doi: 10.1093/icb/7.1.1pmid: N/A
Article PDF first page preview Close This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.2pmid: N/A
Article PDF first page preview Close This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.4pmid: N/A
Article PDF first page preview Close This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.6pmid: N/A
Article PDF first page preview Close This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.7pmid: N/A
Article PDF first page preview Close This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.81pmid: 6040689
Abstract A survey of college courses in endocrinology reveals that about 80 instructors teach 105 such courses, 68 at the basic or introductory level, and the remainder specialized or advanced. Of the 68 introductory courses, only 47 admit undergraduates, and 45 have an associated laboratory. Prerequisite course work in chemistry and biology usually makes endocrinology unavailable to the undergraduate before the third year; when undergraduates are admitted, they most commonly make up about half of the enrollment in the course. The most frequent size of class is 15-20, and about 1700 students per year elect endocrinology. About three-quarters of college instructors in endocrinology have themselves had a course in the subject. It is recommended that endocrinology be used in the form of a seminar or course to integrate prior experience in biology courses for senior students. This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.89pmid: 5342442
Abstract The widespread distribution of certain steroids and amino acid derivatives with hormonal properties is considered evidence in support of the dictum that “it is not the hormones that change, but rather the uses to which they are put.” However, analyses of the distributions, biological activities, immunological cross-reactivities, and sequences of amino acids of five representative peptide and protein hormones or groups of hormones—lactogenic hormone, growth hormone, the corticotropin-MSH-β lipotropin family, insulin, and the neurohypophysial hormones—support a concept of change and of molecular evolution of these polypeptidic molecules. When analyzed in terms of the genetic code, the amino acid interchanges which have been revealed by determination of sequences of amino acids can, most often, be explained by single base mutations in the appropriate codons. In two instances where two base mutations within a single codon are required, intermediate replacements of amino acid have been suggested; one of these would lead to a 2-ALA-β MSH, and the other to a 4-PRO, 8-ILE oxytocin. This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.109pmid: 6040687
Abstract Hormones may act at the molecular level (1) by changing the properties of the cell membrane or the membrane of some intracellular organelle, (2) by inducing an allosteric change in the conformation of a protein molecule so as to alter its enzymatic activity, (3) by altering the rate of synthesis of a specific protein, (4) by serving as a co-substrate in a specific enzymatic reaction, or (5) by initiating the transcription of a specific section of DNA and producing a specific messenger RNA for the production of a specific protein. The last mechanism appears to be involved in the response of the larva of the blowfly to the hormone, ecdysone. These theories are not mutually exclusive, and a given hormone may have more than one mechanism of action. The effects of androgens on the ventral prostate of the rat and the effects of estrogens on the endometrium of the rat's uterus appear to be mediated by the production of the specific kind of RNA. Testosterone increases the weight of the seminal vesicle and prostate of the rat by increasing the synthesis of a specific kind of RNA. RNA extracted from the seminal vesicle of one rat can be instilled into the lumen of the seminal vesicle of another rat and lead to growth similar to that induced by the injection of testosterone. Treatment of the RNA with ribonuclease or by heating destroys this activity. Experiments with luteinizing hormone show that it has three clearly distinct effects on ovarian metabolism and three different mechanisms of action in this one tissue. This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.115pmid: 6040688
Abstract Recent advances in biochemical techniques have resulted in considerable progress in the comparative qualitative analysis of non-mammalian vertebrate steroids. The literature surveyed herein suggests that a number of C21, C19, and C18 steroids occur throughout the subphylum. although there may be important qualitative differences even among closely related forms. The potential importance, from a phylogenetic or a physiological standpoint, of new steroids recently characterized in fishes cannot be evaluated at present. Three widely used techniques—tissue extraction or incubation without added precursors, tissue incubation with exogenous steroid substrates, and the histochemical visualisation of 3βhydroxysteroid dehydrogenases—are discussed, and their application to the study of steroidogenic tissues is illustrated. The adrenocortical homologue (interrenal), the ovary, and the testis appear to function as sources of steroid hormones in those vertebrates which have been examined. However, the existence of additional steroidogenic tissues, or of tissues which may modify the steroid composition of the body fluids in other ways, is also suggested. This content is only available as a PDF. © 1967 American Society of Zoologists
doi: 10.1093/icb/7.1.135pmid: 5342438
Abstract A brief review of relationships between brain and pituitary gland is presented. The primary portal plexus of the pituitary and hypothalamic neurones terminating upon these vessels represent the prime mechanism for neural influence upon adenohypophyseal function. The vascular architecture here may also permit a feedback loop from the adenohypophysis to the hypothalamus. Neurones (“final neural components”) are presumed to be responsible for the elaboration of releasing factors (hypophysiotrophins). Influencing these cells is a wide variety of afferent neural circuits with both excitatory and inhibitory components. In addition to the question of identity of many of these circuits, a major problem for future research is the manner in which this diverse neural information is processed into an integrated signal to the final common neurone. This content is only available as a PDF. © 1967 American Society of Zoologists
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