Showing papers by "University of California, Irvine published in 1974"
TL;DR: Chlorofluoromethanes are being added to the environment in steadily increasing amounts as discussed by the authors and these compounds are chemically inert and may remain in the atmosphere for 40 to 150 years, and concentrations can be expected to reach 10 to 30 times present levels.
Abstract: Chlorofluoromethanes are being added to the environment in steadily increasing amounts. These compounds are chemically inert and may remain in the atmosphere for 40–150 years, and concentrations can be expected to reach 10 to 30 times present levels. Photodissociation of the Chlorofluoromethanes in the stratosphere produces significant amounts of chlorine atoms, and leads to the destruction of atmospheric ozone.
3,888 citations
TL;DR: In this article, a detailed discussion of the properties of bulk polaritons in an isotropic dielectric, with a single infrared active optical phonon is given, and the phonon and photon strength functions, which provide a useful means of characterizing the polariton are introduced.
Abstract: A detailed discussion of the properties of bulk polaritons in an isotropic dielectric, with a single infrared active optical phonon is given. The phonon and photon strength functions, which provide a useful means of characterizing the polariton are introduced, and polaritons examined in magnetic crystals, anisotropic dielectrics, materials in which spatial dispersion effects and absorption are important. Experimental methods of studying polaritons are reviewed, with emphasis on Raman scattering, non-linear interactions between polaritons and recent experimental studies of non-linear optical phenomena where polaritons in the intermediate state play an important role. The properties of surface polaritons at the interfaces of the isotropic dielectric, anisotropic dielectrics and magnetic media, and experimental methods for the study of surface polaritons are also discussed. The paper concludes with the comparison between the properties of coupled magnon-phonon modes in magnetic crystals and polaritons.
416 citations
TL;DR: In this article, for each of the two-dimensional lattice types, the mean value point, the set of generating wave vectors, and the sets of special points in the Brillouin zone are presented.
Abstract: Using the method of Chadi and Cohen, we present, for each of the two-dimensional lattice types, the mean-value point, the set of generating wave vectors, and the sets of special points in the two-dimensional Brillouin zone which are the most efficient in finding accurate averages of a periodic function over the Brillouin zone.
294 citations
TL;DR: This work has developed a procedure for the isolation of PSDs based on their buoyant density and their insolubility in N-lauroyl sarcosinate, which represents the distinctive plasma membrane specialization of this specific synaptic type in isolation.
Abstract: Most synapses in the central nervous system exhibit a prominent electron-opaque specialization of the postsynaptic plasma membrane called the postsynaptic density (PSD). We have developed a procedure for the isolation of PSDs which is based on their buoyant density and their insolubility in N-lauroyl sarcosinate. Treatment of synaptic membranes with this detergent solubilizes most plasma membranes and detaches PSDs from the plasma membrane so that they can be purified on a density gradient. Isolated PSDs appear structurally intact and exhibit those properties which characterize them in tissue. The isolated PSDs are of the size, shape, and electron opacity of those seen in tissue; they stain with both ethanolic phosphotungstic acid and bismuth iodide-uranyl lead and the fraction contains cyclic 3',5'-phosphodiesterase activity. Quantitative electron microscope analysis of the PSD fraction gives an estimated purity of better than 85%. Inasmuch as the PSD is associated primarily with dendritic excitatory synapses, our PSD fraction represents the distinctive plasma membrane specialization of this specific synaptic type in isolation.
229 citations
TL;DR: The cell cycle parameters of interstitial cells in Hydra attenuata have been determined by using maceration preparations and histological sections, and the lengths of G 1, S, G 2 and M were determined by standard methods of cell cycle analysis using pulse-chase and continuous labelling with [ 3 H]- and [ 14 C]thymidine as mentioned in this paper.
