Demonstration of an inwardly rectifying K+ current component modulated by thyrotropin-releasing hormone and caffeine in GH3 rat anterior pituitary cells

 Reduction of an inwardly rectifying K⁺ current by thyrotropin-releasing hormone (TRH) and caffeine has been considered to be an important determinant of electrical activity increases in GH₃ rat anterior pituitary cells. However, the existence of an inwardly rectifying K⁺ current component was recently regarded as a misidentification of an M-like outward current, proposed to be the TRH target in pituitary cells, including GH₃ cells. In this report, an inwardly rectifying component of K⁺ current is indeed demonstrated in perforated-patch voltage-clamped GH₃ cells. The degree of rectification varied from cell to cell, but both TRH and caffeine specifically blocked a fraction of current with strong rectification in the hyperpolarizing direction. Use of ramp pulses to continuously modify the membrane potential demonstrated a prominent blockade even in cells with no current reduction at voltages at which M-currents are active. Depolarization steps to positive voltages at the maximum of the inward current induced a caffeine-sensitive instantaneous outward current followed by a single exponential decay. The magnitude of this current was modified in a biphasic way according to the duration of the previous hyperpolarization step. The kinetic characteristics of the current are compatible with the possibility that removal from inactivation of a fast-inactivating delayed rectifier causes the hyperpolarization-induced current. Furthermore, the inwardly rectifying current was blocked by astemizole, a potent and selective inhibitor of human ether-á-go-go -related gene (HERG) K⁺ channels. Along with other pharmacological and kinetic evidence, this indicates that the secretagogue-regulated current is probably mediated by a HERG-like K⁺ channel. Addition of astemizole to current-clamped cells induced clear increases in the frequency of action potential production. Thus, an inwardly-rectifying K⁺ current and not an M-like outward current seems to be involved in TRH and caffeine modulation of electrical activity in GH₃ cells. Received: 15 May 1997 / Received after revision and accepted: 24 July 1997     

Hepatitis C viremia in HIV/HCV-coinfected patients: lower levels in presence of chronic hepatitis B

Complex reciprocal interactions between hepatitis C (HCV) and hepatitis B (HBV) viruses (HBV) have been reported. We examined the influence of HBV on HCV RNA titers in 376 HCV/HIV-coinfected patients (30 were also HBsAg positive). Regression analyses identified negative HBsAg and male sex as factors associated with HCV RNA values >500,000 IU/mL.     

Seroprevalence of human herpesvirus-8 in blood donors from different geographical regions of Argentina, Brazil, and Chile

Human herpesvirus-8 (HHV-8) causes Kaposi's sarcoma (KS) and lymphoproliferative disorders in both HIV-infected and uninfected patients. HHV-8 has a worldwide occurrence but infection rates vary according to a combination of geographic and behavioral risks. The main transmission route seems to be sexual, nevertheless, nasal secretions, saliva, blood, and organ graft have been proposed. HHV-8 was postulated as a new infectious agent for screening in blood donors. The aim of this study was to evaluate the prevalence of antibodies against HHV-8 antigens in blood donors of South America. Serum samples from 2,470 blood donors from Argentina, Brazil, and Chile corresponding to five geographic regions were studied by indirect immunofluorescence assay (IFA). Seroprevalence rate was 3.7% (92/2,470; 95% CI 2.9-4.5) in the entire blood donor population distributed as follows: Argentina, 4.0% (Buenos Aires city, 4.3%; Bahia Blanca, 2.4%; and Córdoba, 4.0%), Campinas (Brazil), 2.8%; and Santiago de Chile, 3.0%. There was no difference (P>0.05) between men and women or age related, except in Brazil where positive cases were 30-49-year-old males. The present study, which includes different geographical areas of multiple countries from South America, has not been done before. The results show similar prevalence rates among the studied zones corresponding to low-prevalence regions. South America is a large sub-continent with a wide spectrum of population and geographical characteristics, thus, more HHV-8 prevalence studies should be necessary to establish possible regional differences.     

