A single enhanced phase is sufficient for the initial computed tomography evaluation of retroperitoneal tumors in children.

PURPOSE: The goal of this study was to evaluate the incremental value of unenhanced phase in the initial evaluation of retroperitoneal tumors in children by comparison with an enhanced phase alone using computed tomography (CT). MATERIALS AND METHODS: A total of 53 patients (26 girls, 27 boys) with a total of 53 tumors who had CT examination of the abdomen and pelvis for the initial assessment of retroperitoneal tumor were retrospectively included. All CT examinations were obtained with an unenhanced set of CT images and a set of CT images obtained after intravenous administration of iodinated contrast material. One junior and one senior radiologist independently evaluated the two sets in two separate reading sessions. CT images were analyzed for tumor calcifications, tumor location, vascular encasement, local invasion and tumor content. RESULTS: Calcifications were present in 24/53 tumors (45%). On the enhanced set, the senior radiologist was able to detect calcifications in 22/24 tumors (92%) and the junior radiologist in 20/24 tumors (83%), yielding sensitivities of 92% and 83%, and specificities of 96.5% and 100%, respectively. Inter-observer agreement was excellent (Kappa=0.89). Tumor location was correctly determined by the senior radiologist in 53/53 tumors (100%) and 37/53 tumors (70%) by the junior radiologist. Using the unenhanced set, the senior radiologist was able to assess vascular encasement in 26/53 tumors (49%) against 21/53 (39%) for the junior radiologist. For tumor content, agreement between the enhanced and combined unenhanced and enhanced CT was 77% for both radiologists. CONCLUSION: Enhanced CT performs as well as unenhanced CT for evidencing calcifications and is therefore sufficient for the initial assessment of retroperitoneal tumor in children.

The use of computed tomography and nuclear medicine examinations in paediatric oncology: An analysis of practice in a university hospital.

PURPOSE: The purpose of this study is to evaluate, in terms of number of examinations and how effective doses are distributed by location and chronology, the use of CT and nuclear medicine examinations in the management of paediatric oncology patients. MATERIALS AND METHODS: This was a retrospective and descriptive study that included 57 children (13 with neonatal neuroblastoma, 18 with renal tumours, and 26 with lymphoma) over a 5-year period, with the length of monitoring ranging from 1 to 7 years. All CT scans and nuclear medicine examinations were counted, and the effective doses calculated. RESULTS: The majority of the examinations were performed during the first year of management. The cumulative effective doses ranged from 7-152 mSv. The lymphoma group received the highest doses, but fewer than 10% of children received in excess of 100 mSv, as against 40% in the North American study published by Chawla et al. CONCLUSION: The usage of irradiating diagnostic radiological examinations in paediatric oncology produces considerable effective doses, which must lead us to consider evaluating our practices, exploring all possible ways to improve protection from radiation, especially in terms of justifying investigations and using alternatives.

High-resolution cutaneous ultrasonography to differentiate lipoedema from lymphoedema.

BACKGROUND: Lipoedema is an accumulation of fat abnormally distributed in the lower limbs, and lymphoedema is oedema caused by a deficiency of the lymphatic system. High-resolution ultrasound operating at 20 MHz makes it possible to characterize dermal oedema. OBJECTIVES: The purpose of our study was to demonstrate that high-resolution ultrasound imaging of the skin can differentiate lipoedema from lymphoedema. METHODS: Sixteen patients with lymphoedema (22 legs), eight patients with lipoedema (16 legs) and eight controls (16 legs) were included. Patients with lipolymphoedema were excluded. Ultrasound examinations were carried out with a real-time high-resolution ultrasound device on three different sites for each lower limb. The images were then anonymized and examined by an independent dermatologist who was blind to the clinical diagnosis. A new series of images was examined by three dermatologists to check interobserver agreement. RESULTS: A significant difference in dermal thickness was observed between patients with lymphoedema and those with lipoedema and between patients with lymphoedema and controls. No significant difference in dermal thickness was shown between patients with lipoedema and controls at the thigh or ankle. Dermal hypo-echogenicity was found in at least one of the three sites in 100% of patients with lymphoedema, 12.5% of cases with lipoedema and 6.25% of the controls. Hypoechogenicity affected the entire dermis in all cases of lymphoedema except one. In cases of lipoedema and controls, hypoechogenicity was localized at the ankle and prevailed in the upper dermis. The expert correctly diagnosed all lower limbs with lymphoedema. No cases of lipoedema were diagnosed as lymphoedema. Exact interobserver agreement was excellent (0.98). CONCLUSIONS: High-resolution cutaneous ultrasonography makes it possible to differentiate lymphoedema from lipoedema. Obtaining a reliable diagnosis through high-resolution cutaneous ultrasonography might be valuable for improving the treatment of lipoedema and lymphoedema.

