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Biomedical subjects

K Sakabe

Publications and source records attributed to K Sakabe.

At least 37 records · Page 2Linked to original sources
PubMed1999

Inhibitory effect of natural and environmental estrogens on thymic hormone production in thymus epithelial cell culture.

The present study was carried out to assess the direct effect of natural estrogen and environmental estrogens on thymus epithelial cell (TEC) production/secretion of the thymic hormone thymosin-alpha 1 by using the technique of quantitative high-performance liquid chromatography. The presence of estrogen receptors in the TECs was also investigated. Murine TECs were cultured in the experimental DMEM medium containing various concentrations of natural or environmental estrogens, which was followed by determining the production of thymosin-alpha 1. The production of thymosin-alpha 1 by TECs was significantly inhibited by increasing concentrations of 17beta-estradiol (natural estrogen) over 3 x 10(-11) M, genistein (phytoestrogen) over 3 x 10(-9) M, coumestrol (phytoestrogen) over 3 x 10(-9) M, alpha-zearalanol (livestock anabolic) over 3 x 10(-7) and bisphenol-A (plastic) over 3 x 10(-6) M. Small amounts of estrogen receptor were present in the TECs. The above results clearly indicate that natural and environmental estrogens directly modulate TECs to produce thymic hormone probably through an estrogen receptor mechanism. Furthermore, our finding may be useful for evaluating biological effects of chemicals with estrogenic activity.

Animals↗
PubMed1999

Coronary flow velocity immediately after reperfusion reflects myocardial microcirculation in canine models of acute myocardial infarction.

Recent reports indicate that the coronary microcirculation is sometimes injured, despite successful reperfusion in acute myocardial infarction (AMI). However, it is difficult to evaluate the coronary microcirculation immediately after reperfusion by using only angiography. The purpose of this study was to examine the relationship between the pattern of coronary blood flow velocity and myocardial microcirculatory injury immediately after reperfusion in AMI. The authors recorded the left circumflex coronary flow velocity by using the Doppler guide wire method 10 minutes after reperfusion in a canine model of AMI. In addition, myocardial contrast echocardiography was performed with the injection of contrast medium into the left circumflex coronary artery before clamping of the coronary artery and 15 minutes after release of the clamp. From these images, the ratio of the normalized gray-level postreperfusion to preclamping in the contrast-enhanced area was determined. It was compared with coronary flow velocity variables. In the 10 dogs with a diastolic-to-systolic velocity ratio (DSVR) < 4.0, this velocity ratio 10 minutes after reperfusion correlated positively (r = 0.75, p < 0.01) with the normalized gray-level ratio. However, the remaining three dogs with a DSVR > or = 4.0 markedly deviated from this pattern. Coronary flow velocities in the three dogs were characterized by a greater decrease in systolic flow velocity and occurrence of early systolic retrograde flow. Myocardial contrast echocardiographic images in these three dogs demonstrated a lower normalized gray-level ratio. In conclusion, the coronary flow velocity pattern immediately after reperfusion may reflect myocardial microcirculatory injury.

Albumins↗
PubMed1998

Right and left ventricular wall motion velocities as diagnostic indicators of constrictive pericarditis.

The purpose of this study was to examine the usefulness of pulsed tissue Doppler imaging for diagnosing constrictive pericarditis. Motion velocities of the ventricular septum (VS) and left ventricular (LV) posterior wall along the short axis, and those of the anterior right ventricular (RV) wall, VS, and LV posterior wall along the long axis were recorded using pulsed tissue Doppler imaging in 12 patients with constrictive pericarditis, who were diagnosed by cardiac catheterization, and also in 20 normal subjects. Peak early diastolic and atrial systolic velocities (Ew and Aw, respectively) were calculated, and the time between the aortic component of the second heart sound and the peak of the early diastolic velocity (IIA-Ew) was determined. The peak Ew and II A-Ew along the short and long axes were significantly higher and shorter, respectively, in the patient group than in the normal group. In the patient group, the motion velocity of the VS along the short axis showed a "backward" motion with a sharp and marked peak velocity immediately before Ew, or a biphasic early diastolic wave; a clear "downward" motion immediately after Ew was observed in the motion velocities of the anterior RV wall, VS, and LV posterior wall along the long axis. These distinctive backward and downward motions were not observed in any of the ventricular walls of the normal subjects. In conclusion, the early diastolic RV and LV wall motion velocity patterns along the short and long axes as measured by pulsed tissue Doppler imaging provide important information for the diagnosis of constrictive pericarditis.

