Backward walking measures are sensitive to age-related changes in mobility and balance.

Many falls occur from backward perturbations or during transitional movements that require a person to turn and step backwards, suggesting that deficits in backward stepping may negatively impact mobility. Previous studies found significant declines in backward walking (BW) spatiotemporal measures in healthy elderly compared to young adults. No studies to date have examined BW performance in middle-aged adults and in elderly with impaired mobility. This study compared spatiotemporal measures of BW and forward walking (FW) in young, middle-aged, and elderly and in elderly fallers and non-fallers; and compared the strength of the relationship between age and BW and FW spatiotemporal measures to determine the utility of BW performance as a clinical tool for examining safety and mobility. BW measures were significantly more impaired in the elderly (n=62) compared to young (n=37) and middle-aged (n=31) adults and age effects were greater in BW than FW. No significant differences were found between young and middle-aged except for base of support in BW. Stronger correlations were found between age and BW measures than between age and FW measures, particularly correlations between age and BW velocity and stride length. Elderly fallers had greater deficits in BW performance than non-fallers. All elderly fallers had BW velocities<.6m/s. Clinicians are encouraged to assess BW, particularly BW velocity, as part of mobility examinations.

Clinical outcomes of a specialised inpatient unit for adults with mild to severe intellectual disability and mental illness.

BACKGROUND: Limitations of general psychiatric services have led to the development of specialised psychiatric programmes for patients with intellectual disability (ID) and mental health needs. Few studies have examined treatment outcomes of specialised inpatient units, and no studies have explored how the effects of intervention may differ for individuals at varying levels of cognitive ability. The present study examined clinical outcomes of inpatients with mild ID in contrast to inpatients with moderate to severe ID within the same service. METHOD: Thirty-three patients (17 with mild ID and 16 with moderate to severe ID) discharged between 2006 and 2008 from a specialised inpatient unit in Canada for adults with ID and mental illness were studied. In addition to examining change in scores on clinical measures, outcomes with regard to length of stay, diagnostic change, residential change and re-admission to hospital were explored. RESULTS: Both groups demonstrated clinical improvement from admission to discharge. However, only patients with mild ID demonstrated improvements on the Global Assessment of Functioning. CONCLUSIONS: This study is one of the first to consider outcomes of higher and lower functioning individuals with ID on a specialised inpatient unit. Results suggest that outcomes may be different for these groups, and some clinical measures may be more sensitive to changes in patients with more severe disabilities.

Integrating genetics and genomics to identify new leads for the control of Eimeria spp.

Eimerian parasites display a biologically interesting range of phenotypic variation. In addition to a wide spectrum of drug-resistance phenotypes that are expressed similarly by many other parasites, the Eimeria spp. present some unique phenotypes. For example, unique lines of Eimeria spp. include those selected for growth in the chorioallantoic membrane of the embryonating hens egg or for faster growth (precocious development) in the mature host. The many laboratory-derived egg-adapted or precocious lines also share a phenotype of a marked attenuation of virulence, the basis of which is different as a consequence of the in ovo or in vivo selection procedures used. Of current interest is the fact that some wild-type populations of Eimeria maxima are characterized by an ability to induce protective immunity that is strain-specific. The molecular basis of phenotypes that define Eimeria spp. is now increasingly amenable to investigation, both through technical improvements in genetic linkage studies and the availability of a comprehensive genome sequence for the caecal parasite E. tenella. The most exciting phenotype in the context of vaccination and the development of new vaccines is the trait of strain-specific immunity associated with E. maxima. Recent work in this laboratory has shown that infection of two inbred lines of White Leghorn chickens with the W strain of E. maxima leads to complete protection to challenge with the homologous parasite, but to complete escape of the heterologous H strain, i.e. the W strain induces an exquisitely strain-specific protective immune response with respect to the H strain. This dichotomy of survival in the face of immune-mediated killing has been examined further and, notably, mating between a drug-resistant W strain and a drug-sensitive H strain leads to recombination between the genetic loci responsible for the specificity of protective immunity and resistance to the anticoccidial drug robenidine. Such a finding opens the way forward for genetic mapping of the loci responsible for the induction of protective immunity and integration with the genome sequencing efforts.

Sagittal sinus blood flow in the ovine fetus as a continuous measure of cerebral blood flow: relationship to behavioural state activity.

