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Biomedical subjects

M A Vargas

Publications and source records attributed to M A Vargas.

At least 55 records · Page 3Linked to original sources
PubMed1996

Specific IgE detected by ELISA and immunoblot after human cytomegalovirus infection (HCMV) in renal transplant (RT) recipients.

BACKGROUND: Specific HCMV IgE response has been reported by some authors, and was proposed as a valuable virologic marker of CMV infection. OBJECTIVES: we evaluated specific HCMV IgE in renal transplant patients with active (primary and secondary) HCMV infection with special interest to symptomatic infections. STUDY DESIGN: Specific IgE was tested retrospectively by ELISA and immunoblot (IB) on sera of 55 RT patients who were followed before and after transplantation with virologic markers of CMV infection. RESULTS: Total serum IgE levels were similar in control group and in patients with primary and secondary HCMV infections. Anti-CMV specific IgE response by ELISA was more frequently found in patients with primary infection (76.9%) than in patients with secondary infection (47.1%). These specific IgE reacted on immunoblot with a 150 kDa protein in 84.6% of patients with primary infection and 94.1% with secondary infections; and reacted with rp52 (pUL44) in 76.9% of primary infection and 47.1% of secondary infection. CONCLUSIONS: Anti-CMV specific IgE tested by immunoblot and ELISA is a marker of CMV infection. It was clearly detected in cases of active infection (primary and secondary) and was present in cases with severe CMV clinical manifestations. In contrast, anti-CMV specific IgE, was consistently negative among healthy blood donors. This is the first report of CMV proteins detected by IgE immunoblot.

Journal Article↗
PubMed1996

Physical properties of composites cured with conventional light or argon laser.

PURPOSE: To evaluate and compare diametral tensile strength (DTS), compressive strength (CS) and flexural strength (FS) of a hybrid and a microfill resin composite restorative material polymerized by an argon laser for 10 seconds (AL10) and 20 seconds (AL20) vs. a conventional visible light for 40 seconds (VL40). MATERIALS AND METHODS: Five specimens of resin composite, Herculite XRV, shade A-2 and Durafill VS, shade B-2, were made for each set of physical properties tested, for a total of 18 groups and 90 specimens. ANSI/ADA Specification #27 for direct filling resins was used as the protocol for specimen preparation and physical properties testing. An argon laser at approximately 285 mW, 6 mm beam size, power density of approximately 1,000 mW/cm2, and a conventional visible light at approximately 470 mW, 13 mm beam size, power density of approximately 354 mW/cm2, were used to polymerize the composite. Samples were stored in water in light-proof containers at 37 degrees C for at least 7 days and then tested on a Zwick universal testing machine. Mean DTS, CS or FS (MPa) values were calculated for each group. RESULTS: Herculite XRV's physical properties were not significantly affected by light source or exposure time. Light source or exposure time had no significant effect on DTS for Durafill VS. Significantly lower FS was found for Durafill VS, when cured for 10 seconds with the argon laser compared to 20 seconds with the laser or 40 seconds with the conventional light. In addition, significantly lower CS was found for the Durafill VS when polymerized with the laser at 10 seconds compared to the conventional light at 40 seconds.

Analysis of Variance↗
PubMed1995

Depth of cure of resin-modified glass ionomers.

