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Biomedical subjects

C Hughes

Publications and source records attributed to C Hughes.

At least 73 records · Page 4Linked to original sources
PubMed2000

Recurrent non-Hodgkin's lymphoma presenting as pathological fracture of the patella.

We report a case of recurrent non-Hodgkin's lymphoma presenting as anterior knee pain due to pathological fracture of the patella. Anterior knee pains is an extremely common presenting complaint at orthopaedic clinics and the patella is an infrequent site both for primary and recurrent tumours. This case, treated by patellectomy, illustrates the difficulty of treatment of these lesions and highlights the importance of adequate radiological assessment in sites of previous tumour involvement.

Journal Article↗
PubMed2000

Functions of the subunits in the FlhD(2)C(2) transcriptional master regulator of bacterial flagellum biogenesis and swarming.

In enterobacteria like Salmonella, biogenesis of cell surface flagella needed for motility is dependent upon the master operon flhDC at the apex of the flagellar gene hierarchy. The operon products FlhD and FlhC act together in a FlhD(2)C(2 )heterotetramer to induce flagellar gene transcription, while FlhD also represses cell septation. The flhDC operon is pivotal to differentiation into elongated hyperflagellated swarm cells that undergo multicellular migration, most strikingly in Proteus. We set out to establish the mechanism of action of the FlhD(2)C(2) multimer. In Proteus swarm cell extracts, all the FlhC was assembled into the FlhD(2)C(2 )transcription activator, but FlhD additionally formed approximately equimolar amounts of a FlhD(2) homodimer. Both FlhD and FlhC subunits homodimerised in vivo and in vitro, suggesting that self-interactions stabilise the FlhD(2)C(2 )complex. The FlhC and FlhD subunit proteins were separately expressed and purified, and the FlhD(2)C(2)heterotetramer was reconstituted in vitro. Purified FlhC bound specifically and cooperatively to the promoter region of the flhDC-regulated flhB flagellar gene in the absence of FlhD. Purified FlhD was unable to bind this target DNA, but binding by the FlhD(2)C(2)complex was approximately tenfold greater than the FlhC subunit alone, suggesting that FlhD potentiated the FlhC/DNA interaction. In support of this possibility, pre-incubation of FlhC with FlhD reduced the apparent dissociation constant, K(D), for the FlhC/DNA complex from 100 nM to 13 nM. Furthermore, in competition assays, FlhD substantially increased the specificity of DNA recognition by FlhC, and also stabilised the resultant labile protein/DNA complex, prolonging its half-life from around two minutes to more than 40 minutes. FlhD(2)C(2)is therefore an atypical prokaryotic transcription activator in which interaction of the FlhC subunit with DNA target sequences is enhanced by the coexpressed helper subunit FlhD.

Allosteric Site↗
PubMed2000

Crystal structure of the bacterial membrane protein TolC central to multidrug efflux and protein export.

Diverse molecules, from small antibacterial drugs to large protein toxins, are exported directly across both cell membranes of gram-negative bacteria. This export is brought about by the reversible interaction of substrate-specific inner-membrane proteins with an outer-membrane protein of the TolC family, thus bypassing the intervening periplasm. Here we report the 2.1-A crystal structure of TolC from Escherichia coli, revealing a distinctive and previously unknown fold. Three TolC protomers assemble to form a continuous, solvent-accessible conduit--a 'channel-tunnel' over 140 A long that spans both the outer membrane and periplasmic space. The periplasmic or proximal end of the tunnel is sealed by sets of coiled helices. We suggest these could be untwisted by an allosteric mechanism, mediated by protein-protein interactions, to open the tunnel. The structure provides an explanation of how the cell cytosol is connected to the external environment during export, and suggests a general mechanism for the action of bacterial efflux pumps.

Amino Acid Sequence↗
PubMed2000

Prophylactic surgery decisions and surveillance practices one year following BRCA1/2 testing.

BACKGROUND: Although genetic testing for breast cancer risk is clinically available, its impact on health-related behaviors is unknown. This study examined prophylactic surgery and surveillance behavior during the year following BRCA1/2 gene testing. METHODS: Participants were female members (n = 216) of hereditary breast-ovarian cancer families (84 mutation carriers, 83 noncarriers and 49 test decliners). In this prospective observational study, utilization of prophylactic surgery and surveillance behavior were assessed 1-year following BRCA1/2 testing. RESULTS: Only 3% of the unaffected carriers obtained prophylactic mastectomy during the 1-year follow-up period. Among the remaining females, carriers had significantly higher rates of mammography (68%) than noncarriers (44%); (OR = 7.1; C.I. = 1.36-37.1; P = 0.02). However, the adherence rate in carriers was unchanged from baseline, suggesting that this difference is attributable to a reduction in screening among noncarriers. Women ages 25-39 years were significantly less likely to obtain mammograms than those aged 40 years and older. Cancer-related distress had a positive but nonsignificant (P < 0.07) association with adherence in bivariate but not multivariate analysis. With regard to ovarian risk, only 13% of carriers obtained prophylactic oophorectomy; of the remaining female carriers, only 21% reported a CA125 and 15% reported a transvaginal ultrasound. CONCLUSION: The vast majority of BRCA1/2 carriers may not opt for prophylactic surgery, and many do not adhere to surveillance recommendations. Greater attention to risk communication and medical decision-making is warranted.

