The physiological significance of p-Aminobenzoic Acid

Thesis submitted for the Degree of Doctor of Medicine in the University of the Witwatersrand, JohannesburgThe interest of the biochemist in para-aminobenzoic acid is very recent and, indeed, only goes back about five years, but in this time quite a voluminous literature has accumulated on the biological aspects and importance of this aniline derivative. Attention was originally focussed on it indirectly as a result of the intensive research devoted to the understanding of the mode of action of the various sulphonamides, which were shown during the last decade to be very powerful chemothera-peutic agents against many bacteria. Fildes (1940, propounded the hypothesis that p-aminobenzoic acid was an essential meta-bolite for bacteria, that it was normally associated with an enzyme system in the bacterial cell, and that sulphanilamide, being structurally similar to p-aminobenzoic acid, was capable in sufficient concentration of displacing p-aminobenzoic acid from its enzyme and stopping this essential line of metabolism. Fildes further suggested that a substance which was found to be an essential metabolite for bacteria would also be essential in the animal kingdom, so that such a substance might be found to act as a vitamin in the higher animals and even in man. In 19U1 interest in p-aminobenzoic acid was intensified with the announcement by Ansbacher (19U1J that p-eminobenzoic acid was actually a vitamin and should be included in the vita¬min B complex. In this thesis, studies on the absorption and excretion of p-aminobenzoic acid are reported, the estimation of p-amino- bensoic acid being based on its property of antagonising the Bulphonamides. Evidence is presented that p-arainobenzoic acid la excreted ae p-acetylaminobenzoic acid, and that its conjuga- tion with the acetyl radical probably takeB place in the liver. Further it is suggested that the experiments performed do not lend support to the view that p-aminobenzolc acid is a vitamin for man. Finally the various physiological effects of p-aminobenzoic acid are discussed and an attempt is made to gauge its function in the living organism. Preliminary experiments indicating a new, hitherto unreported, role of p-aminobenzoic acid are re¬corded, namely its ability in large doses to increase the re¬sistance of animals to disease.IT201

Investigating the regional variation in rules and best management practices for forestry in New Zealand

Under the Resource Management Act 1991 (NZ), the interpretation and implementation of environmental policy is primarily the responsibility of local government. The management of forestry operations may be influenced by statutory rules published in regional and district plans, and recommended best management practices (BMPs) published in guidelines. There are concerns that inconsistency between jurisdictions’ rules have a negative impact on the forestry industry’s financial and environmental outcomes. This research investigated and quantified the variation in Permitted Activity rules and BMPs, for culvert installation and earthworks, between New Zealand’s 16 Regional Councils. Significant variation in these regional rules and BMPs existed in both the level of control (i.e., the number of rules and BMPs per council), and the nature of control (i.e., the proportion of rules or BMPs utilised). Further, the rules and BMPs of one council are seldom the same as another. This variation is apparent on both a national scale and when considering only neighbouring pairs of councils

Assessment of New Zealand's forest codes of practice for erosion and sediment control

New Zealand's forest industry has several codes of practice available for erosion and sediment control. This article reviews conditions required for a code of practice to succeed in protecting the environment. Internal conditions – those conditions which are written into a code and can be assessed by reading the document alone – were used to assess the strengths and weaknesses of six of New Zealand's forest codes of practice. The study found that overall, the codes scored highly for objectives, communication, planning and comprehensiveness. However they did not score well for regulatory approach, monitoring, foundations and review process. Some preliminary recommendations were made about the development of future codes of practice based on these results

Association between neighbourhood cohesion and physical activity trajectories during the COVID-19 pandemic using data from Understanding Society: The UK Household Longitudinal Study & COVID-19 sub-study

