Measurement of intracellular free Ca2+ concentration in guinea pig spiral ganglion cells

Intracellular free Ca2+ concentration ([Ca2+]i) in spiral ganglion cells (SGC) of guinea pig was measured using the fura-2 fluorescence method. Application of high-K+ external solution increased [Ca2+]i. [Ca2+]i elevation was suppressed by either depletion of external Ca2+ or application of the dihydropyridine Ca2+ channel antagonist, nicardipine. One of the putative hair cell afferent nerve neurotransmitters, L-glutamate (Glu), induced [Ca2+]i elevation in SGC. Pharmacological studies suggested that the Glu receptor may be a non-NMDA subtype. Glu-induced response was suppressed by either depletion of external Ca2+ or application of nicardipine, indicating that Glu-induced [Ca2+]i elevation is mainly carried out by the voltage-dependent Ca2+ channel in SGC.

Fetus-specific CYP3A7 and adult-specific CYP3A4 expressed in Chinese hamster CHL cells have similar capacity to activate carcinogenic mycotoxins

To assess whether CYP3A4 and CYP3A7 have a similar capacity to activate carcinogenic mycotoxins, we established cell lines stably expressing human CYP3A4 and CYP3A7, which are adult- and fetal-specific forms of cytochrome P450 in human livers, respectively. Each cDNA was introduced into CR-119 cells which had been established by introducing guinea pig NADPH-cytochrome P450 reductase cDNA into Chinese hamster lung cells. The cell lines (4-line and 7-line) stably expressed the mRNA and the protein corresponding to CYP3A4 and CYP3A7, respectively. The concentration-response for aflatoxin B1 (AFB1) cytotoxicity in 4-line and 7-line, respectively, was compared. 4-10 and 7-40 cells were approximately 17- and 20 times more sensitive to AFB1 than the parental CR-119 cells, respectively. In addition, the sensitivities to AFB1 of both 4-10 and 7-40 cells were enhanced approximately seven times by the addition of 10 microM alpha-naphthoflavone, a known activator of CYP3A enzyme, while the sensitivities were suppressed approximately four times by the addition of 100 microM troleandomycin, which forms a metabolite intermediate complex with CYP3A enzyme. Moreover, both cell lines showed approximately 10 and 2 times higher sensitivity to sterigmatocystin and aflatoxin G1 than CR-119 cells, respectively. These results indicate that CYP3A4 and CYP3A7 have essentially similar capacities to activate AFB1, sterigmatocystin, and aflatoxin G1 to produce toxic metabolites.

Parvalbumin-positive small myelinated fiber bundles in anterior marginal areas in the human cervical cord

During pathological examinations of amyotrophic lateral sclerosis (ALS) patients, we noticed that bundles of dense small myelinated fibers were relatively well preserved in the anterior marginal areas of the cervical cords in a few ALS patients with diffuse myelin pallor. Moreover, these fibers were strongly immunostained by anti-parvalbumin antiserum. These parvalbumin-positive fiber bundles were also seen in other ALS and non-ALS patients, and they were continuously traced up to the spinothalamic tract areas of the medulla oblongata. Therefore, it is suggested that these fiber bundles belong mainly to the ventral spinothalamic tract. We considered that these fiber bundles became conspicuous in shape since other areas in the anterolateral funiculus showed myelin pallor in such ALS patients.

Disturbance of regulation of sodium by cis-diamminedichloroplatinum in perilymph of the guinea pig cochlea

We studied the acute effects of cis-diamminedichloroplatinum (CDDP) on the cochlear partition and inner ear fluid in the guinea pig. At 48 hours after the administration of a single intramuscular injection of CDDP, 12.5 mg/kg of body weight, the endocochlear resting potential (EP) was significantly decreased to 32.1 +/- 1.8 mV in the treated animals, versus 80.6 +/- 1.0 mV in the control animals. There was a significant rise in potassium (K+), sodium (Na+), and chlorine (Cl-) in the endolymph of the animals treated with CDDP as compared with the control animals. Only Na+ was found to increase significantly in the perilymph, reaching more than twice the level of the control animals; both K+ and Cl- remained within the normal range. Serum electrolytes also remained within the normal range. Evaluation of modified ionic permeabilities across the endolymph-perilymph barrier showed an apparent increase in Na+ permeability and a normal range of K+ and Cl- permeabilities. Histopathologic examination of the cochlea showed a moderate collapse of the endolymphatic space, with atrophy of the stria vascularis and destruction of the outer hair cells. The findings suggest that the acute changes produced in the cochlea by administration of CDDP were attributable to a breakdown in the regulation of Na+ metabolism in the perilymph.

