The influence of clinic care on perceptions and knowledge of non-communicable diseases and physical activity from a low-resourced community: a mixed-method study

Background

Health promotion for the management of risk factors for non-communicable diseases (NCDs) is an integral part of standard care in South Africa. Most persons presenting with NCDs utilise public primary health care centres for disease management. This mixed-methods study aimed at expanding current understanding of the the influence of standard clinic care (usual care) on perceptions and knowledge of risk factors for NCDs and physical activity (PA) among persons from a low-resourced community. Qualitatively the perceptions of women from a low-resourced community about risk factors for NCDs and PA were explored throughout 24-weeks of standard clinic care. Parallel quantitative data was collected to describe changes in risk factors for NCDs and trends in self-reported knowledge about risk factors of NCDs and PA.

Method

A convergent-parallel mixed-methods research design was used. The study was carried out in a public primary health care setting, in the North West Province, South Africa. From a convenience sample of 100 participants, 77 African women aged between 34 and 79 years were recruited for the study. Data were collected at three time-points including baseline, 12 weeks, and 24 weeks of a standard clinic care health-promotion programme. The qualitative data was collected during focus group discussions, and the quantitative data included questionnaires on knowledge of physical activity and risk factors for NCDs as well as anthropometric and biological measurements. Qualitative and quantitative data were analysed independently for each phase and then consolidated for interpretation. All data was collected in the same setting.

Results

Participants' initial understanding and perceptions of NCD risk factors were poor. Qualitative findings showed that participants knew little about the specific physical activity they could engage in and the role of PA in NCD management. Participants preferred low-intensity activities. Heart-disease knowledge improved significantly at 12 weeks intervention compared to baseline MD = -3.655, p < 0.001. There were improvements in PA knowledge at 12 weeks from baseline MD = -0.625 p = 0.02. There were significant weight (MD = 1.420, p = 0.002) and waist circumference reductions (MD = 0.621, p = 0.02) from baseline to 24 weeks.

Conclusion

Standard clinic care improved knowledge of physical activity and risk factors for NCDs, but perceptions of risk factors for NCDs and PA were unchanged. This study offers insight into the perceptions held by women from a low-resource setting and how future interventions to manage and prevent NCDs should be structured.

Trial registration

PACTR201609001771813.

Quality of life, physical activity and cardiorespiratory fitness in black African women: B-Healthy project

PURPOSE

To study the associations between physical activity (PA), cardiorespiratory fitness (CRF), and health-related quality of life (HRQoL) in black African women from a low socioeconomic community in South Africa.

METHODS

Black African women (n = 146) aged 35-75 years from a low socioeconomic community in South Africa participated in this study. We measured PA levels via ActiHeart® accelerometers, and CRF by measuring peak oxygen consumption (V̇O₂ peak). HRQoL was assessed once with the SF-8 Health Survey (SF-8). Participants were classified into groups based on age, moderate to vigorous PA (MVPA), and V̇O₂ peak. Logistic regressions were used to compare the odds of having total HRQoL component scores above reported norms across PA and fitness groups. Two multiple linear regression models were developed using physical component summary (PCS) and mental component summary (MCS) as response variables respectively.

RESULTS

V̇O₂ peak and MVPA varied considerably across the sample and declined with increasing age. Participants in higher quartiles of MVPA and CRF showed trends to higher PCS scores. For CRF these trends were statistically significant, and persisted after adjustment for age and other possible confounders (p = 0.036). PCS was significantly associated with age, relative V̇O₂ peak, and income (all p < 0.05), while MCS was associated with income (p = 0.028).

CONCLUSIONS

CRF is the most significant predictor, together with age and income, on the PCS of the HRQoL among black African women. We recommend that when seeking improvements in HRQoL, interventions should focus on improving CRF, particularly V̇O₂ peak.

Diversity oriented biosynthesis via accelerated evolution of modular gene clusters

Erythromycin, avermectin and rapamycin are clinically useful polyketide natural products produced on modular polyketide synthase multienzymes by an assembly-line process in which each module of enzymes in turn specifies attachment of a particular chemical unit. Although polyketide synthase encoding genes have been successfully engineered to produce novel analogues, the process can be relatively slow, inefficient, and frequently low-yielding. We now describe a method for rapidly recombining polyketide synthase gene clusters to replace, add or remove modules that, with high frequency, generates diverse and highly productive assembly lines. The method is exemplified in the rapamycin biosynthetic gene cluster where, in a single experiment, multiple strains were isolated producing new members of a rapamycin-related family of polyketides. The process mimics, but significantly accelerates, a plausible mechanism of natural evolution for modular polyketide synthases. Detailed sequence analysis of the recombinant genes provides unique insight into the design principles for constructing useful synthetic assembly-line multienzymes.

Reengineering polyketide synthase encoding genes to produce analogues of natural products can be slow and low-yielding. Here the authors use accelerated evolution to recombine the gene cluster for rapid production of rapamycin-related products.

