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Biomedical subjects

L Hu

Publications and source records attributed to L Hu.

At least 73 records · Page 4Linked to original sources
PubMed2000

Gene sequencing for identification of Paragonimus eggs from a human case.

OBJECTIVE: To identify the etiologic agent from a paragonimiasis patient using molecular techniques. METHODS: The complete nuclear ribosomal DNA second internal transcribed spacer (ITS2) gene sequence of eggs in sputum from a paragonimiasis patient was obtained by directly auto-sequencing its PCR product. ITS2 genes from eggs of Paragonimus westermani and Pagumogonimus skrjabini (both from animal hosts) were also sequenced for comparison. In addition, morphological comparisons were made with the eggs of the two species. RESULTS: The ITS2 gene from the human case was 100% identical with the sequence from the eggs of P. westermani from an experimentally infected dog but only 92% identical with the sequence from the eggs of P. skrjabini. Morphologically, the eggs from the human case more resembled those from P. westermani infected dog. CONCLUSION: The patient was diagnosed to be suffered from paragonimiasis westermani by gene sequence analysis.

Animals↗
PubMed1999

Detection of placental growth hormone variant and chorionic somatomammotropin-L RNA expression in normal and diabetic pregnancy by reverse transcriptase-polymerase chain reaction.

Diabetes is a common complication encountered during pregnancy. Earlier studies indicated that diabetic placentas bear morphological alterations consistent with modified placental differentiation, including alterations in the villous cellular content, structure, and total surface. Limited data associating the diabetic status with the expression of terminal placental differentiation markers are available. The human growth hormone/chorionic somatomammotropin (hGH/CS) family consists of five genes, one of which (GH-N) is expressed efficiently in pituitary while the other four (CS-A, B, L, and hGH-V) are expressed in placenta and represent ultimate placental differentiation markers. We developed and applied a sensitive RT-PCR method coupled with diagnostic restriction digestion to determine the relative levels of the hGH/CS family in normal pregnancies and examine whether their mRNA expression pattern is altered in pregnancies complicated by diabetes. We show that relative hCS-L content changes during placental development. Specifically, normal term placentas express higher relative levels of hCS-L, lower relative hGH-V levels and a 70-fold lower hGH-V/CS-L mRNA ratio compared to early placentas. Also, many term placentas from diabetic pregnancies express lower relative levels of hCS-L mRNA and a much higher hGH-V/CS-L mRNA ratio compared to normal term placenta, resembling more an early placenta pattern of expression. Thus, our study suggests that the expression of terminal placental differentiation markers, such as the hGH/CS genes, is altered in term placentas from these diabetics reflecting either impaired placental differentiation or post-differentiation impairment of normal placental function.

Diabetes, Gestational↗
PubMed1999

Numerical Model of Electrokinetic Flow for Capillary Electrophoresis.

A numerical study is presented for the steady electrokinetic flow in intersecting channels in a T-shaped configuration. The electric potential and space charge density distribution along the capillary are obtained numerically by solving the nonlinear Poisson-Boltzmann equation for arbitrary electrokinetic radius and arbitrary surface potential. The velocity and pressure profiles are obtained by solving a modified Navier-Stokes equation using a primitive variable algorithm. A systematic study of flow in T-shaped intersecting channels showed that the hydrodynamic effect is an important factor that influences fluid leakage out of a channel where the electric potential is left floating. It was found that the flow in each channel can be controlled by applying a potential at each reservoir connected to the end of a channel. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Chemoattraction and chemorepulsion of olfactory bulb axons by different secreted semaphorins.

During development, growth cones can be guided at a distance by diffusible factors, which are attractants and/or repellents. The semaphorins are the largest family of repulsive axon guidance molecules. Secreted semaphorins bind neuropilin receptors and repel sensory, sympathetic, motor, and forebrain axons. We found that in rat embryos, the olfactory epithelium releases a diffusible factor that repels olfactory bulb axons. In addition, Sema A and Sema IV, but not Sema III, Sema E, or Sema H, are able to orient in vitro the growth of olfactory bulb axons; Sema IV has a strong repulsive action, whereas Sema A appears to attract those axons. The expression patterns of sema A and sema IV in the developing olfactory system confirm that they may play a cooperative role in the formation of the lateral olfactory tract. This also represents a further evidence for a chemoattractive function of secreted semaphorins.