Superior sagittal sinus blood flow (Q(ss)) was studied over a 6-h period in nine chronically catheterized fetal sheep as a continuous measure of cerebral blood flow to determine the change in blood flow values and in measures of blood flow variability in relation to behavioural state activity. Mean Q(ss) was increased during the low voltage (LV)/rapid eye movement (REM) state compared to the high voltage (HV)/NREM state by approximately 25%, and was further increased during periods of LV/REM with fetal breathing movements. The increase in Q(ss) was abrupt and began at the transition to LV/REM, with the rate of change 2-fold greater than that during transition to HV/NREM, where the decrease in Q(ss) was gradual and began prior to the evident state change. Q(ss) showed considerable fluctuation, which tended to be greater during the HV/NREM state compared to the LV/REM state when analyzed using measures of longer term variability. Q(ss) thus provides for a continuous measure of cerebral blood flow in the ovine fetus, with the approximately 25% increase with change from the HV/NREM to LV/REM state similar to that previously reported using radioactive microspheres. The abrupt increase in Q(ss) at the transition to LV/REM versus the gradual decrease in Q(ss) before transition to HV/NREM would suggest that the state-related change in brain blood flow is better linked to the presence of the LV electrocorticogram and favours its active generation.

Adaptation of cardiovascular responses to repetitive umbilical cord occlusion in the late gestation ovine fetus.

1. The impact of repeated umbilical cord occlusion on the normal maturation of fetal heart rate (FHR) and mean arterial pressure (MAP) and the cardiovascular responses to successive umbilical cord occlusion was investigated over a 21 day period in the latter part of gestation. 2. Fifteen chronically instrumented sheep (control group n = 6; occlusion group n = 9) were studied for 21 days (113-133 days of gestation, term = 145 days) with umbilical cord occlusions (90 s duration) performed every 30 min for 1-4 h each day. On days 1, 9 and 18, FHR, FHR variation and MAP were monitored continuously and fetal arterial blood gases, pH and metabolites were measured at predetermined intervals. The baroreflex response to 75-100 microg phenylephrine (I.V.) was tested on days 1 and 18. 3. Basal FHR decreased (DeltaFHR: control, 34.6 +/- 3.6 beats x min(-1); occlusion, 36.9 +/- 2.7 beats x min(-1)) and MAP increased (DeltaMAP: control, 3.1 +/- 1.7 mmHg; occlusion, 5.2 +/- 2.1 mmHg) to a similar extent in control and occlusion groups between days 1 and 21 of the study. There was a small decline in FHR variation over the 21 day study in occlusion, but not control, group fetuses. 4. The magnitude of the fall in FHR decreased and the rise in MAP increased, despite similar changes in blood gases in response to umbilical cord occlusion, over the course of the 21 day study. Despite a significant decline in the ratio of DeltaFHR to DeltaMAP on days 9 and 18 compared to day 1, there was no difference between control and occlusion groups in baroreflex sensitivity. However DeltaFHR/DeltaPO2, an index of chemoreceptor sensitivity, had decreased by day 9 and 18 compared to day 1. 5. The cardiovascular responses to umbilical cord occlusion are altered with repetitive occlusions during the latter part of gestation, with a decrease in DeltaFHR/DeltaMAP, which does not involve changes in baroreflex sensitivity, but may involve changes in chemoreceptor sensitivity. However, repeated umbilical cord occlusion appears to have no impact on baseline cardiovascular control since there was no change in the normal maturational decrease in FHR and rise in MAP.

In vivo and in vitro development of the protist Helicosporidium sp.

We describe the discovery and developmental features of a Helicosporidium sp. isolated from the black fly Simulium jonesi. Morphologically, the helicosporidia are characterized by a distinct cyst stage that encloses three ovoid cells and a single elongate filamentous cell. Bioassays have demonstrated that the cysts of this isolate infect various insect species, including the lepidopterans, Helicoverpa zea, Galleria mellonella, and Manduca sexta, and the dipterans, Musca domestica, Aedes taeniorhynchus, Anopheles albimanus, and An. quadrimaculatus. The cysts attach to the insect peritrophic matrix prior to dehiscence, which releases the filamentous cell and the three ovoid cells. The ovoid cells are short-lived in the insect gut with infection mediated by the penetration of the filamentous cell into the host. Furthermore, these filamentous cells are covered with projections that anchor them to the midgut lining. Unlike most entomopathogenic protozoa, this Helicosporidium sp. can be propagated in simple nutritional media under defined in vitro conditions, providing a system to conduct detailed analysis of the developmental biology of this poorly known taxon. The morphology and development of the in vitro produced cells are similar to that reported for the achorophyllic algae belonging to the genus Prototheca.

