ABC of palliative care. Special problems of children.
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Bereavement↗
Biomedical subjects
A Goldman
Publications and source records attributed to A Goldman.
Cotinine: effects with and without nicotine.
The purpose of this study was to examine the effects of the metabolite of nicotine, cotinine, in comparison to the effects of the nicotine patch, and a combination thereof during cigarette abstinence. More specifically, this study examined the effects of cotinine on physiological measures, subjective measures assessing craving, withdrawal symptoms and mood, and performance measures. A between-subject, 2 x 2 factorial design was used, with the daily administration of a 15-mg nicotine patch (Nicotrol) versus placebo patch as one factor and 80 mg of oral cotinine fumarate versus placebo drug as the other factor. Baseline measures were obtained while the subjects smoked cigarettes on an ad lib basis for 1 week. Subjects (n = 106) were then randomly assigned to one of four treatment conditions and for the next 14 days were required to be abstinent from cigarettes and take the study drugs. Cotinine administration, with or without nicotine patch, produced serum cotinine concentrations 3 4 times higher than during ad lib smoking. Results showed a reduction of self-reported tobacco withdrawal symptoms using the nicotine patch alone. Cotinine alone had no effect on withdrawal symptoms. However, when nicotine patch was combined with cotinine, the beneficial effect of the nicotine patch on withdrawal symptoms was absent. Therefore, cotinine appears to antagonize the effects of nicotine in the alleviation of withdrawal symptoms at concentrations higher than that attained from normal smoking. This effect does not appear to be mediated by changes in nicotine disposition.
Administration, Topical↗
Effects of cotinine on cigarette self-administration.
Previous studies have shown that cotinine, a metabolite of nicotine, antagonizes some of the effects of nicotine. One study showed that cotinine eliminates the beneficial effects of the nicotine patch in reducing cigarette withdrawal symptoms. The purpose of this study was to examine the effects of various doses of cotinine on cigarette self-administration. Subjects were randomly assigned to one of three doses of cotinine fumarate (40, 80 and 160 mg) and placebo, each for a period of 10 days, in a randomized order. Outcome variables included measures of nicotine intake and subjective responses to smoked cigarettes. Results showed no differences in the number of cigarettes smoked, carbon monoxide levels, and weights of cigarette butts across the various doses of cotinine and placebo. However, higher nicotine serum levels were observed in the 160 mg cotinine fumarate condition compared to placebo and to 40 mg cotinine fumarate. No systematic effects of cotinine on subjective responses to cigarettes were observed. Cotinine appears potentially to have a selective modulatory effect on nicotine withdrawal symptoms but not on cigarette smoking.
Adult↗
A global haplotype analysis of the myotonic dystrophy locus: implications for the evolution of modern humans and for the origin of myotonic dystrophy mutations.
Haplotypes consisting of the (CTG)n repeat, as well as several flanking markers at the myotonic dystrophy (DM) locus, were analyzed in normal individuals from 25 human populations (5 African, 2 Middle Eastern, 3 European, 6 East Asian, 3 Pacific/Australo-Melanesian, and 6 Amerindian) and in five nonhuman primate species. Non-African populations have a subset of the haplotype diversity present in Africa, as well as a shared pattern of allelic association. (CTG)18-35 alleles (large normal) were observed only in northeastern African and non-African populations and exhibit strong linkage disequilibrium with three markers flanking the (CTG)n repeat. The pattern of haplotype diversity and linkage disequilibrium observed supports a recent African-origin model of modern human evolution and suggests that the original mutation event that gave rise to DM-causing alleles arose in a population ancestral to non-Africans prior to migration of modern humans out of Africa.
Alleles↗
Substrate specificity of and product formation by muconate cycloisomerases: an analysis of wild-type enzymes and engineered variants.
Muconate cycloisomerases play a crucial role in the bacterial degradation of aromatic compounds by converting cis,cis-muconate, the product of catechol ring cleavage, to (4S)-muconolactone. Chloromuconate cycloisomerases catalyze both the corresponding reaction and a dehalogenation reaction in the transformation of chloroaromatic compounds. This study reports the first thorough examination of the substrate specificity of the muconate cycloisomerases from Pseudomonas putida PRS2000 and Acinetobacter "calcoaceticus" ADP1. We show that they transform, in addition to cis,cis-muconate, 3-fluoro-, 2-methyl-, and 3-methyl-cis, cis-muconate with high specificity constants but not 2-fluoro-, 2-chloro-, 3-chloro-, or 2,4-dichloro-cis,cis-muconate. Based on known three-dimensional structures, variants of P. putida muconate cycloisomerase were constructed by site-directed mutagenesis to contain amino acids found in equivalent positions in chloromuconate cycloisomerases. Some of the variants had significantly increased specificity constants for 3-chloro- or 2,4-dichloromuconate (e.g., A271S and I54V showed 27- and 22-fold increases, respectively, for the former substrate). These kinetic improvements were not accompanied by a change from protoanemonin to cis,cis-dienelactone as the product of 3-chloro-cis,cis-muconate conversion. The rate of 2-chloro-cis,cis-muconate turnover was not significantly improved, nor was this compound dehalogenated to any significant extent. However, the direction of 2-chloro-cis,cis-muconate cycloisomerization could be influenced by amino acid exchange. While the wild-type enzyme discriminated only slightly between the two possible cycloisomerization directions, some of the enzyme variants showed a strong preference for either (+)-2-chloro- or (+)-5-chloromuconolactone formation. These results show that the different catalytic characteristics of muconate and chloromuconate cycloisomerases are due to a number of features that can be changed independently of each other.
