Dermorphins, Opioid Peptides from Amphibian Skin, Act on Opioid Receptors of Mouse Neuroblastoma x Rat Glioma Hybrid Cells

Dermorphin and its Hyp6 analogue are opiate-like heptapeptides originally discovered in frog skin and characterized by the presence of a D-Ala2 residue in their sequence. They were assayed for their capacity to compete with [3H]Leu-enkephalin for binding to opioid receptors in membranes of neuroblastoma x glioma hybrid cells. In the presence of 7 nM-[3H]Leu-enkephalin, the concentrations at which they caused 50% inhibition of [3H]enkephalin binding (IC50 values) are 0.1 micro M and 0.3 micro M, respectively. In contrast, the synthetic L-Ala2-dermorphin shows very low affinity for the opioid receptors. In addition, like other opioid peptides, dermorphin and hyp6-dermorphin inhibit the elevation by prostaglandin E1 (PGE1) of the level of adenosine 3':5'-cyclic monophosphate (cyclic AMP) (IC50 values 0.2 micro M and 0.4 micro M, respectively). The inhibition is prevented by the opiate antagonist naloxone, L-Ala2-dermorphin is at least three orders of magnitude less potent in inhibiting the PGE1-evoked increase in the level of cyclic AMP. The results show that peptides with an amino acid sequence quite different from that of the enkephalins can bind to opioid receptors of the hybrid cells.     

Distribution of the multiple molecular forms of glucose-6-phosphate dehydrogenase in different physiological states.

The distribution of the multiple molecular forms of rat liver and mammary gland glucose-6-phosphate dehydrogenase was determined by electrophoresis on 5% polyacrylamide gels. In both of these organs, changes in the distribution of enzyme activity among the several forms was slight even when approximately 20- to 40-fold changes in enzyme specific activity were achieved by fasting-refeeding experiments (for liver) or during pregnancy and lactation (for mammary gland). It was concluded that the induction of glucose-6-phosphate dehydrogenase in these two organs occurs without any major redistribution among the multiple molecular forms of this enzyme.     

The effect of copper on frog skin. The role of sulphydryl groups

1. 1. Cu²⁺ at a concentration of 10⁻⁴ M, when applied to the external side of the frog skin produces an increase in the short-circuit current (I_sc).

2. 2. This effect was studied in skins of Rana temporaria adapted to cold (5°C) and room temperature (20°C), skins of Rana pipiens adapted to cold, and the results compared with those obtained previously with Rana ribibunda.

3. 3. The observed effect is less dependent upon the adaptation to cold than upon the functional state of the skin: skins with low short circuit currents have a bigger response to Cu²⁺ than skins with high I_sc.

4. 4. A species difference cannot be ruled out since skins of Rana ribibunda exhibiting high I_sc give good responses to Cu²⁺.

5. 5. 5,5′-dithiobis(2-nitrobenzoic acid), a sulphydryl-oxidizing reagent, produces an effect similar to that of Cu²⁺, and dithiothreitol an SH-reducing agent, reverses the effect of this ion.

6. 6. Cu²⁺ also induces an increase in the unidirectional K⁺ fluxes and unmasks a net outward potassium flux.

7. 7. The outward K⁺ flux induced by Cu²⁺ is sensitive to ouabain.

8. 8. It is concluded that Cu²⁺ increases the permeability of the external barrier of the frog skin to Na⁺ and K⁺, probably by reacting with SH groups.

Characterization of the antibiotic resistance plasmid ERL1 from Streptococcus pyogenes

Summary The streptococcal plasmid ERL1 determining inducible resistance to erythromycin, lincomycin, and staphylomycin S was isolated by dye-buoyant density centrifugation and shown to have a molecular weight of about 17.5 Mdal, as revealed by sedimentation through neutral sucrose gradients. In SM60 cells entering the stationary phase its covalently closed circular form was present to the extent of 5 copies per chromosomal genome equivalent. ERL1 was subject to the DNA restriction and modification mechanism discovered in strain 56188. It did not apear to exercise restriction of phage DNA but mediated a partial release of the restricted growth of A25.     

