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Biomedical subjects

C M Yang

Publications and source records attributed to C M Yang.

At least 19 recordsLinked to original sources
PubMed1992

Measurement of cellular proliferation within the vitreous during experimental proliferative vitreoretinopathy.

Cellular proliferation is an important component in the pathogenesis of complex retinal detachments caused by proliferative vitreoretinopathy (PVR). We used flow cytometry to measure the proliferation of cells recovered from the vitreous cavity in an experimental model of tractional retinal detachment induced by homologous fibroblast injection. Two distinct populations of cells were detected. One population comprised smaller, dense cells representing mostly leukocytes. A second population of larger cells contained not only the injected fibroblasts but also high concentrations of host-derived cells with significant proliferative activity, whose number increased for 3 days following injection. Flow cytometry was useful for analysis of the recovered cells for concentration, morphologic features and proliferation. This technique may be applicable in the identification of patients at high risk for the development of PVR.

Animals↗
PubMed1992

Semicarbazide-sensitive amine oxidase from the smooth muscles of dog aorta and trachea: activation by the MAO-A inhibitor clorgyline.

Semicarbazide-sensitive amine oxidase (SSAO) has been identified in the dog trachea and aorta smooth muscles. The dog SSAO is blocked by hydrazine inhibitors. SSAOs from several different vascular smooth muscle sources, such as the rat and bovine aorta, and human umbilical artery, as well as the bovine plasma, are insensitive to the MAO-A inhibitor clorgyline; the dog SSAO on the other hand is significantly activated by clorgyline. Two methods, i.e. radioenzymatic and fluorometric methods, have been applied to substantiate this clorgyline-induced activation. The activation was detected with respect to the deamination of different substrates, such as benzylamine, beta-phenylethylamine and longer carbon chain aliphatic amines, but not with respect to methylamine. The clorgyline effect is reversible, non-competitive and time-independent; it depends on electrostatic and hydrophobic interactions between clorgyline and hydrophobic regions of the dog SSAO enzyme.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Resistance of proline-containing peptides to ruminal degradation in vitro.

Mixed ruminal bacteria utilized an enzymatic digest of casein at a rate faster than that for an enzymatic digest of gelatin, but neither amino acid source was completely utilized even when the incubation period was as long as 96 h. Since the reaction of ninhydrin with the residual nonammonia, nonprotein nitrogen was more than twofold stronger when the samples were hydrolyzed with 6 N HCl, it appeared that much of the residual nitrogen was from peptides. Approximately 66% of the nonammonia, nonprotein, ninhydrin-reactive material could not be recovered as amino acids, but there was a significant decrease in total amino acid nitrogen when the samples were pretreated with a C18 Sep-Pak column to remove peptides. The resistant peptides had an abundance of proline, and subsequent incubations showed that synthetic dipeptides which contained proline were hydrolyzed slowly. Lysine appears to be the amino acid which is most apt to limit ruminant production. Dipeptides containing proline and lysine were hydrolyzed at least fivefold slower than lysine-alanine. Methionine, another potentially limiting amino acid, was also degraded at a slower (2.5-fold) rate when it was present as part of a proline dipeptide.

Animals↗
PubMed1992

Characterization of muscarinic receptor subtypes in canine left ventricular membranes.

The pharmacological characteristics of muscarinic receptor (mAChR) subtypes in canine left ventricular membranes (LVM) were determined using [3H] quinuclidinyl benzilate ([3H]QNB) and [3H]N-methyl scopolamine ([3H]NMS) as ligands. Binding of [3H]QNB and [3H]NMS was saturable with respect to the radioligand concentrations. Analysis of binding isotherms by Scatchard plot showed that [3H]QNB and [3H]NMS bound to an apparently homogeneous population of mAChRs in LVM, with KD values of 390 +/- 100 and 285 +/- 34 pM and Bmax values of 240 +/- 20 and 133 +/- 9 fmol/mg protein, (n = 6), respectively. The Hill coefficients for [3H]QNB and [3H]NMS binding were 0.95 +/- 0.02 and 0.99 +/- 0.01, respectively. Based on the competitive inhibition of [3H]ligand binding, atropine and NMS as well as the selective M1 antagonist PZ revealed no selectivity for these mAChRs. PZ competed with [3H]QNB or [3H]NMS for a single binding site with a Ki value of 0.23 +/- 0.03 microM and 0.62 +/- 0.10 microM, (n = 6), respectively, which is close to the values of M2 or M3 receptors. The data indicate that the M1 receptor subtype did not exist in canine LVM. Competition of [3H]ligand binding with selective M2 antagonists, AF-DX 116 and methoctramine and the selective M3 antagonists, 4-DAMP and hexahydrosiladifenidol, gave a best fit for a two-binding site model. The inhibition of carbachol-mediated phosphoinositide hydrolysis by PZ, AF-DX 116 and 4-DAMP, generated an affinity profile for this response also dissimilar to that described for the classical cardiac M2 response. Although no other muscarinic receptor mRNA has been detected in this tissue, these data suggest the presence of a second population of muscarinic sites, which may signify an M2 receptor diversity.

