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Biomedical subjects

K Shimada

Publications and source records attributed to K Shimada.

At least 613 records · Page 34Linked to original sources
PubMed1996

Expression of P450(17 alpha) hydroxylase and P450 aromatase genes in the chicken gonad before and after sexual differentiation.

The onset and localization of P450(17-alpha)-hydroxylase (P450(17-alpha)) and P450 aromatase (P450arom) mRNA expression were studied in the gonads of chicken embryos at Days 4-9 of incubation by in situ hybridization analysis, and expression of both mRNAs was measured in the ovary and testis of the chicken after sexual differentiation by Northern and slot-blot analysis and was related to changes in concentration of 17-beta-estradiol (E2) in the gonad. In situ hybridization analysis showed the first detection of P450(17-alpha) mRNA at Days 5-6 of incubation in the genetic male and female gonads and the first detection of P450arom at Day 6.5 of incubation in the female gonad but none was detected in the male gonad. Both mRNAs were observed in the medullary cords of the gonad. Slot-blot analysis demonstrated that levels of P450(17-alpha) mRNA in the ovary remained high during the period between Day 10 of incubation and 7 days of posthatching, while those in the testis remained low at Days 10-14 of incubation but increased at Day 16 of incubation up to posthatching days. Levels of P450arom mRNA in the left ovary were invariably higher than those of the right ovary and testis throughout the period between Day 10 of incubation and 7 days of posthatching. These results suggest that expression of P450arom mRNA occurring in the genetic female gonad around Day 6 is associated, at least in a part, with sexual differentiation toward femaleness by increasing E2 production which may promote cellular proliferation of the left gonad. In contrast, in the genetic male gonad marked expression of P450(17-alpha) mRNA with little expression of P450arom mRNA may lead to production of androgen which promotes the gonadal development to the testis.

Animals↗
PubMed1996

Effects of aromatase inhibitor on sex differentiation and levels of P450 (17 alpha) and P450 arom messenger ribonucleic acid of gonads in chicken embryos.

On Day 5 of incubation fertilized eggs of single-comb White Leghorn hens were injected with an aromatase inhibitor (AI) and the sex reversal effect and levels of mRNA of P450(17alpha-hydroxylase) (P450(17alpha)) and 450(aromatase) (P450(arom)) were evaluated by observation of gonadal phenotype and by Northern and slot blot analysis. Individual genetic sex was evaluated by Southern blot analysis of red blood cells using a female sex chromosomal W-specific DNA probe. Saline injection had no sex reversal effect, whereas AI injection resulted in 50% sex reversal from genetic female but no effect on male. Levels of P450(17-alpha) mRNA were high in both ovary and testis in the control group but these levels were lowered significantly in ovary, testis, and sex-reversed gonad (testis) in the AI-treated group. On the other hand, levels of P450(arom) mRNA in the ovary were higher than those in the testis of the control group. AI treatment significantly suppressed ovarian levels of P450(arom) mRNA. Although estradiol alone failed to prevent the phenotypic male to female change, coadministration of estrogen suppressed the sex-reversal effect of AI and restored mRNA levels of P450(arom) in the ovary to control levels. These results suggest that expression of P450(arom) mRNA and estrogen plays an important role in sex differentiation of the female gonad of the chicken.

Animals↗
PubMed1996

Changes in poly(A) tail length of arginine vasotocin messenger ribonucleic acid in the hypothalamus of water-deprived chickens.

The effects of water deprivation on the secretion of vasotocin (AVT) and expression of the AVT gene were studied in White Leghorn cockerels. Animals deprived of water for 4 days were compared with normally hydrated controls. Blood samples were obtained for measurements of plasma osmolality and AVT levels, and the hypothalamus was collected for extraction of total cellular RNA. A 519-bp AVT cDNA was prepared by reverse transcriptase-polymerase chain reaction and a 209-bp PstI/EcoRI restriction fragment from the 3' region of the fowl AVT cDNA was used as a probe for Northern blot analysis. Plasma osmolality and AVT levels in dehydrated birds were about 30 and 350% greater, respectively, than those in normally hydrated controls. The quantity of hypothalamic AVT mRNA was 2. 3-fold greater in water-deprived birds compared to controls. The size of the hypothalamic AVT transcript was about 100-bp longer in the water-deprived birds. As determined by RNase H treatment in the presence and absence of oligo(dT)12-18, the increase in mean size of the AVT mRNA in dehydrated animals was due to a longer poly(A) tract. Our results indicate that osmotic stress up-regulates expression of the AVT gene and increases the accumulation of AVT mRNA in the hypothalamus. This accumulation may, in part, be due to lengthening of the AVT mRNA poly(A) tail which is a general mechanism associated with stabilization of vertebrate mRNAs.

