Propofol anaesthesia in mice is potentiated by muscimol and reversed by bicuculline

We have examined the role of gamma-aminobutyric acid (GABA) neurones in propofol anaesthesia in mice using the righting reflex. Propofol i.p. increased the percentage of loss of the righting reflex in a dose-dependent manner with an ED50 value of 140 (95% confidence limits 123-160) mg kg-1 (n = 40; eight animals per dose, five doses per dose-response curve). The ED50 for propofol decreased significantly to 66 (58-75) mg kg-1 in the presence of the GABAA receptor agonist muscimol 1 mg kg-1 i.p. (n = 40) (P < 0.05). In contrast, the ED50 increased significantly to 240 (211-274) mg kg-1 in the presence of the antagonist bicuculline 5 mg kg-1 i.p. (n = 40) (P < 0.05). Our results suggest that propofol anaesthesia may be mediated, at least in part by GABA neurons.

Preliminary study on the new self-closing mechanical mitral valve

Anatural mitral valve starts closing before systole. Conventional mechanical mitral valves start their closing motion after systole. In order to let the mechanical mitral valves start closing before systole, we propose a new self-closing valve by adjusting the center of gravity of the leaflet. As a first step, we adjusted the center of gravity by attaching a block of lead to the leaflet of a CarboMedics bileaflet valve and evaluated it using a pulse duplicator and an x-ray high-speed video camera. Comparative study was conducted under 60 bpm and 4 L/min as the mean flow rate. It was clarified that the self-closing valve started closing before systole, no influence on inflow volume was found, the final closing speed of the self-closing valve just before complete closure was slower than the conventional valve (1.9-0.34 m/s), a design strategy of a self-closing valve (sewing ring diameter 29 mm) was obtained from the experiment that momentum of inertia of the leaflet should be less than 14.9 x 10-9 kg.m2 and the torque caused by gravity should be more than 4.2 x 10-6 N. m, and only one leaflet should be designed as self-closing, and surgeons need to pay attention to the positioning of the two leaflets. In conclusion, the preliminary study showed the ability of starting to close before systole and the design strategy for future prototyping.

Experimental study on hemolysis in centrifugal blood pumps: improvement of flow visualization method

To evaluate rotary blood pumps, flow visualization is commonly applied to determine the flow patterns in a centrifugal blood pump, which have a relationship to its hemolytic performance. However, it is very troublesome to visualize the flow near the vanes due to the high rotational speed of the impeller. The rotational speed of the impeller in a centrifugal blood pump is usually several hundred revolutions per minute. In this study, we combined a high-speed video camera based imaging method and an optical system in which the image of the rotating impeller was kept stationary. In the optical system, a prism rotating at half the speed of the impeller reflected the image of the impeller. The resultant reflected image was observed by a high-speed video camera through a half mirror. With this optical setup, the image through the half mirror became stationary, and the path of a specific tracer particle could be traced for a longer duration. A longer duration of measurements and better quality of the obtained images were realized through this improvement. Movement of a specific tracer from the inlet portion to the outlet portion of the impeller could be examined using the developed method.

Hapten-induced colitis is associated with colonic patch hypertrophy and T helper cell 2-type responses

To investigate the potential involvement of T helper (Th)2-type responses in murine models of intestinal inflammation, we used trinitrobenzene sulfonic acid (TNBS)-hapten to induce inflammatory bowel disease in situations where Th1-type responses with interferon (IFN)-gamma synthesis are either diminished or do not occur. Intracolonic administration of TNBS to either normal (IFN-gamma+/+) or Th1-deficient IFN-gamma knockout (IFN-gamma-/-) BALB/c mice resulted in significant colitis. In IFN-gamma-/- mice, crypt inflammation was more severe than in IFN-gamma+/+ mice and was accompanied by hypertrophy of colonic patches with a lymphoepithelium containing M cells and distinct B and T cell zones resembling Peyer's patches. Hapten-specific, colonic patch T cells from both mouse groups exhibited a Th2 phenotype with interleukin (IL)-4 and IL-5 production. TNBS colitis in normal mice treated with anti-IL-4 antibodies or in IL-4(-/-) mice was less severe than in either IFN-gamma+/+ or IFN-gamma-/- mice. Our findings now show that the Th2-type responses in TNBS colitis are associated with colonic patch enlargement and inflammation of the mucosal layer and may represent a model for ulcerative colitis.

