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Biomedical subjects

Z Hasan

Publications and source records attributed to Z Hasan.

At least 37 records · Page 2Linked to original sources
PubMed1996

Exercise at low altitude (Jordan Valley) causes changes in serum levels of ACTH, insulin, cortisol and lactate.

This study was designed to examine the effects of exercise on adrenocorticotropic hormone (ACTH) and cortisol at low altitude (350 meters below sea level) and to compare these effects with those at a moderate level altitude (620 meters above sea level). Ten male trained athletes participated in a 21-K(m) non-competitive race. Serum levels of ACTH, luteinizing hormone (LH), growth hormone and cortisol were measured before and after the race at each of the altitudes. A significant increase in serum levels of ACTH was observed in response to this exercise only at low altitude. Serum levels of growth hormone were increased at both altitudes. Those of LH were not affected. Serum cortisol levels were increased following exercise at both altitudes. It is proposed here that ACTH may play a role in acclimatization to exercise at low altitudes. The role of growth hormone and LH in this conditioning process seems to be insignificant. Additionally, serum levels of insulin and lactate were also measured in these experiments. Exercise caused a decrease in serum insulin levels at both altitudes. Serum levels of lactate were decreased only at low altitude. These changes of serum levels of insulin and lactate suggest a type of metabolic adjustment to meet energy requirements. Changes in energy metabolism can be correlated by changes in the ratio of insulin to serum cortisol levels and those of other counter-regulatory hormones in response to exercise at both altitudes.

Acclimatization↗
PubMed1996

Competitive polymerase chain reaction for the quantification of N-myc gene copy number in neuroblastoma.

An absolute quantification method for the N-myc gene copy number of neuroblastoma specimens was established by applying the competitive polymerase chain reaction (cPCR). The competitor plasmid (pZH2) lacking an MluI site in the exon 2 was constructed to distinguish two product species amplified from genomic DNA and the competitor plasmid. By using this cPCR system, we could obtain qualitative results within 1 day, i.e. amplified or unamplified, and quantitative results by using radiolabelled nucleotides within 4 days. The copy numbers of N-myc in 47 neuroblastoma specimens by cPCR correlated well with those by Southern hybridization (r = 0.85). We conclude that cPCR is a simple and rapid method, requires only a small amount (200 ng) of sample DNA, and is expected to be used for prognostic evaluation in neuroblastomas.

Base Sequence↗
PubMed1996

Acute effects of exercise at low altitude (350 meters below sea level) on hormones of the anterior pituitary & cortisol in athletes.

The purpose of this study was to examine the effects of exercise on anterior pituitary hormones (adrenocorticotropic hormone (ACTH), leutinizing hormone (LH) and growth hormone) as well as on cortisol at low altitude (350 meters below the sea level) and to compare these effects with those at a moderate level altitude (620 meters above the sea level). Ten male athletes with running experience participated in a 21-Km competitive race. Serum levels of ACTH, LH, growth hormone and cortisol were measured before and after the race at each of the altitudes. A significant increase in the serum levels of ACTH and growth hormone were observed in response to this exercise at low altitude. Similar exercise at 620 meters above the sea level resulted in a significant increase only in the serum levels of growth hormone. Serum levels of LH were not affected by this kind of exercise at both altitudes. Serum cortisol levels were increased following exercise at both altitudes. Altogether, these observations show a differential response of the anterior pituitary to exercise at low and normal altitudes. These data suggest that ACTH may have a role in the acclimatization to exercise at low altitudes. The role of growth hormone and LH in this conditioning process seems to be insignificant. The changes in serum cortisol levels in response to exercise at both altitudes correlate well with the effect of exercise on energy metabolism.

Adrenocorticotropic Hormone↗
PubMed1995

Qualitative discrepancies between trunk muscle activity and dynamic postural requirements at the initiation of reaching movements performed while sitting.

