Variation of postprandial plasma glucose, palatability, and symptoms associated with a standardized mixed test meal versus 75 g oral glucose

OBJECTIVE

To compare within-subject variability of plasma glucose measured 2 h after a glucose tolerance test (GTT) with that of plasma glucose measured 2 h after administration of a standardized test meal (diabetes screening product [DSP], Ceapro, Edmonton, Alberta, Canada) and to determine the relationship between the two sets of plasma glucose measurements.

RESEARCH DESIGN AND METHODS

Plasma glucose and insulin responses of 36 overnight-fasted subjects (10 lean normal, 9 obese normal, 9 with impaired glucose tolerance [IGT], and 8 with mild diabetes) were studied on eight different mornings after they consumed 75 g oral glucose or 50 g carbohydrate from the DSP. Each test meal was repeated four times by each subject. Within-subject coefficients of variation (CVs) (CV = 100 x SD/mean) of plasma glucose concentrations 2 h after administration of the GTT and DSP were compared by repeated measures ANOVA and linear regression analysis.

RESULTS

Mean plasma glucose 2 h after administration of the DSP (D) was linearly related to that 2 h after the GTT (G): G = 1.5 x D - 1.6 (r = 0.97, P < 0.0001). The CV of 2-h plasma glucose was significantly lower after administration of the DSP, 10.5 +/- 1.0%, than after the GTT, 12.7 +/- 1.18% (P = 0.025). The effect of test meal on CV differed in different groups of subjects (P = 0.018), with the largest difference found in IGT subjects, in whom the CV after DSP administration was 47% less than after the GTT (P = 0.0005). The DSP was significantly more palatable and produced fewer adverse symptoms than the GTT.

CONCLUSIONS

Plasma glucose concentrations measured 2 h after DSP administration are closely related to those measured 2 h after the GTT but are more consistent than the 2-h post-GTT concentrations within the critical IGT range. This finding suggests that measurement of plasma glucose 2 h after administration of the DSP may allow more precise discrimination among normal glucose levels, IGT, and diabetes than measurement of plasma glucose 2 h after the GTT.

Sortilin is the major 110-kDa protein in GLUT4 vesicles from adipocytes

Vesicles containing the glucose transporter GLUT4 from rat adipocytes contain a major protein of 110 kDa. We have isolated this protein, obtained the sequences of peptides, and cloned a large portion of its cDNA. This revealed that the protein is sortilin, a novel membrane protein that was cloned in another context from a human source while this work was in progress. Subcellular fractionation of rat and 3T3-L1 adipocytes, together with GLUT4 vesicle isolation, showed that sortilin was primarily located in the low density microsomes in vesicles containing GLUT4. Insulin caused a 1.7-fold increase in the amount of sortilin at the plasma membranes of 3T3-L1 adipocytes, as assessed by cell surface biotinylation. The expression of sortilin in 3T3-L1 cells occurred only upon differentiation. Previous characterization of sortilin has led to the suggestion that it functions to sort lumenal proteins from the trans Golgi. The significance of its insulin-stimulated increase at the cell surface and of its expression upon differentiation will require definitive delineation of its function.

Spasticity and strength changes as a function of selective dorsal rhizotomy

This investigation quantified pre- and postsurgery (8 months) hamstring muscle spasticity and strength in children with cerebral palsy (CP) undergoing a selective dorsal rhizotomy. Nineteen children with CP (CP group) and six children with able bodies (AB group) underwent testing with a dynamometer. For the spasticity measure, the dynamometer measured the resistive torque of the hamstring muscles during passive knee extension at four different speeds. Torque angle data were processed to calculate the work done by the machine to extend the knee for each speed. Linear regression was used to calculate the slope of the line of best fit for the work velocity data. The slope simultaneously encompassed three key elements associated with spasticity (velocity, resistance, and stretch) and was considered the measure of spasticity. For the strength test, the dynamometer moved the leg from full knee extension to flexion while a maximum concentric contraction of the hamstring muscles was performed. Torque angle data were processed to calculate the work done on the machine by the child. Hamstring spasticity values for the CP group were significantly greater than similar values for AB group prior to surgery; however they were not significantly different after surgery. Hamstring strength values for the CP group remained significantly less than those for the AB group after surgery, but were significantly increased relative to their presurgery values. The results of spasticity testing in the present investigation agreed with previous studies indicating a reduction in spasticity for the CP group. The results of strength testing did not agree with those in the previous literature; a significant increase in strength was observed for the CP group.

