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Team Africa

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Leo Morgan
Leo Morgan

Extra Fluids



Background: Breastfeeding is known to be the biological norm. Despite this, many women wean their babies because of perceived insufficient breast milk production. Mothers are sometimes advised to increase their fluid intake in the hope that this could improve breast milk production. The effect of extra fluid on human breast milk production is not well established, however.




Extra Fluids


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Main results: Five trial reports were retrieved using the search strategies. Four trials were excluded. We did not identify any randomised controlled trials for inclusion but we included one quasi-randomised study (involving 210 women) that evaluated the effect of extra fluid for breastfeeding mothers on breastfeeding outcomes. The study was considered to be at a high risk of bias. Only one of this review's primary outcomes was reported (breast milk production (as defined by the trialist)) but data were not in a suitable format for analysis (no standard deviations or standard errors were reported). The trialist reported that advising women to drink extra fluids did not improve breast milk production. No data were reported for the review's other primary outcomes: satisfactory weight gain in the infant (as defined by the trialists) and duration of exclusive breastfeeding (months). Similarly, no data were reported for any of this review's secondary outcomes: duration of any breastfeeding; mother's satisfaction with breastfeeding; hydration in mother; dehydration in the infant; or episodes of gastrointestinal illness.


Authors' conclusions: This review only identified one small quasi-randomised controlled trial of low quality and high risk of bias. The study provided limited data on only one of this review's primary outcomes, breast milk production, but the data were not reported in a format that permitted further analysis. The trialist reported that extra fluids did not improve breast milk production. However, this outcome was measured by using test feeds (also known as test weighing). In the 1950s, when the study was conducted, it was common for babies in developed countries to be weighed before and after a feed, known as test weighing or test feeding. However, this practice is not now routinely practiced for term infants due to concerns about lack of precision as a measure of breast milk production. The included study did not report on this review's other primary outcomes (satisfactory weight gain in the infant or duration of exclusive breastfeeding) nor any of the review's secondary outcomes.The effect of additional fluids for breastfeeding mothers remains unknown, due to a lack of well-conducted trials. However, because the physiological basis for any such improvement remains unclear, the conduct of further clinical trials may not be a priority. There is not enough evidence to support an increased fluid intake beyond what breastfeeding mothers are likely to require to meet their physiological needs.


This review aimed to assess whether increasing fluid intake ofbreastfeeding mothers has a beneficial effect on breast milk productionand infant growth. However, the review only identified one smallquasi-randomised controlled trial (involving 210 women). The trial wasof low quality and did not report on two of this review's importantoutcomes (satisfactory weight gain in the infant or duration ofexclusive breastfeeding). The study did report on breast milk production(this review's other main outcome), but the data were not in a formatthat would permit further analysis in this review. The trial reportedthat advising women to consume extra fluids did not result in increasedbreast milk production, as measured by test feeds (also known as testweighing). In the 1950s, when the study was conducted, it was common forbabies in developed countries to be weighed before and after a feed,known as test weighing or test feeding. However, this practice is notnow routinely practiced for term infants due to concerns about lack ofprecision as a measure of breast milk production. The included study didnot report any of this review's secondary outcomes: duration of anybreastfeeding; mother's satisfaction with breastfeeding; hydration inmother; dehydration in the infant; or episodes of gastrointestinalillness.


The effect of additional fluids for breastfeeding mothers remainsunknown, due to a lack of well-conducted trials. However, because thephysiological basis for any such improvement remains unclear, theconduct of further clinical trials may not be a priority. There is notenough evidence to support an increased fluid intake beyond whatbreastfeeding mothers are likely to require to meet their physiologicalneeds.


We describe the protein composition of the digestive fluids of the mygalomorph Acanthoscurria geniculata and the araneomorph Stegodyphus mimosarum, in comparison with previously published data on a third spider species. We found a number of similar hydrolases being highly abundant in all three species. Among them, members of the family of astacin-like metalloproteases were particularly abundant. While the importance of these proteases in spider venom and digestive fluid was previously noted, we now highlight their widespread use across different spider taxa. Finally, we found species specific differences in the protein overlap between venom and digestive fluid, with the difference being significantly greater in S. mimosarum compared to A. geniculata.


