Sex differences in elite swimming with advanced age are less than marathon running.

The sex difference in marathon performance increases with finishing place and age of the runner but whether this occurs among swimmers is unknown. The purpose was to compare sex differences in swimming velocity across world record place (1st-10th), age group (25-89 years), and event distance. We also compared sex differences between freestyle swimming and marathon running. The world's top 10 swimming times of both sexes for World Championship freestyle stroke, backstroke, breaststroke, and butterfly events and the world's top 10 marathon times in 5-year age groups were obtained. Men were faster than women for freestyle (12.4 ± 4.2%), backstroke (12.8 ± 3.0%), and breaststroke (14.5 ± 3.2%), with the greatest sex differences for butterfly (16.7 ± 5.5%). The sex difference in swimming velocity increased across world record place for freestyle (P < 0.001), breaststroke, and butterfly for all age groups and distances (P < 0.001) because of a greater relative drop-off between first and 10th place for women. The sex difference in marathon running increased with the world record place and the sex difference for marathon running was greater than for swimming (P < 0.001). The sex difference in swimming increased with world record place and age, but was less than for marathon running. Collectively, these results suggest more depth in women's swimming than marathon running.

Only women report increase in pain threshold following fatiguing contractions of the upper extremity.

PURPOSE: The perception of pain in response to a noxious stimulus can be markedly reduced following an acute bout of exercise [exercise-induced hypoalgesia (EIH)]. Sex differences in EIH frequently occur after exercise but may be confounded by the sex differences in muscle fatigue. The purpose was to determine if sex differences in pain relief occur after an exercise protocol when muscle fatigue is similar for both young and older men and women. METHODS: Pain perception of 33 men (15 young) and 31 women (19 young) was measured using a pressure pain stimulus on the left index finger before and after maximal velocity concentric contractions of knee extensors or elbow flexors (separate days). During the 2-min pressure pain test, participants verbally indicated the onset of pain (pain threshold) and reported pain intensity (0-10) every 20 s. RESULTS: Only women experienced an increase in pain threshold (30 ± 27 to 41 ± 32 s) following elbow flexor exercise (trial × sex: p = 0.03). Neither men nor women experienced an increase in pain threshold following knee extensor exercise, and pain ratings were unchanged after exercise with either limb (p > 0.05). The pain response to exercise was similar in young and older adults (trial × age: p > 0.05), despite older adults demonstrating greater fatigability than young adults for the elbow flexor and knee extensor exercise tasks. CONCLUSIONS: Under controlled conditions where muscle fatigue is similar, sex differences in EIH occur in young and older adults that is site specific (upper extremity). Only women experience EIH following acute single limb high-velocity contractions.

Effects of type 1 diabetes, sprint training and sex on skeletal muscle sarcoplasmic reticulum Ca2+ uptake and Ca2+-ATPase activity.

Calcium cycling is integral to muscle performance during the rapid muscle contraction and relaxation of high-intensity exercise. Ca(2+) handling is altered by diabetes mellitus, but has not previously been investigated in human skeletal muscle. We investigated effects of high-intensity exercise and sprint training on skeletal muscle Ca(2+) regulation among men and women with type 1 diabetes (T1D, n = 8, 3F, 5M) and matched non-diabetic controls (CON, n = 8, 3F, 5M). Secondarily, we examined sex differences in Ca(2+) regulation. Subjects undertook 7 weeks of three times-weekly cycle sprint training. Before and after training, performance was measured, and blood and muscle were sampled at rest and after high-intensity exercise. In T1D, higher Ca(2+)-ATPase activity (+28%) and Ca(2+) uptake (+21%) than in CON were evident across both times and days (P < 0.05), but performance was similar. In T1D, resting Ca(2+)-ATPase activity correlated with work performed until exhaustion (r = 0.7, P < 0.01). Ca(2+)-ATPase activity, but not Ca(2+) uptake, was lower (-24%, P < 0.05) among the women across both times and days. Intense exercise did not alter Ca(2+)-ATPase activity in T1D or CON. However, sex differences were evident: Ca(2+)-ATPase was reduced with exercise among men but increased among women across both days (time × sex interaction, P < 0.05). Sprint training reduced Ca(2+)-ATPase (-8%, P < 0.05), but not Ca(2+) uptake, in T1D and CON. In summary, skeletal muscle Ca(2+) resequestration capacity was increased in T1D, but performance was not greater than CON. Sprint training reduced Ca(2+)-ATPase in T1D and CON. Sex differences in Ca(2+)-ATPase activity were evident and may be linked with fibre type proportion differences.

