Rhinitis associated with asthma is distinct from rhinitis alone: The ARIA-MeDALL hypothesis

Asthma, rhinitis and atopic dermatitis (AD) are interrelated clinical phenotypes that partly overlap in the human interactome. The concept of "one-airway-one-disease", coined over 20 years ago, is a simplistic approach of the links between upper- and lower-airway allergic diseases. With new data, it is time to reassess the concept. This article reviews (i) the clinical observations that led to Allergic Rhinitis and its Impact on Asthma (ARIA), (ii) new insights into polysensitisation and multimorbidity, (iii) advances in mHealth for novel phenotype definition, (iv) confirmation in canonical epidemiologic studies, (v) genomic findings, (vi) treatment approaches and (vii) novel concepts on the onset of rhinitis and multimorbidity. One recent concept, bringing together upper- and lower-airway allergic diseases with skin, gut and neuropsychiatric multimorbidities, is the "Epithelial Barrier Hypothesis". This review determined that the "one-airway-one-disease" concept does not always hold true and that several phenotypes of disease can be defined. These phenotypes include an extreme "allergic" (asthma) phenotype combining asthma, rhinitis and conjunctivitis. Rhinitis alone and rhinitis and asthma multimorbidity represent two distinct diseases with the following differences: (i) genomic and transcriptomic background (Toll-Like Receptors and IL-17 for rhinitis alone as a local disease; IL-33 and IL-5 for allergic and non-allergic multimorbidity as a systemic disease), (ii) allergen sensitisation patterns (mono- or pauci-sensitisation versus polysensitisation), (iii) severity of symptoms and (iv) treatment response. In conclusion, rhinitis alone (local disease) and rhinitis with asthma multimorbidity (systemic disease) should be considered as two distinct diseases, possibly modulated by the microbiome, and may be a model for understanding the epidemics of chronic and auto-immune diseases.

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

Background

The ongoing outbreak of the recently emerged novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable while there is growing evidence that the outbreak is more widespread than initially thought, and international spread through travellers does already occur.

Aim

We aimed to develop and deploy robust diagnostic methodology for use in public health laboratory settings without having virus material available.

Methods

Here we present a validated diagnostic workflow for 2019-nCoV, its design relying on close genetic relatedness of 2019-nCoV with SARS coronavirus, making use of synthetic nucleic acid technology.

Results

The workflow reliably detects 2019-nCoV, and further discriminates 2019-nCoV from SARS-CoV. Through coordination between academic and public laboratories, we confirmed assay exclusivity based on 297 original clinical specimens containing a full spectrum of human respiratory viruses. Control material is made available through European Virus Archive – Global (EVAg), a European Union infrastructure project.

Conclusion

The present study demonstrates the enormous response capacity achieved through coordination of academic and public laboratories in national and European research networks.

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

BACKGROUND

The ongoing outbreak of the recently emerged novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable while there is growing evidence that the outbreak is more widespread than initially thought, and international spread through travellers does already occur.

AIM

We aimed to develop and deploy robust diagnostic methodology for use in public health laboratory settings without having virus material available.

METHODS

Here we present a validated diagnostic workflow for 2019-nCoV, its design relying on close genetic relatedness of 2019-nCoV with SARS coronavirus, making use of synthetic nucleic acid technology.

RESULTS

The workflow reliably detects 2019-nCoV, and further discriminates 2019-nCoV from SARS-CoV. Through coordination between academic and public laboratories, we confirmed assay exclusivity based on 297 original clinical specimens containing a full spectrum of human respiratory viruses. Control material is made available through European Virus Archive - Global (EVAg), a European Union infrastructure project.

CONCLUSION

The present study demonstrates the enormous response capacity achieved through coordination of academic and public laboratories in national and European research networks.

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

BACKGROUND

The ongoing outbreak of the recently emerged novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable while there is growing evidence that the outbreak is more widespread than initially thought, and international spread through travellers does already occur.

AIM

We aimed to develop and deploy robust diagnostic methodology for use in public health laboratory settings without having virus material available.

METHODS

Here we present a validated diagnostic workflow for 2019-nCoV, its design relying on close genetic relatedness of 2019-nCoV with SARS coronavirus, making use of synthetic nucleic acid technology.

