Notochord vacuoles absorb compressive bone growth during zebrafish spine formation

The vertebral column or spine assembles around the notochord rod which contains a core made of large vacuolated cells. Each vacuolated cell possesses a single fluid-filled vacuole, and loss or fragmentation of these vacuoles in zebrafish leads to spine kinking. Here, we identified a mutation in the kinase gene dstyk that causes fragmentation of notochord vacuoles and a severe congenital scoliosis-like phenotype in zebrafish. Live imaging revealed that Dstyk regulates fusion of membranes with the vacuole. We find that localized disruption of notochord vacuoles causes vertebral malformation and curving of the spine axis at those sites. Accordingly, in dstyk mutants the spine curves increasingly over time as vertebral bone formation compresses the notochord asymmetrically, causing vertebral malformations and kinking of the axis. Together, our data show that notochord vacuoles function as a hydrostatic scaffold that guides symmetrical growth of vertebrae and spine formation.

The desmosomal cadherin Desmogon is necessary for the structural integrity of the Medaka notochord

The notochord is an embryonic tissue that acts as a precursor to the spine. It is composed of outer sheath cells and inner vacuolated cells. Together they ensure the ability of the notochord to act as a hydrostatic skeleton until ossification begins. To date, there is still a paucity in our understanding of how the notochord cell types are specified and the molecular players controlling both their formation and maintenance remain poorly understood. Here we report that desmogon, a desmosomal cadherin, is essential for proper vacuolated cell shape and therefore correct notochord morphology. We trace desmogon+ precursors and uncover an early developmental heterogeneity that dictates the balance of vacuolated and sheath cell formation. We demonstrate that the growth of vacuolated cells occurs asynchronously and reveal the presence of distinct injury sensing mechanisms in the notochord. Additionally, using a small-scale F0 CRISPR screen we implicate uncharacterized genes in notochordal integrity.

Adrenocortical zonation of inbred wild-coloured mastomys, Praomys coucha: a new border zone in the cortex of females

Adrenal glands were examined in the inbred strain of wild-coloured mastomys ( Praomys coucha), MWC. The most characteristic findings were emergence of a border zone between the zona fasciculata and z. reticularis of the cortex in females but not in males, and persistence of broad z. reticularis in males. The border zone was typically comprised of vacuolated cell layers, nodular layers and fibrous tissue. Vacuolated cells increased in number during pregnancy and partially disappeared during lactation. Growth of the nodules was greatly enhanced in both number and size during lactation. Thus, multiparae had very thick border zones composed predominantly of large nodules and, additionally, of vacuolated cells and fibrous tissue. The z. reticularis was compressed into a cord of closely packed cells by the expanded border zone in multiparous females but it continued to thicken with age in males. These changes produced completely different cortical zonation in the adrenal between sexes.

Epididymal Interstitial (Leydig) Cell Tumors in B6C3F1 Mice

Six primary interstitial cell tumors of the epididymis were identified from 46,752 male B6C3F1 mice used in chronic toxicity and carcinogenicity studies. Five of the tumors occurred at the end of 2-year studies; none were attributed to treatment. None of the mice with epididymal tumors had a primary testicular tumor. Histologically, tumors were characterized by a nodular or diffuse proliferation of tumor cells in the epididymal interstitium. Most cells were polygonal with highly vacuolated cytoplasm (vacuolated cells) or eosinophilic cytoplasm (eosinophilic cells). Smaller hyperchromatic cells with scant basophilic cytoplasm (basophilic cells) and cells with yellow-brown pigment characteristic of lipofuscin (pigmented cells) were less common. In each tumor two or more cell types were present. Extension of these tumors through the capsule, invasion of the testis, or metastasis did not occur. By electron microscopy both eosinophilic and vacuolated cell types had a large round or oval nucleus with sparse heterochromatin, abundant mitochondria with tubulovesicular cristae, and frequent desmosome structures between cell membranes. Vacuolated cells contained numerous lipid droplets. Morphological features of the epididymal tumors are similar to those of the testicular interstitial (Leydig) cell tumor in mice and rats.

The Morphology of Vacuolated Cells in the Liver Following Administration of Vitamin A.

Vacuolated cells in the liver of young rats were studied by light and electron microscopy following the administration of vitamin A (200 units per gram of body weight). Their characteristics were compared with similar cells found in untreated animals.In rats given vitamin A, cells with vacuolated cytoplasm were a prominent feature. These cells were found mostly in a perisinusoidal location, although some appeared to be in between liver cells (Fig. 1). Electron microscopy confirmed their location in Disse's space adjacent to the sinusoid and in recesses between liver cells. Some appeared to be bordering the lumen of the sinusoid, but careful observation usually revealed a tenuous endothelial process separating the vacuolated cell from the vascular space. In appropriate sections, fenestrations in the thin endothelial processes were noted (Fig. 2, arrow).