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Biomedical subjects

A Ramirez

Publications and source records attributed to A Ramirez.

At least 55 records · Page 3Linked to original sources
PubMed1997

The effect of ultrasound on collagen synthesis and fibroblast proliferation in vitro.

Ultrasound has been applied therapeutically to accelerate connective tissue healing although there is little direct scientific evidence to support its use. This investigation was conducted to determine the effects of ultrasound on the rate of collagen synthesis and cell proliferation using cultured fibroblasts derived from Achilles tendons of neonatal rats. Ultrasound (intensity = 0.4 W.cm-2; frequency = 1 MHz) was applied to experimental cells growing as monolayers in culture flasks. Ultrasound had no effect on the rate of collagen synthesis by control fibroblasts over a period of 9 d. The addition of vitamin C to culture media stimulated collagen synthesis to the same extent in both control and ultrasound-treated cultures. Partial digestion of cell matrices with collagenase (used to simulate injury) resulted in an approximately 20% increase in the rate of collagen synthesis. Synthesis was further increased with ultrasound treatment (50-67%). For example, after a single ultrasound treatment, the rate of collagen synthesis was 3.0 +/- 0.4 pg.micrograms-1 DNA.h-1 in cultures treated with collagenase, compared with 1.8 +/- 0.3 pg.micrograms-1 DNA.h-1 in collagenase-treated cultures not treated with ultrasound and 1.4 +/- 0.3 pg.micrograms-1 DNA.h-1 in controls. Ultrasound applied to preconfluent cultures resulted in significant increases in the rate of thymidine incorporation and DNA content. Three daily ultrasound treatments caused a 100% increase in the rate of thymidine incorporation and a 28% increase in DNA content. The results indicate that ultrasound stimulates collagen synthesis in tendon fibroblasts in response to an injury of the connective tissue matrix and that ultrasound stimulates cell division during periods of rapid cell proliferation.

Achilles Tendon↗
PubMed1996

Detection of salivary and seric IgG and IgA antipooled pigeon sera activities in patients with pigeon breeder's disease.

Pigeon breeder's disease (PBD) is an interstitial lung disease induced by exposure to pigeon antigens. Search of antipigeon antigen antibodies (APSA) in serum or bronchoalveolar lavage is generally used for auxiliary diagnostic purposes. However, APSA can be present in a number of exposed but asymptomatic individuals as well as in patients with other interstitial lung diseases who live in areas where keeping pigeons is a common domestic habit. In this study, saliva was evaluated as an alternative means to serum for APSA detection by ELISA using pooled pigeon sera as antigen. Serum and saliva samples obtained from 17 patients with PBD, 14 with idiopathic pulmonary fibrosis (IPF), 19 asymptomatic relatives (AR) exposed to pigeon antigens, and 27 clinical healthy voluntary subjects (CHVS) were tested for IgG and IgA APSA. Our results showed that both fluids obtained from PBD patients exhibited a significantly higher specific IgG antibody activity compared to the other groups. Serum optical density (O.D.) values for PBD were 1.187 +/- 0.738 vs. 0.024 +/- 0.033, 0.255 +/- 0.471, and 0.204 +/- 0.346 for CHVS, AR and IPF, respectively (P < 0.05). Salivary O.D. for PBD were 0.801 +/- 0.447 vs 0.010 +/- 0.011, 0.104 +/- 0.151, and 0.22 +/- 0.447 (P < 0.05). In contrast, serum specific IgA did not discriminate between PBD and IPF patients. In addition, although the PBD group exhibited the highest values of IgA salivary APSA, high levels were also observed in saliva specimens from CHVS, a group of normal individuals who deny pigeon exposure. These findings suggest that measurement of IgG salivary APSA can play a role in the evaluation process of patients with pigeon breeder's disease.

Adult↗
PubMed1996

Comparison of manual and automatic CPAP titration in patients with sleep apnea/hypopnea syndrome.

