Covalently modified peptides isolated from aspartate aminotransferase after reaction with pyridoxal 5'-sulfate

The apoenzyme form of cytosolic aspartate aminotransferase of pig hearts was allowed to react at room temperature with 1 equiv of pyridoxal 5'-sulfate. The resulting covalently modified enzyme was degraded with pepsin. Fluorescent tri-, tetra-, and hexapeptides were isolated and characterized as fragments of the active site sequence: Phe-Ser-Lys-Asn-Phe-Gly-Leu. This sequence contains a modified form (Lys) of lysine-258 that is known to form a Schiff base with pyridoxal phosphate in the active site. The peptides were further degraded by acid hydrolysis to give a fluorescent derivative of lysine with light absorption and chemical properties similar to those of the original modified enzyme. A related series of peptides were obtained from apoenzyme after reaction with the 5-carboxyethenyl analogue of pyridoxal 5'-phosphate.

Pyrrolopyridine derivatives from pyridoxal 5'-sulfate

A fluorescent derivative of lysine-258 isolated from the active site of aspartate aminotransferase modified by treatment of the apoenzyme with pyridoxal 5'-sulfate has been characterized as a substituted 2H-pyrrolo[3,4-c]pyridine. Similar pyrrolopyridines are produced in up to 20% yield by reaction of pyridoxal sulfate with simple alkylamines or with amino acids including lysine. The latter forms two products, one of which is identical with that isolated from the enzyme. The pyrrolopyridine derived from ethylamine has been characterized by proton and 13C NMR, ultraviolet-visible, and mass spectroscopy and by its chemical reactions.

Stress fracture of the patella following duopatellar total knee arthroplasty with patellar resurfacing

Stress fracture of the patella can occur with significant frequency following patellar replacement with the duopatellar knee prosthesis. In the first 372 knees with patellar resurfacing, the incidence was 0.7% in rheumatoid arthritis (2 fractures in 286 knees) and 3.5% in osteoarthritis (3 fractures in 86 knees). The incidence may be greater in osteoarthritic patients because they have more function and are generating greater force across the patellofemoral joint. There was an association with osteonecrosis of the patella in at least three cases in which a lateral retinacular release had been performed and the lateral superior genicular artery sacrificed. This vessel should be preserved during a lateral release to save its contribution to the blood supply of both the patella and the lateral skin flap. Initial treatment of the stress fractures can be nonoperative, with surgery necessary only if the patellar prosthesis has become dislodged, or if pain or inadequate active extension persists. If the fracture can not be repaired, patellectomy can yield a good result. To avoid stress fracture, a minimal amount of patellar articular surface should be resected and the peripheral cortex of both the medial and lateral facets preserved. Fewer stress fractures may occur if a smaller fixation lug is used, thereby preserving more patellar bone stock.

The nature of the changes in liver mitochondrial function induced by glucagon treatment of rats. The effects of intramitochondrial volume, aging and benzyl alcohol

(1) The effects of changes in the intramitochondrial volume, benzyl alcohol treatment and calcium-induced mitochondrial aging on the behaviour of liver mitochondria from control and glucagon-treated rats are reported. (2) The stimulatory effects of glucagon on mitochondrial respiration, pyruvate metabolism and citrulline synthesis could be mimicked by hypo-osmotic treatment of control mitochondria and reversed by calcium-induced aging of mitochondria or by treatment with 20 mM benzyl alcohol. Hypo-osmotic treatment increased the matrix volume whilst aging but not benzyl alcohol decreased this parameter. (3) Liver mitochondria from glucagon and adrenaline-treated rats were shown to be less susceptible to damage by exposure to calcium than control mitochondria and frequently showed slightly (15%) elevated intramitochondrial volumes. (4) Aging, benzyl alcohol and hypo-osmotic media increased the susceptibility of mitochondria to damage caused by exposure to calcium. (5) Glucagon-treated mitochondria were less leaky to adenine nucleotides than control mitochondria. (6) These results suggest that glucagon may exert its action on a wide variety of mitochondrial parameters through a change in the disposition of the inner mitochondrial membrane, possibly by stabilisation against endogenous phospholipase A2 activity. This effect may be mimicked by an increase in the matrix volume or reversed by calcium-dependent mitochondrial aging.

