[Methodologic variants on rapid MR imaging of the liver]

The development of rapid imaging methods makes it possible to obtain T1 and T2-weighted MR images in less than 15 seconds. Consequently images can be obtained without respiratory artefacts. An attempt has been made to obtain optimal factors for the fast-field-echo procedure in order to obtain satisfactory images of the liver with T1 and T2 sequences. By moving the examination couch, it is possible to obtain 10 mm transverse sections without gaps throughout the entire liver in a reasonable time. The additional use of contrast medium (Gd-DTPA) provides information about perfusion and leads to an increase in contrast between lesions and normal liver tissue with adequate image quality. The method is particularly valuable before surgery for liver metastases.

[Risks and artifacts in MRT (1.5 tesla) caused by metallic foreign bodies. Studies on phantoms and 60 patients]

Our experience of the effects of metallic foreign bodies on MRT high field examinations is described. In vitro measurements showed moderate magnetic torsion or displacement in a few cases. The findings in 60 patients with various metal foreign bodies and the resulting artifacts are discussed. Despite local loss of information, in the majority of cases there is additional evidence provided by MRT, which suffers less from foreign body artifacts than does CT. Stainless steel implants result in some signal loss and geometric distortion, but do not usually constitute a danger to the patient and do not affect the diagnostic information from surrounding structures.

[Pulse triggering in magnetic resonance tomography in high-field strength]

Gated images of patients with stronger pulsation artefacts in the brain stem were produced on a 1.5 tesla MR-imager, registering blood pulsations by means of a finger plethysmograph. A minimization of movement artefacts was achieved and thus sufficient diagnostic-value of images in these patients was noticeable. This gating method seems to be a promising simple alternative compared to the well known cardiac gating for imaging of the head and neck area. Its advantages and limitations are demonstrated.

Quantitative electroelution of oligonucleotides and large DNA fragments from gels and purification by electrodialysis

We have designed a new device [Biotrap (Elutrap in the U.S.A. and Canada), available from Schleicher & Schuell] for electroelution, -concentration , and -dialysis of DNA and other charged macromolecules above 5 kDa. In an electric field, the DNA migrates in an open channel out of the gel slice through a microporous membrane, BT2, into the trap section, where it is retained by a very dense, non-adsorbant, and inert membrane BT1. Specifically designed for use in an electric field, the matrix of this new membrane is much denser than that of dialysis membranes. In contrast to dialysis membranes, BT1 will not adsorb large DNA fragments nor allow passage of small DNA fragments when subjected to an electric field. In the absence of an electric field, BT1 and BT2 effectively seal the trap, maintaining the final elution volume of the purified sample. The trap can contain from 200-600 microliter and is collected from above with a pipet. In the experiments described here, 85-95% of oligonucleotides (14-mer) and large (150 kb) DNA fragments were recovered, independent of fragment length. The purity of the eluted DNA was demonstrated by restriction enzyme digestion, nick-translation, primer extension, end-labeling with polynucleotide kinase, and ligation. Electrodialysis was successfully used for the complete removal of common contaminants inhibiting the polynucleotide kinase reaction and for the removal of CsCl from DNA samples.

Synthetic oligonucleotide probes complementary to rRNA for group- and species-specific detection of mycoplasmas

A variety of genetic probes has been used for the detection of pathogenic bacteria. Here we present a straightforward approach for the development of group- and species-specific oligonucleotide probes complementary to mycoplasmal rRNA. These probes are useful not only for the identification of mycoplasmas in clinical specimens, but also for the detection of Mollicutes in contaminated cell cultures. Radiolabeled rDNA probes detected less than 1 x 10(3) organisms in an RNA-DNA hybridization procedure.

[Magnetic resonance tomographic studies at 2.0 Tesla. Evaluation of clinically relevant parameters]

After having used a 2 Tesla prototype whole body scanner for about one and a half years, it is now possible to comment on the clinical value of high field strengths. The methods and techniques employed are described. The problems arising from high field strengths are discussed and their effect on clinical diagnosis is indicated.

[Realtime sonography of intrascrotal space-occupying lesions]

In 848 examinations of the testes in 317 patients, including 253 follow-up and/or multiple follow-up examinations and 36 unilateral testicle examinations (e.g., orchidectomy, aplasia or nondescent) it was shown that sonography is a diagnostic method which is on the one hand capable of clearly differentiating cystic from solid space-occupying processes, and on the other hand also offers certain possibilities for evaluating the status of solid findings. Histologic identification of malignant tumors was only achieved with teratomas. The differential diagnostic problem was in differentiating scrotal tumors from focal orchitis, chronic epididymitis, testicular torsion and contusion, and in differentiation between paratesticular neoplasms and epididymitides. The testicular findings included testicular neoplasms, cicatrization and cysts of the tunic, sequelae of trauma, orchitis, cryptorchism, hypoplasia, aplasia, and testicular cysts. Paratesticular findings included hydroceles, spermatoceles, varicoceles, paratesticular neoplasms, epididymitides, paratesticular scars, and thickening of the testicular coat.

In vitro secretion of peptide hormones by the human placenta: I. ACTH

In order to address the question of autonomy of placental hormone secretion, fresh human term placentae were utilized for the preparation of small tissue fragments. The fragment pool was divided over four parallel chambers in a superfusion apparatus and could thus serve as both control and experiment under identical in vitro conditions. Oxygen consumption was substantial and could be maintained for at least 5 h. Adrenocorticotrophic hormone (ACTH) concentrations in the effluent buffer were estimated by radioimmunoassay and bioassay. Both non-specific (membrane depolarization with 45 mM KCl) and specific (isoproterenol at 10(-7) M) stimulation increased the ACTH secretion from 10 to 20 pg/min/g to 60 to 80 pg/min/g. Propranolol blocked the adrenergic stimulation almost completely, indicating the specificity of the effect. Thus, in terms of in vitro ACTH secretion, the human placenta can be stimulated and therefore does not seem to behave in an autonomous manner.

Cell transformation by the left terminal regions of the adenovirus 40 and 41 genomes

To study the transforming capacity of the two fastidious adenoviruses 40 and 41 (Ad40 and Ad41), we have cloned the left terminal regions of their genomes. Transfection with plasmids containing these regions leads to transformation of primary baby rat kidney (BRK) cells. Cell lines derived from transformed cells show an intermediate transformed phenotype. The left terminal region was present in at least 50 copies in cells transformed by Ad41 and in 2-3 copies in Ad40-transformed cells. The integration patterns of the plasmids containing the left terminal region of Ad41 were similar in three different cell lines.

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.

[Stimulant current diagnosis and therapy with pulsed currents]

Thanks to its efficiency and versatility, and the fact that it has none of the frequently negative side-effects of drugs, stimulant-current therapy has become rapidly more important. The use of defined stimulant-current pulses also enables the condition of neuromuscular system to be described accurately in terms of measurements--a valuable diagnostic aid and therapeutic monitoring facility. The method, procedure and criteria for its use, and some special therapies, are described.

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.

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.

[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.

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.

[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.

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.

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%.

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.