A long range restriction map of chromosome 5 of Plasmodium berghei demonstrates a chromosome specific symmetrical subtelomeric organisation.
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Animals↗
Biomedical subjects
R Scotti
Publications and source records attributed to R Scotti.
Structure and superstructure of Plasmodium falciparum subtelomeric regions.
Walking and jumping procedures were employed to obtain a consensus map of the 35-40 kb subtelomeric region shared by many chromosomal extremities in Plasmodium falciparum strain 3D7, and to characterise the portions flanking the rep20 tract, which is known to contain tandemly repeated, apparently degenerate, 21-bp repeats. The borders of rep20 were shown to harbour short (possibly locally homogenised) patterns of non-degenerate 12-, 17-, 23- and 28-bp repeats. The central repetitious portion of the consensus map was estimated to be about 18 kb in length, and to be separated from the telomere by approx. 11 kb of non-repetitious sequence, maintained with high fidelity at different chromosomal ends. Several kilobases of similarly conserved, non-repetitious sequence flank rep20 on its proximal side. Computer analysis of the rep20 sequence suggested that a peculiar superhelical winding originates from the conservation of identical nucleotide groups in phase with the pitch of the double helix, overcoming the effect of repeat degeneration in in other positions of the 21-bp unit.
Animals↗
Reliability of antagonistic arch impression in dental prostheses: clinical evaluation of different preimpression preparation procedures.
This study compared the influence of different methods of preimpression preparation on the quality of occlusal reproduction in irreversible hydrocolloid impressions. A total of 30 impressions of the lower dental arch of a patient were made with five different preimpression preparation procedures. Stone casts were made and analyzed. Critical comparison showed that the preimpression preparation influenced the quality of the occlusal surface of the cast. Fingerpainting the occlusal surface with fluid hydrocolloid before positioning the loaded impression tray, associated with use of a saliva ejector, reduced the incidence of macroscopic defects on the occlusal surface of the impressions.
Adult↗
Antimicrobial activity of MDL 63,246, a new semisynthetic glycopeptide antibiotic.
MDL 63,246 is a semisynthetic derivative of the naturally occurring glycopeptide antibiotic MDL 62,476 (A40926). It was more active in vitro against Staphylococcus aureus and coagulase-negative staphylococci than MDL 62,476, teicoplanin, and vancomycin and was more active than mideplanin (MDL 62,873) against some isolates. MDL 63,246 had excellent activity against streptococci and teicoplanin-susceptible enterococci, and it also had in vitro activity against some VanA enterococcal isolates. It was more active than teicoplanin and vancomycin against acute staphylococcal, streptococcal, and enterococcal septicemia in immunocompetent and neutropenic mice. It was highly efficacious in reducing the bacterial load in the hearts of rats in staphylococcal endocarditis experiments and the bacterial load of Staphylococcus epidermis in a high infection model in neutropenic mice. The excellent in vivo activity of MDL 63,246 appears to correlate both with its in vitro antibacterial activity and with its long half-life in rodents.
Animals↗
New semisynthetic glycopeptides MDL 63,246 and MDL 63,042, and other amide derivatives of antibiotic A-40,926 active against highly glycopeptide-resistant VanA enterococci.
A series of amide derivatives of natural glycopeptide A-40,926 (A), its 6B-methyl ester (MA) and 6B-decarboxy-6B-hydroxymethyl derivative (RA) were prepared with the aim of obtaining activity against glycopeptide-resistant enterococci. These compounds are structurally related to a class of amides of 34-de(acetylglucosaminyl)-34-deoxy teicoplanin which showed interesting activity against strains of Enterococcus faecalis and E. faecium highly resistant to both vancomycin and teicoplanin. Among them, RA-amides MDL 63,246 and MDL 63,042 were the most active derivatives against several Gram-positive bacteria, including VanB and VanC enterococci, and were moderately active (MIC range 0.5 approximately 64 micrograms/ml) against strains of Enterococcus for which vancomycin and teicoplanin MICs were > or = 128 micrograms/ml. The chemical rationale and the synthesis of these new series of glycopeptide derivatives are described. Preliminary in vitro data are reported and structure-activity relationships are discussed.
