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PubMed1988

Differences between monkey visual cortex cells in triplet and ghost doublet informational symbols relationships.

On the basis of the recent discovery that precisely replicating triplets of impulses present in All-Interval histograms of spike trains generated by visual cortex cells of Rhesus monkeys are surrounded by multiple copies of "ghost doublets" of such triplets, we have examined and compared in detail, the spike trains generated by four complex cells in the striate cortex of curarized monkeys with respect to: (1) The number of precisely replicating triplet patterns embedded in trains of discharges generated in response to specific Hubel-Wiesel stimulation; (2) The effect of time separating the occurrence of such replicating triplets on the number and time distribution of their ghost doublets; (3) The effect of decreasing the precision criterion for the detection of replicating (parent) triplets (from the standard 0.14 ms criterion to 0.5 ms) on the relationships between triplets and their ghosts and (4) The comparison of the distributions in time of ghost doublets around the first and second copies of triplets when the time intervals separating them were greater than or less than 0.5 s. We found that the precision of replication of triplets varies somewhat from one cell to another, and that ghosts doublets are more copiously associated with replicating triplets emitted near in time to each other than with triplets emitted after larger time intervals, except in the case of one cell. In order to assess the statistical significance of our findings, we systematically shuffled the order of occurrence of intervals in every burst of all the records of one of the studied cells and repeated the analysis. Both the number of replicating triplets and of associated ghost doublets is significantly depressed (but not totally obliterated) by the above shuffling procedure. Finally, further implications based on a model of neural information transmission in the form of temporal correlations between spikes are discussed.

Animals↗
PubMed2006

Chlorophyll triplet states associated with Photosystem I and Photosystem II in thylakoids of the green alga Chlamydomonas reinhardtii.

The analysis of FDMR spectra, recorded at multiple emission wavelengths, by a global decomposition technique, has allowed us to characterise the triplet populations associated with Photosystem I and Photosystem II of thylakoids in the green alga Chlamydomonas reinhardtii. Three triplet populations are observed at fluorescence emissions characteristic of Photosystem II, and their zero field splitting parameters have been determined. These are similar to the zero field parameters for the three Photosystem II triplets previously reported for spinach thylakoids, suggesting that they have a widespread occurrence in nature. None of these triplets have the zero field splitting parameters characteristic of the Photosystem II recombination triplet observed only under reducing conditions. Because these triplets are generated under non-reducing redox conditions, when the recombination triplet is undetectable, it is suggested that they may be involved in the photoinhibition of Photosystem II. At emission wavelengths characteristic of Photosystem I, three triplet populations are observed, two of which are attributed to the P(700) recombination triplet frozen in two different conformations, based on the microwave-induced fluorescence emission spectra and the triplet minus singlet difference spectra. The third triplet population detected at Photosystem I emission wavelengths, which was previously unresolved, is proposed to originate from the antenna chlorophyll of the core or the unusually blue-shifted outer antenna complexes of this organism.

Animals↗
PubMed1997

Excited triplet state photophysics of the sulphonated aluminium phthalocyanines bound to human serum albumin.

The binding of the sulphonated aluminum phthalocyanines to human serum albumin (HSA) in aqueous phosphate buffer solution at 25 degrees C has been studied by measuring the properties of the triplet excited states of these dyes. The triplet lifetimes were measured by triplet-triplet absorption flash photolysis. The triplet lifetime of the disulphonated AlS2Pc (2.5 microM) varies from 500 +/- 30 microseconds in the absence of protein to 1.100 microseconds and longer with HSA concentrations above 100 microM. Under identical conditions, the maximum triplet lifetimes of the mono-, tri- and tetrasulphonated compounds bound to HSA are shorter than those for the disulphonated species. The increase in the triplet state lifetimes is attributed to the ability of the bulk aqueous phase to interact with the sensitizer at the site of binding; the site of binding being dependent on the degree of sulphonation. For AlS2Pc and AlS3Pc at all HSA concentrations, and regardless of the degree of sulphonation, all the triplet state decay profiles follow simple pseudo-first-order kinetics. The exponential decay of the triplet phthalocyanine at all HSA concentrations is ascribed to the rapid association and dissociation of the phthalocyanine-HSA complex on the time-scales of the triplet state lifetimes. A simplified one-step binding model is utilized to describe the results. The association of AlS1Pc with HSA results in substantial quenching of the triplet state quantum yield, and a more complex model is required to analyze the results. The tetrasulphonated compound (AlS4Pc) binds to the protein at a site where it experiences some protection from the aqueous phase.

