Showing papers by "Michigan State University published in 1979"

Determination of the Pore Size of Cell Walls of Living Plant Cells

Abstract: The limiting diameter of pores in the walls of living plant cells through which molecules can freely pass has been determined by a solute exclusion technique to be 35 to 38 angstroms for hair cells of Raphanus sativus roots and fibers of Gossypium hirsutum, 38 to 40 angstroms for cultured cells of Acer pseudoplatanus, and 45 to 52 angstroms for isolated palisade parenchyma cells of the leaves of Xanthium strumarium and Commelina communis. These results indicate that molecules with diameters larger than these pores would be restricted in their ability to penetrate such a cell wall, and that such a wall may represent a more significant barrier to cellular communication than has been previously assumed.

Teacher praise : a functional analysis

Abstract: Classroom-process data indicate that teachers’ verbal praise cannot be equated with reinforcement. Typically, such praise is used infrequently, without contingency, specificity, or credibility. Often it is not even intended as reinforcement, and even when it is, it frequently has some other function. The meanings and functions of behaviors typically included under the category of teacher praise are determined by the degree of congruence between verbal and nonverbal components and by the context in which the interaction occurs. Much teacher praise is determined more by teachers’ perceptions of student needs than by the quality of student conduct or performance. Considerations of classroom feasibility and probable student response to teachers’ attempts at social reinforcement suggest that teacher praise should remain infrequent, but that it could be made much more effective. Attribution theory is an important supplement to social learning/reinforcement theory for suggesting guidelines for praising effectively.

Phases of denitrification following oxygen depletion in soil

Abstract: The short-term response of soil denitrification to reduced aeration was studied using the acetylene inhibition method for the assay of denitrification. Two distinct phases of denitrification rate were observed. An initial constant rate, termed phase I, was not decreased by chloramphenicol, was increased slightly or not at all by organic carbon amendment, and lasted for 1–3 h. Phase I was attributed to the activity of pre-existing denitrifying enzymes in the soil microflora. Following phase I the denitrification rate increased; chloramphenicol inhibited this increase. In soils without organic-C amendment a second linear phase, termed phase II, was attained after 4–8 h of anaerobic incubation. The linearity of this phase was attributed to the full derepression of denitrifying enzyme synthesis by the indigenous population and to the lack of significant growth of denitrifiers. Phase I rate was dependent on the initial or in situ aeration state of the soil sample; phase II was not. Therefore, phase I may be more directly related to field denitrification rates. Denitrification rate changes following water saturation of soils in aerobic atmospheres were also examined. Rates were greatly increased by wetting but only after a lag of several hours. Our interpretation is that following wetting of natural soils, anaerobic or partially anaerobic conditions are established by respiration and reduced O2 diffusion rate; this first eliminates O2 inhibition then derepresses the synthesis of denitrifying enzymes. Although denitrifying enzymes are apparently present even in relatively dry soils, their activity is low until O2 inhibition is eliminated. From this evidence we reason that most N is lost from soils during brief periods beginning a few hours after irrigation or a rainfall.

Early lexical development: comprehension and production

Abstract: Lists of the first 50 words comprehended and produced by eight infants between 0; 9 and 1; 8 were compared. Comprehension development began earlier (around 0; 9) and reached the 50-word level (age 1; 1) earlier than production development (ages 1; 0 and 1; 6 respectively) and rate of word acquisition for comprehension was twice that of production, confirming the hypothesis that comprehension precedes production for lexical development. Word-class analysis revealed differences in the proportion and type of action words in comprehension and production vocabularies. It is suggested that action is central to lexical development but is expressed differently in comprehension, where action words are used to initiate actions, and production, where non-action words accompany the child's actions.

Elimination of metabolic cooperation in Chinese hamster cells by a tumor promoter

Abstract: Wild-type Chinese hamster V79 cells (6-thioguanine-sensitive) reduce the recovery of 6-thioguanine-resistant cells when they are cultured together at high densities, through a form of intercellular communication (metabolic cooperation). Cooperation is inhibited by 12-O-tetradecanoyl phorbol-13-acetate, rescuing the 6-thioguanine-resistant cells. These results may be useful in the study of an aspect of the mechanism of tumor promotion and in assaying for promoters.

Hydrolytic enzymes in the central vacuole of plant cells.

