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Biomedical subjects

W Han

Publications and source records attributed to W Han.

At least 91 records · Page 5Linked to original sources
PubMed1997

The nuclear hormone receptor Ftz-F1 is a cofactor for the Drosophila homeodomain protein Ftz.

Homeobox genes specify cell fate and positional identity in embryos throughout the animal kingdom. Paradoxically, although each has a specific function in vivo, the in vitro DNA-binding specificities of homeodomain proteins are overlapping and relatively weak. A current model is that homeodomain proteins interact with cofactors that increase specificity in vivo. Here we use a native binding site for the homeodomain protein Fushi tarazu (Ftz) to isolate Ftz-F1, a protein of the nuclear hormone-receptor superfamily and a new Ftz cofactor. Ftz and Ftz-F1 are present in a complex in Drosophila embryos. Ftz-F1 facilitates the binding of Ftz to DNA, allowing interactions with weak-affinity sites at concentrations of Ftz that alone bind only high-affinity sites. Embryos lacking Ftz-F1 display ftz-like pair-rule cuticular defects. This phenotype is a result of abnormal ftz function because it is expressed but fails to activate downstream target genes. Cooperative interaction between homeodomain proteins and cofactors of different classes may serve as a general mechanism to increase HOX protein specificity and to broaden the range of target sites they regulate.

Animals↗
PubMed1997

Neuronal peptide release is limited by secretory granule mobility.

Neuropeptides are slowly released from a limited pool of secretory granules. To visualize this process, GFP-tagged preproatrial natriuretic factor (ANF) was expressed in nerve growth factor-treated PC12 cells. Biochemical and microfluorimetric experiments demonstrate that proANF-EGFP is packaged in granules that accumulate at neurite endings and is released in a Ca2+-dependent manner by secretagogs. Confocal microscopy shows that secretion is associated with depletion of granules distributed throughout the terminal. Fluorescence recovery after photobleaching and time-lapse particle tracking reveal that only a subpopulation of cytoplasmic secretory granules, similar in size to the releasable pool, can move quickly enough (D = 6 x 10(-11) cm2/s) to support release. Therefore, sustained secretory responses are limited by the number of mobile granules and their slow rate of diffusion.

Animals↗
PubMed1997

[Studies on serotyping of sporadic acute viral hepatitis].

Two hundred and forty-eight blood specimens collected from patients of sporadic acute viral hepatitis were serotyped with enzyme immunoassay (EIA), to study its pathogenic components during non-epidemic seasons of hepatitis A (HA). Results showed that HA accounted for 61.3% of the total sporadic acute hepatitis cases during its non-epidemic seasons, occurred mainly in youngsters and decreased with increase of their age. Hepatitis B (HB) ranked the second and accounted for 26.2%, occurred mainly in the middle-aged and the elderly and its prevalence increased with age. Hepatitis C (HC) accounted for 9.9% and hepatitis E (HE) 22.2% of the total cases, without obvious age difference. Prevalence of hepatitis D (HD) was 12.7%, with a positive rate of hepatitis D antigen (HDAg) of 12%. Superinfection accounted for 18.9%, and the viral hepatitis markers were all negative in 0.8% of the total cases. There was very significant difference in prevalence of HCV-IgG and HEV-IgG between sporadic acute hepatitis patients and blood donors during the same periods. Icterus occurred in 68% of the total cases, 86.8% in HA. Patients of HB complicated with HD were liable to chronicity.

Acute Disease↗
PubMed1997

Relative contribution of normal and neoplastic cells determines telomerase activity and telomere length in primary cancers of the prostate, colon, and sarcoma.

Telomerase and telomere length are increasingly investigated as potential diagnostic and prognostic markers in human tumors. Among other factors, telomerase and telomere length may be influenced by the degree of tumor cell content in tumor specimens. We studied telomerase activity and telomere length with concomitant integration of histopathological data to determine whether both were influenced by the amount of tumor cells. We measured telomerase in 153 specimens: in 51 solid tumor blocks; in 51 cryostat sections; and in 51 adjacent normal tissues from patients with sarcoma (n = 10) and colorectal (n = 11) and prostate cancer (n = 30) using the sensitive and rapid detection telomeric repeat amplification protocol assay. Telomere length was determined by telomere restriction fragment Southern blot analysis. From cryostat sections, tumor cell infiltration was assessed. Telomerase activity was detected in all colorectal tumors and sarcomas, as expected. In primary prostate cancer, however, telomerase activity was less frequently observed (14 of 30, 47%). Moreover, a decreased intensity compared to colon cancer and sarcoma was evident (P < 0.001). The median tumor cell infiltration was significantly higher in sarcoma (65%) and colon (30%) compared to prostate cancer (5%; P < 0.001). There was a positive correlation between tumor cell infiltration and telomerase activity (r = 0.89; P < 0.001). Telomere restriction fragments in tumors were shorter compared to the normal tissues with peak differences in colon, sarcoma, and prostate of 1.8, 2.8, and 1 kilobase pairs, respectively (P < 0.002). Our data suggest the presence of a positive correlation between the degree of tumor cell content in human solid tumors and the level of telomerase activity detected. We demonstrated that the amount of tumor cells also affects telomere restriction fragment analysis. Therefore, with the predominance of normal cells in tumor specimens, telomerase activity measured may not reflect the malignant phenotype, and telomere loss may be underestimated. This phenomenon was most evident in prostate cancer. Our results will have implications for the future when telomerase activity and telomere lengths may be used for early screening, diagnosis, and prognosis determinations and when telomerase inhibitors are applied to clinical practice.

