Nutrient Exchange Research Articles

Antenatal risk factors for retinopathy of premature

This literature review presents the antenatal risk factors for the development of retinopathy of prematurity (ROP). Despite advances in antenatal and neonatal therapeutic interventions, screening, and follow-up, ROP remains a potentially vision-threatening retinopathy that requires careful monitoring and timely intervention to prevent the progression of adverse visual impairment or blindness. ROP is a multifactorial disease. The main risk factors are low gestational age and low birth weight. Recent experimental and clinical data support the hypothesis that multiple antenatal factors are involved in the etiology and progression of ROP. These factors include the age of the mother, maternal diseases, pregnancy-associated maternal pathologies, use of drugs to correct these conditions, and inflammatory process. Their roles are ambiguous and often contradictory. The physiology of the mother and placenta can significantly influence the risk of ROP development in preterm infants. The placenta connects the mothers body and the fetus, and it functions in the exchange of nutrients and oxygen between the mother and the fetus. Therefore, any pathological changes in the mothers body entail changes in the placenta, which this directly affects the fetus. A sudden loss of placental support is detrimental to the development of infants in the immediate postnatal period. Thus, these factors should be taken into account when assessing the risk of ROP development to predict and prevent poor vision in children.

The Influence of Symbiosis on the Proteome of the Exaiptasia Endosymbiont Breviolum minutum.

The cellular mechanisms responsible for the regulation of nutrient exchange, immune response, and symbiont population growth in the cnidarian-dinoflagellate symbiosis are poorly resolved. Here, we employed liquid chromatography-mass spectrometry to elucidate proteomic changes associated with symbiosis in Breviolum minutum, a native symbiont of the sea anemone Exaiptasia diaphana ('Aiptasia'). We manipulated nutrients available to the algae in culture and to the holobiont in hospite (i.e., in symbiosis) and then monitored the impacts of our treatments on host-endosymbiont interactions. Both the symbiotic and nutritional states had significant impacts on the B. minutum proteome. B. minutum in hospite showed an increased abundance of proteins involved in phosphoinositol metabolism (e.g., glycerophosphoinositol permease 1 and phosphatidylinositol phosphatase) relative to the free-living alga, potentially reflecting inter-partner signalling that promotes the stability of the symbiosis. Proteins potentially involved in concentrating and fixing inorganic carbon (e.g., carbonic anhydrase, V-type ATPase) and in the assimilation of nitrogen (e.g., glutamine synthase) were more abundant in free-living B. minutum than in hospite, possibly due to host-facilitated access to inorganic carbon and nitrogen limitation by the host when in hospite. Photosystem proteins increased in abundance at high nutrient levels irrespective of the symbiotic state, as did proteins involved in antioxidant defences (e.g., superoxide dismutase, glutathione s-transferase). Proteins involved in iron metabolism were also affected by the nutritional state, with an increased iron demand and uptake under low nutrient treatments. These results detail the changes in symbiont physiology in response to the host microenvironment and nutrient availability and indicate potential symbiont-driven mechanisms that regulate the cnidarian-dinoflagellate symbiosis.

In vitro angiogenesis in response to biomaterial properties for bone tissue engineering: a review of the state of the art.

Bone tissue engineering (BTE) aims to improve the healing of bone fractures using scaffolds that mimic the native extracellular matrix. For successful bone regeneration, scaffolds should promote simultaneous bone tissue formation and blood vessel growth for nutrient and waste exchange. However, a significant challenge in regenerative medicine remains the development of grafts that can be vascularized successfully. Amongst other things, optimization of physicochemical conditions of scaffolds is key to achieving appropriate angiogenesis in the period immediately following implantation. Calcium phosphates and collagen scaffolds are two of the most widely studied biomaterials for BTE, due to their close resemblance to inorganic and organic components of bone, respectively, and their bioactivity, tunable biodegradability and the ability to produce tailored architectures. While various strategies exist to enhance vascularization of these scaffolds in vivo, further in vitro assessment is crucial to understand the relation between physicochemical properties of a biomaterial and its ability to induce angiogenesis. While mono-culture studies can provide evidence regarding cell-material interaction of a single cell type, a co-culture procedure is crucial for assessing the complex mechanisms involved in angiogenesis. A co-culture more closely resembles the natural tissue both physically and biologically by stimulating natural intercellular interactions and mimicking the organization of the in vivo environment. Nevertheless, a co-culture is a complex system requiring optimization of various parameters including cell types, cell ratio, culture medium and seeding logistics. Gaining fundamental knowledge of the mechanism behind the bioactivity of biomaterials and understanding the contribution of surface and architectural features to the vascularization of scaffolds, and the biological response in general, can provide an invaluable basis for future optimization studies. This review gives an overview of the available literature on scaffolds for BTE, and trends are extracted on the relationship between architectural features, biochemical properties, co-culture parameters and angiogenesis.

