The burden of poor glycaemic control in people with newly diagnosed type 2 diabetes in Sweden: A health economic modelling analysis based on nationwide data

AIM

To evaluate the economic and clinical burden associated with poor glycaemic control in Sweden, in people with type 2 diabetes (T2D) initiating first-line glucose-lowering therapy.

MATERIALS AND METHODS

Population data were obtained from Swedish national registers. Immediate glycaemic control was compared with delays in achieving control of 1 and 3 years, with outcomes projected over 3, 10 and 50 years in the validated IQVIA CORE Diabetes Model. Glycaemic control was defined as glycated haemoglobin (HbA1c) targets of 52, 48 and 42 mmol/mol, as recommended in Swedish guidelines, according to age and disease duration. Costs (expressed in 2019 Swedish krona [SEK]) were accounted from a Swedish societal perspective.

RESULTS

Immediate glycaemic control was associated with population-level cost savings of up to SEK 279 million and SEK 673 million versus delays of 1 and 3 years, respectively, as well as small population-level life expectancy benefits of up to 1305 and 2590 life years gained. Reduced levels of burden were a result of lower incidence and delayed time to onset of diabetes-related complications.

CONCLUSIONS

Even in people with T2D initiating first-line glucose-lowering therapy, the economic burden of poor glycaemic control in Sweden is substantial, but could be reduced by early and effective treatment to achieve glycaemic targets.

Evaluation of the Short-Term Cost-Effectiveness of IDegLira Versus Basal Insulin and Basal-Bolus Therapy in Patients with Type 2 Diabetes Based on Attainment of Clinically Relevant Treatment Targets

BACKGROUND

Effective glycemic control can reduce the risk of complications and their related costs in patients with type 2 diabetes (T2D). Many patients fail to reach hemoglobin A1c (HbA1c) ≤ 6.5% or < 7.0%, often due to adverse effects of treatment, such as hypoglycemia and weight gain. Glycemic targets should be individualized and consider multiple factors, including the risk of adverse events and the patient's characteristics and comorbid conditions.

OBJECTIVE

To compare the odds and annual cost of achieving treatment targets, which incorporate HbA1c targets of < 7.5%, < 8.0%, and ≤ 9.0%, with insulin degludec/liraglutide (IDegLira) versus basal insulin and basal-bolus therapy.

METHODS

This is a post hoc analysis of the DUAL V and DUAL VII 26-week trials, which randomized patients with T2D uncontrolled (HbA1c 7%-10%) on insulin glargine 100 units/mL (IGlar U100) and metformin to IDegLira or continued IGlar U100 titration (DUAL V) or IGlar U100 + insulin aspart (DUAL VII), all with metformin. Proportions of patients achieving HbA1c targets (< 7.5%, < 8.0%, and ≤ 9.0%) by the end of trial were assessed via 3 outcomes: alone, without either hypoglycemia or weight gain (double composite outcome), or without a combination of hypoglycemia and weight gain (triple composite outcome). The cost per patient achieving the triple composite outcome at each HbA1c target (< 7.5%, < 8.0%, and ≤ 9.0%) was calculated by dividing the annual cost of treatment by the proportion of patients achieving the target. This short-term (1-year) cost-effectiveness analysis was conducted from the perspective of a U.S. health care payer.

RESULTS

More patients achieved HbA1c < 7.5% (P < 0.0001) and < 8.0% (P = 0.0003), and a similar percentage achieved HbA1c ≤ 9.0% with IDegLira versus IGlar U100 (DUAL V). Similar proportions of patients achieved all 3 HbA1c targets with IDegLira compared with basal-bolus therapy (DUAL VII). The odds of achieving double or triple composite outcomes were significantly higher for IDegLira versus IGlar U100 or basal-bolus for all 3 HbA1c targets (P < 0.0001 in each case) in both trials. For each $1 spent on IDegLira, the equivalent annual costs per patient to achieve HbA1c targets of < 7.5%, < 8.0%, or ≤ 9.0% without hypoglycemia and without weight gain were $2.43, $2.10, and $2.05, respectively, for IGlar U100 and $6.33, $5.80, and $6.06, respectively, for basal-bolus therapy.

CONCLUSIONS

Based on data from DUAL V and DUAL VII, this analysis showed that a greater or similar proportion of patients with T2D reached HbA1c targets with IDegLira compared with IGlar U100/basal-bolus therapy. Odds of achieving double or triple composite outcomes of HbA1c reduction without hypoglycemia and/or without weight gain were greatest for IDegLira. Short-term cost analyses based on the triple composite outcomes suggest that IDegLira is a cost-effective treatment option in the United States compared with either uptitration of IGlar U100 or basal-bolus therapy.

DISCLOSURES

This study was supported by Novo Nordisk A/S. The analysis was based on the DUAL V (NCT01952145) and DUAL VII (NCT02420262) trials, which were funded and conducted by Novo Nordisk. This post hoc analysis was conceived and interpreted by the authors and drafted with medical writing support that was funded by Novo Nordisk. Novo Nordisk also reviewed the manuscript for medical accuracy. Hunt and Malkin are employees of Ossian Health Economics and Communications, which received consulting fees from Novo Nordisk during the conduct of this study and has received consulting fees from Novo Nordisk, unrelated to this study. Mocarski, Ranthe, and Schiffman are employees of Novo Nordisk and Novo Nordisk A/S. Cannon has received speaker fees/honoraria from Abbvie, Amgen, and Janssen; speaker fees from Novo Nordisk; and has stock ownership in Novo Nordisk. Bargiota has received speaker fees/honoraria from AstraZeneca, Eli Lilly, MSD, Novo Nordisk, Sanofi, Boehringer Ingelheim, and Novartis. Billings has received personal fees from Novo Nordisk, Sanofi, and Dexcom, unrelated to this study. Leiter reports grants and personal fees from AstraZeneca, Boehringer Ingelheim, Eli Lilly, Janssen, Merck, Novo Nordisk, Sanofi, Servier, and GSK, unrelated to this study. Doshi has no relevant conflicts of interest to disclose. Parts of this study were presented as a poster at the AMCP Managed Care & Specialty Pharmacy Annual Meeting; April 23-26, 2018; Boston, MA.

Evaluation of the long-term cost-effectiveness of once-weekly semaglutide versus dulaglutide for treatment of type 2 diabetes mellitus in the UK

AIMS

Glucagon-like peptide-1 (GLP-1) receptor agonists are appealing as glucose-lowering therapy for individuals with type 2 diabetes mellitus (T2DM) as they also reduce body weight and are associated with low rates of hypoglycaemia. This analysis assessed the long-term cost-effectiveness of semaglutide 0.5 and 1 mg vs dulaglutide 1.5 mg (two once-weekly GLP-1 receptor agonists) from a UK healthcare payer perspective, based on the head-to-head SUSTAIN 7 trial, to inform healthcare decision making.

