Perception of and adaptation to rectal isobaric distension in patients with faecal incontinence. (49/6480)

BACKGROUND: Perception of, and adaptation of the rectum to, distension probably play an important role in the maintenance of continence, but perception studies in faecal incontinence provide controversial conclusions possibly related to methodological biases. In order to better understand perception disorders, the aim of this study was to analyse anorectal adaptation to rectal isobaric distension in subjects with incontinence. PATIENTS/METHODS: Between June 95 and December 97, 97 consecutive patients (nine men and 88 women, mean (SEM) age 55 (1) years) suffering from incontinence were evaluated and compared with 15 healthy volunteers (four men and 11 women, mean age 48 (3) years). The patients were classified into three groups according to their perception status to rectal isobaric distensions (impaired, 22; normal, 61; enhanced, 14). Anal and rectal adaptations to increasing rectal pressure were analysed using a model of rectal isobaric distension. RESULTS: The four groups did not differ with respect to age, parity, or sex ratio. Magnitude of incontinence, prevalence of pelvic disorders, and sphincter defects were similar in the incontinent groups. When compared with healthy controls, anal pressure and rectal adaptation to distension were decreased in incontinent patients. When compared with incontinent patients with normal perception, patients with enhanced perception experienced similar rectal adaptation but had reduced anal pressure. In contrast, patients with impaired perception showed considerably decreased rectal adaptation but had similar anal pressure. CONCLUSION: Abnormal sensations during rectal distension are observed in one third of subjects suffering from incontinence. These abnormalities may reflect hyperreactivity or neuropathological damage of the rectal wall.  (+info)

Effects of physical and sporting activities on balance control in elderly people. (50/6480)

OBJECTIVE: Balance disorders increase with aging and raise the risk of accidental falls in the elderly. It has been suggested that the practice of physical and sporting activities (PSA) efficiently counteracts these age related disorders, reducing the risk of falling significantly. METHODS: This study, principally based on a period during which the subjects were engaged in PSA, included 65 healthy subjects, aged over 60, who were living at home. Three series of posturographic tests (static, dynamic with a single and fast upward tilt, and dynamic with slow sinusoidal oscillations) analysing the centre of foot pressure displacements or electromyographic responses were conducted to determine the effects of PSA practice on balance control. RESULTS: The major variables of postural control were best in subjects who had always practised PSA (AA group). Those who did not take part in PSA at all (II group) had the worst postural performances, whatever the test. Subjects having lately begun PSA practice (IA group) had good postural performances, close to those of the AA group, whereas the subjects who had stopped the practice of PSA at an early age (AI group) did not perform as well. Overall, the postural control in the group studied decreased in the order AA > IA > AI > II. CONCLUSIONS: The period during which PSA are practised seems to be of major importance, having a positive bearing on postural control. It seems that recent periods of practice have greater beneficial effects on the subject's postural stability than PSA practice only at an early age. These data are compatible with the fact that PSA are extremely useful for elderly people even if it has not been a lifelong habit.  (+info)

Effects of high pressure and temperature on the wild-type and F29W mutant forms of the N-domain of avian troponin C. (51/6480)

The N-domain of troponin C (residues 1-90) regulates muscle contraction through conformational changes induced by Ca2+ binding. A mutant form of the isolated domain of avian troponin C (F29W) has been used in previous studies to observe conformational changes that occur upon Ca2+ binding, and pressure and temperature changes. Here we set out to determine whether the point mutation itself has any effects on the protein structure and its stability to pressure and temperature in the absence of Ca2+. Molecular dynamics simulations of the wild-type and mutant protein structures suggested that both structures are identical except in the main chain and the loop I region near the mutation site. Also, the simulations proposed that an additional cavity had been created in the core of the mutant protein. To determine whether such a cavity would affect the behavior of the protein when subjected to high pressures and temperatures, we performed 1H-NMR experiments at 300, 400, and 500 MHz on the wild-type and F29W mutant forms of the chicken N-domain troponin C in the absence of Ca2+. We found that the mutant protein at 5 kbar pressures had a destabilized beta-sheet between the Ca2+-binding loops, an altered environment near Phe-26, and reduced local motions of Phe-26 and Phe-75 in the core of the protein, probably due to a higher compressibility of the mutant. Under the same pressure conditions, the wild-type domain exhibited little change. Furthermore, the hydrophobic core of the mutant protein denatured at temperatures above 47 degrees C, while the wild-type was resistant to denaturation up to 56 degrees C. This suggests that the partially exposed surface mutation (F29W) significantly destabilizes the N-domain of troponin C by altering the packing and dynamics of the hydrophobic core.  (+info)