Abstract: The hydrolase content of vacuoles isolated from protoplasts of suspension-cultured tobacco cells, of tulip petals, and of pineapple leaves, and the sedimentation behavior of tobacco tonoplasts were studied. Three precautions were found to be important for the analysis of vacuolar hydrolases and of the tonoplast. ( a ) Purification of protoplasts in a Ficoll gradient was necessary to remove cell debris which contained contaminating hydrolases adsorbed from the fungal cell-wall-degrading enzyme preparation. ( b ) Hydrolase activities in the homogenates of the intact cells or the tissue used and of the purified protoplasts had to be compared to verify the absence of contaminating hydrolases in the protoplast preparation. ( c ) Vacuoles obtained from the protoplasts by an osmotic shock had to be purified from the lysate in a Ficoll gradient. Since the density of the central vacuole approximates that of the protoplasts, about a 10% contamination of the vacuolar preparation by surviving protoplasts could not be eliminated and had to be taken into account when the distribution of enzymes and of radioactivity was calculated. The intracellular activities of the following acid hydrolases were primarily localized in the vacuole of tobacco cells: α-mannosidase, β- N -acetylglucosaminidase, β-fructosidase, nuclease, phosphatase, phosphodiesterase. A similar composition of acid hydrolases was found in vacuoles obtained from protoplasts of tulip petals. Proteinase, a hydrolase with low activity in tobacco cells and tulip petals and therefore difficult to localize unequivocally, was found to be vacuolar in pineapple leaves, a tissue containing high levels of this enzyme. Our data support the hypothesis that the central vacuole of higher plant cells has an enzyme composition analogous to that of the animal lysosome. None of the vacuolar enzymes investigated was found to be bound to the tonoplast. When vacuoles were isolated from cells labeled with radioactive choline, the vacuolar membrane was found to contain radioactivity. On sucrose gradients, the label incorporated into tonoplasts banded around a density of 1.10 grams per cubic centimeter (24% sucrose, w/w).

Destruction of dopaminergic nerve terminals in nucleus accumbens: effect on d-amphetamine self-administration.

Abstract: Control rats initiate self-administration of d-amphetamine and achieve stable injection rates within 7-10 days. Rats in which dopamine nerve terminals in nucleus accumbens were destroyed by bilateral microinjections of 6-hydroxydopamine (6-OHDA) did not initiate self-administration of d-amphetamine when tested for as long as 19 days. In rats previously trained to self-administer d-amphetamine, 6-OHDA injections into nucleus accumbens abolished d-amphetamine self-administration. These results suggest that dopaminergic nerve terminals in nucleus accumbens are necessary for both the acquisition and maintenance of d-amphetamine self-administration.

Assay for and enzymatic formation of an ethylene precursor, 1-aminocyclopropane-1-carboxylic acid.

Abstract: A simple and sensitive chemical assay was developed for 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene. The assay is based on the liberation of ethylene from ACC at pH 11.5 in the presence of pyridoxal phosphate, MnCl2 and H2O2. This assay was used to detect ACC in extracts of tomato fruits (Lycopersicon esculentum Mill.) and to measure the activity of a soluble enzyme from tomato fruit that converted S-adenosylmethionine (SAM) to ACC. The enzyme had a Km of 13 μM for SAM, and conversion of SAM to ACC was competitively and reversibly inhibited by aminoethoxyvinylglycine (AVG), an analog of rhizobitoxine. The Ki value for AVG was 0.2 μM. The level of the ACC-forming enzyme activity was positively correlated with the content of ACC and the rate of ethylene formation in wild-type tomatoes of different developmental stages. Mature fruits of the rin (non-ripening) mutant of tomato, which only produce low levels of ethylene, contained much lower levels of ACC and of the ACC-forming enzyme activity than wild-type tomato fruits of comparable age.

Expectations and Performance: An Empirical Test of Bandura's Self-efficacy Theory

Abstract: The present investigation was designed to test the predictions of Bandura's (1977) theory of self-efficacy in a competitive, motor-performance situation. Subjects (30 males and 30 females) were randomly assigned to either a high or low self-efficacy condition in a 2 × 2 × 2 (sex × self-efficacy × trials) factorial design. Self-efficacy was manipulated by having subjects compete against a confederate on a muscular leg-endurance task where the confederate was said to be either a varsity ;rack athlete who exhibited higher performance on a related task (low self-efficacy) or an individual who had a knee injury and exhibited poorer performance on a related task (high self-efficacy). Because self-efficacy theory predicts that expectation-performance differences are maximized in the face of obstacles and aversive consequences, the experiment was rigged so that subjects lost in competition to the confederate on both trials. The results supported self-efficacy predictions with the high self-efficacy subjects exten...

Mothers' speech to children and syntactic development: some simple relationships.