Potent thyrotropic activity of human chorionic gonadotropin variants in terms of 125I incorporation and de novo synthesized thyroid hormone release in human thyroid follicles

Using a highly sensitive bioassay for TSH, in which human thyroid follicles incorporate 125I and release de novo synthesized thyroid hormone into the culture medium, the thyrotropic activities of various hCG preparations were studied. Under the culture conditions employed, bovine TSH (bTSH) was approximately 6- to 9-fold more active than human TSH (hTSH). Highly purified hCG prepared from urine of normal pregnant women (CR 127) had only a trivial thyrotropic activity equipotent to 0.00022 microU bTSH/U hCG or 0.0013 microU hTSH/U hCG (19.7 microU hTSH/mg hCG). Hybrid hCG (AB1ER) also elicited low thyrotropic activity (14.0 microU hTSH/mg), whereas crude hCG had moderate thyrotropic activity (0.041 hTSH microU/U hCG or 127 microU/mg protein). Deglycosylated hCG, a very weak LH/hCG receptor agonist, was the most potent agonist in thyroid follicles (588 microU hTSH/mg protein). hCGs purified from urine of patients with trophoblastic tumors had greater TSH-like activity (37-84 microU hTSH/mg protein) than purified hCG. Asialo-hCG purified from a patient with choriocarcinoma had very potent TSH-like activity (468 microU hTSH/mg). Submaximal doses of bTSH and hCG variants produced additive stimulation of thyroid function. Furthermore, the thyrotropic effect of hCG was inhibited by anti-TSH receptor antibody obtained from patients with myxedema. These in vitro findings suggest that although hCG is reported to exert potent cAMP-stimulating activity on rat thyroid-like cells (FRTL-5) and Chinese hamster ovary cells transfected with hTSH receptor complementary DNA (0.092-0.72 microU hTSH/U hCG), the thyrotropic activity induced by authentic hCG in human thyroid follicles is too weak to cause hyperthyroidism in normal pregnancy. However, hCG produced by some trophoblastic tumors, particularly asialo-hCG, has potent thyrotropic activity sufficient to cause clinically overt hyperthyroidism when produced excessively.

[Percutaneous transluminal angioplasty for cervical carotid artery stenosis]

Percutaneous transluminal angioplasty (PTA) was attempted in 16 patients (17 procedures) with cervical internal carotid artery (ICA) stenosis. Among the 16 patients, 14 were male and 2 were female aged from 44 to 76 years (average 63.4 years). One had cerebral infarction on the acute stage, and the other 15 were in the chronic stage. On CT scan and MRI, there were nine multiple lacunar infarctions and seven watershed infarctions. On angiographical findings, 13 had Rt.-ICA stenosis and 4 had Lt. ICA stenosis. Stenotic lesion existed beyond the level of the third cervical vertebral body in eleven cases, and so-called long segmental stenosis ranged from 3 to 5 cervical vertebral bodies in 3 cases. Before PTA, 14 patients underwent a balloon occlusion test for 3 to 20 minutes (average 9 minutes). Neurological symptoms of hemiparesis or sensory disturbance occurred in 3 patients during balloon inflation, but these disappeared completely after balloon deflation. It took from 1.5 to 2 hours (average 1.7 hours) to carry out PTA including the balloon occlusion test. All cases had satisfactory results with no morbidity or mortality. The mean stenosis ratio of pre-PTA, approximately 80% (55-93%), improved to that of 22% (0-50%) after PTA. Bradycardia and hypotension occurred transiently in 9 cases during and after PTA, but no symptoms remained by atropine sulfate and catecholamine infusion intravenously. In the following 1 to 26 months (mean 9.0 months) after PTA, 3 cases restenosed. The restenosis was recognized by MR angiography after 8 to 26 months (average 15.7 months) of PTA.(ABSTRACT TRUNCATED AT 250 WORDS)

[Successful treatment with administration of systemic high dose methotrexate and intraarterial carboplatin for osteosarcoma of the skull: a case report]

