Insurance reform. These opposites detract.
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Fees and Charges↗
Biomedical subjects
S E White
Publications and source records attributed to S E White.
Outreach. Health care spoken here.
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Community-Institutional Relations↗
Failure of magnesium sulfate infusion to inhibit uterine activity in pregnant sheep.
OBJECTIVES: Our purpose was to determine the effect of magnesium sulfate infusion on nonlabor uterine contractures and corticotropin-induced preterm uterine contractions in pregnant sheep. STUDY DESIGN: Fetal and maternal vascular catheters and uterine electromyographic electrodes were surgically placed in 15 pregnant sheep between 118 and 125 days' gestation. After 3 to 5 days of recovery, magnesium sulfate was infused into 7 ewes with a 0.11 gm/kg bolus over 20 minutes, followed by 0.08 gm/kg/hr. In 8 animals labor was induced with use of an intrafetal corticotropin infusion, after which 4 ewes received magnesium sulfate and 4 received saline solution. Continuous recordings of uterine electromyographic activity, amniotic pressure, fetal heart rate, blood pressure, and tracheal pressure were made. Maternal and fetal magnesium, calcium, albumin concentrations, and blood gases were determined before and during the infusion. RESULTS: Maternal magnesium concentrations increased from an average of 0.94 +/- 0.03 mmol/L to 2.73 +/- 0.1 mmol/L at the end of the bolus, remaining elevated (2.44 +/- 0.17 mmol/L) for 8 hours. Fetal magnesium concentrations (0.89 +/- 0.03 mmol/L before the bolus) did not change with the maternal infusion. In ewes not in labor, uterine contractures occurred 3.7 +/- 0.7 times per 2 hours before and did not change significantly with the infusion of magnesium sulfate. During corticotropin-induced preterm labor uterine contractions were present 13 +/- 3.2 times per hour before infusions and were unchanged by infusion of magnesium sulfate to the ewes. CONCLUSIONS: Magnesium sulfate infusion in pregnant sheep has no effect on either nonlabor uterine contractures or on corticotropin-induced preterm uterine contractions.
Adrenocorticotropic Hormone↗
Patellofemoral joint after total knee arthroplasty. Effect on contact area and contact stress.
Compressive contact stress between the patella and the anterior femur and between the quadriceps tendon and anterior femur was measured before and after total knee arthroplasty in 5 cadaver knee specimens using a digital electronic sensor. Contact stresses were measured in the normal knee and after total knee arthroplasty with an unresurfaced patella, a dome-shaped patella, and a conforming patella. Patellofemoral contact stresses did not change significantly after total knee arthroplasty when the patella was not resurfaced, but they increased significantly after the patella was resurfaced with both the dome-shaped and the conforming components. The conforming patella had the highest contact stresses because it tilted at flexion angles greater than 90 degrees and applied load to a small area on the superior portion of the patellar component. The conforming patella markedly decreased tendofemoral contact force because the thicker superior pole of the patella tented the quadriceps tendon at flexion angles greater than 120 degrees. This further increased patellofemoral contact force in deep knee flexion.
Arthroplasty, Replacement, Knee↗
Fixation of ultrahigh-molecular-weight polyethylene liners to metal-backed acetabular cups.
Locking mechanisms and metal-liner interface surfaces of six modular acetabular systems were evaluated to determine their effect on micromotion and backside wear of the polyethylene liner. Rotational and axial motion between the metal shell and polyethylene liner was measured in the Duraloc (DePuy, Warsaw, IN), Harris-Galante (Zimmer, Warsaw, IN), Impact (Biomet, Warsaw, IN), Lip Loc (Biomet), Precision Osteoloc (Howmedica, Rutherford, NJ), and Reflection (Smith & Nephew Orthopaedics, Memphis, TN) designs at the start of each test, and at 1 million, 5 million, and 10 million cycles. At 10 million cycles, the Lip Loc and Reflection cups had significantly lower rim micromotion than the Duraloc and Harris-Galante cups (F < .0010). The Impact, Precision Osteoloc, and Reflection cups had significantly lower rim subsidence than the Harris-Galante cup (F < .0025). The Harris-Galante cup had significantly greater rotational micromotion than the Lip Loc cup (F < .0074), and had significantly greater interface slippage than the Impact and Reflection cups (F < .0070). The Lip Loc produced significantly lower dome micromotion than the Harris-Galante (F < .0300). The Lip Loc and Reflection cups had significantly less backside wear than the Duraloc and Harris-Galante cups (P < .0001), the Impact cup (P < .0243), and the Precision Osteoloc (P < .0027) cup.
