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W Yuan

Publications and source records attributed to W Yuan.

At least 127 records · Page 7Linked to original sources
PubMed1997

Characterization of Organofunctional Silane Films on Zinc Substrates

Organofunctional silane films formed on pure zinc substrates from aqueous solutions were characterized by ellipsometry, contact angle measurements, reflection absorption infrared spectroscopy (RAIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The silanes studied were gamma-aminopropyltriethoxysilane (gamma-APS) and gamma-ureidopropyltrialkoxysilane (gamma-UPS). The deposition parameters included solution concentration, solution dipping time, and pH value of the applied solution. Effects of these deposition variables on the thickness of the film, the surface energy of the film, the chemical structure of the film, and the surface topography of the film are discussed. The effect of film aging time on the surface energy of silane-coated pure zinc substrates was also studied. It was found that the silane film thickness obtained depends primarily on the applied solution concentration and is independent of the solution dipping time. The molecular orientations of the applied silane film are determined by the pH value of the applied silane solution and the isoelectric point of the metal substrates. The deposition window in terms of pH value for zinc substrates was between 6 and 9. The total surface energy of silane-coated pure zinc substrate decreases steeply with film aging time for gamma-APS but not for gamma-UPS. The stability of both silane films improved after aging in the air.

Journal Article↗
PubMed1997

mefE is necessary for the erythromycin-resistant M phenotype in Streptococcus pneumoniae.

Recently, it was shown that a significant number of erythromycin-resistant Streptococcus pneumoniae and Streptococcus pyogenes strains contain a determinant that mediates resistance via a putative efflux pump. The gene encoding the erythromycin-resistant determinant was cloned and sequenced from three strains of S. pneumoniae bearing the M phenotype (macrolide resistant but clindamycin and streptogramin B susceptible). The DNA sequences of mefE were nearly identical, with only 2-nucleotide differences between genes from any two strains. When the mefE sequences were compared to the mefA sequence from S. pyogenes, the two genes were found to be closely related (90% identity). Strains of S. pneumoniae were constructed to confirm that mefE is necessary to confer erythromycin resistance and to explore the substrate specificity of the pump; no substrates other than 14- and 15-membered macrolides were identified.

Anti-Bacterial Agents↗
PubMed1997

Cloning and characterization of a novel macrolide efflux gene, mreA, from Streptococcus agalactiae.

A strain of Streptococcus agalactiae displayed resistance to 14-, 15-, and 16-membered macrolides. In PCR assays, total genomic DNA from this strain contained neither erm nor mef genes. EcoRI-digested genomic DNA from this strain was cloned into lambda Zap II to construct a library of S. agalactiae genomic DNA. A clone, pAES63, expressing resistance to erythromycin, azithromycin, and spiramycin in Escherichia coli was recovered. Deletion derivatives of pAES63 which defined a functional region on this clone that encoded resistance to 14- and 15-membered, but not 16-membered, macrolides were produced. Studies that determined the levels of incorporation of radiolabelled erythromycin into E. coli were consistent with the presence of a macrolide efflux determinant. This putative efflux determinant was distinct from the recently described Mef pump in Streptococcus pyogenes and Streptococcus pneumoniae and from the multicomponent MsrA pump in Staphylococcus aureus and coagulase-negative staphylococci. Its gene has been designated mreA (for macrolide resistance efflux).

Amino Acid Sequence↗
PubMed1997

Cardiac myocyte volume, Ca2+ fluxes, and sarcoplasmic reticulum loading in pressure-overload hypertrophy.

