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Biomedical subjects

D Dai

Publications and source records attributed to D Dai.

At least 55 records · Page 3Linked to original sources
PubMed1999

Ventrally emigrating neural tube cells differentiate into vascular smooth muscle cells.

A multipotential cell population originating in the ventral part of the hindbrain neural tube, the ventrally emigrating neural tube cells (VENT cells), has recently been shown to migrate into the craniofacial mesenchyme. Because vascular smooth muscle cells develop from this mesenchyme, we sought to determine if the VENT cells contributed to their differentiation. VENT cells were tagged with replication-deficient retroviral vector with LacZ by microinjection into the lumen of the rostral hindbrain of chick embryos on day 2. Embryos were processed for the detection of LacZ positive cells on day 7. LacZ-positive cells were present in the wall of craniofacial arteries and veins. Immunostaining with the smooth muscle alpha-actin confirmed the labeled cells to be smooth muscle cells. It is concluded that some vascular smooth muscle cells differentiate from neural tube cells. the developmental and functional significance of which remains to be established.

Actins↗
PubMed1999

Progesterone regulation of epidermal growth factor receptor in rat decidua basalis during pregnancy.

Ovarian steroid hormones and epidermal growth factor (EGF) play important interactive roles in proliferation and decidualization of mesometrial stromal cells during pregnancy. This study determined the ontogeny of EGF receptor (EGF-R) expression in the decidua basalis (DB) throughout pregnancy and its regulation by estrogen and progesterone (P4). DB were isolated from rats between Days 8-21 of pregnancy and prepared for immunohistochemistry or Western analysis. In one study, rats were ovariectomized (Ovx) on Day 8 or 9 and given estradiol-17beta, P4, or both. In another study, the antiprogestin, mifepristone (RU-486), was administered on Day 9. During normal pregnancy, total EGF-R (phosphorylated and unphosphorylated forms) increased from Day 8 to a maximum level on Days 10 and 12. Tyrosine-phosphorylated EGF-R (pEGF-R), the bioactive form, was also highest on Days 10 and 12. Both forms of receptor decreased to almost undetectable levels during DB regression on Days 17-21. Immunohistochemistry of DB from Ovx rats revealed that only P4 was able to maintain normal expression of EGF-R; RU-486 decreased EGF-R expression within 6 h, and by 24 h EGF-R and pEGF-R were 15% of the Day 10 control group levels. These findings show that EGF-R is a P4-dependent protein associated with stromal cell proliferation and decidualization.

Animals↗
PubMed1999

Protective nutrients and bacterial colonization in the immature human gut.

The normal human microflora is a complex ecosystem that is in part dependent on enteric nutrients for establishing colonization. The gut microbiota are important to the host with regard to metabolic functions and resistance to bacterial infections. At birth, bacterial colonization of a previously germ-free human gut begins. Diet and environmental conditions can influence this ecosystem. A breast-fed, full-term infant has a preferred intestine microbiota in which bifidobacteria predominate over potentially harmful bacteria, whereas in formula-fed infants, coliforms, enterococci, and bacteroides predominate. The pattern of bacterial colonization in the premature neonatal gut is different from that in the healthy, full-term infant gut. Those infants requiring intensive care acquire intestinal organisms slowly, and the establishment of bifidobacterial flora is retarded. A delayed bacterial colonization of the gut with a limited number of bacterial species tends to be virulent. Bacterial overgrowth is one of the major factors that promote bacterial translocation. The aberrant colonization of the premature infant may contribute to the development of necrotizing enterocolitis. Breast-feeding protects infants against infection. Oligo-saccharides and glycoconjugates, natural components in human milk, may prevent intestinal attachment of enteropathogens by acting as receptor homologues. Probiotics and prebiotics modulate the composition of the human intestinal microflora to the benefit of the host. These beneficial effects may result in the suppression of harmful microorganisms, the stimulation of bifidobacterial growth, or both. In the future, control and manipulation of the bacterial colonization in the neonatal gut may be a new approach to the prevention and treatment of intestinal infectious diseases of various etiologies.

