Mechanism of acute lower extremity pain syndrome in fluoride-treated osteoporotic patients

Acute pain in the lower extremity, which has previously been attributed to synovitis or fasciitis, develops in about 15 percent of osteoporotic patients treated with sodium fluoride. This report describes 11 osteoporotic women in whom this syndrome developed while they were being treated with sodium fluoride (mean dose 78 mg per day; range, 60 to 90). [99mTc]Hydroxymethylene diphosphonate scintiscanning showed an increased number of foci of abnormal uptake in the lower extremities (p less than 0.05), when compared with results of scintiscanning in 12 nonsymptomatic osteoporotic women treated with sodium fluoride and 12 osteoporotic women treated with oral calcium carbonate only. The increased uptake was not restricted to the areas of pain. Roentgenography revealed stress microfractures in five of the 11 symptomatic patients. It is concluded that the acute lower extremity pain syndrome during fluoride therapy usually results from intense regional bone remodeling, which may be complicated by stress microfractures.

Dynein structure and function

The structure of dynein isolated from several sources follows the pattern first observed with Tetrahymena 22S dynein, which has three globular heads attached by three flexible strands to a root-like base. Recent biochemical data indicate that there is one ATPase site on each dynein head and that all three heads interact with microtubules in an ATP-sensitive manner. Accordingly, images of dynein in situ can be interpreted in terms of a model for crossbridge action where the roots of the bouquet anchor the dynein to the A-tubule and all three heads reach out to interact with the B-tubule in an ATP-dependent reaction to produce a force for sliding.

Neurilemoma of the lower extremity

A series of 76 patients with 85 neurilemomas of the lower extremity was reviewed. The tumors were located throughout the lower extremity and had varied clinical presentations, which often posed problems in diagnosis. Pain, however, was a consistent symptom, and 63 (83%) of the patients presented with local or radiating (or both) pain. Electromyography was done in seven cases, but the results were abnormal in only two. When evaluating a painful mass or an atypical pain in the lower extremity, the clinician should have a high index of suspicion for neurilemoma.

Rate of ATP synthesis by dynein

The rates of ATP synthesis and release by the dynein ATPase were determined in order to estimate thermodynamic parameters according to the pathway: (Formula: see text). Dynein was incubated with high concentrations of ADP and Pi to drive the net synthesis of ATP, and the rate of ATP production was monitored fluorometrically by production of NADPH through a coupled assay using hexokinase and glucose-6-phosphate dehydrogenase. The turnover number for the rate of release of ATP from 22S dynein was 0.01 s-1 per site at pH 7.0, 28 degrees C, assuming a molecular weight of 750 000 per site. The same method gave a rate of ATP synthesis by myosin subfragment 1 of 3.4 X 10(-4) s-1 at pH 7.0, 28 degrees C. The rate of ATP synthesis at the active site was estimated from the time dependence of medium phosphate-water oxygen exchange. Dynein was incubated with ADP and [18O] Pi, and the rate of loss of the labeled oxygen to water was monitored by 31P NMR. A partition coefficient of 0.31 was determined, which is equal to k-2/(k-2 + k3). Assuming k3 = 8 s-1 [Johnson, K.A. (1983) J. Biol. Chem. 258, 13825-13832], k-2 = 3.5 s-1. From the rates of ATP binding and hydrolysis measured previously (Johnson, 1983), the equilibrium constants for ATP binding and hydrolysis could be calculated: K1 = 5 X 10(7) M-1 and K2 = 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of the dynein adenosinetriphosphatase by microtubules

