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Biomedical subjects

M Kitano

Publications and source records attributed to M Kitano.

317 records · Page 18Linked to original sources
PubMedDate not supplied

Retinotopic and nonretinotopic field potentials in cat visual cortex.

Two types of field potentials were identified in cat visual cortex using contrast reversal of oriented bar gratings: a short-latency fast-local component with a retinotopic organization similar to that seen with single-unit discharges at the same cortical site, and a slow, nonretinotopic component with a longer peak latency. The slow-distributed component had an extensive receptive field mapped by measuring the amplitude of binary kernels and showed strong inhibitory interactions within the receptive field. The peak latency of the slow-local component increased with distance from the retinotopic center, suggesting a possible conduction delay. Both components showed some orientation bias depending on the laminar location, but the bias could be independent of the orientation preferred by single units in the immediate vicinity. The present findings indicate that locally generated field potentials reflect cortical mechanisms for nonlinear integration over wide areas of the visual field.

Animals↗
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Effective suppression of HIV-1 gene expression by a mammalian tRNA 3' processing endoribonuclease and external guide sequence oligozymes.

We examined the suppression of virus expression by cleaveage of the HIV-1 RNA gene using a mammalian tRNA 3' processing endoribonuclease and an External Guide Sequence Oligozyme (EGS) in vivo. We constructed an EGS expression vector that used the tRNA(met) promoter as an expression cassette for EGS. The EGS expression vector was targeted to the upstream region of gag, region. The EGS expression vector was co-transfected into COS cells with the HIV-1 gene plasmid vector. As compared with the EGS non-expressing cells and the EGS expressing cells, the EGS expressing cells with the targeted gag start codon had a clearly decreased amount of the HIV-1 gag p24 protein. The EGS expressing cells with the targeted gag start codon showed effective suppression of HIV-1 gene expression. Thus, these studies describe novel gene targeting agents for the inhibition of gene expression and antiviral activity.

Animals↗
PubMedDate not supplied

Right ventricular performance is impaired by full assist of left heart bypass. Analysis of right ventricular performance against change in afterload in heart failure models.

The purpose of this study was to assess right ventricular (RV) performance during left heart bypass (LHB) and to determine the optimum LHB driving conditions to preserve RV performance. LHB was established with a centrifugal pump in eight mongrel dogs weighing 11-19 kg. Failing heart models were induced by normothermic aortic clamping for 20 min. RV volume was measured by a conductance catheter, and RV performance was evaluated by two parameters. One was the slope of the RV end-systolic pressure-volume relationship (ESPVR) as a load independent index, and the other was the peak RV pressure (PRVP)-RV stroke volume (RVSV) relationship as a "force-velocity relationship." These parameters were measured during varying assist ratios of LHB at 0% to 100% of pulmonary artery flow, and varying afterload as induced by bilateral intrapulmonary balloon inflation. In failing hearts, RV ESPVR showed an inverse correlation, with the assist ratio of LHB significantly decreasing from 4.23 +/- 1.35 (mmHg/ml) to 3.52 +/- 1.30 (mmHg/ml; P < 0.05) after 100% LHB assist. The correlation between PRVP and RVSV also was inversely linear, the slope of this correlation becoming significantly steeper after 100% LHB assist compared to that without LHB (-0.131 +/- 0.042 vs. -0.051 +/- 0.038, P < 0.005). These two slopes intersected, and this intersection was considered the critical point of afterload above which RVSV was decreased by LHB compared to that without LHB. In addition, reducing the assist ratio made the slope of the PRVP-RVSV correlation significantly more gentle (70%: -0.072 +/- 0.037 vs. 100%: -0.131 +/- 0.042, P < 0.05), with the intersection of the two slopes shifting rightward (i.e., higher afterload). Consequently, the critical level of afterload at 70% LHB assist was significantly higher than that at 100% LHB assist (70%: 38.1 +/- 6.9 vs. 100%: 29.2 +/- 6.8, P < 0.05). Therefore, RV performance against afterload was improved by reducing the assist ratio of LHB. This study demonstrates that RV performance is impaired by full LHB assist if the RV afterload is above the critical level, and that reducing the assist ratio may improve RV performance against afterload.

Animals↗
PubMedDate not supplied

In vivo antibacterial activity of a prodrug of NM394, a thiazetoquinoline carboxylic acid derivative.

NM394 (6-fluoro-1-methyl-4-oxo-7-(1-piperazinyl)-4H-[1,3]-thiazeto [3,2-a]quinoline-3-carboxylic acid) has potent, broad-spectrum antibacterial activity in vitro, but not in vivo. To increase the bioavailability of NM394, various prodrugs were synthesized and tested. One of them, NM441, an N-(5-methyl-2-oxo-1,3-dioxol-4-yl) derivative, showed potent in vivo antibacterial activity. Using thin-layer chromatography-bioautography, we confirmed that after oral administration, NM441 was readily absorbed and hydrolyzed to NM394. Other prodrugs of NM394 were only partially metabolized to NM394. In pharmacokinetic studies in mice and monkeys, we found that the blood levels of NM394 were 7.8 and 5.9 times greater, respectively, when NM441 rather than NM394 was administered. These findings suggest that NM441 is an effective prodrug of NM394.

Animals↗
PubMedDate not supplied

Prevalence of hepatitis G virus (HGV) infection in an endemic area of hepatitis C virus (HCV) infection.

