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Biomedical subjects

G Valle

Publications and source records attributed to G Valle.

At least 55 records · Page 3Linked to original sources
PubMed1996

Identification of 4370 expressed sequence tags from a 3'-end-specific cDNA library of human skeletal muscle by DNA sequencing and filter hybridization.

A systematic study on the mRNA species expressed in the human skeletal muscle is presented in this paper. To carry on this study, a new method has been developed for the construction of unbiased cDNA libraries specially designed for the production of ESTs corresponding to the 3'-end portion of the mRNAs. The method has been applied to human skeletal muscle, where the analysis of the transcription profile is particularly difficult for the presence of several very abundant transcripts. To detect and quantify high-level mRNAs, the first 1054 ESTs were obtained from randomly selected clones. The 10 most abundant transcripts accounted for > 45% of the clones. Subsequently, these transcripts were identified by filter hybridization, thus making DNA sequencing more productive. Overall, 4370 clones were identified: 3372 by DNA sequencing and 998 by filter hybridization. The number of groups of sequences identifying individual transcripts was relatively low compared with other tissues, resulting in a total of 934 groups out of 4370 ESTs. Of these, 719 groups were represented by only one sequence.

Cloning, Molecular↗
PubMed1996

Crystallographic characterization of geometry and conformation of TOAC, a nitroxide spin-labelled C alpha,alpha-disubstituted glycine, in simple derivatives and model peptides.

The molecular and crystal structures of one derivative and two oligopeptides of TOAC, a nitroxide spin-labelled C alpha, alpha-disubstituted glycine, have been determined by X-ray diffraction. The derivative is the 5(4H)-oxazolone from Piv-TOAC-OH; the oligopeptides are Z-TOAC-(L-Ala)2-NHtBu sesquihydrate and pBrBz-TOAC-(L-Ala)2-TOAC-L-Ala-NHtBu hemihydrate. Incipient and fully developed right-handed 3(10)-helical conformations are formed by both independent molecules in the asymmetric unit of the terminally blocked tripeptide amide and the terminally blocked pentapeptide amide, respectively. The average geometry and preferred conformation for the piperidine ring of the TOAC residues are also discussed in detail.

Cyclic N-Oxides↗
PubMed1996

Semi-multiplex PCR technique for screening of abundant transcripts during systematic sequencing of cDNA libraries.

The systematic sequencing of cDNA libraries is an efficient approach for the identification of new genes, but the presence of abundant mRNAs is often a major problem. This paper describes a very simple method of "semi-multiplex PCR" that allows specific identification of such abundant transcripts before DNA sequencing without using nonrepresentative subtracted libraries. The PCR utilizes a series of forward primers specific for abundant transcripts with a pair of universal primers used for template generation. cDNA clones corresponding to abundant mRNAs are then revealed by double bands in agarose gel.

Base Sequence↗
PubMed1995

beta-turn conformations in crystal structures of model peptides containing alpha,alpha-di-n-propylglycine and alpha,alpha-di-n-butylglycine.

The crystal state conformations of three peptides containing the alpha,alpha-dialkylated residues, alpha,alpha-di-n-propylglycine (Dpg) and alpha,alpha-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Ala-OMe (I) and Boc-Ala-Dbg-Ala-OMe (II) adopt distorted type II beta-turn conformations with Ala (1) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: phi = 66.2 degrees, psi = 19.3 degrees; III: phi = 66.5 degrees, psi = 21.1 degrees) deviate appreciably from ideal values for the i + 2 residue in a type II beta-turn. In both peptides the observed (N...O) distances between the Boc CO and Ala (3) NH groups are far too long (I: 3.44 A; III: 3.63 A) for an intramolecular 4-->1 hydrogen bond. Boc-Ala-Dpg-Ala-NHMe (II) crystallizes with two independent molecules in the asymmetric unit. Both molecules IIA and IIB adopt consecutive beta-turn (type III-III in IIA and type III-I in IIB) or incipient 3(10)-helical structures, stabilized by two intramolecular 4-->1 hydrogen bonds. In all four molecules the bond angle N-C alpha-C' (tau) at the Dxg residues are > or = 110 degrees. The observation of conformational angles in the helical region of phi,psi space at these residues is consistent with theoretical predictions.

Amino Acid Sequence↗
PubMed1995

99mTc HM-PAO brain perfusion SPECT in brain death.

Diagnosis of brain death must be certain to allow discontinuation of artificial ventilation and organ transplantation. Brain death is present when all functions of the brain stem have irreversibly ceased. Clinical and electrophysiological criteria may be misinterpreted due to drug intoxication, hypothermia or technical artefacts. Thus, if clinical assessment is suboptimal, reliable early confirmatory tests may be required for demonstrating absence of intracranial blood flow. We have easily carried out and interpreted 99mTc HM-PAO SPECT in a consecutive series of 40 comatose patients with brain damage, without discontinuing therapy. Brain death was diagnosed in 7 patients, by recognising absence of brain perfusion, as shown by no intracranial radionuclide uptake. In patients in whom perfusion was seen on brain scans, HM-PAO SPECT improved assessment of the extent of injury, which in general was larger than suggested by CT.