Automatic CPAP (auto-CPAP) is engineered to automatically provide a positive pressure to the upper airway in response to apnea, hypopnea, airflow limitation, or snoring in patients with the sleep apnea/ hypopnea syndrome (SAHS). Self-adjusted CPAP has theoretical advantages over traditional fixed CPAP. We investigated the value of auto-CPAP regulation in 20 patients with SAHS in order to predict future fixed-level CPAP needs, as an alternative method to conventional polysomnographically (PSG)-controlled CPAP titration. This was accomplished through comparison of the optimal CPAP level obtained with PSG with that obtained with auto-CPAP. There were no significant differences between the optimal CPAP level achieved with full PSG or with auto-CPAP. As a secondary analysis, we analyzed auto-CPAP performance with regard to sleep-stage distribution and arousals in a group of nine male patients, and compared it with the previous group of 20 patients in which manually CPAP titration was guided by PSG. After adequate CPAP was reached, upward and downward fluctuations in the CPAP level had no significant effect on sleep architecture or fragmentation. We conclude that auto-CPAP permits the prediction of future fixed-level CPAP needs, and does so without sleep disruption.

Adult↗
PubMed1996

Clinical and epidemiological evaluation of a live, cold-adapted influenza vaccine for 3-14-year-olds.

Reported is a study of live, cold-adapted (CA) reassortant mono-, di-, and trivalent influenza type A and B vaccines in a series of controlled clinical and epidemiological investigations involving nearly 130 000 children aged 3-15 years. The results of clinical, immunological, and morbidity investigations of the vaccinees and a control group over 6-months' follow-up indicated that the vaccines were completely attenuated by the children. Transient febrile reactions occurred in < 1% of the children after vaccination, including double seronegative individuals with low antibody titres. The type A reisolates examined were genetically stable. The reassortants did not suppress each other after simultaneous inoculation of children and stimulated antibody response to influenza virus strains A1, A3, and B. The incidence of influenza-like diseases was approximately 30-40% lower among the vaccinated group than among the control group. The study demonstrates, for the first time, the efficacy of CA vaccine against infections caused by influenza B virus.

Adolescent↗
PubMed1995

Prevalence of antibodies against Entamoeba histolytica in Mexico measured by ELISA.

The prevalence of antibodies against Entamoeba histolytica was studied in the Mexican population using an immunoenzyme assay in solid phase (ELISA) and semiautomatic equipment. The antigen was a mixture of membrane proteins obtained by Triton X-100 extraction from an axenic culture of Entamoeba histolytica HM1-IMSS. The method was standardized by comparing serum samples from amoebic liver abscess patients with healthy volunteers. From the 60,538 samples supplied by the National Seroepidemiology Survey, antibodies were found in 4.49% (4.32-4.65% at 95% confidence limit). More significant titres occurred in the central region of the country. The ratio female to male was 1.25:1. The population living in metropolitan areas had probably been infected at a younger age than those living in the country. Important differences were found in the seroprevalence obtained by ELISA compared with a study which used indirect haemagglutination (IHA) in the same sample frame.

Adolescent↗
PubMed1995

Elective intubation for neurologic deterioration after stroke.

OBJECTIVE: To provide data to guide physicians and family when deciding whether a patient should be electively intubated after ischemic stroke. DESIGN: Chart review and patient interview. Clinical course, neurologic outcome, and financial and psychosocial effect of the decision to intubate were determined. SETTING: Neurology/Neurosurgery critical care unit. PATIENTS: Of our last 250 acute carotid territory ischemic stroke cases, we found 20 patients (8%) who were electively intubated, after CT and neurologic assessment, for neurologic deterioration. INTERVENTIONS: All patients received standard medical therapy. RESULTS: Intubation occurred 3 hours to 7 days (mean, 41 hours) after the onset of symptoms; six of 20 patients required intubation within the first 6 hours. Once clinical deterioration began, 10 of 20 patients required intubation within 1 hour. Six of 20 patients were discharged alive; two subsequently died, one is mostly dependent, two became mostly independent (one of these had a hemicraniectomy and is still improving, and the other died of an intercurrent illness 4 years after her stroke), and one is totally independent. The four "good" outcome survivors were distinguished by higher Glasgow Coma Scale scores (9.2 versus 5.9), and extubation was usually possible within 72 hours. For nonsurvivors, mean hospitalization after intubation was 6.4 days. In survivors, the monthly uninsured cost was $0 to $2,000, and caregivers experienced moderate stress. The same decision would be repeated by 76% of caregivers; 53% of caregivers would want intubation for themselves. CONCLUSIONS: Satisfactory outcome is possible in the 8% of ischemic stroke patients requiring elective intubation. Possible predictors of good outcome include less severe depression of consciousness at the time of intubation, extubation within 3 days, and hemicraniectomy. In retrospect, most families would repeat the decision to intubate. Further study in more patients of the cost/benefit of cerebral resuscitation after stroke is greatly needed.