Previous work has indicated that following the rapid adenosine 5'-triphosphate (ATP) induced dissociation of the microtubule-dynein complex, the rate-limiting step in the ATPase cycle is product release [Johnson, K. A. (1983) J. Biol. Chem. 258, 13825-13832], which occurs at a rate of approximately 2-6 s-1. In this report we complete the analysis of the ATPase cycle by examining the effect of microtubules on the rate of product release. For these studies we used repolymerized Tetrahymena axonemal microtubules and microtubule-associated protein (MAP) free bovine brain microtubules which were shown to be free of any measureable ATPase activity. Tetrahymena 22S dynein bound to these microtubules predominantly by the ATP-sensitive site and at a rate giving an apparent second-order rate constant of (0.2-1) X 10(6) M-1 s-1, which is 50-fold greater than the rate observed with brain microtubules containing MAPs. ATP induced the rapid dissociation of the microtubule-dynein complex with an apparent second-order rate constant vs. ATP concentration equal to 1.6 X 10(6) M-1 s-1; this value is only slightly lower than that observed in the presence of MAPs. After the ATP-induced dissociation, the dynein reassociated with the microtubules following a lag period due to the time required to hydrolyze the ATP. The duration of the lag time for reassociation decreased with increasing microtubule concentration, suggesting that microtubules increased the rate of ATP turnover. Direct measurements at steady state showed that the specific activity of the dynein increased with increasing microtubule concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of neuropathologic consequences of repeated dermal exposure to 2,4-dichlorophenoxyacetic acid in rats

A 24% aqueous solution of the dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D amine) was applied to the legs of male Fischer 344 rats 2 hr/day, 5 days/week, for 2 weeks. Because this concentration caused severe skin lesions, a second group of rats was treated similarly with a 12% solution of 2,4-D amine for 3 weeks. The 12% solution caused only mild skin changes. The plasma 2,4-D content, at the end of exposure, was nearly five times greater in the rats exposed to the 24% solution than to the 12% solution (323 vs 66.5 micrograms/ml). The severe skin changes probably facilitated absorption in the rats treated with the 24% solution. Rats treated with either concentration weighed less than controls. Although histologically normal, kidneys of treated rats weighed more than controls. The increased kidney weights were attributed to physiological adaptation due to active excretion of absorbed 2,4-D. Light microscopic examination of tissues, other than skin, revealed no differences between treated and control animals. There were no nervous system pathologic changes although the rats were exposed to sufficient amounts of 2,4-D amine to cause severe skin lesions, decreased body weights, and increased kidney weights.

Acquired adult flat foot secondary to posterior tibial-tendon pathology

Nineteen patients with the clinical diagnosis of dysfunction of the posterior tibial tendon underwent surgical exploration. Four types of lesions were identified: avulsion of the tendon at the insertion (Group I), mid-substance rupture of the tendon (Group II), an in-continuity tear of the tendon (Group III), and no tendon tear, tenosynovitis only (Group IV). These conditions could not be separated preoperatively by clinical or radiographic means. The patients in Group I were treated by reinsertion of the tendon; in Group II, by flexor tendon transfer; and in Groups III and IV, by synovectomy. At follow-up, most patients in Group I reported no improvement, but the patients in Groups II, III, and IV showed both subjective and objective improvement. The signs and symptoms of dysfunction of the posterior tibial tendon are not specific for mid-substance ruptures of the tendon but also can occur with avulsions or synovitis, or perhaps from other, as yet undefined lesions.

Outpatient percutaneous biopsy of the iliac crest: methods, morbidity, and patient acceptance

Bone histology and histomorphometry have become important in the diagnosis and management of metabolic bone disease, but the invasive nature of the biopsy procedure has limited its use. We describe an outpatient technique for obtaining one or more transiliac bone biopsy specimens. Thirty-eight women with osteoporosis, each of whom had sustained one or more spinal compression fractures, underwent two separate bone biopsies during which two 7.5-mm transiliac cores of bone were removed. No morbidity (such as infection or hemorrhage) was encountered. Subjective responses to the level of pain were surveyed by questionnaire. At the time of biopsy, 46% of the study subjects experienced no or only mild discomfort, and 24% judged their pain to be severe. At 16 hours after biopsy, 64% had no or mild pain and 8% experienced severe pain. At 7 days after biopsy, 79% experienced no or mild pain but 9% judged their pain to be severe. In four patients, temporary ambulatory disability occurred but resolved spontaneously in 7 to 10 days. We conclude that the described outpatient bone biopsy procedure is safe, efficient, and generally acceptable to patients.

