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Biomedical subjects

A Torres

Publications and source records attributed to A Torres.

At least 415 records · Page 23Linked to original sources
PubMed1996

Abnormal calcaemic response to PTH in the uraemic rat without secondary hyperparathyroidism.

BACKGROUND: Skeletal resistance to the calcaemic action of parathyroid hormone (PTH) is an important pathogenic factor in the development of secondary hyperparathyroidism. Since parathyroidectomy normalizes the calcaemic response to PTH in uraemic animals, the increase in PTH levels has been advanced as a cause of skeletal resistance to the calcaemic action of PTH. This study was designed to evaluate in uraemic rats the effect of normal PTH levels on the calcaemic response to PTH. METHODS: To maintain normal PTH levels, rats were parathyroidectomized (PTX) and rat 1-34 PTH was infused at a rate of 0.022 microg/100 g per hour via a subcutaneously implanted miniosmotic pump; this rate of infusion was considered to be the normal PTH replacement dose since it normalized serum calcium and phosphorus in PTX rats with normal renal function. Two separate studies were performed. In the first study, rats were maintained on a moderate-phosphorus (0.6%) diet and rats were divided into four groups: (I) normal; (II) uraemic; (III) PTX with normal PTH replacement; and (IV) uraemic with PTX and normal PTH replacement. In a second study, the groups were the same except that a high-phosphorus (1.2%) diet was given to increase the magnitude of hyperparathyroidism in rats with intact parathyroid glands; an additional group (V) identical to group IV except that rats received daily calcitriol was included. After 14 days, rats received a 48-h infusion of high-dose rat 1-34 PTH (0.11 microg/100 g per hour) to evaluate the calcaemic response to PTH. Results. The calcaemic response to PTH was similar in normal rats and PTX rats replacement on both a moderate and high-phosphorus diet. In uraemic rats, the calcaemic response to PTH was decreased and the maintenance of normal PTH levels by PTH replacement did not correct the decreased calcaemic response to PTH; moreover, calcitriol supplementation did not improve the calcaemic response to PTH. Finally, hypocalcaemia was observed in uraemic rats with PTH replacement and was more profound than in rats on a high-phosphorus diet. CONCLUSIONS: This study demonstrates that the maintenance of a normal PTH level in uraemic rats did not correct the impaired calcaemic response to PTH, suggesting that factors intrinsic to uraemia, independent of phosphorus, calcitriol, and PTH participate in the decreased calcaemic response to PTH in uraemia.

Animals↗
PubMed1996

Experimental vasectomy and testicular structure.

We have performed an experimental study on rats and dogs to evaluate the long term effects (from 1 to 12 months) of vasectomy on the structure of the testis. From four months after vasectomy onwards, the specimens showed very important changes in the seminiferous epithelium and Sertoli cells, with an obvious thickening of the basement membrane that supports the epithelium. The deterioration depended on the time passed and, over six months after vasectomy, the alterations were very clear and the seminiferous tubules became atrophic and shrunk, sometimes without any remains of seminiferous epithelium and with an important hypertrophy of the interlobular interstitial tissue, although we did not see an increase in the number of Leydig cells. Alterations due to vasectomy depend on the animal species, the peculiarities of techniques and, of course, the time passed after surgery.

Animals↗
PubMed1996

Severe pulmonary infections in AIDS patients.

