XPS analysis of 316 LVM corroded in serum and saline

Surface chemical analysis by x-ray photoelectron spectroscopy (XPS) was undertaken on 316 LVM stainless steel in the attempt to better understand corrosion occurring in vivo. Samples were dipped in saline or in blood serum, corroded in serum or saline by the application of a 5 volt anodic potential, or corroded by fretting. The products produced by fretting corrosion were also examined. XPS analysis revealed rapid protein coating of the stainless steel surfaces exposed to serum, changes in the oxidation state of the surfaces, and changes in the chlorine on the surface. In addition it was demonstrated that the corrosion products generated by fretting in saline had an oxidation state similar to that of chronic chloride whereas the corrosion products generated in serum had an oxidation state similar to that of potassium dichromate. These findings may have important implications since the chromium in dichromate is more biologically active than that in chronic chloride.

Stability of the canine shoulder joint: an in vitro analysis

The stability of the canine shoulder joint was assessed with and without the restraining effects of selected supporting structures. Shoulder joints from medium-sized (15 to 30 kg) canine cadavers were dissected, and all soft tissues were removed except for the 4 cuff muscles (supraspinous, infraspinous, teres minor, subscapular), the biceps muscle (m biceps brachii) and the joint capsule with its associated glenohumeral ligaments. The humerus was fixed in position, and with the shoulder extended, the joint was stressed into abduction, adduction, internal rotation, and external rotation. The range of motion was measured from transverse pins placed above and below the joint. Measurements were made before and after severance of the cuff tendons and joint capsule. In selected joints, medial and lateral luxations were created. The biceps tendon was then transposed medially or laterally, respectively, to aid joint stability. Selected medial luxations were stabilized by transferring a portion of the insertion of the supraspinous tendon to a medial location. All joints were stressed as just described, and the range of motion was measured before and after tendon transfer. The joint capsule with its associated glenohumeral ligaments was an important restraint of joint motion. Lateral transfer of the biceps tendon partially corrected lateral joint instability by imposed marked rotational constraints on the joint. Medial transfer of the biceps tendon or the supraspinous tendon partially corrected medial joint instability, but did not resolve rotational abnormalities.

Crevice and fretting corrosion of stainless-steel plates and screws

Mechanisms of corrosion at the areas of contact between screw heads and plate holes were investigated using electrochemical potential recording techniques. Static crevice corrosion was studied with plates and screws in isotonic and hypertonic saline solutions (0.9 to 7.2% NaCl). Fretting corrosion was studied in vitro with plates screwed to tubular bone analogs which were subjected ty cyclic axial loads, and was studied in vivo with plates screwed on the tibia of sheep. Static tests showed that crevice corrosion does not occur in isotonic saline for periods up to one year, but can occur in hypertonic saline solutions. Dynamic loading tests demonstrated immediate potential changes which were related to the magnitude of the applied load, indicating fretting corrosion due to motion between screw head and plate, both in vitro and in vivo. A mechanism for screw-plate relative motion is proposed. It is hypothesized that corrosion seen in clinically retrieved implants is due to fretting corrosion which predisposes the contact area to crevice corrosion attack.

Fretting corrosion in saline and serum

Fretting corrosion of stainless-steel round hole plates and spherical head screws was studied using a simulator that produced a rocking motion of the heads in the plate holes. Experiments were run for 7 days, with the simulator producing 1 oscillation/s for 16 h/day. Fretting corrosion was studied in 0.9% NaCl and in a 10% solution of fetal calf serum in saline. The results showed a tenfold decrease in fretting corrosion when the serum was added to the saline. Measurements of the weight of the two screws and two-hole plate showed those in saline lost 2.9 mg as compared to 0.3 for those in 10% serum. The concentration of nickel in the saline solutions was 12.4 micrograms/mL compared with 0.85 in serum. Visual examination of the solutions and implants revealed that those in saline had a significant amount of corrosion products while those tested in 10% serum were bright and shiny. Recordings of electrical potentials demonstrated that the addition of serum to saline significantly reduced the change in potential from rest to fretting condition.