Animals↗
PubMed1996

Influence of recombinant chicken prolactin on thyroid hormone metabolism in the chick embryo.

The influence of a recombinant chicken prolactin (rcPRL) preparation on thyroid function was studied in 18- and 19-day-old chicken embryos. Displacement studies on hepatic microsomes indicate that this preparation does not compete with radiolabeled chicken growth hormone (cGH) for hepatic GH-receptor binding. In a first series of experiments rcPRL or immunoaffinity-purified cGH was injected intravenously in 19-day-old chicken embryos. After 2 hr, cGH increased plasma T3 in a dose-dependent way by inhibiting hepatic inner ring type III deiodination (IRD-III) and consequently T3 degradation. Outer ring deiodination (ORD-I) was not influenced confirming previous results. The rcPRL preparation (2 and 10 microg) did not influence plasma T3, but depressed T4 and raised hepatic IRD-III activity simultaneously, whereas no influence on hepatic ORD-I activity could be found. In a second experiment on 18-day-old embryos, it could be demonstrated that the effect of 2.5 microg cGH on plasma T3 and liver IRD-III lasted up to 6 hr after injection, whereas 2.5 microg cPRL affected plasma T4 and liver IRD-III up to 2 hr. Both rcPRL and cGH depressed rT3 up to 6 hr, whereas an injection of rcPRL, but not of cGH, elevated plasma concentrations of corticosterone. These results indicate that prolactin may have a role, together with GH, in controlling peripheral thyroid hormone metabolism.

Animals↗
PubMed1996

Cyclic AMP augments cytokine-stimulated nitric oxide synthesis in rat cardiac myocytes.

We investigated the effect of adenosine 3', 5'-cyclic monophosphate (cAMP) on inducible nitric oxide synthase (iNOS) expression in cultured neonatal rat cardiac myocytes. Incubation of cardiac myocytes for 24 h with interleukin-1 beta (IL-1 beta) caused a significant increase in the production of nitrite, a stable metabolite of nitric oxide. Dibutyl cAMP (db-cAMP) significantly augmented nitrite production by IL-1 beta-stimulated, but not by unstimulated cells, in a dose-dependent manner. db-cAMP also dose dependently increased nitrite production by tumor necrosis factor-alpha(TNF-alpha)-stimulated cells. Simultaneous incubation with NG-monomethyl-L-arginine completely inhibited the effect of db-cAMP on nitrite production. cAMP-induced nitrite production by cytokine-stimulated cells was accompanied by increased iNOS mRNA accumulation. The synergistic effect of cAMP on IL-1 beta-induced nitrite accumulation was mimicked by cAMP-generating agonists forskolin and isoproterenol. These results indicate that cAMP upregulates cytokine-induced iNOS expression in cardiac myocytes.

Animals↗
PubMed1996

Alpha-adrenergic stimulation enhances inducible nitric oxide synthase expression in rat cardiac myocytes.

We investigated the effects of alpha 1-adrenergic stimulation on nitric oxide (NO) production by cardiac myocytes. Incubation of cultured neonatal rat cardiac myocytes with interleukin-1 beta (IL-1 beta) caused a significant increase in the production of nitrite, a stable metabolite of NO. Addition of phenylephrine significantly augmented nitrite production by IL-1 beta-stimulated but not by unstimulated myocytes in a dose-dependent manner. The effect of phenylephrine was completely abolished in the presence of NG-monomethyl-L-arginine (L-NMMA) or actinomycin D. Northern blotting revealed increased inducible NO synthase mRNA accumulation in cardiac myocytes treated with IL-1 beta and phenylephrine compared with those treated with IL-1 beta alone. After protein kinase C activity was functionally depleted by treating cells with phorbol 12-myristate 13-acetate for 24 h, phenylephrine did not augment IL-1 beta-induced NO production. The effect of phenylephrine was also abolished in the presence of protein kinase C inhibitor calphostin C. These observations suggest that alpha 1-adrenergic stimulation causes an upregulation of cytokine-induced NO production by cardiac myocytes, which is mediated at least partially via activation of protein kinase C.

Adrenergic alpha-Agonists↗
PubMed1996

A common mutation in methylenetetrahydrofolate reductase gene among the Japanese population.

