Derived structure of the putative sialic acid transporter from Escherichia coli predicts a novel sugar permease domain.

Catabolism of sialic acids by Escherichia coli requires the genes nanA and nanT, which were previously mapped between argG and rpoN (E.R. Vimr and F.A. Troy, J. Bacteriol. 164:845-853, 1985). This organization is confirmed and extended by physical mapping techniques. An open reading frame beginning 135 bp from the nanA translational stop codon could code for a 53,547-Da hydrophobic polypeptide predicted to contain 14 transmembrane segments. Complementation analysis confirmed that nanT is required for sialic acid uptake when expressed in trans. NanT is homologous to a putative permease encoded by open reading frame 425, which maps between leuX and fecE in the E. coli chromosome. However, unlike this hypothetical permease or previously reported monosaccharide transporters, NanT contains a centrally located domain with two additional potential membrane-spanning segments plus one amphiphilic alpha-helix that may be important for the structure and function of sialic acid-permease.     

Mechanism of urinary kallikrein excretion

Urinary kallikrein excretion was compared with urea excretion in the rat and the results showed that they were correlated. Like urea excretion is flow-dependent, we conclude that the principal mechanism regulating kallikrein excretion is a wash-out effect on renal kallikrein.     

Comparative activity of two cholecystokinin analogues with partial agonist activity: effects on food intake and brain monoamines

Two analogues of the C-terminal heptapeptide of cholecystokinin have been synthesized, in which the C-terminal phenylalanine residue has been replaced by a phenylethylester (JMV 180) or a phenylethylamide (JMV 170) group. They have been shown to present partial agonist CCK activity on pancreatic amylase release. In this study, the effects of the two peptides were investigated on food intake and brain monoamine metabolism after intraperitoneal (IP) and intracerebroventricular (ICV) administration. Neither peptide was active on feeding after IP administration but both decreased food intake after ICV injection, with a slightly higher potency for JMV 170. JMV 180 induced no change in monoamine metabolism whatever the route of administration. JMV 170 IP decreased cortical levels of dopamine and its metabolites. This effect was stronger after ICV injection and was accompanied by changes in serotonergic metabolism in the hypothalamus and cortex. Contrary to CCK8 S, which is more active on feeding after peripheral injection, the feeding effects of the analogues obtained by modification of the C-terminal phenylalanine residue appear to involve a central site of action. Furthermore, phenylethylamide substitution (JMV 170) gives rise to greater potency on monoaminergic variations than replacement with a phenylethylester (JMV 180) and the effect is enhanced following central administration.     

Spliceosome-targeted therapies trigger an antiviral immune response in triple-negative breast cancer

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Getting a grip on the intertidal: flow microhabitat and substratum type determine the dislodgement of the crab Pachygrapsus crassipes (Randall) on rocky shores and in estuaries

Hydrodynamic forces can affect survival as well as limit the movement of motile benthic animals. An animal's danger of dislodgement depends on the hydrodynamic forces it experiences in its microhabitat relative to the force required to dislodge it (tenacity) from the substratum. We measured water flow and substratum characteristics in two different habitats of the shore crab Pachygrapsus crassipes: a wave-swept rocky shore and an intertidal mudflat. The maximum water velocities and accelerations in the microhabitats of the crabs at the wave-swept site were three times and two times greater, respectively, than at the mudflat site. In the laboratory, we measured the tenacity of crabs of various sizes on different substrata, and also measured their drag, lift and added-mass coefficients. Using these data, we calculated the flow conditions under which crabs would be overturned or sheared off the substratum in their two habitats. The net horizontal force (drag plus acceleration reaction) required to dislodge a crab on a rugose rock substratum was an order of magnitude greater than on smooth rock and two orders of magnitude greater than on mud. Our calculations indicate that, under non-storm conditions, crabs will not be dislodged from the substratum in either the mudflat or the wave-swept habitat when grasping the substratum with maximum tenacity. Moving crabs have lower tenacity and our calculations predict that hydrodynamic forces will restrict the mobility of large crabs more than that of small ones on smooth, but not on rugose rock.     

Blood pressure lability in the sympathectomized rat

Intra-aortic blood pressure (BP) was measured in conscious rats after early chronic destruction of the peripheral sympathetic nervous system (SNS) with guanethidine. In sympathectomized rats, the mean level of BP was not different from that of control rats but its variability was markedly increased. These results indicate that functional integrity of the SNS is of primary importance for the short-term control of BP but is not essential for its long-term maintenance.