Abstract: The cell cycle parameters of interstitial cells in Hydra attenuata have been determined. Interstitial cells were classified according to cluster size in which they occur (1, 2, 4, 8 or 16 cells) and morphology using maceration preparations and histological sections. The lengths of G 1 , S , G 2 and M were determined by standard methods of cell cycle analysis using pulse-chase and continuous labelling with [ 3 H]- and [ 14 C]thymidine. Nuclear DNA contents were measured microfluorimetrically. All classes of interstitial cells proliferate but the cell cycle of large interstitial cells occurring singly or in pairs is longer than that of interstitial cells occurring in clusters of 4, 8 and 16 cells. The S -phase is 11-12 h long and G 1 is less than 1 h for all classes of interstitial cells. G 2 is 3-4 h long for interstitial cells in clusters of 4, 8 and 16 cells giving these cells a total cell cycle duration of 16-17 h. In contrast, large interstitial cells occurring as singles and in clusters of 2 have G 2 durations ranging from 4 to 22 h. Two subpopulations can be discerned among these cells, one having a G 1 of about 6 h and a total cell cycle of about 19 h, the other having an average G 2 of 14 h and a total cell cycle of about 27 h. The differences in cell cycle duration appear to be associated with interstitial cell function. Cells having a short cell cycle are probably committed to nematocyte differentiation, while large interstitial cells having long and variable cell cycles appear to be undetermined stem cells responsible for proliferating further interstitial cells. The variable length of G 2 in these cells suggest it as a possible control point.
223 citations
TL;DR: Field potential analysis demonstrates that a new short latency evoked potential is a reflection of mono-synaptic activation of the denervated dentate granule cells by the re-innervating contralateral entorhinal fibers, which implies that the new synapses formed in response to a deafferenting lesion are formed rapidly and remain permanently capable of activating the dentategranule cells which had been deprived of ipsilateral entorHinal input.
Abstract: Ablation of the entorhinal cortex of the rat removes the major synaptic input to the granule cells of the ipsilateral dentate gyrus. Following unilateral entorhinal lesions in adult rats, we have examined the efferent projections of the remaining contralateral entorhinal cortex to determine if these might sprout to re-innervate the deafferented dentate gyrus. Autoradiographical tracing of the fiber projections of the remaining contralateral entorhinal cortex 60 days following lesions indicates that new fibers sprout and grow for several hundred microns into the denervated regions, to terminate on portions of the granule cell dendrites which would normally receive ipsilateral entorhinal afferents. These re-innervating fibers form electrophysiologically functional synaptic connections with the denervated dentate granule cells. In the normal animal, unilateral stimulation of the entorhinal cortex does not result in short latency activation of the contralateral dentate gyrus whereas following ipsilateral entorhinal lesions, re-innervation by contralateral entorhinal afferents is reflected electrophysiologically by the appearance of a new short latency evoked potential to contralateral entorhinal stimulation. By field potential analysis, we demonstrate that this new short latency evoked potential is a reflection of mono-synaptic activation of the denervated dentate granule cells by the re-innervating contralateral entorhinal fibers. In addition, the time course of contralateral entorhinal re-innervation is determined electrophysiologically. The new short latency response to contralateral entorhinal stimulation appears as early as 9 days post-lesion, matures functionally between 9 and 15 days, and after 15 days, remains apparently undiminished for as long as 200 days. This implies that the new synapses formed in response to a deafferenting lesion are formed rapidly and remain permanently capable of activating the dentate granule cells which had been deprived of ipsilateral entorhinal input.
198 citations
TL;DR: The postnatal development of acetylcholinesterase activity in the hippocampal formation of the developing rat brain, as demonstrated histochemically by the copper-thiocholine technique, serves as a marker for the ingrowing cholinergic afferent fibers.
197 citations
TL;DR: There is no data on whether spines are replaced when sprouting afferents invade deafferented dendritic zones, which is a critical question if the nature of the morphological reorganisation which follows lesions in the brain is to be understood.
Abstract: SEVERAL studies have reported that there is a loss of dendritic spines after partial deafferentation. It is known that terminals lost to a structure after injury to one of its afferents are replaced in part or whole by sprouting of undamaged inputs1–3. This raises questions as to the nature of the accompanying post-synaptic changes but no attempts have been made to follow the loss of spines over time4–6. Specifically, there are no data on whether spines are replaced when sprouting afferents invade deafferented dendritic zones. This is a critical question if the nature of the morphological reorganisation which follows lesions in the brain is to be understood.
