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Biomedical subjects

C A Morgan

Publications and source records attributed to C A Morgan.

At least 37 records · Page 2Linked to original sources
PubMed1999

Anniversary reactions in Gulf War veterans: a follow-up inquiry 6 years after the war.

OBJECTIVE: The goal of this study was to assess the occurrence of anniversary reactions in Gulf War veterans 6 years after the conclusion of the war. METHOD: Subjects were administered questionnaires and asked to identify specific months of best and worst functioning and months of least or most symptoms of posttraumatic stress disorder (PTSD) for the 12 months before the study. Months of negative experiences were compared with previously documented dates of exposure to traumatic events during the war. Similar reports were also obtained from the veterans' spouses in order to assess corroborative evidence for the occurrence of anniversary reactions. RESULTS: Anniversary reactions occurred with a frequency greater than chance and most often in individuals exposed to a greater number of traumatic events. Overall, spouse reports matched the veterans' reports of anniversary reactions. In addition, spouses identified anniversary reactions that were not endorsed by their veterans. CONCLUSIONS: These data suggest that anniversary reactions occur in numbers greater than those expected by chance, are correlated to the occurrence of traumatic events, and may be a part of the syndrome of PTSD.

Adjustment Disorders↗
PubMed1999

Neurotransmitter alterations in PTSD: catecholamines and serotonin.

In this chapter we review trauma-related studies involving epinephrine (E), norepinephrine (NE), and serotonin (5-HT). Central catecholamine neurons seem to play a critical role in level of alertness, vigilance, orienting, selective attention, memory, fear conditioning, and cardiovascular responses to life-threatening stimuli. Evidence of catecholamine dysregulation in post-traumatic stress disorder (PTSD) includes exaggerated increases in heart rate and blood pressure when exposed to visual and auditory reminders of trauma, elevated 24-hour urine catecholamine excretion, decreased platelet alpha-2 adrenergic receptor number, exaggerated behavioral, cardiovascular, and biochemical responses to IY yohimbine, decreased cortical brain metabolism secondary to IV yohimbine, and clinical efficacy of adrenergic blocking agents. Serotonin seems to play numerous roles in the central nervous system, including regulation of sleep, aggression, appetite, cardiovascular and respiratory activity, motor output, anxiety, mood, neuroendocrine secretion, and analgesia. Evidence of serotonergic dysregulation in PTSD includes frequent symptoms of aggression, impulsivity, depression and suicidality, decreased platelet paroxetine binding, blunted prolactin response to fenfluramine, exaggerated reactivity to m-chloro-phenyl-piperazine, and clinical efficacy of serotonin reuptake inhibitors. It has been suggested that alterations in NE, E, and 5-HT may have relevance for symptoms commonly seen in survivors with PTSD, including hypervigilance, exaggerated startle, irritability, impulsivity, aggression, intrusive memories, depressed mood, and suicidality.

Animals↗
PubMed1998

Effects of experimental context and explicit threat cues on acoustic startle in Vietnam veterans with posttraumatic stress disorder.

BACKGROUND: The hypothesis that exaggerated startle in Vietnam veterans with posttraumatic stress disorder (PTSD) reflects an anxiogenic response to stressful contexts was tested. METHODS: Thirty-four nonmedicated Vietnam veterans with PTSD, and 17 combat and 14 civilian non-PTSD controls participated in two testing sessions over separate days. Acoustic startle stimuli were delivered alone or in a test of prepulse inhibition. In the first session, startle was assessed without experimental stress. In the second session, startle was investigated during a stressful "threat of shock" experiment, when subjects anticipated the administration of shocks during threat periods and during safe periods when no shocks were anticipated. RESULTS: The magnitude of startle did not differ significantly among the three groups in the first session, but was increased throughout the threat of shock experiment in the PTSD veterans in the second session. The actual increase in startle in the threat compared to the safe condition did not significantly differ among the three groups. Prepulse inhibition was reduced in the PTSD veterans, compared to the non-PTSD civilians, but not compared to the non-PTSD veterans. CONCLUSION: Exaggerated startle in Vietnam veterans with PTSD reflects an anxiogenic response to an environment that is experienced as stressful.

