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Biomedical subjects

R M Romero

Publications and source records attributed to R M Romero.

13 recordsLinked to original sources
PubMed2005

[Role of peritoneal drainage in very low birth weight with enterocolitis].

UNLABELLED: Peritoneal drainage (PD) has been proposed as a temporizing procedure for perforated necrotizing enterocolitis (NEC) in very low birth weight neonates. This operation was designed for patients considered too unstable to undergo laparotomy (LAP). Since the introduction of PD some investigators have suggested that it may serve as a definitive therapy. The aim of our study is to determine the efficacy of PD for the stabilization of patients with complicated NEC and its utility as a definitive surgical treatment. METHODS: We review the clinical records from all the patients treated in our unit because of NEC that required surgical therapy. We analyze the mean blood pressure, cardiac and respiratory rate, inspired oxygen concentration, mean airway pressure, diuresis, and arterial blood gases measured 6 and 12 hours after the initial surgical treatment. We divide patients in two different groups according to the initial surgical procedure, peritoneal drainage (PD) or laparotomy group (LAP). Data is shown as media +/- standard deviation, statistical analyses were performed using analysis of variance (ANOVA) for repeated measures and Mann-Withney test. RESULTS: From January 1997 to January 2001 we treated 13 patients with necrotizing enterocolitis that required surgical treatment. Among this group 6 patients were managed initially with PD and 7 with LAP. The gestational age media was 29.07 +/- 3.81 weeks and the birth weight mean 1199.76 +/- 521 gr., without any significant differences between the two groups DP and LAP. All patients improved haemodynamically and respiratory 6 and 12 hours after the surgical treatment. Nevertheless, the mean blood pressure improved even more in the DP group (p<0.005). The DP group showed an improvement in all parameters 6 hours after the drainage was placed, but this effect wasn't maintained for the next 12 hours onwards. From the 12 hours after PD all patients suffered a steady worsening that required further surgical procedures. The overall mortality was 3 patients (23%), without differences between the two groups. The surgical techniques performed (bowel resection, diversion) were similar for both groups. DISCUSSION: DP allows the stabilization for very critically ill patients with complicated NEC. However, this stabilization is temporary. This improvement lasts for a few hours providing a better status for the definitive surgical treatment for the perforated NEC. In our experience DP could not be considered as a definitive surgical treatment.

Child, Preschool↗
PubMed2001

Extrahelical cytosine bases in DNA duplexes containing d[GCC](n).d[GCC](n) repeats: detection by a mechlorethamine crosslinking reaction.

The cytosine-cytosine (C-C) pair is one of the least stable DNA mismatch pairs. The bases of the C-C mismatch are only weakly hydrogen bonded, and previous work has shown that, in certain sequence contexts, they can become unstacked from the core helix, and adopt an 'extrahelical' location. Here, using DNA duplexes with d[GCC](n).d[GCC](n) fragments containing C-C mismatches in a 1,4 bp relationship, we show that cytosine bases of different formal mismatch pairs can be crosslinked by mechlorethamine. For example, in the duplex d[CTCTCGCCGCCGCCGTATC].d[GATACGCCGCCGCCGAGAG], where underlined cytosine bases are present as the formal C-C mismatch pairs C(7)-C(32), C(10)-C(29) and C(13)-C(26), we show that two mechlorethamine crosslinks form between C(13) and C(29) and between C(10) and C(32), in addition to crosslinks at C(7)-C(32), C(10)-C(29) and C(13)-C(26) (we have reported previously the crosslinking of formal C-C pairs by mechlorethamine). We interpret the formation of the C(13)-C(29) and C(10)-C(32) crosslinks as evidence of an extrahelical location of the crosslinkable cytosines. Such extrahelical cytosine bases have been observed previously for a single C-C mismatch pair (in the so-called E-motif conformation). In the E-motif, the extrahelical cytosines are folded back towards the 5'-end of the duplex, consistent with our crosslinking data, and also consistent with the absence of C(7)-C(29) and C(10)-C(26) crosslinks in the current work. Hence, our data provide evidence for an extended E-motif DNA (eE-DNA) conformation in short d[GCC](n).d[GCC](n) repeat fragments, and raise the possibility that such structures might occur in much longer d[GCC](n).d[GCC](n) repeat tracts.

Base Pair Mismatch↗
PubMed2001

DNA interstrand crosslink formation by mechlorethamine at a cytosine-cytosine mismatch pair: kinetics and sequence dependence.

Expansion of the triplet repeat DNA sequence d[CGG]n.d[CCG]n is a characteristic of Fragile X syndrome, a human neurodegenerative disease. Stable intrastrand conformations formed by both d[CGG]n and d[CCG]n, and involving G-G and C-C mismatch pairs, respectively, are believed to be of importance in the development of the disease. We have shown previously that C-C mismatch pairs can be crosslinked covalently by mechlorethamine, a nitrogen mustard alkylating agent, and hence this reaction may be of value as a probe for conformers of d[CCG]n. To characterize the mechlorethamine C-C crosslink reaction further, here we report the kinetics and sequence dependence of formation of the crosslink species, using a series of model duplexes. The rate of reaction depends on the base sequence proximal to the C-C mismatch pair. Hence, in 19mer duplexes containing a central d[M4M3M2M1Cn1n2n3n4].d[N4N3N2N1Cm1m2m3m4] sequence, where M-m and N-n are complementary base pairs, the amount of crosslink increased with increasing G-C content of the eight base pairs neighboring the C-C mismatch and with the proximity of the G-C pairs to the C-C mismatch. Molecular dynamics simulations of the solvated duplexes provided an explanation of these data. Hence, for a C-C pair flanked by G-C base pairs the mismatched cytosine bases remain stacked within the duplex, but for a C-C pair flanked by A-T base pairs, the simulations suggested local opening of the duplex around the C-C pair, making it a less effective target for mechlorethamine.

