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Biomedical subjects

J Hacker

Publications and source records attributed to J Hacker.

At least 235 records · Page 13Linked to original sources
PubMed1978

Total support of the circulation of a patient with post-cardiotomy stone-heart syndrome by a partial artificial heart (ALVAD) for 5 days followed by heart and kidney transplantation.

A patient with acute bacterial endocarditis in whom ischaemic contracture of the left ventricle (stone-heart syndrome) developed during aortic and mitral valve replacement had an emergency implantation of an intracorporeal partial artificial heart (an abdominal left-ventricular assist device of ALVAD). This device functioned as a total artificial heart for nearly 6 days, while a donor heart for transplantation was sought. The ALVAD was then removed, and the patient received allografts of a heart and a kidney. The transplanted heart functioned well, but the patient died 15 days later from gram-negative sepsis. There was no evidence of cardiac or renal allograft rejection.

Acute Disease↗
PubMedDate not supplied

Comparative therapeutic activities of ciprofloxacin, amoxicillin, ceftriaxone and co-trimoxazole in a new model of experimental infection with Escherichia coli.

A new mouse model for systemic infection with Escherichia coli is presented. Whereas in other models 10(7)-10(8) bacteria have to be injected into an animal to induce toxic effects resulting in death within 24 hours, now, only 10(3)-10(4) bacteria of an appropriate strain are required to produce a genuine infection characterized by an increase in the bacterial load over several days. The quantitative determination of bacterial counts per liver allows a more sensitive measurement than recording death rates. Furthermore, few animals are required for a definite result in contrast to the LD50 determination of other models. The salient point regarding this new model is that conditioning of animals has to be achieved by incorporating the inoculum into agar which is injected subcutaneously. The resulting infection is completely dependent on the E. coli strain used. Whereas a hemolytic, uropathogenic strain is so virulent that an overwhelming infection develops within 48 hours after the injection of 10(3) bacterial cells, a non-hemolytic variant of this strain is completely avirulent, being unable to multiply in spite of the potentiating agar. The hemolytic E. coli strain ATCC 25922 is intermediate in virulence. The bacterial counts per liver increase steadily until death occurs five to seven days after the injection of 10(4) bacteria. This bacterial infection can be therapeutically influenced by daily treatment with various drugs. Ciprofloxacin, ceftriaxone and co-trimoxazole are able to cure the infection, whereas amoxicillin given orally is only moderately active against this ATCC strain, which is relatively resistant to amoxicillin.

Amoxicillin↗
PubMedDate not supplied

S-fimbriae mediated adhesion of Escherichia coli to human buccal epithelial cells is age independent.

S-fimbriated Escherichia coli, which cause sepsis and meningitis in the newborn, bind to sialic acid-containing glycoprotein structures on the surface of human buccal epithelial cells. The dependence of this binding on host age was examined. S-fimbriated E. coli adhered in comparable numbers to cells in newborns, infants, children and adults (23.0 +/- 8.6; 23.1 +/- 11.5; 24.7 +/- 7.9; 28.9 +/- 8.8). Thus, the increased susceptibility of neonates to infections caused by S-fimbriated E. coli cannot be explained by enhanced adhesion to epithelial cells.

Age Factors↗
PubMedDate not supplied

Properties of Escherichia coli strains of serotype O6.

Escherichia coli isolates of serotype O6 show a broad spectrum of virulence: virulent strains often cause urinary tract infections; other strains are considered nonpathogenic. In order to analyze the properties of E. coli O6 strains, different phenotypic and genotypic test systems were used. Our data indicate that O6 strains represent a rather heterogenous group of bacteria, which differ in the genotypic presence as well as in the phenotypic expression of virulence factors. In contrast to the isolates 536 (O6:K15) and RZ 475 (O6:K5) the strain DSm 6601, belonging to serotype O6:K5:H1, produces neither toxins nor mannose-resistant hemagglutinating (MRHA) adhesins. However, the strain possesses chromosomally located gene clusters coding for F1C (foc) and type I fimbriae (fim). In addition, the strain secrets the iron-uptake substances aerobactin and enterobactin and produces at least one microcin. The strain is serum-sensitive and is less virulent in in vivo animal tests.

Bacterial Proteins↗
PubMedDate not supplied

The role of macrophages in primary and secondary infection of mice with Salmonella typhimurium.

Elimination of macrophages with high-molecular dextran sulphate (DS) markedly impairs resistance of mice to primary infection with smooth, virulent strains of Salmonella typhimurium, whereas stimulation of this system by killed Bordetella pertussis organisms increases resistance. In infection with rough, avirulent strains of S. typhimurium the elimination of macrophages was not followed by an essential loss of resistance, and it appears that other non-specific defence mechanisms, for example the complement system, may have compensated for the lack of macrophages. Macrophages, therefore, play an important role in defence during primary infection with virulent strains. In immunity to challenge infection with S. typhimurium, macrophages play an even more significant role. Treatment with DS completely removes immunity, and both humoral and cell-mediated immune mechanisms seem to require the participation of macrophages.

Animals↗
PubMedDate not supplied

Nucleotide sequence of the genes coding for minor fimbrial subunits of the F1C fimbriae of Escherichia coli.