MATERIALS AND METHODS

Long-term outcomes were projected using the IQVIA CORE Diabetes Model (version 9.0). Baseline cohort characteristics, changes in physiological parameters and adverse event rates were derived from the 40-week SUSTAIN 7 trial. Costs to a healthcare payer were assessed, and these captured pharmacy costs and costs of complications. Utilities were taken from published sources.

RESULTS

Once-weekly semaglutide 0.5 and 1 mg were associated with improvements in quality-adjusted life expectancy of 0.04 and 0.10 quality-adjusted life years, respectively, compared with dulaglutide 1.5 mg. Clinical benefits were achieved at reduced costs, with lifetime cost savings of GBP 35 with once-weekly semaglutide 0.5 mg and GBP 106 with the once-weekly semaglutide 1 mg, resulting from fewer diabetes-related complications due to better glycaemic control. Therefore, both doses of once-weekly semaglutide were considered dominant vs dulaglutide 1.5 mg (improving outcomes and reducing costs).

CONCLUSIONS

Compared with treatment with dulaglutide, once-weekly semaglutide represents a cost-effective option for treating individuals in the UK with T2DM who are not achieving glycaemic control with metformin, projected to both improve clinical outcomes and reduce costs.

The management of type 2 diabetes with fixed-ratio combination insulin degludec/liraglutide (IDegLira) versus basal-bolus therapy (insulin glargine U100 plus insulin aspart): A short-term cost-effectiveness analysis in the UK setting

AIM

To evaluate the cost-effectiveness of IDegLira versus basal-bolus therapy (BBT) with insulin glargine U100 plus up to 4 times daily insulin aspart for the management of type 2 diabetes in the UK.

METHODS

A Microsoft Excel model was used to evaluate the cost-utility of IDegLira versus BBT over a 1-year time horizon. Clinical input data were taken from the treat-to-target DUAL VII trial, conducted in patients unable to achieve adequate glycaemic control (HbA1c <7.0%) with basal insulin, with IDegLira associated with lower rates of hypoglycaemia and reduced body mass index (BMI) in comparison with BBT, with similar HbA1c reductions. Costs (expressed in GBP) and event-related disutilities were taken from published sources. Extensive sensitivity analyses were performed.

RESULTS

IDegLira was associated with an improvement of 0.05 quality-adjusted life years (QALYs) versus BBT, due to reductions in non-severe hypoglycaemic episodes and BMI with IDegLira. Costs were higher with IDegLira by GBP 303 per patient, leading to an incremental cost-effectiveness ratio (ICER) of GBP 5924 per QALY gained for IDegLira versus BBT. ICERs remained below GBP 20 000 per QALY gained across a range of sensitivity analyses.

CONCLUSIONS

IDegLira is a cost-effective alternative to BBT with insulin glargine U100 plus insulin aspart, providing equivalent glycaemic control with a simpler treatment regimen for patients with type 2 diabetes inadequately controlled on basal insulin in the UK.

Pulsed photoacoustic detection of flash-induced oxygen evolution from intact leaves and its oscillations

Photoacoustic signals from intact leaves, produced upon excitation with single-turnover flashes, were shown to be dependent on their position in the flash sequence. Compared to the signal obtained from the first flash, all the others were time-shifted and had increased amplitudes. The signal from the third flash had the largest deviation, whereas that from the second flash deviated only minimally. The amplitude difference of the signals relative to that from the first flash was measured at a convenient time point (5 ms) and showed oscillations of period 4, similar to the O(2)-evolution pattern from algae. These oscillations were strongly damped, tending to a steady state from about the seventh flash on. The extra photoacoustic signal (relative to the first flash) was shown to be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, heat treatment, or water infiltration. Its change with flash number, its saturation with increasing flash energy, and the above inhibition criteria indicate that it originates in pulsed O(2) evolution. The sound wave produced by the first flash, however, arose by a photothermal mechanism only, as shown by its linear dependence on the flash intensity and insensitivity to the above treatments. The above flash pattern demonstrates that the photocycle of the S states (i.e., positive charge accumulation before two water molecules can be oxidized in a concerted way to produce molecular oxygen) occurs in intact leaves. It proves the applicability of the photoacoustic method for mechanistic studies of O(2) evolution in leaves under physiological conditions. Water content of leaves is readily measured by this method.

Evidence that phosphorylation and dephosphorylation regulate the distribution of excitation energy between the two photosystems of photosynthesis in vivo: Photoacoustic and fluorimetric study of an intact leaf

State 1-state 2 transitions in an intact tobacco leaf were monitored by the photoacoustic method. Modulated oxygen evolution yield and its enhancement by continuous far-red light ("Emerson enhancement") were used to characterize the balance of light distribution between the two photosystems. These measurements were additionally supported by fluorimetry. Adaptation of the leaf to far-red light (lambda [unk] 700 nm), mainly absorbed in photosystem I (light 1), results in state 1, where short-wavelength light (light 2) is distributed in favor of photosystem II. This is shown by a low yield of oxygen evolution, a high extent of Emerson enhancement, a concomitantly high extent of fluorescence quenching by far-red light, and a low ratio of the 77 K emission peaks at 730 and 695 nm. The magnitudes of these parameters were reversed when the leaf was adapted to light 2 (state 2), indicating a change towards a more equal distribution of the excitation between the two photosystems. Preincubation of an intact leaf with NaF, a specific phosphatase inhibitor, stimulated the extent of adaptation to light 2, shown by all the above criteria, and completely abolished adaptation to light 1. Light 1 preillumination prior to NaF treatment resulted initially in state 1, but then a transition to state 2 was irreversibly induced by any light. The NaF effect was specific because NaCl did not affect the state 1-state 2 transitions. Leaching out the NaF restored the original physiological transitions of the leaf. NaF presumably acts here in the same way as it acts in isolated thylakoids-by blocking the dephosphorylation of membranal proteins (particularly the chlorophyll a/b-protein complex) phosphorylated by a light 2-activated kinase. Our results give direct support to the suggestion [Allen, J. F., Bennett, J., Steinback, K. E. & Arntzen, C. J. (1981) Nature (London) 291, 25-29] that it is the phosphorylation level of thylakoid proteins that controls the light distribution between the two photosystems in vivo, shown previously in isolated thylakoids.

Modified cryptochrome in vivo absorption in dim photosporulation mutants of Trichoderma

Mutants of Trichoderma harzianum that are defective in blue-light-induced sporulation were induced by nutritional stresses as an alternative to light. These mutants may be modified in the putative photoreceptor pigment "cryptochrome" or in an early transduction component. dim (dimsighted) mutants induced by a short transient stress were mapped into four complementation groups and were chosen for study of pigment deficiencies by in vivo absorption spectroscopy. Mutants rib(-)10 and lys(-)44 in the dimY complementation group had altered in vivo absorption spectra in the blue region. Difference spectra obtained by subtracting dimY spectra from that of the wild type had difference bands with peaks at 455 and 480 nm. The similarity between the in vivo difference spectra and the action spectrum for sporulation in wild-type Trichoderma suggests that the mutants lack cryptochrome or have a defective cryptochrome. The decrease in photoresponse as well as the modification of the action spectrum near 480 nm in a dimY mutant support these suggestions. Both dimY mutants pleiotropically accumulate a yellow water-soluble pigment absorbing at wavelengths lower than the blue maxima of cryptochrome; this yellow pigment may be related to cryptochrome.

