AC measurements and simulations of hepatic radiofrequency ablation.

INTRODUCTION: The radiofrequency ablation (RFA) of liver cancer is a desirable treatment option, as it is minimally invasive. An accurate numerical simulation can greatly help physicians better plan their surgical protocols. Previously, the displacement current in the RFA process was considered negligible, and therefore RFA simulation was modeled as a direct current (DC) system instead of an alternating current (AC) system. Our study investigated the hypothesis that the displacement current in the RFA process should not always be considered negligible. METHODS: AC measurements of ex vivo bovine liver ablation were performed, and numerical simulations were also conducted to test the hypothesis that the relative permittivity would significantly decrease after the liver tissue reached a high temperature. RESULTS: The displacement current was observed to be a sizable fraction of the conduction current, especially before the onset of the first pause. The simulation results indicated that the relative permittivity is likely to decrease to several hundred or lower at elevated temperatures. CONCLUSIONS: Our study results suggest that the DC model may be inadequate, especially before the first roll-off and that additional information could be available during RFA treatment by considering the AC nature of RFA, which could lead to improved numerical simulation. Additional measurements of tissue parameters are needed to reach the full potential of the AC model for further development of ablation control.

Human adipose cells in vitro are either refractory or responsive to insulin, reflecting host metabolic state.

While intercellular communication processes are frequently characterized by switch-like transitions, the endocrine system, including the adipose tissue response to insulin, has been characterized by graded responses. Yet here individual cells from adipose tissue biopsies are best described by a switch-like transition between the basal and insulin-stimulated states for the trafficking of the glucose transporter GLUT4. Two statistically-defined populations best describe the observed cellular heterogeneity, representing the fractions of refractive and responsive adipose cells. Furthermore, subjects exhibiting high systemic insulin sensitivity indices (SI) have high fractions of responsive adipose cells in vitro, while subjects exhibiting decreasing SI have increasing fractions of refractory cells in vitro. Thus, a two-component model best describes the relationship between cellular refractory fraction and subject SI. Since isolated cells exhibit these different response characteristics in the presence of constant culture conditions and milieu, we suggest that a physiological switching mechanism at the adipose cellular level ultimately drives systemic SI.

Impaired tethering and fusion of GLUT4 vesicles in insulin-resistant human adipose cells.

Systemic glucose homeostasis is profoundly influenced by adipose cell function. Here we investigated GLUT4 dynamics in living adipose cells from human subjects with varying BMI and insulin sensitivity index (Si) values. Cells were transfected with hemagglutinin (HA)-GLUT4-green fluorescent protein (GFP)/mCherry (red fluorescence), and were imaged live using total internal reflection fluorescence and confocal microscopy. HA-GLUT4-GFP redistribution to the plasma membrane (PM) was quantified by surface-exposed HA epitope. In the basal state, GLUT4 storage vesicle (GSV) trafficking to and fusion with the PM were invariant with donor subject Si, as was total cell-surface GLUT4. In cells from insulin-sensitive subjects, insulin augmented GSV tethering and fusion approximately threefold, resulting in a corresponding increase in total PM GLUT4. However, with decreasing Si, these effects diminished progressively. All insulin-induced effects on GLUT4 redistribution and trafficking correlated strongly with Si and only weakly with BMI. Thus, while basal GLUT4 dynamics and total cell-surface GLUT4 are intact in human adipose cells, independent of donor Si, cells from insulin-resistant donors show markedly impaired GSV tethering and fusion responses to insulin, even after overnight culture. This altered insulin responsiveness is consistent with the hypothesis that adipose cellular dysfunction is a primary contributor to systemic metabolic dysfunction.

Topical cooling (icing) delays recovery from eccentric exercise-induced muscle damage.

