Baroreflex dynamics during the rest to exercise transient in acute normobaric hypoxia in humans

Purpose We hypothesised that during a rest-to-exercise transient in hypoxia (H), compared to normoxia (N), (i) the initial baroreflex sensitivity (BRS) decrease would be slower and (ii) the fast heart rate (HR) and cardiac output (CO) response would have smaller amplitude (A(1)) due to lower vagal activity in H than N. Methods Ten participants performed three rest-to-50 W exercise transients on a cycle-ergometer in N (ambient air) and three in H (inspired fraction of O-2 = 0.11). R-to-R interval (RRi, by electrocardiography) and blood pressure profile (by photo-plethysmography) were recorded non-invasively. Analysis of the latter provided mean arterial pressure (MAP) and stroke volume (SV). CO = HRSV. BRS was calculated by modified sequence method. Results Upon exercise onset in N, MAP fell to a minimum (MAPmin) then recovered. BRS decreased immediately from 14.7 +/- 3.6 at rest to 7.0 +/- 3.0 ms mmHg(-1) at 50 W (p < 0.01). The first BRS sequence detected at 50 W was 8.9 +/- 4.8 ms mmHg(-1) (p < 0.05 vs. rest). In H, MAP showed several oscillations until reaching a new steady state. BRS decreased rapidly from 10.6 +/- 2.8 at rest to 2.9 +/- 1.5 ms mmHg(-1) at 50 W (p < 0.01), as the first BRS sequence at 50 W was 5.8 +/- 2.6 ms mmHg(-1) (p < 0.01 vs. rest). CO-A(1) was 2.96 +/- 1.51 and 2.31 +/- 0.94 l min(-1) in N and H, respectively (p = 0.06). HR-A(1) was 7.7 +/- 4.6 and 7.1 +/- 5.9 min(-1) in N and H, respectively (p = 0.81). Conclusion The immediate BRS decrease in H, coupled with similar rapid HR and CO responses, is compatible with a withdrawal of residual vagal activity in H associated with increased sympathetic drive

The effect of lower body negative pressure on phase 1 cardiovascular responses at exercise onset in healthy humans

We tested the hypothesis that vagal withdrawal and increased venous return interact in determining the rapid cardiac output response (Phase I) at exercise onset. We used lower body negative pressure (LBNP) to increase blood dislocation to the heart by muscle pump action and simultaneously reduce resting vagal activity. At exercise start, we expected larger response amplitude for stroke volume and smaller for heart rate at progressively stronger LBNP levels, so that the cardiac output response would remain unchanged. Ten subjects performed 50 W exercise supine in Control condition and during -45 mmHg LBNP exposure. On single beat basis, we measured heart rate (HR), stroke volume (SV), and we calculated cardiac output (CO). We computed Phase I response amplitudes (A1) using an exponential model. SV A1 was higher under LBNP than in Control (p &lt; 0.05). Conversely, the A1 of HR, was 23 ± 56 % lower under LBNP than in Control (although NS). Since these changes tended to compensate each other, the A1 for CO was unaffected by LBNP. The rapid SV kinetics at exercise onset is compatible with an effect of increased venous return, whereas the vagal withdrawal conjecture cannot be dismissed for HR kinetics. The rapid CO response may indeed be the result of two independent yet parallel mechanisms, as hypothesized, one acting on SV, the other on H

Vagal blockade suppresses the phase I heart rate response but not the phase I cardiac output response at exercise onset in humans

Purpose: We tested the vagal withdrawal concept for heart rate (HR) and cardiac output (CO) kinetics upon moderate exercise onset, by analysing the effects of vagal blockade on cardiovascular kinetics in humans. We hypothesized that, under atropine, the φ1 amplitude (A1) for HR would reduce to nil, whereas the A1 for CO would still be positive, due to the sudden increase in stroke volume (SV) at exercise onset. Methods: On nine young non-smoking men, during 0–80 W exercise transients of 5-min duration on the cycle ergometer, preceded by 5-min rest, we continuously recorded HR, CO, SV and oxygen uptake (V˙ O2) upright and supine, in control condition and after full vagal blockade with atropine. Kinetics were analysed with the double exponential model, wherein we computed the amplitudes (A) and time constants (τ) of phase 1 (φ1) and phase 2 (φ2). Results: In atropine versus control, A1 for HR was strongly reduced and fell to 0 bpm in seven out of nine subjects for HR was practically suppressed by atropine in them. The A1 for CO was lower in atropine, but not reduced to nil. Thus, SV only determined A1 for CO in atropine. A2 did not differ between control and atropine. No effect on τ1 and τ2 was found. These patterns were independent of posture. Conclusion: The results are fully compatible with the tested hypothesis. They provide the first direct demonstration that vagal blockade, while suppressing HR φ1, did not affect φ1 of CO

Monoallelic methylation of the APC promoter is altered in normal gastric mucosa associated with neoplastic lesions

