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Biomedical subjects

C F Chang

Publications and source records attributed to C F Chang.

At least 163 records · Page 9Linked to original sources
PubMed1987

Postpartum interval in beef cows shortened by enclomiphene.

This study was designed to determine whether an anti-estrogen can block the negative effect of estrogens on luteinizing hormone (LH) release and therefore decrease the postpartum interval in suckled beef cows. In Exp. I, eight suckled postpartum beef cows were randomly assigned to treatment and control groups. Treatment cows received 1 g/d clomiphene citrate (im) from d 21 to 28 postpartum, while control cows were injected with saline. On d 28 postpartum, there was no difference (P greater than .05) in mean total and basal LH concentrations or LH pulse frequency between treatment and control cows. All control cows exhibited estrus on d 52 +/- 3; treatment cows exhibited estrus on d 134 +/- 12 (P less than .05). In Exp. II, 17 suckled cows were randomly assigned to three treatment groups: 1) control group (n = 6) receiving one empty implant, 2) 10-cm enclomiphene implant group (n = 5) and 3) 30-cm enclomiphene implant group (n = 6). The silastic implants were placed sc on d 20 and removed on d 29 postpartum. Mean total LH concentrations during d 24 to 29 postpartum in the 30-cm enclomiphene implant group were higher than the 10-cm implant (P less than .05) and control group (P less than .05). The postpartum period in the 30-cm enclomiphene group (45 +/- 6 d) was shorter than the 10-cm implant (94 +/- 24 d) and control (96 +/- 20 d) groups (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Increased luteinizing hormone secretion and ovarian function in heifers actively immunized against estrogen and progesterone.

This study was designed to test the effects of active immunization against estrogen and progesterone on patterns of luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion, ovarian characteristics and growth rate of heifers. Heifers were randomly assigned to four treatments: 1) control injection (n = 10); 2) ovariectomy (n = 9); 3) immunization against estrogen (anti-E, n = 10); and 4) immunization against estrogen and progesterone (anti-E+P4, n = 10). Three booster immunizations were administered at 1, 1.5 and 6 mo after primary immunization. Progesterone antibody binding was 40% (34 fmol at 1:600 final dilution) in the anti-E+P4 heifers, and estradiol-17 beta binding was 35% (30 fmol) and 60% (52 fmol at 1:100 final dilution) in the anti-E+P4 and anti-E heifers, respectively, after the final immunization. Anti-E+P4 heifers had more pulses of LH and higher basal concentrations of LH than anti-E or control heifers (P less than .05). Concentrations of LH in anti-E+P4 heifers did not increase to concentrations found in ovariectomized heifers (P less than .05). Immunization against steroids did not alter the secretion of FSH. The number of large follicles (greater than 15 mm diameter) in anti-E+P4 and anti-E heifers was greater than in control heifers (P less than .05). Ovarian weight was increased in anti-E+P4 heifers (P less than .05). Average daily gain was not different among groups (P greater than .05). It was concluded that active immunization against estrogen and progesterone in heifers increased LH secretion and stimulated ovarian function.

Animals↗
PubMed1986

Ovarian response to active immunization against luteinizing hormone in the cow.

Two experiments were conducted to determine whether active immunization against luteinizing hormone (LH) could lead to ovarian cyst development in the cow. In Experiment 1, cyclic beef heifers were randomly assigned to receive bovine LH (bLH) conjugated with ovalbumin (LH-immunized; n=4) or ovalbumin alone (control; n=5). Blood samples were collected at monthly intervals from the LH-immunized heifers to determine antibody titers. Heifers were observed for estrous behavior twice daily. All heifers were slaughtered 4 mo after initial immunization and ovaries examined for follicular status. In Experiment 2, mature dairy cows were immunized with bLH (LH-immunized; n=4) or ovalbumin alone (control; n=3). Weekly blood samples were collected from all cows for 26 wk and ovaries were rectally palpated. Sera from all of the LH-immunized heifers and cows had antibodies to LH. All of the LH-immunized animals stopped cycling 1 mo after immunization. In spite of the fact that serum follicle stimulating hormone levels were unaffected, ovarian cysts could not be found in either the LH-immunized heifers or cows.

Journal Article↗
PubMed1986

Elemental imaging and resolution in energy-filtered conventional electron microscopy.

Energy-filtered transmission electron microscopy (EFEM) was used to image the distributions of uranium and carbon in uranyl acetate stained catalase crystals. The spatial resolution obtained from inelastic C K-edge and U O4,5-edge images, determined from the highest-order reflection in the computed diffraction pattern, was 3.4 nm for both carbon and uranium. The resolution limit imposed by the delocalization of inelastic scattering was estimated from cross-section measurements to be 0.6 nm for U and 0.2 nm for C. Considering both delocalization and the effects of microscope aberrations, for an objective lens chromatic aberration coefficient of 2.8 mm and 10 eV energy window, the calculated resolutions are 2.0 nm for C and 1.2 nm for U. The effects of plural inelastic and elastic-inelastic scattering were sufficiently large to show crystalline structure in unprocessed pre-edge inelastic images. Previously suggested methods for eliminating these artifacts were applied to obtain the compositional information in the catalase EFEM images.

