Search PubMed⌕ Search

Biomedical subjects

B Perez

Publications and source records attributed to B Perez.

At least 19 recordsLinked to original sources
PubMed2005

Towards single screening tests for brucellosis.

This paper describes an indirect enzyme-linked immunosorbent assay (I-ELISA) and a fluorescence polarisation assay (FPA), each capable of detecting antibody in several species of hosts to smooth and rough members of the genus Brucella. The I-ELISA uses a mixture of smooth lipopolysaccharide (SLPS) and rough lipopolysaccharide (RLPS) as the antigen, and a recombinant protein A/G conjugated with horseradish peroxidase as the detection reagent. When using individually determined cutoff values, the SLPS/RLPS combined-antigen I-ELISA detected antibody in slightly more animals exposed to SLPS or to RLPS than did I-ELISA procedures using each individual antigen separately. Similarly, the assay using combined antigens detected antibody in slightly fewer animals not exposed to Brucella sp. When a universal cutoff of 10% positivity was used (relative to strongly positive control sera of each species), the overall performance index (percentage sensitivity plus percentage specificity) value decreased by 1.0 (from 199.4 to 198.4). In the FPA, it was not possible to use a universal cutoff without significant loss of performance. The overall sensitivity value for the FPA using the combined FPA antigen was 1.0% lower than using the O-polysaccharide (OPS) from SLPS and 9.1% higher than using the core antigen (CORE) from RLPS. When the combined antigen was used, the FPA specificity was slightly higher (1.2%) than from only the OPS, and considerably higher (12.6%) than the CORE. Overall, both the I-ELISA and the FPA with combined antigens were suitable as screening tests for all species of Brucella in the animal species tested.

Animal Diseases↗
PubMed2004

Enzyme immunoassay for the diagnosis of brucellosis: chimeric Protein A-Protein G as a common enzyme labeled detection reagent for sera for different animal species.

A recombinant protein combining the immunoglobulin binding sites of Proteins A and G, conjugated with horseradish peroxidase was used as a universal detection reagent for the assessment of antibodies against Brucella spp. The reagent was applied in an indirect enzyme immunoassay for detection of antibodies to smooth lipopolysaccharide antigen in sera from Brucella spp. exposed and non-exposed cattle, sheep, goats and pigs and to antibodies to rough lipopolysaccharide in sheep, dogs and cattle. The results were similar to those obtained when murine monoclonal antibody-enzyme conjugates were used. An added advantage was that a universal cut-off for all tests using the proteins A and G detection reagent could be established, simplifying diagnostic interpretation of the data.

Animals↗
PubMed2004

Spinal anesthesia for cesarean section following inadequate labor epidural analgesia: a retrospective audit.

BACKGROUND: High blocks have been reported when spinal anesthesia is used for cesarean section following inadequate labor epidural analgesia. We have therefore modified the practice at our institution to minimize this risk and conducted a retrospective observational study of outcome following the change of practice. METHOD: The records of 115 women with inadequate epidural labor analgesia who required cesarean section between July 1998 and January 2002 were studied. No epidural boluses were administered in the 30 min preceding spinal anesthesia and a reduced spinal dose, median (range) 9.38 mg (7.5-11.3 mg) of 0.75% hyperbaric bupivacaine and fentanyl 15 microg (10-25 microg) was used. Patients were left sitting for 2 min and then positioned supine with left uterine displacement and were closely monitored for symptoms or signs that would suggest a high block. RESULTS: No parturient developed a high spinal necessitating intubation, and there was no adverse neonatal outcome. CONCLUSION: These findings do not conclusively establish this method as safe, but should spinal anesthesia for cesarean section following suboptimal labor epidural analgesia be considered, avoiding epidural boluses immediately preceding spinal injection, using a lower spinal dose, and delayed supine positioning following spinal injection may be advisable.

