Further evidence for the predictive validity of the unstable elevated exposed plus-maze, a behavioural model of extreme anxiety in rats: differential effects of fluoxetine and chlordiazepoxide

The unstable elevated exposed plus-maze (UEEPM) is a novel model of extreme anxiety which elicits unconditioned flight/escape behaviour in rats. The current studies aimed to investigate further the predictive validity of the paradigm, by examining the effects on UEEPM behaviour of both clinically effective (chronic fluoxetine) and ineffective (acute fluoxetine and chlordiazepoxide) treatments for panic disorder. In the first experiment, male Brown Norway rats received a single injection of fluoxetine (1.0-10.0 mg/kg p.o.) or chlordiazepoxide (CDP, 1.0-10.0 mg/kg i.p.) 30 min prior to UEEPM exposure. In the second experiment, in order to assess the effects of chronic dosing or handling on baseline UEEPM behaviour, subjects received either 21 days vehicle injection (p.o.) or handling, before being exposed to the test. Finally, rats received 21 days fluoxetine (1.0-10.0 mg/kg) in their food, before being tested in the UEEPM. Acute CDP and fluoxetine had no effect on UEEPM behaviour. Chronic handling and vehicle administration (p.o.) significantly reduced escape in the UEEPM, hence preventing the effects of chronic fluoxetine administration from being investigated by p.o. dosing. Chronic fluoxetine in subjects' food (10.0 mg/kg) significantly attenuated animals' propensity to escape from the UEEPM. The results further support the pharmacological similarity between symptoms of panic in humans and escape in the UEEPM and suggest that the UEEPM may represent a paradigm to facilitate investigation into the neurochemical basis of extreme anxiety disorders.

Dynein motors of the Chlamydomonas flagellum

Chlamydomonas is a biflagellate unicellular green alga that has proven especially amenable for the analysis of microtubule (MT)-based molecular motors, notably dyneins. These enzymes form the inner and outer arms of the flagellum and are also required for intraflagellar transport. Dyneins have masses of approximately 1-2 MDa and consist of up to 15 different polypeptides. Nucleotide binding/hydrolysis and MT motor activity are associated with the heavy chains, and we detail here our current model for the substructural organization of these approximately 520-kDa proteins. The remaining polypeptides play a variety of roles in dynein function, including attachment of the motor to cargo, regulation of motor activity in response to specific inputs, and their necessity for the assembly and/or stability of the entire complex. The combination of genetic, physiological, structural, and biochemical approaches has made the Chlamydomonas flagellum a very powerful model system in which to dissect the function of these fascinating molecular motors.

The 'family' context of HIV: a need for comprehensive health and social policies

This paper reports on the findings from a multi-site psychosocial study of Canadian families with HIV-positive mothers. A total of 110 adults, representing 91 families across Canada participated in interviews. Qualitative analysis revealed a number of themes including: a complex web of personal, health and family concerns; the needs of children; family finances; disclosure dilemmas; and social experiences and challenges. These themes reflect an intricate and dynamic picture of parental and family life for adults and children living with HIV infection. Nowhere in the literature do we see HIV framed as a 'family infection'. Surveillance reporting reflects information on infected adults and children but not family groupings. Yet with HIV several family members and multiple generations as well as single or both parents may be infected, highlighting the importance of 'family HIV' as a framework for health policy and programme development. At issue is the problem that medical and other institutions view issues of surveillance, treatment and care through the lens of the infected individual, rather than being family focused. Often it is only in the context of identifying support, or barriers to support, for the medically diagnosed individual that biological or socially created families become a focus of concern. The failure to situate both chronic and life-threatening illnesses within the family setting has serious quality of life and planning consequences for parents and children living with HIV infection as well as other illnesses.