Adult↗
PubMed1998

Characteristics of coronary flow velocity in constrictive pericarditis.

A 50-yr-old man developed constrictive pericarditis following an episode of acute pericarditis. Cardiac catheterization revealed a typical early diastolic dip and plateau configuration in both the right and left ventricular pressure curves. The coronary flow velocity pattern determined using an intracoronary Doppler guidewire showed an abrupt decrease in peak velocity at early diastole and followed by plateau until late diastole, the so-called dip and plateau configuration. After a successful pericardiectomy, cardiac catheterization no longer showed the dip and plateau configuration, but the early diastolic dip in the coronary flow velocity persisted probably because of infiltration of the organic involvement into the myocardium.

Blood Flow Velocity↗
PubMed1998

Right atrial potential profiles during atrial fibrillation predict the success of atrial defibrillation.

The right atrial electric potential was measured in 29 patients with chronic atrial fibrillation, and the clinical utility of these measurements in predicting the success of atrial defibrillation was investigated. The endocardial electric potential was recorded at 12 sites within the right atrium (high, middle, and low loci of anterior, posterior, lateral, and medial sites of the right atrium) with an electrode catheter. The duration and polar displacement of the atrial waves were measured at the one site that showed the maximum atrial electric potential among the 12 sites. The ratio of the maximum to the minimum atrial electric potential (atrial wave ratio) was calculated. Patients were classified into two groups according to the success (n = 6) or failure (n = 23) of atrial defibrillation. Electrophysiologic data were compared between the two groups, and correlations were evaluated between the data and the maximal left atrial diameter obtained from M-mode echocardiography. The two groups did not differ in the duration and polar displacement of the atrial waves. However, the atrial wave ratio was significantly lower in the success group than in the failure group, and the success rate of atrial defibrillation was also significantly greater in the patients with an atrial wave ratio of 10 or lower. This ratio showed a positive correlation with the maximal left atrial diameter; it became more difficult to achieve atrial defibrillation as the atrial wave ratio increased. Thus, the right atrial electric potential profile of patients with atrial fibrillation is a useful predictor of the success of atrial defibrillation.

Adolescent↗
PubMed1998

Estrogenic xenobiotics increase expression of SS-A/Ro autoantigens in cultured human epidermal cells.

SS-A/Ro autoantibodies are detected at high levels in patients with autoimmune diseases such as systemic lupus erythematosus. It has been reported that natural estrogen is capable of inducing cell surface expression of SS-A/Ro autoantigens in human epidermal keratinocytes. In this study, we analysed, by reverse transcriptase polymerase chain reaction and immunohistochemistry, the effects of estrogenic xenobiotics (i.e. environmental estrogens) on the expression of 52-kDa SS-A/Ro autoantigen in cultured keratinocytes. At a concentration of 10 microM, various estrogenic xenobiotics derived from plants, insecticides, or detergents induced up to a 3-fold increase in 52-kDa SS-A/Ro mRNA levels in human keratinocytes compared with untreated cells. The immunohistochemistry results paralleled the reverse transcriptase polymerase chain reaction results. These findings suggest that environmental stimulation can induce the expression of autoantigens such as SS-A/Ro.

Adult↗
PubMed1998

Coronary flow velocity patterns immediately after reperfusion reflect the pathologic characteristics of reperfused myocardium in canine models of acute myocardial infarction.