Bacteria↗
PubMed1999

Postoperative irradiation in malignant tumors of submandibular gland.

A retrospective review of 18 patients with treated primary malignant tumors of submandibular gland is presented. The data revealed that initial control of malignancies was inversely related to the presence of disease and surgical margins. Postoperative radiation therapy was used in cases with positive surgical margins. Of the patients with inadequate surgical margins, 71% achieved local relapse when they had surgery alone, compared with 27% of the group that received postoperative irradiation. This study suggests that adjuvant radiation therapy may improve the local control and survival. Such therapy can serve as the salvage method for those who have inadequate surgical margins. Re-excision is disappointing in its ability to control this disease.

Adenocarcinoma↗
PubMed1998

Blockade of bepridil on IA and IK in acutely isolated hippocampal CA1 neurons.

The effects of bepridil, an antianginal agent with antiarrhythmic action, on voltage-dependent K+ currents in the CA1 pyramidal neurons acutely isolated from rat hippocampus were studied by means of whole-cell patch clamp techniques. Current recordings were made in the presence of TTX to block Na+ current. Depolarizing test pulses activated two components of outward K+ currents: a rapidly activating and inactivating component, IA; and a delayed component, IK. Results showed that bepridil reduced the amplitude of IA and IK, and exerted its inhibitory action in time- and dose-dependent manner. Half-blocking concentrations (IC50) of bepridil on IA and IK were 17.8 microM and 1.7 microM, respectively. 10 microM bepridil suppressed IA and IK by 46.7% and 77.1% at +30 mV of depolarization, respectively. When IK was activated nearly uncontaminated with IA by holding at -50 mV, 10 microM bepridil inhibited IK by 71.6% at +30 mV of depolarization; 10 microM bepridil positively shifted the voltage-dependent of activation curves of IA and IK 12.1 mV and 28.7 mV, respectively. These results suggested that blockade on K+ currents by bepridil is preferential for IK, and contributes to the protection brain against ischemic damage.

Animals↗
PubMed1998

The nitric oxide-cyclic GMP pathway plays an essential role in both promoting cell survival of cerebellar granule cells in culture and protecting the cells against ethanol neurotoxicity.

NMDA has two beneficial effects on primary neuronal cultures of cerebellar granule cells (CGCs) established from 10-day-old rat pups. First, NMDA is neurotrophic and will enhance survival of CGCs in culture in the absence of ethanol. Second, ethanol exposure will induce cell death in CGC cultures, and NMDA can lessen this ethanol-induced cell loss, i.e., NMDA is neuroprotective. Because NMDA can stimulate production of nitric oxide (NO), which can in turn enhance synthesis of cyclic GMP, this study tested the hypothesis that the NO-cyclic GMP pathway is essential for NMDA-mediated neurotrophism and neuroprotection. Inhibiting the synthesis of NO with N(G)-nitro-L-arginine methyl ester eliminated both the NMDA-mediated neurotrophic and neuroprotective effects. Similarly, inhibiting production of cyclic GMP with the agent LY83583 also abolished these effects. The NO generator 2,2'-(hydroxynitrosohydrazono) bisethanamine produced neurotrophic and neuroprotective effects that were similar to those induced by NMDA. Also, 8-bromo-cyclic GMP produced neurotrophic and neuroprotective effects that were quite similar to the effects produced by NMDA. In conclusion, NMDA enhances survival of cerebellar granule cells and protects the cells against ethanol-induced cell death by a mechanism(s) that involves the NO-cyclic GMP pathway.

Aminoquinolines↗
PubMed1998

Regulation of the progesterone receptor and estrogen receptor in decidua basalis by progesterone and estradiol during pregnancy.