Pulmonary infections are a very common complication in acquired immune deficiency syndrome (AIDS) patients. These infections may be severe enough to initiate the admission of these patients to intensive care units (ICU). Pneumocystis carinii pneumonia (PCP) is the most frequent cause of ICU admission because of acute respiratory failure. Mortality of ICU-admitted patients with this infection has changed with time. Initial reports confirmed a high mortality (80% to 90%). After 1985, the mortality rate decreased (50%). Factors such as the use of corticosteroids, better patient care, and a better knowledge of the disease probably explain this change. In recent years (1990 to 1995), mortality has worsened again, perhaps, because ICU facilities were offered more liberally to patients failing aggressive conventional treatment, including adjuvant therapy with corticosteroids. However, for those patients able to be discharged, the prognosis is not worse than expected according to the stage of their human immunodeficiency virus-1 (HIV-1) infection and immunologic status. Consequently, at least a limited period of ICU care and some respiratory support (either continuous positive airway pressure or mechanical ventilation) should be considered and offered to all HIV-1-infected patients with PCP and respiratory failure. Cytomegalovirus may be another cause of severe pulmonary infection in AIDS patients. This infection is difficult to diagnose; hence, it should be suspected when patients with PCP do not progress appropriately, or when no responsible pulmonary pathogen is found. When associated with PCP, mortality is very high. Disseminated tuberculosis is another potential cause of severe respiratory failure and respiratory secretions should be routinely examined for acid-fast bacilli in AIDS patients with pulmonary infiltrates. Finally, bacterial pneumonia (Streptococcus pneumoniae, Neisseria catarrhalis, Haemophilus influenzae, Staphylococcus aureus, and Pseudomonas aeruginosa) may also be the etiological agents of severe acute respiratory failure. Empiric antibacterial treatment to cover these microorganisms should be given when a bacterial agent is suspected.

AIDS-Related Opportunistic Infections↗
PubMed1996

The interaction of PTH and dietary phosphorus and calcium on serum calcitriol levels in the rat with experimental renal failure.

BACKGROUND: Renal failure results in decreased calcitriol production, a key factor in the development of secondary hyperparathyroidism. Phosphorus accumulation and high parathyroid hormone (PTH) levels, both inherent to renal failure, have different effects on calcitriol production; moreover, dietary calcium loading may have a separate inhibitory effect on calcitriol production. This study was designed to evaluate the relative effects of PTH and dietary phosphorus and calcium on serum calcitriol levels. METHODS: Renal failure was surgically induced and rats were divided into normal, moderate renal failure, and advanced renal failure based on the serum creatinine. Each group was subdivided and received either a high-phosphorus diet (HPD, 0.6% Ca, 1.2% P) or high-calcium diet (HCaD, 1.2% Ca, 0.6% P) for 14-16 days to determine the relative effects of dietary calcium and phosphorus loading on serum calcitriol. In addition the effect of PTH and phosphorus on calcitriol stimulation was determined with a 48-h PTH infusion combined with either a low (0.16%) or high (1%) phosphorus diet; both diets had negligible calcium (< 0.05%). RESULTS: With decreasing renal function, PTH increased and was greater in rats fed the HPD than the HCaD; serum calcitriol decreased as renal function decreased and was lower in normal rats and rats with moderate renal failure fed a HCaD (P < 0.01). The calcitriol response to a PTH infusion decreased as renal function decreased (P < 0.05) but was greater on a low- (0.16%) than a high- (1%) phosphorus diet (P < 0.05). CONCLUSIONS: Dietary calcium loading either directly decreases serum calcitriol or acts by modifying the stimulatory effect of PTH; the stimulatory effect of PTH on serum calcitriol is modified by dietary phosphorus; in moderate renal failure, serum calcitriol levels depend on a complex interaction between PTH and dietary calcium and phosphorus; and in advanced renal failure, serum calcitriol levels are low and are difficult to stimulate, presumably because of the loss of renal mass.

Animals↗
PubMed1996

Microbial causes of ventilator-associated pneumonia.