Rapid kinetic analysis of mechanochemical adenosinetriphosphatases

The analysis of a reaction pathway by stopped-flow and chemical quench-flow methods provides the only means of directly measuring the rates of reaction at the active site of an enzyme. The interpretation of data from each technique is similar and involves solution of the differential equations describing the approach of the intermediates to steady state. In the case of the stopped-flow data, I have tried to show how intuition can simplify some of the math to allow the solution of more complex models and to reveal the form of the concentration dependence of the rates. In the case of the chemical quench-flow data, more effort is expended in collecting one time course and accordingly more time is spent in fitting the data directly to a given model. One often is restricted by the quantities of enzyme available so that it is feasible to perform chemical quench-flow experiments at only one or two carefully selected concentrations of substrate. Stopped-flow and chemical quench-flow experiments complement one another because each provides information that is inaccessible, or at least difficult to obtain, by the other method. Our current chemical quench-flow apparatus, requiring only 20 microliter of sample per time point, should allow many more enzymes to be examined by this method.

Bone loss and reduced osteoblast function in primary biliary cirrhosis

The association of bone loss with primary biliary cirrhosis is poorly understood. In 15 premenopausal female patients, only 2 of whom had fractures, mean bone mineral density was reduced at the lumbar spine but not at the midradius or distal radius. Bone loss was not statistically related to the duration or severity of liver disease. Urinary hydroxyproline excretion, an index for bone resorption, was not different from that of 15 age-matched normal women, but the serum concentration of bone Gla-protein (osteocalcin), a specific marker for bone turnover, was decreased (p less than 0.001). Bone histomorphometric examination in 13 patients showed no osteomalacia but a reduced bone formation rate despite normal values for fractional osteoblast-osteoid interface. The substantial early loss of trabecular bone is mediated by a severe reduction in osteoblast function, which may be caused by retained toxic substances associated with cholestasis.

Stopped-flow kinetic studies of metal ion dissociation or exchange in a tryptophan-containing parvalbumin

The rates of dissociation of 2 equiv of various metal ions [Ca(II), Cd(II), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Yb(III), and Lu(III)] from the primary CD and EF metal ion binding sites of parvalbumin (isotype pI = 4.75) from codfish (Gadus callarius L) were measured by stopped-flow techniques. The removal or replacement of metal ions was monitored by changes in sensitized Tb(III) luminescence or in intrinsic protein tryptophan fluorescence as quenching ions [Eu(III) or Yb(III)] were bound or removed or as the apoprotein was formed. In experiments wherein the bound metal ions were removed by mixing the parvalbumin with an excess of 1,2-diaminocyclohexanetetraacetic acid (DCTA), the kinetic traces were best fit by a double exponential with koff rate constants of 1.07 and 5.91 s-1 for Ca(II), 1.54 and 10.5 s-1 for Cd(II), and approximately 0.05 and approximately 0.5 s-1 for all of the trivalent lanthanide ions. In experiments wherein the bound metal ions were exchanged with an excess of a different metal ion, pseudo-first-order rate constants were proportional to the concentration of excess attacking metal ion for both the fast and slow processes in most experiments. In these cases, extrapolation of the rate constants to zero concentration of attacking metal ion gave values which agree well with the DCTA scavenging results. This finding demonstrates that the off rate constants do not depend on the occupancy of the neighboring site and therefore implies that there is no significant cooperativity in metal ion binding between the two sites in parvalbumin.

A review of ruptures of the Achilles tendon

Rupture of the Achilles tendon is a relatively infrequent injury that is often missed by the initial treating physician. The diagnosis can be established on the basis of the physical examination with weakness of plantarflexion, a palpable gap in the tendon, and a positive squeeze test. Special diagnostic studies are rarely necessary. In the majority of cases, the etiologic basis for the rupture appears to be a combination of intratendon degeneration and mechanical stress. Conservative treatment of an acute rupture by immobilization with a cast provides satisfactory results. For the younger, more athletic patient, surgical repair should be considered.