In vivo and in vitro considerations of corrosion testing

In vitro experiments were conducted in which the fretting corrosion rate of stainless steel plates and screws in 0.9% saline was compared with the rate in solutions of 10% calf serum in saline. The results demonstrated a ten-fold decrease in the fretting corrosion rate with the addition of serum to saline. However, it also demonstrated that the lower concentration of nickel in the serum solutions was more biologically active than the higher concentration in saline when the solutions were used to skin test rabbits made allergic to nickel by injection.

Attendance failure at paediatric medical outpatient clinics

Failure in attendance at medical out-patient clinics at Princess Mary Paediatric Hospital occurred in 46 percent of patients. This was due to patient error, administration error and patient non-compliance. Failure in attendance by Polynesians was due to error and non-compliance; caucasians mainly non-compliance. Hospital administrative errors accounted for default in 6 percent of all patients. Methods of reducing the problem of failure in attendance at out-patient clinics are considered. The aim of this study was to determine the incidence of failure in attendance at Princess Mary Paediatric Hospital (PMH) medical out-patient clinics (OPC) and to establish the reasons for default.

Metal allergy and the surgical patient

Allergy to metal implants is under study at the Dartmouth-Hitchcock Medical Center using in vitro examination of white blood cell migration. Retrospective data from 121 patients confirm that allergic responses do occur. Prospective data are being gathered to investigate the incidence, prevalence and relation to morbidity.

Affinity chromatography of Ruta graveolens L. O-methyltransferases. Studies demonstrating the potential of the technique in the mechanistic investigation of O-methyltransferases

Two discrete furanocoumarin (5- and 8-)O-methyltransferases and a caffeic acid 3-O-methyl-transferase from cell cultures of Ruta graveoleus L. have been copurified by affinity chromatography on 1,6-diaminohexane agarose (AH-Sepharose 4B) linked with S-adenosyl-L-homocysteine (SAH). The furanocoumarin O-methyltransferases, which transfer a methyl group from S-adenosyl-L-methionine (SAM) to the 5- or 8-hydroxyls of linear furanocoumarins, were not retarded by 5-(3-carboxypropanamido)-xanthotoxin (CPAX) immobilized to AH-Sepharose 4B, but addition of SAM to the irrigant buffer led to complete retardation of both enzymes on this affinity system. An analogous phenomenon was observed for the caffeic acid O-methyltransferase, with a ferulic acid ligand coupled to the same insoluble support. SAH was as effective as SAM in promoting binding of the furanocoumarin O-methyltransferases to CPAX and caffeic acid 3-O-methyltransferase to immobilized ferulic acid, respectively. The strong and specific adsorption of these enzymes was abolished by exclusion of SAM or SAH from the irrigant buffer. It is concluded that the enzymes bind first to SAM or SAH, and that this binding process in turn induces the binding site for their specific phenolic substrates or their analogs. Based on these findings, a compulsory-ordered kinetic mechanism for the action of these O-methyltransferases is postulated.

Mechanism of obstruction of closed-wound suction tubing

The mechanism of obstruction of closed-wound drainage tubing was investigated by means of coagulation tests performed on wound drainage fluid and by examination of the contents of the tubes after their removal. Although clotting is commonly thought to be responsible for the obstruction, the wound drainage fluid was found to be essentially incoagulable and little fibrin was evident within the tubes. By contrast, bits of tissue were frequently found within the tubes, and these frequently virtually occluded the lumen. This observation, that tissue fragments are responsible for tube obstruction, permits a rational approach to the solution of this problem. For example, meticulous wound flushing and irrigation, or perhaps tubing of different design, might lead to a reduced incidence of tube failure.