Trafficking kinetics of the insulin-regulated membrane aminopeptidase in 3T3-L1 adipocytes

In fat and muscle cells insulin causes the marked translocation of the glucose transporter GLUT4 from its intracellular location to the plasma membrane. We and others have discovered an insulin-regulated membrane aminopeptidase (designated IRAP) that colocalizes with intracellular GLUT4 and also translocates markedly in response to insulin. This study describes the trafficking kinetics of IRAP in 3T3-L1 adipocytes. By means of a surface biotinylation method, the half-time for the increase in IRAP at the plasma membrane in response to insulin was found to be 2 min. The increase was completely blocked by the phosphatidylinositol 3-kinase inhibitor, wortmannin. In insulin-treated cells, biotinylated IRAP, initially at the plasma membrane, equilibrated with the intracellular pool with a half-time of 2 min. Thus, IRAP continuously recycles. Finally, vesicles isolated from the intracellular membranes with antibodies against IRAP and GLUT4 showed the same protein composition. In conjunction with results in the literature, these findings indicate that IRAP and GLUT4 traffic through the same intracellular compartments.

Phytochemical analysis of Geigeria alata and Francoeuria crispa essential oils

Phytochemical analyses of Geigeria alata (Benth. & Hook.) and Francoeuria crispa (Forssk., Cas.) (Asteraceae) essential oils were performed. G. alata oil showed moderate in vitro cytotoxicity (IC50, micrograms/ml against tumor cells; P388: 2.0, A-549: 2.5 and HT-29: 5.0), and also showed weak anti-HIV activity. S-Carvotanacetone, the major component of F. crispa oil (93.0%), was isolated and its structure was elucidated by 2D-NMR analysis.

Small weight loss on long-term acarbose therapy with no change in dietary pattern or nutrient intake of individuals with non-insulin-dependent diabetes

OBJECTIVES

To see if the long-term treatment of non-insulin dependent diabetes (NIDDM) with the alpha-glucosidase inhibitor acarbose affects food intake and body weight.

DESIGN

Randomized, double-blind, placebo-controlled, parallel design clinical trial of 12 months duration.

SUBJECTS

Subjects with NIDDM in four treatment strata: 77 on diet alone, 83 also treated with metformin, 103 also treated with sulfonylurea and 91 also treated with insulin.

MEASUREMENTS

Two 3 day diet records were obtained before randomization to acarbose or placebo therapy, and additional 3 day diet records were obtained at 3, 6, 9 and 12 months after randomization. Body weight was also measured at these times.

RESULTS

Of the 354 subjects randomized, 279 (79%) completed at least 9 months of therapy and, of these, 263 (94%) provided at least one diet record during the baseline period and two diet records during the treatment period. After one year, subjects on acarbose had lost 0.46 +/- 0.28 kg, which differed significantly from the 0.33 +/- 0.25 kg weight gain on placebo (P = 0.027). The difference in weight change between acarbose and placebo did not differ significantly in the different treatment strata. Being in the study had significant effects on diet, including a reduction in energy intake from 1760-1700 Kcal/d (P < 0.05), a reduction in simple sugars intake from 18.5-17.4% of energy (P < 0.001), and reductions in the number of different foods consumed (33-30, P < 0.001) and the number of meals eaten per day (4.7-4.3, P < 0.001). However, compared to placebo treatment, acarbose had no effect on energy intake, nutrient intakes, or dietary patterns.

CONCLUSIONS

In subjects with NIDDM on weight-maintaining diets, long-term acarbose therapy results in a small weight loss, but has no effect on energy or nutrient intakes. The weight loss induced by acarbose may be due partly to reduced doses of concomitant oral agents and insulin and partly to energy loss due to increased colonic fermentation.

Retinoic acid as a therapy for emphysema?

In concert with its action as a morphogen during embryonal development, retinoic acid appears to be able to regenerate lung alveoli in an experimental model of elastase-induced emphysema in rats, thereby inhibiting manifestation of the disease. The application to humans is now an interesting possibility.

Factors influencing the estimation of the albumin excretion rate in subjects with diabetes mellitus

OBJECTIVE

To evaluate alternative methods of calculating the albumin excretion rate (AER) in the absence of complete and accurate patient documentation, since microalbuminuria in patients with diabetes mellitus is associated with serious complications and since patients often make errors in recording the volume and timing of urine collection, making AER calculations inaccurate.