Animals↗
PubMed1992

Effect of monensin on growth, reproductive performance, and estimated body composition in Holstein heifers.

The objective was to determine the effect of feeding monensin on growth performance, average age at breeding, and body composition of Holstein heifers. Forty heifers were divided by weight into two groups, averaging 330 kg (heavy) and 217 kg (light) at the beginning of the trial. Within each weight group, heifers were assigned randomly to either of two treatments: without or with monensin feeding (200 mg per head daily). All heifers were fed diets containing either corn silage at 2% BW or ad libitum grass pasture supplemented with concentrates (1 to 1.5 kg per head daily). Monensin had no effect on BW, average daily gain, height at withers, heart girth, length, coccae width, or body condition score. Feeding monensin significantly decreased the age at breeding by 15 and 24 d and age at calving by 36 and 61 d for heavy and light heifers, respectively. Estimated empty body water, protein, or fat percentages determined by urea space were not affected by monensin. Heavy heifers contained a smaller percentage of empty body water but higher percentages of empty body protein and fat than light ones. The results from this study indicate that monensin can reduce age at puberty in Holstein heifers without affecting BW and composition.

Adipose Tissue↗
PubMed1992

Experimental podophyllotoxin (bajiaolian) poisoning: I. Effects on the nervous system.

Bajiaolian, one of the species in the Mayapple family (Podophyllum pelatum), has been widely used as a traditional Chinese herbal medicine for the remedies of snake bites, general weakness, poisons, condyloma accuminata, lymphadenopathy, and certain tumors in China. In Western medicine, Podophyllum was first used medically as a laxative in the early 19th century. Since 1940, the resin of podophyllum has also been used topically for various skin lesions, such as warts and condyloma. Human poisonings have been reported. An animal model was established to investigate the neurotoxic effects of Bajiaolian. Podophyllotoxin, the major active ingredient in Podophyllum, was injected (ip) to young adult male rats at doses of 0, 5, 10, or 15 mg.kg-1 b.w.. The animals were sacrificed 72 h after injection. Neuronal changes were readily observable in animals treated with 10 or 15 mg.kg-1 of the toxin. Edematous changes of the anterior horn motoneurons were observed in the spinal cord. No neuronal necrosis was found. The type of neuronal swelling is believed to be only a transient change and would probably subside with time if no further assaults occur. More serious and perhaps longer term of changes were found in the dorsal ganglion neurons and the nerve fibers (axons) in the central and peripheral nervous system. Severe depletion of the Nissl substance (RNA/polyribosomes) was observed in the dorsal root ganglion neurons. Alterations in these sensory neurons would give rise to and correlate with the sensory disturbances experienced by the patients. Bodian staining also revealed a dose-related increase in the coarseness (thickness) of the nerve fibers (axons) in the cerebellum, cerebral cortex, brainstem, and spinal cord. This is the first scientific study showing the neurotoxicity of Bajiaolian, a commonly used Chinese herbal medicine. Toxicities on other organ systems by this drug certainly exist. Caution should be exercised in the dispensing and usage of this medicine.

Animals↗
PubMed1992

Experimental podophyllotoxin (bajiaolian) poisoning: II. Effects on the liver, intestine, kidney, pancreas and testis.

Young male rats were orally intubated with podophyllotoxin: Group I, control animals, orally fed with vehicle only; Group II, fed with an initial dose of 5 mg.kg-1 b.w., followed by a daily dose of 1.67 mg.kg-1 b.w. for 7d. Group III, fed with an initial dose of 15 mg.kg-1 b.w., followed by a daily dose of 5 mg.kg-1 b.w. for 7d. All animals were sacrificed 72 h after the last dosing. Histopathological examination revealed dose-related fatty change of the liver, atrophy and degenerative changes of the intestinal epithelial linings and testicular seminiferous tubules. Depletion of the pancreatic acinar cell granules was also apparent in the Group III animals. No pathology, however, was observed in the kidneys. The present study demonstrated for the first time degenerative changes in the liver, intestine, testis, and pancreas of animals ingested podophyllotoxin. These pathological changes correlate well with the clinical signs/symptoms of abnormal liver function, abdominal pain and diarrhea, and reduced serum amylase in humans poisoned by podophyllum. Inhibition of protein synthesis and mitosis (disruption of microtubules) are believed to be the underlying mechanisms of these changes observed in the animals intoxicated by podophyllotoxin.