An 11-year-old boy was admitted with a painless lump in the right frontal area as his chief complaint. On admission, physical and neurological examinations were normal except for the localized lump constituting the frontal lesion. Skull roentgenogram showed an osteoblastic and osteolytic mass with radiating bony spicules "sunray appearance" around the coronal suture. CT scans demonstrated it more clearly. The initial surgery was performed in July 1993. Pathological specimen showed osteosarcoma of the skull. The patient was transferred to our hospital for chemotherapy. The regimen consisted of intravenous high dose methotrexate 9,000 mg given for 6 hours with leucovorin rescue in a single course. Following 4 courses of high dose methotrexate, he underwent residual tumor resection. Two courses of intraarterial carboplatin 150 mg and methotrexate 200 mg were also given. Histologically, the lesion showed complete remission of the tumor, and no viable tumor cells were seen. Two additional courses of high dose methotrexate were given. The patient is doing well without evidence of recurrence. This case indicates that the chemotherapy with systemic high dose methotrexate and intraarterial carboplatin and methotrexate is effective for skull osteosarcoma.

Single photon emission computed tomography to determine effective hepatic blood flow and intrahepatic shunting

The noninvasive determination of effective hepatic blood flow, intrahepatic shunted blood flow, intrahepatic shunt index, and total hepatic blood flow was investigated by using the sequential single photon emission computed tomography. This method was performed for a period of 10 minutes following an intravenous injection of 99mTc-(Sn)-N-pyridoxyl-5-methyltryptophan and a venous blood sampling. This study comprised 8 healthy volunteers, 16 patients with chronic hepatitis, and 33 patients with liver cirrhosis. The intrahepatic shunt index measured with this method coincided with the intrahepatic shunt index determined by catheterization, indicating the high reliability of this procedure. The effective hepatic blood flow in patients with liver cirrhosis was significantly lower than that in the healthy controls and the chronic hepatitis group. The intrahepatic shunted blood flow was significantly higher in patients with liver cirrhosis compared with the flow in healthy controls. The intrahepatic shunt index was also significantly higher in patients with liver cirrhosis compared with the index of healthy controls and those with chronic hepatitis. No substantial differences were noted in the total hepatic blood flow among the three groups. The effective hepatic blood flow, the intrahepatic shunted blood flow, and the intrahepatic shunt index, correlated with the serum albumin concentration, the serum cholinesterase level, and the plasma indocyanine green attenuation rate. From these results, it was concluded that the present procedure constitutes a reliable and effective method for the noninvasive determination of hepatic blood flows. Consequently, it will be of high clinical value for assessing the functional and the pathological alterations of the liver.

Hostility is related to narcissism controlling for social desirability: studies of college students and patients with myocardial infarction

The authors examined the influence of narcissism and social desirability on hostility in two samples of 215 college students and 30 patients with myocardial infarction (MI). Results were as follows: (1) MI patients had stronger cynical hostility and lower social desirability than college students; (2) hostility was related to narcissism before and after controlling for social desirability in both MI patients and college students; and (3) these tendencies were stronger in MI patients than in college students, although there were no significant differences.

Influence of laparotomy on disposition kinetics of diclofenac in CCl4-intoxicated rats

The effect of the acute hepatic failure induced by CCl4 on the pharmacokinetics of diclofenac, which is definitely subject to enterohepatic circulation (EHC) in normal rats, was evaluated. This hepatic failure extinguished the secondary peak on the plasma time course which is usually observed in normal rats due to EHC. In the group without EHC by means of bile cannulation, the total clearance (CL) markedly decreased by CCl4-intoxication from 0.7 l/h/kg down to 0.1 l/h/kg, and mean residence time (MRT) increased from 0.29 h up to 2.8 h. The plasma time curves of the rats with laparotomy and with bile duct-cannulation were almost the same in the CCl4-intoxicated group. The bile excretion ratio of diclofenac markedly decreased by CCl4-intoxication from 43% down to 13%. In both groups, 92% of the total diclofenac excreted into the bile was glucuronide. While EHC made area under the curve (AUC) and MRT obviously increase in the CCl4-free rats, the effect of EHC on these moments was negligible in the CCl4-intoxicated rats. In the CCl4-intoxicated condition, the elimination of diclofenac in the rats with laparotomy was considerably slower than that in the rats without laparotomy. The plasma time courses were obviously monoexponential in the former group, while those were almost biexponential in the latter group.

