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Biomedical subjects

E Blackburn

Publications and source records attributed to E Blackburn.

14 recordsLinked to original sources
PubMed2006

Fermi surface topology and the superconducting gap function in UPd2Al3: a neutron spin-echo study.

We report on a single crystal neutron spin-echo investigation of the low-energy dynamic response in the heavy-fermion superconductor UPd2Al3 in the vicinity of the antiferromagnetic wave vector Q(0)=(0 0 0.5). Well inside the superconducting phase, antiferromagnetic quasielastic scattering, which is present in the normal state, is absent for relaxation times up to 10 ns, equivalent to an energy resolution of approximately 1 microeV. This places strong constraints on possible models for this magnetic superconductor.

Journal Article↗
PubMed2000

[Immunosenescence: delayed cutaneous hypersensitivity tests in independently-living Chilean elderly individuals].

BACKGROUND: Delayed cutaneous hypersensitivity tests are a globally accepted test to assess cellular immunity in vivo. The quality and quantity of the response to these type of tests, varies in different populations. AIM: To study delayed cutaneous hypersensitivity in a group of healthy Chilean elders. MATERIAL AND METHODS: Forty two elders (32 male), aged 60 to 76 years old were studied. Multitest-CMI was applied in the left forearm. This test allows the subcutaneous administration of seven antigens and a glycerin control. Results were compared with those of a group of young adults studied by the authors. RESULTS: Among males there was a mean of 2.7 +/- 1.4 positive responses compared with women, that had 1.7 +/- 1 positive responses (p = 0.016). The sum of response diameters was 4.2 +/- 1.5 and 3.6 +/- 1.9 mm in men and women respectively (p = NS). Compared to young adults, elderly women had a lower response to tetanus and diphtheria toxoids and men had a lower response to diphtheria and Proteus mirabilis. CONCLUSIONS: Elderly people have a less intense response to delayed cutaneous hypersensitivity tests than young adults. This response must be assessed in each population to account for regional variability.

Age Factors↗
PubMed1997

The telomere and telomerase: how do they interact?

The tandemly repeated DNA sequence of telomeres is typically specified by the ribonucleoprotein enzyme telomerase. Telomerase copies part of its intrinsic RNA moiety to make one strand of the telomeric repeat DNA. Recent work has led to the concept of a telomere homeostasis system. We have been studying two key physical components of this system: the telomere itself and telomerase. Mutating the template sequence of telomerase RNA caused various phenotypes: (1) mutating specific residues in the ciliate Tetrahymena and two yeasts showed that they are required for critical aspects of telomerase action; (2) certain mutated telomeric sequences caused a previously unreported phenotype, i.e. a strong anaphase block in Tetrahymena micronuclei; and (3) certain template mutations in the telomerase RNA gene of the yeast Kluyveromyces lactis led to unregulated telomere elongation, which in some cases was directly related to loss of binding to K. lactis Rap1p. Using K. lactis carrying alterations in the genes for Rap1p and other silencing components, we proposed a general model for telomere length homeostasis: namely, that the structure and DNA length of the DNA-protein complex that comprises the telomere are key determinants of telomerase access, and hence the frequency of action of telomerase, at the telomere.

Anaphase↗
PubMed1994

Prevention of hypothermia during anaesthesia.

A study of the hypothermic effects of general anaesthesia during breast surgery and its amelioration by the use of a thermal drape to most of the body exclusive of the operating site. Two groups of patients are compared, using a constant anaesthetic technique, a single surgeon and the same operating conditions except for the omission or inclusion of thermal drapes. A review of the homeostatic mechanisms of temperature control and other methods of maintaining body temperature are included.

Bedding and Linens↗
PubMed1992

Avidity and titer of immunoglobulin G subclasses to Porphyromonas gingivalis in adult periodontitis patients.

The relative avidity and titer of antibodies representing the 4 immunoglobulin G (IgG) subclasses (IgG1-4) reactive with Porphyromonas gingivalis, P. gingivalis-lipopolysaccharide (-LPS), streptokinase (SK) and tetanus toxoid (TT) in the sera of patients having adult periodontitis and of healthy controls were measured. Patient antibody titers to P. gingivalis and P. gingivalis-LPS were found to be significantly elevated for IgG, IgG1 (no P. gingivalis-LPS antibodies) and IgG2. The predominant antibody response to P. gingivalis and P. gingivalis-LPS occurred in the IgG2 subclass. When the relative avidity of the antibodies to P. gingivalis and P. gingivalis-LPS were examined, no significant differences between control and patient sera could be identified. However, anti-P. gingivalis and P. gingivalis-LPS antibodies were found to possess significantly lower relative avidity than either SK or TT antibodies. The IgG1 subclass antibodies to P. gingivalis, SK and TT all appeared to be of high relative avidity. In contrast, anti-P. gingivalis and P. gingivalis-LPS of the IgG2 subclass were of significantly lower relative avidity. Since the predominant humoral response to P. gingivalis occurs in the IgG2 subclass, the low relative avidity of these antibodies predominates in measurements of whole serum activity.

Adult↗
PubMed1987

S1 nuclease sensitivity of a double-stranded telomeric DNA sequence.