Adenomatous polyposis coli (APC) promoter hypermethylation has been reported frequently in normal gastric mucosa, but it remained to be clarified whether this occurs in every individual. In this study, methylation of the APC promoter was analyzed in histologically normal-appearing gastric mucosa samples by methylation-sensitive single-strand conformation analysis and by a methylation-sensitive dot blot assay. Epithelial cell samples were collected by microdissection from tissue sections. Equal amounts of methylated and unmethylated APC alleles were found in all gastric mucosa samples from patients without any gastric lesions (20 samples). Allele-specific methylation analysis showed that the methylation of the APC promoter was monoallelic; however, which allele was methylated depended on the cell type. Increased or decreased methylation was found in 10 of 36 (28%) normal gastric mucosa samples adjacent to a gastric or esophageal adenocarcinoma. No allelic loss was found at the APC locus. Modification of the methylation status was also found in 3 of 21 (14%) normal-appearing gastric mucosa samples adjacent to intestinal metaplasia. In contrast, all normal mucosa samples in cases with chronic gastritis but without metaplasia or dysplasia showed a monoallelic methylation pattern. Our results indicate the following: (a) In normal gastric mucosa, the APC promoter shows monoallelic methylation, which is not due to imprinting but most likely due to allelic exclusion; (b) the excluded allele differs between foveolar and glandular epithelial cells; (c) the APC methylation pattern is frequently altered in normal-appearing gastric mucosa of gastric or esophageal adenocarcinoma patients; and (d) such alterations also occur in normal gastric mucosa adjacent to intestinal metaplasi

A closed-loop approach to the study of the baroreflex dynamics during posture changes at rest and at exercise in humans

We hypothesized that during rapid uptilting at rest, due to vagal withdrawal, arterial baroreflex sensitivity (BRS) may decrease promptly and precede the operating point (OP) resetting, whereas different kinetics are expected during exercise steady state, due to lower vagal activity than at rest. To test this, eleven subjects were rapidly (<2 s) tilted from supine (S) to upright (U) and vice versa every 3 min, at rest and during steady-state 50 W pedaling. Mean arterial pressure (MAP) was measured by finger cuff (Portapres) and R-to-R interval (RRi) by electrocardiography. BRS was computed with the sequence method both during steady and unsteady states. At rest, BRS was 35.1 ms.mmHg-1 (SD = 17.1) in S and 16.7 ms.mmHg-1 (SD = 6.4) in U (P < 0.01), RRi was 901 ms (SD = 118) in S and 749 ms (SD = 98) in U (P < 0.01), and MAP was 76 mmHg (SD = 11) in S and 83 mmHg (SD = 8) in U (P < 0.01). During uptilt, BRS decreased promptly [first BRS sequence was 19.7 ms.mmHg-1 (SD = 5.0)] and was followed by an OP resetting (MAP increase without changes in RRi). At exercise, BRS and OP did not differ between supine and upright positions [BRS was 7.7 ms.mmHg-1 (SD = 3.0) and 7.7 ms.mmHg-1 (SD = 3.5), MAP was 85 mmHg (SD = 13) and 88 mmHg (SD = 10), and RRi was 622 ms (SD = 61) and 600 ms (SD = 70), respectively]. The results support the tested hypothesis. The prompt BRS decrease during uptilt at rest may be ascribed to a vagal withdrawal, similarly to what occurs at exercise onset. The OP resetting may be due to a slower control mechanism, possibly an increase in sympathetic activity

p53 gene mutation and protein accumulation during neoplastic progression in Barrett's esophagus

The aim of the present study was to characterize expression and mutation of p53 during the neoplastic progression from Barrett's esophagus to adenocarcinoma and to test the reliability of immunohistochemistry for p53 overexpression as an indicator of p53 mutation in this context. The association of both gene mutation and protein accumulation with clinicopathological findings and survival was also studied. A total of 77 samples from 30 esophagectomy specimens with Barrett's esophagus and adenocarcinoma of patients in longitudinal clinical follow-up were analyzed. Different lesions (intestinal metaplasia, dysplasia, and adenocarcinoma) as well as normal squamous-cell esophageal epithelia were sampled from formalin-fixed, paraffin-embedded tissues by microdissection. Mutations in p53 Exons 5 to 9 were detected by polymerase chain reaction-single-strand conformation polymorphisms (PCR-SSCP) and confirmed by direct DNA sequencing. Nuclear accumulation of p53 protein was analyzed immunohistochemically from tissue sections adjacent to those used for microdissection. p53 gene mutations were found in 17 and p53 protein accumulation were found in 20 tumor samples. Of the 17 adenocarcinomas with a p53 mutation, 16 stained positive for p53 protein. p53 mutations were detected significantly more frequently in high-grade dysplastic than in low-grade dysplastic lesions (77% versus 29%, P &lt; 0.01). In contrast, nuclear accumulation of p53 was detected in 85% of high-grade and 71% of low-grade dysplastic lesions. In eight cases with p53 mutation, the mutation identified in the tumors was also detected in premalignant lesions, mainly in high-grade dysplasia. In four cases of p53-mutated tumors, clones with different p53 mutations were detected in premalignant lesions. Neither p53 mutations nor p53 protein accumulations were found in metaplastic lesions. In summary, we found that p53 mutations occurred mainly during the transition from low-grade to high-grade dysplasia in the neoplastic progression of Barrett's esophagus but not in the nondysplastic Barrett's mucosa. Mutational analysis of p53 by PCR-SSCP and p53 accumulation by immunohistochemistry were mostly concordant in adenocarcinoma and high-grade dysplastic lesions but frequently discordant in low-grade dysplastic lesions. No correlation between p53 gene mutation or p53 accumulation and clinicopathological findings was observed in this stud