DAMGO, a mu-opioid receptor selective agonist, distinguishes between mu- and delta-opioid receptors around their first extracellular loops

The structural basis of mu-opioid receptor (OPR) for the specificity in its ligand binding was investigated using chimeric mu/delta-OPRs. Replacement of the region around the first extracellular loop of delta-OPR with the corresponding region of mu-OPR gave the resultant chimeric receptor the similar affinity to DAMGO compared with the native mu-OPR. The reciprocal replacement deprived the high affinity to DAMGO from mu-OPR. These results indicate that the difference(s) in the structure around the first extracellular loop is critical for DAMGO to distinguish between mu- and delta-OPRs. Furthermore, displacement studies revealed that this region is partly involved in the discrimination between mu- and delta-OPRs by other peptidic mu-selective ligands, such as dermorphin, morphiceptin and CTOP, but not by non-peptidic ligands, such as morphine and naloxone.

Hemorrhagic colitis with unusual colonoscopy features, complicated with chronic graft-versus-host disease after allogeneic bone marrow transplantation

A 32-year-old man was admitted after bone marrow transplantation because of hematochezia. He had history of chronic graft-versus-host disease (GVHD) of the skin and the liver, and cytomegaloviral pneumonia. Barium enema and colonoscopy showed multiple colon ulcers in the ascending and transverse colon. This feature is very rare in chronic GVHD and resembles the feature in autoimmune disease such as periarteritis nodosa. Thus, this ulceration is thought to be caused by vasculitis due to an autoimmune reaction in chronic GVHD.

[Rheumatoid factor and cryoglobulin are not efficiently related to cold activation of complement]

Cold activation of complement (CA) is a phenomenon characterized by a low hemolytic complement activity in chilled serum. Cryoglobulin and RF have been reported as main causes of CA, and we previously reported the close association between CA and HCV infection in 21 CA patients. Therefore, we assayed CA, RF, cryoglobulin and anti-HCV antibody titers in 304 randomly selected patients with unknown diseases. CA was positive in 26 of the 304 patients, and among them, RF and/or cryoglobulin were found positive in 20 patients, and anti-HCV antibody were positive in all of them. RF was positive in 41 of the 304 patients. 37% of them were anti-HCV antibody positive and 63% were negative. Cryoglobulin was positive in 61 out of 304 patients. Anti-HCV antibody positivity was observed in 59 out of 304 patients, and all CA-positive cases were included in the anti-HCV antibody-titer-positive group. However, either RF or cryoglobulin positive patients were observed in the same degree in both anti-HCV antibody titer positive and negative groups. Therefore, RF or cryoglobulin is not considered the main cause of CA.

The emergence of free radicals after acoustic trauma and strial blood flow

The effect of acoustic trauma on cochlear strial circulation was investigated immunohistologically in the guinea pig. Kanamycin was used as a tracer of blood flow. Moreover, histochemical examinations were made to reveal the emergence of free radicals in the cochlea following acoustic trauma. At 5 min (5 min after intense sound exposure 120-125 dB SPL, 3 h) the blood flow in the stria vascularis was greatly diminished. At 2 h the strial blood flow started to recirculate and at 6 h it appeared to have returned to normal. Superoxide anion radicals (O2-) emerged along the luminal membrane of the marginal cells of the stria vascularis at 5 min. O2- disappeared at 30 min, but reappeared at 2 h. The cause of its emergence at 5 min was obscure. However, the strange phenomenon that O2- emerged again at 2 h seemed ascribable to the re-circulation of strial blood flow after sound exposure.

[A case of cutaneous malignant melanoma metastatic to the choroid]

A case of metastasis of cutaneous malignant melanoma to the choroid was reported. The patient, a 61-year-old man, had undergone an amputation of his right first finger 3 years ago due to cutaneous malignant melanoma. Ophthalmoscopic examination revealed a whitish yellow elevated choroidal lesion and serous retinal detachment in the left eye. Fluorescein angiography demonstrated multiple pinpoint leaks in the early phase and progressive pooling of dye into the subretinal space in the late phase. In magnetic resonance imaging, the tumor showed a hyperintense image in both T1 and T2-weighted images. Autopsy was performed and histopathological examination of the eye showed that the tumor cells were polygonal in shape, and had round or oval nuclei, but the cytoplasms had little melanin pigment. Immunohistochemistry for S-100 and HMB-45 antibody showed positive staining in choroidal tumor and other metastatic lesions, indicating that they were metastatic tumors from cutaneous malignant melanoma (amelanotic melanoma cells).