Alterations in cellular Ca2+ transport and excitation-contraction coupling may contribute to dysfunction in cardiac hypertrophy. Left ventricular myocytes were isolated from rat hearts after 15-18 wk of suprarenal abdominal aortic banding to evaluate the hypothesis that hypertrophy alters the relationship between Ca2+ current (ICa) and sarcoplasmic reticulum (SR) Ca2+ load during steady-state voltage-clamp depolarization. Mean arterial pressure (MAP) and heart weight-to-body weight ratio of banded (B) animals were significantly higher than in control or sham-operated animals (C). Isolated myocyte dimensions and volume increased in parallel with whole heart hypertrophy and elevation in MAP. However, the relationship between membrane surface area (measured by capacitance) and cell volume (measured by laser scanning confocal microscopy) was unaltered (C: 8.9 +/- 0.3; B: 8.5 +/- 0.4 pF/pl). No differences in the voltage dependence of ICa activation, steady-state inactivation, or recovery from inactivation were detected between C and B myocytes. Maximal ICa density for the two groups was also not different either under basal conditions (C: 4.28 +/- 0.98; B: 4.57 +/- 0.60 pA/pF) or in the presence of 1 microM isoproterenol (C: 16.6 +/- 2.3; B: 16.5 +/- 2.3 pA/pF). The fraction of Ca2+ released from the SR by a single twitch was 55.4 +/- 9.4% in C and 37.1 +/- 6.9% in B (not significantly different). Steady-state Ca2+ influx during a twitch was calculated in units of micromoles per liter of nonmitochondrial volume from the integral of ICa (C: 13.4 +/- 0.7 microM; B: 13.3 +/- 0.8 microM). The SR Ca2+ load was similarly calculated by integration of Na+/Ca2+ exchange current induced by rapid caffeine application (C: 140 +/- 9 microM; B: 169 +/- 18 microM). We conclude that significant cellular hypertrophy is associated with proportional increases in sarcolemmal ICa influx, SR Ca2+ loading, and the amount of SR Ca2+ released in this model of pressure overload.

Animals↗
PubMed1997

Programmed cell death in human ovary is a function of follicle and corpus luteum status.

Although extensive investigation on follicular apoptosis (programmed cell death) has been conducted in the infraprimate ovary, there is little information regarding apoptosis and its relationship to follicular status in the human. In this study, apoptosis was investigated in 116 human ovarian follicles (primordial to dominant) and 5 corpora lutea from a total of 27 premenopausal women. Follicles and corpora lutea were evaluated for the presence of DNA fragmentation, characteristic of apoptosis, by two methods: in situ hybridization using 3' end-labeling of DNA with digoxigenin-labeled nucleotides and subsequent digoxigenin antibody and peroxidase staining, and/or biochemical analysis of low molecular weight DNA laddering. Follicle functional status was evaluated by determining follicle sizes and follicular fluid androgen/estrogen (A/E) ratios. No apoptosis was observed in 67 primordial, primary, or secondary follicles. Positive staining for DNA fragmentation was found in a few granulosa cells in 0.1- to 2-mm follicles, whereas abundant staining in granulosa was detected in 2.1- to 9.9-mm follicles. In contrast, no DNA fragmentation was detected in dominant follicles (10-16 mm). The frequency of apoptosis in follicles was calculated to be 37% in 0.1- to 2-mm follicles, 50% in 2.1- to 5-mm follicles, and 27% in 5.1- to 9.9-mm follicles. Abundant low molecular weight DNA laddering was only found in androgen-dominant follicles and not in estrogen-dominant follicles. Positive staining for DNA fragmentation and low molecular weight DNA laddering were observed in degenerating but not healthy-appearing corpora lutea. In the former, DNA fragmentation was found primarily in large luteal cells. These data suggest that follicular atresia in human ovary results from normal programmed cell death and primarily occurs in the granulosa cell layers of the early antral and < 10-mm antral follicles primarily. Furthermore, because apoptosis occurs as early as the 200-mm stage, follicle selection may begin as early as the initial formation of the antrum. The results also suggest that degeneration of the corpus luteum occurs by apoptotic mechanisms.

Adult↗
PubMed1997

Glucose-induced microautophagy in Pichia pastoris requires the alpha-subunit of phosphofructokinase.

