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Biomedical subjects

S Homma

Publications and source records attributed to S Homma.

At least 163 records · Page 9Linked to original sources
PubMed1995

Effects of sensory stimulation on respiratory cardiac cycle variability in humans.

The effects of the phase of respiration on the response of respiratory cardiac cycle variability to sensory stimulation were studied in five healthy young male subjects. Transcutaneous electrical stimulation of the ulnar nerve or hand-grip exercise was applied during inspiration or expiration. Although both electrical stimulation and hand-grip exercise depressed respiratory cardiac cycle variability, the nature of the depression differed according to where in the respiration cycle the stimuli were applied. The amplitude of respiratory cardiac cycle variation was significantly decreased when either stimulus was applied during expiration (P < 0.05), and was unchanged when applied during inspiration (P > 0.05). These findings would suggest that cardiac vagal efferent activity was effectively inhibited by sensory stimulation during expiration, but was not inhibited by such stimulation during inspiration. This mechanism may account, in part, for the known suppression of respiratory cardiac cycle variability during exercise.

Adult↗
PubMed1995

Electrogastrography prior to and following total gastrectomy, subtotal gastrectomy, and gastric tube formation.

On electrogastrography (EGG) spectral analysis, an activity of 3 cycles per minute (cpm) is supposed to be specific for the stomach. After total or subtotal gastrectomy, the original site of the stomach is occupied mainly by the intestine. We attempted to determine if intestinal activity could be recorded in this region with EGG. Epigastric recordings were performed in patients prior and following gastrointestinal or control surgeries. Spectral analysis, using the maximal entropy method and ensemble means was applied to data analysis from these recordings. Preoperatively, the majority of the power peaks were found around 3, 6, and 11 cpm. The postprandial-to-fasting power ratio of all of these power peaks increased significantly postprandially (P < 0.05-0.01). Following total gastrectomy, the power peak around 3 cpm disappeared or was significantly diminished in amplitude (P < 0.05). The postoperative-to-preoperative power ratio ranged from 0.03 to 0.10 (P < 0.001-0.01). However, the power peak around 11 cpm did not significantly change prior to or following total gastrectomy, and the 11 cpm peak appeared relatively dominant. Simultaneous manometric studies in the Roux limb demonstrated a correlation between the power spectral frequency of EGG and manometry at 11 cpm. Therefore, the 11 cpm peak appeared to reflect jejunal or Roux limb electrical activity. The postoperative to preoperative power ratio for the 3 cpm also was significantly reduced following subtotal gastrectomy and gastric tube formation in patients in the postprandial state (P < 0.05-0.001).

Adult↗
PubMed1995

Conductivity ratios of the scalp-skull-brain head model in estimating equivalent dipole sources in human brain.

The dipole tracing (DT) method estimates the position and vector dipole moment of an equivalent current dipole by minimizing the mean squared error of the dipole potentials at the surface electrode positions. In the scalp-skull-brain/DT (SSB/DT) method, which we have developed, the head model consists of three compartments of uniform conductors corresponding to the scalp, skull and brain. The accuracy of the calculations are mainly dependent on the ratios of the conductivities of the three compartments. The best result was obtained with the conductivity ratios of 1:1/80:1 for the scalp, skull and brain compartments, respectively.

Brain↗
PubMed1995

Peptide inhibitors of the ICE protease family arrest programmed cell death of motoneurons in vivo and in vitro.

Members of the CED-3/interleukin-1 beta-converting enzyme (ICE) protease family have been implicated in cell death in both invertebrates and vertebrates. In this report, we show that peptide inhibitors of ICE arrest the programmed cell death of motoneurons in vitro as a result of trophic factor deprivation and in vivo during the period of naturally occurring cell death. In addition, interdigital cells that die during development are also rescued in animals treated with ICE inhibitors. Taken together, these results provide the first evidence that ICE or an ICE-like protease plays a regulatory role not only in vertebrate motoneuron death but also in the developmentally regulated deaths of other cells in vivo.

Amino Acid Sequence↗
PubMed1995

Noninvasive monitoring of cardiac output by Doppler echocardiography in patients treated with volume expansion after subarachnoid hemorrhage.