Cell-permeable succinate prodrugs bypass mitochondrial complex I deficiency

Mitochondrial complex I (CI) deficiency is the most prevalent defect in the respiratory chain in paediatric mitochondrial disease. This heterogeneous group of diseases includes serious or fatal neurological presentations such as Leigh syndrome and there are very limited evidence-based treatment options available. Here we describe that cell membrane-permeable prodrugs of the complex II substrate succinate increase ATP-linked mitochondrial respiration in CI-deficient human blood cells, fibroblasts and heart fibres. Lactate accumulation in platelets due to rotenone-induced CI inhibition is reversed and rotenone-induced increase in lactate:pyruvate ratio in white blood cells is alleviated. Metabolomic analyses demonstrate delivery and metabolism of [(13)C]succinate. In Leigh syndrome patient fibroblasts, with a recessive NDUFS2 mutation, respiration and spare respiratory capacity are increased by prodrug administration. We conclude that prodrug-delivered succinate bypasses CI and supports electron transport, membrane potential and ATP production. This strategy offers a potential future therapy for metabolic decompensation due to mitochondrial CI dysfunction.

Effect of continuous aerobic vs. interval training on selected anthropometrical, physiological and functional parameters of adults with Down syndrome

BACKGROUND

A large percentage of adults with Down syndrome (DS) are overweight and have extremely low aerobic capacities compared with the general population and persons with intellectual disability without DS. Previous aerobic training intervention studies showed limited potential to significantly ameliorate anthropometrical and cardiovascular variables. The primary purpose of this study was to determine the effect of continuous aerobic training (CAT) vs. interval training (IT) on selected anthropometrical, health, physical and functional parameters of adults with DS.

METHODS

Forty-two adults with DS (25 men and 17 women) and a mean age of 33.8 (±8.6) years were randomly allocated to one of three groups (IT, CAT and control). Training was performed for 12 weeks. The IT group performed 10-30 s all out sprints with 90 s (1:3 work-rest ratio) of low cadence, low intensity cycling or walking. The CAT group performed continuous cycling and walking at an intensity of 70-80% of VO₂ peak. Heart rate monitors were used for monitoring training intensities. After 6 weeks of training, the intensity of the CAT was increased to 85% of VO₂ peak, whilst the intensity of the IT group remained 'all out'. An increase of 5 min in duration was implemented after 6 weeks for both training groups. To evaluate pre-post differences between groups, a repeated analysis of covariance with post hoc Bonferroni test was performed RESULTS: After 12 weeks of training, body weight and body mass index decreased significantly more in the IT group compared with control and CAT (P < 0.05). Participants in the IT group decreased their body weight from 71.4 ± 8 to 69.4 ± 8 kg and their body mass index from 29.3 ± 4 to 28.5 ± 4 kg/m² . Significant ameliorations for functional parameters and leg strength were shown for CAT compared with control (P < 0.05). Participants in the CAT group improved their performance in the 6 minute walk distance (499 ± 78 to 563 ± 75 m), 8-ft up-and-go (5.9 ± 1.2 to 4.8 ± 0.9) and leg strength (13.1 ± 2 to 15.2 ± 2). VO₂ peak and time to exhaustion significantly improved in both the IT and CAT group compared with control (P < 0.01). Moreover, a significant improvement for relative VO₂ peak was also determined for IT compared with CAT (P < 0.05). Participants in the IT group increased their VO₂ peak from 32 ± 8 to 37 ± 8 mL/min/kg. Submaximal heart rate and VO₂ values improved significantly within both exercise groups (P < 0.05).

CONCLUSION

Interval training and CAT can both be pursued by adults with DS to positively impact on various parameters of anthropometry, fitness and functional ability, with IT more appropriate for improving body weight and aerobic capacity.

Test-retest reliability and minimal detectable change scores of twelve functional fitness tests in adults with Down syndrome

AIM

The purpose of the study was to explore the test-retest reliability and minimal detectable change of selected functional fitness test items in adults with Down syndrome.

METHODS

Forty-three adults with Down syndrome (24 men and 19 women) aged 18-50 years completed a battery of tests twice in a two-week period. The battery of tests consisted of two balance items, two flexibility items, five muscular strength and endurance items, two aerobic items, and one functional task. All items were considered valid and reliable tests in a general elderly or intellectually disabled population. The test-retest relative reliability for all repeated tests was assessed with intraclass correlation coefficient performing one-way analysis of variance. The test-retest absolute variability was measured by using the standard error of measurement (SEM) to calculate the minimal detectable change at the 90% confidence interval (MDC90). Reliability data was visualised with a Bland-Altman plot.

RESULTS

All tests showed excellent intraclass correlation coefficients (ICC's>0.9). All SEM values demonstrated acceptable measurement precision (SEM<SD/2). Values for MDC90 are provided for all 12 tests. The analyses indicated that there was no major systematic bias in the plots. The scatter around the Bland-Altman was distributed randomly.

CONCLUSION

All twelve functional fitness tests demonstrated adequate feasibility and relative and absolute test-retest reliability in adults with Down syndrome in South Africa. Information of this nature will help to monitor performance alterations over time and success of training interventions.

