Biomedical subjects

K Akagi

Publications and source records attributed to K Akagi.

At least 37 records · Page 2Linked to original sources

PubMed2000

[Surgical treatment of unruptured cerebral aneurysms and complications in patients with ischemic cerebrovascular disease].

Patients who have unruptured intracranial aneurysms associated with ischemic cerebrovascular disease are a high-risk group for surgery. We have done clipping surgery in 15 patients among 40 with ischemic cerebrovascular disease. The criteria for surgery included an age below 65 years, CBF of more than 35 ml/100 g/min, and favorable ADL comparable to Rankin score 0-III. Two patients received simultaneous aneurysm clipping and superficial-middle cerebral artery anastomosis. Only one patient suffered from ischemia-related permanent neurological worsening, and one had direct optic nerve injury. Surgical mortality was 0%, and morbidity was 15%. There were two patients who had transient neurological worsening. These results suggest that surgical treatment of unruptured cerebral aneurysms is not contraindicated in patients with ischemic brain disease, but careful selection and careful perioperative management are mandatory for preventing surgical complications.

Activities of Daily Living↗

PubMed1999

Correlation between Ca(2+) oscillation and cell proliferation via CCK(B)/gastrin receptor.

Gastrin stimulates cell proliferation through the CCK(B) receptor coupled to Gq-protein, whereas the m3 muscarinic receptor, which also couples to Gq, has no trophic effects. In order to elucidate the cause of the difference, we stably transfected CHO cells with human CCK(B) and m3 receptors. Stimulation of the CCK(B), but not the m3 receptor increased cell growth. Activation of MAP kinase via the m3 receptor was to the same extent as that via CCK(B), indicating that there is an initial signaling common to both receptors. Stimulation of either receptor induced a transient increase in [Ca(2+)](i) followed by a sustained plateau phase. After 2 h of stimulation, the [Ca(2+)](i) response to the m3 receptor disappeared, whereas that to the CCK(B) receptor remained as a [Ca(2+)](i) oscillation. Removal of extracellular Ca(2+), which abolished [Ca(2+)](i) oscillation, completely inhibited DNA synthesis via CCK(B). When the C-terminal part of the CCK(B) receptor was truncated, the trophic effect as well as the [Ca(2+)](i) response after 2 h of stimulation disappeared, whereas the chimeric CCK(B) receptor with the C-terminal region of the m3 receptor preserved its ability to elicit both DNA synthesis and [Ca(2+)](i) oscillation. These results suggest that desensitization might be a principal determinant of cell proliferation, and the persistence of the [Ca(2+)](i) response as [Ca(2+)](i) oscillation could be essential for this type of signal transduction.

Amino Acid Sequence↗

PubMed1999

Relation of transmembrane potential to cell survival following hyperthermia in HeLa cells.

Hyperthermia induces cell death and the usual endpoint to study this is the ability of the cells to form colonies. Hyperthermia is also known to alter membrane characteristics, especially transmembrane potential and this has been correlated with duration and degree of heating. The aim of the present study was to see the correlation between changes in membrane potential and clonogenic ability of HeLa cells after heat treatment of 41-44 degrees C. Membrane potential was measured by the fluorescence polarization of the plasma membrane probe 3,3'-dipentyloxacarbocyanine by flow cytometry. Cell survival was assessed by colony formation assay. The fluorescence intensity increased and cell survival decreased with an increase in temperature. The fall in survival following heat treatment closely paralleled the increase in fluorescent intensity, especially heat treatments of 60 min or more. After 2 h of heating at 44 degrees C, the surviving fraction decreased to 1% and the fluorescence intensity increased to 154.84% of the unheated controls. This study suggests that measurement of membrane potential by flow cytometry may potentially be an alternative to colony forming assay for assessing cell survival. Since the results of membrane potential measurements are available immediately, this has implications for its potential use as a predictive assay of thermosensitivity.

Carbocyanines↗

PubMed1999

Blood flow influences vascular growth during tumour angiogenesis.

