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X Han

Publications and source records attributed to X Han.

At least 163 records · Page 9Linked to original sources
PubMed1998

Ultrastructural observation on the transformation of the spermatozoon in spermatogenesis of Taeniid cestodes.

AIM: To study the transformation of taeniid spermatozoon during spermatogenesis on the ultrastructure level. METHODS: Transmission electronmicroscopy. RESULTS: This paper was the second part of the ultrastructural observations on the spermatogenesis in Taeniid cestodes: The transformation of the spermatozoon. The 64-spermatid-plasmodium was generated from the secondary meiosis of the 32 rose-like secondary spermatocytes. The transformation of the spermatozoon was a complex process. Firstly, both the cytoplasm and nucleus of the spermatid elongated while the cytoplasm increased and connected to the cytoplasmic mass (cytophore). Secondly, the chromatins of nucleus polymerized to a thread-bundle-like structure. Finally, it detached from the cytoplasm mass and became a mature spermatozoon. The mature spermatozoon was a thread-like structure, about 16.2-18.6 microns in length and 0.35-0.45 micron in diameter. There were two structurally distinct parts: the part with the nucleus was the head and the part without the nucleus was the tail. The head measured about 5-6 microns in length, 1/3 of the total body length and contained an elongated nucleus which twined around the axoneme without mitochondria. The tail was about 11.2-16.6 microns in length. Throughout the core of the tail was an axoneme with typical "9 + 1" structure. The anterior of the tail, just behind the head, were some mitochondria, about 1.6-1.7 microns in total length which twined around the axoneme. The posterior of the tail contained only an axoneme. In cross-section of the spermatozoon, about 46 microtubules were beneath the plasma membrane. CONCLUSION: The transformation of the spermatozoon is a very complex process.

Animals↗
PubMed1997

Interactions between smooth muscle alpha-actinin and lipid bilayers.

alpha-Actinin has been proposed to be the actin-plasma membrane linker. This assumption is based on the discovery of direct interaction of alpha-actinin with two specific lipids, diacylglycerol and palmitic acid [Burn, P. (1988) Trends Biochem. Sci. 13, 79-83]. In our study, the binding of alpha-actinin with vesicles containing negatively charged phospholipids was measured by the method of 90 degrees light-scattering. Our results show that alpha-actinin is able to bind membranes containing negatively charged phospholipids, but not to bind membranes composed of neutral lipids only. Diacylglycerol and palmitic acid, on the other hand, have little effect on the binding of alpha-actinin to lipid vesicles. Analysis of binding isotherms in terms of a membrane binding model gave apparent dissociation constants which varied between 0.2 and 3 microM over a range of 5-20 mol % negatively charged phospholipid. Comparing the kinetics of alpha-chymotrypsin digestion of alpha-actinin in solution to those of vesicle-bound alpha-actinin, it can be seen that the cleavage site at the junction between the C-terminal and the central rod domain of alpha-actinin and another cleavage site on the C-terminal domain can be most effectively protected by its membrane binding. Analysis of the amide I and II regions of Fourier-transform infrared spectra of alpha-actinin revealed that the association of alpha-actinin with negatively charged phospholipid vesicles resulted in some perturbation of the protein secondary structure. Monolayers containing negatively charged phospholipid were layered and incubated on the surface of a polymerization solution of actin and alpha-actinin, and observed with an electron microscope. The results show that the bundle structure of actin filaments can be formed if diacylglycerol and palmitic acid are present in lipid layers.

Actinin↗
PubMed1997

Adaptive regulation of MDCK cell taurine transporter (pNCT) mRNA: transcription of pNCT gene is regulated by external taurine concentration.

NaCl-dependent taurine transporter (pNCT) activity of MDCK cells (Madin-Darby canine kidney) is up- or down-regulated by medium taurine manipulation. In this study we found that the abundance of pNCT mRNA was up- or down-regulated after cells were incubated in media containing 0 microM taurine or 500 microM taurine for 24 h. Down-regulation was observed after 12 h exposure to high taurine (500 microM) and mRNA abundance was appreciably reduced after 72 h exposure. Nuclear run-off assays show that the gene for pNCT is induced at the transcriptional level by taurine. Addition of cycloheximide blocked the adaptive response and reduced transcription of pNCT mRNA in MDCK cells. Cycloheximide had virtually no effect on pNCT mRNA stability, suggesting that ongoing protein synthesis is required for adaptive regulation of pNCT gene transcription.

