Search PubMed⌕ Search

Biomedical subjects

M H Lin

Publications and source records attributed to M H Lin.

At least 37 records · Page 2Linked to original sources
PubMed2000

Activation of the Notch pathway in the hair cortex leads to aberrant differentiation of the adjacent hair-shaft layers.

Little is known about the mechanisms underlying the generation of various cell types in the hair follicle. To investigate the role of the Notch pathway in this process, transgenic mice were generated in which an active form of Notch1 (Notch(DeltaE)) was overexpressed under the control of the mouse hair keratin A1 (MHKA1) promoter. MHKA-Notch(DeltaE) is expressed only in one precursor cell type of the hair follicle, the cortex. Transgenic mice could be easily identified by the phenotypes of curly whiskers and wavy, sheen pelage hair. No effects of activated Notch on proliferation were detected in hair follicles of the transgenic mice. We find that activating Notch signaling in the cortex caused abnormal differentiation of the medulla and the cuticle, two neighboring cell types that did not express activated Notch. We demonstrate that these non-autonomous effects are likely caused by cell-cell interactions between keratinocytes within the hair follicle and that Notch may function in such interactions either by directing the differentiation of follicular cells or assisting cells in interpreting a gradient emanating from the dermal papilla.

Animals↗
PubMed1999

Modulation of sperm tail protein tyrosine phosphorylation by pentoxifylline and its correlation with hyperactivated motility.

OBJECTIVE: To assess the effect of pentoxifylline on human sperm functions that are crucial to fertilization. DESIGN: Prospective, controlled study. SETTING: Academic tertiary care institute. PATIENT(S): Healthy male sperm donors. INTERVENTION(S): The effects of pentoxifylline (3.6 mM) on hyperactivated motility, sperm binding to the zona pellucida, and sperm protein tyrosine phosphorylation were evaluated. MAIN OUTCOME MEASURE(S): Hyperactivated motility was assessed by computer-assisted motion analysis, and tight binding of sperm to homologous zonae pellucidae was examined using the hemizona assay. Sperm protein phosphorylation was evaluated using indirect immunofluorescence with an antibody to phosphotyrosine (PY20). RESULT(S): Pentoxifylline significantly stimulated hyperactivated motility at 1 hour and 4 hours; it also significantly increased sperm binding to the zona pellucida and enhanced sperm tail tyrosine phosphorylation at 4 hours under capacitating conditions. There was a statistically significant correlation between hyperactivated motility and sperm tail protein phosphorylation. CONCLUSION(S): Pentoxifylline stimulates sperm functions that are essential to achieving fertilization under in vitro conditions in sperm obtained from fertile men. The enhancement of hyperactivated motility is associated with the stimulation of sperm tail tyrosine phosphorylation, suggesting a causal relation and the involvement of a modulatory effect after cyclic adenosine monophosphate-dependent phosphorylation of intermediate proteins.

Fertilization in Vitro↗
PubMed1999

Pentoxifylline stimulates various sperm motion parameters and cervical mucus penetrability in patients with asthenozoospermia.

Pentoxifylline (PTX) was incubated in vitro with human spermatozoa to examine its effects on sperm motility characteristics and bovine cervical mucus penetrability (BCMP). Sperm motion parameters were assessed by computer-assisted motion analysis (CASA) using HTM-IVOS and BCMP was evaluated using the Penetrak kit. In vitro incubation with PTX (1 mg ml-1; 3.6 mM, 30 min) did not significantly change percentage motility, average path velocity (VAP), straight-line velocity (VSL) or beat cross frequency (BCF) of spermatozoa from normozoospermic or asthenozoospermic samples. However, it significantly increased curvilinear velocity (VCL), amplitude of lateral head displacement (ALH) and hyperactivated motility (HA), and significantly decreased linearity (LIN) of spermatozoa from both samples. Pentoxifylline was found to increase BCMP scores for spermatozoa from asthenozoospermic samples, but did not affect scores for spermatozoa from normozoospermic samples. Bovine cervical mucus penetrability (BCMP) was found to be positively and significantly correlated with the percentage motility of both non-PTX-treated and PTX-treated spermatozoa for asthenozoospermic samples. These results demonstrated that PTX enhanced several motion sperm parameters as well as BCMP in asthenozoospermic samples and suggest a potential use of the methylxanthine in infertile patients with motility defects undergoing artificial insemination.