Physical activity and aging research: opportunities abound.

Aging is associated with large between-subjects variability in motor function among older adults, which can compromise identifying the mechanisms for age-related reductions in motor performance. This variability is in part explained by differences among older adults in habitual physical activity. Quantifying and accounting for physical activity levels of the participants in aging studies will help differentiate those changes in motor function associated with biological aging rather than those induced by inactivity. Novelty: Quantification of physical activity levels in studies with older participants will help differentiate the effects of aging rather than physical inactivity.

Rotary culture enhances pre-osteoblast aggregation and mineralization.

Three-dimensional environments have been shown to enhance cell aggregation and osteoblast differentiation. Thus, we hypothesized that three-dimensional (3D) growth environments would enhance the mineralization rate of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. The objective of this study was to investigate the potential use of rotary cell culture systems (RCCS) as a means to enhance the osteogenic potential of pre-osteoblast cells. HEPM cells were cultured in a RCCS to create 3D enviroments. Tissue culture plastic (2D) cultures served as our control. 3D environments promoted three-dimensional aggregate formations. Increased calcium and phosphorus deposition was significantly enhanced three- to 18-fold (P < 0.001) in 3D cultures as compared with 2D environments. 3D cultures mineralized in 1 wk as compared with the 2D cultures, which took 4 wks, a decrease in time of nearly 75%. In conclusion, our studies demonstrated that 3D environments enhanced osteoblast cell aggregation and mineralization.

Relationships among age-associated strength changes and physical activity level, limb dominance, and muscle group in women.

This study investigated the magnitude and rate of age-associated strength reductions in Australian independent urban-dwelling women and the relationship to muscle groups, limb dominance, and physical activity level. Independent urban-dwelling women aged 20 to 89 years (N = 217) performed maximal voluntary contractions with the dominant and nondominant knee extensors, plantar flexors, and handgrip. Anthropometric measurements were made and questionnaire responses used to obtain current physical activity levels. Trend analysis within analysis of variance and regression analysis on strength was performed. Limb muscle strength was found to be associated with increased age, muscle group, limb dominance, and activity. Self-reported physical activity levels declined with age but women who were more physically active for their age group were stronger in all muscle groups and had more lean body mass and lean thigh and leg cross-sectional area than relatively inactive women. Slopes of the linear reductions of maximal voluntary strength of the knee extensors, plantar flexors, and handgrip with age were significantly different (p < .05) at 9.3%, 7.4%, and 6.2% per decade, respectively. The limb muscle strength of healthy Australian independent and urban-dwelling women aged 20 to 89 years was found to be associated with age and three aspects of disuse: muscle group, relative levels of physical activity, and limb dominance.

Sex differences in the fatigability of arm muscles depends on absolute force during isometric contractions.