Light-induced carbon dioxide and oxygen uptake in plant leaves measured by the photoacoustic method

Leaf discs, enclosed in a photoacoustic (PA) chamber, generate two types of PA gas-uptake signals under certain conditions. Type I is manifested by a severe signal decrease that develops slowly under very low-light intensity and often reaches negative values. It is partially reversed by low-intensity far-red light. Type II occurs transiently in modulated far-red light. It is manifested by a rapid and dramatic decrease of the PA signal, upon the addition of short-wave background light, which is subsequently reversed. It differs from type-I uptake in that it occurs at much higher total light intensities. A thorough study, including modulation frequency and atmospheric composition dependencies, indicates different mechanisms for the two types of uptakes. Type-I uptake results from CO2 accumulation in the PA cell by leaf respiration and reflects modulations in CO2 solubilization. Type-II uptake likely reflects oxygen photoreduction in photosystem I, occurring prior to the activation of photosynthesis (i.e. during photosynthesis induction). This is supported by the complete suppression of type-II uptake when O2 was removed. Also, type-II uptake was only mildly sensitive to CO2 elimination, whereas type-I uptake was totally dependent on the presence of CO2. Type-II uptake consists usually of two uptake waves. Fluorescence transients measured in parallel give further support to the reality and interpretation of these two uptake waves. PA could thus provide a unique opportunity to monitor oxygen photoreduction in vivo with high sensitivity and time resolution.

Thermal and structural changes of photosynthetic reaction centers characterized by photoacoustic detection with a broad frequency band hydrophone

Photoacoustic measurements using a broad frequency band hydrophone were carried out in photosynthetic reaction centers (RC) isolated from Rhodobacter sphaeroides R-26 purple bacteria. Data were extracted on enthalpy and volume changes accompanying the primary steps after excitation in the range of 0-500 microseconds aimed at further characterizing the thermodynamic properties of the RC. Quinone titration showed that the volume contraction accompanying the electron transport is sensitive to the molecular species occupying the secondary quinone site. delta VM = 14.4, 7.7 and 4.3 cm3 molar volume contractions were calculated from the measured parameters for 1, 2 and 0.07 quinone/RC after light excitation. Comparing the enthalpy changes (delta H) to the Gibbs free energy data in the literature, a rather large (26%) entropic contribution to the free energy changes (delta G) is estimated for the P*QAQB-->P+QA-QB electron transport (where QA and QB represent primary and secondary quinones, respectively). This is in contrast to previous estimations that delta G = delta H in these processes. On the other hand, only a small (4%) entropic contribution to the delta G of the P*QAQB-->P+QAQB- process is estimated, in agreement with the literature data. Our results are in good agreement with the data obtained earlier (Edens et al. [2000] J. Am. Chem. Soc. 122, 1479-1485).

Oxygen uptake photosensitized by disorganized chlorophyll in model systems and thylakoids of greening barley

Light-dependent oxygen uptake was observed and studied in thylakoids from early greening barley in comparison to oxygen uptake in chlorophyll solutions and in thylakoids from fully green leaves. Substantial oxygen uptake was observed in chlorophyll solutions supplemented with tryptophan, histidine, ascorbic acid or linoleic acid. This uptake was diminished by adding azide, beta-carotene and alpha-tocopherol, which are specific singlet-oxygen quenchers. Illuminated thylakoids from greening barley also exhibited marked oxygen uptake that, likewise, was strongly quenched by azide. In comparison, azide was found not to affect oxygen uptake that is associated with the methyl viologen-catalyzed Mehler reaction. It is reasoned that in the first two cases the oxygen uptake arises from chlorophyll-photosensitized activation of oxygen to the singlet state and its consumption by exogenous or endogenous substrates. In greening, we propose that disorganized chlorophyll photo-sensitizes the oxygen uptake.

Excitation energy transfer in aggregates of Photosystem I and Photosystem II of the cyanobacterium Synechocystis sp. PCC 6803: Can assembly of the pigment-protein complexes control the extent of spillover?

The fluorescence profile of Photosystem I/Photosystem II mixtures in different solvent systems shows that both non-hydrophobic and hydrophobic interactions govern their association and control energy transfer from Photosystem II to Photosystem I. The non-hydrophobic interactions lead to a highly efficient excitation energy transfer from Photosystem II to Photosystem I. In view of this, we propose that similar non-hydrophobic interactions, between the Photosystem II and Photosystem I peripheral proteins, also play a significant role in their association in thylakoids that control state transitions in cyanobacteria.

Differential responses to different light spectral ranges of violaxanthin de-epoxidation and accumulation of Cbr, an algal homologue of plant early light inducible proteins, in two strains of Dunaliella

Unicellular green algae of the genus Dunaliella, similar to higher plants, respond to light stress by enhanced de-epoxidation of violaxanthin and accumulation of Cbr, a protein homologous to early light inducible proteins (Elips) in plants. These proteins belong to the superfamily of chlorophyll a/b binding proteins. Two Dunaliella strains, D. bardawil and D. salina, were compared for these two responses under light in the UVA, blue, green and red spectral ranges. In D. bardawil, the two stress responses were similarly induced under UVA, blue or red light and to a lesser extent under green light. In D. salina, a similar spectral range dependence was exhibited for violaxanthin de-epoxidation. However, Cbr accumulated only under UVA or blue light but not under green or red light. A strong synergistic effect of a low dose of blue light superimposed on red light resulted in Cbr accumulation. These results reveal strain-specific differences in spectral range requirements of the two light-stress responses. In the two strains, violaxanthin de-epoxidation is triggered under photosynthetically-active spectral ranges but at least in D. salina, Cbr accumulation appears to require a specific light signal additionally to a signal(s) generated by light stress.

Bill Arnold and calorimetric measurements of the quantum requirement of photosynthesis-once again ahead of his time

The approach of photocalorimetry to decide on the true quantum requirement of photosynthesis - one of the main issues of the research in the first half of the century and a source of a bitter debate - is described. Bill Arnold's original approach to get into the true answer is reflected from the point of view of present day calorimetric techniques.

Possible Role of Cbr, an Algal Early-Light-Induced Protein, in Nonphotochemical Quenching of Chlorophyll Fluorescence

The unicellular green alga Dunaliella bardawil exhibits typical responses to excessive light when starved for sulfate under normal light (60 [mu]E m-2 s-1) but not under low light (14 [mu]E m-2 s-1). Algae were analyzed during several days of sulfate starvation for nonphotochemical quenching of chlorophyll fluorescence in the absence or presence of the uncouplers SF-6847 (SF) or carbonyl cyanide p- trifluoromethoxyphenyl hydrazone. Parallel analyses followed two light-stress responses: (a) violaxanthin conversion to zeaxanthin and (b) accumulation of Cbr, a protein analogous to plant early-light-induced proteins and implicated in zeaxanthin binding. In cells starved under normal light SF inhibited nonphotochemical quenching during the first 24 h, but not from 40 h onward. In cells starved under low light SF inhibited nonphotochemical quenching throughout the starvation period. Under normal light accumulation of zeaxanthin was nearly maximal by 24 h, but Cbr was fully induced only by 40h. Under low light zeaxanthin accumulated slowly but no Cbr was evident. These results suggest that during exposure to excessive light, the initial pH gradient-dependent, Cbr-independent mode of nonphotochemical quenching is modified to become less dependent on pH gradient and requires Cbr.

