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Biomedical subjects

M Campos

Publications and source records attributed to M Campos.

At least 109 records · Page 6Linked to original sources
PubMed1993

The role of biological response modifiers in disease control.

Immune responses to infectious agents involve a complex set of interactions between cells and the factors they produce that culminate with disease resolution or death. Therefore, the manipulation of the immune system may have a great impact on the preservation and restoration of animal health. Biological response modifiers are agents that modify the host's response to pathogens with resultant beneficial prophylactic or therapeutic effects. The best known example of biological response modifiers are vaccines, by which administration of a nonpathogenic form of a microorganism prepares the immune system to produce a more effective response upon subsequent infection with the pathogenic form. Nevertheless, the use of biological response modifiers other than vaccines that enhance the immune response is now the focus of many investigations. In this review, a brief overview of the immune system is presented, and special emphasis is placed on possible areas of intervention with biological response modifiers and a description of the prophylactic and therapeutic potential of biological response modifiers. Specific examples are presented to demonstrate examples of disease modification by biological response modifiers through stimulation of nonspecific and antigen specific immunities.

Animals↗
PubMed1993

Surface morphology following photorefractive keratectomy.

To examine the effects of surface dehydration on corneal surface morphology before and after photorefractive keratectomy, corneas of fresh porcine eyes were deepithelialized and then immediately fixed or treated according to one of six protocols (four eyes per protocol): dehydrated under the illumination of an operating microscope; dehydrated and then rehydrated with topically applied balanced salt solution; photorefractive keratectomy; photorefractive keratectomy followed by surface dehydration; or photorefractive keratectomy followed by dehydration and subsequent rehydration. Surface smoothness (S) was measured with an image analysis system. The surfaces of the unablated corneas were smooth (S = 0.992 +/- 0.002), and dehydration did not significantly (P = .7) influence the morphology. After ablation, dehydration resulted in apparent fragmentation of the superficial lamellae, with consequent roughening of the surface (P = .0001). Rehydration was only partially successful in reducing surface irregularity. We conclude that corneal dehydration during and following photorefractive keratectomy roughens the corneal surface and should be carefully avoided.

Animals↗
PubMed1993

Topical fluorometholone reduces stromal inflammation after photorefractive keratectomy.

To examine the effectiveness of topical steroids in decreasing corneal stromal inflammation induced by photorefractive keratectomy, four rabbits underwent uniocular corneal deepithelialization, or deepithelialization followed by photorefractive keratectomy. Topical fluorometholone acetate 0.5% was applied topically to half of the eyes after photorefractive keratectomy. Polymorphonuclear leukocytes (PMNs) were counted 24 hours after surgery. The number of PMNs in the corneal stroma was significantly higher after photorefractive keratectomy than after deepithelialization alone (P = .001) and than in normal unoperated corneas; fluorometholone treatment significantly reduced PMN accumulation (P = .001). Photorefractive keratectomy in rabbits induces an intense inflammation of the superficial stroma that can be effectively treated with topical fluorometholone. A short course of topical corticosteroids may, therefore, be appropriate after excimer laser surgery in humans.

Administration, Topical↗
PubMed1993

Effect of five irreversible inhibitors on beta-lactamase from Shigella flexneri UCSF-129.

The effect of five irreversible inhibitors on purified enzyme from Shigella flexneri USCF-129 and also in vitro, was investigated. The I50 was 0.091, 0.30, 0.40 and 0.87 microgram/ml for 6 beta-iodopenicillanic, clavulanic, olivanic and 6 beta-bromopenicillanic acids, respectively, and 255 micrograms/ml for sulbactam. The synergic responses of these inhibitors (10 micrograms/ml) were studied with ampicillin and cephradin on S. flexneri. The MIC of ampicillin was reduced by 128 times using 6 beta-iodopenicillanic, 6 beta-bromopenicillanic and clavulanic acids. This indicates that the beta-lactamase of S. flexneri is a penicillinase. Since these inhibitors have a strong action against the beta-lactamase and last for at least 6 h, further work is expected to reveal their medical value.

Ampicillin↗
PubMed1993

Ablation rates and surface ultrastructure of 193 nm excimer laser keratectomies.