Women are capable of longer endurance times compared with men for contractions performed at low to moderate intensities. The purpose of the study was 1) to determine the relation between the absolute target force and endurance time for a submaximal isometric contraction and 2) to compare the pressor response and muscle activation patterns of men [26.3 +/- 1.1 (SE) yr] and women (27.5 +/- 2.3 yr) during a fatiguing contraction performed with the elbow flexor muscles. Maximal voluntary contraction (MVC) force was greater for men (393 +/- 23 vs. 177 +/- 7 N), which meant that the average target force (20% of MVC) was greater for men (79.7 +/- 6.5 vs. 36.7 +/- 2.0 N). The endurance time for the fatiguing contractions was 118% longer for women (1,806 +/- 239 vs. 829 +/- 94 s). The average of the rectified electromyogram (%MVC) for the elbow flexor muscles at exhaustion was similar for men (31 +/- 2%) and women (30 +/- 2%). In contrast, the heart rate and mean arterial pressure (MAP) were less at exhaustion for women (94 +/- 6 vs. 111 +/- 7 beats/min and 121 +/- 5 vs. 150 +/- 6 mmHg, respectively). The target force and change in MAP during the fatiguing contraction were exponentially related to endurance time (r(2) = 0.68 and r(2) = 0.64, respectively), whereas the change in MAP was linearly related to target force (r(2) = 0.51). The difference in fatigability of men and women when performing a submaximal contraction was related to the absolute contraction intensity and was limited by mechanisms that were distal to the activation of muscle.

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures.

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 +/- 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 +/- 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 +/- 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 +/- 5.3%), but it ended at a similar value (45.4 +/- 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

Leukemia in pregnancy and fetal response to multiagent chemotherapy.

BACKGROUND: Leukemia is rare in pregnancy and treatment with intensive, multiagent chemotherapy produces complete remission in most adults, but might have deleterious effects on fetuses. CASE: A 24-year-old gravida 3 para 2 presented at 24 weeks with pruritus, rash, pancytopenia, and hepatitis. A bone marrow biopsy found acute lymphocytic leukemia. She completed three cycles of intensive multiagent chemotherapy with transient oligohydramnios in each cycle. Although there was decreased fetal growth rate, umbilical artery Doppler scans were normal. She delivered a normal 2150-g male infant at 36 weeks. CONCLUSION: Pregnant women with newly diagnosed leukemia should not delay treatment, but multiagent chemotherapy might have transient effects on fetuses, most notably oligohydramnios. However, if fetal testing is normal, delivery might not be indicated.

Liver transplant after massive spontaneous hepatic rupture in pregnancy complicated by preeclampsia.

BACKGROUND: Spontaneous hepatic rupture associated with preeclampsia is a rare but life-threatening situation. Several different surgical treatments have been described, depending on the severity of the rupture. Liver transplantation has become the mainstay for patients with end-stage liver disease. Transplantation in the setting of liver trauma or massive parenchymal disruption is not well defined. To our knowledge, this treatment has not been reported for spontaneous hepatic rupture in pregnancy. CASE: Massive, spontaneous hepatic rupture occurred in a patient at 36 weeks' gestation as a result of severe preeclampsia. Conventional surgical therapies were unsuccessful in controlling the massive hemorrhage. As a life-saving measure, the patient underwent total hepatectomy with the creation of an end-to-side portcaval shunt, thereby rendering the patient anhepatic. The patient was listed as urgently needing a liver for transplantation through the United Network for Organ Sharing. A suitable donor liver was located approximately 8 hours after the emergency hepatectomy. The patient underwent orthotopic liver transplantation after being maintained in an anhepatic state for almost 13 hours. The patient was discharged on postoperative day 41, suffering only from some ischemic lower extremity neuropathy secondary to hypovolemic hypotension occurring during the hepatectomy procedure. CONCLUSION: In the reported case, spontaneous hepatic rupture resulted in a massive hemorrhage that could not be controlled by previously reported techniques and required total hepatectomy followed by liver transplantation.

Human skeletal sarcoplasmic reticulum Ca2+ uptake and muscle function with aging and strength training.

