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Biomedical subjects

S H Ahmed

Publications and source records attributed to S H Ahmed.

At least 19 recordsLinked to original sources
PubMed1998

Transition from moderate to excessive drug intake: change in hedonic set point.

Differential access to cocaine self-administration produced two patterns of drug intake in rats. With 1 hour of access per session, drug intake remained low and stable. In contrast, with 6 hours of access, drug intake gradually escalated over days. After escalation, drug consumption was characterized by an increased early drug loading and an upward shift in the cocaine dose-response function, suggesting an increase in hedonic set point. After 1 month of abstinence, escalation of cocaine intake was reinstated to a higher level than before. These findings may provide an animal model for studying the development of excessive drug intake and the basis of addiction.

Animals↗
PubMed1998

Amphetamine-induced conditioned activity is insensitive to perturbations known to affect pavlovian conditioned responses in rats.

Psychostimulant-induced conditioned activity is characterized by the presence of a hyperactivity in drug-free rats exposed to an environment previously paired with the effects of a psychostimulant. This phenomenon is thought to result from a Pavlovian conditioning process. This hypothesis predicts that conditioned activity will be sensitive to perturbations known to affect classical conditioned responses. In direct contrast with this prediction, the authors report here that conditioned activity is insensitive to (a) the temporal order between the stimulant injection and the exposure to the environment, (b) unsignaled stimulant injections between drug-environment pairings, and (c) drug preexposures before the start of drug-environment pairings. It is concluded that the stimulant effects responsible for the establishment of conditioned activity may not be amenable to a Pavlovian associative process.

Amphetamine↗
PubMed1998

Acute reversible renal failure in a patient with paroxysmal nocturnal hemoglobinuria.

We present the case of a young male with 2-month history of intermittent upper abdominal pain who developed diarrhea, anorexia, tea-color urine, and decreased urine output. He was found to be in severe acute renal failure requiring hemodialysis, four sessions in 10-day period. By the end of the second week of hospitalization renal function gradually improved with total recovery of function to a baseline creatinine of 1.1 mg/dl 25 days after the diagnosis of acute renal failure. His workup included Ham's test, water sugar test, and RBC fragility test which confirmed the diagnosis of paroxysmal nocturnal hemoglobinuria.

Abdominal Pain↗
PubMed1997

Cocaine- but not food-seeking behavior is reinstated by stress after extinction.

Reinstatement of drug-seeking behavior after extinction constitutes a potential animal model of relapse to drug abuse. In a typical reinstatement experiment, previously drug-trained rats undergo extinction during which responding is no longer followed by drug delivery. After significant extinction is observed, rats are then exposed to an event expected to reinstate drug-seeking behavior. Using this procedure, it has been recently reported that footshock stress leads to reinstatement of drug-seeking in heroin-trained, presently drug-free rats. The purpose of the present study was to assess the generality of this effect of stress. Here we report that 15 min of intermittent footshock (0.86 mA; 0.5 s on, with a mean off period of 40 s) reinstated selectively cocaine-seeking behavior after 14 extinction sessions (rats were previously trained on a FR1 TO 20 s to obtain cocaine at a dose of 0.25 mg/infusion). In contrast, under similar experimental conditions, the same stressor did not reinstate food-seeking in food-trained rats after seven extinction sessions (rats were previously trained on a FR1 TO 20 s to obtain six food pellets). Rather, when the basal level of responding was sufficiently high, footshock stress induced a significant suppression of the instrumental performance. These data are discussed in light of several behavioral mechanisms which may explain the specificity of stress in reinstating drug-seeking behavior and not food-seeking behavior.

Animals↗
PubMed1996

Amphetamine-induced conditioned activity does not result from a failure of rats to habituate to novelty.

Psychostimulant-induced conditioned activity is characterized by the presence of a hyperactivity in drug-free rats exposed to an environment previously paired with the effects of a psychostimulant. According to the habituation hypothesis, conditioned activity arises not through a Pavlovian conditioning process but rather because rats under the effects of the psychostimulant would be unable to habituate normally to the environment paired with these effects. This hypothesis predicts that conditioned activity should not develop in a previously habituated environment. This prediction was tested using a within-subject design. In this design, conditioned activity is evidenced when a group of rats, following a vehicle injection, was more active in a previously amphetamine-paired environment than in a previously vehicle-paired environment. The drug-environment pairing involved administering rats with d-amphetamine (1.25 mg/kg; SC) immediately prior to their placement in one of two distinctive environments. On alternate days, the rats received the vehicle and were placed in the other environment. With this design, it was found that: a) conditioned activity developed in a previously habituated environment; b) its magnitude was independent of the number of amphetamine-environment pairings (two, four or eight pairings); c) this development of conditioned activity did not result from a forgetting of the habituated environment due to a state-dependent retention of the habituation. Taken together, these results do not support the habituation hypothesis of psychostimulant-induced conditioned activity.