Adult↗
PubMed2000

Evaluation and outcome of the delorme procedure in the treatment of rectal outlet obstruction.

PURPOSE: This study was designed to assess the results of the Delorme procedure in the treatment of patients with rectal outlet obstruction. METHODS: A descriptive retrospective study from October 1989 to October 1997 was undertaken. Thirty-four patients with an abnormal defecography documenting rectal outlet obstruction caused by internal rectal prolapse or a combination of internal rectal prolapse and rectocele were included in the study. RESULTS: Thirty-four patients (33 females) ages 35 to 82 (mean, 61.4) years were followed up for the duration of the study (mean follow-up, 43 months). Twenty-six patients (76.4 percent) reported a good to excellent overall result after the Delorme procedure. Eight patients (23.6 percent) reported fair to poor results. Symptomatic improvement was observed in 89.7 percent for patients who had incomplete evacuation, and in 88.5 percent of patients who had constipation. There was improvement in 78.6 percent of patients with bleeding per rectum, in 92.9 percent of patients with straining, and in 82.4 percent of patients with the need to manually assist in defecation by pushing in the perineum or vagina. Discontinuation of laxative use after the procedure was reported by 66.7 percent of patients. Improvement in the patients with some degree of incontinence was seen in 33.3 percent. Twelve patients (35.3 percent) experienced one or more complications. The procedure was performed in an outpatient setting in 71 percent of the patients. CONCLUSIONS: The Delorme procedure for the treatment of rectal outlet obstruction can be done with minimal morbidity, short hospital stay often in an outpatient setting, with good functional results, and with an overall patient satisfaction above 75 percent.

Digestive System Surgical Procedures↗
PubMed2000

In vitro recruitment of the RfaH regulatory protein into a specialised transcription complex, directed by the nucleic acid ops element.

An unusual regulatory mechanism that controls transcription elongation in long fertility and virulence operons in bacteria is effected by two specialised components, the RfaH protein and the nucleic acid ops element. Without direct interaction, ops acts to reduce the concentration of RfaH required to stimulate distal gene transcription, and we have proposed that ops recruits RfaH to the transcription machinery. To provide direct experimental evidence for this view, we used gel fitration to identify potential RfaH complexes assembled in Escherichia coli cell extracts that carry out RfaH-dependent transcription. This novel molecular weight shift assay revealed that RfaH-dependent transcription elongation occurs concomitantly with recruitment of RfaH into a high molecular weight transcription complex, and that this recruitment is specifically directed by the ops element. Assembly of this complex required RNA polymerase and nucleotide hydrolysis, but not processive transcription. Neither assembly of the complex nor RfaH-dependent transcription was observed in in vitro reactions containing only ops, RfaH and purified core (alphabetabeta') RNA polymerase; both processes required the combination of subcellular fractions containing the RNA polymerase complex, the cytoplasmic membrane and ribosomes. The data confirm that the ops element directs recruitment of RfaH into a multi-component RNA polymerase complex that resists transcription termination.

Adenosine Triphosphate↗
PubMed2000

Participation of minorities in cancer research: the influence of structural, cultural, and linguistic factors.

Overall, participation rates in cancer clinical trials are very low, ranging from 3 to 20% of eligible participants. However, participation rates are especially low among the socially disadvantaged and racial/ethnic minority groups that have been historically underrepresented in clinical research. Structural factors such as study duration, treatment or intervention schedule, cost, time, followup visits, and side effects represent more of a barrier to participation among these groups compared with white, non-Hispanics. Attitudes, beliefs, perceptions, and knowledge regarding clinical research, and cultural characteristics of underrepresented minorities pose additional barriers to participation. This article focuses on the structural, cultural, and linguistic factors that affect participation in clinical cancer research for each major U.S. racial/ethnic group. Low socioeconomic status, speaking a primary language other than English, differences in communication styles, mistrust of research and the medical system, fear, embarrassment, and lack of knowledge about the origin of cancer appear to have a negative impact on clinical cancer research participation rates. Much of the information about these factors comes from studies of cancer screening because little data is available on the factors that prevent and facilitate participation of minorities in clinical cancer trials specifically. Such research is needed, and, given the heterogeneity within and between minority populations, should occur in several different geographic settings and with as many different minority subpopulations as possible.