Aspiration of microorganisms colonizing the oropharynx is the main route of bacterial entry to lower airways in mechanically ventilated patients. Examination of the microbial flora involved in ventilator-associated pneumonia shows that only few species, among the many oropharynx microorganisms, are responsible for the majority of lower respiratory tract colonizations and infections in intubated patients. Underlying disease, length of intubation, and type and duration of prior antibiotic therapy are the most important factors related with the causative flora of respiratory infections in these patients. Except in certain populations (eg, chronic obstructive pulmonary disease [COPD] patients who may be colonized by Pseudomonas aeruginosa), methicillin-sensitive Staphylococcus aureus, Streptococcus pneumoniae, and unencapsulated Hemophilus influenzae are the predominant respiratory pathogens within the first week of intubation in critically ill patients. These microorganisms are subsequently replaced by multiresistant flora, such as Pseudomonas aeruginosa, methicillin-resistant staphylococci or Acinetobacter baumanii. This change of flora takes place as a consequence of prior antibiotic therapy among other factors. Fungi have to be taken in account particularly in the presence of severe immunodepression. All of these multiresistant pathogens (particularly P aeruginosa) are responsible for most of the deaths directly related to pneumonia; therefore, the early recognition of causative agents and appropriate antibiotic therapy are of great importance determining outcome. This strategy represents the most efficient approach to managing patients with ventilator-associated pneumonia.

Anti-Bacterial Agents↗
PubMed1996

Inhibition of apoptotic cell death in B-CLL by interferon gamma correlates with clinical stage.

Apoptosis was evaluated in B cells from 41 patients with B-CLL and 20 healthy aged-matched controls. B cells were cultured with and without gamma-IFN and other cytokines; apoptosis was quantified at regular intervals throughout a 5-day culture period. According to Rai's criteria, 17 patients were classified as good risk, 16 as intermediate and eight as high risk. In vitro, purified B cells from B-CLL patients were evaluated for apoptosis. Maximal apoptosis (44.12%) was observed at day 5 in cells from patients with poor prognosis. The addition of gamma-IFN to the culture media prevented apoptosis in a dose-dependent manner. Maximal inhibition of apoptosis was achieved with 100 IU/ml of gamma-IFN. The degree of inhibition of apoptosis by gamma-IFN was greater in cells from the high-risk group patients than in those from the intermediate and good prognosis group (P < 0.0001). The expression of gamma-IFN receptors in B-CLL cells was evaluated using a MnAb against the extracellular domain of gamma-IFN receptor. After 4 days in culture with gamma-IFN, only cells from the intermediate- and high-risk groups showed an increase in the density of gamma-IFN receptors (P < 0.001). gamma-IFN was not detected in the sera of our study patients. However gamma-IFN was detectable in the media from both normal B cells and B-CLL cells in culture; there was no difference in the amount of gamma-IFN released by cells from the three groups of patients studied. Our results show that in vivo gamma-IFN inhibits apoptosis of B cells from B-CLL patients. The inhibitory effect of gamma-IFN on apoptosis correlates directly with the severity of the disease and this is likely explained by a marked upregulation of gamma-IFN receptors in cells from patients in the high-risk group.

Aged↗
PubMed1996

Heart rate responses to intravenous serotonin in rats with acute chagasic myocarditis.

We administered serotonin to rats with experimentally induced chagasic myocarditis in order to study the Bezold-Jarisch reflex. Sixteen 4-month old Wistar rats were inoculated with 200,000 T. cruzi parasites ("Y" strain). Between days 18 and 21 (acute stage), 8 infected rats and 8 age-matched controls received intravenous serotonin as a bolus injection at the following doses: 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, and 14.0 micrograms/kg. Heart rate was recorded before, during and after each dose of serotonin. The remaining 8 infected animals and 8 controls were subjected to the same experimental procedure during the subacute stage, i.e., days 60 to 70 after inoculation. The baseline heart rate of the infected animals studied during the acute stage (327 +/- 62 beats/min, mean +/- SD) was higher than that of the controls (248 +/- 52, P < 0.01). The heart rate changes were expressed as percent changes to correct for the higher baseline heart rate of the infected animals. A dose-response curve was constructed for each group of animals. The slope for the acutely infected animals (r = -0.95, b = -3.98) was not different from that for the control animals (r = -0.92, b = -3.50). The infected animals studied during the subacute stage (r = -0.92, b = -4.33) were not different from the age-matched controls (r = -0.87, b = -4.03). These results suggest that the afferent and efferent pathways which mediate the Bezold-Jarisch reflex are functionally preserved in rats with histologically proved chagasic myocarditis.