Acetabulum↗
Sarcoidosis in a pregnant woman.
Sarcoidosis, a rare multisystem disease, often occurs in women of childbearing age. The disease, which may be improved or exacerbated by pregnancy, presents unique considerations to the anesthesiologist. These considerations are illustrated by the case presented here of complicated sarcoidosis in a parturient who underwent cesarean section.
Adult↗
Intramuscular atropine sulfate in children: comparison of injection sites.
In children undergoing inhaled induction of anesthesia with halothane who suffer bradycardia, submental glossal injection of atropine may result in more rapid onset of vagolysis than traditional intramuscular sites. We compared the intervals between injection and onset of heart rate acceleration (tHR increases) after intramuscular injection of atropine into the deltoid, vastus lateralis, and glossa in children between 1 mo and 10 yr of age scheduled for elective surgery. The tHR increases was determined by measuring the interval between atropine injection and the time point at which the slope of the heart rate curve initially became positive. To ensure that the drug had taken effect before surgical stimulation, heart rate observation was continued until it increased at least 5% above baseline with evidence of continuing acceleration. Anesthesia was induced in all subjects by mask with nitrous oxide and halothane. After tracheal intubation, constant inspired concentrations of the anesthetics were administered for 3 min. While heart rate was monitored, atropine (0.02 mg/kg) was injected into one of the three sites. Each patient's end-tidal anesthetic concentrations were recorded, and minimum alveolar anesthetic concentrations (MAC) were subsequently calculated and adjusted for age. The tHR increases was recorded and averaged for each group. The study groups did not differ by age, weight, end-tidal anesthetic concentrations, age-adjusted MAC, or heart rate at the time atropine was administered. After submental glossal injection (n = 11), tHR increases increase was fastest (3.0 +/- 1.1 min) and was significantly faster than that found with deltoid injection (n = 16; 4.4 +/- 1.1 min) or vastus lateralis injection (n = 8; 6.4 +/- 2.4 min) (P < 0.05 compared with both). The tHR increases also differed significantly between the deltoid and the vastus lateralis (P < 0.05). We conclude that submental glossal injection of atropine results in a more rapid onset of vagolysis than injection at traditional intramuscular sites.
Anesthesia, Inhalation↗
Knee kinematics of posterior cruciate ligament sacrificed total knee arthroplasty.
Two different posterior stabilizing mechanisms in posterior cruciate ligament sacrificing total knee arthroplasty were evaluated to test knee kinematics, tibiofemoral contact location, and the quadriceps force needed to extend the knee. A posterior stabilizing post and a deeply dished polyethylene with a high anterior lip (anterior buildup stabilizing tibial articular surface) were tested in four anatomic specimen knees with a knee kinematics testing device. Both posterior stabilizing mechanisms partially restored anteroposterior stability, but the knees were still more lax than were the normal knees in the anteroposterior direction. The anterior buildup stabilizing tibial articular surface decreased rotational laxity in early flexion. Tibiofemoral contact location in the knees with the anterior buildup stabilizing tibial articular surface did not move posteriorly as the knee flexed, and the knees with this articular surface required significantly more quadriceps force to extend the knee than did the knees with a stabilizing post.
Humans↗
Effect of medial displacement of the tibial tubercle on patellar position after rotational malposition of the femoral component in total knee arthroplasty.
