User:Aangi14/sandbox2

Article Evaluation

This evaluation is in reference to the article on Testosterone.

Content

• The article is relatively well constructed as a whole and does not lead the reader astray from the topic.
• Subsection 1.5 should contain subtopic links in the article contents for ease of access and organization
• Within the above referenced subsection, the subheading titled "Motivation" is unnecessary and can be placed within the introductory section of the subsection
• In my opinion, Other Animals should be placed above History for better continuation of ideas for the reader

Tone

• Tone is generally impersonal and professional throughout most of the article
• Persuasion is not attempted
• In subsection Adult, under subtitle Aggression and criminality, more frequent citation and a possible review of phrasing may be necessary to avoid sounding biased early on in the section, however this issue dissipates toward the end

Sources

• More frequent citation throughout the article would be helpful in avoiding indication of bias
• Citations are reliable

Talk Page

• The article is rated as level-4 Vital Article and is B-Class
• Threads exploring additional new information about the topic have been proposed and are waiting approval and insertion into the article
• there is also the proposition to produce a parent article which would summarize the both Testosterone and Testosterone (medication), or to revise the hormone based article to focus less on the use of testosterone as a drug. This has apparently since been resolved as this issue is no longer apparent.

Picking A Topic

Possible Articles

• Sex Hormone Binding Globulin

   *This page is start class and allows for much room for improvement, however it is more developed than a stub article and I have a starting point to build on

• Growth Hormone 1

    *This is a stub article that does not feature much user friendly information, nor does it elaborate on the hormone itself from a protein product or genetic sequence view

• Pulsatile secretion

     *This stub does not adequately cover the topic beyond a bare-bones definition and has immense room for expansion and refinement

Aangi14 (talk) 01:19, 5 February 2019 (UTC)

Draft Pulsatile Secretion

Pulsatile secretion is a biochemical phenomenon observed in a wide variety of cell types, in which chemical products are secreted in a regular pattern. The most common cellular products observed to be released in this manner are intercellular signaling molecules such as hormones or neurotransmitters. The most common examples of hormones that are secreted pulsatilely include insulin, thyrotropin, TRH, gonadotropin-releasing hormone (GnRH) and growth hormone (GH). In the nervous system, pulatlility is observed in oscillatory activity from pacemakers and central pattern generators. Pulsatile activity is critical to the function of many hormones in order to maintain the delicate homeostatic balance necessary for essential life processes, such as development and reproduction. Pulsatile secretion can be critical to hormone function, as evidenced by the case of GnRH agonists, which cause functional inhibition of the receptor for GnRH due to profound downregulation in response to constant stimulation. Pulsatility may function to sensitize target tissues to the hormone of interest and upregulate receptors, leading to improved responses. This heightened response may have served to improve the animal's fitness in its environment and promote its evolutionary retention.

Pulsatile secretion in its various forms is observed in:

• Glucocorticoids
• Insulin
• Growth Hormone
• Hypothalamic-Pituitary-Gonadal axis (HPG) related hormones
  

Neuroendocrine Pulatility

Nervous system control over hormone release is based in the hypothalamus, from which the neurons that populate the pariventricular and arcuate nuclei originate. These neurons project to the pituitary gland via the hypophysial portal system, and dictate endocrine function via the four Hypothalamic-Pituitary-Glandular axes. Recent studies have begun to offer evidence that many pituitary hormones which have been observed to be released episodically are preceded by pulsatile secretion of its associated releasing hormone from the hypothalamus in a similar pulastile fashion. Novel research into the cellular mechanisms associated with pituitary hormone pulsatility, such as that observed for Leutinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) have indicated similar pulses into the hypophesial vessels of Gonadotropin Releasing Hormone (GnRH).

Glucocorticoids

Regular pulses of glucocorticoids, mainly cortisol in the case of humans, are released regularly from the adrenal cortex at following a circadian pattern in addition to its release as a part of the stress response. Cortisol release follows a high frequency of pulses, with amplitude being the primary variation in its release. Glucocorticoid pulsitlity has been observed to follow a circadian rhythm with highest levels observed before waking and before anticipated mealtimes. This pattern in amplitude of release is observed to be consistent across vertebrates. Studies done in humans, rats and sheep have also observed a similar circadian pattern of release of adrenocorticotropin (ACTH) shortly preceding the pulse in the resulting corticosteroid. It is currently hypothesized that the observed pulsatility of ACTH and glucocorticoids is driven via pulsatility of corticotropin-releasing hormone (CRH), however there exists little data to support this due to difficulty in measuring CRH.

LH

overectemized rats treated with chronically elevated E2 showed LH surges on consecutive days, restricted to late afternoon and early evening

LH frequency is around every 4 hours. in females during the luteal phase of the menstrual cycle, LH pulse amplitude is increased.

Growth Hormone

"Normal GH pulsatility in peripheral blood is tightly regulated, with discrete bursts approximately every 3 h, and achieving the highest concentrations during sleep"

Insulin

Full Article: Insulin Oscillation

Oscillations of intracellular calcium concentration in beta cells within the pancreas produces a basal pulsatile secretion of insulin form the pancreas. Secretion pulses emanating form free beta cells not located within an islet of Lagerhans has been observed to be highly variable (2 to 10 minutes). Beta cells within an islet, however, become synchronized via electrical coupling resulting from gap junctions, and osculate more regularly (3 to 6 minutes). ATP signalling has also been proposed as a method of coordination between beta cells.

Pulsatile insulin secretion from individual beta cells is driven by oscillation of the calcium concentration in the cells. In beta cells lacking contact, the periodicity of these oscillations is rather variable (2-10 min). However, within an islet of Langerhans the oscillations become synchronized by electrical coupling between closely located beta cells that are connected by gap junctions, and the periodicity is more uniform (3-6 min).

Coordination of pulsatile insulin release. In addition to gap junctions, coordination is done by ATP signaling.

Pulsatile insulin release from the entire pancreas requires that secretion is synchronized between 1 million islets within a 25 cm long organ. Much like the cardiac pacemaker, the pancreas is connected to cranial nerve 10, and others, but the oscillations are accomplished by intrapancreatic neurons and do not require neural input from the brain. It is not entirely clear which neural factors account for this synchronization but ATP as well as the gasses NO and CO may be involved. The effect of these neural factors is to induce sudden dramatic elevation of calcium in the cytoplasm by releasing calcium from the endoplasmic reticulum (ER) of the beta cells. This elevation results in release of ATP from the beta cells. The released ATP in turn binds to receptors on neighboring beta cells leading to a regenerative wave of rapid calcium elevation among the cells within the islet. This signal is believed to entrain pulsatile insulin release from the islets into a common pancreatic rhythm.

beta cells have the intrinsic ability to generate 2-5 minutie Ca2+ oscillations

alpha and delta cells share this ability

Circadian Pulsatility

ILL

Might not use