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Biomedical subjects

R Perez

Publications and source records attributed to R Perez.

At least 55 records · Page 3Linked to original sources
PubMed2000

Sylvatic population of Triatoma infestans from the Bolivian Chaco: from field collection to characterization.

A sylvatic Triatoma infestans DM (dark morph) population detected in the Bolivian Chaco was characterized and compared with various domestic ones. The degree of differentiation of DM was clearly within the T. infestans intra-specific level. Nevertheless marked chromatic and morphometric differences as well as differences in antennal pattern, chromosome banding and randomly amplified polymorphic DNA support the hypothesis of a distinct population. Continuous exchange of insects between wild and domestic habitats seems unlikely in the Chaco.

Animals↗
PubMed2000

Appendicolith revealed on CT in children with suspected appendicitis: how specific is it in the diagnosis of appendicitis?

OBJECTIVE: The purpose of this study was to determine the sensitivity, specificity, and positive and negative predictive values of a diagnosis of appendicitis when CT without enteric contrast material reveals an appendicolith in children with suspected appendicitis. MATERIALS AND METHODS: A retrospective review of children who underwent abdominal CT for suspected appendicitis over a 25-month period was performed to identify patients with an appendicolith. An age-matched group of patients examined for trauma served as controls. RESULTS: CT was performed in 104 children. Appendicitis was present in 60 (58%) of 104 children; 39 (65%) of 60 had an appendicolith. Appendicitis was not present in 44 (42%) of 104; six (14%) of 44 had an appendicolith. An appendicolith detected on CT had a sensitivity of 65% and a specificity of 86% for the radiologist diagnosing appendicitis. An appendicolith had a positive predictive value of 74% and a negative predictive value of 26%. Among the control population, two (3%) of 74 children had an appendicolith. This number was statistically significant compared with children in the study group with an appendicolith and abdominal pain, but without appendicitis (p = 0.02). CONCLUSION: Although an appendicolith is significantly associated with appendicitis, the detection of an isolated appendicolith on CT is not sufficiently specific to be the sole basis for the diagnosis of acute appendicitis.

Adolescent↗
PubMed2000

Focused obstetrical clinic for active duty junior enlisted service women: model for improved outcomes.

OBJECTIVE: To evaluate the utility of an interdisciplinary clinic in improving perinatal outcomes for all pregnant patients of junior enlisted rank (E4 and below) in response to previous reports that this group is at higher risk for adverse outcomes. METHODS: The study population included all junior enlisted active duty patients (E4 and below) delivering between January 1, 1993, and June 30, 1996. Outcomes for patients receiving care in a focused active duty obstetrical clinic were compared with outcomes in similar cohorts of senior active duty patients (E5 and above) and non-active duty pregnant patients. Evaluation was based on perinatal outcomes, including chorioamnionitis, postpartum hemorrhage, intrauterine growth retardation, cesarean delivery, preterm delivery rates (< 37 weeks), postterm delivery rates (> 41 weeks), postpartum days, mean gestational age at delivery, mean delivery weights, Apgar scores at 1 and 5 minutes, preeclampsia, and premature labor. Variables with potential to confound perinatal outcomes were also studied. Confounding variables included tobacco use, gestational diabetes, chronic hypertension, thyroid disease, history of substance abuse, and alcohol use. Power analysis accomplished before initiation of the study showed adequate sample size (> 240 patients in each group) to demonstrate statistically different rates of preterm delivery. Statistical analysis was done using the chi 2 test for categorical variables and Student's t test for continuous variables. RESULTS: There were no statistical differences between junior active duty patients, senior active duty patients, and non-active duty patients in preterm delivery and other outcome variables. CONCLUSION: The focused obstetrical clinic, conducted for junior enlisted soldiers by a senior nurse practitioner, appears to provide an intervention that ensures perinatal outcomes equal to those of both the non-active duty and the senior active duty population.