A large Q angle induced by technical error such as an internally rotated femoral component causes patellar failure after total knee arthroplasty. The effect of medial displacement of the tibial tubercle to decrease the Q angle for patellar tracking was studied by evaluating the patellar position relative to the patellar groove on the femoral component in cadaver specimens. A 5 degrees internally rotated femoral component caused the patella to shift medially about 5 mm, and also caused the tibia to rotate internally about 3 degrees at full extension. With a 5 degrees externally rotated femoral component, normal patellar tracking occurred. The distance of medial displacement was determined so that the patellar tendon was parallel to the longitudinal axis of the tibia at full extension. This allowed the quadriceps tendon, the patella, and the patellar tendon to form a straight line. The average distance of medial transposition of the tibial tubercle was 9.32 mm. Medialization of the tibial tubercle caused the patella to shift about 2 mm medially from the patellar groove. The transfer also caused an external rotation of the tibia (2 degrees-5 degrees). Medial transfer of the tibial tubercle changes patellar kinematics and corrects the tendency toward lateral patellar dislocation caused by internally rotating the femoral component; however, it also creates minor patellar and tibial kinematic changes that may have a clinical effect.
Biomechanical Phenomena↗
Effects of sterilization on wear in total knee arthroplasty.
Twenty-nine Ortholoc II ultrahigh molecular weight polyethylene tibial components were retrieved from 27 patients at revision surgery from the same hospital. The polyethylene material grade, method of sterilization, and sterilization dosage for 26 of the tibial components were determined by tracing the material lot number for each component. Each tibial surface was scored for wear using a qualitative scoring system that evaluated delamination, pitting, scratching, cold flow, abrasion, and burnishing. After the wear score analysis, 14 of the 26 components were analyzed to determine the physical and mechanical properties of the polyethylene including toughness and elongation. Seven of these 14 components were sterilized using ethylene oxide and 7 were sterilized using gamma radiation. Tibial components sterilized with gamma radiation had significantly higher wear rates than those sterilized with ethylene oxide. Thirteen of the 18 components sterilized with gamma radiation had delamination of the articular surface compared with 2 of 8 components sterilized with ethylene oxide. Mechanical properties were significantly affected by the sterilization method. Components sterilized with ethylene oxide had significantly higher toughness and percent elongation than those sterilized with gamma radiation. These findings suggest that ethylene oxide sterilization caused less microstructural damage to the polyethylene and resulted in significantly less wear than was found in those components sterilized with gamma radiation.
Adult↗
Rotational stability of noncemented total hip femoral components.
Achieving torsional fixation of the femoral component in total hip arthroplasty is an important factor in success of the implant, so design features that improve fixation are likely to improve clinical results. Four femoral stem designs that allow different levels of femoral neck resection and use different distal fixation techniques were mechanically tested in cadaveric femurs to determine resistance to torsional loads. Five specimens for each stem design were implanted according to the standard procedure, and each was axially and torsionally loaded in a servohydraulic testing machine. Rotational interface micromotion and interface slippage were measured at the bone-implant interface. Decreased micromotion and interface slippage were associated with a distal scratch fit and neck retaining design, and the combination of distal scratch fit and neck retention had the least micromotion and smallest standard deviation of the four designs.
Bone Cements↗
Fetal breathing is not inhibited by ethanol exposure during prolonged reduced uterine blood flow.
When prolonged hypoxemia is induced in fetal sheep by reducing uterine blood flow, fetal breathing movements (FBM) return to normal incidence after their initial decrease. Ethanol also inhibits FBM. These experiments were designed to determine the role of fetal oxygenation status in affecting ethanol-induced inhibition of FBM. A 1-h maternal infusion of 1 g ethanol/kg maternal body weight was given to animals following 20 h of reduced uterine blood flow (RUBF; n = 9), as well as to normoxemic (n = 9) fetal sheep, and the effect on FBM, electrocortical activity (ECoG), and electroocular activity (EOG) was determined. In normoxemic fetuses, the incidence of FBM decreased from 26.1 +/- 5.5% to 2.8 +/- 1.6% (p < 0.05) with ethanol, subsequently returning to baseline values over 6 h, but there was no effect of ethanol on FBM incidence in RUBF fetuses (32.8 +/- 9.1%). Ethanol increased the incidence of intermediate ECoG from 16.6 +/- 2.9% to 49.0 +/- 9.8% (p < 0.01) in normoxemic fetuses, but there was no change in RUBF fetuses. We conclude that the adaptive mechanism(s) invoked by fetal sheep during prolonged RUBF abolishes its ability to respond behaviourally to ethanol.
