Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Triads”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1999

Enzymatic generation of binary block-copolymeric structures: mathematical analysis based on triad frequencies evaluated by NMR.

A mathematical model is derived for describing a multiple-attack pathway for enzymatic generation of block structure in binary linear copolymers having initially a randomized sequential structure. The model is based on sequential information in terms of copolymer monads, diads, and triads estimated by nmr spectroscopy, and is applicable to enzymes attacking next to a reacted unit in the polymer chains. Then the block distribution of unreacted units remains constant and explicit relationships are provided. The probability of triad frequencies as a function of monads, i.e., progress curve of enzyme copolymer sequential structure, allows us to characterize the enzymatic mode of attack independently of enzyme kinetics. The produced fractions of heterogeneous triads centered by reacted units are shown to be affected, to a large extent, by the degree of multiple attack (d) entering into the formula as a variable parameter. The single-chain, d = infinity, and multiple-chain mechanisms, d = 1, representing the two extremes of the treated mechanism, are very clearly discriminated.

Enzymes↗
PubMed1999

The histidine triad superfamily of nucleotide-binding proteins.

Histidine triad (HIT) proteins were until recently a superfamily of proteins that shared only sequence motifs. Crystal structures of nucleotide-bound forms of histidine triad nucleotide-binding protein (Hint) demonstrated that the conserved residues in HIT proteins are responsible for their distinctive, dimeric, 10-stranded half-barrel structures that form two identical purine nucleotide-binding sites. Hint-related proteins, found in all forms of life, and fragile histidine triad (Fhit)-related proteins, found in animals and fungi, represent the two main branches of the HIT superfamily. Hint homologs are intracellular receptors for purine mononucleotides whose cellular function remains elusive. Fhit homologs bind and cleave diadenosine polyphosphates (Ap(n)A) such as ApppA and AppppA. Fhit-Ap(n)A complexes appear to function in a proapoptotic tumor suppression pathway in epithelial tissues. In invertebrates, Fhit homologs are encoded as fusion proteins with proteins related to plant and bacterial nitrilases that are candidate signaling partners in tumor suppression.

Amino Acid Sequence↗
PubMed1979

The triad of gastric epithelioid leiomyosarcoma, functioning extra-adrenal paraganglioma, and pulmonary chondroma.

The triad of gastric epithelioid leiomyosarcoma, functioning extra-adrenal paraganglioma, and pulmonary chondroma was found in two young female Mayo Clinic patients, and two of these tumors occurred in another two. Review of the world literature disclosed nine patients who probably had two or more of the three neoplasms. We are also aware of two other patients with two of the three tumors. The association of gastric epitheloid leiomyosarcoma, functioning extra-adrenal paraganglioma, and pulmonary chondroma may well constitute a syndrome because of 1) the improbability of the coincidental occurrence of this triad of tumors, 2) the multicentricity of the tumors in the organs or system affected, and 3) the development of the tumors at a young age. Because two of the components of the triad are potentially lethal, it is important that patients less than 35 years of age who have any one of the three tumors be examined periodically to search for the others.

Adolescent↗
PubMed1990

Triad of anorectal stenosis, sacral anomaly and presacral mass: a remediable cause of severe constipation.

Two neonates with intestinal obstruction and two children (aged 1 and 4 years) with severe constipation since birth are reported in whom stenosis of the distal rectum was found. In association with the rectal anomaly, three of them had a presacral tumour (teratoma in two, hamartoma in one) and all had a deformed sacrum. An embryological hypothesis to explain this association has been postulated by Currarino, after whom this triad has been named. Two patients were related (father and daughter). The role of hereditary factors in the occurrence of the syndrome has been reported before. Operative treatment of the rectal stenosis was necessary in all patients. Preoperative diverting colostomy was performed in three cases, followed by a posterior sagittal approach to excise the rectal stenosis and the presacral mass. In one case, persistent cerebrospinal fluid leakage required re-exploration for closure of a tear in a congenitally abnormal dural sac. The fourth patient had undergone a low anterior resection in the past via the abdominal route and needed rectal dilatation afterwards for some time. The final result in all patients appears satisfactory, although follow-up is short. Most cases of this triad have been reported in children but a number of patients have been diagnosed only as adults. Recognition of this triad should imply a careful search for neural crest malformations. Operative treatment to correct all soft tissue anomalies leads to good results.