Anti-Bacterial Agents↗
[The biocompatibility of temporary cements. Longitudinal in-vitro analyses of the pH values].
In this longitudinal study the authors analyse the acid-basal characteristics in vitro of seven cements used in dentistry for a period of three weeks. The cements tested were subdivided into three groups based on their composition, whereas Life was presented separately since it is generally used as a sub-base for fillings in conservative treatment. All the materials studied alter the pH of the matter in which they are imbedded. Life and Tempbond present the highest and lowest pH values recorded during the study in vitro. The authors discuss the biological implications of these results.
Cluster Analysis↗
Synergic activity of teicoplanin and ethambutol against Mycobacterium tuberculosis.
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Drug Evaluation, Preclinical↗
Subtelomeric structure of Plasmodium falciparum chromosomes.
Previous studies of subtelomeric regions in Plasmodium berghei led to the identification of subtelomeric repeats (2.3kb long) present in a variable number at many chromosomal ends. Both loss and increase in 2.3kb-repeat copy number are involved in chromosome-size polymorphisms. Subtelomeric losses leading to chromosome-size polymorphisms have been described by several authors in P.falciparum where the structure of subtelomeric regions is not known in detail. We therefore undertook their characterisation, by means of chromosome walking and jumping techniques, starting from the telomere-flanking sequence present in pPftel.1, the P.falciparum telomeric clone described by Vernick and McCutchan (1988). The results indicate that at least 20 (out of 28) chromosomal ends in P.falciparum 3D7 chromosomes share a subtelomeric region, about 40kb long, covering (but not limited to) the Rep20 region. Non repetitive, AT-rich portions flanking the Rep20 region on both sides are also conserved at most chromosomal ends.
Animals↗
Amides of de-acetylglucosaminyl-deoxy teicoplanin active against highly glycopeptide-resistant enterococci. Synthesis and antibacterial activity.
Removal, by selective reduction, of the acetylglucosamine from teicoplanin A2-2 (CTA/2) produced the 34-de(acetylglucosaminyl)-34-deoxy pseudoaglycone (II). This compound was more active in vitro than CTA/2 against coagulase-negative staphylococci (CNS). Amide derivatives obtained by condensation of the carboxyl group of II with primary amines were particularly active against Streptococcus pyogenes and had some in vitro activity against VanA enterococci highly resistant to both teicoplanin and vancomycin. Among them, a carboxamide (VII) with a branched tetramine also had better activity than the corresponding amide of teicoplanin against CNS. In contrast, the dimethylamide (VIII) of II had little activity against VanA enterococci. While the overall structure of the heptapeptide backbone of the secondary carboxamides of II is the same as in CTA/2 and its amide derivatives, in deoxy pseudoaglycone II and its tertiary amide VIII the 51,52-peptide bond undergoes a conformational change from the original cisoid to the transoid orientation. This difference between the secondary amides of II and dimethylamide VIII is reflected in their different antibacterial spectrum. The direct synthesis of the amides of deoxy pseudoaglycone II from parent CTA/2-amides by reaction with sodium borohydride is also described.
Amides↗
[An experimental clinical evaluation of the influence of the blood circulation on the parapulpal thermal levels].
The aim of this study is the evaluation of pulpal blood flow effect on the thermal levels measured at the pulpodentin junction in human anesthetized premolars. The value have been recorded as discrepancies between peak temperatures caused by a thermal stimulus applied on the same tooth in two different conditions: with and without pulpal blood supply. Thermal stimuli ranged from 3 to 9 degrees C on a total of twelve teeth giving a mean peak difference of 1.3 degrees C. This result has been interpreted as the effect of thermal dissipation produced by pulpal blood flow. The small magnitude of the value suggests, however, that anesthetized pulp fails to protect itself from injurious heat by increasing pulpal blood flow.
