Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

A new lipoprotein allotype Lprs and allele Lpr1,3 in the pig

Specific alloprecipitins were found in blood plasma of pigs, immunized by sera of Lpr1 positive donors. These precipitins detected a new allotype of the lipoprotein Lpr system which was designated Lpr3. Genetic studies confirmed its codominant inheritance and subgroup character. This linear subgroup of allotype Lprl is controlled by the allele Lpr^1,3. Investigations in populations of 14 pig breeds showed significant interbreed differences in the frequencies of alleles Lpr¹, Lpr² and Lpr^1,3.     

Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo

The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis.     

The role of the carboxy-terminal membrane-spanning fragment in the biogenesis of Escherichia coli K12 outer membrane protein PhoE

Summary PhoE protein of Escherichia coli K12 is an outer membrane protein which is supposed to span the membrane sixteen times. By creating a deletion which removes the last membrane-spanning fragment and studying the localization of the truncated PhoE, we show that this fragment is indispensable for trimerization and outer membrane localization. In addition, circumstantial evidence for the proposed topology model of the protein was obtained. An insertion mutation in a region supposed to be cell surface-exposed, interferes with the binding of a monoclonal antibody which recognizes a cell surface-exposed epitope of the protein.     

Neuromedin U-immunoreactivity in the nervous system of the small intestine of the pig and its coexistence with substance P and CGRP

Summary In the small intestine of the pig, neuromedin U (NMU)-immunoreactivity was mainly confined to the nerve plexus of the inner submucosal and mucosal regions. After colchicine treatment, a high number of immunoreactive nerve cell bodies was observed in the plexus submucosus internus (Meissner), whereas only a low number was found in the plexus submucosus externus (Schabadasch). The plexus myentericus as well as the aganglionic nerve meshworks in the circular and longitudinal smooth muscle layers almost completely lacked NMU-immunoreactivity. Double-labeling experiments demonstrated the occurrence of distinct NMU-containing neuron populations in the plexus submucosus internus: (1) relatively large type-II neurons revealing immunoreactivity for NMU and calcitonin gene-related peptide (CGRP) and/or substance P (SP); (2) a group of small NMU- and SP-immunoreactive neurons; (3) a relatively low number of small neurons displaying immunoreactivity for NMU but not for SP. Based on its distributional pattern, it is concluded that NMU plays an important role in the regulation and control of mucosal functions.     

Circadian locomotor rhythms in the desert iguana I. The role of the eyes and the pineal

Summary The pineal and the eyes are known to be important components in the circadian system of some species of lizards; their effects may be mediated by the hormone melatonin. We examined the role played by these structures in the desert iguana (Dipsosaurus dorsalis). Surgical removal of the pineal had no effect on circadian locomotor rhythms, even though this procedure abolished the circadian rhythm of melatonin in the blood. Furthermore, when the isolated pineal of Dipsosaurus was studied in organ culture, it showed no circadian rhythm of melatonin secretion, as do pineals of some other lizard species, although it did produce large quantities of this hormone. Bilateral ocular enucleation had only small effects on the freerunning period of locomotor rhythms, without affecting melatonin levels in the blood. Behavioral circadian rhythms persisted in desert iguanas subjected to both enucleation and pinealectomy. These data suggest that neither the pineal nor the eyes are central components of the circadian pacemaking system in Dipsosaurus, nor is melatonin critically involved in maintaining its organization.Abbreviations CT circadian time - ZT zeitgeber time - LL constant light - LD light-dark cycle - DD constant darkness - freerunning circadian period     

Mixed pituitary tumours--effects of bromocriptine treatment: Parlodel MR and Parlodel LAR.

Majority of pituitary tumours secrete one of the named hormones: PRL, GH, ACTH, proopiomelanocortine, alpha and beta subunit of TSH, LH, and FSH. Some of those tumours secrete two or more hormones. The aim of this study was to determine the effect of bromocriptine (Parlodel MR and LAR) upon secretion of hormones and tumour size in 10 patients with mixed pituitary tumours. In all patients pituitary and peripheral hormones, CT scan and visual fields were examined before and after treatment with bromocriptine: Parlodel MR and LAR. Bromocriptine treatment decreased PRL secretion in all 10 patients; GH--in all 6 in whom it was increased; TSH--in 2, FSH--in 2 and alpha-subunit in all 6 in whom they were increased. In 5 patients treatment resulted in shrinkage of the tumour mass by 20 to 35%. In all examined subjects clinical improvement was achieved. Our results demonstrate that bromocriptine (Parlodel MR and LAR) is very effective and well tolerated in the treatment of patients with mixed pituitary tumours particularly those with hyperprolactinemia.