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Biomedical subjects

F Jacob

Publications and source records attributed to F Jacob.

At least 19 recordsLinked to original sources
PubMed1992

[Abscess of the atrium: a complication of central venous catheters].

A 27-year-old female patient was admitted for parenteral feeding and treatment of an acute episode of her steroid dependent Crohn's disease. An intravenous catheter was inserted, the tip being located in the right atrium. This central line was accidentally removed ten days later and replaced with another one also ending in the right atrium. The patient's condition improved over a four-week period. Thereafter, she suddenly became confused and complained of abdominal pain with contracture. She displayed renal failure, coagulation disorders, and decreased blood cell counts. This was followed by a septic shock requiring mechanical ventilation and adrenaline. Laparotomy failed to reveal a cause for the patient's condition. She improved and was extubated four days later. From then on, she had fever (39 degrees C) again. Her catheter was replaced, the tip of this third one being inside the superior vena cava. Staphylococcus epidermidis was obtained from the catheter tip, as well as from four consecutive blood cultures. Despite administration of three different antibiotics, the high fever persisted (40 degrees C). Finally, the occurrence of a systolic murmur led to the discovery, with cardiac ultrasonography, of a mobile right atrial abscess, which engaged into the tricuspid valve at every contraction. Surgery to remove this mass was rapidly carried out. The bacterium was the same as that which had been isolated from the catheter. The patient improved and was able to return home a fortnight later. The diagnosis and prevention of this complication is discussed. The tip of central venous catheter should not be kept inside the atrium.

Abscess↗
PubMed1992

[Bacteriological relationship between organ donor and recipient. A survey apropos of 100 brain dead patients].

The aim of the study was to evaluate the relationship between germs found in samples systematically taken in the organ donors and germs found in the corresponding recipients in the 8 post-operative days. The 100 brain-dead patients received oxacillin (2g every 4 hours) when the bacteriological samples were taken. 41% of the donors were germ carriers. The germs were mainly located in the respiratory track (Staphylococcus aureus meti-S (34%) and Hemophilus (29%)). Among the 86 patients harvested, 40 donors were germ carriers and gave 132 organs, 46 donors were not germ carrier and gave 151 organs. The comparison between these two groups showed no difference. Assessment of infection occurring in organ recipient in the 8 post-operative days (germ, location, evolution) showed no difference, whether organs were removed from germ carrier donors or no. Comparison between the germs found in germ carrier donors and those found in recipients with sepsis showed a similitude in three cases (2.2%). In the other cases, there is no relationship between the germs found in the donors and post-operative sepsis in the recipient.

Brain Death↗
PubMed1991

The mutation Lys234His yields a class A beta-lactamase with a novel pH-dependence.

The lysine-234 residue is highly conserved in beta-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class A beta-lactamase yielded an enzyme the pH-dependence of which was characterized by the appearance of a novel pK, which could be attributed to the newly introduced residue. At low pH, the kcat, value for benzylpenicillin was as high as 50% of that of the wild-type enzyme, demonstrating that an efficient active site was maintained. Both kcat. and kcat/Km dramatically decreased above pH 6 but the decrease in kcat./Km could not be attributed to larger Km values. Thus a positive charge on the side chain of residue 234 appears to be more essential for transition-state stabilization than for initial recognition of the substrate ground state.

Ampicillin↗
PubMed1991

The importance of the negative charge of beta-lactam compounds in the interactions with active-site serine DD-peptidases and beta-lactamases.

The interaction between various penicillins and cephalosporins the carboxylate group of which at C-3 or C-4 had been esterified or amidated and different penicillin-recognizing enzymes was studied. In general, our findings reinforced the common assumption that an anionic group at that position is necessary for the effective acylation of these enzymes. However, the relative activities of the modified beta-lactams as inactivators of the Streptomyces R61 DD-peptidase or as substrates of the Bacillus licheniformis, Streptomyces albus G and Enterobacter cloacae beta-lactamases did not fit a general scheme in which the intrinsic electronic and geometric properties of the beta-lactam compounds would be sufficient to explain their substrate or inactivator properties towards the various types of enzymes investigated.

Acylation↗
PubMed1991

Active-site serine mutants of the Streptomyces albus G beta-lactamase.

By using site-directed mutagenesis, the active-site serine residue of the Streptomyces albus G beta-lactamase was substituted by alanine and cysteine. Both mutant enzymes were produced in Streptomyces lividans and purified to homogeneity. The cysteine beta-lactamase exhibited a substrate-specificity profile distinct from that of the wild-type enzyme, and its kcat./Km values at pH 7 were never higher than 0.1% of that of the serine enzyme. Unlike the wild-type enzyme, the activity of the mutant increased at acidic pH values. Surprisingly, the alanine mutant exhibited a weak but specific activity for benzylpenicillin and ampicillin. In addition, a very small production of wild-type enzyme, probably due to mistranslation, was detected, but that activity could be selectively eliminated. Both mutant enzymes were nearly as thermostable as the wild-type.

