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Biomedical subjects

M Sakamoto

Publications and source records attributed to M Sakamoto.

At least 631 records · Page 35Linked to original sources
PubMed1989

[A case of epidermoid in the fourth ventricle associated with bronchial asthma-like symptom].

A case of large epidermoid located in the fourth ventricle is presented, and the patient's uncommon symptomatology of bronchial asthma-like episode is discussed. The value of magnetic resonance imaging (MRI) is also emphasized in the diagnosis of intracranial epidermoid. A 41-year-old male noticed nausea and vomiting on getting up in the morning about 5 years ago. This was followed by bronchial asthma-like dyspnea one year later. About one week prior to admission, headache and gait disturbance started. On neurological examination, he had choked disk and horizontal nystagmus at lateral gaze bilaterally. His gait was slightly ataxic. Computerized tomography (CT) showed a low density mass with a sharp and irregular margin in the mid-portion of the posterior fossa. That lesion was not enhanced with contrast medium. The MRI appearance was that of an inhomogenous and low signal intensity mass with a slightly irregular margin on T1-weighted spin echo (SE) sequences using TR500 msec/TR30 msec (TR500/TE30). The tumor extended into the aqueduct upward and the C1 level of spinal column downward. T2-weighted SE sequences using TR2000/TE90 showed an inhomogenous and high intensity mass with an irregular margin more apparent than in normal brain tissue. The patient was tentatively diagnosed as having a large fourth ventricle tumor. Suboccipital craniectomy was carried out on 4, March, 1988. The tumor was removed totally and histologically, it turned out to be epidermoid. He was discharged without neurological deficit 2 months after surgery. First, with respect to clinical symptomatology, as specified by Bailey, it is characterized by difficulty in standing or walking, vertigo, and less constantly, psychic disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Histologic features of gastric cancer in relation to patterns of spread.

The modes for growth and spread of gastric cancer were investigated in a surgical series of 115 cases--88 of early disease, and 27 involving the muscular layer. In addition, 93 autopsy cases with advanced disease were examined in order to analyze metastatic spread. In cancers of differentiated type in the mucosal layer, changes in histologic features towards the undifferentiated type were observed in the deeper layers, but no histologic transformation was seen in cancers of undifferentiated type. At autopsy distant metastases were common in cases with primary tumor of differentiated type, whereas peritoneal dissemination predominated when the primary lesion was undifferentiated. From the clinical standpoint, follow-up and recommendations to the patient should focus mainly on risk of peritoneal dissemination when adenocarcinoma of the stomach is of undifferentiated type, whereas metastases to distant organs should be taken into consideration if the malignancy is histologically differentiated.

Autopsy↗
PubMed1988

Increasing incidence of hepatocellular carcinoma possibly associated with non-A, non-B hepatitis in Japan, disclosed by hepatitis B virus DNA analysis of surgically resected cases.

At the National Cancer Center Hospital in Japan, the total number of surgically treated hepatocellular carcinomas (HCCs) has been increasing steadily and rapidly over the last 10 years, whereas the number of cases positive for hepatitis B surface antigen in sera (HBsAg) has remained almost stable. Thus, the relative percentage of HCC cases with serum HBsAg has shown a marked decrease. In order to examine whether this increased proportion of HBsAg-seronegative patients carries hepatitis B virus (HBV) DNA in the liver, we extracted DNA from the formalin-fixed and paraffin-embedded cancerous and noncancerous liver tissues of 79 patients with HCC. The HCCs examined included 49 specimens resected during a period from 1970 to 1980 and 30 resected in 1986 and 1987. We were able to detect reliably the presence of HBV DNA by dot-blot hybridization. The presence of HBV DNA in liver tissues showed a good correlation with positivity for serum HBsAg in both examined groups. In total, HBV DNA was detected in 81% (21 of 26) of HBsAg-seropositive cases and in only 8% (4 of 53) of HBsAg-seronegative cases, indicating that the increased number of HBsAg-seronegative cases had no HBV involvement. Among these HBsAg-seronegative HCC patients, 89.7% showed a histology of cirrhosis or chronic active hepatitis in the noncancerous liver and 29.1% had a history of blood transfusion. These results suggest an increasing incidence of non-A, non-B hepatitis-associated HCCs in Japan and the possible transmission of factors by means other than blood transfusion.

