Coupling biological detection to liquid chromatography: a new tool in drug discovery.

Procedures to characterize drugs that can be obtained from plant extracts or combinatorial chemistry are tedious, and they consume considerable resources (e.g., animals) and time. Thus, we have looked for a way to streamline this process. We describe here a novel system for the pre-characterization of drugs based on liquid chromatography coupled to biological detection using perifused or perfused organs. This novel system allows the on-line detection of pharmacologically active substances in hydrosoluble mixtures from vegetal extracts or combinatorial chemistry libraries. Depending on the volume of drug solution and concentration of the samples, the procedure can work through either medium pressure liquid chromatography or HPLC, and it enables the fingerprints of drugs to be assessed based on their contractile activity on combinations of different isolated tissues. As an example, we show how the system can identify active fractions from an extract of Stevia rebaudiana Bertoni, an activity that was later associated with rebaudioside N. Coupling liquid chromatography to biological detection offers a rapid way to focus attention on active products in complex samples, mostly from hydrosoluble species, helping to considerably reduce the time and cost of the pre-characterization of drugs.

The efficacy and safety of ezetimibe/simvastatin combination compared with intensified lipid-lowering treatment strategies in diabetic subjects with and without metabolic syndrome.

AIMS: The objective was to assess the consistency of effect of switching to ezetimibe/simvastatin 10/20 mg versus doubling the baseline statin dose (to simvastatin 40 mg or atorvastatin 20 mg) or switching to rosuvastatin 10 mg across subgroups of subjects with (n = 617) and without (n = 191) metabolic syndrome (MetS). METHODS: This was a post hoc analysis of a randomized, double-blind, 6-week study of adults 18-79 years with cardiovascular disease and diabetes mellitus with low-density lipoprotein cholesterol (LDL-C) ≥70 and ≤160 mg/dl. The percent change in LDL-C and other lipids was estimated within each subgroup separately. Safety and tolerability were assessed. RESULTS: In subjects with MetS, percent changes in LDL-C and other lipids were greater with ezetimibe/simvastatin versus doubling baseline statin or numerically greater versus switching to rosuvastatin, except high-density lipoprotein cholesterol and apolipoprotein (Apo) AI (mean percent changes in LDL-C were: -22.49% ezetimibe/simvastatin, -9.64% doubled baseline statin and -19.20% rosuvastatin). In subjects without MetS, percent changes in LDL-C, total cholesterol and Apo B were greater with ezetimibe/simvastatin versus doubling baseline statin or numerically greater versus switching to rosuvastatin (mean percent changes in LDL-C were: -25.14% ezetimibe/simvastatin, -4.75% doubled baseline statin and -19.75% rosuvastatin). Safety profiles were generally similar. CONCLUSION: These results showed that switching to ezetimibe/simvastatin 10/20 mg was more effective at reducing LDL-C, total cholesterol and Apo B versus doubling the baseline statin dose to simvastatin 40 mg or atorvastatin 20 mg or switching to rosuvastatin 10 mg regardless of MetS status. These results were generally similar to those of the full cohort.

[Esophageal motor disorders in asymptomatic subjects with Trypanosoma cruzi infection]. / Alteraciones motoras del esófago en sujetos asintomáticos con infección crónica por Trypanosoma cruzi.

BACKGROUND: The indeterminate chronic or "asymptomatic" phase of Trypanosoma cruzi (Chagas' disease) infection is characterized by the absence of gastrointestinal symptoms, and has an estimated duration of 20 to 30 years. However, the intramural denervation that induces dysfunction of the gastrointestinal tract is progressive. Recently, epidemiological studies have shown that the seroprevalence for this infection in our area ranges between 2% and 3% of the population. OBJECTIVE: To detect the presence of esophageal motor disorders in asymptomatic individuals chronically infected with Trypanosoma cruzi using standard esophageal manometry. METHODS: A cross sectional study in 28 asymptomatic subjects (27 men, age 40.39 ± 10.79) with serological evidence of infection with Trypanosoma cruzi was performed. In all cases demographic characteristics, gastrointestinal symptoms and esophageal motility disorders using conventional manometry were analyzed. RESULTS: In this study 54% (n = 15) of asymptomatic subjects had an esophageal motor disorder: 5 (18%) had nutcracker esophagus, 5 (18%) nonspecific esophageal motor disorders, 3 (11%) hypertensive lower esophageal sphincter (LES), 1 (4%) an incomplete relaxation of the LES and 1 (4%) had chagasic achalasia. CONCLUSIONS: More than half of patients that course with Chagas' disease in the indeterminate phase and that are apparently asymptomatic have impaired esophageal motility. Presence of hypertensive LES raises the possibility that this alteration represents an early stage in the development of chagasic achalasia.

