Anatomy of the conduction tissues 100 years on: what have we learned?

Knowledge of the anatomy of the ‘conduction tissues’ of the heart is a 20th century phenomenon. Although controversies still continue on the topic, most could have been avoided had greater attention been paid to the original descriptions. All cardiomyocytes, of course, have the capacity to conduct the cardiac impulse. The tissues specifically described as ‘conducting’ first generate the cardiac impulse, and then deliver it in such a fashion that the ventricles contract in orderly fashion. The tissues cannot readily be distinguished by gross inspection. Robust definitions for their recognition had been provided by the end of the first decade of the 20th century. These definitions retain their currency. The sinus node lies as a cigar-shaped structure subepicardially within the terminal groove. There is evidence that it is associated with a paranodal area that may have functional significance. Suggestions of dual nodes, however, are without histological confirmation. The atrioventricular node is located within the triangle of Koch, with significant inferior extensions occupying the atrial vestibules and with septal connections. The conduction axis penetrates the insulating plane of the atrioventricular junctions to continue as the ventricular pathways. Remnants of a ring of cardiomyocytes observed during development are also to be found within the atrial vestibules, particularly a prominent retroaortic remnant, although that their role has still to be determined. Application of the initial criteria for nodes and tracts shows that there are no special ‘conducting tissues’ in the pulmonary venous sleeves that might underscore the abnormal rhythm of atrial fibrillation.

Interfacing Spinal Motor Units in Non-Human Primates Identifies a Principal Neural Component for Force Control Constrained by the Size Principle

ABSTRACTMotor units convert the last neural code of movement into muscle forces. The classic view of motor unit control is that the central nervous system sends common synaptic inputs to motoneuron pools and that motoneurons respond in an orderly fashion dictated by the size principle. This view however is in contrast with the large number of dimensions observed in motor cortex which may allow individual and flexible control of motor units. Evidence for flexible control of motor units may be obtained by tracking motor units longitudinally during the performance of tasks with some level of behavioural variability. Here we identified and tracked populations of motor units in the brachioradialis muscle of two macaque monkeys during ten sessions spanning over one month during high force isometric contractions with a broad range of rate of force development (1.8 – 38.6 N·m·s-1). During the same sessions we recorded intramuscular EMG signals from 16 arm muscles of both limbs and elicited the full recruitment through neural stimulation of the median and deep radial nerves. We found a very stable recruitment order and discharge characteristics of the motor units over sessions and contraction trials. The small deviations from orderly recruitment were observed between motor units with close recruitment thresholds, and only during high rate of force development. Moreover, we also found that one component explained more than ~50% of the motor unit discharge rate variance, and that the remaining components could be described as a time-shifted version of the first, as it could be predicted from the interplay between the size principle of recruitment and one common input. In conclusion, our results show that motoneurons recruitment is determined by the interplay of the size principle and common input and that this recruitment scheme is not violated over time nor by the speed of the contractions.

Rebus sic stantibus as a Stabilizing Doctrine in the Climate Crisis

In the face of massive, unanticipated and even disjunctive changes, the balance of the respective interests of the state parties to existing treaties may no longer survive the changed—or changing—climate landscape. While, ideally, the co-contracting states to such treaties could mutually agree to terminate or revise their treaty obligations to accommodate such changes and redress the now imbalance of interests in the treaty, some scenarios are bound to be contentious. In such cases, is there any other procedure that can provide for an orderly and fair adjustment of treaties so as to avert a breakdown of the network of treaties and a destabilization of world order? This article proposes that the rebus sic stantibus doctrine may function as a stabilizing doctrine for maintaining and possibly adjusting treaty regimes in an orderly fashion. Unlike the doctrine of necessity or many explicit treaty carve-outs, such as the security exception of the US Model Bilateral Investment Treaty, the doctrine of rebus sic stantibus may allow for both an objective test and also one that must be pleaded before a third-party arbiter. For this reason, rebus operates within controlled limits. Rebus offers an international tribunal the opportunity to set out a fair termination or revision of a climate-impacted treaty. I trace the evolution of rebus as a stabilizing doctrine and illustrate the potentialities of its application to the climate crisis.

