Search PubMed⌕ Search

Biomedical subjects

K Nitta

Publications and source records attributed to K Nitta.

At least 217 records · Page 12Linked to original sources
PubMed1991

A structural study of calcium-binding equine lysozyme by two-dimensional 1H-NMR.

Since 1H-NMR spectra of the calcium bound form (holo) and the calcium free form (apo) of equine lysozyme have an overall similarity, the folded structure of apo equine lysozyme seems to be similar to the holo structure at 25 degrees C and pH 7.0, even at low ionic strengths except for subtle conformational change. However, calcium titration experiments showed that a number of resonances change by a slow exchange process. The changes saturated at one calcium ion per one lysozyme molecule, and no more change was observed by further addition of calcium ions. This shows that just one calcium ion binds to equine lysozyme. To make assignments for these changed proton resonances, two-dimensional 1H-NMR studies, correlated spectroscopy (COSY), two-dimensional homonuclear Hartmann-Hahn spectroscopy (HOHAHA) and nuclear Overhauser effect spectroscopy (NOESY) were carried out. A structural model of equine lysozyme based on the crystal structure of human lysozyme was estimated and used to assign some resonances in the aromatic and beta-sheet regions. It was possible to use some proton signals as a probe to determine the specific conformational change induced by calcium ions. The calcium binding constant KCa was estimated from calcium titration experiments in which changes in the proton signal were monitored. The log KCa value was found to be on the order of 6-7, which is in agreement with the calcium binding constant determined by fluorescence probes. This means that the protons are affected by specific calcium binding.

Amino Acids↗
PubMed1991

The basic health care system for the lunar base crew.

A plan of the health care system for the crew on the lunar base is described in this study. The health care system consists of two subsystems. The first is the daily health care system. The system contains health care menus, similar to those on Earth, and some biochemical and ordinary medical examinations. The second system is a periodic medical inspection for the crew's bones and the determination of natural radioisotopes in the body. These care systems are automatically treated with the examination and data filing. Usually these examinations are carried out without the presence of a medical doctor. Examinations and files of the whole results are controlled by a computer. The daily results of examinations are compared with data in the file. If any abnormal values are found in the results, an appropriate message is sent advising whether he must receive an in-depth examination by a medical doctor, or be reexamined by the same submenu. The automatic health care system also records transactions with the life support monitoring system.

Aerospace Medicine↗
PubMed1991

Lunar base extension program and closed loop life support systems.

Much of papers describing the Lunar Base Construction have been already published. Lunar Base has been considered to be one of the very useful facilities to conduct the excellent scientific program in near future and also to develop the lunar resources such as 3He and oxygen in order to expand the human activities in space. The scale of lunar base and the construction methods to be adopted should be determined based upon the utilization program to be conducted after the initiation of outpost habitation. In order to construct lunar base, it needs to transport lunar base elements such as habitat modules, experiment modules and so on having 20-30 tons weight and to install, connect and activate on lunar surface. The development of transportation system such as OTV enabling to transport over 30 ton payload weight from earth to moon seems to be very difficult in near future, and it seems reasonable to transport three elements per year as described in many papers already published. Therefore, the initial habitat outpost would not have enough volume to produce foods and has to have ECLS system similar to that of space station already going to be developed. After 2-3 years from the initiation of habitation, the addition of food production facilities could be started to expand the habitability of lunar base and finally the complete closed loop life support system could be installed after spending 6-7 years. This paper describes ECLS technologies to be used in the initial habitat outpost and design philosophy of the closed loop technologies to be utilized in the final stage.

Carbon Dioxide↗
PubMed1991

Comparative base specificity, stability, and lectin activity of two lectins from eggs of Rana catesbeiana and R. japonica and liver ribonuclease from R. catesbeiana.

Two lectins with RNase activity obtained from eggs of Rana catesbeiana and R. japonica and RNase obtained from R. catesbeiana liver show 65-83% protein homology. The base specificity of these frog proteins was studied with 8 dinucleoside phosphates as substrates and 8 nucleotides as inhibitors. The base specificities of the B1 and B2 sites of these proteins are U greater than C and G greater than U greater than A, C, respectively. The three frog proteins are more resistant than RNase A to heat treatment, guanidine-HCl and pH-induced denaturation; i.e., they retain their native conformation up to at least 70 degrees C at pH 7.5. Differences in stability and base specificity among RNase A and the three frog proteins are discussed in relation to the primary structures. Although the two lectins agglutinate tumor cells (e.g., Ehrlich, S-180 and AH109A ascites carcinoma cells), the liver RNase has no such activity. Agglutination of AH109A cells by the two lectins is inhibited by nucleotides. Our results indicate that the agglutination sites are not identical with, but are related to, the active sites of the three frog proteins.