BACKGROUND/AIMS: We investigated the prevalence of hepatitis G virus infection among inhabitants of a hepatitis C virus endemic area. METHODOLOGY: Two hundred and eighty-eight inhabitants, who underwent medical examinations for health screening, were enrolled in this epidemiological study. HGV RNA and HCV RNA were detected by polymerase chain reaction. We also examined anti-HGV envelope protein (E2) antibodies in all serum samples. RESULTS: In these 288 inhabitants, we found anti-HCV antibodies (HCV-Ab) and HCV RNA in 28.5% and 17.4%, respectively. HGV RNA and anti-HGV E2 were detected in 9 (3.1%) and 16 (5.5%), respectively. One patient was positive for both HGV RNA and anti-HGV E2. The exposure rate, expressed as the percentage of people with HGV RNA and/or anti-HGV E2, was 8.3%, which was significantly lower than the incidence of positive HCV-Ab. Of the 24 patients with HGV RNA and/or anti-HGV E2, 15 (62.5%) were positive for HCV-Ab, of those HCV RNA was detected in 9 (37.5%). Further, we found a higher prevalence of HGV exposure in patients with HCV-Ab than in those without (8.3% vs. 4.4%). CONCLUSIONS: HGV infection was not identical to the epidemic hepatitis C virus infection among inhabitants of this town, suggesting that hepatitis C virus might be less infectious than hepatitis C virus.

Adult↗
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Surgical indication for aortic arch hypoplasia in infants.

To determine the surgical indications for aortic arch hypoplasia, the distal arch outer diameter, distal arch index (ratio of the distal arch diameter to the normal aortic ring diameter), and postoperative pressure gradient across the aortic arch were studied in 23 patients under 6 months of age who underwent surgery for coarctation and/or aortic arch hypoplasia. The ratio of the pressure gradient across the arch to the right radial artery was used to evaluate the postoperative level of stenosis. The maximum ratio of the pressure gradient that could be tolerated after surgery was considered to be 0.15 from the operative results. Negative correlations were found between the distal arch outer diameter and postoperative pressure gradient ratio (r = 0.80), and the distal arch index and postoperative pressure gradient ratio (r = 0.80). These correlations proved that in order to obtain a postoperative pressure gradient ratio of 0.15 or less, a distal arch outer diameter of 3.9 mm or more and a distal arch index of 0.63 or more were necessary. Consequently, a distal arch outer diameter of 3.9 mm or a distal arch index of 0.63 is considered to indicate that aortic arch hypoplasia is in need of repair.

Aorta, Thoracic↗
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Prolonged aortic cross-clamping in early infancy and method of myocardial preservation.

A cardioplegic solution containing blood with a low level of ionic calcium was prepared independent of pump-oxygenator perfusate blood, so as to contain a constant concentration of each component at any given time. Using this solution, Jatene's anatomic repair under prolonged periods of aortic cross-clamping ranging from 117 to 184 minutes (mean: 149 min) was performed on seven young infants with simple complete transposition. The ages of the patients ranged from 34 days to 3 months, with a median age of 2 months. Four patients, aged 39 days, 41 days, 2 months and 3 months, survived and showed uneventful postoperative hemodynamics. Two of the three non-survivors were considered retrospectively to have been unsuitable candidates for Jatene's anatomic repair due to their low left ventricular pressure (LV/RV pressure ratio less than 0.60 in both). The remaining infant who died had TGA with a large ventricular septal defect of the muscular type and developed a postoperative residual shunt. It was considered unreasonable to attribute the cause of death in this case to inadequate myocardial protection. Judging from our experience with these four survivors who underwent prolonged aortic clamping ranging from 117 to 160 minutes, our cardioplegic solution and the technique of its administration were considered to be effective and promising for heart surgery in young infants and neonates.

Blood↗
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The Blalock-Taussig shunt for simple complete transposition of the great arteries followed by later anatomic correction. Report of 2 cases with conflicting postoperative courses.

The Blalock-Taussig (BT) shunt was performed in two infants with simple transposition of the great arteries (TGA) after poor response to septostomy not only to improve hypoxia but also in expectation of preparing the left ventricle for later anatomic correction. One patient had adequate muscle mass and pressure of the left ventricle after the shunt and underwent successful anatomic correction. The other patient developed intractable heart failure following the shunt. Anatomic correction was performed with success in this patient after pulmonary artery banding and takedown of the BT shunt. Based on these experiences, if heart failure does not develop or is controllable after BT shunt, there may be a possibility of later anatomic correction. However, if uncontrollable failure occurs, the shunt should be taken down and arterial or venous switch correction should be performed as soon as possible.

Female↗
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Rheumatoid synovial cyst of the hip joint: a case report.

Rheumatoid synovial cyst of the hip joint in a 52-year-old man including iliopsoas bursal extension was demonstrated by arthrography and excision biopsy. Surgical excision of the cyst and femoral head replacement were carried out. There was no recurrence for 15 months postoperatively. The condition should be suspected in patients with degenerative changes in the hip joint and adjacent unexplained palpable mass.

Arthritis, Rheumatoid↗
PubMedDate not supplied

The effect of pulsing electromagnetic field on bone ingrowth into a porous coated implant.

Electromagnetic stimulation is known to promote bone formation in cases of fracture and pseudoarthrosis. The possibility of using electromagnetic field to promote bone ingrowth into a porous coated implant was investigated in this study using Japanese albino rabbits. A titanium implant coated with beads of 250-300 microns in diameter around a stem of 1.7 mm in diameter was inserted into the humerus cavity of a Japanese albino rabbit. The humerus was stimulated by pulsing electromagnetic fields at 2 Gauss, 10Hz, 25 microseconds for 14 days. The circumference of grown bone into the implant was measured, and calculated in area equivalent for determination of the area of new bone. Bone ingrowth was significantly promoted by consecutive 14 days. The result suggests that electromagnetic stimulation is useful for achieving further bone ingrowth into a porous coated implant.

Animals↗