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Biomedical subjects

J Rivera

Publications and source records attributed to J Rivera.

At least 19 recordsLinked to original sources
PubMed1992

Interaction of aggregated native and mutant IgE receptors with the cellular skeleton.

When aggregated, cell surface proteins become resistant to solubilization by detergents, presumably because of aggregation-induced or -stabilized interactions between the membrane protein and the cytoskeleton or plasma membrane skeleton. We genetically engineered variants of the tetrameric high-affinity receptor for IgE (Fc epsilon RI) to identify a site on its alpha, beta, or gamma chains that mediates such putative interactions. Using flow cytofluorometry, we studied rat basophilic leukemia cells, transiently transfected COS cells, and stably transfected P815 cells bearing wild-type and mutated receptors. We observed that (i) solubilization was markedly dependent on the degree of aggregation, the extent varying somewhat with the cell type and, particularly at lower levels of aggregation, with the time after addition of detergent; (ii) truncation of no single cytoplasmic domain of the alpha, beta, or gamma chains ablated the insolubilization effect; and (iii) incomplete receptors were also efficiently insolubilized by aggregation. Thus receptors consisting only of alpha and gamma chains, a "receptor" consisting of only the ectodomain of the alpha chain attached to the plasma membrane by a glycosyl-phosphatidyl inositol anchor, and "receptors" consisting only of minimally modified gamma chains were resistant to solubilization after aggregation. We conclude that no unique subunit or domain of Fc epsilon RI mediates the insolubilization phenomenon. Our results support a model in which the bridging of membrane proteins leads to their becoming nonspecifically enmeshed in a network of membrane skeletal proteins on either the outside and/or the inside of the membrane so that dissolution of the lipid bilayer becomes irrelevant.

Animals↗
PubMed1992

Energy expenditure in rats maintained with intravenous or intragastric infusion of total parenteral nutrition solutions containing medium- or long-chain triglyceride emulsions.

Energy expenditure was determined in male Fischer 344 rats (235-246 g) fed by intravenous (IV) or intragastric (IG) infusion with total parenteral nutrition solutions providing 65% of nonprotein energy as fat from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions. Respiratory gas exchange and somatomotor activity were assessed continuously for 24 h during d 5 and 11 of infusion feeding. The MCT infusion resulted in one-third the weight gain noted with LCT infusion (MCT, 10 +/- 2 g/14 d; LCT, 32 +/- 4 g/14 d; P less than 0.0001). Insulin concentration was 60% higher with IV than with IG infusion and approximately 100% higher with IV-MCT than with IG-MCT or LCT infusion (P less than 0.05). Rats receiving IV infusion of MCT displayed similar levels of motor activity but 8-13% greater daily energy expenditure (kJ.kg-0.75.kJ intake-1) than rats receiving IG-MCT or LCT infusion (P less than 0.05). The MCT infusion also resulted in an elevation in respiratory quotient after cessation of nutrient infusion (MCT, 0.87-0.92; LCT, 0.83-0.85; P less than 0.05). Total and resting energy expenditure decreased approximately 13% from 5 to 11 d of infusion feeding. The lower weight gain and greater energy expenditure seen with MCT- compared with LCT-supplemented total parenteral nutrition may be mediated by higher insulin concentrations.

Animals↗
PubMed1992

Effects of staphylococcal enterotoxin B on rodent mast cells.

Staphylococcal enterotoxin B (SEB) was tested in rodent mast cell cultures for the release of serotonin. Both rat RBL-2H3 mast cells and murine peritoneal cells released serotonin after SEB stimulation in culture. Release of serotonin in RBL-2H3 cells depended on the concentration of SEB; an appreciable release was seen at 50 micrograms/ml. The release of serotonin was not due to cell death. Serotonin release could be enhanced by bradykinin but not by vasoactive intestinal peptide, substance P, lipopolysaccharide from Salmonella typhimurium, the calcium ionophore A23187, acetylcholine, adenosine, 5-hydroxyeicosatetraenoic acid, indomethacin, or phorbol myristate acetate. SEB bound directly to the membrane of RBL-2H3 mast cells, and the SEB-binding site, the presumptive receptor, appeared to be a protein. The SEB receptor could not be capped under membrane-capping conditions, and serotonin release could not be enhanced by attempts to cross-link the receptor. These results suggest that mast cells may be an important cell type involved in SEB toxicosis and that release of serotonin may be enhanced by activation of the kinin-kallikrein system.

Acetylcholine↗
PubMed1992

Progesterone increases basal 3',5'-cyclic adenosine monophosphate formation and down-regulates the agonist-induced inositol phosphates generation in human term placenta.

