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L Douglas

Publications and source records attributed to L Douglas.

At least 19 recordsLinked to original sources
PubMed2006

Do voltage-gated calcium channel alpha2delta subunits require proteolytic processing into alpha2 and delta to be functional?

The accessory alpha2delta subunits of voltage-gated calcium channels are type 1 transmembrane proteins that are highly glycosylated and possess multiple disulfide bonds. From studies of the topology and processing of skeletal-muscle alpha2delta-1, it has been shown to be post-translationally cleaved into an alpha2 and a delta subunit, which remain disulfide-bonded. In the present study, we have examined the processing of alpha2delta-2 subunits when stably or transiently expressed, in tsA (temperature-sensitive A)-201, Cos-7 and NG108-15 cells, and compared it with that observed in the cerebellum. Despite showing full functionality and being expressed on the plasma membrane, the vast majority of heterologously expressed alpha2delta-2 is not cleaved into alpha(2)-2 and delta-2, unlike endogenous alpha2delta-2 in the cerebellum. It remains an open question for future research whether alpha2delta-2 is functional in its calcium channel trafficking role in its proteolytically cleaved or non-cleaved state.

Animals↗
PubMed2005

The metal-ion-dependent adhesion site in the Von Willebrand factor-A domain of alpha2delta subunits is key to trafficking voltage-gated Ca2+ channels.

All auxiliary alpha2delta subunits of voltage-gated Ca2+ (Ca(V)) channels contain an extracellular Von Willebrand factor-A (VWA) domain that, in alpha2delta-1 and -2, has a perfect metal-ion-dependent adhesion site (MIDAS). Modeling of the alpha2delta-2 VWA domain shows it to be highly likely to bind a divalent cation. Mutating the three key MIDAS residues responsible for divalent cation binding resulted in a MIDAS mutant alpha2delta-2 subunit that was still processed and trafficked normally when it was expressed alone. However, unlike WT alpha2delta-2, the MIDAS mutant alpha2delta-2 subunit did not enhance and, in some cases, further diminished Ca(V)1.2, -2.1, and -2.2 currents coexpressed with beta1b by using either Ba2+ or Na+ as a permeant ion. Furthermore, expression of the MIDAS mutant alpha2delta-2 reduced surface expression and strongly increased the perinuclear retention of Ca(V)alpha1 subunits at the earliest time at which expression was observed in both Cos-7 and NG108-15 cells. Despite the presence of endogenous alpha2delta subunits, heterologous expression of alpha2delta-2 in differentiated NG108-15 cells further enhanced the endogenous high-threshold Ca2+ currents, whereas this enhancement was prevented by the MIDAS mutations. Our results indicate that alpha2delta subunits normally interact with the Ca(V)alpha1 subunit early in their maturation, before the appearance of functional plasma membrane channels, and an intact MIDAS motif in the alpha2delta subunit is required to promote trafficking of the alpha1 subunit to the plasma membrane by an integrin-like switch. This finding provides evidence for a primary role of a VWA domain in intracellular trafficking of a multimeric complex, in contrast to the more usual roles in binding extracellular ligands in other exofacial VWA domains.

Binding Sites↗
PubMed2005

Randomized phase II study of two doses of gefitinib in hormone-refractory prostate cancer: a trial of the National Cancer Institute of Canada-Clinical Trials Group.