196 citations
TL;DR: Ovariectomized female rats were administered estradiol benzoate and either 10, 25, 50, 100, or 200 μg of progesterone and tested for sexual receptivity and the probability of lordosis was related directly to the dose of both steroids.
188 citations
TL;DR: In this article, a theory for surface polaritons associated with the planar surface of a semi-infinite anisotropic dielectric medium is presented for magnetic fields either perpendicular or parallel to the surface.
Abstract: A theory is presented for surface polaritons associated with the planar surface of a semi-infinite anisotropic dielectric medium. Retardation is included. In general, two attenuating components with different attenuation constants must be superposed within the medium in order to satisfy the boundary conditions, and the macroscopic electric field vector does not lie in the sagittal plane. For special cases, however, only one attenuating component is required, and the electric vector does lie in the sagittal plane. The theory is applied to the specific case of surface magnetoplasmons in a semiconductor for magnetic fields either perpendicular or parallel to the surface. In the latter case, propagation directions parallel and perpendicular to the magnetic field are considered. Possibilities for the experimental observation of the effects predicted are discussed.
169 citations
TL;DR: Less-detailed data on development of ChAc and AChE activities in the hippocampal region as a whole suggest a similar sequence in divisions other than the dentate gyrus, and this finding is interpreted as a correlate of cholinergic synaptogenesis.
TL;DR: Microscopical observations of UV irradiated eggs with and without transplanted polar cytoplasm revealed that UV irradiation delays the migration of cleavage nuclei into the posterior periplasm and prevents cy toplasmic protrusions at the posterior pole from becoming isolated from the periplasms to form pole cells.
TL;DR: Studying the short-tclm rate of amino acid uptake by phytoplankters from dilute solution in conjunction with growth studies at higher concentrations demonstrates uptake of amino acids from low concentrations and their oxidation and assimilation into synthetic pathways by the unicellular algae.
Abstract: Axenic cultures of 25 species of unicellular marine algae were tested for their ability to utilize nine common amino acids, supplied at high concentrations in batch culture, as a nitrogen source; most species were able to use several amino acids, although growth was often slower than on nitrate nitrogen. The algae were also tested for their ability to t,ake up ‘“C-labclcd amino acids supplied at low, natural concentrations. In most cases, species that could grow on an amino acid at high concentration in culture could also take up amino acids at low concentrations. Uptake rates were higher in cells that had been deprived of nitrogen during growth. In some cases, uptake rates at low concentrations-if sustained-would bc sufficient to support moderate growth rates. The ability to accumulate amino acids from dilute solution occurs in many phytoplankters, particularly in spccics that normally occur in inshore and littoral habitats. The growth of phytoplankton in the sea often appears to be controlled by the availability of nitrogen (Dugdalc and Goering 1967). Ambient concentrations, uptake rates, assimilation and metabolism of the inorganic forms of nitrogen-nitrate and ammonia-have been studied to explore the relation between nitrogen nutrition and phytoplankton ecology, but the role of organic nitrogen has received much less attention. We wish to focus attention on the potential significance of amino acids as a nitrogen source for phytoplankters under natural conditions. Concentrations of dissolved free amino acids are usually in the range of 0.2 to 2.0 pg-atoms N liter-” for total amino acids (Bohling 1970; Clark et al. 1972; Riley and Segar 1970). A number of phytoplankters have been grown axenically with various organic sources of nitrogen, including amino acids ( Guillard 1963). However, in such growth experiments nitrogenous compounds are usually 1,000 times more concentrated than in natural waters. The ability of phytoplankton to use amino acids as nitrogen sources at high concentrations does not necessarily provide any insight into their potential significance at low concentrations. ‘This work was supported by NSF Grant GA 33904x. ’ N. Kaji and V. Cooke provided technical assistance and help in manuscript preparation. D. Staley assisted in the uptake measurements. To study growth directly in laboratory culture at natural concentrations it would be necessary to maintain axenic conditions in a large volume, to supply nutrients continuously to mimic a steady state, and to devise methods of assessing slow growth in a sparse suspension of cells. We have chosen to approach the issue by studying the short-tclm rate of amino acid uptake by phytoplankters from dilute solution