Investigation of polyethylene–wax blends by CRYSTAF and SEC–FTIR

Summary Oxidized wax blends with respectively HDPE, LDPE and LLDPE were investigated using CRYSTAF and SEC–FTIR in order to determine the possibility and extent of co–crystallization of the wax with each of these polyethylenes. CRYSTAF shows very little or no co–crystallization of wax with HDPE and LDPE, while there is a strong indication of co–crystallization in the case of LLDPE. SEC-FTIR analyses show co–elution of wax with LLDPE, indicating some chemical interaction between the oxidized wax and LLDPE.     

Urinary catecholamine excretion and blood serotonin content in juvenile hypothalamic syndrome

Daily urinary adrenalin, noradrenaline, dopamine excretion and blood levels of serotonin were measured over the course of the cycle in 8 healthy girls and in 52 patients with the juvenile hypothalamic syndrome in the acute and chronic stages. These parameters were found virtually the same in healthy girls and in those suffering from the hypothalamic syndrome in the course of the cycle or in patients during the acute and chronic stages of the condition. Urinary catecholamine excretion and blood serotonin levels were increased by 1.5-2 times in the acute stage of the syndrome and somewhat reduced in the chronic stage; this appears to be due to reduced activity of the sympathoadrenal system in the course of disease progress.     

Evidence that a novel thioesterase is responsible for polyketide chain release during biosynthesis of the polyether ionophore monensin

Polyether ionophores, such as monensin A, are known to be biosynthesised, like many other antibiotic polyketides, on giant modular polyketide synthases (PKSs), but the intermediates and enzymes involved in the subsequent steps of oxidative cyclisation remain undefined. In particular there has been no agreement on the mechanism and timing of the final polyketide chain release. We now report evidence that MonCII from the monensin biosynthetic gene cluster in Streptomyces cinnamonensis, which was previously thought to be an epoxide hydrolase, is a novel thioesterase that belongs to the alpha/beta-hydrolase structural family and might catalyse this step. Purified recombinant MonCII was found to hydrolyse several thioester substrates, including an N-acetylcysteamine thioester derivative of monensin A. Further, incubation with a hallmark inhibitor of such enzymes, phenylmethanesulfonyl fluoride, led to inhibition of the thioesterase activity and to the accumulation of an acylated form of MonCII. These findings require a reassessment of the role of other enzymes implicated in the late stages of polyether ionophore biosynthesis.     

Estimation of sea surface temperature from AVHRR data: reply to some comments by J. R. Eyre

Abstract

This paper refers to a previous comment by J. R. Eyre on an earlier paper of ours in which we tried to make the best possible use of 4-channel AVHRR/1 data for the determination of sea surface temperatures in situations where data from the 5-channel AVHRR/2 were not available. Here we clarify certain points regarding the philosophy of our earlier paper and also respond to some specific points made by Eyre.     

葛根的化学成分研究

系统地回顾了近30年来葛根化学成分研究概况，着重介绍了国内外对葛根中异黄酮、三萜及葛酚苷类等具显著生理活性的化学成分研究进展。     

Projected needs of health manpower in Saudi Arabia, 1974-90

Although our projections are not completely accurate, due to inadequate data and crude methods of approximation, three conclusions are inescapable: 1. The nation should give priority to planning new schools for health administrators and rural health workers, and to generally expanding present schools for paramedicals. 2. Plans should proceed rapidly for the two new medical schools. 3. A Health Manpower plan based on census information and special studies should be developed over the next 2 years. This plan should have input from all concerned ministries. (The Ministry of Health has regarded a proposal from University Associate "a group of Harvard, Johns Hopkins and A.U.B. professors" for technical cooperation in health services planning.)