Adult↗
PubMed2000

Intravenous ifosfamide/mesna is associated with depletion of plasma thiols without depletion of leukocyte glutathione.

Depletion of cellular glutathione (GSH) enhances the efficacy of many anticancer agents in preclinical systems. Limited published data showing depletion of GSH in vitro and in patients by ifosfamide and/or mesna provided the rationale for a Phase I trial. Ifosfamide and mesna were infused over 24 and 36 h, respectively, at equal daily doses; carboplatin was given after ifosfamide to a target plasma area under the curve of 4 mg x min x ml(-1). Plasma and peripheral WBC thiols were quantitated by high-performance liquid chromatography. The dose of ifosfamide was escalated from 2 to 8 g/m2; the maximum tolerated dose was 6 g/m2. Significant depletion in plasma cysteine and homocysteine, precursors for GSH synthesis, was observed (maximum, 95% to >99% at 8 g/m2). Plasma mesna and cysteine/ homocysteine levels were inversely correlated; nadir levels of cysteine/homocysteine were maintained for several hours after ifosfamide infusion had stopped and while mesna infusion was continuing. In vitro coincubation experiments confirmed that mesna reduces these thiols from disulfides to sulfhydryls, which are readily cleared, as evidenced by the significantly increased rate of excretion of cysteine in urine. In contrast, ifosfamide/mesna treatment caused a moderate depletion of plasma GSH in only 60% of the patients, with a nadir at 24 h and recovery immediately after the end of ifosfamide infusion. The GSH depletion in these patients was not dose related. The profile of GSH recovery in plasma after ifosfamide and the fact that mesna could not reduce GSH disulfides in vitro suggest that the observed GSH depletion in plasma in 60% of the patients may be related to direct reactions of GSH with ifosfamide metabolites and/or mesna. Our results indicate that mesna is a modulator of GSH precursors and that a prolonged infusion of mesna may be required to achieve GSH precursor starvation and the consequent GSH depletion in cells.

Acetaldehyde↗
PubMed2000

Evolution of techniques for ultrasound-guided palladium 103 brachytherapy in 950 patients with prostate cancer.

PURPOSE: Brachytherapy is an effective, low-morbidity, cost-effective treatment for adenocarcinoma of the prostate. Although both iodine 125 and palladium 103 have been used extensively over the last 14 years, 103Pd (Theraseed) provides a more rapid initial dose and therefore better control of higher Gleason grade tumors. We assessed a highly refined methodology for 103Pd brachytherapy in patients with prostate cancer and compared outcomes before and after making adjustments in technique. MATERIALS AND METHODS: Standard brachytherapy techniques were modified to include combination of preplanning with real-time adjustment, placing all needles at once to minimize prostate movement, using monitored anesthesia control sedation during preoperative volume study and cystoscopy, and several other small but important changes. Charts were reviewed from 950 patients treated with 103Pd implants from 1991 through 1999. Prostate-specific antigen (PSA) and biopsy data before and after 1993 were compared for 733 patients whose data qualified for analysis. RESULTS: At 1 and 5 years after treatment, 85-88% of patients had stable PSA <1.5 ng/mL. Biopsies were negative in 90-94% at 2 years. CONCLUSION: The modification in techniques provides positive results that remain stable over time.

Adenocarcinoma↗
PubMed1999

Effect of optical digitizer selection on the application accuracy of a surgical localization system-a quantitative comparison between the OPTOTRAK and flashpoint tracking systems.

Application accuracy is a crucial factor for stereotactic surgical localization systems, in which space digitization camera systems are one of the most critical components. In this study we compared the effect of the OPTOTRAK 3020 space digitization system and the FlashPoint Model 3000 and 5000 3D digitizer systems on the application accuracy for interactive localization of intracranial lesions. A phantom was mounted with several implantable frameless markers which were randomly distributed on its surface. The target point was digitized and the coordinates were recorded and compared with reference points. The differences from the reference points represented the deviation from the "true point." The root mean square (RMS) was calculated to show the differences, and a paired t-test was used to analyze the results. The results with the phantom showed that, for 1-mm sections of CT scans, the RMS was 0.76 +/- 0. 54 mm for the OPTOTRAK system, 1.23 +/- 0.53 mm for the FlashPoint Model 3000 3D digitizer system, and 1.00 +/- 0.42 mm for the FlashPoint Model 5000 system. These preliminary results showed that there is no significant difference between the three tracking systems, and, from the quality point of view, they can all be used for image-guided surgery procedures.