OBJECTIVE: To assess the validity and potential clinical utility of cardiac output monitoring using Doppler echocardiography in patients treated with volume expansion after subarachnoid hemorrhage. DESIGN: Observational study of patients in a randomized, clinical trial. SETTING: Neurologic intensive care unit. PATIENTS: Simultaneous, blinded measurements of cardiac output by thermodilution and Doppler echocardiography were performed in 48 patients 1 or 2 days after aneurysmal clipping. Follow-up Doppler echocardiography was performed an average of 3.9 days later (range 3 to 6) in 15 patients assigned to normovolemia and 24 patients assigned to hypervolemia. INTERVENTION: Patients received supplemental 5% albumin in order to maintain increased (hypervolemia) or normal (normovolemia) cardiac filling pressures. MEASUREMENTS AND MAIN RESULTS: The overall degree of correlation between the two measures was moderate (r = .67, r2 = .45, p < .0001). Bias and precision calculations (-0.75 +/- 1.34 L/min) showed a tendency for Doppler echocardiography to underestimate thermodilution, particularly when cardiac output was very high. Although hypervolemia patients received more 5% albumin than normovolemia patients, mean percent change in Doppler echocardiography cardiac output did not differ between the two groups. Multiple regression analysis showed that the percent change in Doppler echocardiography cardiac output correlated strongly with changes in heart rate (p < .0001), but not with daily net fluid balance or 5% albumin administration. CONCLUSIONS: Agreement was poor between Doppler echocardiography and thermodilution measurements of cardiac output, and trends reflected variations in heart rate rather than fluid status. Monitoring of cardiac output by this technique cannot be recommended in patients treated with volume expansion after subarachnoid hemorrhage.

Adult↗
PubMed1995

Management strategies for pulmonary vein thrombosis following single lung transplantation.

Pulmonary vein thrombosis following lung transplantation is an infrequently reported and often fatal vascular complication. Two cases of early pulmonary vein thrombosis following single lung transplantation are described. Both patients underwent surgical thrombectomy and anastomotic reconstruction following institution of cardiopulmonary bypass, but died of multiorgan failure within 5 days of diagnosis. The efficacy of transesophageal echocardiography as a diagnostic modality, as well as medical and surgical management strategies for thrombectomy, are discussed.

Adult↗
PubMed1995

Activation of protein kinase C stimulates cAMP phosphodiesterase in rat renal collecting tubule.

The present study was undertaken to evaluate whether protein kinase C (PKC) affects adenosine 3',5'-cyclic monophosphate phosphodiesterase (cAMP-PDIE) activity in microdissected rat renal medullary collecting tubules (MCT). Phorbol 12-myristate 13-acetate (PMA, 10(-8) M), an activator of PKC, significantly stimulated cAMP-PDIE activity in intact MCT (29.5 +/- 1.5 to 38.3 +/- 3.7 fmol.min-1.mm-1, P < 0.05) but not in the proximal straight tubule [4.7 +/- 0.8 vs. 4.8 +/- 0.8, not significant (NS)] or the medullary ascending limb of Henle's loop (20.5 +/- 2.1 vs. 22.4 +/- 2.8, NS). PMA-stimulated cAMP-PDIE activity was reversed by PKC inhibitors, staurosporine (10(-8) M) and calphostin C (10(-8) M), but not by the cyclooxygenase inhibitor, indomethacin (5 x 10(-6) M). 1,2-Dioctanoyl-sn-glycerol (50 micrograms/ml), a synthetic analogue of diacylglycerol that stimulates PKC, also increased cAMP-PDIE activity in broken-cell preparations from MCT. This stimulation was also suppressed by staurosporine (10(-8) M) and calphostin C (10(-8) M). The stimulatory effect of PMA on cAMP-PDIE activity was lost with rolipram (10(-4) M), a type IV PDIE inhibitor, whereas it was preserved with N-(6-amino-hexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7) (10(-4) M), a calmodulin inhibitor, or vinpocetin (10(-4) M), a direct inhibitor of type I PDIE. From these results, we suggest that activation of PKC specifically stimulates rolipram-sensitive cAMP-PDIE, but not the calmodulin-sensitive isozyme, in rat MCT.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

Localization of platelet-derived growth factor and insulin-like growth factor I in the fibrotic lung.

To better understand the mechanisms responsible for the increase in numbers of fibroblasts and increased collagen synthesis in fibrotic intestitial lung diseases, platelet-derived growth factor (PDGF)-A and PDGF-B, PDGF receptor-alpha and -beta, insulin-like growth factor I (IGF-I), and IGF-I receptor were evaluated immunohistochemically. Additionally, the messenger ribonucleic acids (mRNAs) for PDGF-A and PDGF-B, PDGF receptor-alpha and -beta, and IGF-I were investigated by in situ hybridization in alveolar macrophages and lung tissues from patients with interstitial lung disease. In specimens of bronchoalveolar lavage fluid (BALF), PDGF-A, PDGF-B, and IGF-I were local in alveolar macrophages in patients with idiopathic pulmonary fibrosis (IPF), patients with sarcoidosis (Sar), and normal individuals. Although there were no differences between IPF and Sar in terms of the staining intensity or number of positive cells, the number of such cells was smaller in the normal controls. In lung tissues with early-stage IPF, PDGF and IGF-I proteins were localized exclusively in alveolar macrophages, mononuclear phagocytes, fibroblasts, alveolar Type II cells, vascular endothelial cells, and vascular smooth-muscle cells. In lung tissues with late-stage IPF and those from normal controls, only alveolar macrophages contained PDGF and IGF-I proteins. Interestingly, the cellular localizations of PDGF receptor-alpha and -beta, and of IGF-I receptor were the same as those of the PDGF and IGF-I proteins in early-stage IPF, whereas these cells were not positive for any of these substances in late-stage IPF or normal controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

An adult case of lymphangiomatosis of the mediastinum, pulmonary interstitium and retroperitoneum complicated by chronic disseminated intravascular coagulation.