Estradiol prevents amyloid-beta peptide-induced cell death in a cholinergic cell line via modulation of a classical estrogen receptor.

The pathology of Alzheimer's disease includes amyloid-beta peptide aggregation that contributes to degeneration of cholinergic neurons. Even though the underlying molecular mechanisms remain unclear, recent in vitro evidence supports a protective role for estrogens against several neurotoxic agents. Here we report that, in a murine cholinergic cell line (SN56), the massive cell death induced by 1-40 fragment of amyloid-beta peptide was prevented by 17beta-estradiol through a mechanism that may involve estrogen receptor activation. The protective effect of estradiol was observed in a dose-dependent manner, and was completely blocked by the pure antiestrogen ICI 182,780. In contrast, the inactive isomer 17alpha-estradiol consistently showed weaker neuroprotection than the native hormone that was unaffected by ICI 182,780 treatment. In addition, equivalent concentrations of 17beta-estradiol enhanced luciferase activity in cells transfected with a luciferase reporter gene driven by tandem estrogen response elements. Estrogen-induced luciferase activity was blocked by ICI 182,780, indicating estrogen receptor-dependent transcriptional activity. We also observed by reverse transcription-polymerase chain reaction, Western blot and immunocytochemistry that increasing concentrations of 17beta-estradiol enhanced the expression of estrogen receptor alpha mRNA and protein during amyloid-beta-induced toxicity. Under these conditions, it was found by confocal microscopy that the localization of estrogen receptor alpha in the absence of hormone was mainly extranuclear. However, the receptor was consistently observed also at the nuclear region after estrogen exposure. Overall, these data suggest that estrogen may exert neuroprotective effects against amyloid-beta-induced toxicity by activation of estrogen receptor-mediated pathways. In addition, intracellular estrogen receptors are up-regulated by their cognate hormone even during exposure to neurotoxic agents.

Effect of treatment with the selective oestrogen receptor modulator LY117018-HCl on pituitary sensitivity to GnRH and subsequent ovulation.

The effects of LY117018-HCl (LY; a benzothiophene similar to raloxifene) were examined on various reproductive parameters in female rats. Four-day cyclic rats were treated (10:00 h on dioestrus) with LY (0.01, 0.1, 0.5, 1, 2, 4 or 16 mg kg(-1) p.o.) and assessed for ovulation at oestrus. LY inhibited ovulation at doses as low as 0.5 mg kg(-1), and ovulation did not occur at doses of 4 and 16 mg kg(-1). LY (16 mg kg(-1)) reduced wet uterine mass and LH concentrations at the time of the expected ovulatory surge. Ovulation induced by hCG in pentobarbital-treated rats was not altered by LY treatment, indicating normal ovarian sensitivity to gonadotrophins. LY, however, completely blocked the effects of oestradiol (under either negative or positive feedback modes) on LH secretion in ovariectomized rats. GnRH secretion into hypophyseal portal blood during pro-oestrus was not affected by treatment with LY, whereas the concentrations of serum LH remained reduced. Finally, treatment with LY markedly reduced pituitary sensitivity to GnRH during pro-oestrus, as it completely blocked GnRH-induced LH secretion. These results demonstrate that LY inhibits oestradiol action in the uterus and prevents ovulation in normal cyclic rats. LY-induced inhibition of ovulation is not caused by an alteration of the ovarian response to gonadotrophins or an impairment of GnRH secretion at the hypothalamus, but by a reduction in the sensitivity of gonadotrophs to the stimulatory effects of GnRH during pro-oestrus.

Sex steroids modulate luteinizing hormone-releasing hormone secretion in a cholinergic cell line from the basal forebrain.

