Freeze-fracturing in normal vacuum reveals ringlike yeast plasmalemma structures

The fine structure of the regular arrays of subunits seen on both plasmalemma fracture faces in resting and starved Saccharomyces cerevisiae (baker's yeast) has been compared using different freeze-fracture replication methods. Freeze-cleaving was carried out at 173 degrees, 133 degrees, and 108 degrees K under a vacuum of 2 X 10(-7) torr (2.6 X 10(- 7)mbar) or under liquid nitrogen at atmosphereic pressure. Independent of the preparation conditions (fracturing temperature, and whether cleaved under vacuum or liquid nitrogen), resting and starved yeast show a significant difference in the morphology of the subunits forming the regular arrays. The regularly arranged particles of the P face of the plasmalemma of starved yeast have a clear craterlike structure which has previously been reported to be demonstrated only by freeze-etching at very low temperatures in ultrahigh vacuum. A complementary structure is seen on the plasmalemma E face. Prolonged exposures of fracture faces under the protection of liquid nitrogen-cooled shrouds have shown that, because of the consequent drastic reduction of condensable gases in the specimen area, no detectable condensation contamination of exposed fracture faces occurs within 15 min at a specimen temperature of 108 degrees K. This shows that a complicated ultrahigh vacuum technology is not required for high resolution freeze- etching.     

Enhancing learning objectives by use of simple virtual microscopic slides in cellular physiology and histology: impact and attitudes

The impact and perception of students on the use of a simple, low technology-driven version of a virtual microscope in teaching and assessments in cellular physiology and histology were studied. Its impact on the time and resources of the faculty were also assessed. Simple virtual slides and conventional microscopes were used to conduct the same examinations for the same students. Students performed significantly better in the examination with the virtual slide and also showed a significantly higher preference for virtual slides. The time and cost implications of conducting examinations using the simple virtual slides were reduced by >1,400%. The results reemphasize the need for the design and adoption of simple sustainable technological innovations in developing countries to bridge gaps in purposeful learning environments.     

Comparative evaluation of active learning and the traditional lectures in physiology: A case study of 200 level medical laboratory students of Imo State Unversity, Owerri.

Currently, understanding of Physiology and disease patterns is undergoing a fundamental paradigm shift with attendant shift in education of health professionals worldwide towards active learning to encourage exploration of connections and their relationships. We introduced problem-based learning to Physiology teaching of medial laboratory students to confirm worldwide reports that active learning environments offer better learning opportunities over the traditional methods which is the predominant teaching method in Nigerian universities. Our findings indicate that Problem-based learning increases students' attendance/participation in classes and performance in examination. We recommend the integration of active learning into physiology curriculum of Nigerian Universities.     

Effect of Orthostasis on Endothelial Function: A Gender Comparative Study

As the vascular endothelium has multiple functions, including regulation of vascular tone, it may play a role in the pathophysiology of orthostatic intolerance. We investigated the effect of orthostasis on endothelial function using EndoPAT®, a non-invasive and user-independent method, and across gender. As sex steroid hormones are known to affect endothelial function, this study examined the potential effect of these hormones on the endothelial response to orthostasis by including females at different phases of the menstrual cycle (follicular and luteal—where the hormone balance differs), and females taking an oral contraceptive. A total of 31 subjects took part in this study (11 males, 11 females having normal menstrual cycles and 9 females taking oral contraceptive). Each subject made two visits for testing; in the case of females having normal menstrual cycles the first session was conducted either 1–7 (follicular) or 14–21 days (luteal) after the start of menstruation, and the second session two weeks later, i.e., during the other phase, respectively. Endothelial function was assessed at baseline and following a 20-min orthostatic challenge (active standing). The EndoPAT® index increased from 1.71 ± 0.09 (mean ± SEM) at baseline to 2.07 ± 0.09 following orthostasis in females (p<0.001). In males, the index increased from 1.60 ± 0.08 to 1.94 ± 0.13 following orthostasis (p<0.001). There were no significant differences, however, in the endothelial response to orthostasis between females and males, menstrual cycle phases and the usage of oral contraceptive. Our results suggest an increased vasodilatatory endothelial response following orthostasis in both females and males. The effect of gender and sex hormones on the endothelial response to orthostasis appears limited. Further studies are needed to determine the potential role of this post orthostasis endothelial response in the pathophysiology of orthostatic intolerance.     

BioTRIZ Suggests Radiative Cooling of Buildings Can Be Done Passively by Changing the Structure of Roof Insulation to Let Longwave Infrared Pass

This paper demonstrates the application of a design tool called BioTRIZ. Its developers claim that it can be used to access biological strategies for solving engineering problems. Our aim is to design a roof for hot climates that gets free cooling through radiant coupling with the sky. The insulation in a standard roof stops the sun and convection from warming the thermal mass. But it also restricts the mass＇s longwave view of the cool sky. Different solutions to this conflict are offered by BioTRIZ. The chosen solution is to replace the standard insulation component with an open cell honeycomb. The vertical cells would allow longwave radiation to pass, while arresting convection. The solutions offered by BioTRIZ＇s technological counterpart include no such changes in structure. It is estimated that the thermal mass in the biomimetic roof would remain on average 4.5℃ cooler than in a standard roof over a year in Riyadh, Saudi Arabia.