Biomedical subjects

Yutaka Sakai

Publications and source records attributed to Yutaka Sakai.

12 recordsLinked to original sources

PubMed2006

Computational algorithms and neuronal network models underlying decision processes.

Animals or humans often encounter such situations in which they must choose their behavioral responses to be made in the near or distant future. Such a decision is made through continuous and bidirectional interactions between the environment surrounding the brain and its internal state or dynamical processes. Therefore, decision making may provide a unique field of researches for studying information processing by the brain, a biological system open to information exchanges with the external world. To make a decision, the brain must analyze pieces of information given externally, past experiences in a similar situation, possible behavioral responses, and predicted outcomes of the individual responses. In this article, we review results of recent experimental and theoretical studies of neuronal substrates and computational algorithms for decision processes.

Algorithms↗

PubMed2006

Relation of alcohol use and smoking to glucose tolerance status in Japanese men.

To investigate the relation of alcohol use and cigarette smoking to glucose tolerance status, we performed a cross-sectional study of 3038 male officials aged 46-59 years in the Self-Defense Forces. Glucose tolerance status was determined by a 75-g oral glucose tolerance test. A self-administered questionnaire was used to ascertain alcohol use, smoking habits, and other lifestyle characteristics. Statistical adjustment was made for parental history of diabetes, body mass index, and leisure-time physical activity. Alcohol use was positively associated with impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes mellitus each. The association was dose-dependent, with odds of each category of glucose intolerance increased even among those with moderate alcohol use. Cigarette smoking was not related to any categories of glucose intolerance. Alcohol use may confer increased risks not only of type 2 diabetes mellitus but also of preceding glucose intolerance status. Smoking does not seem to deteriorate glucose tolerance.

Alcohol Drinking↗

PubMed2006

Transperineal extended biopsy improves the clinically significant prostate cancer detection rate: a comparative study of 6 and 12 biopsy cores.

BACKGROUND: We evaluated the improvement in the rate of prostate cancer detection when using a 12-core transperineal biopsy protocol including transitional zone biopsy. METHODS: Between April 2003 and November 2004, 247 consecutive men underwent transperineal systemic 12-core biopsy of the prostate. Six cores were obtained at the peripheral zone, four at the transitional zone and two at the apex. We examined the cancer detection rate in each of the 12 cores, and also determined the improvement of cancer detection resulting from the extensive 12-core versus standard 6-core biopsy. RESULTS: Using the extensive 12-core biopsy, prostate cancer was detected in 98 cases (39.7%). Prostate-specific antigen (PSA), PSA density, the positive rate in digital rectal examination and transrectal ultrasound findings were significantly higher in the prostate cancer group than in the non-prostate cancer group, and prostate volume was larger in non-prostate cancer group. Every site showed almost the same positive rate, between 17.8 and 21.5%. There were 20 cases which were positive in the extended biopsy, but negative in the sextant. The detection improved significantly (20.4%). The improvement of cancer detection in extended biopsy was better in men with PSA levels of 10 ng/mL or less (28.9%), PSA density 0.3 or less (25.8%), negative digital rectal examination (23.3%), and negative transrectal ultrasound (21.6%). Of these twenty patients, no cases with insignificant tumor were detected in the six prostatectomy cases. In particular, three cases of the six were transitional-zone-only cancer. CONCLUSION: Transperineal extended 12-core biopsy including 4 transitional zone cores is a more useful procedure than transperineal 6-core biopsy. Routine transitional zone biopsy, that is different from transrectal biopsy, might be useful for detecting biologically significant cancer.

Aged↗

PubMed2006

Complicated urinary tract infection caused by Pseudomonas aeruginosa in a single institution (1999-2003).

BACKGROUND: Pseudomonas aeruginosa has been an important uropathogen that causes complicated urinary tract infection. We investigated the clinical characteristics of complicated urinary tract infection caused by Pseudomonas aeruginosa in a single institution. METHODS: We studied those patients who had basal disease in their urinary tract that was diagnosed as urinary tract infection caused by more than 10(4) colony forming units (CFU)/mL of Pseudomonas aeruginosa isolated from their urine. In those patients, we analysed infectious risk factors, treatment methods including the use of antimicrobial agents, the presence of a urinary tract catheter, and the relationship between febrile infection and urinary tract catheter. In addition, we examined the various antimicrobial susceptibilities against Pseudomonas aeruginosa. RESULTS: We studied 76 patients (59 men and 17 women). Of their basal diseases of the urinary tract, bladder tumor was the most prevalent (42.1%). Of the 39 patients who had an indwelling urinary tract catheter, 26 (66.7%) experienced a high-grade fever, a higher rate than that of the 37 patients who were not catheterized (40.5%). Seven patients were treated with anticancer chemotherapy drugs and 31 cases of urinary tract infection caused by Pseudomonas aeruginosa were diagnosed in the perioperative period. Piperacillin showed lower susceptibility against Pseudomonas aeruginosa in these 2 years (P<0.05). CONCLUSIONS: Our results indicated that those patients with urinary tract catheterization had a higher incidence of fever than patients without catheterization. Therefore, we must improve not only the antimicrobial treatment of Pseudomonas aeruginosa but also our management of catheters.