Abstract: This study investigated the relationships between children's linguistic environments and their language acquisition. Speech samples taken from seven firstborn children and their mothers when the children were 1; 6 and 2; 3 were analysed within a number of semantic and syntactic categories to determine correlations between mothers' speech and subsequent language development. Several characteristics of mothers' speech (e.g. utterance length, use of pronouns) significantly predicted later child speech. The significant correlations suggested that mothers' choice of simple constructions facilitated language growth. Further, they showed that the motherese code differed from adult-adult speech in ways which aided language development. Differences between our study and previous investigations of environmental effects on language development probably resulted from the failure of earlier investigations to take into account children's level of language competence at the time when environmental effects were assessed.

Role of phospholipids and triglycerides in warmed‐over flavor development in meat model systems

Abstract: The effects of triglycerides and phospholipids on development of warmed-over flavor (WOF) in cooked meat was studied using model systems from beef and from chicken dark and light meat. Triglycerides, total lipids, total phospholipids, phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were added back to the lipid extracted muscle fibers in each system and WOF development was followed by the TBA test and taste panel scores after heating to 70°C and holding at 4°C for 48 hr. Total phospholipids, especially PE, were shown to be the major contributors to development of WOF in cooked meat. The triglycerides enhanced development of WOF only when combined with the phospholipids (as total lipids). Phosphatidyl choline (PC) did not influence WOF in the model system. Changes in the PUFAs of the phospholipids were shown to be related to development of WOF in cooked meat. Addition of 156 ppm of nitrite significantly (P < 0.01) reduced TBA numbers and prevented development of WOF.

Cellular aspects of muscle growth: myogenic cell proliferation

Abstract: Summary Muscle differentiation and growth are accomplished by two fundamental sets of cellular processes, protein accretion and cell proliferation. This review is restricted to a discussion of the role of cell proliferation in the growth of muscle during prenatal and postnatal life. More specifically, the discussion is divided into three topic areas, which include the role of muscle precursor cell proliferation in prenatal and postnatal development and a review of factors that may be regulating the proliferation of myogenic cells. The proliferation of embryonic myogenic cells and their differentiation into multinucleated fibers, as well as the proliferation of myogenic ceils in postnatal muscle (satellite cells) are major factors determining the ultimate mass of muscle that can be produced by an animal.

DNA excision-repair processes in human cells can eliminate the cytotoxic and mutagenic consequences of ultraviolet irradiation.

Abstract: The ability of DNA excision-repair processes in diploid human fibroblasts to eliminate potentially cytotoxic and mutagenic lesions induced by UV radiation (254 nm) was demonstrated in two ways: (1) Cells with normal rates of excision were compared with cells with an intermediate rate of excision (XP2BE) and cells with an excision rate less than or equal to 1% that of normal (XP12BE) for sensitivity to the killing and mutagenic action of UV radiation. The normal cells proved resistant to doses of UV which reduced the survival of the XP cells to 14% and 0.7%, respectively, and increased the frequency of mutations to 8-azaguanine resistance in the XP cells 5- to 10-fold over background. (2) Cells in confluence were irradiated with cytotoxic and mutagenic doses of UV and allowed to carry out excision repair. After various lengths of time they were replated at lower densities to allow for expression of mutations to 6-thioguanine resistance and/or at cloning densities to assay survival. Normal cells and XP cells with reduced rates of excision repair (from complementation groups C and D) exhibited a gradual increase in survival from an initial level of 15--20% to 100% if held approximately 20 h in confluence. In contrast, XP12BE cells showed no increase from an initial survival of 20% even when held for 7 days. Normal cells irradiated in confluence but prevented from replicating for 7 days exhibited background mutation frequencies, whereas the mutation frequency in XP12BE cells did not change with the time in confluence.

An Intrinsic Dimensionality Estimator from Near-Neighbor Information

Abstract: The intrinsic dimensionality of a set of patterns is important in determining an appropriate number of features for representing the data and whether a reasonable two- or three-dimensional representation of the data exists. We propose an intuitively appealing, noniterative estimator for intrinsic dimensionality which is based on nearneighbor information. We give plausible arguments supporting the consistency of this estimator. The method works well in identifying the true dimensionality for a variety of artificial data sets and is fairly insensitive to the number of samples and to the algorithmic parameters. Comparisons between this new method and the global eigenvalue approach demonstrate the utility of our estimator.

Methane efflux from lake sediments through water lilies.