The function of a particular neuronal population is in part determined by its neurotransmitter phenotype. We have found that a neuronal-derived septal cell line (SN56), known for its cholinergic properties, also synthesizes and releases luteinizing hormone-releasing hormone. In addition, these cells express the messenger RNAs encoding estrogen and progesterone receptors. The activation of these receptors by their respective ligands cooperatively modulates the depolarization-induced release of luteinizing hormone-releasing hormone in these cells. We have also found that a number of septal neurons in postnatal (1-week-old) mice are immunoreactive to both choline acetyltransferase and luteinizing hormone-releasing hormone. These results indicate that both neurotransmitters, acetylcholine and luteinizing hormone-releasing hormone, may co-exist in septal neurons of the CNS and that they could be modulated by gonadal hormones, and suggest that luteinizing hormone-releasing hormone could be involved in some of the actions of sex steroids on cholinergic neurotransmission.

Estrogen modulates norepinephrine-induced accumulation of adenosine cyclic monophosphate in a subpopulation of immortalized luteinizing hormone-releasing hormone secreting neurons from the mouse hypothalamus.

A subpopulation of luteinizing hormone-releasing hormone (LHRH)-producing cells that express the intermediate filament protein vimentin and the neuronal marker neurofilament 145, but not neurofilament 200 nor glial fibrillary acidic protein, has been isolated from GT1-7 cultures. These cells express the mRNA encoding estrogen receptor alpha (ERalpha) and respond to physiological concentrations of 17beta-estradiol (E2) by reducing the accumulation of cyclic adenosine monophosphate induced by norepinephrine, but not that induced by direct activation of adenylate cyclase. These results indicate that the activity of LHRH-producing neurons may be directly modulated by estrogen. In addition, they are suggestive of an estrogen-dependent desensitization of the beta-adrenoceptor in these cells.

Smoking: attitudes of Costa Rican physicians and opportunities for intervention.

The aim of this study was to obtain information, using a written questionnaire, on the knowledge, smoking behaviour, and attitudes of Costa Rican physicians about smoking as a health issue. A random sample of 650 physicians was chosen from a list of active physicians; 287 of them were covered by survey between August 1993 and October 1994, and 217 (76%) responded with data for the study. While 40% of the physicians who participated were ex-smokers, 19% were current smokers; 67% of these two groups combined reported smoking in the workplace. Only 49% believed that physicians could be a nonsmoking role model; the majority (87%) had asked patients about their smoking status. The only cessation technique consistently used (90%) was counselling about the dangers of smoking. Measures such as setting a date to quit smoking and nicotine replacement were rarely recommended (< or = 2%). Nearly all the physicians (99%) considered smoking to be a major health issue. These results showed a high prevalence of smoking among Costa Rican physicians, with little recognition of the need for them to set an example as a role model. While they were knowledgeable about the health risks of smoking, they did not recommend any of the proven techniques to help their patients to quit smoking. A clear consensus for more strict tobacco regulation exists, but to date little has been done to act on this.

Interaction of chloramphenicol and metabolites with colony stimulating factors: possible role in chloramphenicol-induced bone marrow injury.

We have recently demonstrated that two chloramphenicol (CAP) metabolites known to be produced by intestinal bacteria, dehydro-CAP (DH-CAP) and nitrophenylaminopropane (NPAP), are much more cytotoxic to bone marrow in vitro than CAP itself. Since colony stimulating factors (CSFs) play an essential role in hematopoietic cell growth, toxicity from CAP metabolites could also involve interaction with CSF or CSF-producing cells. In the present study, we found that increasing concentrations of rhGM-CSF or rhG-CSF completely reversed the inhibitory effect of CAP (2 x 10(-4) M) on human CFU-GM growth and on the growth of KG-1 cells. GM-CSF also reversed the inhibitory effect of CAP on HL-60 cells. Inhibition by DH-CAP (50% at 5 x 10(-7) M), nitroso-CAP (NO-CAP) (60% at 5 x 10(-6) M) and NPAP (35% at 10(-5) M) was not affected by either CSF. In addition to their inhibitory effect on cell growth, DH-CAP (5 x 10(-6) M) and NO-CAP (5 x 10(-6) M) inhibited CSF production by buffy coat cells 50-70% without affecting cell viability. Neither CAP nor NPAP inhibited CSF production. It is suggested that the dual toxic-inhibitory effect of some intestinal metabolites of CAP such as DH-CAP on hematopoietic cell growth on the one hand, and on CSF production on the other, renders them very potent as potential mediators of CAP induced aplastic anemia.