In this study we examined the roles of progesterone (P4) and estradiol-17beta (E2) in regulation of the P4 receptor (PR) and estrogen receptor (ER) in the decidua basalis (DB) during stromal cell proliferation and regression (Days 10 and 14 of pregnancy, respectively). Pregnant rats were ovariectomized (Ovx) on Day 8 or 12 and killed on Day 10 or 14, respectively, following treatment with P4, E2, or both. In some experiments, rats received pellets of the anti-progestin RU-486 on Day 9 and were killed 3, 6, 12, and 24 h later. Immunolocalization of PR and ER showed that both receptors decreased from Day 10 to Day 14. Histologic integrity of the placenta and DB were maintained only when P4 was present. Control and hormone-treated groups expressed established isoforms of PR and ER: PR-B, 110 kDa; PR-A, 80-90 kDa; PR-C, 64-60 kDa; ER-66, 66 kDa; and ER-49, 49 kDa. On Day 10, expression of PR-A, PR-B, and ER-66 decreased 50-99% (p < 0.05) after Ovx or RU-486 treatment but was restored to control levels after Ovx by exogenous P4. On Day 14, PR-B and ER-66 declined 66-75% (p < 0.05) after Ovx and could not be restored by P4 treatment. Estrogen could not substitute for P4, and co-administration of E2 with P4 did not enhance the response over P4 alone. In contrast, PR-C was abundantly expressed on Days 10 and 14 in all treatment groups after Ovx and RU-486. P4 maintained PR mRNA and ER mRNA after Ovx. Thus, regression of the DB may be initiated via changes in relative expression of PR isoforms, which result in impaired stromal cell response to P4 action.

Animals↗
PubMed1998

Progesterone and estrogen regulation of rat decidual cell expression of proliferating cell nuclear antigen.

This study was an examination of the role of progesterone (P4) and estradiol-17beta (E2) as stromal cell mitogens in the decidua basalis (DB) of the rat during pregnancy. Pregnant rats were ovariectomized (Ovx) on Days 8 and 12 of pregnancy, treated with P4, E2, or both, and killed on Days 10 and 14, which correspond to times of stromal cell proliferation and regression, respectively. In some experiments, rats received pellets of the anti-progestin RU-486 on Day 9 and were killed 6, 12, and 24 h later. The mitotic index (MI) and in situ image analysis of expression of proliferating cell nuclear antigen (PCNA) were used to assess cell cycle progression. Highest expression of PCNA occurred on Days 8-12 of pregnancy, and MI was maximum; MI became zero and PCNA expression decreased dramatically thereafter (i.e., Days 14, 17, 21). Percentage of cells expressing intense PCNA on Day 10 (40%) declined to 5% after Ovx and Ovx + E2 (p < 0.05), whereas Ovx + P4 maintained PCNA. By Day 14, only 1% of stromal cells expressed intense PCNA, which was not significantly altered by Ovx, Ovx + E2, or Ovx + P4 but increased after Ovx + P4 and E2 (p < 0.05). By 6 h of RU-486, MI declined 3-fold, and intense PCNA expression was essentially lost. These changes preceded loss of histological integrity of the DB. Cells with undetectable PCNA steadily increased from 8% at 6 h to 28% by 24 h (p < 0.05). Thus RU-486 appeared to block cell cycle progression and enhanced PCNA turnover. P4 was essential for stromal cell proliferation during early pregnancy (Days 8-10), but this action was lost by Day 14.

Animals↗
PubMed1998

Effect of +Gz on plasma levels of calcitonin gene related peptide, endothelin and renal function in pilots.

The effect of positive acceleration on plasma levels of calcitonin gene related peptide (CGRP), and endothelin as well as renal function in pilots were observed in this study. 20 pilots were exposed to +2.5 Gz 10 s and +3.0 Gz 10 s with an interval of 5 min without anti-G suits. Samples of plasma and serum were taken 2Omin before and after exposure. Plasma levels of CGRP and endothelin after the exposure were significantly increased (P<0.01), but alkaline phosphatase(AKP), blood levels of beta 2-microglobulin(beta 2-MG), Ca2+ in serum showed no significant change (P>0.05) as compared with those before exposure. There was a correlation between CGRP and endothlin (r=0.772, P<0.01). It is concluded that positive acceleration(+2.5, +3.0Gz) could increase plasma levels of CGRP and endothlin but did not affect renal function.

