Mukhallad A. Mohammad

Myosin composition and functional properties of smooth muscle from the uterus of pregnant and non-pregnant rats.

The myosin heavy chain stoichiometry and the force-velocity relation have been determined in the myometrium of the non-pregnant and pregnant rat. The relative proportions of the slower migrating heavy chain (MHC1) greatly exceeded that of the faster migrating heavy chain (MHC2) as shown by electrophoresis on SDS 4%-polyacrylamide gels. The ratios of MHC1/MHC2 were 2.2/1 in the non-pregnant rats, 2.6/1 in the pregnant rat, and contrasted with 0.8/1 in the rat portal vein. This stoichiometry was unchanged by extracting the myosin from the smooth muscle as native myosin in a salt extract, as dissociated myosin using sodium dodecyl sulphate (SDS) or by isolating the native myosin first by a non-dissociating (pyrophosphate) electrophoresis step and subsequently analysing the protein bands on the SDS 4%-polyacrylamide gel. Although the unequal proportions of the heavy chains suggested the possibility that the native myosin molecule may be arranged as homodimeric heavy chains, no evidence for or against the existence of native myosin isoforms could be obtained by electrophoresing native myosin extracts on pyrophosphate-polyacrylamide gels. The force-velocity relations of the intact electrically stimulated myometrium from the non-pregnant and pregnant rats gave isometric force of 45 and 135 mN/mm2 andVmax of 0.71 and 0.52 lengths/s (37°C) when measured at 95% of optimal length, whereas in chemically skinned uterine strips at 22°CVmax was 0.09 and 0.13 lengths/s, respectively. The length-force relationship was of similar shape in the non-gravid and gravid skinned tissues. The energetic tension cost (ATP-turnover/active stress) in skinned fibres was also similar. The mechanical and metabolic characteristics of the gravid and non-gravid uterus found in the present study do not suggest an obvious difference in the intrinsic properties of the myosin, although significant functional alterations in the tissue appear during pregnancy. This corresponds to the lack of a difference in the pattern of the heavy chains.

Changes in myosin heavy chain stoichiometry in pig tracheal smooth muscle during development

The stoichiometry of the myosin heavy chains (MHCs) has been measured in the tracheal smooth muscle of the pig after electrophoresis on SDS 4% polyacrylamide gel. The ratio of slower migrating MHC to the faster migrating MHC was 2.1 in neonates, 1.5 in young and 0.95 in old pigs (P<0.01) showing that MHC composition changes with development. The unequal proportion of MHCs was not compatible with a heterodimeric arrangement of the MHCs in the native molecule as proposed earlier by Rovner et al. [(1986) Am. J. Physiol. 250, C861–870] and it is suggested that native molecules may be composed of homodimer heavy chains.

Prevalence of mistreatment and justice of grading system in five health related faculties in Jordan University of Science and Technology.

Background: Many Jordanian university students complain of the behavior of some teaching staff. Also, they complain of the grading systems in universities. Aim: This study concerns the occurrence of different forms of student mistreatment and student mistrust of the grading system in the Jordan University of Science and Technology (JUST) as an example of universities in Jordan. Method: A total of 500 students in five health related faculties in JUST responded to a questionnaire. Results: Our results were as follow: (i) 61% of the students had experienced at least one form of mistreatment; (ii) perceived mistreatment most often (52%) had taken the form of psychological mistreatment (shouting and humiliation); (iii) other forms of mistreatment such as physical harm (32%), mistreatment related to religion (36%), mistreatment related to external appearance (35%), sexual harassment (33%) and mistreatment related to specialty (29%) were also common; (iv) with the exception of mistreatment related to specialty which was high among the nursing students, perceived mistreatment did not vary significantly between the different faculties; (v) the male students (66%) complain more than female students (56%); (vi) perceived mistreatment was exceptionally high among the Israeli Arabs, 83% compared to 59% for the Jordanians and 65% for other non-Jordanian Arabs; (vii) fellow students (44%), professors (37%) and laboratory technicians (19%) were cited as major sources of mistreatment. Many students (66%) believe that grading system in JUST is unfair. Ninety seven percent of the Israeli Arabs did not trust the grading system compared to 64% of the Jordanians and 66% of the non-Jordanian Arabs. Conclusions: This study suggests that, feelings of mistreatment among university students is strong while their trust of the university grading system is low. Perceived mistreatment and an unfair grading system may be a major source of stress among our students and may affect the process of teaching and learning in our country. This should alert the university administration to face these issues and try to solve them.

Effect of Intra-Venous Versus Intra-Arterial Leptin Infusion on Blood Pressure and Heart Rate

Objectives: In this study the effects of different Leptin concentrations on the blood pressure and heart rate in vivo in anesthetized rabbits were studied. Methods: Sixty Rabbits were divided into two groups, first group received Leptin intra-venously and other group received Leptin intra-arterially. Blood pressure and heart rate in were recorded before and after administration of Leptin. Results: A significant increase in mean arterial blood pressure (MABP) was seen after an intra-arterial injection of 3, 5 and 7 � g/kg of Leptin. This increase in MABP was monitored for different durations 10, 20 and 30 minutes after the infu- sion of each Leptin concentrations. The trend of the increase in MABP with time was demonstrated with all three concen- trations. Intra-venous infusion of Leptin caused a significant decrease in MABP after 10 minutes as well as after 20 and 30 minutes, with all three concentrations (3, 5, and 7 μg/Kg). Heart rate (HR) was not changed significantly at the end of 30 min of infusion. Conclusion: this in vivo study demonstrated that intra-venous Leptin infusion has a different effect on the MABP com- pared with intra-arterial infusion and this difference might be due to the site of action of Leptin.

The contribution of noradrenergic nerves to the vasoconstrictor response during local cooling of leg and forearm skin in humans

This study investigated the noradrenergic contribution during the cutaneous vasoconstrictor response to local cooling in the leg and forearm. On each limb, one site was perfused with Yoh/Prop to block the postsynaptic adrenoceptors and another with Lactated Ringers (control) using microdialysis. Blood flow was measured by Laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was calculated as LDF units divided by the mean arterial pressure. After baseline measures, skin was locally cooled to 24°C. Basal CVC was similar at all sites in the leg and forearm (all p > 0.1). During the first 10 min of local cooling, CVC was reduced in the leg (p < 0.005) and unchanged in the forearm control sites (p = 0.2). Yoh/Prop induced an increased CVC in the leg and forearm to a similar level (39.2 ± 11.5, and 41.3 ± 3.3%CVC, respectively; p < 0.35). Late during local cooling, the vasoconstriction was attenuated in the leg and forearm at Yoh/Prop (-38.2 ± 5.3 -37.1 ± 5.3%CVC, respectively; p = 0.5) compared to control sites (-69.1 ± 5.8 vs. -54.5 ± 6.4%CVC, respectively; p < 0.005). Noradrenergic contribution was greater in the leg than the forearm during the late vasoconstrictor response (p = 0.006). These data indicate that the leg skin can induce greater vasoconstriction than forearm during local cooling, possibly via higher noradrenergic sensitivity in the leg skin.