Dominant negative isoform of rat norepinephrine transporter produced by alternative RNA splicing

We have cloned from rat brain a family of alternatively spliced cDNAs from a single gene, which encodes a norepinephrine transporter (NET) having variations at the 3'-region including both coding and noncoding regions. This produces two transporter isoforms, rNETa and rNETb, which differ at their COOH termini. The rNETa isoform reveals a COOH terminus homologous to human NET and transports norepinephrine. In contrast, rNETb revealed no detectable transport function but reduced functional expression of rNETa when both isoforms were expressed in the same cell. Thus, rNETb potentially functions as a dominant negative inhibitor of rNETa activity. Co-expression of rNETb with a gamma-aminobutyric acid transporter (rGAT1), a serotonin transporter (rSERT), and a dopamine transporter (rDAT) reduced their transport activity. No reduction was found with the glutamate/aspartate transporter (rGLAST). Alternative RNA splicing of NET suggests a novel mechanism for the regulation of synaptic transmission.

[Prospect of computer aided surgery]

To develop the new surgical fields of minimally invasive surgery, noninvasive surgery, virtual reality microsurgery, telesurgery, fetal surgery and others in the next century, it is necessary to use various advanced technologies; surgical robots, three-dimensional medical images etc. based on computer technology. Therefore, this new surgical field is called Computer Aided Surgery (CAS). Three-dimensional medical images provide the most recognizable information for medical doctors and the most advanced visualization for surgeons. Surgical robots function as advanced hands for surgeons, but do not perform the same actions as surgeons wielding scissors or scalpel. The advanced vision and hands available to surgeons are creating a new surgical environment. The philosophy behind the development of surgical robots is to assist surgeons in difficult procedures and extend the greatest possible help to patients with incurable disease.

Phospholipid turnover in the inflamed intestinal mucosa: arachidonic acid-rich phosphatidyl/plasmenyl-ethanolamine in the mucosa in inflammatory bowel disease

Cytosolic phospholipase A2 (PLase A2) is activated by low Ca2+ concentrations and translocates from the cytosol to the cell membrane, releasing arachidonic acid; the arachidonic acid cascade then leads to the production of many inflammatory mediators. The aim of this study, accordingly, was to investigate the role of phospholipid metabolism in the intestinal mucosa in inflammatory bowel disease (IBD). Surgically resected specimens from patients with Crohn's disease (CD), ulcerative colitis (UC), and colrectal cancer (non-cancerous tissue; as a control) were submitted to phospholipid analysis and a PLase A2 assay, which measures the degradation of endogenous mucosal phospholipids. A high percentage of plasmenylethanolamine (plas.E) was detected in the glycerophospholipid fraction of CD mucosa. The arachidonic acid content of the phosphatidylethanolamine plus plas.E subfraction was higher in inflamed than in intact mucosa in CD. PLaseA2 activity, resulting in lysophosphatidyl ethanolamine production, was detected only in inflamed mucosa from CD and UC patients, but not in normal mucosa from controls. PLaseA2 activity was highest in moderately inflamed mucosa adjacent to a severely ulcerated area. The PLaseA2 that reacts with endogenous phosphatidylcholine (PC) to form lysoPC was found irrespective of the presence of inflammation. The PLaseA2 that reacts with ethanolamine-containing phospholipids is more closely related to inflammation than other PLaseA2 isoenzymes in IBD mucosa.

Molecular cloning and characterization of rat trp homologues from brain

Identification of trp (transient receptor potential) gene from Drosophila photoreceptor and subsequent molecular cloning of the human cDNA homologues suggest its participation in capacitative calcium entry (CCE) or so called store-operated Ca2+ channel (SOC). We identified five different trp-related amplifications of reverse-transcription-polymerase chain reaction (RT-PCR) from rat brain; these corresponded to mouse trp homologues, mtrp1,3,4,5,6 and were distributed in various tissues with multiple expression levels. Two cDNAs, homologous to Drosophila trp from rat brain, designated rtrp3 and rtrp6, were isolated and characterized. By RT-PCR analysis, mRNAs of rtrp3 and rtrp6 were found to be expressed differently in brain and other tissues. In situ hybridization analysis revealed that rtrp6 mRNA was preferentially expressed in hippocampal dentate gyrus and cortical layers II and III. Expression of rat TRP3 and TRP6 in COS cells revealed an increase in CCE, as compared to that in the mock-transfected COS cells of the control. Isolation of cDNAs of rat trp gene family provides a useful model for studying mechanism of CCE.