Inverse Heat Transfer Analysis of Grinding, Part 2: Applications

Distributions of the heat flux to the workpiece and the convection heat transfer coefficient on the workpiece surface during straight surface grinding are estimated from measured temperatures in the workpiece subsurface using inverse heat transfer methods developed in Part 1. The results indicate that the heat flux to the workpiece is distributed approximately linearly (triangular heat source) along the grinding zone with about 70 to 75 percent of the total energy transported as heat to the workpiece for grinding of steels with a conventional aluminum oxide wheel and only about 20 percent with CBN superabrasive wheels. The wheel-workpiece contact length corresponding to the region of positive heat flux to the workpiece is found to be generally close to but slightly longer than the theoretical geometric contact length. The convection heat transfer coefficient for cooling by the applied grinding fluid is greatest just behind the trailing edge of the grinding zone where fluid is directly applied, and negligible ahead of the grinding zone.

Inverse Heat Transfer Analysis of Grinding, Part 1: Methods

Thermal analyses of the grinding process generally require assumptions concerning the distributions of the heat flux to the workpiece within the grinding zone and convective cooling outside the grinding zone. The present work is concerned with the use of inverse heat transfer methods to estimate the heat flux and convection heat transfer coefficient distributions on the workpiece surface during straight surface grinding from temperature measurements within the workpiece. In the present paper, three inverse heat transfer methods are developed: temperature matching, integral, and sequential methods. Each method is evaluated for accuracy and stability using simulated temperature data. The selection of the sampling frequency of the temperature measurements and location of the temperature sensor are found to be critical for both estimation accuracy and stability. In a second paper, these inverse heat transfer methods are applied to estimate the distributions of the heat flux and convection heat transfer coefficients on the workpiece surface for grinding of steels with aluminum oxide and CBN abrasive wheels.

Analysis of Transient Temperatures in Grinding

Temperatures generated in the workpiece during straight surface plunge grinding follow a transient behavior as the grinding wheel engages with and disengages from the workpiece, and throughout the entire grinding pass for workpieces which are shorter than needed to reach a quasi-steady state condition. In the present paper, a thermal model is developed for the transient temperature distribution under regular and creep-feed grinding conditions. Numerical results obtained using a finite difference method indicate that the workpiece temperature rises rapidly during initial wheel-workpiece engagement (cut in), subsequently reaches a quasi-steady state value if the workpiece is sufficiently long, and increases still further during final wheel-workpiece disengagement (cut out) as workpiece material is suddenly unavailable to dissipate heat. Cooling by a nozzle directed at the end face of the workpiece should significantly reduce the temperature rise during cut out.

Energy Partition to the Workpiece for Grinding with Aluminum Oxide and CBN Abrasive Wheels

An experimental investigation is reported of the energy partition to the workpiece for grinding of steels with aluminum oxide and cubic boron nitride (CBN) abrasive wheels. The energy input to the workpiece was obtained by measuring the temperature distribution in the workpiece using an embedded thermocouple technique and matching the results with analytically computed values. It was found that 60-75 percent of the grinding energy is transported to the workpiece as heat with an aluminum oxide abrasive wheel, as compared to only about 20 percent with CBN wheels. An analysis of the results indicates that the much lower energy partition to the workpiece with CBN can be attributed to its very high thermal conductivity whereby a significant portion of the grinding heat is transported to the abrasive instead of to the workpiece. The much lower energy partition to the workpiece with CBN wheels results in much lower grinding temperatures and a greatly reduced tendency for thermal damage to the workpiece.

Analysis of Energy Partition in Grinding

An analysis is presented for the fraction of the energy transported as heat to the workpiece during grinding. The abrasive grains and grinding fluid in the wheel pores are considered as a thermal composite which moves relative to the grinding zone at the wheel speed. The energy partition fraction to the workpiece is modeled by setting the temperature of the workpiece surface equal to that of the composite surface at every point along the grinding zone, which allows variation of the energy partition along the grinding zone. Analytical results indicate that the energy partition fraction to the workpiece is approximately constant along the grinding zone for regular down grinding, but varies greatly along the grinding zone for regular up grinding and both up and down creep-feed grinding. The resulting temperature distributions have important implications for selecting up versus down grinding especially for creep-feed operations.

The D-E region of the D1 protein is involved in multiple quinone and herbicide interactions in photosystem II

The region between helices D and E (D-E region) of the D1 protein of photosystem II (PSII) is exposed at the stromal side of the photosynthetic membrane, contains the secondary plastoquinone (QB) binding niche, and is involved in processes at the reducing side of PSII. The role of the D-E region was studied in 27 site-directed mutants generated in the psbAII gene of the cyanobacterium Synechocystis sp. PCC 6803. The photochemical performance of the modified PSII reaction centers was assessed with respect to photoautotrophic growth, oxygen evolution, fluorescence induction, and herbicide inhibition. A few mutations, located at positions presumably involved in essential interactions in the QB binding niche, greatly interfered with PSII performance. On the other hand, mutations in the presumptive loop region between helices D and de resulted in relatively minor effects, indicating a flexible region not critical for photochemical function. Indeed, although more than 80% of the D-E region is phylogenetically invariant, the bulk of the mutations affected the measured parameters only moderately. The significance of the conserved residues appears to be in subtle interactions that optimize the thermodynamic balance between some of the redox components of PSII, as indicated by mild changes in the steady state fluorescence. Many mutations modified tolerances to PSII herbicides. The dispersion of these mutations throughout the D-E region indicates the complex nature of the interactions, direct and indirect, affecting herbicide binding in the QB niche. Mutation of codons Ser221 and Ser222 to Leu221 and Ala222 revealed a new location coordinating the herbicide diuron in the D1 protein.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of photothermal radiometry in assessing leaf photosynthesis: II. Correlation of energy storage to Photosystem II fluorescence parameters

Following the first part of this work (Malkin et al. (1991) Photosynth Res 29: 87-96), where modulated photothermal radiometry (PTR) was used to measure energy storage (ES) in intact leaves as a function of P700 redox state, we report here on simultaneous ES and fluorescence measurements, which characterize the state of PS II. PTR monitors the conversion of modulated light into heat by measuring the modulated infra-red radiation emitted from the sample. The ratio [PTR+-PTR-]/PTR+, where PTR indicates the PTR signal and the subscripts +,- indicate the presence or absence of saturating background light, is used to quantitate ES. We searched carefully for the right conditions where the background light does not introduce a significant rise in the leaf temperature, which influences the PTR signal as such, otherwise the above ratio deviates from the true ES. Under such conditions, ES and the fluorescence parameters, F (momentary fluorescence level) Fm' (fluorescence of fully reduced PS II reaction centers) were measured during the induction phase of photosynthesis and in the steady state. ES and the parameter γ=(Fm'-F)/Fm', considered by Genty et al. ((1989) Biochim Biophys Acta 990: 87-92) to reflect the yield of PS II, had similar kinetics during the induction phase. Both reached a final maximum plateau after about 4-5 min. of illumination. In different experiments, where the measuring light intensities varied, γ was approximately linearly related to ES. This linear relationship was found in the same way also in steady-state measurements, where these parameters varied by using different background light intensities. Extrapolation to an ES value of zero indicates a finite non-zero value of γ. A possible explanation for this may be found in the existence an electron transport cycle around PS II which does not store energy in the range corresponding to the modulation frequency used (ca. 3.6 Hz).