A physiological comparison of flutter valve drainage bags and underwater seal systems for postoperative air leaks. (52/6480)

BACKGROUND: A study was undertaken to compare the relative physiological effects of underwater seal (UWS) versus flutter valve (FV) pleural drainage systems in the treatment of postoperative air leaks. METHOD: Fourteen patients with air leaks of 1-11 days duration, following lobectomy (n = 5), bullectomy (n = 4), decortication (n = 4), and pleural biopsy (n = 1) were analysed. Intrapleural pressure (IPP) measurements were made using an in-line external strain gauge connected directly to the intercostal tube. Patients were connected simultaneously to both UWS and FV drainage systems and pressures were measured sequentially, isolating each system in turn. Maximum (IPPmax) and minimum (IPPmin) intrapleural pressures were calculated from graphic traces. The degree of lung expansion was recorded by chest radiography. RESULTS: At resting tidal volume IPPmax was significantly higher with the UWS system (mean difference 0.8 mm Hg, 95% CI 0 to 1.6, p = 0.046) and IPPmin was significantly lower with the FV system (1.8 mm Hg, 95% CI 0.3 to 3.3, p = 0.023). The lung was fully expanded in 50% of patients at the time of study. The mean difference in IPPmin between systems was significantly increased when the lung was fully expanded (mean 2.8 mm Hg, 95% CI 0.1 to 5.5, p = 0.042). The mean difference in IPPmax was not affected by the degree of lung expansion (0.79, 95% CI -0.83 to 2.4, p = 0.31). CONCLUSION: The results of this study suggest that, when postoperative air leak exists without a persistent pleural space, the flutter valve may provide a physiologically more effective alternative to the underwater seal drainage system.  (+info)

Interaction of the GM2-activator protein with phospholipid-ganglioside bilayer membranes and with monolayers at the air-water interface. (53/6480)

Differential scanning calorimetry (DSC) and film balance measurements were performed to study the interactions of the GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta1-->4Glc1 -->1'Cer (GM2)-activator protein with phospholipid/ganglioside vesicles and monolayers. The nonglycosylated form of the GM2-activator protein, added to unilamellar lipid vesicles of different composition, causes differential effects on the gel to liquid-crystalline phase transition peaks. The phase transition temperature (Tm) of pure dimyristoylglycerophosphocholine (DMPC) bilayer is slightly decreased. When lipids which specifically bind the GM2-activator protein are incorporated into the vesicles (e.g. a sulfatide or gangliosides) a shoulder in the thermograms at higher temperatures is observed, indicating an increase of the stability of the gel phase in relation to the liquid-crystalline phase. We also studied the surface activity of a glycosylated and a nonglycosylated GM2-activator protein at the air-water interface. The glycosylated form showed a slightly lower surface activity than the GM2-activator protein without oligosaccharide moiety. When the GM2-activator protein is added to the sub-phase of a surface covered with a lipid monolayer, it can only insert into the monolayer and reach the air-water interface below a monolayer pressure of 25 mN.m-1, depending on the lipid composition, and not when the monolayers are at the bilayer equivalence pressure of 30-35 mN.m-1. Particularly for Galbeta1-->3GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta 1-->4Glc1-->1'Cer (GM1) and GM2 containing films, the critical pressures (picrit) when no additional increase in surface pressure is observed after addition of the protein into the subphase, are much lower. This leads to the conclusion that binding of the GM2 activator protein to the ganglioside headgroups prevents the protein from reaching the air-water interface. The protein is then located preferentially at the lipid-water interface and cannot penetrate into the chain region.  (+info)

Effects of intermittently applied cyclic loading on proteoglycan metabolism and swelling behaviour of articular cartilage explants. (54/6480)

OBJECTIVE: The aim of this study was to evaluate the effect of tissue load, frequency and load duration on the biosynthesis and release of proteoglycans (PGs) as well as on the swelling behaviour of cultured mature bovine articular cartilage superimposed with intermittent loads. METHODS: Cyclic compressive pressure was introduced for 1, 3 or 6 days using a sinusoidal waveform of 0.5 Hz-frequency with a peak stress of 0.1, 0.5 or 1.0 MPa. The loads were applied for a period of 10 seconds (s) followed by a load-free period of 10, 100 or 1000 s. The incorporation of [35S]-SO4 into glycosaminoglycans (GAGs) during the final 18 h, the content of GAGs and DNA as well as the deformation of loaded explants were determined. RESULTS: The PG synthesis is sensitive to changes in the loading conditions applied, whereas the release of newly synthesized PG is not. A maximum PG synthesis is observed at day 3, and under load-free intervals of 100 s. After 6 days of loading the release of endogenous PGs is significantly elevated, the viability of superficial chondrocytes decreased, and cartilage swelling is observed. CONCLUSIONS: Considering numerous reports of elevated PG levels synthesized as well as released from human and experimental osteoarthritic cartilage, our results implicate that degenerative processes can also be mimicked by applying well-defined mechanical conditions as described here.  (+info)