Effects of trendelenburg position and positive intrathoracic pressure on internal jugular vein cross-sectional area in anesthetized children.

STUDY OBJECTIVE: To compare the cross-sectional area (in cm(2)) of the left internal jugular vein (LIJV) and right internal jugular vein (RIJV) in anesthetized children, and measure the response to the Trendelenburg tilt position (TBRG) and a positive inspiratory pressure hold. DESIGN: Prospective, nonrandomized study. SETTING: University medical center. PATIENTS: 45 ASA physical status I and II children, ages 6 months to 8 years, undergoing general anesthesia and mechanical ventilation. INTERVENTIONS: The cross-sectional area of both internal jugular veins was measured with a 5-MHz, two-dimensional surface transducer, at the level of the cricoid cartilage. Three measurements were obtained: 1) with the patient supine, 2) during a 10-second breath-hold with a positive inspiratory pressure (PIP) of 20 cm H(2)O, and 3) with the patient at 20 degrees TBRG. Data were analyzed with two-way analysis of variance (ANOVA) and Student-Newman-Keuls test, with a p < 0.05 considered significant. MEASUREMENTS AND MAIN RESULTS: In supine patients, the cross-sectional area of the RIJV was larger than the LIJV in 31 patients (69%), and equal or smaller in 14 patients (31%) (0.80 +/- 0.38 vs. 0.59 +/- 0.22; p = 0.002). A PIP hold, but not TBRG, significantly dilated the RIJV (0.8 +/- 0.38 at baseline vs. 0.93 +/- 0.42 with TBRG; p = not significant vs. 1.1 +/- 0.46 with PIP; p < 0.05), whereas neither maneuver was effective with the LIJV. CONCLUSION: The cross-sectional area of the RIJV is often greater than the LIJV; the TBRG was not effective to increase the cross-sectional area of the internal jugular veins, and only a PIP hold increased significantly the cross-sectional area of the RIJV. In this study, the LIJV appeared of smaller size and less compliant compared with the RIJV.

The molecular evolution of terminal ear1, a regulatory gene in the genus Zea.

Nucleotide diversity in the terminal ear1 (te1) gene, a regulatory locus hypothesized to be involved in the morphological evolution of maize (Zea mays ssp. mays), was investigated for evidence of past selection. Nucleotide polymorphism in a 1.4-kb region of te1 was analyzed for a sample of 26 sequences isolated from 12 maize lines, five populations of the maize progenitor, Z. mays ssp. parviglumis, six other Zea populations, and two Tripsacum species. Although nucleotide diversity in te1 in maize is reduced relative to ssp. parviglumis, phylogenetic and statistical analyses of the pattern of polymorphism among these sequences provided no evidence of past selection, indicating that the region of the gene studied was probably not involved in maize evolution. The level of reduction in genetic diversity in te1 in maize relative to its progenitor is comparable to that found in previous reports for isozymes and other neutrally evolving maize genes and is consistent with a genome-wide reduction of genetic diversity resulting from a domestication bottleneck. An estimate of the age (1.2-1.4 million yr) of the maize gene pool based on te1 is roughly consistent with previous estimates based on other neutral genes, but may be biased by the apparently slow synonymous substitution rate at te1.

The adenosine A(1)-receptor antagonist 8-CPT reverses ethanol-induced inhibition of fetal breathing movements.

