Evidence Of Antagonism Research Articles

The Effects of Vitamin A and Citral on Epithelial Differentiation in vitro 2. The Chick Oesophageal and Corneal Epithelia and Epidermis

ABSTRACT Differentiation of the oesophageal and corneal epithelia and epidermis of the chick embryo was studied in organ cultures in normal medium and in media containing added vitamin A and/or citral. In normal medium the oesophageal epithelium developed well for the first 6 days, but between 6 and 12 days many superficial layers of cells were sloughed and large mucous cells from the glands spread over the remaining epithelium. Vitamin A inhibited the normal stratification, and the oesophageal epithelium became pseudostratified and folded, with tall, columnar, ciliated cells and many small mucous glands. Citral inhibited the differentiation of ciliated and mucous cells and the epithelium became thicker than in normal medium. Vitamin A and citral together produced either a vitamin A or a citral effect, depending upon the relative concentrations of the two compounds. The corneal epithelium differentiated normally in the control cultures, but under the influence of additional vitamin A it remained thin and the superficial cells secreted mucus. In + citral medium the corneal epithelium became thicker than usual and the conjunctival epithelium keratinized. When both vitamin A and citral were added to the medium the corneal cultures showed a mild vitamin A effect. Skin cultures keratinized well in normal medium, but the epithelium remained thin and became mucus-secreting in response to high concentrations of vitamin A. Citral alone had little effect on epidermis, but it suppressed the vitamin A response almost completely when both compounds were added together. Citral produced changes resembling those of vitamin A deficiency in cultures of oesophagus and cornea, and it reduced the effects of added vitamin A. The results of these experiments therefore give further evidence of antagonism between vitamin A and citral. It is suggested that either deficiency of vitamin A or treatment with citral stimulates, whilst high concentrations of vitamin A inhibit, mitosis in the corneal epithelium. The results of these experiments indicate that each epithelium achieves its maximal synthesis of mucus at a characteristic concentration of vitamin A.

Evidence of antagonism between hydrochlorothiazide and mineralocorticoid active steroids

Evidence of antagonism between hydrochlorothiazide and mineralocorticoid active steroids

Chemical studies of isolated myofibrils in vitro: I. The role of magnesium, calcium and nitrogen-phosphorus partition in contraction induced with adenosinetriphosphate

1. 1. Isolated, structurally intact rabbit skeletal myofibrils contracted instantaneously when ATP was added in the presence of magnesium ions. 2. 2. An ATPase associated with the myofibrils split added ATP, yielding inorganic phosphate and ADP, neither of which was permanently bound to the contracted myofibril. Furthermore, there was no significant loss of nitrogenous material from the myofibrils during contraction unless it was accompanied by an equal shift of nitrogen from the suspending medium into the myofibrils. 3. 3. ATPase was active both before and after contraction. Dialyzed magnesium-depleted myofibrils did not contract but split added ATP, indicating that ATP-splitting alone is not a sufficient event to cause contraction. Fully contracted myofibrils retained ATPase activity despite the absence of structural changes accompanying this activity. 4. 4. Dialyzed magnesium-depleted myofibrils contracted instantaneously and split ATP when first magnesium ions and then ATP were added; but when calcium ions and then ATP were added, contraction did not occur despite ATPase activity. 5. 5. There was no evidence of antagonism between these ions, since myofibrils to which were added both calcium and magnesium ions followed by ATP contracted and split ATP. 6. 6. Although contraction was not obtained without the addition of ATP, it has not been shown that ATP splitting is essential for contraction.

The Effect on Growth of the Level of Manganese in the Diet of Rats, with Some Observations on the Manganese-Thiamine Relationship

Seven different levels of manganese intake have been used in an effort to establish the optimum dietary manganese level for growth in white rats. A wide range of manganese intake (0.1 to 20.0 mg per mother rat per day) is permissible during the lactation period. This is probably a reflection of the inefficient passage of dietary manganese into the milk, as well as of inefficient absorption from the intestinal tract of the mother. The young, therefore, have a lower level and narrower range of manganese intake than are apparently provided by the diet of the mother. After weaning, the optimum manganese intake for growth is 2 mg per rat per day at 30 days of age and about 3.75 mg per day at 50 days of age. At the levels fed in this experiment there is no evidence of antagonism between dietary manganese and thiamine with respect to the growth function.