Acinetobacter calcoaceticus↗
Molecular evidence that fragile X syndrome occurs in the South African black population.
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Adolescent↗
Electroporation therapy of head and neck cancer.
The purpose of this paper is to introduce the concept of electroporation therapy and present our results from using this new technique combined with intralesional bleomycin in head and neck cancer patients. Electroporation therapy is a technique wherein high-voltage electric impulses delivered into a neoplasm transiently increase cell membrane permeability to large molecules, including cytotoxic agents. In this phase I/II study, extremely low-dose bleomycin sulfate was electroporated into head and neck malignant neoplasms in 10 patients. Tumor responses included 2 nonresponders, 3 partial responders, and 5 complete responders, with a mean follow-up of 40 weeks. We conclude that this technique offers promising possibilities in the local treatment of head and neck cancer.
Adult↗
Evidence of genetic heterogeneity in a BALB/c mouse colony as determined by DNA fingerprinting.
A genetic monitoring of the BALB/c mouse foundation colony in our animal facility was carried out. The techniques of choice were skin grafting, coat colour test, flow cytometric analysis for H2 antigens (loci H2-D and H2-A), electrophoretic analysis of isoenzymes (loci Idh1, Pep3, Es3 and Mod1), PCR-amplified microsatellites (loci Igh-V, Ngfg, Plau, Crp, Igh, D16Mit5, D3Mit49 and D17Mit16) and DNA fingerprinting (multilocus probes 33.6, 33.15 and (CAC)5). No evidence of genetic contamination was found, ruling out the possibility of an outcross with AKR, the other albino strain maintained at the facility. Nevertheless, DNA fingerprint patterns revealed evidence of genetic heterogeneity in four out of nine lines of the nucleus colony, interpreted as minisatellite mutations favoured for a single line system with more than 40 generations of separation from the ancestral pair. These mice are mainly used in cancer and immunological research within the institute.
Animals↗
Home care for children with life-threatening illness.
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Caregivers↗
Structural and functional consequences of substitutions at the tyrosine 55-lysine 104 hydrogen bond in Escherichia coli inorganic pyrophosphatase.
Tyrosine 55 and lysine 104 are evolutionarily conserved residues that form a hydrogen bond in the active site of Escherichia coli inorganic pyrophosphatase (E-PPase). Here we used site-directed mutagenesis to examine their roles in structure stabilization and catalysis. Though these residues are not part of the subunit interface, Y55F and K104R (but not K104I) substitutions markedly destabilize the hexameric structure, allowing dissociation into active trimers on dilution. A K104I variant is nearly inactive while Y55F and K104R variants exhibit appreciable activity and require greater concentrations of Mg2+ and higher pH for maximal activity. The effects on activity are explained by (a) increased pK(a)s for the catalytically essential base and acid at the active site, (b) decreases in the rate constant for substrate (dimagnesium pyrophosphate) binding to enzyme-Mg2 complex vs enzyme-Mg3 complex, and (c) parallel decreases in the catalytic constant for the resulting enzyme-Mg2-substrate and enzyme-Mg3-substrate complexes. The results are consistent with the major structural roles of Tyr55 and Lys104 in the active site. The microscopic rate constant for PPi hydrolysis on either the Y55F or K104R variants increases, by a factor of 3-4 in the pH range 7.2-8.0, supporting the hypothesis that this reaction step depends on an essential base within the enzyme active site.
Biopolymers↗
The multisite field trial of the consultation-liaison psychiatry assessment instrument.
