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M Nishitani

Publications and source records attributed to M Nishitani.

28 records · Page 2Linked to original sources
PubMed1994

Effect of BV-araU and acyclovir on varicella-zoster virus replication with various length and timing of drug exposure.

We studied antiviral effects of 1-beta-D-arabinofuranosyl-5-[(E)-2-bromovinyl]uracil (BV-araU) and acyclovir against varicella-zoster virus (VZV) multiplication varying the length or timing of drug exposure. First, residual anti-VZV effect of drugs, exposed to cells for various periods followed by incubation in drug-free medium, was determined by the plaque inhibition assay. None of the drugs showed activity when removed within 24 hr of incubation. Weakened efficacy of BV-araU was seen in 2 days of treatment. When it was removed after 3 or 4 days, the ED50 was as low as that for cultures in which the drug was not removed. Still, plaque inhibition was not complete even at high concentrations. Acyclovir inhibited plaque formation only by 50% or less in 2 days of treatment. It gave a much higher ED50 in 3 days of treatment than that observed without drug removal. In the experiments, in which BV-araU was added to VZV-infected cells 1 day after infection, BV-araU immediately suppressed increase in the number of infective centers at a concentration of 0.001 microgram/ml, and reduced it at concentrations of 0.01 microgram/ml or higher. The reduction of infective centers was seen with a dose-dependent manner when added 2 or 3 days after infection. BV-araU stimulated the decrease in the number of infective centers when added 4 days after infection. This inhibitory effect of acyclovir was very weak. Microscopic observations supported the above results. BV-araU was still much superior to acyclovir in the anti-VZV effect when the length and timing of drug exposure were varied.

Acyclovir↗
PubMed1994

[Hemoperfusion and plasma exchange therapy in patients with paraquat poisoning].

In these past three years, we treated 5 patients who attempted suicide by taking paraquat, a herbicide that had been kept at home, by direct hemoperfusion (DHP) alone or in combination with double filtration plasmapheresis (DFPP) in addition to conservative therapy. DHP alone was performed on 3 patients, 2 of whom recovered. The other 1 patient treated by DHP alone and 2 treated by the combination therapy died. These patients showed a plasma paraquat concentration exceeding the survival curve presented by Proudfoot. In such patients, appropriate combinations among hemodialysis, hemofiltration, DHP, and DFPP may be safer and more effective than each therapy alone.

Adult↗
PubMed1993

[Nephrogenic adenoma of the ureter: a case report].

A 27-year-old male with nephrogenic adenoma of the ureter complicating urolithiasis is reported. Nephrogenic adenoma of the ureter is extremely rare, and this case is the sixth reported in Japan. The lesion was found at the site of the stone in the left ureter. Histopathologically, the tumor consisted of ducts resembling uriniferous tubules, and no signs of malignancy were noted. The cause of nephrogenic adenoma is considered to be metaplastic reaction to stimulation by stones and inflammation.

Adenoma↗
PubMed1992

Perfusion pressure breakthrough threshold of cerebral autoregulation in the chronically ischemic brain: an experimental study in cats.

A study was designed to investigate hyperperfusion syndrome after the restoration of normal cerebral blood flow in a chronically cerebral ischemic state resulting from high-flow arteriovenous malformations or severe carotid stenosis. A fistula between the left distal common carotid artery and the jugular vein was created and the left vertebral artery was simultaneously occluded in 44 cats to produce a chronic cerebral ischemic state. For control experiments, 10 cats underwent occlusion of the left common carotid and vertebral arteries. Six weeks later, pial arterial behavior, disruption of the blood-brain barrier (BBB), and cerebral histological changes were investigated using three experimental methods. In the first, in which a fistula was occluded under normal conditions, pial arteries contracted to some 80% of the resting state; however, no BBB disruption or histological changes were observed. In the second experiment, in which a 20-minute occlusion of the left middle cerebral artery was performed in the cats with a patent fistula, a 30% to 40% dilated state of the pial arteries continued after recirculation, and BBB disruption-induced cerebral edema and infarction were observed. These findings were more prominent in the cats that underwent occlusion of the fistula. On the other hand, in the control group, the pial arteries returned to resting size within 40 minutes, and no BBB disruption or histological changes were observed. In the third experiment, in which moderate hypertension was induced for 1 hour, the pial arteries dilated much more remarkably; BBB disruption and cerebral edema were revealed to be more extensive in the cases of fistula occlusion than within those with a patent fistula. In the control group, however, the pial arteries contracted 10% during hypertension, while BBB disruption and histological changes were not evident. The results indicate that the perfusion pressure breakthrough threshold in the chronically ischemic brain may not be reduced by the restoration of normal blood flow, but may be decreased by the addition of new ischemic insults or hypertension.

Animals↗
PubMed1992

[Purine catabolites and pial arteriolar diameter in transient cerebral ischemia].