RESULTS

The workflow reliably detects 2019-nCoV, and further discriminates 2019-nCoV from SARS-CoV. Through coordination between academic and public laboratories, we confirmed assay exclusivity based on 297 original clinical specimens containing a full spectrum of human respiratory viruses. Control material is made available through European Virus Archive - Global (EVAg), a European Union infrastructure project.

CONCLUSION

The present study demonstrates the enormous response capacity achieved through coordination of academic and public laboratories in national and European research networks.

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

BACKGROUND

The ongoing outbreak of the recently emerged novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable while there is growing evidence that the outbreak is more widespread than initially thought, and international spread through travellers does already occur.

AIM

We aimed to develop and deploy robust diagnostic methodology for use in public health laboratory settings without having virus material available.

METHODS

Here we present a validated diagnostic workflow for 2019-nCoV, its design relying on close genetic relatedness of 2019-nCoV with SARS coronavirus, making use of synthetic nucleic acid technology.

RESULTS

The workflow reliably detects 2019-nCoV, and further discriminates 2019-nCoV from SARS-CoV. Through coordination between academic and public laboratories, we confirmed assay exclusivity based on 297 original clinical specimens containing a full spectrum of human respiratory viruses. Control material is made available through European Virus Archive - Global (EVAg), a European Union infrastructure project.

CONCLUSION

The present study demonstrates the enormous response capacity achieved through coordination of academic and public laboratories in national and European research networks.

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

BACKGROUND

The ongoing outbreak of the recently emerged novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable while there is growing evidence that the outbreak is more widespread than initially thought, and international spread through travellers does already occur.

AIM

We aimed to develop and deploy robust diagnostic methodology for use in public health laboratory settings without having virus material available.

METHODS

Here we present a validated diagnostic workflow for 2019-nCoV, its design relying on close genetic relatedness of 2019-nCoV with SARS coronavirus, making use of synthetic nucleic acid technology.

RESULTS

The workflow reliably detects 2019-nCoV, and further discriminates 2019-nCoV from SARS-CoV. Through coordination between academic and public laboratories, we confirmed assay exclusivity based on 297 original clinical specimens containing a full spectrum of human respiratory viruses. Control material is made available through European Virus Archive - Global (EVAg), a European Union infrastructure project.

CONCLUSION

The present study demonstrates the enormous response capacity achieved through coordination of academic and public laboratories in national and European research networks.

Lack of serological evidence of Middle East respiratory syndrome coronavirus infection in virus exposed camel abattoir workers in Nigeria, 2016

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic threat of global public health concern and dromedary camels are the source of zoonotic infection. Although MERS-CoV is enzootic in dromedaries in Africa as well as the Middle East, zoonotic disease has not been reported in Africa. Methods: In an abattoir in Kano, Nigeria, we tested nasal swabs from camels and investigated 261 humans with repeated occupational exposure to camels, many of whom also reported drinking fresh camel milk (n = 138) or urine (n = 94) or using camel urine for medicinal purposes (n = 96). Results: Weekly MERS-CoV RNA detection in January–February 2016 ranged from 0–8.4% of camels sampled. None of the abattoir workers with exposure to camels had evidence of neutralising antibody to MERS-CoV. Conclusion: There is a need for more studies to investigate whether or not zoonotic transmission of MERS-CoV does take place in Africa.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in Dromedary Camels in Africa and Middle East

Dromedary camels are the natural reservoirs of the Middle East respiratory syndrome coronavirus (MERS-CoV). Camels are mostly bred in East African countries then exported into Africa and Middle East for consumption. To understand the distribution of MERS-CoV among camels in North Africa and the Middle East, we conducted surveillance in Egypt, Senegal, Tunisia, Uganda, Jordan, Saudi Arabia, and Iraq. We also performed longitudinal studies of three camel herds in Egypt and Jordan to elucidate MERS-CoV infection and transmission. Between 2016 and 2018, a total of 4027 nasal swabs and 3267 serum samples were collected from all countries. Real- time PCR revealed that MERS-CoV RNA was detected in nasal swab samples from Egypt, Senegal, Tunisia, and Saudi Arabia. Microneutralization assay showed that antibodies were detected in all countries. Positive PCR samples were partially sequenced, and a phylogenetic tree was built. The tree suggested that all sequences are of clade C and sequences from camels in Egypt formed a separate group from previously published sequences. Longitudinal studies showed high seroprevalence in adult camels. These results indicate the widespread distribution of the virus in camels. A systematic active surveillance and longitudinal studies for MERS-CoV are needed to understand the epidemiology of the disease and dynamics of viral infection.