Adenocarcinoma↗
PubMed1997

Evaluation of the telomeric repeat amplification protocol (TRAP) assay for telomerase as a diagnostic modality in recurrent bladder cancer.

There is a need for the identification of an accurate test for the detection of recurrent bladder cancer. In this study, we evaluate the telomeric repeat amplification protocol (TRAP) assay for detection of telomerase as a potential new method for bladder cancer detection and compare it to voided urine cytology. A urine sample and a bladder wash were obtained from 63 patients with a history of bladder cancer. Cytological evaluation was performed on voided urine, and the TRAP assay was performed on voided urine and bladder wash. The overall clinical sensitivity of the TRAP assay, as defined by the ability to identify correctly the patients with pathologically confirmed bladder cancer, was 35% in voided urine and 50% in bladder wash, whereas the overall clinical sensitivity of voided urine cytology was 71%. The sensitivity of voided urine cytology for the papillary and noninvasive tumors (Ta) was 50%, compared to 92% for the superficially invasive tumors (T1), 62% for the muscle-invasive tumors (T2+), and 100% for the high-grade flat carcinoma in situ (Tis). The clinical sensitivity of the TRAP assay using voided urine was 46% for Ta, 50% for T1, 18% for T2+, and 20% for Tis. The sensitivity of the TRAP assay in Ta disease was similar to that of cytology (50% for cytology versus 46% for the TRAP assay). There was a strong association between the total number of exfoliated malignant cells and the sensitivity of the assay. The sensitivity of the TRAP assay in bladder washes was 44% for Ta, 67% for T1, 46% for T2+, and 43% for Tis. The TRAP assay is reproducible, highly specific, and not dependent on the expertise of the cytopathologist. These results suggest that this assay should be further investigated as a diagnostic tool for bladder cancer.

Carcinoma, Papillary↗
PubMed1996

Reduced expression of transforming growth factor beta type I receptor contributes to the malignancy of human colon carcinoma cells.

Transforming growth factor beta (TGFbeta) type I (RI) and type II (RII) receptors are essential for TGFbeta signal transduction. A human colon carcinoma cell line, designated GEO, is marginally responsive to TGFbeta and expresses a low level of RI mRNA relative to colon carcinoma cells, which are highly responsive to TGFbeta. Hence, the role of RI as a limiting factor for TGFbeta sensitivity and the contribution of low RI levels to the malignant phenotype of GEO cells were examined. Stable transfection of a tetracycline-regulatable rat RI cDNA increased TGFbeta1 binding to RI and resulted in increased growth inhibition by exogenous TGFbeta1. In contrast, although stable transfection of an RII expression vector into the same GEO cells increased TGFbeta1 binding to RII, growth inhibition by exogenous TGFbeta1 was not altered. This indicated that the low level of RI is a limiting factor for the growth-inhibitory effects of TGFbeta in GEO cells. RI-transfected cells were growth-arrested at a lower saturation density than GEO control cells. They also showed reduced growth and clonogenicity in plating efficiency and soft agarose assays, whereas RII-transfected cells did not show any differences from the NEO control cells in these assays. Tetracycline repressed RI expression in transfected cells and reversed the reduction in plating efficiency of RI-transfected clones, confirming that growth effects were due to increased RI expression in transfected cells. TGFbeta1 neutralizing antibody stimulated the proliferation of RI-transfected cells but had little effect on GEO control cells, indicating that increased autocrine-negative TGFbeta activity also resulted from increased RI expression. Tumorigenicity in athymic nude mice was significantly delayed in RI-transfected cells. These results indicate that low RI expression can be a limiting factor for response to exogenous TGFbeta, as well as TGFbeta autocrine-negative activity, and that reduction of RI expression can contribute to malignant progression.

