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Biomedical subjects

A Kawana

Publications and source records attributed to A Kawana.

At least 19 recordsLinked to original sources
PubMed2000

The dynamics of a neuronal culture of dissociated cortical neurons of neonatal rats.

Neuronal networks of dissociated cortical neurons from neonatal rats were cultured over a multielectrode dish with 64 active sites, which were used both for recording the electrical activity and for stimulation. After about 4 weeks of culture, a dense network of neurons had developed and their electrical activity was studied. When a brief voltage pulse was applied to one extracellular electrode, a clear electrical response was evoked over almost the entire network. When a strong voltage pulse was used, the response was composed of an early phase, terminating within 25 ms, and a late phase which could last several hundreds of milliseconds. Action potentials evoked during the early phase occurred with a precise timing with a small jitter and the electrical activity initiated by a localized stimulation diffused significantly over the network. In contrast, the late phase was characterized by the occurrence of clusters of electrical activity with significant spatio-temporal fluctuations. The late phase was suppressed by adding small amounts of D(-)-2-amino-5-phosphonovaleric acid to the extracellular medium, or by increasing the amount of extracellular Mg2+. The electrical activity of the network was substantially increased by the addition of bicuculline to the extracellular medium. The results presented here show that the neuronal network may exist in two different dynamical states: one state in which the neuronal network behaves as a non-chaotic deterministic system and another state where the system exhibits large spatio-temporal fluctuations, characteristic of stochastic or chaotic systems.

Action Potentials↗
PubMed2000

Wortmannin, a radiation sensitizer, enhances the radiosensitivity of WKAH rat cells but not that of LEC rat cells.

No significant cytotoxic effect was observed in WKAH rat cells by the treatment of wortmannin, a radiation sensitizer, at concentrations lower than 30 microM for 24 hr. The relative surviving fractions of LEC rat cells were slightly, but significantly, lower than those of WKAH rat cells at each concentration of wortmannin. When the wortmannin-treated WKAH rat cells were X-irradiated, the relative surviving fractions decreased in a wortmannin concentration-dependent manner. On the contrary, no significant difference was observed between the survival curves of untreated and wortmannin-treated LEC rat cells after X-irradiation.

Androstadienes↗
PubMed1999

Accumulation of specific amino acid substitutions in HLA-B35-restricted human immunodeficiency virus type 1 cytotoxic T lymphocyte epitopes.

HLA is one of the genetic factors that influence the clinical course of HIV-1 infection, and patients with HLA-B35 are prone to rapid disease progression. Nine viral epitopes that are recognized by cytotoxic T lymphocytes (CTLs) in an HLA-B35-restricted manner were determined. To examine how HIV-1 sequences are selected by CTLs in vivo, we sequenced the nine CTL epitopes of the virus in patient plasma. Here we show that certain amino acid substitutions at three epitopes were observed with significantly higher frequency in HLA-B35-positive patients than in HLA-B35-negative patients. By performing experiments with CTL clones established from the HLA-B35-positive patients, it was determined that one of the three substitutions was probably an escape mutation. However, concerning the other two epitopes, representative CTL clones killed target cells pulsed with mutant peptides as efficiently as those pulsed with wild-type peptides, suggesting that CTLs that can be established in vitro are not functioning properly in vivo. Amino acid sequence drift in all HLA-B35-restricted epitopes was rare during the observation period (1 year). Our results may have relevance in understanding the rapid clinical progression in HLA-B35-positive patients.

Amino Acid Sequence↗
PubMed1999

[A trial of povidone-iodine (PVP-I) nasal inhalation and gargling to remove potentially pathogenic bacteria colonized in the pharynx].

OBJECTIVE: Aspiration of potentially pathogenic bacteria (PPB) colonized in the upper airway is a major cause of bacterial pneumonia. We hypothesized that PVP-I nasal inhalation is effective in removing PPB from the upper airway. The aim of this study was to investigate the effectiveness and safety of PVP-I nasal inhalation. METHODS: Patients with asymptomatic PPB (MRSA and/or aerobic GNB i.e. Pseudomonas aeruginosa, Enterobacteriaceae) colonization in the pharynx were enrolled in this study. These patients were divided randomly into two groups as follows: a PVP-I nasal inhalation group (N group) which was asked to inhale 1% PVP-I solution x 2/day nasally by a jet nebulizer and gargling with PVP-I solution x 2/day, and a control group (C group), which was asked to gargle with PVP-I solution x 2/day. The study period was 2 weeks in both groups. RESULTS: Group N consisted of 16 cases, which included 9 (56%) cases with chronic respiratory complications and group C consisted of 14 cases which included 6 (43%) cases with complications. In N and C group, PPB disappearance from the pharynx was observed in 44% and 14% of patients after the study period, respectively. In the patients of group N, without chronic respiratory complication, PPB disappeared in 86% ot the cases. There was no adverse effect correlated with PVP-I nasal inhalation. CONCLUSION: We conclude that PVP-I nasal inhalation is a safe procedure for removing PPB from the upper airway, and this method may contribute to preventing bacterial pneumonia.