The relationship between millisecond luminescence and fluorescence in tobacco leaves during the induction period

Millisecond luminescence and fluorescence, from an intact tobacco (Nicotiana tabacum) leaf, were measured simultaneously during the induction period, as a function of the time. This was accomplished using a luminescence apparatus which separated out the faster luminescence components by subtraction of the accumulated slow-decaying ones. An antiparallel correlation between the two was observed, but only during a part of the induction period starting with the first fluorescence peak where the fluorescence decreases to a quasi plateau level. During this induction phase, luminescence rose very prominently to a maximum while fluorescence decreased. This correlation fits a linear dependence of the luminescence on the extent of RCs openness, as monitored by the photochemical quenching of the fluorescence. It may be concluded that during this induction phase, all other factors, which modulate luminescence (e.g. membrane potential), have become already steady and that the millisecond delayed luminescence reflects the photochemical reaction in an open center (i.e. with QA oxidized). This is further supported by steady-state experiments in thylakoid membranes. No correlations between luminescence and either momentary (F) or maximum (Fm) fluorescence during later induction phases can be pinpointed with confidence, although a trend of a parallel decrease at certain time intervals can be seen occasionally. Likewise, there is no relationship between the two in the very initial induction phase, during the rise of fluorescence from Fo to Fm, as noted earlier. This lack of correlation is presumably due to the dependence of luminescence on other parameters, which vary during these induction phases. The implications of these observations are discussed.

Measurement of red blood cell-vitamin B12: a study of the correlation between intracellular B12 content and concentrations of plasma holotranscobalamin II

We have recently reported a new and rapid assay to measure plasma holotranscobalamin II (holo TC II) as a means of exploring vitamin B12 status. In order to further evaluate the significance of plasma holoTC II in determining tissue cobalamin, we have chosen the red blood cell-vitamin B12 (RBC-B12) assay as a measure of tissue vitamin B12 content and studied the relationship between RBC-B12 and plasma holoTC II levels. Plasma holoTC II and RBC-B12 concentrations were concomitantly assayed in 20 hematologically normal controls and cancer patients. In our groups of controls, the mean value of RBC-B12 was determined as 241 +/- 51 pg/ml of packed erythrocytes (PE) with a range varying from 180 to 355 pg/ml PE. Preliminary results obtained in 32 cancer patients revealed lower holoTC II and RBC-B12 levels than the control group and a required threshold value of 70 pg/ml of holoTC II in order to maintain a normal RBC-B12 greater than 180 pg/ml PE.

The degree of functional separation between the two photosystems in isolated thylakoid membranes deduced from inhibition studies of the imbalance in photoactivities

In order to examine whether the two photosystems, PS I and PS II, are organized in specific electron transporting pairs, or randomly transport electrons from PS II to PS I, the photosystems imbalance of photoactivities (Emerson enhancement) was measured by modulated fluorimetry under different degrees of PS II inhibition in broken chloroplasts, where the granal structures were preserved by the presence of 5 mM MgCl. The results indicate a lack of any measurable specific functional pairing between individual PS I and PS II, in contrast to a previous research work in leaves (Malkin et al. 1986, Photosynth. Res. 10: 291-296). These results and this discrepancy are further discussed.

Enhanced oxidative-stress defense in transgenic potato expressing tomato Cu,Zn superoxide dismutases

The two cDNAs coding for the cytosolic (cyt) and the chloroplast-located (chl) Cu,Zn superoxide dismutases (SODs) of tomato (Perl-Treves et al. 1988) were cloned into respective binary vectors and mobilized into Agrobacterium strains. Potato tuber discs were infected with either of the two agrobacterial strains and cultured on selective medium containing kanaymcin. The integration of either of the cyt or the chl SOD transgenes was verified by Southern-blot hybridization. The enzymatic activity of the additional tomato chl Cu,Zn SOD could be distinguished from endogenous SOD activity since the latter isozyme migrated faster on SOD-activity gels. Several transgenic potato lines harboring either the cyt or the chl SOD genes of tomato showed elevated tolerance to the superoxide-generating herbicide paraquat (methyl viologen). After exposure of shoots to paraquat, tolerance was recorded either by scoring symptoms visually or by measurements of photosynthesis using the photoacoustic method. Root cultures from transgenic lines that harbored the additional cyt Cu,Zn SOD gene of tomato were tolerant to methyl viologen up to 10(-5) M; a lower tolerance was recorded in roots of transgenic lines that expressed the additional chl Cu,Zn SOD of tomato.

Analysis of Fluid Flow through the Grinding Zone

A theoretical model of fluid flow in grinding has been developed by an analysis of fluid flow through a porous medium. Fluid tangential velocity, radial velocity, depth of penetration into the wheel, and the useful flow rate through the grinding zone are predicted by using this model. The analysis indicates that the nozzle position, nozzle velocity (or flow rate), and the effective wheel porosity are the three main factors which most significantly influence the useful flow rate through the grinding zone. A dimensionless effective wheel porosity parameter is introduced which is the ratio of the effective wheel porosity to its bulk porosity. By fitting the theoretical analysis to available experimental results, creep feed wheels were found to have much bigger dimensionless effective porosities than conventional wheels, which enhances their ability to more effectively pump fluid through the grinding zone.

An Improved Model for Force Transients in Turning

An improved model for force transients in turning is introduced to incorporate the geometry of the cut, as well as plowing at the cutting edge and rubbing of the flank wear land against the workpiece surface. This model is compared experimentally with the existing force models and is shown to provide an accurate representation of the force transients.