Adolescent↗
[Materials for dies in fixed prosthesis: a comparative in-vitro analysis of their detail-reproducing capacity and of their surface quality].
The authors examine the detail reproduction capacity and surface roughness of 11 commercially available materials [6 plasters (stones?), 2 epoxy resins and 3 polyurethane resins] indicated for the construction of working models with individually extractable dies. The study was performed in vitro according to the method outlined by the ADA in specification no. 19 relating to materials for elastomeric imprints. This specification describes the use of a steel test-block with which it is possible to prepare a master imprint in polyvinylsiloxane. This imprint allows the grooves of the test-block to be reproduced in the form of angular crest which represent the details to be reproduced. Both the master imprint and the samples to be tested were prepared according to the manufactures instructions. The study was performed in three stages: macroscopic analysis, microscopic analysis, profilometric analysis. The macroscopic analysis did not show any differences between the different materials tested. The microscopic analysis showed that when enlarged 40 times the resins revealed a smoother surface than the plasters. The surface quality of plasters was improved by using a hardening solution recommended by the manufacturer as an alternative to water, or by using spacer paint. The plaster materials gave excellent angular definition contrary to the epoxy and polyurethane resins. The use, where advised, of the hardening solution as an alternative to water did not alter this parameter. The electronic profilometer used for the profilometric analysis comprised a diamond sensor which, when run along the surface, recorded all roughness, translating it into chart form.(ABSTRACT TRUNCATED AT 250 WORDS)
Dental Casting Investment↗
Papanicolaou smear screening augmented by a magnified chemiluminescent exam.
OBJECTIVES: Since the adequacy of screening for cervical cancer and pre-cancer with Papanicolaou smear alone has been questioned, a number of adjunctive tests have been evaluated. This study evaluated whether a magnified chemiluminescent visual screening exam can improve cervical screening when performed coincident with cytologic sampling. METHODS: Patients were evaluated using the Papanicolaou smear, magnified chemiluminescent visual exam (MCE) and colposcopy at 10 study centers. Screening with either Papanicolaou smear alone or in combination with MCE (Pap and MCE), was evaluated using colposcopy directed biopsy as the highest diagnostic standard. RESULTS: The Papanicolaou smear alone detected 9/29 (31%) of women with significant pathology (cervical neoplasia) on biopsy, whereas the combination of the Pap and MCE detected 24/29 (83%) of the women (P < 0.001). Patients in whom both tests results were negative (negative Pap and MCE) were extremely unlikely to harbor significant pathology (1% of those screened). Pap and MCE was especially helpful in the detection of low grade cervical lesions when compared with the Papanicolaou smear alone. CONCLUSIONS: These data indicate that MCE enhances the sensitivity of cervical screening. MCE appears to be particularly useful as a triage instrument in women with otherwise negative Papanicolaou smears. Further studies of cost effectiveness of this combined screening protocol using non-colposcopists is warranted.
Adolescent↗
A 40-kilobase subtelomeric region is common to most Plasmodium falciparum 3D7 chromosomes.
Starting from previous evidence indicating that some features are shared by several Plasmodium falciparum chromosomal extremities, a subtelomeric region present on most P. falciparum 3D7 chromosomes has been mapped. It was shown to occupy about 40 kb, and to include the proximal portion of pPftel. 1, the only telomeric clone described for P. falciparum [12], the complete 21-bp repetitive cluster and some conserved sites (PstI, EcoRI) proximally located with respect to this cluster.
Animals↗
Effect of protein on ramoplanin broth microdilution minimum inhibitory concentrations.