Animals↗
PubMed1999

Characterization of the major physiologic phosphorylation site of human keratin 19 and its role in filament organization.

Keratin polypeptide 19 (K19) is a type I intermediate filament protein that is expressed in stratified and simple-type epithelia. Little is known regarding K19 regulation or function, and the only other type I keratin that has been studied in terms of regulation is keratin 18 (K18). We characterized K19 phosphorylation as a handle to study its function. In vivo, serine is the major phosphorylated residue, and phosphopeptide mapping of 32PO4-labeled K19 generates one major phosphopeptide. Edman degradation suggested that the radiolabeled phosphopeptide represents K19 Ser-10 and/or Ser-35 phosphorylation. Mutation of Ser-10 or Ser-35 followed by transfection confirmed that Ser-35 is the major K19 phosphorylation site. Transfection of Ser-35 --> Ala K19 showed a filament assembly defect as compared with normal or with Ser-10 --> Ala K19. Comparison of K18 and K19 phosphorylation features in interphase cells showed that both are phosphorylated primarily at a single site, preferentially in the soluble versus the insoluble keratin fractions. K19 has higher basal phosphorylation, whereas K18 phosphorylation is far more sensitive to phosphatase type I and IIA inhibition. Our results demonstrate that Ser-35 is the major K19 interphase phosphorylation site and that it plays a role in keratin filament assembly. K19 and K18 phosphorylations share some features but also have distinct properties that suggest different regulation of type I keratins within the same cells.

Animals↗
PubMed1999

Characterization of a reproducible rat model of hepatic veno-occlusive disease.

Lack of a reproducible animal model has hampered progress in understanding hepatic veno-occlusive disease (HVOD). This article characterizes a reproducible model of HVOD. Rats gavaged with monocrotaline, 160 mg/kg, were killed between days 1 and 10. Sections were evaluated by light microscopy with a standardized scoring system, by immunoperoxidase staining with ED-1 (monocytes, macrophages) and ED-2 (Kupffer cells) antibodies, and by transmission (TEM) and scanning electron microscopy (SEM). On days 1 and 2, the earliest manifestations were progressive injury to the sinusoidal wall with loss of sinusoidal lining cells, sinusoidal hemorrhage, and mild damage to central vein (CV) endothelium. On days 3 through 5 ("early HVOD"), there was centrilobular coagulative necrosis, severe injury to sinusoids, severe sinusoidal hemorrhage, and severe CV endothelial damage; inflammation with ED-1-positive cells was most marked on these days. Days 6 and 7 ("late HVOD") were characterized by subendothelial and advential fibrosis of CVs, damage of the CV endothelium with subendothelial hemorrhage, and some restoration of the sinusoidal wall. Between days 8 and 10, sections showed interindividual variation ranging from mild, residual fibrosis to severe, late HVOD. From days 1 through 10, ED-2-positive cells were decreased in number, and the number of ED-1-positive cells was increased. Sinusoidal damage is the earliest change in HVOD. Coagulative necrosis follows sinusoidal injury and resolves with improvement in sinusoidal endothelial cell (SEC) morphology. Moderate-to-severe CV fibrosis occurs after reappearance of sinusoidal lining cells and resolution of hepatocyte necrosis. The inflammatory response within the lobule and CVs is a result of recruitment of monocytes, whereas Kupffer cells are decreased in number.

Animals↗
PubMed1999

Strial dysfunction in the MRL-Fas mouse.

The MRL-Fas(lpr) mouse, a model of multisystemic autoimmune disease, has been proposed as a potential model of autoimmune inner ear disease. Cochlear pathology, consisting of hydropic degeneration of the stria vascularis, has been documented to occur coincident with the establishment of systemic disease in this animal. Because the cochlear pathology is restricted to the stria, this study was designed to evaluate whether the endocochlear potential (EP) would be diminished in these animals because of a loss in strial Na, K-ATPase. Experimental (MRL-Fas(lpr)) mice, with established systemic disease, had auditory brain stem response thresholds and EPs recorded. MRL-+/+ mice served as controls. Animals were then euthanized, and their cochleas were processed for immunohistologic assay for the alpha1 and beta2 subunits of Na,K-ATPase. Density of staining was evaluated by use of quantitative means with densitometry image analysis of digitized images. MRL-Fas(lpr) mice revealed significant elevations in auditory brain stem response thresholds and reductions in EPs but no reductions in Na,K-ATPase levels, as evidenced by immunohistochemical assay. The reduction of EP likely occurs as a result of cellular degeneration within the stria vascularis and likely results from an abrogation of the strial perilymph/endolymph barrier and not from a reduction in strial Na, K-ATPase levels.