Increase in liver acid lipase of thyroidectomized rats by thyroid hormones and its inhibition by actinomycin D

Acid lipase activity in the livers of thyroidectomized rats is increased by administration of L-thyroxine. The response is dose-dependent and can be demonstrated within 12 h after treatment. L-Triiodothyronine also evokes a rapid increase in acid lipase activity, and this increase can be inhibited by coadministration of actinomycin D.

Separation of the S-adenosylmethionine: 5- and 8-hydroxyfuranocoumarin O-methyltransferases of Ruta graveolens L. by general ligand affinity chromatography

Two S-adenosyl-L-methionine:furanocoumarin O-methyltransferases of R. graveolens, acting at the 5- and 8-hydroxyl of the psoralen nucleus, were completely resolved by adsorption on a general affinity ligand, 5-(3-carboxypropanamido) xanthotoxin, followed by specific desorption by bergaptol and xanthotoxol, respectively. The 5-O-methyltransferase was purified 450-fold by this procedure, the 8-O-methyltransferase 112-fold, and both enzyme fractions were electrophoretically homogeneous. No resolution could be achieved of the activity against two 5-hydroxypsoralens or of the activity against two 8-hydroxypsoralens, and conclusive evidence is presented for the existence of only one 5-O-methyltransferase and only one 8-O-methyltransferase acting on linear furanocoumarins.

Acid lipase activity of human lymphocytes

Acid lipase activity was examined in human leukocytes using 4-methylumbelliferyl esters in a fluorimetric assay. Mononuclear leukocytes had 10--15 times the acid lipase activity of polymorphonuclear leukocytes. The enzyme activity was highest using the oleate ester of 4-methylumbelliferone at pH 4.0, in the presence of L-alpha-phosphatidylcholine and taurodeoxycholic acid (sodium salt). Acid lipase activity was inhibited by diethylaminoethoxyhexestrol, sodium chloride and fluoride, potassium chloride, calcium chloride and albumin, but was unaffected by diethyl p-nitrophenyl phosphate or sulphydryl reagents. There were at least two forms of acid lipase activity: one (A form) was sensitive to heart inactivation (56 degrees C) and corresponded to the enzyme deficient in patients with Wolman's disease; the other (B form) was resistant to heat inactivation and corresponded to the residual enzyme activity found in Wolman's disease.

Implant site infection rates with porous and dense materials

The infection rate of implant sites bearing porous and dense implants was studied in mice. In the first model (acute infection) the mice were injected with Staphylococcus aureus subcutaneously at the implant site at the time of implantation. In the second (chronic) model the implants were left in place for four weeks for encapsulation or invasion to occur and then the organisms were inoculated. In the acute model the infection rate with the porous materials was greater. In the chronic model after tissue invasion the infection rate with the dense materials was greater. This supports the hypothesis that microorganisms can evade host defense mechanisms if they enter the pores of the implant before tissue invasion, but that once the implant is invaded with host tissue the bacteria are less apt to establish infection.

The biocompatibility of materials for internal fixation of fractures

Surgically produced fractures of rabbit tibiae were internally stabilized with intramedullary rods of stainless steel (316LVM), titanium (6A1,4V), polyacetal (Delrin), and polyamide (Nylon 101). Periodic radiographs were taken until sacrifice at 16 weeks after fracture. Structural properties of the tibiae were determined in torsion with the rods in situ, and then the tissue was prepared for histology or microradiography. The results demonstrated that fracture remodeling was adversely affected by the metal rods. New bone was seen to have formed over the ends of the metal rods, and cortical bone resorption was observed in the fracture region, suggestive of transfer of mechanical stress to the rods, resulting in stress shielding of the diaphysis. Negligible osseous response to the polymeric rods was observed; fracture callus remodeling was extensive. The torsional test results demonstrated that fractures with polymeric rods were significantly stronger and tougher than those with metallic rods. With the exception of titanium, the strength of healed fractures was inversely related to the elastic moduli of the implant materials.