Administration of either ethanol or adenosine inhibits fetal breathing movements (FBM), eye movements, and low-voltage electrocortical activity (LV ECoG). The concentration of adenosine in ovine fetal cerebral extracellular fluid increases during ethanol-induced inhibition of FBM. The purpose of this study was to determine the effect of a selective adenosine A(1)-receptor antagonist, 8-cyclopentyltheophylline (8-CPT) on the incidence of FBM during ethanol exposure. After a 2-h control period, seven pregnant ewes received a 1-h intravenous infusion of ethanol (1 g/kg maternal body wt), followed 1 h later by a 2-h fetal intravenous infusion of either 8-CPT (3.78 +/- 0.08 microg. kg(-1). min(-1)) or vehicle. Ethanol reduced the incidence of FBM from 44.0 +/- 10.4 to 2.7 +/- 1.3% (P < 0.05) and 51.2 +/- 7.6 to 11.9 +/- 5.0% (P < 0.05) in fetuses destined to receive 8-CPT or vehicle, respectively. In the vehicle group, FBM remained suppressed for 7 h. In contrast, during the first hour of 8-CPT infusion, FBM returned to baseline (31 +/- 11%) and was not different from control throughout the rest of the experiment. Ethanol also decreased the incidence of both low-voltage electrocortical activity and eye movements, but there were no differences in the incidences of these behavioral parameters between the 8-CPT and vehicle groups throughout the experiment. These data are consistent with the hypothesis that adenosine, acting via A(1) receptors, may play a role in the mechanism of ethanol-induced inhibition of FBM.

Evaluation of tibial component fixation in specimens retrieved at autopsy.

Fixation of the tibial component was evaluated in eight knees retrieved at autopsy by comparing their radiographs with measurements of micromovement between the component and the tibial plateau. Micromovement in the one cemented Miller-Galante and seven cementless Ortholoc components, which had been implanted for a range of 3 days to 57 months, was measured with linearly variable differential transducers under anteroposterior shear and axial compressive loads. Micromovement between the tibial component and the screws and between the tibial component and the bone after the screws were removed also was measured in the cementless specimens. Minimal micromovement in most of the implants suggests that the tibial components were well fixed. Micromovement between the tibial tray and the screws also was minimal in the cementless components. Removing the screws did not significantly affect micromovement, except in the specimen retrieved 3 days after surgery and in the specimen with a complete radiolucent line under the component. The cementless tibial components fixed with screws, pegs, and stem were as stable as the component secured with cement. Partial radiolucencies were not associated with greater micromotion than that of bone ingrown areas, but the component with complete radiolucency did have greater micromotion than that of all of the other specimens.

Increased cerebral extracellular adenosine and decreased PGE2 during ethanol-induced inhibition of FBM.

Adenosine and PGE2 are neuromodulators, both of which inhibit fetal breathing movements (FBM). Although circulating PGE2 has been implicated as a mediator of ethanol-induced inhibition of FBM in the late-gestation ovine fetus, a role for adenosine has not been examined. The objective of this study was to determine the effect of maternal ethanol infusion on ovine fetal cerebral extracellular fluid adenosine and PGE2 concentrations by using in utero microdialysis and to relate any changes to ethanol-induced inhibition of FBM. Dialysate samples were obtained from the fetal parietal cortex over 70 h after surgery to determine steady-state extracellular fluid adenosine and PGE2 concentrations. On each of postoperative days 3 and 4, after a 2-h baseline period, ewes received a 1-h infusion of ethanol (1 g/kg maternal body wt) or an equivalent volume of saline, and the fetus was monitored for a further 11 h with 30-min dialysate samples collected throughout. Immediately after surgery, dialysate PGE2 and adenosine concentrations were 3.7 +/- 0.7 and 296 +/- 127 nM, respectively. PGE2 did not change over the 70 h, whereas adenosine decreased to 59 +/- 14 nM (P < 0.05) at 4 h and then remained unchanged. Ethanol decreased dialysate PGE2 concentration for 2 h (3.3 +/- 0.3 to 1.9 +/- 0.4 nM; P < 0.05) and increased adenosine concentration for 6 h (87 +/- 13 to a maximum of 252 +/- 59 nM, P < 0.05). Ethanol decreased FBM incidence from 47 +/- 7 to 16 +/- 5% (P < 0.01) for 8 h. Saline infusion did not change dialysate adenosine or PGE2 concentrations or FBM incidence. These data are consistent with the hypothesis that fetal cerebral adenosine, and not PGE2, is the primary mediator of ethanol-induced inhibition of FBM at 123 days of gestation in sheep.

The effect of varus tilt on contact stresses in total knee arthroplasty: a biomechanical study.

The contact stress produced in the tibiofemoral joint from a varus-tilted tibial component was tested in five total knee prostheses. Peak and mean stresses were measured with a digital electronic sensor under compressive load at 15 degrees and 90 degrees flexion. Stresses were measured with the tibial component tilted 0 degrees and 5 degrees in the mediolateral direction. At a 5 degree tilt, the Advantim, the Miller-Galante II, and the Omnifit prostheses, which have a flat configuration on the femoral and tibial surfaces in the coronal plane, had significantly greater stresses than the LCS and the Profix prostheses, which have tibial and femoral components with matching curved surfaces in the coronal plane. These results suggest that the femoral component surface should have a radius of curvature that matches that of the tibial articular surface in the coronal plane to achieve a large contact area even in varus-valgus tilting.