Mutations in NONO lead to syndromic intellectual disability and inhibitory synaptic defects

The NONO protein has been characterized as an important transcriptional regulator in diverse cellular contexts. Here we show that loss of NONO function is a likely cause of human intellectual disability and that NONO-deficient mice have cognitive and affective deficits. Correspondingly, we find specific defects at inhibitory synapses, where NONO regulates synaptic transcription and gephyrin scaffold structure. Our data identify NONO as a possible neurodevelopmental disease gene and highlight the key role of the DBHS protein family in functional organization of GABAergic synapses.

The association between dyslipidemia and anthropometric indicators in black and white adolescents residing in Tlokwe Municipality, North-West Province, South Africa: the PAHL study

BACKGROUND

The dyslipidemia associated with excess weight is a risk for cardiovascular disease. Worldwide and in South Africa adolescent obesity has been reported.

OBJECTIVES

To determine the association between dyslipidemia and anthropometric indices in black and white adolescents.

METHODS

The study involved 129 black and 69 white adolescents aged 12 to 16 years. Data collected included height, weight, waist circumference (WC) and skinfolds, blood pressure and blood for glucose, insulin, total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), triglycerides (Trig) and C - reactive protein (CRP).

RESULTS

WC correlated negatively with HDL in both blacks (p=0.042) and whites (p=0.008) and in whites it correlated positively with LDL (p=0.006); TC/HDL (p=<0.001) and LDL/HDL ratio (p<0.0001). WC/Hgt correlated negatively with HDL (p=0.028) and positively with LDL/HDL (p=0.026 and p<0.0001) in both races. In whites positive correlations were between WC/Hgt and TC (p=0.049); LDL (p=0.003) and TC/HDL (p<0.0001). BAZ correlated positively with TC/HDL ratio (p=0.004) and LDL/HDL ratio (p=0.002). The most common abnormalities were HDL and LDL.

CONCLUSION

Whites exhibited more associations between dyslipidemia and anthropometric indicators as compared to Blacks, suggesting that there might be differences in the lipid metabolism or even susceptibility to risk factors in adolescents.

Uncovering the origin of Z-configured double bonds in polyketides: intermediate E-double bond formation during borrelidin biosynthesis

The dehydratase domain BorDH3 is assayed with a synthetic surrogate of the predicted tetraketide substrate and shown to be E-selective. Detailed NMR spectroscopic analysis of pre-borrelidin assigns the timing of the E-5 Z-isomerization to the very final steps of borrelidin biosynthesis.

Thoracic posture, shoulder muscle activation patterns and isokinetic strength of semi-professional rugby union players

Background. Shoulder injuries are the most severe injuries in rugby union players, accounting for almost 20% of injuries related to the sport and resulting in lost playing hours.Objective. To profile the thoracic posture, scapular muscle activation patterns and rotator cuff muscle isokinetic strength of semi-professionalrugby union players.Methods. Using the hand-behind-the-neck and -back methods, we manually tested the range of motion (ROM) of the shoulder joints of 91 uninjured semi-professional rugby union players who consented to participate in the study. Profiling and classification of thoracic posture was performed according to the New York Posture Test. Activation patterns of the upper and lower trapezius, serratus anterior and infraspinatus scapular muscles were determined by electromyography. The isokinetic muscle strength of the rotator cuff muscles was determined at 60°/sec by measuring the concentric and eccentric forces during internal rotation (IR) and external rotation (ER).Results. Participants presented with non-ideal or unsatisfactory internal (59%) and external (85%) rotators of the shoulder. A slightly abnormal or abnormal forward head posture was observed in 55% of participants, while 68% had an abnormal shoulder position in the lateral view. The muscle activation sequence of the rotator cuff muscles was: (i) serratus anterior, (ii) lower trapezius, (iii) infraspinatus, and (iv) upper trapezius. The isokinetic ER/IR muscle-strength ratio during concentric muscle contraction was 64% (standard deviation (SD) ±14) for the left shoulder and 54% (SD ±10) for the right shoulder. The ER/IR ratio for eccentric muscle contraction was 67% (SD ±12) and 61% (SD ±9) for the left and right shoulders, respectively.Conclusions. Non-ideal or unsatisfactory flexibility of the external rotators of the shoulder, a forward shoulder posture in the lateral view, and weakness of the external rotators did not result in an abnormal rotator cuff muscle activation pattern in this study. Postural deviations may, however, increase the risk of shoulder injury in rugby union players in the long term, and should be corrected.

Thoracic posture, shoulder muscle activation patterns and isokinetic strength of semi-professional rugby union players

