The cystine/cysteine cycle: a redox cycle regulating susceptibility versus resistance to cell death

The glutathione-dependent system is one of the key systems regulating cellular redox balance, and thus cell fate. Cysteine, typically present in its oxidized form cystine in the extracellular space, is regarded as the rate-limiting substrate for glutathione (GSH) synthesis. Cystine is transported into cells by the highly specific amino-acid antiporter system xc-. Since Burkitt's Lymphoma (BL) cells display limited uptake capacity for cystine, and are thus prone to oxidative stress-induced cell death, we stably expressed the substrate-specific subunit of system xc-, xCT, in HH514 BL cells. xCT-overexpressing cells became highly resistant to oxidative stress, particularly upon GSH depletion. Contrary to previous predictions, the increase of intracellular cysteine did not affect the cellular GSH pool, but concomitantly boosted extracellular cysteine concentrations. Even though cells were depleted of bulk GSH, xCT overexpression maintained cellular integrity by protecting against lipid peroxidation, a very early event in cell death progression. Our results show that system xc- protects against oxidative stress not by elevating intracellular GSH levels, but rather creates a reducing extracellular environment by driving a highly efficient cystine/cysteine redox cycle. Our findings show that the cystine/cysteine redox cycle by itself must be viewed as a discrete major regulator of cell survival.

Post-transcriptional regulation of the let-7 microRNA during neural cell specification

The let-7 miRNA regulates developmental timing in C. elegans and is an important paradigm for investigations of miRNA functions in mammalian development. We have examined the role of miRNA precursor processing in the temporal control and lineage specificity of the let-7 miRNA. In situ hybridization (ISH) in E9.5 mouse embryos revealed early induction of let-7 in the developing central nervous system. The expression pattern of three let-7 family members closely resembled that of the brain-enriched miRNAs mir-124, mir-125 and mir-128. Comparison of primary, precursor, and mature let-7 RNA levels during both embryonic brain development and neural differentiation of embryonic stem cells and embryocarcinoma (EC) cells suggest post-transcriptional regulation of let-7 accumulation. Reflecting these results, let-7 sensor constructs were strongly down-regulated during neural differentiation of EC cells and displayed lineage specificity in primary cells. Neural differentiation of EC cells was accompanied by an increase in let-7 precursor processing activity in vitro. Furthermore, undifferentiated and differentiated cells contained distinct precursor RNA binding complexes. A neuron-enhanced binding complex was shown by antibody challenge to contain the miRNA pathway proteins Argonaute1 and FMRP. Developmental regulation of the processing pathway correlates with differential localization of the proteins Argonaute, FMRP, MOV10, and TNRC6B in self-renewing stem cells and neurons.

Regulation of miRNA expression during neural cell specification

MicroRNA (miRNA) are a newly recognized class of small, noncoding RNA molecules that participate in the developmental control of gene expression. We have studied the regulation of a set of highly expressed neural miRNA during mouse brain development. Temporal control is a characteristic of miRNA regulation in C. elegans and Drosophila, and is also prominent in the embryonic brain. We observed significant differences in the onset and magnitude of induction for individual miRNAs. Comparing expression in cultures of embryonic neurons and astrocytes we found marked lineage specificity for each of the miRNA in our study. Two of the most highly expressed miRNA in adult brain were preferentially expressed in neurons (mir-124, mir-128). In contrast, mir-23, a miRNA previously implicated in neural specification, was restricted to astrocytes. mir-26 and mir-29 were more strongly expressed in astrocytes than neurons, others were more evenly distributed (mir-9, mir-125). Lineage specificity was further explored using reporter constructs for two miRNA of particular interest (mir-125 and mir-128). miRNA-mediated suppression of both reporters was observed after transfection of the reporters into neurons but not astrocytes. miRNA were strongly induced during neural differentiation of embryonic stem cells, suggesting the validity of the stem cell model for studying miRNA regulation in neural development.

