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Results for “Biological Assay”

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At least 19 recordsLinked to original sources
PubMed1975

[Biological assay of hypophyseal gonadotropins in the male rat (statistical study)].

The reproductibility, the experimental and statistical procedures of FSH and LH bioassays are studied. The estrogen pretreatment of animals increases, considerably the responsiveness and reliability of the LH bioassays. FSH levels have been determined, by the methods for parallel line assays, in the pituitary gland of normal rats and three days or seventeen days orchiectomized rats.

Animals↗
PubMed1976

A sensitive biological assay for prostaglandin E and acetylcholine.

Superfused hamster stomach strip has been used in the bioassay of prostaglandin E2 (PGE2) and acetylcholine. The preparation proved very stable and had no spontaneous movements. The sensitivity to PGE2 (and PGE1) was in the range of 10(-9) g ml(-1) and to acetylcholine 10(-12) g ml(-1). After treatment with physostigmine the sensitivity to acetylcholine was 10(-15) g ml(-1). In acetylcholine determination the preparation is more sensitive than any other method.

Acetylcholine↗
PubMed1978

Biological assay of potential trichomonacides in vitro using a counter apparatus.

Utilising the accuracy and speed of a Coulter Counter for cell counting and sizing, a new method of antimicrobial assay has been developed in which the potency of inhibitors is calculated on a mol/cell basis. A total of 72 potential trichomonacides were screened against Trichomonas vaginalis and the ED50 value estimated for 27 of the most interesting and potent compounds. The ED50 value for metronidazole was a mean of 5.12 fmol/cell and only 6 compounds were more potent. After the nitroimidazoles, the acridines were the most potent group of compounds. Only chlortetracycline and gramicidin caused an increase in mean cell size.

Antitrichomonal Agents↗
PubMed1979

Improved lysozyme assay in biological fluids.

We describe a simple, rapid, sensitive, and highly reproducible assay for lysozyme, with use of concentrated cell suspensions of Micrococcus lysodeikticus in Tris-buffered glycerol/water (40/60 by vol), pH 7.5. Stored at -20 degrees C, the cells' susceptibility to lysozyme remains unaltered over long periods. Almost identical concentration curves were obtained with different aliquots of the same preparation during eight months. Lysozyme activity was reflected in the decrease in absorbance of the reaction mixture after incubation for 15 min at 37 degrees C. Concentrations of egg-white lysozyme as low as 0.02 mg/L can be accurately assayed.

Biological Assay↗
PubMed1979

A murine teratocarcinoma stem cell line carries suppressed oncogenic virus genomes.

Murine teratocarcinoma stem cells are nonpermissive for productive infection by a variety of DNA (polyoma and SV40 virus) and RNA (murine leukemia and sarcoma virus) tumor viruses whereas differentiated murine cells derived from the stem cells are permissive for productive (or abortive in the case of SV40) infection by these same viruses. The block to productive infection by these oncogenic viruses is at a postpenetration step in the replication cycle of these viruses but the precise level of the block has not been established for any of these viruses. In this report we describe teratocarcinoma-derived stem and differentiated cell lines which should be especially useful in determining the level of the block to replication of ecotropic murine leukemia virus in murine teratocarcinoma stem cells. The stem cell line, OTT6050AF1 BrdU, which is completely nonpermissive to productive infection by Moloney murine leukemia virus and consists of 97% pluripotent stem cells, contains DNA copies of an RNA tumor virus which is indistinguishable from the N-tropic murine leukemia virus of AKR mice. The stem cells are negative for expression of viral reverse transcriptase, p30 and gp69/71 and no virus is found by XC plaque assay or other biological tests. Differentiated cells established from the same teratocarcinoma tumor are 100% positive for viral gp69/71, p30, and produce large amounts of reverse transcriptase activity and N-tropic virus as detected by biological assay. The virus isolated from the differentiated cells is closely related, if not identical to AKR N-tropic virus by nucleic acid hybridization studies and is thus not an endogenous virus of the 129 strain of mice. The teratocarcinoma tumor from which the cell lines were established had been carried in 129 mice and perhaps at some time in the mouse passage history the tumors were infected (nonproductively) with the N-tropic virus. Regardless of the origin of this viral DNA, the OTT6050A derived stem and differentiated cell lines should be extremely useful in defining in stem cells the step at which ecotropic murine leukemia virus replication is blocked.

Animals↗
PubMedDate not supplied

An enzyme-linked immunosorbent assay for detecting avian leukosis-sarcoma viruses.

Immunoglobulins from antiserum raised against chromatographically purified avian myeloblastosis virus (AMV) group-specific (gs) antigens were used in enzyme-linked immunosorbent assay (ELISA). Readily discernible color was produced with 2--3 ng of AMV protein in microplate wells coated with 4 micrograms of salt-precipitated immunoglobulins. When a biological assay, i.e., phenotypic mixing (PM), was the criterion for the infectious status of specimens, the ELISA consistently identified a greater percentage of virus-positive specimens than direct complement-fixation (DCF) tests. Over 95% concordance was obtained between the ELISA and PM bioassays when meconia and whole-blood samples were tested. Moreover, three DCF(-) egg albumens from one virus shedder hen were positive by the direct ELISA. Complete agreement was found between a biological assay for endogenous virus and the ELISA when blood and albumens from inbred chickens were tested. The ELISA is a rapid and convenient alternative to the DCF test for identifying infected chickens in eradication programs, because virus-rich sources such as meconia and blood that are unsuitable for DCF can be tested directly.

