Showing papers by "Dartmouth College published in 1971"

Early prenatal ontogenesis of the cerebral cortex (neocortex) of the cat (Felis domestica). A Golgi study. I. The primordial neocortical organization.

Abstract: The neocortex of the cat undergoes a series of fundamental transformations of its fibrillar-neuronal organization during the course of early prenatal cortical ontogenesis. Some of these transformations assume structural chracteristics and neuronal features which resemble those of phylogenetically older cortical organizations. Following the arrival of corticipetal fibers at the marginal zone of the cerebral vesicle a very primitive neocortical organization, the primordial plexiform layer develops. It is characterized by the external location of the white matter with both corticipetal and a few corticofugal fibers and a few immature neurons sandwiched between the fibers. The primitive plexiform layer is present in the cat from the 20th to the 25th day of gestation. The external (superficial) location of the white matter of the primordial plexiform layer of the cat neocortex is reminiscent of the amphibian cortical organization. It also resembles other primitive structures (spinal cord) of the central nervous system. In view of its short duration and because of the immaturity of its fibrillar-neuronal elements, the primordial plexiform layer is considered to be a transient neocortical organization possibly without functional activity in the cat.

Expression of differentiated functions in mouse neuroblastoma mediated by dibutyryl-cyclic adenosine monophosphate.

Abstract: CELLS derived from the mouse neuroblastoma (C1300) grown in culture are predominantly round and highly refractile. A small number of the cells are flatter and possess one or more extensions (“neurites”) which may be as long as 3 mm1–3. The proportion of these morphologically differentiated cells increases when the medium lacks serum4 or when 5-bromo-deoxyuridine is added5. The cells also contain enzymes of neural function2,6 and are capable of generating action potentials in vitro7,8. We now show that differentiated characteris-tics of neuroblastoma cells can be induced by N6,O2′-dibutyryl adenosine 3′ : 5′-monophosphate (dibutyryl-cyclicAMP).

The Power of Positive Sanctions

Abstract: Political science has made valuable contributions to the progressive clarification of the concept of power since World War II. In view of the attention political scientists have traditionally lavished on the concept of power, it seems fitting that they should help clarify it. Thanks to the efforts of such men as Harold Lasswell and Robert Dahl, many political scientists today are keenly aware of the need to define power in relational terms, to distinguish power relations from power resources, to specify scope, weight, domain, and so on. There is, however, one distinction that is rarely considered by political scientists—that between positive and negative sanctions. The purpose of this paper is to clarify this distinction and show how and why it matters.

Effects of colchicine on collagenase in cultures of rheumatoid synovium

Abstract: Rheumatoid synovium, cultured in vitro in media not enriched with serum, synthesized and released a specific collagenase. This enzyme appeared in measurable quantities only after three or more days of culture. Enzyme activity correlated well with hydroxyproline content in the culture media, indicating that extracellular matrix collagen in synovial explants was being degraded. Collagenase activity was found to be 2 to 10 times greater when colchicine (0.1 μg/ml) was added to the culture media. This stimulation of enzyme was dependent upon cells which could metabolize glucose and synthesize RNA; it was not dependent upon continued addition of colchicine to fresh culture media. Colchicine was found to depress 14CO2 production from glucose-6-14C, whereas lactate formation and 14CO2 evolution from glucose-1-14C were less markedly depressed. Mitotic figures were not seen in cells of tissue cultures in the absence of serum, nor was mitotic arrest observed in colchicine-treated tissue. The effect of colchicine was not mediated by decreased degradation of the enzyme in culture nor by stimulation of release of stored enzyme, but was associated with an increase in radioactive leucine incorporation into several proteins synthesized by the cell, including collagenase.

IgE in atopic dermatitis.