Aluminum↗
PubMed2002

Inversion of 4-methoxybenzophenone triplet in aqueous solutions.

The triplet state of 4-methoxybenzophenone (4-MBP) has been investigated by laser flash photolysis and emission techniques in several solvents. In non-polar cyclohexane, 4-MBP triplet has an (n,pi*) configuration with the typical triplet-triplet absorption spectrum of benzophenone (lambda(max) ca. 525 nm). However, due to the proximity of the two lowest triplet states of different configuration, some unusual features are observed in polar solvents. Thus, 4-MBP shows in aqueous solutions a transient absorption spectrum with lambda(max) at 450 and 680 nm, which can be attributed to a T1 (pi,pi*) state. Further, transient absorption spectra due to T1 (n,pi*) and T2 (pi,pi*) being simultaneously populated are observed upon laser excitation of 4-MBP in polar solvents such as acetonitrile or methanol. The triplet state inversion (n,pi* to pi,pi*) is also detected by the measurement of triplet quenching rate constants by 1,4-cyclohexadiene (a good hydrogen donor) in acetonitrile and water (kH ca. 2 x 10(8) and 5 x 10(5) M(-1) s(-1), respectively) and by the determination of room-temperature phosphorescence (the emission quantum yield at room-temperature decreases from 0.004 in acetonitrile to less than 1 x 10(-6) in water). Further, the energy of the 4-MBP triplet state is ca. 288 kJ mol(-1) both in polar and non-polar organic solvents, while in water it drops to 275 kJ mol(-1). The photophysical properties of 4-MBP are compared with those of 4-aminobenzophenone (4-ABP), which also possesses an electron-donating group. In polar organic solvents such as acetonitrile, the transient absorption spectrum and the quenching rate constant of hydrogen abstraction for triplet 4-ABP are practically the same as those obtained for 4-MBP in aqueous solutions. On the other hand, a small T2 (pi,pi*) contribution is observed in the triplet-triplet absorption spectrum of 4-ABP in cyclohexane.

Journal Article↗
PubMed2005

Perinatal outcome of spontaneously conceived triplet pregnancies in relation to chorionicity.

OBJECTIVE: The purpose of this study was to determine the perinatal outcome of spontaneously conceived triplet pregnancies in relation to chorionicity. STUDY DESIGN: In this retrospective study, maternal, neonatal, and chorionicity data were collected from 88 sets of triplet pregnancies that were delivered at >20 weeks of gestation from 3 tertiary referral centers in the United Kingdom. The data were collected between January 1986 and December 2000. There were 49 sets of trichorionic triamniotic triplet pregnancies and 39 sets of triplet pregnancies with a monochorionic pair (ie, dichorionic triamniotic triplets). The outcome of each pregnancy was assessed in relation to chorionicity. RESULTS: The overall perinatal mortality rate was 151.5 per 1000 total births, with dichorionic triamniotic triplets having a 5.5-fold higher risk than trichorionic triamniotic gestations (odds ratio, 5.5; 95% CI, 2.5-12.2). The dichorionic triamniotic triplets have a higher risk of delivery at < 30 weeks of gestation (odds ratio, 4.6; 95% CI, 1.6-11.8; P < .05) and birth weight of < 1000 g (odds ratio, 53.6; 95% CI, 17.5-164; P < .05) than those of trichorionic triamniotic pregnancies. The neonatal morbidity in terms of respiratory distress syndrome (P < .001), anemia (P < .01), and intraventricular hemorrhage (P < .001) were higher in dichorionic triamniotic compared with trichorionic triamniotic triplets. The premature rupture of membrane (odds ratio, 7.5; 95% CI, 3.5-15.7) and twin-twin transfusion syndrome (odds ratio, 14.9; 95% CI, 6.6-4) were independent risk factors for perinatal death. CONCLUSION: In spontaneously conceived triplets, the incidence of dichorionicity was 44%. The dichorionic triamniotic triplets have a 5.5-fold higher risk of adverse perinatal outcome predominantly because of twin-twin transfusion syndrome and premature rupture of membranes.

Birth Weight↗
PubMed2006

Temporal changes in rates of stillbirth, neonatal and infant mortality among triplet gestations in the United States.

