Search PubMed⌕ Search

Biomedical subjects

L C Yuan

Publications and source records attributed to L C Yuan.

29 records · Page 2Linked to original sources
PubMed1982

Identification of mammalian sperm surface antigens: II. Characterization of an acrosomal cap protein and a tail protein using monoclonal anti-mouse sperm antibodies.

Monoclonal anti-mouse sperm antibodies have been produced by fusing mouse myeloma cells with spleen cells from rats immunized with epididymal sperm of C3H mice, Immunoprecipitation and immunoperoxidase techniques showed that one such monoclonal antibody, AMS IV-33, recognized a 200 000 dalton protein localized on the acrosomal cap of the sperm cell. Two other monoclonal antibodies AMS IV-54 and -76, reacted with a 68 000 dalton component on the surface of the sperm tail. Both antigenic targets were species specific and were present in about equal amounts on sperm from several different strains of mice. The tail protein was sperm specific, whereas the antibody reacting with the acrosomal cap protein also appeared to react somewhat with antigens present in other mouse tissues.

Acrosome↗
PubMed1982

Identification of mammalian sperm surface antigens. I. Production of monoclonal anti-mouse sperm antibodies.

Surface antigens of mammalian sperm were studied by use of monoclonal antibodies (MAs). Six hybridoma cell lines were obtained by fusion of mouse myeloma cells with spleen cells from rats immunized with unwashed, epididymal sperm from C3H mice. Quantitative assessment of antibody binding, using a solid phase, antibody-protein A assay, indicated that four MAs bound to integral, sperm surface antigens; two others bound to nonintegral sperm antigens or epididymal fluid components. Immunofluorescence studies showed specific binding of individual MAs to localized regions: acrosome, midpiece, and midpiece and tail. All of these MAs inhibited sperm-egg binding, and those to the midpiece and/or tail immobilized sperm cells. The monoclonal antibodies provide probes for immunochemical characterization of sperm antigens and for elucidation of the role of the antigens in sperm.

Animals↗
PubMed1981

An improved method for processing single cells for electron microscopy utilizing agarose.

An improved method is presented for processing single cells for electron microscopy. Agarose, which has a low (30 degrees C) gelling temperature, was used as an initial embedding medium for single cells (spermatozoa and oocytes) and dissociated cell preparations (luteal cells and spleen cells). Dispersed cells of corpus luteum, spleen, and epididymal spermatozoa were placed in 1.5% agarose after aldehyde fixation. These fixed cells, embedded in agarose, were packed into a dense pellet by centrifugation, postfixed, then embedded in Epon. Mammalian eggs were not centrifuged; instead, they were embedded in agarose discs. Cells embedded in agarose were cooled below 30 degrees C to allow for gelling, then processed for electron microscopy. Because agarose has a low gelling temperature, some heat-labile substances were preserved, as demonstrated by retention of peroxidase activity using the DAB histochemical method. The agarose embedding procedure is both rapid and facile, and has proven to be of value in the handling of fragile single cells for electron microscopic studies.

Animals↗
PubMed1980

Progesterone production by dispersed monkey (Macaca mulatta) luteal cells after exposure to trypsin.

In an attempt to justify use of trypsin to achieve more thorough dispersion of luteal cell clumps in vitro, progesterone (P) production by collagenase dispersed monkey luteal cells from the mid-luteal phase corpus luteum (CL) was examined in vitro either after 10 min, or continuous (3h) exposure to trypsin (TR). In the first experiment, cells were pre-incubated in TR, then incubated at 37 degrees C for 3h with human chorionic gonadotropin (hCG) after the addition of soybean-trypsin inhibitor (STI). Pre-incubation of luteal cells with TR had no effect on the level of P production under basal conditions. Cells that were preincubated with TR responded to hCG stimulation with increased progesterone secretion (P less than 0.01) in a fashion similar to untreated cells. P production in response to hCG was independent of TR concentration over the range of 0.05% to 0.2% during the pre-incubation period. However, continuous exposure (3h) of cells to TR significantly depressed (P less than 0.01) basal P secretion and inhibited the response to hCG. We conclude that TR had no effect on the biopotency of hCG per se, but probably the over-exposure to TR had an adverse effect on the LH/hCG receptors. Addition of STI after a 10 min pre-incubation with TR, prevented these deliterious effects, thereby permitting the use of TR to improve the completeness of luteal cell dissociation.