Beta-catenin expression and its association with prognostic factors in adenocarcinoma developed in Barrett esophagus

The majority of the adenocarcinomas arising in Barrett esophagus manifest clinically at an advanced stage and have a poor prognosis. As a result of this poor prognosis, much attention has been directed toward the exploration of markers for neoplastic progression in Barrett esophagus. The objective of the present study was to determine the expression of beta-catenin by immunohistochemical analysis in 70 adenocarcinomas developed in Barrett esophagus and to examine its relationship to various prognostic factors currently in use. Abnormal beta-catenin expression, consisting of the loss of membranous staining and the appearance of the nuclear staining, was found in 43 cases (61%). Of patients with the 43 tumors showing abnormal beta-catenin expression, 25 (58%) survived more than 1 year. In contrast, only 7 (26%) of 27 patients with tumors showing normal beta-catenin expression survived longer than 1 year. Most of the superficial (Tis-T1) tumors (83% [10/12]) exhibited abnormal beta-catenin expression compared with only 53% (31/58) in the T2-T3 group. These results suggest a possible correlation among beta-catenin expression, tumor stage, and length of survival as prognostic factors in patients with adenocarcinoma in Barrett esophagu

Evolution of DNA ploidy during squamous cell carcinogenesis in the esophagus

Image and flow cytometry was used to study the nuclear DNA content (ploidy) during the squamous cell carcinogenesis in the esophagus. The present retrospective study comprised 26 surgical specimens of squamous cell carcinomas (SCC) in patients who underwent surgery alone at the Department of Surgery in CHUV Hospital in Lausanne, between January 1992 and December 1999. We analyzed 53 healthy tissues, 43 tumors, and six lymph node metastases. Diploid DNA histogram patterns were observed in all non-pathologic tissues analyzed, either distant or proximal to the lesion. Aneuploidy was observed in 30 (70%) of 43 lesions; 20 (62.5%) of 32 early squamous-cell carcinomas; and 10 (91%) of 11 advanced carcinomas. In patients with various tumor stages or with multicentric synchronous or metachronous tumors, DNA content was not different among different tumor stages. Four of six lymph node metastases had the same DNA content as the primary tumor. In four patients, discordance between image and flow cytometry analysis was observed for malignant lesions only. Ploidy status was not statistically associated with the differentiation of the tumor, but it was associated with the stage of tumor (P < 0.001). These findings suggest that early malignant changes in the esophagus are already associated with alteration in DNA content, and aneuploidy tends to correlate with progression to invasive SCC. This cell kinetic information could help clinicians in selecting the optimal treatment for the individual patient

Nuclear accumulation of beta-catenin is a common and early event during neoplastic progression of Barrett esophagus

Our aim was to characterize expression and mutation of beta-catenin in the progression of Barrett esophagus to adenocarcinoma. Immunohistochemical analysis of beta-catenin was performed on paraffin-embedded tissue from 30 cases with adenocarcinomas and premalignant lesions. To determine whether there is a correlation between beta-catenin nuclear accumulation and exon 3 mutation of this gene, mutational analysis by polymerase chain reaction-single-strand conformation polymorphism was performed on DNA extracted from the same 30 adenocarcinomas. As a result, the prevalence of reduced expression of beta-catenin on the membrane, with or without nuclear staining, increased significantly from low-grade (LG) to high-grade (HG) dysplasia. Focal nuclear staining for beta-catenin was present in 19 cases of adenocarcinoma, and nuclear staining was associated significantly with progression from metaplasia to LG dysplasia. In addition, in glands with clear histologic transition from metaplasia to LG dysplasia, nuclear accumulation of beta-catenin was found only in the LG dysplastic areas. No mutation in exon 3 of the beta-catenin gene was detected in adenocarcinomas. These results demonstrate that disturbance of the APC/beta-catenin pathway, as indicated by nuclear accumulation of beta-catenin, is a common and early event during neoplastic progression in Barrett esophagu