In transient cerebral ischemia, extracellular purine catabolites and pial arteriolar diameter were measured continuously. Ischemia during one hour was induced by unilateral occlusion of left middle cerebral artery in feline. Extracellular purine catabolites were sampled by in vivo brain microdialysis technique from the gray matter at ectosylvian gyrus. These catabolites were analyzed by HPLC system. Simultaneously, reactivity of pial arteriole was observed and its diameter was measured through the cranial window using intravital microscope and width analyzer. Extracellular concentrations of adenosine, inosine, hypoxanthine and xanthine were found to be 0.80 +/- 0.16 microM, 2.01 +/- 0.95 microM, 4.01 +/- 2.73 microM and 3.93 +/- 2.39 microM, respectively. During ischemia, the concentration of adenosine increased 8.7-fold and arteriolar diameter was 170% of the resting state. These findings in extracellular adenosine concentration and pial arteriolar diameter during ischemia support a role of adenosine in regulation of cerebral blood flow. After reperfusion, arteriolar diameter had returned to 120% of the resting state. But 50 min after reperfusion, pial arteriole began to dilate again coincident with the peak of xanthine concentration. These results suggest that free radicals were produced and could affect pial arterioles 50 min after reperfusion.

Adenosine↗
PubMed1991

Different antiviral potencies of BV-araU and related nucleoside analogues against herpes simplex virus type 1 in human cell lines and Vero cells.

Antiviral potencies against herpes simplex virus type 1 (HSV-1) of 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU) and ten other nucleoside analogues in human embryonic lung fibroblast (HEL) cells were compared with those in Vero cells. 5-Halogenovinylarabinosyluracils, highly active in HEL cells, were inactive against all three laboratory-stocked strains of HSV-1 but exerted moderate antiviral effects on three clinical isolates in Vero cells. The reduction in anti-HSV-1 potencies of other representative nucleoside analogues in Vero cells was much less than those of 5-halogenovinylarabinosyluracils. However, significant antiviral potencies of BV-araU against laboratory strains were observed in other human and monkey fibroblast cells including an immortalized cell line. Significant enhancement of antiviral activity of BV-araU against a laboratory strain and a clinical isolate was demonstrated in Vero cells by the addition of 0.1 microM aminopterin or FUdR, an inhibitor of thymidylate synthesis. The potentiated anti-HSV-1 activity in Vero cells was comparable to the potency in HEL cells without the inhibitor. These results suggested that high activity of thymidylate synthesis and a large thymidylate pool size in Vero cells seem to be related to loss of anti-HSV-1 potency of BV-araU. Original tissue type, species, and the immortality may not be responsible for the reduced antiviral activity of BV-araU in Vero cells.

Aminopterin↗
PubMed1991

[Experimental study on brain reversibility following temporary regional cerebral ischemia; from the point of view of vessel behavior and histological changes].

Using a middle cerebral artery occlusion model in adult cats, we investigated the ischemic time threshold for inflicting damage on cerebral vessel behavior and brain tissue. With the transorbital approach, a middle cerebral artery (MCA) was exposed and temporarily obstructed by a Zen's clip. Animals were divided into ten groups (each group: N = 8) according to the ischemic time of 10, 20, 30 minutes, 1, 2, 4, 6, 8, 12, 24 hours. Five hours after the recanalization, Evans' blue dye was injected intravenously and after further 30 minutes, the brain was fixed with transaortal perfusion for histological examinations. A cranial window was made above the ectosylvian gyrus which has poor anastomosis. The pial vessel behavior was observed through the cranial window and evaluated using an intravital microscope and a videoangiometer. Considering the correlation between functional change of vessel behavior and pathological change in the brain, the threshold time of ischemia inflicting irreversible damage was estimated. In the 30 minute ischemia group, deterioration of vessel behavior began to be observed as well as extravasation of Evans' blue dye. As the ischemic duration became longer, infarction and hemorrhage, which showed close correlation, increased. When the duration of ischemia was 6 hours, the infarcted area was significantly larger than that of the 4-hour ischemia group. Intracranial pressure (ICP) markedly increased as soon as recanalization took place. We think this phenomenon is due mainly to swelling. About three hours after recanalization, ICP further increased due to severe vasogenic edema in addition to the brain swelling.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Drug susceptibilities of isolates of varicella-zoster virus in a clinical study of oral brovavir.

Susceptibilities to brovavir [1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)-uracil] and acyclovir of clinical isolates of varicella-zoster virus obtained from 58 patients with herpes zoster, included in a clinical trial of oral brovavir, were tested by a plaque reduction method. All 101 isolates were significantly susceptible to brovavir; 50% effective dose of brovavir for these isolates ranged between 0.6-4.0 ng/ml (average: 1.29 ng/ml). Brovavir was about 3,000 times more potent than acyclovir against these isolates. No marked change in the susceptibility of isolates from these patients during treatment with brovavir was observed.

Acyclovir↗