Many factors play a role in tumour angiogenesis. We observed growing tumour vessels in vivo to study the relationship between blood flow and vascular enlargement. Mammary adenocarcinoma was implanted into Fisher-344 rat with dorsal skin-fold transparent chambers. Vascular growth was observed and recorded on videotape through a microscope for 6 h. Vascular networks were photographed and traced every 30 min to identify changes over time. Tumour sections were stained with Masson's trichrome and anti-Factor VIII-related antigen. Tumour growth was rapid enough for differences to be seen each hour. Vessels with a high blood flow showed an increase in diameter within a few hours and new branches formed from these vessels. In contrast, vessels without an increase in blood flow showed no change in diameter. Vessels within the interstitium surrounding the tumour were lined by endothelium that was positive for anti-Factor VIII-related antigen staining. Vessels in the tumour had extremely rare endothelial cells detectable by Masson's trichrome or anti-Factor VIII-related antigen staining. In conclusion, increased blood flow may cause vascular enlargement and some primitive vessels seem to lack endothelium.

Adenocarcinoma↗

PubMed1999

Recurrence factors for chronic subdural hematomas after burr-hole craniostomy and closed system drainage.

Recurrence of chronic subdural hematoma after burr-hole craniostomy and closed system drainage is not uncommon. We sought to identify risk factors for recurrence. In 121 patients, various factors including age, initial neurologic status, hematoma thickness, computed tomographic density of the hematoma, midline shift, multiplicity, systemic disease, and drainage volume were compared retrospectively between nonrecurring cases and recurring cases. Recurrence was noted in 10 cases (8.3%). In recurring cases, the drainage volume was significantly larger than in nonrecurring cases, and the recurrence rate increased in proportion to drainage volume. Other factors significantly influencing recurrence were hematoma thickness and associated diabetes mellitus. Drainage contents mainly derived from either exudate within the subdural membrane or cerebrospinal fluid leakage. Entry of cerebrospinal fluid into the hematoma cavity or continuing leakage of serum components through opened endothelial gap junctions are considered to be major causes of increased drainage volume, leading in turn to recurrence of the hematoma.

Adult↗

PubMed1999

Responsiveness of beta-escin-permeabilized rabbit gastric gland model: effects of functional peptide fragments.

We established a beta-escin-permeabilized gland model with the use of rabbit isolated gastric glands. The glands retained an ability to secrete acid, monitored by [14C]aminopyrine accumulation, in response to cAMP, forskolin, and histamine. These responses were all inhibited by cAMP-dependent protein kinase inhibitory peptide. Myosin light-chain kinase inhibitory peptide also suppressed aminopyrine accumulation, whereas the inhibitory peptide of protein kinase C or that of calmodulin kinase II was without effect. Guanosine-5'-O-(3-thiotriphosphate) (GTPgammaS) abolished cAMP-stimulated acid secretion concomitantly, interfering with the redistribution of H+-K+-ATPase from tubulovesicles to the apical membrane. To identify the targets of GTPgammaS, effects of peptide fragments of certain GTP-binding proteins were examined. Although none of the peptides related to Rab proteins showed any effect, the inhibitory peptide of Arf protein inhibited cAMP-stimulated secretion. These results demonstrate that our new model, the beta-escin-permeabilized gland, allows the introduction of relatively large molecules, e.g., peptides, into the cell, and will be quite useful for analyzing signal transduction of parietal cell function.

Aminopyrine↗

PubMed1999

Damage to DNA purified from the radioresistant prokaryote, Deinococcus radiodurans, by acid heating.

Using a highly radioresistant bacterium, Deinococcus radiodurans, the mechanism of degradation of the purified DNA molecules by heating was examined under acidic conditions. Setting the treatment temperature at 55ûC with a duration of 0 to 20 min and adjusting the pH of the cell suspension to 3, 5 or 7, cell viabilities after the treatment were compared. The survival rate decreased in proportion to the reduction of pH. DNA purified from D. radiodurans was then damaged by irradiation with gamma-rays at 0.22 kGy or 1 kGy. It was considered that the radioresistance of D. radiodurans was due to its high repair capability, rather than any specificity of DNA structure. Purified D. radiodurans DNA was resistant to heating up to 90ûC at neutral pH. However, marked DNA damage occurred when it was heated at pH values below 5.0. Then, DNA labeled with [3H]adenine was examined. Treatment at lower pH and higher temperature resulted in release of more adenine base, i.e., the purine ring, from the DNA molecules. Therefore, we assumed that the decrease in survival of D. radiodurans in vivo and damage to its DNA in vitro by acid heating were due to the release of adenine and guanine from the DNA, i.e., depurination.

Acids↗

PubMed1999

[Analysis of intermittent blood flow in experimental tumor using a transparent chamber].