The role of infections in primary hemophagocytic lymphohistiocytosis: a case series and review of the literature

There is a paucity of literature addressing infection-related morbidity and mortality in children with primary hemophagocytic lymphohistiocytosis (HLH), a rare condition characterized by abnormal proliferation of macrophages, hypercytokinemia, and T cell immunosuppression. Therefore, a retrospective chart review was done of patients diagnosed with primary HLH over a 15-year period. Significant infections present at diagnosis, during the course of illness, and just prior to death or at autopsy were noted. Of the 18 children identified with primary HLH, an infectious agent was documented at the initial presentation of HLH in 5. Significant infections occurred during therapy in 10 (56%) of 18. Of the 12 fatal cases, invasive infection was the cause of death in 8 children, and 6 of these deaths were directly attributable to invasive fungal infection. Significant infections were common during therapy in children with primary HLH, and fungal infections were an important cause of mortality in this group.

Update on perinatal HIV

QUESTION

Many patients in my practice come from countries where HIV is endemic. Are there current figures on their risk of being infected during pregnancy?

ANSWER

In Ottawa and Toronto, Ont, about half the pregnant women identified as HIV-positive were born in countries where HIV is endemic. If you suspect a woman has HIV or have other questions, call the Motherisk HIV-Healthline at 1-888-246-5840. Human immunovirus infection among pregnant women continues to be a serious public health concern. Most fetuses can be protected from contracting HIV if appropriate antiretroviral (ARV) therapy is instituted.

Pattern electroretinograms after cerebral hemispherectomy

Cortically blind patients with brain damage restricted to the optic radiations or primary visual cortex may be able to detect and discriminate visual stimuli presented in their field defects, even though they deny seeing them. In contrast, patients who are hemianopic as a result of cerebral hemispherectomy cannot explicitly discriminate visual stimuli in their field defects, even when forced choice procedures are used. A possible explanation for this difference is that retrograde, transneuronal degeneration of the retina, which affects approximately 85% of wavelength-sensitive ganglion cells (approximately 70% of the total) after damage restricted to striate cortex, could be far more extensive after hemispherectomy, rendering the retina incapable of processing and conveying visual information to the brain. To test this, we assessed retinal ganglion cell function by means of electroretinography in three patients with cerebral hemispherectomy who were functionally blind. Steady-state pattern electroretinograms elicited by achromatic and isoluminant-chromatic (red-green) sinusoidal gratings, whose contrast was temporally modulated, were recorded from both blind and sighted hemiretinae. The electroretinograms were qualitatively indistinguishable from those of a control patient with a unilateral striate cortical lesion with documented visual capacity in his field defect. Within-subject analysis of variance revealed significant differences in the amplitude of the second harmonic (2f(0)) component of the averaged signal (diagnostic of retinal ganglion cell function) with respect to stimulus, but no significant differences between blind and sighted hemiretinae. This indicates that many retinal ganglion cells must have survived in the hemispherectomized patients. Isoluminant chromatic stimuli tended to elicit stronger signals than achromatic stimuli, which was unexpected given that wavelength-opponent Pbeta ganglion cells are far more susceptible than broad-band Palpha ganglion cells to transneuronal degeneration after cortical damage. It suggests that the 2f(0) component of the response to isoluminant chromatic stimuli might not reflect the activity of chromatic processes. Overall, the results show that the absence of residual vision in the blind fields of patients with cerebral hemispherectomy cannot be due to complete degeneration of retinal ganglion cells and, by extension, complete degeneration of their subcortical targets. This supports an alternative explanation, which is that intact extrastriate cortex is required for mediating voluntary responses to visual stimuli presented in the scotoma.