China’s economy is slowing in an orderly fashion

Headline CHINA: The economy is slowing in an orderly fashion

China’s growth is slowing in an orderly fashion so far

Headline CHINA: Growth is slowing in an orderly fashion so far

Edu-Crafting Teacher Identities

“Teacher identity” is a popular topic for discussion and reflection in teacher education. We ask pre-service teachers to consider cultural and personal images of teachers (as expert, caregiver, authoritarian, and so on) in order to accept or resist these images as they contribute to the construction of their own teacher identity. Discussed in theory and aspirational language, teacher identity appears to behave in a reasonably orderly fashion; however, once the novice teacher is introduced to the dynamic world of teaching, teacher identity can become an absolute mess to untangle. As an approach to research, posthumanism offers us a chance to see this mess as beautiful in its lively, evolving, and relational condition. This posthumanist project takes to heart that in order to understand concepts such as identity differently, we must also look differently. After Taylor (2018), who describes posthumanist research as “allowing oneself to be lured by curiosity, surprise, and wonder” (p. 377), I conduct a diffractive auto/ethnographic study of several teachers to find out what happens if I take seriously the value of play in research, wondering what can be gained, in terms of understandings of teacher identities, through cartomancy as a potential source of knowledge. Semetsky (2011) has introduced the use of tarot reading to education theory as a semiotic system that can be engaged with to transform education and heal the human psyche. In my own work, I have built a practice that takes cues from Semetsky and also departs from her work, in the spirit of research creation (Chapman and Sawchuk 2012), forging its own unique method and artistic path. Conducting interviews with five self-identified teachers through video conferencing, I host a dialogue between myself, the teacher, and the tarot cards; a combination of friendly discussion, formalized interview, and tarot reading take place. This unconventional approach to research allows me to give generous attention to these teachers’ identities by acknowledging their connections to other selves, other humans, and more-than-humans. I am particularly hoping to find an expanded sense of teachers' self-perception and an increased recognition of a teacher’s multiple, connected, changing, and changeable identities.

Nanoscopical analysis reveals an orderly arrangement of the presynaptic scaffold protein Bassoon at the Golgi-apparatus

Bassoon is a core scaffold protein of the presynaptic active zone. In brain synapses, the C-terminus of Bassoon is oriented toward the plasma membrane and its N-terminus is oriented towards synaptic vesicles. At the Golgi-apparatus Bassoon is thought to assemble active zone precursor structures, but whether it is arranged in an orderly fashion is unknown. Understanding the topology of this large scaffold protein is important for models of active zone biogenesis. Using stimulated emission depletion nanoscopy in cultured hippocampal neurons, we found that an N-terminal intramolecular tag of recombinant Bassoon, but not C-terminal tag, colocalized with markers of the trans-Golgi network. The N-terminus of Bassoon was located between 48 nm and 69 nm away from TGN38, while its C-terminus was located between 100 nm and 115 nm away from TGN38. Sequences within the first 95 amino acids of Bassoon were required for this arrangement. Our data are consistent with a model, in which the N-terminus of Bassoon binds to the membranes of the trans-Golgi network, while the C-terminus associates with active zone components, thus reflecting the topographic arrangement characteristic of synapses also at the Golgi-apparatus.

Section 45 of the Tax Administration Act: An unconstitutional limitation on taxpayer privacy?

The Tax Administration Act 28 of 2011 is a law of general application. Section 45 of the Act empowers a SARS official to enter, without a warrant, premises where a trade or enterprise is reasonably believed to be carried on in order to conduct an inspection aimed at gathering information that will aide SARS in determining whether the business operator is compliant with tax obligations. In a constitutional democracy, the enjoyment of fundamental rights has a high premium. Accordingly, every lawful exercise of the power conferred by s 45 must take place in an orderly fashion, with decency and respect for taxpayers and their privacy. The state may not unduly interfere with this right, whether by withdrawing it altogether, abridging it, or diminishing its scope and ambit. This article hypothesises that inspections undertaken in terms of s 45 limit taxpayers’ privacy in a manner that may not pass muster under s 36(1) of the Constitution of the Republic of South Africa, 1996. On this basis, it is argued that, to cure its deficiencies, s 45 ought to be amended by the introduction of the provisions proposed in this article.

Passion and Love (P/L) with Knowledge and Understanding (K/U): Coherence, Concurrence, Congruence and Coexistence of Passions and Knowledge in Human Mind

This paper deals with the development of personality in two parallel tracks as an infant evolves to be a unique individual in society. The primary track is based on the acquired knowledge that is appended to the genetic code or information that the infant inherits from both parents. This track is essential for survival and is the primary instinct to just live on from one moment to the next. It shapes a baby from an infant in the world, a child in a family, a person in a society. If this progression can be conceived as an evolutionary trail for the progress in an orderly fashion to enhance and grow in a knowledge domain, then a secondary, simultaneous and a parallel track also evolves to shape the emotions of the baby, the feeling of the child and the passion of the person. The feeling, emotions, and passions exist during every stage, however unperceived they might be. The baby smiles and cries, and is happy just as much as a child is joyful or sad, or is excited. As much as this parallelism exists, we extend the parallel evolution of the two tracks deep and prolonged into adulthood, maturity, and old age of the human being in the society. Whereas the knowledge trail enhances the child, adult, and mature human to become educated, knowledgeable, wise, and ethical, the passion trail deeply resident in the mind, makes the person (during all stages of life) realistic, honest, loving, and passionate.