Animals↗
PubMed1998

Plasma membrane integrity of cryopreserved human sperm: an investigation of the results of the hypoosmotic swelling test, the water test, and eosin-Y staining.

OBJECTIVE: [1] To examine the relationship between sperm membrane integrity and motion parameters before and after cryopreservation; [2] to determine the capacity of the membrane integrity tests to predict the outcome of cryopreservation in fertile and infertile men; and [3] to examine the degree of agreement between tail and head membrane integrity of testicular and ejaculated immotile sperm cryopreserved for intracytoplasmic sperm injection. DESIGN: Prospective study. SETTING: Academic tertiary care institution. PATIENT(S): Fertile donors and normozoospermic oligozoospermic, and asthenozoospermic subfertile men. INTERVENTION(S): Semen samples were cryopreserved and thawed for analysis. MAIN OUTCOME MEASURE(S): Sperm membrane integrity and computer-assisted motion parameters. RESULT(S): The hypoosmotic swelling test and water test had a significant and positive correlation in the fresh and cryopreserved ejaculates of all groups. The results of the hypoosmotic swelling test correlated positively with the percent motility in the fresh ejaculates of fertile and subfertile men. None of the membrane integrity tests correlated with the cryosurvival rate in any group. In the ejaculated and testicular samples with no postcryopreservation motility, the simultaneous assessment of hypoosmotic swelling test and eosin showed that of 33% sperm exhibiting coiling with the hypoosmotic swelling test, only 9% were eosin negative, whereas 24% were eosin positive. CONCLUSION(S): [1] The water test may be a simpler replacement for the hypoosmotic swelling test; [2] none of the membrane integrity tests predicted sperm motility after cryopreservation; and [3] there was a high degree of disagreement between the hypoosmotic swelling test and eosin in the samples with no postcryopreservation motility.

Cell Membrane↗
PubMed1998

Reproducibility of the revised American Fertility Society classification of endometriosis using laparoscopy or laparotomy.

OBJECTIVE: To assess the discrepancy between laparoscopic and laparotomic scoring methods using the revised American Fertility Society (AFS) classification of endometriosis. METHOD: In this prospective study, 84 patients with endometriosis were scored twice (laparoscopically and laparotomically) by the same subspecialty-certified reproductive endocrinologist. The magnitude of inter-method variability was reported quantitatively by the S.D. of the differences in scores between the pairs. The differences in the mean endometriosis scores between the two methods were assessed by the paired Student's t-test. P < 0.05 was considered as statistically significant. Discrepancy between the two methods in the staging of endometriosis patients was presented by kappa measure of agreement. RESULT: There was considerable variability in the scores between the two scoring methods by the same observer. Among individual components of the scoring system, the greatest variability occurred in the ovarian endometriosis and cul-de-sac obliteration subscores, with the least variability observed for peritoneum endometriosis. The inter-method variation in score was sufficient to alter the endometriosis staging in 34.5% of patients, including a difference of two stages in 3.6% of patients. The kappa coefficient was 0.49, indicating fair-to-good agreement between the two scoring methods. CONCLUSION: Inter-method variability between laparoscopic and laparotomic scoring methods was high for ovarian endometriosis subscore using the revised AFS classification of endometriosis. Agreement in endometriosis staging between the two methods was fair to good.

Endometriosis↗
PubMed1998

Transactivation of the human MDR1 gene by hepatitis B virus X gene product.

BACKGROUND/AIMS: Persistent hepatitis B virus (HBV) infection may cause hepatocellular carcinoma. Patients with hepatocellular carcinoma are characterized by nonresponsiveness to chemotherapeutic agents. While many studies have been devoted to understanding the hepatocarcinogenesis mechanism of HBV, the possible relationship between HBV and the drug sensitivity phenotype of cancer cells has rarely been addressed. The hepatitis B virus X gene encodes a transcription transactivator which has been suggested to be a potential factor in viral hepatocarcinogenesis. The role of HBV pX in mediating the drug resistance phenotype of hepatoma cell lines was examined in this study. METHODS: Standard transfection and chloramphenicol acetyltransferase assay were utilized to examine the effect of HBV pX transactivator on a reporter gene under the control of the human multidrug resistance (MDR) 1 upstream regulatory elements. Selected Hep G2 clones with or without HBV pX expression were tested for their sensitivity towards various anti-cancer agents by utilization of MTT assay. RESULTS: The expression of HBV pX in both Hep G2 (p53+) and Hep 3B (p53-) cells resulted in transactivation of the reporter gene under control of the human MDR1 upstream regulatory elements. Northern blot analysis indicated that expression of the endogenous MDR1 gene was also elevated in Hep G2 clones with HBV pX expression. Decreased drug sensitivity towards adriamycin, vinblastine, and VP-16 was observed in Hep G2 clones with HBV pX expression. CONCLUSIONS: HBV pX can transactivate the MDR1 gene. Drug sensitivity was altered in Hep G2 cells with HBV pX expression.

