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Biomedical subjects

M Carey

Publications and source records attributed to M Carey.

At least 19 recordsLinked to original sources
PubMed1992

DNA recognition by GAL4: structure of a protein-DNA complex.

A specific DNA complex of the 65-residue, N-terminal fragment of the yeast transcriptional activator, GAL4, has been analysed at 2.7 A resolution by X-ray crystallography. The protein binds as a dimer to a symmetrical 17-base-pair sequence. A small, Zn(2+)-containing domain recognizes a conserved CCG triplet at each end of the site through direct contacts with the major groove. A short coiled-coil dimerization element imposes 2-fold symmetry. A segment of extended polypeptide chain links the metal-binding module to the dimerization element and specifies the length of the site. The relatively open structure of the complex would allow another protein to bind coordinately with GAL4.

Amino Acid Sequence↗
PubMed1992

Polymerase II promoter activation: closed complex formation and ATP-driven start site opening.

Studies on bacterial RNA polymerases have divided the initiation pathway into three steps, namely (i) promoter binding to form the closed complex; (ii) DNA melting to form an open complex, and (iii) messenger RNA initiation. Potassium permanganate was used to detect DNA melting by mammalian RNA polymerase II in vitro. Closed complexes formed in a rate-limiting step that was stimulated by the activator GAL4-VP16. Adenosine triphosphate was then hydrolyzed to rapidly melt the DNA within the closed complex to form an open complex. Addition of nucleoside triphosphates resulted in the melted bubble moving away from the start site, completing initiation.

Adenosine Triphosphate↗
PubMed1992

A synergistic increase in potency of a multimerized VP16 transcriptional activation domain.

Transcriptional synergy in eucaryotes provides a means to control both the level and diversity of gene expression. The mechanism by which multiple activators elicit such effects is unknown. To address this problem we considered whether multimerizing an activation domain was equivalent to oligomerizing an activator's binding sites on DNA. Synthetic activators bearing one, two or four VP16 'core' activation domains, fused to the GAL4 DNA binding domain, were co-transfected into Cos-1 cells with CAT gene reporter templates containing one, two or five upstream GAL4 binding sites. Our results demonstrate that all of the activators elicit synergistic effects when comparing the amounts of transcription on multiple sites versus a single site. In contrast, the multimerized activation domains did not stimulate transcription significantly on a template bearing a single site; a synergistic increase in potency was, however, apparent on a template bearing two sites. Introducing the flexible lambda repressor linker region in between the activation domains increased the ability of activators bearing two or four VP16 domains to stimulate transcription from the single-site template. We discuss the mechanistic implications of this study on gene activation and synergy.

Binding Sites↗
PubMed1992

Relations among self-reported depressive symptoms in clinic-referred children versus adolescents.

Although there is consensus regarding the existence of childhood depression, disagreement remains as to whether symptoms are developmentally isomorphic. Previous studies focused on developmental differences in symptom levels; analyses of relations among symptoms may be more appropriate, however. Here both approaches were used to compare the Children's Depression Inventory responses from 1,030 clinic-referred children and adolescents. Four of nine symptom categories showed significant developmental differences in their correlations with total score. Externalizing behavior and guilt were more strongly related to depression in children than adolescents; affective symptoms and concerns about the future showed the reverse pattern. Results illustrate the importance of considering relations among symptoms as well as differences in symptom levels when evaluating theoretical claims about developmental differences in the nature of clinical syndromes.

Adolescent↗
PubMed1992

The acidic activator GAL4-AH can stimulate polymerase II transcription by promoting assembly of a closed complex requiring TFIID and TFIIA.

The assembly of activated RNA polymerase II (pol II) transcription complexes has been investigated by assaying whether pre-assembly of intermediate complexes reduces the extended time required for start-site melting. The results show that a closed complex requiring factors IIA, IID, and the acidic activator GAL4-AH forms in a rate-limiting step. This directs the templates into a productive assembly pathway. Factor TFIIB is then added rapidly, affording further protection against diversion into nonproductive pathways. These events are followed by a series of rapid steps in which the remaining general factors are assembled onto the template, which is then melted using the energy of ATP hydrolysis.

Base Sequence↗
PubMed1992

Transcriptional synergy by the Epstein-Barr virus transactivator ZEBRA.