Alkylating Agents↗
PubMed1999

Anomalous cross-linking by mechlorethamine of DNA duplexes containing C-C mismatch pairs.

Nitrogen mustards such as mechlorethamine have previously been shown to covalently cross-link DNA through the N7 position of the two guanine bases of a d[GXC].d[GYC] duplex sequence, a so-called 1,3 G-G-cross-link, when X-Y = C-G or T-A. Here, we report the formation of a new mechlorethamine cross-link with the d[GXC].d[GYC] fragment when X-Y is a C-C mismatch pair. Mechlorethamine cross-links this fragment preferentially between the two mismatched cytosine bases, rather than between the guanine bases. The cross-link also forms when one or both of the guanine bases of the d[GCC].d[GCC] fragment are replaced by N7-deazaguanine, and, more generally, forms with any C-C mismatch, regardless of the flanking base pairs. Piperidine cleavage of the cross-link species containing the d[GCC].d[GCC] sequence gives DNA fragments consistent with alkylation at the mismatched cytosine bases. We also provide evidence that the cross-link reaction occurs between the N3 atoms of the two cytosine bases by showing that the formation of the C-C cross-link is pH dependent for both mechlorethamine and chlorambucil. Dimethyl sulfate (DMS) probing of the cross-linked d[GCC].d[GCC] fragment showed that the major groove of the guanine adjacent to the C-C mismatch is still accessible to DMS. In contrast, the known minor groove binder Hoechst 33258 inhibits the cross-link formation with a C-C mismatch pair flanked by A-T base pairs. These results suggest that the C-C mismatch is cross-linked by mechlorethamine in the minor groove. Since C-C pairs may be involved in unusual secondary structures formed by the trinucleotide repeat sequence d[CCG]n, and associated with triplet repeat expansion diseases, mechlorethamine may serve as a useful probe for these structures.

Alkylating Agents↗
PubMed1997

At physiological pH, d(CCG)15 forms a hairpin containing protonated cytosines and a distorted helix.

To investigate potential structures of d(CGG/CCG)n that might relate to their biological function and association with triplet repeat expansion diseases (TREDs), the structure of a single-stranded (ss) oligonucleotide containing d(CCG)15 [ss(CCG)15] was examined by studies of the pH and temperature dependence of electrophoretic mobility, UV absorbance, circular dichroism, chemical modification, and P1 nuclease digestion. ss(CCG)15 had an unusually high pKa (7.7 +/- 0.2). At pH 8.5, ss(CCG)15 formed a relatively unstable (Tm = 30 degrees C in 1 mM Na+) hairpin containing CpG base-pair steps. At pH 7.5, the hairpin contained protonated cytosines but no detectable C x +C base pairs, increased thermal stability (Tm = 37 degrees C), increased stacking of the CpG base-pair steps, and a single cytosine that was flipped away from the central portion of the helix. Examination of ss(CCG)18 and ss(CCG)20, which were designed to adopt hairpins containing alternative GpC base-pair steps, revealed hairpins containing CpG base-pair steps, pKas of approximately 8.2 and approximately 8.4, respectively, and distorted helices. The results suggest that DNA sequences containing (CCG)(n > or = 15) adopt hairpin conformations that contain CpG rather than GpC base-pair steps; the mismatched cytosines are protonated at physiological pH but are not H-bonded. We propose that protonation arises from the stacking of two cytosines in the minor groove of a distorted helix.

Base Sequence↗
PubMed1995

Anthranilate synthase in microorganisms and plants.

The enzymology of anthranilate synthase (EC 5.4.99.6) in microorganisms and plants is reviewed. Aminoacid sequences of the enzyme subunits in different species are compared, and the mechanism of reaction is discussed.

Amino Acid Sequence↗
PubMed1995

Hyskon induced pulmonary hemorrhage.

Hyskon, a distension medium composed of dextran 70 in 10% dextrose in water, is often used during hysteroscopic procedures. Coagulopathy and pulmonary edema are the most commonly reported side effects encountered during its use. We present the first case report in which a healthy patient developed pulmonary hemorrhage from Hyskon use. The major side effects of Hyskon are discussed, as are the possible etiologies of the reported complication and the implications for anesthesiologists.

Anesthesia↗
PubMedDate not supplied

[Peripheral parenteral nutrition: contribution of nursing to the development, preparation and control protocols].

In the present work the role of nursing in peripheric parenteral nutrition (PPN) is described. The main role is framed within the Unit of Nutritional Support along with the design of the corresponding protocols. The outstanding difference in the composition of our PPN vs those manufactured by the pharmaceutical industry, is the inclusion of glucose as the sole source of carbohydrates. These protocols secure similar nursing care in all patients. With respect to the local venous tolerance to our PPN, it was significantly better than that found in the group infused with a commercial PPN. By contrast, no differences in glycosuria were observed. The economical savings were of 1,980 pesetas per nutrition/day.

Clinical Protocols↗