Amino Acid Sequence↗
PubMed1991

Activity of pulmonary surfactant after blocking the associated proteins SP-A and SP-B.

To investigate the role of the pulmonary surfactant-associated proteins SP-A and SP-B, the respective monoclonal antibody (anti-A or anti-B) was added to porcine pulmonary surfactant at a weight ratio of 1:2, and the mixtures were tested on surfactant-deficient immature newborn rabbits (gestational age 26 days). Under pentobarbital sodium anesthesia and mechanical ventilation with a 25-cmH2O peak insufflation pressure, the tidal volumes of the animals given surfactant alone and of those given surfactant containing anti-A were 27.9 +/- 5.1 and 25.1 +/- 9.6 (SD) ml/kg, respectively, whereas that of those given surfactant with anti-B was 5.8 +/- 3.6 ml/kg (P less than 0.05). The surface adsorption times of surfactant alone and of anti-A-containing surfactant were less than 0.8 s compared with greater than 120 s (P less than 0.01) for anti-B-containing surfactant. The anti-B suppressed the surfactant activity until the weight ratio was decreased to 2:100. The role of SP-A could not be clarified, but it was concluded that SP-B is an essential factor for surfactant activity.

Animals↗
PubMed1991

Inactivation of exogenous surfactant by pulmonary edema fluid.

Modified natural porcine surfactant was mixed with edema fluid sampled from the airways of hyperoxia-exposed adult rabbits. By varying the concentration of surfactant lipids (10, 25, and 50 mg/mL) and edema fluid proteins (0-280 mg/mL), we obtained a series of preparations with protein to surfactant lipid weight ratios ranging from 0 to 11.2. The surfactant activity of these various mixtures was analyzed with a pulsating bubble (at a lipid concentration of 10 mg/mL) or in experiments on immature newborn rabbits (at lipid concentrations of 25 or 50 mg/mL). For the latter purpose, animals were delivered at a gestational age of 27 d and ventilated with a standardized sequence of insufflation pressures after receiving 0.1 mL of the surfactant-edema sample into the airways at birth. Nearly complete in vitro inhibition of surfactant (markedly delayed film adsorption and a minimum surface tension of 23 mN/m during pulsation) was observed at a protein to surfactant lipid ratio of 4.5. Under in vivo conditions, nearly complete surfactant inhibition (tidal volumes reduced to less than 20% of the values for littermates ventilated with the same pressure after receiving surfactant without admixture of edema fluid) was documented at a protein to surfactant lipid ratio of 11.2. Our data suggest that the functional properties of an immature neonatal lung, in which serum proteins tend to leak into the airspaces after the onset of ventilation, depend on the stoichiometric relation between surfactant lipids and inhibitory proteins in the lung liquid.

Animals↗
PubMed1991

Antitumor activity of polymorphonuclear leukocytes activated by a beta-1,3-D-glucan.

The antitumor activity of mouse polymorphonuclear leukocyte (PMN) treated with a beta-1,3-D-glucan from Alcaligenes faecalis var. myxogenes IFO 13140 (TAK-N) and its carboxymethylated derivative (CM-TAK) was investigated in vitro and in vivo. ICR mouse PMN showed strong cytotoxicity against sarcoma 180 cells and inhibition of the growth of the tumor cells in vitro in the presence of TAK-N but not in the presence of CM-TAK. Since the cytotoxicity induced by TAK-N was almost completely inhibited by catalase, it seems to be mediated by H2O2 production by PMN. On the other hand, TAK-N induced no cytotoxicity in macrophages and neither did CM-TAK in PMN or in macrophage. Intraperitoneal injection of TAK-N into ICR mice induced a large number of PMN and macrophages in the peritoneal cavity. The peritoneal exudate PMN which were harvested at 10 to 72 h after TAK-N injection showed cytotoxicity against sarcoma 180 cells, but the peritoneal exudate macrophages did not. Treatment of sarcoma 180 ascites tumor-bearing ICR mice with TAK-N at a dose of 100 mg/kg prolonged significantly the survival time over that of the control. These results indicate that TAK-N induces PMN cytotoxicity against sarcoma 180 cells not only in vitro but also in vivo. The antitumor effect of TAK-N on sarcoma 180 ascites tumor seems to be derived from PMN stimulated with TAK-N.

Animals↗
PubMed1991

The regulation and role of prostaglandin biosynthesis in cultured bovine glomerular endothelial cells.