Specific interactions in modified chitosan systems.

This paper concerns the bulk and interfacial properties of a series of alkylated chitosans having different alkyl chain lengths grafted randomly along the main chitosan chain. Chitosan has a low degree of acetylation (5%); on chitosan derivatives, the role of the degree of grafting and of length of the alkyl chains are examined. The optimum alkyl chain length is C12 and the degree of grafting 5% to get physical gelation based on the formation of hydrophobic domains. The cross-linking is essentially controlled by the salt concentration: it is shown that 0.025 M AcONa is needed to screen electrostatic interchain repulsions. Hydrophobic interactions produce highly non-Newtonian behavior with large thinning behavior; this behavior is suppressed in the presence of cyclodextrins able to cap the hydrophobic alkyl chains. The interfacial properties of the chitosan derivatives were tested for the air/aqueous solution interfaces. Specifically, the role of their structure on the kinetic of film formation was examined showing that excess of external salt favors the stabilization of the interfacial film. The derivatives with a higher degree of substitution and longer alkyl chains are more efficient and give a higher elastic modulus compared to the model surfactant as a result of the chain properties.

Antifungal activity of actinomycetes from Cuban soils.

This study reports on the capacity of actinomycete strains isolated from Cuban soils to produce antifungal agents. The antimicrobial activities were determined by susceptibility disk assay methods. We isolated 563 different actinomycetes and 286 produced compounds with antifungal activity. Our screening method indicated the presence of many possible polyene macrolide antibiotics and the important antifungal activity in the soils rich in minerals.

Secretion of human interferon alpha 2b by Streptomyces lividans.

Biologically active human interferon alpha 2b (HuIFNalpha-2b) was secreted into the culture medium by Streptomyces lividans transformed with recombinant plasmids coding for HuIFNalpha-2b fused to the Streptomyces exfoliatus M11 lipase A signal sequence. Levels were low, 15 or 100 ng/ml, depending on the plasmid used. Neither processed nor unprocessed HuIFNalpha-2b was detected in cell lysates of the transformants secreting the recombinant product. However, the secreted recombinant product was found to partially degrade when cultures reached the stationary phase by the action of an, as yet, unidentified mycelium-associated factor. Experimental evidence suggests that the degrading factor is related to mycelium-associated proteolytic activity.

Ecological approach of macrolide-lincosamides-streptogramin producing actinomyces from Cuban soils.

We report in this study the frequency of Streptomyces strains to produce macrolide-lincosamide-streptogramin (MLS) antibiotics isolated from Cuban soils. The screening assay is based on the induction of MLS-resistance phenotype in a clinical isolated strain of Staphylococcus aureus S-18. Our results suggest that of 800 Streptomyces strains isolated from different soil samples, 6% were positives in the screening test used. The ferralitic red soil from Pinar del Río (north) provided the major percentage (3.6%) of MLS producing strains. The other soil samples tested belonging to Guira de Melena and Bauta in Havana, Matanzas City, Topes De Collantes (Villa Clara), and Soroa Mountains (Pinar del Rio) hill reached very low percentages.

A silent ABC transporter isolated from Streptomyces rochei F20 induces multidrug resistance.

In the search for heterologous activators for actinorhodin production in Streptomyces lividans, 3.4 kb of DNA from Streptomyces rochei F20 (a streptothricin producer) were characterized. Subcloning experiments showed that the minimal DNA fragment required for activation was 0.4 kb in size. The activation is mediated by increasing the levels of transcription of the actII-ORF4 gene. Sequencing of the minimal activating fragment did not reveal any clues about its mechanism; nevertheless, it was shown to overlap the 3' end of two convergent genes, one of whose translated products (ORF2) strongly resembles that of other genes belonging to the ABC transporter superfamily. Computer-assisted analysis of the 3.4-kb DNA sequence showed the 3' terminus of an open reading frame (ORF), i.e., ORFA, and three complete ORFs (ORF1, ORF2, and ORFB). Searches in the databases with their respective gene products revealed similarities for ORF1 and ORF2 with ATP-binding proteins and transmembrane proteins, respectively, which are found in members of the ABC transporter superfamily. No similarities for ORFA and ORFB were found in the databases. Insertional inactivation of ORF1 and ORF2, their transcription analysis, and their cloning in heterologous hosts suggested that these genes were not expressed under our experimental conditions; however, cloning of ORF1 and ORF2 together (but not separately) under the control of an expressing promoter induced resistance to several chemically different drugs: oleandomycin, erythromycin, spiramycin, doxorubicin, and tetracycline. Thus, this genetic system, named msr, is a new bacterial multidrug ABC transporter.