Background. Shoulder injuries are the most severe injuries in rugby union players, accounting for almost 20% of injuries related to the sport and resulting in lost playing hours.Objective. To profile the thoracic posture, scapular muscle activation patterns and rotator cuff muscle isokinetic strength of semi-professionalrugby union players.Methods. Using the hand-behind-the-neck and -back methods, we manually tested the range of motion (ROM) of the shoulder joints of 91 uninjured semi-professional rugby union players who consented to participate in the study. Profiling and classification of thoracic posture was performed according to the New York Posture Test. Activation patterns of the upper and lower trapezius, serratus anterior and infraspinatus scapular muscles were determined by electromyography. The isokinetic muscle strength of the rotator cuff muscles was determined at 60°/sec by measuring the concentric and eccentric forces during internal rotation (IR) and external rotation (ER).Results. Participants presented with non-ideal or unsatisfactory internal (59%) and external (85%) rotators of the shoulder. A slightly abnormal or abnormal forward head posture was observed in 55% of participants, while 68% had an abnormal shoulder position in the lateral view. The muscle activation sequence of the rotator cuff muscles was: (i) serratus anterior, (ii) lower trapezius, (iii) infraspinatus, and (iv) upper trapezius. The isokinetic ER/IR muscle-strength ratio during concentric muscle contraction was 64% (standard deviation (SD) ±14) for the left shoulder and 54% (SD ±10) for the right shoulder. The ER/IR ratio for eccentric muscle contraction was 67% (SD ±12) and 61% (SD ±9) for the left and right shoulders, respectively.Conclusions. Non-ideal or unsatisfactory flexibility of the external rotators of the shoulder, a forward shoulder posture in the lateral view, and weakness of the external rotators did not result in an abnormal rotator cuff muscle activation pattern in this study. Postural deviations may, however, increase the risk of shoulder injury in rugby union players in the long term, and should be corrected.

Novel FK506 and FK520 analogues via mutasynthesis: mutasynthon scope and product characteristics

Novel FK506 and FK520 analogues were generated via biosynthetic engineering in order to generate analogue compounds with equal potency but improved pharmacological profiles compared to FK506.

The potential market demand for biokinetics in the private health care sector of South Africa

Objective: Biokinetics, a profession registered with the Health Professions Council of South Africa (HPCSA), address inter alia chronic diseases of lifestyle (CDL) with exercise as treatment modality. The purpose of this investigation is to determine the potential market demand for biokinetic services in the private health care sector of South Africa. Methods: Data from a pharmaceutical benefit management system (PBM) were analysed to determine the prevalence of chronic diseases in the private health care sector for 2007. Telephonic interviews on a sub-sample of 50 biokineticists revealed the average number of patients that can be treated monthly per biokineticist. The number of biokineticists with active practice numbers was obtained from the Board of Health Care Funders (BHF). Results: The results indicate that 47% (747 199/1 600 000) of the patients managed by the PBM are treated with medication for one or more CDL. Non-steroid anti-inflammatory medication (21%), medication for cardiovascular diseases (13%) and bronchodilators (11%) had the highest prevalence. The sub-sample of biokineticists indicated that one biokineticist can treat an average of 100 patients per month. The potential market demand calculated from the above numbers indicated that 7 472 biokineticists are needed in the private health care sector, while only 625 active practice numbers were registered with the BHF in 2007.Conclusion: In conclusion, it is estimated that only 7.6% of patients with CDL can potentially be treated by the current number of registered biokineticists. Therefore an enormous market potential for biokinetics exists in the private health care sector of South Africa.

Borrelidin modulates the alternative splicing of VEGF in favour of anti-angiogenic isoforms

The polyketide natural product borrelidin 1 is a potent inhibitor of angiogenesis and spontaneous metastasis. Affinity biopanning of a phage display library of colon tumor cell cDNAs identified the tandem WW domains of spliceosome-associated protein formin binding protein 21 (FBP21) as a novel molecular target of borrelidin, suggesting that borrelidin may act as a modulator of alternative splicing. In support of this idea, 1, and its more selective analog 2, bound to purified recombinant WW domains of FBP21. They also altered the ratio of vascular endothelial growth factor (VEGF) isoforms in retinal pigmented endothelial (RPE) cells in favour of anti-angiogenic isoforms. Transfection of RPE cells with FBP21 altered the ratio in favour of pro-angiogenic VEGF isoforms, an effect inhibited by 2. These data implicate FBP21 in the regulation of alternative splicing and suggest the potential of borrelidin analogs as tools to deconvolute key steps of spliceosome function.

An expeditious route to fluorinated rapamycin analogues by utilising mutasynthesis

Rapamycin is a drug with several important clinical uses. Its complex structure means that total synthesis of this natural product and its analogues is demanding and lengthy. A more expeditious approach is to utilise biosynthesis to enable the generation of otherwise synthetically intractable analogues. In order to achieve this, rules governing biosynthetic precursor substrate preference must be established. Through determining these rules and synthesising and administering suitable substrate precursors, we demonstrate the first generation of fluorinated rapamycin analogues. Here we report the generation of six new fluororapamycins.

Changes in coronary heart disease risk profile of adults with intellectual disabilities following a physical activity intervention

BACKGROUND

Regular physical activity is one of the modifiable risk factors for coronary heart disease (CHD). With an increasing age profile and similar patterns of morbidity to the general population, persons with intellectual disabilities (ID) and their caregivers would benefit from data that indicate CHD risk factors. Knowledge of the CHD risk factors and the changes a physical activity intervention may have on theses risk factors will facilitate future intervention programmes.

METHODS

A cohort of 100 men and women between the ages of 21 and 73 years with ID living in a community group home in the North-West Province of South Africa was recruited. A CHD risk profile was compiled by means of a questionnaire and physical assessment that included resting blood pressure, body mass index, non-fasting glucose and cholesterol and cardiorespiratory fitness. A 12-week physical activity intervention was then conducted 3 days/week after which the baseline measurements were repeated.

