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At least 433 records · Page 24Linked to original sources
PubMed1992

Investigation of means to improve rates of fertilization in in vitro matured/in vitro fertilized bovine oocytes.

Experiments were conducted with 5,979 oocytes to determine whether detaching some of the cumulus cells from oocytes either before or after maturation would improve the fertilization rate and proportion of oocytes that developed to expanded blastocysts. Oocytes were aspirated from ovaries of slaughtered cows and matured, fertilized and cultured in vitro. Pipetting immature oocytes before maturation to detach some of the cumulus, with all cumulus cells left in the maturation wells, significantly increased fertilization rates, especially of oocytes that initially had a full cumulus investment. In further experiments, pipetting oocytes either before or after maturation to detach most of the cumulus, or treating with hyaluronidase after maturation to disperse the cumulus, significantly increased fertilization rates and proportions of oocytes developing to expanded blastocysts.

Journal Article↗
PubMed1992

In vitro fertilization of water buffalo follicular oocytes and their ability to cleave in vitro.

Water buffalo (Murrah) oocytes were collected from ovaries obtained from a local slaughterhouse. They were classified according to the character of the cumulus cells under a stereomicroscope and then cultured in 25 mM Hepes buffered tissue culture medium-199 (TCM-199) supplemented with 5% estrous water buffalo serum in an atmosphere containing 5% CO2 in air at 39 degrees C. After 20 to 24 hours of in vitro maturation, the oocytes were cultured at 38.5 degrees C in TCM-199 supplemented with 1% estrous water buffalo serum and in an atmosphere containing 5% CO2 in air. Oocytes with compact and dense cumulus cells cleaved significantly further (P<0.01, 67.3%, 33/49) than those with fair, partially denuded oocytes with thin cumulus layers (27.5%, 25/91) or small remnants of cumulus cells and poor naked oocytes (3/100). A substantial variation in fertilization and developmental rates (16.0 to 43.8%) was observed among 4 different bulls. Late morulae were transferred nonsurgically into 14 buffalo recipients on Day 6 or 7 of their estrous cycle. One recipient was diagnosed to be pregnant by palpation per rectum on Day 60 and delivered a calf in October 1991.

Journal Article↗
PubMed1994

Pregnancies established from water buffalo (Bubalus bubalis) blastocysts derived from in vitro matured, in vitro fertilized oocytes and co-cultured with cumulus and oviductal cells.

Buffalo ovaries were collected immediately after slaughter and were transported to laboratory in sterile saline at 37 degrees C. Follicular oocytes with the cumulus mass aspirated from 2 to 6 mm in diameter follicles were cultured in TCM-199 medium supplemented with 10% buffalo estrus serum (BES) in 5% CO(2) at 38.5 degrees C. After 20 to 24 h of incubation, the oocytes were inseminated with precapacitated frozen thawed spermatozoa for 6 h. The fertilization rate was 78.15% of the matured oocytes. Over an in vitro culture period of 3 to 9 d, 4.02% of the inseminated oocytes developed to the morula stage when cultured with cumulus cells alone and 17.83% when cumulus cells plus oviductal epithelial cells were used. The percentage of developed blastocysts was very low (0.57%) when the oocytes were co-cultured with cumulus cells from the original oocytes. However, 8% of the inseminated oocytes that were denuded 3 d after insemination developed to the blastocyst stage when they were co-cultured with cumulus and oviductal epithelial cells. Sixteen early/expanded blastocysts were transferred non-surgically to 16 recipients. Four of the 16 recipients became pregnant, of which 2 delivered normal buffalo male calves.

Journal Article↗
PubMed1996

A serum-free medium for use in a cumulus cell co-culture system for bovine embryos derived from in vitro maturation and in vitro fertilization.