Pulmonary lymphangiomatosis is a rare clinical and pathological entity which is distinct from lymphangiomyomatosis and from pulmonary lymphangiectasis. We report a case of a 20 year old man with diffuse lymphangiomatosis involving the mediastinum, lungs and retroperitoneum. The patient's intrathoracic lymphangiomatosis produced restrictive and obstructive impairment of his pulmonary function, but did not result in chylothorax or chylopericardium, which are two common manifestations of the disease. The patient's clinical course was remarkable for the concomitant development of chronic disseminated intravascular coagulation (DIC). Lymphangiomatosis involving both the mediastinum and pulmonary parenchyma is rare, and DIC is a very unusual complication of lymphangiomatosis.

Adult↗
PubMed1995

Postgastrectomy aspiration pneumonia.

One hundred eighty-six patients who had undergone total gastrectomy were analyzed in regard to pulmonary aspiration. Sixteen patients (8.6%) with recurrent respiratory tract inflammation (r-RTI) and 45 patients (24.2%) with sporadic RTI (s-RTI) were observed. The r-RTI group frequently showed symptoms related to esophageal reflux among the many factors affecting the onset of disease. They were also characterized by marked inflammatory responses with various and atypical clinical courses. The swallowing provocation test showed swallowing disturbances (prolonged latency) in patients with r-RTI. We concluded that the aspiration of esophageal reflux contents was the most important risk factor of recurrent pulmonary complications in patients with total gastrectomy.

Adult↗
PubMed1995

Expression of apogens and engulfens during programmed cell death in the nervous system of the chick embryo.

Two categories of cell death related to antigens, apogens and engulfens, have been reported to be expressed by apoptotic cells and the cells involved in their engulfment in the immune system, and in mesenchymal tissue in the limb of the chick embryo (ROTTELLO et al., 1994). To determine whether these antigens are also expressed during the process of neuronal death, the distribution of immunoreactivity to both anti-apogen and anti-engulfen antibodies was examined in the spinal cord and the dorsal root ganglia of the chick embryo. Anti-apogen antibodies labeled a sub-population of the profiles of dying cells in regions where cell death was occurring. The extent of labeling by anti-apogens varied from 3% to 70% of the total number of dying profiles depending on the specific antibody used and the neuronal region examined. Immunoreactive labeling by the anti-engulfen antibodies mainly involved large cells that contained debris of dead cells. These results indicate that at least some dying neuronal cells express common antigens that are shared by dying mesenchymal cells during programmed cell death, and that phagocytotic cells of the immune system are involved in the engulfment of neuronal cells that have undergone programmed cell death.

Animals↗
PubMed1995

Electrocardiographic markers of abnormal left ventricular wall motion in acute subarachnoid hemorrhage.

A reversible and presumably neurogenic form of myocardial dysfunction may occur following subarachnoid hemorrhage (SAH), but the relationship of this finding to electrocardiographic abnormalities remains unclear. To clarify this issue, serial electrocardiograms (ECGs, mean 6.2 per patient) and echocardiograms (mean 3.4 days after SAH) were obtained in 57 SAH patients without preexisting cardiac disease. The goal was to determine which specific electrocardiographic changes, if any, reflect abnormal left ventricular wall motion in acute SAH. Wall motion abnormalities were identified in five (8%) of 57 patients. Four of these affected patients experienced hypotension (systolic blood pressure < 100 mm Hg) and three exhibited pulmonary edema within 6 hours of SAH, compared to none of the 52 patients with normal wall motion (p < 0.0001). Patients with abnormal wall motion were more likely than patients with normal echocardiograms to have symmetrical T wave inversion (five of five vs. seven of 52, p < 0.001) and severe (> or = 500 msec) QTc segment prolongation (five of five vs. three of 52, p < 0.001) on serial ECGs. These associations maintained their significance with analysis limited to single ECGs performed on or near the day of echocardiography. Abnormal wall motion was also associated with borderline (2% to 5%) creatine kinase MB elevation (five of five vs. three of 52, p < 0.001) and poor neurological grade (p < 0.0001). Although no combination of findings on a single ECG resulted in 100% sensitivity for abnormal wall motion, the presence of either inverted T waves or severe QTc segment prolongation on serial ECGs was associated with 100% sensitivity and 81% specificity. These results demonstrate an association between reduced left ventricular systolic function, mild creatine kinase MB elevation, and electrocardiographic repolarization abnormalities in acute SAH. Symmetrical T wave inversion and severe QTc segment prolongation best identified patients at risk for myocardial dysfunction and may serve as useful criteria for echocardiographic screening following SAH.

