Biomedical subjects

C M Yang

Publications and source records attributed to C M Yang.

At least 91 records · Page 5Linked to original sources

PubMed1994

Bradykinin-stimulated phosphoinositide metabolism in cultured canine tracheal smooth muscle cells.

1. Stimulation of bradykinin (BK) receptors coupled to phosphoinositide (PI) hydrolysis was investigated in canine cultured tracheal smooth muscle cells (TSMCs). BK, kallidin, and des-Arg9-BK, stimulated [3H]-inositol phosphates (IPs) accumulation in a dose-dependent manner with half-maximal responses (EC50) at 20 +/- 5, 13 +/- 4, and 2.3 +/- 0.7 nM, (n = 5), respectively. 2. D-Arg[Hyp3, D-Phe7]-BK and D-Arg[Hyp3, Thi5,8, D-Phe7]-BK, B2 receptor antagonists, were equipotent in blocking the BK-induced IPs accumulation with pKB = 7.1 and 7.3, respectively. 3. Short-term exposure of TSMCs to phorbol 12-myristate 13-acetate (PMA, 1 microM) attenuated BK-stimulated IPs accumulation. The concentrations of PMA that gave half-maximal and maximal inhibition of BK-induced IPs accumulation were 15 +/- 4 nM and 1 microM, n = 3, respectively. The inhibitory effect of PMA on BK-induced response was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC. 4. Prolonged incubation of TSMCs with PMA for 24 h, resulted in a recovery of receptor responsiveness which may be due to down-regulation of PKC. The inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate at 1 microM, did not inhibit this response. 5. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the G protein(s) can be directly activated by AlF4-, which is uncoupled from phospholipase C by PMA treatment. 6. Incubation of TSMCs in the absence of external Ca2+ or upon removal of Ca2+ by addition of EGTA, caused a decrease in IPs accumulation without changing the basal levels. Addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs stimulated IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) or BK. The combination of GTP gamma S and BK caused an additive effect on IPs accumulation.7. Pretreatment of TSMCs with cholera toxin enhanced BK-stimulated IPs accumulation, whereas there was no effect with pertussis toxin.8. These data suggest that BK-stimulated PI metabolism is mediated by the activation of BK B2 receptors coupling to a G protein which is not blocked by cholera toxin or pertussis toxin treatment and dependent on external Ca2+. The transduction mechanism of BK coupled to PI hydrolysis is sensitive to feedback regulation by PKC.

Animals↗

PubMed1994

5-Hydroxytryptamine receptor-mediated phosphoinositide hydrolysis in canine cultured tracheal smooth muscle cells.

1. 5-Hydroxytryptamine (5-HT) has been shown to induce contraction of tracheal smooth muscle. However, the mechanisms of action of 5-HT are not known. We therefore investigated the effects of 5-HT on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and its regulation in canine cultured tracheal smooth muscle cells (TSMCs) labelled with [3H]-inositol. 5-HT-induced inositol phosphates (IPs) accumulation was time- and dose-dependent with a half-maximal response (EC50) and a maximal response at 0.38 +/- 0.05 and 10 microM, respectively. 2. Ketanserin and mianserin (10 and 100 nM), 5-HT2 receptor antagonists, were equipotent in blocking the 5-HT-induced IPs accumulation with pKB values of 8.46 and 8.21, respectively. In contrast, the dose-response curves of 5-HT-induced IPs accumulation were not shifted until the concentrations of NAN-190 and metoclopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased up to 10 microM. 3. Pretreatment of TSMCs with pertussis toxin or cholera toxin did not inhibit the 5-HT-induced IPs accumulation, but partially inhibited the AlF(4-)-induced IPs response. 4. Stimulation of IPs accumulation by 5-HT required the presence of external Ca2+ and was blocked by EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. A further Ca(2+)-dependent increase in IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphoshate) (GTP gamma S) or 5-HT. The combination of GTP gamma S and 5-HT elicited an additive effect on IPs accumulation. 5. Treatment with phorbol 12-myristate 13-acetate (PMA, 1 microM, 30 min) abolished the 5-HT-induced IPs accumulation. The concentrations of PMA that gave a half-maximal and maximal inhibition of 5-HT-induced IPs accumulation were 2.2 +/- 0.4 nM and 1 microM, n = 3, respectively. The protein kinase C (PKC) activator, 4 alpha-phorbol 12,13-didecanoate, at 1 microM, did not influence this response. The inhibitory effect of PMA was reversed by staurosporine, a PKC inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 6. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the effect of PMA is distal to the 5-HT receptor. 7. Acetylcholine-induced IPs accumulation was completely inhibited by atropine, but not affected by ketanserin or mianserin, suggesting that 5-HT-induced IPs accumulation is not due to release of acetylcholine.8. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis via a pertussis toxin- and cholera toxin-insensitive GTP binding protein in canine TSMCs and that this coupling process is negatively regulated by PKC. 5-HT2 receptors may be predominantly mediating IPs accumulation and presumably IP-induced Ca2+ release may function as the transducing mechanism for 5-HT stimulated contraction of tracheal smooth muscle.

