Search PubMed⌕ Search

Biomedical subjects

A Guzman

Publications and source records attributed to A Guzman.

At least 19 recordsLinked to original sources
PubMed2006

Detection and differentiation of Xylella fastidiosa strains acquired and retained by glassy-winged sharpshooters (Hemiptera: Cicadellidae) using a mixture of strain-specific primer sets.

Xylella fastidiosa Wells is a bacterial pathogen that causes a variety of plant diseases, including Pierce's disease (PD) of grapevine, almond leaf scorch, alfalfa dwarf, citrus variegated chlorosis, and oleander leaf scorch (OLS). Numerous strains of this pathogen have been genetically characterized, and several different strains occur in the United States. The dominant vector in southern California is the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae). The high mobility of this insect, and its use of large numbers of host plant species, provides this vector with ample exposure to multiple strains of X. fastidiosa during its lifetime. To learn more about the ability of this vector to acquire, retain, and transmit multiple strains of the pathogen, we developed a polymerase chain reaction (PCR)-based method to detect and differentiate strains of X. fastidiosa present in individual glassy-winged sharpshooter adults. Insects were sequentially exposed to plants infected with a PD strain in grapevine and an OLS strain in oleander. After sequential exposure, a few insects tested positive for both strains (7%); however, in most cases individuals tested positive for only one strain (29% PD, 41% OLS). In transmission studies, individual adults transmitted either the PD or OLS strain of the pathogen at a rate (39%) similar to that previously reported after exposure to a single strain, but no single individual transmitted both strains of the pathogen. PD and OLS strains of X. fastidiosa remained detectable in glassy-winged sharpshooter, even when insects were fed on a plant species that was not a host of the strain for 1 wk.

Animals↗
PubMed2003

Synthesis, pharmacology and pharmacokinetics of 3-(4-aryl-piperazin-1-ylalkyl)-uracils as uroselective alpha1A-antagonists.

Predominance in the urethra and prostate of the alpha(1A)-adrenoceptor subtype, which is believed to be the receptor mediating noradrenaline induced smooth muscle contraction in these tissues, led to the preparation of alpha(1A)-selective antagonists to be tested as uroselective compounds for the treatment of benign prostatic hyperplasia. Thus, a number of selective alpha(1A)-adrenoceptor antagonists were synthesized and assayed in vitro for potency and selectivity. Dog pharmacokinetic parameters of 12 (RO700004) and its metabolite 40 (RO1104253) were established. The relative selectivity of intravenously administered 12, 40 and standard prazosin to inhibit hypogastric nerve stimulation-induced increases in intraurethral prostatic pressure versus phenylephrine-induced increases in diastolic blood pressure in anesthetized dogs was 76, 71 and 0.6, respectively.

Administration, Oral↗
PubMed1998

2D 1H and 13C NMR evidence for stereoselective formation of a new bond C-N, C-S or C-C in the reaction of ivalin acetate with substituted pyrimidines.

Several pyrimidine derivatives of ivalin acetate were synthesized as potential anti HIV agents. High stereoselective Michael addition to ivaline acetate was observed and a new C-C, C-N or C-S bond was formed. 2D NMR 1H and 13C as well as X-ray crystallographic studies were performed on the compounds herein described to establish the structure and stereochemistry.

Alkylation↗
PubMed1997

Detection of somatic mutations in the mitochondrial DNA control region of colorectal and gastric tumors by heteroduplex and single-strand conformation analysis.

Each entire hypervariable region of the mitochondrial DNA control region was screened for mutations from paired normal and tumor DNA corresponding to a group of 21 patients (13 colorectal and 8 gastric adenocarcinomas) using both heteroduplex analysis and single-strand conformation analysis. These two mutation scanning strategies allowed the identification of sequence alterations in 3/13 (23%) colorectal tumors and in 3/8 (37%) gastric tumors. Heteroduplex analysis showed the heteroplasmic state of the majority of these tumor mutations. Sequence analysis revealed two A:T/G:C transitions (nucleotide positions: 16241 and 16166) in hypervariable region 1 (HV1) and two C:G/T:A transitions (nucleotide positions: 76 and 312), one A:T/G:C transition (nucleotide position: 93), a 1-basepair C:G deletion (nucleotide position: 309), and a 2-base-pair CC:GG insertion (nucleotide position: 309) in the HV 2 region. A considerable proportion of these mutations was found in homopolymeric regions which are highly polymorphic among humans. Different mechanisms (clonal expansion, increased oxidative damage, and nuclear mutator mutations) were suggested to explain the increased mitochondrial DNA mutation rate observed in cancer.

