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PubMed1986

Sperm morphologic features as a prognostic factor in in vitro fertilization.

To determine whether there is a prognostic value in the percentage normal sperm morphologic features in a human in vitro fertilization (IVF) program, the authors conducted a prospective study in women with bilateral tubal damage. Based on the percentage of morphologically normal spermatozoa, the patients were divided into four groups: group I, normal morphologic features between 0% and 14%; group II, 15% to 30%; group III, 31% to 45%; and group IV, 46% to 60%. One hundred ninety successful laparoscopic cycles were evaluated. In group I, 104 oocytes were obtained, of which 37% fertilized, but no pregnancy resulted; in group II, 81% of 324 oocytes were fertilized, with a pregnancy rate per embryo transfer (ET) of 22%; in group III, 82% of 309 oocytes were fertilized, with a 31% pregnancy rate; and in group IV, 91% of 69 oocytes were fertilized, with a pregnancy rate of 12%. Probability models indicated that there was a clear threshold in normal sperm morphologic features at 14%, with high fertilization and pregnancy rate in the groups with normal sperm morphologic features greater than 14%.

Embryo Transfer↗
PubMed2000

Solubility of lead, zinc and copper added to mineral soils.

Elevated levels of heavy metals in soils are a result of industrial activities, atmospheric deposition, and the land application of sewage sludges and industrial by-products. Their persistence in the soil environment has created interest in the possible changes in solubility. In this study, total dissolved concentrations of Pb, Zn, and Cu were monitored in seven metal-amended soils (a calcareous and six acid mineral soils). Single metal solutions were added to soils and equilibrated (aged) for 40 days. During the 40 days the soil was allowed to air-dry and was rewetted in cycles of about 5 days. At the end of this reaction period, metal solubility was measured (by atomic absorption spectrometry and direct current plasma spectrometry) at the initial soil pH and at decreased pH values which were induced by addition of small aliquots of acid. As expected, solubility of added Pb, Zn, and Cu increased with a decrease in pH. Furthermore, the results showed that the solubility relationship with pH was similar in all non-calcareous soils. This suggests that metal solubility may be controlled by similar soil components, presumably involving soil characteristics such as pH, organic matter content, and soil mineralogy. For each metal, an approximate pH value was found at which solubility deviated from the solubility of metals when they occur in soils at typical (natural) values. This pH was about (pH+/-0.2): 5.2 for Pb, 6.2 for Zn, and 5.5 for Cu. Thus, pH values below these thresholds may enhance metal mobility, biological availability and toxicity in soils. Metals dissolved at higher pH in the calcareous soil (18.8 g kg(-1) inorganic carbon, initial pH 8.2). In a calcareous soil, a significant fraction of these metals react with carbonates, and decreased pH results in much higher metal dissolution. Yet, metal solubility in soils is not determined by the formation and dissolution of single metal compounds.

Journal Article↗
PubMed2003

Cost-utility analysis of survival with epoetin-alfa versus placebo in stage IV breast cancer.

BACKGROUND: In a multinational trial of anaemic patients with cancer receiving nonplatinum-containing chemotherapy, epoetin-alfa effectively increased haemoglobin levels, reduced red blood cell transfusion requirements, and improved QOL. Although the study was not designed or powered to evaluate survival, a survival trend was noted favouring epoetin-alfa compared with placebo (median survival 17 vs 11 months [p = 0.126]). OBJECTIVES: To determine the incremental cost utility of epoetin-alfa versus placebo in anaemic patients with stage IV breast cancer from a UK National Health Service perspective. METHODS: Patient data regarding transfusions, epoetin-alfa usage, chemotherapy treatment cycles, and adverse events were recorded, with survival follow-up for 12-36 months post-study. Stage IV breast cancer therapy costs were collected by surveying UK oncologists, and utilities for associated health states were from published sources. Costs were in British pounds and year 2000 values. Costs and benefits were jointly determined for the stage IV breast cancer subgroup (n = 55). Incremental cost-utility ratios (ICURs) were calculated assuming a 6% annual discount rate for costs and a 1.5% annual discount rate for benefits. Bootstrap simulations (10,000 iterations) were conducted to account for uncertainty, and sensitivity analyses were conducted to establish robustness. RESULTS: The ICUR for epoetin-alfa treatment was pounds 8,851 per QALY, with a 99% probability of a positive net benefit in QALYs (net benefit = 0.4805 years of perfect life) and a 94% probability of being acceptable using a threshold ICUR of pounds 30,000/QALY. The main cost drivers distinguishing epoetin-alfa from placebo were the costs of drug and patient care due to increased survival. CONCLUSIONS: The available data suggest a high probability of favourable cost-utility outcomes with epoetin-alfa treatment for anaemia in patients with stage IV breast cancer receiving nonplatinum-containing chemotherapy. Additional studies are warranted.

