The learning skills of primates: The rhesus macaque in comparative perspective

Twenty-month-old rhesus monkeys were tested in a modified discrimination-reversal paradigm, which was designed to distinguish abstract learning from stimulus-response associational learning. Previous studies indicate that talapoin monkeys learn associationally and great apes via forming abstract concepts. Adult rhesus monkeys are apparently capable of forming simple abstractions, but learn primarily through associational process. The results of this study show the adolescent rhesus monkeys to be associational learners, with their response patterns indicating more complexity than the talapoins but less than the adult rhesus monkeys. The data suggest that rhesus monkeys develop their low-level capacity of abstract learning with maturation.     

Evolution of enzyme catalytic power. Characteristics of optimal catalysis evaluated for the simplest plausible kinetic model

1. Evolutionary changes in the structure of an enzyme that provide an increase in its K_m value are considered. Provided that K_m increases as a result of increases in the forward rate constants of the catalysis relative to the reverse rate constants, the enzyme catalyses the conversion of a fixed concentration of its substrate more rapidly when its structure provides that K_m>[S] than when K_m<[S]. 2. Catalytic efficiency of enzymes is discussed in terms of the simplest plausible model, the Haldane [(1930) Enzymes, Longmans, London] reversible three-step model: [Formula: see text] The rate equation for the forward reaction of this model (formation of P) may be written in the simple form: [Formula: see text] K_eq. is the equilibrium constant (=[P]_eq./[S]_eq.), and k_cat.=V/[E]_T, where [E]_T is the total enzyme concentration. 3. To assess the effectiveness of an enzyme, it is necessary only to determine the extent to which the constraints of a particular kinetic mechanism permit v₂ (v when K_m»[S]) to approach v_d (the diffusion-limited rate). 4. The value of the optimal rate of catalysis (v_opt., the maximal value of v₂) is dictated by the equilibrium constant for the reaction, K_eq.; v₂=v_d/a, where [Formula: see text] when k₊₁ is assumed equal to k₋₃, and v_opt.=v_d/a_min.. When K_eq.≥1, it is necessary that k₊₂»k₋₁ for a to take its minimum value, a_min.; when K_eq.«1, it is necessary only that k₊₂»K_eq.·k₋₁, i.e. a can equal a_min. even if k₊₂<k₋₁. When K_eq.»1, v_opt.=v_d; when K_eq.=1, v_opt.=v_d/2, and when K_eq.«1, v_opt.=K_eq.·v_d. 5. The analysis, together with predicted effects of evolutionary pressure, suggests that in practice the rates of the fastest enzyme-catalysed freely reversible reactions might be expected to be lower than the value of k₊₁[E]_T[S] by about an order of magnitude, particularly if K_eq.<1. 6. The existing literature suggests that, in general, appropriate values of K_m have evolved for the provision of high rates of catalysis but that many values of k_cat. are not large enough to provide optimal rates of catalysis unless the value of k₊₁ in vivo is lower than its value in free solution.     

Preparation and characterization of isolated parenchymal cells from guinea pig liver

1. A method is described for the preparation of isolated cells from guinea pig liver. This involved perfusion in situ, in the non-physiological direction, with collagenase. 2. The cell yield was 20--30%, comparable with those from the livers of other species. 3. The ratio of lactate dehydrogenase to glutamate dehydrogenase in the cells was similar to that in vivo, indicating that there was negligible leakage of cytoplasmic enzymes. 4. The concentrations of K+ and adenine nucleotides were initially lower than in the perfused liver; normal values were obtained on incubation, particularly in the presence of substrate. 5. The L-lactate: pyruvate ratio is 16:1, close to established values. The total beta-hydroxybutyrate: acetoacetate ratio indicates that the mitochondrial redox state is more oxidised than in the perfused liver, but the intracellular ratio is similar to that of the intact liver. 6. Rates of gluconeogenesis and ureogenesis, are within the physiological range. Maximal gluconeogeneis from L-lactate was preceded by a lag period. L-lysine stimulated glucose production from L-lactate but did not abolish the lag phase. 7. The effects of aminooxyacetate and octanoate on L-lactate gluconeogenesis were similar to those in the perfused liver.     

Common Sequence at the 5′ Ends of the Segmented RNA Genomes of Influenza A and B Viruses

Guanylyl- and methyltransferases, isolated from purified vaccinia virus, were used to specifically label the 5′ ends of the genome RNAs of influenza A and B viruses. All eight segments were labeled with [α-³²P]guanosine 5′-triphosphate or S-adenosyl[methyl-³H]methionine to form “cap” structures of the type m⁷G(5′)pppN^m-, of which unmethylated (p)ppN- represents the original 5′ end. Further analyses indicated that m⁷G(5′)pppA^m, m⁷G(5′)pppA^mpGp, and m⁷G(5′)pppA^mpGpUp were released from total and individual labeled RNA segments by digestion with nuclease P1, RNase T1, and RNase A, respectively. Consequently, the 5′-terminal sequences of most or all individual genome RNAs of influenza A and B viruses were deduced to be (p)ppApGpUp. The presence of identical sequences at the ends of RNA segments of both types of influenza viruses indicates that they have been specifically conserved during evolution.     

