Macrophages play a role in salvaging cholesterol during nerve injury.Macrophages also play a role in inducing the proliferation of Schwann cells that occurs during Wallerian degeneration. Supernatant has been collected from medium in which macrophages are active in myelin phagocytosis where lysosomal processing of the myelin occurs within the macrophage. The supernatant contains a mitogenic factor, a mitosis promoting factor, that is characterized heat and trypsin sensitivity, both of which characterize it as a peptide. Treatment of Schwann cells with the collected supernatant shows that it is a mitogenic factor and thus plays an important role in the proliferation of Schwann cells.Macrophages are also involved in the secretion factors that promote nerve regeneration. Macrophages secrete not only interleukin-1, a cytokine that induces expression of nerve growth factor (NGF) in Schwann cells but also an interleukin-1 receptor antagonist (IL-1ra). Expression of IL-1ra in mice with transected sciatic nerves via implantation of a tube releasing IL-1ra showed the regrowth of fewer myelinated and unmyelinated axons. Macrophage secretion of interleukin-1 is involved in stimulation of nerve regeneration. Role of neurotrophic factors
Neurotrophic factors are those that promote survival and growth of neurons. A trophic factor can be described as a factor that is associated with providing nourishment to allow for growth. In general they are protein ligands for tyrosine kinase receptors; binding to the specific receptor yields autophosphorylation and subsequent phosphorylation of tyrosine residues on proteins that participate in further downstream signaling to activate proteins and genes involved in growth and proliferation.
Cyclothymic depression also leads to difficulty making decisions. In addition, people with this condition tend to be critical and complain easily. Suicidal thoughts are common, even in mild forms of cyclothymia. In the depressive state, people with cyclothymia also experience physical complaints including frequent headaches, tightness in the head and chest, an empty sensation in the head, weakness, weight loss, and hair loss.The distinguishing factor between typical depression and cyclothymic depression is that in cyclothymic depression, there are instances of hypomania. People with cyclothymia can switch from the depressive state to the hypomanic state without warning to them or others. The duration and frequency of phases is unpredictable.In the hypomanic state, peoples thoughts become faster and they become more sociable and talkative. They may engage in spending sprees, spontaneous actions, have heightened self-esteem, and greater vanity. In contrast to a regular manic state that would be associated with bipolar I, symptoms in the hypomanic phase generally occur in a less severe form.Cyclothymia commonly occurs in conjunction with other disorders. Between 20 and 50 percent of people with depression, anxiety, and related disorders also have cyclothymia. When people with cyclothymia seek mental health resources it tends to be for symptoms of their comorbid condition rather than for their symptoms of cyclothymia. In children and adolescents, the most common comorbidities with cyclothymia are anxiety disorders, impulse control issues, eating disorders, and ADHD. In adults, cyclothymia also tends to be comorbid with impulse control issues. Sensation-seeking behaviors occur in hypomanic states.