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Biomedical subjects

J Fastrez

Publications and source records attributed to J Fastrez.

9 recordsLinked to original sources
PubMed1992

Is the bacteriophage lambda lysozyme an evolutionary link or a hybrid between the C and V-type lysozymes? Homology analysis and detection of the catalytic amino acid residues.

The relationship between the bacteriophage lambda lysozyme (lambda L) and the C and V-type lysozymes has been investigated by sequence alignment, secondary structure prediction and pattern recognition methods. The alignment of the amino terminal part of lambda L with that of V-type lysozymes suggests that Glu19 is a residue essential for catalysis. Its mutation to Gln leads to a completely inactive enzyme. In the alignment of the sequence of lambda L with those of the C-type lysozymes a strongly homologous fragment of about 30 amino acid residues is detected. Taking into consideration this observation and the published structural alignments between C and V-type lysozymes, a repetition of the beta-sheet motif in lambda L is proposed. The multiple alignment draws the attention to a possible catalytic role for Asp34 that would be positioned in the middle of the second strand of the beta-sheet as in the C-type lysozymes. This role is confirmed by mutagenesis. The implications of these observations in terms of the evolutionary relationship between lambda L and the other lysozymes is discussed.

Amino Acid Sequence↗
PubMed1992

A large decrease in heat-shock-induced proteolysis after tryptophan starvation leads to increased expression of phage lambda lysozyme cloned in Escherichia coli.

The R gene coding for phage lambda lysozyme (lambda L), cloned under the control of the PL promoter on a multicopy vector, is expressed in an Escherichia coli strain auxotrophic for tryptophan. Induction by a thermal shift after tryptophan supplementation in a culture initially brought into stationary phase by tryptophan starvation leads to highly increased expression. A thermally unstable mutant protein, difficult to obtain under standard conditions, can be easily produced by post-stationary-phase expression. It is shown that this is due to a drastic decrease in the heat-shock-induced proteolysis normally observed on thermal induction. These data are discussed in relation to our present knowledge of stringent and heat-shock responses.

Bacteriophage lambda↗
PubMed1991

Overexpression of the phage lambda lysozyme cloned in Escherichia coli: use of a degenerative mixture of synthetic ribosome binding sites and increase of the protein stability in vivo.

The R gene of the phage lambda coding for a lysozyme expressed at the end of an infection cycle in Escherichia coli has been cloned in a series of vector plasmids. Two methods for improving the efficiency of translation have been tested. First, the use of a bicistronic construction in which the ribosome binding site (RBS) of the first cistron is that of a highly expressed gene or the use of a degenerate mixture of synthetic oligonucleotides for the optimization of a RBS. The second strategy is more efficient: the analysis of a number of clones reveals that the LaL expression levels are increased by a factor between 3 and 6 times compared with the clone using the natural RBS. The expression levels are described by an approximately Gaussian histogram. The translation promoter that was found to afford the best expression (PL) is under the control of a thermolabile repressor. Under the expression conditions, the protein is partially proteolysed. The proteolysis is significantly decreased by adding salt to the growth medium. After optimization, an increase in expression by a factor of 40 is obtained compared with the initial conditions. An efficient purification protocol is described.

Base Sequence↗
PubMed1991

[Hypernephroma with contralateral renal artery stenosis. Therapeutic choices].

We report a case of renal adenocarcinoma with contralateral stenosis of the renal artery. We describe the causes of hypertension in renal cancer and investigative techniques leading to the discover of a vascular implication in hypertension. We debate of the different surgical techniques for renal revascularisation with special regard to splenorenal anastomose. This is the method of revascularisation used in this case.

Aged↗
PubMedDate not supplied

Revascularization of the superior mesenteric artery.

From 1965 to 1973, 7 patients with severe chronic mesenteric vascular insufficiency have been successfully operated upon. Abdominal pain, weight loss and epigastric murmur were the most significant symptoms and signs in these diffusely atheromatous patients. Aortography with exposure in the lateral projection was essential for diagnosis and operative planning. Although two and often all three main splanchnic arteries were involved, revasculariztion of only the superior mesenteric artery restored normal hemodynamics. There was no operative mortality. Weight gain was dramatic and post-prandial pain disappeared in all patients. One patient diedone year and one half after the operation from an acute cerebro-vascular accidnet. Our surgical experience in this field, although small, is very gratifying and rewarding.

Aged↗
PubMedDate not supplied

[Breast tuberculosis: apropos of a case].

The tuberculosis of the breast has rarely been observed. A new case is reported. The characteristic clinical symptoms are a firm, no-fixed, painless mass with adenopathies. The disease is rarely bilateral. The most difficult problem is differentiation between tuberculosis and carcinoma in the older patient. The clinical appearance of a pyogenic breast abscess is also very similar to tuberculosis. The most reliable diagnosis studies include bacteriologic cultures of aspirate and histologic examination. The best treatment is a complete surgical excision of the lesion and at least 6 months' postoperative anti-tuberculous chemotherapy.

Aged↗