The physiological cost of restricted weight bearing

BACKGROUND: To identify the energy cost of placing restrictions on weight bearing status. METHODS: Measurement of the Physiological cost index (PCI) for 11 healthy volunteers carrying out three types of mobilisation over a 100 m course in a physiology laboratory: normal walking fully weight bearing (FWB); non-weight bearing (NWB) and feather touch weight bearing (FTWB). NWB and FTWB were performed using a walking frame for support. FTWB was defined as mobilisation with the foot flat, as in normal gait, but with less than 100 N force generated through the limb. RESULTS: Both NWB and FTWB developed significantly greater PCI than normal walking. There was no physiological cost benefit of FTWB over NWB, p=0.67, but FTWB was perceived by all participants to be less tiring. CONCLUSIONS: Restricting weight bearing status significantly increases energy expenditure; the PCI. FTWB may be a more tolerable form of restricted weight bearing, although the PCI does not reflect this perception. These findings should be borne in mind when recommending such restrictions in clinical practice and encouraging a patient to mobilise early and effectively.     

Plantar pressure analysis in cadaver feet after bony procedures commonly used in the treatment of stage II posterior tibial tendon insufficiency

BACKGROUND: Bony procedures play an essential role in the operative treatment of stage II posterior tibial tendon insufficiency and often substantially alter the loading characteristics of the foot. METHODS: Eight matched pairs of cadaver lower extremities were axially loaded onto a TekScan HR Mat. (TekScan, Inc., South Boston, MA) After intact testing, each specimen had a lateral column lengthening (either a calcaneocuboid distraction arthrodesis [CCDA] or Evans procedure), a medializing calcaneal osteotomy (MCO), and a plantarflexion (Cotton) osteotomy of the medial cuneiform. The measured plantar pressures were divided into three forefoot regions, two midfoot regions, and two hindfoot regions. For each region, average pressure, peak pressure, and contact area data were collected. RESULTS: Despite the fact that both lateral column lengthening procedures resulted in increased lateral forefoot pressures, no significant differences were noted between the CCDA and the Evans procedure. The addition of a MCO did not significantly alter the plantar pressures measured after the lateral column lengthening alone. Although the Cotton osteotomy resulted in increased average pressures within the medial forefoot, a compensatory significant decrease in lateral forefoot pressures was not observed. CONCLUSIONS: The present study demonstrated increased lateral forefoot pressures after a combined lateral column lengthening and MCO and does not support the idea that a Cotton osteotomy significantly reduces loading of the lateral forefoot. CLINICAL RELEVANCE: The incidence of lateral forefoot pain and fifth metatarsal stress fractures subsequent to either lateral column lengthening procedure may not significantly decline after a Cotton osteotomy.     

Involvement of dihydropyridine-sensitive calcium channels in nerve growth factor-dependent neurite outgrowth by sympathetic neurons

We have used a number of pharmacological manipulations of calcium influx to alter the nerve growth factor (NGF)-elicited neurite outgrowth response of SCG neurons. Our results indicate that influx of extracellular calcium is critical to sympathetic SCG neurite outgrowth. Effective blockade of this process was produced by the inorganic calcium channel blockers Cd2+ (with an IC50 of 48 microM), Co2+ (129 microM), and Ni2+ (180 microM). More specifically, there is a significant contribution from dihydropyridine-sensitive L-type calcium channels to NGF-activated neurite outgrowth, as evidenced by the significant inhibition of neurite outgrowth by diltiazem (IC50 of 17 microM) and nifedipine (3 microM). Further, increases in calcium influx can elicit an enhanced neurite outgrowth response, as shown by the calcium channel agonist Bay K 8644 which potentiated neurite outgrowth by up to 40%.     

Interactions in recovery and in residual injury from sequential treatments of mouse haemopoietic and stromal marrow cell populations, using X-rays, cyclophosphamide and busulphan

The acute recovery of populations of day 11 CFU-S, iv-CFC and CFU-F in mouse bone marrow, following a test dose of X-rays, cyclophosphamide (CP) or busulphan (BUS) given to mice previously treated with repeated priming doses of X-rays or CP, was in general predictable from the amount of residual injury after the priming doses. A marked exception was iv-CFC after X-rays, which although amplified to near normal levels during the residual injury phase, recovered after the test irradiation from low levels of CFU-S. The amount of residual injury after sequential treatments of different agents was in general less than expected on the basis of the product of the effects of the individual agents. This was most marked for CP priming treatments, where the long-term recovery of day 11 CFU-S after the test dose remained persistently above control levels. Also, some correlation was found between improved stromal recovery (CFU-F) and the CFU-S content following the sequential treatment protocols.     

A survey of the ultrastructural defects associated with absent or impaired human sperm motility

The sperm tails of 400 patients having absent or impaired sperm motility were examined by electron microscopy. A wide variety of fine-structural defects were observed although all of the patients fell into clearly defined groups. Total or partial dynein arm deficiency was observed in 12 patients (3%). Ninety-one patients (23%) had sperm with a spectrum of fine-structural defects, whereas 90 patients (23%) were necrospermic. Subjects with low motility, but with at least a few tails of normal structure, had a 5% pregnancy rate, whereas those patients with similar overall motility, but in whom no normal sperm were seen, produced no pregnancies. The results confirm the importance of making an electron microscopical examination of the sperm of patients with asthenozoospermia.     