Using a transparent chamber under a microscopic recording system equipped with a CCD camera, we measured real-time fluctuations of microvessel blood flow in an experimental murine tumor. Seven microvessels of the tumor showed 3-4 fluctuations in blood flow (intermittent blood flow) during the observation period (2 hours). Within the 120 min. monitoring period, we obtained approximately a maximum 52.5% of decreased blood flow. The duration of change in blood flow ranged from 15-45 min. Similar temporal fluctuations were seen in experimental animal tumors. Our data clearly demonstrated that fluctuations in blood flow (intermittent blood flow) in tumors are a common feature.

Animals↗

PubMed1999

Preliminary investigation of resistance of plasmid DNA to neon ion beams using transformation into recipient Escherichia coli cells.

The sensitivity of the vector plasmid pKmK8 DNA to neon ion beams was studied under dry conditions. This plasmid contains the cloning vector pJKKmf(-) and a 3.6 kbp segment encoding the Escherichia coli crp gene that can be used in mutagenesis analysis. The survival curve of the plasmid indicated an exponential profile and a D10 value of about 16 kGy in the E. coli wild-type strain for DNA repair capability. This was similar to the D10 value for the shuttle vector plasmid pZ189 DNA. Therefore, it was assumed that the excision repair system in E. coli was not effective for repairing DNA lesions induced by irradiation with heavy ion beams.

DNA Damage↗

PubMed1999

[Cigarette smoking increases the risk of developing a cerebral aneurysm and of subarachnoid hemorrhage].

Despite recent advances in diagnostic and therapeutic techniques, subarachnoid hemorrhage (SAH) is still a serious condition associated with high mortality and morbidity. There are no effective treatments other than surgical intervention. However, another option for decreasing the occurrence of SAH may be prevention of aneurysms formation and of their rupture by controlling risk factors. Cigarette smoking has been recently shown to be one of the major risk factors for SAH. We investigated whether cigarette smoking increased the risk of developing cerebral aneurysms and of SAH. Degree of smoking was investigated in 182 patients with SAH and in 123 patients with an unruptured cerebral aneurysm incidentally detected during investigation of other diseases. Sixty-nine patients with other diseases who were shown to be free of cerebral aneurysms through MR angiography served as controls. Smoking significantly increased the risk of both aneurysm formation and SAH; The odds ratio for SAH was 2.4, and for unruptured cerebral aneurysm 1.7. Smoking especially increased the occurrence of SAH in women and in youngsters. However, smoking did not influence the occurrence of cerebral vasospasm and multiplicity of aneurysms. These data suggest the importance of avoiding smoking to prevent the occurrence of cerebral aneurysms and of SAH.

Age Factors↗

PubMed1998

Helical polyacetylene synthesized with a chiral nematic reaction field

Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.

Journal Article↗

PubMed1998

The influence of DNA ploidy of a human tumor cell line on the frequencies of micronuclei or chromosome aberrations after irradiation.

To develop methods for assessing the intrinsic cellular radiosensitivity, it is important to evaluate the relationship between DNA ploidy of cells and frequencies of micronuclei (MN) or chromosome aberrations after irradiation. From the original human fibrosarcoma cell line HT-1080, we isolated two clones which have different chromosome ploidy: clone 5 is pseudodiploid and clone 1 is heteroploid. We examined the radiosensitivity of the two clones using a clonogenic cell survival assay and a cytokinesis-block MN assay, and by scoring chromosome aberrations using the premature chromosome condensation (PCC) method combined with a fluorescence in situ hybridization (FISH) procedure immediately and at 24 h after irradiation. The MN frequency increased according to the irradiation dose in both clones. The MN frequency of clone 1 was significantly higher than that of clone 5 regardless of whether the assay was performed immediately or 24 h after irradiation. However, when the numbers of MN were normalized by the DNA index of each clone, a significant difference in the frequency of MN was not observed. In the PCC and FISH studies, there was a linear relationship between the radiation dose and the initial breaks of chromosome 4, but the breaks of clone 1 were much more frequent than those of clone 5. Twenty-four h after irradiation, the chromosome 4 breaks of clone 1 were observed much more frequently than those of clone 5 at the same radiation dose. When the numbers of chromosome 4 breaks were normalized by the number of chromosome 4 in each clone without radiation, no such difference in the number of breaks was observed. These findings demonstrated that the DNA content or chromosome ploidy influenced the induction of the MN or chromosome aberrations in HT-1080 cells after irradiation.