Animals↗
PubMed1992

Quantitative assessment of growth stimulating activity of the vitreous during PVR.

This report postulates that the activity of cellular proliferation along the surface of the retina during proliferative vitreoretinopathy (PVR) is reflected in the aggregate effect of proliferation-inducing growth factors in the vitreous. A method for quantifying the "net" proliferation-inducing capacity of an individual vitreous sample was developed and this assay was used to evaluate the vitreous proliferative activity in a model for experimental PVR. Vitreous was aspirated sequentially after onset of fibroblast-induced PVR in a rabbit model. A simple bioassay for the "aggregate" stimulating activity was developed and each sample was assigned a quantitative value in terms of "proliferation units" (PU). Experimental eyes demonstrated a wide range of stimulating activity (0-1765 PU), but control eyes showed uniformly low levels of activity (0-337 PU). Experimental eyes that ultimately developed retinal detachment displayed higher levels of proliferative activity than did those eyes destined to remain attached. The differences were statistically different by day 3, prior to the onset of clinical retinal changes. We conclude that quantification of vitreous proliferation-stimulating activity is possible and that this method might be useful for screening eyes at high risk for the development of recurrent retinal detachment from PVR.

Animals↗
PubMed1991

Software tools for analyzing pairwise alignments of long sequences.

Pairwise comparison of long stretches of genomic DNA sequence can identify regions conserved across species, which often indicate functional significance. However, the novel insights frequently must be windowed from a flood of information; for instance, running an alignment program on two 50-kilobase sequences might yield over a hundred pages of alignments. Direct inspection of such a volume of printed output is infeasible, or at best highly undesirable, and computer tools are needed to summarize the information, to assist in its analysis, and to report the findings. This paper describes two such software tools. One tool prepares publication-quality pictorial representations of alignments, while another facilitates interactive browsing of pairwise alignment data. Their effectiveness is illustrated by comparing the beta-like globin gene clusters between humans and rabbits. A second example compares the chloroplast genomes of tobacco and liverwort.

Animals↗
PubMed1991

Heterogeneous forms of polymerase proteins exist in influenza A virus-infected cells.

In influenza virus-infected cells a virus coded polymerase that consists of three polypeptide subunits, namely PB1, PB2 and PA, mediates both transcription and replication. Radioimmunoprecipitation with monospecific antisera to each of the polymerase proteins revealed additional forms of PB1 and PA proteins in infected cells. PA antiserum detected two additional proteins of 62k and 60k and PB1 antiserum recognized two additional proteins of 85k and 70k. Further investigation was carried out on the 62k PA and 85k PB1 related proteins. Limited proteolysis peptide mapping showed that these proteins are subsets of their normal counter-parts. These new forms of polymerase proteins are designated as "b" forms (PAb and PB1b) to distinguish them from the previously recognized forms designated as "a" forms (PAa and PB1a). Both PAb and PB1b proteins were found in cells infected with all the influenza type A viruses tested indicating that they are evolutionarily conserved. Pulse chase experiments showed that the "b" forms are not derived from "a" forms. This suggested that "b" forms are translated independently. The "b" forms were not detected in purified virus but were found to be associated with intracellular RNP templates, suggesting a role for these proteins in intracellular virus replication events.

Animals↗
PubMed1991

Muscarinic receptors and mucus secretion in swine tracheal epithelium: effects of subacute organophosphate treatment.

This swine trachea study was undertaken to examine the effects of nerve agents on mucus gland cell function. Subacute treatment of swine with soman, sarin, and VX inhibits acetylcholinesterase and leads to down-regulation of muscarinic receptors in tracheal submucosal gland cells. Muscarinic receptor density in isolated cells as determined by [3H]QNB binding was reduced by 60-65% and that measured using [3H]NMS was decreased by 65-73%. Subacute treatment of swine for 7 days with soman and VX caused a small, significant increase in the fraction of receptors with high affinity for carbachol. The decrease in receptor density was accompanied by a decrease in acetylcholine-induced mucus secretion. The decrease in mucus secretion was not due to a decrease in the ability of the cells to produce or release mucus since cross-tolerance did not develop to methoxamine-induced mucus secretion. Therefore, we conclude that in mucus gland cells tolerance development can be linked functionally to muscarinic receptor loss.

