Central vagal activation by alpha(2) -adrenergic stimulation is impaired in spontaneously hypertensive rats

AIM

To elucidate the abnormality of vagal control in spontaneously hypertensive rats (SHR) by measuring left ventricular myocardial interstitial acetylcholine (ACh) release in response to α(2) -adrenergic stimulation as an index of in vivo vagal nerve activity.

METHODS

A cardiac microdialysis technique was applied to the rat left ventricle in vivo, and the effect of α(2) -adrenergic stimulation by medetomidine or electrical vagal nerve stimulation on myocardial interstitial ACh levels was examined in normotensive Wistar-Kyoto rats (WKY) and SHR under anaesthetized conditions.

RESULTS

Intravenous medetomidine (0.1 mg kg(-1) ) significantly increased the ACh levels in WKY (from 2.4 ± 0.6 to 4.2 ± 1.3 nmol L(-1) , P < 0.05, n = 7) but not in SHR (from 2.5 ± 0.7 to 2.7 ± 0.7 nmol L(-1) , n = 7). In contrast, electrical vagal nerve stimulation increased the ACh levels in both WKY (from 1.0 ± 0.4 to 2.9 ± 0.9 nmol L(-1) , P < 0.001, n = 6) and SHR (from 0.9 ± 0.2 to 2.2 ± 0.4 nmol L(-1) , P < 0.001, n = 6). Intravenous administration of medetomidine (0.1 mg kg(-1) ) did not affect the vagal nerve stimulation-induced ACh release in either WKY or SHR.

CONCLUSION

Medetomidine-induced central vagal activation was impaired in SHR, whereas peripheral vagal control of ACh release was preserved. In addition to abnormal sympathetic control, vagal control by the central nervous system may be impaired in SHR.

Maternal and preterm fetal sheep responses to dexmedetomidine

BACKGROUND

The α(2) adrenergic receptor agonist dexmedetomidine has some unique pharmacologic properties that could benefit pregnant patients (and their fetuses) when they require sedation, analgesia, and/or anesthesia during pregnancy. The purpose of the present study was to delineate maternal and fetal responses to an intravenous infusion of dexmedetomidine.

METHODS

This study was conducted on surgically-recovered preterm sheep instrumented for physiologic recording and blood sampling. Maternal and fetal cardiovascular and blood gas parameters and fetal cerebral oxygenation levels were recorded before, during, and after 3h of dexmedetomidine infusion to the ewe at a rate of 1 μg/kg/h.

RESULTS

Drug infusion produced overt sedation but no apparent respiratory depression as evidenced by stable maternal arterial blood gases; fetal blood gases were also stable. The one blood parameter to change was serum glucose, By the end of the 3-h infusion, glucose increased from 49±10 to 104±33mg/dL in the ewe and from 22±3 to 48±16mg/dL in the fetus; it declined post-drug exposure but remained elevated compared to the starting levels (maternal, 63±12mg/dL, P=0.0497; and fetal, 24±4mg/dL, P=0.012). With respect to cardiovascular status, dexmedetomidine produced a decrease in maternal blood pressure and heart rate with fluctuations in uterine blood flow but had no discernable effect on fetal heart rate or mean arterial pressure. Likewise, maternal drug infusion had no effect on fetal cerebral oxygenation, as measured by in utero near-infrared spectroscopy.

CONCLUSIONS

Using a clinically-relevant dosing regimen, intravenous infusion of dexmedetomidine produced significant maternal sedation without altering fetal physiologic status. Results from this initial acute assessment support the conduct of further studies to determine if dexmedetomidine has clinical utility for sedation and pain control during pregnancy.

Influence of ion source configuration and its operation parameters on the target sputtering and implantation process

In the work, investigation of the features and operation regimes of sputter enhanced ion-plasma source are presented. The source is based on the target sputtering with the dense plasma formed in the crossed electric and magnetic fields. It allows operation with noble or reactive gases at low pressure discharge regimes, and, the resulting ion beam is the mixture of ions from the working gas and sputtering target. Any conductive material, such as metals, alloys, or compounds, can be used as the sputtering target. Effectiveness of target sputtering process with the plasma was investigated dependently on the gun geometry, plasma parameters, and the target bias voltage. With the applied accelerating voltage from 0 to 20 kV, the source can be operated in regimes of thin film deposition, ion-beam mixing, and ion implantation. Multi-component ion beam implantation was applied to α-Fe, which leads to the surface hardness increasing from 2 GPa in the initial condition up to 3.5 GPa in case of combined N(2)-C implantation. Projected range of the implanted elements is up to 20 nm with the implantation energy 20 keV that was obtained with XPS depth profiling.