in conjunction with growth studies at higher concentrations. Analysis of the kinetics of uptake allows estimation of entry rates under natural conditions, while growth experiments establish the substrate as a metabolically adequate nutrient. We have demonstrated uptake of amino acids from low concentrations and their oxidation and assimilation into synthetic pathways by the unicellular algae Plutymonas subcorcliformis and Nitxschiu oualis (e.g. North and Stephens 1967, 1969, and later). Amino acid transport systems in phytoplankters are extremely labile. Restriction of nitrogen availability in the culture decreases the nitrogen content of the cells and slows their growth rate; it also greatly accelerates the rate of amino acid uptake. In some cases, no uptake is observed until nitrogen in the growth medium is restricted. The possible contribution of amino acids to the nitrogen required for growth appears to depend on the nutritional history of the cells. Amino acids supplied at low levels LIMNOLOGY AND OCEANOGRAPHY 249 MARC11 1974, V. 19(2)
01 Mar 1974
TL;DR: It is concluded that both genetic and epigenetic neoplasms of Drosophila melanogaster have the same phenotypic expression as the genetic processes at work in wild-type imaginal discs after prolonged culturein vivo.
Abstract: The developmental properties of three neoplasms found in lethal mutants ofDrosophila melanogaster were studied and compared with the development of the corresponding wild-type organs. Two of these neoplasms are found in the late larval lethal mutant,lethal (2) giant larvae 4 (l(2)gl 4) and its allele,lethal (2) giant larvae (l(2)gl). The third neoplasm occurs in the hemizygous lethal male embryos of the mutantNotch 8 (Df(1)N 8).The mutantsl(2)gl 4 andl(2)gl were shown to possess defects involving imaginal primordia of ectodermal origin, such as the imaginal discs of the adult integument and the imaginal optic primordia in the larval brain. They also have enlarged lymph glands and abnormal gonads, salivary and ring glands. Thel(2)gl 4 andl(2)gl mutations transform the imaginal discs into noninvasive, lethal neoplasms and the imaginal optic primordia in the larval brain into an invasive and lethal neuroblastoma. Both neoplasms were serially subcultured in female adult hosts where they grew rapidly and killed their hosts in 7-14 days. The neoplastic development of thel(2)gl 4 imaginal discs and brain proved autonomous at all stages that were investigated from 10 hour old embryos to mature larvae. When exposed to the hormonal conditions of metamorphosis, the neoplastic tissues,in situ as well as those that had been culturedin vivo, ceased to grow but failed to metamorphose into parts of the adult integument or brain. Furthermore, in almost all cases they failed to resume their growth in the adult fly after metamorphosis.Thel(2)gl 4 brain neuroblastoma changed after prolonged subculturein vivo so that although the cells stopped dividing temporarily at the time of metamorphosis of the host, they resumed their growth shortly thereafter and continued to divide throughout adult development and in the emerged adult. Many of thel(2)gl 4 neuroblastoma cells showed abnormal karyotypes, shapes and sizes after prolonged culturein vivo.Thel(2)gl 4 imaginal disc tissue resembles, in both structure and behavior, certain atelotypic tissue sublines which arise from wild-type imaginal discs after prolonged culturein vivo: the ultrastructure of both types of cells are similar and both cease to grow when exposed to hormonal conditions of metamorphosis. Apparently the epigenetic processes which transform wild-type imaginal discs afterin vivo subculture into atelotypic neoplasms have the same phenotypic expression as the genetic processes at work inl(2)gl 4 imaginal discs.An analysis of several other late larval and larval-pupal mutants with defective imaginal discs, such asl(2)gd andl(1)d.lg.-1 revealed that they also had defects in parts of the brain destined to form adult structures. This observation indicates that mutations that affect imaginal discs of the adult integument also affect the imaginal primordia of the adult brain.The neoplasm in the hemizygous male embryo of the embryonic lethalNotch 8 is a teratoma-like growth which is lethal and invasive; when implanted into female adult hosts it gives rise to a mass of tissue which consists of most cell types present in the larval nervous system and a number of other unidentified cell types. It too can be subculturedin vivo for many transfer generations.The relative infrequency of neoplasms in insects is analyzed and an attempt is made to explain this infrequency and the occurrence of neoplasms in specific tissues of insects at specific developmental stages. Genetic and epigenetic neoplasms ofDrosophila are compared with neoplasms of other insects and of vertebrates and it is concluded that both genetic and epigenetic neoplasms ofDrosophila share the essential features of vertebrate neoplasms.