Reaching movements are associated with widespread, nonfocal muscle activity. That activity is often assumed to play a postural role. We tested this assumption for the trunk muscles at the initiation of reaching movements with the following question. Does initial trunk muscle activity play a dynamic postural role by resisting the segmental interactive effects of the arm movement on the trunk? Seated subjects performed bilateral reaching movements while target direction was systematically varied. Muscle activity was recorded from flexors and extensors of the trunk and shoulder. Trunk muscle activity was compared with trunk torques calculated from simulations of reaching movements in which the trunk was modeled to stay still. Recorded trunk muscle activity was in qualitative agreement with torque predictions for only some target directions, suggesting that the target directions to counteract postural disturbances at the initiation of reaching movements.

Adult↗
PubMed1995

Effects of propofol and thiopentone on picrotoxin convulsive threshold in the rabbit.

The purpose of the present study was to examine the effect of intravenous administration of propofol and thiopentone on picrotoxin-induced seizures using the picrotoxin convulsive threshold test in the rabbit. Neither propofol nor thiopentone at a dose of 1.25 mg/kg had any significant effect on picrotoxin seizure threshold. However, at higher doses (2.5, 5, 10 mg/kg) both propofol and thiopentone produced a significant and dose-dependent increase in the picrotoxin convulsive threshold. These findings suggest that propofol is an effective anticonvulsant against picrotoxin-induced seizures in the rabbit.

Animals↗
PubMed1995

Efficacy of ciprofloxacin in enteric fever: comparison of treatment duration in sensitive and multidrug-resistant Salmonella.

The efficacy of two regimens of ciprofloxacin was compared in a randomized study conducted on 69 patients with enteric fever, 52.2% of whom had infection with multidrug-resistant (MDR) strains of Salmonella typhi or S. paratyphi. Patients were randomly assigned to two regimens (10 days versus 14 days) of ciprofloxacin (500 mg twice a day). The mean +/- SD time required for defervescence was similar for both regimens (4.2 +/- 1.9 days in the 10-day group and 4.9 +/- 2.6 days in the 14-day group). A 100% cure was observed in each treatment group and no serious side effects were observed. Relapse occurred in two patients (14-day regimen). Only one patient (14-day regimen) had growth of S. typhi in stool culture at the time of the first follow-up three days after completion of therapy. Follow-up studies on available patients on two, six, and 12 months after completion of therapy revealed that all patients had negative stool cultures for S. typhi and S. paratyphi. This study indicates that ciprofloxacin may be recommended as an initial therapy for enteric fever for adult men and nonpregnant and nonlactating women in areas where MDR strains of S. typhi and S. paratyphi are prevalent, and that 500 mg twice a day of the drug given for 10 days is as effective as 14 days at the same dosage.

Adolescent↗
PubMed1995

Role of a large plasmid in mediation of multiple drug resistance in Salmonella typhi and paratyphi A in Bangladesh.

From 405 patients of suspected typhoid fever, 94 Salmonella typhi and 17 Salmonella paratyphi A, were isolated from blood and/or stool at the Institute of Postgraduate Medicine and Research, Dhaka during March 1992 to February 1993. Forty seven percent of the isolates were resistant to multiple drugs which included amoxicillin, ampicillin, chloramphenicol and co-trimoxazole. A large plasmid of 140 MDa was isolated from 73% of multidrug resistant (MDR) strains. However, no plasmid was isolated from any of the strains sensitive to above mentioned antibiotics. Majority of MDR Salmonella transferred resistance to E. coli K-12 (Lac+, F-, NxR.) by conjugation method. The transconjugants were similarly resistant to multiple drugs. All Salmonella were sensitive to ciprofloxacin and ceftriaxone.

Drug Resistance↗
PubMed1994

Selection of muscles for initiation of planar, three-joint arm movements with different final orientations of the hand.