Activin Receptors, Type I↗
PubMed1996

Telomerase activity is repressed during differentiation of maturation-sensitive but not resistant human tumor cell lines.

The effects of induced differentiation on telomerase activity were examined in human acute promyelocytic leukemic (NB4) and human embryonal carcinoma (NTERA-2) cells exposed to all-trans-retinoic acid or hexamethylene bisacetamide. Retinoic acid treatment of NB4 and NTERA-2 cells, and hexamethylene bisacetamide treatment of NTERA-2 cells caused a decline in telomerase activity in differentiation-sensitive but not in resistant clones of these cell lines. Changes in telomerase activity as measured by the PCR-based telomeric repeat amplification protocol assay were noted by 24-72 h of exposure to the inducer, suggesting that its regulation may precede terminal differentiation. The degree of telomerase activity decline was greater in NB4 cells than in NTERA-2 cells, probably reflecting in part a more mature state of NB4 cells after 5 days of exposure to the inducer. Mixing of protein extracts from treated and untreated cells did not suggest the presence of diffusible telomerase inhibitors. Expression of the RNA component of telomerase was also examined in NB4 cells, and its decline correlated with the reduced telomerase activity measured by the telomeric repeat amplification protocol assay during induced differentiation of these tumor cells. Taken together, these findings indicate that telomerase is a regulated enzyme system during induced human tumor cell differentiation, showing an inverse relationship between the degree of differentiation and telomerase activity. These models will be be useful to study the regulation and role of telomerase during induced differentiation of human tumor cells.

Acetamides↗
PubMed1996

Tec family protein-tyrosine kinases and pleckstrin homology domains in mast cells.

Tec family protein-tyrosine kinases (PTKs) have been recognized as a distinct subfamily for only a few years. Two of them, Btk and Emt, are tyrosine-phosphorylated and enzymatically activated upon cross-linking of the high-affinity IgE receptor (Fc epsilonRI), suggesting their involvement in mast cell activation. Since Lyn and other Src family PTKs phosphorylate Btk at Tyr-551 and activate the latter kinase, the receptor-associated Lyn seems to activate Btk in mast cells. The Btk kinase activity, on the other hand, is regulated negatively by phosphorylation by protein kinase C (PKC) that is associated with Btk via Btk's pleckstrin homology (PH) domain. PH domains also bind to phospholipids and the beta subunit of heterotrimeric GTP-binding proteins. Therefore, it has been hypothesized that PH domains play roles in membrane localization.

Binding Sites↗
PubMed1996

Thalamic haemorrhage.

Thalamic haemorrhage is usually considered a single entity although the thalamus is composed of anatomically as well as functionally discrete subregions receiving blood from different arteries. The clinical features vary according to the intrathalamic location of the haematomas and the bleeding artery. We investigated the impact of haematoma location and vascular territory on the clinical symptoms and signs, neuro-imaging findings and clinical courses of patients with thalamic haemorrhages by a retrospective analysis of 175 consecutive patients with thalamic haemorrhage. Based on the neuro-imaging findings we classified thalamic haematomas into four regional types and one global type according to the primary bleeding sites: (i) anterior type occurring in the territory of the tuberothalamic arteries, (ii) posteromedial type occurring in the territory of the thalamic-subthalamic paramedian arteries, (iii) posterolateral type occurring in the territory of the thalamogeniculate arteries. (iv) dorsal type occurring in the territory of the posterior choroidal arteries and (v) global type occupying the entire area of the thalamus. We studied the clinical and neuroimaging characteristics of each type. Eleven patients (7%) had the anterior type: these were the smallest haematomas and often ruptured into the anterior horn of the lateral ventricle. The major clinical signs were acute behavioural abnormalities: the clinical course was usually benign. Twenty-four patients (14%) had the posteromedial type in which haematomas often ruptured into the third ventricle, causing marked hydrocephalus, and often extended mediocaudally, involving the mesencephalon. The prognoses of this type depended on the presence of mesencephalic involvement which was associated with the worst outcome among the types even if the size of the haematoma itself was not large. The posterolateral type was most frequent (77 patients, 44%) and was characterized by large haematomas, rupture into the posterior horn of the lateral ventricle and frequent extension into the posterior limb of the internal capsule. Clinical signs included marked sensory and motor signs, hemineglect in right-side haematomas and language abnormalities with left-side haematomas. The case fatality with this type was relatively high (35%) and permanent neurologic sequelae frequently resulted. In the dorsal type (32 patients, 18%) haematomas were best visualized at the level of the body of the lateral ventricle on CT scans. The size was moderate and haematomas often extended posterolaterally into the adjacent subcortical white matter. Sensory and motor signs were common and about one third of the patients were first misdiagnosed as having lacunar infarcts. The prognoses were excellent. The global type (31 patients, 18%) of thalamic haemorrhage was clinically and radiologically very similar to the posterolateral type except that the haematomas were too large to define the bleeding focus. Severe sensory and motor signs were almost always present. In this type 25 patients died (the case fatality was 81%).

