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Biomedical subjects

K Kawamata

Publications and source records attributed to K Kawamata.

At least 19 recordsLinked to original sources
PubMed1997

[A case of primary HIV-1 infection].

A previously healthy 28 year old Japanese man came to us with a genital ulcer which appeared 13 days before admission to our hospital. He had subsequently fever (40 degrees C), arthralgia, a sore throat and oral aphtha 6 days before admission. He had a history of sexual contact with a female commercial sex worker one week before his illness. On the day of admission, he had shallow ulcers on the lip, tongue and penis. Initial laboratory test included leukopenia and thrombocytopenia. His fever abated 3 days after admission. His condition and bicytopenia recovered completely after 12 days of admission. Although, his serum HIV-1 antibody was negative when he was admitted, 3 months later the antibody was seroconverted. And p24 antigen and HIV-1 RNA of stocked serum were positive. Diagnosis of primary HIV-1 infection was made. Recently, HIV-1 infection has been increasing in Japan. Consideration of this disease in differential diagnosis of acute febrile illness is necessary.

Adult↗
PubMed1994

[Immunohistochemical studies on mycobacteria in tuberculous necrotizing granulomas].

For the purpose to know the pathogenesis of caseous necrosis in tuberculous lesion, authors compared the presence and the number of mycobacteria in the pulmonary tubercles of various histological types. Forty pulmonary tubercles obtained from 16 patients (9 males, 7 females; mean age 51) were examined. By Ziehl-Neelsen (ZN) method, acid-fast bacilli were detected in 40% of 5 proliferative, in 12.5% of 24 productive and none of 11 sclerotic granulomas. By immunohistological staining with anti-BCG antiserum, positive staining was observed in 60%, 87.5% and 91% of each type of granuloma, respectively. Types of necrosis were classified by silver-staining as necrosis after exudative reactions (EN), necrosis after productive reactions (PN) and filled materials after softening and liquification of necrotic lesions (LN). EN was observed in 24 tubercles, and mycobacteria were stained in 8% of EN by ZN method and in 75% by immunohistological method. PN was observed in 21 tubercles, and mycobacteria were detected in none and 5% of such type of necrosis by respective method. LN was observed in 28 tubercles, and mycobacteria were detected in 11% and 71% of these lesions by respective method. So, positive ratio by immunochemical method was significantly higher in EN and LN than in PN. Further, mycobacteria were stained with anti-BCG antiserum as granules and the number of such granules were much more numerous in EN and LN than in PN (p < 0.01). From these results, it was suggested that necrosis might occur by different mechanisms in exudative reactions and in productive reactions.

Adult↗
PubMed1990

Electron microscopic study of immunocytochemically labeled centrifugal fibers in the goldfish retina.

The centrifugal fibers innervating the goldfish retina were studied quantitatively by light and electron microscopy. These fibers originating from cell bodies in the olfactory bulb were labeled by antiserum to the tetrapeptide Phe-Met-Arg-Phe-NH2 (FMRFamide). The number of FMRFamide-immunoreactive (ir) centrifugal fibers in each eye of the adult goldfish (body length: 12-15 cm) was 65 +/- 14 (mean +/- S.D., n = 7). All of these fibers in the optic nerve and the retina were unmyelinated. Each FMRFamide-ir centrifugal fiber runs along the optic fiber layer and gives several terminal arborizations in the outermost layer (layer 1) of the inner plexiform layer. Layer 1 is, therefore, densely covered by a plexus of terminal arborizations. Along these terminal arborizations, we found output synapses characterized by a cluster of small clear vesicles (40 nm in diameter) at the presynaptic site and a thickened membrane in the apposed retinal cell processes. In a sample area of 2,000 microns 2, such synapses occurred at a density of one per 105 microns 2, or about 13,000 per centrifugal fiber. Thus, the FMRFamide-ir centrifugal fibers are likely to modulate retinal cell activity through an estimated total of 840,000 output synapses per retina.

Animals↗
PubMed1990

Telodendrial contact of HRP-filled photoreceptors in the turtle retina: pathways of photoreceptor coupling.

Synaptic contacts of photoreceptors in the turtle retina were studied by intracellular injection of horseradish peroxidase (HRP) and electron microscopy. Both cone and rod photoreceptors radiated basal processes (telodendria) from their terminal endings. These telodendria ran laterally in the outer plexiform layer. The telodendria of cones gave rise to many fine branches that penetrated synaptic cavities of several neighboring cones. Tips of these branches terminated near the walls of synaptic cavities. Some of the telodendrial contact formed two types of basal junction: symmetrical and punctate. The distribution of cones that made telodendrial contacts with the HRP-filled cone were quantitatively investigated. Green-sensitive cones (n = 3) made telodendrial contacts with neighboring red- and blue-sensitive cones, blue-sensitive cones (n = 4) with red- and green-sensitive cones, and red-sensitive cones (n = 9) with red- and green-sensitive cones. In contrast to these cone connections, rod telodendria did not penetrate neighboring photoreceptors. Direct synaptic contacts were not found between rods and cones. Our results clarify the variety of cone couplings in turtle retina: the three chromatic classes of cones are selectively coupled by the basal junctions at the ends of telodendrial processes.