Carcinoma, Hepatocellular↗
PubMed1988

Response of medial preoptic/anterior hypothalamic neurones to ventrolateral medulla stimulation and its attenuation by adrenoceptor antagonists.

Extracellular single-unit recordings were made from medial preoptic/anterior hypothalamic (MPOAH) neurones in urethane-anaesthetized female rats, and the responses of these neurones to electrical stimulation of the ventrolateral medulla (VLM) were investigated. Of 189 neurones tested, 20% were excited and 21% were inhibited following VLM stimulation. The latency of inhibitory responses showed a normal distribution and the mean latency was 47 ms, whereas the latency of excitatory responses showed a bimodal distribution with peaks in the ranges of 0-10 ms and 40-50 ms, respectively. Excitatory responses with latencies greater than 15 ms and inhibitory responses were significantly attenuated by intravenous injections of the alpha-adrenoceptor antagonist phenoxybenzamine but not the beta-adrenoceptor antagonist propranolol. In the light of these observations and the known anatomical and electrophysiological findings, it is suggested that A1 noradrenergic and/or C1 adrenergic inputs from the VLM to MPOAH neurones are, at least in part, mediated by alpha-adrenoceptors.

Animals↗
PubMed1988

Potent depressor action of leumorphin, a kappa-opioid agonist, in conscious rats.

To investigate the role of leumorphin, a kappa-opioid agonist derived from proenkephalin B (neoendorphin/dynorphin precursor) in the central cardiovascular control, the effects of intracerebroventricular (ICV) administration of leumorphin on basal blood pressure and angiotensin II (AII)-stimulated pressor response were examined in conscious unrestrained rats. The ICV injection of 0.06 and 0.6 nmol of leumorphin caused a significant decrease in basal blood pressure (delta mean arterial pressure (MAP): -6.5 +/- 2.7 and -7.2 +/- 1.7 mm Hg, respectively). The ICV injection of AII (0.1 nmol) elicited a pressor response (delta MAP: 21.4 +/- 1.1 mm Hg). This pressor response was significantly reduced by the simultaneous administration of leumorphin, and furthermore, the blood pressure was lowered below the basal level. These depressor actions of leumorphin were partially antagonized by the preadministration of naloxone, an opiate antagonist. These results together with our previous works on the potent inhibitory actions of leumorphin on drinking and vasopressin secretion suggest the possible involvement of leumorphin in the central regulation of blood pressure and body fluid homeostasis.

Animals↗
PubMed1988

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on murine skin.

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on skin of congenic haired and hairless newborn and adult HRS/J mice was studied. In all adult animals topical application of TCDD caused an involution of sebaceous glands. Epidermal/epithelial hyperplasia and hyperkeratinization was induced in the hairless, but not the haired mice. Trans-glutaminase (TG) activity was stimulated in both haired and hairless animals. A single application of 1 microgram of TCDD did not stimulate significant ornithine decarboxylase activity in the skin in either strain. Other than a reduction in the density of the inflammatory cell infiltrate in the dermis, topical treatment with antiinflammatory agents fluocinolone acetonide and indomethacin did not affect the cutaneous response to TCDD. Skin of newborn mice treated topically with TCDD over a 2-wk period reacted much the same as adult skin in that sebaceous glands were reduced in size and TG activity was stimulated in both haired and hairless neonates; but epidermal hyperplasia occurred only in the hairless, not the haired newborns.

Animals↗
PubMed1988

Implication of leumorphin in inhibitory control of vasopressin secretion in conscious rats.

The effects of leumorphin, a kappa-agonist derived from proenkephalin B (neoendorphin and dynorphin precursor), on vasopressin secretion were studied under basal and stimulated conditions in conscious, unrestrained rats. Intracerebroventricular injection of leumorphin (60 or 600 pmol) significantly inhibited basal vasopressin secretion. The vasopressin response induced by intracerebroventricular injection of angiotensin II (100 pmol) was significantly suppressed, in a dose-dependent fashion, by the simultaneous intracerebroventricular injection of leumorphin (6, 60, or 600 pmol). Intravenous pretreatment with naloxone (0.5 mg/kg body weight) diminished the inhibitory action of leumorphin (60 pmol) on vasopressin secretion. Moreover, naloxone (0.5 mg/kg body weight) prolonged the vasopressin secretion induced by intracerebroventricular injection of angiotensin II (100 pmol). These results indicate that leumorphin possesses a potent inhibitory effect on vasopressin secretion and that, alone or in combination with other endogenous opioid peptides, it plays an important role in the control of vasopressin secretion.