PURPOSE: To determine whether photorefractive keratectomy can be performed at lower energies than are currently employed in clinical trials. METHODS: Fresh pig corneas were ablated using a clinical excimer laser to study the effects of various energy densities (100-200 mJ/cm2) and beam diameters on ablation rates and on the surface ultrastructure of the ablated cornea. RESULTS: A 20-mJ increase in energy density was associated with a 0.03 micron per pulse increase in the ablation rate. A nearly linear increase in the pseudomembrane thickness occurred with increasing energy densities (r2 = 0.83) or decreasing ablation area diameter (r2 = 0.86). CONCLUSIONS: Our findings suggest that fluences less than those currently used in clinical trials (160-180 mJ) are capable of ablating tissue while producing thinner electron-dense pseudomembranes on the corneal surface. The relationship between pseudomembrane thickness and clinical factors such as reepithelialization and postoperative haze remains to be determined. Operating at lower fluences does have the advantages of allowing larger diameter ablations, reducing possible shockwave damage, and reducing the maintenance requirements for the laser.

Animals↗
PubMed1993

Inactivation of beta-lactamase from Shigella flexneri UCSF-129 by BRL 42715, a potent inhibitor.

The effect of a powerful inhibitor, BRL 42715, on beta-lactamase from Shigella flexneri UCSF-129, to overcome the problem of shigellosis and its resistance to ampicillin, was studied. The I50 was determined for BRL 42715 [C6-(N1-methyl-1,2,3 triazolylmethylene)penem] as 0.0049 microgram/ml being 20-fold lower than the best inhibitor, 6-beta-iodopenicillanic acid, previously reported. The MIC fell from 2,048 to 2 micrograms/ml in the presence of 1 microgram/ml of BRL 42715. The synergism of the ampicillin plus this inhibitor lasted for 9 h. BRL 42715 is an irreversible inhibitor, according to the dialysis results, and a substrate analogue.

Ampicillin Resistance↗
PubMed1993

An arginine residue at the active site of beta-lactamase from Shigella flexneri UCSF-129.

The role of a residue of arginine at the active site of beta-lactamase from Shigella flexneri UCSF-129 was studied. It is a local pathogenic strain which produces intestinal problems, especially in children. Purified enzymes were obtained by affinity chromatography on phenylboronic acid-agarose gels. The enzyme was serine dependent with a molecular weight of 23.6 kD. It was specifically modified with phenylglyoxal (1/830 molar ratio) and incubated for 20 min in the presence of 50 mM sodium phosphate buffer at pH 8.3. The chemical change was established by isoelectric focusing, since a loss of one positive charge was detected. Protection by cephradine, a substrate, indicated the presence of a residue of arginine at its active site. Controls were conducted by differential spectroscopy. Similar results were obtained with 2,3,butanedione. This vital arginine stabilizes the negative charge of the carboxylic group of C-3 or C-4 from the substrates.

Arginine↗
PubMed1993

[Treatment of acute lymphoid leukemia (ALL) in the child].

PURPOSE: To analyse the results of the therapy administered to children with ALL in Cuba. PATIENTS AND METHODS: Four-hundred and twenty-five children (aged below 15 years), diagnosed of ALL in 8 different Cuban hospitals between 1973 and 1991, were evaluated. Five different therapeutic regimes were used: three "classic" GLATHEM protocols in the first period (1973-1981) and two intensive BFM-like protocols in the second period (1982-1991). The Kaplan-Meier method was applied for survival analysis, and the differences were evaluated by the log-rank and Mantel-Cox methods. RESULTS: Two-hundred and sixty-five patients were included in the first period, 81 with low-risk disease, 133 with standard risk and 51 with poor-risk leukaemia. The second period comprised 160 cases, 50 of low-risk, 83 with standard risk and 27 with poor-risk leukaemia. The disease-free survival probability at 60 months was 35% for the first group and 55% for the second (p < 0.0001). The 60-month survival (SV) as a whole was 45% for the "classic" treatments and 60% for the BFM-like protocols (p < 0.01). The disease-free survival (DFS) probability for each prognostic group was as follows: 50% for low-risk, 43% for standard risk, and 25% for poor-risk (p < 0.001) and the probability of survival as a whole was, respectively, 65%, 49% and 28% (p < 0.001). as for this compilation, 172 patients were out of any treatment for periods ranging between 14 and 168 months. CONCLUSIONS: 1) The percentage of remissions was similar for both groups of treatments. 2) The results attained with BFM-like protocols were better than those of the "classic" therapy with regard to the SV and DFS differences. 3) Significant differences can be appreciated between good- and poor-prognosis groups for both types of treatment.