Adolescent↗
PubMed1996

A factor from Trypanosoma cruzi induces repetitive cytosolic free Ca2+ transients in isolated primary canine cardiac myocytes.

An unusual 120-kDa alkaline peptidase contained in a trypomastigote soluble fraction (TSF) of Trypanosoma cruzi is associated with the induction of repetitive Ca2+ transients and subsequent invasion by the parasite of a number of mammalian cell lines, including tissue culture L6E2 myoblasts (B. A. Burleigh and N. W. Andrews, J. Biol. Chem. 270:5172-5180, 1995; S. N. J. Moreno, J. Silva, A. E. Vercesi, and R. Docampo, J. Exp. Med. 180:1535-1540, 1994; A. Rodríguez, M. G. Rioult, A. Ora, and N. W. Andrews, J. Cell Biol. 129:1263-1273, 1995; I. Tardieux, M. H. Nathanson, and N. W. Andrews, J. Exp. Med. 179:1017-1022, 1994). Using single cell spectrofluorometry and whole-cell patch clamping, we show that TSF produces rapid repetitive cytosolic Ca2+ transients (each associated with cell contraction) in primary cardiac myocytes isolated from dogs. The response of myocytes to TSF was dose dependent in that increasing numbers of cells responded to increasing concentrations of TSF. The TSF-induced Ca2+ transients could be obliterated when TSF was heated or treated with trypsin or the protease inhibitor leupeptin. Aprotinin, pepstatin A, and E-64 did not affect TSF activity. The TSF-induced Ca2+ transients and trypomastigote cell invasion could not be inhibited by alpha (prazosin)- or beta (propanolol)-adrenergic blockers or L-type Ca2+ channel blockers (verapamil, nisoldipine, or cadmium) or by removal of extracellular Ca2+. However, inhibition of pertussis toxin-sensitive G proteins and Ca2+ release from the sarcoplasmic reticulum (with thapsigargin or ryanodine) prevented the TSF-induced Ca2+ transients and cell invasion by trypomastigotes. These data suggested that cardiac myocyte pertussis toxin-sensitive G proteins are associated with the regulation of TSF-induced Ca2+ transients and myocyte invasion by trypomastigotes but are independent of Ca2+ entry into the cytosol via L-type Ca2+ channels. The Ca2+ transients are dependent on release of Ca2+ from sarcoplasmic reticulum Ca2+ stores, but this release is not dependent on extracellular Ca2+ or on the classic model of Ca2+ -induced Ca2+ release in cardiac myocytes. Further, subthreshold depolarizations, together with cell contraction as demonstrated by whole-cell patch clamping, occurred with each Ca2+ transient. However, the depolarizations were of magnitude insufficient to generate an action potential, providing further evidence for a lack of dependence on L-type Ca2+ channels and other voltage-dependent channels (Na+ and K+ channels) in the generation of TSF-induced Ca2+ transients. Our findings suggest that primary canine cardiac myocytes respond to TSF and parasite invasion in ways similar to those of the in vitro cell lines studied to date. Since cardiac myocytes are primary targets for T. cruzi in the vertebrate host, our study indicates that TSF may play a role in the pathogenesis of Chagas' disease in humans.

Animals↗
PubMed1996

[Inotropic effect of novel cardiotonic agent, vesnarinone--tests on anaesthetized dogs].

We studied the positive inotropic effect of the novel cardiotonic agent, vesnarinone on open chest and intact anaesthetized dogs hearts. The results indicate that vesnarinone has a dose-effect relationship on increasing the contractile force, LV dp/dt max and stroke volume, and it shortens the ejection time 21%. No effect on blood pressure and heart rate was noted. Vesnarione is more effective than amrinone in terms of positive inotropic effect.

Animals↗
PubMed1995

Cryo atomic force microscopy: a new approach for biological imaging at high resolution.