FUNDAMENTAL STUDIES ON A SALTANT OF HELMINTHOSPORIUM SATIVUM

A saltant of H. sativum disappeared from six different soils in which it was cultured in the laboratory within four weeks, whereas the indigenous flora persisted for nine weeks. During this nine week period numbers of bacteria showed no obvious trend, but numbers of fungi decreased. When cultured in sterilized portions of the above soils, the saltant showed a downward trend in numbers in the nine week period, a trend that was more obvious in some cultures than in others. Twenty-two of 221 isolates of fungi from soil, grain, and air, 45 of 286 isolates of Streptomyces, and 33 of 193 isolates of other bacteria produced evidence of antagonism to the saltant in spot inoculation studies. Filtrates prepared from two of the fungal isolates suppressed the growth of the saltant, as did also autoclaved portions of the nitrates. On the contrary, filtrates from three cultures of bacteria failed to suppress growth of the saltant, even though cultures of the bacteria did. The same 22 fungal isolates and 25 of the Streptomyces, when introduced separately into sterile soil along with the saltant, reduced the disease rating of barley seedlings below that produced by the saltant alone. The direct-count method of estimating numbers of spores of the saltant in a suspension was found to be reliable. Estimates based on the direct count were significantly greater than those made by the plate method. Estimates based on numbers of the saltant developing on potato dextrose agar containing small amounts of sterile soil were smaller than those made on the same medium without the soil. Even though the soil in the medium changed the pH of the medium, the difference in pH was considered not to be the primary factor in producing the lower estimates. Soil, either natural or heat sterilized, would contain the thermostable filterable substance or substances found to be produced by two species of fungi and probably produced by other species, likewise normally present in soil.

TTHE INHIBITION OF COMB GROWTH IN COCKERELS AND CAPONS BY ESTRONEW123

A NTAGONISTIC as well as augmentative effects of the simultaneous ad'JLX. ministration of male and female sex hormones in mammals have been the subjects of numerous reports in the literature. The antagonistic effect is usually interpreted as an inhibition of the gonadotropic activity of the pituitary as suggested by Moore and Price (i), while the synergistic effects have not as yet been explained In Brown Leghorn capons, Juhn, D'Amour and Womack (2) found neither an ntagonism nor an intensification of effect when purified testis'tissue concentrates (2, capon units per day) and a urinary estrogen preparation (150 R.U. per day) were injected simultaneously for 34 days. Juhn, Gustavson and Gallagher (3) administered urinary estrogenconcentrates (10 R.U. per 25 gm. body weight) to young cockerels of various ages and found no evidence of antagonism except a shrinkage of the comb in a few birds in the group 12weeks of age. Since the testes of these birds were normal histologically.

Detoxification of Amidopyrine by Sodium Amytal

The antidotal action of sodium amytal against convulsant drugs has been demonstrated in both animals and men.1, 2, 3, 4 In view of the fact that large doses of amidopyrine cause convulsions of central origin,5 it appears interesting to ascertain whether or not sodium amytal will similarly reduce its toxicity. Evidence of antagonism between amidopyrine and other barbituric acid derivatives has already been observed by several European workers.6, 7White mice numbering 272 and rats numbering 221 were employed in the present investigation. They were all starved over night prior to medication. The drugs were injected by the tail vein. It is a coincidence that amidopyrine and sodium amytal when given alone have the same toxicity. The M.L.D. (minimal lethal dose) of each was found to be 150 mg. per kg. in mice and 135 in rats—using dose increments of 5 mg., and groups of 5 animals. The determined dose killed at least 3 animals out of an injected group of 5.In the next series of experiments, sodium amytal was add...

Investigations dealing with the phenomena of “clot” formations. Part IV.—The diphasic erosive action of salts on the cholate gel

In the last communication† of this series, attention was called to the fact that the cholate gel is eroded when immersed in solutions of sodium chloride and other chlorides, and that this erosive action can be “antagonised” by addition to the chloride solutions of relatively small amounts of calcium chloride. The analogy between this action and the biological “antagonistic” action of calcium towards sodium and other salts was also commented upon and illustrated by examples from the researches of Loeb, Osterhout and other investigators. In addition, however, to the antagonism between calcium salts on the one hand and sodium, potassium and magnesium salts on the other hand, Loeb has shown in the case of Fundulus that there is evidence of antagonism between potassium and sodium salts, that is to say that the toxic action of one salt can be rendered more or less innocuous by the addition of the other. Osterhout has shown that certain marine plants will retain their vital activities for a longer period in a solution which contains, in addition to sodium and calcium salts, also potassium and magnesium salts, and has formulated the conception of “balanced” salt solutions as necessities for the maintenance of the maximal activities of plants.