Improvement of an in vitro stem cell assay for developmental toxicity: the use of molecular endpoints in the embryonic stem cell test

The embryonic stem cell test (EST) takes advantage of the potential of murine embryonic stem (ES) cells to differentiate in culture to test embryotoxicity in vitro. The EST represents a reliable, scientifically validated in vitro system for the classification of compounds according to their teratogenic potential based on the morphological analysis of beating cardiomyocytes in embryoid body (EB) outgrowths compared to cytotoxic effects on undifferentiated murine ES cells and differentiated 3T3 fibroblasts. In order to identify more objective endpoints of differentiation other than the microscopic evaluation of "beating areas" and to adapt the EST to applications in high-throughput screening systems we improved and expanded the EST protocol by establishing molecular endpoints of differentiation. The quantitative expression of sarcomeric myosin heavy chain (MHC) and alpha-actinin genes under the influence of test compounds was studied employing intracellular flow cytometry. Strong embryotoxicants exerted a dose-dependent effect on both the expression levels of MHC and alpha-actinin and the differentiation into beating cardiomyocytes. Furthermore, quantitative FACS (fluorescence-activating cell sorting) analysis showed the same sensitivity for the classification of substances as the conventional endpoint but allowed a significant reduction of the test period. Within 7 days, maximal expression of sarcomeric marker proteins was observed. Our findings indicate that structural proteins of the sarcomere apparatus, alpha-actinin and myosin heavy chain (MHC), seem to be promising candidates to predict developmental toxicity in vivo from in vitro data. Thus, the improved EST holds promise as a new predictive screen for risk assessment with respect to developmental toxicity using stem cell technology and technological advances in the field of gene expression analysis.

Validation of the Embryonic Stem Cell Test in the International ECVAM Validation Study on Three In Vitro Embryotoxicity Tests

A detailed report is presented on the performance of the embryonic stem cell test (EST) in a European Centre for the Validation of Alternative Methods (ECVAM)-sponsored formal validation study on three in vitro tests for embryotoxicity. Twenty coded test chemicals, classified as non-embryotoxic, weakly embryotoxic or strongly embryotoxic on the basis of their in vivo effects in animals and/or humans, were tested in four laboratories. The outcome showed that the EST can be considered to be a scientifically validated test, which is ready for consideration for use in assessing the embryotoxic potentials of chemicals for regulatory purposes.

Validation of the Postimplantation Rat Whole-embryo Culture Test in the International ECVAM Validation Study on Three In Vitro Embryotoxicity Tests

A detailed report is presented on the performance of the postimplantation rat whole-embryo culture (WEC) test in a European Centre for the Validation of Alternative Methods (ECVAM)-sponsored formal validation study on three in vitro tests for embryotoxicity. Twenty coded test chemicals, classified as non-embryotoxic, weakly embryotoxic or strongly embryotoxic on the basis of their in vivo effects in animals and/or humans, were tested in four laboratories. The outcome showed that the WEC test can be considered to be a scientifically validated test, which is ready for consideration for use in assessing the embryotoxic potentials of chemicals for regulatory purposes.

Trends in improving the embryonic stem cell test (EST): an overview

The embryonic stem cell test (EST) is an in vitro assay that has been developed to assess the teratogenic and embryotoxic potential of drugs and chemicals. It is based on the capacity of murine ES cells (cell line D3) to differentiate into contracting myocardial cells under specific cell culture conditions. The appearance of beating cardiomyocytes in embryoid body (EB) outgrowths is used as a toxicological endpoint to assess the embryotoxic potential of a test substance. Applying linear analysis of discriminance, a biostatistical prediction model (PM) was developed to assign test chemicals to three classes of embryotoxicity. In an international validation study the EST predicted the embryotoxic potential of chemicals and drugs with the same reliability as two other in vitro embryotoxicity tests, which employed embryonic cells and tissues from pregnant animals. In a joint research project with German pharmaceutical companies we have successfully improved the EST by establishing molecular endpoints of differentiation in cultured ES cells. The quantification of cardiac-specific protein expression by intracellular flow cytometry has been studied in the presence of chemicals of different embryotoxic potential. The results obtained using molecular endpoints specific for differentiated cardiomyocytes employing FACS (fluorescence-activated cell sorting) analysis will be presented in comparison to the validated endpoint - the microscopic analysis of beating areas. FACS analysis provides a more objective endpoint for predicting the embryotoxic potential of chemicals than the validated method. Furthermore, flow cytometry promises to be suitable for high-throughput screening systems (HTS). In addition, our partners from the joint project have improved the EST by developing protocols that stimulate differentiation of ES cells into neural and endothelial cells, chondrocytes and osteoblasts, because some substances might have embryotoxic effects on specific cell-types other than cardiomyocytes. These protocols have been successfully established at ZEBET and in the participating laboratories. Additionally, molecular endpoints have been established for the detection of specific differentiation pathways. Furthermore, new prediction models (PMs) have been developed using single endpoints of the EST.

