Structure and molecular weight of the dynein ATPase

Dynein has been examined by scanning transmission electron microscopy (STEM). Samples of 30S dynein from tetrahymena cilia were applied to carbon films and either were freeze- dried and examined as unstained, unfixed specimens, or were negatively stained with uranyl sulfate. A totally new image of the dynein molecule was revealed showing three globular heads connected by three separate strands to a common base. Two of the heads appeared to be identical and exhibited a diameter of 10 nm while the third head was somewhat larger (approximately 12 nm). The overall length of the particle was 35 nm. Mass analysis, based upon the integration of electron scattering intensities for unstained particles, gave a molecular weight of 1.95 (+/-)0.24) megadaltons. Mass per unit length analysis was performed using bovine brain microtubules decorated with dynein under conditions where the dynein shows a linear repeat of 24 nm with seven dynein molecules surrounding a microtubule made up of 14 protofilaments. Undecorated microtubules gave a molecular weight per unit length of 21,000+/-1,900 daltons/A, compared to a value of 84,400+/-2,200 daltons/A for the fully decorated microtubules. Taken together, these data give a molecular weight of 2.17 (+/- 0.14) megadaltons per dynein molecule, in agreement with measurements on the isolated particles. Mass analysis of individual globular heads observed in isolated particles gave a molecular weight distribution with a mean of 416+/- 76 kdaltons. These data could also be viewed as the sum of two populations of head with two-thirds of the heads at approximately 400 kdaltons and one-third at approximately 550 kdaltons, although more precise data will be required to distinguish two classes of heads with confidence. The mass of the dynein-microtubule complex as a function of distance from the midline of the particle was analysed to distinguish which end of the dynein molecule was bound to the microtubule. The projected mass distribution was consistent with a model where the three dynein heads were oriented toward the microtubule and clearly not consistent with the opposite orientation. These data indicate that the three globular heads form the ATP-sensitive site in this heterologous dynein-microtubule system and suggest that the rootlike base of the dynein molecule forms the structural attachment site to the A-subfiber of the outer doublet in cilia and flagella. The structure and function of the dynein are dicussed in terms of these new results.

The interaction of Tetrahymena 30S dynein with bovine brain microtubules

The binding of Tetrahymena 30S dynein to bovine brain microtubules has been examined. The dynein was bound by its B-end or ATP sensitive site with a stoichiometry of 1 dynein arm per 6 tubulin dimers. Addition of ATP released virtually all the dynein from the surface of the microtubule. Following hydrolysis of the ATP, the dynein reassociated with the microtubule.

Behaviour of the Bilby, Macrotis lagotis (Reid), (Marsupialia : Thylacomyidae) in Captivity

The behaviour was observed, in captivity, of the bilby Macrotis lagotis, a fossorial bandicoot of central Australia. Most of the observations were made at night, but some were of below-ground behaviour during the daylight hours. Bilbies proved to be relatively passive in comparison with other bandicoots, and a rigid dominance hierarchy amongst males was maintained without destructive fighting. Dominant males chased subordinate males out of and away from burrows and the alpha male maintained priority of access to all the well used burrows in the enclosure. Males scent-marked around burrows; the dominant male usually marked over scents left by other bilbies. Males shared burrows freely with females, and copulation appears to take place down burrows. Information is also given on female-female and mother-young behaviour, and some suggestions are made concerning the social structure of wild bilbies. Activity cycles, feeding behaviour, etc. are described.

Colles' fracture and subsequent hip fracture risk

The prevention of hip fractures, a major cause of morbidity and mortality in the elderly, is hampered by insufficient knowledge of the population at risk. A Colles' fracture associated with minor trauma is indicative of an overall 50% increase in the risk of a subsequent hip fracture. The relative risk of a subsequent hip fracture is greater for men with Colles' fracture (RR = 6.4) than for women (RR = 1.3). Among women, the risk is increased more than twofold for those whose Colles' fractures occurred at the age of 70 or older but is not increased for younger women. That greater predictive power was not achieved may be due to differences in the pathophysiology of osteoporosis at various fracture sites.

Changes in bone mineral density of the proximal femur and spine with aging. Differences between the postmenopausal and senile osteoporosis syndromes