Adult↗
PubMed2006

Serum interleukin-6 levels are elevated in women with minimal-mild endometriosis.

BACKGROUND: There is a need for a reliable marker of endometriosis, especially in early stages of peritoneal disease during which imaging is not effective. The use of serum interleukin (IL)-6 as a marker is controversial. To readdress the matter, patients undergoing laparoscopy were prospectively evaluated for serum IL-6 levels. MATERIALS AND METHODS: A total of 119 women 31 years old who underwent laparoscopy were divided into groups: control patients (n = 38) with no pathologic findings; endometriosis sufferers (n = 47) with minimal-mild (MM, n = 11) or moderate-severe (MS, n = 36) endometriosis; uterine myomas (n = 13) and benign ovarian pathologies (n = 21). Blood was drawn on cycles days 5-12 and stored for subsequent analysis of IL-6 and carbohydrate antigen (CA)-125 levels. RESULTS: Serum IL-6 levels were significantly (P = 0.002) higher in women with MM endometriosis (29.4 9.0 pg/ml) than in controls (15.7 9.3 pg/ml). When all the non-endometriosis patients were grouped together (n = 72) and serum IL-6 (17.8 12.1 pg/ml) compared with MS (n = 36; 17.6 10.3 pg/ml) and MM (n = 11; 29.4 9.0 pg/ml) endometriosis significantly (P < 0.01) higher levels in MM endometriosis were observed as compared to the other two groups. Serum Ca-125 levels were significantly (P < 0.01) elevated in MS endometriosis. A serum IL-6 threshold of 25.75 pg/ml afforded a sensitivity of 75% and specificity of 83% in the diagnosis of MM endometriosis. Sensitivity and specificity for CA-125 in the diagnosis of MS endometriosis, using 35 IU/ml as the cut-off value, were 47% and 97%, respectively. CONCLUSIONS: IL-6 is a reliable non-invasive marker of MM endometriosis, whereas Ca-125 is of use as a marker of severe cases.

Adult↗
PubMed1985

Time series analysis of plasma LH and FSH concentrations as a method of assessing episodic secretion.

Time series analysis was used to detect LH and FSH episodes in untreated seasonally anoestrous ewes and prepubertal heifers, and in these animals when treated with low doses of GnRH. For comparison, these profiles were also assessed for episodic secretion by subjective, visual appraisal methods and by cycle detection-an objective threshold method. In untreated animals, time series analysis detected recurring events in the LH and FSH profiles, the period lengths of which varied between individual animals. When GnRH was injected at 2-h intervals, cycles in LH secretion with period lengths of 120 min were recorded in all animals, of 60 min in all ewes and 11/12 heifers, and of 40.5 min in 22/24 ewes and 10/12 heifers. The cycles with period lengths of 60 and 40.5 min are probably artefacts of this method of analysis. No consistent cycles in FSH release were detected in GnRH-injected anoestrous ewes, but 120-min cycles were recorded in 8/12 GnRH-injected heifers. When GnRH was administered to seasonally anoestrous ewes by continuous infusion, recurring cycles in both LH and FSH secretion were evident. However, there was no consistency in their period lengths and the mean number and frequency of cycles were similar to pretreatment values. The number of episodes detected by visual appraisal was influenced by the choice of episode definition. Both methods identified LH, but not FSH, episodes in response to each injection in all GnRH-injected animals. Cycle detection, which does not identify individual episodes, recorded LH and FSH episode frequencies similar to those detected by the more stringent method of visual appraisal. Time series analysis detected an FSH response to GnRH injections in prepubertal heifers that was not identified by the other methods of analysis. However, because of the asymmetric nature of LH episodes, it also detected cycles in LH profiles that were probably spurious. Subjective decisions influenced the frequencies of LH and FSH episodes recorded by visual appraisal, and the variation in episode amplitude in these profiles made cycle detection inappropriate. Each of these methods can contribute to the interpretation of hormone profiles, but their constraints and limitations must be recognized.

