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Biomedical subjects

M T Ramos

Publications and source records attributed to M T Ramos.

7 recordsLinked to original sources
PubMed2001

Intramolecular Friedel-Crafts-type reactions involving N-acyliminium ions derived from glycine templates.

Enantiomerically pure 4-substituted 2-aralkyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones (1b-m) in which the alkyl chain is (CH(2))(n), n = 1-3, behave as glycine templates giving by treatment with [hydroxy(tosyloxy)iodo]benzene in ethyl acetate cis-1-tosyloxy derivatives. When these compounds contain electron-rich aryl substituents with n = 2, they spontaneously cyclize through intramolecular Friedel-Crafts-type diastereoselective reactions to give penta- or hexacyclic compounds. Otherwise, they give by solvolysis cis-1-alkoxy derivatives, which in a second step, may be cyclized in acid if n = 2, 3. All these reactions must occur through N-acyliminium species in S(N)1-like mechanisms. 1-Alkoxy-2-arylmethyl derivatives are reluctant to cyclize, giving trans-1-hydroxy compounds as the only isolated reaction products.

Journal Article↗
PubMed1996

Molecular bureaucracy: who controls the delays? Transient times in branched pathways and their control.

Analysis of metabolic control has until now been mainly confined to systems at steady state. This includes studies of the control of "transition time", which is actually a steady-state transit time that does not refer to the transient state. In this paper we examine the control of the transition state of a metabolic pathway in the approach to a stable steady state, showing that the time needed to attain it can be decreased or increased in different branches. Our analysis only applies to branched pathways, and we discuss why similar deviations cannot occur in unbranched pathways. In systems with several branches the acceleration of some branches during the transient phase, so that they reach their steady states more quickly, occurs at the expense of others, which are thus delayed. We present theorems that describe properties of the transient variables and their control.

Animals↗
PubMed1996

Synthesis and antitumour activity of fluorinated 1-aza and 1,8-diazaanthraquinones.

A series of 3-fluoro-1-aza- and 1,8-diazaanthraquinones, structurally related to the antitumour antibiotic diazaquinomycin A, have been prepared by Diels-Alder reactions of 2-fluoro-2-propenal N, N-dimethylhydrazone and the corresponding quinones. These compounds showed potent in vitro activity against different tumour cell lines. They also showed some selectivity towards rapid-growth tumours when compared to other non-fluorinated analogues. In contrast with diazaquinomycin A, the azaanthraquinones studied here have not shown significant activity as thymidylate synthase inhibitors. Some compounds showed a high activity as inhibitors of protein, DNA and RNA biosynthesis.

Animals↗
PubMed1995

Cerebrospinal fluid beta 2-microglobulin in neonates with central nervous system infections.

Beta 2-microglobulin (beta 2m) determination in CSF of 72 neonates who underwent a spinal tap as part of a sepsis or meningo-encephalitis workup was performed to evaluate the usefulness of this test in the diagnosis of CNS infections. Beta 2m was measured by enzyme immunoassay. Sixty neonates had sterile culture and normal neurological status at discharge. Twelve infants had CNS infections: 8 bacterial meningitis, 3 TORCH infections (T = toxoplasmosis, O = others, R = rubella, C = cytomegalovirus and H = herpes simplex) and 1 viral meningitis. Neonates with CNS infection exhibited significantly higher CSF beta 2m levels compared to neonates with sterile culture (6.24 +/- 2.66 vs 1.74 +/- 0.5 mg/l; P < 0.0001). CSF beta 2m levels did not correlate with the white cell count, total protein concentration or glucose level in CSF. When serum and CSF levels were measured simultaneously, the CSF beta 2m level was significantly higher than the corresponding serum level in patients with CNS infection (6.98 +/- 2.5 vs 3.2 +/- 0.25 mg/l; P < 0.01). Sensitivity, specificity, and predictive values were estimated for different cut-off points. The best operational diagnostic cut-off value was 2.25 mg/l. Receiver operating characteristic curve analysis showed an appropriate trade-off between specificity and sensitivity and indicated that CSF beta 2m was accurate in distinguishing between neonates with and without CNS infection. Conclusion. CSF beta 2m may be a useful ancillary tool in neonates when CNS infection is suspected.

Female↗