PubMed Health⌕ Search

Biomedical subjects

L Rivera

Publications and source records attributed to L Rivera.

At least 37 records · Page 2Linked to original sources
PubMed2000

Blunt splenic injury in adults: Multi-institutional Study of the Eastern Association for the Surgery of Trauma.

BACKGROUND: Nonoperative management of blunt injury to the spleen in adults has been applied with increasing frequency. However, the criteria for nonoperative management are controversial. The purpose of this multi-institutional study was to determine which factors predict successful observation of blunt splenic injury in adults. METHODS: A total of 1,488 adults (>15 years of age) with blunt splenic injury from 27 trauma centers in 1997 were studied through the Multi-institutional Trials Committee of the Eastern Association for the Surgery of Trauma. Statistical analysis was performed with analysis of variance and extended chi2 test. Data are expressed as mean +/- SD; a value of p < 0.05 was considered significant. RESULTS: A total of 38.5 % of patients went directly to the operating room (group I); 61.5% of patients were admitted with planned nonoperative management. Of the patients admitted with planned observation, 10.8% failed and required laparotomy; 82.1% of patients with an Injury Severity Score (ISS) < 15 and 46.6% of patients with ISS > 15 were successfully observed. Frequency of immediate operation correlated with American Association for the Surgery of Trauma (AAST) grades of splenic injury: I (23.9%), II (22.4%), III (38.1%), IV (73.7%), and V (94.9%) (p < 0.05). Of patients initially managed nonoperatively, the failure rate increased significantly by AAST grade of splenic injury: I (4.8%), II (9.5%), III (19.6%), IV (33.3%), and V (75.0%) (p < 0.05). A total of 60.9% of the patients failed nonoperative management within 24 hours of admission; 8% failed 9 days or later after injury. Laparotomy was ultimately performed in 19.9% of patients with small hemoperitoneum, 49.4% of patients with moderate hemoperitoneum, and 72.6% of patients with large hemoperitoneum. CONCLUSION: In this multicenter study, 38.5% of adults with blunt splenic injury went directly to laparotomy. Ultimately, 54.8% of patients were successfully managed nonoperatively; the failure rate of planned observation was 10.8%, with 60.9% of failures occurring in the first 24 hours. Successful nonoperative management was associated with higher blood pressure and hematocrit, and less severe injury based on ISS, Glasgow Coma Scale, grade of splenic injury, and quantity of hemoperitoneum.

Adult↗
PubMed2000

Glycaemic and insulinaemic indices of Mexican foods high in complex carbohydrates.

For the purpose of enriching the knowledge on the glycaemic (GI) and insulinaemic (InIn) indices of indigenous foods, 3 single foods and 3 realistic high complex carbohydrate meals (bread=100) were studied in 8 healthy subjects. Observed GI (mean+/-SEM) were: beans (B) 19.3+/-3.4, wheat tortilla (WT) 42.5+/-6.9, corn tortilla (CT) 73.8+/-6.5, wheat tortilla beans taco (BWT) 39.9+/-12.8, corn tortilla beans taco (BCT) 56.2+/-8.2 and corn tortilla potato taco (PT) 111.0+/-11.5. The glycaemic index of all foods was lower than white bread (WB) (p<0.01) except for PT. B represented the lowest GI. InIn indices of B (41.7+/-4.5), WT (62.4+/-6.7) and CT (85.5+/-7.8) were lower than WB (p<0.01), whereas PT (171.3+/-11.4) was higher. B InIn was the lowest except for WT, and the highest InIn was for PT. B, WT and CBT might be included in a regular diet for weight maintenance and control of hunger. It is suggested to moderate the ingestion of CT and PT in subjects with obesity and hyperglycaemia complications. It is important to study single and realistic foods with varied composition in diabetic subjects, whose glycaemic responses in reference to their insulinaemic responses might be different to those reported in the present study.

Adult↗
PubMed1999

Hepatitis B seroprevalence in Latin America.