Anestrus↗
PubMed1993

The hemizona assay: its role in identifying male factor infertility in assisted reproduction.

OBJECTIVES: To identify male factor infertility among a group of patients in an assisted reproductive program (phase 1) and to evaluate the hemizona assay (HZA) in the diagnosis and prognosis of such a program (phase 2). DESIGN: The IVF performance of normal gametes in the Tygerberg program were critically evaluated. Female patients were classified as pure tubal factor infertility, having a normal FSH:LH ratio on day 3 of the menstrual cycle. All participating women produced three or more preovulatory oocytes at retrieval and were inseminated with sperm considered normal by all present diagnostic criteria. The total and normal fertilization rate thresholds were defined in that group. Using those thresholds, couples tested for sperm binding in the HZA (n = 48) were used and divided into two groups according to their fertilization rates, namely group 1, low fertilization (< 55%) and group 2, normal fertilization (> 55%). SETTING: University-based tertiary care center. PATIENTS: Ninety-nine couples (589 oocytes) with pure tubal factor infertility and normal male factor were used in phase 1. Forty-eight couples with normal and abnormal male factors that had both HZA performed and IVF treatment were included in phase 2. RESULTS: Investigation of the performance of normal gametes in 99 couples (589 oocytes) revealed the total fertilization rate (total number of oocytes fertilized/total number of oocytes inseminated) was (mean +/- SD) 88.6% +/- 16.8% and the normal fertilization rate (total number of oocytes with normal fertilization/total number of oocytes inseminated) was 81.3% +/- 22%. The minimum total fertilization rate that can be considered normal in the Tygerberg program using mean--2 SD is therefore 55% and for normal fertilization rate is 37%. The group with low fertilization rate (< 55%) showed a mean hemizona index (HZI) significantly lower; nevertheless, the distribution overlapping indicates a low discriminating power of the HZA. A sensitivity of 75% and a specificity of 75% were found; the positive and negative predictive values were 81% and 68%, respectively. CONCLUSIONS: The results indicated the HZA and HZI contribute important information and can serve in conjunction with other semen characteristics as useful tools during the diagnosis of the male factor in assisted reproduction.

Chorionic Gonadotropin↗
PubMed2001

Impact of starting strategy on cycling performance.

In order to determine an optimal starting technique, the first four-min of two 20 km time trials (TT) were manipulated. Thirteen competitive, male cyclists (22.7 +/- 0.8 yr, 180.6 +/- 2.2 cm; 77.1 +/- 2.8kg; 8.3+/-0.7% fat; 4.9+/-0.21 x min(-1), 71.7+/-1.4% of VO2max) performed three, 20 km TTs. The pace of the first TT was self-selected (SS). Min 1-4 of the subsequent, randomly assigned TTs were performed 15% below and 15% above the average power output (PO) of min 1-4 of the SS TT, subjects then completed the TT as quickly as possible. As a percent change from the SS TT, the 15% below TT was (p < 0.05) faster than 15% above TT. Lactic acid values at min 4 of the 15% below TT (4.87+/-0.73mM x l(-1)) were lower (p<0.05) than both SS TT (9.78+/-1.05mM x l(-1)) and 15% above TT (11.54+/-1.00mM x l(-1)). Following min 4 to the finish there were no differences in VE, HR, or RPE. However, VO2, VO2 with respect to lactic acid threshold, and PO were all elevated in the 15% below TT as compared to both SS TT and 15% above TT. The initially high LA resulting from the starting strategies of the SS TT and 15% above TT may have reduced the work capacity of active muscle.