Whether the placenta is a target tissue for estrogens and progesterone, and their putative mechanism of action, is still a controversial question in the literature. The effect of progesterone and estradiol on 3',5'-cyclic adenosine monophosphate (cAMP) and inositol phosphates generation in human term placenta was investigated. Placental explants were incubated in vitro for up to 48 h in the absence and in the presence of estradiol, progesterone or both steroids (0.1 mumol/l final concentration in all cases), and were stimulated with terbutaline, a beta-adrenergic agonist, (0.1 mmol/l) or angiotensin II (1 mumol/l). The cAMP content was measured by a competitive protein binding assay, and the generation of labelled inositol phosphates formation in explants prelabelled with 3H-myo-inositol was measured by anion exchange chromatography. Progesterone increased significantly basal cAMP concentrations in comparison with control or estradiol-treated tissues (169 +/- 13, 72 +/- 8, and 69 +/- 2 pmol/g wet wt tissue, mean +/- SEM, respectively). However, following terbutaline stimulation cAMP levels (mean +/- SEM) increased to similar values under all conditions (182 +/- 33, 197 +/- 36, and 237 +/- 17 pmol/g wet wt tissue for control, estradiol-, and progesterone-treated tissues, respectively). Angiotensin II stimulated inositol phosphates generation in placental explants by an average of fivefold, but this increase was significantly reduced in the presence of progesterone (5.2 +/- 0.7, 3.7 +/- 0.4, and 2.2 +/- 0.3 fold increase vs non-angiotensin-stimulated tissues, for control, estradiol-, and progesterone-treated placenta, mean- +/- SEM, respectively). These data suggest that progesterone modulates the formation of second messengers in human placenta at term.

Angiotensin II↗
PubMed1992

Septic arthritis in patients with acquired immunodeficiency syndrome with human immunodeficiency virus infection.

We have evaluated the presence and characteristics of septic arthritis in intravenous (iv) drug users with human immunodeficiency virus (HIV) infection. Sixteen patients with both HIV infection and septic arthritis were studied and compared with 5 patients with septic arthritis but no HIV infection. Clinical profile, laboratory findings at the time of onset, localization, causative organisms, mean hospitalization time and presence of complications were the same in HIV positive and HIV negative patients. Staphylococcus aureus was the most commonly isolated organism in both groups. We conclude that septic arthritis in HIV infected iv drug users is not uncommon, it is produced by the same organisms and presents similar characteristics to the ones found in iv drug users without HIV infection. Therefore, the presence of HIV infection does not appear to modify the characteristics of septic arthritis.

Acquired Immunodeficiency Syndrome↗
PubMed1992

[Ovulation induction by the chronic administration of naltrexone in a patient with secondary hypothalamic amenorrhea].

An ovulatory cycle was induced by oral administration of a specific opiate antagonist: naltrexone, at a dose of 50 mg/day for 26 days in a woman suffering from secondary hypothalamic amenorrhea. The follicular growth was monitored by ultrasound and serial blood measurement of LH, FSH, E2 and progesterone. The hormonal and ultrasound profiles showed an ovulatory cycle with a single dominant follicle. After discontinuation of the treatment, the patient became amenorrheic again. The gonadotropin as well as estradiol plasma levels declined, to that observed before treatment. Naltrexone may be a useful agent for induction of ovulation in women suffering from hypothalamic amenorrhea.

Adolescent↗
PubMed1992

Effect of inclusion of beans in a mixed diet for the treatment of Peruvian children with acute watery diarrhea.

A double-masked clinical trial was conducted to assess the effects of inclusion of beans in a mixed diet for young Peruvian children with acute diarrhea. Dietary treatment consisted of either rice, beans, and vegetable oil (group RB, n = 25) or rice, soy-protein isolate, corn syrup solids, and vegetable oil (group RS, n = 21), each given in amounts up to 150 kcal/kg body weight per day immediately following rehydration therapy. The groups were generally similar at the time of admission, and there were no differences in the rates of treatment failure (8% in group RB, 14% in group RS; P = .65). Mean stool outputs were 83 +/- 46 (SD) g/kg body weight in group RB and 71 +/- 43 g/kg body weight in group RS on day 1, and these outputs consistently ranged from 25% to 40% greater in group RB than in group RS (P = .058). By contrast, the median duration of liquid stool excretion was substantially less in group RB than in group RS (60 vs 121 hours, P = .01). The fractional absorption of carbohydrate, fat, and total energy was significantly greater by children in group RS, but there were no differences in net apparent absorption of these nutrients because the children in group RB consumed significantly more of their assigned diet. Children in group RS gained significantly more weight during the whole period of observation (194 g vs 1 g, P = .047), but these differences could be entirely explained by the weight (and presumably fluid) changes on day 1. There were no consistent differences by dietary group in any of the other anthropometric indicators.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1991

Isolation and primary structure of glucagon from the endocrine pancreas of Thunnus obesus.

Glucagon has been isolated from the endocrine pancreas of a tunid, Thunnus obesus. The primary structure of the glucagon molecule was established as H S E G T F S N D Y S K Y L E T R R A Q D F V Q W L K N S. The sequence is identical to those of sculpin and flounder glucagon and glucagon II from anglerfish. It also shows high homology to the mammalian hormone (76%). The mass determined by fast-atom bombardment (3508) was consistent with the proposed structure. Immunological properties of the tuna glucagon were analyzed by radioimmunoassay, showing a high degree of cross-reactivity with the 30K antibody.