Secretome of Paenibacillus sp. S-12 provides an insight about its survival and possible pathogenicity.

Our aim in this study was to characterize and investigate the secretome of Paenibacillus sp. S-12 by nanoLC-MS/MS tool-based analysis of trypsin digested culture supernatant proteins. Using a bioinformatics and combined approach of mass spectrometry, we identified 657 proteins in the secretome. Bioinformatic tools such as PREDLIPO, SecretomeP 2.0, SignalP 4.1, and PSORTb were used for the subcellular localization and categorization of secretome on basis of signal peptides. Among the identified proteins, more than 25% of the secretome proteins were associated with virulence proteins including flagellar, adherence, and immune modulators. Gene ontology analysis using Blast2GO tools categorized 60 proteins of the secretome into biological processes, cellular components, and molecular functions. KEGG pathway analysis identified the enzymes or proteins involved in various biosynthesis and degradation pathways. Functional analysis of secretomes reveals a large number of proteins involved in the uptake and exchange of nutrients, colonization, and chemotaxis. A good number of proteins were involved in survival and defense mechanism against oxidative stress, the production of toxins and antimicrobial compounds. The present study is the first report of the in-depth protein profiling of Paenibacillus bacterium. In summary, the current findings of Paenibacillus sp. S-12 secretome provide basic information to understand its survival and the possible pathogenic mechanism.

Grassland ecosystem type drives AM fungal diversity and functional guild distribution in North American grasslands.

Nutrient exchange forms the basis of the ancient symbiotic relationship that occurs between most land plants and arbuscular mycorrhizal (AM) fungi. Plants provide carbon (C) to AM fungi and fungi provide the plant with nutrients such as nitrogen (N) and phosphorous (P). Nutrient addition can alter this symbiotic coupling in key ways, such as reducing AM fungal root colonization and changing the AM fungal community composition. However, environmental parameters that differentiate ecosystems and drive plant distribution patterns (e.g., pH, moisture), are also known to impact AM fungal communities. Identifying the relative contribution of environmental factors impacting AM fungal distribution patterns is important for predicting biogeochemical cycling patterns and plant-microbe relationships across ecosystems. To evaluate the relative impacts of local environmental conditions and long-term nutrient addition on AM fungal abundance and composition across grasslands, we studied experimental plots amended for 10 years with N, P, or N and P fertilizer in different grassland ecosystem types, including tallgrass prairie, montane, shortgrass prairie, and desert grasslands. Contrary to our hypothesis, we found ecosystem type, not nutrient treatment, was the main driver of AM fungal root colonization, diversity, and community composition, even when accounting for site-specific nutrient limitations. We identified several important environmental drivers of grassland ecosystem AM fungal distribution patterns, including aridity, mean annual temperature, root moisture, and soil pH. This work provides empirical evidence for niche partitioning strategies of AM fungal functional guilds and emphasizes the importance of long-term, large scale research projects to provide ecologically relevant context to nutrient addition studies.

Hyphosphere interactions between Rhizophagus irregularis and Rahnella aquatilis promote carbon-phosphorus exchange at the peri-arbuscular space in Medicago truncatula.

Arbuscular mycorrhizal (AM) fungi form a continuum between roots and soil. One end of this continuum is comprised of the highly intimate plant-fungus interface with intracellular organelles for nutrient exchange, while on the other end the fungus interacts with bacteria to compensate for the AM fungus' inability to take up organic nutrients from soil. How both interfaces communicate in this highly complex tripartite mutualism is widely unknown. Here, the effects of phosphate-solubilizing bacteria (PSB) Rahnella aquatilis dwelling at the surface of the extraradical hyphae of Rhizophagus irregularis was analysed based on the expression of genes involved in C-P exchange at the peri-arbuscular space (PAS) in Medicago truncatula. The interaction between AM fungus and PSB resulted in an increase in uptake and transport of Pi along the extraradical hyphae and its transfer from AM fungus to plant. In return, this was remunerated by a transfer of C from plant to AM fungus, improving the C-P exchange at the PAS. These results demonstrated that a microorganism (i.e., a PSB) developing at the hyphosphere interface can affect the C-P exchange at the PAS between plant and AM fungus, suggesting a fine-tuned communication operated between three organisms via two distantly connected interfaces.