Adult↗
PubMed2004

Rough lipopolysaccharide of Brucella abortus RB51 as a common antigen for serological detection of B. ovis, B. canis, and B. abortus RB51 exposure using indirect enzyme immunoassay and fluorescence polarization assay.

Rough lipopolysaccharide (RLPS) antigens were prepared from cultures of Brucella abortus RB51, B. ovis, and B. canis. The preparations were standardized by weight and tested with sera from cattle immunized with B. abortus RB51, sheep infected with B. ovis, and dogs infected with B. canis. Populations of unexposed animals of each species were also tested. The tests used were the indirect enzyme immunoassay (IELISA) using RLPS and the fluorescence polarization assay (FPA) using RLPS core fractions, labeled with fluorescein isothiocyanate. The IELISA using B. abortus RB51 RLPS antigen resulted in sensitivity and specificity values of 94.8% and 97.3%, respectively, when testing bovine sera, 98.5% and 97.8% when testing ovine sera, and 95.8% and 100% when testing dog sera. The IELISA using B. ovis RLPS antigen gave sensitivity and specificity values of 80.5% and 91.7%, respectively with bovine sera, 98.9% and 93.8% with sheep sera, and 70.8% and 79.8% with dog sera. The IELISA using B. canis RLPS antigen resulted in sensitivity and specificity values of 97.0% and 97.4%, respectively, with bovine sera, 96.2% and 96.3% with sheep sera, and 95.8% and 98.8% with dog sera. Labeling RLPS core from B. ovis and B. canis with fluorescein was not successful. B. abortus RB51 core labeled with fluorescein resulted in sensitivity and specificity values of 93.5% and 99.8%, respectively, with bovine sera and 78.1% and 99.0% with sheep sera. It was not possible to test the dog sera in the FPA.

Animals↗
PubMed2001

Fluorescence polarization assay for the diagnosis of bovine brucellosis: adaptation to field use.

A fluorescence polarization assay (FPA) was used to test whole blood samples prepared by mixing blood cells from cattle without exposure to Brucella abortus (B. abortus) with sera from animals with confirmed (bacteriologically) infection. A cut-off value between negative and positive values was initially established to be 87.2mP. This value was changed to 95mP to increase assay specificity without loss of sensitivity when testing blood samples from negative animals. The FPA technology was applied to whole blood samples in the field and to stored whole blood samples using two diluent buffers. Relative sensitivity and specificity values for the FPA performed in the field, based on buffered antigen plate agglutination test and competitive enzyme immunoassay results were 95.3 and 97.3%, respectively. However, to obtain maximum sensitivity and specificity, a cut-off value of 105mP was determined for fresh whole blood samples. The relative sensitivity and specificity values of the FPA when testing stored whole blood samples were 100% each using a 95mP cut-off.The usefulness of the FPA for testing whole blood samples in the field was demonstrated.

Agglutination Tests↗
PubMed2001

Validation of the fluorescence polarization assay for detection of milk antibody to Brucella abortus.

A fluorescence polarization assay (FPA) for detection of antibody to Brucella abortus in individual milk samples was developed and validated. Samples from 190 cattle from which B. abortus was isolated; milk samples from cattle in herds infected with B. abortus (n = 1,086) and positive in the milk ring test (MRT), as well as milk samples from Canadian cattle (with no evidence of brucellosis, n = 2,974) were tested by the indirect enzyme immunoassay (IELISA) and the FPA. The sensitivity (based on samples from culture positive cattle) and specificity (based on Canadian milk samples) of the IELISA and the FPA were 100%. The relative sensitivity value obtained with milk from cattle of infected herds and the specificity values of the IELISA were 98.5 and 99.9%, respectively. The relative sensitivity and specificity of the FPA with the same samples were 82.2 and 99.4% using a cutoff value of 90 millipolarization units (mP). The low relative sensitivity value of the FPA was shown, by competitive enzyme immunoassay (CELISA), to be due to vaccinal antibody (assumed as vaccinal antibody against B. abortus Sl19 is excluded by the FPA and CELISA but not by the MRT and the IELISA), present in some of the milk samples. The FPA is a homogeneous assay which, unlike the MRT and the IELISA, may be used for testing in the field.