The Tctex1/Tctex2 class of dynein light chains. Dimerization, differential expression, and interaction with the LC8 protein family

The Tctex1/Tctex2 family of dynein light chains associates with the intermediate chains at the base of the soluble dynein particle. These components are essential for dynein assembly and participate in specific motor-cargo interactions. To further address the role of these light chains in dynein activity, the structural and biochemical properties of several members of this polypeptide class were examined. Gel filtration chromatography and native gel electrophoresis indicate that recombinant Chlamydomonas flagellar Tctex1 exists as a dimer in solution. Furthermore, yeast two-hybrid analysis suggests that this association also occurs in vivo. In contrast, both murine and Chlamydomonas Tctex2 are monomeric. To investigate protein-protein interactions involving these light chains, outer arm dynein from Chlamydomonas flagella was cross-linked using dimethylpimelimidate. Immunoblot analysis of the resulting products revealed the interaction of LC2 (Tctex2) with LC6, which is closely related to the highly conserved LC8 protein found in many enzyme systems, including dynein. Northern dot blot analysis demonstrated that Tctex1/Tctex2 family light chains are differentially expressed both in a tissue-specific and developmentally regulated manner in humans. These data provide further support for the existence of functionally distinct populations of cytoplasmic dynein with differing light chain content.

Challenges of parenting for families living with HIV/AIDS

Given the continual rise of HIV infection in our communities and the improved life span for many who are HIV-positive, social workers in all fields of practice have clients whose lives have been touched by HIV/AIDS. This article reviews relevant literature and reports on the parenting needs that emerged in a Canadian study that examined the experiences of 105 mothers and fathers living with HIV/AIDS. The majority of the children in the study were not HIV-positive. Some themes related to parenting in the literature, and evident in this study, were chronic sorrow, stress and burden, normalization, stigma, secrecy, and disclosure. In the study parenting was found to be a source of joy and an additional challenge in an already complicated life. Important new themes were family life as precious time, focused parenting, the different effects of HIV/AIDS, the parenting preparation needs of fathers, and the efforts to parent affected and infected children differently. Parenting when living with HIV/AIDS requires attention from clinicians and researchers in a range of settings.

Safety of the Canadian blood supply in 1980-85: using a paediatric cohort for risk assessment of human immunodeficiency virus (HIV) infection

The risk of HIV from transfusions in Canada in the period 1980-85 was estimated, using the information from a transfused paediatric cohort. Children who were transfused between January 1980 and November 1985 at a tertiary care paediatric hospital were contacted by letter. With this notification, HIV testing for recipients was recommended. HIV testing histories were obtained. The number tested for HIV was estimated from the questionnaire responses and from data matching with the HIV-testing laboratory. Cases of HIV infection were identified through multiple sources. In this cohort, 11,028 children were transfused a mean of 21 units. Of the 10,220 living recipients, the estimated proportion tested for HIV was 86% to 91%. Thirty-one cases of HIV infection were identified, representing 0.28% of the cohort but 0.34% of those expected to have been tested. The estimated HIV incidence per 1,000 units transfused ranged from 0.028 [95% CI 0.0007, 0.155] in 1980 to 0.445 [95% CI 0.2592, 0.712] in 1985. This suggests that the risk of HIV from transfusions in Canada continued to rise until the implementation of HIV testing of donors in November 1985.

Influence of circadian phase and test illumination on pre-clinical models of anxiety

Pre-clinical models of anxiety, particularly the elevated plus-maze (EPM), have been shown to be sensitive to a variety of methodological variations. Recent research has implicated circadian phase of testing in influencing the behavioural profile of 5-HT(1A) ligands on the EPM. The present study investigated the effects of testing animals during the dark and light phases and in light and subjective dark test conditions on baseline behaviour in animal models of anxiety. Eighty singly housed male Sprague-Dawley rats were exposed to a battery of unconditioned, exploratory tests (EPM, open field arena, holeboard) and a new model of extreme anxiety, the unstable elevated exposed plus-maze (UEEPM). Circadian phase of testing failed to consistently alter behaviour on any model. Level of test illumination had no effect on subjects' response to the open field arena, holeboard or UEEPM. Dark testing increased locomotor activity on the EPM (total arm entries, closed arm entries and distance moved) without decreasing open-arm avoidance. The construct of anxiety as measured by a number of different paradigms withstood major intra-laboratory manipulation of circadian phase of testing and illumination of apparatus. It is suggested that the effects of circadian rhythmicity may be confined to the behavioural profiles of serotonergic, particularly 5-HT(1A), ligands on the EPM.