Acute Disease↗
PubMed1996

[Color loss evaluation of a dietary formulation in function of temperature, storage time and packaging].

Color loss of a dietetic formulae based on pumpkin (Cucurbita maxima), rice, hen and vegetable oils was evaluated. The product was under an accelerated test at temperatures of 40, 50 and 70 degrees C for a month. The kinetic reaction of color loss (quality loss indicator) was obtained with n = 1 and Ea = 11.5 Kcal/mol. The product was also stored for sixth months at temperatures of 25, 30, 35 and 40 degrees C using glass containers, laminated and composite cans (non metallic). The color was measured by a colorimetric method and by sensory evaluation under the defined conditions of time, temperature and package. The statistical analyses of the color loss measured by instrument was performed by a randomized block design with a significance level of p < 0.05. The results obtained both by the instrument and by the sensory evaluation method, showed that the temperature and storage time has significant effect (p < 0.05) on the other hand, the package does not have a significant effect. It was concluded from this study that the product could be stored for 6 months at temperatures below 35 degrees C without changes in color.

Color↗
PubMed1995

Plasma norepinephrine, myocardial damage and left ventricular systolic function in Chagas' heart disease.

The functional status of the sympathetic nervous system in Chagas' heart disease is still the subject of intense controversy. To determine the nature of the abnormalities of the sympathetic nervous system, we measured the plasma norepinephrine concentration of chagasic patients with varying degrees of myocardial damage. Thirty-six patients with positive serology for Chagas' disease were studied. Twenty patients were in Functional Class I (New York Heart Association), 10 were in Functional Class II and six were in Functional Classes III-IV. Cardiac catheterization was performed in 24 patients. The asymptomatic patients had a plasma norepinephrine concentration (121 +/- 37 pg/ml, mean +/- S.D.) not different from normal controls (103 +/- 59 pg/ml). The symptomatic patients, however, had a significantly elevated plasma norepinephrine concentration (665 +/- 354 pg/ml, P < 0.001). The baseline heart rate of the asymptomatic and symptomatic patients directly correlated with the plasma norepinephrine concentration (r = 0.69, P < 0.0001). The symptomatic patients had larger ventricular volumes, higher left ventricular end-diastolic pressures and lower ejection fractions than the asymptomatic patients and normal controls. The plasma norepinephrine concentration correlated linearly with the left ventricular end-diastolic volume (r = 0.77, P < 0.0001), and non-linearly with the ejection fraction (r = -0.70, P < 0.0001) and the left ventricular end-diastolic pressure (r = 0.53, P < 0.007). These results indicate that, in Chagas' heart disease as in most other cardiac diseases, sympathetic nervous system activation is a late and compensatory phenomenon. In other words, sympathetic activation is very likely related to the progressive impairment of left ventricular function.

Adult↗
PubMed1995

[Minimal residual disease in chronic myeloid leukemia in patients with long survival after allogeneic bone marrow transplantation].

BACKGROUND: The study of the minimum residual disease in a series of patients diagnosed with chronic myeloid leukemia (CML) treated with non manipulated allogeneic bone marrow transplantation (BMT) reporting a survival longer than 6 months is presented. METHODS: The positivity of the chimeric transcription bcr-abl was studied in 18 long surviving BMT patients. The complementary DNA (cDNA) corresponding to this transcription was amplified by the polymerase chain reaction (PCR) technique. Double internal PCR (PCR nested) was performed to increase the sensitivity of the determination. RESULTS: The first determination was performed in different post BMT stages with a median of 27 months (4-97). Fourteen out the 18 patients were positive for the bcr-abl transcription. On the second determination carried out in 11 cases with a sample obtained 24 months after the first 7 out of the 10 positive cases evaluated presented an identical pattern while the patient who originally was negative, remained so. The original transcription became negative in three patients. Only one of the positive cases developed hematologic relapse during the study period. CONCLUSIONS: Aggressive chemo-radiotherapy does not eradicate the leukemic clone in all patients with chronic myeloid leukemia. The persistence of positive results in a high number of patients with chronic myeloid leukemia in remission for over 6 months after bone marrow transplantation is not predictive of imminent relapse.