Streptothricin biosynthesis is catalyzed by enzymes related to nonribosomal peptide bond formation.

In a search for strains producing biocides with a wide spectrum of activity, a new strain was isolated. This strain was taxonomically characterized as Streptomyces rochei F20, and the chemical structure of the bioactive product extracted from its fermentation broth was determined to be a mixture of streptothricins. From a genomic library of the producer strain prepared in the heterologous host Streptomyces lividans, a 7.2-kb DNA fragment which conferred resistance to the antibiotic was isolated. DNA sequencing of 5.2 kb from the cloned fragment revealed five open reading frames (ORFs) such that ORF1, -2, -3, and -4 were transcribed in the same direction while ORF5 was convergently arranged. The deduced product of ORF1 strongly resembled those of genes involved in peptide formation by a nonribosomal mechanism; the ORF2 product strongly resembled that of mphA and mphB isolated from Escherichia coli, which determines resistance to several macrolides by a macrolide 2'-phosphotransferase activity; the ORF3 product had similarities with several hydrolases; and the ORF5 product strongly resembled streptothricin acetyltransferases from different gram-positive and gram-negative bacteria. ORF5 was shown to be responsible for acetyl coenzyme A-dependent streptothricin acetylation. No similarities in the databases for the ORF4 product were found. Unlike other peptide synthases, that for streptothricin biosynthesis was arranged as a multienzymatic system rather than a multifunctional protein. Insertional inactivation of ORF1 and ORF2 (and to a lesser degree, of ORF3) abolishes antibiotic biosynthesis, suggesting their involvement in the streptothricin biosynthetic pathway.

Resistance patterns to beta-lactams and quinolones in clinical isolates of bacteria from Cuban hospitals.

The resistance patterns to 26 beta-lactams and 8 quinolones of clinical isolates from Cuban hospitals were evaluated using the disk susceptibility test, according to the NCCLS guidelines (1992). The genera studied were Escherichia sp (320), Enterobacter sp (10), Klebsiella sp (90), Proteus sp (10), Pseudomonas sp (90), Serratia sp (20), and Staphylococcus sp (80). Higher resistance to beta-lactams was observed in the genera Pseudomonas, Escherichia and Klebsiella. For fluoroquinolones we found no significant resistance, with the exception of the genus Klebsiella. The most effective antibiotics were cephalosporins of the second and third generations, fluoroquinolones, and non-classical beta-lactams (cephamycins, moxalactam and monobactams). On the contrary, a pronounced resistance was found to penicillin, oxacillin, ticarcillin, ampicillin, methicillin, nalidixic acid and cinoxacin. These resistance patterns correspond to the high consumption of these antibiotics throughout the country.

Antimicrobial activity of beta-lactams against multiresistant micro-organisms from the family Enterobacteriaceae, and genus Pseudomonas.

The antimicrobial activity of twenty beta-lactams was determined against multiresistant micro-organisms from the Enterobacteriaceae family (450) and the genus Pseudomonas (90). The antimicrobial susceptibility was assessed by the disk diffusion method. The most effective antibiotics were cephalosporins of the second and third generation, and non-classical beta-lactams (imipenem and moxalactam). A pronounced resistance was found to carbenicillin, ampicillin, cephalotin and cefazolin. These resistance patterns corresponded to a high consumption of these antibiotics.

Hybridization of Saccharomyces cerevisiae with Candida utilis through protoplast fusion.

Auxotrophic mutants of Saccharomyces cerevisiae and Candida utilis were hybridized through protoplast fusion. Spontaneous, UV- and FPA-induced mitotic segregation indicated that after cell fusion, exclusion of the S. cerevisiae nucleus or nuclear fusion followed by preferential loss of S. cerevisiae chromosomes can take place. Some of the hybrids were stable. One of them, expressed mating and sporulation functions of the S. cerevisiae parent. Thus, markers from both parents could be recovered as mitotic and meiotic segregants.

Diploid formation of Candida tropicalis via protoplast fusion.

Haploid auxotrophic mutants were produced from Candida tropicalis, and protoplast usion was induced by polyethylene glycol. The resulting nutritional complementation was due to heterokaryon formation and, at a much lower frequenty, to spontaneous diploidization. During cultivation, heterokaryotic clones regularly gave rise to heterozygous diploids from which, in turn, haploids could be isolated. The technique of protoplast fusion gives an opportunity for genetic analysis of this and similarly asexual fungal species.