Adolescent↗
PubMed2000

The effects of social interactive training on early social communicative skills of children with autism.

Growing attention has been directed at the relation between early social communicative skills of children with autism and subsequent development of these children's social and communicative functioning. We reviewed 16 empirical studies that investigated the effects of social interactive interventions designed to increase early social communicative skills of young children with autism by increasing their role as initiator of social interactions. To identify factors relating to treatment effectiveness, we analyzed studies in relation to participant characteristics, settings, target behaviors, training methods, and results. To determine durability of treatment, we analyzed generalization effects across persons, settings, stimuli, and time. Increases were found for social and affective behaviors, nonverbal and verbal communication, eye contact, joint attention, and imitative play. Limited generalization or maintenance of target behaviors was reported. Findings are discussed in relation to critical variables that may relate to treatment effectiveness in future research and practice efforts.

Autistic Disorder↗
PubMed2000

Low-speed centrifugation of retroviral vectors absorbed to a particulate substrate: a highly effective means of enhancing retroviral titre.

For many gene therapy applications the effective titre of retroviral vectors is a limiting factor both in vitro and in vivo. Purification and concentration of retrovirus from packaging cell supernatant can overcome this problem. To this end we have investigated a novel procedure which involves complexing retrovirus to a dense and particulate substrate followed by a short low-speed centrifugation. The study reported here uses heat-killed, formaldehyde fixed Staphylococcus aureus (Pansorbin) absorbed to PG13 derived retrovirus. This complex was then used to harvest retrovirus from packaging cell supernatant: centrifugation and washing of this complex allows the retrovirus to be both purified and concentrated. This procedure increases the effective titre of retrovirus by up to 7500-fold after an only 200-fold reduction in volume. The affinity of Pansorbin for retrovirus allows concentration regardless of its encoded genes and makes this protocol applicable to other popular packaging cells and envelope proteins. Possible explanations for the marked increase in titre of concentrated virus and the mechanism governing the complexing of retrovirus to Pansorbin are discussed.

Animals↗
PubMed2000

Fusagene vectors: a novel strategy for the expression of multiple genes from a single cistron.

Transduction of cells with multiple genes, allowing their stable and co-ordinated expression, is difficult with the available methodologies. A method has been developed for expression of multiple gene products, as fusion proteins, from a single cistron. The encoded proteins are post-synthetically cleaved and processed into each of their constituent proteins as individual, biologically active factors. Specifically, linkers encoding cleavage sites for the Golgi expressed endoprotease, furin, have been incorporated between in-frame cDNA sequences encoding different secreted or membrane bound proteins. With this strategy we have developed expression vectors encoding multiple proteins (IL-2 and B7.1, IL-4 and B7.1, IL-4 and IL-2, IL-12 p40 and p35, and IL-12 p40, p35 and IL-2 ). Transduction and analysis of over 100 individual clones, derived from murine and human tumour cell lines, demonstrate the efficient expression and biological activity of each of the encoded proteins. Fusagene vectors enable the co-ordinated expression of multiple gene products from a single, monocistronic, expression cassette.

Animals↗
PubMed2000

Change in perceived barriers and facilitators to treatment among women with HIV/AIDS as a function of psychosocial service utilization.

Using a repeated assessment of 185 women with HIV in three national service demonstration projects that focus on reducing barriers to care, self-reported barriers to obtaining services decreased significantly over time. At the earliest time asked, participants scored an average of 5.23 on a measure of barriers to obtaining care. At the most recent time asked, they scored an average of 4.05 on the barrier measure. In a subsample of 122 women with HIV, it was found that self-reported facilitators to obtaining services increased significantly over time. At the first time asked, participants scored an average of 8.40 on a measure of facilitators to receiving services. At the most recent time asked, they scored an average of 8.98 on the facilitator measure. Results are discussed in terms of implications for designing services to minimize barriers and maximize facilitators to care for people living with HIV/AIDS.

Adolescent↗
PubMed2000

Chunnel vision. Export and efflux through bacterial channel-tunnels.

The Escherichia coli TolC protein is central to toxin export and drug efflux across the inner and outer cell membranes and the intervening periplasmic space. The crystal structure has revealed that TolC assembles into a remarkable alpha-helical trans-periplasmic cylinder (tunnel) embedded in the outer membrane by a contiguous beta-barrel (channel), so providing a large duct open to the outside environment. The channel-tunnel structure is conserved in TolC homologues throughout Gram-negative bacteria, and it is envisaged that they are recruited and opened, through a common mechanism, by substrate-specific inner-membrane complexes.

Bacterial Outer Membrane Proteins↗
PubMed2000

Rapid turnover of FlhD and FlhC, the flagellar regulon transcriptional activator proteins, during Proteus swarming.