Muscle activities and joint rotations were examined at the shoulder, elbow, and wrist joints for pointing movements to targets in the horizontal plane. In such movements, multiple arm configurations are possible for a given target location. Thus, starting from the same initial configuration and for the same target location in space, the joint excursions could be varied. When no constraints were placed on the final orientation of the hand, the choice of muscles initially activated at the wrist joint was consistent with a function to resist inertial effects of proximal segment motion on the wrist joint. When subjects were asked to produce different final orientations of the hand for the same target location, the initial choice of muscles at the three joints was preserved in most trials, whether wrist flexion or extension was required to reach the final hand orientation. The relative onset times of muscle activity at the different joints were also not correlated with wrist excursion. This suggests a predetermined initial selection of muscles that is related to target location, not to joint angular excursion. The fact that the required final hand orientation was nevertheless achieved suggests that the planning of these pointing movements is not a unitary process, but is comprised of two components: a fixed initial muscle selection for a given target location in space, and a selection appropriate for the required joint excursions.

Arm↗
PubMed1993

Thyroid function in children with beta-thalassemia major in north Jordan.

Basal thyroid function was assessed by serum thyroxine, tri-iodothyronine and thyroid-stimulating hormone levels in 90 patients 2-10 years old with beta-thalassaemia major. Based on measured serum ferritin levels, patients were classified into two groups: group (I) which included 63 patients with ferritin concentrations ranging from 300 to 7000 ng/ml (mild iron overload) and group (II) which included 27 patients with ferritin concentrations higher than 7000 ng/ml (severe iron overload). The results of thyroid function in both groups were compared with those of 50 control subjects. In group (I), the mean concentrations of all measured hormones were not significantly different from those of the controls. In group (II), the mean concentrations of thyroxine and tri-iodothyronine decreased by 29 and 35 per cent (P < 0.05), respectively, and the mean concentration of thyroid-stimulating hormone showed a 2.6-fold increase (P < 0.01) in comparison with those of the controls. The data clearly demonstrate the occurrence of impaired thyroid function and its possible association with iron overload in a considerable proportion of transfusion-dependent beta-thalassaemic patients.

Case-Control Studies↗
PubMed1992

The comparative effects of propofol, thiopental, and diazepam, administered intravenously, on pentylenetetrazol seizure threshold in the rabbit.

The anticonvulsant effects of propofol, thiopental, and diazepam, administered intravenously, on pentylenetetrazol (PTZ) seizure threshold were studied and compared in the rabbit. The PTZ seizure threshold determined in various rabbit groups during the control phase of conducted experiments, was found to be in the range of 10.1 +/- 2.0 to 13.5 +/- 3.7 mg/kg. Intravenous administration of comparable doses of propofol, thiopental, and diazepam resulted in marked and significant increases in PTZ seizure threshold. At all administered doses (1.25-10.0 mg/kg), propofol was found to be more effective than thiopental in increasing the PTZ threshold dose. However, the anticonvulsant effects of diazepam were more marked than those of propofol, except at a dose of 10 mg/kg where both agents exhibited equipotent activities. These data demonstrate that propofol enjoys a considerable degree of anticonvulsant activity in the rabbit. This anticonvulsant action is greater than that of thiopental at doses ranging from 2.5 to 10 mg/kg and equipotent with diazepam at the 10 mg/kg dose.

Animals↗
PubMed1992

Role of proprioceptors in neural control.

The conventional notion that peripheral muscle-related signals provide the basis for resistance to external perturbations is no longer sufficient. Proprioceptive information seems to be required for spatial steering of multi-joint movements, and also for temporal coordination among the joints in certain tasks. In rhythmic movements, peripheral and centrally generated signals appear to interact in a complementary manner. The complex effects of proprioceptive afferents on motor output continue to be delineated vigorously. Global effects of local perturbation in multi-joint contexts are emerging as being particularly significant.

Animals↗
PubMed1992

Estimates of the prevalence of childhood seizure disorders in communities where professional resources are scarce: results from Bangladesh, Jamaica and Pakistan.