Adenocarcinoma↗
PubMed1997

Sulfatides inhibit binding of Helicobacter pylori to the gastric cancer Kato III cell line.

Helicobacter pylori adhere to Kato III and Hela S3 cells in monolayer cultures. To explore whether cell surface glycoconjugates on these two cell lines mediate binding of H. pylori, various carbohydrates, glycoproteins, and glycolipids were tested to inhibit H.pylori cell adhesion. The adhesion was measured (i) with a urease-based assay and (ii) by cells stained with fluorescein. Sodium periodate and sialidase treatment (but not alpha- or beta-galactosidase, heparitinase,lysozyme, or trypsin) inhibited H. pylori binding to both cell lines. Sulfatides and sulfated glycoconjugates (50 microg/ml) but not heparin or a number of simple carbohydrates inhibited binding (1 mg/ml). The two H.pylori strains studied (CCUG 17874 and strain 25) showed high binding of soluble 125I-labeled heparin and other sulfated carbohydrate compounds.

Bacterial Adhesion↗
PubMed1997

Corrosion behavior of 2205 duplex stainless steel.

The corrosion of 2205 duplex stainless steel was compared with that of AISI type 316L stainless steel. The 2205 stainless steel is a potential orthodontic bracket material with low nickel content (4 to 6 wt%), whereas the 316L stainless steel (nickel content: 10 to 14 wt%) is a currently used bracket material. Both stainless steels were subjected to electrochemical and immersion (crevice) corrosion tests in 37 degrees C, 0.9 wt% sodium chloride solution. Electrochemical testing indicates that 2205 has a longer passivation range than 316L. The corrosion rate of 2205 was 0.416 MPY (milli-inch per year), whereas 316L exhibited 0.647 MPY. When 2205 was coupled to 316L with equal surface area ratio, the corrosion rate of 2205 reduced to 0.260 MPY, indicating that 316L stainless steel behaved like a sacrificial anode. When 316L is coupled with NiTi, TMA, or stainless steel arch wire and was subjected to the immersion corrosion test, it was found that 316L suffered from crevice corrosion. On the other hand, 2205 stainless steel did not show any localized crevice corrosion, although the surface of 2205 was covered with corrosion products, formed when coupled to NiTi and stainless steel wires. This study indicates that considering corrosion resistance, 2205 duplex stainless steel is an improved alternative to 316L for orthodontic bracket fabrication when used in conjunction with titanium, its alloys, or stainless steel arch wires.

Chromium↗
PubMed1994

The role of guided tissue regeneration and guided bone regeneration.

The goal of periodontal therapy includes not only the halting of the progressive loss of connective tissue attachment but also the restitution of those parts of the supporting apparatus which have been destroyed. The cells which repopulate this area may originate from any number of the different tissue components of the periodontium: the dentogingival epithelium, the gingival connective tissue, the alveolar bone, and the periodontal ligament (PDL). The size and shape of the wound and the potential of the different types of tissues cells to migrate, determines the type of healing. Previous studies have revealed that root resorption was found to occur when granulation tissue derived from the gingival connective tissue or alveolar bone was proliferating into contact with the root surface, while re-epithelialization of the surface prevented both connective tissue attachment and root resorption. The only cells which appear to have the capacity to form a new attachment were cells originating from the PDL. Based on this knowledge of the biological behaviour of the different periodontal tissues during wound healing, the principle of Guided Tissue Regeneration (GTR) was introduced and tested. A membrane section was placed over the debrided root surface in such a way that all periodontal tissues except the PDL cells were prevented from reaching contact with the root. Healing resulted in extensive amounts of new connective tissue attachment, that is, the formation of new cementum with inserting collagen fibres. The objective was, and is, assessment of how predictably new attachment may form when treatment included GTR.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗
PubMed1989

Excitatory effect of serotonin on pacemaker neurons in spinal cord cell culture.