Base Sequence↗
PubMed1991

Prion diseases in man.

Human spongiform encephalopathies (HSE) are uncommon neurodegenerative diseases of unknown etiology. Whilst numerous observations provide arguments for an infectious disorder mediated by an unconventional agent of the so-called prion-type, the recent discovery of predisposing allelic variants suggests that HSE might be considered as genetically linked diseases.

Animals↗
PubMed1991

[Value of hormonal treatment with triiodothyronine and cortisone in brain dead patients].

Brain death leads to substantial falls in the plasma levels of cortisol and tri-iodothyronine (T3). These alterations may be responsible for physiological instability in these patients, and impairment in donor organ function. A double-blind study was therefore designed to assess the possible improvement in metabolism and haemodynamic stability in brain-dead organ donors treated with T3 and cortisone. Forty adult brain-dead patients were randomly assigned to two groups, the patients of the treated group were given every hour, or half hour, 2 or 4 micrograms T3 and 100 mg hydrocortisone intravenously, and those of the placebo group normal saline. Both groups of patients received conventional management for brain-dead donors. The main assessment criterion was the haemodynamic course, appreciated by the Pasys, the CVP and the needs in dobutamine; the secondary criterion was the start, or worsening, of a metabolic acidosis, as judged by the pH, the level of arterial bicarbonate, and the needs in sodium bicarbonate. The two groups were comparable for age, sex, aetiology of brain death, the delay between brain death and the start of the experimental protocol, and the duration of this protocol. There were differences between the two groups, which were not statistically significant: improvement in haemodynamic profile (hormone group 9/20 versus placebo group 10/20); worsening in haemodynamic profile (2/20 vs 4/20); increased requirements in dobutamine (2/20 vs 4/20); decreased requirements in inotropic support (15/20 vs 13/20); mean dose of dobutamine (3.1 +/- 4.2 micrograms.kg-1 vs 2.5 +/- 3.8 micrograms.kg-1); metabolic acidosis (5/20 vs 5/20); mean bicarbonate dose (30.0 +/- 67.7 mmol vs 45.0 +/- 74.2 mmol); donors harvested (20/20 vs 18/20).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1990

Role of the conserved amino acids of the 'SDN' loop (Ser130, Asp131 and Asn132) in a class A beta-lactamase studied by site-directed mutagenesis.

Ser130, Asp131 and Asn132 ('SDN') are highly conserved residues in class A beta-lactamases forming one wall of the active-site cavity. All three residues of the SDN loop in Streptomyces albus G beta-lactamase were modified by site-directed mutagenesis. The mutant proteins were expressed in Streptomyces lividans, purified from culture supernatants and their kinetic parameters were determined for several substrates. Ser130 was substituted by Asn, Ala and Gly. The first modification yielded an almost totally inactive protein, whereas the smaller-side-chain mutants (A and G) retained some activity, but were less stable than the wild-type enzyme. Ser130 might thus be involved in maintaining the structure of the active-site cavity. Mutations of Asp131 into Glu and Gly proved to be highly detrimental to enzyme stability, reflecting significant structural perturbations. Mutation of Asn132 into Ala resulted in a dramatically decreased enzymic activity (more than 100-fold) especially toward cephalosporin substrates, kcat. being the most affected parameter, which would indicate a role of Asn132 in transition-state stabilization rather than in ground-state binding. Comparison of the N132A and the previously described N132S mutant enzymes underline the importance of an H-bond-forming residue at position 132 for the catalytic process.

Amino Acid Sequence↗
PubMed1990

An immortalized osteogenic cell line derived from mouse teratocarcinoma is able to mineralize in vivo and in vitro.

The hybrid plasmid pK4 containing the early genes of the simian virus SV-40, under the control of the adenovirus type 5 E1a promoter, was introduced into the multipotent embryonal carcinoma (EC) 1003. Expression of the SV-40 oncogenes was observed at the EC cell stage, and this allowed the derivation of immortalized cells corresponding to early stages of differentiation. Among the immortalized mesodermal derivatives obtained, one clone, C1, is committed to the osteogenic pathway. C1 cells have a stable phenotype, synthesize type I collagen, and express alkaline phosphatase activity. Although immortalized and expressing the SV-40 T antigen, the cells continue to be able to differentiate in vivo and in vitro. In vivo, after injection into syngeneic mice, they produce osteosarcomas. In vitro, the cells form nodules and deposit a collagenous matrix that mineralizes, going to hydroxyapatite crystal formation, in the presence of beta-glycerophosphate. This clonal cell line, which originates from an embryonal carcinoma, therefore differentiates into osteogenic cells in vivo and in vitro. This immortalized cell line will be useful in identifying specific molecular markers of the osteogenic pathway, to investigate gene regulation during osteogenesis and to study the ontogeny of osteoblasts.