PURPOSE: Overexpression of the epidermal growth factor receptor has been demonstrated in advanced prostate cancer and is associated with a poor outcome. A multi-institutional, randomized, phase II study was undertaken by the National Cancer Institute of Canada-Clinical Trials Group to evaluate the efficacy and toxicity of two doses of oral gefitinib in patients with minimally symptomatic, hormone-refractory prostate cancer (HRPC). PATIENTS AND METHODS: Between July and November 2001, 40 patients with HRPC and increasing prostate-specific antigen (PSA) or progression in measurable disease who had not received prior chemotherapy were randomly assigned to 250 mg (n = 19) or 500 mg (n = 21) oral gefitinib daily continuously. The primary end points were PSA response rate and objective measurable response. Functional Assessment of Cancer Therapy Prostate Cancer Subscale (FACT-P) quality-of-life questionnaires were completed at baseline and during treatment. RESULTS: None of the patients demonstrated a PSA or objective measurable response. Five (14.3%) of 35 assessable patients had stable PSA (one patient at 250 mg and four patients at 500 mg), and five patients (14.3%) had a best response of stable disease (duration, 2.5 to 16.8 months). No significant effect on the rate of increase in PSA was seen. The most common drug-related nonhematologic toxicities observed were grade 1 to 2 diarrhea (250 mg, 65%; 500 mg, 56%), fatigue (250 mg, 29%; 500 mg, 33%), and grade 1 to 2 skin rash (250 mg, 24%; 500 mg, 39%). FACT-P scores decreased during treatment, indicating worsening of symptoms compared with baseline. CONCLUSION: Gefitinib did not result in any responses in PSA or objective measurable disease at either dose level. Gefitinib has minimal single-agent activity in HRPC.

Adenocarcinoma↗
PubMed2005

A phase I study of oral ZD 1839 given daily in patients with solid tumors: IND.122, a study of the Investigational New Drug Program of the National Cancer Institute of Canada Clinical Trials Group.

PURPOSE: To define the maximum tolerated dose (MTD), the dose limiting toxicity (DLT), the biological active (BA) dose and the pharmacokinetics (PK) of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor ZD1839 (Iressa) when administered continuously as a once daily dose in patients with advanced, incurable solid tumours. PATIENTS AND METHODS: Twenty-eight patients were enrolled in cohorts of three from three National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) centers. ZD1839 was given at doses from 150 to 800 mg daily orally and patients underwent a pretreatment and a 28 day post treatment tumor biopsy, while PK sampling was performed on days 8, 15, 22, 29, and a toxicity assessment every 28 days. RESULTS: All twenty-eight patients were evaluable for non-hematological and hematological toxicity. Twenty-seven were evaluable for response. The MTD was not reached but DLT included reversible rash and diarrhea. One patient with urachal cancer had a transient 55% decrease in tumor size and two other patients (breast and non-small cell lung cancer) had minor responses; three additional patients had pharmacodynamic evidence of target effect. PK demonstrated steady state within the first 2 weeks of dosing and dose dependent exposure. CONCLUSION: It appears that ZD 1839 at a dose of 800 m/day was tolerable, although some patients required dose modification for diarrhea. Doses above 250 m/day demonstrate biologic activity and could be consider for future study in a variety of EGFR positive tumor types.

Administration, Oral↗
PubMed2003

A caspase-8-independent component in TRAIL/Apo-2L-induced cell death in human rhabdomyosarcoma cells.

Tumor necrosis factor related apoptosis inducing ligand (TRAIL) belongs to the Tumor necrosis factor (TNF) family of death-inducing ligands, and signaling downstream of TRAIL ligation to its receptor(s) remains to be fully elucidated. Components of the death-inducing signaling complex (DISC) and TRAIL signaling downstream of receptor activation were examined in TRAIL - sensitive and -resistant models of human rhabdomyosarcoma (RMS). TRAIL ligation induced DISC formation in TRAIL-sensitive (RD, Rh18, Rh30) and TRAIL-resistant RMS (Rh28, Rh36, Rh41), with recruitment of FADD and procaspase-8. In RD cells, overexpression of dominant-negative FADD (DNFADD) completely abolished TRAIL-induced cell death in contrast to dominant-negative caspase- 8 (DNC8), which only partially inhibited TRAIL-induced apoptosis, growth inhibition, or loss in clonogenic survival. DNC8 did not inhibit the cleavage of Bid or the activation of Bax. Overexpression of Bcl-2 or Bcl-xL inhibited TRAIL-induced apoptosis, growth inhibition, and loss in clonogenic survival. Bcl-2 and Bcl-xL, but not DNC8, inhibited TRAIL-induced Bax activation. Bcl-xL did not inhibit the early activation of caspase-8 (<4 h) but inhibited cleavage of Bid, suggesting that Bid is cleaved downstream of the mitochondria, independent of caspase-8. Exogenous addition of sphingosine also induced activation of Bax via a caspase-8-and Bid-independent mechanism. Further, inhibition of sphingosine kinase completely protected cells from TRAIL-induced apoptosis. Data demonstrate that in RMS cells, the TRAIL signaling pathway circumvents caspase-8 activation of Bid upstream of the mitochondria and that TRAIL acts at the level of the mitochondria via a mechanism that may involve components of the sphingomyelin cycle.

