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Biomedical subjects

R Maas

Publications and source records attributed to R Maas.

At least 127 records · Page 7Linked to original sources
PubMed1985

Detection of genes for heat-stable enterotoxin I in Escherichia coli strains isolated in Brazil.

Heat-stable enterotoxin I (STI) can be assayed in intestinal loops of pigs and rabbits and in the gut of infant mice. To produce a simpler and more discriminating assay procedure, we used three gene probes corresponding to three forms of STI called STIa, STIb, and STIc. We tested 159 Brazilian isolates, of which 40 were positive in the infant mouse assay. The STIb and STIc probes are similar (93% DNA homology) and are both different from the STIa probe (70% DNA homology). Of 33 strains that were still active for STI 3 years after their isolation, 25 reacted with both the STIb and STIc probes, 4 reacted with the STIc probe only, and 7 reacted strongly with the STIa probe and weakly or not at all with the other probes. Two strains reacted with all three probes. Further analysis showed that each of these two strains contains a small plasmid that reacts with the STIa probe and a large plasmid that reacts with the STIc probe in one strain and weakly with both the STIa and STIc probes in the other strain. It was also shown that the STIa probe reacts with the cloning vehicle pACYC184 used for the cloning of STIc. We conclude that the gene probes used can identify most STI-producing strains and that in cases of positive responses with several probes careful scrutiny is necessary for analysis.

Bacterial Toxins↗
PubMed1983

An improved colony hybridization method with significantly increased sensitivity for detection of single genes.

By introducing a simple modification of existing methods, colony hybridization has been used to detect single copy genes coding for a heat-stable enterotoxin in wild-type strains isolated from patients with diarrhea. The modification described in this communication results in an approximately 100-fold increase in sensitivity, probably by increasing the total denatured plasmid DNA fixed to the paper.

Cloning, Molecular↗
PubMed1983

Digital venous subtraction angiography of pulmonary embolism in dogs.

Digital venous subtraction angiography makes it possible to obtain satisfactory images of the pulmonary vessels and thus to evaluate changes in the segmental and subsegmental arteries caused by pulmonary embolism. Morphologic as well as functional images can be produced in the course of a single examination. Semi-quantitative information about the vessels under examination as compared with the corresponding contralateral vessels is thus achieved. This procedure is valuable both in primary diagnosis and in subsequent repeat examinations after treatment.

Angiography↗
PubMed1983

Purification of the flavoproteins 6-hydroxy-D- and 6-hydroxy-L-nicotine oxidase using hydrophobic affinity chromatography.

A systematic study of the homologous series of omega-aminoalkyl-agaroses revealed differences in the affinities of 6-hydroxy-D- and 6-hydroxy-L-nicotine oxidase. In contrast to supports with nonpolar alkyl chains, omega-aminoalkyl-agarose showed high affinity towards the L-specific enzyme, while the D-specific oxidase was bound most firmly by omega-aminododecyl-agarose. 6-Hydroxy-L-nicotine oxidase could be desorbed by 1.3M NaCl only in the presence of the substrate L-6-hydroxynicotine. Using the omega-aminoalkyl-agarose, a complete separation of the enantiozymes was accomplished and an efficient purification procedure for both oxidases established.

Arthrobacter↗
PubMed1983

[Intestinal perforation in juvenile abdominal typhoid].

Eight of 19 children with typhus abdominalis who were between 4 and 12 years of age, showed perforation of the intestine. The terminal ileum was always the site of the perforation. Besides the clearly visualized air, meteorism of the small intestine was always seen. In individual cases, segments of the small intestine were seen in close proximity to each other, or an ileus developed. The x-ray film in typhus abdominalis in childhood shows the same signs as an adult x-ray. A characteristic feature of the perforation is its localization in the terminal ileum and the time at which it occurs, namely, between the end of the 2nd and the end of the 4th week of the diseased condition.

Child↗
PubMed1982

[Computer tomographic findings in tumours of the oesophagus (author's transl)].