Animals↗
PubMed2000

In vitro expression analysis of R68G and R68S mutations in phenylalanine hydroxylase gene.

Phenylketonuria (PKU), an autosomal recessive disorder caused be a deficiency of hepatic phenylalanine hydroxylase (PAH), is clinically very heterogeneous. At the molecular level, more than 400 mutations in the PAH gene are known to date, which in different genotype combinations could account for biochemical and clinical variability of symptoms. In vitro expression studies on R68G and R68S mutations causing mild phenylketonuria are presented.

Adult↗
PubMed1999

Validation of the fluorescence polarization assay as a serological test for the presumptive diagnosis of porcine brucellosis.

Sera from Canadian pigs (brucellosis free, n = 14037) and sera from pigs infected with Brucella suis (n = 401) were tested by the buffered antigen plate agglutination test, the complement fixation test, an indirect and a competitive enzyme immunoassay and a fluorescence polarization assay. The results were analysed and assay sensitivity and specificity estimates were calculated. The sensitivity and specificity of the tests were as follows: the buffered antigen plate agglutination test, 77.1 and 96.9%; the complement fixation test (considering anticomplementary sera as negative), 93.3 and 95.5%; the complement fixation test (considering anticomplementary sera as positive), 58.1 and 99.9%; the indirect enzyme immunoassay, 94.0 and 97.9%; the competitive enzyme immunoassay, 90.8 and 96.6%; and the fluorescence polarization assay, 93.5 and 97.2%; respectively. It was concluded that the fluorescence polarization assay was a valuable asset to the diagnosis of porcine brucellosis because of its accuracy, ease of performance and relative cost.

Agglutination Tests↗
PubMed1998

Diagnosis of bovine brucellosis using a homogeneous fluorescence polarization assay.

To evaluate the fluorescence polarization assay (FPA) for the serological diagnosis of bovine brucellosis, 118 sera from cattle which were culture positive for Brucella abortus, 1751 sera from cattle from premises containing cattle infected with B. abortus, 1222 sera from cattle vaccinated with B. abortus strain 19 and 1199 sera from cattle with no evidence of brucellosis were tested in Argentina, Chile, Mexico and in the American states of Iowa, Missouri and Texas. Initial determination of serological positivity and negativity was based upon reactivity in currently used serological tests, consisting of a rapid screening test, the rose-bengal or the buffered plate antigen tests, followed by a second serological test, the complement fixation test. Sensitivity of the FPA (sera from culture positive animals) ranged from 87.5% to 100%. Serological positivity of cattle from infected premises ranged from 65.5% to 99.0% while the % negative cattle in herds without evidence of brucellosis was between 94.9 and 100%. Of B. abortus strain 19 vaccinated cattle which were positive in at least one in-use serological tests, 88.2% were negative in the FPA. In contrast, previous Canadian studies, sensitivity values were 99.0% and 100% and the specificity in both cases was 100%. This discrepancy was probably due to the use of less well characterized sera in the current study.

Animals↗
PubMed1998

Gamma knife radiosurgery for trigeminal neuralgia: results and expectations.

