Nutritional advantages of barnyard millet and opportunities for its processing as value-added foods

Barnyard millet (Echinochloa species) has received appreciable attention for its susceptibility to biotic and abiotic stresses, multiple harvests in a year and rich in micronutrients, fibers and phytochemicals. It is believed that the consumption of barnyard millet can possess various health benefits against diabetes, cardiovascular diseases, obesity, skin problems, cancer and celiac disease. The flour of barnyard millet is gluten-free and can be incorporated into the diet of celiac and diabetic patients. Considering the nutritional value of millet, various millet-based food products like bread, snack, baby foods, millet wine, porridge, fast foods and millet nutrition powder can be prepared. Future research and developments on barnyard millet and its products may help cope with various diseases known to humans. This paper discusses barnyard millet's nutritional and health benefits as whole grain and its value-added products. The paper also provides insights into the processing of barnyard millet and its effect on the functional properties and, future uses of barnyard millet in the field food industry as ready-to-cook and ready-to-eat products as well as in industrial uses, acting as a potential future crop contributing to food and nutritional security.

Adaptive design with bayesian informed interim decisions: application to a randomized trial of mechanical circulatory support

Background

Cardiovascular trials increasingly require large sample sizes and long follow-up periods. Several approaches have been developed to optimize sample size such as adaptive group sequential trials, samples size re-estimation based on the promising zone, and the win ratio. Traditionally, the log-rank or the Cox proportional hazards model is used to test for treatment effects, based on a constant hazard rate and proportional hazards alternatives, which however, may not always hold. Large sample sizes and/or long follow up periods are especially challenging for trials evaluating the efficacy of acute care interventions.

Purpose

We propose an adaptive design wherein using interim data, Bayesian computation of predictive power guides the increase in sample size and/or the minimum follow-up duration. These computations do not depend on the constant hazard rate and proportional hazards assumptions, thus yielding more robust interim decision making for the future course of the trial.

Methods

PROTECT IV is designed to evaluate mechanical circulatory support with the Impella CP device vs. standard of care during high-risk PCI. The primary endpoint is a composite of all-cause death, stroke, MI or hospitalization for cardiovascular causes with initial minimum follow-up of 12 months and initial enrolment of 1252 patients with expected recruitment in 24 months.

The study will employ an adaptive increase in sample size and/or minimum follow-up at the Interim analysis when ∼80% of patients have been enrolled. The adaptations utilize extensive simulations to choose a new sample size up to 2500 and new minimal follow-up time up to 36 months that provides a Bayesian predictive power of 85%.

Bayesian calculations are based on patient-level information rather than summary statistics therefore enabling more reliable interim decisions. Constant or proportional hazard assumptions are not required for this approach because two separate Piece-wise Constant Hazard Models with Gamma-priors are fitted to the interim data. Bayesian predictive power is then calculated using Monte-Carlo methodology. Via extensive simulations, we have examined the utility of the proposed design for situations with time varying hazards and non-proportional hazards ratio such as situations of delayed treatment effect (Figure) and crossing of survival curves. The heat map of Bayesian predictive power obtained when the interim Kaplan-Meier curves reflected delayed response shows that for this scenario an optimal combination of increased sample size and increased follow-up time would be needed to attain 85% predictive power.

Conclusion

A proposed adaptive design with sample size and minimum follow-up period adaptation based on Bayesian predictive power at interim looks allows for de-risking the trial of uncertainties regarding effect size in terms of control arm outcome rate, hazard ratio, and recruitment rate.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Abiomed, Inc Figure 1

GnRH agonist and hCG (dual trigger) versus hCG trigger for final follicular maturation: a double-blinded, randomized controlled study

STUDY QUESTION

Does co-administration of GnRH agonist and Human chorionic gonadotropin (hCG; dual trigger) in IVF cycles improve the number of mature oocytes and pregnancy outcome compared to hCG alone?

SUMMARY ANSWER

Using the dual trigger for final follicular maturation increases the number of oocytes, mature oocytes and number of blastocysts (total and top-quality) compared to triggering with hCG alone.