Cell Survival↗

PubMed1998

Slight promotion effects of intermittent administration of testosterone propionate and/or diethylstilbestrol on 3,2'-dimethyl-4-aminobiphenyl-initiated rat prostate carcinogenesis.

In order to determine the effects of intermittent hormonal manipulation on the promotion stage of rat prostate carcinogenesis, testosterone and/or estrogen were administered to F344 rats for 40 weeks after 20-weeks treatment with the prostate carcinogen, 3,2'-dimethyl-4-aminobiphenyl. For this purpose testosterone propionate (TP) and diethylstilbestrol (DES) were introduced into silastic tubes, 2- and 0.5-cm long, respectively, and implanted into the subcutis for seven repeated cycles of 30 days treatment and 10 days withdrawal. Intermittent administration of TP resulted in suppression of ventral prostate adenocarcinoma development and slight but non-significant increases in the incidences of invasive carcinomas of the lateral prostate and seminal vesicles. Intermittent administration of DES completely suppressed tumorigenesis in all sites and the combination of TP and DES generally inhibited prostate tumor development. Thus, under the present experimental conditions, no strong enhancing effects of cyclic hormonal manipulation were observed on rat prostate carcinogenesis. Indeed, the opposite appeared to be the case.

Aminobiphenyl Compounds↗

PubMed1998

Precise distribution of neuronal nitric oxide synthase mRNA in the rat brain revealed by non-radioisotopic in situ hybridization.

Regional distribution of neurons expressing neuronal nitric oxide synthase mRNA in the rat brain was examined by non-radioisotopic in situ hybridization, using digoxigenin-labeled complementary RNA probes. Clustering of intensely positive neurons was observed in discrete areas including the main and accessory olfactory bulbs, the islands of Calleja, the amygdala, the paraventricular nucleus of the thalamus, several hypothalamic nuclei, the lateral geniculate nucleus, the magnocellular nucleus of the posterior commissure, the superior and inferior colliculi, the laterodorsal and pedunculopontine tegmental nuclei, the nucleus of the trapezoid body, the nucleus of the solitary tract and the cerebellum. Strongly-stained isolated neurons were scattered mainly in the cerebral cortex, the basal ganglia and the brain stem, especially the medulla reticular formation. In the hippocampus, an almost uniform distribution of moderately stained neurons was observed in the granular cell layer of the dentate gyrus and in the pyramidal cell layer of the Ammon's horn, while more intensely stained isolated neurons were scattered over the entire hippocampal region. These observations can serve as a good basis for studies on function and gene regulation of neuronal nitric oxide synthase.

Animals↗

PubMed1998

Relevance of a new impedance matching, or subtrap, method for the reduction of pain during hyperthermia.

Capacitive heating is widely used in hyperthermic treatment of human malignancies. However, the pain on the body surface or thermoesthesia in the subcutaneous fatty layer may prevent an elevation of temperature in the tumors. Impedance matching is improved by a subtrap method entailing the application of two copper plates (10 x 850 x 0.06 mm) as a subtrap circuit to each of two capacitive electrodes. In a clinical trial the Tmax, Tave, Tmin for the subtrap method were all higher in comparison with those for the conventional technique (42.5 +/- 0.7 degrees C, 41.9 +/- 1.0 degrees C, 41.3 +/- 1.1 degrees C vs. 41.1 +/- 1.5 degrees C, 40.6 +/- 1.3 degrees C, 40.0 +/- 1.3 degrees C). Although the maximal radiofrequency (RF) power applied to patients was higher with the subtrap method (875 +/- 189 W vs. 763 +/- 200 W), the incidence of surface pain was reduced dramatically. It is concluded that the subtrap method substantially improves the RF capacitive heating of deep-seated tumors.

Adolescent↗

PubMed1998

Epidemiology, clinical characteristics and natural history of vertically transmitted human immunodeficiency virus-1 infection in Japan.