Guidance to 2018 good practice: ARIA digitally-enabled, integrated, person-centred care for rhinitis and asthma

Aims

Mobile Airways Sentinel NetworK (MASK) belongs to the Fondation Partenariale MACVIA-LR of Montpellier, France and aims to provide an active and healthy life to rhinitis sufferers and to those with asthma multimorbidity across the life cycle, whatever their gender or socio-economic status, in order to reduce health and social inequities incurred by the disease and to improve the digital transformation of health and care. The ultimate goal is to change the management strategy in chronic diseases.

Methods

MASK implements ICT technologies for individualized and predictive medicine to develop novel care pathways by a multi-disciplinary group centred around the patients.

Stakeholders

Include patients, health care professionals (pharmacists and physicians), authorities, patient’s associations, private and public sectors.

Results

MASK is deployed in 23 countries and 17 languages. 26,000 users have registered.

EU grants (2018)

MASK is participating in EU projects (POLLAR: impact of air POLLution in Asthma and Rhinitis, EIT Health, DigitalHealthEurope, Euriphi and Vigour).

Lessons learnt

(i) Adherence to treatment is the major problem of allergic disease, (ii) Self-management strategies should be considerably expanded (behavioural), (iii) Change management is essential in allergic diseases, (iv) Education strategies should be reconsidered using a patient-centred approach and (v) Lessons learnt for allergic diseases can be expanded to chronic diseases.

Cohort profile: the China Ageing REespiratory infections Study (CARES), a prospective cohort study in older adults in Eastern China

PURPOSE

This study was established to provide direct evidence on the incidence of laboratory-confirmed influenza virus and respiratory syncytial virus (RSV) infections in older adults in two cities in Jiangsu Province, China, and the potential impact of acute respiratory infections on frailty.

PARTICIPANTS

The cohort was enrolled in Suzhou and Yancheng, two cities in Jiangsu Province in Eastern China. Between November 2015 and March 2016, we enrolled 1532 adults who were 60-89 years of age, and collected blood samples along with baseline data on demographics, general health, chronic diseases, functional status and cognitive function through face-to-face interviews using a standardised questionnaire. Participants are being followed weekly throughout the year to identify acute respiratory illnesses. We schedule home visits to ill participants to collect mid-turbinate nasal and oropharyngeal swabs for laboratory testing and detailed symptom information for the acute illness. Regular follow-up including face-to-face interviews and further blood draws will take place every 6-12 months.

FINDINGS TO DATE

As of 3 September 2016, we had identified 339 qualifying acute respiratory illness events and 1463 (95%) participants remained in the study. Laboratory testing is ongoing.

FUTURE PLANS

We plan to conduct laboratory testing to estimate the incidence of influenza virus and RSV infections in older adults. We plan to investigate the impact of these infections on frailty and functional status to determine the association of pre-existing immune status with protection against influenza and RSV infection in unvaccinated older adults, and to assess the exposure to avian influenza viruses in this population.

Longitudinal study of Middle East Respiratory Syndrome coronavirus infection in dromedary camel herds in Saudi Arabia, 2014-2015

Two herds of dromedary camels were longitudinally sampled with nasal and rectal swabs and serum, between September 2014 and May 2015, and the samples were tested for Middle East Respiratory Syndrome (MERS) coronavirus RNA and antibodies. Evidence of MERS-CoV infection was confirmed in one herd on the basis of detection of virus RNA in nasal swabs from three camels and significant increases in the antibody titers from three others. The three viruses were genetically identical, thus indicating introduction of a single virus into this herd. There was evidence of reinfection of camels that were previously seropositive, thus suggesting that prior infection does not provide complete immunity from reinfection, a finding that is relevant to camel vaccination strategies as a means to prevent zoonotic transmission.