The enterobacterial flhDC master operon activates expression of the flagellar biogenesis gene hierarchy and also represses cell division. During Proteus mirabilis differentiation into elongated hyperflagellated swarm cells, flhDC transcription is strongly but transiently increased. We show that concentration of the FlhD and FlhC proteins is also tightly controlled at the posttranslational level. This is achieved by protein degradation, which is most severe after differentiation when the half-life of both proteins is ca. 2 min. Degradation is energy dependent and putatively involves the Lon protease.

Bacterial Proteins↗
PubMed2000

Detection of endocrine disrupting chemicals in samples of second trimester human amniotic fluid.

Man-made chemicals that have been shown to modulate endocrine function in animal models, so-called "endocrine disrupters", are suspected to play a role in the development of male reproductive tract abnormalities and neurobehaviroal deficits in children. However in utero exposure to environmental contaminants has not been documented previously. The present study was performed to test our hypothesis that man-made chemicals can be quantified in human amniotic fluid during the second trimester. Gas chromatographic/mass spectrometric (GC/MS) analysis was performed on amniotic fluid samples (n=53) from women (n=51) undergoing routine amniocentesis with a mean (+/- SEM) age of 36.5 +/- 0.5 years and between 15 and 23 weeks of gestation. Analytes included common PCB congeners, the DDT metabolites p,p'-DDE, and o,p'-DDE as well as the pesticides: hexachlorobenzene (HCB); and the three isomers of hexachlorocyclohexane (alpha,beta and gamma-HCH). The limit of quantitation (LOQ) for PCBs was 0.01 ng/ml and for the other organochlorines contaminants is was 0.1 ng/ml. The contaminants alpha-HCH with a mean (+/- SD) concentration of 0.15 +/- 0.06 (ng/ml) and p,p'-DDE with a mean (+/- SD) concentration of 0.21 +/- 0.18 ng/ml were detected in the amniotic fluid. PCB specific congeners were detected with a much lower frequency and levels were in the range of the LOQ. Overall one in three amniotic fluid samples tested positive for at least one environmental contaminant. Therefore, we conclude that approximately one in three fetuses in the Los Angeles area are exposed to endocrine modulatory environmental contaminants in utero the consequences of which remain unknown at this time.

Adult↗
PubMed2000

Critical windows of exposure for children's health: the reproductive system in animals and humans.

Drugs and environmental chemicals can adversely affect the reproductive system. Currently, available data indicate that the consequences of exposure depend on the nature of the chemical, its target, and the timing of exposure relative to critical windows in development of the reproductive system. The reproductive system is designed to produce gametes in far greater excess than would seem to be necessary for the survival of species. Ten to hundreds of millions of spermatozoa are generated daily by most adult male mammals, yet very few of these germ cells succeed in transmitting their genetic material to the next generation. Although the number of oocytes produced in mammalian females is more limited, and their production occurs only during fetal life, most ovaries contain several orders of magnitude more oocytes than ever will be fertilized. Toxicant exposures may affect critical events in the development of the reproductive system, ranging from early primordial germ cell determination to gonadal differentiation, gametogenesis, external genitalia, or signaling events regulating sexual behavior. Although there are differences between the human reproductive system and that of the usual animal models, such models have been extremely useful in assessing risks for key human reproductive and developmental processes. The objectives for future studies should include the elucidation of the specific cellular and molecular targets of known toxicants; the design of a systematic approach to the identification of reproductive toxicants; and the development of sensitive, specific, and predictive animal models, minimally invasive surrogate markers, or in vitro tests to assess reproductive system function during embryonic, postnatal, and adult life.

Adult↗
PubMed2000

Antisocial, angry, and unsympathetic: "hard-to-manage" preschoolers' peer problems and possible cognitive influences.

This study is the first to provide direct observations of dyadic interactions with friends for preschool-aged disruptive children. Forty preschoolers (mean age 52 months) rated by parents as "hard to manage" on Goodman's (1997) Strengths and Difficulties Questionnaire (SDQ), as well as 40 control children (matched for age, gender, school, and ethnic background) were filmed for 20 minutes on two occasions playing with a teacher-nominated best friend. The videos were transcribed and coded for antisocial behaviour, displays of negative emotion, and empathic/prosocial responses to friend's distress. Individual differences in social behaviour were considered in relation to false-belief performance, affective perspective taking, and executive function skills (planning and inhibitory control). Compared with controls, the hard-to-manage group showed significantly higher rates of both antisocial behaviour and displays of negative emotion, as well as significantly lower rates of emphatic/prosocial responses. Across both groups combined, frequencies of angry and antisocial behaviours were related to poor executive control. Mental-state understanding was not significantly correlated with antisocial behaviour, emotion display, or empathy, suggesting that the interpersonal problems of young disruptive children owe more to failure of behavioural regulation than to problems in social understanding per se. However, given the relatively low power of the study, these findings require replication with a larger sample.

Anger↗