Biomedical subjects

H H Yao

Publications and source records attributed to H H Yao.

9 recordsLinked to original sources

PubMed2001

Germinal disc-derived epidermal growth factor: a paracrine factor to stimulate proliferation of granulosa cells.

The germinal disc (GD) of the chicken oocyte produces factors that influence proliferation and differentiation of granulosa cells. Granulosa cells proximal to the GD are more proliferative, whereas granulosa cells distal to the GD are more differentiated. Previously, we had found epidermal growth factor (EGF) was present in the GD. In this study, we tested the hypothesis that EGF is the GD-derived paracrine factor that stimulates proliferation of granulosa cells. Northern analysis, reverse transcription-polymerase chain reaction, and radioimmunoassay indicated that the GD and granulosa cells but not theca cells are the sources of EGF in chicken preovulatory follicles. However, only the conditioned medium from the GD region (GDR = GD + overlying granulosa cells) but not the granulosa cell-conditioned medium stimulated proliferation of granulosa cells. Pretreatment of conditioned media with EGF antibody abolished the proliferation-stimulating effect of the GDR-conditioned medium. We conclude that EGF is one of the paracrine factors produced by the GD to stimulate proliferation of granulosa cells. Granulosa cells proximal to the GD express a proliferative phenotype possibly because they are exposed to a greater amount of EGF derived from the GD.

Animals↗

PubMed2001

Chicken granulosa cells show differential expression of epidermal growth factor (EGF) and luteinizing hormone (LH) receptor messenger RNA and differential responsiveness to EGF and LH dependent upon location of granulosa cells to the germinal disc.

Granulosa cells in the chicken follicle exhibit different phenotypes according to their location relative to the germinal disc (GD). Granulosa cells proximal to the GD (referred to as proximal granulosa cells) are more proliferative, whereas granulosa cells distal to the GD (referred to as distal granulosa cells) are more differentiated. We have shown that epidermal growth factor (EGF) derived from the GD stimulated proliferation of granulosa cells proximal to the GD, whereas extraovarian LH promoted differentiation. We tested the hypothesis that phenotypic differences of granulosa cells are the result of differential responsiveness of granulosa cells to EGF and LH. We found that both granulosa and theca layers of chicken preovulatory follicles expressed mRNA for EGF receptor (EGFr) by polymerase chain reaction (PCR) analysis. However, only the granulosa layer showed differential expression of EGFr and LH receptor (LHr) mRNA. Competitive reverse transcription-PCR revealed that proximal granulosa cells expressed more EGFr mRNA but less LHr mRNA than distal granulosa cells. In addition, proximal granulosa cells proliferated more in response to EGF than their distal counterparts. We further demonstrated that EGF decreased LHr mRNA expression by granulosa cells in a dose-dependent manner, whereas EGF and LH had no effect on EGFr mRNA expression except at one dose of LH (15 ng/ml) that stimulated EGFr mRNA expression. Our findings suggest that EGF derived from the GD influences the phenotypes of granulosa cells. Granulosa cells proximal to the GD exhibit a proliferative phenotype possibly because they are exposed to and are more responsive to GD-derived EGF. Furthermore, GD-derived EGF decreases LHr mRNA expression by proximal granulosa cells and therefore results in less differentiated granulosa cell phenotype. In contrast, granulosa cells distal to the GD are not under the influence of EGF and exhibit a more differentiated phenotype.

Animals↗

PubMed1999

Restricted expression of WT1 messenger ribonucleic acid in immature ovarian follicles: uniformity in mammalian and avian species and maintenance during reproductive senescence.

WT1 is a zinc finger protein with transcriptional repressor activity on several growth factor and growth factor receptor genes. In the ovary, a potential role for WT1 in the suppression of the development of immature follicles has been demonstrated. Here, gel retardation assays further showed that recombinant WT1 protein interacted with consensus DNA sequences in the inhibin-alpha gene promoter. We investigated the pattern of WT1 expression in a wide variety of species and also over the reproductive life span in rats. In chicken ovaries, Northern blot analysis revealed the presence of WT1 transcript in small healthy white follicles (1-5 mm in diameter) and its absence in small yellow (6-12 mm in diameter) or larger follicles (F1-F5). In pig and monkey ovaries, WT1 expression was limited to granulosa cells of preantral follicles, as shown by in situ hybridization analysis. In rats, Northern blot analyses demonstrated the presence of WT1 transcript in the ovaries of young (3-mo-old) and middle-aged (9-mo-old) rats on the proestrous day, with a decrease in old (12-mo-old) rats in persistent estrus. In situ hybridization analysis further suggested that the decrease in WT1 expression in aging ovaries was associated with fewer immature follicles. Thus, WT1 expression is restricted to immature follicles in diverse avian and mammalian species and over the reproductive life span in rats. These data demonstrated that WT1 is a marker for immature follicles and suggested a potential role of this transcriptional repressor in the slow growth of early follicles.