Equipment Design↗
PubMed1999

Donor cell induced CD69 expression and intracellular IL-2 and IL-4 production by peripheral blood lymphocytes isolated from kidney transplant recipients.

Flow cytometry assays, which measure CD69 activation and intracellular cytokine production, have been used to measure peripheral blood lymphocyte (PBL) responses to in vitro antigen exposure. In the present study, we show that, in healthy individuals and immunosuppressed kidney transplant recipients, CD69 expression and intracellular cytokine production by peripheral blood T cells compare favorably to thymidine uptake as a measure of PBL response to alloantigen in mixed leukocyte culture (MLC). Heparinized whole blood from 23 healthy individuals was incubated for 24-48 h with 3rd party allogeneic monocytes; blood from twelve kidney transplant recipients was incubated with monocytes from their kidney donor and with monocytes from unrelated individuals. The percentage of T cells expressing surface CD69 or intracellular IL-2 or IL-4 was determined by 3-color flow cytometry. We identified 5 donor-specific response patterns in our kidney transplant group. One transplant recipient was hyporesponsive; his cells did not express CD69 or produce IL-2 in response to either donor or 3rd party allogeneic cells. All other transplant recipients expressed CD69 and IL-2 in response to 3rd party allogeneic cells. Two had no response to donor cells (donor-specific hyporesponsiveness), three had donor-specific anergy (CD69 expression without cytokine production in response to donor cells), five had a donor-specific Thl response (CD69 expression and IL-2 production in response to donor cells), and one had a donor-specific Th2 response (CD69 expression and IL-4 but not IL-2 production in response to donor cells). Rapid measures of donor-specific hyporesponsiveness such as CD69 activation antigen expression and intracellular cytokine production may prove valuable in monitoring lymphocyte function and aid in the long-term management of kidney transplant recipients.

Antigens, CD↗
PubMed1999

Role of cytomegalovirus infection in allograft rejection: a review of possible mechanisms.

Several lines of evidence indicate that viral infections, particularly with cytomegalovirus (CMV), play a role in the pathogenesis of solid organ allograft rejection. A diagnostic feature of acute rejection is infiltration of allograft parenchyma by lymphocytes, a process regulated by induction of adhesion molecules on vascular endothelial cells and their ligand on leucocytes. Data derived from biopsies of CMV-infected transplant recipients, as well as from experimental models of transplantation, indicate that CMV infection can result in an upregulation of such adhesion molecules, thereby facilitating the inflammatory process. Infection with CMV is also associated with an increased expression of MHC class II on multiple cell types. Since recognition of nonself MHC antigens is the major determinant of allograft rejection, an upregulation of these molecules could contribute to graft failure. Infection with CMV has also been implicated in the induction of smooth muscle proliferation and intimal thickening, both hallmarks of transplant atherosclerosis, which constitutes the most common cause of heart allograft failure. CMV can be classified into four, possibly five, different genotypes based on restriction length polymorphism of the envelope glycoprotein B gene; these genotypes may exhibit varied geographic and demographic frequency distributions and also differ in their pathogenicity and cell tropism. Further studies are needed to evaluate these issues and in particular the genetic contribution of the recipient to CMV modulation of rejection.

Animals↗
PubMed1999

Relationship between ethylene response manipulation and volatile production in Jonagold variety apples.

