Early glycogenesis in the uterine glandular cells of the rabbit induced by progestins: a quantitative investigation

A single administration of progesterone (P) to primed immature rabbits induces the appearance of glycogen in uterine glandular cells. This phenomenon, which is rapid and transitory, precedes a mitotic surge in the glandular epithelium. Ultrastructural studies allowed us to observe the beginning of glycogenesis as early as 1 h after the injection of P. Quantitative image analysis in the course of a kinetic study showed that glycogen levels reached a maximum at the sixth h and after 24 h had fallen dramatically. Promegestone, a potent progestomimetic compound, gave similar results, but estradiol, testosterone and dexamethasone failed to induce the appearance of glycogen in the uterine glands. Mifepristone (RU 486) had an antagonistic effect on the action of P. These results suggest that early P-dependent glycogenesis in the endometrial glandular cells of the rabbit may play an important role in the increased rate of mitosis and cellular proliferation that are necessary events in preparing the endometrium for implantation.     

Sequence Analysis of Spiroplasma phoeniceum and Spiroplasma kunkelii Spiralin Genes and Comparison with Other Spiralin Genes

The spiralin genes from two phytopathogenic spiroplasmas, Spiroplasma phoeniceum and Spiroplasma kunkelii, were amplified by PCR, cloned, and sequenced. Comparison of the amino acid sequences of the five spiralins analyzed to date confirm that the spiralins have a general amphiphilic character and possess a conserved lipoprotein signal peptide. It also shows that a conserved central region and an amino acid repetition, including a VTKXE consensus sequence, are present in all spiralins analyzed. Received: 11 March 1997 / Accepted: 14 April 1997     

Salmonella enterica Serotype Bredeney: Antimicrobial Susceptibility and Molecular Diversity of Isolates from Ireland and Northern Ireland

Salmonella enterica serotype Bredeney has emerged as the third most commonly identified serotype among human clinical isolates referred to the Irish National Salmonella Reference Laboratory in the years 1998 to 2000. A collection of 112 isolates of S. enterica serotype Bredeney collected during the period 1995 to 1999 from animal, food, and human sources from both Ireland and Northern Ireland were studied. Antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), and DNA amplification fingerprinting (DAF) were performed on all isolates. Plasmid profiles were examined on a subset of 33 isolates. A high proportion (74%) of isolates were susceptible to all antimicrobial agents tested. Resistance to both sulfonamide and trimethoprim was observed in 21% of isolates, and resistance to multiple (five) antimicrobial agents was observed in a single isolate (0.9%). Eight different PFGE patterns were obtained, with 87% of isolates grouping as PFGE type A. PFGE type A was predominant in animals, food, and humans. There was good overall concordance between the groups identified by PFGE and DAF. Overall results indicate that most S. enterica serotype Bredeney isolates in Ireland and Northern Ireland from animal and human sources are clonally related.     

Biochemistry and comparative genomics of SxxK superfamily acyltransferases offer a clue to the mycobacterial paradox: presence of penicillin-susceptible target proteins versus lack of efficiency of penicillin as therapeutic agent.

The bacterial acyltransferases of the SxxK superfamily vary enormously in sequence and function, with conservation of particular amino acid groups and all-alpha and alpha/beta folds. They occur as independent entities (free-standing polypeptides) and as modules linked to other polypeptides (protein fusions). They can be classified into three groups. The group I SxxK D,D-acyltransferases are ubiquitous in the bacterial world. They invariably bear the motifs SxxK, SxN(D), and KT(S)G. Anchored in the plasma membrane with the bulk of the polypeptide chain exposed on the outer face of it, they are implicated in the synthesis of wall peptidoglycans of the most frequently encountered (4-->3) type. They are inactivated by penicillin and other beta-lactam antibiotics acting as suicide carbonyl donors in the form of penicillin-binding proteins (PBPs). They are components of a morphogenetic apparatus which, as a whole, controls multiple parameters such as shape and size and allows the bacterial cells to enlarge and duplicate their particular pattern. Class A PBP fusions comprise a glycosyltransferase module fused to an SxxK acyltransferase of class A. Class B PBP fusions comprise a linker, i.e., protein recognition, module fused to an SxxK acyltransferase of class B. They ensure the remodeling of the (4-->3) peptidoglycans in a cell cycle-dependent manner. The free-standing PBPs hydrolyze D,D peptide bonds. The group II SxxK acyltransferases frequently have a partially modified bar code, but the SxxK motif is invariant. They react with penicillin in various ways and illustrate the great plasticity of the catalytic centers. The secreted free-standing PBPs, the serine beta-lactamases, and the penicillin sensors of several penicillin sensory transducers help the D,D-acyltransferases of group I escape penicillin action. The group III SxxK acyltransferases are indistinguishable from the PBP fusion proteins of group I in motifs and membrane topology, but they resist penicillin. They are referred to as Pen(r) protein fusions. Plausible hypotheses are put forward on the roles that the Pen(r) protein fusions, acting as L,D-acyltransferases, may play in the (3-->3) peptidoglycan-synthesizing molecular machines. Shifting the wall peptidoglycan from the (4-->3) type to the (3-->3) type could help Mycobacterium tuberculosis and Mycobacterium leprae survive by making them penicillin resistant.