OBJECTIVES: The cure of all resin-modified glass ionomer materials depends to some degree on light activation. However, the materials have chemical-cure mechanisms that could increase depth of cure. Thus, this study was conducted to evaluate the depth of cure of five resin-modified glass ionomer restorative materials. METHODS: Five specimens of Fuji II LC (GC America), Geristore (Den-Mat), Photac-Fil (ESPE America), VariGlass (Caulk/Dentsply), and Vitremer (3M Dental Products) were fabricated in Teflon molds. Each material was visible light-activated for 40 s. Specimens were 5 mm x 5 mm x 9 mm (depth), but material at depths greater than 5 mm was too soft to measure. Microhardness (KHN) at the surface and at 1 mm increments below the surface of each specimen was measured at 10 min, 1 d, and 7 d after light-curing. RESULTS: At 10 min post-irradiation, the top layers (0-1 mm) of each material were significantly harder than the deeper layers (4-5 mm). However, at 1 d, Geristore, Photac-Fil, Vitremer and Fuji II LC had uniform hardness, regardless of depth. In contrast, VariGlass hardness decreased significantly with depth, from 43.3 at the surface to 11.7 at 5 mm. At 7 d, Photac-Fil, Vitremer and Fuji II LC had more uniform hardness regardless of depth than either Geristore or VariGlass. Data were analyzed using ANOVA and Duncan's multiple range tests. SIGNIFICANCE: Immediately following light activation, the upper layers of each material were harder than the deeper layers, but the degree of cure in the deeper layers improved over time. VariGlass was the only material in which bottom hardness (5mm) and top hardness remained significantly different at 1 d, suggesting that VariGlass has less effective chemical-cure mechanisms than the other materials tested.

Acrylic Resins↗
PubMed1995

Bond strengths of glass ionomers using a dentin adhesive.

PURPOSE: To determine the effect of All-Bond 2 adhesive on the shear bond strengths to dentin of Fuji II LC, Photac-Fil, and Vitremer. MATERIALS AND METHODS: The occlusal surfaces of 60 extracted human third molars were ground flat to expose dentin and were polished to 600 grit. The teeth were randomly assigned to six groups (n = 10). In three groups, dentin was treated using the conditioner or primer recommended by the manufacturer. In the remaining groups, dentin was treated with All-Bond 2 etchant, primer, and adhesive. Restorative materials were applied to the treated surfaces in gelatin capsule matrices and were light-cured. Specimens were thermocycled, and shear bond strengths were determined using a materials testing machine. RESULTS: The use of All-Bond 2 improved the mean bond strength of Photac-Fil from 1.7 to 8.7 MPa, but decreased the bond strength of Vitremer from 7.3 to 5.5 MPa. The bond strengths of Fuji II LC were 7.5 and 7.9 MPa, with and without the use of All-Bond 2, respectively. ANOVA and Duncan's multiple range test showed that only the difference for Photac-Fil was statistically significant.

Composite Resins↗
PubMed1995

Bonding of resin composites to resin-modified glass ionomers.

PURPOSE: To evaluate the bonding between resin composites and resin-modified glass ionomer restorative materials. MATERIALS AND METHODS: Bar-shaped specimens of Fuji II LC, Photac-Fil, and Vitremer were fabricated in a mold. After application of unfilled resin, resin composite (either Silux Plus or Restorative Z100) was condensed into the mold against the glass ionomer substrate and was light-cured. These bonded specimens, as well as intact specimens of each material, were placed on a three-point bending apparatus and were loaded until failure using a Zwick testing machine. The transverse strength of each specimen was calculated. RESULTS: Mean transverse strengths of bonded specimens ranged from 50% to 78% of the transverse strength of the intact glass ionomer materials. The lowest transverse strength was 18.1 MPa, for Photac-Fil/Z100, and the highest was 29.6 MPa, for Fuji II LC/Silux. Statistical analysis indicated that the type of composite used had no significant effect on transverse strength. However, the type of resin-modified glass ionomer used was significant. Although there was much overlap between materials, bonded specimens made with Fuji II LC had the highest absolute strength, and those made with Photac-Fil had the lowest absolute strength. Bonded Vitremer specimens had the highest transverse strength relative to the cohesive strength of the material.

Analysis of Variance↗
PubMed1994

Pyroglutamyl peptidase II activity is not in the processes of bulbospinal TRHergic neurons.

Pyroglutamyl peptidase II (PPII) is a neuronal ectoenzyme involved in released thyrotropin-releasing hormone (TRH) inactivation. In an attempt to define if it is present in the pre or postsynaptic membrane, we induced neuronal degeneration of serotonin-TRHergic cells that project from raphe nuclei to the spinal cord. 2-4 weeks after intracisternal injection of 5,7-dihydroxytryptamine, TRH levels decreased over 70% in the cervical, thoracic or lumbar regions of spinal cord. In contrast, no change of PPII activity was observed. Longer times after injection (6-8 weeks), a 59-66% increase in activity was detected in the lumbar region. These data suggest that PPII is not localized in these TRHergic neurons but probably in the target cells.