Adult↗
PubMed1995

Effect of temperature on opioid dependence and on the abstinence response in the isolated guinea pig ileum.

This paper explores, in the isolated guinea-pig ileum, the effects of temperature on the acute development of opioid dependence and on the precipitation of the abstinence response, using as reference the effect of temperature on the response to a standard nicotine concentration. Additionally, the influence of temperature on acute morphine neurodepression was examined. Three experimental groups were included. In the first, the bath temperature was adjusted and maintained along the experimental session (2.5 h) at one of the following values: 28, 32, 36 or 40 degrees C. In the second, the different values of bath temperature were applied only during the period of morphine exposure before testing the abstinence response at 36 degrees C. In the third, all segments were initially incubated at 36 degrees C for 1 h, and afterwards, abstinence and the nicotine response were elicited at the different temperatures mentioned. In all the series, a single challenge naloxone dose (3.1, 10, 31, 100, 316, 1000 or 3160 nM) was administered after 1h of morphine and complete naloxone concentration-response curves were obtained. The abstinence response was expressed as a percentage of the nicotine reference response. All segments showed robust nicotine responses at all the experimental protocols tested indicating that, at the temperature range studied, the contractile mechanisms were impaired. This study showed that changes in bath temperature modify the magnitude of acute morphine neurodepression, and of the abstinence response but did no affect the development of acute opioid dependence. These data, along with several lines of evidence, strongly suggest that acute neurodepression, the development of opiate dependence and antagonist-precipitated abstinence are separable. Results are discussed on the basis of drug-receptor interactions.

Acute Disease↗
PubMed1995

Bone disease in predialysis, hemodialysis, and CAPD patients: evidence of a better bone response to PTH.

The spectrum of bone disease in predialysis and dialysis patients has changed during the last decade. The incidence of aplastic bone disease has increased and this can not be attributed to bone aluminum deposition; moreover, low bone cellular activity is present despite a moderate elevation in PTH levels. This study compares PTH levels and types of bone disease in both predialysis and dialysis patients from the same geographical area. We prospectively studied 119 unselected end-stage renal disease patients: 38 were immediately predialysis (PreD), 49 on hemodialysis (HD), and 32 on CAPD. A bone biopsy was performed in all patients. Aplastic bone disease with < 5% bone surface aluminum was a common finding (48%, 32%, and 48%, in PreD, HD, and CAPD, respectively). In all groups, an intact PTH level below 120 pg/ml was highly predictive of low bone turnover. Conversely, a PTH level above 450 pg/ml was always associated with histologic features of hyperparathyroid bone disease. Among the bone histomorphometric parameters, osteoblast surface showed the best correlation with intact PTH in each group, and the slope of the regression line for this correlation was significantly steeper in HD and CAPD than PreD patients. Thus, the range of PTH (95% confidence limit bands) needed to obtain a normal osteoblast surface of 1.5% was greater in preD than in HD and CAPD patients (300 to 500 vs. 75 to 260 pg/ml, respectively). In all groups some degree of marrow fibrosis was observed when PTH levels were greater than 250 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1995

Intrapartum prophylaxis with ceftriaxone decreases rates of bacterial colonization and early-onset infection in newborns.