Acid Phosphatase↗
PubMed1990

Evidence for mitotic recombination in Wei/+ heterozygous mice.

A number of alleles at coat color loci of the house mouse give rise to areas of wild-type pigmentation on the coats of otherwise mutant animals. Such unstable alleles include both recessive and dominant mutations. Among the latter are several alleles at the W locus. In this report, phenotypic reversions of the Wei allele at the W locus were studied Mice heterozygous in repulsion for both Wei and buff (bf) [i.e. Wei+/+bf] were examined for the occurrence of phenotypic reversion events. Buff (bf) is a recessive mutation, which lies 21 cM from W on the telomeric side of chromosome 5 and is responsible for the khaki colored coat of nonagouti buff homozygotes (a/a; bf/bf). Two kinds of fully pigmented reversion spots were recovered on the coats of a/a; Wei+/+bf mice: either solid black or khaki colored. Furthermore phenotypic reversions of Wei/+ were enhanced significantly following X-irradiation of 9.25-day-old Wei/+ embryos (P less than 0.04). These observations are consistent with the suggestion of a role for mitotic recombination in the origin of these phenotypic reversions. In addition these results rise the intriguing possibility that some W mutations may enhance mitotic recombination in the house mouse.

Alleles↗
PubMed1990

Engineering a novel beta-lactamase by a single point mutation.

beta-Lactamases are widespread and efficient bacterial enzymes which play a major role in bacterial resistance to penicillins and cephalosporins. In order to elucidate the role of the residues lying in a conserved loop of the enzymatic cavity of the active-site serine Streptomyces albus G beta-lactamase, modified proteins were produced by oligo-directed mutagenesis. Mutation of Asn116, which lies on one side of the active site cavity pointing to the substrate-binding site, into a serine residue resulted in spectacular modifications of the specificity profile of the enzyme. That replacement yielded an enzyme with a nearly unchanged activity towards good penicillin substrates. In sharp contrast its efficiency in hydrolysing cephalosporins was drastically reduced, the best substrates suffering the largest decrease in the second-order rate constant for serine acylation. In fact that single mutation generated a truly new enzyme behaving exclusively as a penicillinase, a situation which is never encountered to the same degree in any of the numerous naturally occurring variants of class A beta-lactamases.

Acylation↗
PubMed1990

Cloning, partial sequence, expression, and antigenic analysis of the filamentous hemagglutinin gene of Bordetella pertussis.

The gene coding for the filamentous hemagglutinin (FHA), one of the main factors involved in mediating adherence of Bordetella pertussis to ciliated host cells, was cloned in Escherichia coli, and the 3,500-base-pair nucleotide sequence encoding the amino-terminal region was determined. Molecular cloning, together with the characterization of recombinant FHA-related proteins produced in E. coli, revealed that the primary translation product is a protein of about 370 kilodaltons (kDa). The mature 220-kDa FHA polypeptide secreted by B. pertussis is most probably generated by proteolytic processing that eliminates a carboxy-terminal portion of about 150 kDa. The 1,087 amino-terminal residues of the predicted FHA sequence showed a number of remarkable features. Extensive homology to the Serratia marcescens and Proteus mirabilis hemolysin proteins was found between amino acids 91 and 205 of the FHA sequence, suggesting involvement of this FHA domain in host cell binding or secretion of FHA from B. pertussis. In addition, two regions containing repetitive amino acid sequences were identified. One region, extending from residues 382 to 664, was formed by six repeats, and a second, extending from residues 701 to 912, contained three repeats. The reactivities of several recombinant FHA-derived proteins with a panel of monoclonal antibodies identified at least four epitopes composing an immunoreactive domain present in the carboxy-terminal moiety of the mature FHA.

Adhesins, Bacterial↗
PubMed1989

Pattern of expression of ecotropic murine leukemia virus in gonads of inoculated SWR/J mice.