F1C fimbriae allow uropathogenic Escherichia coli to adhere to specific epithelial surfaces. This adhesive property is probably due to the presence of minor fimbrial components in F1C fimbriae. The foc gene cluster encoding F1C fimbriae has been cloned, as described previously. Here we present the nucleotide sequence (2081 bp) coding for the F1C minor fimbrial subunits. The structural genes code for polypeptides of 175 (FocF), 166 (FocG), and 300 (FocH) amino acids. The deduced amino acids of the F1C minor subunits were compared with the reported sequences of the minor subunits of other types of fimbriae. The data show that the Foc minor subunits are highly homologous to the corresponding Sfa proteins, whereas homology to the minor subunits of type 1 and P fimbriae is much lower.

Bacterial Adhesion↗
PubMedDate not supplied

Salmonella typhimurium strains carrying haemolysin plasmids and cloned haemolysin genes from Escherichia coli.

Like all other Salmonella typhimurium strains examined, the smooth variants SF1397 (LT2) and 1366 and also their semi-rough and rough derivatives are non-haemolytic. Nevertheless, two haemolysin (Hly) plasmids of E. coli belonging to the inc groups incFIII,IV (pSU316) and incI2 (pHly152) were able to be introduced into these strains by conjugation and stably maintained. A considerable percentage of the Hly+ transconjugants obtained had lost parts of their O-side chains, a result of selection for the better recipient capability of "semi-rough" variants rather than the direct influence of the Hly+ plasmids themselves. In contrast to the incFIII,IV plasmid pSU316, which exhibited higher conjugation rates with rough recipients, the incI2 plasmid pHly152 was accepted best by smooth strains. Transformation with cloned E. coli haemolysin (hly) determinant was inefficient (less than 10(-6)) for smooth strains, but 10(2) - 10(3) times higher for rough recipients, and was increased by the use of Salmonella-modified DNA. The transformants and transconjugants were relatively stable and showed the same haemolytic activity as the E. coli donor strains. The virulence of the Hly+ smooth, semi-rough and rough S. typhimurium strains was tested in two mouse models, and neither the mortality rate nor the ability to multiply within the mouse spleen was influenced by the hly determinants.

Animals↗
PubMedDate not supplied

Molecular analysis of bacterial cytolysins.

Results of molecular and pathogenic studies of three different bacterial hemolysins (cytolysins) are presented. These exoproteins derive from the two gram-negative bacteria Escherichia coli and Aeromonas hydrophila and from the gram-positive pathogen Listeria monocytogenes. The hemolysin of E. coli is determined by an 8-kilobase (kb) region that includes four clustered genes (hlyC, hlyA, hlyB, and hlyD). This hemolysin determinant is part either of large transmissible plasmids or of the chromosome. The genes located chromosomally are found predominantly in E. coli strains that can cause pyelonephritis and/or other extraintestinal infections. A detailed analysis of the chromosomal hyl determinants of one nephropathogenic E. coli strain revealed the existence of specific, large chromosomal insertions 75 kb and 100 kb in size that carry the hly genes but that also influence the expression of other virulence properties, i.e., adhesion and serum resistance. The direct involvement of E. coli hemolysin in virulence could be demonstrated in several model systems. The genetic determinants for hemolysin (cytolysin) formation in A. hydrophila (aerolysin) and L. monocytogenes (listeriolysin) are less complex. Both cytolysins seem to be encoded by single genes, although two loci (aerB and aerC) that affect the expression and activity of aerolysin have been identified distal and proximal to the structural gene for aerolysin (aerA). Cytolysin-negative mutants of both bacteria were obtained by site-specific deletion and/or transposon mutagenesis. These mutants show a drastic reduction in the virulence of the respective bacteria.

Aeromonas↗
PubMedDate not supplied

Antibiotic and cytotoxic activity of brominated compounds from the marine sponge Verongia aerophoba.

Analysis of the marine sponge Verongia aerophoba from the Canary Islands afforded eight brominated secondary metabolites including the small molecular weight compounds aeroplysinin-1 (5) and the dienone (7) which were previously shown to arise by enzymatically catalyzed degradation of aerophobin-2 (4) and isofistularin-3 (1) following breakdown of the cellular compartmentation of the sponge. All compounds were identified from their NMR and mass spectra. Aeroplysinin-1 as well as dienone which arise from isofistularin-3 or aerophobin-2 by biotransformation within the sponge showed a significantly higher antibiotic as well as cytotoxic activity than their biogenetic precursors. Antibiotic activity was studied with respect to several gram-positive and gram-negative bacteria including B. subtilis, S. aureus and E. coli. The MICs (MBCs) of aeroplysinin-1 (5) and the dienone (7) varied between 12.5-25 (50-100) micrograms/ml respectively. Cytotoxicity was tested in vitro towards HeLa cells, a human cervix uteri tumour cell line. Aeroplysinin-1 (5) and the dienone (7) displayed pronounced cytotoxic activity with IC50s of 3.0 and 3.2 microM respectively. A five-fold increase in cytotoxicity was observed after O-acetylation of the dienone (7). The IC50 of the dienone O-acetate (0.6 microM) was comparable to that of the clinically used anticancer drug cisplatin (0.7 microM).

Animals↗
PubMedDate not supplied

Passing the orals.

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Allied Health Personnel↗