Child, Preschool↗
PubMed2003

Controlling short- and long-range electron transfer processes in molecular dyads and triads.

Novel pi-extended tetrathiafulvalene (exTTF)-based donor acceptor hybrids-dyads and triads-have been synthesized following a multistep synthetic procedure. Cyclic voltammetry and absorption spectroscopy, conducted in room temperature solutions, reveal features that are identical to the sum of the separate donor and acceptor moieties. Steady-state and time-resolved photolytic techniques confirm that upon photoexcitation of the fullerene chromophore, rapid (1.25 x 10(10) s(-1)) and efficient (67 %) charge separation leads to long-lived, charge-separated radical pairs. Typical lifetimes for the dyad ensembles range between 54 and 460 ns, with the longer values found in more polar solvents. This indicates that the dynamics are located in the 'normal region' of the Marcus curve. In the triads, subsequent charge shifts transform the adjacent radical pair into the distant radical pair, for which we determined lifetimes of up to 111 micros in DMF-values never previously accomplished in molecular triads. In the final charge-separated state, large donor-acceptor separation (center-to-center distances: approximately 30 A) minimizes the coupling between reduced acceptor and oxidized donor. Analysis of the charge recombination kinetics shows that a stepwise mechanism accounts for the unusually long lifetimes.

Journal Article↗
PubMed2003

Time-resolved spectroscopic study on photoinduced electron-transfer processes in Zn(II)porphyrin-Zn(II)chlorin-fullerene triad.

Femtosecond time-resolved transient absorption studies have been performed to investigate the photoinduced energy and electron-transfer processes in Zn(II)porphyrin-Zn(II)chlorin-fullerene triad in which energy and oxidation potential gradients are directed along the donor-acceptor-linked arrays. Fast energy transfer (approximately 450 fs) from photoexcited Zn(II)porphyrin to Zn(II)chlorin was observed upon selective photoexcitation of Zn(II)porphyrin unit in the triad. In a nonpolar solvent such as toluene, the energy transfer from the excited singlet state of Zn(II)chlorin to fullerene occurs and is followed by the formation of an intermediate state with a time constant of nanoseconds, which was attributed to the intramolecular exciplex between Zn(II)chlorin and fullerene. In benzonitrile, on the other hand, the photoexcitation of the triad results in the fast electron transfer (< 1 ps) from photoexcited Zn(II)chlorin to fullerene. The generated charge-separated species recombine with a time constant of approximately 12 ps. The relatively fast charge separation and charge recombination rates imply that the strong electronic coupling between Zn(II)chlorin and fullerene moieties is probably induced by the folded conformation between Zn(II)chlorin and fullerene moieties which enhances direct through-space interaction between the approximately contacted pi systems.

Journal Article↗
PubMed2006

Practical use of the International Olympic Committee Medical Commission Position Stand on the Female Athlete Triad: a case example.

UNLABELLED: The female athlete triad consists of the interrelated problems of disordered eating, amenorrhea, and osteoporosis, and it is believed to affect female athletes in all sports and at all levels of competition. OBJECTIVE: The current article highlights the Position Stand on the Female Athlete Triad of the International Olympic Committee's Medical Commission (IOCMC). METHOD: The literature related to disordered eating, energy availability, amenorrhea, and bone loss in athletes is briefly reviewed. A hypothetical case is presented to illustrate some of the common issues and problems encountered when working with athletes affected by the triad, such as the effect of weight on performance in "thin" sports, coach involvement, sport participation by symptomatic athletes, and treatment resistance/motivation. RESULTS: Strategies recommended by the position stand for managing those issues and problems are presented regarding the referral, evaluation, and treatment phases of the management process. CONCLUSION: Implications of the position stand are discussed in terms of the IOCMC's endorsement of the athlete's health being primary to her performance.

