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Biomedical subjects

M Campos

Publications and source records attributed to M Campos.

At least 127 records · Page 7Linked to original sources
PubMed1992

Effect of Haemophilus somnus on phagocytosis and hydrogen peroxide production by bovine polymorphonuclear leukocytes.

The interactions between bovine polymorphonuclear leukocytes (PMNs) and the bacterium Haemophilus somnus are known to be complex. In this paper, we evaluated the effect of H. somnus on PMN function using a flow cytometric (FC) technique that simultaneously determined the extent of phagocytosis and hydrogen peroxide production by PMNs, as well as using conventional techniques, such as the nitroblue tetrazolium (NBT) and chemiluminescence assays, to analyse the PMN respiratory burst. Results from the FC and chemiluminescence assays demonstrated that in vitro exposure of PMNs to logarithmically growing H. somnus reduced the respiratory burst of PMNs obtained from healthy calves. However, this reduction was not detected by the NBT assay. A decrease in phagocytosis by PMNs could also be shown using the FC assay. In addition, PMNs from calves with acute Hemophilosis (i.e. exposed to H. somnus in vivo) showed reduced activity when compared to PMNs from healthy calves. These in vitro and in vivo observations indicate that the modulation of bovine PMN function by H. somnus may contribute significantly towards the pathogenesis of the disease.

Animals↗
PubMed1992

Corneal wound healing after excimer laser ablation. Effects of nitrogen gas blower.

PURPOSE: To examine the effects of blowing nitrogen gas over the cornea during photorefractive keratectomy. METHODS: Excimer laser ablations for myopia were performed on rabbit corneas with or without the blowing of nitrogen across the surface of the cornea. All eyes underwent a 5-diopter myopic ablation; in 8 eyes, a ring was used to blow nitrogen gas across the cornea, and, in 8 eyes, the same ring was used, but no nitrogen gas was blown. RESULTS: Epithelial healing occurred more rapidly in the eyes that were not treated with the gas (3.8 +/- 1.3 days) than in the gas-treated group (6.1 +/- 0.8 days; P = 0.0025). Corneal haze was greater in the group treated with gas. Results of histologic examination showed the ablated area to have a smoother surface when nitrogen was not blown across the cornea surface. CONCLUSION: Superficial corneal deturgescence produced by the nitrogen gas appears to result in a rougher surface immediately postoperatively with undesirable effects on surface healing, but further studies will be necessary to determine the applicability of these results to humans.

Animals↗
PubMed1992

The role of bovine intraepithelial leukocyte-mediated cytotoxicity in enteric antiviral defense.

The defense of a mucosal surface against viral infection is dependent in part on the leukocyte population resident at that site. In this study, leukocytes from the bovine intestinal epithelium were isolated and assessed for their ability to inhibit in vitro replication of an enteric pathogen, bovine coronavirus (BCV). As well, the intraepithelial leukocytes (IEL) were tested for their ability to mediate different types of cytotoxicity. The IEL were able to inhibit virus replication, and this activity was markedly enhanced by interleukin-2 and tumor necrosis factor. This combination of cytokines has similar effects on IEL-mediated cytotoxicity, which implicated cytotoxicity as a mechanism by which viral replication was limited. The IEL demonstrated enhanced cytotoxic function when compared with lymphocytes isolated from other sites in the gut-associated or systemic immune system. The IEL mediated higher levels of IL-2-activated, antibody-dependent, and lectin-dependent cytotoxicity than did lymphocytes from mesenteric lymph nodes, Peyer's patches, or the spleen. This function may be a reflection of the type of cell recruited to the epithelium, as indicated by the increased prevalence of T cells, and particularly CD8+ cells in the IEL population. Cytokine activation and the presence of a recognition signal, such as antibody, resulted in a synergistic increase in the level of IEL-mediated cytotoxicity. This type of interaction could serve to enhance the efficiency of IEL cytotoxic cells in vivo. Thus IEL-mediated cytotoxicity has the potential to serve as a mechanism of defense to enteric viral infection.

Animals↗
PubMed1992

Comparison of high titer Edmonston-Zagreb, Biken-CAM and Schwarz measles vaccines in Peruvian infants.