Animals↗
PubMed1997

G alpha(o) is necessary for muscarinic regulation of Ca2+ channels in mouse heart.

Heterotrimeric G proteins, composed of G alpha and G betagamma subunits, transmit signals from cell surface receptors to cellular effector enzymes and ion channels. The G alpha(o) protein is the most abundant G alpha subtype in the nervous system, but it is also found in the heart. Its function is not completely known, although it is required for regulation of N-type Ca2+ channels in GH3 cells and also interacts with GAP43, a major protein in growth cones, suggesting a role in neuronal pathfinding. To analyze the function of G alpha(o), we have generated mice lacking both isoforms of G alpha(o) by homologous recombination. Surprisingly, the nervous system is grossly intact, despite the fact that G alpha(o) makes up 0.2-0.5% of brain particulate protein and 10% of the growth cone membrane. The G alpha(o)-/- mice do suffer tremors and occasional seizures, but there is no obvious histologic abnormality in the nervous system. In contrast, G alpha(o)-/- mice have a clear and specific defect in ion channel regulation in the heart. Normal muscarinic regulation of L-type calcium channels in ventricular myocytes is absent in the mutant mice. The L-type calcium channel responds normally to isoproterenol, but there is no evident muscarinic inhibition. Muscarinic regulation of atrial K+ channels is normal, as is the electrocardiogram. The levels of other G alpha subunits (G alpha(s), G alpha(q), and G alpha(i)) are unchanged in the hearts of G alpha(o)-/- mice, but the amount of G betagamma is decreased. Whichever subunit, G alpha(o) or G betagamma, carries the signal forward, these studies show that muscarinic inhibition of L-type Ca2+ channels requires coupling of the muscarinic receptor to G alpha(o). Other cardiac G alpha subunits cannot substitute.

Acetylcholine↗
PubMed1997

A computer screening approach to immunoglobulin superfamily structures and interactions: discovery of small non-peptidic CD4 inhibitors as novel immunotherapeutics.

The interaction between CD4 and major histocompatibility complex (MHC) class II proteins is critical for the activation of CD4+ T cells, which are involved in transplantation reactions and a number of autoimmune diseases. In this study we have identified a CD4 surface pocket as a functional epitope implicated in CD4-MHC class II interaction and T-cell activation. A computer-based strategy has been used to screen approximately 150,000 non-peptidic organic compounds in a molecular data base and to identify a group of compounds as ligands of the proposed CD4 surface pocket. These small organic compounds have been shown to specifically block stable CD4-MHC class II binding, and exhibit significant inhibition of immune responses in animal models of autoimmune disease and allograft transplant rejection, suggesting their potential as novel immunosuppressants. This structure-based computer screening approach may have general implications for studying many immunoglobulin-like structures and interactions that share similar structural features. Furthermore, the results from this study have demonstrated that the rational design of small non-peptidic inhibitors of large protein-protein interfaces may indeed be an achievable goal.

Animals↗
PubMed1997

Tumor lymphocytes in patients with advanced ovarian cancer: changes during in vitro culture and implications for immunotherapy.

Tumor specimens and ascites of patients with advanced ovarian cancer were utilized to obtain both primary ovarian carcinoma cell cultures and lymphocytes: tumor-infiltrating lymphocytes (TILs) from solid tumor tissue and tumor-associated lymphocytes (TALs) from peritoneal fluid. Tumor lymphocytes were grown in coculture with autologous tumor cells and recombinant human IL-2 (rhIL-2) for up to 4 weeks and at weekly intervals these were examined with respect to phenotype and cytotoxicity. The phenotype was studied using flow cytometry for a variety of human immunocompetent cell surface markers (CD3, CD4 CD8, CD16, CD56, TCR alphabeta, TCRgammadelta). Cytotoxicity was investigated using 4-hr 51Cr-release assays with the primary ovarian carcinoma cell cultures and the K562 cell line as target cells. The tumor lymphocytes did not demonstrate any obvious trend in phenotype changes during culture, although for different cultures a large range was noted for the various lymphocyte populations studied. Cytotoxicity against both autologous and allogeneic targets declined with culture length for the majority (6/7) of the lymphocyte cell lines tested (greatest at 1 week and least at 3 weeks). These initial results indicate that an in vitro non-MHC-restricted cytotoxic function of peritoneal lymphocytes can be effectively activated with IL-2 and autologous tumor cells. However, if activated lymphocytes are to be employed as a form of immunotherapy, they should be given within the first week of culture for maximum cytotoxic effect.

