Humoral factors

Humoral factor. A general term referring to biologically active substances found in the body fluids. 

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

The delicate balance maintained by these factors is altered in patients with cancer by two principal mechanisms tumor production of humoral factors that alter calcium metabolism (humoral hypercalcemia) and local osteolytic activity from bone metastases.27 Humoral hypercalcemia causes around 80% of all hypercalcemia cases and is mediated primarily by systemic secretion of parathyroid hormone-related protein... 

Regardless of the etiology, fall in blood pressure (BP) is compensated by an increase in sympathetic outflow, activation of the renin-angiotensin system, and other humoral factors that stimulate peripheral vasoconstriction. Compensatory vasoconstriction redistributes blood away from the skin, skeletal muscles, kidneys, and GI tract toward vital organs (e.g., heart, brain) in an attempt to maintain oxygenation, nutrition, and organ function. 

I, Immediate (reaginic) Food additives (Gl allergies anaphylactic) Penicillin uticaria and dermatitis Mast cells IgE Anaphylaxis, asthma, urticaria, rhinitis, dermatitis IgE binds to mast cells to stimulate release of humoral factors... 

The humoral factors include numerous cytokines and growth factors, which act as classical endocrine, paracrine or autocrine regulators. Developing cells are sensitive to a range of such factors at all times during their maturation and, in the case of white blood cells, during their existence within the circulation. To ensure responsiveness during their development, cells must express on their surface a variety of receptors at different times. 

Thymic factors are naturally occurring substances that promote T-lymphocyte differentiation and differentiation of early stem cells into prothymocytes. Each of the available preparations (e.g., thymic humoral factor, thymosin fraction 5, and thymodulin) are mixtures of several polypeptides isolated from a calf thymus extract. 

Retroviruses require proliferative target cells to mediate effective gene transfer. Lentiviruses, the class of retrovirus that includes human immunodeficiency virus, are an exception. They can also integrate in nondividing cells. An additional obstacle for retroviruses is the high susceptibility of the virus particle to humoral factors that ablate their gene transfer capacity. Perhaps most important, retroviruses, even when used ex vivo, pose a low but real risk of cancer. 

The mechanism of this residual hypertension has been assumed by many to be neurogenic. The evidence for this is not conclusive, and even if the central nervous system is involved (it is involved in most things going on in the body), it is not improbable that humoral factors in addition may act in this self-perpetuating hypertension. 

Hemostasis as defined by Virchow in the last century is a fine balance between blood flow, humoral factors, and cellular elements of the vascular system. Today, molecular and... 

Kolpakov W. 1971. [Effect of barium chloride on production of humoral factors stimulating leukopoiesis], Patol Fiziol EkspTer 14 64-66. (Russian)... 

Vasoconstriction reduces ingress of inflammatory cells and humoral factors to the inflamed area this action (blanching effect on human skin) has been used to measure the potency of individual topical corticosteroids (see below). 

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