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Biomedical subjects

K Homma

Publications and source records attributed to K Homma.

At least 91 records · Page 5Linked to original sources
PubMed1992

The fate of the prosegment in the acute-phase and programmed synthesis of sapecin, an antibacterial peptide of the flesh fly (Sarcophaga peregrina).

The nucleotide sequence of sapecin cDNA suggested that this antibacterial peptide of the flesh fly (Sarcophaga peregrina) is produced from preprosapecin by post-translational processing. We examined the production of sapecin and its prosegment by radioimmunoassay under two different physiological conditions in which its gene is activated, assuming that the prosegment has some biological role. Results suggested that the prosegment is degraded selectively during production of sapecin. We also found that imaginal discs synthesize sapecin when cultured in the presence of 20-hydroxyecdysone.

Amino Acid Sequence↗
PubMed1992

Non-Hodgkin's lymphoma with histological features of neoplastic angioendotheliosis.

Three cases of non-Hodgkin's lymphoma, B-cell type, identical histologically to so-called neoplastic angioendotheliosis (NAE), are reported. All showed a rapidly progressive clinical course and were not properly diagnosed before death. The lymphoma cells were distributed in many vessels of systemic organs with a tendency to form aggregates. The primary sites in the three cases were probably the adrenal gland, lymph node, and spleen, respectively. In particular, in one case it was suggested that the lymphoma cells had spread from the adrenal tumor to other organs, showing the histological features of NAE. In the literature, the primary sites of NAE have been scarcely mentioned. However, gross tumors were present in some cases. In such cases, it is possible that the tumors could be the primary sites of NAE. We conclude that some non-Hodgkin's lymphomas can exhibit the features of NAE during their course, particularly in the terminal stages.

Adrenal Gland Neoplasms↗
PubMed1992

Reversible lung lesions in rats due to short-term exposure to ultrafine cobalt particles.

Using an ultrasonic nebulizer, cobalt aerosols (MMAD = 0.76 microns, sigma g = 2.1) were generated from an aqueous suspension of ultrafine metallic cobalt particles (Uf-Co) with a primary diameter of 20 nm. Rats were exposed to Uf-Co aerosols at 2.72 +/- 0.44 mg/m3 for 5 hours (Exp. 1) or at 2.12 +/- 0.55 mg/m3 for 4 days at 5 hours/day (Exp. 2). Only minimum histopathological changes were observed in the lungs in Exp. 1. In Exp. 2, evidence of slight injury was noted, including focal hypertrophy or proliferation of the epithelium in the lower airways, damages of macrophages, intracellular edema of the type I alveolar epithelium, interstitial edema, and proliferation of the type II alveolar epithelium. A new finding in this study was the morphological transformation of some damaged type I cells to the juvenile form, which appeared to indicate the capability of self-repair of this cell type. The return to a juvenile form seemed to be a key response of type I cells during the early process of repair without cell division following non-lethal injury. Cobalt accumulated in the lungs after inhalation and was transferred rapidly to the blood. In conclusion, inhaled Uf-Co induced reversible pulmonary injury even after short-term exposure.

Administration, Inhalation↗
PubMed1992

Primary extramedullary plasmacytoma of the small intestine.

We report a case of primary extramedullary plasmacytoma (PEMP), IgA kappa type, with a long clinical history, in a 64-year-old Japanese woman. In this case, PEMP occurred primarily in the jejunum and then recurred in several organs, specifically the spleen and stomach, and in the subcutaneous tissue, over a period of about 16 years. However, examination of bone marrow aspirates on several occasions continued to show no plasmacytoma involvement. The patient is still living. Immunohistochemical examinations revealed monoclonal IgA kappa immunoglobulin in the cytoplasm of infiltrating plasma cells in all surgical specimens examined. Immunoelectrophoresis revealed serum M-component only when the patient had a splenic tumor. Soon after splenectomy, the serum M-component disappeared. PEMP of the small intestine is rare.

Female↗
PubMed1992

Neuropeptide release from the isolated, perfused, lower esophageal sphincter region of the rabbit and the effect of vasoactive intestinal peptide on the sphincter.

