generation of separate chromatograms for each different composition from tetrachloro through nonochloro PCB. Most coelutants are resolved in this way. Response factors for the 12 coplanar congeners that exhibit dioxin-like toxicity relative to octachloronaphthalene vary from 1.6 to 580. Results of the analysis of an Aroclor 1242 sample for the coplanar congeners compare well with previously determined values.

A strategy to locate cysteine residues in proteins by specific chemical cleavage followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A simple methodology has been developed to characterize the number and location of free cysteine and cystine groups in peptides and proteins, using chemical modification and matrix-assisted laser desorption/ ionization time-of flight mass spectrometry (MALDITOF MS). This new approach employs a specific reaction between free sulfhydryls and 2-nitro-5-thiocyanobenzoic acid (NTCB) to selectively cyanylate cysteine thiols. The N-terminal peptide bond of the modified cysteinyl residue can then be cleaved under alkaline conditions to form an amino-terminal peptide and a series of 2-iminothiazolidine-4-carboxylyl peptides which can be mapped to the sequence by MALDI-MS. The number and location of cysteines can be deduced from mass analysis of the peptide mixture resulting from NTCB chemical processing of the original protein of known sequence under nonreducing conditions. Similar experiments are then performed following disulfide bond reduction to further characterize both cysteine and cystine groups. Experimental conditions are described for protein disulfide bond reduction, sulfhydryl cyanylation, and cleavage reactions performed both in solution and on Zetabind membranes.

Early versus delayed treatment of severe ankle fractures: a comparison of results

A retrospective review of 202 closed Weber B bimalleolar or bimalleolar equivalent ankle fractures treated using open reduction and internal fixation (ORIF) from January 1, 1991, through January 1, 1994 was completed at our institution. A total of 105 ankles (52%) were treated using ORIF within 5 days of injury (early group), with a mean 1.5 days from injury to surgery. A total of 97 ankles (48%) were treated after 5 days (delayed group), with a mean of 13.6 days from injury to surgery. Operative time, length of hospital stay, postoperative range of motion, adequacy of reduction, wound and other complications, and other sequelae were compared between the two groups. No significant difference in range of motion at latest follow-up or in operative time was evident between the groups. Minor wound complications were present in 4.8% of the early group compared with 6.2% in the delayed group. No deep infections or osteomyelitis were present in either group. Anatomic reductions were present in 89% and poor reductions (> 2 mm displacement) in 1% of those ankles treated within 5 days versus 83% anatomic reductions and 3% poor reductions in those treated after 5 days. The differences in wound complications and anatomic reductions between groups was not statistically significant. There was a significantly longer median hospital stay in the early (3 days) versus delayed groups (2 days). We conclude that the results and complications of early versus delayed treatment is not significantly different, except for a shorter median hospital stay in the delayed group. Delayed ORIF is an acceptable alternative when soft-tissue swelling, fracture blisters, or abrasions are present that offer an undesirable environment for surgical incisions. Using contemporary, a traumatic techniques, delayed surgery can provide anatomic reduction with minimal complications in severe ankle fractures.

Retrograde intramedullary nailing, without reaming, of fractures of the femoral shaft in multiply injured patients

Twenty consecutive multiply injured patients who had a total of twenty-two fractures of the femoral shaft were managed with intramedullary nailing without reaming. A retrograde technique through the intercondylar notch of the knee was used. All patients were followed for at least one year or until union of the fracture. The operative time for the nailing averaged seventy-five minutes (range, thirty-five to 105 minutes). Union of the fracture occurred at an average of fifteen weeks. There were three non-unions and one rotational malunion. There were no infections, and no nail or screw failed. Normal motion of the knee was regained by all patients, except one who had had an ipsilateral dislocation of the knee. On the basis of these preliminary results, we concluded that retrograde nailing is a safe and effective technique for multiply injured patients. The apparently higher prevalence of non-union compared with that reported with antegrade nailing with reaming warrants additional study.