Duopatellar total knee replacement: the Brigham experience

Over the past 25 years at the Brigham Hospital we have seen prosthetic knee arthroplasty evolve from metal interpositional hemi-arthroplasty to the current generation of metal-to-plastic total knee replacements. Surely this evolutionary process will continue for may more years. Time will help us answer many of the questions and controversies that exist regarding posterior cruciate retention, patellar resurfacing, and unicompartmental replacement. We have yet to establish the optimal tibial stem length and shape and whether metal backing is truely beneficial. It is still to be determined whether the standard condylar femoral component should have condylar lugs to enhance fixation or an intramedullary stem with no condylar lugs. In the meantime, we have the use of a graduated system of prostheses that can be tailored to the individual needs of each patient and can predictably relieve pain and improve function in well over 90 per cent of cases. Late complications requiring revision surgery (most often patellar problems or tibial loosening) are occurring at a rate of 1 per cent per year of follow-up, and we hope these will be minimized by the recent advances we have discussed.

Unicondylar unicompartmental replacement for osteoarthritis of the knee

Unicompartmental knee replacement is an attractive concept that offers several potential advantages over bicompartmental or tricompartmental replacement, including preservation of bone stock, of the anterior and posterior cruciate ligaments, of the patellofemoral joint, and of the normal opposite compartment. Of our first 100 consecutive knees that had unicompartmental arthroplasty for osteoarthritis and were followed for two to six years (average, three and one-half years), eighty-eight were medial and twelve were lateral replacements. The ages of the patients at the time of operation ranged from forty-six to eighty-five years, with an average age of seventy-one years. At follow-up, pain relief was good to excellent in 92 per cent of the knees. The average amount of flexion was 114 degrees (range, 90 to 140 degrees); one-half of the knees had at least 120 degrees of flexion. The average flexion contracture was 1 degree. There were no infections and no peroneal palsies. At the time of writing, three failures had required revision. Radiolucent lines at the bone-cement interface were present around 8 per cent of the femoral components and 27 per cent of the tibial components. Two femoral components subsided in obese patients. There was no tibial loosening in the series. The most common complications, per anserinus bursitis, occurred in 12 per cent of the knees and was treated satisfactorily by injection of local anesthetics and steroids. Surgical technique must be precise to prevent subluxation of the tibia on the femur due to either improper positioning of the components or too tight a fit (too much pressure) between them. We view unicompartmental replacement as an attractive alternative for the treatment of unicompartmental osteoarthritis in elderly patients. However, we are strong advocates of proximal tibial osteotomy for unicompartmental osteoarthritis associated with a varus deformity in selected patients.

Capitellocondylar total elbow arthroplasty

Sixty-nine non-constrained capitellocondylar metal-to-plastic total elbow-replacement prostheses were implanted in sixty-four patients with rheumatoid arthritis. These patients were followed for an average of 3.5 years. Postoperative flexion and pronation were significantly improved, but no significant increase in postoperative extension or supination could be demonstrated. Based on a rating system evaluating pain and function, there were 87 per cent good or excellent results. The complication rate based on the total number of prostheses implanted was 39 per cent. Eight patients required revision of the arthroplasty: four for dislocation of the prosthesis, two for sepsis, one for loosening, and one for a fracture. Eight other asymptomatic patients showed minimum radiolucent lines adjacent to the ulnar component. No patient demonstrated radiolucent lines adjacent to the humeral component.

Prosthetic replacement of the patellofemoral joint

We are just beginning to fully appreciate the significant role of the patellofemoral joint in total knee replacement surgery. Most of the new generation prostheses have a flanged femoral component. The tendency is to make the flange more anatomic in shape as more attention is paid to patellar tracking. Most systems have an optional polyethylene button to resurface the patellar side of the patellofemoral joint, and indications for its use are increasing. Although pain relief with patellar buttons seems uniform, the potential complications of stress fracture, loosening, and wear must temper our enthusiasm for their use until there is longer follow-up. Vitallium hemiarthroplasty of the patella is available in prostheses with and without the requirement for cement fixation. Most investigators have good results in chondromalacia (as a secondary procedure), but the experience in the literature is small. Results have been poor when the femoral side of the joint has been involved. Metal to plastic isolated patellofemoral prostheses have been designed to treat disease on both sides of the patellofemoral joint or to salvage unflanged total knee replacements with residual patellofemoral symptoms. Short term experience has been promising.