5,7-Dihydroxytryptamine↗
PubMed1994

In vitro TRH release from hypothalamus slices varies during the diurnal cycle.

We have previously described a daily rhythm in thyrotropin releasing hormone (TRH) and TRH mRNA in the rat hypothalamus. To determine whether TRH release fluctuates in a diurnal manner, we have measured basal and potassium stimulated release from hypothalamic slices, and compared it to release from olfactory bulb slices, during the diurnal cycle. Basal TRH release was higher at 7:00 h than at any other time (1:00, 13:00 or 19:00 h) in either hypothalamus or olfactory bulb. The ratio of stimulated over basal release was higher in the hypothalamus at 19:00 h, when TRH content was highest. Potassium stimulated TRH release from olfactory bulb was not different from basal release at any time. TRH release fluctuations were not due to a rhythm of extracellular inactivation: the activity of pyroglutamyl aminopeptidase II, an ectoenzyme responsible for TRH inactivation, was constant throughout the cycle. Our data demonstrate that diurnal variations of TRH release occur in vitro and that the enhanced responsiveness to potassium stimulation in hypothalamus is correlated with increased levels of peptide.

Aminopeptidases↗
PubMed1994

Thyrotropin-releasing hormone downregulates pyroglutamyl peptidase II activity in adenohypophyseal cells.

Pyroglutamyl peptidase II (PPII) is a thyrotropin-releasing hormone (TRH) hydrolyzing ectoenzyme with a narrow specificity. In the adenohypophysis, it is present on lactotropes. This study was undertaken in order to determine whether TRH itself regulates PPII activity in the adenohypophysis. After 5 days in culture, dispersed cells from female pituitaries expressed detectable levels of PPII activity when 10(-8) M 3,3',5'-triiodo-L-thyronine was present throughout the culture. 10(-6) M TRH decreased PPII activity with a maximal effect (down to 46% of initial values) at 16 h and an ED50 of 10(-9) M. [3Me-His2]TRH, a potent agonist of the TRH receptor was effective at lower concentrations (ED50: 1.6 x 10(-10) M). Phorbol-12-myristate-13-acetate (PMA; 10(-6) M), a protein kinase C (PKC) activator, diminished PPII activity to 61% or initial values with an ED50 of 2.2 x 10(-8) M. Maximal effects of PMA and TRH were not additive. Neither PMA nor TRH effects were reversed by inhibitors of protein kinases (1-(5-isoquinolinesulfonyl)-2-methyl-piperazine or sphingosine or staurosporine); TRH-induced downregulation of the enzyme was not modified by PMA pretreatment. TRH had no effect on two other ectopeptidases, endopeptidase 24.11 and dipeptidyl aminopeptidase IV. These data demonstrate that TRH specifically downregulates PPII activity in adenohypophyseal cells through TRH receptor activation and suggest that the activation of a presumably calcium-independent PKC mimics the TRH effect. TRH regulation of PPII activity may contribute to adjust lactotrope responsiveness to TRH.

Amino Acid Sequence↗
PubMed1994

Microleakage of resin composites with wet versus dry bonding.

PURPOSE: To evaluate the effects of wet and dry bonding on microleakage of Class V composite restorations. MATERIALS AND METHODS: Cavity preparations were made in the buccal and lingual surfaces of 25 extracted human third molars. Half of each preparation was in enamel and the other half was in cementum/dentin. The preparations were randomly assigned to five groups for bonding with Scotchbond Dual-Cure (control), Scotchbond Multi-Purpose, or All-Bond 2. Scotchbond Multi-Purpose and All-Bond 2 were applied using both wet and dry techniques. All preparations were restored with a microfill composite after bonding. The specimens were thermocycled 300 times between 5 degrees and 55 degrees C and were subjected to a silver nitrate staining technique to detect marginal leakage. RESULTS: Specimens bonded with All-Bond 2 and Scotchbond Multi-Purpose had significantly less leakage than the control. However, there was no statistically significant difference between wet and dry bonding techniques for either material.

