Showing papers by "Michigan State University published in 1970"

An experimental approach to the production dynamics and structure of freshwater animal communities1

Abstract: The effects of three levels of inorganic nutrients and two predator densities on aquatic animal communities were examined in a series of twenty 0.07-ha freshwater ponds. The treatments were cross-classified in a randomized block design and continued over 3 years. Analyses of the responses include community composition, secondary production, and demographic description of the dominant species of both zooplankton and benthos. The fish populations and their feeding behavior are described in detail. Ancillary data on water chemistry and primary production were available. Nutrients generally increased production of the zooplankton but had little effect on community composition. Fish predation had profound effects on the diversity and size distribution of the zooplankton but only affected production at lower nutrient levels. The benthos responded markedly to nutrients during the first year, but this was not apparent the second and third years. The response of the benthos to both nutrients and predation was best shown by changes in the distribution of body size. Both zooplankton and benthic communities showed complementary responses between large- and small-bodied organisms. Differences in the physical structure of the environment (i.e., macrophytes) also produced significant changes in production and composition of both systems. The biomass production of the fish populations was clearly related to nutrient level. Both fish and invertebrate predators were size selective, but the fish had a much greater influence on the prey populations.

Clay-Organic Complexes and Interactions

Abstract: Publisher Summary Clays interact with many organic compounds to form complexes of varying stabilities and properties. These interactions are of great importance in nature and in industry. The clays in soils and sediments often have organic material with which they are intimately associated. This chapter describes the bonding mechanisms involved in clay-organic complexes, the nature of some clay-organic complexes and reactions, and the nature and importance of clay-organic complexes in soils. The dominant factors determining the nature of clay-organic interactions are the properties of the organic molecule, the water content of the system, the nature of the exchangeable cation on the clay surface, and the unique properties of the clay mineral structures. The exchangeable cations determine the surface acidity, and therefore the possibilities of protonation of the organic compound. Much remains to be learned regarding the clay-organic systems and the reactions taking place at this interface. In particular, it is quite likely that many reactions that have not yet been recognized are catalyzed by the clay minerals.

Serum prolactin levels in rats during different reproductive states.

Abstract: Rat serum prolactin as determined by radioimmunoassay during the estrous cycle was found to be highest during estrus (68.5 ±7.4 ng/ml) and lowest in diestrus (27.6 ± 5.0 ng/ml). Serum prolactin levels during proestrus, estrus and metestrus were not significantly different. There were no cyclic changes in serum prolactin levels in mature male rats. Estrogen injections increased both pituitary and serum prolactin, whereas ovariectomy decreased both. During the first 3 days of pregnancy, serum prolactin was higher (19.1 ±7.4 to 30.2 ±4.5 ng/ml) than during the following 18 days (8.3 ± 1.1 to 10.9 ±1.2 ng/ml). On the 22nd day of pregnancy serum prolactin levels rose to 29.2 ±13.8 ng/ml. On the 1st day post partum, serum prolactin increased to 65.5 ±19.0 ng/ml, and a high serum concentration was maintained by the suckling stimulus for at least 8 days. On the 15th and 23rd days post partum, serum prolactin fell to about half (25.7 ±5.5 ng/ml) of the level on the first day post partum. Removal of litters from mo...

Inhibitory effects of anti-tumor platinum compounds on DNA, RNA and protein syntheses in mammalian cells in virtro.