The objective of this study was to develop a serum-free medium for the co-culture of bovine embryos that would yield a percentage of blastocysts equal to that obtained with fetal bovine serum (FBS)-supplemented medium. Cumulus cell-enclosed oocytes (CEO) matured and inseminated in vitro were cultured in a tissue culture medium (TCM)-199 or in a serum-free medium (bovine embryo culture medium; BECM) until 240 h post insemination. Replacement of 10% (v/v) FBS with either 3 mg crystallized bovine serum albumin (BSA)/ml or 3 mg fatty acid-free BSA/ml in TCM-199 had no effect (P > 0.14) on embryo development to the >or= 2-cell (51 to 60%), >or= 8-cell (24 to 33%), blastocyst (16 to 19%) and hatched-blastocyst (7 to 10%) stages at 48, 96, 192 and 240 h post insemination, respectively. Oocyte-enclosing cumulus cells in BSA-supplemented medium grew in clusters rather than in layers, as was noted in FBS-supplemented medium. When CEO were cultured in fatty acid-free BSA-supplemented media (TCM-199 and BECM), a significantly (P < 0.001) higher percentage of oocytes developed to blastocysts after culture with (22%) or without (18%) a cumulus cell monolayer than after denuding the oocytes (7%). Glucose in concentrations of 0 to 5.56 mM added for periods of 18 and 120 h post-insemination had neither a stimulatory nor a deleterious effect on preimplantation development. In conclusion, a serum-free medium supplemented with BSA can be successfully used in a cumulus cell co-culture system for bovine embryos.

Journal Article↗
PubMed1988

Chicken hepatic metabolism in vitro. Protein and energy relations in the broiler chicken--VI. Effect of dietary protein and energy restrictions on in vitro carbohydrate and lipid metabolism and metabolic hormone profiles.

1. Ross male broiler chicks growing from 14 to 28 days of age were fed 14 and 20% protein diets (4 kcal day-1/body wt0.66) or 20 and 28% protein diets (2.8 kcal day-1/body wt0.66) in a 2 x 2 factorial arrangement to determine the effects of protein and energy intakes on in vitro lipogenesis (IVL) and net glucose production (NGP). Plasma concentrations of insulin, glucagon, thyroid hormones (T3 and T4) and somatomedin-C (Sm-C) were estimated by radioimmunoassay. 2. There was a significant (P less than 0.05) decrease in IVL in the chicks given the higher daily protein intake. 3. The higher protein intake increased (P less than 0.05) NGP while the lower energy intake decreased (P less than 0.05) NGP. 4. Insulin, both thyroid hormones and Sm-C were affected by dietary energy and protein intakes.

Animals↗
PubMed1980

Preliminary studies on the validity of in vitro measurement of drug toxicity using HeLa cells. I. Comparative in vitro cytotoxicity of 27 drugs.

Combined drug toxicity to HeLa cells was studied in vitro with use of the microtitre MIT-24 test system. Whether drug toxicity to HeLa cells is representative of drug toxicity to other cultivated cells was investigated by a comparison of the MIT-24 toxicity of 27 drugs to HeLa cells with their toxicity to various permanent cell lines and more differentiated primary cell cultures as reported in the literature, together with original recordings of the MIT-24 toxicity of 9 of the drugs to human fetal kidney cells. A similarity of drug toxicity to all cell types was found. Thus the MIT-24 recordings may be representative of a basal drug cytotoxicity, probably corresponding to local drug irritation and to causal systemic drug toxicity.

Cell Survival↗
PubMed1994

Multicenter evaluation of the in vitro activity of piperacillin-tazobactam compared with eleven selected beta-lactam antibiotics and ciprofloxacin against more than 42,000 aerobic gram-positive and gram-negative bacteria. In Vitro Susceptibility Surveillance Group.

The in vitro activities of piperacillin-tazobactam, 11 other beta-lactam antibiotics, and ciprofloxacin were evaluated in a large multicenter study. A total of 42,208 organisms, collected from 79 listed medical centers and large community hospitals, were tested using the National Committee for Clinical Laboratory Standards broth microdilution procedure. Imipenem (94.7% inhibition), ciprofloxacin (93.8%), and ceftazidime (90.8%) were the most active antibiotics against 31,426 Gram-negative bacilli. Piperacillin-tazobactam (88.8%) and ticarcillin-clavulanate (86.4%) were the most active combination antibiotics against these organisms. Ampicillin-sulbactam (97.8%), piperacillin-tazobactam (96.4%), and imipenem (96.9%) were the most active antibiotics against 10,782 Gram-positive cocci. Overall, the most active antibiotics against all organisms tested were imipenem (95.2%), ciprofloxacin (91.0%), and piperacillin-tazobactam (90.8%).

Anti-Bacterial Agents↗
PubMed2006

In vitro and in vivo efficacy and in vitro metabolism of 1-phenyl-3-aryl-2-propen-1-ones against Plasmodium falciparum.