We measured bone mineral density (BMD) of the proximal femur, lumbar spine, or both by dual photon absorptiometry in 205 normal volunteers (123 women and 82 men; age range 20 to 92 yr) and in 31 patients with hip fractures (26 women and 5 men; mean age, 78 yr). For normal women, the regression of BMD on age was negative and linear at each site; overall decrease during life was 58% in the femoral neck, 53% in the intertrochanteric region of the femur, and 42% in the lumbar spine. For normal men, the age regression was linear also; the rate of decrease in BMD was two-thirds of that in women for femoral neck and intertrochanteric femur but was only one-fourth of that in women for lumbar spine. This difference may explain why the female/male ratio is 2:1 for hip fractures but 8:1 for vertebral fractures. The standard deviation (Z-score) from the sex-specific age-adjusted normal mean in 26 women with hip fracture averaged -0.31 (P < 0.05) for the femoral neck, -0.53 (P < 0.01) for the intertrochanteric femur, and +0.24 (NS) for the lumbar spine; results were similar for 5 men with hip fractures. By contrast, for 27 additional women, ages 51-65 yr, with only nontraumatic vertebral fractures, the Z-score was -1.92 (P < 0.001) for the lumbar spine. Thus, contrary to the view that osteoporosis is a single age-related entity, our data suggest the existence of two distinct syndromes. One form, "postmenopausal osteoporosis," is characterized by excessive and disproportionate trabecular bone loss, involves a small subset of women in the early postmenopausal period, and is associated mainly with vertebral fractures. The other form, "senile osteoporosis," is characterized by proportionate loss of both cortical and trabecular bone, involves essentially the entire population of aging women and, to a lesser extent, aging men, and is associated with hip fractures or vertebral fractures or both.

Use of sodium nitroprusside in complications of gestational hypertension

Sodium nitroprusside is a potent and ultrafast-acting antihypertensive agent. Limited clinical experience and uncertainty about toxicity have restricted its use in obstetrics. The authors have used nitroprusside concomitantly with hemodynamic monitoring in 4 obstetric patients with severe pregnancy-induced hypertension unresponsive to conventional therapy. The patients with acute congestive heart failure and pulmonary edema responded rapidly and dramatically to nitroprusside. No signs of fetal distress associated with lowering of the arterial pressure were observed, and significant cyanide levels were not detected in a fetal cord blood sample. Nitroprusside should be reserved for refractory hypertensive emergencies in pregnancy. Hemodynamic monitoring is required for adjusting nitroprusside administration and fluid balance. In short-term usage, the authors' experience suggests that maternal and fetal toxicity may not be serious concerns.

Ethyl chloride: a two-week inhalation toxicity study and effects on liver non-protein sulfhydryl concentrations

Male and female Fischer 344 rats (6/sex/exposure concentration) and male beagle dogs (2/exposure concentration) exposed to 0, 1600, 4000 or 10 000 ppm ethyl chloride (EtCl) for 6 hr/da, 5 da/wk for 2 weeks showed no toxicologically significant treatment-related effects on body weights; clinical chemistry, hematology, or urinalysis parameters; neurology (dogs only were examined); gross pathology or histopathology. The only treatment-related differences in organ or relative organ weights (in rats or dogs) were slight, but statistically significant increases in liver to body weight ratios of male rats exposed to 4000 or 10,000 ppm EtCl (4.9 and 7.5% respectively). Liver non-protein sulfhydryl (NPSH) concentration was measured in male Fischer rats and male B6C3F1 mice that were exposed for 6 hours to 0, 1600, 4000 or 10,000 ppm EtCl (mice were exposed to 0 or 4000 ppm EtCl only). Liver NPSH, measured 1/2 hr post exposure, was less than control values in 4000 ppm exposed rats (88% of control value), 4000 ppm exposed mice (64%), and 10,000 ppm exposed rats (89%). The slight decreases in rat liver NPSH seem consistent with the increased liver to body weight ratios. The toxicity data indicate that 2-week repeated exposures to EtCl concentrations that were up to 10 times the current A.C.G.I.H. T.L.V. (1000 ppm) caused minimal treatment-related effects in dogs and rats.

Incidence of Colles' fracture in a North American community

In a 30-year period, 1,137 adult residents of Rochester, Minnesota experienced 1235 Colles' fractures. Fracture incidence among women increased over sixfold between ages 35-39 and 60-64 and then leveled off. Male rates were lower in every age group and did not rise as dramatically. Fractures associated with moderate trauma were responsible for the increased incidence with age and the excess among women. Overall, Rochester rates were 30 per cent or more greater than those reported from communities in other countries (Am J Public Health 1982; 72:605-607.).

1,25-Dihydroxyvitamin D3: short- and long-term effects on bone and calcium metabolism in patients with postmenopausal osteoporosis

We evaluated the effects of therapy with a small dose (0.5 microgram/day) of 1,25-dihydroxyvitamin D3 in 12 previously untreated patients with postmenopausal osteoporosis. Combined radiocalcium kinetic and balance studies showed that at base line, net calcium absorption (mean +/- SEM) was low (7 +/- 3%), calcium balance was negative (-59 +/- 22 mg/day), and bone resorption rate (297 +/- 40 mg/day) exceeded bone formation rate (239 +/- 36 mg/day). After short-term therapy (6-8 months), calcium absorption was normal (27 +/- 3%, P less than 0.001 for difference from base line), calcium balance had improved (+2 +/- 26 mg/day, P less than 0.05), and bone resorption rate (195 +/- 35 mg/day, P less than 0.01) had decreased more than bone formation rate (197 +/- 26 mg/day, NS). Compared with base-line values, after long-term therapy (2 years) the increased level of calcium absorption was maintained (27 +/- 3%, P less than 0.001), but calcium retention declined to a level intermediate (-27 +/- 24 mg/day, NS) between base-line and short-term treatment values, and both bone resorption rate (294 +/- 33 mg/day, NS) and bone formation rate (267 +/- 34 mg/day, NS) increased. Urinary hydroxyproline excretion was lower than before treatment (26.3 +/-2.0 mg/day) after both short-term (21.1 +/- 1.6 mg/day, P less than 0.001) and long-term (22.0 +/- 1.8 mg/day, P less than 0.01) treatments. Trabecular bone volume was 11.3 +/- 1.0% at base line and increased to 16.0 +/- 1.2% (P less than 0.01) after long-term treatment. By contrast, the eight patients studied before and after 6-8 months of placebo treatment had no significant change in any variable.

