Effects of amino acids and derivatives of cyclic adenosine 3′, 5′-monophosphate on the production of three exoenzymes by Staphylococcus, simulans biovar staphylolyticus

The extracellular protease, endopeptidase, and hexosaminidase produced by $\text{Staphylococcus}\text{,}\text{simulans}\text{biovar}\text{staphylolyticus}$ were neither induced nor repressed by amino acids but required a tryptic digest of casein for their production. Catabolite repression of exoenzyme production by glucose was not affected by exogenous cyclic adenosine 3′, 5′-monophosphate but was partially relieved by di- or monobutyryl derivatives of this compound.     

Classical Raman spectroscopic studies of NADH and NAD+ bound to liver alcohol dehydrogenase by difference techniques

We report the Raman spectra of reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD+, respectively) and adenosine 5'-diphosphate ribose (ADPR) when bound to the coenzyme site of liver alcohol dehydrogenase (LADH). The bound NADH spectrum is calculated by taking the classical Raman difference spectrum of the binary complex, LADH/NADH, with that of LADH. We have investigated how the bound NADH spectrum is affected when the ternary complexes with inhibitors are formed with dimethyl sulfoxide (Me2SO) or isobutyramide (IBA), i.e., LADH/NADH/Me2SO or LADH/NADH/IBA. Similarly, the difference spectra of LADH/NAD+/pyrazole or LADH/ADPR with LADH are calculated. The magnitude of these difference spectra is on the order of a few percent of the protein Raman spectrum. We report and discuss the experimental configuration and control procedures we use in reliably calculating such small difference signals. These sensitive difference techniques could be applied to a large number of problems where the classical Raman spectrum of a "small" molecule, like adenine, bound to the active site of a protein is of interest. The spectrum of bound ADPR allows an assignment of the bands of the bound NADH and NAD+ spectra to normal coordinates located primarily on either the nicotinamide or the adenine moiety. By comparing the spectra of the bound coenzymes with model compound data and through the use of deuterated compounds, we confirm and characterize how the adenine moiety is involved in coenzyme binding and discuss the validity of the suggestion that the adenine ring is protonated upon binding. The nicotinamide moiety of NADH shows significant molecular changes upon binding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lysis of sensitized sheep erythrocytes in human sera deficient in the second component of complement

Analysis of C-dependent lysis of sensitized SRBC by C2-deficient sera (C2D) led to the characterization of a C2 bypass pathway. Lysis in the total hemolytic C assay by C2D sera was Ca2+-dependent and required a high concentration of hemolysin to sensitize E. Selective component depletion indicated a requirement for C1 and C4 of the classical pathway (CP) and proteins B, P, and probably D of the alternative pathway (AP). Total hemolytic C could be restored to normal in these C2D sera by utilizing heavily sensitized E or by the addition of a supranormal concentration of B. This system most closely resembles a pathway described by J. E. May and M. M. Frank which requires antibody, C1, and the AP but not C4 or C2. It differs in its requirement for C4. We hypothesize that this pathway represents vestiges of a more primitive C pathway. It becomes evident and possibly clinically important in the setting of C2 deficiency, by allowing C activation, other than the AP, and perhaps in normal individuals, by damaging microorganisms that have evolved means to inhibit early components of the CP.     

Template-directed synthesis of oligonucleotides under eutectic conditions

Summary One of the most important sets of model prebiotic experiments consists of reactions that synthesize complementary oligonucleotides from preformed templates under nonenzymatic conditions. Most of these experiments are conducted at 4°C using 0.01–0.1 M concentrations of activated nucleotide monomer and template (monomer equivalent). In an attempt to extend the conditions under which this type of reaction can occur, we have concentrated the reactants by freezing at –18°C, which is close to the NaCl–H₂O eutectic at –21°C.The results from this set of experiments suggest that successful syntheses can occur with poly(C) concentrations as low at 5×10^–4 M and 2MeImpG concentrations at 10^–3 M. It was also anticipated that this mechanism might allow the previously unsuccessful poly(A)-directed synthesis of oligo(U)s to occur. However, no template effect was seen with the poly(A) and ImpU system. The failure of these conditions to allow template-directed synthesis of oligo(U)s supports the previously proposed idea that pyrimidines may not have been part of the earliest genetic material.Because of the low concentrations of monomer and template that would be expected from prebiotic syntheses, this lower temperature could be considered a more plausible geologic setting for template-directed synthesis than the standard reaction conditions.     

On the relationship between evolutionary and psychological definitions of altruism and selfishness

I examine the relationship between evolutionary definitions of altruism that are based on fitness effects and psychological definitions that are based on the motives of the actor. I show that evolutionary altruism can be motivated by proximate mechanisms that are psychologically either altruistic or selfish. I also show that evolutionary definitions do rely upon motives as a metaphor in which the outcome of natural selection is compared to the decisions of a psychologically selfish (or altruistic) individual. Ignoring the precise nature of both psychological and evolutionary definitions has obscured many important issues, including the biological roots of psychological altruism.     