DESIGN

Prospective study.

SETTING

Recruitment sites, including all native reserves, across southern Alberta.

PARTICIPANTS

Population-based group of 1286 subjects with diabetes mellitus participating in the Southern Alberta Study of Diabetic Retinopathy.

INTERVENTIONS

Timed AERs were measured in the subjects; urinary albumin concentration was measured by radioimmunoassay.

OUTCOME MEASURES

A formula for the prediction of AER was based on the clinical data from the subjects. Several factors were considered in developing the formula: insulin-using status, weight, sex and urine and serum creatinine concentrations.

RESULTS

A mathematical model for estimation of the AER was developed; incorporation of insulin use, sex and weight provides a more accurate estimate of AER. According to this model, women typically appear to have a lower AER than men and heavier people appear to have a higher AER than people with lower body weight.

CONCLUSIONS

The use of mathematical formulae to calculate the AER provides an accurate estimate of the AER, particularly when data related to the volume and timing of urine collection are missing. These formulae will be valuable in large epidemiologic screening programs.

Membrane amine oxidase cloning and identification as a major protein in the adipocyte plasma membrane

A 97-kDa protein present in the glucose transporter (GLUT4 isotype)-containing vesicles from rat adipocytes has been isolated, the sequences of two tryptic peptides were obtained, and on the basis of these its cDNA partially cloned. The 97-kDa protein is almost certainly identical to a major integral glycoprotein of this size in the rat adipocyte plasma membrane, since its predicted N-terminal sequence is the same as that recently determined for this glycoprotein by amino acid sequencing. Moreover, the predicted partial sequence (322 amino acids) of the 97-kDa protein is highly homologous to the corresponding region of a human placental amine oxidase, which was cloned simultaneously and proposed to be a secreted protein. The amino acid sequence of the 97-kDa rat/human amine oxidase indicates that the protein consists of a very short N-terminal cytoplasmic domain followed by a single transmembrane segment and a large extracellular domain containing the catalytic site. Thus this study establishes the 97-kDa rat/human amine oxidase as the first integral membrane amine oxidase to be cloned. The membrane amine oxidase was more abundant in the plasma membranes than the low density microsomes of the adipocyte, and in contrast to some other proteins found in GLUT4 vesicles, it did not redistribute to the plasma membrane in response to treatment of the cells with insulin.

Insulin stimulates cell surface aminopeptidase activity toward vasopressin in adipocytes

We previously discovered that insulin stimulates the marked translocation of a novel membrane aminopeptidase, designated vp165 for vesicle protein of 165 kDa, to the cell surface in adipocytes. To examine the hypothesis that this enzyme acts on peptide hormones, we assessed the relative affinity of the enzyme for 22 peptide hormones by measuring the inhibitory effect of each on the hydrolysis of a fluorogenic substrate, and we directly assayed the cleavage of four of these. Angiotensin III, angiotensin IV, and Lys-bradykinin bound to the enzyme with half-saturation constants between 20 and 600 nM and were cleaved by vp165. Vasopressin bound with lower affinity but at saturation was cleaved more rapidly. Subsequently, the effect of insulin on the rates of cleavage of 125I-labeled vasopressin by intact 3T3-L1 and rat adipocytes was determined. With both cell types, vasopressin cleavage was stimulated approximately threefold. These findings indicate that a physiological role for vp165 may be the processing of peptide hormones and that insulin could enhance the cleavage of extracellular substrates by eliciting the translocation of vp165 to the cell surface.

Cytosine-specific chemical probing of DNA using bromide and monoperoxysulfate

Bromination of cytosine and formation of a piperidine-labile site are observed when two simple salts, KBr and KHSO5, are allowed to react with single-stranded oligodeoxynucleotides. Selectivity for C compared with T, G or A is typically a factor of 4 or more; selectivity for Cs in a single-stranded region such as a C-bulge is nearly a factor of 10 compared with duplex Cs. Low reactivity and little base selectivity are observed using duplex DNA, although increased concentrations of reagents lead to complete degradation of the DNA. The results suggest that these conditions for in situ generation of Br2 constitute a useful tool for examination of the exposure of a non-duplex cytosine base in folded DNA structures.