Adult↗
PubMed2006

Effects of twenty-eight days of beta-alanine and creatine monohydrate supplementation on the physical working capacity at neuromuscular fatigue threshold.

The purpose of this study was to examine the effects of 28 days of beta-alanine (b-Ala) and creatine monohydrate (CrM) supplementation on the onset of neuromuscular fatigue by using the physical working capacity at neuromuscular fatigue threshold (PWC(FT)) test in untrained men. Fifty-one men (mean age +/- SD = 24.5 +/- 5.3 years) volunteered to participate in this 28-day, double-blind, placebo-controlled study and were randomly assigned to 1 of 4 groups: placebo (PLA; 34 g dextrose; n = 13), CrM (5.25 g CrM plus 34 g dextrose; n = 12), b-Ala (1.6 g b-Ala plus 34 g of dextrose; n = 12), or b-Ala plus CrM (CrBA; 5.25 g CrM plus 1.6 g b-Ala plus 34 g dextrose; n = 14). The supplement was ingested 4 times per day for 6 consecutive days, then twice per day for 22 days before posttesting. Before and after the supplementation, subjects performed a continuous incremental cycle ergometry test while a surface electromyographic signal was recorded from the vastus lateralis muscle to determine PWC(FT). The adjusted mean posttest PWC(FT) values (covaried for pretest PWC(FT) values) for the b-Ala and CrBA groups were greater than those for the PLA group (p < or = 0.05). However, there were no differences between the CrM vs. PLA, CrBA vs. b-Ala, CrM vs. b-Ala, or CrM vs. CrBA groups (p > 0.05). These findings suggested that b-Ala supplementation may delay the onset of neuromuscular fatigue. Furthermore, there appeared to be no additive or unique effects of CrM vs. b-Ala alone on PWC(FT).

Adult↗
PubMed2026

EWAS in a polyphenol dense, DNA methylation-targeted, controlled diet and lifestyle study.

BACKGROUND: Dietary and lifestyle factors can influence DNA methylation patterns. We previously reported epigenetic age attenuation following a controlled study using an 8-week polyphenol-dense, DNA methylation-targeted diet and lifestyle intervention in healthy males (Methylation Diet and Lifestyle Study), with phytonutrient/polyphenol-rich foods (green tea, oolong tea, curcumin, garlic, and berries) being most predictive of this effect. METHODS: Here we conducted an epigenome-wide association study (EWAS) in 38 participants from the Methylation Diet and Lifestyle Study. The intervention included a dietary pattern intentionally rich in substrate and cofactor nutrients for methylation pathways, and components known to alter DNA-methyltransferase (DNMT) enzyme activity. In line with prior EWAS studies with small sample sizes where FDR-significant findings are unlikely, we used pre-specified nominal P-value thresholds (0.001, 0.0001) for the exploratory analyses. RESULTS: At P < 0.001 (unadjusted), 676 differentially methylated loci (DML) were identified in the intervention group versus 286 in controls. At P < 0.0001 (unadjusted), 50 DML were identified in the intervention group compared to 13 in controls. Fifteen DML were in transcription start site-proximal regions of genes including those involved in zinc homeostasis and nutrient sensing, development and pluripotency, proteostasis and genome stability, tumor suppression, and synaptic function. A group-by-time interaction analysis identified 70 intervention-specific DML at P < 0.0001, with nominal enrichment including autophagy, mTOR signaling, and chromatin remodeling pathways. A regional DMR analysis identified 128 within-group and 129 interaction-specific DMRs. DMR functional enrichment analyses revealed convergent nominal associations with lipid metabolism (alpha-linolenic acid, lipoic acid, biosynthesis of unsaturated fatty acids, PPAR signaling, cholesterol homeostasis), central energy metabolism (TCA cycle, glycolysis/gluconeogenesis, pentose phosphate, pyruvate), and nutrient sensing (PI3K-Akt, mTOR, AMPK, autophagy as well as other pathways). As expected for the limited cohort size and short intervention duration, none of the single CpG findings or enrichment analyses survived multiple test correction and are therefore considered exploratory and hypothesis-generating only. CONCLUSION: This EWAS identified a larger number of nominally changing CpGs in the intervention group compared to controls as well as biologically coherent methylation changes. These findings provide mechanistic hypotheses for previously observed epigenetic age attenuation. Replication in larger cohorts, longer intervention durations, and functional validation remain essential.

