Temperature dependence of the magnetic susceptibility of cobalt (II) stellacyanin.

Magnetic susceptibility measurements on cobalt(II) stellacyanin ($\text{Rhus vernicifera}$) have been performed between 2.2 and 50 K. The effective magnetic moment of Co(II) in the protein is 3.91 ± 0.12 (μ_B). Nonlinear behavior below 3 K evidences the presence of zero-field splitting attributable to a low-symmetry component of the ligand field. The results are consistent with a structural model based on a distorted tetrahedral Co(II) site involving one or more extremely covalent metal-ligand bonds.     

Interaction between phloretin and the red blood cell membrane

Phloretin binding to red blood cell components has been characterized at pH6, where binding and inhibitory potency are maximal. Binding to intact red cells and to purified hemoglobin are nonsaturated processes approximately equal in magnitude, which strongly suggests that most of the red cell binding may be ascribed to hemoglobin. This conclusion is supported by the fact that homoglobin-free red cell ghosts can bind only 10% as much phloretin as an equivalent number of red cells. The permeability of the red cell membrane to phloretin has been determined by a direct measurement at the time-course of the phloretin uptake. At a 2% hematocrit, the half time for phloretin uptake is 8.7s, corresponding to a permeability coefficient of 2 x 10(-4) cm/s. The concentration dependence of the binding to ghosts reveals two saturable components. Phloretin binds with high affinity (K diss = 1.5 muM) to about 2.5 x 10(6) sites per cell; it also binds with lower affinity (Kdiss = 54 muM) to a second (5.5 x 10(7) per cell) set of sites. In sonicated total lipid extracts of red cell ghosts, phloretin binding consists of a single, saturable component. Its affinity and total number of sites are not significantly different from those of the low affinity binding process in ghosts. No high affinity binding of phloretin is exhibited by the red cell lipid extracts. Therefore, the high affinity phloretin binding sites are related to membrane proteins, and the low affinity sites result from phloretin binding to lipid. The identification of these two types of binding sites allows phloretin effects on protein-mediated transport processes to be distinguished from effects on the lipid region of the membrane.     

Nonelectrolyte diffusion across lipid bilayer systems

The permeability coefficients of a homologous series of amides from formamide through valeramide have been measured in spherical bilayers prepared by the method described by Jung. They do not depend directly on the water:ether partition coefficient which increases regularly with chain length. Instead there is a minimum at acetamide. This has been ascribed to the effect of steric hindrance on diffusion within the bilayer which increases with solute molar volume. This factor is of the same magnitude, though opposite in sign to the effect of lipid solubility, thus accounting for the minimum. The resistance to passage across the interface has been compared to the resistance to diffusion within the membrane. As the solute chain length increases the interface becomes more important, until for valeramide it comprises about 90% of the total resistance. Interface resistance is also important in urea permeation, causing urea to permeate much more slowly than an amide of comparable size, after allowance is made for the difference in the water:ether partition coefficient. Amide permeation coefficients have been compared with relative liposome permeation data measured by the rate of liposome swelling. The ratios of the two measures of permeation vary between 3 and 16 for the homologous amides. The apparent enthalpy of liposome permeation has been measured and found to be in the neighborhood of 12 kcal mol-1 essentially independent of chain length. Comparison of the bilayer permeability coefficients with those of red cells shows that red cell permeation by the lipophilic solutes resembles that of the bilayers, whereas permeation by the hydrophilic solutes differs significantly.     

Intermolecular tritium transfer in the transcarboxylase reaction.

Transfer of tritium from [3-3H]pyruvate into propionyl-CoA is found during the reaction of transcarboxylase: Methylmalonyl-CoA + pyruvate leads to oxalacetate + propionyl-CoA. About 5% of the tritium counts that are labilized in the reaction are found in a position of the propionate that exchanges rapidly with water in the presence of transcarboxylase. Transfer from [2-3H]propionate of propionyl-CoA to pyruvate is real but only about one-tenth as great. The tritium transfers between reactants on two subunits are difficult to explain by a "carbanion" mechanism of --C--H bond cleavage and support the cyclic mechanism in which carboxybiotin itself is the base and the enol form of biotin is the proton-transferring agent.     