A low-temperature atomic force microscope (cryo-AFM), operated in liquid nitrogen vapor, has been constructed for biological applications. The system provides an adjustable imaging temperature from 77 to 220 K with atomic resolution achieved on crystalline specimens. Imaging with NaCl microcrystals demonstrates that the system is free from surface contamination. Below 100 K, several biological specimens, including immunoglobulins and DNA as well as red blood cell ghosts, were imaged at high spatial resolution. Measurements on individual macromolecules showed that the mechanical strength is significantly greater at cryogenic temperatures with an estimated Young's modulus 1000-10,000 times that of a hydrated protein at room temperature, providing a solid basis for future improvements and applications of cryo-AFM in structural biology.

DNA↗
PubMed1995

[The application of the pattern visual-evoked potential in the diagnosis and treatment of amblyopia].

PURPOSE: To research into the value of the application in the diagnosis and treatment of amblyopia, and to discuss the mechanism of amblyopia. METHODS: The subjects were divided into three groups: 108 amblyopia eyes; 180 normal eyes and 26 amblyopia eyes during the treatment with Madopar. PVEP was observed with black-white checks pattern-reversal stimulation at several spatial frequencies (30', 60', 90'). RESULTS: P1 latency of the amblyopia eyes prolongs at the high frequency (30' angle of view), in which the occurrence rate of abnormal PVEP is 68.5%. Through detecting PVEP during the treatment of amblyopia with Madopar, we found P1 latency shortened and amplitude increased (P < 0.05). CONCLUSION: It is better to use P1 latency to observe the visual function of patients with amslyopia with stimulation at 30' angle of view. PVEP is an important objective index in diagnosis and evaluating the curative effect of amblyopia.

Adolescent↗
PubMed1994

Magnetic resonance imaging measurement of posterior fossa structures in schizophrenia.

OBJECTIVE: Previous research has yielded conflicting results regarding the hypothesis that structural abnormalities of the cerebellar vermis and other posterior fossa structures are associated with schizophrenia. The purpose of this study was to apply techniques of measuring posterior fossa structures from magnetic resonance imaging scans that have proven reliable in identifying structural abnormalities in other patient populations. METHOD: Midsagittal areas of cerebellar vermis and its subsections (anterior vermis, lobules VI-VII, and lobules VIII-X), brainstem (pons, medulla, and midbrain), and fourth ventricle, as well as intracranial area and cortical area, were measured. Subjects included 36 schizophrenic patients and 51 normal comparison subjects. Groups were matched on age, sex, race, and family socioeconomic status. RESULTS: No significant group differences were detected for any posterior fossa structure. When corrected for intracranial area, fourth ventricle area was significantly larger in patients than in the comparison group. Fourth ventricle area was not, however, correlated with any measures of symptom severity. CONCLUSIONS: The size of posterior fossa structures is not abnormal in schizophrenia.

Adolescent↗
PubMed1994

Complications of ethmoidectomy: a survey of fellows of the American Academy of Otolaryngology-Head and Neck Surgery.

A survey regarding complications of sinus surgery was mailed to 6969 otolaryngologists; 3933 responses (56.44%) were obtained, and 3043 of these physicians (77.37%) reported that they performed ethmoidectomy. Completed questionnaires were available for review from 42.21% of all Academy fellows (2942 physicians). Responses were tabulated and summarized question by question. Physicians generally did not rate their residency training in ethmoidectomy highly. The survey confirmed that there has been a marked rise in the frequency of ethmoidectomy and in the amount of training in ethmoidectomy since 1985. Empirical complication rates were calculated for different procedures and time periods. Poisson regression models were then constructed to describe the rate of complications under varying conditions such as the type of surgery performed, time period, experience and training of the surgeon, and type of complication encountered. The models permitted determination of the statistical significance of variables in relation to incidence or complications. The study did not demonstrate a clear and consistent statistical relationship between the incidence of complications, the type of surgery performed, and the quality of training. Moreover, physicians who provided data from record review tended to report higher rates than those who estimated responses. The majority of physicians discussed specific potential complications with their patients before surgery and routinely performed preoperative computed tomography. The study demonstrated that physicians who experienced complications at higher rates were more likely to discuss these complications with patients before surgery.

Ethmoid Sinus↗
PubMed1994

[Inotropic effect of novel domestic cardiotonic agent, vesnarinone--test in vitro].

This paper reports the studies on the positive inotropic effect of the novel domestic cardiotonic agent, vesnarinone on isolated papillary muscle and atrium of guinea pigs and rabbits, and on the comparison of the positive inotropic effect and toxicity of vesnarinone with amrinone, milrinone and strophanthin. The result suggests that vesnarinone has an apparent dose-effect relationship on a positive inotropic effect, the strength of which is between amrinone and milrinone. The positive inotropic effect of vesnarinone is higher and the toxicity is lower than that of strophanthin.

Amrinone↗