Adult↗
PubMed1993

Specific expression in adult mice and post-implantation embryos of a transgene carrying the histone H1(0) regulatory region.

Histone H1(0), a variant of the H1 group, has been found associated with the repressed state of chromatin and its content is increased in terminally differentiated cells. We have cloned a mouse H1(0) histone gene and introduced the promoter region, ligated to the beta-galactosidase reporter gene, into transgenic mice. By histochemistry we demonstrated a strong expression of the transgene in adult kidney, testis and brain. Intestine, uterus and ovarium were also positive. This expression followed the same pattern as that of the endogenous H1(0) gene, as demonstrated by in situ hybridization with a non-coding fragment of the mRNA, by Northern analysis, and by immunofluorescence with specific antibodies. In post-implantation embryos, the expression was very low up to day ten p.c. At this time, most of the X-Gal staining was found in the brain, retina and some of the large blood vessels. Hence, expression of the transgene as well as of the endogenous H1(0) gene is not exclusively linked to a differentiated phenotype or to a reduced cell proliferation capacity.

Animals↗
PubMed1993

Pressure diuresis and natriuresis in cirrhotic rats.

Arterial hypotension in liver cirrhosis has been proposed as a major mechanism contributing to renal sodium and water retention. To evaluate kidney excretory responses at different levels of arterial pressure (AP), we have characterized the relationships between renal perfusion pressure (RPP) and sodium and water excretion in carbon tetrachloride cirrhotic rats. Experiments were performed in anesthetized control (n = 9) and cirrhotic rats with (Asc, n = 6) and without ascites (Cir, n = 6) by mechanically adjusting vascular resistance in animals with renal denervation and infused with main systemic hormones. Control and Cir animals showed similar glomerular filtration rates (GFR), renal blood flows, hematocrits (Hct), and plasma proteins (PP). However, Hct, PP, and GFR were significantly lower in the Asc rats. For the same level of RPP, both cirrhotic groups excreted significantly less water and sodium than controls. Then, the pressure diuresis and natriuresis relationships of the Cir animals were significantly depressed, but those of the Asc animals were more reduced than those of the Cir rats. These results indicate that the cirrhotic kidney is not able to normally increase the sodium and water excretion in response to changes in AP. Intrarenal mechanisms, and not mainly RPP, are likely mediators of the renal alterations of liver cirrhosis.

Animals↗
PubMed1993

[Mechanical reperfusion in acute myocardial infarction after failure of thrombolysis with intravenous streptokinase].

AIM: to report the clinical evolution of four patients with acute myocardial infarction that were subjected to immediate coronary angioplasty due to the failure of reperfusion with streptokinase. BACKGROUND: the limitations for the use of thrombolytic agents, an accepted treatment of acute myocardial infarction, or their uncertain results in selected groups of patients has prompted the search for mechanical revascularization infarction subjected to thrombolytic therapy with streptokinase (1.500.000 U i.v.) after administration of hydrocortisone (100 mg i.v.) and acetyl salicylic acid (500 mg od). After 60 min thrombolytic therapy and due to hemodynamic depression with requirement of inotropic agents or the absence of clinical signs of reperfusion, the patients were subjected to coronary angiography. In view of a total occlusion or severe stenosis of the artery responsible for the infarction, an immediate transluminal angiography was performed to improve coronary flow. RESULTS: transluminal coronary angioplasty revascularized arteries with total occlusion or increased the lumen of those with severe residual stenosis. This was accompanied by reduction in pain and hemodynamic improvement. In one patient with complete AV block, conduction was improved and sinus rhythm was recovered. Echocardiographic controls showed preservation of ventricular function with persistence of segmental motility alterations. CONCLUSIONS: transluminal coronary angioplasty can be a revascularization alternative in patients with acute myocardial infarction and failure of reperfusion with systemic streptokinase.

Aged↗
PubMed1993

The reproducibility of the 50-g, 1-hour glucose screen for diabetes in pregnancy.