Alpharetrovirus↗
PubMed1979

Comparison of specific protein assays in biological fluids by radial immunodiffusion and laser nephelometer.

Laser immuno-nephelometry is presently being used for measuring concentrations of specific proteins in biological fluids. Our findings have not substantiated the highly correlative results with radial immunodiffusion that have been reported. The reason for our poor correlation was found in the lack of uniformity in expressing concentrations of the different specific proteins in the calibrating standards. One value of the laser nephelometer was the greater precision obtained when comparing results to those measured by radial immuno-diffusion. Also, the laser was found to be more sensitive for measuring low level concentrations.

Blood Proteins↗
PubMed1976

Antiandrogens.

Many antiandrogens, mainly steroidal and some nonsteroidal agents, have been synthesized and tested in several available biological assays. Unfortunately, many of these compounds have other biological activities which make it difficult to ascertain the precise mechanism of antiandrogenic action. The blocking of androgen action can be accomplished by a number of ways: (1) the inhibition of gonadotropin release and/or synthesis, (2) the interference with testosterone and/or dihydrotestosterone biosynthesis, (3) the blocking of protein synthesis, and (4) the competition with androgens at receptor sites. Although the major reason for the development of antiandrogens is to utilize them in certain clinical situations, some have become important tools in studying androgen action, particularly on the molecular level. The clinical effectiveness of some antiandrogens in prostatic hyperplasias, hirsutism, and acne represents an important advance in therapeutics, but the search for more potent antiandrogens with minimal side effects should continue.

Acne Vulgaris↗
PubMed1978

Comparison of high pressure liquid chromatographic and chemical methods for vitamin D3 concentrates. II. Collaborative study.

A collaborative study was carried out which compared the official chemical method, 43.B14-43.B24, the official rat bioassay, 43.165, and the high pressure liquid chromatographic method for vitamin D3 resin, vitamin D3 resin in oil, and dry concentrate. A total of 340 samples were distributed to 17 collaborators for analysis. Five laboratories performed both the chemical and HPLC methods on 5 sets of blind duplicates. A 2-way analysis of variance comparing both methods for each sample showed a significant (P less than 0.01) difference between methods only for Sample 5. When the 2 methods were compared over all the samples, no significant (P less than 0.05) difference was found. Except for Sample 5, there were no differences in the repeatability of the methods. Per cent recoveries on Sample 3, which contained exactly 0.200 X 10(6) IU/g, showed 98.2% for the chemical method and 100.6% for the HPLC method for the 5 laboratories that performed both methods. The assay results of the HPLC and chemical methods are in good agreement with those found by the biological assay on Samples 1-4, but not for Sample 5. Evidence indicates that Sample 5 degraded partially to isotachysterol, and while the HPLC method yielded a reasonable value on this material, the chemical method erroneously showed full potency. An amendment is included for the collaboratively studied HPLC method which detects and eliminates 5,6-trans-vitamin D3, a possible interferant.

Animals↗
PubMed1975

Preparation of lutropin with acetyl or acetimidinyl substituents on the amino groups of the beta-subunit.

The free amino groups in ovine lutropin beta subunit were acylated with acetic anhydride and methyl acetimidinate-HCl to produce the corresponding acetyl and acetimidinyl ovine lutropin beta derivative. These two derivatives recombined with ovine lutropin alpha as well as native ovine lutropin beta, but produced lutropin derivatives which were 33-50% less active than the ovine lutropin alpha + ovine lutropin beta in biological assays.

Acetylation↗
PubMed1979

Determination of vitamin D in foods: a review.

Determining vitamin D content in foods is difficult because in natural foods of highest vitamin D activity, and even in vitamin D-fortified foods, only small quantities are present, and many other compounds are extracted along with vitamin D that cause difficulties in purifying the extract or in the spectrophotometry or colorimetry that follows. Several physicochemical methods--such as spectrophotometric, colorimetric, thin-layer chromatographic, adsorption, partition, gas-liquid, and high-performance column chromatographic--have been tried for assay foods for vitamin D, but none of them have been accepted for official or routine use; they are time consuming and expensive, or lack the required sensitivity, precision, or accuracy. Curative biological assays, based on degree of healing of a leg bone of rats previously made rachitic, is the generally accepted method to determine vitamin D content of foods. However, that method also requires too much time and is expensive. The recently developed high-performance liquid chromatographic method may offer the most for establishing a satisfactory physicochemical method for determining vitamin D in foods. Many of the difficulties and problems in assaying foods for vitamin D are discussed.

Animals↗