Analysis of Variance↗
PubMed1993

Entamoeba histolytica: changes in the zymodeme of cloned nonpathogenic trophozoites cultured under different conditions.

In this paper we report the occurrence of changes in the migration of certain isoenzymes of a cloned strain (MAV-CINVESTAV) of Entamoeba histolytica. This strain was isolated from an asymptomatic carrier and showed an initial nonpathogenic zymodeme I. The transfer of polyxenic trophozoites from Robinson's medium (7% serum) to Jones' medium (30% serum) provoked changes in isoenzyme expression, resulting in the conversion of zymodeme I to a zymodeme that was similar to the XVII zymodeme except for two slow-running bands and a single fast-running band that were detected for hexokinase (HK). This XVII-like zymodeme reverted to zymodeme I when trophozoites were cultured under monoxenic conditions in TY1-S-33 medium (10% serum). When we cultured cloned strain MAV-CINVESTAV under axenic conditions in TY1-S-33 medium, trophozoites expressed a pathogenic zymodeme with two fast-running HK bands and a beta-phosphoglucomutase band. In addition, phagocytosis and the ability of the trophozoites to destroy cell-culture monolayers were expressed only in trophozoites cultured under axenic conditions. The axenization procedure required the presence of live Fusobacterium symbiosum and is also described herein.

Animals↗
PubMed1993

The effects of alprazolam on corticotropin-releasing factor neurons in the rat brain: implications for a role for CRF in the pathogenesis of anxiety disorders.

Considerable evidence indicates that corticotropin-releasing factor (CRF) is responsible for integrating not only the endocrine, but the autonomic and behavioral responses of an organism to stress. We have investigated the effects of the anxiolytic triazolobenzodiazepine, alprazolam, on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and of CRF neurons following acute and chronic administration. In addition, because many of the signs and symptoms observed in animals and humans following abrupt discontinuation of benzodiazepines resemble those of the stress response, we examined the effect of alprazolam withdrawal on CRF neurons and HPA axis activity. Alprazolam decreases CRF concentrations in the locus coeruleus 0.5-3.0 hours following acute injection. Similarly, chronic (14 days) alprazolam administration also results in decreased CRF concentrations in the locus coeruleus. CRF concentrations return to control values 24 hours following abrupt alprazolam withdrawal. Moreover, abrupt alprazolam withdrawal results in increased plasma ACTH and corticosterone concentrations and decreased anterior pituitary CRF receptor concentrations 24 hours following drug discontinuation. Thus, abrupt alprazolam withdrawal profoundly activates the HPA axis. These indices of HPA axis activity return to control values by 48 hours post-withdrawal. These actions of alprazolam on CRF neurons are opposite to those observed following acute or chronic stress. These results support the hypothesis that CRF-containing neurons innervating the locus coeruleus may be involved in the pathogenesis of anxiety, and in the actions of clinically efficacious anxiolytics.

Alprazolam↗
PubMed1993

Post-traumatic stress disorder.

In the past few years, there has been a growing interest in the neurobiology of PTSD. A number of models have been proposed including possible structural changes. We have now seen the appearance in the literature of controlled and double-blind trials. Of interest are positive outcome studies associated with the use of drugs with serotonergic actions for a period of 8 weeks. Symptom relief provided by pharmacotherapy enables the patient to participate more thoroughly in individual, behavioral, or group therapy.

Arousal↗
PubMed1992

Ontogenesis of pyroglutamyl peptidase II activity in rat brain, adenohypophysis and pancreas.

Pyroglutamyl peptidase II (PPII; E.C. 3.4.19.-) is a highly specific membrane-bound ectoenzyme degrading thyrotropin releasing hormone (TRH). The ontogenesis of this enzyme was measured in rat brain regions, adenohypophysis and pancreas. In hypothalamus PPII activity was maximal at day 8 postnatal, decreasing to adult values at day 45. The postnatal ontogenic patterns in posterior cerebral cortex and hypothalamus were similar. In olfactory bulb, two peaks of activity were observed (3th and 22nd day) while in adenohypophysis it appeared only at day 8, increased to day 30, decreasing thereafter to adult values.