The seroprevalence of hepatitis B was investigated in over 12,000 subjects in six countries of Latin America: Argentina, Brazil, Chile, the Dominican Republic, Mexico, and Venezuela. Each study population was stratified according to age, gender, and socioeconomic status. Antibodies against hepatitis B core antigen (anti-HBc) were measured in order to determine hepatitis B infection. The highest overall seroprevalence was found in the Dominican Republic (21.4%), followed by Brazil (7.9%), Venezuela (3.2%), Argentina (2.1%), Mexico (1.4%), and Chile (0.6%). In all the countries an increase in seroprevalence was found among persons 16 years old and older, suggesting sexual transmission as the major route of infection. In addition, comparatively high seroprevalence levels were seen at an early age in the Dominican Republic and Brazil, implicating a vertical route of transmission.

Adolescent↗
PubMed1999

Hepatitis A in Latin America: a changing epidemiologic pattern.

In a multicenter study, hepatitis A virus (HAV) seroprevalence was surveyed in six countries in Latin America in which in 12,000 subjects were stratified for age. The highest rates of seroprevalence were recorded in the Dominican Republic (89.0%) and Mexico (81.0%), with lower rates in Brazil (64.7%), Chile (58.1%), Venezuela (55.7%), and Argentina (55.0%). The seroprevalence of HAV in children between 1 and 5 years of age was less than 50%, except in the Dominican Republic. In the 5-10-year-old age group, seroprevalence rates have also decreased compared with previous reports. This suggests that the epidemiology is shifting from high to intermediate endemicity, with the population susceptible to HAV infection shifting from children to adolescents and adults. Furthermore, data from Brazil, Argentina, and Mexico show that HAV seroprevalence is significantly lower in people living in medium and high socioeconomic conditions. This study suggests the need for appropriate vaccination programs to be implemented targeting children, adolescents, and adults, particularly in higher socioeconomic groups.

Adolescent↗
PubMed1999

[Effectiveness educational programs for school dental health. Experimental trial].

This paper is a limited-scope experimental study to evaluate the effectiveness of the Dental Health Educational Programs implemented in Venezuelan schools by the Dentistry Division of the Ministry of Health and Social Welfare. Two hundred and ninety-six six-to-twelve year olds were randomly selected from two schools, one private, the other public, located in the Municipality of Maracaibo, State of Zulia, Venezuela. The children assigned to each school were randomly distributed among the experimental and control groups. A general hypothesis was set up, stating that reinforcement and motivation generate changes in the gingival health of the children under study, but with different results for each, depending on their psycho-social characteristics. Two approaches were used: instruction/supervision and instruction/supervision/reinforcement/stimulation. These two approaches were then measured against a "psycho-social profile" which is based on material conditions and the developmental stages of the children. Instructions were given to the experimental group on how to brush their teeth. They were supervised, reinforced and stimulated for a period of six months, with a post-test assessment. The control group was only given instructions on how to brush their teeth and supervised. A scale based on Massler's classification was used to determine the developmental stages. Standardized indices were used to evaluate the dependent variable: Plaque Index and Gingival Index. The results showed that: the material living conditions and developmental stage of the child are elements that influence the assimilation of pre-established behavior, the basis of preventive programs.

Child↗
PubMed1998

Characterization of the muscarinic receptor mediating contraction of the dog prostate.

1. We have studied the effects of muscarinic cholinoceptor agonists and subtype-preferring antagonists on the isometric contraction of smooth muscle strips from dog prostate. 2. Acetylcholine and carbachol induced contraction of prostate strips from the peripheral zone, ('the capsule'). Bethanechol contracted the tissue but not at lower doses. McN-A-343 and oxotremorine-M showed the same effects. 3. Blocking alpha- and beta-adrenoceptors with phentolamine and propranolol, respectively, did not modify carbachol-induced contractions. 4. The nicotinic receptor blocker, hexamethonium (10(-6)-10(-4) M) did not affect the contractile response evoked by a single dose of carbachol (10(-5) M), whilst the muscarinic receptor antagonist, atropine (10(-11)-10(-9) M), inhibited it in a competitive manner. 5. The muscarinic M1 (pirenzepine), M2 [AF-DX 116, himbacine (M2/M4) and methoctramine], M3 (HHSID and f-F-HHSID), and putative M4 (tropicamide) antagonists reduced significantly the carbachol-induced contractions. The pIC50 values were: atropine (10.01) > himbacine (8.3) > methoctramine (7.85) > AF-DX 116 (7.60) > HHSID (7.21) > p-F-HHSID (7.10) > pirenzepine (7.30) > tropicamide (7.00). 6. The antagonist profile indicates that an predominant M2 receptor subtype could mediate the muscarinic contraction in the canine prostate.