Animals↗

PubMed1994

Antimuscarinic action of liriodenine, isolated from Fissistigma glaucescens, in canine tracheal smooth muscle.

1. The antimuscarinic properties of liriodenine, isolated from Fissistigma glaucescens, were compared with methoctramine (cardioselective M2 antagonist) and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, smooth muscle selective M3 antagonist) by radioligand binding tests, functional tests and measurements of second messenger generation in canine cultured tracheal smooth muscle cells. 2. Liriodenine, pirenzepine, methoctramine and 4-DAMP displaced [3H]-N-methyl scopolamine ([3H]-NMS) binding in a concentration-dependent manner with Ki values of 2.2 +/- 0.4 x 10(-6), 3.3 +/- 0.7 x 10(-7), 8.9 +/- 2.3 x 10(-8) and 2.3 +/- 0.6 x 10(-9) M, respectively. The curves for competitive inhibition of [3H]-NMS with liriodenine, methoctramine and 4-DAMP were best fitted according to a two site model of binding, but pirenzepine was best fitted according to a model with one site. 3. Liriodenine and 4-DAMP displayed a high affinity for blocking tracheal contraction (pKB = 5.9 and 9.1, respectively) and inositol phosphate formation (pKB = 6.0 and 8.9, respectively), but a low affinity for antagonism of cyclic AMP inhibition (pKB = 4.7 and 7.8, respectively). 4. Methoctramine blocked cyclic AMP inhibition with a high affinity (pKB = 7.4), but it antagonized tracheal contraction and inositol phosphate formation with a low affinity (pKB = 6.1 and 6.0, respectively). 5. In conclusion, both M2 and M3 muscarinic receptor subtypes coexist in canine tracheal smooth muscle and are coupled to the inhibition of cyclic AMP formation and phosphoinositide breakdown, respectively. The antimuscarinic characteristics of liriodenine are similar to those of 4-DAMP. It may act as a selective M3 receptor antagonist in canine tracheal smooth muscle.

Adenylyl Cyclase Inhibitors↗

PubMed1994

Sarafotoxin-induced calcium mobilization in cultured dog tracheal smooth muscle cells.

Sarafotoxin b (S6b)-induced changes in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) by a fluorescent Ca2+ indicator fura-2. S6b elicited an initial transient peak followed by a sustained elevation of [Ca2+]i. BQ-123, an endothelin-A (ETA) receptor antagonist, had a high affinity to block the rise in [Ca2+]i response to S6b. In the absence of external Ca2+, only an initial transient peak of [Ca2+]i was seen, the sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+. Ca2+ influx was required for the changes of [Ca2+]i, since the Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to S6b. TSMCs pretreated with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min attenuated Ca2+ mobilization induced by S6b, which was reversed by staurosporine, a protein kinase C (PKC) inhibitor. The change of [Ca2+]i induced by S6b was attenuated by cholera toxin pretreatment, but not by pertussis toxin. These data demonstrate that the initial detectable increase in [Ca2+]i stimulated by S6b is due to the activation of ETA receptors and subsequent release of Ca2+ from internal stores, whereas the contribution of external Ca2+ follows and partially involves a diltiazem- and verapamil-sensitive process. The inhibition of PMA on S6b-induced Ca2+ mobilization was inversely correlated with membraneous PKC activity.