Cyclic ADP-ribose induces Ca2+ release from caffeine-insensitive Ca2+ pools in canine salivary gland cells

Cyclic ADP-ribose (cADPR), a novel putative messenger of the ryanodine receptor, was examined regarding its ability to mobilize Ca2+ from intracellular Ca2+ stores in isolated cells of parotid and submandibular glands of the dog. cADPR induced a rapid and transient Ca2+ release in the digitonin-permeabilized cells of salivary glands. cADPR-induced Ca2+ release was inhibited by ryanodine receptor antagonists ruthenium red, ryanodine, benzocaine, and imperatoxin inhibitor but not by the inositol 1,4,5-trisphosphate (IP3)-receptor antagonist heparin. Thapsigargin, at a concentration of 3 to 30 microM, inhibited IP3-induced Ca2+ release, while higher concentrations were required to inhibit cADPR-induced Ca2+ release. Cross-potentiation was observed between cADPR and ryanodine or SrCl2, suggesting that cADPR sensitizes the Ca2+-induced Ca2+ release mechanism. Cyclic AMP plays a stimulatory role on cADPR- and IP3-induced Ca2+ release in digitonin-permeabilized cells. Calmodulin also potentiated cADPR-induced Ca2+ release, but inhibited IP3-induced Ca2+ release. Acetylcholine and ryanodine caused the rise in intracellular free Ca2+ concentration ([Ca2+]i) in intact submandibular and parotid cells. Caffeine did not produce any increase in Ca2+ release or [Ca2+]i rise in any preparation. ADP-ribosyl cyclase activity was found in the centrifuged particulate fractions of the salivary glands. These results suggest that cADPR serves as an endogenous modulator of Ca2+ release from Ca2+ pools through a caffeine-insensitive ryanodine receptor channel, which are different from IP3-sensitive pools in canine salivary gland cells. This system is positively regulated by cyclic AMP and calmodulin.

MPP+ toxicity and plasma membrane dopamine transporter: study using cell lines expressing the wild-type and mutant rat dopamine transporters

The Parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium (MPP+) causes specific cell death in dopaminergic neurons after accumulation by the dopamine transporter (DAT). COS cells, a non-neuronal cell line insensitive to high doses of MPP+, becomes sensitive to MPP+ when transfected with the rat DAT cDNA. We analyzed the bi-directional transport of MPP+ and its toxicity in several cell lines expressing wild or mutant DATs. Cell death in COS cells expressing wild DAT by exposure to MPP+ was concentration-dependent and cocaine-reversible. Increased wild DAT expression caused higher sensitivities to the toxin in HeLa cells. Although several mutant DATs demonstrated greater transport activity than the wild-type, they displayed similar or lower sensitivity to MPP+ toxicity. Reverse transport of preloaded [3H]MPP+ through DAT was facilitated in COS cells expressing certain mutant DATs, which consistently displayed less sensitivity to MPP+ toxicity. These results suggest that re-distribution of MPP+ due to influx/efflux turnover through the transporter is a key factor in MPP+ toxicity.

Volumegraph (overlaid three-dimensional image-guided navigation). Clinical application of augmented reality in neurosurgery

OBJECTIVE

We have developed an overlaid three-dimensional image (Volumegraph)-guided navigation system that allows navigation during operative procedures. The three-dimensional image is superimposed on the patient's head and body via a semi-transparent mirror. The Volumegraph can display three-dimensional images in the air by a light beam which is based on CT/MRI.

METHOD

The system consists of a Volumegraph (thin plate of three-dimensional recorded medium), a Volumegraphscope and an original designed triangular-shaped marker system for registration. The three-dimensional data obtained from CT and MRI before the operation were processed by a computer. Such image data are applied for preoperative investigation to recognize the three-dimensional structure of organs and tumor. These reconstructed three-dimensional images were superimposed and registered at the patient's head according to a fiducial marker (registration). Then the operator can operate with this three-dimensional-image-guided navigation system.

