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Biomedical subjects

K Nader

Publications and source records attributed to K Nader.

30 records · Page 2Linked to original sources
PubMed1992

Neurobiology of motivation: double dissociation of two motivational mechanisms mediating opiate reward in drug-naive versus drug-dependent animals.

Separate brain manipulations double dissociate two motivational mechanisms underlying the rewarding effects of opiates. Lesions of the brain stem tegmental pedunculopontine nucleus block the rewarding properties of morphine in drug-naive, but not in drug-dependent, rats. Neuroleptics (which block the action of the neurotransmitter dopamine) abolished opiate motivational effects in drug-dependent, but not in drug-naive, rats in place conditioning paradigms. This second dopaminergic opiate reward mechanism mediates morphine's alleviation of the withdrawal distress associated with abstinence in opiate-dependent animals. Furthermore, neuroleptic-induced blockade of food-related motivational effects in food-deprived, but not in food-sated (non-food-deprived), animals suggests that the neural substrates of motivational events do not dissociate along the line between different rewarding stimuli but along the line between deprivation and nondeprivation.

Animals↗
PubMed1991

Stress responses after pediatric bone marrow transplantation: preliminary results of a prospective longitudinal study.

This paper reports the preliminary findings of a longitudinal prospective study of young children undergoing bone marrow transplantation. Symptoms of post-traumatic stress were seen in these children up to 12 months after transplant. The bone marrow transplantation survivors demonstrated more denial and avoidance and fewer arousal symptoms than has been noted in children traumatized by a violent life threat, such as a sniper attack. These data suggest the use of post-traumatic stress as a model in understanding some of the symptoms of pediatric bone marrow transplantation survivors and may be applicable to other children exposed to the double life threat of serious illness and intensive medical intervention.

Adaptation, Psychological↗
PubMed1990

Children's PTSD reactions one year after a sniper attack at their school.

Fourteen months after a sniper attack at an elementary school, level of exposure to that event remained the primary predictor of ongoing posttraumatic stress reactions in 100 schoolchildren who were followed up. Guilt feelings and knowing the child who was killed were associated with a greater number of symptoms. Grief reactions occurred independent of degree of exposure to the event. The authors discuss the public health implications of these longitudinal findings.

Age Factors↗
PubMed1989

Children's memory and proximity to violence.

The study examined 133 school-age children's memory of a sniper attack at their elementary school. Researchers analyzed the role that spatial representation, memory markers, inner plans of action, and strategies of recall played in the memory process. In recalling the event, exposed children reduced their degree of life threat, while nonexposed children increased their proximity to the violence. Clinical and forensic implications are discussed.

Anxiety↗
PubMed1987

Life threat and posttraumatic stress in school-age children.

One hundred fifty-nine children (14.5% of the student body) were sampled after a fatal sniper attack on their elementary school playground. Systematic self-reports of posttraumatic stress disorder (PTSD) symptoms were obtained by use of a child PTSD Reaction Index. Analysis of variance revealed significant differences by exposure but not by sex, ethnicity, or age. Additional analyses were conducted of individual item response, overall severity of PTSD reaction, symptom grouping, and previous life events. The results provide strong evidence that acute PTSD symptoms occur in school-age children with a notable correlation between proximity to the violence and type and number of PTSD symptoms. Sampling at approximately one month after the trauma provided adequate delineation among exposure groups. The symptom profile of highly exposed children lends validity to the diagnosis of acute PTSD in childhood.

Acute Disease↗
PubMed1981

Blood pressure of Qash'qai pastoral nomads in Iran in relation to culture, diet, and body form.

Blood pressure, diet, urinary electrolyte excretion, and body form were studied in 264 traditional nomadic herdsmen of the Qash'qai tribe, southern Iran. The population sample included male and female members over 14 yr of age at six winter campsites. Interviews established biological age, any experience of nonnomadic living, and 24-h dietary recall. Height, weight, triceps skinfolds, and blood pressure were measured. Overnight urine samples were analyzed for sodium, potassium, and creatinine. Samples of dietary staples were analyzed for selected nutrients and electrolyte content. Urinary sodium excretion averaged 186 mEq/24 h in males, and 141 mEq/24 h in females. Urinary Na/K ratios were 3.64 and 3.24 in males and females, respectively. Systolic, diastolic, and mean blood pressure in both males and females increased significantly with age. Blood pressure greater than or equal to 140/90 was found in 12% of males and 18% of females age 30 yr or over. Body weight showed no tendency to increase with age in either sex. Systolic and mean blood pressure correlated with urinary sodium excretion in males and with urinary Na/K ratio in females. From cultural observations, the population sample was considered to be at a low level of acculturation. The data suggest that blood pressure trends in this population are related to habitual dietary electrolyte intake.

Adolescent↗
PubMedDate not supplied

Damage to the lateral and central, but not other, amygdaloid nuclei prevents the acquisition of auditory fear conditioning.

It is well established that the amygdala plays an essential role in Pavlovian fear conditioning, with the lateral nucleus serving as the interface with sensory systems that transmit the conditioned stimulus and the central nucleus as the link with motor regions that control conditioned fear responses. The lateral nucleus connects with the central nucleus directly and by way of several other amygdala regions, including the basal, accessory basal, and medial nuclei. To determine which of these regions is necessary, and thus whether conditioning requires the direct or one of the indirect intra-amygdala pathways, we made lesions in rats of the lateral, central, basal, accessory basal, and medial nuclei, as well as combined lesions of the basal and accessory basal nuclei and of the entire amygdala. Animals subsequently underwent fear conditioning trials in which an auditory conditioned stimulus was paired with a footshock unconditioned stimulus. Animals that received lesions of the lateral or central nucleus, or of the entire amygdala, were dramatically impaired, whereas the other lesions had little effect. These findings show that only the lateral and central nuclei are necessary for the acquisition of conditioned fear response to an auditory conditioned stimulus.

Acoustic Stimulation↗
PubMedDate not supplied

Lesions of periaqueductal gray dissociate-conditioned freezing from conditioned suppression behavior in rats.

It is commonly assumed that suppression of an ongoing behavior is an indirect measure of freezing behavior. We tested whether conditioned suppression and freezing are the same or distinct conditioned responses. Rats were trained to press a bar for food and then given fear-conditioning sessions in which a tone was paired with a foot shock (two pairings a day for 2 days). They then received either sham or electrolytic lesions of the periaqueductal gray (PAG). Post-training PAG lesions blocked freezing to the conditioned stimulus (CS), but had no effect on the suppression of operant behavior to the same CS. Thus, conditioned suppression and freezing, which both cause a cessation in activity, appear to be mediated by separate processes.

Analysis of Variance↗