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Biomedical subjects

R Rivera

Publications and source records attributed to R Rivera.

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

Computed tomography vs clinical and multidisciplinary procedures for early evaluation of severe abdomen and chest trauma--a cost analysis approach.

OBJECTIVE: To compare contrast computed tomography (CT) for evaluating abdominal and vascular chest injuries after emergency room resuscitation with multidisciplinary management based on bedside procedure (BP), e.g., peritoneal lavage, abdomen ultrasonography urography and, if indicated, CT and/or aortography or transesophageal echocardiography. DESIGN: Randomized study. SETTING: Emergency, critical care and radiology departments in a trauma center. PATIENTS: The study was performed in 103 severe blunt trauma patients with a revised trauma index < 8, admitted over a 16 month period and divided into group (G1, n = 52, CT management) and group 2 (G2, n = 51, BP management). INTERVENTIONS: A relative direct cost scale used in our trauma center was applied, and cost units (U) were assigned to each diagnostic test for cost-minimization analysis (abdomen ultrasonograph = 7.5 U, peritoneal lavage = 8 U, urography = 9 U, computed tomography = 9 U, transesophageal echocardiography = 13.5 U, and aortography = 15 U). One unit is approximately equivalent to $43.7. RESULTS: Injury severity score (ISS) was 31.7 +/- 15.4 in G1 and 33.8 +/- 18.3 in G2. Sensitivity for CT was 90.4% (G1) vs 72.5% for BP (G2) in abdomen (P < 0.01) and 60% in chest for evaluating mediastinal hematoma etiology (G1). As Table 2 shows, G1 needed 59 tests for evaluating injuries (1.1 +/- 0.3 tests patient) while G2 required 81 tests (1.68 +/- 0.8 tests/patient) (P < 0.01). The total relative cost was 538 U for G1, 7.04 +/- 2.2 U cost/injury and 10.3 +/- 3.3 U/evaluation of trauma vs 698 U for G2, 9.84 +/- 5.03 U cost/injury and 13.68 +/- 8.5 U/evaluation (P < 0.05). CONCLUSIONS: This cost-minimization study suggests that CT is a more cost-effective method for the post-emergency room resuscitation evaluation of severe abdominal blunt trauma than the multidisciplinary BP. Chest CT is a screening method for mediastinal hematoma but not for etiology.

Abdominal Injuries↗
PubMed1996

Papillary thyroid carcinoma in Mexican patients: clinical aspects and prognostic factors.

The present study characterizes papillary thyroid carcinoma (PTC) in a Mexican patient sample and evaluates potential prognostic factors for recurrence. Clinical records of 229 patients with PTC were analyzed. Surgical specimens were rereviewed and DNA ploidy determined. Cox logistic regression was used to explore prognostic factors. Mean age +/- SD of the patients was 42 +/- 16 years, with a male/female ratio of 24:205. A thyroid mass was the initial manifestation in 99%. Extrathyroid invasion occurred in 45% and nodal metastases in 38%. Mean size +/- SD of the tumors was 3 +/- 2 cm. By flow cytometry 88% of the tumors were DNA euploid and 12% aneuploid. Complete tumor resection was achieved in 83% with an operative mortality of 0.4%. Postoperative hormone suppression was administered in 65% and remnant 131I thyroid ablation in 84%. The 10-year recurrence-free survival was 85%. In the group of patients with tumors totally removed and without distant metastases, none of the 14 evaluated variables demonstrated statistical significance as an independent prognostic factor for recurrence. However, the group of patients in whom a combination of the following factors was present--age > or = 40 years, tumor size > or = 3 cm, local invasion, and lymph node metastases--showed a higher incidence of tumor recurrence.

Adult↗
PubMed1996

A comparative study of two techniques used in immediate postplacental insertion (IPPI) of the Copper T-380A IUD in Shanghai, People's Republic of China.