OBJECTIVE: The purpose of this study was to examine temporal changes in stillbirth, neonatal and infant mortality rates among triplet births in the US, and to assess the contributions of triplet delivery at < 34 weeks to these changes. STUDY DESIGN: Data on triplet live births, and fetal and infant deaths (1990-2002) delivered at > or = 22 weeks and fetuses weighing > or = 500 g (n = 66,986) were derived from the US linked birth/infant death data files. Relative risk (RR), quantifying changes in triplet stillbirth, neonatal (death within the first 28 days) and infant mortality (death within the first year) rates between 1990 and 1991 and 2001 and 2002, were derived. Temporal changes in triplet births at < 34 weeks, and changes in stillbirth, and neonatal and infant mortality rates were examined through logistic regression models before and after adjusting for confounders. RESULTS: Triplet births at < 34 weeks increased by 25% between 1990 and 1991 (48.7%) and 2001 and 2002 (60.9%). Stillbirth, neonatal and infant mortality rates declined by 52% (RR 0.48, 95% confidence interval [CI] 0.36-0.63), 32% (RR 0.68, 95% CI 0.58-0.80), and 38% (RR 0.62, 95% CI 0.53-0.71), respectively, between 1990 and 1991 and 2001 and 2002. The increase in triplet births at < 34 weeks was not associated with the stillbirth decline, but was associated with an excess 14% and 12% increase in neonatal and infant deaths, respectively. CONCLUSION: Our findings suggest that the increase in triplet births at < 34 weeks' gestation is not associated with changes in triplet stillbirths, but is associated with increases in triplet neonatal and infant mortality.

Female↗
PubMed2003

Birth weight discordance and adverse fetal and neonatal outcomes among triplets in the United States.

OBJECTIVE: To examine the association between intratriplet birth weight discordance, fetal and neonatal mortality, and smallness for gestational age. METHODS: The 1995-1997 Centers for Disease Control and Prevention's Matched Multiple Birth file was used for this analysis. Birth weight discordance was calculated as the difference in birth weight between the largest and the smallest triplet's weight and expressed as percentage of the largest triplet's weight. For the middle-weight triplet, we also used the largest triplet's weight as a reference in calculating percentage birth weight discordance, which was then grouped into quintiles. RESULTS: Among 15,511 triplet live births and fetal deaths (at least 20 weeks' gestation), 35% had less than 10% birth weight discordance, 19.3% had 10-15%, 16.4% had 15-21%, 15.2% had 21-29%, and 14.1% had 29% or more. After controlling for confounders, the risk of fetal death associated with quintile V was significantly higher than that associated with quintile I for smallest (odds ratio [OR] 10.88; 95% confidence interval [CI] 4.87, 26.56), middle (OR 22.6; 95% CI 11.05, 46.3), and largest (OR 2.41; 95% CI 1.01, 5.89) triplets. Smallest and middle triplets in quintile V were more likely than quintile I triplets to be born small for gestational age (OR 26.0; 95% CI 17.1, 39.9 for smallest, and OR 13.4; 95% CI 8.01, 22.3 for middle). Birth weight discordance quintile was not associated with smallness for geatational age among largest triplets nor consistently with neonatal mortality among smallest, middle, or largest triplets. CONCLUSION: Increasing birth weight discordance was associated with increased risk of fetal death and smallness for gestational age. A birth weight discordance threshold of at least 29% should alert obstetricians for appropriate decision making.

Adult↗
PubMed2001

Infant mortality rates in single, twin and triplet births, and influencing factors in Japan, 1995-98.

The infant mortality rate (IMR) was analysed among single, twin and triplet births during the period from 1995 to 1998 using Japanese Vital Statistics. This study also investigated the effects of order of multiple births and of birthweight on the IMR. Proportions of neonatal deaths among total infant deaths were about 1/2 for singletons and 3/4 for both twins and triplets. Thus, to reduce the IMR, intensive care of multiple births is likely to be very important during the first month of life. The IMR was higher in males than females for both singletons and twins, but not in triplets. Relative risks of the IMR in multiples relative to singletons were 5-fold in twins and 12-fold in triplets. The IMR was higher in the second-born (18 per 1000 live births) than the first-born (16) twin and higher in the third-born (51) than the first-born (31) and the second-born (34) triplet. The higher risk in the second-born than the first-born twin may be related to delivery complications. The IMR decreased rapidly as birthweight increased in singletons, twins, and triplets. IMRs for < or =1500 g were 2.4 per 1000 live births in singletons, 5.9 in twins and 6.1 in triplets. The corresponding proportions of infant deaths were 75%, 33% and 10% respectively. The higher relative risks of multiple births are almost entirely the result of the lower birthweight distribution among twins and triplets. To reduce the IMR, birthweight is an important factor in twins, triplets and singletons. The overall early neonatal death rate decreased as gestational age rose in singletons, twins and triplets. For birthweights <1000 g, higher IMRs were related to gestational ages of <28 weeks.