Teratological evaluation of picloram potassium salt in rabbits

The embryotoxic and teratogenic potential of orally administered picloram potassium salt was evaluated in New Zealand white rabbits. Artificially inseminated rabbits were given 0, 40, 200 or 400 mg picloram acid equivalent/kg body weight/day in the form of picloram potassium salt in aqueous solution on days 6 to 18 of gestation. The foetuses were removed for examination on day 29 of gestation. Transient weight loss was observed among rabbits given 200 or 400 mg/kg/day of the test material, though the total weight gain of the treated groups during gestation was comparable to that of controls. A few isolated, sporadic cases of foetal malformations were observed in the dosed groups, but there was no indication of a dose-related embryotoxic or teratogenic response to treatment.

Rate-limiting steps in the DNA polymerase I reaction pathway

The initial rates of incorporation of dTTP and thymidine 5'-O-(3-thiotriphosphate) (dTTP alpha S) into poly(dA) X oligo(dT) during template-directed synthesis by the large fragment of DNA polymerase I have been measured by using a rapid-quench technique. The rates were initially equal, indicating a nonrate-limiting chemical step. However, the rate of thionucleotide incorporation steadily diminished to 10% of its initial value as the number of consecutive dTMP alpha S residues in the primer strand increased. This anomalous behavior can be attributed to the helix instability inherent in phosphorothioate-containing duplexes. Positional isotope exchange experiments employing the labeled substrate [alpha-18O2]dATP have revealed negligible alpha, beta-bridging----beta-nonbridging isotope exchange in template-directed reactions of Escherichia coli DNA polymerase I (Pol I) both in the presence and in the absence of added inorganic pyrophosphate (PPi), suggesting rapid PPi release following the chemical step. These observations are consistent with a rate-limiting step that is tentatively assigned to a conformational change of the E X DNA X dNTP complex immediately preceding the chemical step. In addition, the substrate analogue (Sp)-dATP alpha S has been employed to examine the mechanism of the PPi exchange reaction catalyzed by Pol I. The net retention of configuration at the alpha-P is interpreted in terms of two consecutive inversion reactions, namely, 3'-hydroxyl attack, followed by PPi attack on the newly formed primer terminus. Kinetic analysis has revealed that while alpha-phosphorothioate substitution has no effect upon the initial rate of polymerization, it does attenuate the PPi exchange reaction by a factor of 15-18 fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathway of the microtubule-dynein ATPase and the structure of dynein: a comparison with actomyosin

Dynein and myosin show several important similarities in design as well as some interesting differences in detail. Both ATPases function as crossbridges that undergo microscopic movements to drive the sliding of filaments, which results in macroscopic movements. They share a common design employing globular heads attached to flexible strands. Each head contains one ATP-binding site and one filament-binding site, and the binding of ATP induces an extremely rapid dissociation of the crossbridge-filament "rigor" complex. Following ATP hydrolysis, which is readily reversible, the crossbridge reassociates with the filament and returns to its original state with the release of products. Thus, the nucleotide-induced changes in conformation are effectively used to couple the hydrolysis of ATP to the dissociation and reassociation of the crossbridge in order to produce a force for net movement according to the Lymn-Taylor-Eisenberg model. The utilization of nucleotide-binding energy to induce a change in conformation can be rationalized in terms of our understanding of enzyme catalysis in general, whereby substrate binding energy is used to induce a change in conformation that stabilizes the transition state for catalysis. In these crossbridge ATPases, the substrate-induced change in conformation also serves to weaken the crossbridge-filament interaction. The pathway is symmetrical, with a return to the tight (filament) binding state coupled to product release. The ball on a string design may provide a reasonable basis to explain how a unidirectional force is obtained from a symmetrical cycle; opposite changes in conformation with the binding and release of the nucleotide produce a significant force only when pulling on the flexible strand. Moreover, the very rapid dissociation of the crossbridge following ATP binding limits the time that a negative force is in effect and also prevents a rigor crossbridge from retarding the sliding movements generated by other crossbridges. Myosin and dynein exhibit nearly identical kinetic constants governing ATP binding and the ATP-induced dissociation of the crossbridge. These appear as invariant steps that may reflect the basic principles of enzyme catalysis as applied to the mechanochemical cycle. The rates of ATP hydrolysis and synthesis by myosin and dynein differ slightly, but in each case the reactions are readily reversible with an equilibrium constant less than one. Steps involving the loss and rebinding of products occur at rates two to three orders of magnitude faster for dynein than for myosin.(ABSTRACT TRUNCATED AT 400 WORDS)