WHAT IS KNOWN ALREADY

hCG is used at the end of controlled ovarian hyperstimulation as a surrogate LH surge to induce final oocyte maturation. Recently, based on retrospective studies, the co-administration of GnRH agonist and hCG for final oocyte maturation (dual trigger) has been suggested to improve IVF outcome and pregnancy rates.

STUDY DESIGN, SIZE, DURATION

A single center, randomized controlled, double-blinded clinical trial between May 2016 and June 2018 analyzed by intention to treat (ITT).

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

One hundred and fifty-five normal responder patients were randomized either to receive hCG or dual trigger for final oocyte maturation. Data on patients age, BMI, AMH, number of oocytes retrieved, number of metaphase 2 (MII) oocytes, zygotes and blastocysts, clinical pregnancy rate and live birth rate were assessed and compared between the dual trigger group and the hCG group. We performed a planned interim analysis after the recruitment of 50% of the patients. Based on the totality of outcomes at the interim analysis we decided to discontinue further recruitment.

MAIN RESULTS AND THE ROLE OF CHANCE

One hundred and fifty-five patients were included in the study. The age (36 years versus 35.3 years P = NS), BMI (24 kg/m2 versus 23.7 kg/m2) and the AMH (20.1 pmol/l versus 22.4 pmol/l) were comparable between the two groups. Based on ITT analysis, the number of eggs retrieved (11.1 versus 13.4, P = 0.002), the MII oocytes (8.6 versus 10.3, P = 0.009), total number of blastocysts (2.9 versus 3.9, P = 0.01) and top-quality blastocysts transferred (44.7% versus 64.9%; P = 0.003) were significantly higher in the dual trigger group compared to the hCG group. The clinical pregnancy rate (24.3% versus 46.1%, OR 2.65 (1.43-1.93), P = 0.009) and the live birth rate per transfer (22% versus 36.2%, OR= 1.98 (1.05-3.75), P = 0.03) were significantly higher in the dual trigger group compared to the hCG group.

LIMITATIONS, REASONS FOR CAUTION

None.

WIDER IMPLICATIONS OF THE FINDINGS

The enhanced response observed with the dual trigger might lead to better IVF outcomes were it used more widely.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by TRIO Fertility. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT02703584.

DATE OF TRIAL REGISTRATION

March 2016.

DATE OF FIRST PATIENT'S ENROLLMENT

May 2016.

REDUCE-IT: accumulation of data across prespecified interim analyses to final results

Background

REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial), an event-driven trial, randomized 8,179 statin-treated patients with elevated triglycerides (TGs) and increased cardiovascular (CV) risk to icosapent ethyl (IPE); pure, stable prescription eicosapentaenoic acid, 4g/day or placebo. 1,612 primary endpoint events (CV death, nonfatal myocardial infarction [MI], nonfatal stroke, coronary revascularization, or hospitalization for unstable angina) projected 90% power to detect 15% relative risk reduction (5% 2-sided alpha). The key secondary composite endpoint was CV death, nonfatal MI, or nonfatal stroke. An independent data and safety monitoring committee (DMC) performed prespecified interim analyses (IAs) at ∼60% (IA1 31 May 2016 data cutoff; 2.9 y median primary endpoint follow-up) and ∼80% (IA2 01 May 2017; 3.7 y) of events; final analysis included 1,606 events (06 Sep 2018; 4.9 y median study follow-up).

Purpose

Explore REDUCE-IT efficacy and safety across prespecified IAs for insight into progression of robustness and consistency of conclusions.

Methods

The interim statistical analysis plan guided study continuation decisions by a prespecified decision-making process, including assessment of safety, treatment arm performance, primary composite endpoint formal analyses, and informal robustness analyses, with no futility or efficacy stopping requirements. Prior to DMC IA study continuation decisions, the need for a mature dataset to support the robustness of final efficacy and safety findings was discussed. Sponsor, Steering Committee, and Clinical Endpoint Committee were blinded throughout.

Results

Primary and key secondary endpoints achieved statistical significance at IA1 and IA2 that persisted at final analyses (p-value below final adjusted 2-sided alpha of 0.0437); hazard ratios also remained consistent and similar robustness was observed across individual endpoint components; clarity of findings across endpoints and subgroups improved with more events. Stopping for overwhelming efficacy was discussed at each IA; prior to IA study continuation recommendations, the DMC considered historical examples of failed CV outcome studies for TG-lowering and mixed omega-3 therapies, reflected on the potential for overestimating final demonstrated benefit using incomplete data, and weighed societal impacts of fuller datasets relative to patient therapy access.