An ecotropic murine leukemia virus (MuLV) isolate has recently been shown to be able to infect the germ line or the early embryo or both when inoculated at birth to SWR/J females (J. J. Panthier, H. Condamine, and F. Jacob, Proc. Natl. Acad. Sci. USA 85:1156-1160, 1988). We have used this isolate to further study this phenomenon. By using the techniques of RNA-RNA in situ hybridization, immunocytochemistry, and transmission electron microscopy, the identities of two important cell types that are infected by ecotropic MuLV in the gonads of inoculated mice were determined. These cells are the thecal cells surrounding the follicles in the ovary and the Leydig cells in the testis. Both types actively synthesize viral RNA and express a viral antigen. Furthermore, we documented the production of viral particles by the thecal cells. The expression of ecotropic MuLV by nonlymphoid cells in vivo may play a key role in the vertical transmission of these viruses by females as well as in their horizontal transmission.

Animals↗
PubMed1986

Cloning of the chicken progesterone receptor.

Monospecific antibodies directed against the chicken progesterone receptor (PR) form B were used to screen a randomly primed phage lambda gt11 cDNA expression library prepared from size-fractionated chicken oviduct mRNA. Two independent immunoreactive clones, lambda cPR1 and lambda cPR2, were isolated. Antibodies selected from anti-PR form B antiserum on matrices of lambda cPR1 and lambda cPR2 fusion proteins detected two proteins on electrophoretic immunoblots of crude and purified PR preparations. These proteins had the same apparent molecular weights as did PR forms A and B crosslinked with the tritiated progestin R 5020. Thus, lambda cPR1 and lambda cPR2 fusion proteins contain epitopes present in both PR forms A and B. A cDNA clone, lambda cPR3, containing the inserts of both lambda cPR1 and lambda cPR2, was isolated from a randomly primed lambda gt10 oviduct cDNA library, indicating that both cDNA inserts were derived from the same oviduct mRNA. Additional evidence that these cDNAs correspond to PR mRNA was provided by sequencing the lambda cPR3 cDNA insert, since it was found to encode the sequence of three tryptic peptides prepared from purified PR form B. A fourth and a fifth cDNA clone, lambda cPR4 and lambda cPR5, were sequentially isolated from the same lambda gt10 cDNA library beginning with a probe derived from the 3' end of the lambda cPR3 insert. Partial DNA sequencing of lambda cPR4 and lambda cPR5 revealed the presence of a sequence coding for a cysteine-rich domain that is strikingly homologous to the amino acid sequences present in the putative DNA-binding domain of the human and chicken estrogen receptors, human glucocorticoid receptor, and v-erbA gene product of the avian erythroblastosis virus.

Amino Acid Sequence↗
PubMed1985

Characterization of antigens recognized by monoclonal and polyclonal antibodies directed against uvomorulin.

Uvomorulin is a cell surface glycoprotein involved in compaction of early mouse embryo. Antibodies, either monoclonal or polyclonal, raised against a purified tryptic fragment of uvomorulin recognize, in a detergent lysate of embryonal carcinoma cells metabolically labeled with 35S, three molecules (120, 100, and 88 kDa) that are not related, as judged by peptide mapping. Only the 120-kDa form is related to the tryptic fragment of uvomorulin and, thus, is considered as the native form of uvomorulin. Although all three products are apparently detectable at the cell surface, only the 120-kDa form is glycosylated. Coimmunoprecipitation of the three different polypeptides is probably due to shared epitopes rather than to their presence in a multimeric complex.

Animals↗
PubMed1985

Expression of the cytokeratin endo A gene during early mouse embryogenesis.

Expression of cytokeratin endo A has been analyzed during mouse blastocyst formation and embryonal carcinoma cell differentiation. To study the regulation of endo A expression, nuclease S1 mapping experiments have been performed on RNA extracted from two-cell to 7.5-day embryos. Low levels of endo A mRNA begin to be detectable in eight-cell embryos. The amount of this mRNA increases at the blastocyst stage, suggesting that endo A expression is regulated at the mRNA level during blastocyst formation. At this stage, in situ hybridization studies show that endo A mRNA is present in the trophectoderm but not in the inner cell mass. In 7.5-day embryos, endo A mRNAs are also detectable in the endoderm layer and in the amnion.

Animals↗
PubMed1985

One gene and one pseudogene for the cytokeratin endo A.

The recombinant cDNA RecXVI, which hybridizes to the endo A mRNA, detects two specific bands on a Southern blot of EcoRI-digested genomic mouse DNA. We have screened a mouse genomic library with this cDNA and isolated these two sequences. Endo A is encoded by a 7.5-kilobase gene and by a 1.6-kilobase pseudogene devoid of introns. A repetitive sequence belonging to the B2 family is located in the third intron of the gene. We have observed that transcription of B2 sequences and of the endo A gene are mutually exclusive.

Animals↗