Multiple regulation of nucleoside catabolizing enzymes in Escherichia coli: effects of 3:5'' cyclic AMP and CRP protein.

Summary The regulation of the synthesis of nucleoside metabolizing enzymes has been studied in cya and crp mutant strains of Escherichia coli.The synthesis of the cyt-enzymes, cytidine deaminase and uridine phosphorylase regulated by the cytR gene product, is activated by the cAMP-CRP complex. On the other hand the synthesis of the deoenzymes: deoxyriboaldolase, thymidine phosphorylase, phosphodeoxyribomutase and purine nucleoside phosphorylase, appears to be increased if an active cAMP-CRP complex cannot be formed.It also seems that nucleosides serve as poor carbon sources for cya and crp mutants; this could not solely be explained by low levels of nucleoside metabolizing enzymes nor by a deficiency in nucleoside uptake. Addition of casamino acids stimulated the growth of cya and crp mutants, with nucleosides as carbon sources. When grown on glucose and casamino acids growth could be stimulated by adenine and hypoxanthine nucleosides; these results suggest an impaired nitrogen metabolism in cya and crp mutants.Abbreviations and Symbols cAMP cyclic adenosine 3:5-monophosphate - CRP cAMP receptor protein. Genes coding for: adenyl cyclase - cya cAMP receptor protein - crp cytidine deaminase - cdd uridine phosphorylase - udp thymidine phosphorylase - tpp purine nucleoside phosphorylase - pup; cytR regulatory gene for cdd, udp, dra, tpp, drm, and pup - deoR regulatory gene for dra, tpp, drm, and pup     

Immobilization of enzymes based on hydrophobic interaction. III. Adsorbent substituent density and its impact on the immobilization of β-amylase

Hexyl-groups have been introduced into crosslinked Sepharose 6B, yielding gels with degrees of substitution which range from 0.02 to 0.70 mol hexyl-side chain per mole galactose residue. The gels were exposed to β-amylase in solution, and the resulting adsorbates indicated a monotonic increase in adsorption capacity with an increasing hexyl-content. Adsorbate activity, by contrast, displayed a maximum for a carrier gel with a hexyl–galactose ratio of 0.51. Adsorbates based on gels with different hexyl-content were used in column reactors for continuous maltose production from a soluble starch substrate.     

Bladder tissue characterization using probe‐based Raman spectroscopy: Evaluation of tissue heterogeneity and influence on the model prediction

Existing approaches for early‐stage bladder tumor diagnosis largely depend on invasive and time‐consuming procedures, resulting in hospitalization, bleeding, bladder perforation, infection and other health risks for the patient. The reduction of current risk factors, while maintaining or even improving the diagnostic precision, is an underlying factor in clinical instrumentation research. For example, for clinic surveillance of patients with a history of noninvasive bladder tumors real‐time tumor diagnosis can enable immediate laser‐based removal of tumors using flexible cystoscopes in the outpatient clinic. Therefore, novel diagnostic modalities are required that can provide real‐time in vivo tumor diagnosis. Raman spectroscopy provides biochemical information of tissue samples ex vivo and in vivo and without the need for complicated sample preparation and staining procedures. For the past decade there has been a rise in applications to diagnose and characterize early cancer in different organs, such as in head and neck, colon and stomach, but also different pathologies, for example, inflammation and atherosclerotic plaques. Bladder pathology has also been studied but only with little attention to aspects that can influence the diagnosis, such as tissue heterogeneity, data preprocessing and model development. The present study presents a clinical investigative study on bladder biopsies to characterize the tumor grading ex vivo, using a compact fiber probe‐based imaging Raman system, as a crucial step towards in vivo Raman endoscopy. Furthermore, this study presents an evaluation of the tissue heterogeneity of highly fluorescent bladder tissues, and the multivariate statistical analysis for discrimination between nontumor tissue, and low‐ and high‐grade tumor.