Abstract: The inhibitory effects of anti-tumor, bacterial filament forming platinum compounds, Cis-Pt(II) (NH3)2Cl2 (A), Cis-Pt(IV) (NH3)2Cl4 (B), and Pt(II) (NH2)2(CH2)2Cl2(C) on DNA, RNA and protein syntheses was measured by the incorporation of 3H-thymidine, 3H-uridine, and 3H-L-leucine, respectively, into an acid-insoluble polymer in human amnion AV3 cells. Compound A, the most effective tumor-inhibiting platinum compound, was shown to selectively inhibit DNA synthesis below 5μM and to inhibit 3H-thymidine incorporation more rapidly than 3H-uridine or 3H-leucine incorporation at 25μM. Like A, compounds B and C were also shown to inhibit all three processes after a 24-hour period of treatment at 25μM. A correlation was established between the relative anti-tumor effectiveness of compounds A, B, and C and the extent of their inhibitory effects. On the other hand, two non-tumor-inhibiting platinum compounds, [Pt(II) (NH3)4]Cl2 (D) and Trans-Pt(IV) (NH3)2Cl4 (E) had no inhibitory effects, except compound E, which exhibited a rapid initial inhibition of 3H-L-leucine incorporation at 100μM. The inhibition of 3H-thymidine incorporation into cells pretreated 4 h with 5μM of compounds A, B, and C was shown to be irreversible. Finally the inhibition of the incorporation of 3H-thymidine into DNA by A was shown not to be caused by the inhibition of the uptake of the tracer into the acid-soluble pool. A number of possible explanations for the greater sensitivity of DNA synthesis and the sequential inhibition of DNA, RNA and protein synthesis at higher concentrations are suggested.

Dietary Obesity in Rats: Body Weight and Body Fat Accretion in Seven Strains of Rats

Abstract: Ten male and 10 female rats from each of seven strains were fed a grain ration for 10 or 20 weeks from weaning. Body weight and body fat of these rats were compared with those of 20 rats of the same age and sex fed a ration containing 60% hydrogenated fat. Also, five male and five female rats of the same seven strains were killed at weaning. Mean weanling weights and the percentage of hody fat for the seven strains of rats were similar. Mean weights of five male rats fed grain for 20 weeks ranged from 304 g for S 5B/P1 rats to 445 g for Osborne-Mendel rats; for five female rats, mean weights ranged from 163 g for S 5B/P1 to 301 g for OsbornjMendel rats. Male rats fed the high fat ration ranged in weight from 346 g for S 5B/P1 to 693 g for Osborne-Mendel males. Females fed the high fat ration ranged in weight from 170 g for S 5B/P1 to 452 g for Osborne-Mendel rats. After 20 weeks of experiment (at 23 weeks of age), carcasses of both male and female rats fed grain contained from 10 (S 5B/P1) to 16% fat (Sprague-Dawley). Rats fed high fat ranged from 14 (S 5B/P1) to 40% (Osborne-Mendel) body fat. For rats of the same sex and age, body weight was influenced nearly equally by genetics (strain differences) and ration, but the percentage of body fat was influenced largely by the ration (74% of variation due to ration difference). In some human families all or nearly all members are obese. Other families appear to be free from obesity. This has led to the assumption on the part of many investi gators that, for the family whose members are overweight, the children have been ex posed to overeating at an early age. Con sequently, the environmental rather than the genetic factor has been emphasized as the primary cause of obesity. Yet, even in countries where food is plentiful and read ily available, and where expenditure of energy is minimal, many individuals main tain an \"ideal\" body weight throughout their lives. These people adjust their caloric intake to expenditure of energy without any conscious effort. A number of investigators have sug gested that genetic factors may be involved in human obesity; for reviews, see (1, 2). Studies of obesity in twins (3) and other near relatives of obese individuals (2, 4—6) have a number of limitations. These in clude the difficulty of securing data on food intake and physical activity over a long term. Although genetic data obtained from humans can be evaluated statisti cally, designed verification of any sugges tions that might develop from such statis tics is not feasible because mating cannot be controlled. Studies with rats have indicated differ ences among strains in their propensity toward obesity when fed a ration high in fat (7). Similar observations have been made with mice (8-10). Therefore, it appeared possible to approach the genetic aspects of dietary obesity by experiments with animals. As an approach to this problem, the present report provides data on the gains in body weights and body fat of seven strains of rats fed a semipurified diet high in fat or a grain ration low in fat.