We have characterized biochemically, morphologically, and genetically two distinct pathways for the selective degradation of peroxisomes in Pichia pastoris. These pathways are independently regulated and analogous to microautophagy and macroautophagy that have been defined in mammalian cells. When P. pastoris is grown in methanol, cytosolic and peroxisomal enzymes necessary for methanol assimilation are synthesized. During adaptation from methanol to glucose, these enzymes are rapidly and selectively degraded within the yeast vacuole by microautophagy. We have isolated gsa mutants that are defective in glucose-induced selective autophagy of peroxisomes. In this study, we have shown that gsa1 is unable to sequester peroxisomes into the yeast vacuole. In addition, we provide evidence that the glucose-induced selective autophagy 1 (GSA1) protein is the alpha subunit of the phosphofructokinase enzyme complex encoded by PFK1. First, we can rescue the gsa1 mutant by transformation with a vector containing PFK1. Second, cellular levels of both PFK1 mRNA and phosphofructokinase activity are dramatically reduced in gsa1 when compared to the parental GS115. Third, a PFK1 knockout (delta pfk1) is unable to degrade alcohol oxidase during glucose adaptation. As observed in gsa1, the peroxisomes in delta pfk1 remain outside the vacuole during adaptation. Our data are consistent with the concept that PFK1 protein is required for an event upstream of vacuole degradation (i.e. signaling, selection, or sequestration). However, the degradation of peroxisomes does not require a catalytically active phosphofructokinase. The inability of delta pfk1 cells to degrade alcohol oxidase can be rescued by transformation with either normal PFK1 or mutant pfk1 whose catalytic site had been inactivated by a single amino acid mutation. We propose that PFK1 protein directly modulates glucose-induced microautophagy independent of its ability to metabolize glucose intermediates.

Amino Acid Sequence↗
PubMed1997

Progesterone production in vitro by mouse luteal cells: response to follicle-stimulating hormone, luteinizing hormone, and prolactin.

The purpose of this study was to determine the effects of ovine follicle-stimulating hormone (FSH), luteinizing hormone (LH); prolactin, and recombinant FSH and a protein kinase C activator (phorbol 12-myristate 13-acetate [PMA]) on progesterone production by dispersed luteal cells (large + small) from Day 4 pregnant mice. Corpora lutea (CL) were collected on Day 4 of pregnancy (Day 1 = sperm positive smear), and dispersed luteal cells were isolated using collagenase. After overnight incubation, the luteal cells were incubated with or without FSH, LH, prolactin, or recombinant human FSH or PMA for 4 hr or an additional 24 hr at 37 degrees C; media were collected and progesterone was determined by RIA. Ten nanograms and 100 ng of ovine FSH, LH and prolactin were all equally effective in stimulating progesterone synthesis in media recovered after 24 hr of incubation. Moreover, the combination of all three gonadotropins yielded maximum levels of progesterone indicating a luteotrophic complex in vitro, paralleling previous in vivo findings. Recombinant human FSH-devoid of LH contamination-at doses of 10 and 100 ng also significantly stimulated progesterone synthesis, which strongly suggests that FSH has luteotropic activity in the mouse, thus agreeing with our previous in vitro results with CL of the pregnant hamster and rat. One hundred nanomolar PMA by itself did not affect progesterone production but significantly decreased dibutyrl cAMP-, forskolin-, FSH-, and LH-induced progesterone production, suggesting that activation of protein kinase C may block the luteotropic effects of LH and FSH during murine pregnancy.

Animals↗
PubMed1997

Protein kinase C activity and its effect on progesterone production by large and small porcine luteal cells.

