Biomedical subjects

Kazumasa Torimoto

Publications and source records attributed to Kazumasa Torimoto.

7 recordsLinked to original sources

PubMed2005

Early molecular-level changes in rat bladder wall tissue following spinal cord injury.

Previously, we demonstrated using a rat model of spinal cord injury (SCI) that bladder wall tissue compliance significantly increased within the first 2 weeks following injury. In order to explore the potential molecular-level mechanisms of this event, the present study quantified molecules pertinent to bladder tissue remodeling and changes in mechanical properties. An initial gene array analysis followed by real-time qPCR revealed that the message levels for tropoelastin and lysyl oxidase were as high as 8-fold in SCI rats compared to normal. Furthermore, both the message and protein levels of TGF-beta1 and IGF-1, known stimulators of elastin synthesis, in SCI rat bladders were significantly higher compared to those of normal rats. Taken together, it can be speculated that functional changes of the bladder associated with SCI induce release of select growth factors, which, in turn, stimulate elastogenesis that lead to alteration of biomechanical properties of the wall tissue.

Adaptation, Physiological↗

PubMed2005

alpha1-Adrenergic mechanism in diabetic urethral dysfunction in rats.

PURPOSE: We investigated the contribution of alpha1-adrenoceptor mechanisms to urethral dysfunction associated with diabetes mellitus (DM) in rats. MATERIALS AND METHODS: Eight weeks after streptozotocin injection (65 mg/kg intraperitoneally) the effects of DM on urethral relaxation mechanisms were evaluated with subjects under urethane anesthesia by simultaneous recordings of intravesical pressure in isovolumetric conditions and urethral perfusion pressure (UPP). RESULTS: In diabetic rats the intravesical pressure thresholds for inducing urethral relaxation and the lowest urethral pressure (UPP nadir) during urethral relaxation were significantly higher by 142% and 86%, respectively, than in normal rats, while baseline UPPs were not significantly different. The mean rate of high frequency oscillations of urethral striated muscle in diabetic rats was also significantly lower by 23% than in normal rats. After alpha-bungarotoxin treatment (333 mug/kg intravenously) to eliminate striated muscle sphincter contractions the SD of baseline UPPs was significantly larger by 93% than in normal rats. Intravenous administration of terazosin (0.4 mg/kg), an alpha1-adrenoceptor antagonist, significantly decreased the UPP nadir, intravesical pressure thresholds inducing urethral relaxation and the SD by 41%, 87% and 138%, respectively, in diabetic rats but not in normal rats. In the 2 groups of animals after alpha-bungarotoxin treatment urethral relaxation during a reflex bladder contraction was inhibited by Nomega-nitro-L-arginine (40 mg/kg intravenously), a nitric oxide synthase inhibitor. CONCLUSIONS: During reflex bladder contractions streptozotocin induced diabetic rats showed smooth and striated muscle dysfunctions of the urethra. The inhibition of alpha1-adrenoceptors, which decreased the UPP nadir and UPP fluctuation, may be useful for treating urethral dysfunction in DM.

Animals↗

PubMed2004

The role of bladder-to-urethral reflexes in urinary continence mechanisms in rats.