Adult↗
PubMed2003

Variants of developmental genes (TGFA, TGFB3, and MSX1) and their associations with orofacial clefts: a case-parent triad analysis.

We selected 262 case-parent triads from a population-based study of orofacial clefts in Norway, and examined variants of developmental genes TGFA, TGFB3, and MSX1 in the etiology of orofacial clefts. One hundred seventy-four triads of cleft lip cases (CL+/-P) and 88 triads of cleft palate only cases (CPO) were analyzed. There was little evidence for an association of any of these genes with CL+/-P. The strongest association was a 1.7-fold risk with two copies of the TGFB3-CA variant (95% CI=0.9-3.0). Among CPO cases, there was a 3-fold risk with two copies of the TGFA TaqI A2 allele, and no increase with one copy. Assuming this to be a recessive effect, we estimated a 3.2-fold risk among babies homozygous for the variant (95% CI=1.1-9.2). Furthermore, there was strong evidence of gene-gene interaction. While there was only a weak association of the MSX1-CA variant with CPO, the risk was 9.7-fold (95% CI=2.9-32) among children homozygous for both the MSX1-CA A4 allele and the TGFA A2 allele. No association of CPO with the TGFA variant was seen among the other MSX1-CA genotypes. In conclusion, no strong associations were found between CL+/-P and variants at these three genes. There was a possible recessive effect of the TGFA TaqI variant on the risk of CPO, with a 3-fold risk among children homozygous for the variant. The effect of this TGFA genotype was even stronger among children homozygous for the MSX1-CA A4 allele, raising the possibility of interaction between these two genes.

Adult↗
PubMed1994

Carney's triad: apropos of a new case.

Carney's triad is defined by the coexistence of at least two of three rare disorders, including gastric epithelioid leiomyosarcoma (malignant leiomyoblastoma), pulmonary chondroma, and paraganglioma, most often extra-adrenal and functioning. We report a new case in a 10-year-old girl. The paraganglioma, although nonfunctioning, was detected after it was searched for, as Carney's triad was suspected. Unrelated seems the development of breast fibroadenomas in the same patient. Whenever a patient with one component of the triad is encountered, the possibility of this syndrome should be considered and the other two components sought.

Breast Neoplasms↗
PubMed1995

6-Pyruvoyl tetrahydropterin synthase, an enzyme with a novel type of active site involving both zinc binding and an intersubunit catalytic triad motif; site-directed mutagenesis of the proposed active center, characterization of the metal binding site and modelling of substrate binding.

6-Pyruvoyl tetrahydropterin synthase (PTPS) is an enzyme involved in tetrahydrobiopterin biosynthesis, the cofactor for several aromatic amino acid monooxygenases and the nitric oxide synthases. The crystal structure of PTPS was recently solved and showed a homohexameric enzyme composed of a dimer of trimers. A transition metal binding site formed by the three histidine residues 23, 48 and 50 was found in each subunit. We showed by metal analysis and reconstitution of apo-PTPS that Zn(II) was the bound transition metal and responsible for the enzymatic activity. Site-directed mutagenesis of each of these three histidine residues resulted in a complete loss of metal binding and enzymatic activity. The three residues, Cys42, His89 and Glu133, located close to the metal binding site, were previously postulated to be involved in the catalytic reaction. We altered these residues and found a complete loss of enzymatic activity for the mutant C42A. The two mutants, H89N and E133Q, showed 4.3% and 1.3% enzymatic activity, respectively, but had similar KM values for the substrate as compared to wild-type PTPS. Based on these results we propose a model of the substrate fitted into the active site and we described a novel intersubunit catalytic triad motif composed of the amino acid residues Cys42, His89 and Asp88. Different from most other catalytic triads that catalyse the hydrolysis of an amide or ester bond, the catalytic triad in the active site of PTPS seems to be involved in the deprotonation of the substrate's side-chain carbons. Our model also proposes Zn(II) as the coordination site for the two substrate side-chain hydroxy groups as well as the involvement of Glu133 as putative stereospecific proton server.