Animals↗
PubMed1990

Monoclonal antibody labels both rod and cone outer segments of turtle photoreceptors.

We have studied the immunoreactivity of turtle photoreceptors to a monoclonal antibody (MAb 15-18) which binds to the external loop connecting bovine rhodopsin helices IV-V. Three chromatic types of cone photoreceptors were identified by the presence and color of oil droplets. MAb 15-18 intensely labeled the outer segments of both rods and green cones. In addition, a weak cross-reactivity was also found in the outer segments of red cones having a pale-green oil droplet, and of blue cones. Other morphological subtypes of red cones, cones with a red oil droplet and both members of double cones, showed no labeling. Our results indicate that rhodopsin and green cone opsin have a similar antigenic determinant, and that two different structural forms of red cone opsin may be present in the turtle retina.

Animals↗
PubMed1990

Dose-dependent pharmacokinetics and first-pass metabolism of acetaminophen in rats.

In order to investigate the in vivo first-pass metabolism of acetaminophen (AAP) following the oral and intraduodenal administration in rats, a pharmacokinetic compartment model including absorption process was developed. Using the parameters for the disposition kinetics of AAP and its metabolites, sulfate and glucuronide, which were determined in the separate study, the extent of the first-pass metabolism and the contribution of sulfation and glucuronidation to the total first-pass metabolism in vivo were quantitatively estimated. As for the results, the first-pass metabolism of AAP following the oral and intraduodenal administration was mainly attributable to the sulfo-conjugation pathway in rats. The sulfation of AAP in the intestine and/or in the liver during the first-pass was proved to be a saturable process. Then, the sulfation in the first-pass metabolism showed the dose- and absorption rate-dependent kinetics. Thus, the pharmacokinetic model including the absorption process proposed in the present study was proved to be valid and useful for the estimation of in vivo first-pass metabolism of AAP in rats.

Acetaminophen↗
PubMed1987

Daily changes of structure, function and rhodopsin content in the compound eye of the crab Hemigrapsus sanguineus.

The compound eye of the crab hemigrapsus sanguineus undergoes daily changes in morphology as determined by light and electron microscopy, both in the quantity of chromophore substances studied by HPLC and in visual sensitivity as shown by electrophysiological techniques. 1. At a temperature of 20 degrees C, the rhabdom occupation ratio (ROR) of an ommatidial retinula was 11.6% (maximum) at midnight, 8.0 times larger than the minimum value at midday (1.4%). 2. Observations by freeze-fracture revealed that the densities of intra-membranous particles (9-11 nm in diameter) of rhabdomeric membrane were ca. 2000/microns 2 and ca. 3000/microns 2 for night and daytime compound eyes, respectively. 3. Screening pigment granules migrated longitudinally and aggregated at night, but dispersed during the day. Reflecting pigment granules migrate transversally in the proximal half of the reticula layer i.e. cytoplasmic extensions containing reflecting pigment granules squeeze between neighbouring retinula cells causing optical isolation (Fig. 4). Thus the screening pigment granules within the retinula cells show longitudinal migration and radial movement so that the daytime rhabdoms are closely surrounded by the pigment granules. 4. At 20 degrees C, the total amount of chromophore of the visual pigment (11-cis and all-trans-retinal) was 1.4 times larger at night than during the day i.e. 46.6 pmol/eye at midnight and 33.2 pmol/eye at midday. Calculations of the total surface area of rhabdomeric membrane, total number of intra-membranous particles in rhabdomeric membrane and the total number of chromophore molecules in a compound eye, indicate that a considerable amount of chromophore-protein complex exists outside the rhabdom during the day. 5. The change in rhabdom size and quantity of chromophore were highly dependent on temperature. At 10 degrees C both rhabdom size and amount of chromophore stayed close to daytime levels throughout the 24 hours. 6. The intracellularly determined relative sensitivity of the dark adapted night eye to a point source of light was about twice as high as the dark-adapted day eye. Most of the increase in the sensitivity is attributed primarily to the effect of reflecting pigment migration around the basement membrane and, secondarily, to the changes in the amount and properties of the photoreceptive membrane. The results form the basis of a detailed discussion as to how an apposition eye can function possibly as a night-eye.

Animals↗