Adolescent↗
PubMed1993

[The urinary tract in pregnancy].

Pregnancy is associated with morphologic alterations of the urinary tract, of which physiological ureterohydronephrosis is the most common. Acute pyelonephritis and obstruction by stones are the two most frequent urinary tract diseases of pregnancy. Medical imaging aims at differentiating physiological ureterohydronephrosis from obstruction and at detecting infections. Ultrasonography plays a central role. Limited roentgenographic investigations can be performed during the second and third trimester. Magnetic resonance imaging can be expected to gain more widespread use in the near future.

Diagnosis, Differential↗
PubMed1992

Photorefractive keratectomy for severe postkeratoplasty astigmatism.

We performed cylindric corneal ablations with the excimer laser on 12 patients to correct severe, disabling astigmatism after keratoplasty. In some patients, an additional ablation was performed to correct myopia. Patients were followed up for an average of eight months (range, six to 14 months). Uncorrected visual acuity improved in nine patients, and nine of the 12 patients had a decrease in refractive cylinder at last follow-up. The mean preoperative refractive cylinder was 7.0 +/- 3.6 diopters, which decreased to a mean of 3.1 +/- 2.6 diopters at one month (P = .0003) and 4.3 +/- 2.9 diopters at last follow-up (P = .03). Keratometric astigmatism decreased from 7.5 +/- 3.9 diopters preoperatively to 5.2 +/- 3.9 diopters at the last follow-up (P = .001). Mean spherical equivalent was reduced from -7.4 +/- 4.2 diopters preoperatively to -3.3 +/- 4.4 diopters postoperatively (P = .003). Postoperative corneal haze, when present, did not reduce visual acuity. Excimer laser superficial keratectomy thus appears to be safe when used for postkeratoplasty ametropia, although substantial regression may limit its effectiveness in some patients.

Adult↗
PubMed1992

Role of the endothelial system in Bay K 8644 enantiomer and nifedipine vasomodulator action in rat aorta.

The potential importance of the endothelial system in regulating the effects of (-)-Bay K 8644 (0.1 microM), (+)-Bay K 8644 (0.1 microM) and nifedipine (10 nM) on resting tension, on contractile responses to noradrenaline (NA) and Ca2+ (in a Ca(2+)-free high-K+ solution), and on basal, NA-induced and K(+)-induced 45Ca2+ uptake, was investigated in rat aorta rings. Mechanical removal of endothelium considerably potentiated the contractile response induced by NA in standard medium and by Ca2+ in Ca(2+)-free high-K+ (15 mM) medium, but did not modify the response induced by Ca2+ in Ca(2+)-free high-K+ (55 mM) medium or by NA in Ca(2+)-free medium. Furthermore, the basal 45Ca2+ uptake and that induced by NA (10 microM) or KCl (15 and 55 mM) were similar in endothelium-rubbed and intact rings. (-)-Bay K 8644 (0.1 microM) shifted the NA and Ca2+ concentration-response curves to the left with potentiation of the maximal contraction. However, (+)-Bay K 8644 (0.1 microM) and nifedipine (10 nM) caused a shift to the right, with depression of the maximal contraction. The NA concentration-response curves, and those of Ca2+ in Ca(2+)-free high-K+ (55 mM) medium, were affected by the drugs to similar extents, and were not modified by the presence or absence of endothelial cells. The drugs tested did not affect resting tension. Basal 45Ca2+ uptake was not modified by either nifedipine or the Bay K 8644 enantiomers.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Corneal sensitivity after photorefractive keratectomy.