Adaptor Proteins, Signal Transducing↗
PubMed2003

A phase II study of ZD0473 given as a short infusion every 3 weeks to patients with advanced or metastatic breast cancer: a National Cancer Institute of Canada Clinical Trials Group trial, IND 129.

BACKGROUND: ZD0473 is a new generation platinum compound with activity against a wide range of human tumor cell lines and xenografts, including carboplatin- and cisplatin-resistant lines. A phase II study of ZD0473 in advanced breast cancer was initiated by the National Cancer Institute of Canada Clinical Trials Group. PATIENTS AND METHODS: Women with metastatic breast cancer, measurable disease, an Eastern Cooperative Oncology Group performance status of up to two, and a maximum of one prior cytotoxic agent for recurrent disease were enrolled and treated at 120 mg/m(2) every 3 weeks. After 13 patients were enrolled, the dose was increased to 150 mg/m(2) on the basis of emergent data from studies ongoing at the time. RESULTS: Thirty-three women were evaluable for toxicity and 26 patients for response. Toxicity was mainly hematological with grade 3/4 thrombocytopenia in 12 of 20 patients (60%) treated at 150 mg/m(2) and grade 3 thrombocytopenia in three of 13 patients (23%) at 120 mg/m(2). Grade 3/4 neutropenia occurred in 15 patients (75%) at 150 mg/m(2) and two patients (10%) at 120 mg/m(2). Non-hematological toxicities were generally mild or moderate. There was one partial response seen for a response rate of 3.8% (95% confidence interval 0.1% to 19.5%) and stable disease in 15 patients. CONCLUSION: ZD0473 has minor activity as a single agent in metastatic breast cancer. Combinations with other drugs including docetaxel are ongoing and may be of interest.

Adult↗
PubMed2002

Crystal structures of Zidovudine- or Lamivudine-resistant human immunodeficiency virus type 1 reverse transcriptases containing mutations at codons 41, 184, and 215.

Six structures of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) containing combinations of resistance mutations for zidovudine (AZT) (M41L and T215Y) or lamivudine (M184V) have been determined as inhibitor complexes. Minimal conformational changes in the polymerase or nonnucleoside RT inhibitor sites compared to the mutant RTMC (D67N, K70R, T215F, and K219N) are observed, indicating that such changes may occur only with certain combinations of mutations. Model building M41L and T215Y into HIV-1 RT-DNA and docking in ATP that is utilized in the pyrophosphorolysis reaction for AZT resistance indicates that some conformational rearrangement appears necessary in RT for ATP to interact simultaneously with the M41L and T215Y mutations.

Adenosine Triphosphate↗
PubMed2001

UV-damaged DNA-binding proteins are targets of CUL-4A-mediated ubiquitination and degradation.