ZEBRA is an Epstein-Barr virus (EBV) transcriptional activator that mediates a genetic switch between the latent and lytic states of the virus by binding to the promoters of genes involved in lytic DNA replication and activating their transcription. A computer survey revealed that 9 of 23 potential or known ZEBRA-responsive EBV genes contained two or more upstream binding sites; this suggested that ZEBRA can stimulate transcription synergistically. By using a series of synthetic promoters bearing one, two, three, five, and seven upstream recognition sites, we showed that ZEBRA activates transcription synergistically when templates bearing multiple sites were compared with a template bearing a single site. This phenomenon was observed in both uninfected and EBV-infected B-lymphoid cells and in vitro in a HeLa cell nuclear extract. DNase I footprinting was used to show that the synergy was not due to cooperative DNA binding mediated by direct contact between ZEBRA dimers. The in vitro experiments revealed two manifestations of synergy. One was seen when the levels of transcription observed with the same amounts of ZEBRA added to templates bearing different numbers of sites were compared. The other was observed when the two lowest concentrations of ZEBRA that stimulated measurable transcription from any given template were compared. On the basis of both the number of sites and the calculated Kd of ZEBRA for a single site, we estimated that the critical concentration of ZEBRA needed to elicit transcriptional synergy corresponds to a site occupancy of two or three bound ZEBRA dimers. Our results have biologic implications for both the EBV lytic cycle and other processes in which the concentration of an activator changes either temporally or spatially.

Base Sequence↗
PubMed1992

The sinking bullet.

We report a case of a missile injury to the brain with an unusual complication. The bullet migrated by its mere weight to a distant location through the brain parenchyma after it initially lodged in a superficial site. Instances of similar phenomena reported in the literature are reviewed.

Adolescent↗
PubMed1992

Disability in Western Highlands Province.

During late 1987 and early 1988 the Mount Hagen Handicapped Children's Centre (as it was then known) set out to determine if substantial numbers of persons with disabling conditions lived within 15km of Mount Hagen town. The investigation located 1408 persons, deemed by themselves, family members or neighbours to have a disability.

Adolescent↗
PubMed1991

Some reasons for the lack of progress in the treatment of acute myelogenous leukemia: a review of three consecutive trials of the treatment of poor prognosis patients.

The failure of three consecutive treatment protocols to significantly increase the complete remission rate for poor prognosis newly diagnosed patients with acute myelocytic leukemia led to a detailed investigation of the causes of treatment failure. In the majority of cases treatment failure was attributable to "clinical resistance" to therapy. Upon close examination two types of "clinical resistance" were discernible: the failure of chemotherapy to produce adequate cytotoxic effects ("classical" drug resistance), and treatment failure attributed to the rapid regrowth of leukemia cells subsequent to the substantial killing of leukemia cells by cytotoxic therapy ("biological" resistance). Each form of resistance accounted for one-half of the treatment failures.

Aged↗
PubMed1991

The objective evaluation of alternative treatment plans: II. Score functions.

A series of six patients with adenocarcinoma of the prostate, Stages A2, B1, or B2, were planned for treatment using a four-field box technique at 25 MV. Plans were prepared by three techniques: composite, mid-plane, and conformal. The dose distributions at the central plane and at two planes offset by +/- 2 cm were evaluated by means of score functions which quantify the magnitude of regret for target dose gradient, target over- and under-dose, non-target tissue overdose, and for overdose to the rectum, bladder, and femoral heads. The score functions are normalized to give values in the range from 10 (ideal) to zero (limit of acceptability), with negative values indicating unacceptable deviations from the prescribed dose limits. The scores for off-axis conformal plans were found to be essentially the same as for mid-plane plans on the central plane. However, mid-plane planning was shown to be totally inadequate for off-axis planes, where the average target gradient and underdose scores were reduced by 10 units. Composite planning resulted in adequate target coverage on all planes, but at the expense of unacceptable overdose to non-target tissue. The effect of reducing the posterior beam weight to half that of the other three beams was to reduce the target gradient score by 1.6 +/- 0.5 units and to increase the rectal score by 0.9 +/- 0.3 units.

Adenocarcinoma↗
PubMed1991

Variable resistance loadings in anaerobic power testing.

The aim of this study was to establish optimal test conditions for maximal anaerobic testing on a frictionloaded bicycle ergometer. Power and work outputs of 15 subjects during a 60-s all-out effort were tested under five conditions on a specially modified Monark ergometer. Test conditions were produced by altering the commencement resistance loading and either holding it constant (0.065C, 0.075C kg/kg. BW) for the entire duration of the 60-s work test or by reducing it by a specific amount to a more manageable load if pedalling rate dropped below 90 rpm (0.075R, 0.085R, 0.095R kg/kg. BW). Resistance and pedalling rate were continuously monitored with power outputs being determined every 100 ms, breath by breath oxygen consumption (VO2) was measured and capillary blood lactate (HLa) analyzed before and 5 min post each test condition. The test condition with the highest initial load (0.095R) produced the greatest peak power (PP). The reduced test procedure with the higher initial loads resulted in the greatest mean power (MP) and total work outputs (0.095R and 0.085R). Post-exercise blood HLa was not significantly different in any test condition. Peak power and MP correlated highly with both body weight (r = 0.77-0.85 and r = 0.75-0.83) and lean body weight (r = 0.84-0.88 and r = 0.90). During the last 30 s of the test, subjects reached between 90-100% of their measured maximal aerobic capacity (VO2max). The results of this study indicate that for a 60-s maximal all-out effort, a reduced test condition with a high initial resistance setting is required to produce the highest anaerobic test parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Efficacy of induction therapy in cadaveric renal transplantation comparing rabbit antithymocyte serum and Minnesota antilymphoblast globulin.