This study investigated the adaptations of skeletal muscle sarcoplasmic reticulum (SR) Ca2+ uptake, relaxation, and fiber types in young (YW) and elderly women (EW) to high-resistance training. Seventeen YW (18-32 yr) and 11 EW (64-79 yr) were assessed for 1) electrically evoked relaxation time and rate of the quadriceps femoris; and 2) maximal rates of SR Ca2+ uptake and Ca2+-ATPase activity and relative fiber-type areas, analyzed from muscle biopsies of the vastus lateralis. EW had significantly slower relaxation rates and times, decreased SR Ca2+ uptake and Ca2+-ATPase activity, and a larger relative type I fiber area than did YW. A subgroup of 9 young (YWT) and 10 elderly women (EWT) performed 12 wk of high-resistance training (8 repetition maximum) of the quadriceps and underwent identical testing procedures pre- and posttraining. EWT significantly increased their SR Ca2+ uptake and Ca2+-ATPase activity in response to training but showed no alterations in speed of relaxation or relative fiber-type areas. In YWT none of the variables was altered after resistance training. These findings suggest that 1) a reduced SR Ca2+ uptake in skeletal muscle of elderly women was partially reversed with resistance training and 2) SR Ca2+ uptake in the vastus lateralis was not the rate-limiting mechanism for the slowing of relaxation measured from electrically evoked quadriceps muscle of elderly women.

Impaired calcium pump function does not slow relaxation in human skeletal muscle after prolonged exercise.

This study examined the effects of prolonged exercise on human quadriceps muscle contractile function and homogenate sarcoplasmic reticulum Ca2+ uptake and Ca2+-adenosinetriphosphatase activity. Ten untrained men cycled at 75 +/- 2% (SE) peak oxygen consumption until exhaustion. Biopsies were taken from the right vastus lateralis muscle at rest, exhaustion, and 20 and 60 min postexercise. Peak tension and half relaxation time of the left quadriceps muscle were measured during electrically evoked twitch and tetanic contractions and a maximal voluntary isometric contraction at rest, exhaustion, and 10, 20, and 60 min postexercise. At exhaustion, homogenate Ca2+ uptake and Ca2+ adenosinetriphosphatase activity were reduced by 17 +/- 4 and 21 +/- 5%, respectively, and remained depressed after 60 min recovery (P

The gamete and embryo compatibility of various synthetic polymers.

Several popular and well-characterized polymeric materials were evaluated for their biocompatibility toward the cells unique to reproduction. To accomplish these studies, several in vitro tests were developed that evaluated biocompatibility between the polymers and spermatozoa, ova, and embryos. The data indicated significant differences between the materials with respect to their biocompatibility toward sperm motility, the sperm's ability to penetrate zona-free hamster eggs, and the ability of two-cell mouse embryos to divide. Polytetrafluoroethylene (PTFE-Teflon; PTFE, Chemplast Inc., Wayne, NJ), polyethylene glycol (PEG), and polyhydroxyethyl methacrylate (PHEMA) appear to be the most inert of the materials studied. Polyvinyl chloride (PVC; Tygon-Norton, Akron, OH) was found to be the most detrimental material toward gametes and embryos, with gross physiologic and morphologic changes observed in the PVC-exposed cells.

Developing an artificial fallopian tube: successful in vitro trials in mice.

This report describes the design and testing of an artificial fallopian tube for the treatment of tubal infertility. Within the device, mouse eggs incubated with sperm were fertilized and a microinfusion pump was used to transport the fertilized ova through the tube. Normal offspring resulted from transfer of the developing embryos into pseudopregnant recipients. These results provide encouraging evidence that an artificial fallopian tube warrants further investigation as a potential alternative to in vitro fertilization.

Peripheral stimulus localization by infants with eye and head movements during visual attention.

The effect of attention to a focal stimulus on 14, 20 and 26-week-old infant's peripheral stimulus localization with eye and head movements was examined in this study. Fixation was engaged on a stimulus in the central visual field and a stimulus was presented in the periphery immediately or after a delay. Peripheral stimulus localization occurred less frequently near the beginning of fixation and when a significant heart rate deceleration had occurred (sustained attention), compared with when no focal stimulus was present or after heart rate had returned to prestimulus level (attention termination). Localization was accompanied by head movements on more than two-thirds of the trials, and the likelihood of head movements was positively associated with stimulus eccentricity. The saccades to localize the peripheral stimulus had unusually high velocities in the attention conditions for the two older aged groups relative to their saccades in inattentive conditions. There were unusual "localizing head movements" in the attention conditions in the absence of localizing saccades or changes in fixation for the two older age groups. Infant attention modulates eye movement characteristics of infants. These data also support the hypothesis that eye and head movement systems are relatively independent in the infant, and that eye-head relations during infant attention may be different from during inattention.

