title: Measurement of Bremsstrahlung radiation for in vivo monitoring of ¹⁴C tracer distribution between fruit and roots of kiwifruit (Actinidia arguta) cuttings

authors: Black, Marykate Z.

subjects: ¹⁴C

abstract: In vivo measurements of ¹⁴C tracer distribution have usually involved monitoring the b- particles produced as ¹⁴C decays. These particles are only detectable over short distances, limiting the use of this technique to thin plant material. In the present experiments, X-ray detectors were used to monitor the Bremsstrahlung radiation emitted since b- particles were absorbed in plant tissues. Bremsstrahlung radiation is detectable through larger tissue depths. The aim of these experiments was to demonstrate the Bremsstrahlung method by monitoring in vivo tracer-labelled photosynthate partitioning in small kiwifruit (Actinidia arguta (Siebold & Zucc.) Planch. ex Miq.) plants in response to root pruning. A source shoot, consisting of four leaves, was pulse labelled with ¹⁴CO₂. Detectors monitored import into a fruit and the root system, and export from a source leaf. Repeat pulse labelling enabled the comparison of pre- and post-treatment observations within an individual plant. Diurnal trends were observed in the distribution of tracer, with leaf export reduced at night. Tracer accumulated in the roots declined after approximately 48 h, which may have resulted from export of ¹⁴C from the roots in carbon skeletons. Cutting off half the roots did not affect tracer distribution to the remaining half. Tracer distribution to the fruit was increased after root pruning, demonstrating the higher competitive strength of the fruit than the roots for carbohydrate supply. Increased partitioning to the fruit following root pruning has also been demonstrated in kiwifruit field trials.

text: Measurement of Bremsstrahlung radiation for in vivo monitoring of ¹⁴C tracer distribution between fruit and roots of kiwifruit (Actinidia arguta) cuttings In vivo measurements of ¹⁴C tracer distribution have usually involved monitoring the b- particles produced as ¹⁴C decays. These particles are only detectable over short distances, limiting the use of this technique to thin plant material. In the present experiments, X-ray detectors were used to monitor the Bremsstrahlung radiation emitted since b- particles were absorbed in plant tissues. Bremsstrahlung radiation is detectable through larger tissue depths. The aim of these experiments was to demonstrate the Bremsstrahlung method by monitoring in vivo tracer-labelled photosynthate partitioning in small kiwifruit (Actinidia arguta (Siebold & Zucc.) Planch. ex Miq.) plants in response to root pruning. A source shoot, consisting of four leaves, was pulse labelled with ¹⁴CO₂. Detectors monitored import into a fruit and the root system, and export from a source leaf. Repeat pulse labelling enabled the comparison of pre- and post-treatment observations within an individual plant. Diurnal trends were observed in the distribution of tracer, with leaf export reduced at night. Tracer accumulated in the roots declined after approximately 48 h, which may have resulted from export of ¹⁴C from the roots in carbon skeletons. Cutting off half the roots did not affect tracer distribution to the remaining half. Tracer distribution to the fruit was increased after root pruning, demonstrating the higher competitive strength of the fruit than the roots for carbohydrate supply. Increased partitioning to the fruit following root pruning has also been demonstrated in kiwifruit field trials.

year: 2012

title: Characterisation of the FitAB Toxin-Antitoxin  System in Neisseria gonorrhoeae

authors: Warrender, Annmaree Keely

subjects: VapBC

abstract: Neisseria gonorrhoeae is the causative agent of the sexually transmitted infection, gonorrhoea. In a standard infection, N. gonorrhoeae invade epithelial cells lining the urogenital tract and exit into the sub-epithelial layer. This triggers an immune response that causes the noticeable symptoms of gonorrhoea. Asymptomatic infection occurs when the bacteria persist inside epithelial cells, avoiding detection by the human immune system. Bacterial persistence has been linked to the development of antibiotic resistance, and as such, is a major contributing factor to the success of the pathogen. Mechanisms of adherence and invasion by N. gonorrhoeae have been well researched, but little is known about the intracellular lifecycle of the bacteria during infection and persistence.