Adult↗

PubMed2006

Hydronephrosis caused by intra-abdominal abscess from cecal perforation by an ingested fish bone.

A patient was treated for hydronephrosis caused by an intra-abdominal abscess arising from cecal perforation by an ingested fish bone. To the authors' knowledge there is no previous report of such ureteral obstruction. Ureteral stenting, drainage of the abscess, and ileocecal resection were performed. Six months of stenting were required to attain ongoing ureteral patency following removal.

Abdominal Abscess↗

PubMed2003

Adrenocorticotropin-independent macronodular adrenal hyperplasia treated by simultaneous bilateral laparoscopic adrenalectomy.

A 61-year-old woman was admitted to our hospital with hypertension and diabetes mellitus, and was found to have Cushing's syndrome. Radiological and endocrinological findings suggested adrenocorticotropic hormone-independent macronodular adrenal hyperplasia. Simultaneous bilateral laparoscopic adrenalectomy was performed, minimizing the number of trocar sites and operation time. Success was attributed to the careful selection of trocar sites to permit safe dissection.

Adrenal Glands↗

PubMed2003

Synchronous firing and higher-order interactions in neuron pool.

The stochastic mechanism of synchronous firing in a population of neurons is studied from the point of view of information geometry. Higher-order interactions of neurons, which cannot be reduced to pairwise correlations, are proved to exist in synchronous firing. In a neuron pool where each neuron fires stochastically, the probability distribution q(r) of the activity r, which is the fraction of firing neurons in the pool, is studied. When q(r) has a widespread distribution, in particular, when q(r) has two peaks, the neurons fire synchronously at one time and are quiescent at other times. The mechanism of generating such a probability distribution is interesting because the activity r is concentrated on its mean value when each neuron fires independently, because of the law of large numbers. Even when pairwise interactions, or third-order interactions, exist, the concentration is not resolved. This shows that higher-order interactions are necessary to generate widespread activity distributions. We analyze a simple model in which neurons receive common overlapping inputs and prove that such a model can have a widespread distribution of activity, generating higher-order stochastic interactions.

Neurons↗

PubMed2002

Bone marrow chimerism prevents atherosclerosis in arterial walls of mice deficient in apolipoprotein E.

OBJECTIVE: apolipoprotein E (apoE) is a key regulator in cholesterol-rich lipoprotein metabolism. Inherited deficiency of this protein results in type III hyperlipoproteinemia in humans. ApoE, especially that derived from macrophages, can efficiently protect against development of atherosclerotic lesion. To use stem cell gene therapy or mini-transplant in treating abnormal lipid metabolism and preventing atherosclerosis, a minimal level of bone marrow chimerism must be determined. METHODS: lethally irradiated apoE deficient mice (12-16 weeks of age) fed on normal chow were transplanted with normal bone marrow cells (C57BL/6.Ly5.1) mixed with those of apoE deficient mice (C57BL/6.Ly5.2) at various ratios. Plasma cholesterol levels were determined every 3 weeks for up to 42 weeks. Areas of atherosclerotic lesion in the aortas were quantified 6 months post-transplant. Plasma apoE was measured by Western blot analysis. RESULTS: bone marrow transplantation (BMT) in apoE (-/-) mice resulted in a detectable level of plasma apoE as determined by Western blot analysis. The plasma cholesterol levels in mice with > or = 60% chimerism were normalized by 6 weeks post-transplant. Mice with < or = 40% chimerism showed significant reductions, but not normalization, in the plasma cholesterol levels even at 42 weeks posttransplant. However, atherosclerotic areas observed in 10%-chimeric mice were significantly smaller than those in control mice (P<0.01). Immunohistochemical studies in 10%-chimeric mice revealed foam cells derived from donor marrow (apoE (+/+)) and expressed immunoreactive apoE in the atherosclerotic lesion. The positive signals by Western blot analysis were represented in the plasma of up to 8% of the chimeric mice. CONCLUSION: chimerism of 10%, the minimum level analyzed, was sufficient to reduce the severity of atherosclerosis, although the plasma cholesterol levels were not completely normalized. The results indicate that stem cell gene therapy and mini-transplant may provide possible therapeutic approaches to treat patients with abnormal lipid metabolism and atherosclerosis.