Hyperhomocysteinemia has been reported as an independent risk factor for atherosclerotic cerebrovascular and coronary heart diseases. 5, 10-Methylenetetrahydrofolate reductase (MTHFR) is one of the enzymes responsible for hyperhomocysteinemia. The C to T transition of the MTHFR gene at nucleotide position 677 results in decreasing the enzymatic activity and increasing the plasma homocysteine level. We studied the distribution of the MTHFR gene mutation among the Japanese population. The subjects were 129 Japanese males (aged 40-59 years). The allele frequency of the mutation was 0.38. The frequencies of the three genotypes were as follows: +/+, 11%; +/-, 54%; -/-, 35% (+ and-indicate the presence and absence of the mutation, respectively). We also studied the frequency of the MTHFR gene mutation in the middle-aged Japanese males with hypertension to investigate the possibility that this mutation is related to essential hypertension. The normotensive and hypertensive subjects were identical in the distribution of the mutated allele and the frequencies of the three genotypes. Furthermore, the prevalence of hypertension in each genotype group was same, although the mean diastolic pressure of the group with homozygous mutation was significantly higher than that of other groups (p < 0.05). Therefore, we concluded that there was no significant relationship between the MTHFR gene mutation and hypertensive subjects studied in this study.

Adult↗
PubMed1996

Alpha N-catenin expression in the normal and regenerating chick sciatic nerve.

The Ca(2+)-dependent intercellular adhesion molecule cadherin is known to be linked to the cytoskeleton by the protein catenin, an association of which appears to be important for the cell-adhesion function of cadherin. Catenin consists of three subtypes-alpha, beta, and gamma. In our previous study, N-cadherin was shown to be localized on the plasmalemma of normal and regenerating chick peripheral nerve. Thus, as alpha N-catenin is a subtype of alpha-catenin (which is specifically associated with N-cadherin), we investigated the immunolocalization of alpha N-catenin in normal and regenerating chick sciatic nerve. In normal nerve, unmyelinated axons exhibited either intense or weak alpha N-catenin immunoreactivity throughout the axoplasm, whereas myelinated axons were completely immunonegative. Regenerating axons, including those derived from parent myelinated axons, showed alpha N-catenin immunoreactivity of variable intensities in growth cones and axon shafts. Schwann cells were invariably devoid of immunoreactivity. Thus alpha N-catenin is not necessarily bound to the surface plasmalemma, but is distributed throughout the cytoplasm, suggesting that most alpha N-catenin molecules are dissociated from N-cadherin.

Animals↗
PubMed1996

CT diagnosis of intraductal papillary neoplasm of the pancreas in comparison with histopathologic findings.

CONCLUSION: The existence of excrescent nodules in the cystic component of intraductal papillary neoplasms (IPN) on computed tomography (CT) is useful for differentiating between malignant and benign lesions. BACKGROUND: We sought to evaluate the ability of CT to differentiate malignant from benign lesions in IPN of the pancreas. METHODS: CT findings in 20 cases of IPN (11 benign and 9 malignant lesions) were compared with histopathological findings from subsequent surgery. RESULTS: The size of the cystic portion on CT did not correlate with the malignant potential of the lesion. Seven (78%) of 9 malignant lesions had excrescent nodules on CT, whereas 1 (9%) of 11 benign lesions did.

Adenoma↗
PubMed1996

Monocyte-endothelial cell interaction induces expression of adhesion molecules on human umbilical cord endothelial cells.

OBJECTIVE: The adhesive interaction of monocytes and endothelial cells has been implicated as a regulatory signal in the cell activation that is involved in the pathogenesis of atherosclerosis. We investigated the effect of monocyte-endothelial cell interaction on the expression of adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), in human umbilical cord vein endothelial cells (HUVECs). METHODS: ICAM-1 and VCAM-1 protein and mRNA expression were determined by cellular ELISA and Northern blot analysis, respectively. RESULTS: The addition of unstimulated human monocytes, as well as interleukin-1 beta (IL-1 beta: 25 U/ml) and tumor necrosis factor-alpha (TNF: 100 U/ml), to HUVECs rapidly induced the expression of ICAM-1 and VCAM-1 protein and mRNA in HUVECs, whereas the addition of polymorphonuclear leukocytes (PMNs) had no significant effect on their expression. The induction of ICAM-1 and VCAM-1 by the co-culture of HUVECs and monocytes was significantly, but partially, inhibited by the combination of anti-IL-1 alpha, anti-IL-1 beta and anti-TNF Abs. Actinomycin D and genistein, but not calphostin C, also significantly inhibited the co-culture-induced adhesion molecule expression. CONCLUSIONS: These results suggest that the monocyte-endothelial cell interaction induces the expression of ICAM-1 and VCAM-1 in endothelial cells partially through the production of IL-1 and TNF. These findings also suggest that the monocyte-endothelial interaction further augments their interaction through the up-regulation of endothelial adhesion molecules, as a positive feedback mechanism.