Acoustic Stimulation↗
PubMed1998

Anniversary reactions in Gulf War veterans: a naturalistic inquiry 2 years after the Gulf War.

The goal of this study was to assess the occurrence of anniversary reactions in Gulf War veterans 2 years after the conclusion of Operation Desert Storm. Subjects were administered questionnaires and asked to identify specific months of best and worst functioning, and months of least or most symptoms of posttraumatic stress disorder (PTSD). Negatively experienced months were compared to documented dates of exposure to traumatic events during the war. Anniversary reactions occurred with a frequency greater than chance and were seen most in individuals exposed to a greater number, and to more severe types, of traumatic events. This suggests that anniversary reactions are etiologically linked to traumatic events and may be a part of the syndrome of PTSD.

Chi-Square Distribution↗
PubMed1998

Effect of darkness on acoustic startle in Vietnam veterans with PTSD.

OBJECTIVE: Exaggerated startle is a symptom of posttraumatic stress disorder (PTSD), but empirical studies have not consistently documented elevated baseline startle in PTSD. The authors proposed in a previous study that Vietnam veterans with PTSD exhibit exaggerated startle only under stressful conditions. They reported that darkness facilitated startle in humans, suggesting that the startle reflex is sensitive to the aversive nature of darkness. In the present study they tested the hypothesis that the magnitude of facilitation of startle by darkness would be greater in Vietnam veterans with PTSD than in comparison groups of subjects without PTSD. Prepulse inhibition was also investigated. METHOD: The magnitude of startle and prepulse inhibition were assessed in alternating periods of darkness and light in 19 nonmedicated Vietnam veterans with PTSD, 13 Vietnam veterans without PTSD, and 20 civilians without PTSD. RESULTS: The overall startle level was higher in the veterans with PTSD than in either of the two groups of subjects without PTSD. Startle was facilitated by darkness, and the magnitude of this facilitation was greater in the veterans with PTSD than in the civilians without PTSD, but it was not greater in the veterans without PTSD. Prepulse inhibition was not affected by darkness and did not significantly differ among groups. CONCLUSIONS: Contrary to the hypothesis, elevated sensitivity to darkness was specific to individuals with combat experience, not to individuals with PTSD, perhaps because veterans had become aversively conditioned to darkness during their combat experiences. The more general increase in startle reactivity in the veterans with PTSD is consistent with clinical observations and descriptions of symptoms in DSM-IV.

Acoustic Stimulation↗
PubMed1997

Noradrenergic and serotonergic function in posttraumatic stress disorder.

BACKGROUND: Yohimbine hydrochloride produces marked behavioral and cardiovascular effects in combat veterans with posttraumatic stress disorder (PTSD). In the present study, yohimbine was used as a probe of noradrenergic activity, and meta-chlorophenylpiperazine (m-CPP) as a probe of serotonergic activity. To our knowledge, this is the first study to describe the behavioral and cardiovascular effects of meta-CPP in patients with PTSD, and to compare these effects with those of yohimbine. METHOD: Twenty-six patients with PTSD and 14 healthy subjects each received an intravenous infusion of yohimbine hydrochloride (0.4 mg/kg), m-CPP (1.0 mg/kg), or saline solution on 3 separate test days in a randomized balanced order and in double-blind fashion. Behavioral and cardiovascular measurements were determined at multiple times. RESULTS: Eleven (42%) of the patients with PTSD experienced yohimbine-induced panic attacks and had significantly greater increases compared with controls in anxiety, panic, and PTSD symptoms, but not in cardiovascular measurements. Eight patients (31%) with PTSD experienced m-CPP-induced panic attacks and had significantly greater increases compared with controls in anxiety, panic, and PTSD symptoms, and in standing diastolic blood pressure. Yohimbine-induced panic attacks tended to occur in different patients from m-CPP-induced panic attacks. CONCLUSION: These data suggest the presence of 2 neurobiological subgroups of patients with PTSD, one with a sensitized noradrenergic system, and the other with a sensitized serotonergic system.