Acceleration↗
PubMed1998

Structure-activity relationships of indole- and pyrrole-derived cannabinoids.

Early molecular modeling studies with Delta9-tetrahydrocannabinol (Delta9-THC) reported that three discrete regions which interact with brain cannabinoid (CB1) receptors corresponded to the C-9 position of the cyclohexene ring, the phenolic hydroxyl and the carbon side chain at the C3 position. Although the location of these attachment points for aminoalkylindoles is less clear, the naphthalene ring, the carbonyl group and the morpholinoethyl group have been suggested as probable sites. In this study, a series of indole- and pyrrole-derived cannabinoids was developed, in which the morpholinoethyl group was replaced with another cyclic structure or with a carbon chain that more directly corresponded to the side chain of Delta9-THC and were tested for CB1 binding affinity and in a battery of in vivo tests, including hypomobility, antinociception, hypothermia and catalepsy in mice and discriminative stimulus effects in rats. Receptor affinity and potency of these novel cannabinoids were related to the length of the carbon chain. Short side chains resulted in inactive compounds, whereas chains with 4 to 6 carbons produced optimal in vitro and in vivo activity. Pyrrole-derived cannabinoids were consistently less potent than were the corresponding indole derivatives and showed pronounced separation of activity, in that potencies for hypomobility and antinociception were severalfold higher than potencies for hypothermia and ring immobility. These results suggest that, whereas the site of the morpholinoethyl group in these cannabinoids seems crucial for attachment to CB1 receptors, the exact structural constraints on this part of the molecule are not as strict as previously thought.

Animals↗
PubMed1997

Stromal cell progesterone and estrogen receptors during proliferation and regression of the decidua basalis in the pregnant rat.

This study examines the distribution and abundance of progesterone receptors (PR) and estrogen receptors (ER) in the decidua basalis (DB) during proliferation (Days 8-12 of gestation) and regression (Days 14-21) in the rat. Stromal cells of the DB and metrial gland exhibited strong nuclear immunostaining for PR throughout gestation. Nuclear localization of ER was detectable only between Days 8-12. The heavily granulated natural killer cells were always negative for PR and ER. DB were dissected between Days 8 and 17 to measure progesterone (P4)-binding sites and receptor proteins by Western blotting. The latter revealed four specific PR isoforms: B (110 kDa), A1 (90 kDa), A2 (76-82 kDa), and C (60-64 kDa). Stromal cell nuclei contained more than 50% of P4-binding sites during DB proliferation but less than 22% during regression (p < 0.05). PR-A and PR-B expression was greatest at proliferative stages (p < 0.05). PR-C increased in relative abundance during DB regression. Two ER isoforms of 66 kDa and 49 kDa were revealed. The 66-kDa ER, the most abundant form, was maximally expressed during proliferation, declining 71% by Day 12 (p < 0.01), whereas the 49-kDa form accounted for up to 90% of ER during regression. Northern blot analysis revealed three prominent transcripts of approximately 11, 7, and 4 kilobases (kb) for PR mRNA, which declined markedly at Days 14 to 17 (p < 0.05), and one of 6.0 kb for ER mRNA, which declined markedly on Day 17 (p < 0.05). Our study establishes that the DB expresses heterogeneity of receptor message and proteins. We propose that preferential expression of receptor isoforms in late pregnancy limits P4 action and promotes DB regression in spite of invariant levels of serum P4, P4-binding sites, and total receptor protein.

Animals↗
PubMed1997

Image quality versus statistical power.

We investigated whether SPET studies of neuroactivation might benefit from a similar approach used in PET; that is, increase the number of scans per task and accept poorer individual scan quality. Different study paradigms were simulated by varying the scanning parameters: (1) administered radiation activity per scan, (2) number of scans per task and (3) scan acquisition time. The maximum total dose received by each simulated subject remained the same. Areas of activation of varying signal strength were added to the scans using a customized graphics package. To establish the statistical benefits of a replication paradigm versus a non-replication paradigm, the datasets were analysed using SPM95 statistics software. This simulation was able to show that, when an SPM investigation is used for data analysis, study replication is more important than the individual image quality typically available from a high-performance SPET system.

