The effect of harmaline on intestinal sodium transport and on sodium-dependentd-glucose transport in brush-border membrane vesicles from rabbit jejunum

Harmaline inhibition of sodium uptake and of sodium-dependentd-glucose transport was investigated using brush-border membrane vesicles from frozen rabbit jejunum. Under sodium-gradient conditions, initiald-glucose uptake (20 s) was inhibited by harmaline at concentrations above 0.5 mM, but at lower harmaline concentrationsd-glucose uptake was stimulated by 10–15%. When a similar potassium gradient was used, harmaline had no effect. At concentrations upt to 2 mM, harmaline did not alter the equilibrium uptake ofd-glucose ord-mannitol. After pre-equlibration with sodium (25 mM),d-glucose uptake was inhibited at harmaline concentrations ranging from 0.1 to 2 mM. Sodium (10 mM) uptake was also inhibited by harmaline. Increasing the sodium concentration reduced the inhibitory effect of harmaline on tracer sodium uptake as well as on sodium-dependentd-glucose uptake. Similar to phlorizin, harmaline (1 mM) was able to prevent glucose-induced sodium influx across the brush-border membrane.Sodium uptake into brush-border membrane vesicles seems to be inhibited at lower harmaline concentrations than sodium-dependentd-glucose uptake. At high (2 mM) inhibitor concentrations, however, sodium-dependent glucose uptake is more strongly inhibited than sodium uptake. These results suggest that harmaline inhibits both sodium and sodium-dependent transport across intestinal brush-border membranes by interacting with specific sodium-binding sites.     

ERP correlates of transposed-letter similarity effects: Are consonants processed differently from vowels?

Recent research has shown that pseudowords created by transposing letters are very effective for activating the lexical representation of their base words (e.g., relovution activates REVOLUTION). Furthermore, pseudoword transpositions of consonants are more similar to their corresponding base words than the transposition of vowels. We report one experiment using pseudowords created by the transposition of two consonants, two vowels, and their corresponding control conditions (i.e., the replacement of two consonants or two vowels) in a lexical decision task while Event Related Potentials (ERPs) were recorded. The results showed a modulation of the amplitude of the N400 component as a function of the type of pseudoword (transposed-letter versus replacement letter pseudowords), and this modulation was different for transposed consonants and vowels. These results suggest that consonants and vowels play a different role during word processing.     

Lymphoepithelioma-like carcinoma of the bladder: three cases with clinicopathological and p53 protein expression study

Lymphoepithelioma-like carcinoma of the bladder is an uncommon neoplasm, of which 49 cases have been described in the English literature, none of which has been studied for p53 protein expression. We studied three muscle-infiltrating cases of this tumor using immunohistochemical, in situ hybridization and polymerase chain reaction (PCR) methods. The three cases were positive for epithelial markers and negative for lymphoid antigens in the tumoral syncytial areas. The intensive infiltrate of small cells was negative for epithelial and positive for lymphoid markers. This population was mainly made up of cytotoxic T-lymphocytes, positive for TIA-1. p53 protein was intensely positive in more than 90% of the epithelial component nuclei, being negative in the lymphoid cells. PCR study did not show mutations on p53. Both lymphocytes and epithelium were negative for Epstein–Barr virus markers, such as the latent membrane protein and EBER (Epstein–Barr-encoded RNA). The prognosis was very good after radiotherapy and chemotherapy treatment, preserving the bladder despite the muscle infiltration. The presence of an intense cytotoxic T-lymphocyte population may be related to this good prognosis. Both aspects, p53 protein status and T-lymphoid population, had never been studied before in bladder lymphoepithelioma-like carcinoma.     

Retinoids and spermatogenesis: lessons from mutant mice lacking the plasma retinol binding protein.

Using Rbp4-null mice as models, we have established for the first time the kinetics of the spermatogenetic alterations during vitamin A deficiency (VAD). Our data demonstrate that the VAD-induced testicular degeneration arises through the normal maturation of germ cells in a context of spermatogonia differentiation arrest. They indicate that retinoic acid (RA) appears dispensable for the transition of premeiotic to meiotic spermatocytes, meiosis, and spermiogenesis. They confirm that RA plays critical roles in controlling spermatogonia differentiation, spermatid adhesion to Sertoli cells, and spermiation, and suggest that the VAD-induced arrest of spermatogonia differentiation results from simultaneous blocks in RA-dependent events mediated by RA receptor gamma (RARgamma) in spermatogonia and by RARalpha in Sertoli cells. They also provide evidence that expression of major RA-metabolizing enzymes is increased in mouse Sertoli cells upon VAD and that vitamin A-deficient A spermatogonia differ from their RA-sufficient counterparts by the expression of the Stra8 gene.     