DNA methylation↗
PubMed1986

Influence of beta-adrenergic blockade on the control of sweating in humans.

To evaluate the role of beta-adrenergic receptors in the control of human sweating, we studied six subjects during 40 min of cycle-ergometer exercise (60% maximal O2 consumption) at 22 degrees C 2 h after oral administration of placebo or nonselective beta-blockade (BB, 80 mg propranolol). Internal temperature (esophageal temperature, Tes), mean skin temperature (Tsk), local chest temperature (Tch), and local chest sweat rate (msw) were continuously recorded. The control of sweating was best described by the slope of the linear relationship between msw and Tes and the threshold Tes for the onset of sweating. The slope of the msw-Tes relationship decreased 27% (P less than 0.01), from 1.80 to 1.30 mg X cm-2 X min-1 X degree C-1 during BB. The Tes threshold for sweating (36.8 degrees C) was not altered as the result of BB. These data suggest that BB modified the control of sweating via some peripheral interaction. Since Tsk was significantly (P less than 0.05) reduced during BB exercise, from a control value of 32.8 to 32.2 degrees C, we evaluated the influence of the reduction in local skin temperature (Tsk) in the altered control of sweating. Reductions in Tch accounted for only 45% of the decrease in the slope of the msw-Tes relationship during BB. Since evaporative heat loss requirement during exercise with BB, as estimated from the energy balance equation, was also reduced 18%, compared with control exercise, we concluded that during BB the reduction in sweating at any Tes is the consequence of both a decrease in local Tsk and a direct effect on sweat gland.

Adult↗
PubMed1996

Ultrasound of the abdomen in endurance athletes.

This project evaluated, if athletes show adaption of their abdominal organs in response to endurance training. Abdominal sonography was performed in 26 sedentary male subjects [CO; age: 26 (SD 5) years; mass (BM): 78.7 (SD 10.6) kg; lean body mass [LBM): 67.1 (SD 7.4) kg; height (HE): 183 (SD 6) cm, individual anaerobic threshold (cycle ergometry; IAT): 2.1 (SD 0.1) W*kg(-1)], 14 moderately endurance trained athletes [EA1; age: 27 (SD 4) years; BM: 74.0 (SD 5.9) kg; LBM: 64.6 (SD 4.5) kg; HE: 178 (SD 5) cm, IAT: 3.0 (SD 0.5) W*kg(-1)] and 27 well endurance trained athletes [EA2; age: 27 (SD 4) years; BM: 72.1 (SD 4.3) kg; LBM: 65.4 (SD 3.2) kg; HE: 179 (SD 4) cm, IAT: 3.7 (SD 0.4) W*kg(-1)]. One subject of EA2 had cholecystolithiasis and another one renal redoublication. 3 persons showed uncomplicated parapelvine or subcapsular renal cysts (CO, EA1). The transverse area of the large abdominal arteries (abdominal aorta, common iliac arteries) was significantly greater in EA2 than in both EA1 and CO and partly greater in EA1 than in CO. Also, the ratios of sagittal and transverse diameters of the left and right lobes of the liver to LBM showed higher values for EA2 than for both EA1 and CO. These results indicate morphological adaptive processes of the great abdominal arteries in endurance athletes.

