Quantitative microscopy and imaging tools for the mechanical analysis of morphogenesis

The importance of mechanical signals during embryogenesis and development, through both intercellular and extracellular signals, is coming into focus. It is widely hypothesized that physical forces help to guide the shape, cellular differentiation and the patterning of tissues. To test these ideas many classical engineering principles and imaging technologies are being adapted. Recent advances in microscopy, mechanical testing and genetic and pharmacological techniques, alongside computational models are helping to dissect the activity of mechanical signals in development at the cellular and molecular level. These inroads are providing maps of mechanical changes in tissue structure and stiffness, and will permit deeper insights into the role of mechanics in both developmental biology and disease.     

An appeal to our government for nationwide policies in the prevention of cardiovascular disease

Netherlands Heart Journal - The high prevalence and burden of cardiovascular diseases (CVD) is largely attributable to unhealthy lifestyle factors such as smoking, alcohol consumption, physical...     

Expression of a nonpolymorphic MHC class I-like molecule, CD1D, by human intestinal epithelial cells.

The human CD1 locus encodes three nonpolymorphic MHC class I-like cell surface glycoproteins, CD1a-c, which are expressed primarily by immature thymocytes. A mAb and antipeptide antiserum were utilized to determine the tissue distribution of a fourth CD1 molecule, CD1d. Within the lymphoid lineage, CD1d was expressed on B cells but not on thymocytes. Immunoperoxidase staining of fresh frozen intestinal tissues demonstrated that the majority of intestinal epithelial cells, with the exception of cells at the base of some crypts, expressed CD1d. The CD1d staining was observed in the cytoplasm and along the basolateral membranes of the epithelial cells. The intestinal epithelial cell expression of CD1d was confirmed by immunoblotting with a CD1d antipeptide antiserum. Further immunoperoxidase studies indicated that CD1d, unlike murine CD1, was also expressed by nonlymphoid tissues outside of the gastrointestinal tract. The expression of CD1d outside the lymphoid and myeloid lineages clearly distinguishes this molecule from CD1a-c and suggests that it may serve a distinct function. The prominent expression of CD1d by intestinal epithelial cells suggests that this molecule may be an important ligand for T lymphocytes within the gut-associated lymphoid tissue.     

Differentiation and maturation of cultured fetal rat jejunum.

To determine whether differentiation and maturation of mammalian intestinal mucosa require influences available only in vivo or whether they can occur in vitro, fetal rat jejunum was cultured in chemically defined medium using organ culture methodology. Segments of jejunum from 18-day fetal rats were cultured in modified Liebowitz L-15 medium in room air at 37°C. Segments harvested after 24, 48, and 72 hr of culture were examined by light and electron microscopy. Uncultured jejunum from 18-day fetuses had either no or very few rudimentary villi and was lined largely by undifferentiated stratified epithelium. Goblet cells were not seen. In contrast, villi were present in the majority of 24-hr cultures, and simple columnar rather than stratified epithelium predominated. After 48 and 72 hr, villi were present in over 90% of cultured jejunal segments and stratified epithelium had disappeared. Goblet cells were seen in jejunal segments cultured 48 hr or longer in 47 of 74 fetuses. Electron microscopy further documented progressive differentiation of the epithelium during culture. Microvilli increased in number and height, a terminal web developed in the apical cytoplasm and the number of apical vesicles, mitochondria and formed elements of endoplasmic reticulum increased in absorptive cells. Jejunal lactase and alkaline phosphatase activity increased nine- and sevenfold, respectively, during 72 hr of culture, while the activity of the mitochondrial enzyme, ornithine carbamoyl transferase, increased fourfold. These observations indicate that jejunum from 18-day fetal rats can be cultured in vitro for at least 72 hr in chemically defined medium and that, during culture, maturation of the jejunal mucosa takes place with the appearance of villi, conversion of stratified to columnar epithelium and differentiation of individual epithelial cells.     