Alcohol Oxidoreductases↗
PubMed2001

A double chain reversal loop and two diagonal loops define the architecture of a unimolecular DNA quadruplex containing a pair of stacked G(syn)-G(syn)-G(anti)-G(anti) tetrads flanked by a G-(T-T) Triad and a T-T-T triple.

The architecture of G-G-G-G tetrad-aligned DNA quadruplexes in monovalent cation solution is dependent on the directionality of the four strands, which in turn are defined by loop connectivities and the guanine syn/anti distribution along individual strands and within individual G-G-G-G tetrads. The smallest unimolecular G-quadruplex belongs to the d(G2NnG2NnG2NnG2) family, which has the potential to form two stacked G-tetrads linked by Nn loop connectivities. Previous studies have focused on the thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2), where Nn was T2 for the first and third connecting loops and TGT for the middle connecting loop. This DNA aptamer in K(+) cation solution forms a unimolecular G-quadruplex stabilized by two stacked G(syn)-G(anti)-G(syn)-G(anti) tetrads, adjacent strands which are antiparallel to each other and edge-wise connecting T2, TGT and T2 loops. We now report on the NMR-based solution structure of the d(G2T4G2CAG2GT4G2T) sequence, which differs from the thrombin-binding DNA aptamer sequence in having longer first (T4) and third (GT4) loops and a shorter (CA) middle loop. This d(G2T4G2CAG2GT4G2T) sequence in Na(+) cation solution forms a unimolecular G-quadruplex stabilized by two stacked G(syn)-G(syn)-G(anti)-G(anti) tetrads, adjacent strands which have one parallel and one antiparallel neighbors and distinct non-edge-wise loop connectivities. Specifically, the longer first (T4) and third (GT4) loops are of the diagonal type while the shorter middle loop is of the double chain reversal type. In addition, the pair of stacked G-G-G-G tetrads are flanked on one side by a G-(T-T) triad and on the other side by a T-T-T triple. The distinct differences in strand directionalities, loop connectivities and syn/anti distribution within G-G-G-G tetrads between the thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2) quadruplex reported previously, and the d(G2T4G2CAG2GT4G2T) quadruplex reported here, reinforces the polymorphic nature of higher-order DNA architectures. Further, these two small unimolecular G-quadruplexes, which are distinct from each other and from parallel-stranded G-quadruplexes, provide novel targets for ligand recognition. Our results demonstrate that the double chain reversal loop connectivity identified previously by our laboratory within the Tetrahymena telomere d(T2G4)4 quadruplex, is a robust folding topology, since it has now also been observed within the d(G2T4G2CAG2GT4G2T) quadruplex. The identification of a G-(T-T) triad and a T-T-T triple, expands on the available recognition alignments for base triads and triples.

Aptamers, Nucleotide↗
PubMed1997

Pancreatic damage resulting from temporary portal triad interruption during partial hepatectomy: protective effect of a prostaglandin I2 analogue.

