Effects Of Experimental Treatments Research Articles

Intercellular Cohesion and Expansion Growth in Higher Plants

FREQUENTLY the growth of plant organs such as the root or coleoptile is considered in terms of the changing number, or size, of the component cells, and the effect of experimental treatments (or environmental changes) on the overall growth is considered in relation to the primary metabolism of the average component cell. Such an approach must fall short of describing in full the growth of the organ if it assumes that tissue behaviour is no more than the summation of the behaviour of individual isolated cells. In a healthy tissue the constituent cells are always firmly attached to each other, and this attachment and any change in it are likely to be of great importance to the growth of the tissue.

Preservation of Honey Bee Semen

Fertilized eggs have been obtained from queen honey bees (Apis mellifera L.) inseminated with sperm that had been stored in vitro at above-freezing temperatures for up to 68 days. The effects of various experimental storage treatments on semen are described. Semen shipped by ordinary mail has been successfully used for artificial insemination.

The effect of various experimental treatments on the development of the embryo of the fernThelypteris palustris

The effect of various experimental treatments on the development of the embryo of the fernThelypteris palustris

The Comparison of the Sensitivities of Similar Experiments: Applications

effects of experimental treatments is a difficult one in certain areas of research. We are concerned with means of comparing the sensitivities of two available experimental techniques, where we use the term in a very general sense, that might be used to yield data for specified treatment comparisons. It is often not possible to determine on a priori grounds which of two techniques should be used and it may be desirable to use both techniques in separate experiments with a view to deciding on the technique to be used in future experimentation. When the two experiments are indeed independent of each other in probability, the methods of this paper may be used. Let us consider several typical situations indicated by subj ectmatter headings. Taste Testing: Hopkins [1950, 1953] investigated the use of discrete scoring scales in taste testing experiments as they are commonly used and Baten [1946] suggested the use of a continuous line scoring system. The latter obtained results which he interpreted as showing an increase in sensitivity for his method over the use of discrete scores. Procedures discussed in this paper provide means of comparing the sensitivities of the two scoring systems if data were available from two identically designed but statistically independent experiments, one for each scoring system, in a form suitable for analysis of variance. Many other comparable situations arise in taste testing. The sensitivities of two taste panels, two methods of preparation of test items, two environmental situations during tasting, or two methods of storage may be compared.

A Follow-Up of an Experimental Teaching Method in Music at the Fourth and Fifth Grade Levels

IN THE MARCH, 1955, issue of the Journal of Experimental Educationl* the author report ed the results of an experiment he conducted in 1952-53 at the Concord School, Edina, Minne sota. The purpose of that study was to deter mine what effects might be observed when i n strumental training is introduced into the con ventional music curriculum. A compar i s o n was made between two types of music programs: instrumental-vocal and vocal alone. In order that main effects of experimental treatment and grade level could be measu red simultaneously the writer set up a 2 x 2 factor ial design. Thus a control and experim ental group were selected at the fourth grade and the same procedure followed at the fifth grade lev el, making a total of four subclasses. The con trol subgroups were taught primarily by the singing approach while the experimental class es had equal amounts of instruction time in vo cal and instrumental performance. Both the control and experimental subgroups had music class daily for the entire school year of 1952-53. Each class period was thirty min utes in duration. In order to minimize the ef fect of the instructor, the investigator taught all four classes. However, due to c i r c urn stances beyond the control of the author, the treatment differences could be extended only over a period of twenty-five consecutive weeks, rather than the entire school year. The tests used to measure the gains over the period of the experiment were selected to measure criteria of knowledge of musical nota tion, audio-visual discrimination, and music preference. The latter criterion was tested by means of the Keston Music Preference Test* and the former criteria by two tests the author constructed for this purpose. Test 1 measured knowledge of musical notation and Test 2 was designed to measure the discrimination pow er of the subjects with respect to musical audio visual stimuli. All the tests were administered before and after the experimental treatment. The technique of analysis of variance and co variance served as the main tool in the anal ysis of the data thus compiled. This device was useful not only because it yielded an exact test of the effects but also because it took into account the subjects' inequalities in initial abili ties and achievements.