The effects of hyperammonemia in learning and brain metabolic activity

Ammonia is thought to be central in the development of hepatic encephalopathy. However, the specific relation of ammonia with brain energy depletions and learning has not been studied. Our work attempts to reproduce an increase in rat cerebral ammonia level, study the hyperamonemic animals’ performance of two learning tasks, an allocentric (ALLO) and a cue guided (CG) task, and elucidate the contribution of hyperammonemia to the differential energy requirements of the brain limbic system regions involved in these tasks. To assess these goals, four groups of animals were used: a control (CHA) CG group (n?=?10), a CHA ALLO group (n?=?9), a hyperammonemia (HA) CG group (n?=?7), and HA ALLO group (n?=?8). Oxidative metabolism of the target brain regions were assessed by histochemical labelling of cytochrome oxidase (C.O.). The behavioural results revealed that the hyperammonemic rats were not able to reach the behavioural criterion in either of the two tasks, in contrast to the CHA groups. The metabolic brain consumption revealed increased C.O. activity in the anterodorsal thalamus when comparing the HA ALLO group with the CHA ALLO group. Significant differences between animals trained in the CG task were observed in the prelimbic, infralimbic, parietal, entorhinal and perirhinal cortices, the anterolateral and anteromedial striatum, and the basolateral and central amygdala. Our findings may provide fresh insights to reveal how the differential damage to the brain limbic structures involved in these tasks differs according to the degree of task difficulty.     

Predictors and implications of residual plaque burden after coronary stenting: an intravascular ultrasound study

Background Residual plaque burden after coronary stenting may be visualized by use of intravascular ultrasound. Determinants and implications of residual atherosclerotic plaque burden after coronary stenting are not well established. In particular, the implications of residual plaque burden, after adjusting for confounding factors, are still unknown. Methods Sixty-two consecutive patients (age 56 ± 9 years) undergoing coronary stenting under intravascular ultrasound imaging guidance were prospectively studied. A total of 616 slices were analyzed (every 2 mm of stent length) from motorized pull-back recordings. Residual plaque burden was calculated as residual plaque/vessel area × 100. Results In 565 slices (89%), both residual plaque area and stent area could be measured. Mean residual plaque burden was 46.5% ± 6%. By use of multiple regression analysis, lesion plaque area and reference segment plaque burden were identified as independent predictors of residual plaque burden after stenting. In addition, a significant correlation was found between residual plaque burden and most relevant angiographic parameters at follow-up (including minimal lumen diameter, percent diameter stenosis, and loss index), which persisted after adjustment. Furthermore, stents with a residual plaque burden ≥46% had higher a restenosis rate (relative risk [RR] 4.4, 95% CI 1.09-18.2, P = .03). On logistic regression analysis, residual plaque burden (RR 4.8, 95% CI 4.1-5.6, P = .01) and diabetes (RR 4.3, 95% CI 3.6-5.1, P = .03) emerged as the only independent predictors of restenosis. Conclusions The amount of residual plaque burden after coronary stenting plays an independent role on the late angiographic outcome of these patients. (Am Heart J 2003;145:254-61.)     

Mitral valve aneurysm. Its diagnosis by transesophageal echocardiography]

Aneurysm of the mitral valve is a rare complication of infectious endocarditis. We report a 65-years-old woman with left heart failure and mitral regurgitation secondary to a mitral valve aneurysm. The diagnosis was made by transesophageal echocardiography.     

Feasibility of intravascular ultrasound studies: Predictors of imaging success before coronary interventions