Cul-4A, which encodes a member of the cullin family subunit of ubiquitin-protein ligases, is expressed at abnormally high levels in many tumor cells. CUL-4A can physically associate with the damaged DNA-binding protein (DDB), which is composed of two subunits, p125 and p48. DDB binds specifically to UV-damaged DNA and is believed to play a role in DNA repair. We report here that CUL-4A stimulates degradation of p48 through the ubiquitin-proteasome pathway, resulting in an overall decrease in UV-damaged DNA binding activity. The R273H mutant of p48 identified from a xeroderma pigmentosium (group E) patient is not subjected to CUL-4A-mediated proteolysis, consistent with its inability to bind CUL-4A. p125 is also an unstable protein, and its ubiquitination is stimulated by CUL-4A. However, the abundance of p125 is not dramatically altered by Cul-4A overexpression. UV irradiation inhibits p125 degradation, which is temporally coupled to the UV-induced translocation of p125 from the cytoplasm into the nucleus. CUL-4A is localized primarily in the cytoplasm. These findings identify DDB subunits as the first substrates of the CUL-4A ubiquitination machinery and suggest that abnormal expression of Cul-4A results in reduced p48 levels, thus impairing the ability of DDB in lesion recognition and DNA repair in tumor cells.

Animals↗
PubMed2001

Comorbidity of psychiatric and substance use disorders in late adolescence: a cluster analytic approach.

Cluster analysis was used to identify subgroups of youths with past-year substance and/or psychiatric disorders (N = 110, mean age 19.0 years). Data for this study came from a community-based, prospective longitudinal investigation of speech/language (S/L) impaired children and matched controls who participated in extensive diagnostic and psychosocial assessments at entry into the study at 5 years of age and again at follow-up. Clustering variables were based on five DSM diagnostic categories assessed at age 19with the University of Michigan Composite International Diagnostic Interview. Using Ward's method, the five binary variables were entered into a hierarchical cluster analysis. An iterative clustering method (K-means) was then used to refine the Ward solution. Finally, a series of analyses of variance (ANOVAs) were run to analyze group differences between clusters on measures of Global Assessment of Functioning (GAF), criminal involvement, anxiety and depressive symptomatology, and frequency of drug use and heavy drinking. The analysis yielded eight replicable cluster groups, which were labeled as follows: (a) anxious (20.9%); (b) anxious drinkers (5.5%); (c) depressed (16.4%); (d) depressed drug abusers (10%); (e) antisocial (16.4%); (f) antisocial drinkers (10%); (g) drug abusers (8.2%); (h) problem drinkers (12.7%). These groups were differentiated by external criteria, thus supporting the validity of our cluster solution. Cluster membership was associated with a history of S/L impairment: A large proportion of the depressed drug abusers and the antisocial cluster group had S/L impairment that was identified at age 5. Clarification of the developmental progress of the youths in these cluster groups can inform our approach to early intervention and treatment.

Adolescent↗
PubMed2001

Fourteen-year follow-up of speech/language-impaired and control children: psychiatric outcome.

OBJECTIVE: To examine the association between early childhood speech and language disorders and young adult psychiatric disorders. METHOD: In a longitudinal community study conducted in the Ottawa-Carleton region of Ontario, Canada, interviewers administered structured psychiatric interviews to age 19 participants who were originally identified as speech-impaired only, language-impaired, or nonimpaired at age 5. The first stage of the study took place in 1982 when participants were 5 years old, and the latest stage of the study took place between 1995 and 1997 when participants had a mean age of 19 years. This report examines the association between early childhood speech/language status and young adult psychiatric outcome. RESULTS: Children with early language impairment had significantly higher rates of anxiety disorder in young adulthood compared with nonimpaired children. The majority of participants with anxiety disorders had a diagnosis of social phobia. Trends were found toward associations between language impairment and overall and antisocial personality disorder rates. Males from the language-impaired group had significantly higher rates of antisocial personality disorder compared with males from the control group. Age of onset and comorbidity did not differ by speech/language status. The majority of participants with a disorder had more than one. CONCLUSIONS: Results support the association between early childhood speech and language functioning and young adult psychiatric disorder over a 14-year period. This association underscores the importance of effective and early interventions.

Adult↗
PubMed2001

Vocal behavior of male sperm whales: why do they click?