Adult↗
PubMed1997

Evidence of acoustic startle hyperreflexia in recently detoxified early onset male alcoholics: modulation by yohimbine and m-chlorophenylpiperazine (mCPP).

Preclinical studies suggest that acoustic startle amplitude is increased during ethanol withdrawal. The current study evaluated the effects of intravenous infusion of the alpha 2-adrenergic antagonist, yohimbine (0.4 mg/kg), the serotonin partial agonist m-chlorophenylpiperazine (mCPP, 0.1 mg/kg), and placebo administered to 22 male patients meeting DSM-III-R criteria for alcohol dependence and 13 male healthy subjects. Patients and healthy subjects completed 3 test days under double-blind conditions in a randomized order. Patients were sober for 12-26 days prior to testing. On each test day, participants completed startle testing 80 min following drug infusion. Stimuli with varying intensities (90, 96, 102, 108, 114 dB) were presented in a randomized order balanced across four blocks. Stimuli consisted of 40-ms bursts of white noise administered every 45-60 s for 15-20 min through headphones. Analyses indicated that patients exhibited elevated acoustic startle magnitudes on the placebo day relative to healthy subjects. In patients, the magnitude of startle amplitudes elicited at 90 dB, but not 114 dB, correlated significantly with the number of previous alcohol detoxifications. Yohimbine increased startle magnitudes and reduced startle latencies relative to placebo and mCPP in both patients and healthy subjects. mCPP did not alter startle magnitude in either group. Yohimbine also increased the probability that a 90-dB stimulus produced a startle response in healthy subjects, but not in patients. Blunting of yohimbine effects on startle probability may reflect the baseline elevations in startle probability levels in patients, but may also be consistent with other evidence of reduced postsynaptic, but not presynaptic, noradrenergic function in these same patients. These data replicate and extend previous reports indicating that yohimbine facilitates the acoustic startle response in humans. They also further implicate the number of episodes of ethanol withdrawal as a factor influencing subsequent neurobiological responsivity in chronic alcoholic patients. Based on the current data, future research should explore whether measurement of the acoustic startle response provides an objective quantitative severity measure of ethanol withdrawal.

Acoustic Stimulation↗
PubMed1997

Consistency of memory for combat-related traumatic events in veterans of Operation Desert Storm.

OBJECTIVE: The nature of traumatic memories is currently the subject of intense scientific investigation. While some researchers have described traumatic memory as fixed and indelible, others have found it to be malleable and subject to substantial alteration. The current study is a prospective investigation of memory for serious combat-related traumatic events in veterans of Operation Desert Storm. METHOD: Fifty-nine National Guard reservists from two separate units completed a 19-item trauma questionnaire about their combat experiences 1 month and 2 years after their return from the Gulf War. Responses were compared for consistency between the two time points and correlated with level of symptoms of posttraumatic stress disorder (PTSD). RESULTS: There were many instances of inconsistent recall for events that were objective and highly traumatic in nature. Eighty-eight percent of subjects changed their responses on at least one of the 19 items, while 61% changed two or more items. There was a significant positive correlation between score on the Mississippi Scale for Combat-Related Posttraumatic Stress Disorder at 2 years and the number of responses on the trauma questionnaire changed from no at 1 month to yes at 2 years. CONCLUSIONS: These findings do not support the position that traumatic memories are fixed or indelible. Further, the data suggest that as PTSD symptoms increase, so does amplification of memory for traumatic events. This study raises questions about the accuracy of recall for traumatic events, as well as about the well-established but retrospectively determined relationship between level of exposure to trauma and degree of PTSD symptoms.

Adult↗
PubMed1997

Startle reflex abnormalities in women with sexual assault-related posttraumatic stress disorder.