The ripening of Jonagored Jonagold apple fruit (Malus x domestica Borkh.) during development was manipulated with preharvest applications of ReTain or a combination of ReTain plus Ethrel. The fruits, harvested preclimacteric at approximately the same stages of maturity, were stored in refrigerated air (RA) for 45 days or in controlled atmosphere (CA) for 180 days at 0 degrees C. Volatile evolution, ethylene production, and respiration of stored fruit were studied during poststorage holding at 22 degrees C. ReTain reduced volatile production by 19%, but application of Ethrel to ReTain-treated fruit increased production to control levels. The inhibition of volatile production by ReTain appears to be independent of respiration but may be related to the ethylene-producing capacity of the fruit. Although ReTain reduced flavor-related volatile esters, it did not affect levels of the compound responsible for the typical spicy flavor in Jonagored Jonagold fruit, 4-methoxy-2-propenylbenzene. The CA-stored fruit had a much reduced production of volatile compounds compared to RA-stored fruit, with more discernible effects in ReTain-treated fruit. Ethrel application to ReTain-treated fruit improved the volatile production intermediate between the ReTain alone and control in CA-stored fruit. The data collectively suggest that ReTain may have some promise for better scheduling of harvest of apples with no appreciable loss in RA-stored fruit quality. Reduction in production of alpha-farnesene by ReTain may also reduce the potential for scald development in CA-stored fruit.

Chromatography, Gas↗
PubMed1999

Interocular temporal delay sensitivity in the visual cortex of the awake monkey.

Due to the separation of the eyes, temporal retinal disparities are created during binocular stimulation and they have been proposed to be the basis of several stereo-visual effects. This paper studies the sensitivity of cortical neurons from area V1 to interocular temporal delay in the awake monkey (Macaca mulatta). Forty-four cells were included in this study. Temporal delay sensitivity was observed in 59% of them. About half of these temporal-delay-sensitive cells were also sensitive to the stimulation sequence of the eyes. The cells that preferred one eye to be stimulated first were termed asymmetrical (46%); those which were not sensitive to the eye sequence of stimulation were termed symmetrical (54%). No clear differences were observed in the distribution of delay-sensitive cells according to their eye dominance. Fifty-six percent of balanced cells and 65% of unbalanced cells were sensitive to interocular delay. These data underline the importance of temporal cues for depth perception.

Animals↗
PubMed1999

Novel cross-reactive anti-idiotype antibodies with properties close to the human intravenous immunoglobulin (IVIg).

The most important link between the immune network theory and clinically useful therapies so far is the use of human intravenous immunoglobulin (IVIg) in the treatment of autoimmune diseases. Although still controversial, one of the main mechanisms that has been postulated for the in vivo effects of IVIg, is the selection of immune repertoires through idiotypic interactions. We describe here anti-idiotype IgG monoclonal antibodies (MAbs), which were obtained by immunization of syngeneic mice (Balb/c) with an anti-ganglioside antibody. These anti-idiotype MAbs show multiple idiotypic connections and share some of the properties of the IVIg pool. The antiidiotype (Ab2) MAbs B7 and 34B7 showed heterogeneous binding with the idiotypes of several anti-ganglioside antibodies, MAbs obtained from splenocytes of nonimmunized newborn mice, F(ab')2 fragments of IgG human myeloma proteins, and nonimmunoglobulin antigens. The recognition pattern of the B7 MAb to the idiotypes of human immunoglobulins was also studied using a phage display library obtained from the variable region genes of an asymptomatic AIDS patient and also F(ab')2 fragments obtained from an IVIg pool of healthy human donors. We also demonstrated that these MAbs produced some of the in vitro effects reported for the human IVIg pool, such as the inhibition of cell proliferation of human B and T cell lines and of normal human lymphocytes activated with different mitogens. Another striking property of the MAb B7 was its ability to induce a dose-dependent specific antibody T-cell response in vivo in syngeneic mice. Both anti-idiotype MAbs showed anti-metastatic effect in vivo when injected intravenously to mice inoculated with MB16-F10 melanoma cells. The antimetastatic effect of the antiidiotype MAbs was not observed in athymic mice inoculated with the same tumor. This kind of antibody can become an interesting tool for further exploration of the role of idiotypic network connections in the regulation of the immune system and to study the effects of interventions on network connectivity in experimental autoimmune disease, using a reagent better chemically defined than the IVIg pool.