Cloning, Molecular↗
PubMed1998

Separating X-bearing human spermatozoa through a discontinuous Percoll density gradient proved to be inefficient by double-label fluorescent in situ hybridization.

PURPOSE: Double-label fluorescence in situ hybridization (FISH) was used to evaluate the efficiency of separating X- and Y-chromosome-bearing spermatozoa through 12-step discontinuous Percoll gradients. METHODS: Liquefied normal semen samples from 10 healthy donors were overlaid onto 25% Percoll and centrifuged. Parts of the sperm pellet were saved as control, while the remaining portion was separated by 12-step Percoll gradient. After centrifugation, the spermatozoa in the 80% Percoll layer were collected. The X:Y ratio of the control and separated spermatozoa was verified by double-label FISH (CEP SOX/SGY probes) and scored blindly by one observer. Differences in the X:Y ratios between matched groups were analyzed by paired t tests. RESULTS: The overall average labeling efficiency was 99.2%. A significant enrichment (P = 0.02) of X-bearing spermatozoa was obtained in Percoll separated fractions (mean X:Y ratio = 52.2:46.4) compared with the control group (X:Y ratio = 49.5:48.4). Discontinuous Percoll gradients also decreased the proportion of aneuploid spermatozoa (from 1.0 to 0.8%), but the differences were nonsignificant. CONCLUSIONS: Discontinuous Percoll separation did increase the X:Y ratio significantly, but the enrichment of X-bearing spermatozoa is insufficient for clinical use in preconceptional sex selection.

Centrifugation, Density Gradient↗
PubMed1998

Comparison of various methods of processing human cryopreserved-thawed semen samples.

We compared the efficacy of various methods of processing cryopreserved-thawed samples for the recovery of functionally adequate spermatozoa as assessed by the response to the sperm stress test (SST), an index of temperature activated sperm membrane lipid peroxidation, and immediate and delayed changes in sperm viability and motion parameters. Donor semen samples (n = 28) were cryopreserved-thawed and divided into six equal parts, one part was used as control and the remaining parts were used to compare five methods of sperm processing as follows: direct Percoll gradient processing, washing by one-step or stepwise addition of the washing medium followed by Percoll processing, and washing by one-step or stepwise addition of the washing medium. Additional samples (n = 10) were evaluated for the immediate and delayed (6 h at 37 degrees C) impact of one-step and stepwise washing (without Percoll separation). Compared with wash-only methods, samples processed using Percoll had a significantly higher SST score (P = 0.001), motility, rapid spermatozoa (>50 microm/s), curvilinear velocity and motility index (P < 0.001). Comparing various Percoll methods, direct Percoll processing resulted in the highest number of motile spermatozoa recovered (P < 0.00001) and a higher SST score based on curvilinear velocity (P = 0.001). Stepwise washing gave a significantly higher number of motile spermatozoa (P < 0.001) but with a significantly lower SST score based on the concentration of motile spermatozoa (P = 0.001), motility (P = 0.001) and motility index (P = 0.01). Sperm viability and motion parameters after 6 h of incubation showed no difference between one-step and stepwise washing. In conclusion, compared with wash-only methods, Percoll processed samples resulted in the recovery of spermatozoa with superior quality as assessed by SST and motion analysis. One-step washing of the samples gave an overall comparable recovery compared to the samples prepared stepwise. Having significantly higher SST scores, similar viability and the maintenance of motility, one-step washing may be a better method of processing thawed samples than the stepwise washing.

Cell Survival↗
PubMed1998

Effects of blocked atrial beats on the atrioventricular nodal recovery property: facilitation or depression?

