Biomedical subjects

D S Weiss

Publications and source records attributed to D S Weiss.

At least 19 recordsLinked to original sources

PubMed2003

Mutations at the GABA receptor selectivity filter: a possible role for effective charges.

An important feature of ligand-gated ion channels is their exquisite ability to discriminate between ions. Still, little is known about the mechanisms underlying, or structural determinates of, this ability. We examined the structural elements underlying the ionic selectivity of rho1 GABA receptors expressed in Xenopus oocytes and human embryonic kidney cells using site-directed mutagenesis and two-electrode voltage-clamp or patch-clamp techniques. The wild-type GABA receptor was chloride selective, with a small but significant permeability to potassium (PNa+ : PK+ : PCl- = 0 : 0.03 :1). Mutation of an alanine to glutamate at position 291 (thought to be located at the intracellular end of the second transmembrane domain), formed a channel that exhibited little discrimination among ions (0.70:0.87:1), while deletion of a neighbouring proline (290) was chloride selective, but had elevated cation permeabilities compared to the wild-type channel (0.12 : 0.14 : 1). Together, the two mutations (DeltaP290/A291E) caused a reversal of selectivity (2.72 : 3.59 : 1). We also examined the effects of neutralizing and reversing the charge of the adjacent, and highly conserved, arginine. Mutation of the neighbouring arginine to glutamate (R292E) increased the cation permeability similar to the DeltaP290/A291E double mutant (2.4 : 3.0 : 1), whereas neutral mutations at this position (R292M or R292C) retained chloride selectivity (0 : 0.11 : 1.0 and 0 : 0.14 : 1.0, respectively). Our experiments suggest that the effective charge near the presumed intracellular mouth of the pore is critical for ionic selectivity.

Algorithms↗

PubMed2001

Decreased hippocampal N-acetylaspartate in the absence of atrophy in posttraumatic stress disorder.

BACKGROUND: Previous magnetic resonance imaging studies of posttraumatic stress disorder reported hippocampal volume loss. The goals of this study were 1) to determine the relationship between hippocampal atrophy and posttraumatic stress disorder in the absence of alcohol abuse, and 2) to test if loss of N-acetylaspartate (a neuron marker) in the hippocampus of posttraumatic stress disorder occurs separate from atrophy. In addition, volume changes in the entorhinal cortex were also explored. METHODS: Eighteen male patients with combat-related posttraumatic stress disorder (mean age 51.2 +/- 2.5 years) and 19 male control subjects (mean age 51.8 +/- 3.2 years) were studied using magnetic resonance imaging and Proton magnetic resonance spectroscopic imaging. Both groups had no alcohol and drug abuse during the past 5 years. RESULTS: Posttraumatic stress disorder and control subjects had similar volumes of hippocampus and entorhinal cortex. In contrast to volume, N-acetylaspartate was significantly reduced by about 23% bilaterally in the hippocampus of posttraumatic stress disorder when compared with control subjects, and creatine-containing compounds were reduced by 26% in the right hippocampus of posttraumatic stress disorder. CONCLUSIONS: N-acetyl asparate and creatine reductions imply that there are hippocampal abnormalities in posttraumatic stress disorder. Furthermore, these metabolite changes seem to be better indicators of posttraumatic stress disorder pathology than volume losses.

Aspartic Acid↗

PubMed2001

Positive allosteric modulation by ultraviolet irradiation on GABA(A), but not GABA(C), receptors expressed in Xenopus oocytes.

