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S Adam

Publications and source records attributed to S Adam.

At least 91 records · Page 5Linked to original sources
PubMed1989

Use of a laser diffraction particle sizer for the measurement of mean diameter of multicellular tumor spheroids.

Increasing use is being made of tumor cell lines cultured as cell aggregates (generally referred to as multicellular spheroids) in in vitro radiosensitivity and/or chemosensitivity tests. Conventional procedures for the determination of mean spheroid diameters for the construction of growth delay curves employ a microscope-image analyzer. However, this approach can prove excessively time consuming when large numbers of samples have to be measured. We have, therefore, been exploring the use of a Laser Diffraction Particle Sizer, the Malvern 2600 long bench model, for the measurement of mean spheroid diameter and size distribution. We report here a direct comparison between measurements carried out by the instrument and under the microscope. Also a comparison of growth curves for six cell lines constructed from measurements by the microscope and by the instrument. A number of factors that might affect the accuracy of spheroid diameter measurement by the instrument have been investigated: The effect of stirring to maintain the spheroids in suspension during measurement. Sampling error due to removal of a series of spheroid samples from culture flasks for measurement. Optimum numbers of scans to be carried out by the instrument to reach a constant value for mean diameter, and minimum SE of the mean.

Animals↗
PubMed1988

Conformational flexibility in the right-handed and in the left-handed double helices of Na+-d(m5C-G-T-A-m5C-G) studied by IR spectroscopy.

The X ray diffraction study of a d(m5C-G-A-T-m5C-G) crystals has shown the existence of a 2 conformation while the Raman spectroscopy study of the same fragment in solution showed that then the oligonucleotide adopted a B geometry. Infrared spectroscopy has allowed us to study this sequence in films in a wide range of hydrations and to vary the water content of the sample at different rates. We have thus obtained four I.R. spectra, of the B and 2 conformations respectively at 100% and 98% relative humidities, of another 2 form with a different geometry of the phosphate groups at relative humidities below 98% and in addition a fourth spectrum recorded after a rapid dehydration of the sample which is then blocked in a right-handed form at low R.H. In this case the structure of the phosphodiester chain may be not uniform. The results are discussed by comparison with previously obtained I.R. spectra of poly d(G-C), poly d(A-C). d(G-T), d'm5C-G-A-m5C-G-T-G-C-G) d(m5C-G-C-G-m5C-G) and d(C-G-m5C-G).

DNA↗
PubMed1988

[Nuclear medicine diagnosis of Alzheimer type dementia].

Eleven patients with Alzheimer type dementia were investigated by single-photon-emission computed tomography (SPECT) using 99mTc-hexamethylpropylene-aminoxim (HM-PAO). Nine had a typical, symmetrically reduced enrichment in the parieto-temporo-occipital area. In three of these nine patients a similar pattern was recorded additionally in the frontal, in the remaining two in the temporal or parietal region. In a semi-quantitative evaluation radioactivity concentrations in the cerebrum and cerebellum were compared. It demonstrated that there was in relation to the cerebellum a reduced concentration in seven of the eight studied cerebral regions. The relative blood flow of the parieto-temporo-occipital region was most markedly affected and in patients with Alzheimer type dementia was reduced by 25% below that of normal subjects. The results indicate that cerebral SPECT with HM-PAO is a reasonable method of investigation to confirm the diagnosis of "Alzheimer type dementia" and exclude other cerebral disease, especially if pathognomonic findings are to be obtained.

Alzheimer Disease↗
PubMed1988

IR and UV studies on stability and conformations of short DNA duplexes containing a no-base residue: coexistence of B and Z conformations.

Tridecamers containing a central no-base residue (X) have been synthesized and hybridized to their complementary strands, so as to constitute duplexes consisting of two hexamers separated by central mismatched X-A or X-T pairs. The effect of the introduction of this deoxyribose derivative on duplex stability was investigated by measuring UV absorbance as a function of salt concentration and temperature. As expected, the duplexes containing the abnormal base pairs (X-T and X-A) are less stable when compared to the totally complementary duplexes (A-T and T-A). The X-T mismatched duplex shows the most unstable thermodynamical behaviour. The conformational changes of these duplexes were studied by IR spectroscopy in condensed phase as a function of water content. At high relative humidity, the IR spectra show that these tridecamers form B-type double stranded duplex structures. If the water content is decreased, only the duplexes m5CGm5CGCTXAGCTTC GCGCGAATCGAAG and, to a lesser degree, m5CGm5CGCTXAGCTTC GCGGCATTCGAAG undergo a partial B---Z transition involving the methylated hexamer, the conformation of the second segment remaining of the B type. These results show that only one apurinic residue leads to a flexible junction between B and Z forms in a short duplex containing 5-methyl-2'-deoxycytidines.