BACKGROUND: The aim was to evaluate the isolated, vascularly perfused, lower esophageal sphincter (LES) as a model for investigating the functional role of neuropeptides such as vasoactive intestinal peptide (VIP). METHODS: At laparotomy the LES was removed along with the distal esophagus, stomach, and left gastric artery and vein. The LES area, isolated from the body of the stomach by a custom-made clamp, was perfused with oxygenated Krebs-Ringer bicarbonate solution (pH 7.4, 38 degrees C) via the left gastric artery. The LES pressure was monitored continuously with a custom-made Dent sleeve catheter. LES pressure and release of neuropeptides were investigated after carbachol and VIP were administered alone or in combination. VIP, calcitonin gene-related peptide (CGRP), and somatostatin were measured in the venous perfusate collected from the left gastric vein. RESULTS: LES tone and contraction frequency were similarly increased by 10 and 100 nmol/L carbachol (increment, 4.0 +/- 0.26 mm Hg with 10 nmol/L carbachol; p less than 0.0003). Perfusion with 10 nmol/L VIP decreased basal tone and completely abolished the contraction induced by 100 nmol/L carbachol. VIP, CGRP, and somatostatin were released from the LES in response to 10 nmol/L carbachol (VIP rose from 55 +/- 13 to 179 +/- 24 pmol/L, CGRP, from 114 +/- 30 to 239 +/- 33 pmol/L, and somatostatin from 15 +/- 2 to 27 +/- 4 pmol/L; all p less than 0.001). CONCLUSIONS: These findings support a role for VIP in the inhibitory reflex of the LES but suggest that other neuropeptides may also be involved. The isolated, perfused LES provides a new tool for investigating neuropeptide interactions.

Animals↗
PubMed1991

Involvement of sapecin in embryonic cell proliferation of Sarcophaga peregrina (flesh fly).

Addition of antibodies against sapecin to the culture medium of NIH-Sape-4 cells derived from a Sarcophaga embryo greatly inhibited cell proliferation, whereas addition of sapecin stimulated cell proliferation. These results suggest that sapecin is involved in the proliferation of embryonic cells of Sarcophaga. Sapecin is known to have potent antibacterial activity, so it seems to have two different biological functions: i.e. protection against bacterial infection and stimulation of embryonic cell proliferation.

Animals↗
PubMed1991

Angiocentric immunoproliferative lesion of the stomach.

We report here a rare case of angiocentric immunoproliferative lesion (AIL) of the stomach. The patient was a 61-year-old Japanese female whose medical history was unremarkable. Following a complaint of abdominal discomfort, a submucosal tumour of the stomach was found and gastrectomy was done. Histological examination of the tumour revealed multiple angiocentric or angiodestructive lesions with numerous lymphocytic infiltrates. These vascular lesions were histologically the same as those in benign lymphocytic vasculitis with granulomatosis (BLV) of the respiratory tract. AIL is a distinct entity, including BLV, lymphomatoid granulomatosis and angiocentric lymphoma with BLV representing a good prognosis group of AIL. A survey of the literature suggests that AIL is a spectrum of T-lymphocyte proliferative disorders. To our knowledge, this is the first case of AIL involving the stomach primarily.

Female↗
PubMed1990

Development of an inhalation system of high melting point metal fumes and its use for exposure of rats to chromium and nickel fumes.