Animals↗

PubMed1981

Inhibitory mechanisms of the hyper-irritability caused by picrotoxin in the rat.

Topically applied norepinephrine, dopamine, serotonin, GABA and glycine, and systemically administered clonidine, L-DOPA (plus carbidopa) and 5-hydroxytryptophan completely suppressed the cutaneous hyper-irritability produced in the trigeminal sensory distribution by picrotoxin overlying the caudal medulla. Cholinergic agents and apomorphine were ineffective. Of the positive compounds, norepinephrine, serotonin and GABA showed the shortest latencies and norepinephrine and serotonin required the lowest concentrations in order to inhibit the hyper-irritability. If L-DOPA (plus carbidopa) was injected after pre-treatment with FLA-63, the effects of L-DOPA did not appear. Similar depression of the hyper-irritability was caused by electrical stimulation of the central gray. The inhibitory effects of stimulation of the central gray was suppressed after administration of tetrabenazine, but again it produced markedly by injection of L-DOPA. From these observations it was concluded that the hyper-irritability could be suppressed by serotonergic as well as noradrenergic fibers terminating at the spinal trigeminal nucleus caudalis. The potential clinical use of L-DOPA in patients with hyperesthesia is discussed.

Animals↗

PubMed1979

An experimental model of hyper-irritability in the trigeminal skin field of the rat.

Cutaneous hyper-irritability was produced in the trigeminal sensory distribution of chronically prepared rats by injecting various central stimulants into the dorsal subarachnoid space overlying caudal medulla. Effective substances were classified into three groups according to the behavioral patterns induced. These were (1) picrotoxin and penicillin G-K, (2) strychnine and brucine, and (3) D,L-homocysteic acid. Of these substances, picrotoxin was the most effective. The hyper-irritability elicited by picrotoxin or penicillin G-K was associated with a relatively localized trigger zone in the face, while that elicited by strychnine or brucine spread beyond the trigeminal region to the first cervical dermatome. D,L-homocysteic acid evoked only spontaneous scratching and vocalization. Picrotoxin-induced hyper-irritability involved facilitation of impulse transmission from cutaneous afferent terminals to second-order neurons in the trigeminal nucleus caudalis.

Animals↗

PubMedDate not supplied

Spike independency in feed-forward networks.

A cortical neuron puts thousands of synaptic contacts on other neurons. The effect of the spike event spreads over a large number of neurons. So it is possible for spike timings to be correlated to each other. But there have not been so many reports of spike timing correlations, while there have been many reports of somewhat longer time range correlations through mean spike rates. Can independent firings be preserved in spite of a number of connections? The present study attempts to determine whether independent firings can be propagated through a simple feed-forward neural network. It is assumed that each unit obeys a threshold mechanism at each discrete time and that connections are statistically uniform with the excitation balanced to the inhibition and delay distributed. It is found that the independent firings can be stably propagated through the feed-forward network at a network parameter region, which contains the physiologically reasonable range. Another interesting result is that the independency-stable spike probability has a lower limit 0.0323.

Action Potentials↗

PubMedDate not supplied

Recording site dependence of the neuronal spiking statistics.

Spiking characteristics of neurons in the middle temporal (MT) area and the medial superior temporal (MST) area in the visual cortex of a monkey are compared with the ones in the principal sulcus (PS) area in the prefrontal cortex. The comparison is based on the basis of three inter-spike interval statistical measures: the coefficient of variation (CV), the skewness coefficient (SK) and the correlation coefficient of consecutive intervals (COR). Even for the spike sequences recorded from the same neuron, three coefficients computed from 100 intervals do not always exhibit similar values, but distribute rather widely. The distribution of three coefficients obtained from a single neuron in the MST area does not largely deviate from the distribution obtained from multiple neurons in MT and MST areas. Those distributions, however, largely deviate from the distribution obtained from neurons in the PS area. In this way, the distribution of those statistical coefficients reflects the nature of the recording site.

Action Potentials↗