A new metabolite of retinol: all-trans-4-oxo-retinol as a receptor activator and differentiation agent

All-trans-4-oxo-retinol, a metabolite of retinol synthesized in mouse embryonal carcinoma F9 cells, is active in inducing differentiation of these cells. It also functions as a ligand of retinoic acid receptors and a transcriptional activator of reporter genes. These findings may dispel the notion that retinoic acids are the only transactivators of retinoid receptor-dependent pathways. However, there are weaknesses that need to be addressed in order to confirm the relevance of this retinol-mediated signaling pathway.

Neuron-specific enolase as an aid to outcome prediction in head injury

A statistically significant elevation was observed in serum and CSF neuron-specific enolase (NSE) levels in patients with major head injury, relative to control individuals. No correlation was noted between serum NSE and either APACHE II, Injury Severity Score (ISS), Glasgow Outcome Score (GOS) or Glasgow Coma Scale (GCS). A significant correlation was noted between CSF NSE levels and GCS, but not between CSF NSE and APACHE II, ISS or GOS. Of the patients with major head injury, 100% had NSE CSF levels above the normal level, while 47% had elevated serum NSE levels. In nine patients with major head injury, changes in CSF levels reflected changes in serum NSE levels. In all nine patients, serum NSE decreased to reach normal values, regardless of the outcome as predicted by the GOS. Therefore, while NSE would appear to be a marker of neuronal cell damage, other markers are also essential.

Beta-carotene increases lung cancer incidence in cigarette smokers

Clinical trials were designed to validate the protective effect of beta-carotene in populations of cigarette smokers at high risk for lung cancer development. Strikingly, an increase in lung cancer resulted following beta-carotene supplementation in two separate studies in Finland and the United States. These trials were conducted without any evidence that beta-carotene prevents lung cancer in animal models.

Quantitative clinical measure of spasticity in children with cerebral palsy

OBJECTIVE

This investigation developed an objective measure to quantify the degree of spasticity.

DESIGN

Specifications included a single variable that integrated key elements characterizing spasticity: velocity, range of motion, and resistance to passive motion. A dynamometer at a children's hospital quantified the passive resistance of the hamstrings to knee extension for a range of motion at 4 different speeds for the prospective descriptive investigation.

PATIENTS

A convenience sample of six children with able bodies and 17 children with spastic diplegic cerebral palsy volunteered. DATA PROCESSING: Torque-angle data were processed to calculate the work done by the machine on the children for each speed and then determine the slope of the work-velocity curves. This slope was considered to be the measure of spasticity and it was hypothesized that children with cerebral palsy would have a greater slope than children with able bodies. An independent test determined whether a significant difference existed between groups (p < .05).

RESULTS

Torque-angle data for children with able bodies indicated little change in passive resistance as a function of speed. Similar data for children with cerebral palsy indicated larger resistive torques with increasing speed. Slope from the work-velocity data was close to zero for children with able bodies [.003 J/(degrees/sec)], while the corresponding slope for children with cerebral palsy was approximately 10 times greater [.031 J/(degrees/sec)] and significantly different (p < .05).

CONCLUSION

The slope of the work-velocity data integrates three major components characterizing spasticity, it is a single number that can easily be evaluated and interpreted in a clinical setting, and it utilizes a machine that is available at many centers.

Homobotcinolide: a biologically active natural homolog of botcinolide from Botrytis cinerea

A novel natural product exhibiting biological activity was isolated from a strain of Botrytis cinerea that had infected raspberry fruit (Rubus ideaus). Liquid fermentation and bioassay-directed fractionation of the organism yielded a compound with molecular formula C22H38O8 that is trivially named homobotcinolide. It significantly inhibited etiolated wheat coleoptile growth. Greenhouse-grown bean, corn, and tobacco plants were also affected by exogenous application of homobotcinolide, severe chlorosis and necrosis being exhibited in corn. The compound is a polyhydroxylated nonalactone esterified with 4-hydroxy-2-decenoic acid.