Effects of Estrogen and Progesterone on Serum and Pituitary Prolactin Levels in Ovariectomized Rats

Abstract: Serum and anterior pituitary (AP) prolactin levels from mature ovariectomized rats were assayed after injection with daily doses of 0.1–500 ng estradiol benzoate (EB) or 0.5–10 mg progesterone for 6 days. Doses of 0.1, 1 or 5 μg EB increased serum prolactin concentration 2-, 3- and 10-fold, respectively, over ovariectomized controls, and doses of 10–500 μg EB evoked smaller increases in serum and AP prolactin levels. AP prolactin concentration and content were increased 3- to 4-fold. Doses of 0.5, 1 or 4 mg progesterone partially inhibited the increase in serum prolactin levels evoked by 1 μg EB, but only the inhibition by 4 mg progesterone was significant. A daily dose of 4 mg progesterone injected alone appeared to have no effect on serum and AP prolactin levels, but a 10 mg dose significantly increased prolactin secretion. These results indicate that low doses of estrogen are more effective than high doses for increasing AP and serum prolactin levels, and provide no evidence that large doses of estroge...

Structural and functional relationships of enzyme activities induced by nitrate in barley

Abstract: 1. Nitrate induces the development of NADH-nitrate reductase (EC 1.6.6.1), FMNH2–nitrate reductase and NADH–cytochrome c reductase activities in barley shoots. 2. Sucrose-density-gradient analysis shows one band of NADH–nitrate reductase (8S), one band of FMNH2–nitrate reductase activity (8S) and three bands of NADH–cytochrome c reductase activity (bottom layer, 8S and 3.7S). Both 8S and 3.7S NADH–cytochrome c reductase activities are inducible by nitrate, but the induction of the 8S band is much more marked. 3. The 8S NADH–cytochrome c reductase band co-sediments with both NADH–nitrate reductase activity and FMNH2–nitrate reductase activity. Nitrite reductase activity (4.6S) did not coincide with the activity of either the 8S or the 3.7S NADH–cytochrome c reductase. 4. FMNH2–nitrate reductase activity is more stable (t½ 12.5min) than either NADH–nitrate reductase activity (t½ 0.5min) or total NADH–cytochrome c reductase activity (t½ 1.5min) at 45°C. 5. NADH–cytochrome c reductase and NADH–nitrate reductase activities are more sensitive to p-chloromercuribenzoate than is FMNH2–nitrate reductase activity. 6. Tungstate prevents the formation of NADH–nitrate reductase and FMNH2–nitrate reductase activities, but it causes superinduction of NADH–cytochrome c reductase activity. Molybdate overcomes the effects of tungstate. 7. The same three bands (bottom layer, 8S and 3.7S) of NADH–cytochrome c reductase activity are observed irrespective of whether induction is carried out in the presence or absence of tungstate, but only the activities in the 8S and 3.7S bands are increased. 8. The results support the idea that NADH–nitrate reductase, FMNH2–nitrate reductase and NADH–cytochrome c reductase are activities of the same enzyme complex, and that in the presence of tungstate the 8S enzyme complex is formed but is functional only with respect to NADH–cytochrome c reductase activity.

Absence of excision of ultraviolet-induced cyclobutane dimers in xeroderma pigmentosum.

