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 and Vmax of 0.71 and 0.52 lengths/s (37 degrees C) when measured at 95% of optimal length, whereas in chemically skinned uterine strips at 22 degrees C Vmax 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.

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 nonJordanian 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.

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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 neonates, 1.5 in young and 0.95 in old pigs (P less than 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.

Changes in the expression of heavy chains of myosin during development determine the functional characteristics of striated muscles. The distribution of heavy-chain isoforms of smooth-muscle myosin was determined in the airways of adult and infant humans to see whether it might underlie the hyperreactivity of human airways. The protein bands corresponding to myosin were separated using SDS/polyacrylamide-gel electrophoresis (4% gels) and identified by immunoblotting using both monoclonal and polyclonal antibodies against smooth-muscle myosin and non-muscle myosin. The relative proportion of each heavy chain stained by Coomassie Blue was measured by densitometric scanning. Three major bands corresponding to myosin heavy-chain isoforms were found; the two slower migrating bands (MHC1 and MHC2) were smooth-muscle myosin, and the third band was non-muscle myosin. The MHC1/MHC2 ratio was 0.69:1 in adult bronchus, and in infant bronchus and trachea. This contrasted with the airway smooth muscle in pigs, which was run concurrently, where the smooth-muscle heavy-chain ratio changed with development [Mohammad & Sparrow (1988) FEBS Lett. 228, 109-112]. The non-muscle myosin heavy chain comprised 63% of the smooth-muscle myosin. In both adult and infant lungs an additional putative myosin heavy chain which migrated slightly more rapidly than non-muscle myosin heavy chain was identified using the monoclonal smooth-muscle myosin antibody BF 48. This was unique to the human species.