Periodontal disease in pregnancy complicated by type 1 diabetes mellitus.

BACKGROUND: Systemic disease and hormonal changes have been implicated as complicating factors for periodontal disease. Diabetes has been identified as a risk factor for periodontal disease, and diabetics can experience periodontal destruction at an earlier age than non-diabetic individuals. Increased hormone levels during pregnancy can contribute to increased gingival inflammation. The purpose of this study was to examine the association of type 1 diabetes mellitus (DM) on the periodontal status of pregnant women. METHODS: Thirty-three (13 diabetic and 20 non-diabetic) subjects, 20 to 39 weeks gestation, participated in this study. The mean age of the diabetics and non-diabetics was 28.5 +/- 7.1 (SD) and 27.0 +/- 7.3 years, respectively. The following parameters were assessed at Ramfjord's reference teeth: plaque index (PI), gingival inflammation (GI), probing depth (PD), gingival margin (GM) location, and clinical attachment level (CAL). RESULTS: Diabetic subjects had significantly (P<0.001) higher PI (1.48 +/- 0.69) and GI (1.77 +/- 0.44) scores than non-diabetics (PI = 0.63 +/- 0.38; GI = 0.93 +/- 0.48). Mean PD for diabetics (2.95 +/- 0.69 mm) was significantly different (P<0.024) from that of non-diabetics (2.44 +/- 0.32 mm). Although mean GM location was coronal to the cemento-enamel junction (CEJ) in both groups, gingival margins were at a more apical position (P<0.001) in the diabetics (-0.20 +/- 1.24 mm) compared to non-diabetics (-1.76 +/- 0.53 mm). Mean CAL values also varied significantly (P<0.001) between diabetics (2.60 +/- 1.54 mm) and non-diabetics (0.68 +/- 0.65 mm). Significant differences were seen for GI (P<0.001), PD (P=0.005), GM location (P<0.001), and CAL (P<0.001) when assessing the effect of diabetes and controlling for plaque. When assessing the effect of plaque and controlling for diabetes, the only significant difference was GI (P=0.001). CONCLUSIONS: The results of this study demonstrate that periodontal inflammation and destruction are increased in pregnant diabetics as compared to non-diabetic pregnant patients. These findings may have implications for diabetic control and, hence, maternal and fetal outcomes in pregnant diabetic patients.

Mathematical modeling of myoglobin facilitated transport of oxygen in devices containing myoglobin-expressing cells.

Low pO(2) is perhaps the most significant factor in artificial pancreas failure. In these environments, not only is the beta cell production of insulin reduced, but the cell death rate is also significantly higher. Mathematical models are developed to test the feasibility of facilitated oxygen transport in enhancing O(2) flux to genetically engineered cells in a bioartificial device such as a pancreas. For this device, it is proposed that beta cells be genetically engineered to express myoglobin throughout the cell. In addition, the significance of including myoglobin throughout the alginate matrix present to provide immuno-protection for the transplanted cells is considered. The mathematical analysis predicts that myoglobin facilitated oxygen transport has the potential of increasing the oxygen concentration at the centre of a cluster of cells (islet) with an effective radius of 100 microm by 50%. These theoretical models for myoglobin facilitated oxygen transport with homogeneous Michaelis-Menten consumption also indicate that including myoglobin in the alginate gel would beneficially improve the flux of oxygen to the transplanted cells.

Bioartificial pancreas use in diabetic pregnancy.