We examined structural properties of poly d(C4A2).d(T2G4), the telomeric DNA sequence of the ciliated protozoan Tetrahymena. Under conditions of high negative supercoiling, poly d(C4A2).d(T2G4) inserted in a circular plasmid vector was preferentially sensitive to digestion with S1 nuclease. Only the C4A2 strand was sensitive to first-strand S1 cutting, with a markedly skewed pattern of hypersensitive sites in tracts of either 46 or 7 tandem repeats. Linear poly d(C4A2).(T2G4) showed no preferential S1 sensitivity, no circular dichroism spectra indicative of a Z-DNA conformation, no unusual Tm, and no unusual migration in polyacrylamide gel electrophoresis. The S1 nuclease sensitivity properties are consistent with a model proposed previously for supercoiled poly d(CT).d(AG) (Pulleyblank et al., Cell 42:271-280, 1985), consisting of a double-stranded, protonated, right-handed underwound helix. We propose that this structure is shared by related telomeric sequences and may play a role in their biological recognition.

Base Sequence↗
PubMed1986

Sensitization with Fusobacterium nucleatum targets antibody-dependent cellular cytotoxicity to mammalian cells.

Incubation of mammalian tumor cells with either soluble of insoluble fractions (10 to 100 micrograms/ml) of Fusobacterium nucleatum sensitizes them to the destructive activity of antibody-dependent cellular cytotoxicity (ADCC) effector cells in the presence of anti-F. nucleatum antisera. All three types of ADCC effector cells are capable of destroying F. nucleatum-sensitized target cells with varying degrees of effectiveness (lymphocytes much greater than monocytes greater than neutrophils). Hyperimmune rabbit anti-F. nucleatum antisera were active at a dilution as high as 1/100,000. Our studies indicated that F. nucleatum must be bound to the target cells since if either the effector cells are treated with F. nucleatum or F. nucleatum is directly to an ADCC reaction, there is no significant effect on cytotoxicity. The kinetics of F. nucleatum-targeted ADCC are identical to those of classical ADCC, suggesting a similar mechanism. The specificity of F. nucleatum-targeted ADCC was demonstrated by cold target inhibition studies and by showing that other antibacterial antisera were incapable of mediating the activity.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1981

Tandemly repeated C-C-C-C-A-A hexanucleotide of Tetrahymena rDNA is present elsewhere in the genome and may be related to the alteration of the somatic genome.

The ribosomal RNA genes of the Tetrahymena macronucleus exist as extrachromosomal, linear molecules. The termini of these molecules have been shown to contain the tandemly repeated hexanucleotide (C-C-C-C-A-A)n. In this study the same or related sequences were found in other locations of the genome. Using the depurination method, we showed that macronuclear DNA contained this sequence even after rDNA had been removed. The sequence was found mainly in the repetitive fraction of the DNA. The presence of this sequence in both the macronucleus and the micronucleus was also shown by Southern hybridization using C-C-C-C-A-A repeat as a probe. Comparison between the hybridization patterns of macronuclei and micronuclei reveals interesting differences. Whereas the two nuclei share the same genetic origin, the majority of the restriction enzyme digestion sites flanking the C-C-C-C-A-A repeat appear to be different. Such a difference was found to be specific for this sequence, because it was not detected when other sequences were used for hybridization. These results suggest that some kind of alteration has occurred in the genome during the formation of the macronucleus, and that the C-C-C-C-A-A repeat may be related to this process.

Animals↗
PubMedDate not supplied

The telomere and telomerase: how Do they interact?

The ribonucleoprotein (RNP) enzyme telomerase synthesizes telomere DNA and maintains telomere length in eukaryotic cells. This review describes recent findings that provide new understanding, of the functions of telomeres and telomerase. Telomerase has an essential RNA moiety in which a short sequence acts as the template for synthesis of telomeric DNA. Recent results show that, besides acting as a template, the telomerase RNA plays essential roles in the enzymatic functions of telomerase that are as critical as those provided by the protein reverse transcriptase subunit of telomerase. Analysis of telomerase RNA mutants in yeast has provided evidence that telomerase is an oligomeric/dimeric enzyme containing at least two telomerase RNA molecules and two enzyme-active sites. Recent data suggest that this telomerase RNP also plays a critical role in capping short telomeres. Thus, the length of a telomere is only one determinant of whether it is sufficiently long to function as a cap, stabilizing the chromosome end. Several lines of evidence converge on the notion that for telomere length regulation and other telomere functions, the very few last repeats at the tip of the telomere are the most crucial.

Homeostasis↗
PubMedDate not supplied

Parental loss due to HIV: caring for children as a community issue--the Rochester, New York experience.

The number of children in the United States who will lose a parent to AIDS is increasing. Permanency planning to help families affected by AIDS includes case management, mental health, medical care, child welfare, and legal services. These services are provided by a number of different professions, and have largely been reactive and noncoordinated. This article presents the efforts of one community in a midsize city to develop and implement a multidisciplinary coordinated plan for providing services to children affected by the illness or death of a parent from HIV/AIDS.

Bereavement↗