1. Recombinant rat GABA(A) (alpha1beta2, alpha1beta2gamma2, beta2gamma2) and human GABA(C) (rho1) receptors were expressed in Xenopus oocytes to examine the effect of ultraviolet (UV) light on receptor function. 2. GABA-induced currents in individual oocytes expressing GABA receptors were tested by two-electrode voltage clamp before, and immediately after, 312 nm UV irradiation. 3. UV irradiation significantly potentiated 10 microM GABA-induced currents in alpha1beta2gamma2 GABA receptors. The modulation was irradiation dose dependent, with a maximum potentiation of more than 3-fold. 4. The potentiation was partially reversible and decayed exponentially with a time constant of 8.2 +/- 1.2 min toward a steady-state level which was still significantly elevated (2.7 +/- 0.3-fold) compared to the control level. 5. The effect of UV irradiation on GABA(A) receptors varied with receptor subunit composition. UV irradiation decreased the EC50 of the alpha1beta2, alpha1beta2gamma2 and beta2gamma2 GABA(A) receptors, but exhibited no significant effect on the rho1 GABA(C) receptor. 6. UV irradiation also significantly increased the maximum current 2-fold in alpha1beta2 GABA(A) receptors with little effect on the maximum of alpha1beta2gamma2 (1.1-fold) or beta2gamma2 (1.1-fold) GABA(A) receptors. 7. The effect of UV irradiation on GABA(A) receptors did not overlap the effect of the GABA receptor- allosteric modulator, diazepam. 8. The UV effect on GABA(A) receptors was not prevented by the treatment of the oocytes before and during UV irradiation with one of the following free-radical scavengers: 40 mM D-mannitol, 40 mM imidazole or 40 mM sodium azide. In addition, the effect was not mimicked by the free-radical generator, H2O2. 9. Potential significance and mechanism(s) of the UV effect on GABA receptors are discussed.

Allosteric Regulation↗

PubMed2001

Recombinant GABA(C) receptors expressed in rat hippocampal neurons after infection with an adenovirus containing the human rho1 subunit.

1. A recombinant adenovirus was generated with the human rho1 GABA(C) receptor subunit (adeno-rho). Patch-clamp and antibody staining were employed to confirm functional expression of recombinant rho1 receptors after infection of human embryonic kidney cells (HEK293 cell line), human embryonic retinal cells (911 cell line), dissociated rat hippocampal neurons and cultured rat hippocampal slices. 2. Standard whole-cell recording and Western blot analysis using rho1 GABA(C) receptor antibodies revealed that recombinant rho1 receptors were expressed in HEK293 and 911 cells after adeno-rho infection and exhibited properties similar to those of rho1 receptors after standard transfection. 3. Cultured rat hippocampal neurons (postnatal day (P)3-P5) did not show a native GABA(C)-like current. After adeno-rho infection, however, a GABA(C)-like current appeared in 70-90 % of the neurons. 4. Five days after infection, expression of GABA(C) receptors in hippocampal neurons significantly decreased native GABA(A) receptor currents from 1200 +/- 300 to 150 +/- 70 pA (n = 10). The native glutamate-activated current was unchanged. 5. Hippocampal slices (P8) did not show a native GABA(C)-like current, although recombinant rho1 receptors could be expressed in cultured hippocampal slices after adeno-rho infection. 6. These data indicate that an adenovirus can be used to express recombinant GABA(C) receptors in hippocampal neurons. This finding could represent an important step towards the gene therapy of CNS receptor-related diseases.

Adenoviridae↗

PubMed2001

Modulation of GABA(A) receptors by benzodiazepines and barbiturates is autonomous of PKC activation.

Previous studies have suggested that activation of calcium-phospholipid-dependent protein kinase (PKC) enhances benzodiazepine (BZD)- and pentobarbital (PB)- mediated potentiation of alpha(1)beta(1)gamma(2) GABA(A) receptors (GABA(A)-Rs). To delineate the underlying mechanism(s), voltage-clamp recordings were performed on recombinant alpha(1)beta(1)gamma(2) GABA(A) receptors functionally expressed in Xenopus laevis oocytes. GABA(A)-Rs were tested for their sensitivity to diazepam and PB before and after incubation in phorbol 12-myristate 13-acetate (PMA). PMA (25 nM) significantly attenuated the GABA(A) current (p<0.05, n=12-19) up to 90%. PMA treatment, however, did not alter the sensitivity to diazepam or pentobarbital. Similar results were obtained with recombinant alpha(1)beta(2)gamma(2) GABA receptors. These data suggest that PKC activation does not alter the allosteric modulation of GABA(A)-Rs by benzodiazepines and barbiturates and is consistent with the observation from other studies in oocytes that PMA decreases the amplitude of the GABA-activated currents via receptor internalization rather than modification of receptor kinetics.