Characterization of the insulin-regulated membrane aminopeptidase in 3T3-L1 adipocytes

A novel membrane aminopeptidase has been identified as a major protein in vesicles from rat adipocytes containing the glucose transporter isotype Glut4. In this study we have characterized this aminopeptidase, referred to as vp165, in 3T3-L1 adipocytes. The subcellular distributions of vp165 and Glut4 were determined by immunoisolation of vesicles with antibodies against both proteins, by immunofluorescence, and by subcellular fractionation and immunoblotting. Relative amounts of vp165 at the cell surface in basal and insulin-treated cells were assayed by cell surface biotinylation. These experiments showed that vp165 and Glut4 were entirely colocalized and that vp165 increased markedly at the cell surface in response to insulin, in a way similar to Glut4. When intact cells were assayed with a novel, membrane-impermeant fluorogenic substrate for vp165, we found that insulin stimulated aminopeptidase activity at the cell surface. This observation provides direct evidence for the functional consequence of vp165 translocation.

A role for the disulfide bond spacer region of the Chlamydomonas reinhardtii coupling factor 1 gamma-subunit in redox regulation of ATP synthase

The gamma-subunit of chloroplast coupling factor 1 contains a disulfide bond which is involved in the redox regulation of the enzyme. In all the sequence plant gamma-subunits this disulfide bond is separated by a five amino acid spacer region. To investigate the regulatory significance of this region genetic transformation experiments were performed with Chlamydomonas reinhardtii. C. reinhardtii strain atpC1 (nitl-305, cw 15, mt-), which does not accumulate the CF1 gamma-subunit polypeptide, was independently transformed with two constructs, each bearing mutations within the disulfide bond spacer region between Cys198 and Cys204 of the gamma-subunit. Successful complementation was confirmed by phenotypic selection, Northern blot analysis, and reverse transcription polymerase chain reaction. Whereas wild-type thylakoid membrane particles catalyze in vitro, PMS-dependent photophosphorylation that is stimulated 2-fold by the addition of DTT, similar particles from each of the mutant strains exhibit rates of ATP synthesis that are independent of DTT. Consistent with these results, wild-type CF1 ATPase activity is stimulated by DTT which is in contrast to the ATPase activities of both the mutant strains which are independent of DTT addition. These results suggest a role of the gamma-subunit disulfide bond spacer region in the redox regulation of chloroplast ATP synthase.

Retinoic acid response elements as positive and negative regulators of the expression of the homeobox b-1 gene

Retinoic acid-dependent homeobox Hoxb-1 gene expression offers an unanticipated example of both a positive and a negative transcriptional activity of RA, as exerted at different times during embryogenesis. A paradigm for the transduction of positive and negative signaling is the discovery that retinoic acid response elements (RAREs), positioned in the 3' enhancer and 5' promoter of the Hoxb-1 gene, may function respectively as positive and negative regulators, thereby permitting a diffused (early positive) as well as segmentally specified and limited (late negative) expression of the gene. This molecular action of retinoic acid may provide a mechanism for our understanding of normal embryogenesis and of the interference with this process by ectopic retinoic acid, thereby leading to teratogenesis.

A Clinical Informatics Network (CLINT) to support the practice of evidence-based health care

CLINT, which stands for Clinical Informatics NeTwork, is one of the clinical informatics initiatives in development at McMaster University's Health Information Research Unit. CLINT is a microcomputer-based system of over 60 workstations providing 24 hour availability of a set of clinical information resources to clinicians throughout our teaching hospital. CLINT encompasses three domains: (1) a user adaptable clinician-computer interface, (2) unique evidence-based health care content, and (3) automated data collection and viewing tools. An objective of the CLINT project is to determine CLINT's impact on the practice of health care. Early analysis of our data has revealed that over the past year, there has been widespread use of CLINT by clinicians from all clinical domains. Our next task is to evaluate CLINT's usefulness.

The volatile oil composition of fresh and air-dried buds of Cannabis sativa

The composition of the steam-distilled volatile oil of fresh and air-dried, indoor-grown marijuana was studied by GC/FID and GC/MS. In all, 68 components were detected of which 57 were fully identified. Drying of the plant material had no effect on the qualitative composition of the oil and did not affect the ability of individuals familiar with marijuana smell to recognize the odor.

Clinical experience with acarbose: results of a Canadian multicentre study

Current therapeutic options for the treatment of non-insulin-dependent diabetes mellitus (NIDDM) focus on regimens that primarily lower fasting blood glucose concentrations. In several short-term studies, the alpha-glucosidase inhibitor, acarbose, has been reported to significantly lower post-prandial plasma glucose levels as well as HbA1c. The primary objective of this present study was to assess the long-term efficacy of adjunctive acarbose therapy to improve metabolic control. Over a 1-y period, acarbose or placebo was administered to 4 groups of patients: those managed by diet only, diet and sulfonylurea, diet and biguanide, and diet and insulin. In all treatment groups, the addition of acarbose resulted in significant reductions in postprandial blood glucose levels. Additionally, HbA1C was significantly lower after 12 months of acarbose therapy, compared with placebo, in all groups except the diet and insulin group. The addition of acarbose consequently expands the armamentarium available to clinicians for the optimization of glycemic control in patients with NIDDM.