Urethral closure mechanisms during passive increments in intravesicular pressure (P(ves)) were investigated using microtip transducer catheters in urethane-anesthetized female rats. After a block of reflex bladder contractions by spinal cord transection at T8-T9, abruptly raising P(ves) to 20, 40, or 60 cmH(2)O for 2 min induced a bladder pressure-dependent contractile response in a restricted portion of the middle urethra (12.5-15 mm from the urethral orifice) that was abolished by cutting the pelvic nerves bilaterally. In pelvic nerve-intact rats, the bilateral transection of either the pudendal nerves, the nerves to the iliococcygeous/pubococcygeous muscles, or the hypogastric nerves significantly reduced (49-74%) the urethral reflex response induced by passive P(ves) increases, and combined transection of these three sets of nerves totally abolished the urethra-closing responses. In spinal cord-intact rats, similar urethral contractile responses were elicited during P(ves) elevation (20 or 40 cmH(2)O) and were also eliminated by bilateral pelvic nerve transection. After spinal cord and pelvic nerve transection, leak point pressures, defined as the pressure inducing fluid leakage from the urethral orifice during passive P(ves) elevation by either bladder pressure clamping in 2.5-cmH(2)O steps or direct compression of the bladder, were significantly lowered by 30-35% compared with sham-operated (spinal cord-transected and pelvic nerve-intact) rats. These results indicate that 1) passive elevation of P(ves) can elicit pelvic afferent nerve-mediated contractile reflexes in the restricted portion of the urethra mediated by activation of sympathetic and somatic nerves and 2) bladder-to-urethral reflexes induced by passive P(ves) elevation significantly contribute to the prevention of stress urinary incontinence.

Abdomen↗

PubMed2004

A model of intrinsic sphincteric deficiency in the rat: electrocauterization.

AIMS: Intrinsic sphincteric deficiency (ISD) denotes a malfunction of the distal urethral sphincter. Our objective was to produce a durable model of ISD in the rat. METHODS: Surrounding tissues lateral to the mid-urethra were cauterized to produce sphincteric injury in 24 adult female Sprague-Dawley rats. The rats were divided into four groups of six rats each and followed for 2, 4, 6, and 16 weeks. Sphincteric function was studied by using the vertical tilt table/intravesical pressure clamp model to measure leak point pressures (LPPs). Muscle and nerve damage were assessed with hematoxylin and eosin (H&E) and anti-protein gene product (PGP) 9.5 staining, respectively. As a control, 12 rats underwent a sham operation and subsequent LPP testing at 2, 4, 6, and 16 weeks. RESULTS: The mean LPPs of the rats 2, 4, 6, and 16 weeks after cauterization were 18.7 +/- 0.8 cm H2O, 27.6 +/- 1.6 cm H2O, 24.3 +/- 1.7 cm H2O, and 19.1 +/- 2.2 cm H2O, respectively. The mean LPPs of the rats 2, 4, 6, and 16 weeks after the sham operation were 49.8 +/- 1.3 cm H2O, 51.2 +/- 1.5 cm H2O, 51.6 +/- 2.0 cm H2O, and 49.7 +/- 0.6 cm H2O, respectively. When compared to time-matched control groups, the decreased LPPs in each cauterized group were significantly lower (P < 0.001). Histological analysis showed muscle damage and fewer nerves in all cauterized groups. CONCLUSIONS: Cauterization of tissues lateral to the mid-urethra decreased LPP without affecting bladder function. This electrocauterization model produced low LPPs that, after 2 weeks, were maintained for up to 16 weeks. Histology suggests that damage to striated muscle and nerves might have contributed to the change in LPP in this model for ISD.

Animals↗

PubMed2004

Urethral dysfunction in diabetic rats.

PURPOSE: We investigated the effects of diabetes mellitus (DM) on urethral relaxation mechanisms during reflex bladder contractions in rats. MATERIALS AND METHODS: Five weeks after streptozotocin injection (65 mg/kg intraperitoneally) the effects of DM on urethral relaxation mechanisms were evaluated by simultaneous recordings of intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) using urethane anesthesia. RESULTS: In diabetic rats the UPP nadir during urethral relaxation and intravesical pressure thresholds for inducing urethral relaxation were significantly higher (199% and 92%, respectively) than in normal rats, while baseline UPPs were not significantly different. The mean rate and amplitude of high frequency oscillations of urethral striated muscle in diabetic rats were also significantly lower (17% and 64%, respectively) compared with normal rats. Following alpha-bungarotoxin treatment to eliminate striated muscle sphincter contractions intravenous administration of L-arginine (200 mg/kg) [corrected] , the substrate of nitric oxide (NO) synthase, decreased the UPP nadir (36% and 22%, in diabetic and normal rats) as well as intravesical pressure thresholds (49% and 22%, respectively). The effect was greater (61% to 126%) in diabetic rats than in normal rats. In each group of rats the effect of L-arginine was inhibited by Nomega-nitro-L-arginine (100 mg/kg intravenously) [corrected], a NO synthase inhibitor. CONCLUSIONS: During reflex bladder contractions streptozotocin induced diabetic rats exhibited smooth and striated muscle dysfunctions of the urethral outlet. L-arginine therapy, which could augment urethral smooth muscle relaxation by increasing NO production, may be useful for partially restoring the urethral relaxation mechanism in DM.