Off Kaikoura, New Zealand, we recorded individually identified male sperm whales (Physeter macrocephalus) for entire dive cycles in order to investigate vocal behavior of individual whales and to examine possible functions of sperm whale clicks. In our study, sperm whales were almost always silent at the surface. They consistently started clicking within 25 s after fluking-up and diving. During the first 10 s of clicking, interclick intervals were significantly correlated with water depths at the location of fluke-up. The first "creak" was produced on average 7.5 min into a dive. Interclick intervals usually decreased substantially before clicks turned into "creaks." The highest click rate recorded in this study was 90.9 click/s, and clicks-within-creaks were much shorter than "usual clicks" (mean of 3.6 ms versus 17 to 30 ms). The number of creaks per minute of dive and the length of a dive were significantly correlated. On average, sperm whales were silent for the last 3.6 min before surfacing. Short sequences of "surface clicks" (3 to 8 metallic clicks with mean interclick interval of 5.5 s) were often produced at the end of a dive (in 57% of the dives), but their function remains puzzling. The results of this study suggest that usual clicks and creaks are both used for echolocation purposes, the former to gather information about acoustically reflective features and the latter to detect prey.

Animals↗
PubMed2001

Misconceptions and misuse of the MMPI-2 in assessing personal injury claimants.

The MMPI-2 enjoys widespread popularity in the psychological assessment of personal injury claimants, in part due to its long history, massive research literature, strong empirical basis, and the availability of commercial interpretative and scoring services. However, the relative paucity of studies examining the forensic role of the MMPI-2, raises concerns about the applicability of traditional interpretative guidelines in the medicolegal arena. This paper analyses MMPI-2 protocols of 2080 cases derived from a forensic psychiatric practice in Brisbane, Australia. The data presented here challenges these traditional MMPI-2 interpretations and calls into question assumptions and commonly employed techniques when applied in this setting. In particular, the validity of codetype-based interpretations, the role the MMPI-2 plays in differential diagnosis, and assumptions regarding diagnostically-specific patterns on the test are challenged. MMPI-2 interpretative cookbooks, computer report-writers, adherence to the intent of the test-developers, and appeals to authority are inadequate substitutes for empirical accuracy, and an active hypothesis-testing interpretative approach, based upon setting-specific base-rate data, is recommended.

Attitude of Health Personnel↗
PubMed2000

Pediatric rhabdomyosarcoma cell lines are resistant to Fas-induced apoptosis and highly sensitive to TRAIL-induced apoptosis.

Seven pediatric rhabdomyosarcoma (RMS) cell lines were resistant to the induction of apoptosis via the Fas death receptor. In contrast, four of seven lines (RD, Rh1, Rh18, and Rh30) were highly sensitive to tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL). TRAIL induced apoptosis within 4 h and also reduced clonogenic survival, both reversible by caspase inhibitors. DR5 (but not DR4) was expressed at high level in all cell lines. Expression of the decoy receptors DcR1 and DcR2 did not correlate with TRAIL sensitivity. All RMS lines expressed the adapter molecule FADD, and six of seven expressed procaspase-8. Expression of the inhibitory proteins c-FLIPL and c-FLIPs was high in three TRAIL-sensitive (RD, Rh1, and Rh30) and two TRAIL-resistant (Rh28 and Rh41) lines. All RMS lines expressed Bid and procaspases-3, -6, -7, and -9. Procaspases-8 and -10 were highest in TRAIL-sensitive RMS (RD, Rh1, and Rh30), and procaspase-10 was not expressed in Rh18, Rh36, or Rh41. TRAIL induced loss of mitochondrial membrane potential in TRAIL-sensitive Rh1 but not in TRAIL-resistant Rh41 cells. There was no correlation between expression of members of the Bcl-2 family (Bcl-2, Bcl-xL, Bax, and Bak) and TRAIL sensitivity. TRAIL-sensitive Rh18 expressed procaspase-8 in the absence of procaspase-10 and c-FLIP, and procaspase-10 was not detected in TRAIL-resistant Rh41 in the presence of procaspase-8 and c-FLIP. Data suggest that caspase-8 may be sufficient to deliver the TRAIL-induced apoptotic signal in the absence of both caspase-10 and c-FLIP (Rh18) but not in the presence of c-FLIP (Rh41). In RD, Rh1, and Rh30, the presence of c-FLIP may require amplification of the apoptotic signal via caspase-10.