Abstract: Intradermal tests with anti-IgE and measurements of serum IgE levels were done in patients with atopic dermatitis who did not have concurrent hay fever or asthma, patients with psoriasis, and nonatopic volunteers. The minimal amount of anti-IgE required to elicit a standard wheal and flare reaction 15 minutes after injection in patients with atopic dermatitis did not differ significantly from the two control groups. Also, there was no correlation between the results of the intradermal testing and severity of the dermatitis. The mean serum of IgE levels in patients with atopic dermatitis were higher than those of the two control groups. In addition, in patients with atopic dermatitis there was a strong correlation between the level of serum IgE and the severity of dermatitis, whether or not a positive history for asthma or hay fever was elicited.

Parthenogenesis in Rotifers: The Control of Sexual and Asexual Reproduction

Abstract: synopsis. The class Rotifera includes species which reproduce solely by apomictic female parthenogenesis and species which alternate this "asexual" reproduction with ordinary sexual reproduction. The transition between asexual and sexual reproduction is controlled by the environment. Laboratory studies with the genus Asplanch? na have shown that it is possible to identify specific molecules as inducers, which act on embryos in utero to modify their development and determine whether they will mature as sexually or asexually reproducing females. Moreover, an evolutionary rationale can be provided for the response to these particular environmental control? ling agents, which are such that sexual reproduction will occur only when it will result in successful fertilization. Rotifers are opportunistic or colonising organisms, which implies selection for rapid reproduction. We suggest that this may account, at least in part, for the origin of both apomicitc parthenogenesis and certain features of the pattern of macromolecular syntheses during development. To account for the success of those rotifers which have lost sexual reproduction entirely, we note that accumulation of mutations during periods of exponential apomictic parthenogenetic reproduction, together with "mitotic" crossing-over, could theoretically produce sufficient genotypic diversity to provide evolutionary flexibility. This would eliminate a major advantage of sexual reproduc? tion.

Hudson Geotraverse: Geology of the Mid-Atlantic Ridge at 45 degrees N

Abstract: A strip across the Crest Mountains and High-Fractured Plateau of the Mid-Atlantic Ridge has been surveyed systematically between latitudes 45 and 46° N. Continuous bathymetric, magnetic and gravimetric data have been obtained. Seismic refraction experiments have revealed a complex structure lineated parallel to the axis of the Ridge. Seismic reflexion studies have revealed a picture of the sediment cover, and have shown the possible existence of block faulting of the underlying rocks, with faults alined both parallel and at right angles to the axis of the Ridge. The major rock types found in 46 dredge stations can be grouped as follows: (1) Ubiquitous basalts and tuffs (ranging from theoleiites to alkali basalts, with a few ferro-basalts and high-Al basalts). Basalts rich in resorbed high-calcic plagioclase xenocrysts are common; these occur both on the slopes of shield volcanoes and in the deepest hole of the Median Valley. A nearby fault scarp yielded coarse-grained gabbros. (2) Serpentinized mafic and ultramafic rocks are not restricted to elongated, presumably blockfaulted seamounts, but are also common on the slopes of what had been interpreted on morphological grounds as shield volcanoes; they are absent, however, on the Median alley floor and its immediate scarp slopes. The pre-serpentinization rock types include dunites, harzburgites, gabbros, troctolitic gabbros and amphibolitic peridotites showing crude cumulate textures. (3) The lower parts of the steep inner walls of the Median Valley have yielded metabasalts and metadiabases showing alteration within the greenschist facies of etamorphism, whilst still retaining original igneous characteristics. (4) Restricted to the fault scarps of elongated seamounts further removed from the Median Valley are higher grade metamorphic rocks of the almandine amphibolite facies of metamorphism. These rocks have lost all igneous textures and exhibit a strong gneissic fabric. (5) Three localities yielded dioritic rocks in association with serpentinized ultramafics. The diorites vary in character from hornblende-rich quartz diorites to more siliceous, almost hornblende-free trondhjemites. The latter show considerable albitization. The whole suite of rocks shows great affinities with similar suites found as late stage intrusives in alpine-type ultramafic complexes. About 23% of the specimens collected included gneissic, granitic and sedimentary rock types of erratic origin, ice rafted into the area in the Pleistocene. A study of their distribution indicates that there are no erratics in the Median Valley, that they are scarce on the mountain ranges immediately flanking the Valley, but beyond these areas they are abundant and are randomly distributed over the whole area. Such a distribution may be a result of ocean-floor spreading, indicating that the Median Valley is younger than the last ice age, or that extrusions subsequent to the last ice age have engulfed any erratics present in the Median Valley. The thickness of manganese coating on extrusive rocks and their K/Ar and fission track ages increase systematically with distance on either side of the axis of the M.A.R., strongly supporting the ocean-floor spreading hypothesis. The ages and coatings both show a marked change in their rate of increase beyond a distance of 50 to 60 km on either side of the axis. The position at which this occurs coincides with the thickening in these areas of sediments found in the inter-volcanic valleys, and the morphological changes between the Crest Mountains and the High-Fractured Plateau. The combined data strongly suggest that there was either a quiescent period sometime in the Pliocene during which ocean-floor spreading was inactive, or that the rate of spreading had accelerated during the Pliocene from less than 1 cm a -1 to a computed 2.5 cm a -1 in Pleistocene times.