A photoacoustic study of water infiltrated leaves

Photoacoustic measurements of photosynthetic energy storage were conducted on water infiltrated pea and sugar maple leaves. The samples were vacuum infiltrated with pure water or with a suitable buffer. The use of such methodology permitted an accurate determination of the energy storage parameter at low modulation frequencies, where in non-infiltrated leaves oxygen evolution dominates the photoacoustic signal and does not allow energy storage measurements. Differences between infiltration media were not essential, however the use of pure water as infiltration medium sometimes caused instability of the measured energy storage, particularly at longer experimental time. Values of energy storage in individual samples ranged mostly between 0.2 to 0.35. Measured as a function of the modulation frequency, energy storage was found to be constant from about 10 to 200 Hz for pea leaves. In sugar maple leaves, the energy storage slightly increased between 100 and 500 Hz. Obtaining an accurate value for energy storage also allowed an accurate estimation of the O2 evolution contribution to the photoacoustic signal of an unfiltrated leaf. In a maple leaf its frequency dependence showed only the effect of diffusion in the entire frequency range (10-500 Hz). Energy storage transients were observed after long periods (ca. 1/4-2 hrs) of dark adaptation upon the transition to light. In this case the initial energy storage was roughly about 1/2 that of the steady state value indicating strong PS I activity, while PS II was transiently incompetent. Energy-storage increased during illumination in a way to correspond to photosynthetic induction events as previously measured by fluorescence and O2 evolution. Transients in energy storage were also found following high light to low light transitions (i.e., switch off of the saturating background light), that paralleled similar transients in oxygen evolution, showing initial transient inactivation followed by progressive reactivation of PS II.

A new way to monitor by-pass restorations of electron transport in inhibited chloroplasts by cyclic electron flow cofactors--a study by modulated fluorimetry

Inhibition of electron transport in broken chloroplasts by DBMIB, under light-limiting conditions, is shown to be bypassed by PMS in a manner similar to the known effects of the phenylenediamine derivatives TMPD and DAD. These bypasses were demonstrated and further studied by modulated fluorimetry, monitoring DBMIB inhibition by the shift of the steady-state fluorescence towards the Fm level and the release of inhibition by a reverse shift together with establishment of a quenching effect by background far-red light. Comparative studies were also made with electron transport blocked by DCMU or BNT. A weak bypass by TMPD and a weaker one by PMS of the block created by DCMU was observed by modulated fluorimetry. The block created by BNT is similarly shown to be bypassed by TMPD but hardly or not at all by PMS. Bypass effects persisted even in the presence of ascorbate. It appears that, following reduction of the different cofactors by ascorbate in the stroma side, illumination caused the accumulation of a pool of oxidized cofactor molecules in the lumen, which is able to mediate electron transport between reduced plastoquinone and plastocyanin or P-700. The existence and the size of this pool were found to depend largely on the internal pH at the lumen, presenting an artificial system in which electron flow is controlled by the lumenal pH. The bypassing electron transport in the presence of DBMIB presumably avoids the participation of the cytochrome b6f complex. During its occurrence, there is also a strong imbalance in the activities of the two photosystems for linear electron flow, in favor of PS II. These experiments may thus serve to establish an in vitro model system for a future investigation of effects related to changes in the imbalance between the two photosystems and its regulation. Furthermore, this experimental system may also be utilized to study the role of the internal lumenal pH in control of photosynthesis.

Experimental Measurement of Fluid Flow Through the Grinding Zone

An experimental test rig was developed to measure the amount of grinding fluid which flows through the grinding zone in straight plunge grinding. Proportional relationships were generally obtained between the flow rate from the nozzle and the useful flow rate of fluid passing through the grinding zone. The percentage of applied fluid passing through the grinding zone was found to depend mainly on the bulk porosity of the grinding wheel and the nozzle position. Wheel dressing has only a secondary influence, which is attributed to its influence on the surface porosity of the wheel. The workspeed and wheel depth of cut have virtually no influence.

Turning Process Identification Through Force Transients

A method is presented for identifying the chip formation, plowing, and sliding forces in turning from force transients. For this purpose, a simple model is used which separates the cutting force into a sharp tool chip formation component and a residual component associated with both rubbing between the wear land and the workpiece and plowing at the cutting edge. Variations of the cross-sectional area of the cut during a transient are used to tune the model and estimate its parameters.

Quantitative study of state 1-state 2 transitions in broken chloroplasts-comparison to in-vivo properties

A detailed quantitative study was conducted on state 1-state 2 transition and its reversal in broken chloroplasts by modulated fluorimetry. The characteristics of the transition obtained supported other previous in-vitro findings. More importantly, a very close quantitative similarity was obtained under suitable conditions to previous in-vivo studies, particularly in approaching a constancy of Fm/F0 during the transition and the equality of the fractional change of these fluorescence parameters with the calculated light distribution fraction to PS II. This confirms that in broken chloroplasts too, the state transitions involve reciprocal changes in the absorption cross-sections of PS II and PS I.

The use of photothermal radiometry in assessing leaf photosynthesis: I. General properties and correlation of energy storage to P700 redox state

Energy storage measurements by modulated photothermal radiometry (PTR) were carried out on intact leaves to assess the value of the PTR method for photosynthesis research. In particular, correlations to the redox state of P700 under various conditions were examined. PTR monitors modulated light conversion to heat by sensing the resulting modulated infra-red radiation emitted from the leaf. It is, therefore, a complementary method to photoacoustics for estimating energy storage and its time variation, particularly under controlled leaf atmosphere.With modulated light-1 (λ>690 nm) the energy storage approached zero and P700 was maximally oxidized. When background light of shorter wavelength (λ<690 nm-light-2) was added, energy storage momentarily increased (a manifestation of Emerson enhancement) while P700 was reduced. The values of both parameters varied as a function of the background light intensity, keeping a mutual linear relationship. Following the initial change, there was a slow reversal transient of P700 oxidation with a parallel decrease in energy storage. Temporal correlation to P700 redox state after dark adaptation was observed also for the energy storage measured in modulated light 2 when combined with background actinic light of medium intensity (about 50 W m(2)). Under these circumstances P700 was almost totally oxidized initially and then gradually reduced while energy storage was initially low and then increased parallel to P700 reduction.A comparison between the maximum energy storage in modulated light 1, enhanced by background light 2, to the energy storage with short wavelength light (where light tends to be more evenly distributed) indicates a comparable contribution to energy storage from each active photosystem. The above experiments indicate that energy storage contribution from PS I is directly related to the extent of openness of its reaction-centers.While some aspects of the data call for more experimentation, these experiments already establish PTR as a valuable method to monitor photosynthetic energy storage activity in vivo, particularly when used simultaneously with other non-invasive methods.

Proton flow through the ATP synthase in chloroplasts regulates the distribution of light energy between PS I and PS II

The involvement of ATP synthase in the imbalance between the photoactivities of PS I and PS II under light-limiting conditions, was examined in broken lettuce chloroplasts using modulated fluorimetry. The imbalance, in favor of PS II, was minimal and roughly constant between pH 6.5-7.3 (ratio of PS II/PS I activities about 1.1), and maximal at pH 8.5 (ratio of PS II/PS I activities about 1.4). This increase was strongly inhibited by a treatment of the chloroplasts with the CF0 ATP synthase inhibitor DCCD, but unaffected by the CF1 ATPase inhibitor, tentoxin. However, tentoxin plus ADP-P1 did inhibit the high pH-induced increased imbalance. These results, when considered with the previous results on the effect of high pH on proton flux through the ATP synthase, suggest that the rate of such proton flow controls the imbalance between the two photo-systems. It is possible that there is an in vivo fine-tuning regulating mechanism of the photosystems imbalance via the opening and closing of proton gradient dissipation through the ATP synthase. This mechanism may help alleviate photoinhibitory damage.