Marked hypocholesterolemia in a case with adrenal adenoma--enhanced catabolism of low density lipoprotein (LDL) via the LDL receptors of tumor cells

A 16-yr-old girl was hospitalized because of amenorrhea and virilism, and was diagnosed with an adrenal tumor on the right side. Her serum androgen levels were markedly elevated, and severe hypocholesterolemia (total cholesterol, 0.59 mmol/L) was observed. After resection of the tumor, her serum cholesterol level dramatically rose to normal, suggesting a role of this tumor in her marked hypocholesterolemia. To investigate the mechanism of hypocholesterolemia in this case, we examined the effects of dehydroepiandrosterone and dehydroepiandrosterone sulfate on the low density lipoprotein (LDL) receptor activity of fibroblasts. These hormones did not have any effect on LDL receptor activity. Northern blot analysis demonstrated that the LDL receptor messenger ribonucleic acid level of this tumor tissue was increased about 8-fold compared with that of normal adrenal cortex. The LDL receptor activity of the cultured cells established from this tumor was 2-fold higher than that of Hep G2 cells. Furthermore, the LDL receptor activity could not be down-regulated by an excessive dose of 25-hydroxycholesterol. These results suggest that increased LDL receptor activity and unrestricted uptake of LDL by the adrenal tumor may have caused the marked hypocholesterolemia in this patient.

Murine nursing thymic epithelial cell lines capable of inducing thymocyte apoptosis express the self-superantigen Mls-1a

Two cloned thymic epithelial cell (TEC) lines, D2.TEC-A3 and AKR TEC-K1, were established from minor lymphocyte-stimulating (Mls)-1a-positive normal, 4-week-old DBA/2 (H-2d, Mls-1a2a) mice and AKR (H-2k, Mls-1a2b) mice, respectively. Both cell lines were MHC class I and class II (both I-A and I-E) positive without stimulation by interferon-gamma. They were capable of infolding immature thymocytes to form thymic nurse cells (TNC; we call this type of TEC "nursing TEC") and induced apoptosis with DNA fragmentation in immature thymocytes. Using a primary Mls mixed lymphocyte reaction (MLR) we demonstrated that self-superantigen Mls-1a was expressed on these cloned nursing TEC lines. D2.TEC-A3 cells stimulated nylon-wool-purified splenic T cells obtained from H-2d-compatible BALB/c (Mls-1b2a) and B10.D2 (Mls-1b2b) mice with a maximal response at a stimulator:responder ratio of 1:40 after 4 days of the coculture. AKR TEC-K1 cells also stimulated purified T cells from H-2k-compatible C3H/He mice (Mls-1b2a) in a similar manner. The Mls MLR induced by the nursing TEC lines was completely inhibited in the presence of anti-mouse I-A and anti-mouse I-E monoclonal antibodies. These results suggest that nursing TEC/TNC could be involved in negative selection due to apoptosis.

13C-UBT using an infrared spectrometer for detection of Helicobacter pylori and for monitoring the effects of lansoprazole

The stable isotope [13C]-labeled urea breath test (13C-UBT) is very useful for detecting Helicobacter pylori. Conventionally, a mass spectrometer is used to measure the presence of 13CO2 in breath. However, this technique is complex and expensive. Therefore, we carried out the 13C-UBT using an easy-to-operate infrared spectrometer, and we studied its usefulness. The 95 subjects included 35 patients with gastric ulcers, 32 with duodenal ulcers, 13 with gastroduodenal ulcers, some patients with nonulcer gastroduodenal disease, and normal controls. The 13C-UBT was negative in normal controls and positive in 86 of 91 (95%) patients with illness. Peaks appeared 15 to 30 min after [13C]urea administration. The 33 patients who were 13C-UBT-positive were then given lansoprazole 30 mg/day and the 13C-UBT was repeated after 8 to 16 weeks. Lansoprazole was found to be effective in patients who exhibited peak 13CO2 values that were at least two-thirds less than the pretreatment values. This effect was seen in 16 patients (48%), 13 of whom (81%) had gastric ulcers. Thirteen of the 17 patients (76%) who exhibited no effect had duodenal ulcers, and there were clear treatment response differences between the two types of ulcers.