RESULTS

The results indicated that 85% of the participants were inactive, while 67% were overweight and obese. Hypertension (6.1%) and smoking (6.1%) were relatively low in this population with ID. Glucose concentrations above the recommended cut-off values were observed in 28% of the participants. Total cholesterol concentrations above normal were measured in 23% of the participants. The physical activity intervention reduced inactivity to 50% and resulted in a significant increase in cardiorespiratory fitness and a decrease in percentage body fat in both men and women.

CONCLUSION

Inactivity is a major risk factor in this population with ID living in a community group setting. The implementation of the physical activity intervention significantly reduced the risk factors for CHD.

Optimizing natural products by biosynthetic engineering: discovery of nonquinone Hsp90 inhibitors

A biosynthetic medicinal chemistry approach was applied to the optimization of the natural product Hsp90 inhibitor macbecin. By genetic engineering, mutants have been created to produce novel macbecin analogues including a nonquinone compound (5) that has significantly improved binding affinity to Hsp90 (Kd 3 nM vs 240 nM for macbecin) and reduced toxicity (MTD > or = 250 mg/kg). Structural flexibility may contribute to the preorganization of 5 to exist in solution in the Hsp90-bound conformation.

Separation of anti-angiogenic and cytotoxic activities of borrelidin by modification at the C17 side chain

A set of novel borrelidin analogues have been prepared by precursor-directed biosynthesis. Structure-activity relationship analysis suggests that steric structural arrangement within the C17 side chain is important for differentiating cytotoxic and anti-angiogenic activities. A C17-cyclobutyl analogue 3 was found to have markedly increased selectivity for in vitro angiogenesis inhibition over cytotoxicity and is therefore potentially useful as an anticancer agent.

On the Biosynthetic Origin of Methoxymalonyl-Acyl Carrier Protein, the Substrate for Incorporation of “Glycolate” Units into Ansamitocin and Soraphen A

Feeding experiments with isotope-labeled precursors rule out hydroxypyruvate and TCA cycle intermediates as the metabolic source of methoxymalonyl-ACP, the substrate for incorporation of "glycolate" units into ansamitocin P-3, soraphen A, and other antibiotics. They point to 1,3-bisphosphoglycerate as the source of the methoxymalonyl moiety and show that its C-1 gives rise to the thioester carbonyl group (and hence C-1 of the "glycolate" unit), and its C-3 becomes the free carboxyl group of methoxymalonyl-ACP, which is lost in the subsequent Claisen condensation on the type I modular polyketide synthases (PKS). d-[1,2-(13)C(2)]Glycerate is also incorporated specifically into the "glycolate" units of soraphen A, but not of ansamitocin P-3, suggesting differences in the ability of the producing organisms to activate glycerate. A biosynthetic pathway from 1,3-bisphosphoglycerate to methoxymalonyl-ACP is proposed. Two new syntheses of R- and S-[1,2-(13)C(2)]glycerol were developed as part of this work.

Biosynthesis of the angiogenesis inhibitor borrelidin: directed biosynthesis of novel analogues

We report the directed biosynthesis of borrelidin analogues and their selective anti-proliferative activity against human cancer cell lines.

Generating rapamycin analogues by directed biosynthesis: starter acid substrate specificity of mono-substituted cyclohexane carboxylic acids

We report a convenient synthesis of 4-fluorocyclohexanoic acid, and an insight into the rules governing acceptance of starter acid analogues in the precursor-directed biosynthesis of rapamycin.

Biosynthetic engineering of natural products for lead optimization and development

It is now possible to rapidly and rationally modify, at a genetic level, the machinery responsible for natural product biosynthesis. This provides the opportunity to design new structures and to optimize natural product lead compounds in a way that would be extremely difficult through synthetic chemistry means alone. The technology can also be used to overcome limitations of compound supply, which might otherwise preclude natural products from progressing into clinical trials. Described herein are some recent examples which highlight how biosynthetic engineering has been applied to drug discovery and development, and which attempt, in particular, to demonstrate how the technology functions most effectively when combined with synthetic organic and medicinal chemistry.

Towards safer neonatal transfer: the importance of critical incident review

BACKGROUND

Critical incidents are common during the inter-hospital transfer of sick patients, and infants are an especially vulnerable group.

AIMS

To examine the effect of critical incident review on the number of adverse events during inter-hospital transfer of sick infants.

METHODS

Critical incidents over an eight year period are reported from a single neonatal transfer service before and after major service changes were made. The changes were instigated as part of ongoing critical incident reviews.

RESULTS

Changes made as a result of critical incident review significantly reduced the number of incidents contributed to by poor preparation, transport equipment or clinical problems, ambulance delays, and ambulance equipment failure.

CONCLUSIONS

The continuous process of critical incident reporting and review can reduce the number of adverse events during the transfer of critically ill infants.

