La Trobe University

About: La Trobe University is a education organization based out in Melbourne, Victoria, Australia. It is known for research contribution in the topics: Population & Health care. The organization has 13370 authors who have published 41291 publications receiving 1138269 citations. The organization is also known as: LaTrobe University & LTU.

Effects of sarcomere length on the force—pCa relation in fast‐ and slow‐twitch skinned muscle fibres from the rat

Abstract: 1. Steady-state force-pCa relations were determined for mechanically skinned fibres of fast- and slow-twitch rat skeletal muscle, extensor digitorum longus (e.d.l.) and soleus respectively, at varied sarcomere lengths and temperatures (3-35 degrees C).2. This relation was different for the two fibre types at all sarcomere lengths, with soleus fibres having lower Ca(2+) concentration threshold for activation and requiring a wider Ca(2+) concentration range to reach force saturation.3. An increase in sarcomere length within the range 2.2-3.6 mum reversibly shifted the steady-state force-pCa curves for both fast- and slow-twitch fibres toward lower Ca(2+) without affecting the steepness of the curves.4. The results are consistent with the idea that the sensitivity of the contractile apparatus to Ca(2+) is increased with increasing sarcomere length.5. The change in apparent Ca(2+) sensitivity (measured as the change in pCa corresponding to 50% Ca-activated force (DeltapCa(50))) was approximately proportional to the change in sarcomere length (DeltaSL) at all temperatures for both types of muscle fibre.6. The proportionality coefficient (DeltapCa(50)/DeltaSL) was higher for slow-twitch fibres than for fast-twitch fibres by a factor of 1.5-2.0 at all temperatures investigated.7. The force-pCa relation was less affected by changes in sarcomere length at lower (3-5 degrees C) than at higher temperatures (22-35 degrees C).8. The sarcomere length-maximum force relation obtained with skinned fibres for sarcomere lengths between 2.10 and 4.05 mum was similar for both fibre types at all temperatures despite large temperature dependent variations in maximum Ca-activated force response. Maximum force decreased linearly to zero between ca. 2.8 and 3.95 mum; remained high and essentially constant between ca. 2.40 and 2.80 mum, and decreased significantly below 2.40 mum.9. Myofilament-generated tension oscillations produced by partially activated soleus skinned fibres are highly length dependent, disappearing completely when sarcomere length is increased above 3.15 mum.

The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa

Abstract: Species of ancient humans and the extinct relatives of our ancestors are typically described from a limited number of fossils. However, this was not the case with Homo naledi. More than 1500 fossils representing at least 15 individuals of this species were unearthed from the Rising Star cave system in South Africa between 2013 and 2014. Found deep underground in the Dinaledi Chamber, the H. naledi fossils are the largest collection of a single species of an ancient human-relative discovered in Africa. After the discovery was reported, a number of questions still remained. Not least among these questions was: how old were the fossils? The material was undated, and predictions ranged from anywhere between 2 million years old and 100,000 years old. H. naledi shared several traits with the most primitive of our ancient relatives, including its small brain. As a result, many scientists guessed that H. naledi was an old species in our family tree, and possibly one of the earliest species to evolve in the genus Homo. Now, Dirks et al. – who include many of the researchers who were involved in the discovery of H. naledi – report that the fossils are most likely between 236,000 and 335,000 years old. These dates are based on measuring the concentration of radioactive elements, and the damage caused by these elements (which accumulates over time), in three fossilized teeth, plus surrounding rock and sediments from the cave chamber. Importantly, the most crucial tests were carried out at independent laboratories around the world, and the scientists conducted the tests without knowing the results of the other laboratories. Dirks et al. took these extra steps to make sure that the results obtained were reproducible and unbiased. The estimated dates are much more recent than many had predicted, and mean that H. naledi was alive at the same time as the earliest members of our own species – which most likely evolved between 300,000 and 200,000 years ago. These new findings demonstrate why it can be unwise to try to predict the age of a fossil based only on its appearance, and emphasize the importance of dating specimens via independent tests. Finally in two related reports, Berger et al. suggest how a primitive-looking species like H. naledi survived more recently than many would have predicted, while Hawks et al. describe the discovery of more H. naledi fossils from a separate chamber in the same cave system.

Chromosomal inversion polymorphisms and adaptation.

Abstract: Chromosomal inversion polymorphisms continue to be identified from an increasing number of populations of insects, plants, bacteria and humans. In the fruit fly Drosophila, chromosomal polymorphisms were used in classic studies of natural selection. Recent molecular genetic studies suggest that inversion polymorphisms are dynamical systems. These studies also indicate patterns of disequilibrium and variation that are consistent with co-adapted gene complexes. Although these complexes have yet to be identified, recent studies have identified traits, such as body size, that are linked to inversion polymorphisms. Selection acting on these polymorphisms is strong because latitudinal clines in inversion frequency become re-established rapidly after a new continent is colonized. A combined molecular and phenotypic approach is helping to identify the role of inversion polymorphisms in adaptive divergence, but the genes responsible for associations between traits and inversion polymorphisms remain to be identified.

Voice characteristics in the progression of Parkinson’s disease

Abstract: This study examined the acoustic and perceptual voice characteristics of patients with Parkinson's disease according to disease severity. The perceptual and acoustic voice characteristics of 30 patients with early stage PD and 30 patients with later stage PD were compared with data from 30 normal control subjects. Voice recordings consisted of prolongation of the vowel /a/, scale singing, and a 1-min monologue. In comparison with controls and previously published normative data, both early and later stage PD patients' voices were characterized perceptually by limited pitch and loudness variability, breathiness, harshness and reduced loudness. High modal pitch levels also characterized the voices of males in both early and later stages of PD. Acoustically, the voices of both groups of PD patients demonstrated lower mean intensity levels and reduced maximum phonational frequency ranges in comparison with normative data. Although less clear, the present data also suggested that the PD patients' voices were characterized by excess jitter, a high-speaking fundamental frequency for males and a reduced fundamental frequency variability for females. While several of these voice features did not appear to deteriorate with disease progression (i.e. harshness, high modal pitch and speaking fundamental frequency in males, fundamental frequency variability in females, low intensity and jitter), breathiness, monopitch and monoloudness, low loudness and reduced maximum phonational frequency range were all worse in the later stages of PD. Tremor was the sole voice feature which was associated only with later stage PD.