Chevron osteotomy: analysis of factors in patients' dissatisfaction

The results of all Chevron osteotomies for hallux valgus performed at the Mayo Clinic between January 1976 and June 1982 were reviewed at least 1 year after surgery. Of the total 157 patients with 228 operations eligible for inclusion in this study, 154 patients with 225 operations were interviewed. Complete satisfaction was expressed for 79.1% of the procedures, satisfaction with minor reservations for 12.9%, and dissatisfaction for 8%. For the osteotomies producing incomplete satisfaction, further investigation identified failure to achieve correction and technical errors as the most prominent factors. There were no cases of avascular necrosis, osteotomy nonunion, or hallux varus.

Teratogenic potential of inhaled dichlorobenzenes in rats and rabbits

Orthodichlorobenzene (ODCB) and paradichlorobenzene (PDCB) were evaluated for teratogenic potential in rats (ODCB only) and rabbits. Groups of bred rats and inseminated rabbits were exposed to 0, 100, 200, or 400 ppm of ODCB; groups of inseminated rabbits were exposed to 0, 100, 300, or 800 ppm of PDCB. Animals were exposed for 6 hr/day on Days 6 through 15 (rats) or 6 through 18 (rabbits) of gestation. Maternal toxicity, as evidenced by a significant decrease in body weight gain, was observed in all groups of ODCB-exposed rats and liver weight was significantly increased in the 400-ppm ODCB-exposed group. Slight maternal toxicity was observed in groups of rabbits exposed to 400 ppm ODCB or 800 ppm PDCB as indicated by significantly decreased body weight gain during the first 3 days of exposure. Inhalation of up to 400 ppm of ODCB was not teratogenic or fetotoxic in rats, and neither ODCB nor PDCB was teratogenic or fetotoxic in rabbits at exposure levels up to 400 or 800 ppm, respectively.

Inhalation teratology study on monochlorobenzene in rats and rabbits

The embryotoxic and teratogenic potential of inhaled monochlorobenzene (MCB) was evaluated in rats and rabbits. Bred Fischer 344 rats and inseminated New Zealand White rabbits were exposed to 0, 75, 210, or 590 ppm of MCB via inhalation for 6 hr/day during the period of major organogenesis. Exposure to 590 ppm caused elevated liver weights in both species and decreased body weight gain and feed consumption in rats. Inhalation of MCB vapors during gestation was not embryotoxic or teratogenic in rats. In rabbits, a few MCB-exposed fetuses exhibited visceral malformations which were not observed among concurrent controls, though no dose-related increase in malformations occurred. To further evaluate the effects of MCB in rabbits, additional groups were exposed to 0, 10, 30, 75, or 590 ppm. This subsequent study did not result in any increase in malformations in the MCB-exposed groups. Fetal effects were limited to a slight delay in skeletal development which occurred only in rats exposed to 590 ppm, a maternally toxic concentration.

Extensor hallucis longus transfer for hallux varus deformity

The hallux varus deformity results from a dynamic imbalance of the tendons that cross the first metatarsophalangeal joint. This condition most frequently occurs after McBride-type operative treatment for hallux valgus. A new procedure, developed to correct this imbalance, involves transferring the extensor hallucis longus beneath the first intermetatarsal ligament into the base of the proximal phalanx, along with an arthrodesis of the first interphalangeal joint. This procedure in fifteen affected great toes gave over-all satisfactory correction of the hallux varus deformity.