BACKGROUND: It is difficult to evaluate the extent of myocardial injury after successful reperfusion following acute myocardial infarction (AMI). We investigated the relationship between the coronary flow velocity pattern immediately after reperfusion and pathologic characteristics after myocardial reperfusion injury in dogs. METHODS: We measured distal coronary flow velocity variables in the left circumflex coronary artery in a canine model of AMI (n = 12) 10 min after the release of a clamp (3-10 h clamp procedure) using a 0.35 mm Doppler guide-wire. Dogs were divided into two groups according to presence or absence of early systolic retrograde coronary flow. Hearts were excised 2 h after reperfusion and examined histopathologically. RESULTS: The clamping time tended to be longer in dogs with early systolic retrograde coronary flow. Neutrophil infiltration was observed in the myocardium of dogs without systolic retrograde flow (n = 9); hemorrhage was rarely detectable and the myocardium maintained a bundle form. However, the bundle form of the myocardium became rough, and the severity of the incidence of hemorrhage tended to increase as the ratio of the diastolic coronary flow velocity to systolic velocity (DSVR) decreased. Vacuolar degeneration of the myocardium was also observed in hearts with a relatively low DSVR. In the group with systolic retrograde flow (n = 3), hearts were characterized by coagulation necrosis, marked vacuolar degeneration of the myocardium and diffusely distributed red cells in the intermyocytes. Systolic antegrade flow velocity was much reduced in this group, resulting in a markedly increased DSVR. These findings appeared to be related to severe myocardial damage. CONCLUSIONS: Coronary flow velocity patterns immediately after successful reperfusion appear to reflect the pathologic characteristics of the reperfused myocardium in dogs with AMI.

Animals↗
PubMed1998

[Flow cytometric analysis of the effects of 50 Hz magnetic fields on mouse spermatogenesis].

The cellular effects of an extremely-low-frequency (ELF) magnetic field on mouse spermatogenesis were assessed by DNA flow cytometry and serum testosterone. Seven week old male ICR mice were exposed to a 50 Hz magnetic field the strength of which was 1.0 m Tesla. Seven mice per treatment group were exposed for 13, 26, 39 or 52 days. For each experimental point, an equal number of mice per sham-treated group were used as a control and were exposed only to the background field below 1 mu Tesla in the same room as the treatment group. In the control mice, the testis cellular DNA content distribution by flow cytometory was characterized by four quantifiable populations; round spermatids (1C), spermatogonia and other diploid cells (2C), spermatogonial cells synthesizing DNA (S-phase) and primary spermatocytes (4C). In animals exposed for 26 days the number of cells in the 4C and the 4C:2C ratio was significantly lower, and the 1C:4C ratio (meiotic transformation) was significantly higher than the corresponding control groups. In animals exposed for 52 days the cell population in 1C and the 1C:2C ratio (total germ-cell transformation) was significantly higher, and the cell population in 2C was significantly lower than the corresponding control groups. The concentration of serum testosterone in animals exposed for 13 days was significantly higher than in the corresponding control group. These changes suggest that long-term exposure to an ELF magnetic field had a possible effect on the proliferation and differentiation of spermatogonia.

Animals↗
PubMed1998

The effects of nicorandil on electrophysiological changes in acute myocardial ischemia and reperfusion.

This study was undertaken to clarify the effects of nicorandil on electrophysiological changes during acute ischemia and following reperfusion. We prepared an acute ischemic heart model by ligating the left anterior descending coronary artery in 27 dogs. After 10 minutes, reperfusion was performed. The changes in ventricular effective refractory period (ERP) and intramyocardial conduction time (ICT) were compared between the nicorandil group (n = 12) which received nicorandil intravenously before the coronary ligation and the control group (n = 15). In the control group, the ERP was shortened during ischemia, and rapidly shortened immediately after reperfusion, but was slightly prolonged 10 minutes after reperfusion. The ICT was prolonged during ischemia, but returned to the pre-ischemia value after reperfusion. In the nicorandil group, the changes in ERP and ICT were significantly inhibited compared to those in the control group. The incidence of ventricular fibrillation (VF) during reperfusion was 42% in the control group. However, there was no VF during reperfusion in the nicorandil group. Therefore, nicorandil may correct both the delayed conduction and the uneven ventricular effective refractory period detected during acute ischemia and following reperfusion, inhibiting the development of ventricular arrhythmia during reperfusion.

Acute Disease↗
PubMed1998

Basic fetoprotein in normal and pathologic urine.