INTRODUCTION: Blocked atrial beats (A(B)) usually have concealed AV nodal penetration, which can change the nodal conduction time (AH) of a subsequent beat. However, without an output marker it is difficult to assess their effect on the node. In this report we used all possible parameters as nodal resting time after A(B) and plotted them against the AH of testing beats to study their effects on the node. METHODS AND RESULTS: Atrial extrastimulation studies were done in 21 patients in whom one blocked atrial beat (A(2B)) was observed. Nodal recovery curves were obtained for basic pacing (A1), after a conducted premature beat (A2), and after A(2B). In six patients there were 2 to 3 consecutively blocked beats (A(nB)) and recovery curves were constructed after each A(nB). Nodal recovery curves were plotted with AH of the testing beat against different nodal resting parameters and fitted to a single exponential equation. We found contradicting phenomena when using different formats. (1) For recovery curves of A(2B), there was a rightward shift from that of the basic curve when using H1A3 or A1A3 as the gauge (depression phenomenon). On the contrary, there was a leftward shift of the curves when using A(2B)A3 (facilitating phenomenon). (2) For recovery curves after multiple blocked beats there was a marked rightward shift of all curves except A(n-1)(B)An-curves, which were all leftward shifted. CONCLUSION: Because these contradicting phenomena were dictated by the presenting formats, the terms "depression" and "facilitation" cannot be considered intrinsic AV nodal properties outside of the strict context of the pacing protocol and the format of data presentation.

Adolescent↗
PubMed1998

A defective interference-like phenomenon of human hepatitis B virus in chronic carriers.

Defective interfering (DI) particles have been found in many RNA and DNA viruses of bacteria, plants, and animals since their first discovery in influenza virus. However, this fundamental phenomenon has not been demonstrated in human natural infections. Using a new approach, here we provide the first experimental evidence for the existence of DI-like viruses in human chronic carriers of hepatitis B virus (HBV). Functional characterization of naturally occurring core internal deletion (CID) variants of HBV revealed all of the features of DI particles. When equal amounts of wild-type and CID variant DNAs were cotransfected into a human hepatoma cell line, Huh7, a three- to fivefold enrichment of CID variants was most often observed. The fluctuations of the virus populations between CID variants and helper HBV in three chronic carriers are reminiscent of the cycling phenomenon in other DI viral systems. This finding has important implications for chronic viral hepatitis and other chronic progressive viral diseases.

Amino Acid Sequence↗
PubMed1998

Functional characterization of naturally occurring variants of human hepatitis B virus containing the core internal deletion mutation.

Naturally occurring variants of human hepatitis B virus (HBV) containing the core internal deletion (CID) mutation have been found frequently in HBV carriers worldwide. Despite numerous sequence analysis reports of CID variants in patients, in the past decade, CID variants have not been characterized functionally, and thus their biological significance to HBV infection remains unclear. We report here two different CID variants identified from two patients that are replication defective, most likely due to the absence of detectable core protein. In addition, we were unable to detect the presence of the precore protein and e antigen from CID variants. However, the production of polymerase appeared to be normal. The replication defect of the CID variants can be rescued in trans by complementation with wild-type core protein. The rescued CID variant particles, which utilize the wild-type core protein, presumably are enveloped properly since they can be secreted into the medium and band at a position similar to that of mature wild-type Dane particles, as determined by gradient centrifugation analysis. Our results also provide an explanation for the association of CID variants with helper or wild-type HBV in nature. The significance of CID variants in HBV infection and pathogenesis is discussed.

Carcinoma, Hepatocellular↗
PubMed1998

Detection of endogenous digitalis-like immunoreactive factors in human blood.

Digitalis-like immunoreactive factors (DLIF) are special types of steroids with lactone rings in their structures. Clinically, this type of compound can be used as medicine for heart failure; thus, the elevated endogenous DLIF found under certain pathological conditions are interferent substances in digoxin immunoassay. Endogenous DLIF with biological and immunological properties similar to cardiotonic drugs, such as digoxin, have been found in several tissues and body fluids of animals and humans. Since these endogenous Na+, K(+)-ATPase inhibitors can be considered hormones in nature, immunoassays must be selected detection of them to achieve the required sensitivity and specificity. In this study, we used three sets of in-house formulated immunoassays for DLIF and ouabain-like factors (OLF) detection. Using a polyclonal antibody-based ouabain enzyme immunoassay, the mean +/- S.E.M. of OLF in the sera of 10 healthy individuals were determined to be (9.1 +/- 0.9) x 10(-11) M. Using a monoclonal antibody-based ouabain enzyme immunoassay, the mean +/- S.E.M of OLF in the sera of 10 healthy individuals was (8.2 +/- 1.2) x 10(-11) M while using a antibody fragment Fab-based enzyme immunoassay for digoxin, the mean +/- S.E.M of DLIF in 11 healthy individuals was (4.0 +/- 1.2) x 10(-10) M. In conclusion, our immunological data indicate that DLIFs are normal constituents of human blood. Although DLIF is the major component, coexistence of OLF with DLIF in healthy individuals can not be excluded.