The purpose of this study was to evaluate the feasibility and effectiveness of Bioartificial Pancreas (BAP) technology use during diabetic pregnancy. In particular, the study asked 1) can microencapsulated islet cells effectively correct carbohydrate metabolism during diabetic pregnancy and 2) will such therapy, if initiated before conception, eliminate diabetes-induced congenital malformations in the fetus? Streptozotocin-induced diabetic female mice (ICR) received transplants of rat islets encapsulated within alginate microbeads. Animals were placed with male mice and bred. Random, nonfasting blood glucose (BG) determinations were made posttransplantation and throughout pregnancy. Pups were delivered by cesarean section on day 19 of gestation. Outcome parameters from transplanted animals (Tx) were compared to nondiabetic control animals and to untreated diabetic (DM) animals. Transplanted animals had significantly lower BG levels throughout pregnancy, compared with DM animals, but also had levels that were often lower than those seen in control nondiabetic animals, and had increased episodes of documented hypoglycemia. The malformation and fetal loss rate in the Tx group was significantly lower than the untreated group (ICR: 5.4% vs. 40%). Only 3 of 84 pups from the Tx group had major malformations, but all had anencephaly, a malformation not seen in any other study group. Both maternal BG levels and fetal malformation rates are significantly reduced using BAP technology in our animal models. However, the possible role these encapsulated islets may play in producing increased episodes of hypoglycemia or specific congenital malformations in pregnancy must be thoroughly investigated before any clinical studies.

Promotion of neovascularization around hollow fiber bioartificial organs using biologically active substances.

A limiting factor of the long-term function of bioartificial organs is oxygen delivery to the encapsulated tissue. This study determined whether incorporation of endothelial cell growth factor (ECGF) into the alginate core of a hollow fiber bioartificial organ will induce neovascularization around the hollow fiber. Polyethersulfone (PES) and polyvinylidine difluoride (PVDF) hollow fibers were examined. Endothelial cell growth factor was incorporated into sodium alginate, extruded into the lumen of hollow fibers, and cured in calcium chloride. Samples without ECGF were fabricated and used as controls. Hollow fibers were implanted into 16 rats. For each rat, two implants were placed subcutaneously and two intraperitoneally, one with and one without ECGF at each site. Implants were placed on opposite sides of each animal. Implants were removed 65 days later and examined using immunohistochemical methods and light microscopy to determine the extent of neovascularization. A total of 64 implants were used. Most intraperitoneal implants were found free floating but were encased within a 100-microm thick avascular fibrotic reaction. This finding was independent from the presence of ECGF. Hollow fibers without ECGF, implanted subcutaneously, also had an avascular fibrotic reaction surrounding each implant. Subcutaneous implants with incorporation of ECGF within the alginate core had marked neovascularization within the fibrotic overgrowth that surrounded these implants. This was most prevalent in hollow fibers, with the thin separation layer facing the fiber lumen irrespective of limiting pore size. Potent angiogenic factors, such as ECGF, incorporated into diffusion chamber bioartificial organs can promote neovascularization around the subcutaneously implanted hollow fiber and may improve oxygen delivery to the tissue encapsulated within devices based on this technology.

Sex differences in human fatigability: mechanisms and insight to physiological responses.

Sex-related differences in physiology and anatomy are responsible for profound differences in neuromuscular performance and fatigability between men and women. Women are usually less fatigable than men for similar intensity isometric fatiguing contractions. This sex difference in fatigability, however, is task specific because different neuromuscular sites will be stressed when the requirements of the task are altered, and the stress on these sites can differ for men and women. Task variables that can alter the sex difference in fatigability include the type, intensity and speed of contraction, the muscle group assessed and the environmental conditions. Physiological mechanisms that are responsible for sex-based differences in fatigability may include activation of the motor neurone pool from cortical and subcortical regions, synaptic inputs to the motor neurone pool via activation of metabolically sensitive small afferent fibres in the muscle, muscle perfusion and skeletal muscle metabolism and fibre type properties. Non-physiological factors such as the sex bias of studying more males than females in human and animal experiments can also mask a true understanding of the magnitude and mechanisms of sex-based differences in physiology and fatigability. Despite recent developments, there is a tremendous lack of understanding of sex differences in neuromuscular function and fatigability, the prevailing mechanisms and the functional consequences. This review emphasizes the need to understand sex-based differences in fatigability to shed light on the benefits and limitations that fatigability can exert for men and women during daily tasks, exercise performance, training and rehabilitation in both health and disease.