Risk factors for MERS coronavirus infection in dromedary camels in Burkina Faso, Ethiopia, and Morocco, 2015

Understanding Middle East respiratory syndrome coronavirus (MERS-CoV) transmission in dromedary camels is important, as they consitute a source of zoonotic infection to humans. To identify risk factors for MERS-CoV infection in camels bred in diverse conditions in Burkina Faso, Ethiopia and Morocco, blood samples and nasal swabs were sampled in February-March 2015. A relatively high MERS-CoV RNA rate was detected in Ethiopia (up to 15.7%; 95% confidence interval (CI): 8.2-28.0), followed by Burkina Faso (up to 12.2%; 95% CI: 7-20.4) and Morocco (up to 7.6%; 95% CI: 1.9-26.1). The RNA detection rate was higher in camels bred for milk or meat than in camels for transport (p = 0.01) as well as in younger camels (p = 0.06). High seropositivity rates (up to 100%; 95% CI: 100-100 and 99.4%; 95% CI: 95.4-99.9) were found in Morocco and Ethiopia, followed by Burkina Faso (up to 84.6%; 95% CI: 77.2-89.9). Seropositivity rates were higher in large/medium herds (≥51 camels) than small herds (p = 0.061), in camels raised for meat or milk than for transport (p = 0.01), and in nomadic or sedentary herds than in herds with a mix of these lifestyles (p < 0.005).

A determination of institutional and patient factors affecting uncompensated hospital care

For this study, a sample of 985 patients classified as "charity" and "bad debt" cases in 1986 were identified from 28 Indiana hospitals. In a multiple regression model, insurance coverage, total hospital charge, pregnancy-related diagnoses, marital status, employment status, discharge status, urban location, and total hospital revenue were significant factors in predicting unpaid hospital bills, when controlling other demographic characteristics. Sixty percent had some form of insurance and were responsible for 40 percent of the uncompensated amount, justifying the need to examine the adequacy of patient insurance coverage. However, providing insurance coverage will not entirely eliminate the problem of uncompensated care; hospitals also need to increase collection efforts for all unpaid bills.

The use of a break-even analysis: financial analysis of a fast-track program

OBJECTIVE

To calculate the financial break-even point and illustrate how changes in third-party reimbursement and eligibility could affect a program's fiscal standing.

METHODS

Demographic, clinical, and financial data were collected retrospectively for 446 patients treated in a fast-track program during June 1993. The fast-track program is located within the confines of the emergency medicine and trauma center at a 1,050-bed tertiary care Midwestern teaching hospital and provides urgent treatment to minimally ill patients. A financial break-even analysis was performed to determine the point where the program generated enough revenue to cover its total variable and fixed costs, both direct and indirect.

RESULTS

Given the relatively low average collection rate (62%) and high percentage of uninsured patients (31%), the analysis showed that the program's revenues covered its direct costs but not all of the indirect costs.

CONCLUSIONS

Examining collection rates or payer class mix without examining both costs and revenues may lead to an erroneous conclusion about a program's fiscal viability. Sensitivity analysis also shows that relatively small changes in third-party coverage or eligibility (income) requirements can have a large impact on the program's financial solvency and break-even volumes.

Microsampling homogeneous immunoassay with Cedia digoxin reagents on the Technicon CHEM 1 chemistry analyzer

We report the determination of digoxin concentration in serum with Microgenics Cedia digoxin reagents on the Technicon CHEM 1. The Technicon CHEM 1 clinical chemistry analyzer has a throughput of 720 tests per hour and uses only 7 microliters each of two reagents. A 100 test kit can perform 2,640 tests. The within-run coefficient of variation (CV) range is 2.3-0.9% and the total CV is 6.3-2.9% at concentrations tested ranging from 1.10 to 2.94 ng/ml. The results of the Technicon CHEM 1 (y) assay correlated well with those by the Technicon RA 1000 system (x) with 31 clinical serum samples (y = -0.03 + 1.11x, r = 0.96). We concluded that the Cedia digoxin assay on the Technicon CHEM 1 provides a very cost-effective, precise, rapid, and accurate means to determine digoxin concentration in serum.