Corneal anesthesia or hypesthesia can complicate refractive surgical procedures such as epikeratophakia and radial keratotomy. An esthesiometer was used to measure the corneal sensitivity in unoperated-on corneas and fellow corneas after excimer laser photorefractive keratectomy. Decrease in corneal sensitivity was noted within six postoperative weeks, with mean sensitivity being 75.2% +/- 13.3% of normal. Within the first three postoperative months, the patients operated on for correction of compound astigmatism recovered 95.7% +/- 5.3% of the corneal sensitivity, whereas the patients operated on for correction of severe myopia recovered 86.2% +/- 11.2% (P = .07). None of the patients had delayed epithelial healing or recurrent corneal erosions during the time of decreased corneal sensitivity. In otherwise normal myopic eyes, photorefractive keratectomy measurably reduced corneal sensitivity for several postoperative weeks.

Adult↗
PubMed1992

Effects of magnesium and ATP on pre-steady-state phosphorylation kinetics of the Na+,K(+)-ATPase.

The aim of the present work was to elucidate the role played by ATP and Mg2+ ions in the early steps of the Na+,K(+)-ATPase cycle. The approach was to follow pre-steady-state phosphorylation kinetics in Na(+)-containing K(+)-free solutions under variable ATP and MgCl2 concentrations. The experiments were performed with a rapid mixing apparatus at 20 +/- 2 degrees C. The concentrations of free and complexes species of Mg2+ and ATP were calculated on the basis of a dissociation constant of 0.091 +/- 0.004 mM, estimated with Arsenazo III under identical conditions. A simplified scheme were ATP binds to the ENa enzyme, which is phosphorylated to MgEPNa and consequently dephosphorylated returning to the ENa form, was used. In the absence of ADP and phosphate four rate constants are relevant: k1 and k-1, the on and off rate constants for ATP binding; k2, the transphosphorylation rate constant and k3, the constant that governs the dephosphorylation rate. The values obtained were: k1 = 0.025 +/- 0.003 microM-1 ms-1 for both free ATP and ATPMg; k-1 = 0.038 +/- 0.004 ms-1 for free ATP and 0.009 +/- 0.002 ms-1 for ATPMg; k2 = 0.199 +/- 0.005 ms-1; k3 = 0.0019 +/- 0.0002 ms-1. The model that seems best to explain the data is one where (i) the role of true substrate can be played equally well by free ATP or ATPMg, and (ii) free Mg2+, an essential activator, acts by binding to a specific Mg2+ site on the enzyme molecule.

Adenosine Triphosphate↗
PubMed1992

Structural, functional, and immunological characterization of bovine herpesvirus-1 glycoprotein gl expressed by recombinant baculovirus.

The major glycoprotein complex gl of bovine herpesvirus-1 was expressed at high levels (36 micrograms per 1 x 10(6) cells) in insect cells using a recombinant baculovirus. The recombinant gl had an apparent molecular weight of 116 kDa and was partially cleaved to yield 63-kDa (glb) and 52-kDa (glc) subunits. This processing step was significantly less efficient in insect cells than the analogous step in mammalian cells, even though the cleavage sites of authentic and recombinant gl were shown to be identical. The oligosaccharide linkages were mostly endoglycosidase-H-sensitive, in contrast to those of authentic gl, which has mostly endoglycosidase-H-resistant linkages and an apparent molecular weight of 130/74/55 kDa. Despite the reduced cleavage and altered glycosylation, the recombinant glycoprotein was transported and expressed on the surface of infected insect cells. These surface molecules were biologically active as demonstrated by their ability to induce cell-cell fusion. Fusion was inhibited by three monoclonal antibodies specific for antigenic domains I and IV on gl. Domain I maps to the extracellular region of the carboxy terminal fragment glc and domain IV to the very amino terminus of the glb fragment, indicating that domains mapping in two distinct regions of gl function in cell fusion. Monoclonal antibodies specific for eight different epitopes recognized recombinant gl, indicating that the antigenic characteristics of the recombinant and authentic glycoproteins are similar. In addition, the recombinant gl was as immunogenic as the authentic gl, resulting in the induction of gl-specific antibodies in cattle.

Amino Acid Sequence↗
PubMed1992

Characterization and activation requirements of bovine lymphocytes acquiring cytotoxic activity after interleukin-2 treatment.