Animals↗
Egg production by Strelkovimermis spiculatus (Nematoda:Mermithidae).
Egg production by the mermithid nematode Strelkovimermis spiculatus, a parasite of mosquitoes, was examined over a period of 34 days. Oviposition did not occur in the absence of males. Egg production was best when males were continuously present (6.4 x 10(3) +/- 0.9 x 10(3) eggs/female). Fewer eggs were produced when males were removed after 7 days (2.8 x 10(3) +/- 0.2 x 10(3) eggs/female) and oviposition partially recovered after males were returned 11 days later (4.4 x 10(3) +/- 0.5 x 10(3) eggs/female). The nematodes deposited substantially more eggs in sand (6.4 x 10(3) +/- 0.9 x 10(3)/female) than in water (1.9 x 10(3) +/- 0.3 x 10(3)/(female).
Animals↗
Patellar tracking measurement in the normal knee.
Eleven fresh frozen cadaveric knee specimens were mounted in a knee kinematics test device, and normal patellar movements were evaluated with use of an external device for direct measurement of patellar movements. The effects of four different measurement conditions were assessed through alteration of one condition and determination of its effect on patellar kinematics with the use of six specimens. The four conditions included (a) change of the measuring axis from an axis parallel to the central axis of the femur (femoral axis) to one parallel to the central axis of the tibia (tibial axis), (b) rotation of the femoral axis internally 6 degrees, (c) change of the direction of the quadriceps force from parallel to the mechanical line of the lower extremity to a direction parallel to the femoral shaft, and (d) increase of the magnitude of the quadriceps force from 111 to 500 N. During knee flexion, the patella shifted laterally after a slight initial medial shift, tilted laterally from midflexion to 90 degrees, and gradually rotated medially. The patellar shift relative to the tibial axis appeared to be more medial than the shift measured relative to the femoral axis; the discrepancy was caused by the valgus position of the tibia relative to the femur. Changing the rotational angle of the femoral axis artificially changed the patellar position. Varying the direction of the quadriceps within the narrow range and increasing the quadriceps force did not affect patellar movements.(ABSTRACT TRUNCATED AT 250 WORDS)
Humans↗
LTR-retrotransposons and MITEs: important players in the evolution of plant genomes.
Retrotransposons are an abundant and ancient component of plant genomes, yet recent evidence indicates that element activity in many modern plants is restricted to times of stress. Stress activation of plant retrotransposons may be a significant factor in somaclonal variation, in addition to providing an important means to isolate new active elements. Long terminal repeat retrotransposons and a second class of elements we have called miniature inverted-repeat transposable elements (MITEs) have recently been found to be associated with the genes of diverse plants where some contribute regulatory sequences. Because of their sequence diversity and small size, MITEs may be a valuable evolutionary tool for altering patterns of gene expression.
Animals↗
Effect of rotational malposition of the femoral component on knee stability kinematics after total knee arthroplasty.