Economic development and the health care system in Hong Kong

This article describes parallel developments of the Hong Kong economy and its health care system. The purpose is to illustrate how the Hong Kong health system evolved in response to external and internal pressures generated by economic prosperity. The Hong Kong system illustrates the importance of clear policy making in the face of these pressures. In particular, issues of investment, financing and distribution of health services are examined in relation to hospital cost control and service accessibility. In the past, health care costs in Hong Kong have been controlled at the expense of limited accessibility of health services. At present, Hong Kong policy-makers are faced with the challenge of maintaining a sharp focus on cost control as they face pressure to expand and improve health care coverage for the citizens. So far they have responded by emphasizing management efficiency through reorganization. It remains to be seen whether this strategy can be successful without passing increased health care costs to the consumers.

Tangential fluoroscopic guidance of the anesthetizing needle during transthoracic needle lung biopsy: a randomized controlled clinical trial

The effectiveness of tangential fluoroscopic guidance of the anesthetizing needle to avoid transgression of the pleura and therefore lower pneumothorax and chest tube insertion rates after transthoracic needle lung biopsy (TNB) was investigated. Tangential guidance was used in 41 patients (group A) and was not used in 51 (group B). The pneumothorax rate was 39% (16 of 41) for group A and 31% (16 of 51) for group B. The chest tube insertion rate was 12% (five of 41) for group A and 4% (two of 51) for group B. None of the differences in rates were significant. Use of this technique does not lower pneumothorax or chest tube insertion rates in patients undergoing TNB.

Global budgeting of hospitals in Hong Kong

Policy-makers in industrialized countries face the dilemma of having to contain soaring hospital costs while resisting any reduction in the quality and quantity of hospital services. Among the many hospital financing systems, centralized control via global budgeting is advocated by some to be the most effective in containing hospital costs. Containing hospital costs, however, is but one aspect of the trade-off between cost containment and quality of care. The hospital financing system of Hong Kong provides some insights into the extent to which cost control can be achieved through global budgeting; and its impact on the accessibility of hospital care. The case of Hong Kong highlights three necessary conditions for effective cost control: (1) the payer must have a clear policy stance on overall public spending; (2) the payer must have a clear policy stance on the importance of hospital care relative to other goods and services; and (3) the payer must also have the will and ability to limit hospital spending within finalized global budgets. However, successful cost containment in Hong Kong affects the accessibility of hospital care. In a time of population growth and economic prosperity, new community needs seem to have preceded government plans and actions to build hospital facilities.

Uncompensated hospital care for pregnancy and childbirth cases

BACKGROUND

The large number of medically indigent patients in the United States is a major concern to policymakers and may be due to recent increases in the number of uninsured people. The purpose of this study was to identify the factors that affect the amount of unpaid hospital charges for services provided to pregnant women.

METHODS

Individual and hospital data were collected on a representative set of 235 pregnancy and childbirth patients with unpaid hospital charges from 28 hospitals in the state of Indiana.

RESULTS

Most of these patients did not have insurance coverage (63.8%), yet the majority were employed in the public or private sector (72.3%). Over half (55.5%) of the total uncompensated care amount for this group was from the $1000 to 2499 debt category. The median charge for these patients was $1468, of which the typical hospital was able to collect only 25.5%.

CONCLUSIONS

The findings support the belief that any national effort to expand the availability of health insurance coverage to women through increased employment will not totally eliminate the uncompensated care problem. The findings also indicate that rural hospitals face the uncompensated care problem mainly because a significant portion of rural patients are without adequate health insurance coverage.

The effect of centralized hospital administration on financial control and hospital service delivery: the case of Hong Kong

Administration, financial control and service delivery are three mutually influential dimensions of a hospital system. The centralized hospital system of Hong Kong is a case-in-point that illustrates such influence. By spending only a small fraction of the Gross Domestic Product each year, the government has been able to provide limited modern health care services at nominal financial cost to the public. At the same time, hospitals are subject to a strict system of administrative and financial controls. Consequently, Hong Kong hospitals must utilize their limited facilities effectively to provide modern health services to the public. However, the trade-off between low-cost health services and limited facilities is the incurrence, by the public, of non-monetary costs in obtaining hospital admission.