Protein kinase C (PKC) activity and its effect on progesterone production were investigated using porcine large and small luteal cells (LLC and SLC). Corpora lutea (CL) were surgically collected from pigs on Day 10 of the estrous cycle (Day 0 = onset of standing estrus). Luteal cells were dissociated by collagenase; LLC and SLC were further separated on a discontinuous Ficoll gradient. In a dose-response experiment with phorbol 12-myristate 13-acetate (PMA, a stimulator of PKC), progesterone production was not affected by 0.01 and 0.1 microM PMA, but was stimulated by 1 microM PMA. In a time series experiment, progesterone secretion was increased by 1 and 10 microM PMA in LLC by 60-150 min, and by 1 microM PMA in SLC during 120 and 150 min of incubation. However, 4 alpha-phorbol ester did not affect progesterone synthesis. H-7, a PKC inhibitor, blocked PMA-stimulated progesterone secretion by LLC during 3 hr of incubation. Of the PKC activators tested at 10 microM, PMA significantly stimulated cytosolic PKC activity over that of natural PKC activators in both LLC and SLC, whereas 4 alpha-phorbol ester did not affect PKC activity. H-7 inhibited PMA-stimulated PKC activity. PS (1-phosphatidyl-L-serine) + CA+2 and PS+DG (1,2-dioleoyl-sn-glycerol) + Ca+2 stimulated PKC activity. The results demonstrate that activation of PKC can increase progesterone secretion by porcine luteal cells from Day 10 of the estrous cycle and suggest PKC can have multiple effects in regulating luteal function.

Animals↗
PubMed1997

[Antagonistic effect of calcitonin gene related peptide on arrhythmia in rats].

Premature ventricular contraction (PVC), ventricular tachycardia (VT) and ventricular fibrillation (VF) were developed by endothelin-1 (ET-1) injected into the coronary ostia at the dose of 900 pmol/kg in anesthetized rats. No arrhythmia was elicited but blood pressure fell temporarily by calcitonin gene related peptide (CGRP), the injection into the coronary ostia. After pretreatment with CGRP incidence and severity of arrhythmia decreased at the same ET-1 dose. Arrhythmia score in CGRP 1200 pmol/kg + ET-1 group was lower than that in ET-1 group (P < 0.01). The results revealed that antiarrhythmic effect of CGRP may be partially brought about by its antagonistic effect against ET-1 induced arrhythmia.

Animals↗
PubMed1997

[Expression of IL-4 and IL-10 by PBMC and tumor tissues in cancer patients].

Using biological activity assay, the production of IL-4 and IL-10 by peripheral blood mononuclear cells (PBMC) was studied in patients with nasopharyngeal carcinoma and lymphoma. The IL-2, IL-4 and IFN gamma levels in both cancer patients were lower than that in normal subjects. In contrast, the IL-10 level was higher in both cancer patients. When rIL-2 was added into the cytokine production system, IL-2, IL-4, and IFN gamma level were upregulated in lymphoma patients. However, in the patients of nasopharyneal carcinoma, only IL-2 level was upregulated. IL-10 activity could not be affected by exogenous IL-2 in both cancer patients. The results of negative IL-4 activity and higher positive percentage (84.6%) of IL-10 activity in ascites from patients with ovarian carcinoma were corresponded to the patients with nasopharyngeal carcinoma and lymphoma. By using in situ hybridization technique, the expression of IL-4 and IL-10 was studied in tumor tissues from patients with gastric, esophageal and breast carcinomas. There was no differences of the percentage of IL-4 and IL-10 expression among three kinds of tumor tissues, the range of positive percentage was 40%-70%. These results indicate that the correction of abnormal upregulation of IL-10 activity should be considered for cancer immunotherapy.

Breast Neoplasms↗
PubMed1997

Comparative study of the effects of ouabain and digoxin on blood pressure of rats.