A multisite field trial was conducted at 11 institutions to test the clinical reliability of a 29-item consultation-liaison (C-L) psychiatry assessment instrument. Twenty-five raters viewed videotapes of two "trainees" conducting clinical interviews with a simulated patient. One trainee was a medical student, the other was a fellow in psychiatry. Raters completed the 29-item assessment instrument for each trainee. The mean value scores reflected the skill of each trainee. The medical student had a mean score of 1.93, whereas the C-L fellow had a mean score of 3.13 which parallels the expected level of skill for the two interviewers. Eighty-six percent of the items (25/29) had a standard deviation (SD) of less than 1.0. Each of the remaining four items (14%) had a SD minimally greater than 1.0. These results reflect clear wording of items with measurable parameters defined for assessing trainees' skills. The authors present different uses for the assessment instrument, including giving feedback to trainees regarding interviewing techniques and skills; setting "gold" and "lead" standards for clinical C-L interviewing skills; and training supervisors in evaluation using a standardized assessment instrument.
Curriculum↗
On-site, rapid HIV testing with same-day results and counseling.
BACKGROUND: New rapid HIV antibody tests have allowed provision of results and result-specific counseling on the day on initial visit, and have the potential to increase the efficiency of HIV counseling and testing. METHODS: To evaluate the use of rapid testing with same-day results in public clinics, the Single Use Diagnostic System HIV-1 rapid assay was used for a 3-month period at an anonymous testing clinic and a sexually transmitted disease (STD) clinic in Dallas, Texas. Non-reactive rapid test results were reported as HIV-negative. Reactive results were reported as 'preliminary positive'. These procedures were compared with standard testing during a baseline period, with respect to number of clients receiving results and post-test counseling, client satisfaction, counselor acceptance, cost and effectiveness at reducing HIV risk. RESULTS: Rapid testing resulted in an increase in the number of persons learning their serostatus: a 4% increase for uninfected and a 16% increase for infected clients at the Anonymous Testing Clinic; a 210% increase for uninfected patients and a 23% increase for infected patients at the STD clinic. Rapid testing resulted in a cost saving of US$ 11 per test in both the anonymous and STD clinics. Of those previously tested, 88% responded that they preferred the rapid test. In the year following initial HIV test, clients tested with rapid and standard procedures were equally likely to return to the clinic with a new STD (odds ratio, 0.97; 95% confidence interval, 0.7-1.4). CONCLUSIONS: Rapid, on-site HIV testing was feasible, preferred by clients, and, resulted in significant improvement in the number of persons learning their serostatus, without increasing the costs or decreasing the effectiveness of counseling and testing.
Counseling↗
Fragile X syndrome occurs in the South African black population.
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Adolescent↗
[Coevolutive mechanisms between retroviruses and their hosts. The murine mammary tumor model].
Mouse mammary tumor virus (MMTV) is a type B retrovirus that is transmitted as an infectious milk-borne particle and that causes mammary carcinomas by insertional activation of cellular protooncogenes. Germ line infections result in endogenous Mtv proviruses integrated in the genome of most mouse strains. These endogenous proviruses have been integrated into the genomes of mice for only the past 3-5 million years. The open reading frame present in the 3' long terminal repeat (LTR) of the provirus encodes a superantigen (SAg) which is able to stimulate a large proportion of T cells sharing a common T-cell receptor beta chain variable domain (v beta). Expression of this SAg is critical to the MMTV life cycle. After expression of the SAg in B cells a significant number of T cells are recruited to respond to these MMTV infected cells. As a consequence both the T cells expressing the relevant TCR V beta domain and the infected B cells become activated and start dividing. This would facilitate integration of MMTV and amplify the number of virus infected lymphocytes. Most likely during lactation the mammary glands become receptive to viral infection. The presence of endogenous Mtvs induces an early clonal deletion of reactive T cells. For this reason it has been argued that the presence of these proviruses confers a selective advantage to the mouse population by protecting the host from infection with an exogenous MMTV coding for a cross-reactive SAg. However, recent results discussed herein suggest that Mtv proviruses may also be detrimental to the mouse population by participating in recombinations with exogenous MMTVs, giving rise to highly tumorigenic recombinant particles. These results are discussed in the light of recent reports suggesting the involvement of viral sequences with a high homology to MMTV in human mammary tumorigenesis.
Animals↗
[Superantigens and murine mammary tumor retrovirus].
Hosts and their pathogens have co-evolved for millions of years, developing multiple and intimate interactions. Vertebrates have evolved a very complex immune system which pathogens have often been able to circumvent, in some cases even managing to appropriate some of its components for their own purpose. Among the pathogens which do use components of the immune system to survive and propagate, those coding for the expression of superantigens (SAgs) are now under intense scrutiny. Investigations concerning one of these pathogens, the mouse mammary tumor virus (MMTV), led to the understanding of how the expression of such components is a critical step in their life cycle. A number of milk-borne exogenous MMTV infect mice shortly after birth and, when expressed, produce superantigens. Herein, we describe the biological effects of new variants of MMTV. Two of these, BALB14 and BALB2 encoding SAgs with V beta 14+ and V beta 2+ specificities, respectively, were present in BALB/c mice of our colony (BALB/cT); a third variant, termed MMTV LA, originated in (BALB/cTxAKR)F1 mice from recombination between BALB 14 and Mtv-7 endogenous provirus. The recombinant LA virus induces the deletion of V beta 6+ and V beta 8.1+ T cells as a consequence of the acquisition of SAg hypervariable coding region of Mtv-7. The SAg encoded by MMTV LA strongly stimulates cognate T cells in vivo leading to a very effective amplification of lymphoid cells in BALB/c mice, correlating with a high incidence of mammary tumors. These results suggest that the presence of non-productive endogenous proviruses--generally considered to confer a selective advantage to the host by protecting it from infection with exogenous MMTVs encoding cross-reactive SAgs--could also be advantageous for the pathogen by increasing its variability, thus broadening the host range and allowing the expansion of highly tumorigenic variants.