Polymeric fixation and ultrasonic assessment of fractures and healing

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Characteristics and postnatal development of the acid lipase activity of the rat small intestine

Acid lipase was identified in the rat small intestine by using esters of 4-methylumbelliferone as substrates. Maximum activity towards the oleate ester was found at pH 4.0. In adult animals, the activity of acid lipase exhibited both latency and sedimentability, indicating a lyosomal localization. The activity of acid lipase was practically the same along the height of the villus, thus paralleling the distribution of acid beta-galactosidase. In adult rats, the activity of acid lipase in proximal (jejunum) and middle (mid-jejunum) sections of the small intestine was practically the same and exceeded the activity in the distal (ileum) section by a factor of 2. In suckling rats, the activity of the enzyme in the mid-jejunum exceeded that in the jejunum and ileum by 2.5- and 1.5-fold respectively. During postnatal development, the acid lipase activity of the mid-jejunum showed a peak between days 10 and 15, at which time it exceeded the adult mid-jejunum activity by 5--6-fold.

The biosynthesis of isopimpinellin

Bergapten and xanthotoxin, labelling in the methyl group wich carbon-14 or tritiated at three skeletal carbons, were administered to leaves of Heracleum lanatum and to cell cultures of Ruta graveolens. In all experiments xanthotoxin was the more efficient precursor of isopimpinellin, although bergapten was always incorporated to a measurable extent. Double-labelling experiments showed that both precursors, especially bergapten, underwent considerable demethylation (and presumably remethylation) before conversion to isopimpinellin. 5-Hydroxyxanthotoxin and 8-hydroxybergapten were both O-methylated by cell-free extracts of Ruta cells to isopimpinellin, in reactions mediated by discrete O-methyltransferases. 8-Hydroxy[Me-14C]bergapten was converted with a high degree of incorporation to isopimpinellin by Ruta cells in vivo, and it is suggested that the preference for the pathway via xanthotoxin may be due to more rapid hydroxylation of this substrate.

Bone ingrowth into dynamically loaded porous-coated intramedullary nails

Research to determine whether porous-coated Vitallium intramedullary rods could be used to bridge segmental defects in long bones was performed using rabbit tibias as a suitable model for human bone growth. One-centimeter segments of the midshaft of tibias of mature rabbits were removed surgically and replaced with equal-sized segments of Silastic tubing to maintain leg length. A coated rod was inserted through the proximal tibial segment, through the tubing, and into the distal bone segment. The legs were taken out of plaster at 3 weeks, and x-rays were taken periodically until sacrifice. At sacrifice, 30 weeks postoperatively, the mechanical properties of both tibias from each rabbit were measured destructively in a torsional testing machine. The load at failure of the tibia with the segmental defect averaged 90% of the contralateral control tibia. Rod pullout data and electron-probe x-ray micro-analysis indicated that a substantial rod-endosteal bone bond existed due to ingrowth into the porous coating. The torsional data may have been somewhat obscured by the presence of bony callus which grew over the Silastic tubing and bridged the segmental defect exosteally in every case.

Ultrasonic assessment of early callus formation

A 0.5 MHz pulse-transmission ultrasonic device is described and results obtained with an animal model presented. Two waveform components have been identified which correlate with the healing process. The "bone wave" is indicative of endosteal callus formation and the strength of cortical union. The "callus wave" is indicative of early periosteal callus formation. Recordings are presented to demonstrate the nature of the in vivo recordings, and the changes seen during the early stages of healing. In vitro recordings are presented to demonstrate that the signals are indicative of the properties of the bone and fracture, and are not soft tissue artifacts.