Conclusions

Consistent, potent efficacy emerged early and persisted across the two prespecified interim and final analyses. The mature dataset demonstrated highly statistically significant reductions in the primary (25%; p=0.00000001) and key secondary (26%; p=0.0000006) endpoints and allowed robust analyses to support overall efficacy and safety conclusions. Allowing the REDUCE-IT dataset to fully mature provided clinicians with robust, consistent, and reliable data upon which to base clinical decisions for IPE in CV risk reduction.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The study was funded by Amarin Pharma, Inc.

Impact of timing of randomization after an acute coronary syndrome and subsequent events in patients with type 2 diabetes mellitus: an analysis of the EXAMINE trial

Background

The timing of enrolment following an acute coronary syndrome (ACS) may influence cardiovascular (CV) outcomes and potentially treatment effect in clinical trials. Using a large contemporary trial in patients with type 2 diabetes mellitus (T2DM) post-ACS, we examined the impact of timing of enrolment on subsequent CV outcomes.

Methods

EXAMINE was a randomized trial of alogliptin versus placebo in 5380 patients with T2DM and a recent ACS. The primary outcome was a composite of CV death, non-fatal myocardial infarction [MI], or non-fatal stroke. The median follow-up was 18 months. In this post hoc analysis, we examined the occurrence of subsequent CV events by timing of enrollment divided by tertiles of time from ACS to randomization: 8–34, 35–56, and 57–141 days.

Results

Patients randomized early (compared to the latest times) had less comorbidities at baseline including a history of heart failure (HF; 24.7% vs. 33.0%), prior coronary artery bypass graft (9.6% vs. 15.9%), or atrial fibrillation (5.9% vs. 9.4%). Despite the reduced comorbidity burden, the risk of the primary outcome was highest in patients randomized early compared to the latest time (adjusted hazard ratio [aHR] 1.47; 95% CI 1.21–1.74) (Figure 1). Similarly, patients randomized early had an increased risk of recurrent MI (aHR 1.51; 95% CI 1.17–1.96) and HF hospitalization (1.49; 95% CI 1.05–2.10).

Conclusion

In a contemporary cohort of T2DM with a recent ACS, early randomization following the ACS increases the risk of CV events including recurrent MI and HF hospitalization. This should be taken into account when designing future clinical trials.

Figure 1

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Takeda Pharmaceutical

Flexible bronchoscopic removal of a three piece foreign body from a child's bronchus

Foreign body aspiration can be a life-threatening event especially in young children because they have smaller diameters of airway lumen, moreover, the delay in the diagnosis and subsequent therapeutic intervention can further increase the risk of morbidity.(1, 2) A retained foreign body can result in inflammatory response and granulation tissue formation around the object which make the foreign body removal difficult.(3) In such situations surgical intervention is usually needed but with interventional pulmonology modalities we can restrict the need for surgery.(4) Rigid bronchoscopy under general anaesthesia is the gold standard of diagnosis and management of foreign body aspiration.(1) However, nowadays flexible bronchoscopy is more widely available and most pulmonary physicians are trained in its use so it can be used to remove such foreign bodies. We hereby report a case of a neglected foreign body which remained in the bronchus of a child for 11 days, successfully removed by flexible bronchoscopy.

Complication after abdominoperineal resection of the rectum

Treatment of rectal cancer commonly involves pre-operative short-term external beam radiotherapy along with curative surgery. We describe a case that was treated with the standard multi-modality treatment but developed some very unusual complications.

How to achieve balloon stability in aortic valvuloplasty using rapid ventricular pacing

Balloon aortic valvuloplasty is now the treatment of choice for congenital aortic stenosis. Balloon stability may be difficult to achieve and this may result in a suboptimal result or even valve damage. We describe the technique of rapid ventricular pacing as a safe and effective option for achieving balloon stability during aortic valvuloplasty.

