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Biomedical subjects

A Aoki

Publications and source records attributed to A Aoki.

At least 109 records · Page 6Linked to original sources
PubMed1994

The mammosomatotroph: a transitional cell between growth hormone and prolactin producing cells? An immunocytochemical study.

In this report the occurrence of mammosomatotroph (MS) cells was correlated with changes in the somatotroph population of adult rat pituitary gland submitted to various experimental conditions (ovariectomized, orchidectomized and intact males, and after treatment with oestradiol benzoate). Cell and volume density of somatotrophs were assessed in sections stained with the immunogold-silver enhancement technique. Mammosomatotrophs were identified by double immunogold labelling at the electron microscopic level. Colocalization of prolactin (PRL) and growth hormone (GH) in the same cell was rarely observed. Only a few MS cells (0.1-0.2% of all parenchymal cells) were found in some experimental models. Oestrogen treatment decreased both cell and volume density of somatotrophs in ovariectomized rats. In this model, serum GH increased significantly but no changes in the pituitary content of the hormone were observed. Our results demonstrate that MS cells are an uncommon cell type in the pituitary of adult ovariectomized, orchidectomized and intact male rats. The oestrogen treatment, which is well known to induce proliferation of lactotrophs, has no effects on the MS population. Data presented in this report do not support the suggested role for mammosomatotrophs as transitional cells in the presumptive interconversion of PRL and GH producing cells.

Animals↗
PubMed1994

Protection of mice against Clostridium chauvoei infection by anti-idiotype antibody to a monoclonal antibody to flagella.

Polyclonal rabbit anti-idiotypic antibody (anti-Id) against the protective monoclonal antibody specific to the flagella of Clostridium chauvoei was produced, purified, and characterized. Anti-Id inhibited the binding of its related monoclonal antibody to the flagellar antigen, suggesting that the anti-Id bore an internal image of the flagellar antigen. When mice were immunized with anti-Id intraperitoneally, the survival rate increased significantly, compared with mice immunized with normal rabbit IgG (P < 0.01), and specific anti-flagellar antibodies were induced.

Animals↗
PubMed1994

Stunned myocardium following prolonged cardiopulmonary bypass: effect of warm versus cold cardioplegia in the canine model.

"Stunned myocardium" is defined as the prolonged but transient postischemic contractile dysfunction of viable myocardium that has been salvaged by reperfusion. This phenomenon, although first characterized in the experimental canine model of coronary artery occlusion/reperfusion, also occurs following transient global ischemia. Moreover, despite the superb cardioprotection conferred by administration of cold cardioplegia during aortic cross-clamping, stunned myocardium is a well-recognized sequela of prolonged cardiopulmonary bypass. Using the anesthetized open chest dog, we tested the concept that continuous retrograde infusion of warm blood cardioplegia would effectively prevent ischemia during prolonged aortic cross-clamping and thereby preclude the development of stunned myocardium following bypass. Thirteen dogs were placed on cardiopulmonary bypass and randomized to receive: (1) continuous retrograde administration of warm blood cardioplegia (n = 8); or (2) intermittent retrograde cold blood cardioplegia (n = 5) during a 3-hour cross-clamp period. Left ventricular (LV) systolic function (i.e., area LV ejection fraction and posterior LV free wall thickening assessed by two-dimensional echocardiography) and hemodynamic parameters were monitored at baseline and at 1 and 2 hours postbypass and, at the end of the protocol, transmural myocardial biopsies were obtained for electron microscopic analysis. All dogs in both treatment groups showed electron microscopic evidence of mild and reversible morphological injury indicative of stunned myocardium, with no difference between dogs that received warm versus cold cardioplegia. Direct comparison of LV function between the two groups was confounded by a profound decrease in afterload in dogs that received cold cardioplegia. However, incorporation of systemic vascular resistance as a covariate revealed that LV function following bypass was modestly depressed at approximately 85% of baseline values, and that continuous administration of warm cardioplegia did not prevent this hypokinesis. Thus, in our canine model: (1) morphological injury and LV dysfunction induced by 3 hours of aortic cross-clamping is subtle; and (2) continuous retrograde infusion of warm blood cardioplegia during the cross-clamp period failed to preclude myocardial stunning following prolonged cardiopulmonary bypass.

Animals↗
PubMed1994

In vitro studies on laser scaling of subgingival calculus with an erbium:YAG laser.