Continuous-flow analysis for glucose in serum, with use of hexokinase and glucose-6-phosphate dehydrogenase co-immobilized in tubular form

Hexokinase and glucose-6-phosphate dehydrogenase, co-immobilized at the inner wall of plastic tubing, were used with continuous-flow analyzers to measure serum glucose. The performance of the enzyme-containing coils meets the hydraulic requirements of the continuous-flow instruments, and the average carryover does not exceed 2.2%. A glucose concentration change of 1 g/L yields a 0.08 change in absorbance. There is no significant deviation from linearity for glucose concentrations up to 5 g/L. The method is similar to the Reference Method proposed by the Food and Drug Administration, and results by the two methods agree and correlate well (r = 0.999). The operational stability of the enzyme tubes is sufficient to allow the analysis of at least 10 000 serum samples. We investigated in detail the effect of reagent concentrations and temperature on the performance of the enzyme coils, and the results shed light on the nature of the heterogeneous dual-enzymic reaction.

Continuous-flow analysis for glucose in serum, with use of hexokinase and glucose-6-phosphate dehydrogenase co-immobilized in tubular form

Hexokinase and glucose-6-phosphate dehydrogenase, co-immobilized at the inner wall of plastic tubing, were used with continuous-flow analyzers to measure serum glucose. The performance of the enzyme-containing coils meets the hydraulic requirements of the continuous-flow instruments, and the average carryover does not exceed 2.2%. A glucose concentration change of 1 g/L yields a 0.08 change in absorbance. There is no significant deviation from linearity for glucose concentrations up to 5 g/L. The method is similar to the Reference Method proposed by the Food and Drug Administration, and results by the two methods agree and correlate well (r = 0.999). The operational stability of the enzyme tubes is sufficient to allow the analysis of at least 10 000 serum samples. We investigated in detail the effect of reagent concentrations and temperature on the performance of the enzyme coils, and the results shed light on the nature of the heterogeneous dual-enzymic reaction.

Continuous-flow analysis for glucose in serum, with use of hexokinase and glucose-6-phosphate dehydrogenase co-immobilized in tubular form

Hexokinase and glucose-6-phosphate dehydrogenase, co-immobilized at the inner wall of plastic tubing, were used with continuous-flow analyzers to measure serum glucose. The performance of the enzyme-containing coils meets the hydraulic requirements of the continuous-flow instruments, and the average carryover does not exceed 2.2%. A glucose concentration change of 1 g/L yields a 0.08 change in absorbance. There is no significant deviation from linearity for glucose concentrations up to 5 g/L. The method is similar to the Reference Method proposed by the Food and Drug Administration, and results by the two methods agree and correlate well (r = 0.999). The operational stability of the enzyme tubes is sufficient to allow the analysis of at least 10 000 serum samples. We investigated in detail the effect of reagent concentrations and temperature on the performance of the enzyme coils, and the results shed light on the nature of the heterogeneous dual-enzymic reaction.

Regulation of ribulose 1,5-diphosphate carboxylase by substrates and other metabolites: further evidence for several types of binding sites

Ribulose 1,5-diphosphate carboxylase (RuDPCase, EC 4.1.1.39) isolated from spinach leaves is metabolically regulated at 10 mm Mg(2+) and low CO(2) concentrations by its substrates (RuDP and CO(2)) and by effectors which include 6-phosphogluconate (6-PGluA), NADPH, and fructose 1,6-diphosphate (FDP), but not fructose 6-phosphate. Physiological concentrations of RuDP severely inhibit the enzyme activity when the enzyme has not been preincubated with HCO(3) (-) and Mg(2-), and this inactivity persists for 20 minutes or longer after 1 mm HCO(3) (-) and 10 mm Mg(2+) are added. Maximum activity requires that the preincubation mixture also include either 0.01 mm 6-PGluA or 0.5 mm NADPH.When the enzyme, following preincubation with HCO(3) (-) and Mg(2+), is presented with RuDP plus either 6-PGluA or FDP, competitive inhibition is observed with respect to RuDP. The Ki value for 6-PGluA is 0.02 mm and the Ki value for FDP is 190 mum. NADPH or 3-phosphoglycerate (PGA) at physiological concentrations does not have any effect when presented simultaneously with RuDP. Other studies on the order of addition of substrates and effectors, concentration effects, and kinetics provide additional information that serves as a basis for a proposed model of allosteric regulation combined with competitive inhibition.In this model, there are catalytic sites at which the substrates and 6-PGluA and FDP can bind, and at least four allosteric regulatory sites, which we designate I, A(1), A(2), and A(3). RuDP binds very tightly to site I (in the absence of Mg(2+) or HCO(3) (-)), causing a conformational change in the protein to an inactive form which persists for as long as 20 minutes in the subsequent presence of Mg(2+) and 1 mm HCO(3) (-). Mg(2+) and HCO(3) (-) (or CO(2)) bind to site A(3) (in the absence of RuDP), holding the enzyme in an active form which has a much lower affinity for RuDP at site I, so that when physiological levels of RuDP are then added, only part of the enzyme activity is lost. This active form of the enzyme can bind 6-PGluA or FDP at site A(1) and NADPH at site A(2) during preincubation with Mg(2+) and HCO(3) (-). With optimal levels of bound effectors, 6-PGluA or NADPH, enzyme activity is fully maintained, even when RuDP is subsequently added. Without one of these effectors present, addition of RuDP following preincubation reduces enzyme activity to about 40% at the levels of substrates and effectors studied. FDP is a much poorer effector, and this is ascribed to a possible binding of FDP at site I, as well as at site A(1).The physiological role of this regulation is discussed, particularly with respect to protection of "C-3" plants against oxidation of RuDP to phosphoglycolate.