It is generally thought that topical cooling can interfere with blood perfusion and may have positive effects on recovery from a traumatic challenge. This study examined the influence of topical cooling on muscle damage markers and hemodynamic changes during recovery from eccentric exercise. Eleven male subjects (age 20.2 ± 0.3 years) performed 6 sets of elbow extension at 85% maximum voluntary load and randomly assigned to topical cooling or sham groups during recovery in a randomized crossover fashion. Cold packs were applied to exercised muscle for 15 minutes at 0, 3, 24, 48, and 72 hours after exercise. The exercise significantly elevated circulating creatine kinase-MB isoform (CK-MB) and myoglobin levels. Unexpectedly, greater elevations in circulating CK-MB and myoglobin above the control level were noted in the cooling trial during 48-72 hours of the post-exercise recovery period. Subjective fatigue feeling was greater at 72 hours after topical cooling compared with controls. Removal of the cold pack also led to a protracted rebound in muscle hemoglobin concentration compared with controls. Measures of interleukin (IL)-8, IL-10, IL-1ß, and muscle strength during recovery were not influenced by cooling. A peak shift in IL-12p70 was noted during recovery with topical cooling. These data suggest that topical cooling, a commonly used clinical intervention, seems to not improve but rather delay recovery from eccentric exercise-induced muscle damage.

Parasympathetic nervous activity mirrors recovery status in weightlifting performance after training.

Heart rate variability (HRV) and parasympathetic power are closely related to the well-being and health status in humans. The main goal of the study was to determine whether these measures can reflect recovery status after weight training. After a 10-day detraining period, 7 weightlifters were challenged with a 2-hour weight training which elicited approximately fourfold increases in circulating muscle creatine kinase level and protracted pain feeling (p < 0.05). Weightlifting performance was then evaluated 3, 24, 48, and 72 hours after training to determine the degree of recovery from fatigue. Heart rate variability, circulating dehydroepiandrostendione sulfate (DHEA-S), and muscle damage markers were measured before each performance test. An electrocardiogram was recorded for 5 minutes continuously at rest in seated positions. After training, weightlifting performance of the subjects decreased below baseline in paralleled with suppressed parasympathetic power (high-frequency [HF] HRV), whereas sympathetic power (normalized low-frequency HRV) was slightly elevated at 3 hours of recovery (p < 0.05). Both weightlifting performances and parasympathetic power returned to baseline values in 24 hours and further increased above baseline during 48-72 hours of recovery in a similar fashion (p < 0.05). Circulating DHEA-S level dropped at 24 hours (p < 0.05) and returned to normal values by 48 hours. Muscle pain increased at 3 hours after training and remained higher than baseline values for the 72-hour recovery period (p < 0.05). Our data suggest that parasympathetic power, indicated by HF HRV, is able to reflect the recovery status of weightlifters after training.

Measurement of cervical multifidus contraction pattern with ultrasound imaging.

Deep muscle training has become the focus of research and exercise for patients with chronic neck pain. The objective of this in vivo study was to establish a non-invasive assessment tool for the activation of deep cervical muscles. The pattern of the change in the thickness of the cervical multifidus is described with a mathematical equation and used to compare the changes among different levels of resistance (0%, 25%, 50%, 75%, and 100%) and at different cervical levels (fourth, fifth, and sixth cervical (C4, C5, and C6) vertebrae). Twenty asymptomatic subjects (five women and 15 men; 24.3+/-4.7 years old) were recruited for this experiment. Ultrasonography (US) with synchronized force recording was used to measure the thickness of the cervical multifidus during progressive isometric extension against resistance. Linear and quadratic models were used to estimate the patterns of change in the thickness of cervical multifidus in relation to force. Two-way analysis of variance with repeated measurement and post hoc analysis were used to investigate the differences in thickness. The change in thickness and force was better fitted by quadratic model (y=ax(2)+bx+c) than by the linear model. The thickness at 50% of maximum contraction was significantly increased compared with that at 25% of maximum contraction. This quantitative non-invasive measurement may provide an assessment tool for further investigation for the physiological function of the deep muscles. Further research is required to investigate whether the change of thickness was predominately determined by the recruitment of muscle fibers or the extensibility of non-contractile tissues.

Effect of transcutaneous electrical nerve stimulation on primary dysmenorrhea.