BACKGROUND: According to the Ministry of Health and Welfare AIDS Surveillance Committee's report on vertically transmitted human immunodeficiency virus (HIV) infection, there have been eight children with acquired immune deficiency syndrome (AIDS) and 18 children with HIV infection in Japan, totalling 26 in all as of February 1997. A search of the literature fails to reveal any report that deals with many cases of vertically transmitted HIV infection in Japan. METHODS: A primary questionnaire survey was taken of the main medical institutions across the country, followed by a secondary questionnaire survey of physicians and pediatricians who treated the disease. A clinical review was made of 19 children with vertically transmitted HIV infection (including eight AIDS children) according to the 1994 Revised Classification System for HIV Infection in Children. RESULTS: The mean age at diagnosis was 14.5 months and the diagnosis was made at less than 18 months of life in approximately 70% of infected children. In the mean observation period of 16 months, six of eight AIDS children (75%), and one child of group B died. The mean period of observation for the seven dead children was 7 months, and six of seven children died by 36 months of life. The survival period after the diagnosis of AIDS was 15 months. The diagnosis of HIV infection was made based on the clinical symptoms of all children with AIDS. Of 11 children, six (45%) presented with symptoms of HIV infection by 6 months of life, and 10 of 11 children (91%) presented with symptoms by 26 months of life. The noteworthy clinical findings included hepatomegaly, splenomegaly, recurrent respiratory tract infection, lymph node swelling, oral candidiasis, hepatitis, wasting syndrome, HIV encephalopathy and severe pneumonia. The favored age for the start of complications and the magnitude of decrease in the HIV helper cell count varied with each case of complications of HIV infection (wasting syndrome, HIV encephalopathy) or opportunistic infections (cytomegalovirus infection, Mycobacterium avium complex infection). Anti-HIV drugs (mainly zidovudine) had been used in five of eight children with AIDS and were effective in two long survivors alone. CONCLUSIONS: Children who are diagnosed with HIV infection, based on their clinical symptoms, carry a poor prognosis. In this respect, early diagnosis and progress in anti-HIV therapy are necessary.

Child, Preschool↗

PubMed1998

Posterior lobe of the pituitary gland: correlation between signal intensity on T1-weighted MR images and vasopressin concentration.

PURPOSE: To correlate the signal intensity on magnetic resonance (MR) images in the posterior lobe of the pituitary gland with the vasopressin content. MATERIALS AND METHODS: Fourteen rabbits were studied: 12 water-deprived rabbits (two each at 48, 74, 96, 120, 144, or 168 hours of deprivation) and two control rabbits. Sagittal T1-weighted MR images were obtained before and after water deprivation. The signal intensity ratio of the posterior lobe to the pons was correlated with the vasopressin content in the posterior lobe, which was measured by means of radioimmunoassay. RESULTS: Before water deprivation, high signal intensity in the posterior lobe was demonstrated clearly in all rabbits. The signal intensity ratio and vasopressin content in the posterior lobe gradually decreased with water deprivation. The signal intensity ratio correlated strongly with the vasopressin content in the posterior lobe (Pearson correlation coefficient, .809; P < .001). CONCLUSION: The signal intensity ratio on T1-weighted MR images may be used as an indicator for the quantitative evaluation of the vasopressin content in the posterior lobe. The results strongly suggest that the origin of the high signal intensity in the posterior lobe on T1-weighted MR images is the vasopressin-neurophysin II-copeptin complex.

Animals↗

PubMed1998

Gastric acid secretion is augmented by the replacement of extracellular Na+ with K+ or other ions.

We examined the validity of the high K+ condition, widely used as a model to investigate the mechanism of acid secretion, employing isolated rabbit gastric glands. When Na+ in the nutrient solution was replaced with K+, the acid secretion monitored by the accumulation of 14C-aminopyrine increased K+-concentration-dependently. Stimulation of carbachol or dbcAMP was also greatly enhanced by K+. The responses to forskolin, phorbol ester, gastrin and submaximal dose of histamine were potentiated in the high K+ condition, but the responses to isobutylmethylxanthine, calyculin A and the maximal dose of histamine were not. The augmented response to carbachol was not dependent on [Ca2+]o. Replacement of Na+ with any other ions, including Rb+, Cs+, Li+, tetramethylammonium and choline, increased the basal aminopyrine ratio. Most of these ions were also effective in enhancing the response to dbcAMP, but failed to augment the effect of carbachol. Replacement of Na+ with K+, Rb+, Cs+ and Li+ transiently elicited acid secretion in the isolated mouse whole stomach. These results suggest that the high K+ is not a simple model for the direct activation of the proton pump, but the augmentation consists of two components, i.e., the combined effects of low Na+ and high K+. The former augments basal and cAMP-stimulated acid production, whereas the latter augments acid production by any agonist except calyculin A.

1-Methyl-3-isobutylxanthine↗