Acute Disease↗
PubMed1994

Programmed cell death during the earliest stages of spinal cord development in the chick embryo: a possible means of early phenotypic selection.

The spatiotemporal distribution of cell death in the chick embryo neural tube and spinal cord (brachial region) was examined between stage (St.) 12 and 22, in plastic semithin sections. Between St. 12 and 16, the total number of pycnotic cells per segment was low, whereas after St. 16 the number of pycnotic cells was substantially increased. Between St. 17 and 19 three cell death foci or regions could be recognized. One region, the dorsal pycnotic zone, was located in the most dorsal part of the spinal cord, including the neural crest, with the highest number of pycnotic cells observed at St. 18. The second region, or ventral pycnotic zone, was located between motoneurons and the floor plate and had the highest number of dying cells at St. 17. The third region, the floor plate pycnotic zone, was located in the midportion of the floor plate and had the greatest amount of cell death at St. 19. Although low numbers of pycnotic cells were also observed in other regions between St. 17 and 19, no pycnotic cells were found in the ventrolateral region that gives rise to motoneurons. Ultrastructural observations as well as data from in situ nick end labeling indicate that the pycnotic cells observed in the neural tube die by apoptosis and that the debris from the dead cells is phagocytized primarily by adjacent healthy neuroepithelial cells. Although the spatiotemporal distribution of pycnotic cells suggests that cell death at these early stages could play a role in establishing the pioneer axonal pathway for spinal commissural neurons, preliminary observations following perturbations of cell death do not support this notion. Alternatively, early cell death may be involved in the regulation of cellular patterning along the dorsoventral axis of the neural tube by a kind of negative selection of specific progenitor cells.

Animals↗
PubMed1994

Proteasomes (prosomes) inhibit the translation of tobacco mosaic virus RNA by preventing the formation of initiation complexes.

Proteasomes (prosomes) are large multiprotein complexes. They are involved in protein degradation of ubiquitin-conjugated proteins and in the generation of MHC class I peptides. We gave further evidence that they interfere with in vitro protein synthesis. Proteasomes inhibit the translation of Tobacco mosaic virus RNA. Analysis of cell-free systems by sucrose gradient centrifugation revealed that they prevent the formation of 80S initiation complexes but not the early phase of initiation.

Animals↗
PubMed1994

Location of electric current sources in the human brain estimated by the dipole tracing method of the scalp-skull-brain (SSB) head model.

Using a realistic, 3-shell head model including the scalp (S), skull (S) and brain (B) with conductivity ratios of 1:1/80:1, respectively, the electrical activity in the human brain recorded by conventional electroencephalography was approximated by 1 or 2 equivalent current dipoles. The dipole locations and vector moments were estimated by minimizing the squared difference between the potentials actually recorded from the scalp and those theoretically calculated from the equivalent dipoles. The validity of this dipole tracing method (the DT of the SSB head model) was tested in patients with focal epileptic seizures undergoing presurgical evaluation with intracranial subdural strip electrodes. Weak currents were passed through 1 or 2 pairs of subdural electrodes to create artificial dipoles. The dipole estimations correctly distinguished between single and double generator sources, but there were certain dislocations of the calculated dipoles. The average error of dislocation was found to be 8.5 mm for the 1-dipole model. That for the 2-dipole model was 6 mm for one of the components and 18 mm for the other. It was concluded that the DT method of the SSB head model can be a valuable clinical tool in 3-dimensional localization of focal epileptic discharges in the human brain.

Brain↗
PubMed1994

Spectral analysis of intraluminal pressure in the anastomosed ileal segment of the rat in vitro.

Spectral analysis of the spontaneous intraluminal pressure of the isolated ileal segments in vitro was performed (1) before transection and soon after union (acute model) and (2) until 67 days after anastomosis (chronic model). A single peak was found in the spectral arrays of the acute model before transection. However, more than two peaks were clearly found in spectral arrays of both acutely or chronically anastomosed models. Motor activities of both oral and anal part of the anastomosis seem to be reflected in the spectral analysis of the intraluminal pressure of the isolated segments in vitro. More than two peaks in spectral arrays suggest that the synchronized and coordinated motor activity was not recovered, at least, until 67 days after anastomosis.

Anastomosis, Surgical↗