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61.
62.
63.
H. M. Katz 《Journal of fish biology》1978,12(6):609-614
Swimming activity (in cm s−1 ) of a school (55 individuals) of young-of-the-year ( total length=110 mm) American shad, Alosa sapidissima , was determined under a variety of photoperiod conditions. These included a normal (ambient), a shifted, and constant-light day. Swimming activity was measured over 4-day periods. During normal days swimming speeds followed periods of about 24 h, with fast speeds (up to 45 cm s−1 ) and schooling occurring during the photoperiod. Under dark conditions speeds were slower (8 cm s−1 ) with most fish swimming as individuals. During a shifted day swimming speeds and schooling corresponded to the imposed day. Under constant light (equivalent to bright moonlight) no schooling was evident, and a constant, but slow, swimming speed was observed in each 24-h period. These shad demonstrated an exogenous rhythm with respect to the imposed day length. It is hypothesized that an endogenous circadian rhythm would only be of use to a fish required to hunt or chase its prey. Shad, being plankton feeders, do not chase prey and therefore can exhibit an exogenous circadian rhythm with no detrimental feeding results. 相似文献
64.
A re-examination of curare action at the motor endplate. 总被引:19,自引:0,他引:19
B Katz R Miledi 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1978,203(1151):119-133
Recent evidence indicates that curare, in addition to its competitive' interference with endplate receptors, can block open ionic channels by a 'non-competitive' action on the activated acetylcholine-receptor complex. These findings called for further study of the kinetic behaviour of endplate channels and their modification by curare. Examining impulse-evoked endplate currents and acetylcholine-induced current fluctuations, it is found that the lifetime of the open channel is shortened by relatively high concentrations of curare (greater than 5 micrometer), an effect which shows up most strikingly at hyperpolarized levels of membrane potential (-130 mV and above). No shortening of this kind is observed when a neuromuscular block of equal or greater intensity is produced by a dose of alpha-bungarotoxin. Two other neuromuscular blocking agents, gallamine and pancuronium are shown to have an action on channel kinetics which cannot be explained by competitive receptor binding, but conforms to the hypothesis of rapidly repeated blocking and unblocking of individual ion channels, which had been proposed originally to account for the endplate action of local anaesthetics. 相似文献
65.
J.M. Katz S.J.M. Skinner T. Wilson D.H. Gray 《Prostaglandins & other lipid mediators》1983,26(4):545-555
Mouse calvaria were maintained in organ culture without serum additives. Basal active resorption, as measured by 45Ca and hydroxyproline release, was significantly inhibited to 74% control levels by indomethacin (1.4 × 10−7 M). Prostaglandin F and prostaglandin E2 production, determined by radioimmunoassay, were both significantly lowered by this concentration of indomethacin. DNA, protein and hydroxyproline synthesis, as indices of cell toxicity, were unaffected by low concentrations of indomethacin, while concentrations of 1.4 × 10−6M inhibited protein synthesis (p<0.005). In the presence of indomethacin (1.4 × 10−7M) both PGE2 and PGF2α stimulated resorption in a dose-dependent manner, with PGE2 being the more potent. Neither prostaglandin affected hydroxyproline synthesis at low concentrations, but PGE2 had a marked inhibitory action at a higher concentration (10−6M). In combination, the effects of PGE2 and PGF2α showed no evidence of synergism or any antagonistic action. The study shows that in vitro calcium and hydroxyproline resorption in the unstimulated mouse calvaria are inhibited by indomethacin at concentrations measured in serum during human therapy. The decreased PGF and PGE2 production associated with this decreased bone resorption in the presence of non-toxic concentrations of indomethacin would suggest a role for these prostaglandins in maintaining the basal resorption of cultured bone. 相似文献
66.
67.
Collagen-induced arthritis in mice. Relationship of collagen-specific and total IgE synthesis to disease. 总被引:3,自引:0,他引:3
J F Marcelletti J Ohara D H Katz 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(12):4185-4191
The relationship between production of IgE and collagen-induced arthritis in mice was examined. Collagen-specific IgE was produced as a consequence of immunization of DBA/1 mice with chicken type II collagen emulsified in CFA. We observed a rise in collagen-specific IgE antibody levels at the onset of CIA clinical and histologic signs in DBA/1 mice. This rise in IgE paralleled that of IgG2a anticollagen antibodies, an isotype implicated in the pathogenesis of CIA by other laboratories. The collagen-specific IgE contained in the plasma of mice with CIA could arm basophils for Ag- (collagen) dependent degranulation. Collagen-specific IgE may thus contribute to CIA by promoting mast cell degranulation in the synovia of susceptible mice immunized with chick type II collagen; but, further work is required to establish such a role for IgE in CIA. However, genetic differences in disease susceptibility could not be accounted for by quantitative differences in collagen-specific IgE production. Further, comparable levels of IgE anticollagen antibodies were observed in animals with active CIA and after spontaneous remission, thereby confirming that the presence of such antibodies is insufficient for disease. Total IgE levels peaked just before spontaneous remission indicating active production of IL-4. IL-4 was administered to animals with CIA to determine if this lymphokine could be involved in the remission process. IL-4 facilitated remission of CIA. Enhanced total IgE production may thus be a marker for activation of Th2 cells that produce lymphokines such as IL-4 and IL-10, factors that may be involved in the spontaneous remission process. 相似文献
68.
M Carey J Kolman D A Katz L Gradoville L Barberis G Miller 《Journal of virology》1992,66(8):4803-4813
69.
Identification and induction of keratinocyte-derived IL-10. 总被引:23,自引:0,他引:23
70.
Prostaglandin release by normal and osteomyelitic human bones 总被引:1,自引:0,他引:1
D Plotquin S Dekel S Katz A Danon 《Prostaglandins, leukotrienes, and essential fatty acids》1991,43(1):13-15
The release of prostaglandin E (PGE) and prostacyclin (as 6-keto PGF1 alpha) by human osteomyelitic bone, compared with normal (control) bone, incubated in vitro was evaluated. Prostacyclin was the main arachidonic acid metabolite released by normal human bone, and similar quantities were released by osteomyelitic bone. However, PGE production was 5-30-fold higher in osteomyelitic bone, compared with control, thus becoming the major prostanoid in this disease. It is concluded that PGE production is probably involved in the inflammatory and/or bone resorption processes that occur in osteomyelitis. 相似文献