TL;DR: The medial geniculate body of mammals is not a homogeneous structure, and has thus been subdivided into a varying number of component nuclei, and the question of whether or not each cell group projects to the telencephalon in a distinct fashion is raised.
TL;DR: Maternal isoagglutinins may exert a suppressive influence on the development of specific isoag Glutinin in the first year of life, and this slow development of anti‐B in group A children persisted through the second year.
TL;DR: A new method for tracing connections in the central nervous system is described where Horseradish peroxidase is injected into the area of interest where it is taken up by cell bodies and dendrites and transported to their axons and terminals.
TL;DR: An analysis was made of the protein composition of a fraction of postsynaptic densities (PSDs) prepared from rat brain, which apparently consists of a structural matrix formed primarily by a single polypeptide or class ofpolypeptides of 53,000 molecular weight.
Abstract: An analysis was made of the protein composition of a fraction of postsynaptic densities (PSDs) prepared from rat brain. Protein makes up 90% of the material in the PSD fraction. Two major polypeptide fractions are present, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major polypeptide fraction has a molecular weight of 53,000, makes up about 45% of the PSD protein, and comigrates on gels with a major polypeptide of the synaptic plasma membrane. The other polypeptide band has a molecular weight of 97,000, accounts for 17% of the PSD protein, and is not a prominent constituent of other fractions. Six other polypeptides of higher molecular weight (100,000–180,000) are consistently present in small amounts (3–9% each). The PSD fraction contains slightly greater amounts of polar amino acids and proline than the synaptic plasma membrane fraction, but no amino acid is usually prominent. The PSD apparently consists of a structural matrix formed primarily by a single polypeptide or class of polypeptides of 53,000 molecular weight. Small amounts of other specialized proteins are contained within this matrix.
TL;DR: Clinical manifestations are varied, and have been presented as related to the primary tumor, to tumor extension or metastases, to systemic effects, and to several syndromes associated with lung cancer.
TL;DR: Results indicate that cAMP plays a role in the control of morphogenesis in Mucor racemosus and induces yeastlike development in young aerobic hyphae grown in media containing 2% glucose.
Abstract: Yeastlike cells of Mucor racemosus grown under 100% CO(2) underwent morphogenesis to hyphae after exposure to air. The addition of dibutyryl cyclic adenosine monophosphate (dbcAMP) to yeastlike cultures inhibited this morphogenesis in media containing 2% glucose. The maintenance of uniformly spherical, budding cells required 1 mM dbcAMP in a defined medium containing Casamino Acids, and 3 mM dbcAMP in a medium containing yeast extract and peptone. At these concentrations, dbcAMP also induced yeastlike development in young aerobic hyphae grown in media containing 2% glucose. Removal of dbcAMP resulted in hyphal development. The endogenous cyclic AMP (cAMP) content of yeastlike cultures was measured after a shift from CO(2) to air. A fourfold decrease in intracellular cAMP preceded the appearance of hyphal germ tubes. These results indicate that cAMP plays a role in the control of morphogenesis in Mucor racemosus.
TL;DR: In this paper, the effect of the male parent on growth and development of the pups was found to be due to his keeping them warm, and the possible significance of this for mice in the wild state is discussed.
TL;DR: A photoreactivating enzyme has been found in human leukocytes and the specificity of the enzyme for cyclobutyl pyrimidine dimers in DNA may allow direct evaluation of the role of dimer in ultraviolet-induced carcinogenesis in man.