Birth Order↗
PubMed2005

Prenatal diagnosis and obstetric outcomes in triplet pregnancies in relation to chorionicity.

OBJECTIVE: This study describes the frequency, pregnancy complications and outcomes of non-trichorionic triplet pregnancies. DESIGN: A retrospective observational study. SETTING: Two tertiary level referral centres of Obstetrics and Prenatal Medicine, Germany. POPULATION: All women booked to receive targeted ultrasound screening between January 1998 and June 2003. The mixed low and high risk population included 36,430 women with ultrasound examinations between 11 and 24 weeks of gestation. Of those with available outcome, 176 were triplet pregnancies with three viable fetuses. METHODS: Analysis of ultrasound data and perinatal outcome in triplet gestations who had first and second trimester targeted ultrasound examination. Pregnancies with monochorionic or dichorionic placentation were identified and pregnancy outcome was compared to trichorionic triplets. MAIN OUTCOME MEASURES: Intrauterine fetal death, fetal growth restriction (FGR), mean discordance and survival rate in non-trichorionic versus trichorionic triplets. RESULTS: Triplets were trichorionic in 81.8% and had a monochorionic or dichorionic placentation in the remaining 18.2%. The rate of monochorionicity and dichorionicity was significantly higher after spontaneous conception than after assisted reproductive technologies (44.8%vs 12.9%, P < 0.001). In non-reduced monochorionic and dichorionic triplets compared with non-reduced trichorionic triplets, there was a higher rate of intrauterine fetal death (8.8%vs 1.5%, P < 0.01), FGR (33.3%vs 25.5%), mean discordance (20.5%vs 12.7%, P < 0.01), discordance >30% (26.3%vs 2.9%, P < 0.01) and delivery <32 weeks of gestations (47.4%vs 32.2%). There was a lower survival rate in non-trichorionic triplets (84.2%) than in trichorionic ones (91.7%). CONCLUSION: Triplet pregnancies with a monochorionic or dichorionic placentation are at significantly higher risk of adverse pregnancy outcome compared with trichorionic pregnancies. First trimester evaluation of chorionicity is strongly emphasised.

Chorion↗
PubMed2000

The outcome of triplet versus twin pregnancies.

OBJECTIVE: The purpose of this study was to examine and to determine whether triplet pregnancies are associated with a significantly greater risk of adverse outcome than are twin pregnancies. METHODS: Maternal and perinatal outcomes were evaluated retrospectively in 41 sets of triplets and twin pregnancies that were matched for maternal age, parity, mode of delivery, preterm delivery, mode of conception, and antepartum complications. MAIN OUTCOME MEASURES: Perinatal outcome in triplet versus twin gestation. RESULTS: Triplets had a significantly lower mean average birth weight than in twin gestation (1,596 vs. 2,317 g, p<0.018) and gestational age at delivery (32.9 vs. 35.9 weeks; p< 0.03). Preterm labour occurred significantly more often in triplet than in twin gestation (80.5 vs. 41.5%) as did preterm delivery (87.8 vs. 46.2%). Triplets required a longer hospital stay than did twins (25 vs. 9 days; p<0.04). There were no significant differences between the groups in number of administrations to the Special Care Baby Unit (32.5 vs. 30.5%). Apgar score <7 at 5 min was significantly more in triplet as compared with twin gestation (17 vs. 6%; p<0.0015). Neonatal deaths occurred significantly more in triplets than in twins (26 vs. 8.5%; p< 0.0001). There were no significant differences between the groups in maternal antepartum or neonatal complications such as anaemia, pregnancy-induced hypertension, placental abruption, respiratory distress syndrome or intraventricular haemorrhage. Preterm labour was the only complication that occurred significantly more often in the triplet than in the twin gestation. CONCLUSIONS: We concluded that this information could be useful in counseling patients with respect to the anticipated perinatal outcome of triplet pregnancies.

Adult↗
PubMed1995

Sex ratio in triplets.