Adolescent↗
PubMed1995

The preferred solid-state conformation of (alpha Me)Trp peptides.

The two Z-L-Ala-DL-(alpha Me)Trp-NH2 diastereomeric dipeptides were synthesized from (Z-L-Ala)2(O) and H-DL-(alpha Me)Trp-NH2. The latter racemate, prepared by phase-transfer catalyzed alkylation of the N alpha-benzylidene derivative of alanine amide followed by acidic hydrolysis of the resulting Schiff base, was characterized by X-ray diffraction. The molecular and crystal structure of Z-L-Ala-L-(alpha Me)Trp-NH2, separated from its diastereomer by silica-gel column chromatography, was determined by X-ray diffraction analysis. Both independent molecules in the asymmetric unit of the dipeptide adopt a type-II beta-bend conformation. However, only the more regularly folded conformation of molecule B is stabilized by a 1<--4 C = O...H--N intramolecular H bond. The present results indicate that: (i) the C alpha-methylated (alpha Me)Trp residue is a strong beta-bend and helix former, and (ii) the relationship between (alpha Me)Trp chirality and helix screw sense tends to be opposite to that of protein amino acids. The implications for the use of the (alpha Me)Trp residue in designing conformationally restricted analogs of bioactive peptides are briefly discussed.

Amino Acid Sequence↗
PubMed1994

N alpha-benzyloxycarbonyl-alpha-aminoisobutyryl-glycyl-L-isoleucyl- L-leucine methyl ester monohydrate.

(Z)-Aib-Gly-L-Ile-L-Leu-OMe.H2O, C27H42N4O7.H2O, is a protected analogue of the C-terminal sequence of the membrane-active peptaibol antibiotic trichogin A IV. The peptide backbone is folded. The urethane carbonyl O atom acts as the acceptor of two intramolecular hydrogen bonds which give rise to a beta bend and to an alpha bend. The geometry of the latter is significantly distorted from that observed in alpha helices. This structure represents the first observation of an alpha bend in a protected tetrapeptide sequence.

Amino Acid Sequence↗
PubMed1994

Ancestral hemoglobin switching in lampreys.

A very simple hemoglobin switching was discovered in the lamprey Lampetra zanandreai. A single larval globin cDNA and two adult globin cDNAs were fully sequenced and their differential expression during lamprey development was investigated. The evolutionary positions of these new globin sequences are also discussed.

Amino Acid Sequence↗
PubMed1994

Tc-99m HMPAO SPECT in a cerebral gunshot wound.

The authors examined regional cerebral blood flow by using Tc-99m HMPAO SPECT studies in a patient who received a gunshot wound to the brain. Although the presence of the retained bullet's fragments adversely affected the quality of CT images and contraindicated MRI studies, the SPECT examination did not have the same constraints and allowed both therapy assessment and prognostic evaluation. The repair of the cortical defect could also be assessed.

Adult↗
PubMed1994

[Plasma levels of basal beta-endorphin and after effort in patients with severe left ventricular dysfunction and heart failure].

BACKGROUNDS: Purpose of the study was to evaluate beta-endorphin plasma levels at rest and after exercise, and the beta-endorphin release, in relation to exercise capacity, in patients with severe left ventricular dysfunction and heart failure. METHODS: Beta-endorphin plasma levels were assayed by radio-immunoassay before and after cardiopulmonary exercise testing in 28 heart failure patients with radionuclide ejection fraction < 35%, left ventricular end-dyastolic dimension > 60 mm and heart failure, and in 9 age-matched normal subjects. According to Weber's classification, 10 patients were in class A, 9 in class B, and 9 in class C. RESULTS: Beta-endorphin plasma levels at rest were respectively 3.52 +/- 2.31 pmol/L in patients, and 1.77 +/- 0.84 pmol/L (p < 0.05) in normals. In patients, baseline beta-endorphin correlated to VO2max (r = -0.76), peak rate-pressure product (r = -0.60) and exercise time (r = -0.56), then progressively increasing from class A to C. After exercise, beta-endorphin plasma levels increased respectively to 6.42 +/- 3.44 pmol/L (p < 0.001 vs baseline) in patients, and to 5.46 +/- 2.14 pmol/L (p < 0.001 vs baseline and NS vs patients) in normals. In patients, the release during exercise of beta-endorphin (exercise - baseline/baseline x 100) correlated to VO2max (r = 0.82), peak rate-pressure product (r = 0.64) and exercise time (r = 0.55), then progressively decreasing from class A to C. At multivariate analysis beta-endorphin release showed the greater correlation to exercise capacity parameters. CONCLUSIONS: In heart failure patients, beta-endorphin plasma levels are elevated at rest and its release during exercise is reduced in relation to functional impairment.

Adult↗
PubMed1994

[Quantitative scintigraphic detection of 111In sources].