Molecular epidemiology of hepatitis B virus in Afro-Venezuelan populations

Summary.  Hepatitis B virus (HBV) infection among Venezuelan populations of African origin was analyzed. These populations exhibited lower HBV prevalence than the one found in the African continent. Sequence analysis of 6 isolates showed that 3 belonged to genotype F, while the 3 others were HBV genotype A. HBV genotype A was more common in the Afro-Venezuelan groups than in the general Venezuelan population. This might reflect the introduction of genotype A during the slavery period. The absence of the African genotype E among these isolates supports the hypothesis of a recent origin for this HBV genotype. HBV genotype F has already been introduced to these relatively isolated communities. Received February 18, 2002; accepted March 8, 2002 Published online July 22, 2002     

Effect of different types of high carbohydrate diets on glycogen metabolism in liver and skeletal muscle of endurance-trained rats

Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.     

Potentiation of human alpha4beta2 neuronal nicotinic receptors by a Flustra foliacea metabolite

The effects of various Flustra foliacea metabolites on different types of human neuronal nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes were investigated. Whereas most of the compounds tested had a small blocking effect, one of them, deformylflustrabromine, selectively increased the current obtained in alpha4beta2 receptors when co-applied with acetylcholine (ACh). The current increase was reversible and concentration-dependent. This potentiating effect was still present at saturating concentrations of acetylcholine, and no changes in single-channel conductance or reversal potential were observed, thus suggesting a modification in the gating of alpha4beta2 receptors. Dwell time analysis of single channel records indicates that the mechanism of action of deformylflustrabromine could be both an increase of the opening rate constant and a decrease of the closing rate constant on alpha4beta2 receptors. Thus, deformylflustrabromine may constitute an excellent starting point for the future development of related agents able to potentiate human neuronal nicotinic receptor function.     

Experimental study of the development of the truncus arteriosus of the chick embryo heart. I. Time of appearance

The time of appearance of the truncus arteriosus was studied in the chick embryo using an in ovo labeling technique. Three hundred embryos at stages 13–18 of Hamburger and Hamilton were selectively labeled at the distal end of the heart tube, using gelatine-india ink label; 122 of these embryos were reincubated and 111 of them reached stages 25–28. In these stages the final location of the label was determined. Only 95 of these embryos showed both a normal heart and a label located in it. The remaining embryos were discarded due to abnormal cardiac morphology or because the label was not found. Embryos labeled at stages 13–14 had label in the conus in 42.8% of the cases and in the boundary between the conus and the truncus arteriosus in 57.1% of the cases. Label placed at stages 15–16 was located in the conus in 6.1% of the cases, in the boundary between the conus and the truncus arteriosus in 44.8% of the cases, and in the truncus arteriosus in 48.9% of the cases. Finally, label placed at stages 17–18 was located in the boundary between the conus and the truncus arteriosus in 18.7% of the cases and in the truncus arteriosus in 81.2% of the cases. Our results permit us to conclude that the truncus arteriosus appears in the chick embryo as early as stages 15–16 of Hamburger and Hamilton (50–56 hours of incubation). © 1993 Wiley-Liss, Inc.     

Virilizing mature ovarian cystic teratomas

 Three further cases of mature benign cystic teratomas of the ovary associated with virilization are added to the three previously reported in the literature. They were found in postmenopausal, obese, diabetic women aged 52, 61, and 67 years. The patients presented with hirsutism and voice changes and clitoromegaly was present in one. Testosterone and androstenedione levels were elevated but promptly regressed after removal of the tumours. Histologically, sheets of stromal luteinized cells were found peripherally at the interface between the neoplasm and ovarian tissue. Luteinization of ovarian stroma induced by an unknown factor related to diabetes mellitus is the origin of the virilization. Received: 8 January 1997 / Accepted: 28 February 1997     

The ancillary proteins of HATs: SLC3 family of amino acid transporters

The heteromeric amino acid transporters (HATs) are composed of a light and a heavy subunit linked by a disulfide bridge. The heavy subunits are the SLC3 members (rBAT and 4F2hc), whereas the light subunits are members of the SLC7 family of amino acid transporters. SLC3 proteins are type II membrane glycoproteins (i.e., one single transmembrane domain and the C-terminus located outside the cell) with a bulky extracellular domain that shows homology with alpha-glucosidases. rBAT heterodimerizes with b(0,+)AT (SLC7A9) constituting the amino acid transport b(0,+), the main system responsible for the apical reabsorption of cystine in kidney. The defect in this system causes cystinuria, the most common primary inherited aminoaciduria. 4F2hc subserves various amino acid transport systems by dimerization with different SLC7 proteins. The main role of SLC3 proteins is to help routing of the holotransporter to the plasma membrane. A working model for the biogenesis of HATs based on recent data on the rBAT/b(0,+)AT heterodimeric complex is presented. 4F2hc is a multifunctional protein, and in addition to its role in amino acid transport, it may be involved in other cellular functions. Studies on two SLC7 members (Asc-2 and AGT1) demonstrate heterodimerization with unknown heavy subunits.