RESULTS

Based on clinical application in 7 cases, the system was found to be advantageous because the surgical procedures could be navigated easily by augmented reality in the surgical field. Invisible parts of the surgical field were supplemented with the overlaid three-dimensional images (Volumegraph) as if it were the virtual operative field. At another time, spatial positioning and overlaid visualization by the Volumegraph was useful for identifying anatomical structures and functional location in the image.

CONCLUSION

This preliminary study of overlaid three-dimensional-image-guided navigation demonstrated its clinical usefulness. The application of augmented reality in the surgical field makes it possible to do a neurosurgical intervention easily and accurately.

[Evaluation of the cystic duct and cysticohepatic junction with MR cholangiography: comparison of various techniques and clinical evaluation with respiratory-triggered three-dimensional multislab technique]

The purpose of this study was to evaluate depiction of the cystic duct and cysticohepatic junction by MR cholangiography (MRC). In 10 volunteers, MR cholangiograms were obtained by breath-hold two-dimensional (2D), respiratory-triggered 2D, respiratory-triggered three-dimensional (3D) single slab, and 3D multislab techniques. The images then were compared qualitatively. MRC using the respiratory-triggered 3D multislab techniques was evaluated as better than the other techniques, and was performed in 35 patients. Depiction of the anatomy of the cystic duct and cysticohepatic junction were evaluated. In 8 of 35 patients, MRC images were compared with those obtained by endoscopic retrograde cholangiography (ERC). The cystic duct and cysticohepatic junction were visualized adequately in 93% of volunteers and patients by the respiratory-triggered 3D multislab technique. Anatomic variations in the cystic duct and cysticohepatic junction were evaluated. The frequency of anatomic variations was the same as previously reported. The anatomic evaluations obtained by MRC were correlated closely with those obtained by ERC in 8 patients. In conclusion, MRC with the respiratory-triggered 3D multislab techniques is useful in evaluation of the cystic duct and cysticohepatic junction.

Management of the pancreatic metastases from renal cell carcinoma: report of four resected cases

The pancreas is an uncommon site for metastasis from renal cell carcinoma. In most cases, pancreatic metastases occur as part of widespread nodal and visceral involvement, and there is thus evidence of metastatic disease elsewhere in the body. We present 4 cases with resectable pancreatic metastases arising from renal cell tumors without involvement of the regional lymph nodes at the operation. Three cases out of 4 were asymptomatic and the pancreatic metastases were detected by routine follow-up examination of renal cell carcinoma. Aggressive surgical treatment for the solitary metastatic lesion is advocated. Spread of renal cell carcinoma to the pancreas is, however, via the hematogenous route, and even solitary pancreatic metastasis may be one of the manifestations of the systemic metastasis of renal cell carcinoma. No pancreatic regional lymph nodes metastases were noted. Pancreatectomy should be undertaken to remove the tumor with adequate resection margins while preserving as much of the gland as possible. The prognosis of pancreatic metastases arising from a renal cell carcinoma is discussed with a review of the literature. Adjuvant chemo- and endocrine therapy should also be considered in these cases.

[Dysregulation of mucosal immunity and inflammatory bowel diseases]

Normal mucosal immunity is regulated in a delicate balance between up- and down-regulatory responses to dietal or bacterial antigens. Recent studies demonstrated that pathogenesis of inflammatory bowel disease could be dysregulation of the balance of mucosal immunity. Recent advances in animal models of inflammatory bowel disease, pathogenic roles of mucosal immunoregulatory T cells, cytokines and intestinal flora are reviewed.

Tyrosine-533 of rat dopamine transporter: involvement in interactions with 1-methyl-4-phenylpyridinium and cocaine

To improve our understanding of structure-function relationships for neurotransmitter transporters, we performed site-directed mutagenesis of the rat dopamine transporter (DAT) and assessed the functions of the mutants in transiently-expressing COS cells. Tyrosine-533 of rat DAT lies in the 11th transmembrane region, where the corresponding amino acid of human DAT is phenylalanine. Alanine substitution of tyrosine-533 (Y533A) conferred an increased affinity for 1-methyl-4-phenylpyridinium (MPP+). Phenylalanine substitution of tyrosine-533 (Y533F) increased the velocity of MPP+ uptake but decreased DAT's affinity for MPP+. Cocaine's potency in inhibiting dopamine uptake was unchanged with Y533A, but increased with Y533F. Differences in the uptake kinetics and inhibitory potency of cocaine between rat and human DATs were similar to the differences observed between the wild-type and Y533F mutants DATs. Tyrosine-533 may be important for the DAT function and for species differences in transporter functions, including differential sensitivities to cocaine and 1-methyl-1,2,3,6-tetrahydropyridine (MPTP) in humans and rats.