Chinese women in Shanghai who delivered vaginally and who chose to use an IUD for contraception received a Copper T-380A IUD inserted vaginally within 10 minutes after delivery of the placenta (i.e., immediate postplacental insertion, IPPI). Among them, 97.7% were primipara. The women were randomly divided into two groups: IUD inserted by hand and IUD via ring forceps. The follow-up rate of six months was 95.2%. Using Tietze's life table method and log rank test, the expulsion and other discontinuation rates were compared at three and six months postinsertion between these two different insertion techniques. Expulsions were the main reason for discontinuation. The six-month gross cumulative expulsion rates were 13.3 and 12.7 per 100 women in the hand-insertion group and ring forceps-insertion group, respectively. Discontinuation rates for medical removals (bleeding/pain) were 2.1 and 1.0 in these two groups, respectively. Neither of the differences was statistically significant (p > 0.05). No uterine perforation, infection or pregnancy occurred. The results suggest that these two different insertion techniques do not significantly affect discontinuation rates in vaginal IPPI using the TCu 380A, and the TCu 380A appears to be suitable for postpartum insertion in Chinese women. Other relevant issues, such as breastfeeding and IUD placement in uterine cavity, are also analyzed and discussed in this report.

Adult↗
PubMed1996

Transforming growth factor-alpha (TGF-alpha) and epidermal growth factor-receptor (EGF-R) immunoreactivity in normal and pathologic brain.

Transforming growth factor alpha (TGF-alpha) and epidermal growth factor-receptor (EGF-R) immunoreactivity is observed in the majority of neurons, and in maturing astrocytes, in the developing and adult brain of humans and different species of animals. TGF-alpha and EGF-R co-localize in most neurons and maturing astrocytes, suggesting that most TGF-alpha-producing cells are EGF-R-expressing cells. TGF-alpha and EGF-R immunoreactivity decrease in damaged areas following different insults. However, EGF-R appears in reactive glia, mostly reactive astrocytes, within and surrounding the damaged areas. TGF-alpha and EGF-R immunoreactivity is found in neurons of patients affected by Alzheimer's disease and other forms of dementia, and in neurons of patients suffering from epilepsy owing to different causes, thus pointing to the conclusion that TGF-alpha does not play a significant role in these pathologies. However, EGF-R immunoreactivity occurs in reactive astrocytes and microglia in subacute but not chronic lesions in human cases. Since TGF-alpha is a membrane-anchored growth factor, which may be cleaved leading to the formation of soluble forms, and both the membrane-anchored and soluble forms have the capacity to activate the EGF-R, it is feasible that TGF-alpha in the nervous system may act upon EGF-R-containing neurons through different mechanisms. In addition to distant effects resulting from the release of soluble TGF-alpha, local effects may be produced by establishing direct cell-to-cell contacts (juxtacrine stimulation), or in cells expressing both TGF-alpha and EGF-R (autocrine stimulation).

Animals↗
PubMed1996

In vivo distribution of radioactivity in mice after injection of biodegradable polymer microspheres containing 14C-labeled tetanus toxoid.

Radiolabeled tetanus toxoid (TT) was prepared by detoxifying chromatographically purified tetanus toxin with 14C-labeled formaldehyde. 14C-TT was encapsulated inside poly (D,L-lactide-co-glycolide, 50/50) microspheres (MS) of varying average size (approximately 10 microns and approximately 50 microns). Balb/c mice were injected subcutaneously with 5 Lf (approximately 15 micrograms) of 14C-TT, encapsulated in MS, mixed with blank MS without encapsulated antigen, as soluble antigen or adsorbed onto aluminum phosphate (AlPO4) and radioactivity was monitored at the site of injection, draining lymph nodes, blood, liver, spleen, and kidneys at various intervals. At one day, approximately 95% and 90% radioactivity disappeared from site of injection for soluble TT or blank MS mixed TT and AlPO4 adsorbed TT, respectively, whereas approximately 55% and 70% radioactivity disappeared from site of injection for MS of average size approximately 50 microns and approximately 10 microns, respectively. By 7 days, 99% of radioactivity disappeared from site of injection for soluble TT or blank MS mixed TT, whereas 2-3% radioactivity persisted at the site of injection for AlPO4 adsorbed TT for 4 weeks. In contrast, approximately 20% radioactivity stayed at the site of injection for MS injected mice up to 4 weeks. At all time points, large MS (approximately 50 microns) showed more radioactivity at the site of injection than small MS (approximately 10 microns). Other organs showing radioactivity were draining lymph nodes and kidneys. Small MS with encapsulated TT showed highest level of radioactivity in lymph nodes at 4 h. In kidneys, soluble and AlPO4 adsorbed TT showed a peak of radioactivity at 4 h whereas TT encapsulated in MS showed a peak of radioactivity at 7 days. These results indicate that AlPO4 did not act as a depot for TT at the site of injection, but TT encapsulated in MS did form a depot for approximately 1 month.