Acetylcholine↗
PubMed1998

Anatomic, age, and sex distribution of colorectal cancer in a New York City Hispanic population.

This study was undertaken to examine the regional distribution of colorectal cancer, the age of presentation for different subsite locations of the disease and whether there is any intersex difference in frequency of the disease, in New York City Hispanics. The charts of Hispanic patients on file with the tumor registry at Bellevue Hospital Center in New York City from 1976 to 1995 were reviewed. Demographic and pathologic data including patient age and cancer location were analyzed. Lesions of the distal colon and rectum accounted for more than 70%, while right-sided lesions were found in 20.7% of patients. The male to female ratio was 47.6% to 52.4%. The overall mean age of patients was 60.4 years. Proximal lesions presented at a later age than distal lesions, 63.2 years for the right colon and 58.5 years for the rectum; this difference in ages was significant. These results suggest that Hispanic-American patients with colorectal cancer appear to be presenting at an earlier age than the general American population. Further study is needed to determine whether Hispanic women are presenting with a higher frequency of colorectal cancer than their male counterparts and whether Hispanic patients are presenting at an earlier age than the general population with colorectal malignancies and why.

Adenocarcinoma↗
PubMed1997

Distribution and functional effects of neuropeptide Y on equine ureteral smooth muscle and resistance arteries.

The distribution of neuropeptide Y (NPY)-immunoreactive (IR) nerves, as well as the functional effects of NPY and the Y1- and Y2-receptor agonists, [Leu31,Pro34]NPY and NPY(13-36), respectively, have been investigated in vitro in both visceral and arterial smooth muscle of the horse intravesical ureter. NPY-IR nerve fibres were widely distributed along the entire length of the ureter, although the intravesical part was the most richly innervated region, and the only one where NPY-IR ganglion cells were found. NPY (10(-7) M) did not affect either basal tone or spontaneous rhythmic contractions of the isolated intravesical ureter, but significantly enhanced the increases in both tone and frequency of phasic activity elicited by noradrenaline (10(-6) and 10(-5) M). The Y1-receptor agonist, [Leu31,Pro34]NPY (10(-7) and 10(-6) M) did not significantly alter either ureteral basal tone or the contractile activity induced by noradrenaline, whereas the Y2-receptor agonist, NPY(13-36) (10(-7) M), mimicked the potentiating effect of NPY on noradrenaline responses. In ureteral resistance arteries (effective lumen diameters of 130-300 microm), NPY (10(-10) to 10(-7) M) elicited concentration-dependent contractions, which were inversely correlated with the arterial lumen diameter. Submaximal concentrations of NPY (10(-8) M) significantly increased the sensitivity of ureteral arteries to noradrenaline. [Leu31,Pro34]NPY (10(-10) to 10(-7) M), but not NPY(13-36), induced a contractile effect of similar magnitude and potency as those of NPY, and also potentiated noradrenaline responses. The present results demonstrate a rich NPY-innervation in the intravesical ureter and reveal functional effects of the peptide enhancing motor activity in both ureteral and arterial smooth muscles, although the receptors mediating such effects seem to be different. Thus, NPY potentiates the phasic contractions and tone elicited by noradrenaline through Y2-receptors, whereas it both contracts and potentiates noradrenaline vasoconstriction in ureteral arteries via Y1-receptors.

Animals↗
PubMed1997

Involvement of a glibenclamide-sensitive mechanism in the nitrergic neurotransmission of the pig intravesical ureter.