Base Composition↗
PubMed1988

[Significance of the specialized treatment clinic for the rehabilitation of diabetic patients].

Since January 1, 1986 all our diabetes mellitus patients have participated in a structured diabetes education programme of two weeks duration. A systematic review of 260 diabetic patients treated by us up to June 30, 1987, has shown that only 25 (9.6%) had been suitably informed about their disease. Necessary therapeutic consequences, such as strict dietetic measures, additional insulin therapy or intensified conventional insulin therapy, were more readily understood and accepted after the education course. The basic conditions present in a specialized rehabilitation clinic are more favourable in view of good longterm metabolic control than in the acute hospital or in general practice.

Adult↗
PubMed1986

Right- and left-handed helixes of poly[d(A-T)].poly[d(A-T)] investigated by infrared spectroscopy.

The secondary structures of double-stranded poly[d(A-T)].poly[d(A-T)] in films have been studied by IR spectroscopy with three different counterions (Na+, Cs+, and Ni2+) and a wide variety of water content conditions (relative humidity between 100 and 47%). In addition to the A-, B-, C-, and D-form spectra, a new IR spectrum has been obtained in the presence of nickel ions. The IR spectra of Ni2+-poly[d(A-T)].poly[d(A-T)] films are analyzed by comparison with previously assigned IR spectra of left-handed poly[d(G-C)].poly[d(G-C)] and poly[d(A-C)].poly[d(G-T)], and it is possible to conclude that they reflect a Z-type structure for poly[d(A-T)].poly[d(A-T)]. The Z conformation has been favored by the high polynucleotide concentration, by the low water content of the films, and by specific interactions of the transition metal ions with the purine bases stabilized in a syn conformation. A structuration of the water hydration molecules around the double-stranded Ni2+-poly[d(A-T)].poly[d(A-T)] is shown by the presence of a strong sharp water band at 1615 cm-1.

Nucleic Acid Conformation↗
PubMed1986

Interaction of transition metal ions with Z form poly d(A-C).poly d(G-T) and poly d(A-T) studied by I.R. spectroscopy.

Interactions between Ni2+, Co2+ and purine bases have been studied by I.R. spectroscopy in the case of double stranded regularly alternating purine-pyrimidine polynucleotides poly d(A-T), poly d(A-C).poly d(G-T) and poly d(G-C). The spectra of polynucleotide films have been recorded in hydration and salt content conditions which correspond to the obtention of the classical right-handed (A,B) and left-handed (Z) helical conformations. Selective deuteration of the 8C site of purines has been obtained and is used to detect interactions between the transition metal ions and the adenine or guanine bases. The spectral region between 1500 and 1250 cm-1 corresponding to base in-plane vibrations and involving also the glycosidic linkage torsion is discussed in detail. The selective interaction between the transition metal ion and the 7N site of the purine base is considered to be partly responsible for the stabilization of the base in a syn conformation, which favours the adoption by the polynucleotide (poly d(G-C), poly d(A-C).poly d(G-T) or poly d(A-T)) of a Z type conformation.

Cobalt↗
PubMed1986

NMR, CD and IR spectroscopies of a tridecanucleotide containing a no-base residue: coexistence of B and Z conformations.

The synthesis of the tridecadeoxynucleotide d(CGm5CGCGxACATGT), where x is the 1-cyano-2-deoxy-beta-D-erythropentofuranose, is described. The NMR, IR, CD studies at various salt concentrations and temperatures of this oligomer show that the B and Z conformations are simultaneously present in the same short DNA fragment. A single apurinic residue is sufficient for the coexistence of the B and Z helices on this oligomer.

Base Sequence↗
PubMed1986

Infrared spectral studies of the non regularly alternating purine-pyrimidine hexamers d(m5CGGCM5CG), d(CBr8GGCCBr8G) and d(CGCGGC).