Allosteric Regulation↗

PubMed2001

Fluvoxamine and sleep disturbances in posttraumatic stress disorder.

This study assesses the efficacy of fluvoxamine treatment on different domains of subjective sleep quality in Vietnam combat veterans with chronic posttraumatic stress disorder (PTSD). Medically healthy male Vietnam theater combat veterans (N = 21) completed a 10-week open label trial. Fluvoxamine treatment led to improvements in PTSD symptoms and all domains of subjective sleep quality. The largest effect was for dreams linked to the traumatic experience in combat. In contrast, generic unpleasant dreams showed only a modest response to treatment. Sleep maintenance insomnia and the item "troubled sleep" showed a large treatment response, whereas sleep onset insomnia improved less substantially. These therapeutic benefits contrast with published reports that have found activating effects of Selective Serotonin Reuptake Inhibitors on the sleep electroencephalogram.

Adult↗

PubMed2001

Spinal cord and nerve root monitoring during surgical treatment of lumbar stenosis.

The author describes application of intraoperative neurophysiologic monitoring to surgical treatment of lumbar stenosis. Benefits of somatosensory and motor evoked potential studies during surgical correction of spinal deformity are well known and documented. Free-running and evoked electromyographic studies during pedicle screw implantation is an accepted practice at many institutions. However, the functional integrity of spinal cord, cauda equina, and nerve roots should be monitored throughout every stage of surgery including exposure and decompression. Somatosensory evoked potentials monitor overall spinal cord function. Intraoperative electromyography provides continuous assessment of motor root function in response to direct and indirect surgical manipulation. Electromyographic activities observed during exposure and decompression of the lumbosacral spine included complex patterns of bursting and neurotonic discharge. In addition, electromyographic activities at distal musculature were elicited by impacting a surgical instrument or graft plug against bony elements of the spine. All electromyographic events provided direct feedback to the surgical team and were regarded as a cause for concern. Simultaneously monitored evoked potential and electromyographic studies protect spinal cord and nerve roots during seemingly low-risk phases of a surgical procedure when neurologic injury may occur and the patient is placed at risk for postoperative myelopathy or radiculopathy.

Decompression, Surgical↗

PubMed2001

Effects of gender and ethnicity on duty-related posttraumatic stress symptoms among urban police officers.

We studied 655 urban police officers (21% female, 48% white, 24% black, and 28% Hispanic) to assess ethnic and gender differences in duty-related symptoms of posttraumatic stress disorder (PTSD). We obtained self-report measures of: a) PTSD symptoms, b) peritraumatic dissociation, c) exposure to duty-related critical incidents, d) general psychiatric symptoms, e) response bias due to social desirability, and f) demographic variables. We found that self-identified Hispanic-American officers evidenced greater PTSD symptoms than both self-identified European-American and self-identified African-American officers. These effects were small in size but they persisted even after controlling for differences in other relevant variables. Contrary to expectation, we found no gender differences in PTSD symptoms. Our findings are of note because: a) they replicate a previous finding of greater PTSD among Hispanic-American military personnel and b) they fail to replicate the well-established finding of greater PTSD symptoms among civilian women.

Adult↗

PubMed2001

Release of Toll-like receptor-2-activating bacterial lipoproteins in Shigella flexneri culture supernatants.