Animals↗
PubMed1977

Association of microperoxisomes with the endoplasmic reticulum in the granulosa lutein cells of the Rhesus monkey (Macaca mulatta).

Aldehyde fixed tissue from monkey (Macaca mulatta) corpus luteum was incubated in alkaline 3,3inch-diaminobenzidine (DAB), and prepared for electron microscopic histochemical observations. The association of microperoxisomes with the granular (GER) or agranular (AER) endoplasmic reticulum was reconstructed from serially sectioned tissues and by tilting of specimens in the microscope. Out of 107 microperoxisomes, 106 were directly associated with the AER. Two different forms of attachment were found between microperoxisomes and the AER and that of the microperoxisome are confluent. In the second, lingulate type of connection, a blunt-end structure either is inserted into an invagination of the AER, or penetrates into the lumen of the AER. The lumen of the lingula is confluent with the microperoxisome, but not with the AER. In addition to these connections, fine thread-like structures were observed extending between AER and adjacent microperoxisomes.

Animals↗
PubMed1975

Microperoxisomes in the late pregnancy corpus luteum of rhesus monkeys (Macaca mulatta).

Microperoxisomes were identified in the franulosa lutein cells from the corpora lutea of rhesus monkeys (Macaca mulatta). These organelles were histochemically visualized in aldehyde-fixed tissues icubated in alkaline 3,3'-diaminobenzidine (DAB). The DAB staining of the microperoxisomes was abolished when the tissues were preincubated in specific inhibitors for catalse or when the H2O2 was omitted from the DAB medium. Microperoxisomes were differentiated from primary lysosmes by the Gomori acid phosphatase staining. Tortuous undulating agranular endoplasmic reticulum (ER) was usually closely associated with microperoxisomes. Those regions of the granular ER which were closely associated with microperoxosomes lacked ribsomes. Micropersoxisomes were often contiguous with lipid droplets, and in some instances the limiting membrane of the moroperosisomes appeared discontinous at the point of contiguity, and the DAB staining substance diffused onto the surface of the lipid droplet. In these instances, the adjacent area of the lipid droplet showed electron-lucent staining.

3,3'-Diaminobenzidine↗
PubMedDate not supplied

Kinetic studies of the degradation of oxycarbonyloxymethyl prodrug of Adefovir and Tenofovir in solution.

The decomposition kinetics of bis-POC PMEA and bis-POC PMPA followed pseudo-first order kinetics with the corresponding mono-POC ester detected as the only observable degradation product for all the pH values studied. The rates of hydrolysis of bis-POC PMEA over the pH range studied was described by [formula: see text] The 18O incorporation studies revealed that hydrolysis of bis-POC PMEA at pH 7.0 primarily proceeds via P-O cleavage with an additional minor pathway involving C-O bond cleavage. Hydrolysis of bis-POC PMPA was found to be about 2 fold slower than bis-POC PMEA at pH values above 6.0.

Adenine↗
PubMedDate not supplied

Characterization of metal-ion-nucleotide based particulate matter in solutions of 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA).

The antiviral drug 9-[2-(phosphonomethoxy)ethyl]adenine, PMEA, was developed as an intravenous product for the treatment of human immunodeficiency virus infection. During the course of stability monitoring, PMEA i.v. injection was found to undergo particulate matter formation under extended storage at ambient temperature. Isolation and characterization of the particulates revealed them to be metal ion-PMEA complexes. The principle metal ions associated with the particulates were iron and zinc, present as trace impurities (< or = 40 ppm) in PMEA drug substance determined by inductively coupled argon plasma spectroscopy. These visible particles are characterized by energy-dispersive x-ray spectrometry and fourier transform infrared spectroscopy. This study describes the systematic evaluation of the observed solution phenomena and details alternative formulation systems to eliminate particulate formation in the PMEA injectable product.

Adenine↗