Decay rate of inspiratory muscle pressure during expiration in man.

Decay rate of inspiratory muscle pressure (PmusI) was studied in 4 subjects during post-inspiratory period of zero flow (TEz) occurring under discontinuous inspiratory elastic load (DIL). End-inspiratory pressure (PmuseI) was increased by dead spaces or exercises. Decay rate was related to PmuseI by a power function with exponent greater than 1. It was not directly affected by concomitant changes of PCO2. It did not increase when an expiratory resistive load was added, i.e. when braking action of inspiratory muscles was no longer required. Time course of PmusI during TEz was more straight than exponential. Relative decay rate increased with PmuseI and with decrease of inspiratory or expiratory time. Experiments with resistive loads suggest that relative rate is mainly related to timing factors. During voluntary inspiratory efforts with closed airways, relative decay rate was not related to PmuseI, while decay rate increased linearly with PmuseI.     

Work-rate affects cardiopulmonary exercise test results in heart failure

AIMS: Cardiopulmonary exercise test (CPET) is used to evaluate patients with chronic heart failure (HF) usually by means of a personalized ramp exercise protocol. Our aim was to evaluate if exercise duration or ramp rate influences the results. METHODS AND RESULTS: Ninety HF patients were studied (peak V (O(2)): >20 ml/min/kg, n=28, 15-20 ml/min/kg, n=39 and <15 ml/min/kg, n=23). Each patient did four CPET studies. The initial study was used to separate the subjects into three groups, according to their exercise capacity. In the remaining studies, work-rate was increased at three different rates designed to have the subjects reach peak exercise in 5, 10 and 15 min from the start of the ramp increase in work-rate, respectively. The order was randomized. The work-rate applied for the total population averaged 22.7+/-8.0, 11.6+/-3.7, 7.5+/-2.9 W/min with effective loaded exercise duration of 5 min and 16 s+/-29 s, 9 min and 43 s+/-49 s and 14 min and 32 s+/-1 min and 12 s for the 5-, 10- and 15-min tests, respectively. Peak V (O(2)) averaged 16.9+/-4.3*, 18.0+/-4.4 and 18.0+/-5.4 ml/min/kg for the 5-, 10- and 15-min tests, (*=p<0.001 vs. 10 min). The shortest test had the lowest peak heart rate and ventilation and highest peak work-rate. Peak V (O(2)) and heart rate were lowest in 5-min tests regardless of HF severity. The DeltaV (O(2))/Deltawork-rate was lowest in 5-min tests and highest in 15-min tests. At all ramp rates, DeltaV (O(2))/Deltawork-rate was lower for the subjects with the lower peak V (O(2)). The V (e)/V (CO(2)) slope and V (O(2)) at anaerobic threshold were not affected by the protocol for any grade of HF. CONCLUSIONS: In chronic HF, exercise protocol has a small effect on peak V (O(2)) and DeltaV (O(2))/Deltawork but does not affect V (O(2)) at anaerobic threshold and V (e)/V (CO(2)) slope.     

Contribution of lymphatic drainage through stomata to albumin removal from pleural space

The contribution of lymphatic drainage through the stomata of parietal mesothelium to the overall removal of labeled albumin from the pleural space was found 89% in sheep with very large hydrothoraces (10 ml/kg), a condition involving a approximately 20 times increase in lymphatic drainage [Broaddus et al., J. Appl. Physiol. 64 (1988) 384]. We determined this contribution in anesthetized rabbits with small (0.12 ml/kg) and large (2.4 ml/kg) hydrothoraces of Ringer-albumin with labeled albumin and labeled dextran-2000 kDa. This dextran was used as marker of liquid removal through the stomata because it should essentially leave the pleural space through the stomata only, owing to its size. The removal of labeled albumin by lymphatic drainage through the stomata was 39% of the overall removal in the small hydrothoraces, and 64% in the large ones. Hence, lymphatic drainage through the stomata does not contribute most of protein and liquid removal from the pleural space under physiological conditions, as it has been maintained. It markedly increases with the increase in pleural liquid volume.     

Early protein intakes and adiposity: reloaded or downloaded?

It has been hypothesized that feeding human milk through the first year of life may have a protective effect towards a later adiposity development, in contrast with formula feeding. The low protein content of human milk has been hypothesized as a plausible biological hypothesis. Regardless, it is often underscored that feeding human milk is associated with a higher rate of weight gain in the first two months of life.

Conclusion: In our opinion, it seems that the protective effect of human milk, if any, on adiposity development is far more complex, and tightly bound to the peculiarity of human milk composition and breastfeeding practice.     

Nondigestible carbohydrates in the diets of infants and young children: a commentary by the ESPGHAN Committee on Nutrition

The consumption of nondigestible carbohydrates is perceived as beneficial by health professionals and the general public, but the translation of this information into dietary practice, public health recommendations, and regulatory policy has proved difficult. Nondigestible carbohydrates are a heterogeneous entity, and their definition is problematic. Without a means to characterize the dietary components associated with particular health benefits, specific attributions of these cannot be made. Food labeling for "fiber" constituents can be given only in a general context, and the development of health policy, dietary advice, and education, and informed public understanding of nondigestible carbohydrates are limited. There have, however, been several important developments in our thinking about nondigestible carbohydrates during the past few years. The concept of fiber has expanded to include a range of nondigestible carbohydrates. Their fermentation, fate, and effects in the colon have become a defining characteristic; human milk, hitherto regarded as devoid of nondigestible carbohydrates, is now recognized as a source for infants, and the inclusion of nondigestible carbohydrates in the diet has been promoted for their "prebiotic" effects. Therefore, a review of the importance of nondigestible carbohydrates in the diets of infants and young children is timely. The aims of this commentary are to clarify the current definitions of nondigestible carbohydrates, to review published evidence for their biochemical, physiologic, nutritional, and clinical effects, and to discuss issues involved in defining dietary guidelines for infants and young children.     