BACKGROUND: Trigeminal neuralgia is a disabling pain syndrome responsive to both medical and surgical therapies. Stereotactic radiosurgery using the gamma knife can be used to inactivate a specified volume in the brain by cross firing 201 photon beams. We evaluated pain relief and treatment morbidity after trigeminal neuralgia radiosurgery. METHODS: All evaluable patients (n = 106) had medically or surgically refractory trigeminal neuralgia. A single 4-mm isocenter of radiation was focused on the proximal trigeminal nerve just anterior to the pons. For follow-up an independent physician who was unaware of treatment parameters contacted all patients. RESULTS: After radiosurgery, 64 patients (60%) became free of pain and required no medical therapy (excellent result), 18 (17%) had a 50% to 90% reduction (good result) in pain severity or frequency (some still used medications), and 9 (9%) had slight improvement. At last follow-up (median, 18 months; range, 6-48 months), 77% of patients maintained significant relief (good plus excellent results). Only 6 (10%) of 64 patients who initially attained complete relief had some recurrent pain. Radiosurgery dose (70-90 Gy), age, surgical history, or facial sensory loss did not correlate with pain relief. Poorer results were found in patients with multiple sclerosis. Twelve patients developed new or increased facial paresthesias after radiosurgery (10%). No patient developed anesthesia dolorosa. There was no other procedural morbidity. CONCLUSIONS: Gamma knife radiosurgery is a minimally invasive technique to treat trigeminal neuralgia. It is associated with a low risk of facial paresthesias, an approximate 80% rate of significant pain relief, and a low recurrence rate in patients who initially attain complete relief. Longer-term evaluations are warranted.

Adult↗
PubMed1998

Judicious resection and/or radiosurgery for parasagittal meningiomas: outcomes from a multicenter review. Gamma Knife Meningioma Study Group.

BACKGROUND: Parasagittal meningiomas, especially when associated with the middle or posterior third of the superior sagittal sinus, pose difficult management challenges. Initial surgical excision is associated with high morbidity and frequent tumor recurrence after subtotal resection. Neurological deficits are cumulative when multiple resections are required. No consistent management approach exists for patients with such tumors. In addition to observation, management options include resection, stereotactic radiosurgery, or fractionated radiation therapy used alone or in combination. METHODS: Sixteen centers where resection, gamma knife radiosurgery, and/or radiation therapy were available provided management data on 203 patients with histologically benign meningiomas from the time of initial diagnosis through follow-up after radiosurgery. The timing of resections, parameters of radiosurgery, rates of tumor control, morbidity, and functional patient outcomes were studied. The median follow-up duration in this study was 3.5 years (maximum, 33 yr after presentation and 6 yr after radiosurgery). RESULTS: The tumors were located in the anterior superior sagittal sinus in 52 patients, at the middle of the sinus in 91, and at the posterior portion of the sinus in 60. The mean tumor volume at the time of radiosurgery was 10 cc. In patients who underwent radiosurgery as the primary therapy (n = 66), the 5-year actuarial tumor control rate was 93 +/- 4%. No clinical failure (need for additional therapy or worsened neurological function) occurred in patients who had smaller tumors (<7.5 cc) and who had never undergone resection (n = 41). The 5-year control rate for patients with previous surgery was only 60 +/- 10%; the control rate for the radiosurgery-treated volume was 85%. Most failures resulted from remote tumor growth. Multivariate analyses identified significantly decreased tumor control with increasing tumor volume (P = 0.002) and previous neurological deficits (P = 0.002). The rate of transient, symptomatic edema after radiosurgery was 16%, was more common with larger tumors, and occurred within 2 years. Of 33 patients who were employed at the time of radiosurgery for whom a minimum of 1 year of follow-up data were available, 30 remained employed (91%). A decrease in functional status after radiosurgery was noted in only 3 of 33 (9%) employed and 7 of 77 (9%) unemployed patients. CONCLUSION: In patients with smaller tumors (<3 cm in diameter) and patent sagittal sinuses, we advocate radiosurgery alone as the first surgical procedure. Patients with larger tumors and those with progressive neurological deficits resulting from brain compression should first undergo resection. Planned second-stage radiosurgery should be performed soon afterward for any residual tumor nodule or neoplastic dural remnant. Multimodality management may enhance long-term tumor control, reduce the need for multiple resections, and maintain the functional status of the patient.