Animals↗

PubMed1994

Experimental podophyllotoxin (bajiaolian) poisoning: III. Biochemical bases for toxic effects.

The biochemical mechanism underlying the toxicity of podophyllotoxin is investigated. Previous studies from our laboratories suggested that hepatocytes were extremely sensitive to the toxicity of podophyllotoxin and a disruption of protein synthesis was suspected. Dose-response and time-course studies on the effects of podophyllotoxin on protein. RNA, and DNA syntheses on hepatocellular cultures were made. Inhibitions of protein, RNA, and DNA syntheses were demonstrated, and a direct correlated dose-response relationship on such effects was also evident. Inhibition of protein synthesis appeared to be a direct toxic effect of podophyllotoxin and occurred independently from that of RNA. The reduction of DNA synthesis was reflected by a reduction of H3-thymidine incorporation, which is believed to be the consequence of inhibition on the mitotic activity by podophyllotoxin.

Cells, Cultured↗

PubMed1994

Pancreatoblastoma: a case report.

Primary neoplasms of the pancreas are rare in children. One variant of these tumors is pancreatoblastoma, comprising 0.5% of epithelial tumors of the pancreas. It usually affects children at 1-8 years of age, with quite equal sex ratio. The tumor can be found at any site of pancreas, but it most commonly arises in the head of pancreas. Histopathologically, pancreatoblastoma is an encapsulated tumor with distinct organoid structures and sometimes squamoid corpuscles. Acinar cells with zymogen granules are occasionally found. The tumor has favorable prognosis. We present a 14-year-old female who was admitted due to prolonged jaundice for about 2 months. Physical examination revealed pale conjunctiva, yellowish skin color and hepatosplenomegaly. Abdominal sonography and CT scan showed dilated common bile duct and a tumor mass about 2 x 2 cm in dimension located a pancreatic head. She received surgical operation to relieve obstructive jaundice and later Whipple's operation for radical resection. Six months after operation, the patient received the examination of abdominal sonography, CT scan and gallium tumor scan but there was no evidence of local recurrence or distant metastasis. Now the patient is living well for more than one year. Because of its rare occurrence, we demonstrate this case and review the literature.

Adolescent↗

PubMed1993

Dose rate effect of 125I irradiation on normal rabbit eyes and experimental choroidal melanoma.

The dose rate effect of radiation by 125I plaque on choroidal melanoma and normal intraocular tissue was studied. In the first part of the experiment, high activity plaques (HAP) and low activity plaques (LAP) were implanted on rabbit eyes with experimental Greene choroidal melanoma to deliver a total dose of 10,000 cGy to the tumor apex. The mean dose rate calculated at 0.5 mm from the inner sclera in eight eyes with high activity plaques was 3341.5 cGy hr-1 (1 cGy = 1 rad) while that in ten eyes with low activity plaques was 239.9 cGy hr-1. For tumors less than 1.0 mm in height, both groups showed complete tumor regression at the tumor implantation site after plaque treatment. For tumors more than 1.0 mm in height, two out of two eyes in the low activity plaque group and one of four eyes in the high activity plaque group failed to show complete tumor regression. Both LAP and HAP were effective in eradicating tumors, but logistic regression analysis demonstrates that HAP was more effective than LAP when adjustment was made for initial tumor height (P = 0.032). Nine tumor control eyes without 125I plaque implantation demonstrated marked tumor growth within 3 weeks. In the second part of the experiment, 125I plaques were implanted on the sclera of 12 normal rabbits' eyes. Six received high dose rate plaque treatment, while the other six received low dose rate plaque treatment. Clinical and histologic examinations demonstrated more damaging effects to the normal chorioretinal tissues at the plaque implantation site in the high dose rate plaque group at 24 weeks of follow-up. These results suggest that high dose rate plaques are more effective than low dose rate plaques when tumor height is statistically controlled. However, high dose rate delivery increases the damaging effects on normal intraocular tissue.

Animals↗

PubMed1993

The effects of continuous ruminal dosing with dioctyl sodium sulphosuccinate on ruminal and metabolic characteristics of lactating Holstein cows.