Animals↗
PubMed1996

Diphtheria antitoxin levels in US blood and plasma donors.

Plasma samples from 500 blood donors were titrated for diphtheria antitoxin (DAT) by the toxin neutralization (TN) test. Only 1.6% of donors had <0.01 IU/mL DAT, the minimum protective level against diphtheria; 15% had levels between 0.01 and <0.1 IU/mL, indicating basic protection, and 83.4% had levels > or =0.1 IU, indicating full protection. Three hundred fifty samples were studied by ELISA for diphtheria toxoid IgG antibodies to assess the utility of the assay as a quick, convenient method for evaluating diphtheria immunity. Although the correlation between TN and ELISA titers for the 350 samples was high (r = .80), there was no correlation (r = .07) for samples with antitoxin titers <0.1 IU/mL, the level of special interest for serosurveys for protection. Titration of 62 immune globulin samples (prepared from 1957 to 1994) showed that DAT levels in Massachusetts blood donors increased concurrently with increased use of tetanus-diphtheria vaccine in the state.

Animals↗
PubMed1996

Ventilation with positive end-expiratory pressure reduces extravascular lung water and increases lymphatic flow in hydrostatic pulmonary edema.

OBJECTIVE: To analyze the effect of different levels of positive end-expiratory pressure (PEEP) on extravascular lung water and on lymphatic drainage through the thoracic duct during hydrostatic pulmonary edema. DESIGN: Randomized, controlled, experimental study. SETTING: Research laboratory of a tertiary care hospital. SUBJECTS: Eighteen beagle dogs weighing between 10 and 19 kg. INTERVENTIONS: Dogs were anesthetized and cannulated via a thoracic duct. Hydrostatic pulmonary edema was provoked by inflating the balloon of a Foley catheter in the left atrium. Different amounts of PEEP were applied. MEASUREMENTS AND MAIN RESULTS: Extravascular lung water was determined by the double indicator dilution method (indocyanine green in glucoside solution at 0 degree C), and lymphatic drainage was measured every 30 mins. After a baseline measurement, the left atrial pressure was increased to 24 to 26 mm Hg, and measurements were recorded after 30, 60, 90, and 120 mins. The animals were divided into three groups. Group I (n = 6): PEEP of 20 cm H2O was instituted at 120 mins, and the other determinations were made without PEEP; group II (n = 7): PEEP of 10 cm H2O was instituted at 60 and 90 mins; group III (n = 5): PEEP of 20 cm H2O was instituted at 60 and 90 mins. Extravascular lung water increased after the increase of left atrial pressure in all three groups. After 90 mins, the extravascular lung water was significantly greater (p < .01) in group I (no PEEP application) at 21.2 +/- 5.1 mL/kg than in groups II and III (with 10 and 20 cm H2O of PEEP) at 12.8 +/- 2.01 and 14.8 +/- 4.8 mL/kg, respectively. Lymphatic drainage tended to increase over time in all three groups. Ninety minutes after the left atrial pressure increase, lymphatic drainage was significantly greater (p < .05) in group II, at 6.06 +/- 2.53 mL/kg/30 mins, than in group I, at 2.83 +/- 0.76 mL/kg/30 mins. CONCLUSIONS: a) The application of PEEP levels of between 10 and 20 cm H2O limits the increase of extravascular lung water in cases of hydrostatic pulmonary edema; and b) the application of 10 cm H2O of PEEP increases the lymphatic flow through the thoracic duct.