Social planning in Canada for families with HIV infection

Parents living with HIV and their children face complex medical and social problems. Whether the children are infected or not, they are all affected by the presence of HIV in a parent. The purpose of this article is to describe the problems of families with HIV and to propose social planning measures to respond to their psychosocial needs. It is based on a multicentre study that included in-depth interviews with 110 parents representing 91 Canadian families living with HIV. The study's findings and recommendations were reviewed by parents with HIV, social workers specializing in helping affected families, and a multidisciplinary consensus conference. This process identified six areas needing attention: stigma and disclosure; promoting and supporting family health; planning and transitions for the care of children; economic issues; cultural and immigrant issues; and education, advocacy, policy development, and research. Recommendations for action were made in each area.

The light chain composition of chicken brain myosin-Va: calmodulin, myosin-II essential light chains, and 8-kDa dynein light chain/PIN

Class V myosins are a ubiquitously expressed family of actin-based molecular motors. Biochemical studies on myosin-Va from chick brain indicate that this myosin is a two-headed motor with multiple calmodulin light chains associated with the regulatory or neck domain of each heavy chain, a feature consistent with the regulatory effects of Ca(2+) on this myosin. In this study, the identity of three additional low molecular weight proteins of 23-,17-, and 10 kDa associated with myosin-Va is established. The 23- and 17-kDa subunits are both members of the myosin-II essential light chain gene family, encoded by the chicken L23 and L17 light chain genes, respectively. The 10-kDa subunit is a protein originally identified as a light chain (DLC8) of flagellar and axonemal dynein. The 10-kDa subunit is associated with the tail domain of myosin-Va.

Investigation of protein-protein interactions within flagellar dynein using homobifunctional and zero-length crosslinking reagents

The dynein molecular motor is a highly complex enzyme containing up to 15 different protein components and consists of several distinct domains identifiable by electron microscopy. One of the current challenges is to understand the supramolecular organization of this motor and to determine the location and function of the various components. Recently, we have used covalent crosslinking by amine-selective reagents and a carbodiimide, which results in zero-length crosslink, to investigate protein-protein associations within Chlamydomonas flagellar dynein. This approach also has enabled us to identify previously undescribed interactions between the dynein arms and other components of the flagellar axoneme. In this report, we detail methods we have developed to probe intradynein and intraaxonemal interactions and discuss the variety of factors that need be addressed to perform a successful crosslinking experiment.

Social planning in Canada for families with HIV infection

Parents living with HIV and their children face complex medical and social problems. Whether the children are infected or not, they are all affected by the presence of HIV in a parent. The purpose of this article is to describe the problems of families with HIV and to propose social planning measures to respond to their psychosocial needs. It is based on a multicentre study that included in-depth interviews with 110 parents representing 91 Canadian families living with HIV. The study's findings and recommendations were reviewed by parents with HIV, social workers specializing in helping affected families, and a multidisciplinary consensus conference. This process identified six areas needing attention: stigma and disclosure; promoting and supporting family health; planning and transitions for the care of children; economic issues; cultural and immigrant issues; and education, advocacy, policy development, and research. Recommendations for action were made in each area.

AAA domains and organization of the dynein motor unit

Dyneins contain one-three microtubule motor units that are each derived from the C-terminal globular head of a heavy chain. The N-terminal regions of the heavy chains form stems that are required for intra-dynein associations. The microtubule-binding sites are located at the terminus of a short stalk that emanates from each globular head. Recent electron microscopic analysis indicates that the dynein head has a heptameric toroidal organization. This finding is echoed by the identification of six AAA (ATPases associated with cellular activities) domains and a seventh unrelated unit within this heavy chain region. At least two of these AAA domains can bind nucleotide, although only one appears able to hydrolyze ATP. Several other AAA domain proteins exhibit a similar annular organization of six AAA units. Detailed structural information is available for several AAA proteins, including N-ethylmaleimide-sensitive vesicle-fusion protein and the RuvB motor involved in DNA migration and resolution of Holliday junctions. The resulting structural parallels allow intriguing predictions to be made concerning dynein organization and motor function.

