Characteristic increases in neuronal activity coincident with the pulsatile release of luteinizing hormone from the pituitary gland have been recorded from electrodes chronically implanted in the medial basal hypothalamus of the rhesus monkey. This electrophysiologic manifestation of the hypothalamic ‘pulse generator’ which governs the secretion of hypothalamic luteinizing hormone releasing hormone provides, for the first time, direct access to the central component of the neuroendocrine control system which regulates reproductive processes in this higher primate.

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Effects of heat stress, mechanical stretching or a combination of both on the expression of heat shock proteins (HSPs) and total protein level were studied in a culture system. Rat skeletal muscle cells (L6) were cultured on flexible-bottomed culture plates. They were subjected to one of the four following conditions: (1) 97 h incubation at 37 degrees C, (2) 1 h incubation at 41 degrees C followed by 96 h incubation at 37 degrees C, (3) 1 h incubation at 37 degrees C followed by 96 h cyclic stretching (18% of initial length, 2-s stretch and 4-s release) at 37 degrees C or (4) 1 h incubation at 41 degrees C followed by 96 h cyclic stretching at 37 degrees C. The expression of HSP72 and HSP90 and total protein was determined in the crude homogenates, supernatant and pellets. Cellular protein concentrations in the homogenates and pellets were increased by heat stress and/or mechanical stress (stretch). A cumulative effect of the combination of heating and stretch on the protein concentration in the homogenates and in the pellets was noted. The expressions of HSP72 and HSP90 in the pellets were also increased by heat stress and/or stretch. However, HSP90 in the supernatant did not change following heat stress and/or stretch. The regulation of HSP72 and HSP90 expression in skeletal muscle cells may be closely related to total protein, the abundance of which is also stimulated by mechanical and heat stresses. These observations suggest strongly that heating and passive stretch of muscle may be useful as a means of increasing muscle mass, not only in athletes but also in patients during rehabilitation.

Hatching of medaka embryos from the fertilized egg envelope involves two enzymes, HCE and LCE. HCE swells the envelope and then LCE completely dissolves it. We determined HCE and LCE cleavage sites on the egg envelope that are primarily constructed of two groups of subunit proteins, ZI-1,2 and ZI-3. HCE and LCE cleaved different target sequences on the egg envelope proteins but shared one common cleavage site. HCE cleaved the N-terminal region of ZI-1,2 and ZI-3, mainly the Pro-Xaa-Yaa repeat sequence of ZI-1,2 into hexapeptides, but not the site within a zona pellucida (ZP) domain that is considered to be the core structure of the egg envelope. The cleavage of these N-terminal regions results in swelling and softening of the envelope. LCE cleaved the middle of the ZP domain of ZI-1,2, in addition to the upstream of the trefoil domain of ZI-1,2 and the ZP domain of ZI-3. This middle site is in the intervening sequence connecting two subdomains of the ZP domain. Cleaving this site would result in the solubilization of the swollen egg envelope by the disruption of the filamentous structure that is thought to be formed by the non-covalent polymerization of ZP domains.