Carbon↗
PubMed1986

Electron probe analysis, X-ray mapping, and electron energy-loss spectroscopy of calcium, magnesium, and monovalent ions in log-phase and in dividing Escherichia coli B cells.

The elemental composition of individual cells of rapidly frozen and cryosectioned Escherichia coli B was measured with electron optical microanalytic methods. The Ca content was high (26.2 mmol/kg) in a 10-nm-wide region of the cell envelope. Amounts of cytoplasmic Ca in actively dividing cells were significantly higher (32.6 mmol/kg [dry weight]) than in the log-phase (1.5 mmol/kg) cells. Cellular Mg was 205 mmol/kg (dry weight) and it was uniformly distributed throughout the cell. Cells washed in distilled water before freezing lost monovalent ions (Na, Cl, and K), but the membrane-bound Ca and cellular Mg were not reduced, indicating that cellular Mg and membrane Ca are more tightly bound.

Calcium↗
PubMed1986

Milk progesterone enzyme immunoassay: modifications and a field trial for pregnancy detection in dairy cows.

A milk progesterone enzyme immunoassay was modified to shorten the antibody:antigen incubation time and tested in a field trial. Coupling the antibody to paper fibers at pH 7 increased the binding activity of the paper-antibody conjugate to allow incubation for 3 h at room temperature with no significant loss of competitive binding of progesterone. The relationship between progesterone concentrations measured by the modified and original enzyme immunoassays was r = .94 (n = 80 pairs). Milk samples (n = 67) collected 21 d after artificial insemination were classified by the original and modified methods as being from pregnant or nonpregnant cows using both spectrophotometric and visual evaluations. Comparison to subsequent rectal palpation or return to estrus showed that the two methods were comparable. A field trial was conducted involving 622 cows and 40 producers using the modified enzyme immunoassay method. The overall field trial accuracy of the enzyme immunoassay in diagnosing the cow's reproductive status for a single sample on d 21 after breeding was 71% for correct diagnosis of pregnancy and 81% for correct diagnosis of nonpregnancy. It was concluded that the modified method is a valuable technique for rapid monitoring of milk progesterone concentrations.

Animals↗
PubMed1986

Competitive conditions and hospital strategies: a Memphis case study.

The authors explore the strategies Memphis hospitals employ to compete in a market dominated by a few large competitors. Several key strategies are identified, including horizontal integration, product diversification, product specialization, resource-based quality improvement, institutional differentiation, and public relations and physician-centered marketing. Several forces that have caused health care delivery to become more competitive are identified and discussed. The argument is made that these forces were responsible for an altering of the assumptions on which strategies were based in the Memphis market. Evidence is presented to show that the strategies were both widened in scope and refocused to encompass a larger number of market segments. The authors conclude with an analysis of the implications of these changes.

Economic Competition↗
PubMed1985

Projected structure of the pore-forming OmpC protein from Escherichia coli outer membrane.

A single-projection structure analysis of a bacterial outer membrane protein, OmpC, has been carried out by electron microscopy of frozen hydrated specimens. Two distinct crystal polymorphs have been observed in the frozen-hydrated samples, and projection structures of both forms have been obtained to a resolution of 13.5 A. Preliminary examination of negatively stained samples revealed the expected, trimeric appearance of pores in the OmpC specimens. Electron microscopy of unstained, frozen-hydrated OmpC reveals the trimeric pore structure with equal clarity. In addition, the overall molecular envelope of the protein is readily discerned, and a major lipid-containing domain can also be seen. Because of the small coherent patch size, mosaic disorder, and unpredictable polymorphism of the presently available specimens, three-dimensional reconstruction of frozen-hydrated OmpC has not been carried out.

Bacterial Outer Membrane Proteins↗
PubMed1983

Development of a direct enzyme immunoassay of milk progesterone and its application to pregnancy diagnosis in cows.