Combined intracellular stimulation and high speed video motion analysis of motor control neurons in the cockroach

A complete understanding of motor control circuitry requires detailed analysis of the behavior produced by the circuitry as well as the connections between individual neurons. A technique is described for combining high speed video motion analysis of leg movements in the cockroach with electrophysiological techniques such as intracellular stimulation/recording from central neurons and EMG recording from leg muscles. Using a restrained preparation, we have quantified leg movements evoked by intracellular stimulation of individual motor neurons and local interneurons. By incorporating motion analysis into the recording paradigm, the transfer functions from electrical activity to movements can be derived. Because distinct and characteristic responses to single and multiple action potentials are seen in slow, intermediate, and fast motor neurons, it is often possible to identify the motor neuron targets of local interneurons. The ability to analyze movement in any plane is especially useful in situations such as blind neuropilar penetrations, where a more restricted motion transducer arrangement may not be in register with the impaled cell. In addition, it is possible to record and analyze such complex phenomena as coordinated movements in multiple joints produced by local interneurons and reflexes produced by proprioceptive feedback due to activity of one motor neuron.

Fatty acid substrate specificities of human prostaglandin-endoperoxide H synthase-1 and -2. Formation of 12-hydroxy-(9Z, 13E/Z, 15Z)- octadecatrienoic acids from alpha-linolenic acid

Human prostaglandin-endoperoxide H synthase-1 and -2 (hPGHS-1 and hPGHS-2) were expressed by transient transfection of COS-1 cells. Microsomes prepared from the transfected cells were used to measure the rates of oxygenation of several 18- and 20-carbon polyunsaturated fatty acid substrates including eicosapentaenoic, arachidonic, dihomo-gamma-linolenic > alpha-linolenic (delta 9, 12, 15), gamma-linolenic, and linoleic acids. Comparisons of kcat/Km values indicate that the order of efficiency of oxygenation is arachidonate > dihomo-gamma-linolenate > linoleate > alpha-linolenate for both isozymes; while the order of efficiency was the same for hPGHS-1 and hPGHS-2, alpha-linolenate was a particularly poor substrate for hPGHS-1. Gamma-Linolenate and eicosapentaenoate were poor substrates for both isozymes, but in each case, these two fatty acids were better substrates for hPGHS-2 than hPGHS-1. These studies of substrate specificities are consistent with previous studies of the interactions of PGHS isozymes with nonsteroidal anti-inflammatory drugs that have indicated that the cyclooxygenase active site of PGHS-2 is somewhat larger and more accommodating than that of PGHS-1. The major products formed from linoleate and alpha-linolenate were characterized. 13-Hydroxy-(9Z,11E)-octadecadienoic acid was found to be the main product formed from alpha-linoleate by both isozymes. The major products of oxygenation of alpha-linolenate were determined by mass spectrometry to be 12-hydroxy-(9Z,13E/Z,15Z)-octadecatrienoic acids. This result suggests that alpha-linolenate is positioned in the cyclooxygenase active site with a kink in the carbon chain such that hydrogen abstraction occurs from the omega 5-position in contrast to abstraction of the omega 8-hydrogen from other substrates.

Obturator internus pyomyositis. A case report

Pyomyositis appears to be increasing in prevalence in temperate climates, and often the orthopaedist is integral in the decision making and care of these patients. This is the first reported case of spontaneous bacterial pyomyositis involving the obturator internus muscle. Deep pelvic infections involving the psoas, iliacus, piriformis, and obturator internus can be a significant cause of morbidity and mortality. The infection subsequently may exit the pelvis, and conceivably may progress to a septic hip, bursitis, or lower extremity cellulitis. Improvements in noninvasive imaging such as ultrasound, computed tomography, and magnetic resonance imaging have produced finer resolution of tissue planes. Because of the pathology's deep location within the pelvis of the patient described here, all 3 tests were integral in the surgical planning, exposure, and proper diagnosis. Although 95% of pyomyositis cases are caused by Staphylococcus aureus, cases of pyomyositis with negative cultures have been described. Consideration should be made of disseminated Neisseria gonorrhoeae in sexually active individuals, and cultures should include Thayer-Martin agar to decrease the likelihood of a false-negative culture result.