Primary intraorbital ectopic meningioma

We report a case of intraorbital meningioma. Operative findings and histopathological examination revealed the tumoc to be meningothelial meningloma and to be located entirely outside the optic dura. This case demonstrates the occurrence of primary intraorbital ectopic meningioma, and the tumor was removed through a modified Dolenc approach. The primary intraorbital ectopic meningioma is discussed and the surgical approach to the orbital apex region is reviewed.

Amyloid β inhibits ectodomain shedding of N-cadherin via down-regulation of cell-surface NMDA receptor

Dysfunction in the synapse is recognized as an early and the primary pathological process in Alzheimer's disease (AD). N-cadherin, an essential adhesion molecule for excitatory synaptic contact, forms a complex with presenilin 1 (PS1) and beta-catenin in the synaptic membrane. N-cadherin is sequentially cleaved by ADAM10 and PS1/gamma-secretase, producing a cytoplasmic fragment, N-cadherin C-terminal fragment (Ncad/CTF2) after NMDA receptor stimulation [Marambaud P, Wen PH, Dutt A, Shioi J, Takashima A, Siman R, Robakis NK (2003) A CBP binding transcriptional repressor produced by the PS1/epsilon-cleavage of N-cadherin is inhibited by PS1 FAD mutations. Cell 114:635-645; Reiss K, Maretzky T, Ludwig A, Tousseyn T, de Strooper B, Hartmann D, Saftig P (2005) ADAM10 cleavage of N-cadherin and regulation of cell-cell adhesion and beta-catenin nuclear signalling. EMBO J 24:1762]. Ncad/CTF2 translocates to the nucleus together with beta-catenin to enhance beta-catenin nuclear signaling [Uemura K, Kihara T, Kuzuya A, Okawa K, Nishimoto T, Bito H, Ninomiya H, Sugimoto H, Kinoshita A, Shimohama S (2006a) Activity-dependent regulation of beta-catenin via epsilon-cleavage of N-cadherin. Biochem Biophys Res Commun 345:951-958]. To examine whether an impairment of N-cadherin metabolism is involved in AD pathogenesis, we investigated the effect of amyloid beta peptide (Abeta) treatment on sequential N-cadherin cleavage. Here, we demonstrate that both synthetic and cell-derived Abeta species inhibit ectodomain shedding of mouse N-cadherin. Inhibition of N-cadherin cleavage by Abeta treatment was suggested to be mediated by the enhanced endocytosis of NMDA receptor, resulting in reduced turnover of N-cadherin. Since both N-cadherin and beta-catenin are essential for synaptic plasticity, impairment of N-cadherin cleavage caused by Abeta may underlie the synapse toxicity involved in AD pathogenesis.

A comprehensive physiological model of circulation enables automatic piloting of hemodynamics in patients with acute heart failure

A comprehensive physiological model of the whole circulation is mandatory to quantitatively diagnose pathophysiology and to guide an appropriate treatment. Such a model would enable automatic piloting of hemodynamics in patients with acute heart failure. By extending Guyton's model, so as to deal with heart failure predominantly affecting left heart and to quantify left atrial pressure, we constructed such a model consisting of a venous return (VR) surface and a cardiac output (CO) curve. VR surface, the integrated property of systemic and pulmonary vascular beds, relates VR and left and right atrial pressures (P(LA), P(RA)) linearly as VR = V/W - G(R)P(RA) - G(L)P(LA), given total blood volume (V). CO curve, the pumping ability of hearts, relates CO and either P(LA) or P(RA) approximately by logarithmic functions, respectively, as CO = S(L) [ln (P(LA)- B(L)) + C(L)] = S(R) [ln (P(RA) - B(R)) + C(R)]. The slopes (S(R) and S(L)) of CO curve mainly describes the pump performance. W, G(R), G(L), B(R), B(L), C(R) and C(L) are parameters. We validate the model with animal experiments. Parameters W, G's, B's and C's were relatively constant in 19 dogs. In other 8 dogs, with or without acute left heart failure, we determined V and S's from a single set of CO, P(RA), P(LA) and standard parameter values. We then predicted hemodynamics (CO, P(RA), P(LA)) for altered V from -8 to +8 ml/kg. We identified standard values of parameters as W (0.13 min), G(R) (19.6 ml/min/kg/mmHg), G(L) (3.5 ml/min/kg/mmHg). B(L) (2.1 mmHg), C(L) (1.9), B(R) (2.0 mmHg) and C(R) (0.80). Using these, we could accurately predict CO (y = 0.93x + 6.5, r2 = 0.96, Figure 2), P(RA) (y = 0.87x + 0.4, r2 = 0.91) and P(LA) (y = 0.90x + 0.48, r2 = 0.93). Our comprehensive physiological model of circulation is useful in accurately predicting hemodynamics from the measurement of a single set of CO, P(RA) and (P(LA) following blood volume changes. Therefore, this model enables continuous monitoring of blood volume and pump performance for automatic hemodynamic piloting.

