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In mammals, the major factors involved in the regulation of body growth are known: insulin-like growth factors (IGF) are key regulators of somatic growth. Growth hormone (GH), secreted by the pituitary gland, directly regulates circulating levels of IGF-I, which is the major coordinator of spatio-temporal growth of the organism. In humans, growth is even more complex, involving a number of specific characteristics not found in other species. These include rapid intrauterine growth, deceleration just after birth, a mid-childhood growth spurt, a second deceleration before puberty, an adolescent growth spurt, and finally full statural growth, which is seen somewhat later. The combined knowledge concerning the endocrine and paracrine aspects of growth have led to the introduction of treatment regimens, most effective in GH-deficient children. However, size depends on the combination of a number of genetic factors, and there remain several aspects of this complex process still poorly understood.
Multicellular organisms require a means of intracellular
communication to organize and develop the complex body plan that
occurs during embryogenesis and then for cell and organ systems to
access and respond to an ever changing environmental milieu.
Mediators of this constant exchange of information are growth
factors, neurotransmmitters, peptide and protein hormones which
bind to cell surface receptors and transduce their signals from the
extracellular space to the intracellular compartment. Via multiple
signaling pathways, receptors of this general class affect growth,
development and differentiation. Smaller hydrophobic signaling
molecules, such as steroids and non-steroid hormones, vitamins and
metabolic mediators interact with a large family of nuclear
receptors. These receptors function as transcription factors
affecting gene expression, to regulate the multiple aspects of
animal and human physiology, including development, reproduction
and homeostasis.
Growth is a complex process that is essential to life. Not only does size play an important role in the process of cellular proliferation, but body size is also a critical factor in determining which organisms live longer. Evolution has been characterised by a dramatic increase in an organism's body size, which is not only limited to the size of the brain.
Endocrinology is a field in which enormous advances have been made in the last decade; the rate of discovery of new hormones, hormone-like molecules, receptors, and mechanisms of action is continually advancing. The development of techniques in immunology and molecular biology has led to the possibility of describing in detail the gene structure of many of the compounds involved in hormonal systems. Remarkable homology has been shown between oncogene products and various components of the endocrine network, leading to the asser tion that deregulation of hormonal function is involved in the generation and/or development of cancer. We now know that the central nervous system is both a target and a production site of many hormonal products, and that hormones, neurotransmitters, growth factors and immunopeptides all act through similar mechanisms. The only second messenger known ten years ago was cAMP; today calcium, derivatives of membrane phospholipids, and protein kinases are also known to be mediators of hormone action. The very concept of hormonal systems has been expanded to include not only endocrine secretions but also para- and autohormones and their mechanisms of action; an understanding of their functions will be central to the immediate future of medicine. The discovery of hormonal molecules and endocrine interactions and the subsequent understanding of hormone related pathophysiology has led to the development of new strategies in medical treatment such as fertility control and the management of diabetes.
The Church of Latter-day Saints renounced the practice of plural marriage in 1890. In the mid to late nineteenth century, howeverthe heyday of Mormon polygamyan average of three out of every ten Mormon women became polygamous wives. Paula Kelly Harline delves deep into the diaries and autobiographies of twenty-nine such women, opening a rare window into the lives they led and revealing their views of and experiences with polygamy, including their well-founded belief that their domestic contributions would help to build a foundation for generations of future Mormons. Polygamous wives were participants in a controversial and very public religious practice that violated most social and religious rules of a monogamous America. Harline considers the questions: Were these women content with their sacrifice? Did the benefits of polygamous marriage for the Mormons outweigh the human toll it required and the embarrassment it continues to bring? Polygamous wives faced daunting challenges not only imposed by the wider society but within the home, yet those whose writings Harline explores give voice to far more than just unhappiness and discontent. Following two or three women simultaneously and integrating their own words within a lively narrative, Harline focuses on the detail of their emotional and domestic lives over time, painting a vivid and sometimes disturbing picture of an all but vanished and still controversial way of life.
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