BACKGROUND: Hyperamylasemia often occurs after hepatectomy, but the detailed mechanism of this phenomenon remains unclear. This study was designed to examine the influence on the pancreas and other organs of temporary portal triad interruption during hepatectomy and to evaluate the protective effect of a prostaglandin I2 analogue. METHODS: Sprague-Dawley rats were intravenously administered normal saline (NS group) or a prostaglandin I2 analogue (PG group) and underwent 70% hepatectomy with temporary portal triad interruption. The 7-day survival rate and the levels of plasma liver enzymes, portal pancreatic enzymes, and endotoxin were determined. Intestinal permeability was evaluated from the portal blood concentration of fluorescein isothiocyanate-labeled dextran administered into the small intestine. The liver, pancreas, small intestine, and lung were examined histologically. Apoptosis in the pancreas was observed by the terminal transferase-mediated dUTP-biotin nick end labeling method. RESULTS: The survival rate of the NS group was 50%, whereas that of the PG group was significantly higher at 100% (P < 0.05). Plasma liver enzymes increased in both groups and showed no significant difference. Portal amylase and lipase levels were significantly lower in the PG group than in the NS group at 12 and 24 h after hepatectomy. Tissue damage in the pancreas and other organs was observed histologically along with the elevation of pancreatic enzymes. Although there were no significant differences between the two groups on hematoxylin and eosin staining, apoptotic acinar cells were only seen in the NS group. The portal endotoxin level (at 3 and 6 h after hepatectomy) and small intestinal permeability (at 1 and 3 h after hepatectomy) were significantly lower in the PG group compared to the NS group. CONCLUSIONS: Temporary portal triad interruption induced hyperamylasemia, congestive damage to the pancreas, and portal endotoxemia due to increased small intestinal permeability. A prostaglandin I2 analogue was able to protect the pancreas and small intestine from such damage.

Alanine Transaminase↗
PubMed1998

Quantumchemical study of the catalytic triad in subtilisin: the influence of amino acid substitutions on enzymatic activity.

In the catalytic reaction of serine proteases the basicity of a histidine and the nucleophilicity of a serine, both residues together with an aspartate residue belonging to the catalytic triad, are of great importance. The influence of amino acid substitution on the basicity and the fast nucleophilicity of these important amino acids was investigated using a very simple and fast procedure. The amino acids of the triad were calculated at an ab initio level with the environment residues represented by point charges obtained with the CHelpG population analysis. Basicity trends were found to be reflected by the charge on the basic nitrogen and the "protonation energy", calculated for the triad. The serine nucleophilicity was found to correlate with the charge on the hydroxyl atom and with the minimum of the Molecular Electrostatic Potential in the vicinity of this oxygen.

Amino Acid Substitution↗
PubMed1990

Molecular interactions of the junctional foot protein and dihydropyridine receptor in skeletal muscle triads.

Isolated triadic proteins were employed to investigate the molecular architecture of the triad junction in skeletal muscle. Immunoaffinity-purified junctional foot protein (JFP), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), aldolase and partially purified dihydropyridine (DHP) receptor were employed to probe protein-protein interactions using affinity chromatography, protein overlay and crosslinking techniques. The JFP, an integral protein of the sarcoplasmic reticulum (SR) preferentially binds to GAPDH and aldolase, peripheral proteins of the transverse (T)-tubule. No direct binding of JFP to the DHP receptor was detected. The interactions of JFP with GAPDH and aldolase appear to be specific since other glycolytic enzymes associated with membranes do not bind to the JFP. The DHP receptor, an integral protein of the T-tubule, also binds GAPDH and aldolase. A ternary complex between the JFP and the DHP receptor can be formed in the presence of GAPDH. In addition, the DHP receptor binds to a previously undetected Mr 95 K protein which is distinct from the SR Ca2+ pump and phosphorylase b. The Mr 95 K protein is an integral protein of the junctional domain of the SR terminal cisternae. It is also present in the newly identified "strong triads" (accompanying paper). From these findings, we propose a new model for the triad junction.

Animals↗
PubMed2002

Sodium transport in triads isolated from rabbit skeletal muscle.

