Thrombolytic Therapy in Haemolytic-Uraemic Syndrome

The treatment of five children with the haemolytic-uraemic syndrome using streptokinase is described to illustrate the difficulties and limitations of thrombolytic therapy in this disease. This experience is germane to the design of multicentre clinical trials.A multivariate analysis relating clinical outcome to the data obtained at the time of admission was also carried out for 31 children with the disease treated in four centres. The results suggest that this technique may help to identify those patients likely to have a fatal outcome. An expanded form of this type of analysis should be incorporated in future clinical trials.     

Port Health Control

Almost 950,000 of the 21 million passengers passing through London (Heathrow) Airport in 1973 were seen by the health control unit, which is run by the London Borough of Hillingdon. The unit provides 24-hour medical cover and its responsibilities include x-ray examination for tuberculosis and screening passengers from smallpox-infected areas. It is suggested that, in view of changing epidemiological patterns throughout the world, there is a need to modify existing procedures rather than to abandon them. The development of a follow-up system for tracing passengers at risk and improvements in presenting information about health risks to intending travellers are advocated. While such proposals might be opposed, they could be practicable.     

Determinants of growth-promoting activity reside in the A-domain of insulin-like growth factor I

A two-chain, disulfide linked, insulin-like compound embodying the A-domain of insulin-like growth factor I (IGF-I) and the B-chain of insulin has been synthesized and characterized with respect to insulin-like biological activity and growth-promoting potency. The compound displays a potency of ca. 41% relative to insulin in assays for insulin-like activity (e.g., lipogenesis) but significantly higher activity than insulin, ca. 730% relative to insulin, in growth factor assays (e.g., thymidine incorporation). The compound is, however, a less potent growth factor than IGF-I itself, ca. 26.5% relative to IGF-I, and is not recognized by IGF carrier proteins. We conclude that structural features contained in the A-domain of IGF-I are primarily responsible for the growth-promoting ability displayed by IGF-I, while features in the B-domain are responsible for recognition by IGF carrier proteins.     

Ecosystem function and species loss – a microcosm study

There are too many kinds of organisms to be able to study and manage each, yet the loss of a single species can sometimes unravel an ecosystem. Such `fusewire species'– critical in the same sense that an electrical fuse can cut out a whole circuit – would be a rewarding focus for research and management effort. However, this approach can only be effective if these `fusewires' represent but a small proportion of the number of species in the system.  

Aim

To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.  

Methods

The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.  

Results

No single genus deletion caused changes in key characteristics of the system.  

Main conclusions

Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem.     

Nucleic acid-like structures III. Oligomerization of 3′-deoxyadenosine 2′,5′-diphosphoimidazolide

Summary The activated dimonophosphate of 3-deoxyadenosine (cordycepin) undergoes oligomerization to produce a new family of pyrophosphate-linked oligomers in which the average repeating unit involves a nine-atom structural group. The presence of a poly(U) template increase the relative yields of higher oligomers, although the template-free reaction is itself extremely efficient.For the previous paper in this series see Schwartz et al. (1987)     

The unfolding story of T cell receptor gamma

Antigen-specific, major histocompatibility complex-restricted recognition by classical T cells is mediated by a T cell receptor (TCR) consisting of a disulfide-linked alpha beta heterodimer. During the search for the genes encoding the alpha and beta proteins, a third immunoglobulin-like gene, termed gamma, was uncovered. Like the TCR alpha and beta genes, the TCR gamma gene consists of variable and constant segments that rearrange during T cell development in the thymus. Although the physiological role of TCR gamma remains an enigma, much has been learned with the recent identification of the protein products of this gene family in both mice and humans. The gamma chain is associated with a partner chain, termed delta. The gamma delta heterodimer is associated with an invariant T3 complex, very similar to that associated with the alpha beta heterodimer, and appears predominantly, if not exclusively, on cells with a CD4-, CD8- phenotype both in the thymus and in the periphery. TCR gamma delta is the first T3-associated receptor to appear during thymocyte development and defines a separate T cell lineage distinct from alpha beta-bearing cells. Although TCR alpha beta-bearing cells and TCR gamma delta-bearing cells follow parallel developmental pathways, the diversity of expressed gamma delta receptors is extremely limited relative to that of alpha beta receptors.     

Immunogold cytochemistry of cytochromes P-450 in porcine adrenal cortex. Two enzymes (side-chain cleavage and 11 beta-hydroxylase) are co-localized in the same mitochondria

In order to study the distribution of mitochondrial cytochromes P-450 in porcine adrenal glands, the glands of anesthetized pigs were fixed in situ. Polyclonal antibodies against two cytochromes P-450, i.e., C27 side-chain cleavage enzyme and 11 beta-hydroxylase, were used to study the distribution of these enzymes in cryosections of the adrenal cortex. Ultrathin cryosections were evaluated by both protein-A/gold/silver immunocytochemistry and immunoelectron microscopy using double labeling with protein-A/colloidal-gold. At light microscopy, the two cytochrome P-450 enzymes were found to be broadly distributed in both the fasciculata and glomerulosa zones of the adrenal cortex. Quantitative immunoelectron microscopy revealed that both enzymes were localized only in mitochondria, in which they were present on the inner aspects of the inner mitochondrial membrane. Both cytochromes P-450 were demonstrable in all of the mitochondria examined, and statistical evaluation of the ratios of the two enzymes present in individual mitochondria yielded a normal distribution curve. Since no evidence was found for the preferential localization of either enzyme in a special population of mitochondria, we conclude that all mitochondria of the adrenal cortex contain both enzymes. We discuss implications of these findings with respect to the regulation of steroidogenesis.