Abstract: During winter, when water lilies have no surface leaves, the gases in the rhizome lacunae approach equilibrium with the gases of the sediment water. The resulting increase of internal pressure is manifested by the sustained streams of bubbles (up to 37 percent methane and 6 percent carbon dioxide) that escape when emerging leaves are torn in the spring. Methane continues to enter the roots and rhizome during summer, rapidly moves up the petioles, and passes out through the emergent leaves into the atmosphere.

Temporal Change in Nitrous Oxide and Dinitrogen from Denitrification Following Onset of Anaerobiosis

Abstract: Similar temporal patterns were found in three mineral soils for the composition of the gaseous products of denitrification following the onset of anaerobic conditions. During the early period of anaerobiosis (0 up to 1 to 3 h), N2 was the dominant product of denitrification. The NO3− → N2O activity then increased, but was not accompanied by a corresponding increase in N2O-reducing activity. This resulted in a relatively extended period of time (1 to 3 up to 16 to 33 h) during which N2O was a major product. Eventually (after 16 to 33 h), an increase in N2O-reducing activity occurred without a comparable increase in the N2O-producing activity. The increase in the rate of N2O reduction did not occur in the presence of chloramphenicol and required the presence of N2O or NO3− during the preceding anaerobic incubation. During the final period (16 to 33, up to 48 h), N2 was generally the sole product of denitrification, since the rate of N2O reduction exceeded the rate of N2O production. A similar sequential pattern was also found for a culture of a denitrifying Flavobacterium sp. shifted to anaerobic growth. A staggered synthesis of the enzymes in the denitrification sequence apparently occurred in response to anoxia, which caused first a net production of N2O followed by consumption of N2O.

Selenium, vitamin E and the response to swimming stress in the rat.

Abstract: Experiments were conducted to determine the effects of exercise on rat glutathione peroxidase system enzymes and lipid peroxidation among animals supplemented and unsupplemented with selenium (Se) and vitamin E (E). Liver, muscle and blood were taken before, immediately after and 24 hours after exercising to exhaustion by swimming. No effect of exercise was found on muscle or liver enzymes, although exercise resulted in depressed glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) activities in erythrocytes immediately after exercise. Dietary Se supplementation did result in increased hepatic muscle and erythrocyte glutathione peroxidase activity, and decreased hepatic GR, G6PD and "malic enzyme" activities. Thiobarbituric acid reactive substances, and indicator of lipid peroxidation, increased in liver and muscle subsequent to exercise. This increase was reduced in liver, but not eliminated, by dietary E supplementation. The increase was not affected by dietary E in muscle, nor by dietary Se in either tissue.

Further tests of the Schmidt-Hunter Bayesian validity generalization procedure.

Abstract: Using an improved version of the Bayesian validity generalization model presented in Schmidt and Hunter (1977), this study showed that most of the between-study variation in observed validity coefficients of various aptitude and ability tests for two types of clerical work and for the job of first-line supervisor is artifactual in nature. These results cast additional doubt on the traditional belief that employment test validities are situationally specific. In addition, the results showed that generalization of validities to new settings was justified even where the hypothesis of situational specificity could not be rejected under the standards used in this study. Implications for the use of aptitude and ability tests in selection and for theory development in industrial-organizational psychology are discussed.

Behavioral Responses of the Gypsy Moth in a Wind Tunnel to Air-Borne Enantiomers of Disparlure

Abstract: Mate gypsy moths ( Lymantria dispar L.) in a wind tunnel fitted with a moving floor pattern to provide optomotor feedback to flying moths respond to (+)- cis -7,8-epoxy-2-methyloctadecane [(+)-disparlure] by flight with apparent positive optomotor anemotaxis and reversing anemomenotaxis (an upwind, zigzag flight). From quiesence, the latency to preflight wing fanning decreases with an increasing (+)-disparlure dispenser dosage. Ground speed of flight (the rate of floor movement required to maintain flight in the center of the wind tunnel) decreases with increasing (+)-disparlure concentration suggesting that the attractant concentration can provide an orthokinetic modulation of ground speed. The lowest dispenser dosages of (+)-disparlure tested (1 ng) resulted in greater lateral displacement in the zigzag than 10–1000 ng dosages. At wind velocities of 0.7 and 2.5 m/sec males maintained virtually identical ground speeds by adjusting their airspeed. The (−) enantiomer of disparlure when admixed to (+)-disparlure acts antagonistically to decrease the distance flown, the ground speed and the distance of flight, but the (−) enantiomer does not appear to affect preflight wing fanning latency. Considerable variation occurs in the mean ground speed of individuals, possibly optimum strategies related to orientation in well-defined aerial plumes (rapid flight) and meandering plumes (slow flight).