An all-acousto-optically switched picosecond Nd:YAG regenerative amplifier has been developed for operation at pulse repetition rates in the 20–100-kHz range. The amplifier produces stable 50-ps pulses at 1064 nm in a TEM00 transverse mode with pulse energies of the order of 20–100 μJ. Generation of the second harmonic at 532 nm in KTP crystal results in conversion efficiencies greater than 40%. Using the frequency-doubled TEM00 output of the regenerative amplifier to pump a two-pass dye amplifier, we have amplified the 50-fs output pulses from an antiresonant ring dye laser to the 200-nJ level and have successfully produced a stable white-light continuum at a 100-kHz repetition rate. This preliminary demonstration of synchronous dye-laser amplification and continuum generation attests to the overall quality of the regenerative amplifier output and the general utility of this approach for high-repetition-rate amplification. Limitations of the current regenerative amplifier design and scaling to higher pulse energies are briefly discussed.

The National Poisons Information Services (NPIS) covering the United Kingdom and the Republic of Ireland currently receive over 40 000 telephone inquiries a year.Over the years there has been little change in the proportion of inquiries related to each of the main categories of poisons (drugs, household, chemical, agricultural, animals, and plants).More detailed analysis, however, shows pronounced changes in the inquiries relating to specific types of poisoning, particularly with drugs.By monitoring these trends and assessing the risks of toxicity, the NPIS has an important role in informing the medical profession of the need for preventive measures and for improved methods of treatment.At present, the NPIS cannot make full use of the available data due to inadequate staffing and lack of computer facilities.It is argued that for a modest increase in funding a much more comprehensive service could be provided.

SUMMARY Experiments on colour change of Xenopus laevis were performed to investigate the possibility that melatonin is the physiological antagonist to melanophore-stimulating hormone (MSH). Various amounts of substandard (SS) extract of ox posterior pituitary plus melatonin were injected into the dorsal lymph sac of adult male Xenopus laevis. Normal light-adapted, completely hypophysectomized, and anterior lobectomized animals were used. Dose—response curves were obtained for different SS dosages over a wide range of melatonin concentrations. Melatonin at very low concentrations inhibited the darkening reaction to both injected SS and endogenous MSH. In all cases more melatonin was required to inhibit the effect of SS in hypophysectomized than in normal animals. The results indicate that melatonin may be a physiological MSH antagonist in Xenopus laevis and the pituitary either contains some lightening factor itself ( Hogben's 'W' substance?) or has control over another organ (pineal gland?) where a lightening factor may be present. The unusual linear-logarithmic dose—response curves are discussed.

The Journal of PhysiologyVolume 152, Issue 3 p. 459-466 ArticleFree Access Melanophore-expanding substances in human blood J. N. Karkun, J. N. KarkunSearch for more papers by this authorF. W. Landgrebe, F. W. LandgrebeSearch for more papers by this authorR. A. Main, R. A. MainSearch for more papers by this authorG. M. Mitchell, G. M. MitchellSearch for more papers by this author J. N. Karkun, J. N. KarkunSearch for more papers by this authorF. W. Landgrebe, F. W. LandgrebeSearch for more papers by this authorR. A. Main, R. A. MainSearch for more papers by this authorG. M. Mitchell, G. M. MitchellSearch for more papers by this author First published: 01 July 1960 https://doi.org/10.1113/jphysiol.1960.sp006500Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume152, Issue3July 1, 1960Pages 459-466 RelatedInformation

SUMMARY Slices cut from mammary glands of rats and mice during gestation and lactation were incubated in vitro in the presence of pig posterior pituitary lobe extracts rich in melanophore-dispersing ('B') activity. Slices taken in early lactation but not during gestation or late lactation showed increased net gas evolution compared with control slices. Similar tissue from rabbits and guinea-pigs did not give rise to this effect, nor did slices of other tissues taken from lactating rats. The increased net gas evolution was not observed in the absence of glucose from the incubation medium. Treatment of the 'B' extract with NaOH or hypophysectomy of the rats prior to use decreased the response.

SUMMARY Three regions of the human pituitary, viz. (1) anterior lobe, (2) posterior lobe, and (3) intermediate zone (areas of 'basophil cell invasion') in the posterior lobe have been separately assayed for 'B' and corticotrophin in four specimens. The anterior lobe gave the highest levels for both hormones, the posterior lobe contained little of either, while the intermediate zone (of 'basophil cell invasion') yielded some corticotrophin but significantly high levels of 'B'. It is suggested that 'B' may be secreted by the δ cells and corticotrophin by the β cells of the human pituitary.

1. A method is described for the preparation of an extract of melanophore dispersing hormone 500 times as potent as International Standard posterior lobe powder.2. Evidence is recorded suggesting that the polypeptide derived from pig glands is different from that obtained from ox material.

1. A simple and rapid method of preparation of highly potent extracts of C.G. is described.2. The method consistently produces a product containing about 4000 I.U./mg. with a yield of about 30 per cent.3. The potency of such a product is found to be about the same whether it is tested on amphibia or mammals.