Biosynthesis of the angiogenesis inhibitor borrelidin by Streptomyces parvulus Tü4055: insights into nitrile formation

The 18-membered polyketide macrolide borrelidin exhibits a number of important biological activities, including potent angiogenesis inhibition. This has prompted two recent total syntheses as well as the cloning of the biosynthetic gene cluster from Streptomyces parvulus Tü4055. Borrelidin possesses some unusual structural characteristics, including a cyclopentane carboxylic acid moiety at C17 and a nitrile moiety at C12 of the macrocyclic ring. Nitrile groups are relatively rare in nature, and little is known of their biosynthesis during secondary metabolism. The nitrile group of borrelidin is shown here to arise from the methyl group of a methylmalonyl-CoA extender unit incorporated during polyketide chain extension. Insertional inactivation of two genes in the borrelidin gene cluster, borI (coding for a cytochrome P450 monooxygenase) and borJ (coding for an aminotransferase), generated borrelidin non-producing mutants. These mutants accumulated different compounds lacking the C12 nitrile moiety, with the product of the borI-minus mutant (12-desnitrile-12-methyl-borrelidin) possessing a methyl group and that of the borJ-minus mutant (12-desnitrile-12-carboxyl-borrelidin) a carboxyl group at C12. The former but not the latter was converted into borrelidin when biotransformed by an S. parvulus mutant that is deficient in the biosynthesis of the borrelidin starter unit. This suggests that 12-desnitrile-12-methyl-borrelidin is a competent biosynthetic intermediate, whereas the carboxylated derivative is a shunt metabolite. Bioconversion of 12-desnitrile-12-methyl-borrelidin into borrelidin was also achieved in a heterologous system co-expressing borI and borJ in Streptomyces albus J1074. This bioconversion was more efficient when borK, which is believed to encode a dehydrogenase, was simultaneously expressed with borI and borJ. On the basis of these findings, a pathway is proposed for the formation of the nitrile moiety during borrelidin biosynthesis.

Biosynthesis of the angiogenesis inhibitor borrelidin by Streptomyces parvulus Tü4055: cluster analysis and assignment of functions

The biosynthetic gene cluster for the angiogenesis inhibitor borrelidin has been cloned from Streptomyces parvulus Tü4055. Sequence analysis indicates that the macrolide ring of borrelidin is formed by a modular polyketide synthase (PKS) (borA1-A6), a result that was confirmed by disruption of borA3. The borrelidin PKS is striking because only seven rather than the nine modules expected for a nonaketide product are encoded by borA1-A6. The starter unit of the PKS has been verified as trans-cyclopentane-1,2-dicarboxylic acid (trans-1,2-CPDA), and the genes involved in its biosynthesis identified. Other genes responsible for biosynthesis of the nitrile moiety, regulation, and self-resistance were also identified.

Loss of co-linearity by modular polyketide synthases: a mechanism for the evolution of chemical diversity

Modular polyketide synthases biosynthesise natural products through successive Claisen-type condensations, where one module is responsible for one round of chain extension. This review describes recent findings where this rule of co-linearity is broken, either by one module being bypassed (skipping) or through one module being used for multiple chain extension events (stuttering).

Evidence from engineered gene fusions for the repeated use of a module in a modular polyketide synthase

Functional evidence for programmed loss of co-linearity on the borrelidin modular polyketide synthase (PKS) is presented.

Identification of asm19 as an acyltransferase attaching the biologically essential ester side chain of ansamitocins using N-desmethyl-4,5-desepoxymaytansinol, not maytansinol, as its substrate

The potent antitumor activity of the ansamitocins, polyketides isolated from Actinosynnema pretiosum, is absolutely dependent on a short acyl group esterified to the C-3 oxygen of the macrolactam ring. Asm19, a gene in the ansamitocin biosynthetic gene cluster with homology to macrolide O-acyltransferase genes, is thought to encode the enzyme catalyzing this esterification. A mutant carrying an inactivated asm19 no longer produced ansamitocins but accumulated N-desmethyl-4,5-desepoxymaytansinol, rather than maytansinol, indicating that the acylation is not the terminal step of the biosynthetic sequence. Bioconversion experiments and in vitro studies with recombinant Asm19, expressed in Escherichia coli, showed that the enzyme is very specific toward its alcohol substrate, converting N-desmethyl-4,5-desepoxymaytansinol (but not maytansinol) into ansamitocins, but rather promiscuous toward its acyl substrate, utilizing acetyl-, propionyl-, butyryl-, isobutyryl-, as well as isovaleryl-CoA.