Animals↗
[Superantigens and retroviral infections. Increase of mammary tumorigenicity due to recombination between exogenous and endogenous MMTV viruses].
A number of milk-borne exogenous mouse mammary tumor viruses (MMTV) infect mice shortly after birth and, when expressed, produce superantigens. Herein we describe the biological effects of new variants of exogenous MMTV: one of them (BALB14) present in BALB/c mice and showing a low ability to induce mammary tumors, and the other (MMTV-7) being the result of recombination between the BALB14 and the Mtv-7 endogenous provirus. The recombinant virus which has the SAg-specificity of Mtv-7 was amplified in BALB/c mice this fact correlating with a high incidence of mammary tumors. The role of strong SAgs in the mechanism by which the recombinant virus increases its title in a susceptible host is discussed. The results obtained suggest that the presence of non-productive endogenous proviruses--considered as conferring a selective advantage to the mouse population by protecting it from infection with exogenous MMTV--should also be advantageous to the pathogen by increasing its variability, thus broadening the host range and allowing the expansion of highly tumorigenic variants.
Animals↗
The structural basis for pyrophosphatase catalysis.
BACKGROUND: Soluble inorganic pyrophosphatase (PPase), an essential enzyme central to phosphorus metabolism, catalyzes the hydrolysis of the phosphoanhydride bond in inorganic pyrophosphate. Catalysis requires divalent metal ions which affect the apparent pKas of the essential general acid and base on the enzyme, and the pKa of the substrate. Three to five metal ions are required for maximal activity, depending on pH and enzyme source. A detailed understanding of catalysis would aid both in understanding the nature of biological mechanisms of phosphoryl transfer, and in understanding the role of divalent cations. Without a high-resolution complex structure such a model has previously been unobtainable. RESULTS: We report the first two high-resolution structures of yeast PPase, at 2.2 and 2.0 A resolution with R factors of around 17%. One structure contains the two activating metal ions; the other, the product (MnPi)2 as well. The latter structure shows an extensive network of hydrogen bond and metal ion interactions that account for virtually every lone pair on the product phosphates. It also contains a water molecule/hydroxide ion bridging two metal ions and, uniquely, a phosphate bound to four Mn2+ ions. CONCLUSIONS: Our structure-based model of the PPase mechanism posits that the nucleophile is the hydroxide ion mentioned above. This aspect of the mechanism is formally analogous to the "two-metal ion' mechanism of alkaline phosphatase, exonucleases and polymerases. A third metal ion coordinates another water molecule that is probably the required general acid. Extensive Lewis acid coordination and hydrogen bonds provide charge shielding of the electrophile and lower the pKa of the leaving group. This "three-metal ion' mechanism is in detail different from that of other phosphoryl transfer enzymes, presumably reflecting how ancient the reaction is.
Alkaline Phosphatase↗
A site-directed mutagenesis study of Saccharomyces cerevisiae pyrophosphatase. Functional conservation of the active site of soluble inorganic pyrophosphatases.
We report the expression and initial characterization of 19 active-site variants of Saccharomyces cerevisiae inorganic pyrophosphatase (PPase), including measurements of thermostability, oligomeric structure and specific activity at pH 7.2. 13 of the 19 conservative substitutions resulted in at least a fivefold decrease in activity, indicating that these residues are important for yeast PPase catalysis. The E58D, D117E, D120E and D152E variants had no activity under the conditions tested, suggesting that Glu58, Asp117, Asp120 and Asp152 may have crucial roles in catalysis. The effects of the mutations on catalytic activity were very similar to those observed with the corresponding variants of Escherichia coli PPase, proving conclusively that the active site and mechanism of soluble PPases are conserved. The D71E variant was more thermostable and the K56R, R78K, D115E and K154R variants were more thermolabile than the wild-type enzyme, whereas subunit:subunit interactions were somewhat weakened by the K56R, R78K, Y89F and K154R substitutions. These results suggest that Lys56, Asp71, Arg78, Tyr89, Asp115 and Lys154 are structurally important for yeast PPase.
Binding Sites↗