Galectin 9 is the sugar-regulated urate transporter/channel UAT

UAT, also designated galectin 9, is a multifunctional protein that can function as a urate channel/transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the transporter. The properties of recombinant UAT are compared with those of urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed. Published in 2004.     

Mesocyclops longisetus effects on survivorship of Aedes aegypti immature stages in car tyres

Abstract .The effect of the introduction of the entomophagous copepod Mesocyclops longisetus (Acuacultura F.C.B. strain) on the survival of Aedes aegypti immature stages in car tyres was evaluated under semi-natural conditions in the municipality of Merida, Yucatan, Mexico. Life tables were constructed for the immature stages of the mosquito in the presence and absence of M. longisetus , and the survival data were compared using log–linear models. The data set was adjusted using the GLIM statistical package and the quality of adjustment was evaluated with a chi-squared test . Survivorship curves were constructed for each treatment.
In the absence of M. longisetus , the survivorship of Ae. aegypti immature stages averaged 9%. The highest mortality rate was observed during the fourth larval instar (54%) and the resulting survival pattern corresponded to a type II survivorship curve. The mortality rate of Ae. aegypti first-instar larvae (fifty per tyre) increased more than 200-fold in the presence of M. longisetus (twenty per tyre) and the highest mortality was during the first two larval instars, where it reached 98.9%, with a resulting survivorship of 0.2%. Overall mortality was sixfold greater in the presence of the copepod than in its absence. The survival pattern of immature stages of Ae. aegypti in the presence of the copepod corresponded to a type III survivorship curve. As M. longisetus was so effective against Ae. aegypti immature stages in tyres under semi-natural conditions, its long-term effectiveness should be evaluated under socially and ecologically realistic field conditions in Mexico.     

Distinct neurotrophic factors from skeletal muscle and the central nervous system interact synergistically to support the survival of cultured embryonic spinal motor neurons

Motor neurons isolated from 6-day-old embryonic chick spinal cords require muscle extract for survival in culture; however, it was found, that some motor neurons, identified by retrograde labeling with rhodamine, will survive in mixed spinal cell cultures in the absence of the extract. The motor neuron survival-promoting activity produced by spinal cells is soluble and differs from the factor present in muscle extract, the two activities acting in a synergistic manner: the spinal cell activity potentiated that of muscle to decrease its ED50 by an order of magnitude, the motor neuronal survival (30%) seen in the presence of both factors being more than the sum of their individual activities. This synergism was shown to be restricted to the action of the spinal cell factor on motor neurons, no effect of the factor being noted with sympathetic neurons. As a series of defined growth and survival factors present in the central nervous system (nerve growth factor, brain-derived neurotrophic factor, acidic and basic fibroblast growth factors) had no effect on motor neuron survival, we conclude that the molecule responsible for the motor neuron survival-promoting activity of the spinal cells is a previously undefined factor.     

The cellular interactions of laminin fragments. Cell adhesion correlates with two fragment-specific high affinity binding sites

The molecular interactions of laminin with several tumor cell lines and skin fibroblasts were investigated by radioligand binding studies and cell attachment assays using laminin, the laminin-nidogen complex, and laminin fragments as substrates and also domain-specific antibodies as inhibitors of cell attachment. The majority of cells showed a dual binding pattern for fragments 1 and 8 which originate from short-arm or long-arm structures of laminin, respectively. Both of these fragments in solution bind to suspended cells with high affinity (KD = 1-10 nM), with the receptor numbers for each fragment depending on the cell type. Competition studies and independent variation of receptor numbers demonstrated that the cell-binding structures on each fragment are different, implicating the existence of two distinct cellular receptors for laminin. The ability of these fragments to act as substrates for cell adhesion correlated with the presence of high affinity binding sites on the cells. However, only antibodies to fragment 8 were able to block cell adhesion to laminin, despite the presence of binding sites for fragment 1. A few cells had very low numbers of high affinity receptors for either fragment 1 or 8. The latter cell type was used to demonstrate that complex formation between laminin and nidogen, which binds to fragment 1 structures, reduces the potential of laminin for cell binding.     

Intrinsic and extrinsic innervation of the amphibians esophagic myenteric plexuses

The innervation of Rana ridibunda esophagus myenteric plexuses has been studied by the following methods: demonstration of cholinesterase activity; FIF method for catecholamines; immunohistochemistry for VIP, SP and SOM, and conventional electron microscopy. The cholinergic innervation is important in the esophagus wall where, in addition to the well known extrinsic component, there is a rich intrinsic plexus with cells and fibres widely distributed. The esophagus, together with the intestine, are the Rana gut portions where the adrenergic component is more broadly expressed. The adrenergic innervation seems to be almost entirely of extrinsic origin. We have shown that, for the tested peptides, there is an intrinsic innervation represented by VIP, SP and SOM like plexuses. We do not discard nonetheless an extrinsic component. The ultrastructure reveals the morphological characteristics of the enteric neurons as well as the fine inter-relationships between the nervous elements and the functional components of the esophagic wall.     