OBJECTIVE: This investigation was designed to assess the acoustic startle response in treatment-seeking women with sexual assault-related posttraumatic stress disorder (PTSD). METHOD: Thirteen patients with sexual assault-related PTSD and 16 healthy female comparison subjects were recruited for participation in the study. Each patient met the full criteria for PTSD according to the Structured Clinical Interview for DSM-III-R. All subjects in the study were right-handed. The acoustic stimuli were bursts of white noise (92 dB and 102 dB) with a nearly instantaneous onset delivered binaurally through headphones. RESULTS: The magnitude of the startle response (eye blink) to the first stimulus was asymmetrically distributed in the PTSD patients but not in the comparison subjects: it was greater for the left eye than the right eye in the PTSD patients only. There was a differential asymmetry of startle response in the two subgroups of patients (recent PTSD and long-standing PTSD): the startle reflex was larger for the left eye than the right in the subgroup with recent PTSD but not in the group with long-standing PTSD. CONCLUSIONS: This study provides the first objective evidence of startle abnormalities in women with PTSD. The significantly greater startle responses for the left eye compared with the right in the PTSD subjects suggest a laterality effect. As suggested by the preclinical model of shock sensitization, it is possible that in a subgroup of individuals with PTSD, trauma may sensitize the startle reflex. This model may hold true in humans and is supported by the findings of greater startle response in the patients with recent-onset PTSD.

Acoustic Stimulation↗
PubMed1996

Baseline startle amplitude and prepulse inhibition in Vietnam veterans with posttraumatic stress disorder.

Although an exaggerated startle response is a symptom of posttraumatic stress disorder (PTSD), empirical support for elevated baseline startle in PTSD has been weak. The present study investigated the eyeblink component of the acoustic startle reflex and prepulse inhibition (PPI) in 21 unmedicated Vietnam veterans with PTSD and in 17 civilian and 10 combat veteran comparison subjects. Patients with PTSD exhibited normal acoustic startle amplitude, but showed a significant reduction in PPI relative to the civilian subjects. There was only a trend toward a reduction in PPI in the PTSD group compared with the combat control group. The study does not support the hypothesis of exaggerated baseline startle in Vietnam veterans with PTSD but suggests abnormal startle modulation by a prepulse (i.e., PPI). Discrepancies between studies concerning the amplitude of startle in PTSD are discussed.

Acoustic Stimulation↗
PubMed1996

Learning and retention of conditioned aversions by freely feeding chicks.

The present experiments assessed poison-based aversion learning and retention in freely feeding and drinking domestic chicks whose drinking water was colored blue and adulterated with LiCl for a 24-hr period. The amount of LiCl self-administered by 11-day-old chicks and their subsequent avoidance of unadulterated water of the same color was examined. The results of four experiments demonstrated that chicks self-administered large and often lethal doses of the LiCl solution. Chicks subsequently avoided blue water during two-bottle preference tests administered 3 to 7 days but not 14 days after exposure. These data indicate that neophobia alone is insufficient to prevent nondeprived chicks from ingesting large quantities of a toxin during their initial encounter with it. The lack of long-term retention in the present experiments indicates that naturally occurring aversions based on visual and illness cues, while effective in the short term, may not be a major factor in the choices made by freely feeding and drinking chicks over the long term.

Animals↗
PubMed1996

The effects of tropicamide on mydriasis in young rats exhibiting a natural deficit in passive-avoidance responding.