Lectin histochemistry for detecting cadmium-induced changes in the glycosylation pattern of rat placenta

Cadmium (Cd) is an industrial and environmental pollutant that produces toxic effects on gametogenesis, pre- and post-implantation embryos, and the placenta. Because the effects of acute Cd intoxication on the placenta are not well understood, we investigated changes in its glycosylated components in Cd treated dams at days 4, 7, 10 and 15 of gestation using lectin histochemistry. CdCl₂ was administered to pregnant rats; control animals received sterile normal saline. Placentas were processed for DBA, Con A, SBA, PNA, UEA-I, RCA-I and WGA lectin histochemistry to evaluate changes in the carbohydrate pattern of the placenta that might modify cell interactions and contribute to embryonic alterations. Lectin binding was analyzed in the yolk sac; trophoblast giant cells; trophoblast I, II and III; spongiotrophoblast cells and endovascular trophoblast cells in the chorioallantoic placenta. Our lectin binding patterns showed that Cd caused alteration of SBA and DBA labeling of trophoblast-derived cells, which suggested increased expressions of α and β GalNAc. Cd also caused decreased UEA-1 binding affinity, which indicated fewer α-L-Fuc residues in placentas of Cd treated dams. The nonreactivity in trophoblast I of the control placentas incubated with Con-A contrasted with the labeling in placentas of experimental dams, which indicated increased expression of terminal α-D-Man, and α-D-Glc residues. We found that Cd altered the reactivity of placenta to several lectins, which indicated modification of the glycotype presented by the fetal component of the placenta. We report that Cd exerts a deleterious effect on the glycosylation pattern of the placenta.     

Heavy metal concentrations in,and human health risk assessment of,three commercially valuable fish species in the lower Niger River,Nigeria

The concentrations of Fe, Mn, Ni, Pb and V in water, sediment and the gill, liver and muscle tissues of Synodontis resupinatus, Heterotis niloticus and Clarias gariepinus, all commercially important fish species of the lower Niger River, were investigated in 2015. Water, sediment and fish samples were collected for six months and heavy metals were determined using an Atomic Absorption Spectrometer. Fe ranked highest in water and sediment, with concentrations of 2.74 mg l^?1 and 61.60 mg kg^?1, respectively. Metals followed the magnitude of Fe > Mn > Ni > V > Pb in the water and Fe > Mn > V > Ni > Pb in the sediments. Metal concentrations were higher in the tissues of S. resupinatus compared with H. niloticus and C. gariepinus. Fe was also highest in the gills, liver and muscle of the three fish species. Its highest concentration of 132.97 mg kg^?1 dry weight was recorded in the gills of S. resupinatus. Bioconcentration factors of metals ranged from 8.79 for Mn in H. niloticus muscle to 67.99 for Ni in S. resupinatus gills. The fish species studied pose no health risk for all metals studied, because the target hazard quotient was less than 1 and the estimated daily intakes of the metals were below the reference doses.     

Junctional complexes in fetal rat small intestine during morphogenesis

During the 7 days prior to birth (Days 15–22), the small-intestinal epithelium of the fetal rat changes from primitive stratified to simple columnar epithelium which lines villi at 19 days. As seen in thin sections, this remodeling involves rapid formation of new junctional complexes and secondary lumens between epithelial cells deep in the stratified epithelium. We have examined the formation and reorganization of junctional complexes in proximal small intestine of 15- to 19-day fetal rats using freeze-fracture techniques. On Days 15 and 16 the epithelial cells surrounding the primary lumen are joined by conventional apical junctional complexes. Additionally, macular junctional complexes are located on deeper epithelial cells. These display no polarity and consist of tight-junction strands intermixed with gap junction-like arrays and desmosomes. On Days 17 and 18 nonluminal, macular junctional complexes enlarge and secondary lumens develop within their centers. As the secondary lumens expand, microvilli appear and the junctional complex polarizes about the secondary lumen; tight-junction strands become parallel to the luminal surface, desmosomes migrate basolaterally, and gap junction-like arrays disappear. By Day 19, secondary lumens have fused with the primary lumen; concomitant loss of apical cells results in formation of villi lined by simple columnar epithelium with polarized apical tight junctions. The observed pattern of junctional complex formation may play a role in maintaining barrier function and establishing epithelial cell polarity as the epithelium is remodeled.     

Selective retention of T cell precursors in bone marrow. Cell populations after filtration through anti-immunoglobulin columns.

Lethally irradiated mice transplanted with normal syngeneic bone marrow have restored their immunocompetence 2–4 weeks after transplantation. During regeneration T cells seem to develop more slowly than B cells. We have studied the impact of anti-Ig column fractionation of bone marrow cells on their subsequent development into T cells. The results showed that in mice grafted with anti-Ig column-passed bone marrow cells (a) the number of θ-positive cells which develop was very much reduced, and (b) the development of GVH reactive cells and helper cells was much delayed when compared with mice grafted with normal unpassed bone marrow cells. In contrast, the development of B cell function and of the hematopoietic system was always normal. It was concluded that one possible explanation for such findings was the existence of immunoglobulin on T cell precursors.