Inhibition of Na+,K(+)-ATPase by platelet-activating factor in dog submandibular glands

Physiological stimulation of dog submandibular gland has been shown to generate platelet-activating factor (PAF). However, PAF is not released from cells in the tissue. To assess its intracellular activity, the effect of PAF on Na+,K(+)-ATPase was examined in dog submandibular gland cells. PAF inhibited Na+,K(+)-ATPase in membrane preparations, and the inhibitory effect was dependent on the protein concentration in the enzyme preparation. The inhibitory effect of a low concentration of PAF was antagonized by a PAF-receptor antagonist, BN 50,739, but at high concentrations, PAF was not antagonized. Kinetic analysis of PAF inhibition of Na+,K(+)-ATPase suggests that the inhibition of Na+,K(+)-ATPase by PAF is not due to competition by PAF at K(+)- or Na(+)-binding sites on the enzyme, but by complex inhibitory mechanisms. These results suggest that PAF may interact with specific and nonspecific site of action resulting in the inhibition of Na+,K(+)-ATPase. Ouabain increased mucin release from dog submandibular gland cells. Because Na+,K(+)-ATPase and ion exchange pathways are important in the secretory responses of acinar cells, PAF may regulate intracellularly the secretory function of acinar cells by modulating Na+,K(+)-ATPase and ionic homeostasis.

Case report: rupture of a gastric varix in liver cirrhosis associated with glycogen storage disease type III

Glycogen storage disease type III, or Cori's disease, is caused by a deficiency of amylo-1,6-glucosidase (debranching enzyme), which leads to the storage of an abnormal glycogen in the liver and in skeletal and heart muscle. Glycogen storage disease type III is usually characterized by hepatic symptoms, growth failure and myopathy. Even though liver cirrhosis is reported, portal hypertension is a rare complication of this disease. We describe the case of a glycogen storage disease type III patient who was diagnosed at 3 years of age and developed complications (liver cirrhosis and rupture of a gastric varix) at 31 years of age. We discuss the histological progression to cirrhosis of the liver and describe the liver enzyme profile at 3 and 31 years of age.

Dihydroheptaprenyl and dihydrodecaprenyl monophosphates induce apoptosis mediated by activation of caspase-3-like protease

Dolichyl phosphate, an essential carrier lipid in the biosynthesis of N-linked glycoprotein, has been found to induce apoptosis in rat glioma C6 cells and human monoblastic leukemia U937 cells. In the present study, dolichyl phosphate and structurally related compounds were examined regarding their apoptosis-inducing activities in U937 cells. Dihydroheptaprenyl and dihydrodecaprenyl phosphates, of which isoprene units are shorter than that of dolichyl phosphate, induced apoptosis in U937 cells. This phenomenon occurred in a dose- and time-dependent manner, as seen with dolichyl phosphate-induced apoptosis. Derivatives of the same isoprene units of dolichyl phosphate, such as dolichol, dolichal or dolichoic acid, did not induce DNA fragmentation. Farnesyl phosphate and geranylgeranyl phosphate also failed to induce apoptosis. During apoptosis, the caspase family of cysteine proteases play important roles. We observed that apoptosis induced by dihydroprenyl phosphate was mediated by caspase-3-like (CPP32-like) activation but not by caspase-1-like (ICE-like) activation. This caspase-3-like activation was inhibited by a specific inhibitor of caspase-3, DEVD-CHO, but not by an caspase-1 inhibitor YVAD-CHO. We interpret these results to mean that dihydroprenyl phosphates with more than seven isoprene units have apoptosis-inducing activity and that their signal is mediated by caspase-3-like activation.