Rumen-cannulated Holstein cows were used to study the effect of intraruminal dosing of dioctyl sodium sulphosuccinate (DSS; 0.07 g/kg body weight per d) for 4 weeks. DSS was suspended in nylon bags to allow it to be released slowly into the rumen. Cows were offered a diet containing grass silage and concentrate (45:55, w/w). Intakes of control cows were regulated to those of DSS-dosed cows. Cows dosed with DSS had no rumen ciliate protozoa, lower rumen NH3-N concentrations and acetate and butyrate proportions, higher propionate, isovalerate, and valerate proportions. In vitro fibre digestion by non-ciliate rumen fluid from DSS-dosed cows was apparently impaired. When cows were dosed with DSS, levels of neutral- and acid-detergent fibre in whole rumen contents were increased, rumen solids turnover rate was slower, and whole tract apparent digestibility of cellulose and diethyl ether extract was decreased. Dosing of DSS led to reduced concentrations of blood acetoacetate but elevated plasma glucose levels. Milk protein content was higher, however, lactose content was lower for DSS-dosed than control cows. Milk fat of DSS-dosed cows had a smaller proportion of short-chain fatty acids but a greater proportion of unsaturated fatty acids.

Acetoacetates↗

PubMed1993

Phylogeny of the ammonia-producing ruminal bacteria Peptostreptococcus anaerobius, Clostridium sticklandii, and Clostridium aminophilum sp. nov.

In previous studies, gram-positive bacteria which grew rapidly with peptides or an amino acid as the sole energy source were isolated from bovine rumina. Three isolates, strains C, FT (T = type strain), and SR, were considered to be ecologically important since they produced up to 20-fold more ammonia than other ammonia-producing ruminal bacteria. On the basis of phenotypic criteria, the taxonomic position of these new isolates was uncertain. In this study, the 16S rRNA sequences of these isolates and related bacteria were determined to establish the phylogenetic positions of the organisms. The sequences of strains C, FT, and SR and reference strains of Peptostreptococcus anaerobius, Clostridium sticklandii, Clostridium coccoides, Clostridium aminovalericum, Acetomaculum ruminis, Clostridium leptum, Clostridium lituseburense, Clostridium acidiurici, and Clostridium barkeri were determined by using a modified Sanger dideoxy chain termination method. Strain C, a large coccus purported to belong to the genus Peptostreptococcus, was closely related to P. anaerobius, with a level of sequence similarity of 99.6%. Strain SR, a heat-resistant, short, rod-shaped organism, was closely related to C. sticklandii, with a level of sequence similarity of 99.9%. However, strain FT, a heat-resistant, pleomorphic, rod-shaped organism, was only distantly related to some clostridial species and P. anaerobius. On the basis of the sequence data, it was clear that strain FT warranted designation as a separate species. The closest known relative of strain FT was C. coccoides (level of similarity, only 90.6%). Additional strains that are phenotypically similar to strain FT were isolated in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1993

Intracellular calcium in canine cultured tracheal smooth muscle cells is regulated by M3 muscarinic receptors.

