Search PubMed⌕ Search

Biomedical subjects

M Mena

Publications and source records attributed to M Mena.

At least 19 recordsLinked to original sources
PubMed2001

Rhodium/iridium-titanium azaheterometallocubanes.

Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures.

Journal Article↗
PubMed2001

Titanium alkali metal nitrido complexes.

Treatment of [(Ti(eta5-C5Me5)(mu-NH))3(mu3-N)] with alkali metal bis(trimethylsilyl)amido reagents in toluene afforded the complexes [M(mu3-N)(mu3-NH)2[Ti3(mu5-C5Me5)3(mu3-N)]]2 (M = Li (2), Na, (3), K (4)). The molecular structures of 2 and 3 have been determined by X-ray crystallographic studies and show two azaheterometallocubane cores [MTi3N4] linked by metal-nitrogen bonds. Reaction of the lithium derivative 2 with chlorotrimethylsilane or trimethyltin chloride in toluene gave the incomplete cube nitrido complexes [Ti3(eta5-C5Me5)3(mu-NH)2(mu-NMMe3)(mu3-N)] (M = Si (5), Sn (6)). A similar reaction with indium(I) or thallium(I) chlorides yielded cube-type derivatives [M(mu3-N)(mu3-NH)2[Ti(eta5-C5Me5)3(mu3-N)] (M=In (7), Tl (8)).

Journal Article↗
PubMed2000

[{Ti]

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

Ammonolysis of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives.

Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives [Ti(eta5-C5Me5)X3] (X = NMe2, Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido) derivative [Ti(eta5-C5Me5)(NMe2)3] with excess of ammonia at 80-100 degrees C gives the cubane complex [[Ti(eta5-C5Me5)]4(mu3-N)4] (1). Treatment of the trimethyl derivative [Ti(eta5-C5Me5)Me3] with NH3 at room temperature leads to the trinuclear imido-nitrido complex [[Ti(eta/5-CsMes)(mu-NH)]3(mu3-N)] (2) via the intermediate [[Ti(eta5-C5Me5)Me]2(mu-NH)2] (3). The analogous reaction of [Ti(eta5-C5Me5)Me3] with 2,4,6-trimethylaniline (ArNH2) gives the dinuclear imido complex [[Ti(eta5-C5Me5)Me])2(mu-NAr)2] (4) which reacts with ammonia to afford [[Ti(eta5-C5Me5)(NH2)]2(mu-NAr)2] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives [Ti(eta5-C5H5-nRn)(NMe2)3], as precursor of the cubane nitrido systems [[Ti4(eta5-C5Me5)3(eta5-C5H5-nRn)](mu3-N)4] [R = Me n = 5 (1), R = H n = 0 (6), R = SiMe3 n = 1 (7), R = Me n = 1 (8)] via dimethylamine elimination. Reaction of [Ti(eta5-C5Me5)Cl3] or [Ti(eta5-C5Me5)(NMe2)Cl2] with excess of ammonia at room temperature gives the dinuclear complex [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) where an intramolecular hydrogen bonding and a nonlineal nitrido ligand bridge the "Ti(eta5-C5Me5)Cl(NH3)" and "Ti(eta5-C5Me5)Cl2" moieties. The molecular structures of [[Ti(eta5-C5Me5)Me]2 (mu-NAr)2] (4) and [[Ti2(eta5-C5Me5)2Cl3(NH3)](mu-N)] (9) have been determined by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex 9 to confirm the existence of an intramolecular N-H...Cl hydrogen bond and to evaluate different aspects of its molecular disposition.

Journal Article↗
PubMed2000

Construction of Heterometallic Cubanes

Incorporation of M(CO)(3) fragments by trinuclear Ti complexes [{Ti(3)Cp<![IGNORE[$\curr {\brol{{\stern}}{3}}$]]>(µ(3)-CR)}(µ-O)(3)] and [{Ti(3)Cp<![IGNORE[$\curr {\brol{{\stern}}{3}}$]]>(µ(3)-N)}(µ-NH)(3)] (Cp*=eta(5)-C(5)Me(5)) leads to the formation of an unprecedented class of heterometallic clusters with cubane structure [e.g., Eq. (a)]. Density functional calculations on these complexes indicate the existence of electron delocalization in the Ti(3)M cores (M=Cr, Mo, W).