Seed glycoproteins of Lupinus angustifolius

The seed globulins of Lupinus angustifolius are glycoproteins containing 1.4–1.9% (α-conglutin), 2.8–6.4 % (β-conglutin) and 1.2–3.8% (γ-conglutin) carbohydrate. The highest values were obtained after acid hydrolysis and determination by phenol—H₂SO₄, (α, γ-conglutins) or by methanolysis and sugar determination by GLC (β-conglutin). TCA denaturation of β- and γ-conglutins was necessary to remove adsorbed galactomannans before determination of glycoprotein carbohydrates. All 3 conglutins contained mannose, galactose and glucosamine, though the ratio of mannose to galactose, and to a lesser extent neutral sugars to hexosamine varied. Small amounts of fucose were found associated only with γ-conglutin.     

The effects of cholesterol on the time-resolved emission anisotropy of 12-(9-anthroyloxy)stearic acid in dipalmitoylphosphatidylcholine bilayers

The time-resolved fluorescence emission anisotropy of 12-(9-anthroyloxy)stearic acid (12-AS) and 1,6-diphenyl-1,3,5-hexatriene (DPH) have been measured in dipalmitoylphosphatidylcholine liposomes in the presence and absence of 40 mol% cholesterol at temperatures above and below the phase transition temperature (41°C). By using a synchronously-pumped mode-locked frequency-doubled dye laser and single photon counting detection with an excitation response function of 300 picosecond, rotational correlation times down to less than 1 nanosecond could be resolved. Whereas DPH showed only small changes in the limiting anisotropy on the addition of cholesterol, 12-AS showed significant increases in this parameter with the effect being potentiated at higher temperatures. This difference in behaviour has been attributed to a fluorophore-cholesterol interaction that resulted in a change in the fluorophore geometry. Not only do DPH and 12-AS sense different depolarizing rotations due to the different directions of their emission dipoles but also differ in their lipid interactions which alter their limiting anisotropies. The implication is that the comparison of steady-state anisotropy measurements between chemically identical fluorophores in different lipid environments may be complicated by molecular distortions that change the motions to which the steady-state fluorescence parameters will be sensitive.     

Continuous culture system for production of biopolymer levan using erwinia herbicola

The optimal production of the fructan biopolymer levan by the bacterium Erwinia herbicola was investigated, including variations in nitrogen, carbon and phosphorous sources, pH, incubation time, culture yields up to 19% by weight produced based on conversion of sucrose as the carbon source when grown in a continuous culture system and processed by tangential flow filtration. Product identity was confirmed with gas chromatography (GC) and (13)C nuclear magnetic resonance (NMR). Gel permeation chromatography (GPC) and low-angle laser light scattering (LALLS) determination of the molecular weight of the product showed a significant difference in molecular weight values dependent on the method of analysis. Analysis by GPC resulted in molecular weight one order of magnitude lower than LALLS independent of sample, underscoring the unusual nature of this biopolymer.     

Retinol-induced modification of the extracellular matrix of endothelial cells: Its role in growth control

Summary The growth of the endothelial cell (EC) is tightly regulated throughout the body. Many factors have been implicated in modulating EC growth including diffusible compounds, cell-to-cell interactions, and the extracellular matrix (ECM). Retinol, or vitamin A alcohol, has recently been shown to inhibit the growth of bovine capillary ECs, in vitro. Retinoids are known to modify ECM in other cell systems, and pure ECM components have been shown to effect EC growth rates. We, therefore, examined the role of the matrix in the retinol-induced inhibition of ECs. Cell-free matrices from control and vitamin A-treated ECs were prepared by removing cells with EGTA treatment after 7 d of culture. Matrix proteins were analyzed by solubilizing the matrices in 5M quanidine-HCl and performing Western blot analysis using specific antibodies to matrix proteins. In isolating the ECM, we observed that retinol-treated cultures of ECs were resistant to EGTA removal; retinol-treated ECs required twice the exposure time to EGTA to detach from their matrix than did controls cells. Western blot analysis of matrix proteins derived from control and retinol-treated EC cultures demonstrated a 1.6-fold increase in lamininβ chains and a 2.5-fold increase in fibronectin in the ECM of retinol-treated EC compared to control cell matrix. Functional properties of these matrices were assessed by plating control and Day 6 retinol-treated ECs onto the matrices and measuring attachment and growth by determining cell numbers at 24, 72, and 144 h. These studies revealed that control cells attached in greatest numbers to a control matrix whereas retinol-treated ECs preferentially attached to a matrix derived from retinol-treated cells. Furthermore, control ECs which grew rapidly on a control matrix were growth inhibited on a retinol-derived matrix. These data indicate that vitamin A treatment of ECs effects both their phenotype and influences the composition and the functional properties of their underlying ECM. These studies also demonstrate that alterations of the matrix are at least in part responsible for the growth inhibition of EC by retinol.