Investigation of a series of 1-phenyl-3-aryl-2-propen-1-ones resulted in the identification of nine inhibitors with submicromolar efficacy against at least one Plasmodium falciparum strain in vitro. These inhibitors were inactive when given orally in a Plasmodium berghei infected mouse model. Significant compound degradation occurred upon their exposure to a liver microsome preparation, suggesting metabolic instability may be responsible for the lack of activity in vivo.

Animals↗
PubMed2004

Assessment of primary eye and skin irritants by in vitro cytotoxicity and phototoxicity models: an in vitro approach of new arginine-based surfactant-induced irritation.

Extensive efforts have been made, recently, to find surfactants with lower irritation potential than those presently commercially available, for use in pharmaceutical and cosmetic preparations. Cytotoxic and phototoxic effects of a novel family of dicationic arginine-diglyceride surfactant compounds, 1,2-diacyl,3-O-(l-arginyl)-rac-glycerol with alkyl chain lengths in the range from 8 to 14 carbon atoms, were compared to three commercial surfactants. The end-points used to assess toxicity were the red blood cell lysis assay and uptake of the vital dye neutral red 24h after dosing (NRU), respectively. Two immortalized cell lines, murine fibroblast cell line, 3T3, and one human keratinocyte cell line, HaCaT, were used as in vitro models to predict the potential phototoxicity which could result in irritation, determined by resazurin reduction to resorufin and neutral red uptake (NRU). All tested surfactants had cytotoxicity effects as demonstrated by and decrease of NR uptake, which showed a clear concentration-response relationship. Concentrations resulting in 50% inhibition of NR uptake (IC(50)) range from 1 microM(-1) (hexadecyl trimethyl ammonium bromide) to 565 microM(-1) (12,12-l-arginine). Erythrocyte haemolysis also showed a clear concentration-response relationship, the 50% of haemolysis ranged from 37 microM(-1) (10,10-l-arginine) to 151 microM(-1) (sodium lauryl sulphate). Phototoxicity was performed with 12,12-l-acetyl-arginine, the most stable chemical structure. The validated 3T3 NRU photoxicity assay was used and revealed a phototoxic potential.

Animal Testing Alternatives↗
PubMed1997

Morphological events during in vitro fertilization of prepubertal goat oocytes matured in vitro.

Experiments were carried out to study morphological changes temporally associated with in vitro fertilization (IVF) of prepubertal goat oocytes and to elucidate some of the abnormalities occurring during this process. The effects of different intervals of insemination on subsequent embryonic development were also studied. Prepubertal goat oocytes collected at slaughter were matured in TCM199 supplemented with estrous goat serum (20%), FSH (10 microg/ml), LH (10 microg/ml) and estradiol-17 beta (1 microg/ml) for 27 h at 38.5 degrees C. Matured oocytes were inseminated with freshly ejaculated spermatozoa following capacitation as described by Younis et al. (37) but with 100 microg/ml heparin. Representative oocytes were fixed every 2 to 4 h from 2 to 28 h after insemination for a study of sperm penetration, sperm head decondensation, meiotic activation, female chromosome decondensation, and male and female pronuclear formation. At the same intervals after insemination, some of the ova were co-cultured on granulosa cell monolayers for up to 9 d. Sperm penetration into the ooplasm was first observed at 4 h post insemination; decondensation of male and female chromatin and formation of male and female pronuclei occurred at 6 to 8 and 10 to 16 h after insemination, respectively. Highest proportions of oocytes were penetrated after exposure to spermatozoa for 8 h. There were no significant differences in ovum penetration after longer insemination intervals. Cleavage was first observed 24 h after insemination. Three types of abnormalities were observed. These were polyspermy, polygyny and asynchrony in the development of the female and male pronuclei, apparently due to a delay in the decondensation of the male pronucleus. Significantly higher proportions of oocytes cleaved (31.2 to 45.5%) after 20, 24 or 28 h insemination intervals than following shorter intervals of exposure to spermatozoa. However, the sperm exposure interval did not significantly affect subsequent embryonic development to the blastocyst stage. Embryos resulting from oocytes exposed to sperm cells for at least 12 h developed further than the 8-cell stage.

Journal Article↗
PubMed1997

Effects of extracellular potassium concentrations on acrosome reaction and polyspermy during in vitro fertilization and subsequent development in vitro in the pig.