Retinoic acid and methotrexate specifically increase PHA-E-lectin binding to a 67-kDa glycoprotein in LA-N-1 human neuroblastoma cells

Retinoic acid (RA) decreased growth and increased morphologic differentiation of human neuroblastoma LA-N-1 cells. These phenomena correlated with a specific enhancement of PHA-E lectin binding to a glycoprotein of MW 67 kDa (gp67). Gp67 was found susceptible to N-glycanase and displayed BSA binding by affinity chromatography analysis. The chemotherapeutic agent methotrexate (MTX) also reduced growth and induced differentiation of LA-N-1 cells. In addition, the cells responded to MTX as well as to doxorubicin by a marked increase in PHA-E binding to gp67. We conclude that reduced growth and induction of morphological differentiation of LA-N-1 cells correlates with increased binding of PHA-E to gp67.

Effects of enalapril and nitrendipine on the excretion of epidermal growth factor and albumin in hypertensive NIDDM patients

OBJECTIVE

To compare the effect of the antihypertensive drugs nitrendipine and enalapril on the excretion of epidermal growth factor (EGF) and albumin in hypertensive non-insulin-dependent diabetes mellitus (NIDDM) subjects.

RESEARCH DESIGN AND METHODS

After a 4-week washout period, mildly hypertensive (systolic blood pressure [sBP] > or = 140 mmHg and/or diastolic blood pressure [dBP] > or = 90 mmHg) NIDDM patients with albuminuria (15-200 micrograms/min) were randomized into an 8-month-long therapy with either nitrendipine (n = 11) or enalapril (n = 10). Blood pressure, EGF, and microalbumin excretion were measured at baseline and throughout the treatment period.

RESULTS

A significant fall in sBP was noticed in the enalapril group and in dBP in the nitrendipine group. In the enalapril group, EGF excretion progressively increased from 188 to 214 nmol/mmol creatinine after 6 weeks and to 274 after 8 months of therapy (P = 0.03). There was a significant fall in albumin excretion while patients were on enalapril, but in the nitrendipine group, neither albuminuria nor EGF excretion changed significantly. There was no correlation of improved EGF excretion with a decrease in albuminuria or BP.

CONCLUSIONS

The angiotensin-converting enzyme inhibitor enalapril has been effective in decreasing albumin and increasing EGF excretion. Measurement of urinary EGF may provide a new valuable index of renal function.

Role of the Chlamydomonas reinhardtii coupling factor 1 gamma-subunit cysteine bridge in the regulation of ATP synthase

The gamma-subunit of coupling factor 1 (CF1) contains a cysteine bridge that is thought to be involved in the redox control of enzymatic activity. In order to test the regulatory significance of this disulfide bond, genetic transformation experiments with Chlamydomonas reinhardtii were performed. C. reinhardtii strain atpC1 (nit1-305, cw 15, mt-), which is null for the gamma-subunit, was transformed and complemented with gamma-subunit constructs containing amino acid substitutions localized to the cysteine bridge between Cys198 and Cys204. Successful complementation was confirmed by phenotypic selection, Northern blot analysis, reverse transcription polymerase chain reaction, and cDNA sequencing. CF1 ATPase activities of the soluble enzymes were measured in the presence and absence of dithiothreitol (DTT). Mutant CF1 enzymes showed no effect of DTT although increased activity was observed for the wild-type enzyme. In vitro, phenazine methosulfate-dependent photophosphorylation assays revealed that wild-type CF1 exhibits a 2-fold stimulation in the presence of 25 mM DTT, whereas each of the mutant enzymes has activities that are DTT-independent. Growth measurements indicated that despite the absence of a regulatory disulfide/dithiol, the mutant strains grew with the same kinetics as wild type. This study provides evidence to illustrate the involvement of the gamma-subunit in the redox regulation of ATP synthesis in vivo. This work is also the first demonstration in C. reinhardtii of stable nuclear transformation using mutated genes to complement a known defect.