Isolation of dimethylallylpyrophosphate: umbelliferone dimethylally transferase from Ruta graveolens

The enzyme catalyzing the first reaction specifically directed to furanocoumarin synthesis has been isolated from suspension cultures and young leaves of Ruta graveolens. With umbelliferone, Mn2+, and dimethylallylpyrophosphate as substrates the enzyme converts umbelliferone to 6-dimethylallylumbelliferone (demethylsuberosin), an established intermediate in the biosynthesis of linear furanocoumarins, but not to 8-dimethylallylumbelliferone (osthenol), the analogous intermediate in angular furanocoumarin biosynthesis. Herniarin does not substitute for umbelliferone, nor geranylpyrophosphate for dimethylallylpyrophosphate. The enzyme activity is associated with particles that sediment readily at high centrifugal force.

The role of dihydropsoralen in furanocoumarin metabolism

Trapping experiments with [2-14C]umbelliferone and 2′,3′-dihydropsoralen (DHP) administered to Ruta graveolens yielded negative results over metabolic periods of 5–24 h. Specific radioactivities of psoralen were comparable to those previously observed, but those of DHP were about two orders of magnitude lower. These results do not support the theory (Z. Naturforsch. 25b, 700 (1970)) that DHP is the immediate precursor of psoralen in furanocoumarin biosynthesis, and it is proposed instead that DHP is not on the main pathway, but is in an equilibrium with psoralen that greatly favors dehydrogenation.

Comparison of (+)- and (-)-marmesin as intermediates in the biosynthesis of linear furanocoumarins

Marmesin has been identified by chromatography and ultraviolet absorption spectrum in extracts of Ruta graveolens, in confirmation of earlier conclusions from tracer experiments that it is an intermediate in furanocoumarin biosynthesis in this species. Trapping experiments with [2-14C]umbelliferone and (+)- or (−)-marmesin were inconclusive, but indicated that only the (+)-form is metabolically active in R. graveolens. This was confirmed in Ruta and also in Heracleum lanatum and Angelica archangelica by direct comparison feedings of [3-14C](+)- and (−)-marmesin. The (+)-isomer was an efficient furanocoumarin precursor, as before, while little if any utilization of (−)-marmesin could be demonstrated.

Biosynthesis of linear furanocoumarins

Labelling experiments with 14C and 3H have shown that linear furanocoumarins of Ammi majus, Angelica archangelica, Heracleum lanatum (Umbelliferae), and Ruta graveolens (Rutaceae) are formed from umbelliferone via the dihydrofuranocoumarin, marmesin. The unsubstituted furanocoumarin psoralen is formed first, and hydroxylation and O-methylation then lead to methoxy-substituted derivatives, with other alkylated psoralens assumed to be formed analogously. No evidence was obtained for oxygenation of the coumarin nucleus before attachment of a side chain, since oxygenated umbelliferones were poorly utilized for furanocoumarin biosynthesis. A detailed biosynthetic route to linear furanocoumarins, consistent with known stereochemistry, is proposed.A separation of furanocoumarins by column partition chromatography on formamide-impregnated silica, and syntheses of [3-14C]umbelliferone, [2-14C]- and [3-14C]skimmin, [3-14C]daphnetin, [2-14C]-7-hydroxy-8-methoxycoumarin, and [2-14C]5-methoxy-7-hydroxycoumarin are described.

Biosynthesis of angular furanocoumarins

The biosynthesis of angular furanocoumarins from umbelliferone in Angelica archangelica and Heracleum lanatum has been shown by isotope studies to parallel that of linear furanocoumarins, via the dihydrofuranocoumarin columbianetin. Angelicin, the first angular furanocoumarin formed, is converted by hydroxylation and O-alkylation to a range of substituted angelicins. A detailed biosynthetic route to angular furanocoumarins, consistent with known stereochemistry, is proposed. By variations of this pathway, it is possible to account for the elaboration of pyranocoumarins, furanoquinoline alkaloids, furanochromones, and possibly other plant products which frequently co-occur with furanocoumarins.A separation of furanocoumarins by column absorption chromatography on silicic acid, and a synthesis of [2-14C]angelicin, are described.