Shigella spp. cause dysentery, a severe form of bloody diarrhea. Apoptosis, or programmed cell death, is induced during Shigella infections and has been proposed to be a key event in the pathogenesis of dysentery. Here, we describe a novel cytotoxic activity in the sterile-culture supernatants of Shigella flexneri. An identical activity was identified in purified S. flexneri endotoxin, defined here as a mixture of lipopolysaccharide (LPS) and endotoxin-associated proteins (EP). Separation of endotoxin into EP and LPS revealed the activity to partition exclusively to the EP fraction. Biochemical characterization of S. flexneri EP and culture supernatants, including enzymatic deactivation, reverse-phase high-pressure liquid chromatography analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and a Toll-like receptor-2 (TLR2) activation assay, indicates that the cytotoxic component is a mixture of bacterial lipoproteins (BLP). We show that biologically active BLP are liberated into culture supernatants of actively growing S. flexneri. In addition, our data indicate that BLP, and not LPS, are the component of endotoxin of gram-negative organisms responsible for activating TLR2. The activation of apoptosis by BLP shed from S. flexneri is discussed as a novel aspect of the interaction of bacteria with the host.

Apoptosis↗

PubMed2001

The Peritraumatic Distress Inventory: a proposed measure of PTSD criterion A2.

OBJECTIVE: Meeting criterion A2 for the diagnosis of posttraumatic stress disorder (PTSD) in DSM-IV requires that an individual have high levels of distress during or after the traumatic event. Because of the paucity of valid and reliable instruments for assessing such responses, the authors developed a 13-item self-report measure, the Peritraumatic Distress Inventory, to obtain a quantitative measure of the level of distress experienced during and immediately after a traumatic event. METHOD: The cross-sectional study group comprised 702 police officers and 301 matched nonpolice comparison subjects varying in ethnicity and gender who were exposed to a wide range of critical incidents. RESULTS: The Peritraumatic Distress Inventory was found to be internally consistent, with good test-retest reliability and good convergent and divergent validity. Even after controlling for peritraumatic dissociation and for general psychopathology, the authors found that Peritraumatic Distress Inventory scores correlated with two measures of posttraumatic stress symptoms. CONCLUSIONS: The Peritraumatic Distress Inventory holds promise as a measure of PTSD criterion A2. Future studies should prospectively examine the ability of the Peritraumatic Distress Inventory to predict PTSD and its associated biological and cognitive correlates in other trauma-exposed groups.

Adult↗

PubMed2001

Posttraumatic stress disorder, trauma exposure, and the current health of Canadian bus drivers.

OBJECTIVE: Previous studies of veterans have linked posttraumatic stress disorder (PTSD) after combat-related trauma to increased reports of health problems. It is unclear whether this association between PTSD and increased health problems generalizes to civilians who are exposed to a broader array of traumatic events. We also do not know whether trauma exposure is associated with increased health problems in individuals who do not develop PTSD. Using a non-treatment-seeking civilian sample, we examined whether lifetime PTSD or trauma exposure by itself was associated with current health problems. METHODS: Using a cross-sectional design and self-report measures, we evaluated urban Canadian bus drivers (n = 342) on trauma exposure, lifetime PTSD, and current health problems. Based on their responses, we divided our sample into individuals who had never experienced trauma (n = 91), trauma-exposed individuals who had never developed PTSD (n = 218), and persons who developed PTSD at some point after trauma (n = 33). We compared these groups on health problems, treatment service use, and health assessment measures. RESULTS: The PTSD group reported increased health complaints, more frequent use of health treatments, and poorer health self-ratings compared with the exposed non-PTSD and nonexposed groups. Trauma-exposed drivers without PTSD did not differ from unexposed drivers on any health measure. Controlling for sex and trauma frequency did not alter our findings. CONCLUSIONS: Trauma exposure that leads to PTSD is associated with increased health problems, while trauma exposure alone is not. Our results extend previous findings to a broader civilian context and clarify associations between trauma exposure and health.

Adult↗

PubMed2001

Crewmember and ground personnel interactions over time during Shuttle/Mir space missions.