The biosynthetic gene cluster of the maytansinoid antitumor agent ansamitocin from Actinosynnema pretiosum

Maytansinoids are potent antitumor agents found in plants and microorganisms. To elucidate their biosynthesis at the biochemical and genetic level and to set the stage for their structure modification through genetic engineering, we have cloned two gene clusters required for the biosynthesis of the maytansinoid, ansamitocin, from a cosmid library of Actinosynnema pretiosum ssp. auranticum ATCC 31565. This is a rare case in which the genes involved in the formation of a secondary metabolite are dispersed in separate regions in an Actinomycete. A set of genes, asm22-24, asm43-45, and asm47, was identified for the biosynthesis of the starter unit, 3-amino-5-hydroxybenzoic acid (AHBA). Remarkably, there are two AHBA synthase gene homologues, which may have different functions in AHBA formation. Four type I polyketide synthase genes, asmA-D, followed by the downloading asm9, together encode eight homologous sets of enzyme activities (modules), each catalyzing a specific round of chain initiation, elongation, or termination steps, which assemble the ansamitocin polyketide backbone. Another set of genes, asm13-17, encodes the formation of an unusual "methoxymalonate" polyketide chain extension unit that, notably, seems to be synthesized on a dedicated acyl carrier protein rather than as a CoA thioester. Additional ORFs are involved in postsynthetic modifications of the initial polyketide synthase product, which include methylations, an epoxidation, an aromatic chlorination, and the introduction of acyl and carbamoyl groups. Tentative functions of several asm genes were confirmed by inactivation and heterologous expression.

Cyclic AMP-dependent protein kinase phosphorylation facilitates GABA(B) receptor-effector coupling

GABA (gamma-aminobutyric acid)(B) receptors are heterodimeric G protein-coupled receptors that mediate slow synaptic inhibition in the central nervous system. Here we show that the functional coupling of GABA(B)R1/GABA(B)R2 receptors to inwardly rectifying K(+) channels rapidly desensitizes. This effect is alleviated after direct phosphorylation of a single serine residue (Ser892) in the cytoplasmic tail of GABA(B)R2 by cyclic AMP (cAMP)-dependent protein kinase (PKA). Basal phosphorylation of this residue is evident in rat brain membranes and in cultured neurons. Phosphorylation of Ser892 is modulated positively by pathways that elevate cAMP concentration, such as those involving forskolin and beta-adrenergic receptors. GABA(B) receptor agonists reduce receptor phosphorylation, which is consistent with PKA functioning in the control of GABA(B)-activated currents. Mechanistically, phosphorylation of Ser892 specifically enhances the membrane stability of GABA(B) receptors. We conclude that signaling pathways that activate PKA may have profound effects on GABA(B) receptor-mediated synaptic inhibition. These results also challenge the accepted view that phosphorylation is a universal negative modulator of G protein-coupled receptors.

Identification of a set of genes involved in the formation of the substrate for the incorporation of the unusual "glycolate" chain extension unit in ansamitocin biosynthesis

The unusual "glycolate" extender unit at C-9/C-10 of ansamitocin is not derived from 2-hydroxymalonyl-CoA or 2-methoxymalonyl-CoA, as demonstrated by feeding experiments with the corresponding 1-13C-labeled N-acetylcysteamine thioesters but is formed from an acyl carrier protein (ACP)-bound substrate, possibly 2-methoxymalonyl-ACP, elaborated by enzymes encoded by a subcluster of five genes, asm12-17, from the ansamitocin bisosynthetic gene cluster.

3-acetylpyridine reduces tongue protrusion force but does not abolish lick rhythm in the rat

Data from other laboratories suggest that neurons in the inferior olivary nucleus (IO) may play a role in the modulation of rhythmic tongue movements in rats. Because of its known harmful effects on neurons of the IO, it was suspected that administration of the neurotoxin 3-acetylpyridine (3AP) would affect subsequent tongue dynamics during rat licking. In the present study, the task of licking water from a force-transducing disk was investigated in water-restricted rats that received systemic administration of 3AP (12.5, 25, and 50 mg/kg). After recovery from the acute toxic effects of 3AP, tongue dynamics were assessed by measuring lick force, lick rhythm, variability of timing within bursts of licking, and number of licks per 2-min session. At 50 mg/kg, 3AP resulted in: (1) reduced lick force; (2) reduced number of licks; and (3) increased variance in the timing within bursts. Lick rhythm was not significantly affected by any dose of 3AP. All 3AP treatment groups and the vehicle control group displayed slowing of lick rhythm after harmaline challenge. Compared to vehicle controls, rats receiving lower and mid-range doses of 3AP displayed indistinguishable lick behaviors, with one exception--when the lick task was made incrementally more difficult by extending the distance required to make contact with the lick-disk, rats that had received 25 mg/kg 3AP persevered at the task more than all other rats. The various changes in lick dynamics may be due to the detrimental effects of 3AP at the IO, and possibly at the hypoglossal nucleus and other sites.

Comparison of two intracranial self-stimulation (ICSS) paradigms in C57BL/6 mice: head-dipping and place-learning

A variety of intracranial self-stimulation (ICSS) paradigms have been utilized for investigations of reward. Among them, nose-poking and spatial-preference paradigms are known to be relatively more resistant to the effects of drug-induced motor-deficits in rat studies, although these two ICSS paradigms have not been directly compared in previous studies. In the present study, head-dipping and place-learning (forms of nose-poking and spatial-preference tasks, respectively) paradigms with lateral hypothalamus stimulation were systematically analyzed using C57BL/6 mice in the presence and absence of two motor-deficit-inducing drugs: tolperisone and harmaline. Rapid acquisition and rapid extinction patterns of ICSS responding were observed in the head-dipping and place-learning paradigms. In contrast to these pre-drug similarities in responding, dramatic differences were noted after drug administration. Tolperisone significantly reduced head-dipping but not place-learning ICSS responding. Similarly, reduction of ICSS responding after harmaline was more pronounced in the head-dipping task. Therefore, the place-learning paradigm may be superior for the assessment of reward values under motor-deficit-inducing conditions in C57BL/6 mice. The relative benefits and disadvantages of both ICSS paradigms are discussed. Combinations of complementary ICSS paradigms using mice may be useful for further investigations of the molecular bases of reward.