Inhibition of inspiratory motor output by high-frequency low-pressure oscillations in the upper airway of sleeping dogs. (55/6480)

1. We utilized a chronically tracheostomized, unanaesthetized dog model to study the reflex effects on inspiratory motor output of low-amplitude, high-frequency pressure oscillations (HFPOs) applied to the isolated upper airway (UA) during stable non-rapid eye movement (NREM) sleep. 2. HFPOs (30 Hz and +/-2 to +/-4 cmH2O) were applied via a piston pump during eupnoea, inspiratory resistive loading and tracheal occlusion. 3. When applied to the patent UA during expiration, and especially during late expiration, HFPOs prolonged expiratory time (TE) and tonically activated the genioglossus muscle EMG. When applied to the patent UA during inspiration, HFPOs caused tonic activation of the genioglossus muscle EMG and inhibition of inspiratory motor output by either: (a) a shortening of inspiratory time (TI), as inspiration was terminated coincident with the onset of HFPOs; or (b) a prolonged TI accompanied by a decreased rate of rise of diaphragm EMG and rate of fall of tracheal pressure. These effects of HFPOs were observed during eupnoea and inspiratory resistive loading, but were maximal during tracheal occlusion where the additional inhibitory effects of lung inflation reflexes were minimized. 4. During eupnoea, topical anaesthesia of the UA abolished the HFPO-induced prolongation of TE, suggesting that the response was mediated primarily by mechanoreceptors close to the mucosal surface; whereas the TE-prolonging effects of a sustained square wave of negative pressure (range, -4.0 to -14.9 cmH2O) sufficient to close the airway were preserved following anaesthesia. 5. These results demonstrate that high-frequency, low-amplitude oscillatory pressure waves in the UA, similar to those found in snoring, produce reflex inhibition of inspiratory motor output. This reflex may help maintain UA patency by decreasing the collapsing pressure generated by the inspiratory pump muscles and transmitted to the UA.  (+info)

The renal lesions that develop in neonatal mice during angiotensin inhibition mimic obstructive nephropathy. (56/6480)

BACKGROUND: Inhibition of angiotensin action, pharmacologically or genetically, during the neonatal period leads to renal anomalies involving hypoplastic papilla and dilated calyx. Recently, we documented that angiotensinogen (Agt -/-) or angiotensin type 1 receptor nullizygotes (Agtr1 -/-) do not develop renal pelvis nor ureteral peristaltic movement, both of which are essential for isolating the kidney from the high downstream ureteral pressure. We therefore examined whether these renal anomalies could be characterized as "obstructive" nephropathy. METHODS: Agtr1 -/- neonatal mice were compared with wild-type neonates, the latter subjected to surgical complete unilateral ureteral ligation (UUO), by analyzing morphometrical, immunohistochemical, and molecular indices. Agtr1 -/- mice were also subjected to a complete UUO and were compared with wild-type UUO mice by quantitative analysis. To assess the function of the urinary tract, baseline pelvic and ureteral pressures were measured. RESULTS: The structural anomalies were qualitatively indistinguishable between the Agtr1 -/- without surgical obstruction versus the wild type with complete UUO. Thus, in both kidneys, the calyx was enlarged, whereas the papilla was atrophic; tubulointerstitial cells underwent proliferation and also apoptosis. Both were also characterized by interstitial macrophage infiltration and fibrosis, and within the local lesion, transforming growth factor-beta 1, platelet-derived growth factor-A and insulin-like growth factor-1 were up-regulated, whereas epidermal growth factor was down-regulated. Moreover, quantitative differences that exist between mutant kidneys without surgical obstruction and wild-type kidneys with surgical UUO were abolished when both underwent the same complete surgical UUO. The hydraulic baseline pressure was always lower in the pelvis than that in the ureter in the wild type, whereas this pressure gradient was reversed in the mutant. CONCLUSION: The abnormal kidney structure that develops in neonates during angiotensin inhibition is attributed largely to "functional obstruction" of the urinary tract caused by the defective development of peristaltic machinery.  (+info)