1. The regulation of cytosolic Ca2+ concentrations ([Ca2+]i) during exposure to carbachol was measured directly in canine cultured tracheal smooth muscle cells (TSMCs) loaded with fura-2. Stimulation of muscarinic cholinoceptors (muscarinic AChRs) by carbachol produced a dose-dependent rise in [Ca2+]i which was followed by a stable plateau phase. The EC50 values of carbachol for the peak and sustained plateau responses were 0.34 and 0.33 microM, respectively. 2. Atropine (10 microM) prevented all the responses to carbachol, and when added during a response to carbachol, significantly, but not completely decreased [Ca2+]i within 5 s. Therefore, the changes in [Ca2+]i by carbachol were mediated through the muscarinic AChRs. 3. AF-DX 116 (a selective M2 antagonist) and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, a selective M3 antagonist) inhibited the carbachol-stimulated increase in [Ca2+]i with pKB values of 6.4 and 9.4, respectively, corresponding to low affinity for AF-DX 119 and high affinity for 4-DAMP in antagonizing this response. 4. The plateau elevation of [Ca2+]i was dependent on the presence of external Ca2+. Removal of Ca2+ by the addition of 2 mM EGTA caused the [Ca2+]i to decline rapidly to the resting level. In the absence of external Ca2+, only an initial transient peak of [Ca2+]i was seen which then declined to the resting level; the sustained elevation of [Ca2+]i could then be evoked by the addition of Ca2+ (1.8 mM) in the continued presence of carbachol. 5.Ca2+ influx was required for the changes of [Ca2+]i, since the Ca2+-channel blockers, diltiazem(10 microM), nifedipine (10 microM), verapamil (10 microM) and Ni2+ (5 mM), decreased both the initial and sustained elevation of [Ca2+], in response to carbachol. These Ca2+-channel blockers also decreased the sustained elevation of [Ca2+], when applied during the plateau phase.6. In conclusion, we have demonstrated that the initial detectable increase in carbachol-stimulated[Ca2+]J is due to the release of Ca2+ from internal stores, followed by the flux of external Ca2+ into the cells. This influx of extracellular Ca2+ partially involves an L-type Ca2+-channel. M3 muscarinic receptors appear to mediate the Ca2+ mobilization in canine TSMCs.

Animals↗

PubMed1993

Muscarinic regulation of cytosolic free calcium in canine tracheal smooth muscle cells: Ca2+ requirement for phospholipase C activation.

1. The relationship between muscarinic receptor-mediated phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown and the increase of intracellular Ca2+ ([Ca2+])i has been examined in canine cultured tracheal smooth muscle cells (TSMCs). 2. Addition of acetylcholine (ACh) and carbachol led to a 2-3 fold increase in [Ca2+]i over the resting level as determined by fura-2, with half-maximal stimulation (EC50) obtained at concentrations of 97 and 340 nM, respectively. Addition of the partial agonist, bethanechol, showed a smaller increase in PIP2 turnover and [Ca2+]i than did ACh or carbachol. 3. Addition of ACh or carbachol to TSMCs that had been prelabelled with [3H]-inositol led to the rapid (5-15 s) release of inositol mono, bis and trisphosphates IP1, IP2 and IP3. The time course of IP3 accumulation is correlated with the time course of the peak rise in [Ca2+]i. 4. Inclusion of EGTA lowered the resting [Ca2+]i and markedly reduced the extent of the agonist-induced rise in [Ca2+]i. When assayed under conditions similar to those used for the [Ca2+]i measurements, EGTA reduced the muscarinic agonist-stimulated inositol phosphates (IPs) accumulation. Conversely, ionomycin could stimulate IPs accumulation and elevate [Ca2+]i. The addition of Ca2+ (2.7-617 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. 5. Both Ca2+ and guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) stimulated the formation of IPs in digitonin-permeabilized TSMCs prelabelled with [3H]-inositol. A further calcium-dependent increase in IPs accumulation was obtained by inclusion of either GTP gamma S or carbachol. The combined presence of carbachol and GTP gamma S elicited a synergistic effect on IPs accumulation, with half-maximal stimulation observed at approximately 8 nM free Ca2+.6. These results indicate that (i) the magnitude of the initial rise in [Ca2+], is directly related to the production of IPs and (ii) the phospholipase C-mediated PIP2 breakdown in TSMCs is sensitive to regulation by physiologically relevant concentrations of free Ca2+ ([Ca2+]f).

Animals↗

PubMed1993

Effect of monensin on the specific activity of ammonia production by ruminal bacteria and disappearance of amino nitrogen from the rumen.