1. The present study was designed to investigate whether potassium (K+) channels are involved in the relaxations to nitric oxide (NO) of pig intravesical ureteral preparations suspended in organ baths for isometric tension recordings. In ureteral strips treated with guanethidine (10(-5) M) and atropine (10(-7) M) to block adrenergic neurotransmission and muscarinic receptors, respectively, NO was either released from nitrergic nerves by electrical field stimulation (EFS, 0.5-10 Hz., 1 ms duration, 20 s trains), or exogenously-applied as an acidified solution of sodium nitrite (NaNO2, 10(-6)-10(-3) M). 2. Incubation with an inhibitor of guanylate cyclase activation by NO, methylene blue (10(-5) M) did not change the basal tension of intravesical ureteral strips but inhibited the relaxation induced by EFS or exogenous NO on ureteral preparations contracted with the thromboxane analogue U46619 (10(-7) M). 3. Incubation with charybdotoxin (3 x 10(-8) M) and apamin (5 x 10(-7) M), which are inhibitors of large and small conductance calcium (Ca2+)-activated K+ channels, respectively, did not modify basal tension or the relaxations induced by EFS and exogenous NO. Treatment with charybdotoxin or apamin plus methylene blue (10(-5) M) significantly reduced the relaxations to EFS and exogenous NO. However, in both cases the reductions were similar to the inhibition evoked by methylene blue alone. The combined addition of charybdotoxin plus apamin did not change the relaxations to EFS or exogenously added NO of the porcine intravesical ureter. 4. Cromakalim (10(-8) 3 x 10(-6) M), an opener of ATP-sensitive K+ channels, evoked a dose-dependent relaxation with a pD2 of 7.3 +/- 0.2 and maximum relaxant effect of a 71.8 +/- 4.2% of the contraction induced by U46619 in the pig intravesical ureter. The blocker of ATP-sensitive K+ channels, glibenclamide (10(-6) M), inhibited markedly the relaxations to cromakalim. 5. Glibenclamide (10(-6) M) had no effect on the basal tone of ureteral preparations but significantly reduced the relaxations induced by both EFS and exogenous NO. Combined treatment with methylene blue (10(-5) M) and glibenclamide (10(-6) M) did not exert an effect greater than that of methylene blue alone on either EFS- or NO-evoked relaxations of the pig ureter. 6. The present results suggest that NO acts as an inhibitory neurotransmitter in the pig intravesical ureter and relaxes smooth muscle through a guanylate cyclase-dependent mechanism which seems to favour the opening of glibenclamide-sensitive K+ channels.

Animals↗
PubMed1997

Dynamic ventilatory characteristics during weaning in postoperative critically ill patients.

Postoperative patients occasionally require more than 48 h of mechanical ventilation. This study examined whether there were distinct differences in dynamic respiratory variables between patients who successfully weaned from mechanical ventilation and those who failed. Forty general and thoracic surgery patients underwent a standardized weaning sequence: 25 min of synchronous intermittent mandatory ventilation (SIMV) at 8 bpm plus 5 cm H2O pressure support ventilation (PSV), then SIMV at 4 bpm plus 5 cm H2O PSV, followed by continuous positive airway pressure (CPAP) plus 5 cm H2O PSV and, finally, CPAP without PSV. Twenty-eight patients successfully weaned and 12 failed. During SIMV at 4 bpm plus 5 cm H2O PSV, the spontaneous respiratory rate to spontaneous tidal volume ratio (sRR/sV(T)) and total and spontaneous respiratory rates were higher (P < 0.01) in the failure group. sRR/sV(T) values (threshold 65 bpm/L, sensitivity 1.00, specificity 0.82) and sRR values (threshold 12 bpm, sensitivity 0.95, specificity 0.84) were distinctive. During CPAP plus 5 cm H2O of PSV, respiratory rate, minute ventilation, patient work of breathing, and P0.1 were higher (P < 0.01) in those who failed. P0.1 (threshold 4.5 cm H2O, sensitivity 1.00, specificity 1.00), patient work of breathing (threshold 1.3 J/L, sensitivity 0.92, and specificity 0.98), and the sRR/sV(T) ratio (threshold 65 bpm/L, sensitivity 0.90, specificity 0.80) were distinctive. Most unique was the analysis of spontaneous breaths during low SIMV rates. This appears to permit an early determination of whether weaning would succeed.