In an effort to identify the optimal dose and strain of measles vaccination for early immunization, Peruvian infants were randomly assigned to receive one of three measles vaccines in varying doses at 5 to 6 or 8 to 9 months of age. Edmonston-Zagreb vaccines were significantly (P < 0.001) more immunogenic than equivalent or higher titers of Schwarz or Biken-CAM vaccines as determined by neutralization antibody response 3 months after vaccination. Eighty-two percent of infants who received high titer Edmonston-Zagreb vaccine at 5 to 6 months of age developed protective concentrations of measles antibody, a response rate similar to that observed after standard titer Schwarz (81%) or high titer Biken-CAM vaccine (81%) at 8 to 9 months of age. No significant differences in the rates of fever, rash or other adverse events were noted by vaccine group 10 to 14 days after vaccination. Although the high titer vaccines are more immunogenic in young infants than standard vaccines, long term safety must be assured before these vaccines can be put into widespread use.

Antibodies, Viral↗
PubMed1992

Effects of platelet activating factor on contractions and 45Ca influx induced by noradrenaline and potassium in rat rubbed and intact aorta. Comparison with its hypotensive effect in anaesthetized normotensive rats.

In order to clarify the mechanism of hypotensive activity of platelet activating factor (PAF), the effects of this drug on blood pressure in anaesthetized normotensive rats, on KCl- and noradrenaline-induced 45Ca uptake and contractile responses in rat aorta rings with and without endothelium were studied. PAF (3 micrograms kg-1, i.v.) showed long-lasting hypotensive effects in anaesthetized normotensive rats accompanied by a significant increase in heart rate. PAF (0.1-10 microM) did not relax the contractions induced by noradrenaline (10 microM) or K+ (60 mM) in rubbed or intact rat aorta. PAF did not affect the basal uptake of 45Ca2+ nor that induced by the two vasoconstrictor agents. In experiments in a calcium free medium, PAF (10 microM) had no effect on the noradrenaline- (10 microM) induced contractions. These results suggest that the hypotensive activity of PAF in normotensive anaesthetized rats is not due to a direct effect on rubbed and intact rat aorta rings (acting within the cell or blocking Ca2+ influx through L-type transmembrane calcium channels).

Anesthesia↗
PubMed1992

Molecular chimerization of Pasteurella haemolytica leukotoxin to interleukin-2: effects on cytokine and antigen function.

A chimeric recombinant protein composed of the lktA gene product from Pasteurella haemolytica fused to bovine interleukin-2 (IL-2) was made. The LKT-IL-2 chimera was compared with recombinant bovine IL-2 with regard to the ability to induce proliferative responses and LAK cell activity in bovine peripheral blood mononuclear cells in vitro. In both instances, chimerization had no effect on IL-2 activity. Similarly, the LKT component was unaffected in its ability to induce an effective immune response after immunization. The adjuvant properties of IL-2 have been established in a number of models, and this effect was tested by using the chimera. A multiple-injection protocol of LKT-IL-2 was compared with single-dose administration of LKT. The results obtained indicate that while there was no increase in specific antibody production, the IL-2 component of the chimera may be able to affect antigen-specific proliferation, as assessed by limiting-dilution analysis. Use of cytokine-antigen chimeras may provide a valuable antigen-adjuvant formulation that is simple to produce and purify and thus have economic advantages over conventional preparations. Furthermore, chimerization will also ensure that the adjuvant acts at the same site as the antigen, thus optimizing immunostimulatory activity.

Animals↗
PubMed1992

Ocular integrity after refractive surgery: effects of photorefractive keratectomy, phototherapeutic keratectomy, and radial keratotomy.