Scandium, Chromium(VI), Gallium, Yttrium, Rhodium, Palladium, Indium in Mice: Effects on Growth and Life Span

Abstract: In order to evaluate possible innate toxic effe'cts of small doses of scandium, hexavalent chromium, gallium, yttrium, indium, rhodium and palladium in terms of growth and survival, 958 mice divided as to sex were raised in an environment limited in metallic contamination and given 5 ppm metal in drinking water from weaning until natural death. Body weight was measured at monthly intervals up to 6 months, at 1 year and at 18 months of age. The feeding of gallium was accompanied by significant but not marked sup pression of weight at 14 of 16 intervals in both sexes; the feeding of scandium was associated with growth suppression at 10, of indium at 8, of palladium at 7 and of rhodium at 6 of 16 intervals compared to mean weights of controls. The feeding of yttrium and hexavalent chromium were associated with significant lessening of growth at 12 and 8 of 16 intervals, respectively. Survival of gallium- fed females at older ages was less than that of controls, whereas survival of pal ladium-fed males and yttrium-fed mice of both sexes were greater. Tumors were found at necropsy in 16.3% of one group of controls, 27.4% of the scandium, 26.0% of the gallium, 13.0% of the indium, 28.8% of the rhodium and 29.2% of the palladium groups. Malignant tumors were increased in rhodium and pal ladium groups, at a minimally significant level of confidence (P < 0.05), all but one tumor being malignant. In a second series, tumors were present in 26.8% of controls, 27.6% of the mice fed chromium (VI) and 33% of the mice fed yttrium. All rumors in these latter two groups were malignant. Rhodium and palladium appear to exhibit slight carcinogenic activity in mice. J. Nutr. 101: 1431-1438, 1971. Continuing studies of the innate effects reported. We have also reported effects of of low doses of various abnormal trace elements in the second transitional series elements in drinking water on mice and and related groups: zirconium, niobium, rats exposed for life are being conducted cadmium, tin, antimony (1-3); molyb- in an environment built so as to exclude denum and tellurium (IV and VI) are corn- metallic contaminants. We have reported pleted. To complete the second series, ex- alterations in growth, survival and life eluding technetium, ruthenium and silver, span, or lack of them, associated with the we hereby report on yttrium, rhodium, feeding of titanium, vanadium, chro- palladium and indium. Innate long term mium(in), nickel, germanium and arsenic effects of fluorine and lead have also been to mice ( 1, 2 ), and the study of the effects studied ( 1, 3 ). In this way the subtoxic of selenium(IV and VI) is completed, effects of elements with atomic numbers Other trace elements of the first transi- 21 to 34, and 39 to 52 with three excep tional series of the Periodic Table, man- Received for publication june 8, 1971. gaA±ese, iron, Cobalt, Copper, Zinc are es- i Supported by the Public Health Service Research sential for mammals. In order to complete £rant,HE,,05376 A­romth? Nati^S^ S?art Institute,-

Density, habitat, and the mating system of the Western Sandpiper (Calidris mauri).