[Improving the embryonic stem cell test (EST) by establishing molecular endpoints of tissue specific development using murine embryonic stem cells (D3 cells)]

Blastocyst-derived pluripotent embryonic stem (ES) cells of the mouse can be induced to differentiate in culture into a variety of cell types, including cardiac muscle cells. In the embryonic stem cell test (EST) the capacity of ES cells of the mouse cell line D3 to differentiate into contracting cardiomyocytes is used to assess the embryotoxic potential of test compounds and in addition, the effects on the viability of ES cells and differentiated mouse fibroblasts (cell line 3T3) are compared. The three endpoints are used to classify the embryotoxic potential of chemicals after 10 days of exposure: (i) the inhibition of differentiation of ES cells into cardiomyocytes (ID50) and (ii) the decrease of viability of 3T3 cells (IC503T3) and (iii) ES cells (IC50D3) in a MTT cytotoxicity test. Applying linear analysis of discriminance, a biostatistical prediction model (PM) was developed to assign test chemicals to three classes of embryotoxicity. In an international validation study funded by ECVAM it could be demonstrated that the EST can predict the embryotoxic potential of a test compound as good as frequently used mammalian systems based on pregnant animals. In a joint project with major German pharmaceutical companies we are attempting to improve the EST by establishing molecular endpoints of differentiation (e.g. cardiac, neuronal, chondrogenic) in cultured ES cells. We have studied the expression of tissue specific proteins in ES cell cultures in the presence of embryotoxic chemicals by immunofluorescent antibody techniques, e.g. FACS analysis. The other groups are focusing on endogenous gene expression in early development by RT-PCR methods or the DNA microarray technique. The results obtained recently using molecular markers specific for cardiac differentiation and employing intracellular flow cytometry for quantification will be presented. Molecular endpoints will allow improvement of the EST by measuring gene expression patterns in a small number of murine ES cells.

The ECVAM international validation study on in vitro embryotoxicity tests: results of the definitive phase and evaluation of prediction models. European Centre for the Validation of Alternative Methods

From 1996 to 2000, ZEBET (Centre for Documentation and Evaluation of Alternative Methods to Animal Experiments at the BgVV, Berlin, Germany) coordinated the European Centre for the Validation of Alternative Methods (ECVAM) prevalidation and validation study on three embryotoxicity tests: a) a test employing embryonic stem cell lines (EST); b) the micromass (MM) test; and c) the postimplantation rat whole-embryo culture assay (WEC test). The main objectives of the study were to assess the performance of these three in vitro tests in discriminating between non- embryotoxic, weakly embryotoxic and strongly embryotoxic compounds. Phase I of the study (1997) was designed as a prevalidation phase, for test protocol optimisation, and for the establishment of a comprehensive database of in vivo and in vitro data on embryotoxic compounds. Phase II (1998-2000) involved a formal validation trial, conducted under blind conditions on 20 test compounds selected from the database, which were coded and distributed to the participating laboratories. In the preliminary phase of the validation study, six chemicals out of the 20, which showed embryotoxic potential, were tested. These results were used to define new biostatistically based prediction models (PMs) for the MM and WEC tests, and to evaluate those developed previously for the EST. As a next step, the PMs were evaluated by using the results for the remaining 14 chemicals of the definitive phase of the validation study. The three in vitro embryotoxicity tests proved to be applicable to testing a diverse group of chemicals with different embryotoxic potentials (non-embryotoxic, weakly embryotoxic, and strongly embryotoxic). The reproducibility of the three in vitro embryotoxicity tests were acceptable according to the acceptance criteria defined by the Management Team. The concordances between the embryotoxic potentials derived from the in vitro data and from the in vivo data were good for the EST and the WEC (PM2) test, and sufficient for the MM test and the WEC (PM1) tests according to the performance criteria defined by the Management Team before the formal validation study. When applying the PM of the EST to the in vitro data obtained in the definitive phase of the formal validation study, chemicals were classified correctly in 78% of the experiments. For the MM and the WEC tests, the PMs provided 70% and 80% (PM2) correct classifications, respectively. And, very importantly, an excellent predictivity (100%, except for PM1 of the WEC test, with 79%, considered as good) was obtained with strong embryotoxic chemicals in each of the three in vitro tests.