Abstract: A photoreactivating enzyme has been found in human leukocytes. The specificity of the enzyme for cyclobutyl pyrimidine dimers in DNA may allow direct evaluation of the role of dimers in ultraviolet-induced carcinogenesis in man.
TL;DR: Parental behavior was observed in Peromyscus californicus parasiticus that had been live trapped as adults and bred in the laboratory, indicating that male P. califORNicus participate in the care of their pups.
01 Mar 1974
TL;DR: It is concluded that amphibian blastemas in common with a number of other systems can develop according to the presumptive fates of their cells, or they can regulate when they are given the opportunity for growth and cell division.
Abstract: 1. The regulative ability of the regeneration blastema of the newt limb (Notophthalmus viridescens) was tested by operationsin situ. Either the anterior, posterior, dorsal, or ventral half of the blastema was removed at various stages during regeneration. 2. All blastemas operated on prior to the stage of four early digits showed a delay in reaching the subsequent stages of regeneration. 3. The blastema is capable of extensive regulation in the anterior-posterior and dorsoventral axes even after many of its cells have begun to differentiate. 4. Early digital stages of regeneration were found to be defective in regulative ability. Additional skeletal elements were present in limbs which had been operated on at the stage of three early digits. Supernumerary digits as well as additional skeletal elements were present in limbs which had been operated on at the stage of four early digits. Removal of the posterior half of the regenerate at one of these late stages resulted in more severe abnormalities than did removal of the anterior half. 5. Either the anterior or the posterior half of a mature limb was removed back to the level of the wrist. In several cases, an almost complete autopodium developed alongside the remaining half autopodium. 6. Removal of half of a regenerate at digital stages gave results similar to those obtained following removal of half of a mature limb. 7. The results are discussed in the context of other experiments on regenerating limbs, and of experiments on other developing systems. It is concluded that amphibian blastemas in common with a number of other systems can develop according to the presumptive fates of their cells, or they can regulate when they are given the opportunity for growth and cell division.
TL;DR: In this paper, three procedures for magnitude estimation were investigated, and a sufficient number of responses were obtained to make reasonable estimates of both the mean and variance of the responses, and the conventional magnitude estimate procedure appeared to produce the most sensible data.
Abstract: Three procedures for magnitude estimation were investigated, and a sufficient number of responses were obtained to make reasonable estimates of both the mean and variance of the responses. The conventional magnitude estimate procedure, without a standard signal, appeared to produce the most sensible data. The best method of establishing the central tendency of the data appears to be the plot of the mean ratio of successive responses against the intensity ratio of the corresponding signal intensities. When this is done, the average response ratio increases roughly as a power function of the signal ratios. The coefficient of variation, σ/m, varies from about 0.1 for small signal ratios and increases to 0.3 at about 20 dB and greater signal separations. The distribution of response ratios appears to be reasonably well approximated by a beta distribution. The change in σ/m with signal ratio is suggestive of an attention mechanism in which the sample size depends on the location of the attention band. The ratio estimation procedure suffers badly from discrete number tendencies.
TL;DR: The production rates of 18 marine macrophytes near Wilson Cove, San Clemente Island, are close to those for other marine algal communities and no apparent relationship was revealed between the productivity of an alga and the division to which it belongs; however, productivity was associated with growth form.
Abstract: This study represents the first report of primary production rates for Southern California intertidal producers. The production rates of 18 marine macrophytes near Wilson Cove, San Clemente Island, are close to those for other marine algal communities. No apparent relationship was revealed between the productivity of an alga and the division to which it belongs; however, productivity was associated with growth form. Encrusting prostrate forms were the lowest producers in terms of g C/m2/h and g C/g dry weight/h; sheet-like and finely-branched forms showed a greater productivity than coarsely-branched forms. Gelidium pusillum and Ulva californica had considerably greater production rates than the other algae measured.
TL;DR: Prolonged extracorporeal circulation (ECC) was carried out for cardiac or pulmonary support in 6 patients; one survived; all patients who died had irreversible pulmonary damage.