Abstract: XERODERMA pigmentosum is a rare human skin disease which is inherited as an autosomal recessive mutation and has been known by dermatologists for nearly a century [ 1-31. The major clinical symptom is high actinic skin carcinogenesis [ 1.4.51. There are two forms of the disease: one shows only the skin symptoms, the other more uncommon form shows additional neurological symptoms and is known as the de Sanctis Cacchione syndrome [5-71. Whether the neurological symptoms should be regarded as part of xeroderma pigmentosum or due to separate genetic factors is as yet unknown [2,5-71. Fibroblasts[& 91 and epithelial cells[lO] from the skin in both forms of this disease appear to perform low or negligible amounts of DNA repair replication after irradiation with ultraviolet (u.v.) light, but the level of such residual amounts cannot yet be correlated with the two forms of the disease since the number of cases studied thus far is too small[& 111. Previous studies on DNA repair in de Sanctis Cacchione skin fibroblasts suggested that an early step in DNA repair involving enzymatic strand breakage is defective [9,12]. Such an hypothesis has also been advanced by Setlow et al. [ 131 for skin fibroblasts from the non-neurological form of xeroderma pigmentosum. They showed that thymine-containing dimers are excised after U.V. damage of normals cells but not of xeroderma cells. Since the two forms of the disease might show some biochemical differences, we have now investigated the excision of thyminecontaining dimers in cultured cells from patients with the de Sanctis Cacchione syndrome. Preliminary results of this investigation have already been reported [9, 121. Sterile 1 mm punch biopsies were taken from apparently normal regions of the arms of three de Sanctis Cacchione patients and two normal persons. Fibroblast cultures were developed in Eagle's minimum essential medium with 3 mglml dextrose, non-essential amino acids, and 15 percent fetal calf serum. Usually, 1-5-2 months elapsed between the time of biopsy and the start of any experiments with fibroblast cultures. They were then used throughout the period of steady growth until cultures degenerated[ 14, IS]. Human embryonic fibroblasts (WI-38) were also used and these

Calculation of the Dielectric Function for a Degenerate Electron Gas with Interactions. I. Static Limit

Abstract: A new procedure for calculating the frequency- and wave-vector-dependent dielectric response function is described. It is based on decoupling and solving the equations of motion for the Green's functions of the charge-density operators by a moment-conserving method which is discussed. By use of this method an expression for the dielectric function in the static limit ($\ensuremath{\omega}\ensuremath{\rightarrow}0$) is obtained; it depends on a function $G(k)$, for which numerical values are calculated and tabulated. Evidence that the procedure described here leads to reliable values of $G(k)$ for small, intermediate, and large values of $k$ is presented.

Modernization and the Politics of Communalism: A Theoretical Perspectve1

Abstract: It has been said that technological and economic development lead ultimately to the decline of communal conflict, and that the emergence of new kinds of socio-economic roles and identities undercuts the organizational bases upon which communal (that is, “racial,” “ethnic,” “religious,” or “tribal”) politics rests. In the past decade, several scholars working in culturally plural societies have challenged this conventional view. They have suggested that communalism may in fact be a persistent feature of social change, and that the dichotomous traditionmodernity models which have often guided our empirical investigations have obscured this theoretical alternative and thereby produced false expectations concerning the direction of change. This paper attempts to synthesize the various elements of this emerging theoretical perspective through the formulation of several propositions which link modernization to communalism. While our discussion will draw primarily upon the Nigerian experience for illustrative material, the propositions are intended to be applicable across societies. “Communalism,” in this paper, refers to the political assertiveness of groups which have three distinguishing characteristics: first, their membership is comprised of persons who share in a common culture and identity and, to use Karl Deutsch's term, a “complementarity of communication;” second, they encompass the full range of demographic (age and sex) divisions within the wider society and provide “for a network of groups and institutions extending throughout the individual's entire life cycle;” and, third, like the wider society in which they exist, they tend to be differentiated by wealth, status, and power.

Reconstruction of Educational Research

Abstract: If there are some subjects on which the results obtained have finally received the unanimous assent of all who have attended to the proof, and others which .. .have never succeeded in establishing any considerable body of truths, so as to be beyond denial or doubt; it is by generalizing the methods successfully followed in the former enquiries, and adapting them to the latter, that we may hope to remove this blot on the face of science.

Chemical composition of exosporium from spores of Bacillus cereus.