Animals↗

PubMed1998

Destruction of the germinal disc region of an immature preovulatory chicken follicle induces atresia and apoptosis.

The germinal disc region (GDR), which contains the germinal disc and overlying granulosa cells, is essential for completion of maturation of the preovulatory chicken follicle. The current study was conducted to test the hypothesis that destruction of the GDR (GDRX) of an immature preovulatory chicken follicle blocks ovulation, induces apoptosis, and causes atresia. The GDR of immature preovulatory follicles (F2) were destroyed by freezing with dry ice (3 mm in diameter) 48-50 h before ovulation. As a control for the effect of freezing, a nonGDR portion (a portion of the follicular wall opposite to the GDR relative to the follicular stalk) of other F2 follicles were destroyed (nonGDRX). Treatment of F2 follicles by GDRX caused atresia and blocked ovulation of all treated follicles (6 of 6), whereas none of the nonGDRX follicles (0 of 5) underwent atresia. Treatment of follicles by GDRX induced apoptotic DNA fragmentation (laddering) in theca and granulosa layers obtained from the frozen area and in the theca layer obtained from the follicular wall distal to the frozen area. In contrast, apoptosis was only present in theca and granulosa layers in the frozen area of the nonGDRX follicle. Furthermore, the in situ DNA end-labeling technique demonstrated that in the GDRX follicle 24 h after treatment, cells in the theca interna, endothelial cells in blood vessels of the theca externa, and a few granulosa cells underwent apoptosis. These results indicate that destruction of the GDR of an immature preovulatory follicle causes atresia and apoptosis and blocks ovulation. These novel findings suggest that the GDR maintains development of the chicken preovulatory follicle by producing one or more survival factors. Without the GDR, chicken follicles cannot develop further and they eventually die.

Animals↗

PubMed1998

Epidermal growth factor in the germinal disc and its potential role in follicular development in the chicken.

The germinal disc region (GDR; germinal disc + overlying granulosa cells) of the hen's ovarian follicle secretes one or more factors that stimulate proliferation of, and decrease progesterone (P4) production by, granulosa cells. Destruction of the GDR results in apoptosis and atresia of the follicle. These data suggested that the GDR produces a growth factor(s) to sustain the development of the follicle. These findings prompted us to investigate two questions: 1) Is epidermal growth factor (EGF) or transforming growth factor alpha (TGFalpha), which binds to the EGF receptor, present in the GDR? 2) Does EGF regulate granulosa cell functions in the hen? Immunocytochemistry revealed that EGF, but not TGFalpha, was present in the germinal disc of the four largest preovulatory follicles of the hen. TGFalpha was found only in the theca interna. To determine whether EGF regulates granulosa cell functions, granulosa layer explants (13 mm in diameter) from the second-largest preovulatory follicle were cultured for 36 h with 0,0.017, or 0.17 microM EGF. Proliferation, apoptosis, and P4 production of granulosa layer explants were then measured by using a colorimetric method for determining viable cell number, gel electrophoresis, and RIA, respectively. EGF regulates several functions of granulosa layer explants by stimulating proliferation, inhibiting apoptosis, and decreasing basal P4 production. These data indicate that EGF is present in the germinal disc and may be one of the factors that regulate follicular development in the hen.

Animals↗

PubMed1997

Laboratory and clinical evaluation of assays for beta-hydroxybutyrate.

We have performed a two-part evaluation of assays for beta-hydroxybutyrate (beta HB). In Part I, we evaluated the analytical acceptability of a dry film, self-contained analyzer for beta HB measurement (KetoSite; GDS Diagnostics, Elkhart, Ind). The assay response is linear and between-day imprecision is acceptable. Acetoacetate (AcAc) interferes severely with this assay. This interference could be minimized by dilution of serum before the assay. With this predilution protocol, KetoSite beta HB results compare favorably with an automated Sigma (St. Louis, Mo) beta HB assay. In Part II, we compared the clinical utility of beta HB measurements (Sigma) with the qualitative measurement of ketones using the nitroprusside test (Acetest; Bayer, Elkhart, Ind) for the diagnosis and management of diabetic ketoacidosis (DKA). Test results for both assays were abnormal for all patients with DKA on admission. However, frequent monitoring with either test during the management of uncomplicated DKA added little if any additional clinical information over routine measurements of serum glucose and total carbon dioxide.