When unadapted mixed ruminal bacteria (312 mg of protein per liter) were treated with monensin (5 mM) in vitro, the rates of ammonia production from enzymatic digests of casein, gelatin, and soy protein (0.5 g of N per liter) were decreased from 46 +/- 2 to 24 +/- 1, 20 +/- 1 to 7 +/- 1, and 40 +/- 2 to 18 +/- 2 nmol/mg of protein per min, respectively. Monensin also caused a decrease in ammonia production in vivo. Nonlactating dairy cows which were fed 0.56 kg of timothy hay 12 times per day had a steady-state ruminal ammonia concentration of 2.7 +/- 0.1 mM, and the ammonia concentration decreased to 1.2 +/- 0.2 mM when monensin (350 mg/day) was added to the diet. The decrease in ammonia production was associated with a 10-fold reduction (4.1 x 10(6) versus 4.2 x 10(5)/ml) in the most probable number of ammonia-producing ruminal bacteria that could use protein hydrolysate as an energy source. Monensin had little effect on the most probable number of carbohydrate-utilizing ruminal bacteria (6.5 versus 7.0 x 10(8)/ml). The addition of protein hydrolysates (560 g) to the rumen caused a rapid increase in the ammonia concentration, but this increase was at least 30% lower when the animals were fed monensin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1993

Pharmacological characterization of muscarinic receptors in neonatal rat cardiomyocytes.

[N-methyl-3H]scopolamine methylchloride ([3H]NMS) was used to characterize the muscarinic receptors (mAChRs) in the intact cardiomyocytes. The specific binding of [3H]NMS was proportional to cell concentration, saturable with respect to [3H]NMS concentration, and time dependent. Scatchard analysis of binding isotherms showed that [3H]NMS bound to the freshly isolated and cultured cardiomyocytes with dissociation constants of 275 +/- 64 and 207 +/- 20 pM as well as maximum receptor densities of 0.13 +/- 0.09 and 5.36 +/- 0.20 fmol/10(5) cells, respectively. Heterogeneity of mAChRs was demonstrated by competitive binding experiments against [3H]NMS with M2 and M3 antagonists. These receptors (80%) exhibited high affinities for 11-([2-[(diethylamino)methyl]-1-piperidinyl]-acetyl)-5,11-dihydro- 6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX-116) and methoctramine similar to those of M2 subtype. The low-affinity M2 antagonist binding constants were close to those reported for M3 receptors and possessed high affinity for 4-diphenylacetoxyl-N-methylpiperidine (4-DAMP) and hexahydrosiladifenidol. On the basis of biochemical studies, AF-DX-116 blocked adenosine 3',5'-cyclic monophosphate (cAMP) inhibition with high affinity (pKB 7.4), while it antagonized inositol phosphate formation with low affinity (pKB 6.5). 4-DAMP possessed high affinity in blocking inositol phosphate formation (pKB 9.0) and low affinity for antagonism of cAMP inhibition (pKB 7.7). Although no other muscarinic receptor mRNA has been detected in these cells, these data suggest the presence of a second population of mAChRs, which may not be identical to the classical cardiac "M2" receptors.

Animals↗

PubMed1993

The effect of monensin supplementation on ruminal ammonia accumulation in vivo and the numbers of amino acid-fermenting bacteria.

When nonlactating Holstein cows (685 +/- 59 kg) were fed chopped timothy hay (9% CP, 7.0 kg/d) 12 times daily, the steady-state ruminal ammonia concentration was 2.6 mM, and the specific activity of ammonia production by mixed ruminal bacteria was 27.4 nmol/mg of protein-1.min-1. The addition of soybean meal (53% CP, 1 or 2 kg/d) to the basal diet caused a linear increase in ruminal ammonia (7.0 and 12.4 mM, respectively; P < .001), but there was only a small increase in the specific activity of ammonia production (30.7 and 33.8 nmol/mg of protein-1.min-1, respectively; P < .05). The addition of monensin (350 mg/d) to the diets caused more than a 30% decrease (P < .01) in ruminal ammonia at all levels of soybean supplementation, and there was a similar decrease (P < .001) in the specific activity of ammonia production. Before monensin addition, the most probable number of bacteria that could utilize peptides and amino acids, but not carbohydrates, as an energy source for growth was 5.8 to 7.0 x 10(6)/mL. When monensin was added to the diets, these bacteria decreased (P < .001) nearly 10-fold. Based on these results, it seemed that monensin inhibited highly active amino acid-fermenting ruminal bacteria, and this inhibition, in turn, decreased ruminal amino acid deamination and ammonia production. Because monensin did not increase soluble protein, peptides, or amino acids in ruminal fluid, it did not seem that the decrease in ammonia increased flow of dietary amino N to the lower gut.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1993

Primary culture of canine tracheal smooth muscle cells in serum-free medium: effects of insulin-like growth factor I and insulin.