Transmission of the Ambystoma tigrinum virus to alternative hosts

Ambystoma tigrinum virus (ATV) is a lethal virus originally isolated from Sonora tiger salamanders Ambystoma tigrinum stebbinsi in the San Rafael Valley in southern Arizona. USA. ATV is implicated in several salamander epizootics. We attempted to transmit ATV experimentally to fish and amphibians by injection, water bath exposure, or feeding to test whether ATV can cause clinical signs of infection or be recovered from exposed individuals that do not show clinical signs. Cell culture and polymerase chain reaction of the viral major capsid protein gene were used for viral detection. Salamanders and newts became infected with ATV and the virus was recovered from these animals, but virus could not be recovered from any of the frogs or fish tested. These results suggest that ATV may only infect urodeles and that fish and frogs may not be susceptible to ATV infection.

[Results of the first phase of the ECVAM project "prevalidation and validation of three in vitro embryotoxicity tests"]

The results of the experimental prevalidation of three in vitro embryotoxicity tests in an ECVAM study are reported: the rat whole embryo culture assay (WEC), the micromass assay (MM) and the embryonic stem cell test (EST). Three test chemicals assigned to the three classes of embryotoxicity, non-, moderate- and strong embryotoxic, and also a positive and a negative control chemical were repeatedly tested in each test in two laboratories. The data obtained were evaluated independently by a biostatistician. It could be shown that the standard protocols (SOPs) for the three in vitro embryotoxicity tests could be transferred to a second laboratory and that reproducible results were obtained. The three methods were able to discriminate the test chemicals according to their embryotoxic potential. In addition, within the scope of this study, a test chemical database for in vitro embryotoxicity testing was established that will be used in the following formal validation of the three in vitro tests.

Interpregnancy interval as a risk factor for placenta accreta

OBJECTIVE

To determine if the interval from a previous delivery or cesarean to the next conception differs between patients with abnormally adherent placentas as compared to those with normally implanted placentas.

METHODS

We identified all histologically confirmed placentas--accreta, increta, and percreta--at our hospital from 1992-1999. Subjects were excluded for primigravidity in the affected pregnancy or inability to identify matched controls. Cases were matched to the next three consecutive women delivering for maternal age (> or = 35 years or < 35 years), placenta previa (yes or no), prior cesarean (yes or no), prior uterine curettage (yes or no), and prior vaginal delivery (yes or no). The primary outcomes were delivery-to-conception and cesarean-to-conception intervals. Secondary outcomes included measures of maternal and neonatal morbidity.

RESULTS

Delivery-to-conception intervals for cases and controls were 37.1 +/- 18.7 months and 37.9 +/- 22.7 months, respectively (P = .91). Cesarean-to-conception intervals for cases and controls were 35.2 +/- 18.2 and 48.1 +/- 31.0 months, respectively (P = .35). Cases were more likely to require uterine curettage (54.5 vs 0%), hysterectomy (81.8 vs 0%), and transfusion (72.7 vs 0%), all P < .001. Subjects with accreta delivered earlier (31.7 +/- 9.4 vs 38.1 +/- 2.6 weeks, P = .054) and smaller infants (2,158 +/- 1,180 g vs 3,159 +/- 781 g, P = .006) who were more likely to have five-minute Apgar scores < 7 (18.2% vs 0%, P = .038).