The oligonucleotides d(m5CGGCm5CG), d(CBr8GGCCBr8G) and d(CGCGGC) have been prepared and studied by infrared spectroscopy. The three sequences contain two GC pairs which are out of purine-pyrimidine alternation with the rest of the sequence. From the IR data of the d(m5CGGCm5CG) hexamer, it is shown that all of the dG residues adopt a syn conformation. The marker IR bands for the C3' endo syn conformation are at 1410, 1354, 1320 and 925 cm-1 whereas those for the C2' endo anti conformation at 1420, 1374 and 890 cm-1 are clearly absent. This result implies that the two adjacent guanines of the d(m5CGGCm5CG) sequence are in syn conformation. It is suggested that duplex formation occurs in d(CGCGGC) films and that all of the guanines are in syn conformation. In contrast, the central non-brominated guanine of the d(CBr8GGCCBr8G) hexamer is found in anti conformation, as expected in a Z type structure of the non-alternating region.

Base Sequence↗
PubMed1986

Potential prodrugs of 6-acetylmethylenepenicillanic acid (Ro 15-1903).

The synthesis and biological activities of a series of non-classical penicillins are described. These compounds were synthesized by treating the pivaloyloxymethyl ester of 6-acetylmethylenepenicillanic acid (Ro 15-1903) with various nucleophiles. They were found to be less active against the beta-lactamases from Proteus vulgaris 1028, Escherichia coli 1024, Klebsiella pneumoniae NCTC 418 and E. coli RTEM than the parent compound. Nevertheless, synergy with ampicillin against whole bacterial cells producing beta-lactamases was evident, although the single compounds did not exhibit antibacterial properties. With the compounds 2a and 2b, synergistic interaction with ampicillin could also be demonstrated in mice.

Ampicillin↗
PubMed1984

Left-handed helical structure of poly[d(A-C)].poly[d(G-T)] studied by infrared spectroscopy.

Infrared spectroscopic studies demonstrate the ability of poly[d(A-C)].poly[d(G-T)] to adopt a Z-type conformation. The Z form of the unmodified polynucleotide is induced by Ni2+ counterions and not by Na+. The B----Z equilibrium is shifted at room temperature, in the presence of 1 Ni2+/nucleotide, by an increase in the concentration of poly[d(A-C)].poly[d(G-T)]. The importance of specific binding of Ni2+ ions on the N7 site of purines in the stabilization of the Z form is also discussed.

Cations↗
PubMed1984

The B----Z transition in two synthetic oligonucleotides: d(C-2-amino-ACGTG) and d(m5CGCAm5CGTGCG) studied by IR, NMR and CD spectroscopies.

The sequences CA'CGTG (where A' = 2-aminodeoxyadenosine) and m5CGCAm5CGTGCG are prepared and studied by IR, CD and 1H-NMR. Infrared spectra demonstrate the capacity of the modified hexamer and decamer to adopt a Z conformation. The influence of the NH2 substitution on the adenine or of the methylated terminal part of the decamer acting with the increase of the DNA concentration stabilizes the Z conformation at room temperature in low humidity films. Very weak proportion of Z conformation is detected in UV dilute solutions. In more concentrated NMR solutions, the Z proportion induced by high salt content is only 20-25%. The effects of the concentration and of the covalent modification of the bases are discussed.

5-Methylcytosine↗
PubMed1983

Mechanism of inactivation of TEM-1 beta-lactamase by 6-acetylmethylenepenicillanic acid.

The interaction between 6-acetylmethylenepenicillanic acid (compound Ro 15-1903; AMPA) and TEM-1 beta-lactamase was investigated in order to elucidate the mechanism of action of AMPA. Formation of the enzyme-inhibitor complex (EA) was accompanied by a shift of the absorbance maximum from 292 nm to 303 nm and an increase in the absorption. Regeneration of activity was very slow and incomplete, reaching about one-third of the initial activity after 48 h at 37 degrees C. This behaviour indicated a branched pathway of the decay of the inactivated enzyme. Kinetic and isoelectric-focusing experiments proved this assumption. The first-order constant of regeneration of active enzyme was 6 X 10(-6)-10 X 10(-6) s-1, whereas the rate constant leading to inactive enzyme (EA') was 10 X 10(-6)-15 X 10(-6) s-1 at pH 7.0. Both constants became larger at higher pH. Inactive enzyme (EA') consisted of two major species, with pI 5.36 (EA'1) and 5.30 (EA'2). The former increased at the beginning of incubation but decreased after prolonged incubation. From consideration of these results and previous data [Arisawa & Then (1983) Biochem. J. 209, 609-615], a likely mechanism of inactivation of TEM-1 beta-lactamase by AMPA is discussed.

Binding Sites↗