We developed a latex agglutination nephelometric immunoassay for urinary basic fetoprotein (BFP) that functioned well and had good specificity, precision, and recovery. Reference intervals started below 0.5 microgram/L, the lower limit of the range of sensitivity of the assay, and went up to 7.0 micrograms/L at the 97.5th percentile without age- or sex-related variation, in accordance with the NCCLS guidelines. BFP was unstable at pH 5.0 at 4 degrees C and 25 degrees C. The western blot method showed BFP found in the semen to be structurally identical to purified BFP from hepatoma ascites, in which concentration ranged from 94.2 to 145.2 micrograms/L and, further, to have the same molecular weight and reactivity with a monoclonal antibody. BFP levels were elevated in cases urinary BFP concentration included ureter stone, infection, and prostate and bladder cancer. Moreover, BFP concentration correlated closely with that of alpha 2-macroglobulin, indicating that BFP is probably secreted locally in close pathophysiologic association with post-renal hemorrhage. We thus conclude that BFP is a urinary nonspecific marker for inflammation or tumor. The best indication for BFP as a tumor marker may be follow-up when diagnosis of genitourinary cancer is definite.

Adult↗
PubMed1997

Large-format imaging plate and weissenberg camera for accurate protein crystallographic data collection using synchrotron radiation.

Off-line and on-line protein data-collection systems using an imaging plate as a detector are described and their components reported. The off-line scanner IPR4080 was developed for a large-format imaging plate ;BASIII' of dimensions 400 x 400 mm and 400 x 800 mm. The characteristics of this scanner are a dynamic range of 10(5) photons pixel(-1), low background noise and high sensitivity. A means of reducing electronic noise and a method for finding the origin of the noise are discussed in detail. A dedicated screenless Weissenberg camera matching IPR4080 with synchrotron radiation was developed and installed on beamline BL6B at the Photon Factory. This camera can attach one or two sheets of 400 x 800 mm large-format imaging plate inside the film cassette by evacuation. The positional reproducibility of the imaging plate on the cassette is so good that the data can be processed by batch job. Data of 93% completeness up to 1.6 A resolution were collected on a single axis rotation and the value of R(merge) becomes 4% from a tetragonal lysozyme crystal using a set of two imaging-plate sheets. Comparing two types of imaging plates, the signal-to-noise ratio of the ST-VIP-type imaging plate is 25% better than that of the BASIII-type imaging plate for protein data collection using 1.0 and 0.7 A X-rays. A new on-line protein data-collection system with imaging plates is specially designed to use synchrotron radiation X-rays at maximum efficiency.

Journal Article↗
PubMed1997

Time-resolved protein crystallography with large-angle oscillations: an application of a protein data-collection system using the Weissenberg technique and a large-format imaging plate.

A diffraction-intensity data-collection system with synchrotron radiation X-rays utilizing the screenless Weissenberg technique and incorporating a large-format imaging plate is one of the most suitable apparatus for time-resolved protein crystallography with larger angle oscillations than hitherto described. The time resolution and data quality of the system have been tested using a tetragonal lysozyme crystal as a test sample in a flow-cell experiment at the bending-magnet beamline 18B at the Photon Factory, and a time resolution of 15 min is confirmed.

Journal Article↗
PubMed1997

Sex hormones and the thymus in relation to thymocyte proliferation and maturation.

This paper reviews the mechanism of sex hormone actions on the thymus, presenting mainly our data obtained at the cellular and molecular levels. First, data supporting the "genomic" action via the nuclear sex hormone receptor complexes are as follows: 1) sex hormone receptors and the thymic factor (thymulin) are co-localized in thymic epithelial cells, but not in T cells; 2) production/expression of thymic factors (thymulin, thymosin alpha 1) are remarkably inhibited by sex hormone treatment; 3) sex hormones cause changes in T cell subpopulations in the thymus; and 4) sex hormones strongly influence the development of thymus tumors in spontaneous thymoma BUF/Mna rats through their receptor within the tumor cells. Secondly, data indicating the "non-genomic" action of sex hormones via a membrane signal-generating mechanism are as follows: 1) the proliferation/maturation of thymic epithelial cells is mediated through protein kinase C activity introduced by sex hormones; 2) sex hormones directly influence DNA synthesis and cdc2 kinase (cell cycle-promoting factor) activity.

