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Human limbs emerge during the fourth post-conception week as mesenchymal buds, which develop into fully formed limbs over the subsequent months1. This process is orchestrated by numerous temporally and spatially restricted gene expression programmes, making congenital alterations in phenotype common2. Decades of work with model organisms have defined the fundamental mechanisms underlying vertebrate limb development, but an in-depth characterization of this process in humans has yet to be performed. Here we detail human embryonic limb development across space and time using single-cell and spatial transcriptomics. We demonstrate extensive diversification of cells from a few multipotent progenitors to myriad differentiated cell states, including several novel cell populations. We uncover two waves of human muscle development, each characterized by different cell states regulated by separate gene expression programmes, and identify musculin (MSC) as a key transcriptional repressor maintaining muscle stem cell identity. Through assembly of multiple anatomically continuous spatial transcriptomic samples using VisiumStitcher, we map cells across a sagittal section of a whole fetal hindlimb. We reveal a clear anatomical segregation between genes linked to brachydactyly and polysyndactyly, and uncover transcriptionally and spatially distinct populations of the mesenchyme in the autopod. Finally, we perform single-cell RNA sequencing on mouse embryonic limbs to facilitate cross-species developmental comparison, finding substantial homology between the two species.

In this study, the composition and content of vitamin D and its esters in 108 human milk samples from different lactation stages (colostrum on days 0–7, transition milk on days 8–15 , and mature milk after day 16) were analyzed by ultra-high performance liquid chromatography/quadrupole time of flight mass spectrometry (UPLC/Q-TOF-MS). The results showed that human milk contained 4 kinds of vitamin D and 20 kinds of vitamin D esters, 16, 18 and 14 kinds of vitamin D esters being found in colostrum, transition milk and mature milk, respectively. During the whole lactation period, the average contents of vitamin D2 and 25(OH)-D3 in colostrum were highest, 26.83 and 160.67 ng/L, respectively; the average content of vitamin D3 in transition milk was highest, 119.87 ng/L; and the average content of 1,25(OH)2-D3 in mature milk was highest, 1.82 ng/L. The average contents of vitamin D esters in colostrum, transition milk and mature milk were 11.89, 10.73 and 11.47 ng/L, respectively, and the content of vitamin D2 tetradecenoate (C14:1) was highest throughout the lactation period. Through partial least squares-discriminant analysis (PLS-DA), colostrum, transition milk and mature milk could be well separated, indicating that the types and contents of vitamin D and vitamin D esters in human milk change from colostrum to mature milk. There was a correlation between different vitamin D esters. This study could provide data support for the development of infant formula.

For a vertex set X $X$ in a graph, the edge cut∂(X) $\partial (X)$ is the set of edges with exactly one end vertex in X $X$. An edge cut ∂(X) $\partial (X)$ is tight if every perfect matching of the graph contains exactly one edge in ∂(X) $\partial (X)$. A matching covered bipartite graph G $G$ is a brace if, for every tight cut ∂(X) $\partial (X)$, |X|=1 $|X|=1$ or |X¯|=1 $|\bar{X}|=1$, where X¯=V(G)⧹X $\bar{X}=V(G)\setminus X$. Braces play an important role in Lovász's tight cut decomposition of matching covered graphs. The bicontraction of a vertex v $v$ of degree two in a graph, with precisely two neighbours v1 ${v}_{1}$ and v2 ${v}_{2}$, consists of shrinking the set {v1,v,v2} $\{{v}_{1},v,{v}_{2}\}$ to a single vertex. The retract of a matching covered graph G $G$ is the graph obtained from G $G$ by repeatedly the bicontractions of vertices of degree two. An edge e $e$ of a brace G $G$ with at least six vertices is thin if the retract of G−e $G-e$ is a brace. McCuaig showed that every brace of order at least six has a thin edge. In a brace G $G$ of order six or more, Carvalho, Lucchesi and Murty proved that G $G$ has two thin edges, and conjectured that G $G$ contains two nonadjacent thin edges. Further, they made a stronger conjecture: There exists a positive constant c $c$ such that every brace G $G$ has c|V(G)| $c|V(G)|$ thin edges. By showing that, in every cubic brace G $G$ of order at least six, there exists a matching M $M$ of size at least |V(G)|∕10 $|V(G)|\unicode{x02215}10$ such that every edge in M $M$ is thin, we prove that the above two conjectures hold for cubic braces. [ABSTRACT FROM AUTHOR]

The development of nanomaterials is crucial to upgrading of modern industry. MXene nanosheets have attracted significant attention due to their superb resistance to permeation, diverse surface chemical properties, impressive mechanical properties, and metal‐like electrical and thermal conductivity, etc., providing unique advantages in various technical fields. When MXene nanosheets are combined with polymers to form functional coatings, their applications span multiple fields, including anticorrosion, wear resistance, flame‐retardancy, electromagnetic interference (EMI) shielding, and de‐icing. This review, in conjunction with MXene's barrier property, lubricity, thermal stability, conductivity, and photothermal conversion property, discusses in detail the various applications of MXene‐based polymer coatings. Additionally, it examines the dispersion and interaction of MXene within polymer coatings and the role of functionalized MXene in polymers. Finally, based on the current research status and emerging needs, the development challenges and future research opportunities of MXene‐based polymer coatings in a targeted manner are discussed. This review aims to summarize the existing research results and put forward an objective and fair point of view, providing a constructive reference for upgrading modern nanofunctional polymer coatings. [ABSTRACT FROM AUTHOR]

Lutein in human breast milk plays an important role in the development of vision and cognitive function in infants. In this study, ultra-high performance liquid chromatography tandem mass spectrometry was used to determine the composition and contents of lutein and lutein esters in human breast milk collected at different ages for giving childbirth and lactation stages. Finally, lutein and 16 lutein esters in human breast milk were qualitatively and quantitatively analyzed. A strong positive correlation was found between lutein and lutein esters contents in human breast milk (Pearson correlation coefficient was 0.721). The contents of lutein and lutein esters in human breast milk in the age-appropriate group (childbith age<35 years) was similar to that of the older age group (childbirth age ≥35 years), and the difference between the two was insignificant (P>0.05), indicating that the age for giving childbirth had little effect on the contents of lutein and lutein esters in human breast milk. The contents of lutein and lutein esters decreased gradually with the extension of the lactation period, and the contents of both in colostrum were the highest, with the average content of lutein reaching 183.78 µg/L and the average content of lutein esters reaching 45.89 µg/L. There were 10, 14 and 6 kinds of lutein esters detected in the colostrum, transitional milk and mature milk, respectively, with the content of lutein palmitate-stearate being the highest throughout the whole lactation period, followed by lutein distearate. The research results can provide certain experimental and theoretical bases for the research of human milk composition and the research and development of infant formula foods. [ABSTRACT FROM AUTHOR]