Apoptosis↗
PubMed1999

Fourteen-year follow-up of children with and without speech/language impairments: speech/language stability and outcomes.

This report concerns the speech and language outcomes of young adults (N = 242) who participated in a 14-year, prospective, longitudinal study of a community sample of children with (n = 114) and without (n = 128) speech and/or language impairments. Participants were initially identified at age 5 and subsequently followed at ages 12 and 19. Direct assessments were conducted in multiple domains (communicative, cognitive, academic, behavioral, and psychiatric) at all three time periods. Major findings included (a) high rates of continued communication difficulties in those with a history of impairment; (b) considerable stability in language performance over time; (c) better long-term outcomes for those with initial speech impairments than for those with language impairments; and (d) more favorable prognoses for those with specific language impairments than for those with impairments secondary to sensory, structural, neurological, or cognitive deficits. These general conclusions held when either a liberal or a more stringent criterion for language impairment was employed. Some of these findings are consistent with those from earlier follow-up studies, which used less optimal methods. Thus, the present replication and extension of these findings with a sound methodology enables greater confidence in their use for prognostic, planning, and research purposes.

Adolescent↗
PubMed1999

Adolescent substance use disorders: findings from a 14-year follow-up of speech/language-impaired and control children.

Intervening on the development of adolescent addiction requires an understanding of the role of precursors. In a community sample of youth with and without early childhood speech/language (S/L) impairments, 12.7% of participants had a substance use disorder (SUD). Among these participants, 42.0% met criteria for more than 1 SUD. Interestingly, rates of SUDs did not differ by S/L status. However, S/L-impaired participants did show greater psychiatric comorbidity and poorer functioning. A total of 80% of S/L participants with SUDs had a concurrent diagnosis of antisocial personality disorder, compared with 43.8% of SUDs controls. In a logistic regression analysis, we found age 5 mother-rated problem behavior scores and an interaction between S/L status and teacher-rated conduct problem scores were predictive of SUDs. High conduct scores were predictive of SUDs development among control participants but not among S/L-impaired participants. First substance use and initial SUDs symptoms suggest that a window of opportunity exists to reach these troubled young people before they spiral into addiction.

Adolescent↗
PubMed1997

Age-specific associations between emotional responses to separation and cognitive performance in infancy.

Associations between emotional responses to maternal separation and cognitive performance were expected to change with cognitive development over the first year. In this longitudinal study of 39 infants, measures of separation and reunion distress at 2, 6, and 10 months were interleaved with measures of sensorimotor coordination at 4, 8, and 13 months. Separation distress at 2 months predicted lower sensorimotor scores, whereas separation distress at 6 and 10 months corresponded with higher scores. Duration of distress in reunion showed the same pattern of associations, when controlled for general emotionality Infants' positive engagement and physical touch with their mothers at 10 months predicted higher sensorimotor scores as well. Emotional responses and cognitive performance may be linked by individual differences in self-regulation and attentional engagement, as mediated by age-specific developmental issues.

Age Factors↗
PubMed1997

Easy visualization of the membranous urethral stump in radical prostatectomy.

PURPOSE: Access to the urethral stump is sometimes difficult during radical retropublic prostatectomy. MATERIALS AND METHODS: A 20F Foley catheter with the 5 ml. balloon inflated with 10 ml. in the bulbous urethra was used to elevate the urethral stump into the operative field. RESULTS: Easy access to the urethral stump was achieved in all patients, which assisted with accurate anastomosis. There was decreased leakage of urine and no anastomotic stricture. No urethral trauma or incontinence was attributable to the technique. CONCLUSIONS: This simple and safe technique allowed easy access to the urethral stump.

Catheterization↗