OBJECTIVE: To compare the effect of ouabain on the blood pressure of rats with that of digoxin to find the evidences of the relationship between endogenous ouabain (EO) and development of hypertension. METHODS: Sprague-Dawley rats, which were divided into 3 groups, were infused with ouabain (23 x 75 micrograms.kg-1/day, i.p.), digoxin (36 x 84 micrograms.kg-1/day, i.p.) and normal saline (NS) once a day respectively. Systolic blood pressure and body weight were recorded weekly. Five weeks later, rats of ouabain group were randomly assigned to three infusion subgroups: Oc group, continued with ouabain infusion; Od group, added digoxin (73 x 68 micrograms.kg-1/day, i.p.) and Os group, stopped administration of ouabain. Another week later, direct blood pressure was recorded in aorta. Systolic and diastolic cardiac function, plasma renin activity and aldosterone levels of all the rats were measured. RESULTS: After a latent period of one week, blood pressure of Ouabain group increased significantly [95.4 +/- 11.8 mmHg (1 mmHg = 0.133 kPa) at the beginning of the experiment vs 122.5 +/- 16.9 mmHg at the end of week 6, P < 0.05] with normal plasma renin activity and higher aldosterone (1.28 +/- 0.45 ng/ml vs 0.69 +/- 0.27 ng/ml, P < 0.05). The blood pressure decreased after either withdrawal of ouabain or addition of digoxin (116.3 +/- 14.4 mmHg vs 100 +/- 10.7 mmHg, P < 0.05; 123.9 +/- 13.9 vs 103.3 +/- 10.5 mmHg, P < 0.05, respectively). No difference of blood pressure was found between the digoxin and NS group. CONCLUSIONS: Our results suggested that EO might be one of the causes of the development of hypertension. Aldosterone might play some role in the mechanism of ouabain-induced hypertension. Digoxin can not induce hypertension. There is a great difference between the effect of ouabain and digoxin on the blood pressure. Moreover, digoxin can reverse the hypertension induced by ouabain.

Animals↗
PubMed1996

Comparison of sarcolemmal calcium channel current in rabbit and rat ventricular myocytes.

1. Fundamental properties of Ca2+ channel currents in rat and rabbit ventricular myocytes were measured using whole cell voltage clamp. 2. In rat, as compared with rabbit myocytes, Ca2+ channel current (ICa) was half-activated at about 10 mV more negative potential, decayed slower, was half-inactivated (in steady state) at about 5 mV more positive potential, and recovered faster from inactivation. 3. These features result in a larger steady-state window current in rat, and also suggest that under comparable voltage clamp conditions, including action potential (AP) clamp, more Ca2+ influx would be expected in rat myocytes. 4. Ca2+ channel current carried by Na+ and Cs+ in the absence of divalent ions (Ins) also activated at more negative potential and decayed more slowly in rat. 5. The reversal potential for Ins was 6 mV more positive in rabbit, consistent with a larger permeability ratio (PNa/PCs) in rabbit than in rat. ICa also reversed at slightly more positive potentials in rabbit (such that PCa/PCs might also be higher). 6. Ca2+ influx was calculated by integration of ICa evoked by voltage clamp pulses (either square pulses or pulses based on recorded rabbit or rat APs). For a given clamp waveform, the Ca2+ influx was up to 25% greater in rat, as predicted from the fundamental properties of ICa and Ins. 7. However, the longer duration of the AP in rabbit myocytes compensated for the difference in influx, such that the integrated Ca2+ influx via ICa in response to the species-appropriate waveform was about twice as large as that seen in rat.

Action Potentials↗
PubMed1996

Human p300 protein is a coactivator for the transcription factor MyoD.

Human p300 protein is a cellular target of adenoviral E1A oncoprotein and a potential transcriptional coactivator. Both p300 and Rb family protein-binding regions of E1A are required for the repression of muscle gene expression, which is regulated by MyoD family transactivators. This implies that p300 is involved in MyoD-dependent transactivation. We show that the repression of MyoD-mediated E box (MyoD consensus) reporter activity by E1A is correlated with its interaction with p300, indicating that p300 participates in MyoD-dependent transactivation. In addition, p300 is able to interact both in vivo and in vitro with MyoD through a portion at the carboxyl-terminal cysteine/histidine-rich domain and associates with the components of the basal transcriptional complex through its two separate transactivation domains at the amino and carboxyl termini. Consistent with its role as a coactivator, p300 potentiates MyoD-activated transcription.

Cysteine↗
PubMed1996

Messenger ribonucleic acid expression for growth hormone receptor, luteinizing hormone receptor, and steroidogenic enzymes during the estrous cycle and pregnancy in porcine and bovine corpora lutea.