Power and sample size for ordered categorical data

We propose a new method for computing power and sample size for linear rank tests of differences between two ordered multinomial populations. The method is flexible in that it is applicable to any general alternative hypothesis and for any choice of rank scores. We show that the method, though asymptotic, closely approximates existing exact methods. At the same time it overcomes the computational limitations of the exact methods. This advantage makes our asymptotic approach more practical for sample size computations at the planning stages of a large study. We illustrate the method with data arising from both proportional and non-proportional odds models in the two ordered multinomial setting.

Langerhans cell histiocytosis of the orbit

Langerhans cell histiocytosis (LCH) accounts for less than 1% of all orbital tumours. Though rare, orbital involvement in LCH is not uncommon. Most reports so far have been in Western literature. We report here a case of LCH of orbit with intracranial extension. To the best of our knowledge, this is the first case of single system multifocal LCH reported from India.

Computational tools for exact conditional logistic regression

Logistic regression analyses are often challenged by the inability of unconditional likelihood-based approximations to yield consistent, valid estimates and p-values for model parameters. This can be due to sparseness or separability in the data. Conditional logistic regression, though useful in such situations, can also be computationally unfeasible when the sample size or number of explanatory covariates is large. We review recent developments that allow efficient approximate conditional inference, including Monte Carlo sampling and saddlepoint approximations. We demonstrate through real examples that these methods enable the analysis of significantly larger and more complex data sets. We find in this investigation that for these moderately large data sets Monte Carlo seems a better alternative, as it provides unbiased estimates of the exact results and can be executed in less CPU time than can the single saddlepoint approximation. Moreover, the double saddlepoint approximation, while computationally the easiest to obtain, offers little practical advantage. It produces unreliable results and cannot be computed when a maximum likelihood solution does not exist.

An exact trend test for correlated binary data

The problem of testing a dose-response relationship in the presence of exchangeably correlated binary data has been addressed using a variety of models. Most commonly used approaches are derived from likelihood or generalized estimating equations and rely on large-sample theory to justify their inferences. However, while earlier work has determined that these methods may perform poorly for small or sparse samples, there are few alternatives available to those faced with such data. We propose an exact trend test for exchangeably correlated binary data when groups of correlated observations are ordered. This exact approach is based on an exponential model derived by Molenberghs and Ryan (1999) and Ryan and Molenberghs (1999) and provides natural analogues to Fisher's exact test and the binomial trend test when the data are correlated. We use a graphical method with which one can efficiently compute the exact tail distribution and apply the test to two examples.

Power comparisons for tests of trend in dose-response studies

The Cochran-Armitage test for trend is a popular statistical procedure for detecting increasing or decreasing probabilities of response when a categorical exposure is ordered. Such associations may arise in a variety of biomedical research settings, particularly in dose-response designs such as carcinogenicity experiments. Previously, computing limitations mandated the use of the asymptotic trend test, but with the availability of new algorithms, increased computing power, and appropriate software the exact trend test is now a practical option. Nevertheless, the exact test is sometimes criticized on the grounds that it is conservative. In this paper we investigate the implications of this conservatism by comparing the true type I error and power of three alternative tests of trend - the asymptotic test, the exact test and an admissible exact test proposed by Cohen and Sackrowitz. The computations are performed by an extension to the network algorithm of Mehta et al. This allows us to make precise power comparisons between the tests under any given design without resorting to simulation. We show how this tool can guide investigators in choosing the most appropriate test by considering the design of two-year carcinogenicity studies carried out by the National Toxicology Program. We additionally compare the tests for various other combinations of sample sizes and number of groups or levels of exposure. We conclude that the asymptotic test, while more powerful where it is valid, generally does not preserve the type I error. This violation of the a priori testing level can be greatly affected by imbalance in the data or unequal spacing of dose levels.

Tracheal duplication as a cause of congenital stridor

A six-week-old child with tracheal duplication presenting with congenital stridor is being reported. To the best of our knowledge, a tracheal web or tracheal duplication (as the present condition may be named) has not been described as a causative factor of infantile stridor.