Activation of ribulose 1,5-diphosphate carboxylase by nicotinamide adenine dinucleotide phosphate and other chloroplast metabolites

Ribulose 1,5-diphosphate carboxylase, when activated by preincubation with 10 mm MgCl(2) and 1 mm bicarbonate in the absence of ribulose 1,5-diphosphate, can be further activated about 170% with 0.5 mm NADPH present in the preincubation mixture. NADP(+), NADH, and NAD(+) are ineffective. The activation by NADPH is comparable to that previously seen with 0.05 to 0.10 mm 6-phosphogluconate in that these specific preincubation conditions are required, but the effects of NADPH and 6-phosphogluconate are not additive. Moreover, where higher concentrations of 6-phosphogluconate inhibited the enzyme, higher concentrations of NADPH give a greater activation, saturating at about 1 mm and 200%. Under the specified conditions of preincubation, fructose 1,6-diphosphate has an activation curve similar to that of 6-phosphogluconate, peaking at 0.1 mm and 70%. Above this level, activation decreases, and inhibition is seen at still higher concentrations. Other metabolites tested produced smaller or no effects on the enzyme activity assayed under these conditions. When either reduced NADP or 6-phosphogluconate are present in the preincubation mixture, it becomes possible to determine the Km for bicarbonate using a Lineweaver-Burk plot, and the Km for bicarbonate under these conditions is 2.8 mm, corresponding to 0.3% CO(2) at pH 7.8 and 25 C.

Activation and inhibition of ribulose 1,5-diphosphate carboxylase by 6-phosphogluconate

Ribulose 1,5-diphosphate carboxylase, when activated by preincubation with 1 mm bicarbonate and 10 mm MgCl(2) in the absence of ribulose 1,5-diphosphate, remains activated for 20 minutes or longer after reaction is initiated by addition of ribulose diphosphate. If as little as 50 mum 6-phosphogluconate is added during this preincubation period, 5 minutes before the start of the reaction, a further 188% activation is observed. However, addition of 6-phosphogluconate at the same time or later than addition of ribulose diphosphate, or at any time with 50 mm bicarbonate, gives inhibition of the enzyme activity. Possible relevance of these effects in vivo regulatory effects is discussed.

Inhibition of ribulose 1,5-diphosphate carboxylase by 6-phosphogluconate

6-Phosphogluconate is a much more effective inhibitor of the photosynthetic carboxylation enzyme, ribulose-1, 5-diphosphate carboxylase, than other sugar phosphates and sugar acids of the reductive and oxidative pentose phosphate cycles. The inhibition appears to be noncompetitive with ribulose 1,5-diphosphate. Since 6-phosphogluconate is unique to the oxidative cycle and inhibits at concentrations comparable to those found in vivo, it is proposed that its inhibition of the carboxylase may be a regulatory factor. If so, it would operate during darkness as a different control factor from those factors postulated to activate the carboxylase during photosynthesis.