Inclusion of an S-nitrosylating agent in the insufflating gas does not alter gastric activity in rats following pneumoperitoneum

BACKGROUND

We have previously shown that mixing the S-nitrosylating agent ethyl nitrite with carbon dioxide can attenuate pneumoperitoneum-induced decreases in splanchnic blood flow, but it was unclear if this agent would alter gastric function. This question was answered using rats by assessing gastric emptying and gastrointestinal transit times following gavage with radioactive chromium.

METHODS

There were five experimental groups: absolute control, anesthesia control, and carbon dioxide alone or with 100 or 300 parts per million ethyl nitrite. The period of insufflation was 1 h, and all animals were euthanized 6.5 h after chromium administration.

RESULTS

The mean amount of radioactivity remaining in the stomach ranged between 16% and 27% of the total administered; these differences were not statistically significant (p > 0.05). Modest differences in chromium distribution were identified in the gastrointestinal tract, but for all treatments, the peak amount of radioactivity was located in the distal portion. Location of the peak, expressed as a percentage of total tract length, varied between 70% and 85% (p = 0.366).

CONCLUSIONS

This study found no adverse effect of ethyl nitrite on postoperative gastric emptying or gastrointestinal transit time following pneumoperitoneum. The findings support continued assessment of the clinical utility of ethyl nitrite in the setting of laparoscopic surgery.

Sudden death of a patient with primary hypereosinophilia, colon tumours, and pulmonary emboli

A 33 year old man was admitted to hospital six days after the onset of abdominal pain. There was hypereosinophilia, but the cause could not be identified (primary hypereosinophilia). The hypereosinophilia, high C reactive protein concentration, and gastrointestinal symptoms were alleviated by corticosteroid treatment. Unexpectedly, after this apparent recovery, he was found dead on the 27th day after admission. Necropsy disclosed two solid tumours primarily composed of eosinophils in the ascending and transverse colon. The cause of the sudden death was pulmonary artery emboli, derived from a thrombus in the left iliac vein.

Magnitude of abdominal incision affects the duration of postoperative ileus in rats

BACKGROUND

The pathogenesis of reduced postoperative ileus (POI) in laparoscopic gastrointestinal (GI) surgery still remains controversial. The aim of this study was to investigate the effect of surgical incision on postoperative ileus.

METHODS

The effects of length, depth, and site of the incision on GI transit were compared using the geometric center of 51Cr in rats. The inhibitory mechanism of abdominal incision on GI transit also was studied.

RESULTS

The findings showed that 5 cm of abdominal skin and the 5-cm back muscle incision had no significant effect on GI transit. However, the 5-cm abdominal muscle-fascia incision and a 5-cm laparotomy significantly delayed GI transit. Gastrointestinal transit after a 5-cm laparotomy was significantly delayed, as compared with that of a 1-cm laparotomy regardless whether intestinal manipulation was performed or not. Guanethidine and yohimbine, but not propranolol, significantly improved the impaired GI transit after a 5-cm laparotomy.

CONCLUSIONS

The results suggest that the longer and deeper abdominal incision more profoundly inhibits GI transit. The inhibitory effect of abdominal incision is mediated via the activation of the somatosympathetic reflex and alpha-2 adrenoceptors.

Perfusion-weighted MRI of spinal dural arteriovenous fistula

A 72-year-old woman was admitted with rapidly progressive paraplegia and sphincter disturbance. T2-weighted images of the thoracic spine showed intramedullary high signal with flow voids suggesting dilated medullary veins. Conventional spinal angiography demonstrated a dural arteriovenous fistula draining into perimedullary veins. Perfusion-weighted MRI demonstrated a prolonged mean transit time and increased blood volume in the high-signal area. The loss of normal perfusion gradient and venous hypertension and were thought to produce these differences. The time-to-peak was almost identical in the high-signal and isointense areas, although the bolus of contrast medium arrived earlier in the former. Arteriovenous shunting was thought to cause faster inflow. These changes may have resulted in increased blood volume in the spinal cord. The high signal has been attributed to oedema due to venous congestion, but there has been no histological confirmation. Perfusion MRI in this case supports this hypothesis.