Animals↗
PubMed1995

Social deprivation enhances the vulnerability of male Wistar rats to stressor- and amphetamine-induced behavioral sensitization.

The aim of the present study was to assess the influence of experiential factors on the vulnerability of rats to develop amphetamine (AMPH)- and stressor-induced behavioral sensitization. Young male Wistar rats with previous social experience were isolated from their peers for 2 weeks. 1) The effect of this short-lasting social deprivation were: a) a reduced tendency to explore a fearful environment; b) a prolonged exploratory activity in response to a novel but little fearful environment; and c) a dose-dependent increase in the psychomotor stimulation induced by systemic AMPH injection. 2) After repeated AMPH injections (injection every other day for 10 days), isolated rats exhibited behavioral sensitization at lower doses (0.5 and 0.75 mg/kg) than those required for group-housed rats (1 mg/kg). 3) After being submitted to a repeated stressor (3, 7 or 14 footshock sessions, with 2 days between sessions), the isolated rats exhibited a greater increase in the behavioral responsivity to a subsequent AMPH challenge (1 mg/kg) than did the group-housed rats regardless of the number of stress sessions. In conclusion, these results suggest that experiential factors such as privation of contact with peers (social isolation) may make rats more vulnerable to the long-term repercussions of chronic environmental and pharmacological challenges.

Amphetamine↗
PubMed1995

Amphetamine-induced conditioned activity in rats: comparison with novelty-induced activity and role of the basolateral amygdala.

A within-subject design was used to investigate the behavioral and neural basis of the conditioned activity induced by amphetamine in male Wistar rats. In this design, conditioned activity was inferred when the activity of a given rat following a vehicle injection was greater in its amphetamine-paired environment (CS+) than in its vehicle-paired environment (CS-). Conditioned activity (a) did not change in magnitude with the number of conditioning sessions, (b) did not differ from the level of activity recorded during the first exposure to the CS- (novelty), (c) had an extinction rate that was similar to the rate of habituation to the CS-, and (d) was not impaired by a bilateral excitotoxic lesion of the basolateral amygdala. Results are discussed in light of the incentive conditioning and habituation theories of conditioned activity.

Animals↗
PubMed1992

Corticotropin-releasing factor induces a place aversion independent of its neuroendocrine role.

The purpose of the present experiment was to test the hypothesis that corticotropin-releasing factor (CRF), a polypeptide of 41 amino acids, when administered either intracerebroventricularly (i.c.v.) or subcutaneously (s.c.), has aversive properties in the conditioned place-preference paradigm. Five doses of CRF (0, 0.005, 0.05, 0.5, 5 micrograms) were tested. i.c.v. CRF induced a specific dose-dependent reduction of the amount of time spent in the environment previously paired with the administration of CRF. Furthermore, this CRF-induced place aversion was prevented by pretreatment with alpha-helical-CRF(9-41), a specific CRF antagonist, administered i.c.v. In order to test whether the aversive effects induced by i.c.v. CRF could result from the stimulation of the HPA axis accompanying i.c.v. CRF injection, the reinforcing properties of s.c. CRF were studied using the same dose range. Only the higher s.c. dose was effective in producing a place aversion suggesting that the aversive effects of CRF could not be due solely to the stimulation of the pituitary-adrenocortical system, measured by plasmatic levels of adrenocorticotropic hormone (ACTH) and corticosterone, because the lower doses consistently activate the pituitary-adrenocortical system without producing any behavioral changes. Altogether, these data indicate that the non-neurosecretory CRF neurons may mediate the aversive state occurring during stress.

Animals↗
PubMed1992

Assessment of "insight" understanding of mental illness in developing countries.

'Insight', which is an indication of patient's understanding about his/her illness, needs particularly sensitive measures for its assessment. A questionnaire regarding insight, and brief psychosocial profile of the patients was applied to 103 cases. The cases were categorized according to the diagnosis and initial understanding of mental illness and 'insight' by the patients in our culture. The study did not support the popular belief that neurotics have and psychotics do not have insight.

Adolescent↗
PubMed1991

Circulating growth hormone, insulin-like growth factor I, cortisol and free thyroxine in children with schistosomiasis with and without hepatic fibrosis.