Cardiovascular and metabolic responses to intermittent umbilical cord occlusion in the preterm ovine fetus.

OBJECTIVE: To determine the cardiovascular and metabolic responses to umbilical cord occlusion in the preterm ovine fetus and the impact of repetitive intermittent insults over a 4-day period. METHODS: Repetitive umbilical cord occlusions (experimental group, n = 7; control group, n = 7) were performed daily (112-115 days' gestation, term = 147 days). Mean arterial pressure (MAP), fetal heart rate (FHR), and FHR variation were monitored, and arterial blood was sampled at predetermined intervals. RESULTS: During umbilical cord occlusions, arterial oxygen pressure (PaO2) (approximately 17 mmHg) and glucose (approximately 0.3) millimoles per liter (mmol/L) fell and arterial carbon dioxide pressure (approximately 8 mmHg) rose (P < .01) to a similar extent on days 1 and 4. Umbilical cord occlusion produced a rise in lactate over the course of successive umbilical cord occlusions each day, the magnitude of which tended to be reduced by day 4 (0.3 +/- 0.1 versus 0.6 +/- 0.1 mmol/L). Control hour FHR and MAP were unaltered over the 4 days, but the delta (delta) FHR to delta PaO2 ratio during umbilical cord occlusions was less on day 4 than on day 1 (6.0 +/- 0.4 versus 10.9 +/- 1.5 beats per minute/mmHg; P < .01). During occlusion hours, high FHR variation episodes, as a measure of fetal activity, were reduced (14.6 +/- 1.5 versus 4.2 +/- 1.3 min/h; P < .01), whereas the reduction in short-term (7.4 +/- 0.7 to 5.8 +/- 0.6 milliseconds; P < .05) and long-term (34.9 +/- 2.7 to 30.0 +/- 0.6 milliseconds; P < .05) FHR variation reached significance only on day 4. CONCLUSION: The increase in lactate and reduced high-FHR variation episodes over successive umbilical cord occlusions may affect fetal growth and development. Furthermore, repeated umbilical cord occlusions over several days alter the preterm FHR response to subsequent stresses, suggesting an altered chemoreflex response.

Knee stability in meniscal bearing total knee arthroplasty.

The effect of a meniscal bearing on knee laxity in anterior cruciate ligament-sacrificing total knee arthroplasty was evaluated in 7 cadaver knees using a knee testing device that measured knee flexion angle as well as laxity to medial-lateral, anterior-posterior [AP], and rotational loads. A standard fixed tibial component and mobile tibial components (AP sliding, rotationally sliding, and AP and rotationally sliding) were used to evaluate AP, rotational, and varus-valgus stability and maximal flexion and extension with the neutrally positioned and malrotated tibial tray. The AP movable components increased AP laxity, and the fixed component decreased rotational laxity significantly when compared with the normal knees. The rotationally movable components did not change knee laxities significantly even when the tibial tray was malrotated. No significant difference among the components was detected when the maximal flexion and extension angles were compared in the neutrally positioned tibial tray. Malrotation of the tibial tray decreased the maximal extension angle in the fixed component. This study showed that the rotationally movable component can achieve near-normal laxity regardless of tibial tray rotation, but AP mobility of the bearing produces AP laxity that could lead to implant failure.

Altered fetal cardiovascular responses to prolonged hypoxia after sinoaortic denervation.