Physicians's reports on the impact of living wills at the end of life in Japan

CONTEXT

A growing number of Japanese people have completed advance directives, especially living wills, even though there is no legislation recognising such documents and little empirical research on their impact on clinical care at the end of life in Japan.

OBJECTIVES

To investigate physicians' attitudes about living wills and their experiences with patients who had completed a living will and later died.

DESIGN

Self administered survey and qualitative study using open question and content analysis.

SETTING

Japan.

PARTICIPANTS

Physicians known to have cared for a patient who had presented a living will prior to death.

MEASUREMENTS

The physician's response to receiving a living will, communication about the living will, the impact of the living will on clinical care, demographics, and their opinion on advance directives, especially living wills.

MAIN RESULTS

Fifty five per cent of respondents approved of advance directives in general, and 34% had more opportunities to communicate with a patient and his/her family after receiving the living will. Sixty nine per cent of the physicians who received a living will did not, however, change their course of therapy as a consequence of receiving the living wills. Based on the analysis, we identified three areas of concern in the comments on living wills: (1) concerns relative to patients, physicians, and families; (2) social context, and (3) clinical and administrative concerns. The physicians raised various topics for discussion; they tended to describe the issues from a clinical perspective.

CONCLUSIONS

Our identified areas of concern should prove helpful in better understanding the clinical and ethical implications of living wills in Japan.

Rise in plasma leptin levels after stimulation of hypothalamic cholinoceptive neurons by neostigmine in rats

To investigate the role of hypothalamic cholinergic neurons in the regulation of plasma leptin levels, we injected neostigmine, a cholinesterase inhibitor, or vehicle alone into the third cerebral ventricle in free moving male Wistar rats and then measured plasma leptin levels. The administration of neostigmine (5 x 10(-9) or 5 x 10(-8) mol) increased plasma leptin levels 3-6 h after stimulation in a dose-dependent manner, while intravenous injection of neostigmine (5 x 10(-8) mol) had no effect. Atropine (5 x 10(-8) mol) concomitantly injected with neostigmine (5 x 10(-8) mol) prevented neostigmine-induced increase in plasma leptin. The expression of leptin messenger ribonucleic acid (mRNA) in epididymal white adipose tissue was significantly increased at 4 and 6 h after neostigmine injection compared with that before the injection. Plasma levels of corticosterone were significantly increased at 30 min after stimulation with neostigmine and this increase was sustained for 6 h after stimulation. Furthermore, bilateral adrenalectomized rats showed no increase in plasma leptin levels after stimulation. In conclusion, stimulation of hypothalamic cholinoceptive neurons increased plasma leptin levels in rats by increasing leptin production in adipocytes. This increase may be due to an increase in glucocorticoids from the adrenal glands. These results suggest that plasma leptin levels can be regulated by hypothalamic cholinoceptive neurons.

Noninvolvement of hypertriglyceridemia and hyperleptinemia in blood pressure increases induced by dietary lard in rats

We investigated whether hypertriglyceridemia and hyperleptinemia are involved in the development of increases in blood pressure induced by dietary lard. Rats received either chow alone or chow in which 50% of the energy content was from substituted lard. Each group was divided into two groups according to whether the diet included bezafibrate or not. In another series of experiments, rats were fed either chow alone or chow in which 50% of the energy content was from substituted lard, safflower oil, or sucrose. Systolic blood pressure (SBP) was measured every week during each 7-week feeding period. A steady-state plasma glucose method was used to determine insulin sensitivity after lard substitution with or without bezafibrate. After the 7-week feeding period, the plasma levels of glucose, immunoreactive insulin, triglyceride and leptin were measured. In rats fed with a high lard diet, SBP, plasma levels of immunoreactive insulin, triglyceride, leptin and steady-state plasma glucose concentrations significantly increased, compared with levels of these substances in controls. Bezafibrate treatment completely reversed these effects. In rats fed with a high safflower oil or a high sucrose diet, no significant change was seen in SBP and plasma immunoreactive insulin levels. However, the plasma triglyceride levels were increased by dietary lard or sucrose. Moreover, the plasma leptin level was also increased by dietary lard and safflower oil. Neither dietary hypertriglyceridemia nor hyperleptinemia were involved in the development of increases in blood pressure induced by dietary lard.