Development of a frameless and armless stereotactic neuronavigation system with ultrasonographic registration

OBJECTIVE

We have developed a frameless stereotactic neuronavigation system that allows navigation during neurosurgical procedures through an image formed from integrating ultrasonography and preoperative magnetic resonance (MR) imaging and/or x-ray computed tomography.

METHODS

The system consists of a ultrasound imaging scanner, a workstation with an image capture board, and an ultrasonic tracking sensor with a 5-MHz ultrasonographic transducer. The ultrasonic tracking sensor measures the position and orientation of the ultrasonographic transducer. The oblique plane of the MR/computed tomographic image corresponding to the ultrasound image is then displayed on the workstation monitor. A three-dimensional computer graphic representation of the integrated image is also reported as a preliminary test. For the patient-image registration, the coordinates of digitized and imaged markers on a specifically developed reference frame are used. The reference frame is noninvasive because it is not bolted but only fastened to the patient's head with silicon.

RESULTS

Based on the findings from the clinical application of the system in three cases, the system was advantageous because of the surgical procedures could be controlled by intraoperative ultrasonography as well as by preoperative MR/computed tomographic images. Missing parts in the ultrasonogram were supplemented with preoperative MR/computed tomographic images. At other times, spatial positioning and visualization by ultrasonography were useful for identifying anatomical objects in the image.

CONCLUSION

This preliminary study of the frameless integration of ultrasonography into stereotactic space demonstrated its clinical usefulness. We believe that the concept of pre- and intraoperative image-guided surgery presented here will find increasing use in the future.

Comparison of the closing dynamics of mechanical prosthetic heart valves

To compare the closing dynamics of mechanical tilting disk prosthetic heart valves (OmniScience 25 [OS25], Medtronic-Hall 25 [MH25], Bjork-Shiley Monostrut 29 [BS29]) and bileaflet valves (CarboMedics 29 [CM29]) in the mitral position, an x-ray high speed video camera (XHVC) and a mechanical mock circulator were used. From the continuous images taken with the XHVC, the starting point of closing and the period during closing (PDC) were measured. Pressures and flow rate were recorded at 500 Hz synchronously with the XHVC. A pressure difference across the valves at the onset of closing (dpc) was newly introduced to compare the closing response. Using 60 and 100 bpm, the following results were obtained: 1) the CM29 had less PDC and maximum backflow rate than the BS29; 2) the dpc and the PDC at 100 bpm were larger than those at 60 bpm; 3) the dpc of the MH25 was the lowest; and 4) the PDC of the CM29 was the shortest. With regard to the effect of valve design on closing dynamics, it was shown that: 1) less momentum of inertia of the occluder and disk traveling angle resulted in lower dpc and shorter PDC, and 2) the higher the dpc and the PDC became, the larger the maximum backflow rate that was generated, and 3) low final closing speed will be achieved for small disk travelling angle.

Stimulation of cyclic ADP-ribose synthesis by acetylcholine and its role in catecholamine release in bovine adrenal chromaffin cells

Cyclic ADP-ribose (cADPR) is suggested to be a novel messenger of ryanodine receptors in various cellular systems. However, the regulation of its synthesis in response to cell stimulation and its functional roles are still unclear. We examined the physiological relevance of cADPR to the messenger role in stimulation-secretion coupling in cultured bovine adrenal chromaffin cells. Sensitization of Ca2+-induced Ca2+ release (CICR) and stimulation of catecholamine release by cADPR in permeabilized cells were demonstrated along with the contribution of CICR to intracellular Ca2+ dynamics and secretory response during stimulation of intact chromaffin cells. ADP-ribosyl cyclase was activated in the membrane preparation from chromaffin cells stimulated with acetylcholine (ACh), excess KCl depolarization, and 8-bromo-cyclic-AMP. ACh-induced activation of ADP-ribosyl cyclase was dependent on the influx of Ca2+ into cells and on the activation of cyclic AMP-dependent protein kinase. These and previous findings that ACh activates adenylate cyclase by Ca2+ influx in chromaffin cells suggested that ACh induces activation of ADP-ribosyl cyclase through Ca2+ influx and cyclic AMP-mediated pathways. These results provide evidence that the synthesis of cADPR is regulated by cell stimulation, and the cADPR/CICR pathway forms a significant signal transduction for secretion.