This study examines the role of the peripheral chemoreceptors in mediating fetal cardiovascular responses to prolonged hypoxia secondary to reduced uterine blood flow (RUBF). Fetal sheep were chronically instrumented for continuous heart rate (FHR), blood pressure (FBP), and carotid blood flow (CBF) measurements after bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Four days postoperatively, uterine blood flow was mechanically restricted, reducing fetal arterial oxygen saturation by 47.3% (P < 0.01). An initial bradycardia was observed in intact (184.0 +/- 10.7 to 160.5 +/- 10.7 beats/min, not significant) but not denervated fetuses, followed by a tachycardia (180.0 +/- 2.2 to 193.7 +/- 2.7 beats/min, P < 0.05). FHR increased in denervated fetuses (175.5 +/- 8.7 to 203. 0 +/- 17.9 beats/min, P < 0.05). FBP increased transiently in intact fetuses from 45.1 +/- 1.0 to 55.4 +/- 3.0 mmHg at 2 h (P < 0.01), whereas denervated fetuses demonstrated a decrease in FBP from 47.1 +/- 4.2 to 37.2 +/- 3.7 mmHg (not significant). CBF increased (P < 0. 05) in both intact and denervated fetuses from 39.3 +/- 2.8 and 29.7 +/- 3.8 ml. min-1. kg-1 to 47.7 +/- 0.4 and 39.1 +/- 0.3 ml. min-1. kg-1, respectively, whereas carotid vascular resistance decreased only in denervated fetuses (1.7 +/- 0.1 to 1.1 +/- 0.02 mmHg. ml-1. min. kg-1, P < 0.05). We conclude that the peripheral chemoreceptors play an important role in mediating fetal cardiovascular responses to prolonged RUBF.

Multivariate prediction of skeletal Class II growth.

Prediction of craniofacial growth is one of the keys to successful orthodontic treatment and stability. Despite numerous attempts at growth forecasting, our ability to accurately predict growth is limited. The present study outlines a possible new approach to prediction of craniofacial growth that differs from any previous attempt because of both the methods used and type of patients studied. The purpose of this study is to create and test prediction equations for forecasting favorable or unfavorable patterns of growth in skeletal Class II preadolescents. The subjects for this study include 19 females and 12 males from the Bolton growth center in Cleveland, Ohio. The patients were all untreated orthodontically, had lateral cephalometric headfilms taken biannually from the ages of 6 through 18 and had a Class II skeletal relationship at age 8. Twenty-six skeletal and dental landmarks were identified and digitized, and 48 linear, angular, and proportional measurements were calculated. The subjects were divided into two groups based on anterior-posterior changes in the relationship between the maxilla and mandible. Eleven patients were in the favorable growth group, with an average improvement of 4.13 degrees in the ANB angle; 20 patients were in the unfavorable growth group with an average increase of 0.16 degrees in the ANB angle. The following prediction formula was created with Bayes theorem and assuming a multivariate Gaussian distribution: P(Good¿Fn) = ke (-(0.5)) ¿Fn - mu(ng)¿sigma(g)(-1)¿Fn - mu(ng)¿T. The equation's sensitivity and specificity was calculated from serial cephalometric data from ages 6, 8, 10, and 12. The results obtained with this equation indicate 82.2% sensitivity, 95% specificity with a overall positive predictive value of 91%. This corresponds to 17.8% of patients being incorrectly identified as Poor Growers and only 5% of our patients were incorrectly identified as Good Growers. We conclude that this prediction formula improves the ability to predict favorable or unfavorable patterns of growth in this sample of skeletal Class II preadolescents.

Contact stress analysis in meniscal bearing total knee arthroplasty.

The effect of a mobile meniscal bearing on tibiofemoral contact stress was tested with a standard fixed tibial component and with movable tibial components (anteroposterior sliding, rotationally sliding, and anteroposterior and rotationally sliding). A digital electronic sensor was used to detect tibiofemoral contact location in five cadaver knees, then the location was reproduced while peak and mean stresses were measured under compressive load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. Stresses were measured when the tibial component was normally aligned and at 15 degrees internal and 15 degrees external rotation. To evaluate the effect of excessive overhang of the polyethylene articular surface, undersurface stress of the rotationally sliding component was also measured with a 30 degrees and a 45 degrees malrotated tibial tray. Uppersurface stresses of the fixed-bearing components were significantly higher at full extension than those recorded in components with rotational mobility. Undersurface stresses were always lower than uppersurface stresses, but correlated with uppersurface stresses. Undersurface stresses of the rotationally sliding component gradually increased as the malrotation angle of the tray increased. A mobile meniscal bearing surface appears to offer an advantage over a standard fixed component when rotational malalignment of the tibial component occurs. However, with severe rotational malalignment, edge contact markedly increases undersurface stresses, which could cause deformity and subluxation.

Effect of partial release of the posterior cruciate ligament in total knee arthroplasty.