OBJECTIVE: To explore the day-to-day reproducibility of the 50-g, 1-hour glucose screening test performed on 2 consecutive days in the same women. METHODS: Eight women at 12-23.6 weeks' gestation (early subjects) and 80 women at 24-28 weeks (late subjects) without known diabetes mellitus were studied. The glucose screening test was performed in the morning on 2 consecutive days in the same women, under an identical or opposite sequence of fasting and fed conditions. The women were thus divided into four subgroups: fast-fast, fed-fed, fast-fed, and fed-fast. Duplicate serum glucose concentrations were measured by the glucose oxidase method. Paired Student t test was used to analyze day-1 versus day-2 glucose levels in each woman of each subgroup. RESULTS: The serum glucose concentrations were higher on day 1 than on day 2 in the subgroups fast-fast and fast-fed (P < .05) in both early and late patients, whereas the opposite was seen in the subgroups fed-fast (P < .05). No significant differences were observed in the subgroups of fed-fed. At three different glucose thresholds (130, 135, and 140 mg/dL), there was more than 90% daily reproducibility for normal results in both groups, and nearly 50 and 83% daily reproducibility for abnormal results in the early and late patients, respectively. CONCLUSIONS: Up to 28 weeks of pregnancy, the screening test had a high reproducibility for normal results. For abnormal results, daily reproducibility was better after than before 24 weeks' gestation, regardless of prior testing conditions. Depending on the pre-testing conditions, the use of a different serum glucose threshold seems warranted.

Adult↗
PubMed1992

Effects of cyclic AMP and butyrate on cell cycle, DNA, RNA, and purine synthesis of cultured astrocytes.

Dibutyryl cyclic monophosphate (dBcAMP) has been shown to inhibit growth, and alter the morphology of astrocytes. However, the potential contribution of its hydrolytic product, butyrate, in inducing some of the changes that have been attributed to dBcAMP, is not clear. DNA, RNA, and purine synthesis were therefore studied in primary astrocyte cultures after 24 hours of exposure to varying concentrations of butyrate, dBcAMP, and agents that increase intracellular cAMP levels. Progression of cells through cell cycle was also studied by flow cytometry. Dibutyryl cAMP partially arrested cells in Go/G1 phase of cell cycle while sodium butyrate increased the percentage population of cells in G2/M phase. DNA synthesis and de novo purine synthesis were inhibited after treatment with dBcAMP, sodium butyrate, and various drugs that increase intracellular cAMP levels. RNA synthesis was increased with cAMP but was not affected by sodium butyrate. Our study shows that at millimolar concentrations, butyrate is capable of altering the cell cycle and inhibiting DNA synthesis in primary astrocyte cultures, in a manner that is similar although not identical to the effects of dBcAMP.

Animals↗
PubMed1992

Inhibition of the transepithelial potential difference and short circuit current in the isolated frog skin by alloxan.

1. Electrical parameters: short circuit current (SCC), transepithelial potential difference (PD) and electrical resistance (R) were measured in isolated frog skin (Rana pipiens) in the presence and in the absence of alloxan. 2. Alloxan decreased SCC and PD in a concentration-dependent pattern, while R remained unchanged. 3. The effect on SCC and PD was observed after 25 min of exposure to the drug. Maximal average effect was 20% in SCC and 17.5% in PD. 4. These results suggest that alloxan decreased epithelial sodium transport, through interference with the activity of the Na(+)-K(+)-ATPase.

Alloxan↗
PubMed1991

Experimental glaucoma significantly decreases atrial natriuretic factor (ANF) receptors in the ciliary processes of the rabbit eye.

ANF binding sites were analysed in the ciliary processes of rabbits with unilateral experimental glaucoma which had been induced by injecting alpha-chymotrypsin into the posterior chamber of the right eyes. The intraocular pressure (IOP) of glaucomatous eyes was significantly greater (28.4 +/- 4 mmHg) than that of normotensive control eyes (13.1 +/- 1.4 mmHg, mean +/- S.E.M., n = 23, P less than 0.05). ANF concentrations in aqueous humour and the ciliary processes were significantly higher in glaucomatous eyes (91 +/- 2 pg ml-1 and 30.4 +/- 4.2 pg g-1 wet weight) than in normal eyes (3.1 +/- 2.2 pg ml-1 and 10.2 +/- 2.7 pg g-1 wet weight, respectively, n = 6, P less than 0.01). The number of ANF-binding sites (Bmax) in the ciliary processes of glaucomatous rabbit eyes was significantly decreased in comparison to the controls (24 +/- 4 vs. 13 +/- 3 fmol mg-1 protein, n = 10, P less than 0.05). These data suggest that ANF receptors in the ciliary processes are down-regulated and that ANF may play an important role in the pathophysiology of experimental glaucoma.

Animals↗
PubMed1991

Effects of methotrexate on RNA and purine synthesis of astrocytes in primary culture.