Journal Article↗
PubMed2000

[Fetal drug addiction as a consequence of maternal cocaine free base abuse during pregnancy].

BACKGROUND: Fetal drug addiction is a serious public health problem. In the United States 10 to 15% of children have been exposed "in utero" to cocaine. In a Chilean public health service, more than 200 offspring of cocaine free base abuser have been detected. AIM: To analyze the clinical and social features of 100 children exposed to cocaine free base during fetal development. PATIENTS AND METHODS: Clinical features of children born from cocaine free base consume mothers were described at birth. During subsequent follow up, growth and development, disease episodes, developmental alterations and social situation were recorded. Data was compared with other newborns from the same health service. RESULTS: Compared to their normal counterparts, exposed children has a lower birth weight, the frequency of premature babies was thrice higher, and small-for-gestational age children were four times more common. There was also a higher prevalence of cardiac malformations, seizures and apnea. Hospital admissions were more frequent, prolonged and required more complex facilities. During follow up, undernutrition and stunting were more prevalent. Psychomotor retardation was present in 67% of children and behavioral disturbances in 93%. Most of these children are governmental protection. CONCLUSIONS: Strategies to prevent drug abuse during pregnancy and its devastating medical and social consequences should be urgently developed (Rev Méd Chile 2000; 128: 1093-1100).

Case-Control Studies↗
PubMed1998

An endosperm-specific DOF protein from barley, highly conserved in wheat, binds to and activates transcription from the prolamin-box of a native B-hordein promoter in barley endosperm.

A cDNA encoding a DNA-binding protein of the DOF class of transcription factors was isolated from a barley endosperm library. The deduced amino acid sequence for the corresponding protein is 94% identical through the DOF domain to the prolamin-box (P-box) binding factor PBF from maize. The gene encoding the barley PBF (BPBF) maps to chromosome 7H, and its expression is restricted to the endosperm where it precedes that of the hordein genes. The BPBF expressed in bacteria as a GST-fusion binds a P-box 5'-TGTAAAG-3' containing oligonucleotide derived from the promoter region of an Hor2 gene. Binding was prevented when the P-box motif was mutated to 5'-TGTAgAc-3'. A P-box binding activity, present in barley and wheat endosperm nuclei, interacted similarly to BPBF with this synthetic oligonucleotide, and the binding was abolished by 1,10-phenanthroline. Transient expression experiments in developing barley endosperms demonstrate that BPBF transactivates transcription from the P-box element of a native Hor2 promoter and that direct binding of BPBF to its target site is essential for transactivation since mutations in the DOF DNA-binding domain or in the P-box motif of this promoter abolished both binding and transactivation. Evidence was also obtained for the presence in wheat of a Pbf homologue having similar DNA-binding properties to that of BPBF. These results strongly implicate this endosperm-specific DOF protein from barley as an important activator of hordein gene expression and suggest the evolutionary conservation of the Pbf gene function among small grain cereals.

Amino Acid Sequence↗
PubMed1997

Differential expression of pathogen-responsive genes encoding two types of glycine-rich proteins in barley.

Gene-specific probes (3' ends of cDNAs) were obtained from barley cDNAs encoding two types of glycine-rich proteins: HvGRP2, characterized by a cytokeratin-like and a cysteine-rich domain, and HvGRP3, whose main feature was an RNA-binding domain. Expression of genes Hvgrp2 and Hvgrp3, which are present at one (or two) copies per haploid genome, was ubiquitous and gene Hvgrp3 was under light/darkness modulation. Cold treatment increased Hvgrp2 and Hvgrp3 mRNA levels. Methyl jasmonate (10 microM) switched off the two genes. Expression of Hvgrp2, but not that of Hvgrp3, was induced by ethylene treatment (100 ppm). Fungal pathogens Erysiphe graminis and Rhynchosporium secalis increased the mRNAs levels of the two genes, both in compatible and in incompatible interactions, while bacterial pathogens did not.