CONCLUSIONS

Cesarean-to-conception intervals but not delivery-to-conception intervals are shorter in patients with abnormally adherent placentas. Placenta accreta is associated with significant maternal and perinatal morbidity.

[Liver transplantation in a small center: feasibility, efficacy and prospects]

Today, orthotopic liver transplantation is the treatment of choice for the end-stage of various liver diseases, and a 1-year survival rate of 80% and a 5-year survival rate of 70% in elective patients without tumor are reported in international surveys. The liver transplant programme of the Inselspital in Bern is small compared with international centres, which may raise questions about the results and the justification for such a programme. Over a period of 66 months, 62 liver transplantations were performed in 60 patients at the Inselspital. The hospital mortality was 3.3%, and the 2.5-year overall survival rate was 92% for elective cases without tumor. After a median follow-up of 30 months, 68% of all patients were re-integrated in housework or full- or part-time in their profession, and 83% were independent from the help of others. We conclude that a small liver transplant programme based only on routine resources can achieve results comparable to the international standards.

Clonal descent and microevolution of Neisseria meningitidis during 30 years of epidemic spread

Serogroup A meningococci of subgroups III, IV-1 and IV-2 are probably descended from a common ancestor that existed in the nineteenth century. The 10.5kb sequences spanning five distinct chromosomal loci, encoding cell-surface antigens, a secreted protease or housekeeping genes and intergenic regions, were almost identical in strains of those subgroups isolated in 1966, 1966 and 1917 respectively. During the subsequent two to three decades, all of these loci varied as a result of mutation, translocation or import of DNA from unrelated neisseriae. Thus, microevolution occurs frequently in naturally transformable bacteria. Many variants were isolated only once or within a single geographical location and disappeared thereafter. Other variants achieved genetic fixation within months or a few years. The speed with which sequence variation is either eliminated or fixed may reflect sequential bottlenecks associated with epidemic spread and contrasts with the results of phylogenetic analyses from bacteria that do not cause epidemics.

Allelic polymorphism and site-specific recombination in the opc locus of Neisseria meningitidis

The opc gene is widespread in epidemic and endemic Neisseria meningitidis, but most strains of certain epidemic clones (ET-37 complex, Cluster A4) and a few random endemic isolates lack an opc gene. Four percent of the 1148 bp that contain opc plus the surrounding intergenic region was polymorphic (18 alleles), and many of the alleles contained a 230 bp insertion at a fixed location in the intergenic region. The presence or absence of the insertion reflects site-specific recombination. The alleles are stably inherited within clonal groupings for up to at least 50 years, with rare cases of horizontal genetic exchange. Most statistical methods indicated significant intragenic recombination events within this dataset.

Different hemodynamic effects of celipropol and atenolol in patients with mild to moderate hypertension

The hemodynamic effects of celiprolol (CAS 56980-93-9), a betablocker with beta 1 antagonist and beta 2 agonist properties, were compared with those of atenolol (CAS 29122-68-7) in 12 patients with mild to moderately severe hypertension (diastolic BP 95-110 mmHg). Celiprolol and atenolol lead to a similar and significant reduction of systolic and diastolic blood pressure (p < 0.005). However, with celiprolol heart rate at rest was significantly less depressed then with atenolol (p = 0.004) and showed a distinctly less pronounced depression of heart rate with exercise (p = 0.004). Cardiac output at rest was reduced by 19% under atenolol, but was increased by 9% under celiprolol treatment; in this respect, the two medications differed significantly (p = 0.03). The adaptation of heart rate and cardiac output to exercise was better with celipropol as compared to atenolol treatment. The difference between arm arterial pressure and ankle occlusion pressure at rest was not significantly influenced by atenolol, whereas celiprolol treatment increased this difference by a mean of up to 16 mmHg (p = 0.009). This different effect on peripheral arterial circulation was even more pronounced after exercise. Both celiprolol and atenolol increased blood cell flow velocity in the nailfold capillaries, but this increases was statistically only significant with celiprolol (p = 0.047). These results demonstrate that the hemodynamic effects of celiprolol were significantly different from those of atenolol; celiprolol produces less bradycardia, increases cardiac output at rest and decreases peripheral arterial resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