Although numerous estimates of the prevalence of seizure disorders in populations in the less developed world have now been published, these estimates are difficult to interpret due to lack of comparability of study methods and criteria for case definition. The results reported in this paper are from a large, collaborative study of disabilities in 2- to 9-year-old children in which standard research procedures and case definitions were used in three diverse populations (located in Bangladesh, Jamaica and Pakistan). A two-phase study design (screening followed by professional evaluations) was used in this study allowing for the professional evaluation to serve as the criterion in the estimation of prevalence, even for rare disorders. As a result, the prevalence estimates reported here have a high degree of comparability across populations and exhibit unusually strong validity for population surveys. Febrile seizures were the most common type of seizure history in all three populations, with point estimates of lifetime prevalence ranging from 10.9 to 62.8 per 1000. The lifetime prevalence rates of epilepsy (recurrent unprovoked seizures) ranged from 5.8 to 15.5 per 1000. Lifetime prevalence rates of neonatal, all provoked and all unprovoked seizures, as well as estimates of the prevalence of active epilepsy, are also reported.

Age Factors↗
PubMed1991

Activity of wrist muscles elicited during imposed or voluntary movements about the elbow joint.

To examine the coordination of muscles during multijoint movement, we compared the response of wrist muscles to perturbations about the elbow joint with their activation during a volitional elbow movement. The purpose was to test the following two predictions: (a) Responses can occur in muscles not stretched by the perturbation, as has been reported for other multijoint systems; and (b) the motor pattern in response to a perturbation mimics an opposing volitional motor pattern across the two joints. We recorded the electromyographic (EMG) activity of elbow and wrist muscles as well as the flexion/extension motions at the elbow and wrist joints during individual trials that either involved a response to a torque perturbation that extended the elbow or required volitional elbow flexion. The results of this study confirmed that responses were elicited in the nonstretched wrist muscles when the elbow joint was perturbed. The same motor sequence of elbow and wrist flexors was present for both the volitional and perturbation task (with the forearm supinated), regardless of whether the wrist joint was immobilized or freely moving. The findings suggest that the nervous system relies on the purposeful coupling of elbow and wrist flexors to counter the inertial effects during the unrestricted voluntary movement, even though the coupling does not appear to be purposeful during the perturbation or with the wrist immobilized. The coupling of elbow and wrist flexors, however, was not rigidly fixed, as evidenced by muscle onsets that adapted over repeated perturbation trials and a reversal of the wrist muscle activated (wrist extensor) when the forearm was pronated. Hence, the coupling of muscle activities can be modified quantitatively when not beneficial and can be altered qualitatively with different initial configurations of the arm.

Journal Article↗
PubMed1991

A comparison of the anticonvulsant effects of propofol and thiopentone against pentylenetetrazol-induced convulsions in the rat.

1. The anticonvulsant effects of subanaesthetic doses of propofol and thiopentone against PTZ-induced seizures and mortality were examined in the rat. 2. Administration of propofol (50 mg/kg, i.p.) 5 min prior to PTZ treatment increased the 2 h CD50 and the 24 h LD50 of PTZ by 3.4-fold, whereas thiopentone pretreatment (20 mg/kg, i.p.) increased these values by more than five-fold. 3. Both propofol and thiopentone prolonged the latency to the onset of clonic seizure but the effects of the former were more marked. 4. The data demonstrate that propofol was more effective than thiopentone in providing complete protection against PTZ-induced seizures for the first 30-40 min of observation and that thiopentone, because of its sustained effects, was more effective in reducing the cumulative incidence of seizures and mortality over 2 and 24 h, respectively. 5. We conclude that propofol is a very effective anticonvulsant and provides complete protection of short duration against PTZ-induced seizures in the rat.

Animals↗
PubMed1991

Initiation rules for planar, two-joint arm movements: agonist selection for movements throughout the work space.