Animals↗
PubMed1991

Characterization of muscarinic receptors in dog tracheal smooth muscle cells.

1. The tritiated muscarinic antagonist N-methyl scopolamine, [3H]-NMS, was used to characterize the muscarinic receptors associated with the intact dog tracheal smooth muscle cells. Based on receptor binding assays, the intact tracheal smooth muscle cells had specific, saturable, high-affinity binding sites for [3H]-NMS. 2. Specific binding was cell concentration- and time-dependent. The specific binding of [3H]-NMS was increased linearly with increasing cell concentrations. The equilibrium for association of [3H]-NMS with the muscarinic receptors was attained within 30 min at 37 degrees C. 3. Binding was saturable with respect to [3H]-NMS concentrations. Analysis of binding isotherms yielded an apparent equilibrium dissociation constant (KD) of 320 +/- 20 pM and a maximum receptor density (Bmax) of 13.7 +/- 1.4 fmole per 5 x 10(4) cells. The Hill coefficient for [3H]-NMS binding was 1.00 +/- 0.01. The association (K1) and dissociation (K-1) rate constants were determined to be (1.19 +/- 0.23) x 10(8) M-1 min-1 and 0.034 +/- 0.09 min-1, respectively. KD, calculated from the ratio of K-1 and K1, was 286 +/- 65 pM; this value is close to the value of KD calculated from Scatchard plots of binding isotherms. 4. The non-selective muscarinic antagonist atropine and M1 selective antagonist pirenzepine did not reveal any selectivity of these muscarinic receptors. Pirenzepine competed with [3H]-NMS for a single binding site with a Ki value of (6.02 +/- 0.69) x 10(-7) M which is close to the value of M2 or M3 receptors, indicating that the M1 receptor subtype did not exist in the intact tracheal smooth muscle cells. 5. Competition with cardioselective antagonist (M2), methoctramine; smooth muscle selective antagonists (M3), hexahydrodifenidol and hexahydrosiladifenidol; as well as carbachol, were best fit by a two-binding site model. The results suggest that both M2 and M3 receptor subtypes exist at the cell surface of tracheal smooth muscle cells.

Animals↗
PubMed1991

Muscarinic receptor subtypes coupled to generation of different second messengers in isolated tracheal smooth muscle cells.

1. Activation of muscarinic receptor subtypes leads to contraction, an increase in the accumulation of inositol phosphates (IPs) and a decrease in adenosine 3': 5'-cyclic monophosphate (cyclic AMP) synthesis in tracheal smooth muscle. The concentrations of carbachol that produced a half-maximal effect (EC50) in inhibition of cyclic AMP generation, stimulation of IPs formation and contraction were 15 nM, 2.0 microM and 0.17 microM, respectively. 2. Pirenzepine, a selective M1 antagonist, displayed a low affinity for antagonizing cyclic AMP inhibition, IPs formation and contraction induced by carbachol (pKB = 6.8, 7.0, and 7.1, respectively). 3. Methoctramine, a cardioselective M2 antagonist, blocked cyclic AMP inhibition with a high affinity (pKB = 7.5), while it antagonized IPs formation and contraction with a low affinity (pKB = 6.2 and 6.1, respectively). 4. 4-Diphenylacetoxy-N-methylpiperidine (4-DAMP), a selective smooth muscle M3 antagonist, possessed a high affinity in blocking IPs formation (pKB = 8.8) and contraction (pKB = 9.2) as well as a low affinity for antagonism of cyclic AMP inhibition (pKB = 8.1). 5. In conclusion, we have demonstrated that M2 and M3 receptor subtypes are coupled to different effector systems in tracheal smooth muscle. An M1 receptor subtype is not involved in the generation of the second messengers examined. Inhibition of cyclic AMP formation may be coupled to the M2 receptor subtype. The accumulation of IPs and presumably IP-induced Ca2+ release may function as the transducing mechanism for cholinergic contraction of tracheal smooth muscle through the activation of M3 receptors.

Adenylyl Cyclase Inhibitors↗
PubMed1991

Regulation of functional muscarinic receptor expression in tracheal smooth muscle cells.