BACKGROUND: Anecdotal reports from space and results from simulation studies on Earth have suggested that space crewmembers may experience decrements in their mood and interpersonal environment during the 2nd half of the mission and that negative emotions may be displaced to outside monitoring personnel. METHODS: To evaluate these issues, we studied 5 American astronauts, 8 Russian cosmonauts, and 42 American and 16 Russian mission control personnel who participated in the Shuttle/Mir space program. Subjects completed questions from the Profile of Mood States, the Group Environment Scale (GES), and the Work Environment Scale (WES) on a weekly basis during the missions. Subscale scores from these measures were analyzed using a piecewise linear regression approach that analyzed normally distributed subscales using a mixed model and non-normally distributed subscales by dichotomizing the variables and using a generalized estimating equation. RESULTS: After protecting against possible Type I errors due to multiple significance tests, only weak support was found for the biphasic model: the only significant findings in favor of the hypothesized 2nd half decrements in the interpersonal environment were in crewmember GES Leader Support and astronaut WES Work Pressure. Strongly consistent confirmation was found on all six tested measures for the hypothesized displacement of tension and dysphoria from crewmembers to mission control personnel. The hypothesized displacement of tension and dysphoria from mission control personnel to management was found on five of the six tested measures. CONCLUSIONS: The absence of moderate to strong support for the biphasic model suggests that crewmember interpersonal functioning does not depend appreciably on 1st half/2nd half time effects. The consistent support found for the displacement of tension and dysphoria suggests that countermeasures need to be developed to deal with this phenomenon in both crewmembers and mission control personnel.

Astronauts↗

PubMed2001

Toll-like receptor-2 transduces signals for NF-kappa B activation, apoptosis and reactive oxygen species production.

The innate immune system coordinates the inflammatory response to pathogens. To do so, cells of the innate immune system must rapidly discriminate between self and non-self. All bacteria express membrane-associated lipoproteins. These molecules activate cells of the innate immune system to initiate host defense mechanisms. However, it is currently unknown how the innate immune system recognizes bacterial lipoproteins. Here, we describe that in response to bacterial lipoprotein, human Toll-like receptor-2 activates three different cellular responses: nuclear factor-kappaB dependent transcription, programmed cell death and reactive oxygen species production. We propose that Toll-like receptor-2 fulfils multiple roles in the genesis of the immune response to bacterial pathogens.

Antibodies, Blocking↗

PubMed2001

Psychosocial issues in space: results from Shuttle/Mir.

Important psychosocial issues involving tension, cohesion, leader support, and displacement of negative emotions were evaluated in a 4 1/2-year study involving five U.S. and four Russian Shuttle/Mir space missions. Weekly mood and group climate questionnaires were completed by five U.S. astronauts, eight Russian cosmonauts, and 42 U.S. and 16 Russian mission control subjects. There were few findings that supported our hypothesized changes in tension, cohesion, and leader support in crew and ground subjects using various time models, although crewmembers reported decreasing leader support in the 2nd half of the missions, and astronauts showed some evidence of a novelty effect in the first few weeks. There was no evidence suggesting a 3rd quarter effect among crewmembers on any of the 21 subscales evaluated. In contrast, there was strong evidence to support the hypothesized displacement of tension and negative emotions from crewmembers to mission control personnel and from mission control personnel to management. There were several significant differences in response between Americans vs. Russians, crewmembers vs. mission control personnel, and subjects in this study vs. people in comparable groups on Earth. Subject responses before, during, and after the missions were similar, and we did not find evidence for asthenia in space. Critical incidents that were reported generally dealt with events on-board the Mir and interpersonal conflicts, although most of the responses were from a relatively small number of subjects. Our findings have implications for future training and lead to a number of countermeasures.

Adaptation, Psychological↗

PubMed2000

The apoptotic signaling pathway activated by Toll-like receptor-2.