Animals↗
PubMed1999

Antibody deposition in the stria vascularis of the MRL-Fas(lpr) mouse.

The MRL-Fas(lpr) mouse, a model of multisystemic, organ non-specific autoimmune disease, has been proposed as a model of immune-mediated inner ear disease. Preliminary studies indicate that it develops cochlear pathology focused in the stria vascularis including intracellular edema and degeneration which develops in the absence of an inflammatory infiltrate but in the presence of antibody deposition. It was thus hypothesized that the antibodies found in the stria were mediating a direct pathologic effect on this structure, without recruiting classical inflammatory mediators. It was further hypothesized that the antibodies deposited within the stria would be derived from the non-complement fixing isotypes and subclasses, which are known to be able to mediate direct pathologic effects on target tissues. This study utilized immunohistologic techniques to identify the antibody isotypes and subclasses deposited within the stria vascularis of the MRL-Fas(lpr) mouse. Results indicate that all antibody isotypes and subclasses can be identified within the stria vascularis in the absence of complement. Thus, antibody deposition was not restricted to non-complement fixing antibodies. While it is possible that antibodies are mediating direct pathologic effects within the stria, the non-specific nature of the antibody deposition may indicate that these antibodies are not responsible for the observed pathology. Rather, other mechanisms, such as metabolic and genetic etiologies, must also be considered.

Animals↗
PubMed1999

Induction and characterization of human glioma clones with different radiosensitivities.

To facilitate investigation of the molecular mechanisms of tumor cell radiosensitivities, we have generated a set of clones with different radiosensitivities from a human glioma cell line U-251 MG-Ho. Forty-four colonies were isolated by subjecting parent cells to the mutagen N-methylnitrosourea and then irradiating these cells with increasing doses of x-rays. About half of the clones displayed different radiosensitivities than the parent cells. We selected one of the most sensitive clones (X3i) and one of the most resistant clones (Y6) for further study. Isoeffective doses for these two clones differed by about a factor of 1.7; the relative radiosensitivities of both clones were stable for at least 30 cell culture passages. These two clones do not differ significantly in either the induction or repair of radiation-induced DNA double-strand breaks as measured by pulsed field gel electrophoresis. Radiation-induced apoptosis measured by terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay and micronucleus formation were similar in both clones. However, potentially lethal damage repair was greater in the radioresistant Y6 clone than in the radiosensitive X3i clone as determined by colony-forming efficiency assay.

Alkylating Agents↗
PubMed1999

Killing of brain tumor cells by hypoxia-responsive element mediated expression of BAX.

The presence of radioresistant hypoxic cells in human brain tumors limits the overall effectiveness of conventional fractionated radiation therapy. Tumor-specific therapies that target hypoxic cells are clearly needed. We have investigated the expression of suicide genes under hypoxia by a hypoxia-responsive element (HRE), which can be activated through hypoxia-inducible factor-1 (HIF-1). We transfected plasmids containing multiple copies of HRE into U-87 MG and U-251 MG-NCI human brain tumor cells and tested their ability to induce LacZ gene expression under anoxia. Gene expression under anoxia versus oxia was increased about 12-fold for U-87 MG cells and about fourfold for U-251 MG-NCI cells. At intermediate hypoxic conditions, increased LacZ gene expression in U-87 MG cells was induced by the plasmid that contained three HREs, but not by the plasmid with two HREs. Lastly, when we placed a suicide gene BAX under the control of HREs, cells transfected with the BAX plasmids were preferentially killed through apoptosis under anoxia. Our studies demonstrate that HRE-regulated gene expression is active in brain tumor cells, and that the amount of increased gene expression obtained is dependent on the cell line, the HRE copy number, and the degree of hypoxia.