Recent studies have shown that cultured tracheal smooth muscle cells (TSMCs) do not respond to muscarinic agonists with a significant increase in intracellular Ca2+ concentration. This may be due to a downregulation of muscarinic receptors (mAChRs) in TSMCs. We report here that the individual component of growth factors or hormones at the concentration used is not sufficient to stimulate growth of TSMCs in the primary culture with 1% fetal bovine serum (FBS). In the presence of 1% FBS, TSMCs withdraw from the cell cycle and express high levels of cell surface mAChRs. Furthermore, insulin-like growth factor I (IGF-I) and insulin (Ins), alone or in combination, could stimulate the expression of mAChRs on the cultured TSMCs in 1% FBS without changing the affinity of receptors. Heparin could inhibit these stimulatory effects on mAChR expression. The pharmacological response of functional mAChRs, determined as accumulation of inositol phosphates induced by carbachol, is greater in the medium containing IGF-I and Ins than those cultured in 1% FBS. This action may be partially mediated through a cholera toxin-sensitive protein. The results conclude that IGF-I and Ins are necessary for TSMCs to express functional mAChRs.

Animals↗
PubMed1991

Rapid procedure for obtaining tracheal apical membranes.

Apical membranes from cow tracheal epithelium were prepared in a two-step process. First, most of the unwanted membranes in the crude homogenate were aggregated with Mg and removed by a low-speed spin. The membranes remaining in the supernatant were pelleted by a high-speed spin, resuspended, and exposed to ouabain-affinity chromatography. This step removed approximately 50% of the protein, all the Na-K-adenosinetriphosphatase, but had no effect on total levels of alkaline phosphatase (a marker for apical membranes). The specific activity of the apical membrane marker, alkaline phosphatase, was 21 +/- 7-fold (mean +/- SD) greater in the apical membranes than in the homogenate. Markers for nuclei, mitochondria, and basolateral membranes were excluded compared with the homogenate. Similar results were obtained with primary cultures of cow tracheal epithelium. The vesicular nature of the membranes was demonstrated in isotope uptake studies that revealed an osmotically active space.

Alkaline Phosphatase↗
PubMed1991

Glucuronidation and sulfation in subcellular fractions and in the isolated perfused rabbit lung: influence of ethanol.

Glucuronidation and sulfation of 1-naphthol, 7-hydroxycoumarin, 4-nitrocatechol and phenolphthalein were studied in rabbit lung and liver. Pulmonary UDP-glucuronyltransferase and sulfotransferase activities in subcellular fractions were approximately 20-50% of those determined in the liver. Ethanol did not markedly induce these enzymes in either tissue. Glucuronidation and sulfation of 1-naphthol and 7-hydroxycoumarin were also studied in the isolated perfused rabbit lung as an intact cell model. Neither glucuronidation nor sulfation of 1-naphthol was observed. The absence of conjugate formation was due neither to the presence of beta-glucuronidase and/or sulfatase, nor to alternative biotransformation pathways. About 35% of the initial 7-hydroxycoumarin was conjugated, the majority being sulfate conjugate (14.4 nmol/h) with only minor amounts (0.12%) of the glucuronide. These results indicate the importance of studying both whole organ and in vitro metabolism.

Animals↗
PubMed1991

Ocular fundus examination in premature infants.

In order to better acknowledge the ocular fundus picture in premature infants and to determine the incidence and clinical course of retinopathy of prematurity (ROP), from October 1987 to April 1989, 187 cases with a gestational age of less than 38 weeks or a birth weight of less than 2,500 g were enrolled for examination and follow-up study with indirect ophthalmoscope. One hundred and fifty cases (80.21%) were free from ROP bilaterally. Thirty-seven cases (19.79%) had ROP. Except for one case that showed unilateral regressed ROP, all were bilaterally affected. The mean birth weight and gestational age in the nonROP group were 1,824 +/- 426 g and 33.6 +/- 2.9 weeks, respectively, and in the ROP group were 1,395 +/- 490 g and 30.7 +/- 3.9 weeks, respectively. The difference for both factors between the two groups were statistically significant (p less than 0.05). Several specific fundus features were noticed in a high percentage of the nonROP group, these included a small cup to disc (C/D) ratio, pigmented ring around the disc, hypopigmented fundus and a greenish-gray color in the peripheral vascularized retina. In addition, 8.2% of this group had persistent primary vitreous remnant, and 5.6% had retinal hemorrhage. The macular development was subdivided into three stages. In both the ROP and nonROP groups, the difference of gestational age at each advancing stage was statistically significant by the Student t-test. No delay in macular development was noticed in the ROP group.(ABSTRACT TRUNCATED AT 250 WORDS)

Follow-Up Studies↗