Cytotoxicity, Immunologic↗
PubMed1997

Right ventricular collagen type III and IV gene expression increases during early phases of endurance training in hypobaric hypoxic condition.

The objective of this study was to examine the effects of prolonged exposure to hypobaric hypoxic condition, physical training and their combination on collagen type I, III and IV gene expression in the ventricles and atria of rat heart. Male rats were assigned to four groups: normobaric sedentary (NS) and trained (NT), and hypobaric sedentary (HS) and trained (HT). Exposure to and treadmill running training in hypobaric condition were carried out in a hypobaric chamber (770-740 mbar, 2250-2550 m). Experimental periods were 10, 21 and 56 days; the groups of 91 days served as recovery groups from experimental settings of 56 days. Exposure to hypobaric condition as such and in combination with endurance training for 10 days increased right ventricular weight-to-body weight ratio (RV/BW) by 26% (p < 0.001) and 23% (p < 0.01), respectively, when compared to 10NS. RV/BW was significantly increased also in 21HT and 56HT. Left ventricular weight-to-body weight ratio was 13% (p < 0.01) and 14% (p < 0.01) higher in 21HT and 56HT, respectively, than in the respective NS. Right ventricular collagen type III mRNA level was 33% (p = 0.065) and 38% (p < 0.01) higher in 10HT than in 10NS and 10NT, respectively. Right ventricular collagen type IV mRNA level was 29% (p < 0.001) higher in 10HT than in 10NS. Relatively slight left ventricular hypertrophy was not associated with significant changes in collagen mRNA levels. Decreased left ventricular subepicardial prolyl 4-hydroxylase activity in 10HS and 10HT suggests transient corresponding decrease in the rate of collagen synthesis. This study shows that combination of endurance training and moderate hypobaric hypoxic condition leads to increased right ventricular collagen type III and IV gene expression associated with right ventricular hypertrophy.

Animals↗
PubMed1997

Differential regulation of glomerular gelatinase B (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in obese Zucker rats.

The obese Zucker rat represents a model of obesity combined with insulin resistance and hyperlipidaemia, which over a period of several months develops spontaneous glomerulosclerosis. The present study addressed the question as to whether glomerular sclerosis was associated with alterations in the degradation of matrix components. In the early phase (up to 6 months) glomeruli from obese rats displayed increased total collagen content (+64%) and decreased gelatinolytic activity (-34%) as compared to lean control animals. This decline in glomerular gelatinolytic activity was due to a reduction in gelatinase B [matrix metalloproteinase (MMP)-9]. Glomerular MMP-9 mRNA was reduced 4.6 +/- 0.6-fold (n = 3; p < 0.05), MMP-9 protein was not detectable by Western blotting and MMP-9 activity was considerably suppressed in gelatin zymograms. MMP-2, in terms of mRNA expression and activity, was unchanged. Tissue inhibitor of metalloproteinases (TIMP)-1 mRNA expression, TIMP-1 protein (immunohistochemistry) and TIMP-1 activity (reverse zymography) were enhanced in glomeruli from obese rats, while TIMP-2 mRNA remained unchanged. Moreover, mRNA for the alpha 1 IV collagen chain was 2.1 +/- 0.8-fold higher in glomeruli isolated from obese animals (n = 3; p < 0.05). These findings indicate that matrix expansion in glomeruli from obese Zucker rats is due to both enhanced synthesis of matrix components as well as reduced degradation by matrix metalloproteinases. Apparently the latter effect is based on a reduction in MMP-9 and up-regulation of its inhibitor TIMP-1.

