Search PubMed⌕ Search

Biomedical subjects

T Hamaguchi

Publications and source records attributed to T Hamaguchi.

At least 127 records · Page 7Linked to original sources
PubMed1984

Quantitative analysis of electrical properties of dendritic spines.

Several suggestions have been made with regard to the functional significance of dendritic spines in connection with synaptic plasticity. We have shown that for a constant synaptic current, when the synaptic resistance is large compared to the spine-stem resistance, a morphological change in the spine does not produce a marked change in the postsynaptic potential (PSP). When the synaptic resistance is comparable to the spine-stem impedance a morphological change in the spine can induce changes in the synaptic current and the PSP due to the so-called nonlinear effect to the synapse (Kawato and Tsukahara, 1983, 1984). Consequently, in a study of the electrical properties of dendritic spines the input impedance of the parent dendrite, the spinestalk conductance and the conductance change associated with synaptic activity must be considered. We quantitatively estimated all three factors. By comparing electrophysiological data with morphological data, we estimated the synaptic conductance which causes corticorubral EPSP. Its maximum amplitude was 43 nS with a time-to-peak value of 0.3 ms. With this value, the effects of the spine were examined using an improved algorithm based on that of Butz and Cowan (1974). It uses a three-dimensional morphology of the rubrospinal (RS) neurons, which was reconstructed from serial sections containing HRP-filled RS cells. As the spine shortens, the amplitude of the EPSP becomes considerably larger, but its time-to-peak value does not markedly change. Moreover, if unitary EPSP in the RS cell is produced by the activation of several synaptic terminals a morphological change of the spine has a smaller effect on the EPSPs.

Animals↗
PubMed1984

A new method for rapid spermatozoal concentration and motility: a multiple-exposure photography system using the Polaroid camera.

A multiple exposure photography (MEP) system using the Polaroid camera PM-CP (Olympus, Tokyo, Japan) has been developed to accurately estimate the concentration and motility of spermatozoa in routine clinical work for the treatment of infertility. This Polaroid-MEP system is equipped with a xenon stroboscope MS-230 (Sugawara Laboratories Inc., Tokyo, Japan), and Makler's Counting Chamber (Sefi-Medical Instruments, Haifa, Israel). The system immediately produces printed images of spermatozoal tracks at the laboratory of the outpatient clinic, providing objective and exact information about the concentration and the motility of spermatozoa.

Humans↗
PubMed1984

[Clinical study on tissue polypeptide antigen (TPA) as a tumor marker].

We evaluated whether assay of tissue polypeptide antigen (TPA) in sera is valuable for the determination of cancer stages compared to other tumor markers such as CEA, AFP, beta2-microglobulin, ferritin, and elastase-1. The study population consisted of cancer patients (33 gastric cancers, 7 colo-rectal cancers and 15 hepatomas), 169 patients with benign gastro-enteric diseases and 72 healthy volunteers. The percentage of positive cases for TPA (higher than 200 u/l) was 61% in gastric cancer, 71% in colo-rectal cancer and 87% in hepatoma. In certain non-cancerous conditions, such as gastric ulcer (active stage), acute hepatitis and chronic hepatitis, the TPA levels were increased over the level of healthy volunteers. There was no significant correlation between TPA and the other tumor markers. Our study suggests that TPA may be useful in the identification and evaluation of cancer patients.

Adolescent↗
PubMed1984

[A study on Ureaplasma urealyticum and sperm. Comparison of sperm morphology before and after chemotherapy].

Spermiogram (morphology of sperm heads and tails) was evaluated in 21 men visiting our infertility clinic before and after the eradication of genital infection with Ureaplasma urealyticum. The percentage of coiled tails and fuzzy granular tails were decreased after eradication of Ureaplasma but there were no significant changes in the morphologic characteristics of sperm heads. Spermiogram was also analysed in 5 men who were unsuccessfully treated for genital Ureaplasma infection. In this group there were no significant changes in the morphologic characteristics of sperm heads and tails before and after chemotherapy.

Humans↗
PubMed1980

[Experience of peripheral osteosynthesis using single crystal alumina ceramics screws (author's transl)].

As a new kind of material for peripheral osteosynthesis we have developed the single crystal alumina ceramics screws (artificial sapphire screws) taking under consideration of the properties of alumina ceramics, and we have tested them experimentally in animals, and used them clinically too. The results of the mechanical tests and animal experiments were excellent. In the clinical follow-up studies the perfect bone unions has been recognized roentgenologically. The sapphire screws have, sofar, proved to be harmless also as anchor for bone cement. Our experience with our sapphire screws has opened the way for the clinical application of this material instead of metal screws.

Adult↗
PubMed1975

Study on the surface shape and contours of the femoral head and acetabulum of the human joint.

(1) The degree of change and degeneration of the surface of articular cartilage were classified into 6 stages and a distribution chart indicating 6 stages of classification was prepared for each case. (2) The construction of the superficial fine fibrous net-work of the cartilage of the weight-bearing area is different from that of the non-weight-bearing area. (3) The construction of the fiber underneath the surface of the acetabular cartilage is different from that of the surface of femoral head cartilage underneath. (4) When only weight-bearing part was compared, the degeneration at the upper anterior side was least for both femoral head and acetabulum and was most at the slightly posterior part of the upper outer side. (5) The fine fiber of superficial layer of the femoral head and acetabular cartilage were peeling from the periphery toward the center, but no difference of surface roughness was observed by way of measurement directions. (6) Surface roughness of the cartilage increases in proportion to the degree of degeneration and change. (7) The surface roughness of the acetabulum is about twice as large as that of the femoral head cartilage, this being due to the difference in the degree of degeneration. (8) There are 4 kinds of undulations at the surface of the femoral head cartilage. (9) Both femoral head and acetabulum have less waviness of large size at the part bearing large weight. (10) The contour of the femoral head as a whole is slightly ellipsoidal, whose longitudinal axis extends in a craniocaudal direction but the weight-bearing part is nearly circular. (11) The general contour of the acetabulum indicates an ellipsoidal shape with its craniocaudal longitudinal axis slightly inclined forward or backward. The contour of the slightly postero-upper part which is considered to be the maximum weight-bearing part is slightly flat ellipsoidal.

Acetabulum↗