Environmental Impacts of Nitrogen and Phosphorus Nutrient Diffusion Fluxes at a Sediment-Water Interface: The Case of the Yitong River, China

Under the premise of controlling the external input of nitrogen and phosphorus, endogenous release is the main cause of eutrophication in lakes. To investigate the characteristics of endogenous nitrogen and phosphorus release from urban rivers, the Yitong River, an urban river in northern China, was used as an experimental object. Eight sampling sites were set up in the upstream, urban, and downstream regions of an urban section. The nitrogen and phosphorus nutrient exchange fluxes at the sediment-water interface of the Yitong River were assessed by analyzing the sediment and overlying water, and the effects of environmental factors on nitrogen and phosphorus release were investigated using static release experiments. The results showed that the diffusive fluxes of endogenous total nitrogen (TN), ammonia nitrogen (NH4+-N), and total phosphorus (TP) in the urban section of the Yitong River ranged from −1.571 to 19.365 mg·(m2·d)−1, −0.171 to 9.227 mg·(m2·d)−1, and −0.052 to 0.595 mg·(m2·d)−1, respectively. The diffusive fluxes of nitrogen and phosphorus nutrients were all greater under anaerobic conditions than under aerobic conditions. The diffusive fluxes of nitrogen and phosphorus were influenced by changes in pH, DO, and temperature of the overlying water, and the release of phosphorus from the sediment was accelerated by high temperatures in the range of 5–25 °C. Acidic conditions favored the release of TN, whereas alkaline conditions favored the release of TP from the sediment. Furthermore, during the control of nitrogen and phosphorus pollution, it should be noted that fluxes are higher in spring and autumn. Thus, when appropriate techniques should be implemented to achieve better control. These findings are intended to provide a reference for the study of nitrogen and phosphorus diffusion fluxes at the sediment-water interface in urban rivers and other surface waters around the world.

Severity Differences and Mechanisms of Algal Blooms Among Sections in Pengxi River of the Three Gorges Reservoir

Since the impoundment of the Three Gorges Dam, 50% of the first-order tributaries in the reservoir area have had frequent algal blooms but with variations regarding the geographical locations of the seriously bloomed sections and the scope of the latter being influenced by the mainstream. This study took the Pengxi River, a first-order tributary of the reservoir area, as an example in order to explore the difference in eutrophication among the river sections and the influence of the Yangtze River on its tributaries. During the spring bloom season of 2019, sampling was carried out in one-week intervals for a total duration of one month. Seven sampling sections (PX1-PX7) were set up from the confluence to upstream. According to the profiles of vertical water temperature and conductivity of each section, the influence scope and form of the backwater of the Yangtze River were inferred; in addition, severity differences and mechanisms of algal blooms among sections were explored through the comparison of the hydrology, water quality, and sediment nutrients among Gaoyang Lake (PX5), which has had serious algal blooms, and the upstream (PX6) and downstream (PX4) sections of PX5, which are both 4 km away from PX5. The results showed that during the sampling month, the average ρ(Chl-a) in the confluence area of the Pengxi River (PX1-PX4) and in the upstream (PX5-PX7) were in the range of 14.55-44.00 μg·L-1 and 42.66-175.40 μg·L-1, respectively. The ρ(Chl-a) of PX5 was up to 413.00 μg·L-1, which was significantly higher than that of other sections (P<0.05). Temperature and conductivity results showed that the backwater from Yangtze River flowed into the Pengxi River from the middle and bottom layers during the period from April to May. The confluence (PX1-PX4) sections were in the intersection area of the backwater from Yangtze River and the upstream of the Pengxi River; thus, the waterbody was unstable, which was not conducive to the formation of algal blooms. However, the upstream (PX5-PX7) sections were not directly affected by the backwater from Yangtze River, leading the nutrient exchange mainly vertically. Most averages of n(TN)/n(TP) and n(DTN)/n(DTP) of PX4-PX6 were all greater than 16, indicating a phosphorus-limited state. During sampling, the average sediment total phosphorus of PX5 was 91% of that in upstream PX6, which was only 4 km away, whereas the surface water total phosphorus of PX5 was 180% of that in PX6. The important reason for this phenomenon is that the water surface width of PX5 was 3.6-4.7 times that of PX6, indicating longer wind fetch in the former section. Owing to the mountainous landscape in the Three Gorges Reservoir (TGR) region where windy weather is rare, the disturbance effect of wind and waves on PX5 was stronger than that of PX6, and the nutrients released from the sediment at the PX5 section caused by wind and waves resupplied the surface water more easily, causing more serious algal blooms at PX5 than those at the remaining sections in the Pengxi River. The main causes of the algal blooms in the tributaries of the TGR area lied in the stability of water stratification and the supply of internal phosphorus. The stability of water stratification was mainly affected by the backwater from Yangtze River, and the supply of internal phosphorus in the algal bloom season was affected by the special water stratification phenomenon of the tributaries of TGR-the "surface density layers." The duration and degree of weather disturbance to the surface density layers can be used to predict the time and scale of algal blooms.

