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PubMed1990

Excision-repair capacity in Streptococcus pneumoniae: cloning and expression of a uvr-like gene.

Although deficient in photoreactivation and some SOS-like functions, Streptococcus pneumoniae has the capacity to carry out excision repair when exposed to UV light. The repair ability and sensitivity to UV irradiation or treatment with chemical agents in the wild type and a UV-sensitive mutant strain indicate that UV-induced pyrimidine dimers might be repaired in pneumococcus by a system similar to the uvr-dependent system in Escherichia coli. A gene complementing the mutation conferring UV sensitivity of the mutant strain has been cloned. The coding region directs the synthesis of a polypeptide with a molecular weight of 78 kDa. The relationship with uvr-like protein in E. coli is discussed.

Bacterial Proteins↗
PubMed2004

Controlling surface nano-structure using flow-limited field-injection electrostatic spraying (FFESS) of poly(D,L-lactide-co-glycolide).

Improved control of surface micro- and nano-structure may lead to enhanced performance of degradable biomedical devices such as surgical dressings, vascular grafts, tissue engineering scaffolds, sutures, and structures for guided tissue regeneration. An electrohydrodynamic method called flow-limited field-injection electrostatic spraying (FFESS) has been developed as an improved technique for the controlled deposition of polymeric material. Injecting charge using a nano-sharpened tungsten needle in a process called field ionization can efficiently induce an ionic state in a solution of poly(D,L-lactide-co-glycolide) increasing its capacity to carry charge. As a result, sprays have been produced that are finer and more precisely controlled than sprays produced by conventional electrospraying techniques, which employ hypodermic needles as the spray nozzle. Here, the effect of FFESS variables including applied voltage, polymer solution flow rate, and solvent properties (surface tension, viscosity, vapor pressure) on spray performance have been qualitatively evaluated. Under certain conditions, increasing the applied voltage produced an increasingly rough surface morphology. Similarly, by reducing solvent surface tension and increasing solvent vapor pressure, more distinct surface structures could be formed including uniform nanoparticles. Working ranges of the important parameters for the production of specific structure types such as smooth or porous surfaces, non-woven or melded fibers, and distinct or melded nanoparticles have been defined. FFESS technology provides a simple yet powerful technique for fabricating biomedical devices with a precisely defined nano-structure potentially capable of utilizing a broad range of biocompatible polymeric materials.

Biocompatible Materials↗
PubMed2004

Modelling of the acid-base properties of natural and synthetic adsorbent materials used for heavy metal removal from aqueous solutions.

In this paper a comparison about kinetic behaviour, acid-base properties and copper removal capacities was carried out between two different adsorbent materials used for heavy metal removal from aqueous solutions: an aminodiacetic chelating resin as commercial product (Lewatit TP207) and a lyophilised bacterial biomass of Sphaerotilus natans. The acid-base properties of a S. natans cell suspension were well described by simplified mechanistic models without electrostatic corrections considering two kinds of weakly acidic active sites. In particular the introduction of two-peak distribution function for the proton affinity constants allows a better representation of the experimental data reproducing the site heterogeneity. A priori knowledge about resin functional groups (aminodiacetic groups) is the base for preliminary simulations of titration curve assuming a Donnan gel structure for the resin phase considered as a concentrated aqueous solution of aminodiacetic acid (ADA). Departures from experimental and simulated data can be interpreted by considering the heterogeneity of the functional groups and the effect of ionic concentration in the resin phase. Two-site continuous model describes adequately the experimental data. Moreover the values of apparent protonation constants (as adjustable parameters found by non-linear regression) are very near to the apparent constants evaluated by a Donnan model assuming the intrinsic constants in resin phase equal to the equilibrium constants in aqueous solution of ADA and considering the amphoteric nature of active sites for the evaluation of counter-ion concentration in the resin phase. Copper removal outlined the strong affinity of the active groups of the resin for this ion in solution compared to the S. natans biomass according to the complexation constants between aminodiacetic and mono-carboxylic groups and copper ions.

Acid-Base Equilibrium↗
PubMed2006

The case for 8,5'-cyclopurine-2'-deoxynucleosides as endogenous DNA lesions that cause neurodegeneration in xeroderma pigmentosum.