Objectives. Dysmenorrhea is a disturbing problem among women of childbearing age. The purpose of this study is to investigate the effect of high-frequency transcutaneous electrical nerve stimulation (TENS) on primary dysmenorrhea and to compare the placebo effect by sham TENS in a randomized controlled study. Materials and Methods. Twenty-two women participated in the two-month experiment by using TENS or sham TENS in a random order for their dysmenorrhea. Outcome measures included self-reported pain intensity, symptom and function questionnaire related to dysmenorrhea, quality of life, satisfaction after TENS application, and other pain management agents adapted by the participants. Two-way repeated measures analysis of variance (two-way ANOVA) was conducted to compare pain intensity between pre-post values and groups (TENS vs. placebo). One-way repeated measures analysis of variance (one-way ANOVA) was conducted to compare scores from questionnaire of symptoms and quality of life at baseline, and after placebo or TENS stimulation. Results. Pain intensity in TENS is significantly decreased than in the placebo group (p= 0.018). The decrease of pain intensity after TENS and placebo TENS were both significant, with p < 0.00005 and p < 0.00005 respectively. Furthermore, TENS significantly changed the degree of autonomic symptoms (p= 0.048); but not after placebo TENS. Conclusion. This result supports that women in our country who suffer from primary dysmenorrhea could benefit by using TENS, which is consistent with the previous studies. In addition to pain-relieving effects, relief of the autonomic symptoms associated with dysmenorrhea also indicated that the mechanism of TENS might be different from the placebo effect of the sham TENS stimulation. These findings indicate the immediate effects of TENS in women with primary dysmenorrheal.

Suppression of age-dependent increase in insulinemia in early middle-aged females with exercise habit.

Circulating insulin concentration has been suggested as a biomarker for human longevity. The goal of the study was to determine the insulin levels under a glucose-challenged condition for the sedentary and physical active females in early middle age. We measured serum insulin levels for following groups: young sedentary (Y-SED, age 19.7 +/- 0.2 years), middle-aged sedentary (M-SED, age 42.3 +/- 3.1 years), young physically active (Y-EX, age 20.7 +/- 0.5 years), and middle-aged physically active (M-EX, age 40.3 +/- 2.8 years). Oral glucose tolerance test (OGTT) and insulin measurement were performed under overnight fasted condition. Triglyceride, cholesterol, body mass index (BMI), and waist-to-hip ratio (WHR) were also determined in all subjects. While fasted glucose and insulin levels were not different among 4 groups, glucose and insulin levels under OGTT were greater in the M-SED group than those in the Y-SED group. The M-EX subjects exhibited lower insulin levels on OGTT, as compared to the M-SED group, and were similar to the level of Y-SED. BMI and WHR of the M-SED group were comparable to those of the M-EX group. Triglyceride and cholesterol levels were highly associated with age and WHR but not the level of physical activity. The current study found a substantially greater insulin response on OGTT in the healthy sedentary females aged approximately 40, as compared to those in the young sedentary and the middle-aged physically active females, independent of weight status. The result of the study also suggests that accumulating 150 min of weekly exercise is sufficient to counteract the adverse effect of age on insulin sensitivity.

Measurement of segmental cervical multifidus contraction by ultrasonography in asymptomatic adults.

The deep muscles that play significant roles in maintaining segmental stability have been measured using ultrasonography (US). However, few studies have been carried out to determine the reliability and validity of US for measuring the cervical multifidus during contraction. The aims of this investigation were to evaluate the reliability of the dimensions of the cervical multifidus as measured using US and compare the US measurements with those determined with magnetic resonance imaging (MRI), the gold standard. Ten asymptomatic adult subjects (age, 28.5+/-3.5 years) participated in testing-retesting of muscle dimensions at rest and during isometric head extension with the cranio-cervical spine maintained in a flexed position against individual maximum resistance. Ten asymptomatic adult subjects (age, 28.1+/-4.1 years) participated in testing to compare US and MRI measurements of the thickness, width, area, and shape ratio of the cervical multifidus at the C4, C5, and C6 levels. US measurements of muscle thickness at the C4, C5, and C6 levels at rest were 0.67+/-0.14, 0.70+/-0.20 and 0.73+/-0.09 cm, respectively; the corresponding measurements as determined by MRI were 0.70+/-0.12, 0.67+/-0.15 and 0.70+/-0.06 cm. The within-subject coefficient of variation (CV(w)) for thickness at rest and during contraction was less than 10%, indicating acceptable reliability. US measurement of thickness had better reliability and validity. The range of limit of agreement for muscle thickness at the C4, C5, and C6 levels was -0.20 to 0.20 cm, and the range of R(2) was 0.42-0.64. The thickness of the cervical multifidus muscle increased significantly during contraction (1.13+/-0.20, 1.19+/-0.20 and 1.17+/-0.12 cm for the C4, C5, and C6 levels, P<0.05). However, no significant differences were noted among the three levels. The results indicate that US can detect changes in segmental cervical multifidus during contraction.