Constitutive tyrosine phosphorylation of the GABA(A) receptor gamma 2 subunit in rat brain

GABA(A) receptors are the major sites of fast synaptic inhibition in the brain, where they are predominantly composed of alpha, beta and gamma2 subunits. A role for direct tyrosine phosphorylation of residues 365 and 367 (Y365/367) within the intracellular domain of the gamma2 subunit has been suggested to be important in modulating GABA(A) receptor function, based on the study of recombinant receptors. To address the relevance of these observations for neuronal GABA(A) receptors we have studied the phosphorylation of the gamma2 subunit in the brain. In adult rat brain the gamma2 subunit is phosphorylated on tyrosine residues, including Y365/367 as defined using a phosphospecific antisera. In cultured cortical neurones, phosphorylation of Y365/367 is highly regulated and was only evident upon inhibition of tyrosine phosphatases. We also establish that the tyrosine kinase Src is capable of specifically interacting with the intracellular domains of receptor beta and gamma2 subunits. This may specifically localise tyrosine kinase activity to GABA(A) receptors, facilitating rapid receptor tyrosine phosphorylation upon kinase activation. Together our results suggests that tyrosine phosphorylation of the gamma2 subunit, possibly by closely associated Src, may be a dynamic mechanism for regulating GABA(A) receptor function in the brain.

GABA(B2) is essential for g-protein coupling of the GABA(B) receptor heterodimer

GABA(B) receptors are unique among G-protein-coupled receptors (GPCRs) in their requirement for heterodimerization between two homologous subunits, GABA(B1) and GABA(B2), for functional expression. Whereas GABA(B1) is capable of binding receptor agonists and antagonists, the role of each GABA(B) subunit in receptor signaling is unknown. Here we identified amino acid residues within the second intracellular domain of GABA(B2) that are critical for the coupling of GABA(B) receptor heterodimers to their downstream effector systems. Our results provide strong evidence for a functional role of the GABA(B2) subunit in G-protein coupling of the GABA(B) receptor heterodimer. In addition, they provide evidence for a novel "sequential" GPCR signaling mechanism in which ligand binding to one heterodimer subunit can induce signal transduction through the second partner of a heteromeric complex.

Isolation of an aldehyde dehydrogenase involved in the oxidation of fluoroacetaldehyde to fluoroacetate in Streptomyces cattleya

Streptomyces cattleya is unusual in that it produces fluoroacetate and 4-fluorothreonine as secondary metabolites. We now report the isolation of an NAD(+)-dependent fluoroacetaldehyde dehydrogenase from S. cattleya that mediates the oxidation of fluoroacetaldehyde to fluoroacetate. This is the first enzyme to be identified that is directly involved in fluorometabolite biosynthesis. Production of the enzyme begins in late exponential growth and continues into the stationary phase. Measurement of kinetic parameters shows that the enzyme has a high affinity for fluoroacetaldehyde and glycoaldehyde, but not acetaldehyde.

GABA(A) receptor cell surface number and subunit stability are regulated by the ubiquitin-like protein Plic-1

Controlling the number of functional gamma-aminobutyric acid A (GABA(A)) receptors in neuronal membranes is a crucial factor for the efficacy of inhibitory neurotransmission. Here we describe the direct interaction of GABA(A) receptors with the ubiquitin-like protein Plic-1. Furthermore, Plic-1 is enriched at inhibitory synapses and is associated with subsynaptic membranes. Functionally, Plic-1 facilitates GABA(A) receptor cell surface expression without affecting the rate of receptor internalization. Plic-1 also enhances the stability of intracellular GABA(A) receptor subunits, increasing the number of receptors available for insertion into the plasma membrane. Our study identifies a previously unknown role for Plic-1, a modulation of GABA(A) receptor cell surface number, which suggests that Plic-1 facilitates accumulation of these receptors in dendritic membranes.

Fibrin network structure. Changes in characteristics in response to physical activity in combination with a pre-exercise meal

The metabolic environment determines the characteristics of fibrin network structure (FNS) in plasma. Physical activity or changes in the diet (e.g., high and low glycemic index meals) can initiate these changes. The FNS were measured by means of mass-length ratio, turbidity, and compaction of the plasma obtained from male subjects. Samples were taken before and after the introduction of the different diets and physical activity. The results indicate that changes in the FNS do occur, but further investigation is required to obtain conclusive results.

Neurotransmitter receptor trafficking and the regulation of synaptic strength

Modulation of the strength of synapses is thought to be one of the mechanisms that underlies learning and memory and is also likely to be important in processes of neuropathology and drug tolerance. This review focuses on the emerging role of postsynaptic neurotransmitter receptor trafficking as an essential mechanism underlying the dynamic regulation of synaptic strength.