Patients with the genetic disease xeroderma pigmentosum (XP) lack the capacity to carry out a specific type of DNA repair process called nucleotide excision repair (NER). The NER pathway plays a critical role in the repair of DNA damage resulting from ultraviolet (UV) radiation. A subset of XP patients develops a profound neurodegenerative condition known as XP neurological disease. Robbins and colleagues [Andrews A, Barrett S, Robbins J (1978) Xeroderma pigmentosum neurological abnormalities correlate with the colony forming ability after ultraviolet irradiation. Proc Natl Acad Sci U S A 75:1984-1988] hypothesized that since UV light cannot reach into the human brain, XP neurological disease results from some form of endogenous DNA damage that is normally repaired by the NER pathway. In the absence of NER, the damage accumulates, causing neuronal death by blocking transcription. In this manuscript, I consider the evidence that a particular class of oxidative DNA lesions, the 8,5'-cyclopurine-2'-deoxynucleosides, fulfills many of the criteria expected of neurodegenerative DNA lesions in XP. Specifically, these lesions are chemically stable, endogenous DNA lesions that are repaired by the NER pathway but not by any other known process, and strongly block transcription by RNA polymerase II in cells from XP patients. A similar set of criteria might be used to evaluate other candidate DNA lesions responsible for neurological diseases resulting from defects in other DNA repair mechanisms as well.

Cockayne Syndrome↗
PubMed1999

The relation between inter-twin birth weight discordance and total twin birth weight.

OBJECTIVE: We tested the hypothesis that the frequency of growth discordance among twins is not related to the uterine capacity for carrying twins. METHOD: We counted and compared the frequencies of birth weight discordance of more than 25% in an unlike-sexed twin cohort (n = 1244) and in a population-based twin cohort (n = 7570) across the deciles of the total twin birth weight (twin A + twin B) distribution. The birth order of the heavier twin was noted. RESULTS: Similar frequencies of discordant pairs were found in both cohorts (11% and 12%, respectively; Mantel-Haenszel chi2 test: P = .131, odds ratio (OR) 0.9, 99% confidence interval (CI) 0.67, 1.11; Woolf test for heterogeneity: two-tailed P = .472). In the discordant pairs, twin A was considerably more often the heavier twin in all birth weight deciles (unlike-sexed cohort: P < 10(-8), OR 5.9, 99% CI 3.0, 11.7; population-based cohort: P < 10(-8), OR 3.1, 99% CI 2.3, 4.0), and in both cohorts (inter-cohort difference: P = .109, OR 1.4, 99% CI 0.83, 2.32). Both cohorts showed a similar nonlinear trend: given that X = decile order, discordance decreased as a function of 22.0 - 6.54 ln[X] for the unlike-sexed twins cohort and 23.0 - 8.18 ln[X] for the population-based cohort, with r values of 0.967. CONCLUSION: The more favorable the uterine milieu for carrying twins, the smaller the likelihood of discordant twin growth. Birth order of the heavier twin appears to be an integral part of the discordance phenomenon. The similarity of the cohorts suggests that these conclusions are valid for both like and unlike-sexed twins.

Birth Weight↗
PubMed1985

Impact of environmental sanitation and crowding on infant mortality in rural Bangladesh.

In two villages of Bangladesh, 2471 infants born in 1976 and 1977 were followed up for a year to study the impact of environmental sanitation and crowding on their mortality. Neonatal and postneonatal mortality rates in the study cohort were 100 and 75 per 1000 live-births, respectively. Multiple logistic regression analysis was done to estimate the effects of the selected risk factors while controlling for some socioeconomic, demographic, and biological characteristics. Risk of postneonatal mortality (PNNM) in the households which did not use latrines was 3 X 12 times (p less than 0.01) higher than in those which did and 1.5 times (p less than 0.05) higher in the households with 10 or more persons than in smaller households. PNNM in the households which did not use tube-wells (hand-pump) water was higher, but not significantly so, than in those which used tube-well water for all purposes. Neonatal mortality was completely unrelated to the environmental factors investigated.

Bangladesh↗
PubMed1998

Expression of long-patch and short-patch DNA mismatch repair proteins in the embryonic and adult mammalian brain.