Appropriate tension of the posterior cruciate ligament, which often is tight in deep flexion, is difficult to achieve after posterior cruciate ligament retaining total knee arthroplasty. Kinematics and maximum flexion after partial release of the posterior cruciate ligament were evaluated in this study. A partial release improved the maximum flexion angle and maintained anteroposterior stability without causing undesirable changes in kinematics, whereas full resection of the posterior cruciate ligament caused unfavorable anteroposterior instability. Partial posterior cruciate ligament release eliminated excessive rollback movement caused by a tight posterior cruciate ligament and also shifted the point of articular surface contact anteriorly. These results indicate that partial release of the posterior cruciate ligament may improve knee function in patients with a tight posterior cruciate ligament after total knee arthroplasty.

Fetal endocrine responses to prolonged reduced uterine blood flow are altered following bilateral sectioning of the carotid sinus and vagus nerves.

The present study examines the effect of carotid sinus/vagosympathetic denervation on fetal endocrine responses to prolonged reduced uterine blood flow (RUBF). Fetal sheep had vascular catheters inserted following bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Uterine blood flow was mechanically restricted at 126.1 +/- 0.7 days (mean +/- S.E.M.) for 24 h, decreasing arterial oxygen saturation by 47.3 +/- 2.6% (P < 0.01). Fetal plasma samples were obtained at -1, 3, 6, 12 and 24 h for subsequent analyses of arginine vasopressin (AVP), angiotensin II and catecholamines. The AVP response to prolonged RUBF was markedly attenuated in denervated fetuses (15.6 +/- 3.6 to 34.9 +/- 6.0 pg/ml) when compared with intact (10.0 +/- 1.4 to 127.3 +/- 28.4 pg/ml). In contrast, intact fetuses demonstrated no change in plasma angiotensin II concentrations with RUBF whereas denervated fetuses demonstrated a marked increase from 47.5 +/- 18.9 to 128.7 +/- 34.2 pg/ml. The norepinephrine and epinephrine responses to prolonged RUBF were attenuated in denervated fetuses (950.1 +/- 308.9 and 155.8 +/- 58.5 to 1268.3 +/- 474.6 and 290.6 +/- 160.2 pg/ml respectively) when compared with intact (1558.3 +/- 384.4 and 547.3 +/- 304.7 pg/ml to 3289.2 +/- 1219.8 and 896.8 +/- 467.8 pg/ml respectively). These results support a role for the peripheral chemoreceptors in mediating fetal endocrine responses to prolonged RUBF, which may in part lead to the altered cardiovascular responses observed in denervated fetuses under these conditions.

Prostaglandin E2 inhibition of fetal breathing movements is not sustained during prolonged reduced uterine blood flow in sheep.

Fetal breathing movements (FBM) are inhibited by both exogenous prostaglandin E2 (PGE2) and ethanol in sheep. Maternal ethanol exposure in late-gestation sheep also increases fetal [PGE2]. However, during prolonged reduced uterine blood flow (RUBF) when [PGE2] in fetal plasma is already elevated, FBM are not inhibited by ethanol. These experiments were designed, therefore, to test the hypothesis that the FBM response to PGE2 is also diminished during RUBF. PGE2 (594+/-19 ng.min(-1).kg(-1) fetal body weight) was infused for 6 h into the jugular vein of RUBF (PO2 = 14+/-1 mmHg (1 mmHg = 133.3 Pa); n = 7) and control (PO2 = 22+/-1 mmHg (p < 0.01); n = 7) ovine fetuses, and the effect on FBM, electrocortical (ECoG), and electroocular activities was determined. The infusion of PGE2 increased plasma [PGE2] from 881+/-162 to 1189+/-114 pg.mL(-1) in RUBF fetuses and from 334+/-72 to 616+/-118 pg.mL(-1) (p < 0.05) in control fetuses. FBM were initially inhibited by PGE2 from 22.5+/-9.4 and 17.9+/-6.5% of the time to 6.9+/-2.4 and 0.5+/-0.4% (p < 0.01) in RUBF and control fetuses, respectively. FBM remained inhibited in control fetuses throughout the infusion but returned to baseline incidence in RUBF fetuses in the last 2 h of the infusion. These results are consistent with the hypothesis that one component of the adaptative mechanisms of the fetus to prolonged RUBF is an altered response of FBM to exogenous PGE2. We speculate that the lack of a sustained inhibition in FBM during RUBF with infusion of PGE2 may be a result of an alteration in brainstem receptor function or number or local PGE2 removal.