Animals↗
PubMed1996

Choroidal concentration of interferon after retrobulbar injection.

PURPOSE: To determine whether recombinant human interferon alpha-2a (IFN alpha-2a) would diffuse into the choroid in significant amounts from a retrobulbar depot. METHODS: One million international units of IFN alpha-2a were injected into the retrobulbar space of the eyes of 17 rabbits, and choroidal and serum concentrations were measured at 1, 2, 4, 8, 12, and 24 hours. The same dose of IFN alpha-2a was injected subcutaneously into 10 rabbits, and choroidal and serum concentrations were measured at the same intervals for comparison. Parabulbar and ocular tissues were studied by light microscopy for evidence of local toxicity. RESULTS: Peak concentration IFN alpha-2a in the choroid after retrobulbar injection occurred at 2 hours and averaged 32,000 IU/mg. Peak concentration in the serum occurred at 4 hours and averaged 227 IU/ml. Concentrations in choroid and serum fell rapidly, and IFN alpha-2a was not detectible at 24 hours. No IFN alpha-2a was detected in the choroid of the paired eye, and only a trace (< 50 IU/mg) was found in either eye after subcutaneous injection. Light microscopy revealed some lymphocytes in the fat adjacent to the retrobulbar depot after six daily injections of IFN alpha-2a or saline. Sclera, choroid, and retina appeared unaffected. CONCLUSIONS: IFN alpha-2a diffuses into the choroid from a retrobulbar depot in significant amounts. The serum concentration from a retrobulbar injection is < 1% of the choroidal concentration. The retrobulbar route to the choroid may be optimal for testing the effect of IFN alpha-2a on choroidal neovascularization.

Animals↗
PubMed1995

Progestin-only pill use and pill switching during breastfeeding.

The opinions of 20 international experts in reproductive endocrinology and family planning service delivery were solicited concerning contraceptive pill use during breastfeeding and, in particular, to determine whether the experts felt that breastfeeding women who use progestin-only pills (POPs) should be advised to switch to combined estrogen-progestin pills (COCs) during lactation. The experts agreed that POPs can be used safely and effectively throughout the period of lactation and there is no need to switch to another contraceptive method or another type of pill. If, however, a woman wishes to switch to COCs while she is still breastfeeding, it is acceptable for her to do so after six months postpartum.

Contraceptives, Oral, Hormonal↗
PubMed1995

Hereditary spastic paraparesis with dementia, amyotrophy and peripheral neuropathy. A neuropathological study.

Hereditary, probably autosomal recessive, spastic paraparesis in two siblings was associated with dementia of frontal lobe type, amyotrophy and peripheral sensory and motor polyneuropathy. Neuropathological findings correlate with neurological deficits, although neuron loss in the caudate and putamen, substantia nigra, and loss of Purkinje cells were clinically silent. Loss of neurons occurred in all cortical layers of the prefrontal lobe and superior temporal gyrus. Immunohistochemical studies showed reduced parvalbumin immunoreactivity in dendrites, and reduced numbers of calbindin D28k-immunoreactive cells, thus suggesting involvement of cortical local-circuit neurons. Myelin loss, ubiquitin-immunoreactive granular deposits, and nerve fibre degeneration in the white matter of the frontal lobes and corpus callosum were also observed. Cerebral and subcortical white matter abnormalities, together with atrophy of the thalamic dorsomedial complex and anterior nucleus, may have accounted for the development of severe dementia in this patient.

Brain↗
PubMed1995

Cell death induced by gamma irradiation of developing skeletal muscle.

Newborn Sprague-Dawley rats were exposed to a single dose of 2 Gy gamma rays and killed from 6 h to 5 d later. Increased numbers of dying cells, characterised by their extreme chromatin condensation and often nuclear fragmentation were seen in skeletal muscle 6 h after irradiation. Dying cells decreased to nearly normal values 48 h later. In situ labelling of nuclear DNA fragmentation identified individual cells bearing fragmented DNA. The effects of gamma rays were suppressed following cycloheximide i.p. at a dose of 1 microgram/g body weight given at the time of irradiation. Taken together, the present morphological and pharmacological results suggest that gamma ray induced cell death in skeletal muscle is apoptotic, and that the process is associated with protein synthesis. Finally, proliferating cell nuclear antigen-immunoreactive cells, which were abundant in control rats, decreased in number 48 h after irradiation. However, a marked increase significantly above normal age values was observed at the 5th day, thus suggesting that regeneration occurs following irradiation-induced cell death in developing muscle.