Microfiber Fabricated via Microfluidic Spinning toward Tissue Engineering Applications.

Microfibers, a type of long, thin, and flexible material, can be assembled into functional 3D structures by folding, binding, and weaving. As a novel spinning method, combining microfluidic technology and wet spinning, microfluidic spinning technology can precisely control the size, morphology, structure, and composition of the microfibers. Particularly, the process is mild and rapid, which is suitable for preparing microfibers using biocompatible materials and without affecting the viability of cells encapsulated. Furthermore, owing to the controllability of microfluidic spinning, microfibers with well-defined structures (such as hollow structures) will contribute to the exchange of nutrients or guide cell orientation. Thus, this method is often used to fabricate microfibers as cell scaffolds for cell encapsulation or adhesion and can be further applied to biomimetic fibrous tissues. In this review, the focus is on different fiber structures prepared by microfluidic spinning technology, including solid, hollow, and heterogeneous structures, generated from three essential elements: spinning platform, fiber composition, and solidification methods. Furthermore, the application of microfibers is described with different structures in tissue engineering, such as blood vessels, skeletal muscle, bone, nerves, and lung bronchi. Finally, the challenges and future development prospects of microfluidic spinning technology in tissue engineering applications are discussed.

Degradable Biocompatible Porous Microtube Scaffold for Extended Donor Cell Survival and Activity.

Cell therapy has significant therapeutic potential but is often limited by poor donor cell retention and viability at the host implantation site. Biomaterials can improve cell retention by providing cells with increased cell-cell and cell-matrix contacts and materials that allow three-dimensional cell culture to better recapitulate native cell morphology and function. In this study, we engineered a scaffold that allows for cell encapsulation and sustained three-dimensional cell culture. Since cell therapy is largely driven by paracrine secretions, the material was fabricated by electrospinning to have a large internal surface area, micrometer-thin walls, and nanoscale surface pores to allow for nutrient exchange without early cell permeation. The material is degradable, which allows for less invasive removal of the implant. Here, a biodegradable poly(lactic-co-glycolic acid) (PLGA) microtube array membrane was fabricated. In vitro testing showed that the material supported the culture of human dermal fibroblasts for at least 21 days, with paracrine secretion of pro-angiogenic FGF2. In vivo xenotransplantation of human cells in an immunocompetent mouse showed that donor cells could be maintained for more than one month and the material showed no obvious toxicity. Analysis of gene expression and tissue histology surrounding the implant showed that the material produced muted inflammatory and immune responses compared to a permanent implant and increased markers of angiogenesis.

Directed Differentiation of Human Pluripotent Stem Cells to Cytotrophoblast and Syncytiotrophoblast.