[Congenital heart defects: prevalence and course during the school years (8 to 16 years)]

In continuation of former studies regarding the first year of life and the preschool period, the prevalence and course of congenital heart disease in children during compulsory schooling has been studied. Compared with the preschool period, few cardiac defects are discovered, the prevalence up to 16 years of age being 9.9/1000. The mortality rate (2.7%) and also the rate of spontaneous normalization (4%) is significantly lower (compared to 18.7% and 21% respectively in the preschool period). Medical measures are needed less frequently, with 10 times fewer operations and 15 times fewer heart catheterizations being performed. Apart from the decline of hospital stays, checkups in the outpatient clinic also declined 3-4 times in comparison with the period between birth and school entry. School performance is very good. Only 4% of the children are unable to attend a normal school for cardiac reasons, and the percentage of pupils attending secondary school is higher than normal. In 5% of the children exercise tolerance is decreased due to the cardiac condition. In 85%, the quality of life is normal during the compulsory school period. Impairment is most often caused by additional non-cardiac malformations or very severe heart disease.

Microevolution within a clonal population of pathogenic bacteria: recombination, gene duplication and horizontal genetic exchange in the opa gene family of Neisseria meningitidis

Opacity (Opa) proteins are a family of antigenically variable outer-membrane proteins of Neisseria meningitidis. Even among clonally related epidemic meningococcal isolates, there is greater variation of Opa protein expression than can be accounted for by the opa gene repertoire of any individual strain. We characterized the opa genes of eight closely related isolates of serogroup A N. meningitidis (subgroup IV-1) from a recent meningitis epidemic in West Africa. DNA sequence analysis and Southern blot experiments indicated that changes occurred in the opa genes of these bacteria as they spread through the human population, over a relatively short period of time. Such changes in one or a few loci within a clonal population are referred to as microevolution. The distribution of sequences present in hypervariable (HV) regions of the opa genes suggests that duplication of all or part of opa genes into other opa loci changed the repertoire of Opa proteins that could be expressed. Additional variability in this gene family appears to have been introduced by horizontal exchange of opa sequences from other meningococcal strains and from Neisseria gonorrhoeae. These results indicate that processes of recombination and genetic exchange contributed to variability in major surface antigens of this clonal population of pathogenic bacteria.

[Sedation versus general anesthesia in pediatric endoscopy]

Upper endoscopy was performed in 567 patients: 237 under general anesthesia, 261 in intravenous sedation with midazolam and etomidat (mean dosage 0.26 mg/kg bodyweight), 69 without any premedication. In these many patients defended strongly and some investigations have to been interrupted. On the other hand general anaesthesia needed much more time and personnel and produced more costs. In our experience sedation with midazolam and etomidat is most comfortable for patient and endoscopist and the time needed is shorter than in general anaesthesia. Therefore we recommend this method even in therapeutic endoscopy, except only in sclerotherapy of esophageal varices.

[Electron microscopic studies of fimbriae and lectin phagocytosis of Salmonella typhimurium variety copenhagen (STMVC)]

On Salmonella typhimurium variatio copenhagen (STMVC) strains, isolated from pigeons with acute Salmonellosis, two types of fimbriae can be identified, depending on different growth conditions. In addition to the common 7 nm fimbriae we were able to demonstrate in the electron microscope, thin, curled fimbriae 3 nm in diameter which are characterized by a mannose-resistant hemagglutination. The simultaneous expression of both types of fimbriae on a single bacterial cell can be induced by transferring a microcolony from agar medium (3 nm fimbriae), to the surface of a nutrient broth (7 nm fimbriae) and continuing the incubation. One selected strain expresses only the thin fimbriae on nearly all the bacteria on an agar medium. These thin fimbriae seem to play a role in the lectinophagocytosis in macrophage cultures. The attachment of Salmonellae mediated by these fimbriae as well as the internalization of fimbriated cells by macrophages is shown in the electron microscope and discussed in respect to infection and immunization.