Toxin-antitoxin (TA) systems have been linked to the formation of persistent populations in bacteria however the role of TA systems in N. gonorrhoeae is yet to be investigated. In this thesis, the role of a VapBC TA system in intracellular replication of N. gonorrhoeae is investigated and activity of the toxic VapC protein is characterised. The TA system, FitAB, is a protein-protein complex comprised of an antitoxin, FitA, and a toxin, FitB. Activity of FitB is inhibited when in complex with FitA, and the complex is auto-regulatory. Biochemical activity screens using RNA pentaprobe substrates to characterise the activity of FitB show FitB cleaves single-stranded RNA pentaprobes. However, FitB does not cleave short RNA oligonucleotides of the same sequence(s). These results indicate FitB is a magnesium-dependent sequence-specific ribonuclease that cleaves RNA based on sequence and secondary structure. 

The potential role of FitAB in persistence of N. gonorrhoeae was investigated using intracellular replication experiments. Intracellular replication of a N. gonorrhoeae fitAB gene deletion strain showed the most pronounced phenotype seen for a single TA deletion.  Intracellular replication of the fitAB gene deletion strain is considerably faster than the wild-type within epithelial cells. However, a sudden cell death event occurs in the gene deletion strain suggesting the TA system is essential for sustainable, long-term growth during infection. An understanding of how FitAB regulates intracellular growth will provide insight into the intracellular lifecycle of N. gonorrhoeae and the formation of persistent populations.

text: Characterisation of the FitAB Toxin-Antitoxin  System in Neisseria gonorrhoeae Neisseria gonorrhoeae is the causative agent of the sexually transmitted infection, gonorrhoea. In a standard infection, N. gonorrhoeae invade epithelial cells lining the urogenital tract and exit into the sub-epithelial layer. This triggers an immune response that causes the noticeable symptoms of gonorrhoea. Asymptomatic infection occurs when the bacteria persist inside epithelial cells, avoiding detection by the human immune system. Bacterial persistence has been linked to the development of antibiotic resistance, and as such, is a major contributing factor to the success of the pathogen. Mechanisms of adherence and invasion by N. gonorrhoeae have been well researched, but little is known about the intracellular lifecycle of the bacteria during infection and persistence.

Toxin-antitoxin (TA) systems have been linked to the formation of persistent populations in bacteria however the role of TA systems in N. gonorrhoeae is yet to be investigated. In this thesis, the role of a VapBC TA system in intracellular replication of N. gonorrhoeae is investigated and activity of the toxic VapC protein is characterised. The TA system, FitAB, is a protein-protein complex comprised of an antitoxin, FitA, and a toxin, FitB. Activity of FitB is inhibited when in complex with FitA, and the complex is auto-regulatory. Biochemical activity screens using RNA pentaprobe substrates to characterise the activity of FitB show FitB cleaves single-stranded RNA pentaprobes. However, FitB does not cleave short RNA oligonucleotides of the same sequence(s). These results indicate FitB is a magnesium-dependent sequence-specific ribonuclease that cleaves RNA based on sequence and secondary structure. 

The potential role of FitAB in persistence of N. gonorrhoeae was investigated using intracellular replication experiments. Intracellular replication of a N. gonorrhoeae fitAB gene deletion strain showed the most pronounced phenotype seen for a single TA deletion.  Intracellular replication of the fitAB gene deletion strain is considerably faster than the wild-type within epithelial cells. However, a sudden cell death event occurs in the gene deletion strain suggesting the TA system is essential for sustainable, long-term growth during infection. An understanding of how FitAB regulates intracellular growth will provide insight into the intracellular lifecycle of N. gonorrhoeae and the formation of persistent populations.