The effectiveness of a newly-developed Er:YAG laser with a fiber delivery system to remove subgingival calculus was examined in vitro. Fifty-three (53) periodontally-involved human extracted teeth with a band of subgingival calculus were used. Two experiments were conducted: in experiment 1, laser scaling was performed with water irrigation on a straight line and on a broad area, against the subgingival calculus at the energy levels of 10 to 120 mJ/pulse (3.5 to 42.4 J/cm2/pulse) and the pulse repetition rate of 10 pps. The morphological changes of the laser-scaled site were observed by SEM, and the efficiency of laser scaling was determined. In experiment 2, laser scaling was performed with and without water irrigation at 30 mJ/pulse and 10 pps. The morphological changes, the efficiencies, and temperature changes with and without water irrigation were compared. The pulsed Er:YAG laser used with water irrigation was able to remove the subgingival calculus from the tooth root effectively at the energy level of about 30 mJ/pulse (energy density: 10.6 J/cm2/pulse) and 10 pps, under in vitro conditions. Ablation of the tooth substance on laser scaling was generally observed within the cementum. There was little increase in temperature on the root surface during laser scaling. This study suggests the potential for the clinical application of the Er:YAG laser in subgingival scaling.

Analysis of Variance↗
PubMed1994

[Analysis of cases with liver abscess following transcatheter arterial chemoembolization (TAE) for malignant hepatic tumors].

A total of 182 TAE procedures were carried out in 98 patients with malignant hepatic tumors during the last five years. Liver abscess following TAE occurred in 3 cases (3.1%) and in 3 procedures (1.7%). All cases were discharged after successful percutaneous transhepatic abscess drainage. One case had hepatocellular carcinoma. Another case had undergone total gastrectomy and esophagojejunostomy with Roux-Y reconstruction for gastric leiomyosarcoma. The other had undergone right hemicolectomy and pancreatoduodenectomy for colon cancers and carcinoma of the ampulla of Vater. Communication between the abscess and the intrahepatic bile duct was recognized in 2 cases. In the abscess culture, E. coli and Citrobacter freundii were detected. These results suggest the major factor leading to abscess formation is biliary infection. Therefore, a previous bilio-enteric anastomosis should be regarded as a risk factor for liver abscess following TAE.

Aged↗
PubMed1994

Probability of valve repair for pure mitral regurgitation.

The advantages of mitral valve repair are well established. Unfortunately, not all valves can be repaired. This presents a dilemma for the surgeon in terms of advising the patient as to the timing of operation and in decision making during operation. Patients requiring correction for pure mitral regurgitation are a heterogeneous group. By classifying the patients according to the cause of mitral regurgitation and the pathologic anatomy, we determined patterns of repair in our surgical practice for 100 consecutive patients with pure mitral regurgitation treated from January 1990 through June 1991. Patients with degenerative valve disease that spares the central portion of the anterior leaflet were likely to undergo valve repair (22/24), whereas those patients with involvement of the central portion of the anterior leaflet were likely to require replacement (15/17). This disparity may be related to the techniques of repair that were used and has spurred us to use other techniques when faced with this problem. Patients with ischemic mitral regurgitation caused by anulus dilatation were likely to undergo repair (15/17), whereas patients with ruptured papillary muscle usually underwent valve replacement (8/9). Operative mortality in this series was accurately predicted by the Parsonnet risk score. Combining knowledge of the expected operative risk and the likelihood of valve repair based on anatomic and pathologic considerations should allow the surgeon to better inform patients of their surgical options.

Adult↗
PubMed1993

Polyclonal B cell activation and antigen-specific stimulation in mice with chronic graft-versus-host reaction.

Primary chronic graft-versus-host reaction (GVHR) was induced in (C57BL/10 x DBA/2)F1 (BDF1) mice via the transfer of parental DBA/2 derived lymphocytes. A significant increase in the absolute number of IgM- and IgG-secreting cells was found in recipient BDF1 mice at 3 weeks post-transfer. The increase included B cells reactive with both self- and non-self-antigens, without being skewed toward the production of autoantibodies. Later in the disease process (approximately 6-8 weeks post-transfer), we detected an increased number of B cells that secreted antibodies reactive with a select subset of autoantigens in about 30% of BDF1 recipients (3 of 9 mice). These findings suggest that not only antigen-specific stimulation, which was detected in a late stage, but also initial polyclonal activation may account for chronic GVHR.

Animals↗
PubMed1993

Fate of degenerating lactotrophs in rat pituitary gland after interruption of lactation: a histochemical and immunocytochemical study.