Angiotensin II↗
PubMed1988

Inhibitory action of leumorphin on vasopressin secretion in conscious rats.

To elucidate the role of leumorphin, a kappa-agonist derived from proenkephalin-B (neoendorphin/dynorphin precursor), in the control of arginine vasopressin (AVP) secretion, we examined the effects of intracerebroventricular (icv) administration of leumorphin on AVP secretion under basal and stimulated conditions in conscious unrestrained rats. Intracerebroventricular injection of leumorphin (60 or 600 pmol) significantly inhibited basal AVP secretion. In 72-h water-deprived rats, icv injection of leumorphin (60 or 600 pmol) also suppressed AVP secretion in a dose-dependent manner. The AVP response induced by icv injection of angiotensin II (100 pmol) was significantly decreased by the simultaneous icv injection of leumorphin (6-600 pmol) in a dose-dependent manner. Intracerebroventricular administration of leumorphin (600 pmol) also reduced the AVP secretion stimulated by icv injection of carbachol (50 pmol). Intravenous pretreatment with naloxone (0.5 mg/kg BW) diminished the inhibitory action of leumorphin (60 pmol) on AVP secretion. However, no effect on AVP secretion was observed after iv injection of leumorphin (600 pmol). These results indicate that leumorphin possesses a potent inhibitory effect on AVP secretion, suggesting its important role in the regulation of AVP secretion in the brain.

Angiotensin II↗
PubMed1988

Gentamicin dosing and pharmacokinetics in low birth weight infants.

Monitoring of serum gentamicin concentrations and one-compartment pharmacokinetic analysis were performed in 41 preterm low birth weight infants (20 with birth weight of less than 1,500 g and 21 with birth weight of greater than or equal to 1,500 g) in the first week of life. Our dosing regimens, which were 2.0 mg/kg every 24 hr for the less than 1,500 g group and 2.0 mg/kg every 12 hr for the greater than or equal to 1,500 g group, successfully achieved the desired peak (4-8 micrograms/ml; 87.8%) and trough (less than or equal to 3 micrograms/ml; 97.5%) concentrations on the 4th day of treatment. In a one-compartment pharmacokinetic analysis, a large intersubject variability of pharmacokinetic parameters were observed on the 1st day of treatment. When we compared the parameters of the 1st day with those of the 4th day, apparent decreases in Vd and TBC were observed. The mean values for TBC and T1/2 or Kd of the two birth weight groups were significantly different from each other on the 4th day of treatment, suggesting a less maturity of renal functions in the less than 1,500 g group. The modified method of Sawchuk and Zaske was proven impractical in predicting steady-state serum concentrations because of an underestimation probably caused by the dramatic alteration of Vd due to a diuresis soon after birth. Based on these results, we recommend the above-described dosing regimen and emphasize the importance of a close monitoring of serum gentamicin concentrations and toxicities, instead of the individualized dosing approach in low birth weight infants in the first week of life.

Bacterial Infections↗
PubMed1988

Synthesis and structure-activity studies of new 4''-O-acyltylosin derivatives of therapeutic interest.

Eleven 4''-O-acyltylosin derivatives were synthesized and subjected to a two-step screening system consisting of antimicrobial activity and esterase stability assays. The new derivatives were all active against macrolide-resistant Staphylococci and mycoplasmas, but only 4''-O-(4-methoxy)phenylacetyltylosin and 4''-O-(4-acetyl)phenylacetyltylosin showed better resistance to mouse liver esterase than 4''-O-phenylacetyltylosin (reference compound C).

Animals↗
PubMed1988

Collagenase synthesis in clonal monkey kidney epithelial cells (JTC-12 cells).

Cells of clone JTC-12 derived from monkey kidney epithelial cells were found to produce latent collagenase in serum-containing cultures. Collagenase production by JTC-12 cells was stimulated more than ten-fold with the addition of 12-0-tetradecanoyl-phorbol-13-acetate. The JTC-12 cell collagenase was purified 2,370-fold over the conditioned medium to a specific activity of 5,940 units/mg with a yield of 79% by heparin-Sepharose, ion-exchange and immunoadsorption chromatography. Thus the JTC-12 cell culture appears to be a useful model for studying the initial degradation of surrounding connective tissues by epithelial tissue in carcinogenesis.

Animals↗