Potassium (K(+)) concentration in the mammalian oviduct and uterus is particularly interesting due to its unusually high concentration (12 to 25 mM) compared with that in the blood stream (3 to 6 mM). In this study we examined the effects of various K(+) concentrations in the fertilization medium on polyspermy and subsequent in vitro development of porcine oocytes. In the absence of K(+) in the fertilization medium, sperm penetration was not observed. The incidence of polyspermy was significantly higher in the fertilization medium that contained 6 or 12 mM K(+) as compared with 3 mM K(+). The mean number of sperm penetrated in oocytes in medium with 6 and 12 mM K(+) was higher than in medium with 3 mM K(+). The addition of 3, 6 or 12 mM K(+) to the fertilization medium did not significantly affect the proportion of zygotes that developed to the blastocyst stage (14.1, 12.4 and 15.0%, respectively). Chlorotetracycline (CTC) analysis was used to determine the capacitation and acrosome reaction of spermatozoa incubated for 3 h with various concentrations of K(+). The number of acrosome reacted spermatozoa decreased with increasing K(+) concentration. These results suggest that extracellular K(+) in the fertilization medium affects sperm acrosome reaction which may be related to the sperm penetration.

Journal Article↗
PubMed1988

Suitability of in-vitro xenodiagnosis: development of Trypanosoma cruzi in Triatoma infestans depending on larval stage of bugs and number of trypomastigotes taken during in-vitro blood meal.

A study on artificial xenodiagnosis was carried out for the identification of T. cruzi, the causative organism of the American Trypanosomiasis (Chagas Disease) using the natural vector T. infestans. It was investigated whether one single T. cruzi (strain B) is sufficient for successful infection of T. infestans. Since the infection took place by artificial feeding, the average amount of blood taken by larval stages I-V in one meal was determined. On the basis of these results the feeding solution (defibrinated cattle blood) containing the corresponding T. cruzi-concentration/ml was prepared and twenty-one days after the infection feces were investigated for the presence of T. cruzi. It could be shown that one T. cruzi is sufficient for infection of larval stages I-V, although the rate of infection in larval stages IV and V was much lower than in larval stages I-III. These experiments demonstrate that xenodiagnosis can also be performed in-vitro. The possible negative effects due to biting of bugs for in-vivo xenodiagnosis of patients can be avoided. Using this method, far more bugs can be used than in conventional xenodiagnosis increasing the likelyhood of detecting at least one infected T. infestans. Additional experiments simulating postal dispatch during three days at 4 degrees C and 27 degrees C proved that blood samples from far distant places may be sent to be examined at laboratory.

Animals↗
PubMed1997

Dissolution media for in vitro testing of water-insoluble drugs: effect of surfactant purity and electrolyte on in vitro dissolution of carbamazepine in aqueous solutions of sodium lauryl sulfate.

The intrinsic dissolution rate and solubility of carbamazepine was measured in aqueous solutions of sodium lauryl sulfate (SLS) prepared with two different grades of purity, 95 and 99%, and 95% SLS in 0.15 M NaCl to determine the effect of surface-active impurities and electrolytes. Four significant observations resulted from this work: (1) the equilibrium coefficients calculated from the solubility experiments in the 99% SLS, 95% SLS, and 95% with 0.15 M NaCl SLS solutions were 295, 265, and 233 L/mol, respectively; (2) the dissolution rate enhancement in the 99% SLS was 10% greater than that in the 95% SLS and 95% with 0.15 M NaCl solutions, which were not significantly different; (3) the diffusion coefficients of the drug-loaded micelles estimated from the dissolution experiments were 8.4 x 10(-7) cm2/s for the 99% SLS, 9.5 x 10(-7) cm2/s for the 95% SLS, and 1.2 x 10(-6) cm2/s for the 95% with 0.15 M NaCl; and (4) the critical micelle concentrations for the 99% SLS, 95% SLS, and 95% SLS with 0.15M NaCl were 6.8, 4.2, and 0.35 mM, respectively. The results of this study clearly illustrate the sensitivity of the micelle to impurities and electrolytes with regard to size and loading capacity and the effect these changes have on the solubility and dissolution rate. Therefore, when using surfactants in dissolution media for in vitro testing of dosage forms, consideration must be given to the level of impurities present so that the results are consistent and reliable. Intrinsic dissolution rate, surface tension, or solubility measurements may be useful, convenient methods for identifying changes in the surfactant due to either degradation or lot-to-lot variability.