Light Energy Distribution in the Brown Alga Macrocystis pyrifera (Giant Kelp)

The brown alga Macrocystis pyrifera (giant kelp) was studied by a combination of fluorescence spectroscopy at 77 kelvin, room temperature modulated fluorimetry, and photoacoustic techniques to determine how light energy is partitioned between photosystems I and II in states 1 and 2. Preillumination with farred light induced the high fluorescence state (state 1) as determined by fluorescence emission spectra measured at 77K and preillumination with green light produced a low fluorescence state (state 2). Upon transition from state 1 to state 2, there was an almost parallel decrease of all of the fluorescence bands at 693, 705, and 750 nanometers and not the expected decrease of fluorescence of photosystem II and increase of fluorescence in photosystem I. The momentary level of room temperature fluorescence (fluorescence in the steady state, F(s)), as well as the fluorescence levels corresponding to all closed (F(m)) or all open (F(o)) reaction-center states were measured following the kinetics of the transition between states 1 and 2. Calculation of the distribution of light 2 (540 nanometers) between the two photosystems was done assuming both the ;separate package' and ;spill-over' models. Unlike green plants, red algae, and cyanobacteria, the changes here of the light distribution were rather small in Macrocystis so that there was approximately an even distribution of the photosystem II light at 540 nanometers to photosystem I and photosystem II in both states 1 and 2. Photoacoustic measurements confirmed the conclusions reached as a result of fluorescence measurements, i.e. an almost equal distribution of light-2 quanta to both photosystems in each state. This conclusion was reached by analyzing the enhancement phenomenon by light 2 of the energy storage measured in far red light. The effect of light 1 in decreasing the energy storage measured in light 2 is also consistent with this conclusion. The photoacoustic experiments showed that there was a significant energy storage in light 1 which could be explained by cyclic electron transport around photosystem I. From a quantitative analysis of the enhancement effect of background light 2 (maximum enhancement of 1.4-1.5) it was shown that around 70% of light 1 was distributed to this cyclic photosystem I transport.

Photoacoustic measurements in vivo of energy storage by cyclic electron flow in algae and higher plants

Energy storage by cyclic electron flow through photosystem I (PSI) was measured in vivo using the photoacoustic technique. A wide variety of photosynthetic organisms were considered and all showed measurable energy storage by PSI-cyclic electron flow except for higher plants using the C-3 carbon fixation pathway. The capacity for energy storage by PSI-cyclic electron flow alone was found to be small in comparison to that of linear and cyclic electron flows combined but may be significant, nonetheless, under conditions when photosystem II is damaged, particularly in cyanobacteria. Light-induced dynamics of energy storage by PSI-cyclic electron flow were evident, demonstrating regulation under changing environmental conditions.

Increased Tolerance to Photoinhibitory Light in Paraquat-Resistant Conyza bonariensis Measured by Photoacoustic Spectroscopy and CO(2)-Fixation

Tolerance to photoinhibition was compared between a paraquat-resistant and a sensitive biotype of Conyza bonariensis (L.). Cronq. Photoinhibitory damage was measured as a decrease in oxygen evolution or energy storage using photoacoustic spectroscopy, or as a decrease of (14)CO(2)-fixation. Prior to exposure to high fluence rates, both biotypes had similar quantum yields of oxygen evolution and energy storage. After exposure to high intensity light, the resistant biotype continued to evolve oxygen and to store energy with a high quantum yield while both energy storage and oxygen evolution were severely reduced in the sensitive biotype. CO(2)-fixation was less rapidly inhibited in the resistant biotype compared to the sensitive one. The data show that the paraquat resistant biotype with its high constitutive levels of the chloroplast localized enzymes of the oxygen detoxification pathway, is also partially protected from photoinhibition. This supports the theory that an enhanced radical scavenging system can give temporary protection against photooxidative damage from a variety of sources.

Separate photosensitizers mediate degradation of the 32-kDa photosystem II reaction center protein in the visible and UV spectral regions

A component of the photosystem II reaction center, the 32-kDa protein, is rapidly turned over in the light. The mechanism of its light-dependent metabolism is largely unknown. We quantified the rate of 32-kDa protein degradation over a broad spectral range (UV, visible, and far red). The quantum yield for degradation was highest in the UVB (280-320 nm) region. Spectral evidence demonstrates two distinctly different photosensitizers for 32-kDa protein degradation. The data implicate the bulk photosynthetic pigments (primarily chlorophyll) in the visible and far red regions, and plastoquinone (in one or more of its redox states) in the UV region. A significant portion of 32-kDa protein degradation in sunlight is attributed to UVB irradiance.

Safety and effectiveness of cranial electrotherapy in the treatment of tension headache

One hundred patients were enrolled in a multicenter double-blind study to evaluate the safety and effectiveness of the Pain Suppressor Unit, a cranial electrotherapy stimulator for the symptomatic treatment of tension headaches. Treatment consisted of extremely low level, high frequency current applied transcranially. Pain scores before and after 20 minute treatments of individual headaches as well as patient and physician global evaluations were the primary efficacy variables. Following use of the active unit, patients reported an average reduction in pain intensity of approximately 35%. Placebo patients reported a reduction of approximately 18%. The difference was statistically significant (p = 0.01). The active unit was rated as moderately or highly effective in 40% by physicians, and in 36% by patients. Both physicians and patients scored the placebo unit moderately or highly effective for only 16%. The difference in ordered outcomes was statistically significant (p = 0.004). Approximately 10% of patients in each group reported at least one minor adverse experience. Cranial electrotherapy stimulation is distinct from TENS, and is safe and often effective in ameliorating the pain intensity of tension headaches. It should be considered as an alternative to the chronic usage of analgesics.

Grinding Mechanisms and Strength Degradation for Ceramics

This paper presents a critical review and evaluation of our fundamental knowledge of the grinding mechanisms for ceramic materials and their influence on the finished surface and mechanical properties. Two main research approaches are identified: a “machining” approach and an “indentation fracture mechanics” approach. The machining approach has typically involved measurement of the grinding forces and specific energy coupled with microscopic observations of the surface morphology and grinding detritus. Any proposed mechanisms of abrasive-workpiece interaction must be consistent with the magnitude of the specific energy and its dependence on the grinding conditions. The “indentation fracture mechanics” approach assumes that the damage produced by grinding can be modeled by the idealized flaw system produced by a sharp indentor. Indentation of a ceramic body is considered to involve elastic/plastic deformation with two principal crack systems propagating from the indentation site: lateral cracks which lead to material removal and radial/median cracks which cause strength degradation. Each of these approaches provides important insight into grinding behavior and strength degradation, but each has its shortcomings. Further efforts to develop a fundamental model for grinding of ceramics would benefit from the integration of both of these approaches.