[Molecular biologic methods for epidemiological precision characterization of disease agents using Salmonella enteritidis from poultry as an example]

The principles of molecular biological methods for epidemiological investigation of infectious bacteria are described. They were applied for differentiating S. enteritidis isolates originating from poultry. Among the methods described are the determination of the chromosomal DNA fingerprints (BRENDA), the methods of multilocus enzyme electrophoresis, plasmid profiles, and the outer membrane protein as well as lipopolysaccharide pattern. It turned out, that S. enteritidis strains isolated before 1987, in 1988 and the ones originating from Great Britain did not differ in anyone of these criteria. Consequently one has to assume, that the strains recently causing problems originate from the population of S. enteritidis which had existed in poultry before.

[Colonoscopy: indications, procedure, results]

Colonoscopy in childhood is indicated as a valuable procedure mainly in rectal bleeding and suspected inflammatory bowel disease. Because of high efficiency and low complication rates this procedure should be used more often.

[Sonographic diagnosis of solid space-occupying abdominal lesions in childhood]

Between 1981 and May 1986 31 children with solid abdominal tumor masses were observed in our clinic. The first diagnostic procedure was a sonographic examination, followed by further radiological investigations if necessary. 30 cases were examined histologically; in one case the sonographic findings were confirmed by an angiography. The most frequent abdominal masses were neuroblastomas and Wilms tumors (7 cases each). A mesoblastic nephroma was diagnosed in 3 cases, a lymphoma, a hepatoblastoma and a rhabdomyosarcoma 2 times each. One time we found a pancreas carcinoma, a teratoma, a hemangiomatosis of the liver, a malignant Schwannoma, a Ewing sarcoma, an adenoma of the adrenal gland, a pheochromocytoma and an osteosarcoma. According to our own experience and recent reports in the literature it seems possible in most cases, to predict the correct diagnosis of solid abdominal masses using the informations of sonographic imaging. Sonography is a highly specific non-invasive diagnostic tool for planning treatment (e.g. early surgery, cytostatic therapy and/or radiation) of solid abdominal masses. Nevertheless the histological examination should be performed in every case to confirm the definitive diagnosis.

The mom gene of bacteriophage Mu: the mechanism of methylation-dependent expression

Transcription of the DNA modification gene (mom) of bacteriophage Mu requires methylation of three GATC sites upstream of the mom promoter by the Escherichia coli deoxyadenosine methylation function (Dam). The three sites map within a 40-bp segment termed region I. Small deletions, inversions, duplications and specific point mutations have been introduced in region I. Their effect on mom expression has been studied in dam+ and dam strains. Dam-dependent expression of the mom gene requires a specific arrangement of the three GATC sites and the presence of the methylated base in at least two of the three sites. We show that mom specific modification is regulated by a host protein. The Mom function is expressed in dam strains if they are defective in one component of the methylation-instructed mismatch correction system, mutH. We suggest that the product of mutH functions as a transcriptional repressor by binding to region I.

Epidemiology and chromosomal location of genes encoding multiresistance in Salmonella dublin

Multiresistant Salmonella dublin strains isolated between 1971 to 1984 were investigated for their genetic and physical properties. It turned out that the multiresistance of the 1971 to 1973 isolates was plasmid-encoded. In the following years, however, the plasmid profiles of the strains were indistinguishable from sensitive isolates and the genes encoding the multiresistance were located on the Salmonella chromosome.