Carbamazepine↗
PubMed1996

HT29-MTX/Caco-2 cocultures as an in vitro model for the intestinal epithelium: in vitro-in vivo correlation with permeability data from rats and humans.

The diverse secretory and absorptive functions of the intestinal epithelium are conducted by a mixed population of absorptive cells and mucus-producing goblet cells as the major cell types. In order to approach the main characteristics in an in vitro model, a coculture system of absorptive Caco-2 cells and mucus-secreting HT29-MTX cells was developed and the permeability of a range of different drugs was tested. Variable goblet cell frequency can be achieved, preserving a significant barrier to drug transport and maintaining the differentiated features of both cell types. Absorption rates for actively transported drugs are rather underestimated in the cell culture model when compared to in vivo data. However, a good correlation with fraction absorbed in humans was attained separating the range of passively transported drugs into two groups of well-absorbable compounds with Peff > or = 10 x 10(-6) cm/s and drugs that are absorbed 40-70% with Peff = 0.1-1 x 10(-5) cm/s. A permeability of Peff < 0.1 x 10(-5) cm/s is suggested for low absorbable drugs.

Animals↗
PubMed1998

Growth inhibition of human in vitro and mouse in vitro and in vivo mammary tumor models by retinoids in comparison with tamoxifen and the RU-486 anti-progestagen.

Retinoids constitute a very promising class of agents for the chemoprevention or treatment of breast cancer. These retinoids exert their biological activity through two distinct classes of retinoic acid (RA) receptors (R), the RAR isotypes (alpha, beta, and gamma) and the three RXR isotypes (alpha, beta, and gamma) and their numerous isoforms which bind as RXR/RAR heterodimers to the polymorphic cis-acting response elements of RA target genes. With respect to these numerous receptor sub-types, the retinoid-induced effects at the biological level include marked modifications with respect to both cell proliferation and cell death (apoptosis), and also in the induction of differentiation processes. The present study aims to characterize the effect which four retinoids (TTNPB, 9-cis-RA, LGD 1069, 4-HPR) with distinct RAR/RXR binding properties induced on various in vitro and in vivo mouse and human breast cancer models. The experiments with the retinoids were carried out in comparison with the anti-estrogen tamoxifen and the anti-progestagen RU-486 compounds. The results show that the 6 compounds under study were markedly more efficient in terms of growth inhibition in the human T-47D cell line when maintained under anchorage-independent culture conditions than when maintained under anchorage-dependent ones. While RU-486 exhibited a weak statistically significant (p < 0.05) influence on the growth of the T-47D stem cells, tamoxifen had a marked inhibitory influence on the growth of these cells. Of the four retinoids, 4-HPR was the least effective since the lowest doses tested (1 and 0.1 nM) exhibited no statistically (p > 0.05) significant influence on the growth of the stem cells. The most efficient retinoid was TTNPB. It was only at the highest dose (10 microM) that tamoxifen and RU-486 showed a weak inhibitory influence on the growth of the T-47D non-stem cells while all 4 retinoids exerted a significant inhibitory influence on the growth of these non-stem cells, with 4-HPR being the most efficient (P < 0.001) at the highest dose, but ineffective (P > 0.05) at the lowest. Tamoxifen and TTNPB were tested in vivo on hormone-sensitive (HS) and hormone-insensitive (HI) strains of the MXT murine mammary carcinoma. While TTNPB appeared to be equally efficient in terms of growth inhibition in both MXT-HS and MXT-HI models, tamoxifen had only a marginal inhibitory influence on the growth of the MXT-HI strain but did inhibit growth in the case of the MXT-HS one. TTNPB was markedly more efficient than tamoxifen in terms of both inhibiting the cell proliferation level (measured by means of computer-assisted microscopy applied to Feulgen-stained nuclei, a method which enables the percentage of cells in the S phase of the cell cycle to be determined) and triggering cell death (measured by means of the determination of the transglutaminase activity) in both the MXT-HI and MXT-HS models. The very significant TTNPB-induced inhibition of the macroscopic MXT-HS growth rate relates to the triggering of cell death (apoptosis) rather than to an inhibition of cell proliferation. All these results clearly indicate that retinoids are very efficient agents against breast cancer, at least as efficient as tamoxifen.

Alitretinoin↗
PubMed1999

Development of a new in vitro system for continuous in vitro exposure of lung tissue to complex atmospheres: application to diesel exhaust toxicology.