Ramoplanin is a glycolipodepsipeptide antibiotic active against Gram-positive bacteria. We observed that microdilution minimum inhibitory concentrations (MICs) were higher than those obtained in glass tubes or by agar dilution. Initial studies showed that these differences disappeared when 30% bovine serum was added to the broth. Further studies showed that addition of 0.01% bovine serum albumin (BSA) to the broth lowered the microdilution MICs for staphylococci, streptococci, and enterococci by four- to 32-fold. This phenomenon occurred in several commonly used growth media and in different types of commercially available microtiter trays. Precoating of the microtiter wells with a dilute solution of BSA (0.02%) had the same effect. It seems likely that ramoplanin adsorbs to plastic surfaces and is lost from solution, and that protein masks the sites of adsorption. Ramoplanin MICs may be reliably determined by broth microdilution if a small amount of protein is added to the diluent.
Adsorption↗
In vitro antimicrobial activity of a new antibiotic, MDL 62,879 (GE2270 A).
MDL 62,879 (GE2270 A) is a new peptide antibiotic that inhibits protein synthesis through an interaction with elongation factor Tu. MDL 62,879 was very active against gram-positive clinical isolates, particularly staphylococci and enterococci, for which MICs for 90% of isolates were < or = 0.13 micrograms/ml. It was equally active against isolates resistant to beta-lactams, erythromycin, gentamicin, and glycopeptides. It also had activity against Mycobacterium tuberculosis. MDL 62,879 had moderate bactericidal activity against staphylococci.
Anti-Bacterial Agents↗
Octapeptide derivatives of teicoplanin antibiotics.
A series of octapeptide derivatives of teicoplanin-A2 component 2 (CTA/2), its aglycone (TD), and the L-lysyl derivatives of an amide of CTA/2 and TD, were prepared by condensation of the terminal amino group with N-hydroxysuccinimidyl esters of tert-butyloxycarbonyl (BOC) L- and D-amino acids, followed by acidic (TFA) removal of the BOC protecting function. The antimicrobial properties of these compounds were compared with those of the corresponding unmodified antibiotics and their N15-acetyl derivatives. The most active derivatives were the octapeptides with N-terminal glycine or lysine whose in vitro activity was comparable to that of the parent teicoplanins. The glycinyl and lysyl derivatives of CTA/2 showed better activity than CTA/2 against clinical isolates of Staphylococcus epidermidis and S. haemolyticus for which teicoplanin MICs were relatively high. No significant difference in their antibacterial activity was observed between octapeptides containing L- or D-lysine.
Anti-Bacterial Agents↗
N63-carboxamides of N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin and deglucoteicoplanin.
The synthesis and biological properties of a series of N63-carboxamides of 15-N-alkylated derivatives of teicoplanin A2 (CTA) and its aglycone (TD) are described. Among the compounds, those carrying hydrophilic groups or ionizable amino functions on the N15-alkyl chain are more soluble in water than parent N15-methylated or unmodified amides. Selected compounds were more active in vitro than CTA or TD, and a few of them were also slightly more efficacious in vivo than the parent antibiotics in streptococcal septicemia in the mouse. Their degree of activity varied with the structure and length of the N15-alkyl chains.
Alkylation↗
Chromosomal polymorphism and sexual differentiation in Plasmodium.
The correlation observed in several instances between the loss of ability to produce gametocytes and chromosomal rearrangements, prompted us to investigate in further detail the molecular bases of chromosomal polymorphism in Plasmodium. Generation of polymorphic karyotypes in Plasmodium involves important rearrangements, mostly occurring in subtelomeric position. Detailed analysis on the organisation of these regions have been carried out on the rodent malaria P. berghei and the human malaria P. falciparum. A 2.3kb sequence, tandemly organised in long clusters is shared by many P. berghei chromosomal ends. Variations in the copy number of this "module" account for most of the observed polymorphisms. In a P. falciparum cloned line (3D7) a common region spanning at least 40 kb, is present. It does not contain any repetitive structure other than the rep20 cluster, that appears to be completely contained within the common region. Notwithstanding the structural differences, human and rodent Plasmodia share the common feature of possessing long subtelomeric regions showing, thus, a homology between the different chromosomes.
Animals↗