Albuminuria↗
PubMed1997

Regulation of the taurine transporter gene in the S3 segment of the proximal tubule.

Traditionally, bulk amino acid reabsorption in the kidney has been thought to be localized to the early portions of the proximal nephron. Adult Sprague-Dawley rats were fed diets with low, normal, and high taurine content for two weeks. Kidneys were hybridized with an 35S-radiolabeled complementary RNA probe to the rB16a subclone encoding the extracellular and transmembrane domains of the rat brain taurine transporter. Identical fragments were generated by RT-PCR from rat brain and kidneys as confirmed by DNA sequencing. Hybridization was localized to the outer zone of the medulla of all the kidneys. In the normal diet animals, taurine transporter mRNA was localized to the S3 segment of the proximal tubule, to the loop of Henle in the medulla, and to the glomerular epithelial cell layer. With taurine restriction, taurine transporter mRNA expression was up-regulated predominantly in the S3 segment and was virtually absent in this segment in animals supplemented with taurine. These experiments have precisely localized the rat kidney taurine transporter gene, demonstrating regulation that is limited to the S3 segment of the proximal tubule.

Animals↗
PubMed1997

Immunolocalisation of P450(C17) in the fetal sheep adrenal gland during gestation and in response to ACTH and glucocorticoid administration.

In sheep, increased output of cortisol from the fetal adrenal gland is critical to organ maturation and parturition. Cortisol synthesis is determined in part by the activity of P450(C17) enzyme. We have used immunohistochemistry and Western immunoblotting to examine the distribution of P450(C17) in the ovine fetal adrenal during gestation, and after ACTH or dexamethasone administration to fetuses between Days 125 and 130. The patterns were compared with changes in 3beta-hydroxysteroid dehydrogenase (3beta-HSD) localisation and levels. Adrenal tissue was obtained from four fetuses at each of Days 63-65, 100, 125-130 and term (>140 days). Further animals were chronically catheterised and infused with ACTH, dexamethasone or saline for 96 h beginning on Day 125. Immunohistochemistry for P450(C17), 3beta-HSD, and phenylethanolamine-N-methyl transferase (PNMT) was conducted using standard techniques. At Day 63-65 of pregnancy immunoreactive (ir-)P450(C17) was present in cords of cells throughout the adrenal gland. Ir-P450(C17) was reduced or was undetectable at Day 100, but had increased by Day 125-130, and was present throughout the zona fasciculata of the adrenal cortex of term animals. An increase in P450(C17) protein was also seen between Day 100 and 125 by Western blotting, and after ACTH treatment. Dexamethasone administration led to a marked reduction in ir-P450(C17) levels. In contrast, ir-3beta-HSD was present in the fetal adrenal cortex between Day 100 and term, and was less affected by ACTH or dexamethasone treatment. We conclude that P450(C17) in the fetal sheep adrenal is responsive to regulation by ACTH, and that changes in its levels correlate with previously reported alterations in patterns of cortisol output by the fetal adrenal gland.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Effect of in vivo injection of cholera and pertussis toxin on glucose transport in rat skeletal muscle.

Cholera toxin (CTX) and pertussis toxin (PTX) were examined for their ability to inhibit glucose transport in perfused skeletal muscle. Twenty-five hours after an intravenous injection of CTX, basal transport was decreased approximately 30%, and insulin- and contraction-stimulated transport was reduced at least 86 and 49%, respectively, in both the soleus and red and white gastrocnemius muscles. In contrast, PTX treatment was much less efficient. Impairment of glucose transport appeared to develop 10-15 h after CTX administration, which coincided with development of hyperglycemia despite hyperinsulinimia, increased plasma free fatty acid levels, increased adenosine 3',5'-cyclic monophosphate (cAMP) concentrations in muscle, but no difference in plasma catecholamines. Twenty-five hours after CTX treatment, GLUT-4 protein in both soleus and red gastrocnemius muscles was decreased, whereas no change in GLUT-1 protein content was found. In contrast, GLUT-4 mRNA was unchanged, but transcripts for GLUT-1 were increased > or = 150% in all three muscles from CTX-treated rats. The findings suggest that CTX via increased cAMP impairs basal as well as insulin- and contraction-stimulated muscle glucose transport, at least in part from a decrease in intramuscular GLUT-4 protein.