Panosteitis in a cocker spaniel dog

A 12-month-old, desexed female Cocker Spaniel had intermittent bilateral foreleg lameness which was due to panosteitis of the radius and ulna. The disease was in the active 'middle' state. Endosteal and periosteal new bone formation was demonstrated by histological examination and accounted for the diffuse osteosclerotic appearance of the radial and ulnar diaphyses seen on radiographs.

Subchronic dermal toxicity study of trichlorobenzene in the rabbit

Groups of five male and five female New Zealand albino rabbits were treated by skin application with either 0 (distilled water control), 30, 150 or 450 mg/kg undiluted trichlorobenzene (ICB) for 5 days/week for four weeks. No treatment related systemic effects were observed at any of the treatment levels when body weight, clinical chemistry and organ weight parameters were measured. Systemic effects due to dermal application of TCB were present only in rabbits given 450 mg/kg/day. These effects included a slight but statistically significant increase in the urinary coproporphyrin excretion in males and slight pallor of the liver at gross necropsy in both sexes. Localized effects at the site of application were present in all treated rabbits. These effects were characteristic of the response to dermal irritation. Grossly, the fur was matted by a fine white bran-like scales with variable degrees of erythema, fissures, erosions and ulcers. Histopathologically, there was inflammation and thickening of the epidermis. The size of the affected area varied directly with the dose level. Based on the results of the study, it was concluded that a dose level of 450 mg/kg/day of TCB applied dermally to rabbits induced slight systemic toxicity. The no-observable effect level for systemic toxicity was 150 mg/kg/day when TCB was applied to the skin of male and female rabbits over the course of 30 days.

Terbutaline and maternal cardiac function

The effect of terbutaline sulfate on left ventricular size and performance was studied by M-mode echocardiography in pregnant women with premature labor. Patients with uterine activity initiated during either oxytocin challenge testing or induction of labor served as a comparison group. During terbutaline therapy, heart rate, ejection fraction, and cardiac output increased significantly. End-diastolic volume and systolic blood pressure (BP) were unchanged, and diastolic BP and end-systolic volume fell. No changes in echocardiographic or hemodynamic parameters were present during oxytocin-induced uterine activity. Terbutaline, as currently used to prevent premature labor, is a potent inotropic and chronotropic agent. Pulmonary edema accompanying terbutaline treatment is probably not due to cardiac failure.

The intermetatarsal nerve: a microscopic evaluation

Microscopic evaluation of the interdigital neuroma is difficult because the appearance of the normal nerve has not been described precisely. In an effort to characterize the normal interdigital nerve, 104 nerves were removed at autopsy from the intermetatarsal spaces of 14 women who were more than 48 years old. A positive relationship between perineurial width and internal diameter of the nerve fascicle in web spaces 2, 3, and 4 was defined. In addition, the number and the diameter of blood vessels had a positive correlation in all web spaces. These measurements should be of help in the objective differentiation of the common interdigital neuroma from the normal interdigital nerve.

Retardation of endochondral ossification at the distal ulnar growth plate in dogs

Bilateral forelimb deformities associated with retained cartilage cores in the distal ulna were diagnosed in 8 immature giant breed dogs. Five of the dogs were autopsied. Histopathological examination of the distal ulnar growth plate revealed a localised central thickening due to the accumulation of hypertrophic chondrocytes which had failed to undergo the usual development to degeneration. Also the intercellular matrix septa of this cartilage were not calcified. Projections of the abnormal cartilage even persisted into the primary spongiosa. These abnormalities in the process of endochondral ossification of the growth plate produced the lesion of retained cartilage core which was responsible for the development of forelimb deformity.

Total replacement arthroplasty of the first metatarsophalangeal joint

A surface replacement prosthesis for the first metatarsophalangeal joint has been designed to be used in arthritic conditions of this joint. The components are made of stainless steel and polyethylene and fixed with methylmethacrylate. The surgical details of insertion are important in such a complex, small joint. In the series of 20 patients (21 joints), the patient and physician satisfaction rate was 81% at an average follow-up period of 43 months (range 16 to 58 months). Current use of this prosthesis is most reasonable in older patients with painful degenerative arthritis of the first metatarsophalangeal joint and minimal joint imbalance.