Solution structure of a dynein motor domain associated light chain

Dyneins are molecular motors that translocate towards the minus ends of microtubules. In Chlamydomonas flagellar outer arm dynein, light chain 1 (LC1) associates with the nucleotide binding region within the gamma heavy chain motor domain and consists of a central leucine-rich repeat section that folds as a cylindrical right handed spiral formed from six beta-beta-alpha motifs. This central cylinder is flanked by terminal helical subdomains. The C-terminal helical domain juts out from the cylinder and is adjacent to a hydrophobic surface within the repeat region that is proposed to interact with the dynein heavy chain. The position of the C-terminal domain on LC1 and the unexpected structural similarity between LC1 and U2A' from the human spliceosome suggest that this domain interacts with the dynein motor domain.

Identification and molecular characterization of the p24 dynactin light chain

Intracellular transport along microtubules uses the motor proteins cytoplasmic dynein and kinesin. Cytoplasmic dynein is responsible for movement to the minus ends of microtubules and the evidence indicates that dynein interacts with another protein complex, dynactin. In order to better understand how these proteins function, we have sought to identify and clone the subunit polypeptides of these two complexes, in particular their light chains. Dynactin is made up of eight subunits of approximately 24,000 to 160,000 Da. In order to clone the p24 subunit, the components of purified dynactin were resolved by SDS polyacrylamide gel electrophoresis. The amino acid sequence of a tryptic peptide from the 24,000-Mr region of the gel was obtained and a candidate polypeptide identified by a screen of the databases. This polypeptide has a predicted molecular weight of 20,822 Da. Using an antibody to a different region of this protein, we demonstrate that it copurifies with microtubules and elutes from the microtubule pellet with characteristics similar to those of the dynactin complex and distinct from those of cytoplasmic dynein. This polypeptide co-sediments with dynactin on sucrose density gradients and it also co-immunoprecipitates with dynactin, but not with kinesin or cytoplasmic dynein. Together these results demonstrate that this polypeptide is the p24 subunit of dynactin. Analysis of the predicted amino acid sequence of p24 shows that it is a unique protein that has no significant similarity to known enzymes or other proteins. Structural analysis indicates that most of this protein will form an alpha-helix and that portions of the molecule may participate in the formation of coiled-coils. Since stoichiometric analysis of dynactin indicates that there is one molecule of p24 per dynactin complex, these characteristics suggest that this polypeptide may be involved in protein-protein interactions, perhaps in the assembly of the dynactin complex.

The dynein microtubule motor

Dyneins are large multi-component microtubule-based molecular motors involved in many fundamental cellular processes including vesicular transport, mitosis and ciliary/flagellar beating. In order to achieve useful work, these enzymes must contain motor, cargo-binding and regulatory components. The ATPase and microtubule motor domains are located within the very large dynein heavy chains that form the globular heads and stems of the complex. Cargo-binding activity involves the intermediate chains and several classes of light chain that associate in a subcomplex at the base of the soluble dynein particle. Regulatory control of dynein motor function is thought to involve the phosphorylation of various components as well as a series of light chain proteins that are directly associated with the heavy chains. These latter polypeptides have a variety of intriguing attributes, including redox-sensitive vicinal dithiols and Ca(2+)-binding, suggesting that the activity of individual dyneins may be subject to multiple regulatory inputs. Recent molecular, genetic and structural studies have revealed insight into the roles played by these various components and the mechanisms of dynein-based motility.