Because of high rates of neonatal gram-negative sepsis in many Latin American countries, we prospectively enrolled 784 high-risk pregnant women in a study designed to evaluate the effect of a single 1-g dose of ceftriaxone (n = 390) vs. that of no antibiotic prophylaxis (n = 394) on oral, rectal, and umbilical colonization and fatality rates among newborn infants. The mean ceftriaxone concentration in cord blood samples was 26 microgram/mL (range, 9-40 microgram/mL). Compared with infants of untreated mothers, children born to women who were given ceftriaxone were colonized at a lesser rate by gram-negative bacilli (54% vs. 35%; P < .001) and by group B streptococci (54% vs. 21%; P = .03) and endured significantly fewer sepsis-like illnesses in the first 5 days of life (8.1% vs. 3.1%; P = .004). There was also a tendency for them to have fewer episodes of culture-proven early-onset sepsis (2.8% vs. 0.5%; P = .06). Sepsis-related case-fatality rates (0.8% and 0.3%, respectively) were not significantly different. Although intrapartum administration of a single dose of ceftriaxone to high-risk mothers could be a safe and potentially useful strategy for reducing early-onset neonatal infections, additional information is required before this approach can be recommended for routine prophylaxis.

Bacterial Infections↗
PubMed1995

TolC and DsbA are needed for the secretion of STB, a heat-stable enterotoxin of Escherichia coli.

STB secretion-deficient mutants were isolated using the synthetic transposon Tn beta laM. Cultures were plated using a double-membrane system of cellulose acetate and nitrocellulose placed on Luria agar plates containing carbenicillin. The STB bound to the underlying nitrocellulose membrane was detected with anti-STB antibodies. The altered genes of two STB secretion-deficient mutants were identified by conjugation and complementation as tolC and dsbA. In cultures of well-characterized dsbA and tolC mutants, STB was absent from the culture supernatant. The role of TolC and DsbA in the secretion of peptides is discussed.

Bacterial Outer Membrane Proteins↗
PubMed1995

Susceptibility of llamas (Lama glama) to infection with foot-and-mouth-disease virus.

An experimental trial was conducted to evaluate the ability of foot-and-mouth-disease (FMD) virus (serotypes A79, C3, O1) to infect susceptible llamas exposed either directly to affected livestock, or indirectly to llamas that had been directly exposed to affected livestock. In addition, susceptible livestock species (cattle, pigs, goats, and sheep) were exposed to those llamas that had been both directly and indirectly exposed to the FMD virus to further look at potential transmission possibilities. Of 30 llamas directly exposed to the FMD virus, only three (3/30) showed evidence of infection, and of those, only two (2/30) had mild clinical signs. No FMD virus was isolated from either oesophageal-pharyngeal (OP) fluid or blood samples collected from the infected llamas beyond 14 days post-exposure. There was no evidence of virus transmission between the directly exposed and indirectly exposed llamas or between both groups of llamas and susceptible domestic livestock, as determined by the lack of clinical signs, by virus isolation, and by serology results. These results provide further evidence that llamas are resistant to FMD infection, and that they play a minor role, if any, in transmitting the virus to domestic livestock.

Animals↗
PubMed1995

Informed consent and informed refusal.

BACKGROUND: This article continues our medicolegal series that addresses issues affecting current dermatology practice. Informed consent and informed refusal have become cornerstones of modern American healthcare, and can serve to facilitate communication and trust between physician and patient. METHODS: A format with an initial discussion of legal concepts is followed by hypothetical problems and a review of actual cases to illustrate the principles of informed consent and informed refusal. RESULTS: A valid informed consent from a competent patient should be obtained before initiating most dermatologic treatment. When a competent patient refuses a recommended medical test or procedure, the physician should make sure the patient understands the potential negative consequences of refusal. Some form of written documentation in the medical record is advised in either situation. CONCLUSION: Failure to obtain a patient's informed consent prior to beginning treatment or failing to obtain an informed refusal before accepting a patient's decision to forego a test or procedure may subject the dermatologist to multiple later allegations, most commonly negligence.

Adult↗