Abdomen↗
PubMed1996

Solid-phase extraction for the selective isolation of polycyclic aromatic hydrocarbons, azaarenes and heterocyclic aromatic amines in charcoal-grilled meat.

A method for the simultaneous analysis of 12 mutagenic and/or carcinogenic compounds is described; these substances belong to three different chemical groups: polycyclic aromatic hydrocarbons (PAHs), azaarenes, i.e., nitrogen-containing polycyclic aromatic hydrocarbons (PANHs), and heterocyclic aromatic amines (HAAs). The selective enrichment procedure includes coupling of solid-phase extraction (SPE) steps using diatomaceous earth, propylsulfonic acid, silica gel and octadecylsilane columns. The eluted fractions were analysed by high-performance liquid chromatography with UV and electrochemical detection. Levels measured were estimated to be 4-19 ng g-1. Peak confirmation was carried out by GC-MS for both PAHs and PANHs, and by LC with a photodiode array detector for HAAs. The method was applied to the analysis of charcoal-grilled meat and was judged to be generally applicable for detection of these mutagens at the ppb level in processed foods.

Amines↗
PubMed1995

Pain in cognitively impaired nursing home patients.

Pain is an understudied problem in frail elderly patients, especially those with cognitive impairment, delirium, or dementia. The focus of this study was to describe the pain experienced by patients in skilled nursing homes, which have a high prevalence of cognitive impairment. A random sample of 325 subjects was selected from ten community skilled nursing homes. Subjects underwent a cross-sectional interview and chart review for the prevalence of pain complaints, etiology, and pain management strategies. Pain was assessed using the McGill Pain Questionnaire and four unidimensional scales previously utilized in younger adults. Thirty-three percent (33%) of subjects were excluded because they were either comatose (21%), non-English speaking (3.7%), temporarily away (sick in hospital) (4.3%), or refused to participate (3.7%). Of 217 subjects in the final analysis, the mean age was 84.9 years, 85% were women, and most were dependent in all activities of daily living. Subjects demonstrated substantial cognitive impairment (mean Folstein Mini-Mental State exam score was 12.1 +/- 7.9), typically having deficits in memory, orientation, and visual spatial skills. Sixty-two percent reported pain complaints, mostly related to musculoskeletal and neuropathic causes. Pain was not consistently documented in records, and pain management strategies appeared to be limited in scope and only partially successful in controlling pain. None of the four unidimensional pain-intensity scales studied in this investigation had a higher completion rate than the Present Pain Intensity Scale of the McGill Pain Questionnaire (65% completion rate). However, 83% of subjects who had pain could complete at least one of the scales. We conclude that cognitive impairment among elderly nursing home residents present a substantial barrier to pain assessment and management. Nonetheless, most patients with mild to moderate cognitive impairment can be assessed using at least one of the available bedside assessment scales.

Aged↗
PubMed1995

Survey of the provision of supportive care services at National Cancer Institute-designated cancer centers.

PURPOSE: The purpose of this survey was to determine the scope of supportive care services (SCS) designed to promote quality of life during cancer therapies at National Cancer Institute (NCI)-designated cancer centers. METHODS: A survey was mailed to the medical directors and nursing directors of 52 NCI-designated comprehensive (n = 26), clinical (n = 11), and planning cancer centers (n = 15) in the United States. Only one survey was completed from each institution. Survey questions identified services provided such as pain management, terminal care, psychosocial programs, and spiritual care. RESULTS: Thirty-nine questionnaires were received for a total response rate of 75%. Of the respondents, 45% were comprehensive cancer centers, 24% clinical cancer centers, and 29% planning centers. One center did not identify their NCI designation. Sixty-one percent of the centers reported research programs in supportive care. Outside funding was reported in 51% of the respondents, with 39% having American Cancer Society (ACS) or National Institutes of Health (NIH) funding and 28% having private industry funding. Overall SCS self-ratings improved from a 21% rating of excellent to very good 5 years ago to the current 54% rating. CONCLUSION: Survey results provide data on SCS across a representative sample of NCI cancer centers and can be used to develop standards for future cancer control programs.