Animals↗

PubMed2003

Urethral closure mechanisms under sneeze-induced stress condition in rats: a new animal model for evaluation of stress urinary incontinence.

The urethral closure mechanism under a stress condition induced by sneezing was investigated in urethane-anesthetized female rats. During sneezing, while the responses measured by microtip transducer catheters in the proximal and middle parts of the urethra increased, the response in the proximal urethra was almost negligible when the bladder response was subtracted from the urethral response or when the abdomen was opened. In contrast, the response in the middle urethra during sneezing was still observed after subtracting the bladder response or after opening the abdomen. These responses in the middle urethra during sneezing were significantly reduced approximately 80% by bilateral transection of the pudendal nerves and the nerves to the iliococcygeous and pubococcygeous muscles but not by transection of the visceral branches of the pelvic nerves and hypogastric nerves. The sneeze leak point pressure was also measured to investigate the role of active urethral closure mechanisms in maintaining total urethral resistance against sneeze-induced urinary incontinence. In sham-operated rats, no urinary leakage was observed during sneeze, which produced an increase of intravesical pressure up to 37 +/- 2.2 cmH2O. However, in nerve-transected rats urinary leakage was observed when the intravesical pressure during sneezing exceeded 16.3 +/- 2.1 cmH2O. These results indicate that during sneezing, pressure increases elicited by reflex contractions of external urethral sphincter and pelvic floor muscles occur in the middle portion of the urethra. These reflexes in addition to passive transmission of increased abdominal pressure significantly contribute to urinary continence mechanisms under a sneeze-induced stress condition.

Animals↗

PubMed2002

[Assessment of surgical invasiveness of augmentation ileocystoplasty applying the systemic inflammatory response syndrome score in patients with spina bifida].

PURPOSE: Applying the systemic inflammatory response syndrome (SIRS), we investigated the surgical invasiveness of augmentation ileocystoplasty in patients with spina bifida. MATERIALS AND METHODS: A total of 23 patients with spina bifida underwent augmentation ileocystoplasty. We diagnosed the cases as SIRS when they fulfilled at least 2 of the 4 SIRS criteria. We developed SIRS score, the sum of the number of positive items for the duration of SIRS, as a parameter of surgical invasiveness. We investigated the relationships between SIRS score and various factors and compared SIRS scores of augmentation with those of other urological operations as a control, which consisted of radical prostatectomy (25 patients) and radical nephrectomy (20 patients). RESULTS: We found a positive relationship between SIRS score and the operation time of augmentation. SIRS scores were significantly higher in the patients who underwent operations diverting ventriculoperitoneal shunt to ventriculoatrial shunt concurrently with augmentation. However, the operation times were not significantly different between the cases with and without shunt operations. SIRS scores in cases of augmentation were significantly higher than those of the major urological operations compared. CONCLUSION: When evaluated by the SIRS score, the factors related to the surgical invasiveness of augmentation ileocystoplasty were a longer operating time and concurrent shunt diversion. The higher invasiveness of this operation compared with major urological operations was also revealed. These facts should be considered carefully when the indications for augmentation ileocystoplasty are determined.

Adult↗