Animals↗
PubMed1997

Developmental changes of atrioventricular nodal recovery properties.

Atrioventricular (AV) nodal recovery properties can be studied by a periodic premature stimulation protocol performed at a slow basic rate. Developmental aspects of these properties have not been determined. The purpose of this study was to determine the developmental changes of AV nodal recovery properties. Forty-three children and young adults (male:female ratio 25:18) without AV nodal disease (aged 3.3 to 21.9 years) were studied by delivering premature atrial extrastimuli coupled to basic driven atrial beats. The individual recovery curve was fitted to the equation: A2H2 = A0H0 + exp(alpha -H1A2/tau) for H1A2 > or =theta, where A0H0 is the minimum AH interval, H1A2 is any recovery interval that exceeds the nodal effective refractory period, A2H2 is the corresponding nodal conduction time at any given H1A2, alpha is a constant, tau is the recovery time constant, and theta is the nodal effective refractory period. We found that: (1) A0H0 and alpha constant did not change significantly with age; (2) both tau (r = 0.324; p <0.05) and theta (r = 0.401; p <0.05) had a positive correlation with age; and (3) the maximum change in A2H2 with a 10-ms decrement in H1A2 was 32 ms and did not change significantly with age. Our results suggest that AV nodal recovery properties are age-dependent and both the recovery time constant and effective refractory period lengthen with age.

Adolescent↗
PubMed1997

Ectopic expression of MEF2 in the epidermis induces epidermal expression of muscle genes and abnormal muscle development in Drosophila.

Myocyte-specific enhancer-binding factor 2 (MEF2) is a myogenic regulatory factor in vertebrates and Drosophila. Whereas the role of MEF2 in regulating vertebrate myogenesis and muscle genes has been extensively studied, little is known of the role of MEF2 in regulating Drosophila myogenesis. We have shown in a recent analysis of the regulation of the Drosophila Tropomyosin I (TmI) gene in transgenic flies that MEF2 is a positive regulator of TmI expression in the somatic body-wall muscles of embryos, larvae, and adults. To understand further the role of MEF2 in myogenesis and test the role of MEF2 in regulating TmI expression, we have used the yeast GAL4/UAS system to generate embryos in which MEF2 is ectopically expressed in tissues where it is not normally expressed or embryos in which MEF2 is overexpressed in the mesoderm and muscles. We observe that ectopic expression of MEF2 in the epidermis and the ventral midline cells in embryos activates the expression of TmI and other muscle genes in these tissues and that this activation is stage-dependent suggesting a requirement for additional factors. Furthermore, ectopic expression of MEF2 in the epidermis results in a decrease in the expression of signaling molecules in the epidermis and a failure of the embryo to properly form body-wall muscles. These results indicate that MEF2 can function out of context in the epidermis to induce the expression of muscle genes and interfere with a requirement for the epidermis in muscle development. We also find that the level of MEF2 in the mesoderm and/or muscles in embryos is critical to body-wall muscle formation; however, no effect is observed on the development of the visceral muscle or dorsal vessel.

Animals↗
PubMed1997

Prenatal diagnosis of cephalothoracopagus janiceps monosymmetros.

We report a case of cephalothoracopagus janiceps monosymmetros that was diagnosed prenatally by ultrasound at 23 weeks' gestation. Obstetric ultrasound demonstrated conjoined female twins with a single fused cranial vault irregular in contour, duplicated cerebra, one face, two eyeballs, a fused thorax, two hearts, two thoracic spines, eight limbs, and polyhydramnios. The pregnancy was terminated and all the features described prenatally were observed at necropsy. The asymmetrical fused faces consisted of a ventral humanoid face with micrognathia, microphthalmia, low-set ears, a normal nose, and an opposite reduced face with partial facial features of a central narrowed fissure and paired synotic ears. The conjoined twins had fused umbilical cords, omphalocoele, and a single oesophagus, stomach, and duodenum, but duplicated pancreases, spleens, and central nervous, cardiopulmonary, hepatic, and genito-urinary systems. The common gastrointestinal tract bifurcated at the level of the jejunum. Our case documents a very uncommon variety of asymmetrical cephalothoracopagus janiceps with duplicated central nervous systems.

Adult↗