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I S Parhar

Publications and source records attributed to I S Parhar.

22 records · Page 2Linked to original sources
PubMed1994

Gonadotropin releasing hormone (GnRH) neurons project to growth hormone and somatolactin cells in the steelhead trout.

Analysis of gene expression using gonadotropin-releasing hormone (GnRH) antisense oligonucleotide confirmed by immunocytochemical localization the occurrence of GnRH neurons along the nervus terminalis in the steelhead trout (Oncorhynchus mykiss). Double-label immunocytochemistry revealed the distribution of mammalian (m), salmon (s) and chicken II (cII)-type GnRHs and various pituitary hormones. Both sGnRH and mGnRH appeared to be colocalized in the same cells of the nervus terminalis. Chicken GnRH II-immunoreactivity was found only in fibers and terminals. In the younger fish [73 and 186 days after fertilization (DAF)] GnRH neurons were seen rostral to the olfactory bulb. A novel GnRH ganglion, along the nervus terminalis, was found at the cribiform bone (gCB). A few non-immunoreactive rounded cells were seen among the GnRH neurons. A second smaller ganglion was seen at the most rostrally located part of the ventromedial olfactory bulb (gROB). In the older fish (850 DAF) GnRH neurons were also observed in the basal forebrain. A small group of neurons (2-3 cells), at the caudoventromedial border of the olfactory bulb, formed the ganglion terminale. Occasionally isolated GnRH-immunoreactive cells were seen at the base of the olfactory epithelium, along the ventromedial margins of the olfactory nerve. GnRH-immunoreactive and GnRH mRNA expressing neurons were absent from midbrain regions at the ages observed. GnRH-immunoreactive fibers were present only in older fish. The pattern of distribution of fibers that were immunoreactive to all three forms of GnRH was identical. Fibers were seen along the medial side of the olfactory nerve, throughout the brain and in the pituitary, associated with growth hormone and somatolactin cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Central dopaminergic neurons in tilapia: effects of gonadectomy and hypothalamic lesion.

The effects of gonadectomy, testosterone and estrogen on the dopamine (DA) neurons were examined by measuring the concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the brain and pituitary of male tilapia. The tuberal area and the pituitary had significantly high levels of DA and low levels of DOPAC, indicating the existence of a rich dopaminergic innervation in these areas. Gonadectomy and sex steroid replacement had no effect on DA and DOPAC levels. Preoptic lesions (14 days survival period) significantly increased DA levels of the pituitary, indicating a possible existence of a preoptico-hypophysial neural system that inhibits pituitary DA synthesis in tilapia. The lack of effect by preoptic (4 days survival period) and posterior hypothalamic lesions on the DA content of the pituitary indicates the absence of dopaminergic innervation of the pituitary by the preoptic and the posterior hypothalamus. Instead, the overall results do suggest the anterior periventricular area as a possible source of pituitary dopaminergic innervation.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Effects of intrahypothalamic administration of antisense DNA for progesterone receptor mRNA on reproductive behavior and progesterone receptor immunoreactivity in female rat.

Since reproductive behaviors of female rats can be correlated with estrogen-induced increases in progestin binding by hypothalamic neurons, we hypothesized that specific progesterone receptor (PR) antisense DNA sequences might decrease these behaviors. Antisense oligonucleotides (15 bases), spanning the translation start site of rabbit PR mRNA, were microinjected directly among ventromedial hypothalamic neurons, and their behavioral effects were compared to control oligonucleotides composed of the same nucleotide bases in scrambled order. When applied 12 but not 24 hr after estradiol, the PR antisense treatment significantly reduced iordosis behavior, measured either as a reflex or in a mating behavior test. Notably, proceptive behaviors, which are strongly progesterone dependent, were greatly reduced in their occurrence (80% decrease). To see if PR protein was also reduced, antisense DNA was administered near the ventromedial hypothalamus on one side of the brain, while the other side received the scrambled control sequence or vehicle. The total number of PR-immunoreactive cells on the antisense side was significantly lower in the ventromedial nucleus, but not in control measurements from the medial preoptic area. Interrupting gene expression for PR, a transcription factor, in hypothalamic neurons, can have behavioral and immunocytochemical effects.

Animals↗