year: 2019

title: Does within-treatment change on dynamic risk factors and psychopathology predict recidivism for men graduating from Tai Aroha?

authors: Tanner Dempsey, Arden

subjects: dynamic risk factors

abstract: Dynamic risk factors are modifiable aspects of justice-involved people and their environment that can change over time and are associated with criminal behaviour. Because they are considered changeable, they are therefore typically the focus of rehabilitative treatment (Bonta & Andrews, 2024). Research shows that correctional rehabilitation that targets dynamic risk factors effectively reduces recidivism, and psychometric tools assessing these factors generally show improvements during treatment. However, there is a missing link; current research lacks consistent evidence linking changes on dynamic risk factors during treatment to recidivism. Relatedly, there are few studies assessing within-treatment changes in psychopathology and how they may affect recidivism, though they are commonly assessed alongside dynamic risk factors in correctional settings. 
This study, involving 164 people with violent offence convictions who completed the Tai Aroha community treatment programme, aimed to address this missing link. A battery of tests measured pre- and post-programme included dynamic risk factor measures, the Anger Disorders Scale (ADS), Psychological Inventory of Criminal Thinking Styles (PICTS), Criminal Attitudes to Violence Scale (CAVS), and the Millon Clinical Multiaxial Inventory (MCMI-III and IV) which is designed to assess personality and clinical psychopathology. Standardised residual change scores were used to account for variance in pre-treatment scores, and Cox regression hazard ratios to test prediction of general and violent recidivism.
Most subscales for dynamic risk factor measures and the MCMI-III and IV showed substantial improvements during treatment, however, this did not translate to predicting the probability of recidivism. While several hazard ratios indicated effects in a positive direction, none were significant when adjusted for multiple comparisons, and controlling for actuarial risk did not improve predictive accuracy. There was some evidence of increased socially desirable responding which increased at the end of treatment, this included responses on the MCMI-III and IV consistent with the “Normal Quartet.” Interpretations of these findings and both theoretical and empirical implications are discussed.

text: Does within-treatment change on dynamic risk factors and psychopathology predict recidivism for men graduating from Tai Aroha? Dynamic risk factors are modifiable aspects of justice-involved people and their environment that can change over time and are associated with criminal behaviour. Because they are considered changeable, they are therefore typically the focus of rehabilitative treatment (Bonta & Andrews, 2024). Research shows that correctional rehabilitation that targets dynamic risk factors effectively reduces recidivism, and psychometric tools assessing these factors generally show improvements during treatment. However, there is a missing link; current research lacks consistent evidence linking changes on dynamic risk factors during treatment to recidivism. Relatedly, there are few studies assessing within-treatment changes in psychopathology and how they may affect recidivism, though they are commonly assessed alongside dynamic risk factors in correctional settings. 
This study, involving 164 people with violent offence convictions who completed the Tai Aroha community treatment programme, aimed to address this missing link. A battery of tests measured pre- and post-programme included dynamic risk factor measures, the Anger Disorders Scale (ADS), Psychological Inventory of Criminal Thinking Styles (PICTS), Criminal Attitudes to Violence Scale (CAVS), and the Millon Clinical Multiaxial Inventory (MCMI-III and IV) which is designed to assess personality and clinical psychopathology. Standardised residual change scores were used to account for variance in pre-treatment scores, and Cox regression hazard ratios to test prediction of general and violent recidivism.
Most subscales for dynamic risk factor measures and the MCMI-III and IV showed substantial improvements during treatment, however, this did not translate to predicting the probability of recidivism. While several hazard ratios indicated effects in a positive direction, none were significant when adjusted for multiple comparisons, and controlling for actuarial risk did not improve predictive accuracy. There was some evidence of increased socially desirable responding which increased at the end of treatment, this included responses on the MCMI-III and IV consistent with the “Normal Quartet.” Interpretations of these findings and both theoretical and empirical implications are discussed.

year: 2024-01-23