Serum insulin, growth hormone (GH), cortisol, free thyroxine (T4) and plasma insulin-like growth factor I(IGF-I) concentrations were measured in 20 children suffering from schistosomiasis as well as 10 healthy age-matched controls. Circulating GH and insulin levels were determined after an intravenous infusion of arginine HCl (10 per cent solution, 0.5 g/kg). Children with schistosomal hepatic fibrosis (n = 10) had heights more than 2 SD below the mean for their age and sex. Their circulating IGF-I, free T4, and cortisol levels were significantly reduced. They had markedly elevated serum insulin concentrations with normal response to arginine infusion. Their basal GH levels were normal with significantly reduced GH response to arginine provocation. Compared to controls, they had significantly lower serum albumin concentrations, prolonged prothrombin time and elevated alanine transferase (ALT) levels. Free T4 and IGF-I concentrations, and GH increments after provocation correlated significantly with the percentile heights of these patients (r = 0.90, 0.70, and 0.83, P less than or equal to 0.001, less than or equal to 0.05 and less than or equal to 0.01 respectively). Their IGF-I levels correlated closely with the prothrombin time and ALT concentrations (r = 0.87 and 0.77, P less than or equal to 0.002 and less than or equal to 0.01, respectively). It is suggested that the depressed circulating IGF-I and free T4 levels in addition to deficient GH reserve may be responsible for stunted stature in patients with schistosomal hepatic fibrosis.

Anthropometry↗
PubMed1991

Early experience with fluoxetine.

A new antidepressant Fluoxetine, a serotonin re-uptake inhibitor, was tried on 26 resistant depressed patients. There were four drop out due to severe side effects. Improvement was noticeable soon after the first week and was maximum within 3 weeks of medication in 14 (63.6%) patients while in 8 (36.4%) patients it was as late as 6-12 weeks. The decline in improvement after three weeks in 7(31.8%) patients, needs attention in future studies. Bradycardia in 2 patients above the age of sixty indicate that the drug should be used with caution in elderly. GIT disturbance, insomnia, anorexia, restlessness and lethargy were common side effects. A well planned double blind study is recommended before its place is assigned in our patient population.

Depressive Disorder↗
PubMed1991

Psychosocial adjustment after renal transplantation.

Renal Transplantation is fairly new in our country and is expected to be the only satisfactory long-term treatment for patients with End Stage Renal Disease. Such treatment offers them a chance for near normal life. Seventeen patients who underwent kidney transplant during 1987-88 at the department of Nephrourology of J.P.M.C. Karachi, were reviewed. The result of ten patients who were assessed for their psychosocial adaptation is presented.

Adaptation, Psychological↗
PubMed1991

Psychosocial aspects of dialysis and renal transplant.

Keeping in view our socio cultural millieu, the psychological aspects of twenty renal transplants recipients and equal number of patients on dialysis were studied. Socio psychiatric profile in the dialysis and transplanted patients revealed that the frequency of anxiety, depression and hypochondriasis was significantly less (P less than 0.01) in the transplanted group. On Bender Gestalt Scale the transplanted group achieved normal status in significantly higher (P less than 0.05) number compared to the dialysis patients. It was concluded that transplanted patients showed marked improvement in social functioning, psychological symptoms and enduring personality traits compared to patients on maintenance dialysis.

Adaptation, Psychological↗
PubMed1991

Dubai syndrome in Karachi.

This is an attempt to study the effects of migration of earning member (to Gulf States) on the family, specially children left behind. Twenty five families who sought psychiatric help for one of their members were included. A control group (of non-migrant family) attending the out-patient's department was selected for comparison. The wife and children left behind experienced considerable emotional hardship. Twenty two families (88%) reported statistically significant recent maladjustment in 35 children (30%) as compared to control group of twelve families (48%) in 15 children (10%). Undoubtedly the major brunt is faced by the wives but the damage done to children is much less appreciated. This study identifies the current disturbance but the future effects on the personality of other children could manifest much later.

Child↗
PubMed1991

Alexithymia in Karachi.

Alexithymia is a new term which usually means "no words for mood" and used to describe a disorder where patients have difficulty in expressing feelings in words. Such patients therefore express emotions in somatic terms. We have selected headache as a symptom to test the term Alexithymia. A group of thirty patients with the complaint of persistent headache of more than 6 months duration, without any organic pathology or neurological disease entity was taken. This study concludes that Alexithymic traits are not necessarily more prominent in those having psychophysiological symptoms specially tension headache. It also shows that we should not accept any new concept evolved in West without testing it in our own conditions.

Adolescent↗
PubMed1990

Potency disorder among Pathans.

In a working class industrial area of Karachi hundred consecutive Pathans presenting to a family physician with potency disorder were examined. After exclusion of those with structural or drug related conditions, a structured proforma was introduced. Their presentation, associated symptoms and background pointed to masked depression and lack of sex education. Symptoms of anxiety were noticed in 49% and depressive features in 43%. The guilt feelings were reinforced by Hakims and lay literature which stress more on masturbation (79%) and spermatorrhoea (60%) and not extra-marital intercourse (52%) or bestiality (39%).

Adult↗