Expression of the DNA mismatch repair (MMR) pathway was examined in the adult and developing rat brain. Rat homologues of human GTBP and MSH2, which are essential components of the post-replicative DNA MMR system, were identified in nuclear extracts from the adult and developing rat brain. Developmental studies showed that both GTBP and MSH2 levels were higher in nuclei isolated from the embryonic brain (day 16) than adult brain. However, this difference was not as dramatic as the difference in the number of proliferating cells. Levels of thymine DNA glycosylase (TDG), the enzyme which catalyzes the first step in short patch G:T mismatch repair, were also decreased in adult compared to embryonic brain. In the adult brain, MMR proteins were elevated in nuclear extracts enriched for neuronal nuclei. These results suggest that adult brain cells have the capacity to carry out DNA mismatch repair, in spite of a lack of ongoing DNA replication.

Animals↗
PubMed2000

A review on reproduction in South American camelids.

In this paper, aspects of reproductive physiology and endocrinology, as well as sexual behaviour in South American camelids are reviewed. Because of the many unique features of reproduction in these animals, the application of advanced breeding techniques that are routinely used in other domestic species has been slow and, in some cases, are not applicable. Relatively high embryonic loss and the capacity to carry only one offspring at a time limit production in females. Furthermore, some 20% of females do not conceive following mating. Research is needed to elucidate the causes of embryonic loss, particularly in relation to the preferential location of embryos in the left uterine horn and the apparent differential luteolytic activity of the two uterine horns. A fuller understanding of the endocrine changes and mechanisms accompanying folliculogenesis, estrus, induction of ovulation and luteal regression may led to treatments that provide better control of ovulation and enhance the quality and viability of eggs shed. In the male, the hormonal interactions involved in facilitating libido need to be established and the underlying causes of declining libido resulting from continued exposure to estrous females, identified. More importantly, there is a need to develop a routine method to collect semen from animals on farm, or in studs. Deficiencies in this area have long hampered the evaluation of sires through proper assessment of their semen quality and in the application of artificial insemination. In addition, establishment of techniques to freeze semen from these species has obvious advantages for breeding, including crossbreeding between species to improve products such as fibre and to assist in preservation of some of the more endangered New World camelids.

Animals↗
PubMed1998

Severe energy impairment consequent to inactivation of mitochondrial ATP synthase as an early event in cell death: a mechanism for the selective sensitivity to H2O2 of differentiating erythroleukemia cells.

Irreversible damage to Friend's erythroleukemia cells was caused by induction of endogenous heme biosynthesis with the differentiating agent N,N'-hexamethylene bisacetamide followed by a 30-min exposure to 0.25 mM H2O2. Early irreversible ATP depletion was observed concomitant with oxidative inactivation of the mitochondrial ATP synthase. Cell proliferative capacity was also impaired within 2 h of the treatment, and progressive delayed cell lethality, starting 2 h after the insults, was also found. Based on the prevention provided by specific antioxidants and on the absence of malodialdehyde production, all the effects were ascribed to the oxidant action of .OH radicals, or closely related species, generated through iron-catalyzed reactions of H2O2, which apparently caused site-directed oxidative modifications of iron-binding proteins, in particular mitochondrial ATP synthase, rather than peroxidation of membrane lipids. Similar effects were mimicked even in the parental cell line when oligomycin was used to inhibit selectively mitochondrial ATP synthase activity, thereby lowering the enzyme activity to a level similar to that found in H2O2-damaged differentiating cells. Hence, induction of erythroid differentiation makes the mitochondrial ATP synthase a major target of H2O2 by enhancing the availability of redox-active iron in the local environment of the enzyme. Subsequent oxidative inactivation of the mitochondrial ATP synthase, resulting in severe energy impairment, leads to loss of cell growth capacity. Erythroleukemia cells may serve as a model system for the combination of two selective properties: (1) the capacity for carrying out efficient heme synthesis and/or for undergoing iron overload-like state; and (2) subsequent enhanced sensitivity to reactive oxygen species generators. Early severe mitochondrial dysfunction and energy impairment may be a major part of the mechanism of the sensitivity.

ATP Synthetase Complexes↗
PubMed2001

Ganciclovir-loaded albumin nanoparticles: characterization and in vitro release properties.

