Sperm-oviduct interaction: induction of capacitation and preferential binding of uncapacitated spermatozoa to oviductal epithelial cells in porcine species. (1/226)

After mating, inseminated spermatozoa are transported to the oviduct. They attach to and interact with oviductal epithelial cells (OEC). To investigate sperm-OEC interactions, we used chlortetracycline to study the capacitation status of boar spermatozoa in coculture with homologous OEC and cells of nonreproductive origin (LLC-PK1, porcine kidney epithelial cell line). Boar spermatozoa were cocultured with OEC and LLC-PK1 cells for 15, 60, 120, or 240 min. The proportion of capacitated spermatozoa in coculture with the isthmic and ampullar cells increased significantly (p < 0.05) during incubation. However, most spermatozoa in coculture with LLC-PK1 cells or blank (medium only) remained uncapacitated. In addition, preferential binding of uncapacitated, capacitated, or acrosome-reacted boar spermatozoa to OEC and the other cell type was investigated. Our approach was to vary the proportions of uncapacitated, capacitated, or acrosome-reacted boar spermatozoa in suspension using long preincubation and lysophosphatidylcholine treatment of semen prior to a very short incubation with OEC or LLC-PK1 cells. The results showed that the majority of spermatozoa that were bound to OEC or LLC-PK1 cells were uncapacitated and that a significant relationship existed between the relative proportion of uncapacitated spermatozoa in the control samples and those bound to LLC-PK1 cells (r2 = 0.43, p < 0.005). However, there was no correlation between the proportion of uncapacitated spermatozoa in the control samples and the proportion of those bound to isthmic or ampullar cells. In conclusion, the results clearly demonstrated the specific nature of the sperm-OEC interaction in the porcine species. This interaction is initiated by uncapacitated spermatozoa binding to OEC and is continued by the induction of capacitation in cocultured spermatozoa.  (+info)

Effects of oral chlortetracycline and dietary protein level on plasma concentrations of growth hormone and thyroid hormones in beef steers before and after challenge with a combination of thyrotropin-releasing hormone and growth hormone-releasing hormone. (2/226)

The objective of this study was to determine the effect of a subtherapeutic level of chlortetracycline (CTC) fed to growing beef steers under conditions of limited and adequate dietary protein on plasma concentrations of GH, thyroid-stimulating hormone (TSH), and thyroid hormones before and after an injection of thyrotropin-releasing hormone (TRH) + GHRH. Young beef steers (n = 32; average BW = 285 kg) were assigned to a 2x2 factorial arrangement of treatments of either a 10 or 13% crude protein diet (70% concentrate, 15% wheat straw, and 15% cottonseed hulls) and either a corn meal carrier or carrier + 350 mg of CTC daily top dressed on the diet. Steers were fed ad libitum amounts of diet for 56 d, and a jugular catheter was then placed in each steer in four groups (two steers from each treatment combination per group) during four consecutive days (one group per day). Each steer was injected via the jugular catheter with 1.0 microg/kg BW TRH + .1 microg/kg BW GHRH in 10 mL of saline at 0800. Blood samples were collected at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 120, 240, and 360 min after releasing hormone injection. Plasma samples were analyzed for GH, TSH, thyroxine (T4), and triiodothyronine (T3). After 84 d on trial, the steers were slaughtered and the pituitary and samples of liver were collected and analyzed for 5'-deiodinase activity. Feeding CTC attenuated the GH response to releasing hormone challenge by 26% for both area under the response curve (P<.03) and peak response (P<.10). Likewise, CTC attenuated the TSH response to releasing hormone challenge for area under the response curve by 16% (P<.10) and peak response by 33% (P<.02), and attenuated the T4 response for area under the curve by 12% (P<.08) and peak response by 14% (P<.04). Type II deiodinase activity in the pituitary was 36% less (P<.02) in CTC-fed steers than in steers not fed CTC. The results of this study are interpreted to suggest that feeding subtherapeutic levels of CTC to young growing beef cattle attenuates the release of GH and TSH in response to pituitary releasing hormones, suggesting a mechanism by which CTC may influence tissue deposition in cattle.  (+info)

Intracellular divalent cation release in pancreatic acinar cells during stimulus-secretion coupling. I. Use of chlorotetracycline as fluorescent probe. (3/226)