Neighbourhood cohesion is increasingly recognised as a key determinant of health and health-related behaviours. Positive association between social support and physical activity have been demonstrated on an interpersonal level, there is less evidence at group-level. This study aimed to examine the association between neighbourhood cohesion and physical activity trajectories during the COVID-19 pandemic. Hypothesizing that higher neighbourhood cohesion was a protective factor against reduced physical activity during the pandemic. Data from Understand Society (wave 9, Jan 2017–Dec 2019), and the COVID-19 sub-study (waves 1, 5, 7) was used. Participants (N = 14,475) had baseline data and at least one Covid physical activity measure. We used linear mixed models with a random intercept and slope at the individual level and an unstructured correlation matrix to examine the association between neighbourhood cohesion and physical activity during the follow-up period. We found a significant reduction in physical activity (-441 MET-min/wk, (CI 374.51 – 507.65, p < 0.001) through the COVID-19 pandemic, and that higher neighbourhood cohesion was related to higher physical activity after control for covariates. There was a significant difference between neighbourhood cohesion categories and change seen in PA during the 39-month follow-up period (difference in change between lowest and highest neighbourhood cohesion categories = 373 MET-min/wk, p = 0.036), higher neighbourhood cohesion had a protective effect. Strong relationships between public health and urban planning sectors are needed to build communities with structures in place to support a sense of community, social interaction and attraction to the neighbourhood. This will help long-term neighbourhood cohesion and support increased physical activity

First principles numerical model of avalanche-induced arc discharges in electron-irradiated dielectrics

The model consists of four phases: single electron dynamics, single electron avalanche, negative streamer development, and tree formation. Numerical algorithms and computer code implementations are presented for the first three phases. An approach to developing a code description of fourth phase is discussed. Numerical results are presented for a crude material model of Teflon

Spaceflight-Induced Cardiovascular Changes and Recovery During NASA's Functional Task Test

Microgravity-induced physiological changes could impair a crewmember s performance upon return to a gravity environment. The Functional Task Test (FTT) is designed to correlate these physiological changes to performance in mission-critical tasks. The Recovery from Fall/Stand Test (RFST) simulates one such task, measuring the ability to recover from a prone position and the cardiovascular response to orthostasis. The purpose of this study was to evaluate spaceflight-induced cardiovascular changes during the FTT. METHODS: Five astronauts participated in the FTT before 10-15 day missions, on landing day (R+0), and one (R+1), six (R+6) and thirty (R+30) days after landing. The RFST consisted of a 2-minute prone rest followed by a 3-minute stand during which heart rate (HR, Holter) and continuous blood pressure (BP, Finometer) were measured. Spectral heart rate variability (HRV) was calculated during the RFST to approximate autonomic function. Statistical analysis was performed with two-factor repeated measures ANOVA. RESULTS: During RFST, HR was higher on R+0 than preflight (p<0.004). This increase in HR persisted on R+1 and R+6 during the stand portion of RFST (p<0.026). BP was well-regulated on all test days. Parasympathetic activity was diminished on R+0 (p=0.035). Sympathovagal balance tended to be affected by spaceflight (main effect, p=0.072), appearing to be slightly elevated during postflight RFST except on R+30. Additionally, analysis of HR during the functional tasks yielded a higher HR on R+0 than preflight during 8 of 11 tasks analyzed, where all tasks had HR return to preflight values by R+30 (p<0.05). CONCLUSION: Spaceflight causes an increase in HR, decrease in parasympathetic activity, and increase in sympathovagal balance, which we confirmed during RFST. These spaceflight-induced changes seen in the RFST, along with the increased postflight HR in most functional tasks, can be used to assess functional performance after short-duration spaceflight

Adaptive Effects on Locomotion Performance Following Exposure to a Rotating Virtual Environment