The effects of growth factors on cell growth and muscarinic receptor (mAChR) expression of canine tracheal smooth muscle cells (TSMCs) were observed under serum-free medium supplemented with 0.1% BSA. In the presence of 0.1% BSA, TSMCs withdraw from cell cycle as compared with 10% FBS and allow to determine the effects of growth factors on mAChR expression. The individual components of growth factors (IGF-I, insulin, and aFGF) at the concentration used are not sufficient to stimulate growth of TSMCs in the primary culture with 0.1% BSA. IGF-I (10 ng/ml) and insulin (1 microgram/ml), alone or in combination, could stimulate the expression of mAChRs of cultured TSMCs. Heparin could inhibit these stimulatory effects of mAChR expression. The stimulatory effects of IGF-I and insulin on mAChR expression were mediated through their own receptors since these effects were reversed by pretreatment of TSMCs with antibodies of the respective growth factor receptors. The pharmacological response of functional mAChRs, determined as accumulation of inositol phosphates induced by carbachol, is greater in the medium containing IGF-I and insulin than that cultured in 0.1% BSA. These results firmly establish that IGF-I and insulin could stimulate the expression of mAChRs in TSMCs under serum-free culture condition.

Animals↗

PubMed1993

Indocyanine green videoangiography of choroidal neovascular membrane in age-related macular degeneration.

Fluorescein angiography is the traditional tool for the detection of choroidal neovascularization of age-related macular degeneration. However, some limitations exist which impede its efficacy in the detection of subretinal neovascularization. Indocyanine green videoangiography is a recently developed technique which differs from fluorescein angiography in many ways. We performed indocyanine green videoangiography in 18 eyes with occult choroidal neovascularization, demonstrated by fluorescein angiography. Sixteen of the 18 eyes showed an abnormal vessel loop in the early phase of indocyanine green videoangiography. In the late phase, all 18 eyes had abnormal dye retention around the suspected neovascular area; however, only 12 eyes revealed a distinct border of neovascularization. No side effects, such as nausea, vomiting, or allergic reactions, were noted in our patients. Advantages and drawbacks of indocyanine green videoangiography in comparison with fluorescein angiography are discussed.

Choroid↗

PubMed1993

Retinopathy of prematurity: an analysis of risk factors.

In order to investigate the possible clinical factors related to the occurrence of retinopathy of prematurity (ROP), 37 very-low-birth-weight infants documented to have ROP were compared to a group of 50 controls during the period from July 1988 to December 1991. The results revealed that: 1) the overall occurrence rate of ROP was 42.5% (37/87), with a higher occurrence rate in the less mature weight-stratified subgroup; 2) patients in the lower stages of ROP generally regressed during the follow-up, while nearly all of those in the higher stages eventually progressed and received surgical intervention; and 3) after multiple logistic regression analysis, the consistently significant factors were birth weight, duration of PaO2 > or = 80 mmHg, ventilation time > or = five days and a blood exchange transfusion. It is suggested that regular examination for ROP in high-risk premature infants is important in combination with other monitoring modalities in neonatal intensive care units to reduce the possible complications and sequelae of ROP.

Female↗

PubMed1993

Acute pancreatitis in association with L-asparaginase therapy: report of one case.

L-asparaginase has been used clinically for treatment of a wide variety of pediatric neoplastic diseases (e.g. acute lymphocytic leukemia, malignant lymphoma, etc.) A 14-year-old female patient, is a victim of acute lymphocytic leukemia, Pre T type. She got acute pancreatitis after the L-asparaginase therapy. We reported her clinical course and our management. It is concluded that early diagnosis of pancreatitis is usually difficult, because the symptoms are vague, physical findings may be minimal, and laboratory studies are frequently inconclusive until the injury is severe. Therefore, physicians must be cautious to the patient's chief complaint before administering the next dose of L-asparaginase, because it may occur more earlier than the laboratory or image studies and thus could be used to predict pancreatitis.

Acute Disease↗