In the pituitary gland of pregnant and lactating rats a striking proliferation of lactotrophs occurs to meet the increased demands for prolactin. Following interruption of lactation the redundant lactotrophs undergo a massive degeneration until pre-pregnant proportions are re-established. Immunocytochemical detection of prolactin allows the recognition of degenerating lactotrophs until advanced stages of degeneration and leads to the conclusion that this process is autolytic in nature. Histochemistry of acid phosphatase reveals a remarkable accumulation of this enzyme in Golgi cisternae and lysosomes. At later stages of degeneration the acid phosphatase spreads throughout the entire cell. The presence of increased numbers of necrotic cells appears to activate phagocytosis of stellate cells and, to a lesser extent, of follicular cells. Stellate cells responsible for the secondary processing of cell residues are isolated cells characterized by a prominent oval nucleus and an electron-lucent cytoplasm with scarce organelles and extensive cytoplasmic processes. They appear as scavenger cells engulfing cell remnants and debris. Immunocytochemistry of S-100 protein discloses differential staining of two types of cell, one forming clusters of 2-4 cells with faint immunoreactivity, while the other type consists of isolated cells with a stellate profile and stronger labelling to S-100 protein.

Acid Phosphatase↗
PubMed1993

Cardiac operation without hypothermia for the patient with cold agglutinin.

Recently, a new technique for myocardial protection that does not rely on hypothermia has been reported. In this method, the heart is continuously perfused with normothermic hyperkalemic blood cardioplegia during the cross-clamp period. Cardiac arrest is achieved and maintained using high levels of potassium. Hypothermia is not part of this technique; thus, the danger of hypothermia can be avoided in the patient with cold agglutinin disease without compromising myocardial protection. This communication reports our experience using retrograde continuous normothermic blood cardioplegia in one patient with potent cold agglutinins and severe coronary artery occlusive disease. This patient experienced an uneventful operative and postoperative course and remains asymptomatic, now more than two years after operation.

Aged↗
PubMed1993

Time course of acid-base regulation following intraperitoneal CO2 administration in man.

Chronological changes in acid-base status during laparoscopic CO2 insufflation were studied for 2 h in 10 patients who underwent laparoscopic cholecystectomy. Carbon dioxide pressure in alveolar air as well as arterial blood promptly and significantly increased within 5 min whereas amount of pulmonary CO2 elimination significantly increased after 15 min. Pulmonary gas exchange ratio (R) exceeded the level of unity at 10 min and progressively increased toward the end of 2 h observation. These results indicated that CO2 equilibrium process between different body compartments with different time constant took place and apparent equilibrium was not completed during observation. In vivo buffer value of the arterial blood started to decrease after 5 min and decreased to about one-third the in vitro buffer value until the end of observation. This indicated that CO2 equilibrium between blood and interstitial fluids took place slowly during entire period of study and no significant contribution of cellular buffering was developed. We conclude that slower development of acid-base regulation in the present study than those reported in the previous studies may have been derived from small diffusion area and blood perfusion for CO2.

Acid-Base Equilibrium↗
PubMed1993

Augmented arterial to end-tidal PCO2 difference during laparoscopic CO2 insufflation in man.

Acid-base status of the blood and tissue fluids and pulmonary gas exchange were continuously observed during intra-abdominal CO2 insufflation for 2 h in 8 paralyzed and artificially ventilated patients who underwent laparoscopic cholecystectomy or resection of the sigmoid colon. Carbon dioxide pressure in the arterial and mixed venous blood as well as in end-tidal air started to increase already at 5 min CO2 insufflation. On the other hand, appreciable elevation in VCO2 and tissue PCO2 (PTCO2) was noted only after 15 min. In vivo buffer value (beta) was well within the normal physiological range at 5 min and gradually declined up to 2 h. These observations indicated that chemical buffering to CO2 and redistribution of buffer base among the blood and tissue fluids were slowly developed during entire period of observation. In reflecting these experimental findings, arterial to end-tidal PCO2 difference (a-ADCO2) and respiratory gas exchange ratio (R) were promptly and significantly increased at 5 min and maintained slow increment up to 2 h. We conclude that these profiles of a-ADCO2 and R can be explained by initially rapid and subsequently slow augmentation in ventilation-perfusion ratio (VA/Q) during the specific type of respiratory acidosis elicited in this study.

Acid-Base Equilibrium↗
PubMed1993

Combination therapy with rhGM-CSF and rhEpo for two patients with refractory anemia and aplastic anemia.