During long-duration spaceflight, astronauts experience alterations in vestibular and somatosensory cues that result in adaptive disturbances in balance and coordination upon return to Earth. These changes can pose a risk to crew safety and to mission objectives if nominal or emergency vehicle egress is required immediately following long-duration spaceflight. At present, no operational countermeasure is available to mitigate the adaptive sensorimotor component underlying the locomotor disturbances that occur after spaceflight. Therefore, the goal of this study is to develop an inflight training regimen that facilitates recovery of locomotor function after long-duration spaceflight. The countermeasure we are proposing is based on the concept of adaptive generalization. During this type of training the subject gains experience producing the appropriate adaptive motor behavior under a variety of sensory conditions and response constraints. As a result of this training a subject learns to solve a class of motor problems, rather than a specific motor solution to one problem, i.e., the subject learns response generalizability or the ability to "learn to learn." under a variety of environmental constraints. We are developing an inflight countermeasure built around treadmill exercise activities. By manipulating the sensory conditions of exercise by varying visual flow patterns, body load and speed we will systematically and repeatedly promote adaptive change in locomotor behavior. It has been shown that variable practice training increases adaptability to novel visuo-motor situations. While walking over ground in a stereoscopic virtual environment that oscillated in roll, subjects have shown compensatory torso rotation in the direction of scene rotation that resulted in positional variation away from a desired linear path. Thus, postural sway and locomotor stability in 1-g can be modulated by visual flow patterns and used during inflight treadmill training to promote adaptive generalization. The purpose of this study was to determine if adaptive modification in locomotor performance could be achieved by viewing simulated self-motion in a passive-immersive virtual ' environment over a prolonged period during treadmill locomotion

Sex differences in functional limitations and the role of socioeconomic factors: a multi-cohort analysis

Background: Women are more likely to have functional limitations than are men, partly because of greater socioeconomic disadvantage. However, how sex differences vary by severity of functional limitations remains unclear. We examined sex differences in functional limitations, with attention to socioeconomic factors and severity of limitations. Methods: Longitudinal data on limitations in basic activities of daily living (ADL) and instrumental activities of daily living (IADL) and mobility activities were drawn from 62 375 participants from 14 countries. For ADL, IADL, and mobility, participants were categorised based on number of limited activities (0, 1, 2, or ≥3). Sex differences in limitations in four birth cohorts (1895–1929, 1930–38, 1939–45, and 1946–60) were analysed before and after adjustment for socioeconomic factors (education and labour force status). Findings: The prevalence of IADL and ADL limitations was higher in women than in men. After adjustment for socioeconomic factors, this sex difference was attenuated. The sex difference in IADL limitations at age 75 years (in the 1895–1929 cohort) was 3·7% before adjustment for socioeconomic factors (95% CI 2·6–4·7) and 1·7% (1·1–2·2) after adjustment. For ADL, the sex difference in limitations at age 75 years (in the 1895–1929 cohort) was 3·2% (2·3–4·1) before adjustment for socioeconomic factors and 1·4% (0·9–1·8) after adjustment. Sex differences in mobility limitations (16·1%, 95% CI 14·4–17·7) remained after adjustment for socioeconomic factors (14·3%, 12·7–15·9). After age 85 years, women were more likely to have three or more IADL or mobility limitations and men were more likely to have one or two limitations. Interpretation: Socioeconomic factors largely explain sex differences in IADL and ADL limitations but not mobility. Sex differences in mobility limitations in midlife are important targets for future research and interventions. Funding: National Institute on Aging, UK National Institute for Health Research, European Commission, and US Social Security Administration

Functional Task Test: 2. Spaceflight-Induced Cardiovascular Change and Recovery During NASA's Functional Task Test

The overall objective of the functional task test (FTT) is to correlate spaceflight-induced physiological adaptations with changes in performance of high priority exploration mission-critical tasks. This presentation will focus on the recovery from fall/stand test (RFST), which measures the cardiovascular response to the transition from the prone posture (simulated fall) to standing in normal gravity, as well as heart rate (HR) during 11 functional tasks. As such, this test describes some aspects of spaceflight-induced cardiovascular deconditioning and the course of recovery in Space Shuttle and International Space Station (ISS) astronauts. The sensorimotor and neuromuscular components of the FTT are described in two separate abstracts: Functional Task Test 1 and 3