Animals↗
PubMed1991

The effects of alprazolam on corticotropin-releasing factor neurons in the rat brain: acute time course, chronic treatment and abrupt withdrawal.

Considerable evidence indicates that corticotropin-releasing factor (CRF) is responsible for integrating not only the endocrine, but the autonomic and behavioral responses of an organism to stress. We have investigated the time course of action of the anxiolytic triazolobenzodiazepine, alprazolam, on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and of CRF neurons after acute and chronic administration. In addition, because many of the signs and symptoms observed in animals and humans after abrupt discontinuation of benzodiazepines resemble the stress response, we examined the effect of alprazolam withdrawal on CRF neurons and HPA axis activity. Alprazolam decreases CRF concentrations in the locus coeruleus between 0.5 and 3.0 h following acute injection. The half-life of alprazolam in rats is less than 1 h in both plasma and brain. Similarly, chronic (14 days) alprazolam administration also results in decreased CRF concentrations in the locus coeruleus. CRF concentrations return to control values 24 h after abrupt withdrawal. Moreover, abrupt alprazolam withdrawal results in increased plasma adrenocorticotrophic hormone and corticosterone concentrations and decreased anterior pituitary CRF receptor concentrations 24 h after drug discontinuation. These indices return to control values by 48 h postwithdrawal. These results support the hypothesis that both acute and chronic alprazolam administration alters CRF-containing neurons innervating the locus coeruleus. Additionally, abrupt alprazolam withdrawal profoundly activates the HPA axis.

Administration, Oral↗
PubMed1991

Neuronal localization of pyroglutamate aminopeptidase II in primary cultures of fetal mouse brain.

Pyroglutamate aminopeptidase II is a highly specific membrane-bound ectopeptidase proposed to inactivate thyrotropin releasing hormone (TRH) in brain extracellular space. Its activity was measured in primary cell cultures of fetal brain in an attempt to define its cellular localization. Enzyme activity was detected in hypothalamic or cortical cell membrane fractions from 4- to 12-day-old cultures. When proliferation of nonneuronal cells was abolished by cytosine arabinoside treatment, pyroglutamate aminopeptidase II specific activity was increased as compared to untreated cultures, the opposite was observed for pyroglutamate amino-peptidase I activity. Treatment of cortical cells with the neurotoxic agent glutamate reduced simultaneously pyroglutamate aminopeptidase II and glutamate decarboxylase activities. Glial cell cultures expressed pyroglutamate aminopeptidase I or glutamate synthase activities but not pyroglutamate aminopeptidase II. The data suggest that pyroglutamate aminopeptidase II is predominantly localized in neuronal cells. This is consistent with a role for pyroglutamate aminopeptidase II in TRH-ergic synaptic transmission.

Animals↗
PubMed1990

Non-pathogenic Entamoeba histolytica: functional and biochemical characterization of a monoxenic strain.

We have cultured under monoxenic conditions and characterized an Entamoeba histolytica clone, MAV-I CINVESTAV (MAV-I), obtained from feces from an asymptomatic carrier. The clone shows the non-pathogenic E. histolytica zymodeme type I, which did not change through the process of monoxenization. Clone MAV-I was non-pathogenic in both in vivo and in vitro tests, and it did not have a functional 112-kDa adhesin. As far as we know, this is the first non-pathogenic monoxenic strain reported. Clone A (strain HM1:IMSS), a highly virulent clone with pathogenic zymodeme type II, and which has the 112-kDa adhesin, was used as a control. Protein patterns from both clones were almost identical in one-dimensional gels. In two-dimensional gels, differences in high-molecular-weight proteins were detected. Clone MAV-I adhered and phagocytosed only 12% of the red blood cells adhered and phagocytosed by clone A. MAV-I trophozoites did not destroy cell culture monolayers and did not produce hepatic abscesses in hamsters. They also showed deficiency in protease activity. The absence of virulence in clone MAV-I correlated directly with the absence of a functional 112-kDa adhesion, supporting the role that this protein plays in virulence.

Animals↗