Background: Intravascular ultrasound (IVUS) is currently used to study lesions during transcatheter coronary therapy. However, before dilation some lesions cannot be reached or crossed with the imaging catheter. Hypothesis: This study seeks to elucidate which factors determine the feasibility of IVUS examination before coronary interventions. Methods: Accordingly, 100 consecutive patients undergoing IVUS examination before coronary angioplasty were prospectively studied. The clinical and angiographic characteristics of 77 patients with a successful IVUS study (Group A) were compared with those of 23 patients in whom IVUS was attempted but the target lesion could not be interrogated (Group B). The echogenic characteristics of the target lesion [before (n = 77) or after intervention (in 18 patients in Group B)] were also studied. Results: Patients in Group B were significantly older (62 ± 7 vs. 57 ± 10 years, p < 0.05) and more frequently had stable angina [8 (35%) vs. 9 (11%), p < 0.05]. The distribution of lesions within the coronary tree and angiographic lesion characteristics including length, eccentricity, calcification, bend location, and the American College of Cardiology/American Heart Association classification were similar in both groups. However, proximal tortuosities (>45° at end diastole) were more frequently found in Group B [20 (87%) vs. 47 (61%), p < 0.05]. In addition, by quantitative angiography, patients in Group B had smaller arteries (reference diameter 2.8 ± 0.4 vs. 3.1 ± 0.4 mm, p < 0.05) and more severe lesions (minimal lumen diameter 0.46 ± 0.24 vs. 0.65 ± 0.34 mm, p < 0.05). On IVUS, calcified lesions were more frequently visualized in Group B (61 vs. 38%, p < 0.05). On multivariate analysis, catheter size, baseline minimal lumen diameter, angiographic proximal tortuosities, and lesion calcification on imaging were independent predictors of the feasibility of IVUS studies. Conclusions: Unsuccessful IVUS studies before intervention occur more frequently (1) in vessels with proximal tortuosities or severe lumen narrowing, (2) in lesions that are calcified on IVUS, and (3) when large imaging catheters are used.     

Three molecular classifications surrogate to four immunohistochemical markers in 374 invasive breast carcinomas with long follow-up: Which is better?

In the early 21st century, a new way to classify breast cancer appeared, based on their gene expression profiles. Various classifications have been proposed in an attempt to subrogate these molecular groups to an immunohistochemical expression of estrogen and progesterone receptors, HER2 and Ki67. We compared the three major molecular classifications (MCs) of 374 infiltrating breast carcinomas with the assumption that one is better than the others to discriminate the prognosis of patients that are classified by it. We found that [1] there was a significant statistical association with tumor grade and presence of associated HG-DCIS, but with differences in kappa indices [2]; MC3 showed a significant relationship with pathological tumor stage (p = 0.012, CI95% of 0.012–0.017); [3] only MC3 showed convincingly that the observed differences in OS were not due to chance in the univariate analysis (p = 0.04); [4] only MC3 is an independent prognostic factor of OS. In conclusion, these three classifications are not interchangeable; MC3, the only one that includes Ki67 expression in their defining criteria, is better in predicting prognosis than the others.     

Nanocomposite liposomes for pH-controlled porphyrin release into human prostate cancer cells

It is both challenging and desirable to have drug sensitizers released at acidic tumor pH for photodynamic therapy in cancer treatment. A pH-responsive carrier was prepared, in which fumed silica-attached 5,10,15,20-tetrakis(4-trimethylammoniophenyl)porphyrin (TTMAPP) was encapsulated into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) nanocomposite liposomes. The sizes of agglomerates were determined by dynamic light scattering to be 115 nm for silica and 295 nm for silica-TTMAPP-DOPC liposomes. Morphological changes were also found in TEM images, showing liposome formation at pH 8.5 but collapse upon silanol protonation. TTMAPP release is enhanced from 13% at pH 7.5 to 80% at pH 2.3, as determined spectrophotometrically through dialysis membranes. Fluorescence emission of TTMAPP encapsulated in the dry film of liposomes was reduced to half at pH 8.6 when compared to that at pH 5.4, while the production of singlet oxygen was quintupled at pH 5.0 compared to pH 7.6. Upon treatment of human prostate cancer cells with liposomes containing 6.7 μM, 13 μM, 17 μM and 20 μM TTMAPP, the cell viabilities were determined to be 60%, 18%, 20% and 5% at pH 5.4; 58%, 30%, 25% and 10% at pH 6.3; and 90%, 82%, 68% and 35% at pH 7.4, respectively. Light-induced apoptosis in cancerous cells was only observed in the presence of liposomes at pH 6.3 and pH 5.4 but not at pH 7.4, as indicated by chromatin condensation.

Nanocomposite liposomes are relatively stable in weak basic solutions but effectively release porphyrins at acidic pH, as indicated by the difference in fluorescence.