Here we present proteomic analyses of the protein composition of the digestive fluid of two spider species representing different lineages within the spider phylogeny, the mygalomorph species Acanthoscurria geniculata and the araneomorph species Stegodyphus mimosarum (Fig. 2; see also phylogeny in [27]). If EOD has a common origin in spiders we would expect to find a similar protein composition in digestive fluids of both species, and similar to Nephilingis cruentata [15]. However, different prey capture strategies and dietary composition among spider species raises the question of whether adaptation to different dietary niches may lead to fine-tuned differences in protein composition of digestive fluids (see Acanthoscurria: [28]; Stegodyphus: [29, 30]). Our study species A. geniculata hunts without the use of silk, catching and subduing prey only by the use of their strong chelicera and the rapid injection of venom, while S. mimosarum represents a more derived species that uses composite silk threads (cribellate silk) to construct a capture web [31]. Moreover, the latter is also a social species where individuals build communal webs, engage in communal feeding and therefore shared EOD [32, 33]. By contrast, the Nephilingis species studied by Fuzita et al. [15] represents a highly derived, solitary orb weaving spider [31]. In contrast to the study of digestive fluids by Fuzita et al. [15], the novel aspect of our work is a thorough comparison of the compositions of these secretions in species with different dietary niches, distributed across the phylogenetic tree, while thereby particularly focussing on proteins being present in both, digestive fluids and venom. Previous studies only anecdotally reported that some venom proteins are also traceable in digestive fluids [15], yet the extent of the overlap is widely unknown. We systematically explore this issue in our two species, quantify their overlap, and infer functional explanations.


We sampled digestive fluids from 9 adult Stegodyphus mimosarum females from nests that have been collected from a population in Kruger National Park, South Africa and brought to the lab at Aarhus University. Nine juvenile Acanthoscurria geniculata spiders (all of the same developmental stage) that were purchased from a pet store were sampled the same way for comparison. Acanthoscurria geniculata spiders were housed in individual plastic containers, and they were fed a cricket and watered once a week. The social S. mimosarum females were kept in their colonies, which were fed a mix of house flies and small crickets once a week. For the sampling one adult female per colony was chosen and taken out for digestive fluid sampling. In both species the sampling was conducted 7 days after the last feeding.


Apart from polysaccharides, there are fibrous proteins in the extracellular matrix that need to be broken down. Candidate enzymes were found in the form of various cathepsins (2 B, 1 D in A. geniculata; 3 L, 1 B, 1 D in S. mimosarum; cf. Tab. 1 and Additional file 1). In their study on N. cruentata, Fuzita et al. [15] also found cathepsins B and L, which were recently described to have an active function in dissolving the extracellular matrix [25]. Apart from the cathepsins, another enzyme that may help to break down the extracellular matrix was detected (but not quantified) in S. mimosarum only, elastase. Finally, some astacin-like metalloproteases, which we found in high abundance in our study species (see below), have also been described to process proteins of the extracellular matrix [47, 48]. Yet, the exact identification of those enzymes is difficult within the relatively large number of duplicates and without a functional annotation for each of them.


The main prey of spiders is insects, which are rich in protein and lipids [49], yet carbohydrases that break down polysaccharids are also found in the digestive fluids. For example, in our study an alpha-amylase was quantifiably found in S. mimosarum, while only traces of a similar enzyme were found in A. geniculata (Maltase-Glucoamylase). This enzyme has also been found in Nephilingis [15], and further similarities with digestive fluids of S. mimosarum could be seen in the presence of glucose dehydrogenases, Alpha-mannosidases and Enolases (Table 1). Mommsen [50] did an early biochemical characterisation of alpha-amylases in spiders and a more recent study by Eggs & Sanders [51] suggests that carbohydrases like those may help the spiders to digest pollen that is either caught in the web or attached to insect prey. That may explain the presence of these enzymes in the web building species, N. cruentata and S. mimosarum. In Acanthoscurria, however, only a few carbohydrases were detected, which may reflect the different nutritional content of its main diet, more strongly based on cursorial insects, like cockroaches, beetles and crickets [28, 29]. Yet the main fraction of carbohydrases in all three species consisted of the aforementioned chitinases. 041b061a72


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