Amino Acid Sequence↗
PubMed1996

Diversification of C-function activity in maize flower development.

The Arabidopsis gene AGAMOUS is required for male and female reproductive organ development and for floral determinacy. Reverse genetics allowed the isolation of a transposon-induced mutation in ZAG1, the maize homolog of AGAMOUS. ZAG1 mutants exhibited a loss of determinacy, but the identity of reproductive organs was largely unaffected. This suggested a redundancy in maize sex organ specification that led to the identification and cloning of a second AGAMOUS homolog, ZMM2, that has a pattern of expression distinct from that of ZAG1. C-function organ identity in maize (as defined by the A, B, C model of floral organ development) may therefore be orchestrated by two closely related genes, ZAG1 and ZMM2, with overlapping but nonidentical activities.

Alleles↗
PubMed1996

[Alcohol consumption and family: a descriptive study in adolescents].

AIM: To study abnormal alcohol ingestion among parents and family dysfunction of pregnant and non pregnant teenagers. SUBJECTS AND METHODS: Pregnant and non pregnant girls from 12 to 18 years old consulting in the Teenager Health Unit of a public hospital outpatient clinic were studied. Their degree of instruction attained, marital status, social behavior, alcohol, drug intake and history of child abuse was recorded. The level of instruction, marital status, alcohol ingestion and work stability of their fathers was also studied. RESULTS: One hundred sixteen pregnant and 60 non pregnant teenagers were studied. The fathers of pregnant girls had a higher level of alcohol consumption, more civil irregularities and a higher level of family dysfunction. Among these girls, a higher frequency of neurological abnormalities and fetal alcohol syndrome was observed. They had also a lower educational level and a higher degree of alcohol and drug use. CONCLUSIONS: Alcohol consumption among parents leads to family dysfunction and has adverse physical, intellectual and social consequences in the offspring.

Adolescent↗
PubMed1996

Nutritional status of institutionalised elderly in Ecuador.

The nutritional status of 111 elderly men and women aged 60 to 99 years in two institutions in the Ecuadorian Andes was evaluated using dietary, anthropometric and biochemical measurements. Mean daily energy intakes of men and women were 1720 and 1650 kcal, respectively (7.2 and 6.9 MJ), corresponding to 1.5 times the calculated basal metabolic rate (BMR). 6% of subjects had intakes less than 1.2 x BMR and 40% less than 1.5 x BMR. Body mass index (BMI) was below 20 kg/m2 in 21% of subjects; 45% were between 20 and 24. Only one subject had a BMI over 29. Intakes of protein, calcium, iron, riboflavin and vitamin C were satisfactory, in contrast to those of zinc, vitamin A, niacin and thiamin. Using sex- and altitude-specific cutoffs for hemoglobin, anemia was observed in 11% of subjects. Nutritional status, evaluated using biochemical indicators, was satisfactory with respect to riboflavin, vitamin A, vitamin E and copper. 14% of subjects had low serum zinc levels and 17% had serum albumin values below 35 g/L. Low physical activity was associated with low energy intake and low serum albumin levels.

Aged↗
PubMed1995

A characterization of the MADS-box gene family in maize.

Studies on distantly related dicot plant species have identified homeotic genes that specify floral meristem identity and determine the fate of floral organ primordia. Most of these genes belong to a family characterized by the presence of a structural motif, the MADS-box, which encodes a protein domain with DNA-binding properties. As part of an effort to understand how such genes may have been recruited during the evolution of flowers with different organ types such as those found in maize, two members of this gene family in maize, ZAG1 and ZAG2, have been characterized previously. Here, the isolation and characterization of four new members of this gene family, designated ZAP1, ZAG3, ZAG4 and ZAG5, are described and the genetic map position of these and 28 additional maize MADS-box genes is determined. The first new member of this family appears to be the Zea mays ortholog of the floral homeotic gene APETALA1 (AP1) and has been designated ZAP1. One of these genes, ZAG4, is unusual in that its deduced protein sequence includes the MADS domain but lacks the K-domain characteristically present in this family of genes. In addition, its copy number and expression varies among different inbreds. A large number of maize MADS-box genes map to duplicated regions of the genome, including one pair characterized here, ZAG3 and ZAG5. These data underscore the complexity of this gene family in maize, and provide the basis for further studies into the regulation of floral organ morphogenesis among the grasses.