Aged↗
PubMed1998

Enzyme immunoassays for serological diagnosis of bovine brucellosis: A trial in Latin America.

The results of a field trial conducted in Latin America with two indirect enzyme-linked immunosorbent assays (ELISAs) and two competitive ELISAs (CELISAs) for the detection of bovine antibody to Brucella abortus are reported. One of the CELISA formats performed most accurately. The percentage of positive reactions in the CELISA relative to the selected positive rose bengal agglutination test (RBT) and complement fixation test (CFT) results was 97.47%, the percentage of negatives relative to the selected negative RBT and CFT results for unexposed cattle was 98.32%, and the percentage of negatives in cattle vaccinated with B. abortus 19 was 96.51%. The same assay format under Canadian conditions had an actual sensitivity of 100%, a specificity of 99.90% in nonvaccinates, and a specificity of 97.7% in a strain 19-vaccinated population. Overall, the CELISA performed as expected and the results were not dissimilar from the results obtained in the Canadian study. This provided further evidence that this CELISA can in many instances differentiate infected cattle from those that are vaccinated or infected with a cross-reacting organism while still giving very few false-positive or false-negative results.

Agglutination Tests↗
PubMed1997

Incidence of dehiscences in the fallopian canal.

Fifty human temporal bones from necropsies were used to study the frequency of canal dehiscences in detail along the course of the facial nerve. Specifically, the study focused on bony dehiscences in the fallopian canal and vascular communications between the facial nerve and the surrounding bone. High frequency of dehiscences at the oval window (60%) and in the pyramidal segment (54%) were found. These dehiscence rates are in agreement with published reports. A 20% rate of dehiscences at the most anterior segment of the tympanic segment was noted and a non-reported high rate (20%) of multiple dehiscences along the course of the fallopian canal in the same temporal bone in specimens of newborns and young children. The significance of these findings in terms of clinical implications is discussed.

Adolescent↗
PubMed1997

The STR252-IVS10nt546-VNTR7 phenylalanine hydroxylase minihaplotype in five Mediterranean samples.

IVS10nt546 (IVS10nt-11g-->a) is the most common molecular defect of the phenylalanine hydroxylase gene causing phenylketonuria in Mediterranean populations. Previous studies have proposed various and alternative hypotheses concerning the geographical origin and pattern of diffusion of this mutation in this area. In this study, this issue was re-examined on a large sample (149) of "Mediterranean" IVS10nt546 mutant alleles analysed with multiallelic intragenic polymorphisms. The analysis of intragenic microsatellite (STR) and minisatellite (VNTR) polymorphisms shows allelic heterogeneity of the IVS10nt546 mutation. Eight STR and three VNTR alleles were found in association with the splicing defect. Of the ten detected STR-VNTR combinations ("minihaplotypes"), we identified a predominant allelic association (VNTR7-STR252) embedded in a RFLP-haplotype 6 background, which seems to correspond to the ancestral gene originating in the Turkey-Israel area. Analysis of both absolute and relative gene frequencies of the STR252-IVS10nt546-VNTR7 minihaplotypes, shows statistically significant (P < 0.02) variations and may suggest gene flow from Turkey and/or Israel to Italy and Spain. The associated migratory events need not be unique in time (and people) but seem to suggest they may be traced back to the expansion of the Neolithic culture and people, thus allowing dating of the origin of this mutation to at least 5000-10000 years ago. Alternative hypotheses are discussed to explain, in light of the available historical and pre-historical evidence, the pattern of diffusion of the IVS10nt546 mutation in the Mediterranean basin.

Gene Frequency↗
PubMed1997

Immunization with bacterial antigens: piscirickettsiosis.