This paper reports on a quantitative scintigraphic method for 111In sources using counts from isoboundary regions of interest of source images. Accordingly, total counts from regions of the image excluding the counts below a given percentage of the maximum are recorded and attenuation correction is implemented using the Depth Independent Buildup Factor method which corrects the effects of Compton scattering on the transmission function of the photon flux leaving the source. The transmission function of both the 172 and the 247 keV photons of 111In was determined for a set of circular flat sources of varying diameter (33 to 111 mm), using counts recorded in isoboundary regions of interest of images of the sources placed in air and at various depths in water. The images were acquired using a gamma camera equipped with a parallel hole medium energy collimator. The influence of the isoboundary value on the shape of the transmission function was investigated, and thus the chosen isoboundary value was set to no more than 20% of the maximum count on the image. Two parallel and dimetrically opposed views were acquired to determine the unknown activity of the sources placed in a water phantom. This counting geometry was chosen to operate in conditions of depth independent of the source in the phantom. Our results show a high degree of accuracy, the experimental estimate of the activity obtained by using the counts in the regions of interest with the lowest isoboundary value exhibiting 4% error rate. The error rate increases with the increase in the isoboundary values. The method proved to be simple, practical and accurate. Moreover, it overcomes the problem of accurate estimation of sources size, a variable usually not known with sufficient accuracy in clinical scintigraphic studies.

Indium Radioisotopes↗
PubMed1993

Discover 1: a new program to search for unusually represented DNA motifs.

DISCOVER1 (DIStribution COunter VERsion 1) is a new program that can identify DNA motifs occurring with a high deviation from the expected frequency. The program generates families of patterns, each family having a common set of defined bases. Undefined bases are inserted amongst the defined bases in different ways, thus generating the diverse patterns of each family. The occurrences of the different patterns are then compared and analysed within each family, assuming that all patterns should have the same probability of occurrence. An extensive use of computer memory, combined with the immediate sorting of counts by address calculation allow a complete counting of all DNA motifs on a single pass on the DNA sequence. This approach offers a very fast way to search for unusually distributed patterns and can identify inexact patterns as well as exact patterns.

Base Sequence↗
PubMed1993

Structures of peptides from alpha-amino acids methylated at the alpha-carbon.

The structural preferences of peptides (and depsipeptides) from the achiral MeAib and Hib residues, and the chiral Iva, (alpha Me) Val, (alpha Me) Leu, and (alpha Me) Phe residues, as determined by conformational energy computations, x-ray diffraction analyses, and 1H-nmr and spectroscopic studies, are reviewed and compared with literature data on Aib-containing peptides. The results obtained indicate that helical structures are preferentially adopted by peptides rich in these alpha-amino acids methylated at the alpha-carbon. Intriguing experimental findings on the impact of the chirality of Iva, (alpha Me) Val, and (alpha Me) Phe residues on helix screw sense are illustrated.

Amino Acid Sequence↗
PubMed1993

TA-repeat microsatellites are closely associated with ARS consensus sequences in yeast chromosome III.

Microsatellites are repeats of very short sequences of DNA, interspersed in the genome. In this paper, the occurrence of the two-base repeat microsatellites has been investigated in the DNA sequence of yeast chromosome III. Only AT-repeats were found at a significantly high frequency. Some of the regions with the highest concentration of AT-repeats were located and further analysed, showing a close association with the core consensus of autonomously replicating sequences.

Base Sequence↗
PubMed1993

Reverse relationship between alpha-carbon chirality and helix handedness in (alpha Me)Phe peptides.

The crystal-state preferred conformations of two tripeptides, one tetrapeptide, and one pentapeptide, each containing a single residue of the chiral, C alpha, alpha-disubstituted glycine C alpha-methyl, C alpha-benzylglycine [(alpha Me)Phe], have been determined by X-ray diffraction. The tripeptides are Z-L-(alpha Me)Phe-(Aib)2-OH dihydrate and Z-Aib-D-(alpha Me)Phe-Aib-OtBu, the tetrapeptide is Z-(Aib)2-D-(alpha Me)Phe-Aib-OtBu, and the pentapeptide is pBrBz-(Aib)2-DL-(alpha Me)Phe-(Aib)2-OtBu. While the two tripeptides are folded in a beta-bend conformation, two such conformations are consecutively formed by the tetrapeptide. The pentapeptide adopts a regular 3(10)-helix promoted by three consecutive beta-bends. This study confirms the strong propensity of short peptides containing C alpha-methylated alpha-aminoacids to fold into beta-bends and 3(10)-helical structures. Since Aib is achiral, the handedness of the observed bends and helices is dictated by the presence of the (alpha Me)Phe residue. In general, we have found that the relationship between (alpha Me)Phe chirality and helix handedness is opposite to that exhibited by protein aminoacids. A comparison with the preferred conformation of other extensively investigated C alpha-methylated aminoacids is made.

Models, Molecular↗
PubMed1993

Considerations of brain death on a SPECT cerebral perfusion study.

Brain death imaging is often a diagnostic challenge. Cerebral angioscintigraphy is extensively used for this analysis, but this test does not allow the perfusion evaluation of the posterior fossa. The authors report a case in which a SPECT study showed persistence of blood flow in infratentorial structures with total absence of cerebral (supratentorial) perfusion. This finding excluded the diagnosis of brain death.

Adult↗