The split-heel technique in the management of calcaneal osteomyelitis in children. Report of three cases

Three cases are reported in which the split-heel technique was successfully used in the management of calcaneal osteomyelitis in children. Antibiotic therapy and debridement when necessary through medial or lateral incisions will usually eradicate the infection. Gaenslen's technique is recommended for refractory cases or patients with a draining sinus centrally located on the plantar aspect of the heel. An excellent functional result can be obtained. In general, excision of the calcaneus for chronic osteomyelitis in children is not necessary.

Magnesium depletion and hypocalcaemia after removal of parathyroid carcinoma

A case of parathyroid carcinoma is described which presented with severe bone disease, complicated after parathyroidectomy by symptomatic hypocalcaemia and magnesium deficiency, both of which responded dramatically to the administration of magnesium. Urinary cyclic AMP assays were used to monitor parathyroid activity.

Femoral fractures in conjunction with total hip replacement

We reviewed thirty-eight cases, in thirty-six patients, of fracture of the femur distal to the base of the neck incurred in conjunction with total hip replacement. There were thirteen preoperative, eighteen intraoperative, and seven postoperative fractures. The cases were contributed by thirteen surgeons. We found that the preoperative fractures with pre-existing disease in the hip joint were effectively treated by primary total hip replacement using custom-made femoral components with long necks or long stems, or both. The intraoperative femoral fractures usually occurred while the surgeon was reaming the canal, seating the femoral component, or manipulating the femur in patients who were predisposed to fracture. Theoretically these lesions can be treated like preoperative fractures, but this demands immediate access to custom-made femoral components with long necks or long stems, or both, along with an appreciation of the extent and significance of the fracture. Inadequate fixation was found to lead to painful non-union or late loosening of the femoral component in four of eighteen patients. Postoperative fractures occurred too rarely for us to draw any definite conclusions about management, except to say that surgical treatment can be hazardous and traction has been successful in this series and in other reports. Prophylactic measures, however, may help to prevent postoperative femoral fractures. Most of these fractures occur through a cortical defect near the tip of the femoral component. A long-stem femoral component may help to prevent postoperative fractures whenever a proximal cortical defect of the femur is present preoperatively or is created at surgery.

Drug overdoses: Is one stomach washing enough?

Naso-gastric tube aspirates were taken from patients with drug overdoses who had been given a gastric lavage and admitted to the resuscitation ward. Although care was taken to conduct thorough washouts, it was found that these were not always efficient. In several cases an amount equivalent to a therapeutic dose of drug was recovered in later aspirates. There was no correlation between the amount of drug recovered in the initial stomach washings and that found in the aspirates. It was concluded that routine aspiration of gastric contents at hourly intervals after admission was of considerable value in removing any residual drugs.

Treatment of an adrenal cortical carcinoma with a combination of o,p'-DDD and aminoglutethimide

A patient with Cushing's syndrome due to an adrenocortical carcinoma is described. Treatment of residual disease and functional metastases was attempted with o,p′-DDD and later aminoglutethimide. Aminoglutethimide in a daily dose of 1 g appeared to have little effect additional to o,p′-DDD. It is important to maintain replacement therapy with cortico-steroids throughout the use of these drugs.

Treatment of Paget's disease of bone with synthetic salmon calcitonin

Thirteen patients with painful Paget's disease of bone were treated as outpatients with low doses of synthetic salmon calcitonin 22.5-50 mug three times weekly. Treatment produced full remission of pain in a mean time of 5.5 weeks and a mean depression of serum alkaline phosphatase activity of 33%.The interval before symptomatic relief could not be predicted from the variables studied. The ultimate fall in serum alkaline phosphatase activity, however, could be predicted from the initial levels and from the early rate of decrease (P < 0.001). Biochemical resistance to treatment, which occurred in three cases, could be related to the dose and duration of treatment.Prolonged remissions of pain may occur which are not related to biochemical remission, to the dose of calcitonin, or to the duration of treatment. The side effects attributable to salmon calcitonin were transient nausea (in nine patients), transient flushing (in four), diarrhoea (in two), and rash (in one) though in only one patient did treatment have to be withdrawn prematurely because of these effects.