Human pluripotent stem cells (hPSCs) form an ideal system to study the formation of placental cells, from an undifferentiated human embryonic stem cell state. The conventional human in vitro model systems to study the human placenta cannot be employed for understanding placental dysfunctions or the development of specialized placental cell types. Hence, human PSCs make an ideal model system to study human placental development and disorders. Here, we describe an efficient and validated protocol to reproducibly study the formation of human cytotrophoblasts (CTBs) and syncytiotrophoblast (STBs) from undifferentiated hPSCs. CTBs are the trophoblast stem cells that can differentiate into specialized placental cell types such as STBs. The multinucleated STB plays vital role in the exchange of nutrients and gases across the placenta and secretes several hormones during pregnancy, such as human chorionic gonadotropin β (hCGβ). Here we describe two methods of seeding the hPSCs: chemical (clumps method) and enzymatic methods (single cells) to differentiate them to CTB and STB, activating BMP (B) signaling and inhibiting ACTIVIN/NODAL and FGF signaling pathways (2i), thus naming our protocol as "B2i" (Sudheer et al., Stem Cells Dev 21:2987-3000, 2012). This protocol forms the perfect model system for understanding in vitro placentation, modeling diseases arising from abnormal placentation that cause complications such as miscarriage, preeclampsia or intrauterine growth restriction (IUGR), and drug discovery for placental disorders.

Hypertensive disorders of pregnancy and long‐term cardiovascular health: FIGO Best Practice Advice

Hypertensive disorders of pregnancy (HDP) are the most common causes of maternal and perinatal morbidity and mortality. They are responsible for 16% of maternal deaths in high-income countries and approximately 25% in low- and middle-income countries. The impact of HDP can be lifelong as they are a recognized risk factor for future cardiovascular disease. During pregnancy, the cardiovascular system undergoes significant adaptive changes that ensure adequate uteroplacental blood flow and exchange of oxygen and nutrients to nurture and accommodate the developing fetus. Failure to achieve normal cardiovascular adaptation is associated with the development of HDP. Hemodynamic alterations in women with a history of HDP can persist for years and predispose to long-term cardiovascular morbidity and mortality. Therefore, pregnancy and the postpartum period are an opportunity to identify women with underlying, often unrecognized, cardiovascular risk factors. It is important to develop strategies with lifestyle and therapeutic interventions to reduce the risk of future cardiovascular disease in those who have a history of HDP.

A Bioengineered Model for Studying Vascular-Pericyte Interactions of the Placenta.

Investigating the complex cellular interactions of the placenta has remained, until now, a challenge in the field. Given the ethical limitations of studying human placentae, and the interspecies differences that exist between mammals, in vitro models are a valuable tool for investigating developmental and pathologic processes related to the human placenta. A number of in vitro models have been recently employed to investigate various aspects of placental development, with many focusing on the maternal-fetal interface including the trophoblasts and an endothelial barrier. One critical aspect in mimicking the physiology of the placenta is to include perfusable microvessels. As this organ is highly vascularized, it is pertinent to represent the exchange of oxygen and nutrients from the maternal blood to the embedded vessels of the fetus. Using hydrogel-laden microfluidics, it is now possible to bioengineer these and other microvessels in a reproducible manner. By using HUVEC, fetal-like vessels can be generated on a chip and can be studied in a controlled manner. This chapter introduces the concept of generating a triculture vasculature on-chip system, which can be employed to study placental pericyte-endothelial interactions. We describe strategies for generating the vessels on-chip, as well as for quantifying vascular morphology and function. This methodology allows for unique microvessel-related biological questions to be addressed, including how stromal cells impact vascular remodeling over time.

Bioengineering liver microtissues for modeling non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) has become the world's most common chronic liver disease. However, due to the lack of reliable in vitro NAFLD models, drug development studies have faced many limitations, and there is no food and drug administration-approved medicine for NAFLD treatment. A functional biomimetic in vitro human liver model requires an optimized natural microenvironment using appropriate cellular composition, to provide constructive cell-cell interactions, and niche-specific bio-molecules to supply crucial cues as cell-matrix interplay. Such a suitable liver model could employ appropriate and desired biochemical, mechanical, and physical properties similar to native tissue. Moreover, bioengineered three-dimensional tissues, specially microtissues and organoids, and more recently using infusion-based cultivation systems such as microfluidics can mimic natural tissue conditions and facilitate the exchange of nutrients and soluble factors to improve physiological function in the in vitro generated constructs. This review highlights the key players involved in NAFLD initiation and progression and discussed the available cells and matrices for in vitro NAFLD modeling. The strategies for optimizing the liver microenvironment to generate a powerful and biomimetic in vitro NAFLD model were described as well. Finally, the current challenges and future perospective for promotion in this subject were discussed.