Preparation of cell suspensions from plant roots for cytological studies.

A CONSIDERABLE amount of microscope work involved in cytological studies of plant roots can be obviated by the preparation of a cell suspension from a number of roots ; the cell suspension can then be examined instead of a large number of sections or squashes of individual roots. This is of particular advantage in studies in which the examination of a large cell population is required for the evaluation of the cytological effects of a particular experimental treatment, such as X-radiation. A number of techniques have been described for making cell suspensions from plant roots1–3, all of which either produce a large number of broken cells or require the use of enzymes. The following simplified method without the use of enzymes has given satisfactory results with Vicia faba root-tips, the number of cells broken being negligible.

Manuring of grassland. I.—Some effects of heavy dressings of nitrogen on the mineral composition of grassland herbage

AbstractResults are given for the effects of heavy dressings of nitrogen, in the presence and absence of phosphorus and potassium supplements, on: dry‐matter yield; botanical composition of herbage; contents of crude protein, phosphorus, potassium, calcium, magnesium, sodium and manganese. Brief reference is also made to the effects of the various experimental treatments on the uptake of certain other trace‐constituents.The results indicate that high yields of pasture herbage having high protein and normal mineral contents can be maintained over a period of years by the use of fertilizer nitrogen, provided adequate fertilizer dressings of other major nutrients are given. Attention is drawn to various ion‐antagonism effects that may influence the mineral composition of the herbage.

Interrelation of large parenteral doses of estrogen and Vitamin A and their effect on the oral mucosa

The problem is one of potential connection between the hyperkeratinization of oral mucous membranes seen in vitamin A deficiency and that produced in long-term large-dose estrogenic therapy. Hormones and vitamins have specific effects on the organism as a whole. Both of these substances affect epithelial structures in a definite manner. Do they at all times perform as separate entities or, under the conditions described, do they act, directly or indirectly, upon each other? In the first experiment, two subadult female rhesus monkeys, one normal and one ovariectomized, were given 1,000 R.U. of progynon B for fifty-three days, when biopsies showed a definite change in the alveolar and areolar gingivae as evidenced by hyperkeratinization and hyperplasia. Eight days after the observance of these changes, daily doses of vitamin A (10,000 I.U.), plus estrogen (500 R.U.), were given for thirty-one days, after which time the animals were sacrificed and sections of oral mucous membranes and vaginas were studied. The effect of the vitamin A upon the keratinization and hyperplasia produced by estrogen was a suppression or amelioration. In the second experiment on a female rhesus monkey, large doses of vitamin A (10,000 I.U.) daily for thirty days were followed by combined vitamin A (10,000 I.U.) and estrogen (1,000 R.U.) daily for thirty days. In general, the results of the vitamin A administration indicated a degenerative change in the gingivae. The addition of estrogenic hormone to the administration of vitamin A resulted in overcoming the high vitamin A effect, producing hyperplasia of the gingivae with marked restoration of tissue tone. Although the injection of the combined estrogen and vitamin A produced an amelioration of the previous treatment effects in both experiments, the results in each were dissimilar.

THE USE OF A MEASURABLE CAUSE OF DEATH (HEMORRHAGE) FOR THE EVALUATION OF AGING

1. There has been need for a reliable experimental standard for the process of aging. Chronological age is a poor standard owing to irrelevant changes and individual variability. Longevity does not indicate the rate of aging because it depends not only upon aging but also upon intrinsic death rate, individual variability, and the selective effect of experimental treatment upon resistance to specific diseases. 2. The use of a known measurable cause of death (hemorrhage) on healthy animals of various ages reproduces the known mortality curve for rats, and differentiates this measure of the aging process from individual variation. 3. The possibilities for the use of this method in determining the nature of the aging process are pointed out.