Management strategies for bone loss in tibial shaft fractures

Fifty open tibial fractures with circumferential cortical bone loss were reviewed. Prospective treatment protocols included fracture stabilization with repeated irrigation and debridement followed by wound coverage. Bony stabilization was accomplished using external fixators, small diameter unreamed interlocking nails, and, in rare instances, plate fixation. Bone graft procedures included posterolateral bone graft, elevation of the free flap or direct anterolateral grafting, bone transport techniques, and free vascularized fibula transfer. Average followup was 18 months (range, 9-40 months). The index graft procedure was used in 30 patients (60%) for fracture healing. The rate of union was 98%, with an average total treatment time of 42.4 weeks (range, 23-80 weeks). Malunion was more likely to develop in patients treated with external fixation and posterolateral bone graft (p = 0.007). Intramedullary nails with direct bone grafting had shorter times to union and shorter total treatment times. The use of free vascular fibular transfers in acute injuries was not successful. Good results were obtained with bone transport techniques. Developing a healthy soft tissue envelope before reconstruction of these injuries is important. Techniques of reconstruction had no correlation to the development of nonunion or infection. They were valuable in determining malunion and total treatment time. These data confirm that carefully staged reconstruction leads to successful outcomes.

Matrix-assisted laser desorption ionization mass spectrometry: applications in peptide and protein characterization

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has quickly gained notoriety as an analytical tool that can accurately determined the molecular weight of proteins up to (and exceeding) 100 kDa from low-picomole amounts of sample. Beyond simple molecular weight determinations, investigators are developing this mass spectrometric technique to obtain more structural information from proteins using a combination of chemical and enzymatic modifications of the analyte prior to analysis by MALDI-MS. Covalent post-translational modifications such as phosphorylation and disulfide bond formation can be identified and localized. MALDI-MS also can be used to rapidly mass-map protein digests for sequence confirmation, often without requiring peptide fractionation. The potential for direct sequencing of peptides and proteins of unknown structure has been successfully demonstrated using several different MALDI-MS approaches. The objective of this report is to introduce MALDI-MS to the non-mass-spectrometrist and to describe applications of this new analytical technique for acquiring information related to peptide and protein structure.

Intramedullary nailing of aseptic tibial nonunions without the use of the fracture table

Twenty-seven patients with 28 aseptic nonunions were treated with reamed intramedullary (IM) nailing of the tibia and were followed for at least 1 year postoperatively. The management protocol called for a radiolucent operating room table with the limb draped free and manual manipulation of the nonunion with a preference for closed nailing. Nail interlocking was used when residual axial or rotational instability was observed after nail insertion. Iliac crest bone grafting was performed on all patients requiring open nailing. Closed nailing, using the described technique, was accomplished in 20 cases; open nailing was necessary in eight. Although operative time and total blood loss were significantly increased with open nailing, time to union was similar in the two groups. Twenty-seven nonunions healed. The lone persistent nonunion responded to bone grafting, leaving the nail in situ. One infection occurred, which responded to debridement, drainage, and long-term antibiotic therapy without requiring nail removal. Acceptable bony alignment was attained in all patients. Functional results were excellent. This method is recommended for all tibial nonunions amenable to IM nail stabilization. A history of prior acute infection and/or excessive shortening due to bone loss constitute the relative contraindications.

Biomechanical analysis of canine bone lengthened by the callotasis method

The mechanical integrity of tibial bone treated by distraction osteogenesis (callotasis) using an Orthofix external fixator was evaluated in a group of 6 dogs. Diaphyseal corticotomies were performed on Day 0. Distraction was begun on Day 8, at a rate of 0.33 mm every 8 hours. On Day 34, the Orthofix frame was locked. On Day 56, the frames were removed and the dogs were euthanized. Radiographs were taken weekly to assess regenerate bone formation and extent of tibial bone lengthening, which averaged 12 mm (range, 5-20 mm). One dog showed incomplete bony union that was attributed to pin loosening. Torsional testing of lengthened and contralateral control tibiae resulted in spiral diaphyseal fractures. Five of 6 lengthened tibiae bones fractured within the diaphysis, but outside the regenerate area, suggesting that the strength of the lengthened segment exceeded that of the original diaphysis which was exposed to stress shielding by the external fixator. These observations have led to a method to test and evaluate lengthened bone at the time of frame removal and to monitor the effectiveness of this type of technique.