Animals↗
PubMed1995

Na+,K+,Cl- cotransport is a marker of distal tubular function in essential hypertension.

OBJECTIVE: To analyze the natriuretic and diuretic response to frusemide in 33 male essential hypertensive patients as a function of basal renal sodium handling and erythrocyte transport system. METHODS: The natriuretic and diuretic response to an oral dose of frusemide (25 mg) was assessed with a simplified method. Urinary sodium and water excretion were measured in the basal state and every 30 min after the frusemide dose for 240 min. Basal 24h urinary sodium and water excretion, Na+,K+,Cl- cotransport and Li+-Na+ countertransport were measured 24 h before the test. RESULTS: There was a highly significant correlation between the natriuretic and diuretic response to frusemide and Na+,K+,Cl- cotransport and Li+-Na+ countertransport. After a multiple regression analysis the natriuretic and diuretic response to frusemide was not correlated with indices of proximal tubular function (Li+-Na+ countertransport, fractional uric acid excretion and the ratio of fractional sodium excretion to fractional uric acid excretion). CONCLUSION: These results support the hypothesis that erythrocyte Na+,K+,Cl- cotransport is a marker of distal tubular function.

Adult↗
PubMed1994

Parvalbumin immunocytochemistry and calcium deposition in muscle fiber necrosis and subsequent regeneration following intramuscular injection of metoclopramide.

We have studied the sequential change of parvalbumin immunocytochemistry and its correlation with intracellular Ca2+ deposition in an animal model of muscle fiber necrosis and regeneration induced by intramuscular injection of metoclopramide. Twenty-four hours after the drug's injection, extensive muscle fiber necrosis, together with dramatic loss of parvalbumin immunoreactivity and intracellular Ca2+ deposition, was observed. Muscle fiber regeneration began on day 4 after the injection and was complete by the end of the third week. Parvalbumin was not detected in the regenerating fibers, but gradually emerged during the second week as muscle fibers increased in size. It can be suggested that loss of parvalbumin in necrotic fibers is secondary to the loss in integrity of the sarcolemma. Alternatively, loss of parvalbumin in degenerating fibers may impair calcium buffering and act as a contributory factor in the necrotic process. The progressive appearance of parvalbumin immunoreactivity in regenerating fibers parallels that found in normal myogenesis.

Animals↗
PubMed1994

Dose-related effects of cycloheximide on delayed neuronal death in the gerbil hippocampus after bilateral transitory forebrain ischemia.

Degeneration of dendrites followed by punctate chromatin condensation in the CA1 area of the hippocampus is a characteristic of delayed neuronal death following bilateral forebrain ischemia. The effects of the protein synthesis inhibitor cycloheximide on delayed neuronal death following 20 min of bilateral forebrain ischemia were examined in the gerbil hippocampus at the 4th day of reperfusion. Low doses of cycloheximide beginning 10 min after ischemia (1.0 microgram/g body weight in saline followed by 1.0 microgram/g every 24 h) reduced the number of dying cells in the CA1 area, whereas high doses (2.0 micrograms/g, followed by 1.0 microgram/g every 12 h) increased the number of dying cells. No effects were seen when a single dose of cycloheximide was injected 1 h before ischemia. These results indicate that the effects of cycloheximide are dose-dependent, low doses reduce, high doses increase cell death. These findings also indirectly suggest that protein synthesis may play a role in the extent of delayed neuronal death. Some involved proteins could be heat shock proteins, which are induced after ischemia and had been correlated with increased resistance to injury. However, changes of heat shock immunoreactivity in the postischemic hippocampus were not seen in the present study following cycloheximide injection.

Animals↗