The young rat at post-natal day 18-22 exhibits a natural deficit in passive-avoidance responding that can be corrected with the acute systemic administration of different cholinomimetic drugs, such as tacrine. In order to evaluate the generality of this apparent cholinergic hypofunction, different doses of the anticholinergic agent tropicamide, were administered either systemically or dropped directly into the eye of young or adult rats. Tropicamide produced mydriasis in a dose-dependent manner. The ED50 for tropicamide dropped into the eye was 0.025% for adult rats and 0.12% for young rats. When doses between 0.3 and 100 mg/kg were delivered systemically, the mean time course for recovery to baseline pupil size was accelerated in young rats. The average time to recovery across all doses was 112 +/- 27 min (mean+/-SE) for young rats and 274 +/- 70 min for adults. When subcutaneous tacrine was given immediately to young rats after training in a passive-avoidance response (PAR) task, retention was enhanced at testing 24 hours later in a dose-dependent manner. The response latencies were statistically different from saline-treated controls at doses of 0.003 and 0.01 mg/kg. This was not observed in adult rats. Taken together these results suggest that the PAR, along with the mydriacyl response of the young rat to tropicamide, may be regulated by a system of subsensitive cholinergic receptors.

Aging↗
PubMed1996

Isolation and characterization of resin acid degrading bacteria found in effluent from a bleached kraft pulp mill.

Thirteen resin acid degrading bacteria enriched on abietic or dehydroabietic acids were isolated from waste water from the aerated stabilization basin of a bleached kraft pulp mill. Standard biochemical tests were used to characterize each isolate. Each isolate was tested for its ability to degrade six abietane- and pimarane-type resin acids. Resin acid concentrations were determined by high pressure liquid chromatography and UV absorbance. Cluster analysis based on phenotypic characteristics identified two distinct clusters of degraders that differed in their ability to utilize carbohydrates as carbon sources. Fatty acid methyl ester analysis of representative isolates from each cluster identified A19-6a and D11-13 as Comamonas and Alcaligenes species, respectively. To determine genotypic relatedness, enterobacterial repetitive intergenic consensus sequences were used to amplify genomic DNA fragments from 10 isolates. These results supported the phenotypic analysis for all isolates tested except A19-5 and A19-6b. These two organisms were clustered closely together based on phenotype but had distinctly different banding patterns, suggesting that they are not related genotypically. All isolates degraded a subset of the six resin acid congeners. Isolates A19-3, A19-6a, A19-6b, and D11-37 were the most effective at degrading all six congeners.

Alcaligenes↗
PubMed1996

Exaggerated acoustic startle reflex in Gulf War veterans with posttraumatic stress disorder.

OBJECTIVE: Exaggerated startle reflex is reputed to be one of the cardinal symptoms of posttraumatic stress disorder (PTSD). The goal of this study was to assess the magnitude of the acoustic startle reflex in Gulf War veterans with PTSD. METHOD: The eye-blink component of the startle reflex was measured in response to six blocks of pseudorandomized 40-msec white noise bursts of varying intensities (90, 96, 102, 108, and 114 dB) in 10 Gulf War veterans with PTSD, seven Gulf War veterans without PTSD, and 15 civilian subjects without PTSD. RESULTS: The magnitude of the first startle response, as well as the magnitude of startle response averaged across blocks of testing, was significantly greater in Gulf War veterans with PTSD than in veteran and civilian comparison groups. CONCLUSIONS: Consistent with some clinical studies investigating the startle response in Vietnam veterans with PTSD, this investigation provides evidence for exaggerated startle response in this disorder. Preclinical studies of shock sensitization of the startle response suggest that the higher levels of startle response seen in the PTSD subjects may reflect a sensitization of the fear/alarm response created by the stress of combat trauma.

Acoustic Stimulation↗
PubMed1996

Preliminary evidence of an association between sensorimotor gating and distractibility in psychosis.

Impaired sensory gating and increased distractibility are key information-processing deficits in schizophrenia. This study evaluated the hypothesis that distractibility is related to reduced sensory gating. Performance on vigilance and distractibility tasks was compared to prepulse inhibition (PPI) of the acoustic startle reflex in 28 stable chronic psychotic patients. PPI significantly correlated with distractibility task score on a continuous performance test and lateralized attention on the Posner test. These results suggest that performance on tests of distractibility and lateralized attention are related to a measure of sensory gating.

Acoustic Stimulation↗