Arteriosclerosis↗
PubMed1996

Shortening of the window period in diagnosis of HIV-1 infection by simultaneous detection of p24 antigen and antibody IgG to p17 and reverse transcriptase in serum with ultrasensitive enzyme immunoassay.

Following HIV infection, there is a window period of 6-8 weeks, during which HIV antibodies are not detectable and the infection cannot be diagnosed by methods for detecting HIV antibodies. However, HIV antigens are detectable in the latter part of the window period, although the level of HIV antigens declines as the level of HIV antibodies increases. We developed an ultrasensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) for the simultaneous detection of both p24 antigen of HIV-1 and antibody IgGs to p17 and reverse transcriptase of HIV-1 in a single assay tube and tested 11 HIV-1 seroconversion serum panels and serum samples randomly collected from 79 HIV-1 seropositive subjects and 100 HIV-1 seronegative subjects. The simultaneous detection was shown not only to shorten the window period significantly as compared with conventional methods for HIV-1 antibody detection but also to make possible a reliable diagnosis of HIV-1 infection from the time of seroconversion until late stages of the infection.

Antibodies, Viral↗
PubMed1996

Transfection of wild-type TP53 induces differentiation in human gingival carcinoma cells.

We investigated the effects of transfection of wild-type TP53 on the growth properties of a human gingival carcinoma cell line, KOSC-3, in which the TP53 gene is mutated at codon 248 and overexpressed. The wild-type TP53 expression plasmid, pCDM8-p53/neo and the control plasmid, pCDM8/neo, were each stably transfected into KOSC-3 cells by using the calcium phosphate method. The number of G418-resistant colonies from wild-type TP53-transfected cells was approximately half that from plasmid controls. Exogenous wild-type TP53 transcripts were identified in four of the 20 G418-resistant clones analysed by reverse transcription PCR. Although the growth rates of the wild-type TP53+ clones did not drastically change during log phase, their saturation density was significantly reduced. The wild-type TP53+ cells were morphologically flat and enlarged when cultured in vitro, and were less able to form colonies in soft agar. In nude mice, the wild-type TP53+ clones formed subcutaneous tumours with conspicuous keratinisation and notable cell death that was not manifested in the parental and plasmid control cells. These findings indicate that the wild-type TP53 gene, even when it coexists with a mutated form, may function as a growth suppressor and differentiation inducer under restricted conditions in gingival squamous cell carcinoma.

Animals↗
PubMed1996

Structure-activity relationships of HIV-1 PR inhibitors containing AHPBA--II. Modification of pyrrolidine ring at P1' proline.

Systematic replacement in the 3- or 4-position of the pyrrolidine ring at P1' proline was carried out. Compound 26, which has a Cl atom in the 4(S)-position was the most active among inhibitors substituted with other halogen atoms or other substituents. Furthermore, the replacement of the Z group in compound 26 with five- or six-membered fused aromatic heterocycle carbonyl groups produced more potent inhibitors. 7-Methoxybenzofuran-2-carbonyl derivative (44) was the best of these and showed Ki = 4.5 nM against HIV PR and IC90S 0.58 microM and 0.06 microM in chronic and acute infections, respectively. These results suggest that the combination of the 4(S)-CI atom and fused bicyclic heterocycles may be effective in improving their cellular penetration.

Cells, Cultured↗
PubMed1996

C-reactive protein as a predictor of cardiac rupture after acute myocardial infarction.

Although cardiac rupture is the second most common cause of death after ventricular failure in acute myocardial infarction, no diagnosis has ever been made before an episode of clinical compromise, and no significant predictive factors have been described. This study was designed to determine whether high serum C-reactive protein (CRP) levels could predict the incidence of subacute cardiac rupture after acute myocardial infarction. Nine consecutive patients with cardiac rupture were compared retrospectively with 28 consecutive control patients without rupture after acute myocardial infarction. In the rupture group, peak serum CRP levels increased rapidly and markedly after infarction, reaching more than 20 mg/dl on day 2, and persisted at high levels compared with those in the control group. However, the time course and levels of serum creatine phosphokinase were not significantly different between the two groups. High serum CRP levels ( > 20 mg/dl) had a high diagnostic sensitivity (89%) and specificity (96%) for cardiac rupture. Patients with persistently high serum CRP levels, particularly above 20 mg/dl, might have high probability of occurrence of sub-acute cardiac rupture after acute myocardial infarction.

