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Biomedical subjects

H Sakata

Publications and source records attributed to H Sakata.

302 records · Page 17Linked to original sources
PubMed1968

Neuronal coding by cortical cells of the frequency of oscillating peripheral stimuli.

One class of neurons in the somatic sensory cortex of unanesthetized monkeys is rhythmically entrained by sinusoidal mechanical stimulation of the skin of the hand at low frequencies. A second class, which is linked to Pacinian afferents, increases its rate of discharge in response to high-frequency peripheral stimuli but is not entrained. The vibratory sense is served by two distinct classes of cortical cells. The code for the group sensitive to low-frequency stimuli is the temporal order of impulses; for the high-frequency group the code is the labeled line.

Animals↗
PubMed1968

Effect of external and internal pH changes on K and Cl conductances in the muscle fiber membrane of a giant barnacle.

The membrane potential and conductance of the giant muscle fiber of a barnacle (Balanus nubilus Darwin) were analyzed in relation to changes in the external (3.5-10.0) and the internal (4.7-9.6) pH, under various experimental conditions. A sharp increase in membrane conductance, associated with a large increase in conductance to Cl ions, was observed when the external pH was lowered to values below 5.0. The ratio of Cl to K conductance in normal barnacle saline is between (1/6)-1/7 at pH 7.7, whereas at pH 4.0 the ratio is about 6-9. The behavior of the membrane in response to pH changes in a Cl-depleted muscle fiber shows that the K conductance decreases with decreasing external pH for the whole range of pH examined. A steep increase in Cl conductance is also observed when the internal pH of the fiber is lowered below 5.0. The K to Cl conductance ratio increases with increasing internal pH in a manner very similar to that found when the external pH is raised above 5.0. These facts suggest that the membrane is amphoteric with positive and negative fixed charge groups having dissociation constants such that at pH greater than 5, negative groups predominate and cations permeate more easily than anions, while at lower pH positive groups predominate, facilitating the passage of anions through the membrane.

Biological Transport, Active↗
PubMedDate not supplied

Neural mechanisms of visual guidance of hand action in the parietal cortex of the monkey.

We studied the functional properties of the hand manipulation task-related neurons (N = 136) in the posterior bank of the intraparietal sulcus (IPS) using four kinds of objects for manipulation. We performed cluster analysis by comparing the profiles of activity of these neurons across objects during manipulation in the light, and classified them into nine groups, four highly selective, four moderately selective, and one nonselective group. Activity profiles of these neurons across objects were analyzed in four task conditions: object manipulation and object fixation both in the light and in the dark. Cells were classified as "motor-dominant," "visual-dominant," and "visual and motor" neurons, and the latter two were further subdivided into object type and non-object type. Most of the highly selective neurons (35 of 136) preferred the same object for manipulation in the dark as in the light. The object type "visual and motor" neurons preferred the same object for manipulation and fixation, suggesting that these neurons play an important role in matching the pattern of hand movement to the visuo-spatial characteristics of the object to be manipulated. A large majority of highly selective hand manipulation neurons were localized in the rostral part of the posterior bank of IPS, which we designated as the anterior intraparietal (AIP) area. We propose a conceptual model of the system for visual guidance of hand action including parietal hand manipulation neurons.

Animals↗
PubMedDate not supplied

Selective inhibition of enterobacteriaceae in fecal flora of children by oral trimethoprim-sulfamethoxazole.

Fecal flora of nine pediatric inpatients who were receiving trimethoprim-sulfamethoxazole were studied by quantitative aerobic and anaerobic culture methods. During the course of trimethoprim-sulfamethoxazole, the number of Enterobacteriaceae decreased from 10(8-9) to 10(4-5) bacteria per g feces. The isolation rate and the number of Veillonella were also reduced. Other prominent aerobic and anaerobic flora, including Streptococcus, Bacteroidaceae and Bifidobacterium, were not affected. No overgrowth of Pseudomonas, Staphylococcus, Candida or Clostridium was noted. These results support the usefulness of oral trimethoprim-sulfamethoxazole for the prophylaxis of bacterial infection in the compromised host.

Child↗
PubMedDate not supplied

Papillary carcinoma of the thyroid originating in a thyroglossal cyst. Report of a case and diagnostic criteria.

A 34-year-old female with papillary carcinoma of the thyroid originating in a thyroglossal cyst is described. The patient's chief complaint was a submental mass. The mass was 6 x 4 cm, elastic, soft, and smooth-surfaced. CT examination showed high-density areas in part of the interior of the mass. Resection of the mass was attempted with a diagnosis of thyroglossal cyst. Since papillary carcinoma of the thyroid was noted in the cyst by intraoperative frozen section pathological examination, primary carcinoma of the thyroid was suspected, and the thyroid and surrounding areas were examined. Since no abnormalities were noted in the thyroid, the thyroid was preserved. According to the following reasons, the tumor was considered to be primary papillary carcinoma of the thyroid arising in the thyroglossal cyst: (1) Scar formation was noted in the center of the tumor; (2) tumor cells partly infiltrated into the surrounding tissues, and (3) no tumor was noted in the thyroid. A definitive diagnosis of carcinoma arising in the thyroglossal cyst has required confirmation of the absence of carcinoma in the thyroid by total thyroidectomy. In the present case, however, total thyroidectomy was avoided, because no gross pathological changes were observed in the thyroid during the operation. This decision may be controversial both diagnostically and therapeutically, but we consider from our observation of the course that total thyroidectomy is not always necessary.

Adult↗
PubMedDate not supplied

Visualization of an adrenal pheochromocytoma with thallium-201.

An adrenal pheochromocytoma was visualized with thallium-201 chloride. Tl-201 concentration was observed in the cellular and vascular portion of the tumor immediately after its intravenous injection and decreased with time. Tl-201 may be a useful imaging agent for localizing pheochromocytomas.

Adrenal Gland Neoplasms↗