Fast photoacoustic transients from dark-adapted intact leaves: oxygen evolution and uptake pulses during photosynthetic induction - a phenomenology record

Using a photoacoustic technique it has been possible to observe fast oxygen evolution and uptake transients at a high time resolution (approx. 0.2 s), when a dark-adapted leaf is reilluminated. There is initially a rapid pulse of oxygen evolution, correlated with the initial fluorescence rise (total duration under the experimental conditions used about 1-2 s), corresponding presumably to the photoreduction of the plastoquinone pool. This phenomenon may be utilized to calibrate the oxygen-evolution photoacoustic signal. The first pulse is followed by a series of slower bursts of oxygen uptake and evolution, reflecting various pools which are expressed following sequential activation of various parts of the photosynthetic apparatus, until achievement of a steady state.

Photosynthetic Responses of Leaves to Water Stress, Expressed by Photoacoustics and Related Methods : II. The Effect of Rapid Drought on the Electron Transport and the Relative Activities of the Two Photosystems

The effect of rapid dehydration of detached tobacco leaves (Nicotiana tabacum L.) on the photochemical apparatus of photosynthesis was studied in vivo by a combination of methods: photoacoustics, chlorophyll a fluorescence, and cytochrome f difference spectroscopy. It was shown that the inhibition of gross O(2) evolution was mainly caused by inactivation of PSII: (a) The saturation curve of cytochrome-f photooxidation by farred (>710 nanometers) light was resistant to the stress, leading to the conclusion that photosystem I (PSI) was largely unaffected by the stress. (b) The extent of the chlorophyll a variable fluorescence arising from photosystem II (PSII) decreased with the progression of the stress, but was largely unaffected when the leaf was preincubated with electron donors to PSII, such as hydroxylamine. It is concluded that the drought damage to PSII occurred on the photooxidative side. Despite the extensive inhibition of PSII and the relative preservation of PSI, the apparent PSII/PSI activity balance was somewhat larger in stressed leaves than in the control, as indicated by photoacoustic measurements of Emerson enhancement. These measurements were performed continuously under conditions which favor transitions to either state 1 or 2, showing that the transition to state 2 was considerably inhibited. Simultaneous measurements of chlorophyll fluorescence induction at 680 and 730 mm at room temperature were also used to probe changes in energy distribution between PSII and PSI and indicated that the transition from a dark adapted state to state 2 was also affected in water-stressed leaves. The saturation curve of the far-red light effect in Emerson enhancement was not changed by the stress, giving another independent evidence for the drought resistance of PSI activity. This apparent preservation of the imbalance in photochemical activities in favor of PSII, despite the fact that PSII is strongly inhibited, and PSI is not, supports a previous suggestion that the electron transfer between the two photosystems is not random but that a large extent of PSII and PSI units are specifically linked.

Photosynthetic responses of leaves to water stress, expressed by photoacoustics and related methods : I. Probing the photoacoustic method as an indicator for water stress in vivo

The effect of leaf desiccation on the photosynthetic activities in vivo was probed by the photoacoustic method. The aim of this research was: (a) To study the photoacoustic signal per se in varied conditions in order to develop this tool as a probe for stress conditions in vivo. (b) To obtain results pertaining to electron transport activities in vivo, and confirm conclusions based on work with isolated chloroplasts, which could otherwise be the result of nonspecific damage occurring during their isolation. Leaf discs from tobacco (Nicotiana tabacum L.) were routinely used, with other species tested also for comparison. Rapid leaf desiccation caused changes in the low frequency photoacoustic signal, attributed both to the mechanism of signal transduction, influenced by changes in the structural parameters of the leaf, and to the direct (nonstomatal) inhibition of gross photosynthesis. The dependence of the photothermal part of the signal on the frequency indicated the presence of two photothermal components, one of which persisted only at low modulation frequencies (below about 100 Hz) and which largely increased with the desiccation treatment. This component was ascribed to a thermal wave which reaches the leaf surface. The other nonvariable photothermal component was ascribed to a thermal wave propagating from the chloroplasts to the surface of the mesophyll cell. Only this component is considered in the ratio of the O(2) signal to the photothermal signal, which is used to estimate the quantum yield of photosynthesis. The specific dependence of the latter ratio on the frequency yielded a comparative quantum yield parameter from its extrapolation to zero frequency, and also indicated stress induced changes in the diffusion of O(2) through the mesophyll cell, reflected by changes in its characteristic slope. The (zero frequency extrapolated) quantum yield was markedly reduced with the progression of the water stress, indicating the inhibition of (gross) phototosynthetic electron transport in vivo. This result was expressed even more emphatically by the stronger inhibition of the photochemical energy storage, obtained by photoacoustic measurements at a high modulation frequency.

Estimation of the light distribution between photosystems I and II in intact wheat leaves by fluorescence and photoacoustic measurements

Usisng intact leaves, the extent of the decrease in chlorophyll a fluorescenece caused by the addition of continuous 710 nm light superimposed on modulated (20 Hz) 550 nm light was used to determine the distribution of this absorbed light between photosystems I (α) and II (β). The Fo and Fm levels, which defined the total variable fluorescenece, were taken as equal to those obtained with excess 710 nm light and with saturating blue-green light, respectively.An analogous procedure was used with a photoacoustic detector, saturating white light defining a base line for oxygen yield, the levels with an without 710 nm light being used to define β and α respectively.The two methods gave similar values for the distribution of light between the two photosystems for the experimental conditions used, β averaging 0.55 for a range of Triticum genotypes and Brachypodium sylvaticum grown in high or low light.

Analysis of Emerson enhancement under conditions where photosystem II is inhibited - Are the two photosystems indeed separated?

Photoacoustic measurements of photosynthetic oxygen evolution and its enhancement by addition of background far-red light (Emerson enhancement) were made on both intact and inhibited or stressed leaves. The extent of enhancement increased with the dehydration treatment and decreased with a mild heat treatment or with the addition of DCMU. It nevertheless persisted even at a very high degree of inhibition - a result which indicates high population ratio of single pairs of combined photosystem II and photosystem I units, functional in whole chain electron transport. This implies a restriction on the separation between photosystems I and II, in contrast to existing concepts.

Comparison of photosynthetic parameters of an aurea mutant (Su/su) of tobacco and the wild-type by the photoacoustic method

Oxygen evolution and energy storage yields in tobacco (Nicotiana tabacum L.) wild-type (cv. John Williams Broadleaf) and a mutant (Su/su) deficient in chlorophyll were compared using the photoacoustic technique. Oxygen-evolution and energy-storage quantum yields in the mutant were higher when measured in red light (640-690 nm) than green or blue light (540 nm and 440 nm, respectively), indicating that carotenoids in this mutant do not transfer energy efficiently to the photochemical reaction centers. It is suggested that carotenoids may play a role in protecting the photosynthetic apparatus against damage by high energy fluxes. In the wild-type, the oxygenevolution yield did not change drastically throughout the visible spectrum. The mutant had a higher quantum yield of oxygen evolution than the wildtype. Similarly maximum rates obtained from saturation curves for the mutant were more than twice higher per leaf area and about five times higher per chlorophyll, as compared to the wild-type.