Abstract: The hypothesis that intense predation, variable food availability, and increased social interactions in high density populations have been important factors promoting the evolution of polygynous and promiscuous mating systems in certain Calidridine sandpipers (Holmes and Pitelka, 1966) is examined in breeding populations of the Western Sandpiper (Calidris mauri) in subarctic Alaska. Western Sandpipers breed in a habitat consisting of a complex mosaic of wet low-lying marshes and relatively well-drained, heath-covered tundra. They defend small territories and nest on the latter, while some feeding also occurs there. Most foods however are obtained off territory in the wet marshes and along the shores of lakes, rivers and sloughs. Densities in the nesting areas ranged from 132–196 pairs/40 ha at the base of a low range of hills to 200–300/40 ha on hummocks surrounded completely by marsh. These densities, the highest reported for a Calidridine sandpiper, are relatively constant from year to year. The mating system of the Western Sandpiper is monogamous, both sexes incubate and care for young. Correlated with a strong single pair-bond and stable populations is a strong tendency to return to the same site. Of sandpipers marked, an average of 57.6% of males and 48.8% of females returned in succeeding years, frequently to the same territory or its immediate vicinity. Of the pairs returning to the study area in subsequent years, 61.5% reunited. The restriction of nesting activities to heath tundra is considered to be a result of the protection it provides for nests. With the separation of nesting and feeding areas and with relatively abundant food sources that are not significantly affected by weather, a large nesting area is not required, allowing high densities of Western Sandpipers to occupy the patches of heath-covered tundra. In this ecological context, the high intensity of social interactions has not resulted in the evolution of a nonmonogamous mating system. Indeed, the increased protection afforded offspring by the presence of both parents is probably the most important selective force promoting the evolution of the monogamous mating pattern in Western Sandpipers.

Fine Structure Study of Pollen Development in Haemanthus katherinae Baker : II. Microtubules and Elongation of the Generative Cells

Abstract: The newly formed generative cell of the pollen grain of the African blood lily is spheroidal after its detachment from the pollen wall. Plastids are almost always excluded from the generative cell, while dictyosomes, mitochondria, ribosomes, endoplasmic reticulum, and microtubules are present throughout development of the cell. During the time that the generative cell is spheroidal, microtubules are found scattered randomly throughout the cytoplasm. The cell subsequently elongates and concurrently an oriented system of microtubules appears along the wall of the cell. The microtubules are aligned with their long axes parallel to the long axis of the cell. This system of microtubules persists in the generative cell throughout its development. The microtubules can be destroyed by exposure to isopropyl N -phenylcarbamate or colchicine and as a result the generative cell reverts to a near spheroidal shape.

Magnetopause structure during the magnetic storm of September 24, 1961

Abstract: Explorer-12 magnetic-field observations of the magnetopause current layer were made on the inbound pass of September 24, 1961, which occurred during the main phase of a moderately strong magnetic storm. The satellite was located near the subsolar point. The accuracy of the Explorer-12 data reported here has been increased by use of an improved filtering procedure. Five magnetopause penetrations were observed in a time period of about 20 min and for each of these the data were used to calculate the vector normal to the current layer, the magnetic-field component along that vector, and the polarization of the current layer. Normal magnetic-field components significantly different from zero were obtained, and it is suggested that the observations during this pass in general are consistent with the so-called open magnetosphere model. In fact, it appears that the first and last of the boundary penetrations may have occurred on opposite sides of, but very near, the X-type magnetic null line, which is located on the front side of the open magnetosphere model. The direction of the normal magnetic-field component as well as the sense of rotation of the tangential magnetic-field component in the current layer were found to be opposite for these two boundaries.

Organic Compounds in Volcanic Gas from Santiaguito Volcano, Guatemala

Abstract: Gas samples collected at Sapper fumarole, Santiaguito, Guatemala, on December 5, 1969, were analyzed by gas chromatography-mass spectrometry. A number of compounds were found, including saturated and unsaturated hydrocarbons, aldehydes, ketones, alcohols, aromatics, halogenated hydrocarbons, and inorganic sulfur compounds. The compounds are probably produced by heating of fossil soil or sedimentary layers by the magma.