Brain Neoplasms↗
PubMed1999

Delayed recovery of hypertension after single dose losartan in angiotensin II-infused conscious rats.

OBJECTIVE: In a conscious unrestrained rat model, it takes approximately 1 week for angiotensin II to increase blood pressure to maximum levels. We investigated the time required for hypertension to fully recover after acute angiotensin II receptor blockade in this angiotensin II dependent hypertensive model. DESIGN: Conscious unrestrained rats (n = 8) infused with 10 ng/kg per min angiotensin II for 21 days received losartan (10 mg/kg) on day 17 of angiotensin II infusion. Mean arterial pressure (MAP) and heart rate were monitored continuously. The acute pressor response to 50 ng/kg per min angiotensin II was monitored for 2 h on days 15, 17, 18, 19 and 20 of angiotensin II infusion. Plasma renin concentration (PRC) was measured daily. RESULTS: Angiotensin II increased MAP acutely by 26 +/- 2 mmHg and by a further 23 +/- 4 mmHg between days 4 and 8. Losartan acutely reduced MAP by 75 +/- 2 mmHg; 24 h later MAP had partially recovered but remained suppressed by 47 +/- 3 mmHg. MAP had not fully recovered 4 days later. Some 2 h after losartan, the acute pressor response to angiotensin II had fallen from 24 +/- 2 mmHg to zero. This recovered to 13 +/- 5 and 28 +/- 2 mmHg 24 and 48 h post losartan. After losartan PRC rose from 0.1 +/- 0.05 to above 1 ng/ml per h for less than 24 h. CONCLUSION: A single dose of losartan reverses both the fast and slow pressor effects of continuous angiotensin II infusions. While losartan is metabolized, the fast vasoconstrictor effect recovers quickly but the slow pressor effect takes almost a week to build up again to maximum levels. Since the slow pressor effect is mediated via the AT1 receptor, any means of blocking the renin-angiotensin system is likely to keep blood pressure below maximum hypertensive levels for several days after the drug has disappeared from the circulation.

Angiotensin II↗
PubMed1999

Effects of immunosuppression on the development of cochlear disease in the MRL-Fas(lpr) mouse.

OBJECTIVES: The MRL-Fas(lpr) mouse, an animal that spontaneously develops multisystemic autoimmune disease, has been proposed as model of immune-mediated inner ear disease. Previous studies revealed that this mouse manifested elevated auditory brainstem response thresholds, hydropic degeneration of strial cells, and antibody deposition within strial capillaries. As the etiology of the observed strial disease may be immune, genetic, or uremic, a study was designed to attempt to delineate between these possible etiologic factors. STUDY DESIGN: Prospective, controlled animal study. METHODS: Dexamethasone, which is known to suppress autoantibody production and glomerulonephritis in these animals, was administered systemically on a daily basis to experimental animals, beginning at 6 weeks of age. Control animals received no treatment. Animals were allowed to age, with control animals predictably manifesting systemic disease at 20 weeks of age, at which point all animals were sacrificed. RESULTS: Animals receiving dexamethasone treatment manifested a significant reduction in serum immunoglobulin levels, lymphoid hyperplasia, and a significant improvement in the level of renal function. However, morphologic analysis revealed a persistence of strial disease despite the elimination of strial antibody deposition. CONCLUSION: The results of this experiment support the hypothesis that genetic mechanisms may be responsible for the observed strial disease. Further studies are under way to confirm these findings.

Animals↗
PubMed1999

Campylobacter jejuni 81-176 associates with microtubules and dynein during invasion of human intestinal cells.