Functions of the yeast meiotic recombination genes, MRE11 and MRE2

Mutants defective in meiotic recombination were isolated using a disomic haploid strain of S. cerevisiae, and were classified into 11 genes. Two, MRE2 and MRE11, are new genes and nine are previously identified genes. The mre2 and mre11 deletion mutants are proficient in mitotic recombination, but are defective in meiotic recombination and in formation of viable spores. The spore inviability, however, is alleviated by an additional mutation, spo13, which bypasses meiosis I. In addition, neither meiosis specific DSBs at recombination hot-spots nor formation of synaptonemal complex occur in either mutant. Therefore, these two genes are involved in the formation of DSBs in meiotic recombination. While a temperature sensitive mre11-1 mutant is able to form DSBs at a permissive temperature, the formed DSBs are unable to resect at non permissive temperature. Therefore, the MRE11 gene is also involved in some step of the repair process after the DSB formation. Analysis of properties of the mre11 disruption mutant as well as the xrs2 mutant showed a similarity to those of the rad50 disruptant. We found that the mre11 disruption mutation is epistatic to rad50S mutation, as the xrs2 deletion mutation is epistatic to rad50S with regard to DSBs. Therefore, these three genes form an epistatic group. Interaction of the Mre11 protein with the Rad50 and the Xrs2 protein as well as alone was shown in vivo using the two-hybrid system. The MRE2 gene encodes a protein containing two sets of RRM. Deficiency of recombination in a mre2 mutant that has an amino acid substitution in the N-terminal RRM can be suppressed by the MER2 gene on the multicopy plasmid. Further analysis showed that the Mre2 protein is involved in meiosis-specific splicing of the MER2 transcripts in cooperation with the Mer1 protein. In conclusion, MRE genes are involved in the initiation of meiotic recombination through the formation of DSBs at recombination hot-spots in S. cerevisiae.

Interaction between dibucaine and pig erythrocyte membranes as studied by NOESY experiments in 1H-NMR spectroscopy. Which form of dibucaine interacts more strongly, cationic or uncharged?

The interaction between amine local anesthetic dibucaine and pig erythrocyte membranes has been studied by 1H-NMR spectroscopy. Two-dimensional NOESY spectra were observed to obtain the conformations of cationic and uncharged forms of dibucaine. The NMR spectra were measured at pH 7.4, and the temperature was raised (318-348 K) to increase the concentration of the uncharged form of dibucaine, taking the temperature dependence of the pKa value of dibucaine into consideration. The dibucaine in a buffered solution showed the presence of two kinds of distinctly different species; one is assignable to the cationic form and the other to the uncharged form of dibucaine, suggesting that the protonation equilibrium between the two forms is slow in the presently employed experimental condition. The uncharged dibucaine showed well-defined NOE cross-peaks in the NOESY spectra of the solution containing no erythrocyte membranes, suggesting that its conformation is relatively fixed. Interestingly, however, it was only the cationic dibucaine that showed NOE cross-peaks when the solution contained the membranes, and experiments were performed at a much shorter mixing time for the buildup of NOEs, suggesting that it appeared only the cationic form of dibucaine is interacting with the membranes. It was concluded that the uncharged form of dibucaine, which was produced by raising the temperature, formed micelles in a buffered solution. Thus formed micelles didn't interact with membranes owing to the repulsive forces between the structured water surrounding the micelles and those at the surface of the membranes. This conclusion could be a promising reason why the cationic local anesthetics are much more active than their uncharged counterparts in blocking nerve conduction.

Treatment of aortic dissections with a percutaneous intravascular endoprosthesis: comparison of covered and bare stents

PURPOSE

The authors developed a percutaneous endoprosthesis for treatment of aortic dissections. The device is a Gianturco stent wrapped with Dacron or nylon mesh. Effectiveness of the covered stent versus a bare stent was compared in the treatment of acute aortic dissection.

MATERIALS AND METHODS

Experimental aortic dissections were created in 10 mongrel dogs. Occlusion of intimal tears was attempted with covered stents in five dogs (group 1) and with bare stents in the remaining five dogs (group 2).

RESULTS

In group 1, entry tears were obliterated within 1 day (n = 3) or 1 week (n = 2) after stent placement and false lumina were thrombosed within 1 week (n = 3) or 1 month (n = 2). In group 2, entry tears and false lumina remained patent. Histologic specimens showed that the covered stents were entirely covered with smooth neointima.

CONCLUSIONS

This endoprosthesis offers an alternative to surgical treatment for dissections of the descending aorta.

Nicotine improves cognitive disturbance in senescence-accelerated mice

Senescence-accelerated mice (SAM), a murine model of age-related deterioration in learning ability, were studied as to the acetylcholine (ACh) contents in the brain tissues and the effect of nicotine administration. We found that the ACh content of SAM-P/8 (accelerated senescence-prone) mice was lower than that of SAM-R/1 (accelerated senescence-resistant) mice in the midbrain thalamus and the hypothalamus. In addition, an IP administration of nicotine was found to improve learning ability of SAM-P/8 as shown by performance of a passive avoidance task. Nicotine may potentiate cognitive function in SAM-P/8.