Clay Mineral Formation in an Alpine Environment

Abstract: Vermiculite, mixed-layer vermiculite-phlogopite, and smectite are presently forming from igneous and metamorphic bedrock in the alpine zone of the northern Cascades, Washington. In addi- tion, south-facing exposures of quartz-diorites and metadiorites above snow line are weathering to ferruginous bauxite. Calculations indicate that vermiculite is presently forming from phlogopite schists in this environment at a unit area rate that is approximately six times the average estimated rate of clay erosion for North America. The mineralogical data indicate that chemical weathering in this region is a quantitatively significant process, and suggest that in the development of current geomorphic concepts researchers may have generally underestimated the importance of chemical weathering in alpine environments.

Generation of multiple ratio scales with a fixed stitnulus attribute

Abstract: Psychophysical theories differ in the relative weight given to sensory and cogruuve variables. Two opposing theories are described and tested in an experiment designed to vary a cognitive factor while maintaining a constant sensory factor. The method of magnitude estimation was used with the constant stimulus attribute of line length. The cognitive factor was varied by providing Ss with different feedback concerning the numerical values assigned to the largest and smallest lines in the series. This procedure led to multiple ratio scales for the same stimulus attribute. It is argued that these results support a theory which stresses both cognitive and sensory variables in the explanation of psychophysical functions.

An isotope catalogue for instrumental activation analysis. i.

Abstract: This section of the catalogue is a continuation of the previous parts which have appeared in previous issues of this Journal.** This part lists the energies of ~-transitions of the isotopes listed in the previous parts of the catalogue, in the order of increasing energy. A brief explanation of the concept of the catalogue, its structure and applications, was published with the first part, and can be referred to if required.

Urea biosynthesis and excretion in fresh-water and marine elasmobranchs

Abstract: 1. 1. Activity levels of ornithine-urea cycle enzymes in the liver of Potamotrygon , a fresh-water ray, were one-half to one-twentieth those found in marine rays. The rate of incorporation of 14 C-bicarbonate into urea by liver slices was also markedly reduced. 2. 2. In contrast to marine elasmobranchs, Potamotrygon did not actively reabsorb 14 C-urea in its renal tubules.

Fine structure study of pollen development in Haemanthus katherinae Baker. I. Formation of vegetative and generative cells.

Abstract: When microspores of the African blood lily divide, they form pollen grains which consist of 2 cells of unequal size. This is accomplished when the microspore nucleus is displaced from the centre of the grain prior to division. The displacement is always towards the side of the grain opposite the furrow, and large vacuoles form in the cytoplasm between the furrow and the nucleus. During cell division the cell plate curves around one daughter nucleus and fuses with the pollen wall to enclose the generative cell. The cell-plate attachment always occurs with the wall that is opposite the furrow of the grain. Most of the microspore9s organelles become incorporated in the larger vegetative cell, whereas the generative cell has few, if any, plastids and only a small number of other organelles. The wall around the generative cell is composed of finely fibrillar material enclosed within 2 unit membranes. The generative cell eventually becomes detached from the pollen wall, becomes spheroidal, and moves to a position near the centre of the pollen grain. At the same time, the large vacuoles disappear from the vegetative cell and the number of organelles increases substantially.

Opportunity for information search and the effect of false heart-rate feedback.

Abstract: The role of information search in the attribution of physiological states was investigated by manipulating the subject’s opportunity for information search following the presentation of false information about his heart-rate reactions to photographs of female nudes. Consistent with the self-persuasion hypothesis proposed by Valins, the rated attractiveness of the slides was not affected by the false heart-rate feedback for those subjects who were prevented from visually searching the slides. Those subjects who had ample opportunity to view the slides rated those slides accompanied by false information of a heart-rate change as more attractive than those slides which were not paired with a change in heart rate.