Triads and transverse tubules isolated from mammalian skeletal muscle actively accumulated Na+ in the presence of K+ and Mg-ATP. Active Na+ transport exhibited a fast single-exponential phase, lasting 2 min, followed by slower linear uptake that continued for 10 minutes. Valinomycin stimulated Na+ uptake, suggesting it decreased a pump-generated membrane potential gradient (Vm) that prevented further Na+ accumulation. At the end of the fast uptake phase transverse tubule vesicles incubated in 30 mM external [Na+] attained a ratio [Na+]in/[Na+]out=13.4. From this ratio and the transverse tubule volume of 0.35 microl/mg protein measured in this work, [Na+]in=400 mM was calculated. Determinations of active K+ transport in triads, using 86Rb+ as tracer, showed a 30% decrease in vesicular 86Rb+ content two minutes after initiating the reaction, followed by a slower uptake phase during which vesicles regained their initial 86Rb+ content after 10 minutes. Transverse tubule volume increase during active Na+ transport-as shown by light scattering changes of isolated vesicles--presumably accounted for the secondary Na+ and 86Rb+ uptake phases. These combined results indicate that isolated triads have highly sealed transverse tubules that can be polarized effectively by the Na+ pump through the generation of significant Na+ gradients.

Animals↗
PubMed2003

The CT triad of malignancy in meningioma--redefinition, with a report of three new cases.

The CT triad of extracranial soft-tissue tumour, underlying osteolysis and an intracranial tumour was reported as a sign of malignancy in meningioma, by Younis and Sawaya in 1992. We report the clinical and CT spectrum of three new cases with a similar triad, confirmed to be malignant meningioma. However, we redefine this sign and suggest that this triad is an unequivocal indicator of malignancy in meningioma, provided metastases have been excluded.

Adult↗
PubMed1999

Triad assessment of the impact of chromium contamination on benthic macroinvertebrates in the chusovaya river (Urals, russia)

The impact of chromium (Cr) contamination on the benthic macroinvertebrate community of the Chusovaya River in the Ural Mountains of Russia was assessed using a triad approach. The triad consisted of chemical analysis of the contamination in various environmental compartments, examination of the benthic macroinvertebrate community structure, and analysis of ecotoxicological effects on the caddisfly Hydropsyche pellucidula (Trichoptera). Chemical analyses of water, sediments, and detritus indicated that the main contaminant present was indeed Cr and that the level of the Cr contamination near the point source, a severely polluted dead tributary, was extremely high: Downstream Cr concentrations were about 450 times higher in water and 25 times higher in sediments compared with a clean reference site upstream. The contamination at the mouth of the tributary was even more severe: 800 times more Cr in water and 50 times more Cr in sediments. Benthic macroinvertebrate community structure was studied using artificial substrates colonized in situ. Lower species richness was observed at the downstream site compared with the upstream site. Larvae of H. pellucidula collected from the contaminated site on the river bioaccumulated large amounts of Cr and exhibited physical abnormalities. The incidence of tracheal gill damage was significantly higher than at a reference site on the nearby Reshotka River, as was the incidence of discoloration of the anal papillae of these animals. The application of a triad demonstrated that the observed extreme Cr contamination had an adverse effect on aquatic life in the Chusovaya River, both at the community level (reduced diversity) and at the level of individuals (sublethal effects on surviving individuals).http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p182.html

Journal Article↗
PubMed1991

Injuries to the portal triad.

We reviewed the management and clinical course of 21 patients with extrahepatic injuries to the portal triad seen over the past 11 years at a Level I trauma center. These represented only 0.21% of patients with multiple trauma admitted during this time. Portal triad injury was never specifically diagnosed preoperatively. Extrahepatic bile duct injury occurred in 4 patients, portal vein injury in 14, and hepatic artery injury in 7; 3 patients had combined injuries. Eleven patients (52%) died, all due to uncontrolled hemorrhage from either an injured portal vein or associated intra-abdominal injuries. Management of the bile duct injuries included drainage alone, bile duct ligation, and Roux-Y hepaticojejunostomy. Survivors of portal vein injury were managed with lateral venorrhaphy. Ligation of the hepatic artery appeared to be optimal for injuries incurred by this vessel. Complications necessitating reoperation or percutaneous drainage procedures were encountered in 8 of 10 surviving patients (80%). Injuries to the portal triad are uncommon, difficult to diagnose, and technically challenging. Mortality is most directly related to uncontrolled intraabdominal hemorrhage, and salvage requires rapid control of bleeding as the first treatment priority.

Adolescent↗