Cancer Care Facilities↗
PubMed1995

[Hepatitis C virus in plasmapheresis donors].

UNLABELLED: The high prevalence of the hepatitis C virus (HCV) infection among plasmapheresis donors has been reported in several countries and Cuba. We have studied the possible relationship between the laboratory results and the real infectious state of the anti-HCV positive individuals, as well as the possible routes of infection in this population. MATERIALS AND METHODS: Retrospective data were analyzed and a prospective monthly serologic (anti-HCV) and biochemical (alanine aminotransferase) follow-up was established to 61 regular plasmapheresis donors, negative to hepatitis B markers, of a unit, which showed a prevalence of 48.3% of infection among these donors. RESULTS AND CONCLUSION: A direct correlation between the presence of antibodies to HCV and liver injury was found. No significant connection was observed between age, sex, race or sensitizing material with the positivity to anti-HCV, but it was significant with the time in plasma donation. Our results denote the risk of transmission of the HCV infection in the plasmapheresis units, pointing out the importance of the nosocomial route of infection.

Adult↗
PubMed1994

Histochemical and functional evidence for a cholinergic innervation of the equine ureter.

The distribution of acetylcholinesterase (AChE)-positive nerve fibers and cells, as well as the effects of acetylcholine (ACh) on ureteral smooth muscle and small resistance arteries were investigated in the equine ureter by means of histochemical, classic organ baths and myograph techniques. AChE-positive nerve fibers were widely distributed throughout the ureteral wall forming muscular, subepithelial and perivascular nerve plexuses, whose density was highest at the intravesical ureter. AChE-positive nerve cells were also identified grouped as adventitial or intramural ganglia. ACh increased concentration-dependently both the frequency of phasic contractile activity and basal tone of the isolated intravesical ureter, the pD2 values being 6.31 +/- 0.18 and 6.59 +/- 0.13, respectively. The ACh-induced motor effects in ureteral smooth muscle were blocked by atropine, giving pIC50 values of 8.58 +/- 0.08 and 9.68 +/- 0.05 for phasic activity and tone, respectively. Hexamethonium only inhibited ACh-evoked contractile activity at the highest concentration used. ACh elicited a potent endothelium-dependent relaxation of equine ureteral resistance arteries precontracted with 40 mM K-PSS, the pD2 value being 7.94 +/- 0.07. This relaxant response was abolished in the presence of the nitric oxide (NO) inhibitor, NG-nitro-L-arginine (L-NNA), the blockade being reversed by subsequent incubation with the NO exogenous substrate, L-arginine. The ACh-induced relaxation was competitively antagonized by atropine (pA2 = 10.05 +/- 0.18). The present results suggest the existence of a rich cholinergic innervation in the equine ureter which controls both ureteral smooth muscle and resistance arteries motor activity through the muscarinic effects of ACh. In addition, the ACh relaxant response in the ureteral resistance arteries seems to be mediated by NO.

Acetylcholine↗
PubMed1993

Catecholaminergic innervation of the equine ureter.

The aim of the present study was to determine the distribution and density of catecholaminergic nerve fibres and cells in the equine ureter by using immunohistochemical techniques to localise the enzyme tyrosine-hydroxylase (TH). TH-immunoreactive (TH-IR) nerve fibres entered the wall of the ureter as adventitial nerve trunks accompanying the blood vessels. These trunks repeatedly branched as they coursed through the muscular layer towards the epithelium, forming muscular, perivascular and subepithelial nerve plexuses. TH-IR nerve fibres were especially numerous in the pelvic and intravesical ends of the ureter. TH-IR cells have also been identified in the equine ureteral wall, usually grouped as adventitial and intramural nerve ganglia. The results of the present study demonstrated that the equine ureter, like that of other mammals, possesses a rich autonomic supply of catecholaminergic (TH-IR) nerve fibres. These morphological data support a role for the autonomic nervous system in the control of ureteral peristalsis.

Animals↗