Since the introduction of different ovulation induction regimens the incidence of triplet pregnancies increased from a spontaneous rate of about 1:10,000 to the frequency of nearly 1:1000. Sex ratio of trigemini and male/female proportion of the three newborns within the same triplet set is the amazing issue that we attempted to elucidate in the present study. Data on 36 women with triplet pregnancies delivered in our hospital and information regarding 2717 triplet pregnancies reported by 16 relevant papers were included in this study. 36 women delivered 63 (58%) male and 45 (42%) female babies. Triplet sets of same gender comprised 33% of all trigemini. Sex ratios (male/female) for the spontaneous, menotropin and clomiphene group were 2.00, 1.57 and 0.94 respectively. Homogenous male/female set ratio was 5.0, 2.0 and 0.5 in menotropin, spontaneous and clomiphene groups respectively. As the percentage of ovulation induction triplet pregnancies increased constantly from 0% to 100%, a decline in the fraction of homogenous gender triplet sets was observed--from 73% to 23%. It may be concluded that sex ratio in triplet newborns is divergent according to different publications with most of the authors reporting a male/female ratio of less than 1.00. Ovulation induction results in a lower proportion of homogenous sex triplets sets. Superovulation by menotropins cause a higher percentage of male triplet newborns when compared to ovulation induction by clomiphene.

Clomiphene↗
PubMed2004

[Comparison of child-rearing problems and necessary community welfare and health services between mothers with twins or triplets of mothers with singleton children].

PURPOSE: The purpose of this survey was to study child-rearing problems and necessary community welfare and health services in the families with twins or triplets as compared with families with singleton children. METHODS: The subjects were 205 mothers of twins or triplets aged less than 6 and 911 mothers of similarly aged singleton children. RESULTS: 1. Concerning maternal feeling when informed of a pregnancy, a significant difference was observed between the mothers with twins or triplets and the mothers with singleton children: 1.3% of the mothers with singleton children were not delighted when informed of a pregnancy, while the rate for mothers with twins or triplets was 12.4%. Mothers of twins or triplets showed significantly greater anxiety when informed of a pregnancy, and also after delivery, greater anxiety for child-rearing. 2. Mothers of twins or triplets were more likely to feel they could not get information regarding pregnancy and child-rearing. 3. There were higher rates of child-rearing problems with regard to economic burden, attending a hospital when a child become ill, shortage of hands for medical examinations or preventive injections, going out with children, shortage of cooperators for child-rearing, lack of time and difficulty for feeding methods for twins or triplets. 4. Community welfare and health services that mothers of twins or triplets wished for were an allowance for child-rearing in 77.0% of cases, helper or baby-sitter for medical examinations or preventive injections in 59.8%, and meeting for mothers of multiple children in 52.0%. CONCLUSION: This study indicated a tendency for mothers of twins or triplets to show greater anxiety during pregnancy, greater anxiety for child-rearing after delivery, and harder to get information regarding pregnancy and child-rearing as compared with those having singleton children. Mothers of twins or triplets had more child-rearing problems with regard to shortage of cooperators, economic burden and feeding methods for plural infants.

Anxiety↗
PubMed1981

Reaction center triplet states in photosystem I and photosystem II.

A photosystem I (PS I) particle has been prepared by lithium dodecyl sulfate digestion which lacks the acceptor X, and iron-sulfur centers B and A. Illumination of these particles at liquid helium temperature results in the appearance of a light-induced spin-polarized triplet signal observed by EPR. This signal is attributed to the triplet state of P-700, the primary donor, formed by recombination of the light induced radical pair P-700+ A1- (where A1 is the intermediate acceptor). Formation of the triplet does not occur if P-700 is oxidized or if A1 is reduced, prior to the illumination. A comparison of the P-700 triplet with that of P-680, the primary donor of Photosystem II, shows several differences. (1) The P-680 triplet is 1.5 mT (15 G) wider than the P-700 triplet. This is reflected by the zero-field splitting parameters, which indicate that P-700 is a slightly larger species than P-680. The zero-field splitting parameters do not indicate that either P-700 or P-680 are dimeric. (2) The P-700 triplet is induced by red and far-red light, while the P-680 triplet is induced only by red light. (3) The temperature dependences of the P-700 triplet and the P-680 triplet are different.

Chloroplasts↗
PubMed1990

Neurofilament protein-triplet immunoreactivity in distinct subpopulations of peptide-containing neurons in the guinea-pig coeliac ganglion.

