The islets of Langerhans are infiltrated by CD4+, CD8+ T lymphocytes, NK cells, B lymphocytes, dendritic cells, macrophages and neutrophils, similar to the disease process in humans. In addition to sex, breeding conditions, gut microbiome composition or diet also influence the onset of T1D.The BioBreeding Diabetes-Prone (BB) rat is another widely used spontaneous experimental model for T1D. The onset of diabetes occurs, in up to 90% of individuals (regardless of sex) at 8–16 weeks of age. During insulitis, the pancreatic islets are infiltrated by T lymphocytes, B lymphocytes, macrophages, and NK cells, with the difference from the human course of insulitis being that CD4 + T lymphocytes are markedly reduced and CD8 + T lymphocytes are almost absent. The aforementioned lymphopenia is the major drawback of this model. The disease is characterized by hyperglycemia, hypoinsulinemia, weight loss, ketonuria, and the need for insulin therapy for survival. BB Rats are used to study the genetic aspects of T1D and are also used for interventional studies and diabetic nephropathy studies.LEW-1AR1 / -iddm rats are derived from congenital Lewis rats and represent a rarer spontaneous model for T1D. These rats develop diabetes at about 8–9 weeks of age with no sex differences unlike NOD mice. In LEW mice, diabetes presents with hyperglycemia, glycosuria, ketonuria, and polyuria. The advantage of the model is the progression of the prediabetic phase, which is very similar to human disease, with infiltration of islet by immune cells about a week before hyperglycemia is observed.
A crevasse may be as deep as 45 metres (148 ft) and as wide as 20 metres (66 ft). A crevasse may be covered, but not necessarily filled, by a snow bridge made of the previous years accumulation and snow drifts. The result is that crevasses are rendered invisible, and extremely dangerous to anyone attempting to traverse a glacier. Types of crevasses
Longitudinal crevasses form parallel to the ice flow where the glacier width is expanding. Splaying crevasses appear along the edges of a glacier. Transverse crevasses form in a zone of longitudinal extension where the principal stresses are parallel to the direction of glacier flow. Fissure vent
A fissure vent, also known as a volcanic fissure or eruption fissure, is a long volcanic vent through which lava erupts. Fissure vents are connected to deep magma reservoirs and are typically found in and along rifts and rift zones. They are commonly associated with shield volcanoes. Over time fissure vents form spatter cones and can feed lava channels and lava tubes. Karst terrain
Karst terrain or simply karst are vast regions of barren land with rocky ground and generally consisting of nearby caves, fissured ground, and sinkholes. Although these regions normally have moderate to heavy rainfall, they are noticeably devoid of vegetation and characteristically have no lakes, rivers, or streams on their surface. They form when large to massive veins of soluble aggregate like limestone, gypsum, or dolomite are excavated by underground torrents of flowing water.