The effects on ocular integrity of three surgical techniques to correct refractive errors were compared. Ten matched pairs of eyes (right and left eyes) freshly enucleated from pigs underwent radial keratotomy (RK) (four incisions, 3.50-millimeter clear zone) in one eye and photorefractive keratectomy (PRK) with the 193-nanometer excimer laser (10.00- diopter myopic correction, 6.00-millimeter ablation diameter) in the fellow eye. Another 16 eyes under- went phototherapeutic keratectomy (PTK) at various depths; another 10 eyes were used as controls. All eyes were subjected to lateral compression by a bench press, with gradually increasing pressure applied until the globe ruptured. The rupture site was photographed. Of the 10 control eyes, 9 ruptured at the sclera and 1 ruptured at the optic nerve. All eyes that had undergone RK ruptured at the sites of the corneal incisions, whereas the eyes that had PRK ruptured at the sclera (P < .01). After PTK, corneal rupture upon compression occurred when ablations were about 40% depth or greater. Corneas that have been subjected to PRK thus appear less predisposed to rupture due to blunt trauma than do eyes that have undergone RK.

Animals↗
PubMed1992

Corneal surface after deepithelialization using a sharp and a dull instrument.

Manual removal of the corneal epithelium currently precedes excimer laser photorefractive keratectomy. To assess the smoothness of the corneal surface following this procedure, six paired human eye-bank eyes (12 eyes) were manually deepithelialized using a blunt instrument (Paton spatula) on one eye and a sharp instrument (surgical blade) on the contralateral eye; all deepithelializations were done by the same surgeon. The 12 corneas were then resected and processed in an identical fashion for scanning electron microscopy. The microphotographs obtained showed that among the corneas deepithelialized with the blunt spatula, two had a smooth surface, and four had variable amounts of residual epithelial cells and basement membrane, confirmed by light microscopy. The surface of five corneas deepithelialized with the sharp instrument were slightly rougher than the former, with occasional linear scratches; one cornea retained a small amount of basement membrane. Removal of epithelium appears to be more complete when a sharp instrument is used. These findings may have clinical relevance, since residual epithelium and basement membrane after deepithelialization may influence the depth of ablation subsequently achieved with the excimer laser.

Basement Membrane↗
PubMed1992

Cell-mediated cytotoxic responses in lungs following a primary bovine herpes virus type 1 infection.

Non-major histocompatibility complex (MHC) restricted cytotoxicity is an important part of the immune reaction mounted in response to bovine herpes virus type 1 (BHV-1) infection. In this study, we evaluated the effect of BHV-1 infection on the ability of lung parenchyma leucocytes (LPL), cranial tracheobronchial lymph node cells (BLNC) and peripheral blood mononuclear leucocytes (PBML) to mediate this function. While LPL from non-infected calves mediated cytotoxicity against BHV-1-infected cells, a similar activity could not be detected in PBML or BLNC. In contrast, both LPL and PBML from naive calves could mediate cytotoxicity against K562 target cells but only after activation with interleukin-2 (IL-2). BLNC were unable to kill K562 cells. Infection of calves with BHV-1 enhanced the ability of LPL and PBML to kill BHV-1-infected cells. This enhancement was detected as early as Day 1 after infection in LPL whereas it could only be detected in PBML 8 days after infection. The results demonstrate that the leucocyte population present at the site of infection was able to mediate a potentially important antiviral function and that this function was enhanced rapidly in response to infection. Thus LPL-mediated cytotoxicity may be an important mechanism for the recovery from BHV-1 infection.

Animals↗
PubMed1992

Clinical and immunological effects of single bolus administration of recombinant interleukin-2 in cattle.

Recombinant bovine interleukin-2 (rBoIL-2) was administered as a single intramuscular bolus to healthy calves to determine the minimal dose capable of exerting a biological response. Doses ranging from 2.5 to 0.05 micrograms rBoIL-2/kg did not induce pyrexia, diarrhea, or depression, nor did they alter any blood chemistry or hematological parameters commonly associated with IL-2 toxicity. Moreover, the only significant immunological change observed was a reduction in the number of peripheral blood lymphocytes identified with the monoclonal antibodies B7A, BAQ4A (WC1+ cells), CACTB6A (WC2+ cells) and DH59B (monocytes). The decrease in cells associated with these markers did not influence non-MHC restricted cytotoxicity or in vitro lymphocyte proliferative responses to mitogens and IL-2. The treatments had no effect on delayed type hypersensitivity responses to phytohemagglutinin. These results indicate that IL-2 may be involved in the regulation of trafficking patterns of a unique subpopulation of lymphocytes in cattle.