Campylobacter jejuni uptake into cultured INT407 cells was analyzed kinetically over a wide range of starting multiplicities of infection (MOI; from 0.02 to 20,000 bacteria/epithelial cell). The efficiency of internalization was the highest at MOI of 0.02 and decreased steadily at higher MOIs, presumably due to reported C. jejuni autoagglutination at higher densities. Total internalized Campylobacter CFU increased gradually from an MOI of 0.02 to a peak at an MOI of 200 (reaching an average of two bacteria internalized per epithelial cell) and decreased at higher MOIs. The invasion process was apparently saturated within 2 h at an MOI of 200, indicating stringent host cell limitations on this entry process. Furthermore, whereas control Salmonella typhi invaded all monolayer cells within 1 h, only two-thirds of monolayer cells were infected after 2 h with C. jejuni at MOIs of 200 to 2,000. The percentage of Campylobacter-infected host cells gradually increased to 85% after 7 h of infection, suggesting that C. jejuni entry may be host cell cycle dependent. Direct evidence of the involvement of microtubules in C. jejuni internalization, suggested previously by biochemical inhibitor studies, was obtained by time course immunofluorescence microscopic analyses. Bacteria initially bound to the tips of host cell membrane extensions containing microtubules, then aligned in parallel with microtubules during entry, colocalized specifically with microtubules and dynein but not with microfilaments, and moved over 4 h, presumably via microtubules to the perinuclear region of host cells. Orthovanadate, which inhibits dynein activity, specifically reduced C. jejuni 81-176 entry, suggesting that this molecular motor is involved in entry and endosome trafficking during this novel bacterial internalization process. Collectively, these data suggest that C. jejuni enters host cells in a targeted and tightly controlled process leading to uptake into an endosomal vacuole which apparently moves intracellularly along microtubules via the molecular motor, dynein, to the perinuclear region.

Actin Cytoskeleton↗
PubMed1999

Connexin 26 expression and extensive gap junctional coupling in cultures of GT1-7 cells secreting gonadotropin-releasing hormone.

Gap junctions (GJs) are transmembrane channels that permit rapid intercellular transit of various small molecules including ions, second messengers and metabolites. GJs promote communication and coordinated activity between coupled neurons, and may help facilitate the synchronous release and pulsatile secretion of neurohormones. A previous study using GnRH-secreting GT1-7 cells reported that connexin 26 was the major GJ subunit present, and that about 20% of the cultured cells engaged in GJ coupling as assayed by fluorescence recovery after photobleaching of 5,6-carboxyfluorescein diacetate (MW 460 D). To reassess GJ connectivity with a more permeant probe, we grew GT1-7 cells to 70% confluency on Matrigel-coated glass coverslips and microinjected Neurobiotin(TM) (MW 322 D) into single cells. Dye was allowed to diffuse for 30 min before cultures were fixed, and subsequently immunostained for Neurobiotin with 3,3'-diaminobenzidine HCl and examined by light microscopy. Dye coupling between 2 or more GT1-7 cells was observed after 75% of all microinjections. Connectivity involved the somata and neurites of an average of 6.6 +/- 2.0 adjoining cells, but in one instance was seen in a group of 32 GT1-7 neighbors. Western blotting and immunofluorescence staining confirmed that connexin 26 was the predominant GJ subunit expressed by GT1-7 cultures. Our results using Neurobiotin suggest these GJ channels may be smaller than anticipated. In addition, functional GJ connectivity between subconfluent GT1-7 cells is more extensive than previously reported, occurring with higher frequency and coupling significantly greater numbers of cultured cells. Since cAMP, IP3, and Ca(2+) are able to pass through GJs and can elicit secretion of GnRH by GT1 cell cultures, GJs may play an important role in the coordination and synchronization of GnRH release.

Animals↗
PubMed1999

Appropriate regulation of renin and blood pressure in 45-kb human renin/human angiotensinogen transgenic mice.

The renin-angiotensin system is normally subject to servo control mechanisms that suppress plasma renin levels in response to increased blood pressure and increase plasma renin levels when blood pressure falls. In most species, renin is rate limiting, and angiotensinogen circulates at a concentration close to the Km, so varying the concentration of either can affect the rate of angiotensin formation. However, only the plasma renin level responds to changes in blood pressure and sodium balance to maintain blood pressure homeostasis. Therefore, the high plasma human renin levels and the hypertension of mice and rats containing both human renin and angiotensinogen transgenes indicate inappropriate regulation of renin and blood pressure. These anomalies led us to develop new lines of transgenic mice with a longer human renin gene fragment (45 kb) than earlier lines (13 to 15 kb). Unlike their predecessors, the 45-kb hREN mice secrete human renin only from the kidneys, and both the human and mouse renins respond appropriately to physiological stimuli. To determine whether blood pressure is also regulated appropriately, we crossed these new 45-kb hREN mice with mice containing the human angiotensinogen gene. All doubly transgenic mice were normotensive like their singly transgenic and nontransgenic littermates. Moreover, among doubly transgenic mice, both human and mouse plasma renin concentrations were suppressed relative to the singly transgenic 45-kb hREN mice. These findings demonstrate the importance of appropriate cell and tissue specificity of gene expression in constructing transgenic models and affirm the pivotal role played by renal renin secretion in blood pressure control.