A battery of polyclonal and monoclonal antibodies raised against the triplet of identified neurofilament protein subunits was used to investigate neurofilament protein immunoreactivity in neurons of the guinea-pig coeliac ganglion. Using optimal conditions of fixation and tissue processing for each antibody we found that only 20% of the postganglionic sympathetic neurons in the guinea-pig coeliac ganglion contain neurofilament protein-triplet immunoreactivity. Double labelling with neurofilament protein-triplet antibodies raised in different species demonstrated that all of these antibodies labelled the same population of neurons. Double labelling using mouse monoclonal antibodies against neurofilament proteins in combination with rabbit polyclonals to neuronal markers showed that neurofilament protein-triplet immunoreactivity is restricted to specific chemically coded subpopulations of noradrenergic neurons. Approximately 52% of neurons in the ganglion contain neuropeptide Y and are presumed vasomotor neurons projecting to blood vessels in the submucosa of the small intestine. Virtually none of the neuropeptide Y-containing neurons were labelled with neurofilament protein-triplet antibodies. Neurons that contain somatostatin (21%) project to the submucous ganglia of the small intestine. Approximately two-thirds of neurons containing somatostatin are immunoreactive for the neurofilament protein-triplet. The other postganglionic neurons in the ganglion (27%) project to the myenteric plexus of the small intestine and do not contain either neuropeptide Y or somatostatin. Approximately a quarter of these neurons were labelled with neurofilament protein-triplet antibodies. These results suggest that the neurofilament protein-triplet may not be an intrinsic component of the cytoskeleton of all neurons. Furthermore the idea of a chemical coding of neurons should be extended to cytoskeletal proteins. The finding that these neurofilament proteins are confined to specific neuronal subpopulations has important implications for the search for a role of the neurofilament protein-triplet in neurons, for the interpretation of classical neurohistological silver impregnation techniques which appear to stain only neurofilament protein-triplet-containing neurons, as well as for neuropathological conditions that may involve these proteins in disease processes.

Animals↗
PubMed1989

Time-resolved absorption, circular dichroism, and emission of tRNA. Evidence that the photo-cross-linking of 4-thiouridine in tRNA occurs from the triplet state.

The time-resolved optical density (TROD) and time-resolved circular dichroism (TRCD) spectra of the lowest triplet state of 4-thiouridine (4t-Urd) in aqueous solutions of tRNA are reported. The TROD spectrum is consistent with the triplet state being primarily in the thione tautomer. The intersystem crossing yield to the triplet is 0.35 and 0.27 (+/- 10%), respectively, with and without 10(-2) Mg2+ added to the solution. Upon addition of increasing amounts of I- to solutions of tRNA, the initial triplet yield decreases, the rate of the observed triplet decay increases, and the quantum yield of internal photo-cross-linking decreases for the 4t-Urd chromophore. The results show quantitatively that the near-UV-induced photo-cross-linking reaction in tRNA occurs from the triplet state of 4t-Urd. From the TRCD spectrum the dissymmetry factor (delta epsilon/epsilon) of some of the triplet-triplet absorption bands is shown to be significantly larger than for any of the ground-state absorption bands. Two CD transitions are seen in the triplet-triplet spectrum which are obscured in the TROD spectrum by the strong ground-state bleaching signal near 335 nm. This shows that TRCD may be useful, in some cases, in locating electronic transitions that are not observed in TROD spectra.

Chemical Phenomena↗
PubMed2004

The triplet state of cytosine and its derivatives: electron impact and quantum chemical study.

