Izhar A. Khan

Assistant Professor, Department of Marine Science  Research Assistant Professor, Marine Science Institute  Ph.D. (1990), Banaras Hindu University, Varanasi, India M.S. (1983), B.S. (1981), Aligarh Muslim University, Aligarh, India  Home page

Mariculture/Neuroendocrinology

Reproductive physiology and neuroendocrinology of marine fishes; neuroendocrine control of puberty, sexual maturation, and spawning, induced breeding of captive broodstock fishes, and mechanisms of neuroendocrine toxicity of environmental chemicals. 

Research Interests

Marine fishes present an enormous diversity of reproductive structures, functions and strategies, and are excellent vertebrate models to investigate the mechanisms of neuroendocrine control of reproduction. I have been investigating the roles of neuropeptides, neurotransmitters, gonadal steroids and other factors in the control of reproduction using selected marine fishes as experimental models.  In particular, I am interested in understanding the mechanisms of neuroendocrine control of gonadotropin-releasing hormone and gonadotropin release and their gene regulation. I am interested also in understanding how multiple neuroendocrine pathways control puberty and sexual maturation in fishes. I plan to apply this basic understanding of the neuroendocrine system in fishes for the development innovative tools to enhance aquaculture productivity and alternative vertebrate models to investigate the mechanisms of neuroendocrine toxicity of environmental chemicals. 

A major problem in aquaculture is the lack of spontaneous spawning in captive broodstock fishes, primarily due to alterations in neuroendocrine pathways in the absence of appropriate environmental, hormonal and/or behavioral cues. The absence of appropriate cues for spawning in an enclosed environment leads to disruption of neuroendocrine pathways that control the surge of luteinizing hormone required for gamete maturation. Neuroendocrine status of captive broodstock fishes will be compared with their counterparts collected from natural spawning grounds. The measures to determine neuroendocrine status will include neurotransmitter metabolism, and synthesis and/or secretion of gonadotropin-releasing hormones and gonadotropins (FSH and LH).  We need to understand the nature and extent of these alterations in order to develop innovative tools to modify and restore normal physiological responses in species of interest. 

Environmental chemicals can disrupt vertebrate reproduction by acting at multiple levels on the brain-pituitary-gonadal axis. I would like to elucidate the mechanisms by which environmental neurotoxic chemicals influence vertebrate reproduction, acting at the hypothalamic-pituitary (neuroendocrine) axis. These studies involve biochemical, cellular and molecular biological approaches to understand the complex mechanisms of chemical interference with neuroendocrine pathways. This line of research is being conducted in collaboration with Dr. Peter Thomas at UTMSI. 

Selected Publications

Khan, I.A. and Thomas, P. 2001. Disruption of neuroendocrine control of luteinizing hormone secretion by Aroclor 1254 involves inhibition of hypothalamic tryptophan hydroxylase activity. Biol. Reprod. 64: 955-964. 

Khan, I.A. and Thomas, P. 1999. GABA exerts stimulatory and inhibitory influences on gonadotropin II secretion in the Atlantic croaker (Micropogonias undulatus). Neuroendocrinology 69: 261-268. 

Khan, I.A., Hawkins, M.B. and Thomas, P. 1999. Gonadal stage-dependent effects of gonadal steroids on gonadotropin II secretion in the Atlantic croaker (Micropogonias undulatus). Biol. Reprod. 61: 834-841. 

Khan, I.A. and Thomas, P.  1998. Ovarian cycle, teleost fish.  In: “Encyclopedia of Reproduction,” Ernst Knobil and Jimmy D. Neill, Eds., Volume 3, pp. 552-564, Academic Press, San Diego. 

Contact: Izhar A. Khan
Created: Wed Sep 25 15:05:22 GMT-0500 (Central Daylight Time) 2002