Evaluation of an implantable ventricular assist system for humans with chronic refractory heart failure. Measuring quality of life

The development of a multidimensional quality of life protocol to be used in a clinical trial of an LVAS was presented. The complexity of the new LVAS technology being evaluated added a unique dimension for HQL assessment. The rationale and procedures used in developing this protocol were described. Although we have elucidated the development of a protocol for a specific clinical trial, the principles and procedures employed are widely applicable. To summarize, these procedures are as follows: 1. Determine what quality of life domains are important to measure. This decision should be based upon the domains expected to be affected by treatment, those expected to change as a result of the natural course of the disease or condition, and those that may be affected by changes in the primary domains. 2. Once the domains are selected, identify specific measures for these domains. Where possible, the measures chosen should be standardized, well validated, and appropriate to the study population. Instrument length and mode of administration are additional considerations. 3. Consider any unique aspects of the study population or intervention and develop specific questions to address them. 4. Identify and measure important variables that may moderate or influence quality of life. 5. Test the protocol on an appropriate population for length, flow, and ease of administration. Copies of the complete HQL protocol are available by writing to: Dr. Nancy Avis, New England Research Institute, 9 Galen Street, Watertown, MA 02172.

Ultrasound for the early diagnosis of fracture healing after interlocking nailing of the tibia without reaming

Fourteen fractures (8 open, 6 closed) were treated with small-diameter interlocking tibial nails and observed for at least 1 year. Radiographs were obtained to monitor the maintenance of reduction and fracture healing. The treating orthopaedic surgeon was blinded to the results of ultrasound studies, which were obtained at 2-week intervals for 10 weeks postoperatively and read by a radiologist who was blinded to the clinical and radiographic progress. Ultrasound correctly predicted fracture healing in all 9 fractures that subsequently progressed to fracture union. Of the 5 fractures that did not heal and required secondary procedures, ultrasound predicted delayed healing in 4 fractures. Overall, ultrasound was able to predict fracture healing before it was radiographically evident. Ultrasound may provide important prognostic information concerning tibial fracture healing after treatment using interlocking nails without reaming. Additional study is warranted.

Dual pathways for tactile sensory information to thoracic interneurons in the cockroach

The escape system of the American cockroach is both fast and directional. In response to wind stimulation both of these characteristics are largely due to the properties of the ventral giant interneurons (vGIs), which conduct sensory information from the cerci on the rear of the animal to type A thoracic interneurons (TIAs) in the thoracic ganglia. The cockroach also escapes from tactile stimuli, and although vGIs are not involved in tactile-mediated escapes, the same thoracic interneurons process tactile sensory information. The response of TIAs to tactile information is typically biphasic. A rapid initial depolarization is followed by a longer latency depolarization that encodes most if not all of the directional information in the tactile stimulus. We report here that the biphasic response of TIAs to tactile stimulation is caused by two separate conducting pathways from the point of stimulation to the thoracic ganglia. Phase 1 is generated by mechanical conduction along the animal's body cuticle or other physical structures. It cannot be eliminated by complete lesion of the nerve cord, and it is not evoked in response to electrical stimulation of abdominal nerves that contain the axons of sensory receptors in abdominal segments. However, it can be eliminated by lesioning the abdominal nerve cord and nerve 7 of the metathoracic ganglion together, suggesting that the relevant sensory structures send axons in nerve 7 and abdominal nerves of anterior abdominal ganglia. Phase 2 of the TIA tactile response is generated by a typical neural pathway that includes mechanoreceptors in each abdominal segment, which project to interneurons with axons in either abdominal connective. Those interneurons with inputs from receptors that are ipsilateral to their axon have a greater influence on TIAs than those that receive inputs from the contralateral side. The phase 1 response has an important role in reducing initiation time for the escape response. Animals in which the phase 2 pathway has been eliminated by lesion of the abdominal nerve cord are still capable of generating a partial startle response with a typically short latency even when stimulated posterior to the lesion.

Evaluation of an implantable ventricular assist system for humans with chronic refractory heart failure. Study overview. LVAS Study Group. Left Ventricular Assist System

In this summary, the authors provide the background of and proposed protocol for a clinical evaluation of the safety and efficacy of the Novacor N120 Left Ventricular Assist System, sponsored by the National Heart, Lung, and Blood Institute. Although the clinical trial was never carried out, the protocol developed for this trial may be useful to other investigators considering a clinical trial of a circulatory support device. The protocol is summarized here and in five more detailed articles in this issue.