Animals↗
PubMed1999

Urinary incontinence among female soldiers.

A self-administered questionnaire was developed to assess the prevalence of urinary incontinence among active duty female soldiers. The questionnaire also addressed basic demographic information, including height, age, weight, and the subjects' present and past military activities. Adaptive measures that the soldiers commonly used to continue exercising and perform their duties were also explored. Seven hundred thirteen questionnaires were handed out to female soldiers at Fort Lewis (Washington), Fort Benning (Georgia), and Fitzsimons Army Medical Center (Colorado) during preparation for physical fitness tests. Of the 563 soldiers (79%) who returned completed questionnaires, 31% indicated that they commonly experienced urinary incontinence during duty and/or training to the extent that it interfered with job performance, hygiene, or was socially embarrassing. Thus, urinary incontinence is a pervasive problem among female soldiers.

Activities of Daily Living↗
PubMed1999

Dorzolamide effect on ocular blood flow.

PURPOSE: To evaluate the effect of dorzolamide on ocular blood flow in normal and glaucomatous eyes. METHODS: Twenty-six eyes with documented open-angle glaucoma of 26 patients and 13 normal control eyes of 8 age-matched subjects were included in this study. All eyes underwent color Doppler imaging for measuring peak-systolic velocity, end-diastolic velocity, and resistance index in the ophthalmic and central retinal arteries and the maximal and minimal velocities in the central retinal vein. Eyes were grouped in control and initial and advanced glaucoma categories. Measurements were made in all groups before and after application of topical dorzolamide. Intragroup comparisons between baseline and dorzolamide conditions were made using paired Student's t-test. Intergroup comparisons under baseline conditions between normal and glaucomatous eyes were made by using the one-way ANOVA test. Statistical significance was set at P < 0.05. RESULTS: The peak-systolic velocity of the central retinal artery in glaucomatous eyes and the end-diastolic velocity of the ophthalmic and central retinal arteries in all groups were significantly higher after application of dorzolamide. The minimal velocity of the central retinal vein showed significantly higher values after dorzolamide, whereas the maximal velocity remained unchanged. The peak-systolic velocity of the ophthalmic artery in all groups and the peak-systolic velocity of the central retinal artery in normal eyes also remained unchanged. The resistance index was significantly lower in the ophthalmic and central retinal arteries in all groups after dorzolamide. The intraocular pressure was significantly reduced in all groups after dorzolamide. Under baseline conditions normal control eyes and glaucomatous eyes showed differences in various measurements. Peak-systolic velocity was significantly lower in glaucomatous eyes than in normal control eyes with the exception of the ophthalmic artery in the initial glaucoma group. End-diastolic velocity was lower in glaucomatous eyes than in control eyes in both arteries. Maximal and minimal velocities of the central retinal vein were lower in glaucomatous eyes than in normal control eyes. Resistance index was higher in glaucomatous eyes than in normal control eyes in the ophthalmic artery but not in the central retinal artery. CONCLUSIONS: Most hemodynamic parameters of intraocular and periocular vessels improve after application of topical dorzolamide in both normal control and glaucomatous eyes. Dorzolamide should be regarded as a useful drug for treatment of glaucoma not only because it reduces intraocular pressure but also because it improves the ocular blood supply.

Aged↗
PubMed1998

Sodium butyrate upregulates Kupffer cell PGE2 production and modulates immune function.