The experiments described in this article were designed to investigate the regulation of, and functional response to, prostaglandin (PG) synthesis in cultured bovine glomerular endothelial cells. Glomerular endothelial cells in culture synthesized PGE2 much greater than PGF2 alpha greater than thromboxane A2 greater than PGI2 in the presence of 30 microM arachidonate. Basal levels of PGE2 synthesis in these cells were one sixth less than that of bovine mesangial cells. PGE2 synthesis was time dependent and required the continuous presence of serum. Moreover, PGE2 synthesis was regulated by phospholipase A2 as shown by ionomycin-stimulated PGE2 accumulation as well as by bradykinin- and thrombin-stimulated PGE2 accumulation. Even though acidic fibroblast growth factor and heparin were required to support glomerular endothelial cell growth in culture, these agents downregulated PGE2 synthesis. PG endoperoxide synthase activity, as shown by arachidonate-stimulated PGE2 accumulation, also regulated PGE2 synthesis. PGE2 and PGF2 alpha, as well as thromboxane A2 and PGI2 mimetics (1 microM) evoked mitogenesis in quiescent glomerular endothelial cells. PGE2 and PGF2 alpha were most potent, and threshold doses of these PG were 10 nM. These data suggest that glomerular endothelial cells are similar to other microvascular endothelial cells in their regulation of PG synthesis and that, under physiological conditions, the proliferation of glomerular endothelial cells might be regulated by PG in an autocrine or paracrine fashion.

Animals↗
PubMed1991

Myelopathy due to thickened ligamenta flava and abnormal fibrous tissue of the cervicothoracic junction--case report.

A 49-year-old female with subacute myelopathic symptoms due to thickened cervicothoracic yellow ligament and abnormal epidural fibrous tissue is reported. Myelography showed a complete block at the Th3 level. Magnetic resonance imaging demonstrated an extra-axial mass lesion in the spinal canal at the cervicothoracic junction causing the spinal cord compression. Laminectomy with resection of the lesion resulted in good neurological recovery. Histological examination revealed a thickened ligamenta flava and abnormal epidural fibrous tissue without calcification foci.

Cervical Vertebrae↗
PubMed1991

Effects of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (DHPG) eye drops and cyclosporine eye drops in the treatment of herpetic stromal keratitis in rabbits.

The effect of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (ganciclovir, DHPG) eye drops and the anti-inflammatory effect of cyclosporine (CYA) eye drops on experimental herpetic stromal keratitis in rabbits with herpes simplex virus (HSV) were studied. Ten rabbits were presensitized by subcutaneous injection of HSV, type 1, on days 14 and 7 before intrastromal inoculation of the same virus. These rabbits were divided into 2 groups and treatment was started 48 hours after virus inoculation. The eye drops used were 0.1% DHPG, 0.1% CYA or the vehicles of these eye drops. Eye drops were given 5 times a day and eyes were scored every day for 3 weeks after inoculation. The right eyes of Group 1 were treated with 0.1% DHPG and 0.1% CYA eye drops, and the left eyes with 0.1% DHPG and the vehicle of CYA eye drops. The right eyes of Group 2 were treated with 0.1% CYA and the vehicle of DHPG eye drops, and the left eyes with the vehicles of CYA and DHPG eye drops. The combination of DHPG and CYA was the most effective in decreasing the severity of herpetic stromal keratitis. Treatment with DHPG alone was also effective, but CYA alone was less effective.

Administration, Topical↗
PubMed1991

[Neuro-otological study on Behçet disease].

It seems acceptable that pathological brain stem lesions exist in the patient with Neuro-Behçet disease (NB). However, only few reports have been published in this field. We report the neuro-otological findings in 33 patients who fulfilled the diagnostic criteria of Behçet disease completely or incompletely. The patients were classified into 2 groups: one is group of NB and the other is a group of Behçet disease without NB (non-NB). Furthermore, the latter was divided into 2 subgroups of patients with dysequilibrium and patients with normal equilibrium. They underwent equilibrium function tests, such as body balance test, gaze test, spontaneous and positional nystagmus test, eye tracking test (ETT) and optokinetic pattern test (OKP) by using electro-nystagmography (ENG). The following results were obtained. 1. Cerebellar and brain stem lesions were confirmed in all cases of NB group. 2. Most cases (6 of 8 cases) in the subgroup of dysequilibrium of the non-NB group showed peripheral vestibular disturbance. The other two patients were diagnosed to be vertebro-basilar insufficiency (VBI) and vascular Behçet disease with CNS disorder, respectively. 3. Nine of 13 patients in the normal equilibrium subgroup of the non-NB group were diagnosed to be neuro-otologically normal. However, we found two patients with peripheral vestibular disturbance and CNS disorder associated with hearing disturbance of the retrocochlear origin, respectively. 4. The neuro-otological examination is assumed to be useful to diagnose neuro-Behçet disease, to reveal the lesion site and the state of dysequilibrium in patients with Behçet disease.

Adolescent↗
PubMed1991

[Comparative studies on the antitumor activity of fluorinated pyrimidine derivatives against human bladder, cervical and ovarian cancer xenografts in nude mice].