There is increasing evidence to indicate that astrocytes are primary targets for methotrexate (MTX) neurotoxicity. However, the mechanism by which MTX exerts its deleterious effect on astroglial cells is not known. Methotrexate acts by inhibiting dihydrofolate reductase and in other cell systems has been reported to inhibit thymidylate synthesis, purine synthesis or both. To determine the mechanism involved in MTX-induced toxicity to the nervous system, RNA synthesis was studied in two week-old primary astrocyte cultures by measuring [3H]Uridine (Urd) incorporation 24 hours after exposure to varying concentrations of MTX. De novo purine synthesis was also studied by measuring incorporation of [14C]glycine and [14C]formate in cultured astrocytes. The radioactivity level of incorporated Urd in culture decreased to 48%, 53% and 43% after exposure to 1, 10 and 100 microM MTX. Total [14C]glycine incorporation was not affected while incorporation of [14C]formate was almost completely inhibited by MTX. The MTX-induced inhibition of [3H]Urd incorporation was not reversed by concomitant addition of exogenous purine bases (1 and 10 microM adenine, guanine and hypoxanthine) or nucleosides (1 and 10 microM adenosine, guanosine and inosine) to the MTX-treated cultures. On the other hand, addition of formyl-tetrahydrofolate reversed the MTX-induced reduction in [3H]Urd incorporation, indicating that the RNA inhibition was due to depletion of folate-dependent substrates for purine synthesis. Our results provide evidence that inhibition of purine and RNA synthesis may be the underlying mechanism involved in MTX-induced injury to the astrocytes, and may be important in the pathogenesis of MTX encephalopathy.

Animals↗
PubMed1990

Inhibition of gamma-glutamyl transpeptidase decreases amino acid uptake in human keratinocytes in culture.

Acivicin inhibits gamma-glutamyl transpeptidase activity in human keratinocytes in culture. Treatment of these cells with acivicin produces a decrease in the uptake of L-[U-14C]alanine, 2-amino-[1-14C]-isobutyrate, L-[U-14C]leucine and 1-aminocyclopentane-1-[14C]carboxylate. D-[U-14C]glucose uptake is not affected by the presence of acivicin. These results support, for the first time in vitro, the hypothesis that the gamma-glutamyl cycle may be involved in amino acid uptake by human cells.

Amino Acids↗
PubMed1990

Enhanced spatial discrimination learning in rats following 5,7-DHT-induced serotonergic deafferentation of the hippocampus.

Learning in rats trained in the Stone 14-unit T-maze, a complex, positively reinforced spatial discrimination task was assessed following cytotoxic (5,7-dihydroxytryptamine; 5,7-DHT) deafferentation of the serotonergic inputs to the hippocampus. Serotonergic deafferentation was accomplished by infusing the cytotoxin in to the fornix-fimbria/cingulum bundle. Lesioned rats reached criterion (i.e. learned) in significantly fewer trials and made significantly fewer errors throughout training than either vehicle-injected or sham-operated controls. This represents the first time that the effects of selective chronic destruction of serotonergic inputs to the hippocampus have been investigated. The present results provide, therefore, evidence in support of a neuromodulatory role for serotonin (5-HT) within the rat hippocampus in the mediation of the processes underlying learning and memory for this task. Other studies are, therefore, warranted in order to determine whether hippocampal 5-HT also plays a role in the mediation of the processes underlying learning and memory in other types of tasks.

5,7-Dihydroxytryptamine↗
PubMed1990

Immunoreactive atrial natriuretic factor in aqueous humor: its concentration is increased with high intraocular pressure in rabbit eyes.

Atrial natriuretic factor (ANF) concentration in the aqueous humor (AH) was studied in rabbits with experimental glaucoma induced by injecting alpha-chymotrypsin into the posterior chamber. In normal rabbit eyes, the ANF concentration in AH was 3.1 +/- 1.2 pg/ml (mean +/- SEM; n = 12), ranging from 0 to 5.8 pg/ml, whereas it was significantly higher in AH from glaucomatous rabbit eyes, being 81.0 +/- 9.8 pg/ml (n = 12). These findings were correlated with intraocular pressure (IOP), which was 13.0 +/- 2.4 mmHg (n = 12) in normal rabbit eyes and significantly greater in glaucomatous eyes: 24.4 +/- 3.0 mmHg (n = 12). Our data indicate that enhanced ANF release in AH during experimental glaucoma may play an important physiological role in modulating IOP.

Animals↗