Abstract: Homogeneous fragments of exosporium were extricated in centigram amounts from dormant spores of Bacillus cereus and analyzed for intrinsic constituents. The membrane proved to be chemically complex but not unique, consisting mainly of protein (52%), amino and neutral polysaccharides (20%), lipids (18%), and ash (4%). Seventeen common amino acids were identified by chromatography, and were present in usual proportions except for low levels of cystine-cysteine, methionine, tyrosine, and histidine. Glucosamine was the only amino sugar, and glucose and rhamnose were the principal neutral sugars. The lipid fraction contained 5.5% cardiolipin as the only phospholipid, 12.5% neutral lipids, and at least 19 fatty acids, among which normal C(16) and C(18) ones predominated. Calcium and phosphorus occurred in the ash. Small amounts of teichoic, ribonucleic, and dipicolinic acids were believed to represent contamination.

Synthesis of Cellulase during Abscission of Phaseolus vulgaris Leaf Explants

Abstract: When abscission in leaf explants from Phaseolus vulgaris, cultivar Red Kidney, was allowed to proceed while the explants were in (2)H(2)O, a 1.25% increase in the buoyant density of cellulase in a cesium chloride gradient was observed. These data indicate that the increase in cellulase activity during abscission is a result of the synthesis of new protein. Two differentially soluble forms of cellulase are present in the abscission zone. The form which is soluble only in a high salt buffer seems more closely related to the abscission process than the form which is soluble in dilute buffer. The correlation between changes in pull force and increase in cellulase activity and the effects of several hormones on cellulase activity are discussed.

Enzyme replacement in Fabry's disease, an inborn error of metabolism.

Abstract: Two patients with Fabry's disease were infused with normal plasma to provide active enzyme (ceramide trihexosidase) for hydrolysis of the plasma substrate, galactosylgalactosylglucosylceramide. Maximum ceramide trihexosidase activity occurred 6 hours after infusion of the plasma, attaining a level approximately 150 percent of that in normal plasma; enzymatic activity was detectable for 7 days. The amount of accumulated substrate in the plasma of these recipients decreased about 50 percent on day 10 after infusion. Thus, periodic replacement of ceramide trihexosidase activity in the plasma of patients with Fabry's disease might lead to consistently lower amounts of substrate in the plasma and a decrease in its rate of accumulation in tissues.

Isolation and partial characterization of apiogalacturonans from the cell wall of Lemna minor

Abstract: 1. A mild, reproducible extraction procedure, using 0.5% ammonium oxalate, was developed for the isolation of polysaccharides containing d-apiose from the cell wall of Lemna minor. On a dry-weight basis the polysaccharide fractions extracted with ammonium oxalate made up 14% of the material designated cell walls and contained 20% of the d-apiose originally present in the cell walls. The cell walls, as isolated, contained 83% of the d-apiose present in L. minor. 2. After extraction with ammonium oxalate, purified polysaccharides were obtained by DEAE-Sephadex column chromatography and by fractional precipitation with sodium chloride. With these procedures the material extracted at 22°C could be separated into at least five polysaccharides. On a dry-weight basis two of these polysaccharides made up more than 50% of the material extracted at 22°C. There was a direct relationship between the d-apiose content of the polysaccharides and their solubility in sodium chloride solutions; those of highest d-apiose content were most soluble. 3. All the polysaccharides isolated appeared to be of one general type, namely galacturonans to which were attached side chains containing d-apiose. The d-apiose content of the apiogalacturonans varied from 7.9 to 38.1%. The content of esterified d-galacturonic acid residues in all apiogalacturonans was low, being in the range 1.0–3.5%. Hydrolysis of a representative apiogalacturonan with dilute acid resulted in the complete removal of the d-apiose with little or no degradation of the galacturonan portion. 4. Treatment of polysaccharide fractions with pectinase established that those of high d-apiose content and soluble in m-sodium chloride were not degraded, whereas those of low d-apiose content and insoluble in m-sodium chloride were extensively degraded. When the d-apiose was removed from a typical pectinase-resistant polysaccharide, the remainder of the polysaccharide was readily degraded by this enzyme. 5. Periodate oxidation of representative polysaccharide fractions and apiogalacturonans and determination of the formaldehyde released showed that about 50% of the d-apiose molecules were substituted at either the 3- or the 3′-position.