The excitation of the lowest electronic states and vibrational excitation of cytosine (C) have been studied using electron energy loss spectroscopy (EELS, 0-100 eV) with angular analysis. The singlet states have been found to be in good agreement with UV-VIS absorption results on sublimed films, slightly blueshifted by about 0.1 eV. The EEL spectra recorded at residual energy below 2 eV show clear shoulders at energy losses of 3.50 and 4.25 eV (+/-0.1 eV). They are assigned to the lowest triplet electronic states of cytosine. Energies and molecular structures of the lowest-lying triplet state of C and its methylated and halogenated 5-X-C, 6-X-C, and 5-X, 6-X-C substituted derivatives (X=CH3, F, Cl, and Br) have been studied using quantum chemical calculations with both molecular orbital and density functional methods, in conjunction with the 6-311++G(d,p), 6-311++G(3df,2p), and aug-cc-pVTZ basis sets. The triplet-singlet energy gap obtained using coupled-cluster theory [CCSD(T)] and density functional theory (DFT) methods agrees well with those derived from EELS study. The first C's vertical triplet state is located at 3.6 eV, in good agreement with experiment. The weak band observed at 4.25 eV is tentatively assigned to the second C's vertical triplet excitation. For the substituted cytosines considered, the vertical triplet state is consistently centered at 3.0-3.2 eV above the corresponding singlet ground state but about 1.0 eV below the first excited singlet state. Geometrical relaxation involving out-of-plane distortions of hydrogen atoms leads to a stabilization of 0.6-1.0 eV in favor of the equilibrium triplet. The lowest-lying adiabatic triplet states are located at 2.3-3.0 eV. Halogen substitution at both C(5) and C(6) positions tends to reduce the triplet-singlet separations whereas methylation tends to enlarge it. The vibrational modes of triplet cytosine and the ionization energies of substituted derivatives were also evaluated.

Cytosine↗
PubMed2002

The GAA triplet-repeat sequence in Friedreich ataxia shows a high level of somatic instability in vivo, with a significant predilection for large contractions.

Friedreich ataxia is commonly caused by large expansions of a GAA triplet-repeat (GAA-TR) sequence in the first intron of the FRDA gene. We used small-pool PCR to analyze somatic variability among 7190 individual FRDA molecules from peripheral blood DNA of subjects carrying 12 different expanded alleles, ranging in size from 241 to 1105 triplets. Expanded alleles showed a length-dependent increase in somatic variability, with mutation loads ranging from 47% to 78%. We noted a strong contraction bias among long alleles (>500 triplets), which showed a 4-fold higher frequency of large contractions versus expansions. Some contractions were very large; of all somatic mutations scored, approximately 5% involved contractions of >50% of the original allele length, and 0.29% involved complete reversion to the normal/premutation length (< or =60 triplets). These observations contrast sharply with the strong expansion bias seen in expanded CTG triplet repeats in myotonic dystrophy. No somatic variability was detected in >6000 individual FRDA molecules analyzed from 15 normal alleles (8-25 triplets). A premutation allele with 44 uninterrupted GAA repeats was found to be unstable, ranging in size from 6 to 113 triplets, thus establishing the threshold for somatic instability between 26 and 44 GAA triplets. Analysis of an additional 7850 FRDA molecules from serially passaged lymphoblastoid cell lines carrying nine expanded alleles (132-933 triplets) showed very low mutation loads, ranging from 0% to 6.2%. Our data indicate that expanded GAA-TR alleles in Friedreich ataxia are highly mutable and have a natural tendency to contract in vivo, and that these properties depend on multiple factors, including DNA sequence, triplet-repeat length and unknown cell-type-specific factors.

DNA↗
PubMed2006

Different AIS triplets: Different mortality predictions in identical ISS and NISS.

BACKGROUND: Previous studies demonstrated different mortality predictions for identical Injury Severity Scores (ISS) from different Abbreviated Injury Scale (AIS) triplets. This study elaborates in both scope and volume producing results of a larger magnitude, applicable to specific injury subgroups of blunt or penetrating, traumatic brain injury, various age groups, and replicated on NISS. METHODS: All patients hospitalized after trauma at 10 hospitals, with ISS/NISS (new ISS) generated by two AIS triplets, excluding patients with isolated minor or moderate injuries to a single body region were studied. Patients were separated into two groups based on the different triplets. Inpatient-mortality rates were calculated for each triplet group. Odds ratios were calculated to estimate the risk of dying in one triplet group as compared with the other. The chi test determined whether the difference in mortality rate between the two groups was significantly different. Differences were further explored for various subgroups. RESULTS: There were 35,827 patients who had ISS/NISS scores generated by two different AIS triplets. Significant differences in death rates were noted between triplet groups forming identical ISS/NISS. Odds ratio for being in the second group (always containing the higher AIS score) ranged from 2.3 to 7.4. CONCLUSIONS: ISS and NISS that are formed by different AIS triplets have significantly different inpatient-mortality rates. The triplet with the higher AIS score has higher inpatient-mortality rates, overall and in several sub-populations of varying vulnerability. The comparison of populations and the interpretation of ISS/NISS based outcome data should take this important information into account and the components of AIS triplets creating each ISS and NISS should be reported.

Abbreviated Injury Scale↗