The purposes of this study were to develop an enzyme immunoassay (EIA) for determination of progesterone in unextracted whole milk and to apply it to pregnancy diagnosis. Paper fibers covalently coupled to antibody specifically and competitively bound 3H-progesterone and 11 alpha-hydroxyprogesterone hemisuccinate-horseradish peroxidase and were stable for 9 mo at -20 degrees C. The sensitivity, recovery, precision, and cross reactivity of the EIA and a radioimmunoassay (RIA) of milk progesterone were evaluated, and showed that this EIA was comparable to the RIA. Milk samples were collected once daily for one estrous cycle from ten lactating Holstein cows and the progesterone levels were determined by RIA. Milk progesterone in 70 samples measured by EIA were highly correlated (r = 0.90) with the values of RIA for the same samples. Milk samples for pregnancy diagnosis by EIA of milk progesterone were obtained daily from days 20 to 24 after 115 artificial inseminations of 85 lactating Holstein cows. Pregnancy diagnosis by EIA was confirmed by rectal palpation at 30 to 60 days after insemination or return to estrus. The accuracy based on single, two, three, four, and five consecutive samples was from 67.2 to 80.0%, 77.3 to 84.0%, 79.2 to 87.5%, 82.0 to 85.4%, and 85.4%, respectively, for pregnancy diagnosis; and from 95.0 to 98.3% for nonpregnancy.

Animals↗
PubMed1983

Quantitative evaluation of high-resolution features in images of negatively stained Tobacco Mosaic Virus.

This study investigates the causes of the apparent differences between the optical diffraction pattern of a micrograph of a Tobacco Mosaic Virus (TMV) particle, the optical diffraction pattern of a ten-fold photographically averaged image, and the computed diffraction pattern of the original micrograph. Peak intensities along the layer lines in the transform of the averaged image appear to be quite unlike those in the diffraction pattern of the original micrograph, and the diffraction intensities for the averaged image extend to unexpectedly high resolution. A carefully controlled, quantitative comparison reveals, however, that the optical diffraction pattern of the original micrograph and that of the ten-fold averaged image are essentially equivalent. Using computer-based image processing, we discovered that the peak intensities on the 6th layer line have values very similar in magnitude to the neighboring noise, in contrast to what was expected from the optical diffraction pattern of the original micrograph. This discrepancy was resolved by recording a series of optical diffraction patterns when the original micrograph was immersed in oil. These patterns revealed the presence of a substantial phase grating effect, which exaggerated the peak intensities on the 6th layer line, causing an erroneous impression that the high resolution features possessed a good signal-to-noise ratio. This study thus reveals some pitfalls and misleading results that can be encountered when using optical diffraction patterns to evaluate image quality.

Computers↗
PubMed1983

Cryptosporidiosis in domestic birds.

From March to June 1982, three cases of avian cryptosporidiosis were encountered in chickens, ducklings, and canaries. The bursa of Fabricius of chickens and ducklings were the main target organs and the agents were found to attach the microvillus border of the plical epithelium. In canaries, the parasites adhered to the microvillus border of mucosal epithelium of the proventriculus. Diagnoses were based on the microscopic pathology, the morphology of the parasites, and the type of attachment to epithelium. This represents the first authenticated evidence of cryptosporidial infection in Taiwan.

Animals↗
PubMed1982

Experimental aflatoxicosis in young Japanese quail.

Japanese quail from the university colony fed graded levels of dietary aflatoxin (0, 1.25, 2.5, 5.0, 10.0, and 20.0 micrograms/g) from hatching to 4 weeks of age were comparatively resistant to aflatoxin as growth inhibition occurred at a dose of 5.0 micrograms/g or more as about 50% mortality occurred at a dose of 20 micrograms/g. The acute oral LD50 was 19.5 +/- 4.8 mg/kg. These values are up to ten times those reported in the literature for other quail. The most sensitive indicators of aflatoxicosis were depressed serum proteins and serum carotenoids and enlarged liver and pancreas, all of which occurred at 1.25 micrograms/g, the smallest dose administered. Unlike chickens, the serum lipids, liver lipids, hemoglobin, serum uric acid, and spleen size of quail were not affected significantly (P less than .05). The sizes of the proventriculus and gizzard were increased by doses of 5.0 micrograms/g or higher, whereas the bursa of Fabricius was regressed by the same dose.

Administration, Oral↗
PubMed1982

Increased severity and new symptoms of infectious bursal disease during aflatoxicosis in broiler chickens.

A factorial design for the presence and absence of infection with a mild strain of infectious bursal disease (IBD) virus and graded levels of dietary aflatoxin (0, .625, 1.25, 2.5, 5.0, and 10.0 microgram/g of diet) in young broiler chickens revealed several interactions which greatly changed and character of the IBD infection. An infection that was essentially free of mortality became lethal to about half the birds. A coagulopathy as indicated by prolonged prothrombin times and by the occurrence of slight hemorrhages in skeletal muscles, a hypoproteinemia, a hypocalcemia, and a markedly enlarged kidney were observed in combined aflatoxicosis and IBD, but not in IBD alone. The size of the bursa of Fabricius following an initial hypertrophy was atrophied 4 days after inoculation and the spleen was enlarged. The effects of aflatoxin and IBD on these two glands were additive. Packed blood cell volume and hemoglobin values were decreased by aflatoxin only. Thus, aflatoxin had the effects of making IBD a much more severe disease and of changing the symptoms.

Aflatoxins↗