Animals↗
PubMed1992

Induction of beta-lactamase from Shigella flexneri UCSF-129: purification by affinity chromatography and some properties.

Lincomycin, an inhibitor of protein synthesis, was an excellent inductor of beta-lactamase, and its total activity and specific activity were increased 2.5- and 3.6-fold respectively. The beta-lactamase produced by Shigella flexneri UCSF-129 was purified by affinity chromatography on phenylboronic acid-agarose with a type B column using an hydrophobic spacer arm (6-aminohexanoic acid activated with succinimide). The yield and specific activity were 96% and 29,283 U/mg, respectively. These were 1.7- and 3.8-fold higher, respectively, than those obtained by the traditional method using ion-exchange chromatography and gel filtration. The working-time was reduced to a third, and the enzyme preparation was shown to be pure by several criteria. From nine divalent cations assayed, only Sn(II) inhibited the enzyme by 74%, and the chloride ion did not have any effect on enzyme activity.

Anti-Bacterial Agents↗
PubMed1991

Cloning of coliphage-T4 gene pseT and high-level synthesis of polynucleotide kinase in Escherichia coli.

The gene, pseT, of coliphage T4 which encodes polynucleotide kinase (PNK) was cloned directly into an expression plasmid using the polymerase chain reaction. When placed under the control of the trp promoter, the pse T gene can be maintained stably in Escherichia coli and yields high levels of the enzyme upon induction. The system described facilitates purification and provides very high yields of PNK.

Base Sequence↗
PubMed1991

Demonstration of the in vitro antiviral properties of bovine lymphokine-activated killer (LAK) cells.

In cattle, cells with functional characteristics similar to those of natural killer (NK) cells are difficult to detect. However, lymphokine-activated killer (LAK) cells can be detected readily after in vitro activation of peripheral blood mononuclear leukocytes (PBML) with interleukin-2 (IL-2). In the present study, we demonstrated that IL-2-activated PBML preferentially lyse bovine herpesvirus type 1 (BHV-1)-infected cells and that the cell responsible for the lysis copurified with the cell responsible for lysis of K562. The IL-2-activated effector cells were capable of significant reducing virus production. The reduction in virus yield seemed to be by an interferon (IFN)-independent mechanism, as the amount of IFN induced in effector cells by BHV-1 was not altered by the addition of IL-2. Furthermore, enrichment of cytotoxic cells by passage through nylon wool columns removed the capability of PBML to produce IFN in response to the virus. These results suggest that activation of LAK mechanisms in cattle plays a role in controlling virus spread.

Animals↗
PubMed1991

Measles-associated diarrhea in hospitalized children in Lima, Peru: pathogenic agents and impact on growth.

Because the causes of measles-associated diarrhea are not well known, 0- to 5-year-old children presenting to the hospital with measles-associated diarrhea (cases, n = 77) or acute diarrhea only (controls, n = 77) were compared. Growth and diarrheal morbidity were evaluated for 1 month after acute illness. Campylobacter jejuni was more frequently isolated from cases (31%) than controls (16%; P = .03). Rotavirus was absent in all cases versus 28% of controls (P less than .001). Incidence density for new episodes of diarrhea was significantly greater in cases (6.5 vs. 4.1; odds ratio, 1.6; confidence intervals, 1.09-2.34; P = .01), as was duration of episodes (3 vs. 2 days, P = .02). Both groups showed similar positive cumulative percentage weight gains throughout follow-up. These data support the theory of measles as a risk factor for developing diarrhea. The bacteriologic and virologic findings may reflect the immunologic response of the host to measles infection.

Acute Disease↗
PubMed1991

Non-major histocompatibility complex-restricted cytotoxicity of bovine coronavirus-infected target cells mediated by bovine intestinal intraepithelial leukocytes.

