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Biomedical subjects

Y Sara

Publications and source records attributed to Y Sara.

7 recordsLinked to original sources
PubMed2001

SNARE function analyzed in synaptobrevin/VAMP knockout mice.

SNAREs (soluble NSF-attachment protein receptors) are generally acknowledged as central components of membrane fusion reactions, but their precise function has remained enigmatic. Competing hypotheses suggest roles for SNAREs in mediating the specificity of fusion, catalyzing fusion, or actually executing fusion. We generated knockout mice lacking synaptobrevin/VAMP 2, the vesicular SNARE protein responsible for synaptic vesicle fusion in forebrain synapses, to make use of the exquisite temporal resolution of electrophysiology in measuring fusion. In the absence of synaptobrevin 2, spontaneous synaptic vesicle fusion and fusion induced by hypertonic sucrose were decreased approximately 10-fold, but fast Ca2+-triggered fusion was decreased more than 100-fold. Thus, synaptobrevin 2 may function in catalyzing fusion reactions and stabilizing fusion intermediates but is not absolutely required for synaptic fusion.

Action Potentials↗
PubMed2000

Increased intra-abdominal pressure alters the contractile properties of rabbit bladder.

OBJECTIVE: To evaluate the effects of increased intra-abdominal pressure (IAP) on the contractility of the rabbit bladder, as the dynamics of the bladder may be impaired in conditions associated with a high IAP, e.g. constipation and pregnancy. Material and methods The study comprised 22 adult male New Zealand rabbits; six served as the control group, eight had an IAP of 7 cmH2O imposed for 10 days by instilling air into the abdominal cavity and this IAP was maintained for 60 days in a further eight rabbits. After treatment, the rabbits were killed, and the bladders removed and cut into 3 x 12 mm strips. The contractile activity of the muscle strips was then recorded isometrically. Electrical field stimulation (EFS) was applied using a pair of platinum ring electrodes in trains of 3 s duration every 100 s (1 ms, 100 V, 2-100 Hz). Contractile responses to carbachol and isotonic KCl were also evaluated. RESULTS: EFS induced a frequency-dependent increase in contractile activity in all bladder strips. Ten days of high IAP resulted in an increased responsiveness to EFS, but high IAP for 60 days reduced the EFS-induced responses to the control levels. Carbachol (10-9-10-3 mol/L) elicited concentration-dependent contractions in all groups. From the concentration-response curves of carbachol, the log EC50 values (the concentration producing half the maximum effect) of the control and 60-day treated animals were comparable, at -6.24 (0.05) and -6.25 (0.04), respectively. However, the log EC50 of the 10 day-treated group was -4.97 (0.08) and significantly (P < 0.01) lower than that of both groups. Isotonic KCl produced contractions in all preparations; these contractions in the control and 60-day treated animals were similar, while the 10 day-treated group had significantly (P < 0.05) higher contraction amplitudes. CONCLUSION: Increased IAP alters the contractile properties of the bladder and its responsiveness to carbachol and KCl. As the intravesical pressure closely reflects the IAP, both should be increased in the present experimental design.

Abdomen↗
PubMed1999

Lack of carbachol response indicates the absence of cholinergic receptors in sacs associated with undescended testis.

BACKGROUND/PURPOSE: The mechanism of testicular descent remains controversial. The processus vaginalis (PV) contains smooth muscle and should have contractile activity that may contribute to descent. This study was designed to evaluate the smooth muscle of PVs associated with incomplete obliteration for spontaneous activities and responses to various stimuli, to determine if differences exist according to sex, diagnostic source, or location of the testis. MATERIALS: Peritoneal samples (n = 4); sacs from girls (n = 8) and boys with inguinal hernia (n = 12); and sacs from boys with hydrocele (n = 3), hydrocele of the cord (n = 2), or undescended testis (n = 7) were used for the current study. Tissues were attached to the isometric force displacement transducer in an organ bath containing mammalian Ringer's solution at 37 degrees C. Spontaneous mechanical activity and contractile responses of tissues to the electrical field stimulation, phenylephrine, carbachol, and serotonin were recorded. The values obtained from boys and girls with inguinal hernia and from boys with either undescended or descended testis were compared through Fisher's Exact test. RESULTS: There were no statistically significant differences in patient age between groups. Among the parameters studied, only the carbachol response of the sacs associated with undescended testis showed a significant difference compared with the others (P = .001). None of the sacs associated with undescended testis responded to carbachol, whereas all of the sacs from boys and girls with inguinal hernia responded to carbachol. CONCLUSIONS: Lack of carbachol response suggests the absence of cholinergic receptors within the sacs associated with undescended testis. The lack of cholinergic receptors may play a role in the failure of the process of testicular descent by hindering either PV elongation into the scrotum or a possible propulsive activity of the PV on the testis.