The mom gene of bacteriophage mu: a unique regulatory scheme to control a lethal function

The mom gene of bacteriophage Mu encodes a DNA modification function which converts adenine to acetamido adenine in a sequence-specific manner. The mom gene itself is subject to a complex regulation: gene expression requires methylation by the Escherichia coli Dam methylase of specific sites upstream of the mom promoter and transactivation of the promoter by a Mu gene product. The requirement for transactivation can be overcome when mom is transcribed from foreign promoters. When cloned into various sites in pBR322, the mom gene is always found in an orientation where transcription from vector promoters is excluded. The productive orientation is lethal to the cell. This effect is mediated by the concerted action of the mom gene product and the product of gene com (control of mom, previously termed ORF-x) whose coding region overlaps the 5-coding region of the mom gene. When mom is expressed from its own promoter, internal deletions in com completely abolish expression of the mom gene. Fragments lacking the 5' end of com can be cloned downstream of constitutive plasmid promoters. The com gene product itself is not lethal to the cell. The region encoding mom has been cloned in pL expression vectors. The mom gene product, a peptide of 27 kDal, has been visualized on gels. Efficient expression of Mom from pL requires gene com. A fusion between MS-2 polymerase and com has been generated. The fusion product is made in large amounts, whereas the mom gene product is not overproduced although the gene is present on the same transcriptional unit.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal glycosuria in patients with the nephrotic syndrome

Transient or persistent renal glycosuria may occur in patients with the nephrotic syndrome. In an attempt to elucidate its mechanism, glucose titration experiments were performed in 20 nephrotic patients. The type A titration curve was found in one and type B in four patients with severe organic changes and low glomerular filtration rate. The remaining subjects displayed a particular type of curve (type C) characterized by a low point of splay but an otherwise almost physiological tracing. In type B and C patients the maximal rate of reabsorption per ml glomerular filtrate (TmG/GFR) was significantly increased and correlated inversely with the filtration fraction. In these patients the point of splay correlated with the glomerular filtration rate and the sodium clearance, but not with the plasma albumin concentration or the rate of proteinuria. These observations suggest that type A was due to diffuse tubular atrophy, and type B to increased nephron heterogeneity resulting from chronic organic changes. Type C was presumably caused by a potentially reversible alteration of the late proximal or distal glucose transport related to the nephrotic syndrome itself.

[Galactomannan breakdown in germinating carob seeds (Ceratonia siliqua L.)]

In the first days of germination of carob seeds (Ceratonia siliqua L., Leguminosae) (until penetration of the seed coat by the radicle) oligosaccharides of the raffinose series present in the endosperm and embryo are hydrolysed. The mobilisation of the reserve galactomannan of the endosperm begins after the emergence of the radicle. Its degradation is effected by hydrolytic enzymes (α-galactosidase [EC 3.2.1.22], β-mannanase, [EC 3.2.1.25] and β-mannosidase [EC 3.2.1.25]) and the breakdown products-galactose and mannose-are continuously metabolised by the embryo. At the same time starch synthesis is observed in the embryo.In the germination of Ceratonia siliqua seeds the embryo does not have a direct effect on the mobilisation of the reserve polysaccharide as it does in the case of barley. The endosperm consists of living cells which, independently of the embryo, synthesise the enzymes used for galactomannan breakdown. A weak α-galactosidase activity is already present in the endosperm of mature dry seeds. This activity cannot be suppressed by inhibitors of transcription or translation, so that their presence does not prevent degradation of oligosaccharides of the raffinose series.A high proportion of the α-galactosidase responsible for the breakdown of the galactomannan is synthesised de novo during germination. Such synthesis could be demonstrated by the incorporation of [U-(14)C]serine and could be inhibited by actinomycin D or cycloheximide.

[Treatment of Paget's disease with phosphonates]

A group of 22 patients with Paget's disease of bone was treated with a diphosphonate (sodium etidronate; EHDP), a stable synthetic analogue of inorganic pyrophosphate. This substance was given during 3 months at the dose of 20 mg/kg body weight per day, and proved effective by reducing the raised urinary excretion of total hydroxyproline and by lowering the concentration of serum alcaline phosphatase. It also improved the disease-related osteo-articular pain in 60% of the patients. A rise in serum phosphate under EHDP therapy is due to the increase in renal tubular reabsorption of phosphate. Bone histology showed regression of disease activity and the appearance of lamellar structure in newly formed bone. Because of a transient increase of the amount of uncalcified osteoid, it is advisable to give the diphosphonate in courses not over 3 months or at a reduced daily dose.