Non-specific cellular mechanisms of defence against intestinal virus infections of cattle were investigated using bovine coronavirus (BCV) as a representative enteric virus. Since BCV infection is limited to the epithelial cells of the intestinal tract, defence mechanisms must be capable of acting at that site to be effective. Therefore, the intraepithelial leukocyte (IEL) population of the intestinal mucosa was chosen for initial study. Treatment of intestinal samples with DTT and EDTA in calcium- and magnesium-free buffers allowed recovery of viable IEL populations appropriate for further functional assessment. Studies of IELs isolated from neonatal calves revealed that non-major histocompatibility complex (MHC)-restricted cytotoxicity of BCV-infected target cells was more prevalent in calves with concurrent virus infection, suggesting in vivo activation of the cytotoxic response. Peripheral blood mononuclear cells from the same calves did not mediate cytotoxicity, emphasizing the difference in function of lymphocytes isolated from different anatomical sites. IELs from normal adult animals rarely showed spontaneous non-MHC-restricted cytotoxicity. However, interleukin-2 (IL-2) was a potent activator of IEL cytotoxicity in vitro, enhancing the killing of BCV-infected target cells after just 18 h of treatment. Incubation of IELs with interferon-gamma and tumour necrosis factor (TNF) did not induce cytotoxic activity, but TNF could augment the levels of IL-2-induced cytotoxicity. Although further analysis of the cytotoxic effector cells present in the intestinal epithelium is required, the present study indicates that the IEL population may play a role in enteric antiviral activity.

Animals↗
PubMed1991

Differential induction of tumor necrosis factor alpha in ovine pulmonary alveolar macrophages following infection with Corynebacterium pseudotuberculosis, Pasteurella haemolytica, or lentiviruses.

Soluble mediators such as tumor necrosis factor alpha (TNF-alpha) may be important in the pathogenesis of many chronic pulmonary infections. We examined the ability of Corynebacterium pseudotuberculosis, Pasteurella haemolytica, and ovine lentiviruses (OvLV) to induce TNF-alpha secretion by pulmonary alveolar macrophages (PAM). Bronchoalveolar lavage cells, composed of greater than 90% PAM, were obtained from normal sheep. Bronchoalveolar lavage cells were cultured for 2, 24, 48, 72, or 168 h in endotoxin-free RPMI medium (with 10% autologous serum) or in medium containing one of the following additives: lipopolysaccharide, 1-micron polystyrene beads, C. pseudotuberculosis, P. haemolytica, or one of two plaque-cloned OvLV, 85/28 or 85/34. Lipopolysaccharide, C. pseudotuberculosis, and P. haemolytica induced TNF-alpha activity in PAM cultures as early as 2 h after inoculation, as assessed by a colorimetric cytotoxicity assay. This activity could be blocked by rabbit anti-recombinant bovine TNF-alpha serum. In contrast, medium alone, polystyrene beads, and productive infection by OvLV did not induce TNF-alpha activity in PAM cultures. Bacterial pathogens which infect pulmonary macrophages may elicit the secretion of TNF-alpha within the lungs and lead to the cachectic state associated with chronic pneumonia.

Animals↗
PubMed1991

Expression of bovine herpesvirus 1 glycoprotein gIV by recombinant baculovirus and analysis of its immunogenic properties.

The gene encoding the gIV glycoprotein of bovine herpesvirus 1 has been inserted into the genome of Autographa californica baculovirus in lieu of the coding region of the A. californica baculovirus polyhedrin gene. Recombinant protein was identified by its reactivity with gIV-specific monoclonal antibodies and expressed at high levels (about 85 micrograms per 2.5 x 10(6) cells) in Spodoptera frugiperda (SF9) cells. The recombinant glycoprotein had an apparent molecular mass of 63 kDa, indicating that it was incompletely glycosylated. However, it was transported to and expressed on the cell surface of infected SF9 cells. Furthermore, reactivity with polyclonal and monoclonal antibodies specific for gIV suggested that most epitopes were functionally unaltered on the recombinant gIV. Immunization of cattle with recombinant gIV in crude, partially purified, or pure form resulted in the induction of neutralizing antibodies to BHV-1, which were reactive with authentic gIV. However, the neutralizing antibody titers were lower than those elicited by an equivalent amount of affinity-purified authentic gIV, which appeared to be mainly due to reduced recognition of one of the neutralizing antigenic domains of gIV, designated domain I. The potential use of this recombinant gIV glycoprotein as a vaccine to bovine herpesvirus 1 infection in cattle is discussed.

Animals↗