Brain↗
PubMed1997

[Quantitative analysis of E-cadherin expression and clinicopathologic evaluation in gastric cancer].

OBJECTIVE: To evaluate the relationship of E-cadherin (E-CD) expression to cellular DNA content and biological behavior of gastric cancer. METHODS: E-CD expression and cellular DNA content were quantitatively measured by flow cytometry and immunofluorescence methods in 80 cases of formalin-fixed, paraffin-embedded gastric cancer. Systematic pathological examinations and follow up were performed for all cases. RESULTS: E-CD expression was significantly reduced in all cases of gastric cancer, fluorescence Index (FI) of E-CD expression was 0.67 +/- 0.11 in gastric cancer, 1.0 +/- 0.07 in normal gastric mucosa (P < 0.001). The reduction of E-CD expression was also found in 2 cases of early gastric cancer. Tumors with a decrease in E-CD expression occurred significantly more frequently in undifferentiated, diffuse growth pattern Borrmann 4 type, positive lymph node (LN) metastasis and infiltrated serosa type gastric cancer, of which survival time was within 5 years (P < 0.001). E-CD expression was also reduced in gastric cancer with the number of LN metastasis above 5, metastasis to more than group 2. E-CD expression was lower in uneuploid cancer than that in diploid cancer (P < 0.01). The value of DI and PI with negative E-CD expression was significantly higher than that of positive E-CD expression (P < 0.01). CONCLUSION: Down-regulation of E-CD expression correlates with bad biological behavior and poor prognosis of gastric cancer. The reduction of E-CD expression may take place during early time of gastric cancer. Quantitative analysis of E-CD expression may have some value in evaluating the intensity of LN metastasis of gastric cancer.

Cadherins↗
PubMed1995

Variation of the alkyl side chain in delta 8-THC.

The synthesis of (2'RS)-2'-methyl-, (3'RS)-, (3'S)-3'-methyl-, and 4'-methyl-delta 8-THC has been carried out, and the pharmacology of all four compounds has been investigated. All four compounds showed typical cannabinoid activity both in vitro and in vivo. The 2'-methyl compound is somewhat more active than delta 8-THC, while the 4'-methyl isomer is less active. The 3'-methyl-delta 8-THC has approximately the same activity as the parent cannabinoid.

Analgesics↗
PubMed1995

[Stomach cancer in pregnancy and breast feeding: report of 17 cases].

Much less frequently stomach cancer is found in pregnant woman than in general young man, the misdiagnosis usually takes place for the disease. 17 patients of this series accounted for 0.97% of all patients with stomach cancer during the same period (17/1752). Stomach cancer in pregnancy and breast feeding was usually advanced at the time of diagnosis, and the prognosis was very poor. The predominant pathological features of the cancer were extensive infiltration (17 patients), diffuse growth pattern (13 patients) and undifferention of carcinoma (13 patients) with serious lymphonode metastasis. We suggest that the gastrofiberscopic and ultrasonographic examination can be used with safely at any time during pregnancy and facilitate early detection of stomach cancer in the pregnant women, especially in those who had been previously ill with precancerous diseases or lesions. The treatment of the disease was also discussed.

Adult↗
PubMed1992

Histopathology and immunohistopathology of lymph nodes of the first autopsy with HIV positivity in China.

Nineteen lymph nodes of a HIV-positive boy were studied histologically and immunohistologically. According to Stutte's classification of HIV-related lymphadenopathy, 84% of the lymph nodes were at the third or fourth stages in relation to clinical status ARC/AIDS. Lymph follicle atrophy, angiogenesis, histiocytic proliferation and destruction of the normal reticulum frame were observed. Immunohistochemical studies showed most of the remaining lymphocytes to be T cells and changes in the distribution of S-100 positive cells. Ki 1 positive cells existed mainly at the second stage. The significance of these changes is discussed.

Antigens, CD↗