Surgical treatment of automatic atrial tachycardias

From 1979 to 1989, 18 patients were seen in the Electrophysiology Service, Duke University Medical Center, with automatic atrial tachycardia. There were 8 male and 10 female patients with a mean age of 28.1 +/- 2.9 years. Electrophysiological mapping localized automatic foci to right atrial sites (14 patients) and left atrial sites (4 patients). Depending on origin of the focus, patients were further diagnosed as having either chronic ectopic atrial tachycardia or inappropriate sinus tachycardia. Of the 15 patients with chronic ectopic atrial tachycardia, 6 responded to medical treatment; in 9, the tachycardia was not adequately controlled. Six of them were referred for surgical intervention. All 3 patients with inappropriate sinus tachycardia underwent operative therapy. In the surgical group of patients with chronic ectopic atrial tachycardia, all 6 had a tachycardia-induced cardiomyopathy with ejection fractions ranging from 14% to 27% (mean ejection fraction, 21% +/- 2.7%). Surgical techniques used (alone or in combination) included an isolation procedure in 1 patient, cryoablation in 4 patients, and excision of atrial appendages or portions of atrial free walls in 7. Normal sinus rhythm developed in all surgical patients except 1 patient who had intractable congestive heart failure preoperatively and died of this condition and stroke. The overall success rates for medical and surgical therapy were 33.3% and 88.9%, respectively (p less than 0.01). Long-term follow-up was possible for 7 (87.5%) of 8 patients 3 to 7 years after operation. All patients with chronic ectopic atrial tachycardia were cured, but only 1 of 3 patients with inappropriate sinus tachycardia was in sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recovery of the proliferative and functional integrity of mouse bone marrow in long-term cultures established after whole-body irradiation at different doses and dose rates

Injury inflicted upon the bone marrow stroma following whole-body irradiation and its repair over a 1-year period has been assessed in murine long-term bone marrow cultures established at increasing time intervals after irradiation. Different doses at different dose rates (10 Gy at 0.05 cGy/min, 4.5 Gy and 10 Gy at 1.6 cGy/min, and 4 x 4.5 Gy [3 weeks between doses] at 60 cGy/min) were chosen so as to maximize differences in effect in the stroma. The cellularity of the adherent layer in long-term cultures established 1 month after irradiation was reduced by 40%-90% depending on the dose and dose rate. Simultaneous with the poor ability of the marrow to form adherent layers, the cumulative spleen colony-forming unit (CFU-S) and granulocyte-macrophage colony-forming cell (GM-CFC) production over a 7-week period was reduced to 0% and 30% of control cultures, respectively. The slow recovery of the adherent layer was paralleled by an increase in the numbers of CFU-S and GM-CFC in the supernatant. Cultures established from repeatedly irradiated mice performed poorly over the entire 1-year period. Whereas the regeneration of the stroma was near complete 1 year after irradiation, the CFU-S and GM-CFC levels reached only between 50% and 80% of control cultures, respectively. Also, the concentration of CFU-S and GM-CFC in the supernatant remained persistently lower in cultures established from irradiated mice as compared to control cultures. The levels of sulfated glycosaminoglycans, which have been implicated in the establishment of the functional integrity of the microenvironment, were not reduced in the adherent layers at any time after irradiation. These results indicate that the regeneration of the stroma is accompanied by an incomplete recovery of active hemopoiesis in vitro. However, no evidence was found for persistent functional defects in the stroma after irradiation, using the present endpoints.     

Type 1 rectal duplication: associated congenital malformations and ultrasound diagnosis

Type I duplication of the rectum is a rare condition that in most reported cases does not occur in association with other congenital malformations. We describe three cases, two of which had duplications of other structures: the first had a functioning supernumerary pelvic kidney, the second a duplication of the bladder, urethra, and vagina; the third had no associated malformations but was unusual, because the duplication cyst lay anterior to the rectum, and unique in that the diagnosis of an intra-abdominal cyst was made by ultrasonic examination. Correspondence to: G. M. A. Hendry     

The radiosensitivity of microcolony- and macrocolony-forming cells in mouse tail epidermis

A new microcolony technique is described for measuring the survival of colony-forming cells in mouse tail epidermis. The survival curve is characterised by D0 = 2.70 +/- 0.12 Gy. The number of microcolonies per cm2 is similar to the number of macrocolonies after high doses, which shows for the first time that all microcolonies (greater than or equal to 32 cells) in epidermis develop into macrocolonies. At low doses the number of macrocolonies underestimates the number of colony-forming cells because of coalescence of microcolonies to form macrocolonies. This results in a lower apparent sensitivity of macrocolony-forming cells by a factor of about 1.5. About 3% of basal cells in tail epidermis appear to be capable of colony formation.