Piscirickettsiosis is a septicaemic disease of salmonid fish caused by the obligated intracellular rickettsia, Piscirickettsia salmonis. This disease was first reported in 1989 in salmon cultured in sea water netpens in southern Chile where it is still a major problem causing high mortality among cultured salmonids. In recent years related agents have been reported in farmed salmonids from Ireland, Canada and Norway. Mortality, however, at these locations has been reported to be low. Because of the recent description of piscirickettsiosis and its aetiological agent, knowledge about the immune response of fish against this organism is limited. At present, there is only one paper in the literature dealing with this subject. To standardise challenge methods for testing the efficacy of vaccination, lethal dose 50% and infectivity dose 50% were determined for coho salmon (Oncorhynchus kisutch) and rainbow trout (O. mykiss) using intraperitoneal (i.p.) injections of P. salmonis. Experiments using bath challenge methods failed to reproduce the disease using rainbow trout although low levels of infection in their tissues were found. In a field trial, using formalin killed bacterins injected i.p. into pre-smolt coho salmon, the fish were naturally challenged by placing them in sea water where endemic piscirickettsiosis occurred. The results showed that some of the vaccinated fish groups experienced lower cumulative mortality than the non-vaccinated control group (X < 0.05), suggesting an immunoprotective response in these animals. A trial was also conducted with formalin-killed bacterins in rainbow trout using different antigen concentrations with and without booster injections. Fish were challenged by IP injection of P. salmonis. Vaccinated fish showed less mortality than their respective infected control. Unfortunately the challenge was not strong enough because mortality in the infected control fish was low (20%). Antibody levels measured by radio-immuno-assay increased until day 40 post vaccination. The highest levels of antibody were obtained in the sera of fish vaccinated with concentrated antigen using booster injections.

Alphaproteobacteria↗
PubMed1996

Development and validation of an indirect enzyme immunoassay for detection of antibody to Brucella abortus in milk.

An indirect enzyme immunoassay for detection of antibody to Brucella abortus in bovine milk was developed and validated using 6238 milk samples from Canadian herds (brucellosis free) and 202 samples from herds infected with B. abortus (from Argentina and Chile). The assay utilized lipopolysaccharide as the antigen, immobilized on the polystyrene matrix, whole milk to test and a mouse monoclonal antibody, specific for an epitope of bovine IgG1, conjugated with horseradish peroxidase. The sensitivity of the assay was 95.2% +/- 3.7% at a confidence limit of 95% for samples from B. abortus infected herds obtained from chile and 98.7% +/- 0.3% at a confidence limit of 95% for samples from similar herds in Argentina. Of the negative milk samples tested, 77 gave a result above the threshold value of 0.200 optical density units. When the 77 false positive samples were retested using 7.5 mM (final concentration) of EDTA and ethyleneglycol-bis-aminoether-N,N,N', N'-tetraacetic acid (EGTA), the number of false positive reactions was reduced to 3, giving a diagnostic specificity of 99.95%. The divalent cation chelating agents did not affect positive reactions and the sensitivity remained the same. Based on control samples included with each assay, the performance of the assay was consistent.

Animals↗
PubMed1996

Value of the determination of TNF-alpha in the plasma of patients with non-Hodgkins lymphoma.

The present report describes the value of the plasma determination of TNF-alpha, at diagnosis, in 43 patients with non-Hodgkin's lymphoma (NHL), related to their clinical presentation and the new International Prognosis Index (IPI). We also compare the levels of TNF-alpha with those of LDH, beta-2-microglobulin (beta-2-m), and ferritin. At diagnosis, the mean values of the quotients between the marker values and the maximum value of normal (ratio:r-) are placed 7 times higher than normal for r-TNF-alpha, whereas those of r-beta-2-m and r-LDH are 2,4 and 1,4 times more respectively. We found a relationship between the value of r-TNF-alpha and the ECOG, Ann Arbor stage, the number of affected extranodal sites, and between the values of r-beta-2-m with r-LDH. The best correlation was obtained between the values of r-TNF-alpha and r-beta-2-m and IPI, however r-TNF-alpha best stratify the four risk groups in this prognosis index.

Aged↗