An experimental inhalation system was developed for fumes generated from powders of high melting point metals such as chromium, nickel, manganese and iron. The system consisted of a plasma flame metal sprayer as a fume generator, a granular bed type fume collector, a fluidized bed aerosol generator, an exposure and a control chamber of a horizontal-flow type and inhalant monitoring and controlling units. Performance of the chambers was ensured by a distribution test using flyash as a test aerosol. Using this system, rats were exposed to chromium fumes for one week or to nickel fumes for two months. The exposure concentrations of the chromium and nickel fumes were 1.85 +/- 0.55 mg/m3 and 0.51 +/- 0.15 mg/m3 (mean +/- SD), near the target levels of 2 mg/m3 and 0.5 mg/m3, respectively. The mass median aerodynamic diameter and the geometric standard deviation of the chromium fumes were 2.1 microns and 2.00, respectively. Those of the nickel fumes were 3.7 microns and 1.74, respectively. Species analysis of these fume particles revealed that 26.4% of the total chromium was hexavalent and the residue was trivalent and that 1-3% of the total nickel was nickel(III) and the residue was nickel(II). Inhaled-metal concentrations in the lungs showed steady increases with the exposure periods and were within the normal range of variation. On the basis of these results, it is concluded that this system is useful for long-term inhalation experiments using high melting point metal fumes.

Administration, Inhalation↗
PubMed1990

Historical studies on the striae of Hunter-Schreger.

When the ground section of a human tooth is observed through a microscope, the oblique section, or the cross section, the enamel rod is dark and the vertical section it is light. These striae have been called the bands of Schreger. In his book published in 1961, Professor Fujita quoted a paper presented by Preiswerk (1894) as follows: "Schreger found the striae in 1800 (Rosenmüller's und Isenflamm's Beiträge für die Zergliederungskunst, Bd. I, H. 1, Leipzig), but John Hunter from England reported the same findings earlier. For this reason, such striae were called the bands of Hunter-Schreger in Europe and America. In his paper of 1894, Preiswerk reported that Hunter found the striae in 1780; however, in the second edition of his book, The Natural History of the Human Teeth, published in 1778, Hunter showed an illustration that seemed to be the striae and annotated the illustration. The striae may have been reported even in his first edition (1771), but neither edition of the book is available in Japan." Quoting the first edition of Hunter's book, Hoffmann-Axthelm included the illustration of the striae in his book. Through this book, I found that Professor Fujita's conjecture was correct. Moreover, I recently had an opportunity to read the first and the second editions of John Hunter's book. Accordingly, I am reporting this report.

Dental Enamel↗
PubMed1989

The s phase is discrete and is controlled by the circadian clock in the marine dinoflagellate Gonyaulax polyedra.

Cloned cultures of the dinoflagellate Gonyaulax polyedra grown in a 12-h light-12-h dark cycle (LD 12:12) were synchronized to the beginning of G1 by a two sequential filtration technique. After the second filtration, with the cultures growing in LD 12:12, not many cells had divided after 1 day, but approximately half underwent cell division after 2 days. Flow cytometric measurements of the cells revealed that there is one unique S phase starting about 12 h prior to cell division and lasting for less than 4 h. A majority of cells in cultures synchronized in the same way but maintained in continuous light (LL) after filtration also divided synchronously after 2 days. Just as for the cultures in LD 12:12, those in LL have a similar discrete DNA synthesis phase prior to division. It is concluded that the circadian control of cell division acts before the S phase, giving rise to a discontinuous DNA synthesis phased by the circadian clock.

Animals↗
PubMed1989

Cell growth kinetics, division asymmetry and volume control at division in the marine dinoflagellate Gonyaulax polyedra: a model of circadian clock control of the cell cycle.

A new method of determining the dependence of cell growth on the initial cell volume in the absence of cell division is presented. The assumptions are that volume in a certain period of time is either increasing or decreasing, but not both, and is independent of the history of cells. Applying this method to Gonyaulax polyedra in a 12h light-12h dark cycle, growth in volume between the 3rd and 12th hours of the light period is found to be more exponential-like than linear. The magnitude of growth in the time period is determined solely by cell volume and environmental conditions, not by cell age. All cells decrease in volume slightly in the dark from the 12th to 23rd hour, and then increase a little from the 23rd to 3rd hour of the following day. Cell division in this species is significantly asymmetric, and the extent of asymmetry is estimated mathematically. Simulations based on the growth patterns and the asymmetric division reveal that cell division must at least partly depend on the volume of cells. The dependence of conditional cell division probability on cell volume is then experimentally determined. The probability is zero up to a certain cell volume, and then it gradually increases to a plateau level, which is less than unity. Neither the strict size control model nor the transition probability model is fully consistent with the observed shape of the conditional probability function. A hybrid model postulating a 'sloppy' critical volume with a constant probability of division above that volume adequately accounts for the conditional probability. With the use of the observed volume growth law, cell division dependence on volume, and the extent of asymmetry in cell division, cell volume distributions are successfully simulated for cells growing in a 12h light-12h dark cycle. Another simulation reveals that the true coefficient of variation in generation time is 33%. On the basis of these findings, a model of the cell cycle is presented that incorporates the circadian clock as a cyclic G1 phase. According to this scheme, cells satisfying the minimum cell volume requirement between the 12th and the 18th hour probably exit to the replication/segregation sequence ending in division, and re-enter the cyclic portion after a fixed time interval.