Amino Acid Sequence↗
PubMed1991

P29, an oestrogen receptor-associated protein, is down-regulated by mifepristone in first trimester human placenta and decidua.

P29 is an oestrogen receptor-associated protein which acts as a marker of oestrogen action in several systems. The concentration of P29 was measured in placenta and decidua from women following medical termination of pregnancy with the antiprogesterone steroid mifepristone (RU 38,486) and a prostaglandin E1 analogue, and compared with the concentration of P29 found in matched controls undergoing surgical aspiration of pregnancy. Oestrogen receptors were also measured in the same samples. Placental and decidual P29 concentrations (IU/mg protein) in patients treated with mifepristone were 9.6 (4.6-54) and 4.8 (1.3-13.3) (median and range), respectively. These values were significantly lower than the corresponding values, 39.5 (27-69) and 22.0 (2-107) in the surgical group. In contrast, the levels of oestrogen receptors did not change significantly in either decidua or placenta. These data show that mifepristone causes down-regulation of P29 in placenta and decidua, and therefore its action may disrupt oestrogen function in uterine tissues.

Abortion, Legal↗
PubMed1991

Intestinal calcium absorption and parathyroid hormone secretion in asthmatic patients on prolonged oral or inhaled steroid treatment.

A secondary hyperparathyroidism resulting from decreased intestinal calcium (Ca) absorption has been proposed as a contributory factor to glucocorticoid-induced osteoporosis. Inhaled steroids do not usually suppress adrenal gland function unless daily doses above 1,500 microgram are used. A recent study, however, has shown a reduced total body calcium in patients on regular beclomethasone treatment. In theory, osteopenia in these patients could be due to a direct effect of inhaled steroids on bone or due to an impaired intestinal calcium absorption. In this study, Ca absorption and parathyroid hormone (PTH) secretion were evaluated in three groups: 1) asthmatics on continuous oral and inhaled steroid treatment (11.3 +/- 4.4, range 5-33.5 mg.day-1 prednisone and 660 +/- 265, range 400-1,600 microgram.day-1 beclomethasone, respectively); 2) asthmatics on regular beclomethasone therapy (585 +/- 210, range 400-1,200 microgram.day-1); and 3) healthy subjects. The prevalence of vertebral fractures was evaluated by a spinal X-ray. No differences were found in either Ca absorption or PTH serum levels between asthmatics and healthy subjects (analysis of variance-ANOVA). Vertebral fractures were significantly more frequent in patients from group 1 (14 of 25) than in those from group 2 (2 or 25). We conclude that both prolonged oral steroid treatment and inhaled steroids, at doses lower than 1,600 microgram.day-1 do not cause Ca malabsorption, and that hyperparathyroidism does not contribute to osteoporosis in these patients.

Administration, Inhalation↗
PubMed1991

AIDS and rheumatic manifestations in patients addicted to drugs. An analysis of 106 cases.

We evaluated the rheumatic manifestations in 106 patients with AIDS whose risk factor is intravenous drug addiction. All were intravenous drug addicts and carriers of the human immunodeficiency virus (HIV). Their average age was 28.36 years; 83 were men and 23 were women; 73 were in stage IV of the HIV infection; 12 were in stage III and 21 in stage II. Rheumatic manifestations were found in 21 patients (20%). Specifically, 13 had arthralgias/myalgias, 2 demonstrated oligoarthritis, 1 had tuberculous arthritis of the knee, and 1 patient showed systemic necrotizing vasculitis. Finally, 6 patients had a history of septic arthritis. There was an absence of the Reiter syndrome/reactive arthritis, a low frequency of symptoms of articular swelling, and the marked presence of histories of septic arthritis. The practices that lead to HIV infection may play a decisive role in the appearance of rheumatic manifestations in patients with AIDS, even more than the presence of the virus itself or the immunological alterations thereby produced.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Expression of estrogen receptors, progesterone receptors, and an estrogen receptor-associated protein in the human cervix during the menstrual cycle and menopause.

Estrogen receptors (ERs), progesterone receptors (PRs), and P29, an ER-associated protein, were studied immunohistochemically in human cervix with use of specific monoclonal antibodies. In ectocervical epithelium, homogeneous staining was found for P29 throughout the menstrual cycle and after menopause. Weak or moderate staining was found for ER in the basal and, occasionally, the parabasal layers of ectocervix during the proliferative phase. In contrast, staining decreased in secretory phase and postmenopausal epithelia. Staining was negative for PR in all the exocervical epithelia. Heterogeneous staining, more pronounced for P29, was found for the three antigens of the study in endocervical epithelium. Staining did not change with the hormonal status of patients, except for ER, where staining decreased during the secretory phase. Stromal cells were negative or weakly positive, whereas muscular fibers were positive. This study suggests that the capacity of response of the steroid apparatus of cervical cells to fluctuations of circulating estrogens and progestins is limited compared with some of the cell functions, such as mucus secretion, or with other target tissues, such as endometrium. Additionally, the differences found in the pattern of expression of the three antigens studied suggest that the steroid-dependent growth and differentiation in ectocervix is regulated differently to endocervix.

Biomarkers, Tumor↗