Carbachol↗
PubMed1999

The role of nitrergic system on the contractility of colonic circular smooth muscle in Hirschsprung's disease.

UNLABELLED: The contribution of nitrergic tone on the contractility of colonic smooth muscle in Hirschsprung's disease (HD) was investigated. METHODS: Ganglionic and aganglionic bowel specimens were taken from 8 patients with HD during pull-through operations and electrical field stimulation (EFS)-induced isometric contractions of the circular smooth muscle were recorded in vitro. Isolated circular muscle strips prepared from colonic segments of sex- and age-matched patients (n = 3) who underwent surgery for nonmotility-related colonic diseases formed the control group. Statistical analysis was performed by two way analysis of variance and unpaired Student's ttest. RESULTS: The amplitude of spontaneous rhythmic activity was lower in aganglionic segments than in ganglionic ones. The amplitudes of contractile responses were significantly greater in aganglionic segments. In ganglionic preparations, N(omega)-nitro-L-arginine (L-NNA) addition into the medium increased the contractile responses to the level of aganglionic preparations. This increase was completely blocked by L-arginine application. Neither L-NNA nor L-arginine produced any change in aganglionic segments. A relaxation phase was detected in both ganglionic and aganglionic segments. In ganglionic preparations, this relaxation phase was completely inhibited by L-NNA and restored by L-arginine, whereas no effect was detected in aganglionic ones. Responses obtained from the control group were similar to the ganglionic segments of HD patients. CONCLUSIONS: In normal colon and as well as in ganglionic segments of HD, the evoked contractile activity and relaxations are under the tonic influence of the nitrergic system. Aganglionic segments totally lack the nitrergic activity in both evoked contraction and relaxation responses, while still maintaining an inefficient relaxation capacity under unknown mechanisms.

Child↗
PubMed1998

Contractility and electrophysiological parameters of cremaster muscles of boys with a hernia or undescended testis.

BACKGROUND/PURPOSE: The cremaster muscle (CM) has been considered to participate in regulation of blood flow and temperature of the testis. Its contribution to testicular descent has been suggested. However, there is limited information about the CM in physiological and pathological states. Therefore, an experimental study has been conducted to evaluate and compare the contractile and electrophysiological properties of CM in boys with descended or undescended testes. METHODS: Identical CM strips were obtained from eight boys who underwent orchidopexy with a mean age of 3+/-2.2 years and from eight boys who underwent herniorrhaphy with a mean age of 4+/-1.3 years. Muscle strips of 3 x 8 mm were vertically attached to an isometric force displacement transducer, and direct muscle contractions were elicited by rectangular electrical pulses. Direct isometric muscle contractions were recorded in an organ bath containing mammalian Ringer's solution. In electrophysiological experiments, conventional microelectrode techniques were used. RESULTS: Direct electrical stimulation of CM strips obtained from patients with descended and undescended testes elicited muscle twitches and frequency-dependent contractile responses. Tetanic contractions of undescended testes at 100 Hz were 67% greater in amplitude than that of descended testes (P< .002). Muscle strips of both groups exhibited increased twitch amplitudes by 105%+/-37% when the temperature of the bathing solution was increased from 22 degrees to 37 degrees C (P< .001). The electrophysiological findings were similar. CONCLUSIONS: Contrary to other striated muscles, elevated temperature increases the contractility of CM. If the increased contractility by an increase in temperature is a property unique for CM, it should reflect the attempts at regulating testicular blood flow or temperature. The increased amplitude of contractions encountered among the CM of boys with undescended testis suggests the CM to have a role on the location of the testis.

Body Temperature↗
PubMed1992

Effects of calcium channel blockers on formalin-induced nociception and inflammation in rats.

The possible anti-inflammatory and antinociceptive effects of nitrendipine, nicardipine, diltiazem and verapamil were examined with formalin test in the rat paw. Pretreatment with these calcium channel blockers 1 h before formalin injection diminished formalin-induced inflammatory changes and nociceptive responses. Formalin-induced nociceptive responses were inhibited 20-90% by the calcium channel blockers. Nitrendipine and nicardipine were found to be highly effective in inhibiting the inflammatory changes, whereas the effects of verapamil and diltiazem were partial. Administration of naloxone affected neither the inflammatory changes and nociceptive responses induced by formalin nor the antiinflammatory and antinociceptive effects of the calcium channel blockers. The results suggest the possible anti-inflammatory and naloxone-insensitive antinociceptive properties of calcium channel blockers.

Analgesics↗