Animals↗
PubMed1988

Oviposition pattern of Japanese quail following hypothalamic lesioning with super-absorbent polymer.

The functions of two hypothalamic areas in controlling the female reproductive cycle were investigated by the intracerebral injection of a new type of water-absorbent polymer of high capacity (super-absorbent polymer). After injection of a minute amount of the polymer into the brain tissue, bulging of the polymer produces a discrete lesion at the site of injection. Two lines (T- and J-lines) of Japanese quail were used; T-line, having a characteristic free-running oviposition pattern irrespective of the environmental 14L10D, and J-line, having a regular oviposition pattern which synchronized with 14L10D. Lesions at the preoptic area were without effect in birds of J-line, but the oviposition of T-line was changed from free-running to regular. Lesions at the posterodorsal part of the infundibular complex were without effect in T-line, but the regular oviposition pattern of J-line became free-running. These results suggest that relative dominancy between the two hypothalamic areas may determine basic pattern of oviposition through modification of the ovulation cycle.

Animals↗
PubMed1988

Cell cycle synchronization of Gonyaulax polyedra by filtration: quantized generation times.

A size filtration method to synchronize cultures of the dinoflagellate Gonyaulax polyedra to the beginning of the G1 phase has been developed. This technique selects newly born cells by two sequential filtrations, based on the fact that cell division is restricted to the beginning of the day, so that a decrease in cell volume occurs at this time. The fraction of synchronized cells immediately after the second filtration is about 90%; the procedures do not alter the free-running period or phase of glow rhythm, and the selected cells divide again in a few days. Applying this method, we have found that the generation times of this species in a light-dark cycle (LD 12:12) are indeed quantized to multiples of 24 hr, but are variable from generation to generation.

Animals↗
PubMed1987

Magnetic resonance imaging of acute intracerebral hematomas: in vivo and in vitro studies.

The mechanisms causing unclear differentiation of ICH in the acute phase by MRI are discussed. The increase of the hemoglobin concentration in the hematoma, caused by loss of the plasma component directly after onset, is one of the reasons for the shortening of relaxation times. The clotting system is also responsible for this shortening. Thus, the hematoma reaches the same intensity as the brain in the acute stage. Although knowledge from our animal experiments, in vivo as well as in vitro, cannot be directly transferred to the human, such experiments are useful for the understanding of the pathomechanism influencing MR imaging.

Acute Disease↗
PubMed1987

Detection of neural connection to the infundibular complex by partial or complete hypothalamic deafferentation in male quail.

To elucidate the stimulatory and inhibitory neural systems for photoperiodic control of avian reproduction, immature male Japanese quail were subjected to partial or complete hypothalamic deafferentation, followed by exposure to long and short photoperiods. The results indicated that when the encephalic photosensitive area (infundibular complex, INF) was preserved after hypothalamic deafferentation, birds were able to respond to long days and their gonads eventually recrudesced, and that testicular atrophy under short days was prevented by the semicircular cuts posterior to INF or by orbital enucleation. It is concluded that in male Japanese quail, INF plays the pivotal role in photoperiodic gonadostimulation and regulatory neurons in the retina and anterior hypothalamus may have neural connection to the posterior side of INF.

Animals↗