Metabolic Reprogramming of Castration-Resistant Prostate Cancer Cells as a Response to Chemotherapy.

Prostate cancer at the castration-resistant stage (CRPC) is a leading cause of death among men due to resistance to anticancer treatments, including chemotherapy. We set up an in vitro model of therapy-induced cancer repopulation and acquired cell resistance (CRAC) on etoposide-treated CRPC PC3 cells, witnessing therapy-induced epithelial-to-mesenchymal-transition (EMT) and chemoresistance among repopulating cells. Here, we explore the metabolic changes leading to chemo-induced CRAC, measuring the exchange rates cell/culture medium of 36 metabolites via Nuclear Magnetic Resonance spectroscopy. We studied the evolution of PC3 metabolism throughout recovery from etoposide, encompassing the degenerative, quiescent, and repopulating phases. We found that glycolysis is immediately shut off by etoposide, gradually recovering together with induction of EMT and repopulation. Instead, OXPHOS, already high in untreated PC3, is boosted by etoposide to decline afterward, though stably maintaining values higher than control. Notably, high levels of EMT, crucial in the acquisition of chemoresistance, coincide with a strong acceleration of metabolism, especially in the exchange of principal nutrients and their end products. These results provide novel information on the energy metabolism of cancer cells repopulating from cytotoxic drug treatment, paving the way for uncovering metabolic vulnerabilities to be possibly pharmacologically targeted and providing novel clinical options for CRPC.

The Relationship Between the Weight of the Placenta and Birth Weight of the Neonate

INTRODUCTION Weight of placenta has long been associated with fetal growth and perinatal well-being. Low placental weight (standardized for sex and gestational age) is more common among stillbirths whereas high placental weight is associated with neonatal death, serious neonatal morbidity, low 5-min Apgar score, and respiratory morbidity. Low placental weight is believed to reflect an inadequate placental surface area for nutrient and gas exchange, leading to fetal compromise. However, it has also been proposed that the increased risk associated with high placental weight is the result of villous oedema, which may compress blood vessels and reduce transfer of gas and nutrients to the fetus. MATERIAL AND METHODS A descriptive cross-sectional study of the total, 798 subjects met the inclusive criteria. After consent, age, sex, prepregnancy weight, weight of mother at the time of delivery, neonatal weight and trimmed placental weight were recorded. RESULTS The mean birth weight was 2818±447.19 gm while the placental weight was 489.29±59 gm with mean placental-fetal weight ratio of 17.63. The mean birthweight of male was 2823.97±451.12 gm whereas female was 2811.69±442.93 gm. Similarly, mean placental weight of male was 490.37±57.7 gm and female was 487.98±60.58 gm. As gestational age increases placental and birth weight also increases whereas placental-birth weight ratio decreases. CONCLUSION There is a positive relation between placental weight and weight of the neonate at the time of birth. However, the ratio of the placental and neonatal birth weights at term decreases with advancing gestational age. Thus, prolongation of pregnancy at term may adversely affect the fetus.

Pollutants removal, microbial community shift and oleic acid production in symbiotic microalgae–bacteria system

The functional interaction between microorganisms is key in symbiotic microalga–bacteria systems; however, evaluations of fungi and pathogenic microorganisms are not clear. In this study, the roles of three groups (i.e., microalgae–activated sludge (MAS), Microalgae, and activated sludge) in pollutant removal and biomass recovery were comparatively studied. The data implied that microalgal assimilation and bacterial heterotrophic degradation were the major approaches for degradation of nutrients and organic matter, respectively. According to 16S rRNA and internal transcribed spacer sequencing, the relative abundance of Rhodotorula increased remarkably, favoring nutrient exchange between the microalgae and bacteria. The abundances of two types of pathogenic genes (human pathogens and animal parasites) were reduced in the MAS system. The oleic acid content in the MAS system (51.2 mg/g) was 1.7 times higher than that in the Microalgae system. The results can provide a basis for practical application and resource utilization of symbiotic microalgae–bacteria systems.