Animals↗
PubMed1996

Autonomous control of expression of genes for insulin-like growth factors during the proliferation and differentiation of C2C12 mouse myoblasts in serum-free culture.

The proliferation and differentiation of skeletal muscle cells in culture are usually controlled by serum components, and the differentiation can be induced by a reduction in the serum concentration. Insulin-like growth factors (IGFs) play a critical role in stimulating myoblast differentiation, and the expression of their genes is controlled by serum factors. We have found that C2C12 myoblasts are capable of proliferation and differentiation even in serum-free medium that does not contain peptide mitogens. During these processes in serum-free medium, the accumulation of mRNAs for IGFs in the cells was observed; and their levels increased with concomitant increases in creatine kinase activity and myotube formation and a decrease in DNA synthesis. Thus, the present results suggest that proliferation and differentiation of C2C12 cells are autonomously controlled and that the increase in the expression of the IGFs may be independent of exogenous components.

Animals↗
PubMed1996

A preliminary description of the crystal structure of gamma-glutamyltranspeptidase from E. coli K-12.

The structure of GGT [EC 2.3.2.2] from E. coli K-12 was studied at 3 A resolution by X-ray crystallography. Initial protein phases were calculated using two kinds of Pb2+ derivatives. The phases were refined by non-crystallographic 2-fold symmetry electron density averaging combined with solvent flattening and histogram matching. The GGT molecule has overall dimensions of 60 x 50 x 40 A. There are two antiparallel beta-pleated sheets consisting of 6 and 7 beta-strands. The two beta-sheets form a wall-like structure. Twelve short alpha-helices were detected, of which the maximum length appears to be four helix turns.

Crystallography, X-Ray↗
PubMed1996

Efficacy of coronary angioplasty with a cutting balloon in a case of repeated coronary stenosis.

A 59-year-old man with a 90% stenosis of the left anterior descending coronary artery was treated with percutaneous transluminal coronary angioplasty (PTCA) using a conventional balloon. The stenosis recurred repeatedly and was retreated by PTCA three times. The stenosis again recurred, so coronary angioplasty using a cutting balloon was performed. During the present admission, we planned to place a coronary stent in the LAD to prevent restenosis. Anticoagulation is necessary after coronary stenting. However, anticoagulation was contraindicated in this patient because of ulcerative colitis. Therefore, coronary angioplasty using a cutting balloon was performed instead. The stenosis decreased from 90% to 25%, but a coronary dissection occurred. An angiogram performed 3 months later showed no stenosis, with resolution of the coronary dissection. The use of a cutting balloon preventing coronary artery restenosis following balloon angioplasty is a promising new technique which warrants further study.

Aortic Dissection↗
PubMed1995

Female sex hormone stimulates cultured human keratinocyte proliferation and its RNA- and protein-synthetic activities.

The present study was carried out to assess the effect of female sex hormones, i.e., estrogen and progesterone, on human keratinocyte proliferation, and its RNA- and protein-synthetic activities in a culture system. The presence of receptors for estrogen and progesterone and their messenger ribonucleic acids (mRNAs) in the cultured cells was also investigated. Human keratinocytes were cultured in the experimental DMEM-Ham's F12 medium containing various concentrations of estrogen or progesterone, which was followed by determining cell yields and [3H]thymidine incorporation. The keratinocytes were also tested for RNA- and protein-synthetic activities by measuring [3H]uridine and [3H]leucine incorporation. Both estrogen and progesterone receptors were determined by the enzyme immunoassay method using monoclonal antibodies, and mRNA expression for these hormone receptors was detected by in situ hybridization. Cell yields and [3H]thymidine incorporation increased gradually until 3 x 10(-10) M of both estrogen and progesterone, decreased thereafter until 3 x 10(-7) M, and peaked at 3 x 10(-10) M. [3H]Uridine and [3H]leucine uptake followed almost the same pattern as the cell proliferation, peaking at 3 x 10(-10) M of both hormones. Small amounts of estrogen and progesterone receptors were present in the cultured cells, and their mRNAs were found to be present in the cell cytoplasm. These results clearly suggest that sex hormones play an important role in human keratinocyte proliferation, and its RNA- and protein-synthetic activities, at least in part, via their hormone receptors.

Cell Division↗