Administration, Inhalation↗
PubMed1999

Properties of the evoked spatio-temporal electrical activity in neuronal assemblies.

Properties of neural computation were studied in two types of neuronal networks: isolated leech ganglia and neuronal cultures of dissociated cortical neurons from neonatal rats. With appropriate experimental set-ups it was possible to obtain a precise description of the spread of excitation induced by specific inputs. The evoked spatio-temporal electrical activity was characterized by large variability and the electrical activity of neurons activated by the same stimulation was found to be statistically independent to a high degree. The variability presumably originates from basic properties of synaptic transmission, which is stochastic in nature. As a consequence, the large variability of the evoked spatio-temporal electrical activity appears to be a general property of neural computation and a typical feature of neuronal assemblies. It is shown, however, that the observed statistical independence of co-activated neurons may be used to reduce the effects of variability by appropriately averaging or pooling the electrical activity.

Animals↗
PubMed1999

[Body surface ultrasonography-guided bronchofiberscopy].

Transbronchial lung biopsies and cytologic studies under ultrasonographic guidance from the body surface were conducted in 39 patients whose lesions were adjacent to the thoracic wall. In 26 patients, biopsy, curettage, or brushing forceps were visualized in the mass or infiltrative lesion by thoracic echogram. Positive findings were obtained in 23 patients, for a conclusive diagnostic rate of 88.5%. Of the 13 patients in whom forceps could not be visualized by echogram, 10 had positive findings, for a diagnostic rate of 76.9%. For visualization by thoracic echogram, abnormal lung lesions must be in direct contact with the thoracic wall. Occasionally, diagnostic procedures may be impeded by anatomical structures such as shoulder joints or scapula. Despite these disadvantages, the ultrasonography-guided bronchofiberscope is quite useful because it facilitates real-time confirmation of the positioning of the forceps relative to the lesions. It is also useful in cases when the peripheral lesions are too small or vague to be demonstrated by fluoroscopy alone, because the echo probe can be the target of the forceps instead of the missing shadows. The diagnostic rate should be higher when the forceps are visualized in the lesions ultrasonographically.

Adult↗
PubMed1998

Modification of parallel activity elicited by propagating bursts in developing networks of rat cortical neurones.

Networks of cultured cortical neurones exhibit regular, synchronized, propagating bursts which are synaptically mediated, and which are hypothesized to play a part in activity-dependent formation of connections during development in vivo. The relationship between the strength of synaptic connections and the characteristics of synchronized propagating bursting, however, is unclear. Modification of synchronized activity in cortical cultures in response to electrical stimulation was examined using multisite electrode array recording. By measuring the response of the network to weak, localized, test stimulation (TS), we observed a potentiation of activity following a relatively stronger inducing stimulation (IS). This potentiation was evident as an increased probability of eliciting bursts by TS, an increased frequency of spontaneous bursts and number of spikes per burst, and increased speed of burst propagation, and it lasted for at least 20 min. Changing the parameters of IS revealed that high frequency tetanic stimulation is not necessary to induce potentiation, while it is essential for IS to produce a regeneratively propagating burst. The results provide a direct demonstration of modification of both the spatial and temporal characteristics of synchronized network activity, and suggest an important physiological role for propagating synchronized bursting, as a mechanism for inducing plastic modifications in the developing cortex.

Animals↗
PubMed1998

Strengthening of synchronized activity by tetanic stimulation in cortical cultures: application of planar electrode arrays.

Rat cortical neurons were cultured on planar electrode arrays with 64 embedded electrodes. Whole-cell recording from single neurons and multisite extracellular recording were carried out simultaneously in the cultured cortical networks, and the effects of focal tetanic stimulation of the culture were studied. Both the number of action potentials and the propagation velocity of stimulated bursts were increased after tetanic stimulation. These changes were associated with a marked increase in the number of late components in the synaptic current, but with little or no increase in the early peak synaptic current. The effects of tetanic stimulation were consistent with a widespread increase in the reliability of monosynaptic transmission.

Action Potentials↗
PubMed1998

[Mycobacterial lung infection in 8 patients with AIDS: clinical and radiological features].

