Button osteoma: its etiology and pathophysiology

The present study investigates a circumscribed bony overgrowth on the cranial vault, known as button osteoma (BtO) and referred to here as button lesion (BtL). We discuss its anthropological implications. Data on its histology, location, and population distribution (by age, race, and gender) are provided. Microscopically, BtL is composed of well-organized dense lamellated bone which is poorly vascularized and with very few osteocytes. It forms a dome-shaped roof over an underlying diploeized area which includes the ectocranial table. The frequency of BtL is similar in modern (37.6%) and archaeological (41.1%) populations, in blacks, whites, males, and females, and correlates with age. It is rare in nonhuman primates. Fifty-five percent of the human skulls studied by us had BtL only on the parietal, 23.6% on the frontal, and 3.6% on the occipital bones. Fifteen percent had BtL on both the frontal and parietal bones. No lateral preference was found. Most skulls with BtL (64.1%) had only one lesion, 20.4% had two BtL, and 15.4% demonstrated multiple BtL. The average number of button osteomas on an affected skull was 1.97. The frequency of large osteomas (0.5-1.0 cm) was similar in young and old age groups. The demographic characteristics of BtL, mainly its high frequency among ancient and modern populations, its independence of sex and race, its scarcity in other primates, and the fact that its macro- and microstruture are indicative of an hamartoma (and not an osteoma or exostosis) suggest an evolutionary background to the phenomenon.     

Genotoxic evaluation of the organophosphorous pesticide temephos

The chemical compound temephos (0,0,0',0'-tetrametyl-0,0'-thiodi-p-phenylene phosphorothioate) is an organophosphorous pesticide that has been used in Brazil since 1967 in control campaigns against the mosquito Aedes aegypti, the vector of dengue and yellow fever. We used single cell gel electrophoresis (SCGE), SOS/umu and Ames/Salmonella assays to test the toxicity and mutagenicity of temephos. Temephos was genotoxic in the SCGE assay, inducing severe DNA lesions (type IV lesions) at doses above 1.34 micro M. It was mutagenic, but not toxic, in the SOS/umu assay to Escherichia coli strain PQ37, but not to PQ35, at concentrations above 1.33 micro M, particularly when the S9 mixture was not used in the assay. Temephos was not mutagenic in the Ames assay with S. typhimurium strains TA97, TA98, TA100 and TA102, both with and without metabolic activation. However, temephos at concentrations above 3.33 micro M was mutagenic to TA98NR, YG7104 and YG7108, both with and without metabolic activation. In conclusion, temephos was genotoxic and mutagenic in all the three tests used, and in two of them at concentrations similar to those routinely used to combat Aedes aegypti.     

Interactions of human secretin with sterically stabilized phospholipid micelles amplify peptide-induced vasodilation in vivo

Secretin, a 27-amino acid neuropeptide, is a member of the glucagon/secretin/vasoactive intestinal polypeptide (VIP) superfamily of amphipathic peptides that elicits transient vasodilation in vivo. The purpose of this study was to determine whether association of human secretin with sterically stabilized phospholipid micelles (SSM) amplifies the vasorelaxant effects of the peptide in the peripheral microcirculation in vivo. We found that secretin in saline evoked significant concentration-dependent vasodilation in the intact hamster cheek pouch microcirculation (P < 0.05). This response was potentiated and prolonged significantly when secretin was associated with SSM (P < 0.05). Vasodilation evoked by secretin in saline and secretin in SSM was abrogated by VIP(10-28), a VIP receptor antagonist, but not by PACAP(6-38), a PACAP receptor antagonist, or Hoe140, a selective bradykinin B(2) receptor antagonist. Collectively, these data indicate that self-association of human secretin with SSM significantly amplifies peptide vasoreactivity in the intact peripheral microcirculation through activation of VIP receptors. We suggest that the vasoactive effects of human secretin in vivo are, in part, phospholipid-dependent.     

Structure-activity relationships of heparin-mimicking compounds in induction of bFGF release from extracellular matrix and inhibition of smooth muscle cell proliferation and heparanase activity

A series of nine synthetic polyaromatic compounds were synthesized by polymerization of aromatic ring monomers with formaldehyde, which yield substantially ordered backbones with different functional anionic groups (hydroxyl and carboxyl) on the phenol ring. These compounds were tested for their heparin-mimicking activity: (1) inhibition of heparanase activity; (2) inhibition of SMC proliferation; and (3) release of bFGF from the ECM. We demonstrate that compounds that have two hydroxyl groups para and ortho to the carboxylic group and a carboxylic group at a distance of two carbons from the phenol ring inhibit heparanase activity and SMC proliferation, as well as induced an almost complete release of bFGF from ECM. Addition of a methyl group next to the carboxylic group led to a preferential inhibition of heparanase activity. Similar results were obtained with a compound that contains one hydroxyl group para to the carboxylic group and an ether group near the carboxylic group on the phenol ring. Preferential inhibition of SMC proliferation was best achieved when the position of the hydroxyl group is para and ortho to the carboxylic group and the carboxylic group is at a distance of one carbon from the phenol ring. On the other hand, for maximal release of bFGF from ECM, the position of the carboxylic group should be three carbons away from the phenol ring. These new heparin-mimicking compounds may have a potential use in inhibition of tumor metastasis, arteriosclerosis, and inflammation.     