Stimulus-secretion coupling in pancreatic exocrine cells was studied using dissociated acini, prepared from mouse pancreas, and chlorotetracycline (CTC), a fluorescent probe which forms highly fluorescent complexes with Ca2+ and Mg2+ ions bound to membranes. Acini, preloaded by incubation with CTC (100 microM), displayed a fluorescence having spectral properties like that of CTC complexed to calcium (excitation and emission maxima at 398 and 527 nm, respectively). Stimulation with either bethanechol or caerulein resulted in a rapid loss of fluorescence intensity and an increase in outflux of CTC from the acini. After 5 min of stimulation, acini fluorescence had been reduced by 40% and appeared to be that of CTC complexed to Mg2+ (excitation and emission maxima at 393 and 521 nm, respectively). The fluorescence loss induced by bethanechol was blocked by atropine and was seen at all agonist concentrations that elicited amylase release. Maximal fluorescence loss, however, required a bethanechol concentration three times greater than that needed for maximal amylase release. In contrast, acini preloaded with ANS or oxytetracycline, probes that are relatively insensitive to membrane-bound divalent cations, displayed no secretagogue-induced fluorescence changes. These results are consistent with the hypothesis that CTC is able to probe some set of intracellular membranes which release calcium during secretory stimulation and that this release results in dissociation of Ca(2+)-complexed CTC.  (+info)

Intracellular divalent cation release in pancreatic acinar cells during stimulus-secretion coupling. II. Subcellular localization of the fluorescent probe chlorotetracycline. (4/226)

Subcellular distribution of the divalent cation-sensitive probe chlorotetracycline (CTC) was observed by fluorescence microscopy in isolated pancreatic acinar cells, dissociated hepatocytes, rod photoreceptors, and erythrocytes. In each cell type, areas containing membranes fluoresced intensely while areas containing no membranes (nuclei and zymogen granules) were not fluorescent. Cell compartments packed with rough endoplasmic reticulum or Golgi vesicles (acinar cells) or plasma membrane-derived membranes (rod outer segments) exhibited a uniform fluorescence. In contrast, cell compartments having large numbers of mitochondria (hepatocytes and the rod inner segment) exhibited a punctate fluorescence. Punctate fluorescence was prominent in the perinuclear and peri-granular areas of isolated acinar cells during CTC efflux, suggesting that under these conditions mitochondrial fluorescence may account for a large portion of acinar cell fluorescence. Fluorometry of dissociated pancreatic acini, preloaded with CTC, showed that application of the mitochondrial inhibitors antimycin A, NaCN, rotenone, or C1CCP, or of the divalent cation ionophore A23187 (all agents known to release mitochondrial calcium) rapidly decreased the fluorescence of acini. In the case of mitochondrial inhibitors, this response could be elicited before but not following the loss of CTC fluorescence induced by bethanechol stimulation. Removal of extracellular Ca2+ and Mg2+ or addition of EDTA also decreased fluorescence but did not prevent secretagogues or mitochondrial inhibitors from eliciting a further response. These data suggest that bethanechol acts to decrease CTC fluorescence at the same intracellular site as do mitochondrial inhibitors. This could be due to release of calcium from either mitochondria or another organelle that requires ATP to sequester calcium.  (+info)

Effect of feed intake on antimicrobially induced increases in porcine serum insulin-like growth factor I. (5/226)

This study was conducted to determine whether an antimicrobially induced (ASP-250) increase in serum IGF-I was the result of differences in feed intake. Serum IGF-I concentrations were measured in crossbred pigs that were fed a control diet or a diet supplemented with ASP-250 either for ad libitum consumption or limited to 85% of the control pigs' consumption. The pigs that consumed either diet ad libitum, control or ASP-250, consumed similar quantities of feed. The ASP-250 ad libitum-intake pigs had serum IGF-I concentrations that were greater (P<.01) than those of their ad libitum-intake control littermates. Similarly, the ASP-250 limit-fed pigs had serum IGF-I concentrations that were greater (P<.01) than those of the controls. Although the serum IGF-I concentrations of pigs fed the ASP-250-supplemented diet for ad libitum intake were greater than the serum IGF-I concentrations of the pigs limit-fed the ASP-250-supplemented diet, the differences were not significant (P<.08). The ASP-250-fed pigs had higher serum IGF binding protein (BP)-3 concentrations than did their control littermates (P<.003). A time course of antimicrobially induced alterations in serum IGF-I concentrations revealed that the effect of increased serum IGF-I levels in ASP-250-supplemented pigs (P<.02) was observed within 4 d and was maintained throughout the 4-wk study. These findings show that feed intake is not responsible for the increase in serum IGF-I observed with ASP-250 supplementation. Additionally, the antimicrobially induced increase in serum IGF-I concentrations occurs within a few days after initiation of the treatment.  (+info)

Effects of preshipping vs. arrival medication with tilmicosin phosphate and feeding chlortetracycline on health and performance of newly received beef cattle. (6/226)