Abdomen↗
PubMed1995

Rating of perceived exertion and heart rate relative to ventilatory threshold in women.

Forty women took part in a study designed to investigate self-selected exercise intensity relative to ventilatory threshold during circuit weight training (CWT) and exercise-to-music (ETM) sessions. Subjects were assigned to one of two groups which were beginners (B) or habitual exercisers (HE) on the basis of their exercise habits. All subjects first underwent a laboratory cycle ergometer test involving a continuous incremental exercise protocol from which ventilatory threshold (VT) was determined using piecewise linear regression analysis. This point was expressed in terms of heart rate (VTHR) and rating of perceived exertion (VTRPE). These points were then compared with those determined during exercise training sessions (TRAHR and TRARPE respectively). The results showed that mean(s.d.) TRARPE (13.5(1.1) was not significantly different to mean(s.d.) VTRPE (12.8(0.5); P > 0.05) but that mean(s.d.) VTHR (134.8(13.5) beats min-1) and TRAHR (154.9(12.0) beats min-1) were different (P < 0.05). Beginners trained at a significantly higher percentage above VTHR than habitual exercisers (118(3.1) versus 111(2.8)% P < 0.05). During CWT the mean(s.d.) TRAHR for beginners (143.2(7.6) beats min-1) was significantly lower than that for habitual exercisers (152.5(10.1) beats min-1; P < 0.05), but not different during ETM (P < 0.05). When these TRAHR values were expressed relative to an estimated maximum heart rate (EMHR) they represented 86.5% in ETM and 80.5% in CWT which were different (P < 0.05). These results suggest that regardless of habitual exercise level and training mode, these women selected a common intensity of effort that was compatible with the described RPE.

Adolescent↗
PubMed2001

Physiological and performance characteristics of male professional road cyclists.

Male professional road cycling competitions last between 1 hour (e.g. the time trial in the World Championships) and 100 hours (e.g. the Tour de France). Although the final overall standings of a race are individual, it is undoubtedly a team sport. Professional road cyclists present with variable anthropometric values, but display impressive aerobic capacities [maximal power output 370 to 570 W, maximal oxygen uptake 4.4 to 6.4 L/min and power output at the onset of blood lactate accumulation (OBLA) 300 to 500 W]. Because of the variable anthropometric characteristics, 'specialists' have evolved within teams whose job is to perform in different terrain and racing conditions. In this respect, power outputs relative to mass exponents of 0.32 and 1 seem to be the best predictors of level ground and uphill cycling ability, respectively. However, time trial specialists have been shown to meet requirements to be top competitors in all terrain (level and uphill) and cycling conditions (individually and in a group). Based on competition heart rate measurements, time trials are raced under steady-state conditions, the shorter time trials being raced at average intensities close to OBLA (approximately 400 to 420 W), with the longer ones close to the individual lactate threshold (LT, approximately 370 to 390 W). Mass-start stages, on the other hand, are raced at low mean intensities (approximately 210 W for the flat stages, approximately 270 W for the high mountain stages), but are characterised by their intermittent nature, with cyclists spending on average 30 to 100 minutes at, and above LT, and 5 to 20 minutes at, and above OBLA.

Adult↗
PubMed2003

Glutaraldehyde inhalation exposure of rats: effects on lung morphology, Clara-cell protein, and hyaluronic acid levels in BAL.