Animals↗
PubMed1997

Functional expression of rat renal cortex taurine transporter in Xenopus laevis oocytes: adaptive regulation by dietary manipulation.

Renal brush border taurine transport adapts to changes in the dietary intake of sulfur amino acids with increased rates after dietary restriction and reduced transport after dietary surplus. The Xenopus laevis oocyte expression system was used to define the renal adaptive response to dietary manipulation. Injection of poly(A)+ RNA isolated from rat kidney cortex resulted in a time- and dose-dependent increase in NaCl-taurine cotransport in oocytes. The Km of the expressed taurine transporter was 22.5 microM. In oocytes, injection of 40 ng of poly(A)+ RNA from kidneys of low taurine diet (LTD)-fed rats elicited 2-fold the taurine uptake of normal taurine diet (NTD)-fed rats and >3-fold the uptake of high taurine diet (HTD)-fed rats. Northern blots of rat kidneys using a riboprobe derived from an rB16a (rat brain taurine transporter) subclone revealed 6.2- and 2.4-kb transcripts, the abundance of which were increased or decreased in LTD- or HTD-fed rats, respectively, as compared with NTD-fed rats. A approximately 70-kD protein was detected by Western blot using an antibody derived from a synthetic peptide corresponding to a conserved intracellular segment of rB16a. The abundance of the approximately 70-kD protein was increased or decreased in LTD- or HTD-fed rats, respectively, as compared with NTD-fed rats. In conclusion, expression of the rat renal taurine transporter is regulated by dietary taurine at the level of mRNA accumulation and protein synthesis.

Animals↗
PubMed1997

[Fertility and related hormones before and after female successful renal transplantation].

To evaluate the level of hormones before and after female renal transplantation, we measured pituitary gonadal hormones, estrovite, progestin, and prolactin in 25 renal transplant recipients (RTR) and 25 cases of chronic renal failure (CRF) using engyme immunoassay (EIA). The results indicated that serum RRL, FSH and LH level were reduced in RTR females compared with CRF, whereas E2 and P were normal. Serum PRL levels were elevated in CRF females whereas P levels were significantly lower compared with those of other groups. After clomiphene stimulation test, the plasma levels of LH FSH and E2 elevated, suggesting hypothalamic anovulation. Following successful renal transplantation, uremic hypothalamic disfunction was ameliorated and normal menstrual cycle, fertility was restored. During dialysis, treatment was given using suit therapy rather than trigger the ovulatory. Renal transplantation is the best treatment.

Adult↗
PubMed1997

[Detection of rubella antibody by using indirect mix enzyme immunosorbent assay].

Monoclonal antibody has the characteristics of high purity, specificity and strong activity. For this reason, we adopted a monoclonal antibody (R-McAb), against rubella to coat the polystyrene EIA microtitration plate for the first step. Then we followed an indirect enzyme immunoassay to detect rubella immunoglobulin G antibody. We call this method the indirect mix enzyme immunosorbent assay (IMEIA). The 257 serum specimens collected from different human groups tested by this assay (IMEIA) and rubella hemagglutination inhibitiion (HAI) test gave a 100% agreement.

Antibodies, Monoclonal↗
PubMed1997

[Studies of magnetic circular dichroism and absorption spectra in alpha-NisO4 x 6H2O crystal].

Alpha-NiSO4 x 6H2O crystals were studied by magnetic circular dichroism (MCD) and absorption spectra measurements in the range lambda = 185-3300nm. The results show that there are three aborption bands, of which the peaks are related to the d-d transitions from the ground state to the excited states. The weak peaks of a progression of the three members were observed between the principal structures lambda = 654nm and lambda = 713nm due to spin-orbit coupling interacion. The weak peaks of a progression of four members were also observed around the new absorption peak at lambda = 585nm in MCD spectra.

English Abstract↗