Lack of arginine decarboxylase in Trypanosoma cruzi epimastigotes

The presence of arginine decarboxylase (ADC) enzymatic activity in Trypanosoma cruzi epimastigotes is still a matter of controversy due to conflicting results published during the last few years. We have investigated whether arginine might indeed be a precursor of putrescine via agmatine in these parasites. We have shown that wild-type T. cruzi epimastigotes cultivated in a medium almost free of polyamines stopped their growth after several repeated passages of cultures in the same medium, and that neither arginine nor omithine were able to support or reinitiate parasite multiplication. In contrast, normal growth was quickly resumed after adding exogenous putrescine or spermidine. The in vivo labelling of parasites with radioactive arginine showed no conversion of this amino acid into agmatine, and attempts to detect ADC activity measured by the release of CO2 under different conditions in T. cruzi extracts gave negligible values for all strains assayed. The described data clearly indicate that wild-type T. cruzi epimastigotes lack ADC enzymatic activity.     

Human galanin expresses amphipathic properties that modulate its vasoreactivity in vivo

The purpose of this study was to determine whether human galanin, a pleiotropic 30-amino acid neuropeptide, expresses amphipathic properties in vitro and, if so, whether these properties modulate its vasoactive effects in the intact peripheral microcirculation. We found that human galanin aggregates in an aqueous solution and forms micelles with a critical micellar concentration (CMC) of 0.4 microM. In addition, the peptide interacted with model membrane as indicated by long and significant increase of the surface pressure of the biomimetic monolayer membrane in vitro. Interactions of human galanin with sterically stabilized phospholipid micelles (SMM) were not associated with a significant change in peptide conformation. Using intravital microscopy, we found that suffusion of human galanin alone elicited significant concentration-dependent vasoconstriction in the intact hamster cheek pouch. This response was amplified when human galanin in SSM was suffused onto the cheek pouch. The effects of human galanin alone and in SSM were mediated by galanin receptors because galantide, a galanin receptor antagonist, abrogated galanin-induced vasoconstriction. Collectively, these data show that human galanin expresses amphipathic properties in the presence of phospholipids which in turn amplifies its vasoactive effects in the intact peripheral microcirculation.     

Conformation-dependent effects of VIP on nociception in rats

The purpose of this study was to determine whether intrathecal injection of aqueous (random coil) vasoactive intestinal peptide (VIP) and VIP self-associated with sterically stabilized phospholipid micelles (alpha-helix VIP) at the lower lumbar vertebral level modulates foot withdrawal latency to low and high rate noxious radiant skin heating in anesthetized rats. We found that intrathecal random coil VIP evoked a significant bimodal, concentration-dependent response, early potent antinociception followed by hyperalgesia, during exposure to low and high rates of skin heating (P<0.05). Intrathecal alpha-helix VIP elicited a qualitatively similar response to that of random coil VIP except that the rate of decay of antinociception was faster and slower at low and high rates of skin heating, respectively. In addition, a low concentration of alpha-helix VIP evoked a potent late antinociception not observed with random coil VIP. Taken together, these data indicate that VIP modulates somatosensory processing in the lumbosacral spinal cord of rats in a complex fashion, and that this response is dependent, in part, on the conformation of VIP in the vicinity of target cells in the peripheral nervous system.     

Transmembrane domains in the functions of Fc receptors

In the present study, we use a novel method, PHDhtm, to predict the exact locations and extents of the transmembrane (TM) domains of multisubunit immunoglobulin Fc-receptors. Whereas most previous studies have used single residue hydrophobicity plots for characterizing of these domains, PHDhtm utilizes a system of neural networks and the evolutionary information contained in multiple alignments of related sequences to predict the above. Present PHDhtm application predicts TM domains of immunoglobulin Fc-receptors that in many cases differ significantly from those derived by using earlier methods. Comparisons of helical wheel projections of the presently derived TM domains from PHDhtm with those produced earlier reveal different hydrophobic moments as well as hydrophobic and hydrophilic surfaces. These differences probably alter the character of subunit association within the receptor complexes. This new algorithm can also be used for other membrane protein complexes and may advance both understanding the principles underlying such complexes formation and design of peptides that can interfere with such TM domain association so as to modulate specific cellular responses.     

EspH,a new cytoskeleton-modulating effector of enterohaemorrhagic and enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC) are closely related pathogens. During infection, EPEC and EHEC use a type III secretion system (TTSS) to translocate effector proteins into the infected cells and thereby modify specific host functions. These include transient filopodium formation which is Cdc42-dependent. Filopodia formation is followed by assembly of actin pedestals, the process enhanced by inhibition of Cdc42. We discovered that orf 18 of the enterocyte effacement locus encodes a new effector, which we termed EspH. We show that EspH is translocated efficiently into the infected cells by the TTSS and localizes beneath the EPEC microcolonies. Inactivation of espH resulted in enhanced formation of filopodia and attenuated the pedestals formation. Furthermore, overexpression of EspH resulted in strong repression of filopodium formation and heightened pedestal formation. We also demonstrate that overexpression of EspH by EHEC induces marked elongation of the typically flat pedestals. Similar pedestal elongation was seen upon infection of COS cells overexpressing EspH. EspH transiently expressed by the COS cells was localized to the membrane and disrupted the actin cytoskeletal structure. Our findings indicate that EspH is a modulator of the host actin cytoskeleton structure.