Aged↗
PubMed1996

Relationship between severity of mitral regurgitation and prognosis of mitral valve prolapse: echocardiographic follow-up study.

We investigated the relation between the severity of mitral regurgitation and the development of complications and cardiac events by using two-dimensional and color Doppler echocardiography in 229 consecutive patients with mitral valve prolapse. The frequency of moderate and severe mitral regurgitation was significantly higher in patients with a prolapsed posterior leaflet (61%) than in patients with a prolapsed anterior leaflet (25%), and the older the patient, the greater the severity of mitral regurgitation. The occurrence of complications, such as atrial fibrillation, congestive heart failure, and chordal rupture, was significantly greater in prolapsed posterior leaflet cases than in prolapsed anterior leaflet cases, and the occurrence was closely associated with the degree of severity of mitral regurgitation. Multiple logistic regression analysis showed that the severity of mitral regurgitation is a strong prognostic indicator for developing complications. Furthermore in a subgroup of 49 patients tracked for a mean of 4.8 years, the new development of complications was significantly higher in patients who showed a progression in the severity of mitral regurgitation (52%) that in patients without progression in severity (8%). The initial severity of mitral regurgitation was related to the occurrence of cardiac events (mitral valve replacement, infective endocarditis, cerebral embolism and death). The data indicated that the progression of mitral regurgitation is closely associated with the development of complications and cardiac events and suggest that the severity of mitral regurgitation is an important prognostic indicator for the development of complications and cardiac events in patients with mitral valve prolapse.

Adolescent↗
PubMed1996

Suppression of cell-transferred experimental autoimmune encephalomyelitis in defibrinated Lewis rats.

The role of coagulation-fibrinolysis system in experimental autoimmune encephalomyelitis (EAE) was studied by using batroxobin, derived from the venom of the South American pit viper Bothrops atrox moojeni. Batroxobin converts circulating fibrinogen into an insoluble form and causes a profound degree of afibrinogenemia. Batroxobin treatment (30 BU/kg/day) suppressed clinical signs of cell transferred EAE; the mean cumulative clinical score for batroxobin treated rats was 3.97, while saline treated controls scored 6.9 (P < 0.01). Plasma fibrinogen concentration decreased significantly in batroxobin-treated rats. Histologically, the degree of perivascular mononuclear cell infiltration in the spinal cord was not suppressed in batroxobin-treated rats compared to saline-treated control rats, however, deposition of fibrin around the vessels in the spinal cord was markedly suppressed in batroxobin-treated rats. These findings suggest that batroxobin suppresses EAE by preventing fibrin deposition, and provide evidence that CNS-associated deposition of fibrin and ensuing fibrinolysis, together with increased permeability of blood brain barrier (BBB), are related prerequisites for the clinical manifestation of EAE.

Animals↗
PubMed1996

A simple and secure anchoring system for Caspari's transglenoid multiple suture technique using a biodegradable poly-l-lactic acid button.

To manage a difficulty in tying sutures over the infraspinatus fascia when using Caspari's transglenoid multiple suture technique, we developed a new anchoring system using a biodegradable poly-L-lactic acid (PLLA) button and investigated its clinical efficacy in 28 patients who were followed-up for more than 2 years postoperatively (mean, 26.5 months). Twenty-four patients had Bankart lesions and 4 had detachment of the superior glenoid labrum. The mean age at operation was 22.1 years. The PLLA button measured 8 x 8 x 1.2 mm and had two holes. After multiple sutures were inserted by the routine Caspari technique (mean, 7.3 sutures), the sutures were divided into 2 bundles, passed through the holes in the button, and tied over it on the posterior scapular neck under traction. The arm was immobilized in a Velpeau bandage for 3 weeks after Bankart repair and for 1 to 2 weeks after superior labral repair. The results of Bankart repair were excellent in 13 patients, good in 7, and poor in 4 according to Rowe's rating scale (success rate, 83%), while the outcome of superior labral repair was excellent in 3 and good in 1 according to our own criteria. All 4 patients who showed a poor outcome were contact athletes who developed resubluxation postoperatively. There were no complications, but transient damages to the suprascapular nerve occurred in 2 patients. In conclusion, the PLLA button provided simple and secure suture fixation for the Caspari technique.

Adolescent↗