Fluorinated pyrimidines given orally were examined for their antitumor activity with 11 human cancer xenograft models (4 bladder, 4 cervical and 3 ovarian cancers). The drugs were evaluated to be effective when they inhibited tumor growth over 58%. UFT was not effective against all of 11 cancer xenografts tested. 5-Fluorouracil (5-FU) was effective against only one bladder cancer xenograft among 6 cancer xenografts tested. On the other hand, 5'-deoxy-5-fluorouridine (5'-DFUR) was effective against one bladder, 3 cervical and one ovarian cancer xenografts. The Antitumor activity of 5'-DFUR was correlated with the enzyme activity of pyrimidine nucleoside phosphorylase, which is an essential enzyme for phosphorolysis of 5'-DFUR to 5-FU.

Administration, Oral↗
PubMed1991

[Antitumor spectra of ranimustine against various human tumors].

Ranimustine (MCNU) has been shown to exhibit high antitumor activity and broad antitumor spectra against various experimental tumors. These effects were comparable to those of nimustine (ACNU). However, clinical applications of ACNU are indicated to various types of malignancies including solid tumors, while those of MCNU are almost limited to hematological ones. Therefore, the antitumor activity of MCNU was examined against 55 specimens from 15 types of solid tumors and compared with those of ACNU and 8 other drugs. Drug sensitivity was examined by a morphological method measuring the proportion of degenerative changes in the nucleus of drug-treated and untreated tumor cells. MCNU showed antitumor activities (measured by karyorrhexis) against adenocarcinoma of the lung, squamous cell carcinoma of the lung, renal cell carcinoma, bladder tumor, ovarian cancer and brain tumor. In addition, MCNU and ACNU showed a similar positive rate (15-16%) in this experiment and this was the highest among all drugs examined. Although MCNU and ACNU showed similar antitumor spectra, a clear difference was observed when the antitumor activities of both drugs were compared in each identical specimen. These results clearly suggest that MCNU is worthy of clinical study to examine the antitumor activity against various solid tumors.

Antineoplastic Agents↗
PubMed1991

[A case of giant cell myocarditis associated with a progressive disturbance in the conduction system].

A 73 year old male patient with a history of pulmonary tuberculosis was admitted to our department because of dyspnea and abdominal pain. The chest X-ray film on admission showed bilateral lung congestion. The ECG showed atrial fibrillation, left axis deviation and incomplete right bundle branch block. Five days after admission, the ECG changed into sinus rhythm and complete right bundle branch block. Eight days after admission, the patient complained of chest pain and the ECG showed ST elevation in II, III, aVF, reciprocal ST depression in V, and complete A-V block with junctional rhythm. Emergency coronary angiography revealed no significant stenosis. Echocardiography showed reduced contraction of the inferior wall and diffuse granular echoes in the myocardium. Light microscopic study revealed fibrosis, infiltration of eosinophils and histiocytes, degenerated myocardium and multinucleated giant cells. Some of the giant cells were morphologically similar to myocardium, so the myocardium might be a place of immunological reaction.

Aged↗
PubMed1990

Mechanism of gallium 67 accumulation in inflammatory tissue.

The present study was undertaken to elucidate the accumulation mechanism of gallium 67 in inflammatory tissue. 67Ga accumulation in inflammatory tissue was observed by macro- and microautoradiogram. Permeability indices were calculated for serum albumin from blood vessels into inflammatory and normal tissue. Neutrophils and macrophages did not play a major role in 67Ga accumulation in the inflammatory tissue because 67Ga could hardly be detected in the sites in which neutrophils were crowded; the accumulation was concentrated in the intercellular space around these cells in the tissue. Permeability indices for inflammatory tissue were much greater than those for normal tissues. It is thought from the present study and previously reported results that 67Ga, together with plasma from permeable blood vessels, readily penetrates the inflammatory tissue and stays there by binding to the acid mucopolysaccharide present in the tissue.

Animals↗
PubMed1990

Effects of endothelin on renal hemodynamics and excretory functions in anesthetized dogs.

The effects of endothelin on renal hemodynamics and excretory functions were investigated in anesthetized dogs. Infusion of endothelin at a rate of 1 ng/kg.min resulted in a slight but significant decrease in renal blood flow and an increase in renal vascular resistance and filtration fraction. Endothelin at doses higher than 10 ng/kg.min significantly decreased cardiac output, glomerular filtration rate, urine volume, and urinary sodium and potassium excretion, whereas it increased systemic vascular resistance. Mean arterial pressure and heart rate showed a transient decrease and increase, respectively, at doses higher than 50 ng/kg.min. Plasma renin activity and plasma aldosterone concentrations were increased only at the dose of 100 ng/kg.min. These effects lasted for more than 60 min. These results suggest that endothelin may have an important role in the modulation of renal functions as well as in the modulation of systemic hemodynamics.

Aldosterone↗