The innate immune system uses Toll family receptors to signal for the presence of microbes and initiate host defense. Bacterial lipoproteins (BLPs), which are expressed by all bacteria, are potent activators of Toll-like receptor-2 (TLR2). Here we show that the adaptor molecule, myeloid differentiation factor 88 (MyD88), mediates both apoptosis and nuclear factor-kappaB (NF-kappaB) activation by BLP-stimulated TLR2. Inhibition of the NF-kappaB pathway downstream of MyD88 potentiates apoptosis, indicating that these two pathways bifurcate at the level of MyD88. TLR2 signals for apoptosis through MyD88 via a pathway involving Fas-associated death domain protein (FADD) and caspase 8. Moreover, MyD88 binds FADD and is sufficient to induce apoptosis. These data indicate that TLR2 is a novel 'death receptor' that engages the apoptotic machinery without a conventional cytoplasmic death domain. Through TLR2, BLP induces the synthesis of the precursor of the pro-inflammatory cytokine interleukin-1beta (IL-1beta). Interestingly, BLP also activates caspase 1 through TLR2, resulting in proteolysis and secretion of mature IL-1beta. These results indicate that caspase activation is an innate immune response to microbial pathogens, culminating in apoptosis and cytokine production.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Correlation of the apparent affinities and efficacies of gamma-aminobutyric acid(C) receptor agonists.

gamma-Aminobutyric acid (GABA), trans-4-aminocrotonic acid (TACA), muscimol, imidazole-4-acetic acid (I4AA), cis-4-aminocrotonic acid (CACA), and isoguvacine are all GABA(C) receptor agonists. These compounds have different apparent sensitivities (EC(50)) and efficacies (I(max)) on exogenously expressed human rho1 homomeric GABA(C) receptors. It is not clear if these differences are due to distinct binding affinities and/or distinct gating kinetics. In this study, using a recently developed single oocyte binding technique, we determined the apparent dissociation constants (K(i) values) of these compounds from their IC(50) values for [(3)H]GABA displacement. The apparent K(i) values fell into two distinct groups. The high affinity group was comprised of agonists with longer distances between the nitrogen atom of the amino or imidazole group and the carbon atom of the carboxyl or isoxazole group. The single oocyte binding technique, in conjunction with two-electrode voltage clamp, has allowed a direct correlation of the apparent affinity, efficacy, and potency of agonists on intact functional GABA(C) receptors. The correlation and coupling of these parameters are discussed in terms of a simple proposed activation mechanism.

Animals↗

PubMed2000

Towards single-copy gene expression systems making gene cloning physiologically relevant: lambda InCh, a simple Escherichia coli plasmid-chromosome shuttle system.

We describe a simple system for reversible, stable integration of plasmid-borne genes into the Escherichia coli chromosome. Most ordinary E. coli strains and a variety of pBR322-derived ampicillin-resistant plasmids can be used. A single genetic element, a lambda phage, is the only specialized vector required. The resultant strains have a single copy of the plasmid fragment inserted stably at the lambda attachment site on the chromosome, with nearly the entire lambda genome deleted.

Ampicillin Resistance↗

PubMed2000

Regulation of recombinant gamma-aminobutyric acid (GABA)(A) and GABA(C) receptors by protein kinase C.

Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate induced a continuous decrease in the gamma-aminobutyric acid (GABA)-activated current amplitude from recombinant GABA receptors (formed by rho1 or alphabetagamma subunits) expressed in Xenopus oocytes. This decline was due to internalization of receptors from the plasma membrane as confirmed by a decrease in surface fluorescence with green fluorescence protein-tagged receptors as well as a concomitant decrease in surface [(3)H]GABA binding. PMA specifically caused internalization of GABA receptors, but not neuronal acetylcholine receptors (alpha(7) or alpha(4)beta(2)), indicating the internalization was not a general, nonspecific phenomenon. Mutation of rho1 PKC phosphorylation sites, identified by in vitro phosphorylation, did not prevent GABA receptor internalization, nor did coexpression of the rho1 M3-M4 intracellular loop along with rho1 GABA receptors. It is likely that PKC-mediated phosphorylation of other proteins, rather than rho1 itself, was required for the internalization. Both rho1 and alphabetagamma receptors did not degrade after phorbol 12-myristate 13-acetate-induced internalization, but returned to the membrane surface within 24 h. These data suggest internalized receptors can exist in an intracellular compartment that can be delivered back to the plasma membrane. Thus, by regulating GABA receptor surface expression, PKC may play a key role in the regulation of GABA-mediated inhibition.

Animals↗