Interleukin-2 (IL-2) treatment of cells and generation of non-major histocompatibility complex (MHC)-restricted cytotoxic cells from peripheral blood mononuclear leukocytes (PBML) was studied. Effector-target conjugate assays demonstrated that bovine PBML bound but did not lyse K562, HL60S and HL60R cells unless activated with IL-2. The magnitude of IL-2-activated killing of tumor cells as well as the magnitude of antibody-dependent cellular cytotoxicity depended on the IL-2 concentration. A short treatment (12-18 h) of effector cells with IL-2 was sufficient for development of cytotoxic activity. Withdrawal of IL-2 from the culture resulted in a reduction of cytotoxic activity that could be restored by further addition of IL-2. Cytotoxic activity of IL-2-activated populations obtained after nylon wool or Sephadex G-10 passage, and Percoll gradient centrifugation of PBML suggests that lymphokine-activated killer (LAK) cell activity in PBML is mainly mediated by a non-adherent lymphocyte lacking markers for B-cells. Positive and negative selection experiments using cell sorting confirmed these findings and demonstrated that the cell responsible for LAK cell activity in cattle belongs to a non-monocyte, non-B, CD2+ lymphocyte population. Furthermore, cytotoxic activity could not be generated in CD2+ populations enriched for cells expressing molecules equivalent to human and murine CD4 and CD8. These findings suggest that effector cells mediating non MHC-restricted cytotoxicity in cattle prevail in a population bearing a CD2+, CD4-, CD8- phenotype and that this population depends on the continuous presence of IL-2 for optimal cytotoxic function.

Animals↗
PubMed1992

Multiple administration with interleukin-2 potentiates antigen-specific responses to subunit vaccination with bovine herpesvirus-1 glycoprotein IV.

Interleukin-2 has been described as an effective adjuvant for a number of antigens in different host species. Previously, we demonstrated the adjuvant activity of recombinant bovine IL-2 with a glycoprotein IV (gIV) subunit vaccine from bovine herpesvirus type-1 (BHV-1). In the present study, primary antibody responses were assessed in cattle immunized with either 2 or 50 micrograms of gIV, and treated with multiple doses of IL-2 or combinations of IL-2 and IFN-alpha or IL-2 and IFN-gamma. IL-2 was able to augment significantly antibody responses detected by either ELISA or virus neutralization. More significantly, IL-2 was able to enhance antibody titres in animals immunized with only 2 micrograms gIV to levels similar to those immunized with 50 micrograms gIV in the absence of IL-2. For optimal stimulation, multiple injections of IL-2 and Avridine had to be used in the formulation; other oil adjuvants or IL-2 alone could not induce a primary serum antibody response. Addition of IFN-alpha or IFN-gamma to the IL-2/gIV/Avridine formulation did not affect any of the immune parameters tested. As IFN-alpha is an effective immunoprophylactic agent for infectious bovine rhinotracheitis (IBR), combination vaccine-immunoprophylaxis may become feasible using IL-2 as a co-adjuvant. Thus, extremely low doses of antigen and only one immunization may be an effective vaccine given in combination with interferon prophylactic treatment.

Animals↗
PubMed1992

Effect of urethane on hydralazine-induced tachycardia in rats.

1. In conscious normotensive rats, hydralazine (5-10 mg kg-1 p.o.) produced a dose-related fall in systolic blood pressure, accompanied by a pronounced increase in heart rate. 2. The tachycardia induced by hydralazine (10 mg kg-1 p.o.) in conscious normotensive rats was strongly inhibited after anaesthesia with urethane (1.26 g kg-1 i.p.). 3. In anaesthetized normotensive rats, hydralazine (1 mg kg-1 i.v.) caused a fall in mean blood pressure, accompanied by irregular effects on the heart rate that consisted in a combination of initial tachycardia followed by bradycardia. 4. In pithed rats, hydralazine (1 mg kg-1 i.v.) did not affect mean arterial blood pressure but produced a significant decrease in heart rate. 5. In rat isolated atria, hydralazine (2 mM) produced a positive inotropic/negative chronotropic effect. 6. These results suggest that urethane inhibits the cardiovascular reflex that causes the tachycardia induced by hydralazine in conscious normotensive rats. For this reason, in anaesthetized normotensive rats appear the direct effect of the drug on the heart.

Anesthesia↗