Excessive external rotation of the femoral component can cause an abnormally tight popliteus tendon complex, which induces loss of rotational laxity of the knee in the late phase of knee flexion after total knee arthroplasty. This study evaluated the effect of popliteus tendon release on rotational and varus-valgus laxity of implanted knees with an excessively externally rotated femoral component. Rotational and varus-valgus laxity was measured with a knee kinematics testing device before and after total knee arthroplasty. External rotational positions of the femoral component of 5 degrees and 8 degrees were compared, and the effects of popliteus tendon release on rotational and varus-valgus laxity were evaluated. To further investigate this question, the effect of a conforming articular design was compared with that of a flat tibial surface. External rotational position of 5 degrees did not change rotational or varus-valgus laxity of the knee. With an 8 degrees external rotational position, however, external rotational laxity significantly decreased in knees with a conforming surface at angles of 30 degrees, 45 degrees, 60 degrees, and 90 degrees. After popliteus tendon release, external rotational laxity significantly improved at 90 degrees flexion and was identical to that of the normal knee. Internal rotational range was similar before and after popliteus tendon release. Popliteus tendon release did not affect the varus-valgus laxity (stability) with either articular surface.
Biophysical Phenomena↗
Placental and fetal hepatic growth are selectively inhibited by prolonged reductions of uterine blood flow in pregnant sheep.
Experiments were conducted in eight pregnant sheep to determine the effect on fetal growth of mechanical restriction of uterine blood flow (RUBF) between 120 days and 134 days gestation. Uterine blood flow measured in the middle uterine arteries was 40% less in RUBF animals compared with control animals at the end of the experimental period. There was no change in fetal blood gases, bodyweights, or organ weights between the two groups of animals. The rate of DNA synthesis in the right lobe of the liver was significantly less in RUBF animals (581 +/- 34 dpm micrograms-1 DNA) compared with control animals (845 +/- 44 dpm microgram-1 DNA). There was no difference in the rate of DNA synthesis in the left lobe of the liver or in any of the other organs examined. Autoradiographic examination of the placental cotyledons demonstrated that most DNA synthesis in the placenta was occurring in fetal trophoblastic cells and there was a 40% reduction in the nuclear-labelling index of placental trophoblast cells. These studies show that mild mechanical reductions in uterine blood flow in pregnant sheep results in the selective inhibition of growth in the right lobe of the fetal liver and the placental trophoblastic cells. The mechanism underlying this close association remains to be determined.
Animals↗
Effect of prolonged catecholamine infusion on heart rate, blood pressure, breathing, and growth in fetal sheep.
Norepinephrine and epinephrine were infused into fetal sheep for 24 h to compare the effects on fetal heart rate, blood pressure, breathing movements, and tissue growth with those of prolonged reductions in uterine blood flow. Norepinephrine concentrations increased (p < 0.01) from 871 +/- 71 to 6831 +/- 1090 pg/mL (2 h) with norepinephrine infusion, and epinephrine concentrations increased from 310 +/- 95 to 1424 +/- 288 pg/mL (2 h) with epinephrine infusion. Fetal pH decreased (p < 0.01) from 7.37 +/- 0.01 to 7.29 +/- 0.02 at 0.5 h of the norepinephrine infusion and returned to control values by 2 h, whereas fetal lactate concentrations increased (p < 0.05) from 1.6 +/- 0.2 to 4.6 +/- 1.0 mmol/L at 2 h and remained elevated for 12 h. Lactate concentrations also increased with epinephrine infusion. Fetal heart rate increased (p < 0.05) from 176 +/- 5 to 246 +/- 6 and 220 +/- 6 beats/min in the 1st h of norepinephrine and epinephrine infusions, respectively, with a subsequent decline. Fetal blood pressure increased (p < 0.05) from 43 +/- 3 and 40 +/- 2 to 53 +/- 3 and 47 +/- 2 mmHg (1 mmHg = 133.3 Pa) during the 1st h of norepinephrine and epinephrine infusions, respectively, remaining elevated for 24 h. Fetal body weights were not different between the groups of animals, although liver/body weight ratio was less (p < 0.05) in epinephrine-infused fetuses (0.030 +/- 0.001) compared with vehicle-infused animals (0.036 +/- 0.002). There was no change in DNA synthesis rate in any of the fetal organs, despite changes in organ-specific DNA and protein content. Our results indicate that the changes in fetal cardiovascular and behavioural function, as well as tissue growth, that occur with prolonged reductions in uterine blood flow are not mediated solely by elevated circulating catecholamine concentrations.
Adrenal Glands↗