3-Hydroxybutyric Acid↗

PubMed1996

Simultaneous determination of ethylene glycol and its major toxic metabolite, glycolic acid, in serum by gas chromatography.

We developed a gas-chromatographic procedure for the simultaneous determination of ethylene glycol (EG) and its major toxic metabolite, glycolic acid (GA), suitable for clinical use in instances of EG intoxication. After serum protein precipitation with acetonitrile (containing internal standard), the supernate is treated with 2,2-dimethoxypropane (containing dimethylformamide) to remove water, and the volume is then reduced by evaporation to <100 microL of dimethylformamide (but not to dryness). After trimethylsilyl derivatization, the resulting derivatives are analyzed by capillary column gas chromatography. Only 100 microL of serum is required and the entire determination, including calibrators and controls, takes <2 h. The method gives a linear response to at least 10 g/L EG and 5 g/L GA and has a limit of detection <10 mg/L. Intraassay CV is < or = 2.8% for EG (100 and 1000 mg/L) and GA (100 and 500 mg/L); between-day CV is < or = 6.5%. The absolute recovery from serum was 91% for EG and 77-82% for GA (200 and 2000 mg/L each). Relative to calibrators prepared bovine serum albumin (70 g/L), the recovery was 99-104% for EG (100 - 5000 mg/L) and 95-105% for GA (50 - 2500 mg/L). No clinically important interference was detected for >60 exogenous or endogenous compounds and drugs.

Acetonitriles↗

PubMed1989

Extended relational operators for statistical data manipulations in medical databases.

Conventional relational database management systems fail to address three features of statistical data management in a biomedical/clinical database, namely, that (1) statistical and medical data (SMD) require a great deal of space and need to be stored in a reduced form with minimal duplication; indeed, SMD have many derived/calculated and summary statistics that make the number of attributes in a relation (i.e., a set of records) grow rapidly and dynamically; (2) most SMD have hierarchical structures that are difficult to manage using the relational data model since SMD are stored in separate relations for duplication and space considerations; and (3) the management of SMD is made easier if it is possible to reorganize relations or group data, a capability lacking in conventional relational database management systems. In this paper, we (1) introduce five extended relational operators, (lattice) NEST, (lattice) UNNEST, MERGE, SPREAD, and GEN, to reorganize relations; (2) integrate the extended operators with conventional relational algebra and introduce the concept of the lattice relational model; and (3) give applications of the extended relational operators and the lattice relational model in solving the problems of statistical data manipulation in medical databases.

Database Management Systems↗

PubMedDate not supplied

Simultaneous determination of ethylene glycol and glycolic acid in serum by gas chromatography-mass spectrometry.

We describe a gas chromatographic-mass spectrometric (GC-MS) procedure for the simultaneous determination of ethylene glycol (EG) and its major toxic metabolite, glycolic acid (GA), in serum. In this method, serum (50 microL) is treated with 150 microL of glacial acetic acid/acetonitrile (1:10, v/v; contains internal standard, 1,3-propanediol, 15 mg/dL) to precipitate protein. After centrifugation, 10 microL of supernate is treated with 500 microL of 2,2-dimethoxypropane/dimethylformamide (80:20, v/v) to convert water to methanol, and the volume is then reduced to < 100 microL of dimethylformamide (but not to dryness). After formation of tertbutyldimethylsilyl derivatives, analysis is performed by capillary column GC-MS in selected ion mode. The method gives a linear response to 1000 mg/L each EG and GA (16.1 mmol/L and 13.2 mmol/L, respectively) and has a lower limit of detection and a lower limit of quantitation of 10 mg/L each EG and GA (0.16 mmol/L and 0.13 mmol/L, respectively). Total assay imprecision is CV < or = 6.4% (200 and 800 mg/L EG and GA [3.2 and 12.9 mmol/L EG; 2.6 and 10.5 mmol/L GA, respectively]). Absolute recovery from human serum was 91.1% for EG and 77.6% for GA. The procedure is free from any known interference. A complete analysis set (three calibrators, patient serum neat, patient serum diluted 1:5 (v/v), and two controls) may be completed in about 2 h. A preliminary result, based on a single calibrator and patient serum diluted 1:5 (v/v), is complete in about 1 h. The method has been used to aid the diagnosis and management in 34 cases of EG intoxication. Selected cases are briefly reviewed.

Ethylene Glycol↗