Aging↗
PubMed1999

[A preliminary study on the genetic susceptibility of asthma in a Chinese population].

OBJECTIVE: To study the asthma genetic susceptibility by way of ccandidate region so as to accumulate data on the related loci in Chinese population and determine whether genetic susceptibility to asthma is linked to the chromosome region. METHODS: One hundred ninety-two samples from 32 families were collected from Zhaoan county in Fujian province. Two Rsa I polymorphic sites within uncoded region of the high-affinity IgE receptor beta chain gene (Fc(epsilon) RI-beta) located on chromosome 11q13 were detected by PCR/Rsa I restriction endonuclease digestion. The polymorphic markers D5S436 and D5S393 within chromosome 5q31-33 were amplified by PCR incorporated with radioactive isotope. The asthma family samples were compared with unrelated samples randomly selected from general population. RESULTS: Genotypes containing A allele within intron 2 polymorphic site of Fc(epsilon) RI-beta gene were associated with asthma (P<0.05,OR = 2.039). Significant difference in the level of total serum IgE was noted among three genotypes of intron 2 polymorphic site of Fc(epsilon) RI-beta gene (P<0.05). The association between A allele and elevated total serum IgE was also significant (P<0.05, RR = 1.361). No relationship between exon 7 polymorphic site of Fc epsilonRI-beta gene and asthma was shown. By sib-pair analysis, significant evidence for linkage to asthma was observed with D5S436 (P<0.05) but not with D5S393. No significant linkage to total serum IgE was identified with both of these markers. CONCLUSION: The above-accumulated data suggested that both Fc epsilonRI-beta gene and chromosome 5q31-33 could be very attractive candidate gene and region for further studies in Chinese population, and to confirm these preliminary results, more markers within these regions merit testing in additional population samples.

Adolescent↗
PubMed1999

The isolation results and the antimicrobial agents susceptibility analysis of Haemophilus from the sputum of the elderly suffering from respiratory tract disease.

OBJECTIVE: To inform the isolation and antibiotics susceptibility results of Haemophilus in the sputum of old men suffering from respiratory tract disease so that the epidemiological information and treatment can be available to physicians. METHODS: Two groups-group A, patients=562, group B, healthy volunteers=57 expectorated specimens of sputum were cultured with a special medium for Haemophilus. The isolates were then identified with API NH Identification plates and detected with ATB NH antibiotics susceptibility cards, finally, we got the statistics data of Haemophilus species and antibiotics susceptibility rates from Datatrac statistic system of VITEK 32. RESULTS: Haemophilus were detected in 132 specimens out of 562 (23.5%), which includes 6 strains of H. influenzae (4.5%). 122 strains of H. parainfluenzae, 4 strains of H. aphrophilus (3.1%). At the same time, 3 strains of Haemophilus were isolated from group B. Following are the susceptibility rates of sixteen antibiotics of 132 strains of Haemophilus, 73.4% to amoxicillin, 92.4% to amoxicillin and clavulanic acid, 83.3% to cefactor, 90.9% to cefotaxime, 79.5% to cefuroxime-axetil, 52.3% to kanamycin, 25.0% to gentamycin, 72.0% to spectinomycin, 79.5% to chloramphenicol, 50.0% to tetracycline, 9.1% to erythromycin, 42.4% to pristhomycin, 49.2% to rosoxacin, 62.96% to pefloxacin, 97.7% to rifampin, 33.3% to sulfonamides. CONCLUSION: There is a high isolation rate of Haemophilus in the sputum of the elderly suffering from respiratory tract diseases, The H. parainfluenzae is the main Haemophilus in our area of study, which it deserves good attention by clinical microbiological laboratory. In addition, the antibiotics susceptibility results indicate that this species is more susceptible to beta-lactams antibiotics and is less susceptible to some others such as macrolides and aminoglycosides, etc. So, the drug treatment should be based on these antibiotics susceptibility results in order to guide the specific therapy.

Aged↗