Intracellular recordings were made from fetal mouse spinal cord neurons in primary culture. One type of neuron, with large somata (40-50 microns diameter) and thick neurites exhibited endogenous bursting or beating pacemaker electrical activity. Noradrenaline depolarized this type of neuron by decreasing an M-like conductance. Micropressure application of serotonin (10(-5) M in the delivery pipette) onto the surface of pacemaker neurons evoked a depolarization of the membrane potential in a dose-dependent manner with an increased input resistance. No such response was observed with other types of spinal cord neurons in culture. The response to serotonin was partially voltage-dependent. The serotonin-induced depolarization reversed at holding potential close to -100 mV. However, the input resistance variation evoked by serotonin increased exponentially when membrane potential was depolarized. The reversal potential was modified by increasing extracellular K+ concentration and it was unaltered by increasing the intracellular Cl- concentration. The decrease in K+ conductance induced by serotonin was not suppressed by the application of tetraethylammonium (50 mM) or 4-aminopyridine (10 mM). Furthermore, application of Ba2+ (6 mM) or Cd2+ (0.1 mM) had no effect on this response, suggesting that the depolarization evoked by serotonin application was not calcium-dependent. The serotonin evoked increase in input resistance was mediated by activation of a 5-HT1A-like receptor site. Spiperone, a 5-HT1A antagonist reversibly blocked the response. Methiothepin, a 5-HT1-5-HT2 antagonist (10(-3) M); cocaine, a 5-HT3 antagonist (10(-3) M); ketanserin, a 5-HT2 antagonist (10(-3) M); and prazosin, an alpha 1 antagonist (10(-3) M) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The Spanish Diagnostic Interview Schedule. Reliability and concordance with clinical diagnoses in Puerto Rico.

A Spanish translation of the Diagnostic Interview Schedule (DIS) was assessed using samples of Puerto Rican patients and community subjects from the San Juan area. Concordance between DIS results from psychiatrists' interviews and from laypersons' interviews was similar to results with the DIS in mainland samples. Comparisons of laypersons' DIS results with psychiatrists' clinical diagnoses yielded generally poorer agreement. Levels of agreement improved when diagnoses were clustered into higher-rank categories. These results raise cultural issues related to the use of the DIS in Puerto Rico.

Adolescent↗
PubMed1987

Synthesis and gastric antisecretory properties of allenic 16-phenoxy-omega-tetranor prostaglandin E analogs.

In order to improve the modest oral activity of PGE2 as an inhibitor of gastric acid secretion, analogs were prepared and tested orally in histamine-challenged rats. Insertion of a double bond at C-4, resulting in the 4,5-allene analog of PGE1, gave a small increase in activity. Introduction of the omega-tetranor-16-phenoxy lower sidechain, a modification known to enhance activity in the PGF series, gave an eight-fold increase in activity. The analog having both modifications (enprostil, 2) showed a six hundred-fold increase in oral antisecretory activity over PGE2, which may reflect a potentiation effect. Modification of enprostil at C-1 (various esters) and at C-11 (11-methyl, 11-deoxy) generally resulted in compounds of high activity while modifications at other sites generally resulted in significant reductions in activity.

Animals↗
PubMed1986

11-Deoxy-11 alpha,12 alpha-methanoprostaglandin E2, a potent, short-acting bronchodilator.

11-Deoxy-11 alpha,12 alpha-methanoprostaglandin E2 (1b) and the corresponding methyl ester 7a were highly potent, but short acting, bronchodilators both by the intravenous (80 and 10 times PGE2, respectively) and aerosol (2 and approximately 1 times PGE2) routes, as measured by the Konzett-Rössler assay. The 11 beta,12 beta-methano compound 15a was two orders of magnitude less active than 7a. In rhesus monkeys anesthetized by aerosol administration, 1b was 10-50% as potent as, and had a duration of action similar to, PGE1 in the inhibition of methacholine-induced increases in airway resistance. At doses effective in preventing the methacholine response, 1b increased the heart rate (less than or equal to 30%) and precipitated mild upper airway irritation.

Aerosols↗