Biomedical subjects

T Sawaguchi

Publications and source records attributed to T Sawaguchi.

81 records · Page 5Linked to original sources

PubMed1986

Long-lasting marks of extracellularly recorded sites by carbon fiber glass micropipettes in the frontal cortex of chronic monkeys.

Extracellularly recorded sites were successfully marked by means of carbon fiber-containing glass micropipettes in the frontal cortex of chronically behaving monkeys. A DC current was passed through the tip of the micropipette (typically, anodal, 10 microA, 10 s). The marks were observed as brown spots with sizes of about 100 microns, and lasted for at least 4 months in vivo. Further, during physiological recording sessions, unmarked recording sites along the electrode track could be estimated with 10% error by measuring the distances between the marked sites, or between the marked site and the cortical surface.

Animals↗

PubMed1986

A hypothesis on the primate neocortex evolution: column-multiplication hypothesis.

A hypothesis is proposed, that the primate neocortex has evolved by the multiplication of cortical columns. As the column size is similar across primate species, it is considered that the columns have multiplied to expand the neocortex during primate evolution. This hypothesis would explain the expansion of neocortical sensory-motor-associational areas and multiple sensory and motor areas which had occurred during evolution. Further, the hypothesis predicts the existence of columns neutral for the fitness, genetic control upon the columns, and intraspecies variations of the columns.

Afferent Pathways↗

PubMed1985

Laminar distributions of neurons sensitive to acetylcholine, noradrenaline and dopamine in the dorsolateral prefrontal cortex of the monkey.

Sensitivities of neurons to acetylcholine (ACh), noradrenaline (NA) and dopamine (DA) were investigated at different depths of the dorsolateral prefrontal cortex (PFC) in awake or halothane-anesthetized macaque monkeys, using microiontophoretic techniques with multi-barreled electrodes. The laminar locations of tested neurons (n = 403) were estimated by reconstructing electrode tracks based on the microlesion made by passing a current through the recording barrel, which contained a carbon fiber. Iontophoretically applied drugs induced excitatory or inhibitory responses. Neurons excited by ACh (n = 105) were located mainly in layers III and V, and those inhibited by ACh (n = 126) were in layers III and IV. The majority of the NA-sensitive neurons (n = 123) were NA-inhibited neurons (n = 100), and were found most often in layers III and IV. The ratio of DA-sensitive neurons (excited, n = 74; inhibited, n = 63) to tested neurons was higher in the deep layers than in the superficial ones. These results indicate that sensitivities of the PFC neurons to ACh, NA and DA are not uniform between cortical layers, suggesting that each of these substances may predominantly influence the neuronal activity of particular layers of the monkey PFC.

Acetylcholine↗

PubMed1985

Fractures of the acetabulum.

A critical analysis of the results reveals the following major factors in determining the outcome of an individual acetabular disruption: The damage to the acetabular articular surface, which is reflected by the pattern of fracture and its degree of comminution, impaction, and osteoporosis, and associated damage of the femoral head The adequacy of the reduction, which is reflected by intraoperative inspection and postoperative radiographs The associated complications of the fracture and treatment (e.g., avascular necrosis, sciatic palsy, and heterotopic ossification) We recommend principles of treatment of acetabular fractures comparable to those employed for most other displaced intraarticular fractures, namely an anatomic reduction, stable internal fixation, and early motion, to realize reproducibly optimal results. The principal contraindications to open reduction are osteoporosis and generalized comminution to a degree that precludes a reasonable likelihood for the surgical team to achieve a stable anatomic reduction. We have provided guidelines for the surgical approach, techniques of reduction, and methods of fixation, and an analysis of results, which provide the basis for the successful treatment of these difficult intraarticular injuries.

Acetabulum↗

PubMed1984

Stability of acetabular fractures after internal fixation. A cadaveric study.

The rigidity of a transverse acetabular fracture in a laboratory cadaveric model immobilized by internal fixation was studied. On the application of a longitudinal load imposed on the fifth lumbar vertebra, four modes of displacement of the acetabular fracture were monitored by the use of variable impedance transducers. The rigidity of various combinations of lag screws and plates was assessed. The fracture deformations documented were generally quite small at any observation point with any of the fixation methods, and in most cases they were recoverable on load release. Anterior column lag screw fixation combined with plate fixation of the posterior column provided a degree of stability indistinguishable from that of other methods, and allowed the minimal exposure and devascularization of the pelvis. The 3.5 mm reconstruction plate, which is readily contoured to the intricate peri-acetabular bony structure, showed no significant difference in rigidity compared to the other apparently more rigid plates under study.

Acetabulum↗

PubMed1981