Effect of massive obesity on low and high density lipoprotein binding to human adipocyte plasma membranes.

Adipose tissue is a major cholesterol storage organ in man, and turnover of this slowly exchangeable pool is dependent on low and high density lipoproteins which deliver and remove cholesterol from this site. To determine whether lipoprotein binding is altered in the obese state, we examined the binding of low density lipoprotein (LDL) and high density lipoprotein (HDL2 and HDL3) to purified adipocyte plasma membranes obtained from omental fat depots of massively obese patients (BMI greater than 40 kg/m2) and lean subjects. The specific binding and uptake of 125I-HDL2 and 125I-HDL3 were greater for obese than for lean adipocytes. Scatchard analysis of binding studies using purified adipocyte plasma membranes and varying amounts of labeled HDL2 or HDL3 demonstrated a higher binding affinity (lower Kd) for HDL2 and higher binding capacity (Bmax) value for both HDL2 and HDL3 in obese as compared to lean. 125I-LDL specific binding was somewhat lower in obese than in lean membranes but this difference was not statistically significant. The cholesterol content of isolated omental adipocytes expressed on a cellular basis or as the cholesterol/triglyceride ratio (mg chol/g of lipid) were similar in the obese and lean subjects. Furthermore, 125I-LDL, 125I-HDL2 or 125I-HDL3 specific binding did not correlate with cellular cholesterol content or with cholesterol/triglyceride ratio. These findings indicate that lipoprotein binding to adipocytes is altered in obesity and is characterized by up-regulation of HDL (particularly HDL2) binding with little change in LDL binding. We conclude from this study that obesity has a profound effect on the expression of HDL binding sites in human adipocytes and that LDL and HDL binding in fat cells are regulated differently.

Efecto de la intervención nutricional en pacientes con hiperlipoproteinemia tipo V / Effect of the nutricional intervention in patients with hyperlipoproteinemia type V

La hiperlipoproteinemia tipo V, es una alteración en el metabolismo de las lipoproteínas, que se caracteriza por hipertrigliceridemia servera. El presente estudio muestra el efecto de una intervención nutricional sobre las concentraciones séricas de triglicéridos y colesterol en trece pacientes...

Weight loss in massive obesity: reciprocal changes in plasma HDL cholesterol and HDL binding to human adipocyte plasma membranes.

Human obesity is frequently associated with elevated plasma triglyceride and cholesterol concentrations and reduced high density lipoprotein (HDL) cholesterol, abnormalities that commonly revert to normal levels with weight loss. This study was undertaken to examine possible mechanism(s) associated with the changes in plasma HDL cholesterol concentrations in massively obese patients after weight loss. Ten massively obese patients (two men and eight women, age = 37.8 +/- 2.4 years) were studied before, during, and after 1 year of weight loss and weight maintenance following gastric stapling. Total cholesterol and low density lipoprotein cholesterol were within the normal range for sex and age before weight loss and did not change significantly during or after weight reduction. In the females, HDL cholesterol concentrations increased from 0.96 +/- 0.06 mmol/L to 1.23 +/- 0.3 mmol/L (mean +/- SEM, n = 8, P less than .05) with weight reduction. In the two men, plasma HDL cholesterol concentrations were, respectively, 1.22 and 0.65 mmol/L before and 1.23 and 0.98 mmol/L after weight loss. Specific binding of 125I-HDL2 and 125I-HDL3 to purified plasma membranes was determined using abdominal and omental fat depot before and after weight loss in six of the ten obese patients. An average reduction of 30% to 40% in 125I-HDL2 and 125I-HDL3 binding capacity to these membranes occurred after weight loss. Furthermore, a positive correlation (r = .65, n = 10, P less than .05) was observed between plasma HDL cholesterol and triglyceride concentrations before weight loss but not after weight loss (r = .01).(ABSTRACT TRUNCATED AT 250 WORDS)