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العودة   منتديات الكيمياء الحيوية للجميع > الكيمياء الحيوية > الهرمـونات - Hormones
 
 

الهرمـونات - Hormones الغدد الصماء و هرموناتها

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قديم 04-14-2009, 06:37 PM   #1
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بسم الله الرحمن الرحيم



سااااااااااااااااعدوني بليييييز

عندي بحث ولازم يتسلم في الاسبوع الجاي وانا موعارفه ولا كلمه لان دراستنا للكيمياء الحيويه بالعربي بليز اللي يقدر يترجمه لي يكون شال عني هم كبييييييييييير

لا تقولون استحدم برامج الترجمه لان طلع كلام غير مفهوم وهذا البحث

Cysteine;the phenolic group of tyrosine: the 3carboxy-amide grups of aspargine,and glycina-mide; and the disulfide (s-s)
linkage.
By deleting or substituting these grups,numerous analogs of oxy-tocin have been produced .
for example,deiasion of the free primary amino grup of the terminal half cysteine residue (position1)results in desamino oxytocin ,which has 4-5 times the antidiuretic activity of oxytocin .

Antidiuretic hormone (adh;vasopressin)reguliation of secretion:
The neral implsesthat trigger adh release are activated by a number of different stimuli. Increased osmolality of plsma is the primary physiologic stimulus .
This is mediatd by OSMOECEPTORS iocated in the hypothalamus and by BARORECEPOTORS located in the heart and other regions of the vascular system.
Hemodilution (decreased osmolaity)has the opposite effect . Other stimuli include emotional and physical stress and pharmacologic agents including acetylcholine, nicotine,and morphene. Most of these effects involve increased synthesis of ADH and neurophysin II ,since the depletion of stored hormones is not associated with this action .
Epinephrine and agents that expand plasma volume inhibit ADH secretion,as dose ethanol.
MECHANISM OF ACTION:
The most important physiolic target cells of ADH in mammals are thos of the distal convoluted tubules and collecting structures of the kidney .these ducts pass through the renal medulla,in which the extracellular solute pool has an osmolality gradient up 4 times that of plasma . these cells are relatively impermeable to water ,so that in the absence of ADH ,the urine is not concentrated and may be excreted in amounts exceeding 2 l\d. ADHinmits osmotic equilibration of collecting tuble urine with the hypertonic interstitium , resulting in urine volumes in the range of 0.5 -1 l\d ADH receptors exist on the mucosal (urinary) membrane of these epithelial cells . this receptor is linked to adenylate cyciase ,and cAMP is though to mediate the effects of ADHin the renal tuble .this physiologic action is the basis of the name (antidiuretic hormone ).
cAMP and inhibitors of phosphodiesterase activity (caffeine for example )mimic the actions of ADH.
In vivo ,an elevated leavl of calicum in the medium bathing mucosal surface of the tubular cells inhibitse the actioneِِِِ
ADH on water movement ,apparently by inhibiting the action of cADH per se .
This may account ,in part,for the excessive volumes of urine that are characteristic of patients with hypercalcemia .
PATHOPHYSIOLOGY:
Abnormalities of ADH secretion or action lead to diabetes insipides, which is characterized by the excretion of large volumes of dilute urine . primary diabetes insipidus ,an insufficient amount of the hormone ,is usually due to destruction of the hypothalamic_hypophyseal tract from a basal skull fracture , tumer , or infection ,but it can be hereditary .In heareditary nephrogenic diabetes insipidus,A D H is secreted normally but the target ceel is incapable of responding , presumably because of a receptor defect ( see table 43 – 2) This hereditary lesion is distinguished from acquired nephrogenic diabetes insibidus , which most often is due to the pharmacologic administration of lithiumfor manic-depressive illness . the inappropriate secretion of ADH occurs in association with ectopic production by a variety of tumors ( usually tumors of the lung ) but can also occur in conjunction with diseases of the brain , pulmonary infections , or hypothyroidism , it is called inappropriate secretion because ADH is produced at a normal or increased rate in the presence of hypoosmolality , thys causing a persistent and progressive dilutional hyponatremia with excretion of hypertnic urine .
references
anterior pituitary hormones



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