The prevalence of mycobacterial infection in AIDS patients has increased in Japan. This report describes details of the clinical and radiological features of eight AIDS patients with mycobacterial disease (6 with M. tuberculosis infection and 2 with M. kansasii infection) in our hospital during the period from October 1995 through February 1997. Six of the 8 were men, and two were women. The mean age was 36.5 years. Six were Japanese, one was from Myanmar, and one was Malaysian. The median CD4 positive T lymphocyte counts (CD4 count) at the time of diagnosis of the M. tuberculosis was 75.5 (range 14-569/microliter, and the M. kansasii was 21.5 (range 19-24)/microliter. Clinical findings and symptoms of all patients were non-specific, but almost all patients had a cough and fever. In the radiographic findings, the patients of the M. tuberculosis group presented multiple hilar and mediastinal lymphadenopathy, miliary shadow, and obstructive pneumonia. Both M. kansasii patients showed a multiple infiltration shadow. There were no drug resistant strains in M. tuberculosis except on isolate with moderate resistant. to Streptomycin. These observations suggest that AIDS-associated mycobacterial disease shows atypical clinical and radiological features in some cases, especially in advanced stages of AIDS. Therefore, we need to recognize the characteristics of the clinical and radiological features of the patients with mycobacterial diseases and AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1997

Experimental analysis of neuronal dynamics in cultured cortical networks and transitions between different patterns of activity.

Experimental investigation of the dynamics of biological networks is a fundamental step towards understanding how the nervous system works. Spontaneous activity in cultured networks of cortical neurons has been investigated by using a multisite recording technique with planar electrode arrays. In these networks, the spatiotemporal firing patterns were studied in the presence of different extracellular solutions. Transitions from asynchronous firing dynamics to synchronous firing dynamics were observed when the extracellular Ca2+ concentration was increased from 0.1 mM to 1 mM. Addition of extracellular Mg2+ reduced the spontaneous activity at any Ca2+ concentration, and an increase in the extracellular K+ concentration enhanced the frequency of periodical synchronous bursts. N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptor antagonists inhibited synchronous activity. A spatiotemporal analysis of the data has been performed, and the properties of the network such as the synchronization and the periodicity have been quantified in order to clarify how variations of intrinsic parameters of the network can induce structural transitions in the neural dynamics. This experimental study is a possible approach to investigate the computational properties of a neuronal network.

Animals↗
PubMed1997

Host range conversion of murine leukemia virus resulting from recombination with endogenous virus.

Ecotropic murine leukemia viruses (MuLVs) are classified into B-N-, or NB-tropic MuLV by their host range determined by the Fv-1 gene product. B-tropic MuLV is restricted in N-type mouse cells (Fv-1 n/n) and N-tropic MuLV is restricted in B-type mouse cells (FV-1 b/b). Although forced passages in a restrictive host grant a wider host range (NB-tropism), we show here a host range conversion from B to N tropism. The conversion was most likely a result of recombination between the exogenously infected B-tropic MuLV and an endogenously expressed N-tropic MuLV in a C57BL/6 mouse cell line, YH-7.

Animals↗
PubMed1997

One base change is sufficient for host range conversion of murine leukemia virus from B to NB tropism.

Comparison of the whole p30 (CA) sequence between B-tropic WN1802B murine leukemia virus and its NB-tropic derivative revealed a single base change at the 313th nucleotide. We constructed hybrid proviruses differing only at the 313th nucleotide of p30 along the whole genome, and examined the host range of the produced viruses. The single point mutation in p30 was found sufficient for the B to NB tropism conversion.

Animals↗
PubMed1997

Expression of intercellular adhesion molecule-1 and lymphocyte function-associated antigen-1 on alveolar macrophages in the acute stage of radiation-induced lung injury in rats.

We investigated the expression of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) on alveolar macrophages and on lung tissue in the early stage of radiation-induced lung injury. Cells in the bronchoalveolar lavage and lung tissue were obtained from rats at various times between 1 and 8 weeks after 20 Gy of 60Co gamma irradiation of a hemithorax. These specimens were stained immunohistochemically with anti-ICAM-1 and anti-LFA-1alpha monoclonal antibodies. The expression of these factors was compared with that of a control group. The total number of alveolar macrophages in the bronchoalveolar lavage was significantly reduced from 1 to 3 weeks, and the number of neutrophils was significantly increased 2 and 3 weeks after irradiation. ICAM-1 and LFA-1 expression on alveolar macrophages was significantly increased starting 1 week after irradiation. The expression of ICAM-1 and LFA-1 on lung tissue was not elevated up to 8 weeks after irradiation. In conclusion, the increased expression of ICAM-1 and LFA-1 on alveolar macrophages as early as 1 week after irradiation suggests that adhesion molecules play a role in the development of radiation-induced lung injury.

Analysis of Variance↗