Glutaraldehyde (GA) is a biocide widely used in hospital and laboratory practice. GA is a volatile substance and, under certain circumstances, significant airborne concentrations may be generated at room temperature. Occupational exposure to GA by inhalation is suspected of causing delayed irritating effects. In recent years, GA has emerged as the main cause of occupational asthma among health-care workers. The aim of the present study was to evaluate effects of GA inhalatory exposure (0.025 ppm or 0.1 ppm, for 28 days) in rats exposed corresponding to the occupational shift cycle, at time point 24 h, 48 h, and 7 days postexposure (PE). Numerous vacuoles and dilated spaces in epithelial cells in bronchioles showing a destructive effect of GA on the cellular membrane were observed at 24 h PE in 0.1 ppm exposed rats. Lipid vacuoles observed after 48 h PE in higher GA exposure, in the Clara cells of the bronchial epithelium, and in endothelial cells of the alveolar capillaries are probably attributable to disturbed lipid metabolism. Many foci of collagen fibers were observed already after 7 days postexposure. Monitoring of inflammatory response and repair was made possible by using two biomarkers: Clara-cell protein (CC16) and hyaluronic acid (HA). Our results show that the inflammatory repair response contributed to progenitor Clara cells and HA plays a role in the development of fibrotic changes in the lung of rats. Glutaraldehyde in rats causes fibrotic effects at the actual threshold limit value-time weighted average (TLV-TWA) level for GA as specified by current Polish and other national regulations.

Animals↗
PubMed2006

Changes in motor cortex excitability with stimulation of anterior thalamus in epilepsy.

BACKGROUND: Deep brain stimulation (DBS) is an effective treatment for movement disorders and pain. Recently, bilateral DBS of the anterior nucleus of thalamus (AN) was performed for the treatment of intractable epilepsy. This surgery reduced seizure frequency in an initial group of patients. However, its physiologic effects on the cortex and mechanisms of action remain poorly understood. Different classes of antiepileptic drugs (AEDs) have distinct effects on the excitatory and inhibitory circuits in the motor cortex, which can be studied noninvasively by transcranial magnetic stimulation (TMS). OBJECTIVE: To examine the effects of bilateral AN DBS on motor cortex excitability in epilepsy and compare these to the known effects of AEDs. METHODS: Cortical excitability was assessed in five medicated epilepsy patients with bilateral stimulators implanted in the anterior thalamus and nine healthy controls. Single and paired TMS were used to examine cortical inhibitory and facilitatory circuits. Electromyography was recorded from the dominant hand, and TMS was applied over the contralateral motor cortex. Patients were studied during DBS turned off (OFF condition), DBS with cycling stimulation mode (1 minute on, 5 minutes off; CYCLE), and DBS with continuous stimulation (CONTINUOUS) in random order on 3 consecutive days. RESULTS: Motor thresholds were increased in the patients regardless of DBS condition. Active short-interval intracortical inhibition (SICI) was significantly reduced in the OFF and CYCLE conditions but returned toward normal levels in the CONTINUOUS condition. Rest SICI, long interval intracortical inhibition, and silent period duration were unchanged. CONCLUSIONS: Increased short-interval intracortical inhibition with continuous deep brain stimulation (DBS) suggests that thalamic DBS might drive cortical inhibitory circuits, similar to antiepileptic drugs that enhance gamma-aminobutyric acid inhibition.

Adult↗
PubMed2000

Influence of hysteresis on joint position sense in the human knee joint.

During muscle lengthening in a movement cycle the firing rate of muscle spindles is higher than during shortening. This phenomenon, known as hysteresis, has implications for movement control. Therefore, it should have an impact on joint position sense (JPS), the subject's awareness of the static position of a joint. JPS has been tested on the human knee joint by means of an angle reproduction test. This task included the following sequences. The leg was moved passively, by means of a motor drive, from two different start positions (15 degrees and 75 degrees) to a certain target angle and, after a time of 8 s, it was returned to the start position; subjects had to reproduce the former target angle. Several target angles, mild flexion (30 degrees), intermediate flexion (45 degrees), and strong flexion (60 degrees), were used. Depending on the start position, the movements matching these targets were flexions or extensions. At least for the intermediate position different threshold values should be expected for flexions and extensions, if hysteresis has an impact. Moreover, the JPS measure should show a dependence on movement velocity and independence on distance. Of the variables tested, only movement direction but not movement velocity or distance had a statistically significant impact on the dependent constant angle error (difference between reproduction and target angle). The target angle of 30 degrees was exactly reproduced (-0.14 degrees), independently of the start position. The 45 degrees target angle was significantly underestimated (-4.39 degrees) when matching that position by flexions (starting at 15 degrees) compared to an overestimation (2.27 degrees) when matching that position by extensions (starting at 75 degrees). The target angle of 60 degrees has been constantly underestimated (-3.80 degrees), independently of the start position. Therefore, hysteresis, the dependency of the movement's direction, neglected in the past, should be considered in future tests of JPS or studies considering the role of movement parameters for motor control.