From August 1986 to July 1989, 98 patients receiving primary cadaveric kidney transplants received either RATS (n = 50) or MALG (n = 48) during the induction phase of a quadruple immunosuppressive protocol. Patient groups were well matched. The duration of RATS and MALG treatment and the time of CyA induction were equivalent. Serum creatinine and rejection episodes up to 1 year were not statistically different. Hematologic side effects resulted in dose reduction of MALG in 42% of patients without adverse rejection results. In the RATS group, no dosage reductions were required. One-year patient survivals (96% to 100%), and 1-year graft survival (82% to 85%) were not significantly different in the 2 groups. Infectious complications were 30% higher in the MALG group and a significant factor in 2 deaths. Monitoring of lymphocyte subsets revealed insignificant differences in the percent of decrease of each cell population between MALG and RATS groups during induction.

Adult↗
PubMed1990

Markers of hepatitis B virus infection in schoolchildren in the Kimberley, Western Australia.

In 1986 the Aboriginal community in Western Australia was identified as a high-risk group for hepatitis B virus infection. An immunization programme was commenced in 1988 but concerns were expressed about horizontal transmission, especially in schools, to the low-risk Caucasian group and whether they should also be included in the vaccination programme. To estimate the extent of this occurrence, a survey of schoolchildren from two district high schools in Broome and Derby in the Kimberley Region of Western Australia was carried out in March 1989. A total of 607 students aged 4 to 19 years were included in the study. None of the 300 Caucasian students had any serological markers of hepatitis B virus infection (95% confidence interval (CI) upper limit, 1.3%). Eighteen children were found to be seropositive for hepatitis B surface antigen (HBsAg); 17 were Aboriginal and one Asian. In addition, 61 Aboriginal students and one Asian had hepatitis B surface antibody (antiHBs). The hepatitis B virus infection rate in these Aboriginal children is 28.2% (95% CI, 23.2%-33.7%) with a carrier rate of 6.1% (95% CI, 3.9%-9.6%). This study demonstrates that Caucasian students have a very low risk of infection with hepatitis B virus in this community, and there is therefore no need to extend the hepatitis B vaccination programme beyond the already identified high-risk groups.

Adolescent↗
PubMed1990

How different eukaryotic transcriptional activators can cooperate promiscuously.

A striking characteristic of many different eukaryotic transcriptional activators is their ability to activate gene expression synergistically. Thus, for example, the rat glucocorticoid receptor and the yeast activator GAL4 cooperatively activate transcription of a mammalian gene bearing binding sites for each of the proteins: activation by both activators is greater than the sum of the effects of each working alone. It would seem unlikely that these two proteins from such different organisms directly interact; rather, the idea has been suggested that these and at least some other eukaryotic activators can work synergistically by simultaneously touching some part of the transcriptional machinery. An important prediction of this idea is that synergy between two such activators would be seen under conditions where each is present at concentrations sufficiently high to saturate its site on DNA. In this paper we use transcription in vitro to confirm that prediction using a derivative of the yeast activator GAL4 and the mammalian transcription factor ATF. The accompanying paper describes a similar conclusion comparing the effects of singly and multiply bound GAL4 molecules.

Activating Transcription Factors↗
PubMed1990

A mechanism for synergistic activation of a mammalian gene by GAL4 derivatives.

In prokaryotes and eukaryotes many gene activators work synergistically. For example, two dimers of lambda repressor interact to promote binding of these proteins to DNA, a reaction that is crucial at the repressor concentrations found in lysogens. In this case one of the bound dimers activates transcription, evidently by touching RNA polymerase. In another example, the yeast transcriptional activator GAL4, which can stimulate transcription in many eukaryotes, binds to multiple sites on DNA to activate transcription synergistically; the presence of two such sites can elicit a level of transcription more than twice that found with a single site. In this paper we show that synergistic activation by each of several GAL4 derivatives involves a mechanism different from that illustrated by the lambda repressor: multiple activator molecules can work synergistically under conditions in which their binding sites on DNA are saturated. The accompanying paper shows that under similar conditions of activator excess, GAL4 derivatives work synergistically with a heterologous mammalian gene activator. These results support the idea that eukaryotic activators can cooperate not by directly interacting but by simultaneously touching some component(s) of the transcriptional machinery.

Binding Sites↗