The immunosuppressive effect of portal venous blood transfusions in organ transplantation has been well established and may be mediated by increased Kupffer cell production of the immunosuppressive arachidonic acid metabolite prostaglandin E2 (PGE2). In this study, butyrate, a short-chain fatty acid known to enhance gene transcription, is hypothesized to enhance Kupffer cell PGE2 production by altering cyclooxygenase or phospholipase A2 (PLA2) activity, thus augmenting the immunosuppressive effect of portal venous transfusion. Lewis rats were given a portal venous transfusion of Wistar-Firth blood or saline 1 h prior to Kupffer cell harvest. The in vitro effects of butyrate on Kupffer cell PGE2 production, cyclooxygenase, and PLA2 activity were assessed. Kupffer cell tumor necrosis factor-alpha (TNFalpha) production was also assessed due to its sensitivity to PGE2 and its proinflamatory effects. Kupffer cells from portally transfused animals produced significantly more PGE2 than saline-transfused controls. Addition of butyrate to the culture medium further increased PGE2 production by as much as sevenfold in Kupffer cells of portally transfused animals. Other short-chain fatty acids, propionate and hexanoate, did not increase PGE2 production. Butyrate added to Kupffer cells from transfused animals slightly upregulated inducible cyclooxygenase (COX-2) mRNA levels as measured by both Northern blot and reverse-transcriptase polymerase chain reaction and increased PLA2 activity fivefold as measured by Western blot. Kupffer cell immune function was also affected by in vitro butyrate treatment with a significant decrease in the production of TNFalpha. Thus, butyrate may be a useful immunoregulatory agent in organ transplantation protocols which seek to enhance transcription of immunosuppressive molecules.

Animals↗
PubMed1998

Kupffer cell-mediated lymphocyte apoptosis: a PGE2-dependent mechanism of portal venous transfusion-induced immunosuppression?

BACKGROUND: Kupffer cells, after exposure to alloantigen via the portal vein, mediate an immunosuppressive effect involving enhanced production of PGE2. We hypothesize that up-regulation of Kupffer cell CoA-independent transacylase (CoA-IT) by portal venous transfusion (PVT) is a possible mechanism of increased PGE2 production. Additionally, enhanced lymphocyte apoptosis, a process known to be macrophage dependent and facilitated by PGE2, is postulated as a possible mechanism of PVT-induced, Kupffer cell-mediated immunosuppression. METHODS: Lewis rat Kupffer cells were isolated after portal venous infusion with 1 ml of Wistar-Firth blood (PVT) or saline (PV sal). Kupffer cell PGE2 production and CoA-IT activity was assessed. Lymphocyte apoptosis after exposure to PVT or PV sal-treated Kupffer cells was also assessed by flow cytometry. RESULTS: PVT-treated Kupffer cells produced significantly more PGE2 and had increased CoA-IT activity when compared to PV sal-treated Kupffer cells. Treatment of Kupffer cells with a selective inhibitor of CoA-IT significantly decreased PVT-induced Kupffer cell PGE2 production. Increased lymphocyte apoptosis was observed after coculture with PVT-treated Kupffer cells compared to PV sal-treated cells. CONCLUSIONS: PVT increases Kupffer cell PGE2 production via increased CoA-IT activity and induces Kupffer cell-mediated lymphocyte apoptosis. Lymphocyte apoptosis facilitated by Kupffer cells within the hepatic sinusoid may be an important mechanism of PVT-induced immunosuppression in organ transplantation.

Acyltransferases↗
PubMed1998

Modulation of cell responses to horizontal disparities by ocular vergence in the visual cortex of the awake Macaca mulatta monkey.

Horizontal retinal disparity is the most important cue for stereopsis. However, accurate stereoscopic perception requires additional information on fixation distance. The ocular vergence angle may provide information on fixation distance and therefore may be used to calibrate horizontal disparities. We studied the responses of cells from cortical visual area V1 of one macaca mulatta monkey to dynamic random dot stereograms at different ocular vergence angles. We observed that in about half of cells sensitive to horizontal disparity the vergence angle modifies the cell responses to horizontal disparities. These results suggest that vergence angle may be used to calibrate horizontal disparities for fixation distance.

Animals↗