Because GM-CSF possesses burst-promoting activity (BPA) and megakaryocyte colony-stimulating activity (Meg-CSF) as well as stimulating activity on granulocyte-macrophage progenitors, and erythropoietin (Epo) has thrombopoietin-like activity, the combination therapy of GM-CSF and Epo seems to be more effective for stimulating erythropoiesis and thrombocytopoiesis in patients with pancytopenia. For this reason, the combination therapy of recombinant human GM-CSF (rhGM-CSF) and rhEpo was performed in two patients with refractory anemia (RA) and aplastic anemia (AA). Epo-unresponsive anemia was remarkably improved by adding rhGM-CSF to Epo and the effect lasted for 1 1/2 months in a patient with RA, but severe anemia occurred again immediately after the discontinuation of Epo. The neutralizing antibodies against GM-CSF were not demonstrated at the phase when anemia re-progressed in this patient. In a patient with AA, anemia and thrombocytopenia, which were refractory to previous administration of rhGM-CSF, responded to the combined administration of GM-CSF and Epo. Although the effects were maintained for 3 1/2 months, the anemia and thrombocytopenia became worse again after the administration of rhGM-CSF was changed from daily to every other day. These findings suggest the usefulness of combination therapy of GM-CSF and Epo for patients with pancytopenia.

Adult↗
PubMed1992

Ultrastructural and immunocytochemical study of the myoendocrine cells of the fish Hypostomus cordovae.

The myoendocrine cells of the heart of Hypostomus cordovae (Günther 1880), a teleost fish from South America, were investigated by electron microscopy and immunohistochemistry. By applying antibodies raised against synthetic cardiodilatin 99-126 (CDD/ANP 99-126), a specific labeling of this hormone was found in the heart of this fish, mainly in myoendocrine cells of atrial trabeculae, where specific secretory granules are stored. The distribution of secretory granules exhibited striking seasonal variations. In winter there were fewer differentiated myoendocrine cells, which were easily recognized by the presence of specific secretory granules, most of which occur clustered in perinuclear areas of the cells. By contrast, in summer the majority of the myocardic cells of the atrium are active endocrine cells. They contain abundant secretory granules widely scattered in the cytoplasm, many of them polarized toward the subendocardial aspect of the cell. The secretory granules can be easily differentiated from the Weibel-Palade granules of endothelial cells, the shape, size and content of which were typical at electron-microscopic level. In addition, these endothelial granules did not display CDD immunoreactivity. The presence of cardiodilatin in a fish such as Hypostomus cordovae further supports the view that cardiac hormones are present in many Vertebrates and may preserve analogous roles such as those reported in other species throughout the group.

Animals↗
PubMed1992

Postnatal development of the hypothalamic ventromedial nucleus: neurons and synapses.

1. In this report the postnatal differentiation of the hypothalamic ventromedial nucleus (VMN) was studied. The main maturational changes detected at the fine structural level occurred between 10 and 20 days of postnatal life. 2. In 5-day-old rats the majority of neurons was undifferentiated, with rudimentary cytoplasmic organelles. Dendritic profiles presented an empty appearance due to an electron-lucent matrix and scarce content of organelles. 3. At 10 days there was a significant proliferation of cytoplasmic organelles in the perikaryon, mainly of those involved in protein biosynthesis as the rough endoplasmic reticulum (RER) and the Golgi complex. 4. After 20 days of age the VMN neurons acquired the cytological appearance of adult neurons, with well-organized RER, Golgi complexes, and pleomorphic mitochondria. Concurrent with these changes, there was a marked development of other organelles in the neuropil, which was accompanied by an increase in synaptic density and differentiation of their subsynaptic structures.

Animals↗
PubMed1992

A correlation between IgG class antibody production and glomerulonephritis in the murine chronic graft-versus-host reaction.

A graft-versus-host reaction (GVHR) was induced in (B10 x DBA/2)F1 (BDF1) and (BALB/c x A)F1 (CAF1) murine recipients by injection of their parental or B10.D2-derived spleen cells. The incidences of glomerulonephritis and autoantibody production were then correlated. All of the BDF1 mice that received DBA/2 spleen cells (termed DBA/2----BDF1) and 33% of the CAF1 mice that received BALB/c spleen cells (BALB/c----CAF1) developed glomerulonephritis. However, in other combinations (B10.D2----BDF1, A/J----CAF1) no significant glomerular lesions were observed. An analysis of antibodies by ELISA revealed that the groups with renal disease showed a significant polyclonal elevation of IgG class antibodies, including autoantibodies (anti-DNA, anti-MRBC, and NTA) and a conventional antibody (anti-TNP-KLH). No significant IgG class antibody production was observed in the groups that did not develop glomerulonephritis. Thus, it was suggested that an IgM to IgG class switch is important in the development of glomerulonephritis in GVHR. Other factors also appear to be involved. Only 33% of BALB/c----CAF1 developed glomerulonephritis, even though a level of IgG class antibody production was comparable to that observed in DBA/2----BDF1 in which 100% showed severe glomerulonephritis.

Animals↗