Compliance of present recommendations of fatty acids in formulas for term infants with the actual human milk fatty acid composition in different populations

Fats are the only dietary agents possibly modulating the individual membrane composition, which otherwise is “genetically” determined. In infancy, human milk represents the first natural source of fats. Although the fat intake of breastfed infants is quantitatively and qualitatively unique, it is not known to what extent their varying requirements are met by the fat composition in the milk of their mothers.

Conclusion: The fat composition of arbitrarily chosen human milk is not always the best standard for that in infant formula.     

Concentrations of dioxins and other organochlorines (PCBs,DDTs, HCHs) in human milk from Seveso,Milan and a Lombardian rural area in Italy: a study performed 25 years after the heavy dioxin exposure in Seveso

AIM: To investigate whether those who were exposed to high levels of the dioxin TCDD 25 years ago in Seveso, northern Italy still have higher than the expected levels of dioxins in their fat stores, and to investigate the concentrations of dioxins in the breast milk of mothers in Seveso and in two other regions in Italy. The load of vertically transmitted dioxins to the next generation, if being breastfed, was also investigated. METHODS: As there may be a synergistic effect of mixtures of organic chlorines, the concentrations of pesticides such as DDTs and PCBs have also been studied in the same human milk samples. Breast milk from 12 mothers from Seveso, Central Milan and a Lombardian village was collected for analysis during the first week and 1 and 3 mo after delivery. Individual samples were used for the analysis of pesticides and PCBs, whereas dioxins were analysed in pooled samples from all 12 mothers on each occasion. RESULTS: In human milk from Seveso, the TCDD concentration in fat calculated on a fresh weight basis was more than twice as high as the level in the other two regions, whereas the concentrations of investigated other toxins were lower in Seveso possible due to induction of the enzyme cytochrome P4501A, which means that the total level of dioxins was the same in all three locations. The congener profile, measured as mean toxic equivalency (TEQ) values, was the same in the Italian samples as previously reported from Stockholm. The calculations are based on the most recent WHO TCDD equivalency factors (TEF). The DDE concentration was higher in the samples from Milan than in the samples from the other two Italian regions, which may be due to the fact that, to a greater extent than in the other regions, Milanese food is imported from countries where DDT is still used as a pesticide. CONCLUSION: Twenty-five years after the dioxin catastrophe, human milk from mothers in Seveso has concentrations of the highly toxic dioxin congener TCDD that are more than twice as high as those in central Milan and a Lombardian village. This means that breastfed infants in Seveso still store an appreciable amount of TCDD in their body fat. The health consequences of this fact remain to be elucidated. The effect of the high load of DDTs in central Milan also has to be considered     

Phenylalanine hydroxylase mutations and phenylalanine-tyrosine metabolism in heterozygotes for phenylalanine hydroxylase deficiency

The aim of this study was to determine whether any relationship exists between the severity of mutation of the phenylalanine hydroxylase (PAH) gene and the plasma concentrations of phenylalanine (Phe) and tyrosine (Tyr) under fasting and semifasting conditions among heterozygotes in a matched case-control study. Parents of patients affected by PAH deficiency (n = 25) detected through the Italian Neonatal Screening Program and referred from January 1994 to June 2000, and parents of healthy children were investigated. In total, 68 subjects without any disease, 34 hyperphenylalaninaemia (HPA) heterozygous parents and 34 age- and gender-matched controls, were recruited. Plasma concentrations of Phe and Tyr in fasting and semifasting (1600 mg Phe oral load) conditions were the main outcome measures. DNA analysis for PAH mutations was performed in all 68 subjects. Compared with controls, heterozygotes showed higher fasting and semifasting Phe concentrations (p < 0.0001), lower semifasting Tyr concentrations (p = 0.015), lower Tyr variations (p = 0.003) and a higher Phe/Tyr ratio (p < 0.0001) in switching from fasting to semifasting conditions. Heterozygotes carrying a severe mutation showed semifasting plasma Tyr concentrations lower than controls (p = 0.019) but not significantly different from Tyr levels found in non-severe carriers (p = 0.197). The Tyr variations were minor in severe carriers than controls (p < 0.001) and non-severe carriers too, although with lower significance (p = 0.089). In six carriers of A403V mutation, parents of mild hyperphenylalaninaemics on an unrestricted diet, significant differences in variations from fasting to semifasting conditions were found compared with parents of patients on a diet. CONCLUSION: Although the great heterogeneity of PAH mutations limits any general conclusion, the results suggest that monitoring plasma Tyr variations may be more sensitive than plasma Phe in assessing the severity of PAH mutations in HPA heterozygotes.