The use of emergency contraception in Australasian emergency departments.

OBJECTIVE: To review the prescribing of emergency contraception by emergency departments in Australasia and compare it with other providers. METHODS: A postal questionnaire was sent to the director of each of the 79 Australasian College for Emergency Medicine accredited emergency departments in Australasia inquiring about the availability and prescribing habits for emergency contraception within each department. RESULTS: Of the 79 emergency departments, 69 (87.3%) responded to the questionnaire and were aware of the 'emergency contraception regimen'. The majority of departments prescribed appropriately (56%) and only one department did not arrange adequate follow up. Anti-emetics are always used by 45 departments (78.9%). Discussion of future contraceptive needs at the time of presentation was only undertaken by 25 departments (43.9%). Written clinical guidelines for emergency contraception were present in 28 departments (40.6%). CONCLUSIONS: Emergency departments are accessed by patients requesting contraception following unprotected intercourse or contraceptive failure. The prescribing of emergency contraception in Australasian emergency departments is comparable with other providers but substantial improvements could be made. Suggestions to assist this improvement include written clinical guidelines and patient information and purpose-made medication packs.

The gum exudate from Combretum nigricans gum, the major source of West African 'gum combretum'.

Gum samples from six individual Combretum nigricans trees and two additional reference samples have been characterized. 13C Fourier-transform NMR spectra show that all have the same structure and confirm that the variations observed in their analytical parameters reflect only small fine-structural differences. NMR spectra also reveal that eight West African 'gum combretum' samples from reputable commercial sources originated from Combretum nigricans. This identification is important because gum combretum, which is not permitted as a food additive, has been exploited as an adulterant and misrepresented as gum arabic, for which not even the 1990 Revised Specification is sufficiently rigorous to detect such commercial deceptions. NMR spectroscopy has also shown that the rhamnose and uronic acid contents of gum combretum are located within internal polysaccharide chains. This explains the well-known difference in emulsification functionality between gum arabic, in which all rhamnose and uronic acid groups chain-terminal, and gum combretum which is, in addition, markedly hygroscopic and characterized commercially by its tendency to 'block' in transit and storage.

Gum arabic (Acacia senegal): unambiguous identification by 13C-NMR spectroscopy as an adjunct to the Revised JECFA Specification, and the application of 13C-NMR spectra for regulatory/legislative purposes.

The JECFA Specification for gum arabic was revised in 1990 to reflect more closely the specification of the Test Article used in evaluations that led to its classification 'ADI not specified' in 1982/83. Some producers and traders have objected to the Revised Specification; in contrast, consumer-protection groups consider that it remains too lax to provide the degree of safety assurance expected. This paper presents analytical data that confirm the mean values previously established for nitrogen and the specific rotation of bulk commercial gum arabic from Acacia senegal. The data also establish that natural gum arabic imported into the USA and Europe in 1989/91 met the Revised Specification, but that a disturbingly high proportion of spray-dried, processed gums sold as 'gum arabic' did not. NMR spectroscopy has (a) indicated that some such samples are based on non-permitted gums and (b) confirmed that the 1983 Test Article represents not only typical 1990/91 shipments but also a wide range of reference gum arabic samples from other reputable sources. Details of a representative 13C-NMR spectrum, derived by averaging the relative intensities for the characteristic resonances of 35 gum arabic samples, are given for future regulatory/legislative purposes. Some limitations of the Revised Specification and its susceptibility to commercial exploitation are discussed.

The crystal structure of human muscle aldolase at 3.0 A resolution.

The three-dimensional structure of fructose-1,6-bisphosphate aldolase from human muscle has been determined at 3.0 A resolution by X-ray crystallography. The active protein is a tetramer of 4 identical subunits each of which is composed of an eight-stranded alpha/beta-barrel structure. The lysine residue responsible for Schiff base formation with the substrate is located near the centre of the barrel in the middle of the sixth beta-strand. While the overall topology of the alpha/beta-barrel is very similar to those found in several other enzymes, the distribution of charged residues inside the core of the barrel seems distinct. The quaternary fold of human muscle aldolase uses interfacial regions also involved in the subunit association of other alpha/beta-barrel proteins found in glycolysis, but exploits these regions in a manner not seen previously.

The low-resolution structure of human muscle aldolase.

The three-dimensional structure of human muscle aldolase has been solved at 5 A resolution with the use of two isomorphous heavy atom derivatives. The enzyme's four subunits are arranged about three mutually perpendicular intersecting twofold axes to form a compact spherical molecule. The subunit boundaries are clearly defined but a possible domain structure is not apparent in this preliminary electron density map.