Ganciclovir is one of the most widely used antiviral drug for the treatment of cytomegalovirus retinitis. Due to its short half-life in the vitreous, frequent administrations are necessary to maintain the therapeutic levels. In this context, the aim of this study was to characterise and in vitro evaluate the drug release properties of three different formulations of ganciclovir-loaded albumin nanoparticles. These carriers were prepared by a coacervation method and chemical cross-linking with glutaraldehyde. Depending on the step where the drug and/or cross-linking agent were added three different formulations were obtained, named models A, B and C. For model A nanoparticles, ganciclovir was incubated with the just-formed albumin nanoparticles. For the other two types of nanoparticulate formulations, the drug was added to a solution of albumin (model B) and glutaraldehyde (model C) prior to the formation of the carriers by coacervation. In all cases, the size of the different nanoparticulate formulations was comprised between 200 and 400 nm and the yield ranged from 50%, in model A, to 65% in model B. Concerning the ganciclovir loading, model B nanoparticles offered the higher capacity to carry this antiviral drug (around 30 microg ganciclovir/mg nanoparticle). On the contrary, the drug loading calculated for model A nanoparticles was only 14.6 microg/mg. The in vitro release profiles of the nanoparticles showed a biphasic pattern, with an initial and rapid release, followed by a slower step for up 5 days. This burst effect was especially relevant in model A (around 60% in 1 h), followed by model B (40%) and less important in model C (20%). The addition of trypsin to the release medium did not have a significant influence on the release characteristics. However, the release of the drug was increased in acidic or basic mediums, due to the disruption of the covalent binding between ganciclovir and the protein matrix via glutaraldehyde. This strong linkage was also confirmed by TLC experiences. In summary, a first step of incubation between the drug and the protein, prior to the preparation of nanoparticles, enabled us to obtain albumin carriers able to release ganciclovir in a sustained way.

Antiviral Agents↗
PubMed2002

A single 8,5'-cyclo-2'-deoxyadenosine lesion in a TATA box prevents binding of the TATA binding protein and strongly reduces transcription in vivo.

8,5'-Cyclo-2'-deoxypurine (cPu) lesions result from the action of the hydroxyl radical on DNA. These lesions represent a unique class of oxidative DNA lesions in that they are repaired by the nucleotide excision repair (NER) pathway but not by base excision repair (BER) or direct repair. Previous work has shown that cyclopurines can block mammalian DNA and RNA polymerases. Thus, these lesions are of interest because of their potential role in the neurodegeneration as well as internal cancers observed in patients with xeroderma pigmentosum (XP) who lack the capacity to carry out NER. In the present work, we found that the S-isomer of 8,5'-cyclo-2'-deoxyadenosine (cA) can prevent binding of the TATA binding protein (TBP) to the TATA box from the CMV promoter. To assess the functional importance of this effect in living cells, we transfected constructs containing a single cA in the CMV TATA box into XP cells to determine the effect of the lesion on gene expression in vivo. Using this approach, we found that the lesion reduced gene expression by approximately 75%. This effect was comparable to the effect of an inactivating mutation of the TATA box in the same promoter. These findings identify an additional biological effect of cyclopurine lesions in mammalian cells, which is the ability to interfere with transcription by preventing transcription factor binding to cognate recognition sequences. In addition, the approach we used in this study represents a novel method for assessing the effects of DNA lesions in non-transcribed sequences on gene expression in living cells.

Cells, Cultured↗
PubMed1997

A production limitation in syllable number: a longitudinal study of one child's early vocabulary.

The present paper reports on the phonological form of one child's productive vocabulary from age 0;10 to 1;8 with primary focus on his production of multisyllabic targets. A large percentage of his multisyllabic vocabulary was produced as one syllable until the age of 1;6. This limitation was not due to a tendency to extract only single syllables from the speech stream, but rather due primarily to a limitation on production. While some portion of his one-syllable productions could be interpreted as the result of single syllable extraction, a sizeable portion affirmed that he extracted the target size correctly by his inclusion of first and final target phonemes in his productions (e.g. [po] for piano and [kiz] for candies). The resolution of this limitation coincides with his move toward two-word speech. We conclude that there is a developmental and perhaps maturational limitation in the capacity to carry out the processes underlying word and sentence production.

Child Language↗