Adult↗
PubMed1994

Critical capillary oxygen partial pressure and lactate threshold in patients with cardiovascular disease.

OBJECTIVES: The aim of this study was to determine the relation between femoral vein oxygen partial pressure (PO2) and lactate increase during exercise in patients with cardiovascular disease. BACKGROUND: Considerable controversy surrounds the relation between the increase in lactate during exercise and the oxygen supply to the exercising muscles. We assumed that femoral vein PO2 would be a measure of end-capillary PO2 during leg-cycling exercise and that it would decrease to a "floor" level when the critical capillary PO2 (the PO2 below which the capillary-mitochondrial difference would be too low to allow oxygen consumption) was reached. At the critical capillary PO2, anaerobic metabolism should take place, and lactate should increase in the effluent blood. METHODS: Ten patients with cardiovascular disease performed two 6-min constant work rate tests (moderate and heavy intensity) and an incremental exercise test to the symptom-limited maximum on a cycle ergometer. Femoral vein blood was repeatedly sampled through a percutaneous catheter before and during each exercise test. RESULTS: The PO2 rapidly decreased toward a minimal value with increasing oxygen uptake for all three tests in all patients. After reaching its nadir (18.2 +/- 2.0 mm Hg), the PO2 remained unchanged in five patients but increased in the other five patients despite the further increase in work rate and oxygen uptake. The relation between PO2 and oxygen uptake was characteristic for each patient and independent of the protocol used for the study. Femoral vein lactate did not change appreciably until PO2 reached the minimal (critical) value. Thereafter, it dramatically increased without a further decrease in PO2. The minimal PO2 was positively correlated with the peak oxygen uptake (r = 0.70, p = 0.01). CONCLUSIONS: During leg-cycling exercise, muscle capillary PO2 reaches a minimal value in the midrange of the subjects' work capacity before lactate concentration increases in patients with cardiovascular disease. The lack of further decrease in PO2 at the oxygen uptake at which lactate starts to increase suggests that the minimal capillary PO2 is the "critical" capillary PO2.

Aged↗
PubMed1986

Interaction of growth-determining systems with gravity.

The experiments have been carried out with lettuce shoots on board the Salyut-7 orbital station the Kosmos-1667 biological satellite and under ground conditions at 180 degrees plant inversion. By means of the centrifuge Biogravistat-1M the threshold value of gravitational sensitivity of lettuce shoots has been determined on board the Salyut-7 station. It was found to be equal to 2.9 x 10(-3)g for hypocotyls and 1.5 x 10(-4)g for roots. The following results have been received in the experiment performed on board the Kosmos-1667 satellite: a) under microgravity the proliferation of the meristem cells and the growth of roots did not differ from the control; b) the growth of hypocotyls in length was significantly enhanced in microgravity; c) under microgravity transverse growth of hypocotyls (increase in cross sectional area) was significantly increased due to enhancement of cortical parenchyma cell growth. At 180 degrees inversion in Earth's gravity root extension growth and rate of cell division in the root apical meristem were decreased. The determination of DNA-fuchsin value in the nuclei of the cell root apexes showed that inversion affected processes of the cell cycle preceding cytokinesis.

Cell Division↗