Growth hormone (GH) and luteinizing hormone (LH) are pituitary hormones involved in steroidogenesis in the corpus luteum (CL). The objectives of Experiment I were to determine mRNA expression for GH receptor (GHR) and LH receptor (LHR) in porcine luteal tissues during the estrous cycle and pregnancy and to relate changes in these receptor mRNA with changes in steroidogenic enzyme mRNA for cytochrome P450 side-chain cleavage enzyme (P450sec) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). Ovaries were collected from gilts during the estrous cycle (day 10 [n = 3] and Day 19 [n = 3, regressed CL) and pregnancy (Day 25 [n = 3] and Day 44 [n = 3]). Tissues were frozen in liquid nitrogen and sectioned. Messenger RNA was detected by in situ hybridization, and relative mRNA amounts were determined by image analysis. The mRNA for GHR, LHR, P450sec, and 3 beta-HSD were detected in the CL on Day 10 of the estrous cycle. None of these mRNA were specific to cither large luteal cells (LLC) or small luteal cells (SLC). On Day 19 of the estrous cycle (regressed CL), mRNA for GHR, P450sec, and 3 beta-HSD were decreased (P < 0.01) whereas LHR mRNA disappeared (P < 0.01). During pregnancy, mRNA expression increased 2.1-, 1.4-, 1.4-, and 1.2-fold for GHR, LHR, P450sec, and 3 beta-HSD, respectively (P < 0.05). The luteal location of GHR mRNA in the pig did not agree with that found in our previous studies of GHR mRNA or protein in cattle. Therefore, the objective of Experiment 2 was to measure GHR mRNA by the use of in situ hybridization in bovine CL during the estrous cycle (Day 14; n = 2) and pregnancy (Day 25; n = 2). In situ hybridization demonstrated specific expression of GHR mRNA in the LLC of cattle. Furthermore, GHR mRNA increased 1.8-fold in CL on Day 25 of pregnancy compared with GHR mRNA on Day 14 of the estrous cycle (P < 0.01). In adjacent sections, the LHR mRNA was most highly expressed in clusters of SLC with 1.6-fold more mRNA on Day 25 of pregnancy compared with Day 14 of the estrous cycle (P < 0.01). These results suggest that: 1) mRNA for LHR, GHR, P450sec, and 3 beta-HSD are differentially regulated during the estrous cycle and pregnancy and 2) the cellular location of GHR differs for pigs and cattle, with highly specific expression of GHR in bovine LLC but not porcine LLC. This may suggest different functions for GH in the CL of these species.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Oral alendronate induces progressive increases in bone mass of the spine, hip, and total body over 3 years in postmenopausal women with osteoporosis.

To determine the effects of long-term daily oral alendronate sodium (ALN) on bone mass in postmenopausal women with osteoporosis, 19 centers enrolled 516 postmenopausal women aged 45-80 years with spine bone mineral density (BMD) at least 2.5 SD below the mean for young premenopausal women in a 3-year, double-blind, placebo-controlled study. Subjects were randomly allocated to one of four treatment groups: placebo; alendronate, 5 or 10 mg/day for 3 years; or alendronate, 20 mg/day for 2 years followed by 5 mg/day for the 3rd year. All patients received 500 mg/day of supplemental calcium to ensure adequate calcium intake. BMD was measured by dual-energy X-ray absorptiometry at several skeletal sites. Nonsignificant mean decreases in BMD of the spine, femoral neck, and trochanter of 0.6, 0.7, and 0.4%, respectively, occurred in the placebo group at 3 years. Relative to placebo-treated patients, spine BMD increased by 5.4%, 7.4%, and 8.4% in the 5, 10, and 20/5 mg ALN groups, respectively. Increases at the femoral neck were 3.5%, 5.5%, and 4.3%, and those at the trochanter were 5.1%, 7.2%, and 7.2%, respectively. Thus, efficacy of 10 and 20/5 mg ALN was similar, whereas the 5 mg dose was less effective. BMD continued to increase over the entire 3-year study duration in the ALN-treated groups and, compared with the other dosage groups, 10 mg ALN produced the largest gains in BMD during the 3rd year. Changes in biochemical markers of bone turnover and mineral homeostasis confirmed the effect of ALN to decrease bone turnover to a new steady-state level. The safety and tolerability of ALN were comparable with those of placebo. In summary, 10 mg daily oral ALN given for 3 years significantly and progressively increases bone mass and is a generally well-tolerated treatment for osteoporosis in postmenopausal women.