A case of motor neurone disease with sleep apnoea syndrome

A case of a 63-year-old patient with motor neurone disease (amyotrophic lateral sclerosis) with central sleep apnoea syndrome is being reported. His sleep architecture was fragmented with a high apnea-hypopnea index of 65 per hour and maximum oxygen-desaturation of 78 percent. Total correction of sleep pattern with nasal non-invasive ventilation (BiPAP-ST) was demonstrated.

Bilioma secondary to choledocholithiasis

Bilioma secondary to choledocholithiasis is rare. We report a patient in whom a large common bile duct stone was responsible for leak from the infraduodenal segment of the bile duct. Choledochotomy with extraction of stone followed by T-tube drainage of the bile duct and evacuation of the bilioma resulted in complete recovery.

Antidotal effect of sodium thiosulfate in mice exposed to acrylonitrile

Although acute acrylonitrile (ACN) toxicity is very profound, the mechanism of its toxicity and immediate lethality is unclear. Many have suggested that ACN or its reactive metabolite acts directly at the target tissues, while others have implicated the release of CN ions from the parent compound as the toxic moiety. Since sodium thiosulfate (STS) is both an effective cyanide antidote and neutralizing agent capable of binding to reactive chemicals or metabolites, its antidotal role was investigated in mice exposed to 60 mg/kg intraperitoneal (IP) ACN injection. Treatment with an IP injection of 400 mg/kg of STS from 10 to 30 minutes before ACN administration protected animals from ACN-induced lethality. All mice appeared normal after prophylactic treatment with STS and showed no ill effects from ACN exposure. Similar data was observed when STS was administered 10 and 30 minutes after ACN administration. Non-protein sulfhydryl (NPSH) concentration was determined in the brain, kidneys, and liver of the mice exposed to a single or multiple doses of STS and ACN. The levels of NPSH were significantly lowered by ACN in the liver (45% of the control), and kidneys (51% of the control), whereas in the brain NPSH levels were least affected and decreased modestly (85% of the control) following either acute or chronic administration of acrylonitrile. The data indicate a marked protective effect of STS either before or after ACN exposure and this STS-induced antidotal response does not involve GSH in the brain.

Homozygosity in the major histocompatibility complex region influences natural killer cell activity in man

The effect of homozygosity at HLA loci on natural killer (NK) cell activity has been examined. Lymphocytes obtained from heterozygous and homozygous individuals were incubated with 51Cr-labeled, NK-sensitive K562 cells at different effector/target ratios, and lytic activity was determined. Homozygous cells, obtained from individuals who are known HLA homozygotes (homozygous typing cells) and from selected families, had low NK activity compared to those heterozygous donors. This low cytotoxic activity had no correlation with sex, but did correlate with homozygosity at the HLA-A, B and/or DR loci. A significantly lower number of cells, which bind to anti-Leu 7 antibody, was found in homozygous donors. However, this reduced number of Leu 7+ cells could only partially account for the decrease in NK activity. These studies suggest that in some individuals homozygosity at HLA may be linked to genes that control NK activity.

Enhancement of mitogen response and surface marker analysis of lymphocytes from young and old donors after preliminary incubation in vitro

We have examined the detailed kinetics of PHA induced proliferation of freshly isolated mononuclear cells from young and old human donors. Our studies confirm that donors over the age of 60 years may have a decreased number of PHA responsive cells and that these cells have a significantly diminished rate of entry into the first cell cycle. Age of the donor does not affect the time at which significant numbers of cells appear in first S-phase, the duration of first S-phase, the doubling time in exponential growth, and thymidine uptake per cell. Cells from young and old donors were also cultured in medium supplemented with pooled human serum for 1 or 2 days prior to the PHA response assay. After 2 days of preliminary culture, the PHA response in both young and old is significantly enhanced, with a greater enhancement in the old. The basis of this enhancement appears to be a significant increase in rate of entry into the first cell cycle. None of the other kinetic parameters were significantly altered. The magnitude of the rate enhancement in old donors' cells eliminated the difference in entry rate between young and old after 2 days of preliminary culture. The same rate enhancing effects were seen in the presence of serum pooled from young or old donors. There is no statistically significant change in the number of responding cells after preliminary culture. We had previously suggested, based on lactate dehydrogenase (LD) subunit ratio and patterns of T cell associated surface markers, that less differentiated subpopulations of T cells exist in elderly donors. After preliminary culture, no significant change was seen in the proportions of cells positive for T3, T4, T8, T10 and Ia surface antigens and the unusual pattern of surface marker distribution was still present on the old donors' cells. It appears that the greater rate enhancement in old donors' cells after preliminary culture may not be due to induced maturation of the possibly less differentiated T cell populations described previously. The results do suggest that these subpopulations may be non-responsive to PHA.