Our objective was to determine the effects of preshipping (PRE) vs. arrival (ARR) medication with tilmicosin phosphate (MIC; Exp. 1 and 2) and feeding chlortetracycline (CTC; 22 mg/kg of BW from d 5 to 9; Exp. 2) on health and performance of beef calves received in the feedlot. Ninety-six steers (Exp. 1; pay weight 236 kg) and 240 (Exp. 2; average pay weight 188 kg) steer and bull calves were used. For Exp. 1, treatments included no MIC (CON), PRE, and ARR. For Exp. 2, treatments were arranged in a 3x2 factorial. Treatments included CON, PRE, and ARR, either with CTC or without CTC. For Exp. 2, serum concentrations of immunoglobulin (Ig)G and alpha-1-acid glycoprotein (AGP) were determined on samples collected on d 0, 5, 10, and 28 and d 0, 5, and 10, respectively. No MIC x CTC interactions were observed. No differences were noted among MIC or CTC treatments in any of the experiments for ADG, daily DMI, or gain:feed ratio for the overall receiving periods. For Exp. 1, percentage of steers treated for bovine respiratory disease (BRD) was decreased (P<.05) for MIC-treated animals vs CON (71.9, 45.2, and 46.9 for CON, PRE, and ARR, respectively), and the week that calves were treated for BRD differed (P<.10) among treatments. For Exp. 2, the number of calves treated for BRD was decreased (P<.01) for MIC-treated steers vs CON and decreased (P<.05) for ARR vs. PRE (40.0, 18.7, and 7.5% for CON, PRE, and ARR, respectively). Averaged across days, serum IgG was decreased (P<.05) for MIC-treated steers vs. CON, with no differences noted among treatments for AGP. Results suggest that preshipping medication programs are no more effective than arrival medication programs using tilmicosin phosphate.  (+info)

Effects of temperature on calcium-sensitive fluorescent probes. (7/226)

The effect of temperature on the binding equilibria of calcium-sensing dyes has been extensively studied, but there are also important temperature-related changes in the photophysics of the dyes that have been largely ignored. We conducted a systematic study of thermal effects on five calcium-sensing dyes under calcium-saturated and calcium-free conditions. Quin-2, chlortetracycline, calcium green dextran, Indo-1, and Fura-2 all show temperature-dependent effects on fluorescence in all or part of the range tested (5-40 degrees C). Specifically, the intensity of the single-wavelength dyes increased at low temperature. The ratiometric dyes, because of variable effects at the two wavelengths, showed, in general, a reduction in the fluorescence ratio as temperature decreased. Changes in viscosity, pH, oxygen quenching, or fluorescence maxima could not fully explain the effects of temperature on fluorescence. The excited-state lifetimes of the dyes were determined, in both the presence and absence of calcium, using multifrequency phase-modulation fluorimetry. In most cases, low temperature led to prolonged fluorescence lifetimes. The increase in lifetimes at reduced temperature is probably largely responsible for the effects of temperature on the physical properties of the calcium-sensing dyes. Clearly, these temperature effects can influence reported calcium concentrations and must therefore be taken into consideration during any investigation involving variable temperatures.  (+info)

Rifaximin versus chlortetracycline in the short-term treatment of small intestinal bacterial overgrowth. (8/226)

BACKGROUND: Bacterial overgrowth of the small intestine is a condition characterized by nutrient malabsorption due to an excessive number of bacteria in the lumen of the small intestine. Current treatment is based on empirical courses of broad spectrum antibiotics; few controlled data, with respect to the duration and choice of antibiotic drug, exist at present. The recent availability of rifaximin, a non-absorbable rifamycin derivative, highly effective against anaerobic bacteria, prompted us to carry out a randomized, double-blind controlled trial in order to compare its efficacy and tolerability to those of tetracycline, currently considered the first-choice drug. METHODS: In 21 patients affected by small intestinal bacterial overgrowth, fasting, peak and total H2 excretion after ingestion of 50 g glucose and severity of symptoms were evaluated before and after a 7-day course of rifaximin, 1200 mg/day (400 mg t.d.s.), or chlortetracycline, 1 g/day (333 mg t.d.s. ). RESULTS: Fasting, peak and total H2 excretion decreased significantly in the group of patients treated with rifaximin whereas chlortetracycline did not modify these parameters. The H2 breath test normalized in 70% of patients after rifaximin and in 27% of patients after chlortetracycline. The improvement in symptoms was significantly higher in patients treated with rifaximin. CONCLUSIONS: Rifaximin is a promising, easily-handled and safe drug for the short-term treatment of small intestinal bacterial overgrowth.  (+info)

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