The polymorphism ApoB/4311 in patients with myocardial infarction and controls: the ECTIM study

Summary The polymorphism affecting codon 4311 of the apolipoprotein B gene (ApoB/4311) was investigated in a large case-control study in two French and one Northern Irish geographically defined populations. Cases were recruited 3 to 9 months after a myocardial infarction (MI) and controls were randomly selected from the population. The polymorphism was assessed using allele-specific oligonucleotides (ASO). The genotype frequencies of the ApoB/4311 polymorphism did not differ in Northern Ireland and France and were in Hardy-Weinberg equilibrium in all groups; strong associations with three other polymorphisms of the ApoB gene (XbaI, EcoRI, VNTR(34 repeats)) were observed and it was possible to identify highly sensitive and specific markers of the ApoB/4311 rare variant. Homozygotes for the ApoB 4311 rare variant were slightly less frequent in cases than in controls: 22 (4.4%) and 35 (6.7%) respectively (population adjusted ²=3.3 P<0.07), especially in Belfast: 6 (3.1%) and 12 (7.6%), respectively (P<0.06). Several lipid and lipoprotein parameters were measured. Consistently among control groups, rare homozygotes had lower mean levels of ApoB (P<0.02), triglycerides (P<0.02), and lipoprotein particles containing ApoE and ApoB (LpE:B; P<0.001) and a higher mean level of lipoprotein particles containing ApoAI and not ApoAII (LpAI; P<0.02) than heterozygotes and frequent homozygotes combined. The strong association between the ApoB/4311 polymorphism and LpE:B was also observed in patients with MI. When present in the homozygous form, the ApoB/ 4311 AsnSer variant is associated with a lipoprotein profile that is apparently favourable.     

Laminin increases both levels and activity of tyrosine hydroxylase in calf adrenal chromaffin cells

We have investigated the effects of substrate-bound laminin on levels of enzymes of the catecholamine biosynthetic pathway in primary cultures of calf adrenal chromaffin cells. Laminin increases the levels of the enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyl-transferase. This effect is selective, in that levels of other enzymes (lactate dehydrogenase, aromatic amino acid decarboxylase, and acetylcholinesterase) are not increased. The effect of laminin can be blocked by antibodies directed against a fragment of the heparin-binding domain of the molecule, whereas antibodies directed against other fragments do not block the increase in tyrosine hydroxylase. Thus the laminin domain involved in enzyme regulation in chromaffin cells is apparently the same as that previously implicated in laminin's interactions with neurons to potentiate survival and stimulate neurite outgrowth (Edgar, D., R. Timpl, and H. Thoenen, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1463-1468). The increase in chromaffin cell tyrosine hydroxylase levels is preceded by an activation of the enzyme in which the Vmax (but not the Km) is altered. The effects of laminin appear to be developmentally regulated, since neither activation nor increased levels of tyrosine hydroxylase occur in adult adrenal chromaffin cells exposed to laminin.     

Nerve growth factor changes the relative levels of neuropeptides in developing sensory and sympathetic ganglia of the chick embryo

The effects of chronic nerve growth factor administration on the development of neuropeptides in the embryonic chick peripheral nervous system were quantitated by radioimmunoassays. Starting at embryonic Day 3.5, daily doses of 20 micrograms of nerve growth factor (NGF) increased the substance P content of lumbosacral spinal sensory ganglia at all ages studied (Days 10-14), while having no effect on substance P levels of thoracic sensory ganglia. In contrast, the contents of somatostatin were increased in both thoracic and lumbosacral ganglia, but only at comparatively late time points (Day 14). Nerve growth factor administration was also found to decrease the somatostatin contents of lumbosacral paravertebral sympathetic ganglia at early time points (Day 8) while increasing levels at later stages (Day 14), thus acting to accelerate the normally occurring developmental changes in level of this peptide. These changes were shown to be specific for somatostatin by demonstrating that NGF increased tyrosine hydroxylase levels in sympathetic neurons at Day 8, and had no effect on sympathetic vasoactive intestinal polypeptide levels at Day 14. It has been concluded that exogenous NGF does not simply act to increase or prolong the expression of neuron-specific phenotypes in the chick, but rather its action is time and location dependent to accelerate development.