The purpose of this study was the development of a new incubation system that can allow continuous exposure of lung tissue to complex atmospheres as a tool for the assessment of aerial environmental lung toxicology. To assess the pertinence of this new exposure system, we studied the impact of diesel engine exhausts as a complex atmosphere containing both gaseous and particulate fractions and have been able to discriminate between the toxicological impacts of the gaseous phase and particulate matter from diesel exhausts. Continuous flow-through rotating chambers with controlled PO2, pCO2, and hygrometry have been designed in which lung slices are positioned in rolling inserts that allow free access of atmosphere to the exposed lung tissue. Under control conditions, cell viability was preserved for at least 48 h as assessed by intracellular ATP, GSH, and K+ levels and slice O2 consumption levels. Short-term exposure (1 h) to diesel whole exhausts did not affect intracellular potassium or slice O2 consumption, while intracellular ATP and GSH levels were markedly decreased. Exposure to filtered exhausts showed less marked effects on both ATP and GSH levels. Superoxide dismutase activity was decreased in a similar way by both total and filtered exhausts while Se(+)-dependent glutathione peroxidase activity was induced by filtered exhausts to a larger extent than after total exhaust exposure, showing different response patterns of lung tissue after exposure to whole or filtered exhausts. In conclusion, this newly designed model opens a promising area in in vitro environmental lung toxicology testing.

Adenosine Triphosphate↗
PubMed1985

The effect of passage in vitro and in vivo on the properties of murine fibrosarcomas. II. Sensitivity to cell-mediated cytotoxicity in vitro.

The sensitivity of cultured and mouse-passaged cloned lines of chemically-induced murine fibrosarcomas to killing by NK and NC cells, and to cell-mediated immunity, has been studied in in vitro assays, using target cells labelled with 51Cr or 125IUDR. None of the lines tested proved sensitive to NK cells. Three cultured lines were, at most, only slightly sensitive to NC cells; a fourth cultured line was moderately sensitive and became less so, but not completely insensitive, after passage in susceptible hosts. The primary object of these experiments was to test the hypothesis that cultured cell lines which ordinarily fail to grow in normal mice are able to grow after being passaged in a susceptible immunodeficient host because, during this passage, they become resistant to NK or NC cells. This has been shown to occur with one clone, but will not serve as a general explanation because, with other clones, both cultured and mouse-passaged lines were NC-insensitive. The cell-mediated immunity assays confirm our previous conclusion that cultured and mouse-passaged lines of the same clone differ little, if it all, in immunogenicity.

Animals↗
PubMed1983

The folding of ovalbumin. Renaturation in vitro versus biosynthesis in vitro.

Hen ovalbumin, the major secretory product of oviduct cells, is a 43 000-dalton glycoprotein. Many studies have led to controversy over the question of whether ovalbumin (OA) can be fully renatured after chemical denaturation. We have studied the renaturation of OA after denaturation with guanidinium chloride, urea or alkaline pH. Denatured OA displays an intrinsic viscosity consistent with nearly complete unfolding of the protein. Removal of the denaturant results in a complete reversal of the changes in intrinsic viscosity. However, closer examination of the renatured protein reveals major differences from the native form. Renatured OA (OAR) can be completely separated from the native form (OAN) by affinity chromatography on phenyl-Sepharose. OAR displays altered tryptophan fluorescence, u.v.-absorption and c.d. spectra. Only OAR binds anilinonaphthalenesulphonate (as measured by fluorescence enhancement). OAR, but not OAN, binds about 2 mol of the covalent hydrophobic affinity probe phenyl isothiocyanate/mol. Renaturation, and the production of OAR, occurs regardless of the oxidation state of the disulphide bonds, of phosphorylation of the protein, and of the presence or the absence of the single carbohydrate chain. OAR may be either monomeric or an irreversible aggregate. Which of these two states is formed depends on the protein concentration during renaturation. Monomeric and aggregated OAR can be distinguished on the basis of some spectroscopic characteristics, but they share the essential hydrophobic characteristics that distinguish them from OAN. OAN and OAR do not spontaneously interconvert. Antibodies raised to each can be made monospecific by immunoabsorption. Thus two stable forms of OA can be obtained, one of which, OAR, displays hydrophobic characteristics. OAN, but not OAR, is formed when OA is synthesized in vitro in a translation system.

Animals↗