Amino Acid Sequence↗
PubMed1993

Identification and molecular characterization of ZAG1, the maize homolog of the Arabidopsis floral homeotic gene AGAMOUS.

Recent genetic and molecular studies in Arabidopsis and Antirrhinum suggest that mechanisms controlling floral development are well conserved among dicotyledonous species. To assess whether similar mechanisms also operate in more distantly related monocotyledonous species, we have begun to clone homologs of Arabidopsis floral genes from maize. Here we report the characterization of two genes, designated ZAG1 and ZAG2 (for Zea AG), that were cloned from a maize inflorescence cDNA library by low stringency hybridization with the AGAMOUS (AG) cDNA from Arabidopsis. ZAG1 encodes a putative polypeptide of 286 amino acids having 61% identity with the AGAMOUS (AG) protein. Through a stretch of 56 amino acids, constituting the MADS domain, the two proteins are identical except for two conservative amino acid substitutions. The ZAG2 protein is less similar to AG, with 49% identity overall and substantially less similarity than ZAG1 outside the well-conserved MADS domain. Like AG, ZAG1 RNA accumulates early in stamen and carpel primordia. In contrast, ZAG2 expression begins later and is restricted to developing carpels. Hybridization to genomic DNA with the full-length ZAG1 cDNA under moderately stringent conditions indicated the presence of a large family of related genes. Mapping data using maize recombinant inbreds placed ZAG1 and ZAG2 near two loci that are known to affect maize flower development, Polytypic ear (Pt) and Tassel seed4 (Ts4), respectively. The ZAG1 protein from in vitro translations binds to a consensus target site that is recognized by the AG protein. These data suggest that maize contains a homolog of the Arabidopsis floral identity gene AG and that this gene is conserved in sequence and function.

AGAMOUS Protein, Arabidopsis↗
PubMed1993

[Alcohol drinking in parents and its relation with intellectual score of their children].

Among children living in orphanages of the Metropolitan Region, the paternal alcohol ingestion patterns were investigated. According to abnormal parental alcohol ingestion, a sample of 291 children was studied, of whom 32% were living in simple protection homes for infants with normal intellectual coefficient and 52% in homes for mentally retarded boys. There was a higher frequency and intensity of abnormal alcohol ingestion among parents of infants living in homes for the mentally retarded. Among these, 29% of mothers were illiterate and 11% had incomplete primary school education compared to mothers of simple protection homes in whom the frequency of illiteracy was 10% and of incomplete primary education, 50%. Twenty percent of fathers of children living in homes for the mentally retarded were unemployed, 16% had occasional jobs and 11% had a stable work; these numbers were 11, 30 and 15% respectively for fathers of simple protection homes. Among infants living in homes for the mentally retarded, undernutrition was found in 44%, growth retardation in 51% and microcephaly in 34% compared to 33, 30 and 11% in children living in simple protection homes. Sixteen percent of the sample had fetal alcohol syndrome, 24% among those living in homes for the mentally retarded and 12% in simple protection homes. There was an inverse relationship between offspring intellectual coefficient and the number of drinking parents.

Adolescent↗
PubMed1992

Homologous sucrose synthase genes in barley (Hordeum vulgare) are located in chromosomes 7H (syn. 1) and 2H. Evidence for a gene translocation?

The chromosomal location of the two types of sucrose synthase genes, Ss1 and Ss2, has been investigated in barley by Southern blot analysis of wheat-barley addition lines using non-cross-hybridizing-specific probes corresponding to the C-terminal regions of their respective cDNA clones (congruent to 250 bp). The Ss1 gene, whose cDNA of 2,667 bp has been entirely sequenced, is located in the beta-arm of chromosome 7H (syn. 1), while that corresponding to the homologous Ss2 is in the short arm of 2H, suggesting the existence of a translocation event between these two chromosomes in cultivated barley after an initial gene duplication and divergent evolution.

Amino Acid Sequence↗