1. The question we addressed was the following: what rules does the CNS employ, given the initial and final positions of the arm for a pointing movement, to decide which shoulder and elbow muscles ("agonists") to activate for initiating movement? 2. Widely varying initial and final positions were used, so that the movements studied encompassed much of the reachable work space within the horizontal plane. For each movement, the initial electromyographic (EMG) activity at each joint was classified qualitatively in terms of the "sign," i.e., flexor or extensor muscle activity, and quantitatively in terms of the integral of the rectified EMG. 3. The sign of initial muscle activity at each joint was found to be related to the angular excursions at both joints during movement to the final position. 4. Two different hypothesized rules, derived from previously proposed strategies for control of multijoint limb movements, were tested for their ability to predict correctly the sign of initial muscle activity at each joint. Although four variables are needed to describe the initial and final positions of a two-segment arm, only two combinations of these four were relevant for testing the rules. The two positional variables were the spatial direction of the final tip position with respect to the initial forearm orientation (psi) and the initial elbow angle (theta Einit). 5. According to one of the rules tested, which was based on statics, the initial muscle activity at each joint should be such that the distal tip of the limb exerts an initial force in the direction of the final tip position. Our data concerning the sign of initial shoulder muscle activity clearly contradicted this rule in two distinct regions of the (psi, theta Einit) plane. 6. According to the other rule tested, which was based on dynamics, the initial muscle activity at each joint should be such that the initial acceleration of the distal tip is in the direction of the final tip position. The data contradicted the predicted sign of initial shoulder muscle activity for a certain range of psi. This shows that the activation of muscles is not always appropriate even qualitatively for a straight-line path. Furthermore, the effects of added inertial loads predicted by this rule were not observed for trials in which a 1.8-kg mass was attached to the distal portion of the limb.(ABSTRACT TRUNCATED AT 400 WORDS)

Arm↗
PubMed1991

Timing and magnitude of electromyographic activity for two-joint arm movements in different directions.

1. We studied electromyographic (EMG) and kinematic features of self-paced human arm movements involving rotations about the shoulder and elbow joints. Movements were initiated from various positions and covered much of the reachable work space in the horizontal plane. The attempt was to characterize robust features of the relative timing and magnitude of the EMG activity at the two joints, and to correlate them with variables related to the initial and final positions. 2. The pattern of muscle activity at each joint was typically characterized by bursts of alternating agonist and antagonist activity, comparable with the three-burst pattern associated with single-joint movements. As the spatial direction of the target was altered, the magnitude of each burst was modulated over a continuous range. Modulation down to zero activity was observed, not only for later bursts, as has been shown in some cases of single-joint movements, but for the first agonist burst as well. 3. In the preceding paper we showed that the choice of agonists (i.e., flexors or extensors) at each joint is predictable on the basis of the target direction relative to the distal segment (psi). Here, we present quantitative analyses of initial agonist EMG activity at the shoulder and elbow, which reveal that the onset-time difference between agonists at the two joints also varied systematically with psi, and so did their relative magnitude. 4. For most target directions, initial EMG activity at the shoulder preceded that at the elbow by 5-40 ms. Exceptions were observed mainly for target directions near the transitions between initial flexor and initial extensor activity at the shoulder. In these cases the initial agonist activity at the shoulder was greatly reduced or, in some cases, appeared entirely suppressed, although the later bursts were present in their usual temporal alignment with the corresponding bursts at the elbow. 5. Antagonist onset at the elbow tended to precede antagonist onset at the shoulder, but the difference in timing did not vary consistently with psi. 6. Despite the consistency of initial agonist timing between the two joints, the agonist onset-time difference was poorly correlated with the apparent difference in the onset times of shoulder and elbow joint rotations. The latter difference, which is affected by mechanics, cannot therefore be imputed directly to the CNS.(ABSTRACT TRUNCATED AT 400 WORDS)

Arm↗
PubMed1989

Muscle activity for initiation of planar, two-joint arm movements in different directions.

We studied planar, point-to-point arm movements to various target positions, starting from a fixed initial position. The movements involved coordinated rotations about the shoulder and elbow joints. One of our aims was to determine for each joint whether flexion was always initiated by flexor muscle activity and, similarly, whether extension was always initiated by extensor activity. Based on electromyographic records we found for all subjects that this was not the case for movements to certain areas of the workspace. An alternative hypothesis, that the initial muscle activity should be appropriate for exerting an isometric force in the direction of the final position, was also contradicted by our observations. Nevertheless, the data for each joint revealed that flexor-initiated movements occurred for final positions in a certain region of the workspace that was distinct from the region of final positions for extensor-initiated movements.

Adult↗