Hydrogeochemistry of low agricultural soil yield in Sahelian and sub-tropical watersheds, Northern Cameroon

Bound to the north by the Sahara and to the south by the Sudanian savannah, watersheds in the African Sahelian belt supply food and water to an estimated 135 million people. Being one of the Earth's most vulnerable zones to climate change impacts, the Sahel covers a 3.1 million km2 corridor from the Atlantic Ocean in the west to the Red Sea in the east. It is predicted that decadal timescale migration of Sahelian arid conditions southwards, and associated changes in water-rock interaction patterns resulting from desertification and reduction in rainfall trends, would increasingly alter soil nutrients availability. In this pilot study, we developed a hydrogeochemical approach by linking local geology to elemental dynamics, while focusing on nutrient enrichment, depletion, mobility, flux, and exchange between bedrock and groundwater. This approach was successfully applied to two watersheds in Northern Cameroon: the Sahelian Douka Longo sedimentary watershed (SDLSW) and the tropical Bidou igneous watershed (TBIW). Comparative inorganic nutrient budgets and availability suggest that carbonates and plagioclases are prone to weak and intermediate chemical weathering, compared to stronger rates recorded for granite, basalt, trachyte, and sandstone. Collectively, these sources contribute to significant trace element nutrients enrichment of local water bodies within the watersheds. Non-isochemical dissolution produces highly mobile Ca, Mn, Na, Cu, Zn, K, Ni and Fe compared to elements not part of plant nutrients. Acidic groundwater recharged by rainwater through preferential flow pass has a Ca + Mg–NO3 and Ca + Mg–HCO3 chemical signature in the SDLSW and the TBIW, respectively. Both watersheds are characterised by distinct solute flux patterns, with lower annual nutrient loss rates associated with the TBIW. The data indicate that surface water runoff needs to be managed to control nutrient deficiencies and excesses, and that low-yield capacity in both watersheds appear to be partly linked to P, Fe, and Mo deficiencies.

Thermosensitive hydrogel for cartilage regeneration via synergistic delivery of SDF-1α like polypeptides and kartogenin

Regeneration of injured articular cartilage is limited by low early-stage recruitment of stem cells and insufficient chondrogenic differentiation. Hydrogels are widely used to repair cartilage because they have excellent mechanical and biological properties. In this study, a dual drug-loaded thermosensitive hydroxypropyl chitin hydrogel (HPCH) system was prepared to release stromal-derived factor-1α-like polypeptides (SDFP) and kartogenin (KGN) for stem-cell recruitment and chondrogenic differentiation. The hydrogel had a network structure that promoted cell growth and nutrient exchange. Moreover, it was temperature sensitive and suitable for filling irregular defects. The system showed good biocompatibility in vitro and promoted stem-cell recruitment and chondrogenic differentiation. Furthermore, it reduced chondrocyte catabolism under inflammatory conditions. Animal experiments demonstrated that the dual-drug hydrogel systems can promote the regeneration of articular cartilage in rats. This study confirmed that an HPCH system loaded with KGN and SDFP could effectively repair articular cartilage defects and represents a viable treatment strategy.

Effect of biomass retention time on performance and fouling of a stirred membrane photobioreactor

Co-culture of microalgae-activated sludge has the potential to purify wastewater while reduce energy demand from aeration. In this work, a mechanically stirred membrane photobioreactor (stirred-MPBR) was used to evaluate the impact of the biomass retention time (BRT) on the treatment performance and membrane fouling. Results showed that stirred-MPBR was affected by BRT during treating domestic wastewater at a flux of 16.5 L m−2 h−1. The highest productivity was attained at BRT 7d (102 mg L−1 d−1), followed by BRT 10d (86 mg L−1 d−1), BRT 5d (85 mg L−1 d−1), and BRT 3d (83 mg L−1 d−1). Statistical analysis results showed that BRT 7d had a higher COD removal rate than BRT 10d, however, there is no difference in total nitrogen removal rate. The highest TP removal occurred when the biomass operated at BRT as short as 3d. Reduced BRTs caused a change in the microalgae-activated sludge biomass fraction that encouraged nitrification activity while simultaneously contributing to a higher fouling rate. The bound protein concentrations dropped from 31.35 mg L−1 (BRT 10d) to 10.67 mg L−1 (BRT 3d), while soluble polysaccharides increased from 0.99 to 1.82 mg L−1, respectively. The concentrations of extracellular polymeric substance fractions were significantly altered, which decreased the mean floc size and contributed to the escalating fouling propensity. At the optimum BRT of 7d, the stirred-MPBR showed sufficient access to light and nutrients exchange for mutualistic interactions between the microalgae and activated sludge.