The human calcitonin gene is located on the short arm of chromosome 11

By molecular hybridization of human calcitonin cDNA probes to DNA from human-rodent hybrid cells containing identified human chromosomes, we have mapped the human calcitonin gene to the short arm of chromosome 11. This location has been confirmed by in situ hybridization, which further localized the calcitonin gene to region 11p13-15. The significance of this region regarding gene linkage and possible markers for inherited cancers is discussed.     

Active site kinetics of horse serum cholinesterase

Horse serum Cholinesterase hydrolyzes choline and p-nitrophenol esters at different rates. Deacylation and acylation seem to be the rate-limiting step for charged and uncharged substrates respectively. Activation energy is similar for the acetic, propionic, and butyric esters of thiocholine, but it is higher for p-nitrophenylpropionate. Inhibition by the tetramethyl-ammonium ion is competitive. Tetraethyl-, tetrapropyl-, and tetrabutyl-ammonium ions are mixed-type inhibitors. The pH studies demonstrated the existence of a residue, pK = 6.33, involved in catalysis.     

The identification of the periodic behaviour in an epidemic model

In this paper we study a method for the identification of the unknown parameter of the periodic function and also the first component of the state vector, in a mathematical model which describes the evolution of some diseases with an oro-fecal transmission.To solve the identification problem we use a numerical method to integrate the differential equations system, which reproduces the stability properties of the above mentioned continuous system.The numerical methods which we propose can be applied also to a spatial semi discretization of the reaction-diffusion model which is a diffusive generalization of the system that we consider in this paper.Finally, through an analysis on both the continuous and the discrete system we also obtain a necessary condition on the experimental data in order that a periodic trajectory of the system exists.Work supported by: Progetto Finalizzato Controllo Malattie da Infezione-CNR and by Ministero Pubblica Istruzione     

Regioelectronic factors in metabolic hydroxylation of aliphatic carbon atoms

EHT calculations have been performed on model molecules acting as substrates for mammalian mono-oxygenases. C_α---H bonds are consistently found to have larger overlap populations compared with C_β---H and C_γ---H bonds. It is known on the other hand that metabolic hydroxylation of aliphatic carbon atoms shows a marked regioselectivity for α-carbons. The quantum-mechanical results sustain the view that C---H bonds of relatively high electronic density are preferred target sites for the cytochrome P-450-mediated oxygenation, and that the oxygen atom being activated is transformed into an electrophilic species capable of C---H bond insertion.     

Biochemical changes of rat brain membranes with aging

Modification of membrane composition and enzymatic activities both in total brain homogenate and purified synaptic plasma membrane of 3 and 24 month old rats has been investigated. Protein, cholesterol and phospholipid content and (Na+, K+)ATPase and 2',3' cyclic nucleotide phosphohydrolase activities were determined. The major changes occurred in the whole homogenate where a general increase in total protein and cholesterol content with age and a significant increase of the cholesterol/phospholipids molar ratio has been detected. In S.P.M. aging process induced a decrease of protein, cholesterol and phospholipids content associated with an increased membrane viscosity and a decrease of delta E. These data are consistent with a change in the structural organization and in the distribution pattern of different cell population in the aging brain. A possible artifactual effect of freezing on the reported parameter is also discussed.     

The differential effects of PGE on the immune response in normal and immunosuppressed mice

The effect of 16,16-dimethyl-PGE₂-methyl ester (di-M-PGE₂) on humoral and cellular immunoresponsiveness has been compared in normal mice and in mice immunosuppressed by splenectomy and thymectomy plus antithymocyte serum (ATS). Splenectomy resulted in immunosuppression manifested by augmentation of B-16 melanoma growth; this stimulatory effect was reversed by di-M-PGE₂. In animals immunosuppressed by thymectomy plus ATS, di-M-PGE₂ augmented the humoral and cellular immune responses; this was manifested by slowing of the growth of B-16 melanoma and by stimulating the number of plaque-forming cells, hemagglutinin titers, and delayed-hypersensitivity reactions to sheep erythrocytes. In contrast, in normal (nonthymectomized) mice, di-M-PGE₂ was mildly immunosuppressive. Finally, adriamycin-immunosuppressed normal mice and this suppression were reversed by the addition of di-M-PGE₂ to the treatment regimen.     

Transferrin binding to K562 cell line : Effect of heme and sodium butyrate induction

Experiments demonstrating the existence of receptors for iron-saturated transferrin on K562 cells are described. Binding of ¹²⁵I-labelled transferrin is rapid, saturable and reversible, and can be specifically inhibited by unlabelled transferrin, but not by other proteins. The number of receptors determined by Scatchard analysis significantly decreased when K562 cells moved from the exponential to the quiescent phase of growth. Induction by hemin or sodium butyrate resulted in a marked reduction of transferrin binding. This phenomenon was due entirely to reduction in the number of receptors and was without effect on the affinity of interaction. The effect of butyrate and hemin on the number of transferrin receptors in other hematopoietic cell lines was investigated. Butyrate on the various cell lines was variable in its effect, whereas hemin constantly elicited a significant reduction in the number of transferrin receptors.     

Further observations relating sex size ratios to mating success in calanoid copepods

Mating experiments using 153 pairs of Diaptomus leptopus Forbeswere video-taped in the laboratory. The following were measuredand scored: attempted capture of the female by the male, timeto successful capture and mounting, duration of copulation,spermatophore placement, time to clutch extrusion, prosome lengthsof all individuals and sex size ratios (female:male lengths)of all pairs. Mating success was not a function of sex sizeratio for D.leptopus at ratios commonly observed in nature inthe populations tested. However, this lack of relationship maynot be true of all populations. Photographic analysis of D.leptopusas well as D.birgei Marsh showed that males always held ontofemale genital segments in the vicinity of the spines with theirright fifth legs. Pearson correlations were calculated comparingprosome lengths to a variety of genital parts. The strongestrelationships were found with female genital segment width atthe level of the spines for both species, and male right fifthleg claw length for D.birgei. These data support the hypothesisthat the relationship between sex size ratio and mating successmay be species specific.