Administration, Oral↗
PubMed1996

Molecular cloning and functional analysis of a novel macrolide-resistance determinant, mefA, from Streptococcus pyogenes.

Several streptococcal strains had an uncharacterized mechanism of macrolide resistance that differed from those that had been reported previously in the literature. This novel mechanism conveyed resistance to 14- and 15-membered macrolides, but not to 16-membered macrolides, lincosamides or analogues of streptogramin B. The gene encoding this phenotype was cloned by standard methods from total genomic digests of Streptococcus pyogenes 02C1064 as a 4.7 kb heterologous insert into the low-copy vector, pACYC177, and expressed in several Escherichia coli K-12 strains. The location of the macrolide-resistance determinant was established by functional analysis of deletion derivatives and sequencing. A search for homologues in the genetic databases confirmed that the gene is a novel one with homology to membrane-associated pump proteins. The macrolide-resistance coding sequence was subcloned into a pET23a vector and expressed from the inducible T7 promoter on the plasmid in E. coli BL21(DE3). Physiological studies of the cloned determinant, which has been named mefA for macrolide efflux, provide evidence for its mechanism of action in host bacteria. E.coli strains containing the cloned determinant maintain lower levels of intracellular erythromycin when this compound is added to the external medium than isogenic clones without mefA. Furthermore, intracellular accumulation of [14C]-erythromycin in the original S. pyogenes strain was always lower than that observed in erythromycin-sensitive strains. This is consistent with a hypothesis that the gene encodes a novel antiporter function which pumps erythromycin out of the cell. The gene appears to be widely distributed in S. pyogenes strains, as demonstrated by primer-specific synthesis using the polymerase chain reaction.

Bacterial Proteins↗
PubMed1996

Messenger ribonucleic acid for insulin-like growth factors-I and -II, insulin-like growth factor-binding protein-2, gonadotropin receptors, and steroidogenic enzymes in porcine follicles.

Several aspects of growth, development, and steroidogenesis in ovarian follicles are controlled by the interaction of insulin-like growth factors (IGF-I and IGF-II) and gonadotropins (LH and FSH). The objective of this study was to determine the developmental stage and location at which mRNA for IGF, IGF-binding protein (IGFBP)-2, gonadotropin receptors, and steroidogenic enzyme genes are expressed within porcine follicles. Ovaries from pigs on Days 10 (n = 3; midluteal phase) and 19 (n = 3; preovulatory phase) of the estrous cycle were collected, frozen, and sectioned. The mRNA for IGF-I, IGF-II, IGFBP-2, LH receptor, FSH receptor, cytochrome P450 side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17 alpha-hydroxylase (P45017 alpha), and aromatase (P450arom) were detected by in situ hybridization, and relative amounts were determined by image analysis. Expression of mRNA for IGF-I and IGF-II was cell specific (granulosa and theca interna cells, respectively) and increased with follicular size. The IGFBP-2 mRNA was expressed in greater amounts for theca interna cells than for granulosa cells. The pattern of expression for LH and FSH receptors diverged as follicles grew. For LH receptor, mRNA was detected in the theca interna cells of small antral follicles and in both the theca interna and granulosa cells of large antral follicles. Amount of LH receptor mRNA increased with follicular diameter. For FSH receptor, mRNA increased as follicles grew to a small antral size. However, FSH receptor mRNA disappeared in large antral follicles on Day 19 of the estrous cycle. Steroidogenic enzyme mRNA for 3 beta-HSD (theca interna cells), P450scc (theca interna cells), P45017 alpha (theca interna cells), and P450arom (granulosa cells) increased with follicular diameter. In summary, coordinated expression of IGF, IGFBP-2, gonadotropin receptors, and steroidogenic enzyme mRNA throughout different stages of follicular development was observed. Changes in mRNA suggested increased IGF-I and -II action and a switch from FSH to LH dependence in porcine preovulatory follicles.

3-Hydroxysteroid Dehydrogenases↗