The computer tomographic findings in 55 patients with histologically confirmed oesophageal carcinomas and in three benign oesophageal tumours are described. In 49 cases, the carcinoma was clearly visible on computer tomography, but in six cases, the tumour was not seen. In another six cases, infiltration into the mediastinum and trachea was demonstrated. In seven patients, regional lymph node metastases were found. The value of computer tomography in oesophageal carcinomas lies in the ability to demonstrate axial spread of the tumour, and the presence of lymphatic or haematogenous metastases during the one examination. This helps in the choice of surgery or in the planning of radiation treatment. Demonstration of the thickness of the oesophageal wall in the region of the tumour can be improved by using a flour-gastrografin paste.

Adenocarcinoma↗
PubMed1981

Structure of a naturally occurring plasmid with genes for enterotoxin production and drug resistance.

A physical map of the 117-kilobase conjugative plasmid pCG86 was constructed using electron microscope heteroduplex analysis. This plasmid carries the genes elt, for heat-labile enterotoxin, and estA, for heat-stable enterotoxin, as well as the genes for resistance to tetracycline, streptomycin, sulfonamides, and mercury. These genes were mapped using deletions and Tn5 insertions as physical markers. Analysis of a heteroduplex between pCG86 and a previously described enterotoxin plasmid (EntP307) showed a 48-kilobase region of complete homology which included the genes elt and estA. An 8.8-kilobase BamHI fragment of EntP307 carrying elt, cloned by others, was also shown to be completely homologous with pCG86. The position of elt on the fragment was verified, and it was shown to carry estA as well. A 44-kilobase region of pCG86 showed partial homology with the region of EntP307 previously shown to contain conjugal transfer genes. The gene for tetracycline resistance is carried on a stem-loop structure with the dimensions of Tn10, and the genes for the other drug resistance markers are carried on a 14.6-kilobase segment that forms an insertion loop in heteroduplexes with EntP307. These studies suggest that pCG86 arose either by recombination between an enterotoxin plasmid of incompatibility group FI, like EntP307, and a multiple resistance factor of incompatibility group FII, or by transposition into EntP307 of two transposons.

Cloning, Molecular↗
PubMed1980

Transfer of a CFA/I-ST plasmid promoted by a conjugative plasmid in a strain of Escherichia coli of serotype O128ac:H12.

Escherichia coli strains belonging to serotype O128ac:H12 and producing heat-stable enterotoxin (ST) and colonization factor CFA/I were found in Sao Paulo in children with diarrhea, but not in normal children. Segregants occurred in such strains with a frequency of about 10%, which have lost the ability to produce ST and CFA/I at the same time. From one strain, both properties were transformed jointly in matings to an E. coli K-12 strain. All such ST+ CFA/I+ progeny had received two plasmids of length 97 and 64 kilobases in the matings. Insertion of a transposon, Tn5, carrying a gene for kanamycin resistance, into the two plasmids enabled us to select for kanamycin-resistant progeny in further matings. Analysis of such progeny strains in terms of plasmid content and production of ST and CFA/I revealed that the larger plasmid carries the genes for St and CFA/I and is not self-transmissible, whereas the smaller plasmid does not carry any recognizable phenotypic traits, but is conjugative and promotes cotransfer of the larger plasmid with a frequency of about 30%.

Colony-Forming Units Assay↗
PubMed1978

Magnetic relaxation analysis of dynamic processes in macromolecules in the pico- to microsecond range.

A formalism based on the theory of Markov processes and suitable for the analysis of multiple internal motions in macromolecules is presented. Computer calculations of specific motional models for (13)C nuclear magnetic resonance (NMR) relaxation, treated as special cases of the proposed formalism, demonstrate the potential of this approach for discriminating between different motional models on the basis of NMR relaxation data.

Macromolecular Substances↗
PubMed1977

[Not Available].

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History, Early Modern 1451-1600↗
PubMed1976

[On the method of indirect electrogastrography and its diagnostic applicability (author's transl)].

The cutaneous recording of the gastric electrical activity according to the modified method of Sobakin was utilized. In fasting individuals changes in potential occured between 2 and 5 per min., in most of the cases after standard breakfast the frequency increased while lower amplitudes appeared. The frequency of electrical waves from the duodenum increased remarkably. It could be demonstrated that the peristalsis recorded by gastroscopy was synchronous with the electrogastrographic potentials. The applicability of the method for clinical diagnostic purposes is limited at the present time, because a "normal" electrogastrogram has not yet been established. Specific changes of the electrogastrogram have not been observed in various gastric diseases, which may be verified by routine diagnostic procedures.

Electrodiagnosis↗