Ancient T-independence of mucosal IgX/A: gut microbiota unaffected by larval thymectomy in Xenopus laevis.

Many studies address the influence of the gut microbiome on the immune system, but few dissect the effect of T cells on gut microbiota and mucosal responses. We have employed larval thymectomy in Xenopus to study the gut microbiota with and without the influence of T lymphocytes. Pyrosequencing of 16S ribosomal RNA genes was used to assess the relative abundance of bacterial groups present in the stomach, small and large intestine. Clostridiaceae was the most abundant family throughout the gut, while Bacteroidaceae, Enterobacteriaceae, and Flavobacteriaceae also were well represented. Unifrac analysis revealed no differences in microbiota distribution between thymectomized and unoperated frogs. This is consistent with immunization data showing that levels of the mucosal immunoglobulin IgX are not altered significantly by thymectomy. This study in Xenopus represents the oldest organisms that exhibit class switch to a mucosal isotype and is relevant to mammalian immunology, as IgA appears to have evolved from IgX based upon phylogeny, genomic synteny, and function.

Reversal of deteriorated fractal behavior of heart rate variability by beta-blocker therapy in patients with advanced congestive heart failure.

INTRODUCTION: The slope of the power spectrum in heart rate variability (HRV) reflects the fractal or scaling behavior in HR dynamics and recently was confirmed as an independent predictor of postmyocardial infarction survival. Whether or not the new measurement in HRV foresees the functional evolution in patients with advanced congestive heart failure treated by beta blockers is unclear. METHODS AND RESULTS: Sequential 24-hour Holter ECG recordings were obtained at baseline, and 1 and 3 months after addition of atenolol therapy for advanced congestive heart failure in 10 patients. The slope and intercept of the regression line of power-law behavior, the short- and intermediate-term of detrended fluctuated analysis (DFA), the approximate entropy (ApEn), and the standard frequency spectra of the 24-hour HRV were compared sequentially as well as with those in 12 age-matched normal controls. The results showed that the slope (-1.70 +/- 0.45 vs -1.22 +/- 0.21; P < 0.05) and the intercept (5.11 +/- 0.46 vs 5.62 +/- 0.24; P < 0.05) of the regression line of power-law behavior and the short-term DFA (for 4 to 11 beats) (0.78 +/- 0.18 vs 1.13 +/- 0.21; P < 0.05) increased after 3 months of atenolol treatment. However, the change in intermediate-term DFA (>11 beats) and ApEn was not apparent (1.24 +/- 0.21 vs 1.22 +/- 0.15 and 1.34 +/- 0.14 vs 1.36 +/- 0.11; both P > 0.05). The evolution of the slope or intercept of the regression line of the HRV power spectrum did not correlate with the echocardiographic or clinical cardiac function, or with the frequency spectral components of the HRV (P > 0.05). CONCLUSION: Additional beta-blocker therapy upregulated the fractal behavior control of the HRV in patients with advanced congestive heart failure. The improvement was independent of subjective and objective global cardiac performance.

Long-term beta-blocker therapy improves autonomic nervous regulation in advanced congestive heart failure: a longitudinal heart rate variability study.

BACKGROUND: beta-Blocker therapy is believed to modulate the detrimental effect of overcompensating neurohormonal activation in chronic heart failure. However, clinical doubts remain, particularly the physiologic sympathovagal balance. METHODS: To respond to clinical concern about worsening autonomic nervous perturbation in beta-blocker therapy of advanced congestive heart failure, 15 consecutive patients were longitudinally studied to elucidate the evolution of cardiac function versus 24-hour heart rate variability (HRV) before and after 1, 3, and 6 to 9 months of atenolol-combined therapy. RESULTS: Two patients died prematurely within 1 month. All 13 surviving patients showed improvement in New York Heart Association functional class, with decrease in left ventricular end-systolic and end-diastolic dimensions and increase in fraction shortening and ejection fraction by echocardiography after at least 3 months of atenolol use. The retarded therapeutic effect was accompanied by a general rise of total, very low, low-, and high-frequency components (9.0 +/- 0.5, 8.8 +/- 0.5, 6.2 +/- 0.6, and 6.1 +/- 0.5 vs 10.9 +/- 0.3, 10.7 +/- 0.4, 8.6 +/- 0.3, and 7.8 +/- 0.3; all P <.02) of daily HRV. This implied recovery of parasympathetic and baroreceptor function. Return of sympathovagal interaction was further supported by the suppression of Cheyne-Stokes type HRV as detected by Wigner-Ville distribution. CONCLUSIONS: Long-term beta-blocker therapy for advanced congestive heart failure upwardly regulates the autonomic nervous interaction in synchrony with the evolution of cardiac function performance.

Time-frequency distribution of heart rate variability below 0.05 Hz by Wigner-Ville spectral analysis in congestive heart failure patients.

The Wigner-Ville spectral analysis was utilized to demonstrate a high-resolution time-frequency distribution of heart rate variability below 0.05 Hz. There are different time-frequency characteristics between the normal subject and the patient with severe congestive heart failure. The former consists of multiple and broad-band spectral peaks, while the latter presents unique spectral peaks. Based on Bayes theory, a classifier for the unique spectral peaks was developed. After the beneficial improvement with low-dose beta-blockers, the unique spectral peaks had disappeared or the time of occurrence was reduced in most patients.

Motor unit discharge behavior in older adults during maximal-effort contractions.

A reduction in maximal force production is a common observation in older individuals. In an effort to determine whether aging is accompanied by reductions in central motoneuron drive limiting motor performance, motor unit discharge records were obtained from seven young (21-33 yr) and seven older (> 67 yr) adults. Informed consent was obtained from all subjects. The task required the subject to perform a maximal abduction of the second digit under isometric conditions. Motor unit potentials in the first dorsal interosseous were monitored by using a selective four-wire needle electrode and identified off-line with the aid of a Dantec electromyograph. The maximal discharge rate in the older adults (31.1 impulses/s) was significantly smaller (P < 0.05) than that in the younger subjects (50.9 impulses/s). These findings suggest that reductions in maximal force capability in older adults are partially due to an impaired ability to fully drive the surviving motor units.

Pathological studies of CT findings in supratentorial astrocytoma. Correlation between low-density lesions and changes in fine structure.

CT findings and pathological features of 102 supratentorial astrocytomas were evaluated, and the surgically removed specimens of 10 cases studied by electron microscopy. Five pathological indices-anaplasia, vascularity, interstitial water content, necrosis and tumor fibers were graded from 1 to 4, and studies by the double-blind method. CT scans were divided into 4 groups according to attenuation coefficients and contrast enhancement. The data were statistically analysed. The results showed that the interstitial water content and tumor fibers were statistically different in low-density lesions and isodensity or hyperdensity lesions. The peritumoral low-density specimens correlated well with infiltrated tumor cells, which had swollen mitochondria. No definite correlation was found between the histological subtypes of astrocytomas and CT images. These findings suggest that high water content and lower physical density are responsible for the low-density of astrocytomas. Abnormalities of capillary ultrastructure result in the accumulation of contrast medium. The peritumoral area of low-density seen on CT scans is the real extent of the edematous tumor. But it is impossible to distinguish the histological subtypes of astrocytomas by CT findings.