Temperature dependence of N-phenyl-1-naphthylamine binding in egg lecithin vesicles

The temperature dependence of the binding of PhNapNH₂ ($\text{N-}\text{phenyl-1-naphthylamine}$) to vesicles of egg phosphatidylcholine has been determined. The Arrhenius plot of the association constant exhibits a discontinuity at 20.9 °C, some 30 °C above the broad phase transition region of the phospholipid. In the temperature range above 20 °C, $\text{ΔH}{}^0\text{= ?6100}\text{cal·mol}{}^{\mathrm{?1}}$ and $\text{ΔS}{}^0\text{= 9.7}\text{e. u.}$; in the temperature range below 20 °C, $\text{ΔH}{}^0\text{= 0}\text{cal · mol}{}^{\mathrm{?1}}$ and $\text{ΔS}{}^0\text{= 30.4}\text{e. u.}$ These values are consistent with the view that there are well ordered lipid-lipid bonds below 20 °C which are significantly less important above this temperature. The order in the temperature range of 5 to 20 °C, though significantly greater than that above 20 °C, is still significantly less than that in the crystalline state.     

Adenosine 3'',5''-cyclic monophosphate and morphology in Neurospora crassa: drug-induced alterations.

Grown in liquid culture in the presence of a variety of structurally unrelated drugs, mycelia of wild-type Neurospora assume a colonial or semicolonial growth habit similar to that of known morphological mutants. Drugs that produce these morphological changes include atropine, theophylline, histamine, and several of the quinoline-containing antimalarials. Each of these drugs decrease the endogenous adenosine 3',5'-cyclic monophosphate (cAMP) concentration of mycelia as a result of their effect on the activity of adenyl cyclase, the cAMP-dependent phosphodiesterase, or both. The evidence indicates a relationship between the degree of morphological abnormality, the degree to which intracellular cAMP is reduced, and the action of the drugs on the adenyl cyclase and phosphodiesterase.     

Sister chromatid exchanges--a sensitive assay of agents damaging human chromosomes.

Sister chromatid exchange frequencies in human lymphocyte chromosomes are greatly increased by alkylating agents, but ionizing radiation has little if any such effect. Scoring these exchanges may provide a useful technique for exploring the mechanisms of chromosome breakage and repair.     

Ovarian and adrenal function during the estrous cycle of the sow.

The concentrations of plasma estrogens, progesterone, and corticosteroids and of urinary pregnanediol, pregnanetriol, ketogenic steroids, and corticosteroids were determined as indicators of ovarian and adrenal function throughout a normal sow's estrous cycle. Two broad peaks of plasma estrogen, one lasting 11–12 days during estrus and another 6-day peak period during the early part of the luteal phase were detected. Plasma progesterone was elevated during the late follicular and luteal phase. Two broad peaks of plasma corticoids appeared, one following the decrease of plasma progesterone and the second 7–14 days later. Those elevations in plasma corticoids occurred when estrogen titres were elevated. Urinary determinations generally reflected plasma findings. Estrogen levels began to rise during the follicular phase while a reasonably high progesterone level was evident. Estrogen titres never decreased to non-detectable levels. An interrelationship between adrenal function and ovarian estrogen production is suggested.     

Immune Response to Dengue Virus Infection in Pediatric Patients in New Delhi,India—Association of Viremia,Inflammatory Mediators and Monocytes with Disease Severity

Dengue virus, a mosquito-borne flavivirus, is a causative agent for dengue infection, which manifests with symptoms ranging from mild fever to fatal dengue shock syndrome. The presence of four serotypes, against which immune cross-protection is short-lived and serotype cross-reactive antibodies that might enhance infection, pose a challenge to further investigate the role of virus and immune response in pathogenesis. We evaluated the viral and immunological factors that correlate with severe dengue disease in a cohort of pediatric dengue patients in New Delhi. Severe dengue disease was observed in both primary and secondary infections. Viral load had no association with disease severity but high viral load correlated with prolonged thrombocytopenia and delayed recovery. Severe dengue cases had low Th1 cytokines and a concurrent increase in the inflammatory mediators such as IL-6, IL-8 and IL-10. A transient increase in CD14⁺CD16⁺ intermediate monocytes was observed early in infection. Sorting of monocytes from dengue patient peripheral blood mononuclear cells revealed that it is the CD14+ cells, but not the CD16+ or the T or B cells, that were infected with dengue virus and were major producers of IL-10. Using the Boruta algorithm, reduced interferon-α levels and enhanced aforementioned pro-inflammatory cytokines were identified as some of the distinctive markers of severe dengue. Furthermore, the reduction in the levels of IL-8 and IL-10 were identified as the most significant markers of recovery from severe disease. Our results provide further insights into the immune response of children to primary and secondary dengue infection and help us to understand the complex interplay between the intrinsic factors in dengue pathogenesis.