Attachment tissues of the teeth in Caiman sclerops (Crocodilia)

As the Crocodilia are the only non-mammalian vertebrates with tooth sockets, the attachment tissues of the teeth were studied in Caiman sclerops mainly at the ultrastructural level and were compared with those of mammals. All three attachment tissues (alveolar bone, cementum and periodontal ligament) in the Caiman showed both similarities and differences with their mammalian counterparts. Highly organized, lamellated structures, probably representing specialized sensory nerve endings were observed within the Caiman ligament. No such structure has ever been described in the mammalian ligament.     

Nuclear magnetic relaxation studies of the conformation of adenosine 5'-triphosphate on pyruvate kinase from rabbit muscle.

The conformation of adenosine 5'-triphosphate in the manganese complex of pyruvate kinase from rabbit muscle was determined from six metal to nucleus distances derived by nuclear magnetic relaxation techniques. On the enzyme, no direct metal-ATP coordination exists. The phosphorous atoms of ATP are 4.9 to 5.1 A away from manganese, a distance which indicates either a predominantly (greater than or equal to 94%) second sphere complex or, less likely, a highly distorted inner sphere complex. Thus, water ligands or ligands from the protein might intervene between the ATP molecule and the divalent metal ion and facilitate their interaction. The metal-gammaP distance of 5 A for pyruvate kinase-bound ATP is equal to that found for the phosphorous atom of phosphoenolpyruvate and cobalt(II) on pyruvate kinase (Melamud, E., and Mildvan, A. S. (1975) J. Biol. Chem. 250, 8193-8201), which is consistent with the overlap in space of the P-enolpyruvate-phosphorus and the gammaP of ATP at the active site. This observation explains the competitive binding of these two substrates to the enzyme, as detected by NMR and by early kinetic studies. From the phosphorus data and from measurements of the relaxation rates of 3 protons of ATP in the pyruvate kinase-metal-ATP complex, the conformation of ATP was characterized as extended with distances of 6.0, 9.1, and 7.5 A from manganese to the H8, H2, and H'1 protons, respectively. The torsion angle about the glycosidic bond (chi) which defines the conformation of the enzyme-bound riboside and adenine rings was determined to be 30 degrees. In contrast, the conformation of the binary Mn(II)-ATP complex in solution is folded around the metal with direct manganese coordination of the alpha-, beta-, and gamma-phosphorus atoms, and with metal to proton distances of 4.5, 6.4, and 6.2 A for the H8, H2, and H'1 protons, suggesting a second sphere manganese-adenine interaction. The chi angle equals 90 degrees for the binary complex primarily because of the metal-base interaction. Thus, a profound change in the conformation and structure of Mn(II)-ATP from a folded chelate to an extended second sphere complex results when the nucleotide binds to pyruvate kinase.     

HETEROTROPHY OF FOUR MARINE PHYTOPLANKTERS AT LOW SUBSTRATE CONCENTRATIONS1

Three pelagic marine phytoplankters, Coccolithus huxleyi, Skeletonema costatum, and Thalassiosira rotula, and a facultative heterotroph, Cyclotella cryptica, have been exposed to three organic substrates, viz, glucose, acetate, and glutamate, at low concentrations (organic carbon 0.25 mg/liter). Experiments were performed in the dark and light and the net assimilation of substrate was measured by using radiocarbon. The dark uptake of carbon dioxide was also determined, together with photosynthesis at near optimum light intensity. The expected heterotrophy was detected with Cyclotella cryptica. Thalassiosira rotula was found to assimilate glutamate at an appreciable rate. In all cases, however, the short-term uptake of carbon dioxide in the dark was the greatest assimilation rate measured. Values are discussed in relation to their ecological significance and it is concluded that heterotrophic survival of these and probably most other algae in the open ocean would be impossible unless they were in contact with a high concentration of substrate in the form of particulate matter.     

Pancreatic polypeptide immunoreactivity in medullary carcinoma of the thyroid: identification and characterisation by radioimmunoassay, immunocytochemistry and high performance liquid chromatography

Pancreatic polypeptide immunoreactivity has been identified in primary medullary carcinoma of thyroid using radioimmunoassay and immunocytochemistry and subsequently characterised by HPLC. Two region-specific PP antisera were used in the study; one C-terminal and one non-C-terminal. These antisera demonstrate variable cross-reactivity with the molecular species of PP identified in the tumours. The immunoreactive material in the tumours corresponded to human PP and not PYY or NPY on the basis of immunoreactivity and HPLC behaviour. It was identified in all patients with familial-type disease but not in the two sporadic cases examined. We propose that estimation of the PP content of medullary carcinoma of thyroid may be a useful means of differentiating familial and sporadic types.