Rapid and sensitive quantitative immunoassay for the large simian virus 40 T antigen

A quantitative, enzyme-linked immunoadsorbent assay has been developed for the simian virus 40 large T antigen. When hamster anti-simian virus 40 tumor serum was used, this method permitted specific identification of large T antigen and its analog, the D2 hybrid protein, a molecule with the same C-terminal approximately 600 amino acids as large T antigen. The sensitivity limit of this test was 0.63 ng of protein. The slopes of the regression lines of the enzyme-linked immunosorbent assay titrations performed with highly purified D2 or simian virus 40 large T antigen and with crude extracts of simian virus 40-infected monkey and transformed human cells were identical. Thus, the curve generated with a purified protein, such as D2, can serve as a quantitative standard for the measurement of large T antigen in a wide variety of extracts. Furthermore, solutions containing high salt concentrations and buffers containing up to 0.1% Nonidet P-40 did not interfere with the assay, making it applicable to the measurement of large T antigen in a variety of chromatographic fractions. The enzyme-linked immunosorbent assay was three times more sensitive, was significantly faster to perform, and was quantitatively valid over a much broader large-T-antigen concentration range than the complement fixation test. As such, it should be useful in future studies of the structure and function of this protein.

Kinetics of human lymphocyte responses in vitro: the phase of exponential growth

The kinetics of thymidine uptake in human peripheral lymphocytes stimulated by allogenic cells, antigen E (ragweed allergen) and a variety of mitogens can generally be divided into four consecutive phases. First, a lag period with no increase in thymidine uptake, then a short period of rapid change in uptake, followed by a log-linear growth period and finally a decay phase. In this report we examine in detail the characteristics of the third, log-linear growth phase. Since, as discussed in the preceding paper, thymidine uptake is proportional to the number of cells acumulating thymidine, we can calculate from the log-linear growth period an apparent doubling time. We show that for five different stimulating agents the cells reach a log-linear growth phase of varying length and that the doubling times show little variation. This invariance indicates that, despite possible variation in cell death and recruitment rates, the rate of proliferation is in all cases dominated by the generation time of human lymphocytes.

Quantitation of [3H] thymidine uptake by stimulated human lymphocytes

We have investigated the relationship between cell numbers and the amount of tritiated thymidine ([3H]TdR) taken up by stimulated human peripheral lymphocytes, as a function both of labeling time and of the specific activity of the thymidine. Cells responding either to mitogens or to allogenic cells show simple first order kinetics for the uptake of thymidine. Fitting the data to a Michaelis-Menten type of model, we observe for labeling times of 12 hr and longer, non-competitive inhibition of thymidine uptake by increased specific activity of tritium label, regardless of the mode of stimulation. However, for an individual responder in MLC at any arbitrary but fixed specific activity, dose of [3H]TdR and labeling interval, we still observe a linear relationship between cell mass and incorporated label. In contrast, if specific responding combinations in mixed lymphocyte culture are compared, the inhibition by specific activity at longer time intervals becomes significant and influences the quantitative interpretation of results. Specific activities of less than 10 Ci/mmole and labeling times of 6 hr or less avoid inhibition and ensure a linear relationship between dividing cell number and CPM (counts per minute recorded) of incorporated label.

Kinetics of human lymphocyte responses in vitro: determination of clone size and initial rate of entry into DNA synthesis

In this third paper on the kinetics of lymphocyte stimulation we present a simple stochastic model for the entry of mitogen stimulated human lymphocytes into the proliferative cycle. The model is based on the assumption that responder 'recruitment' is a process of simple exponential decay. The model can be applied to the initial rapid rise in thymidine uptake after stimulation and successfully predicts the behavior of colchicine inhibited mitogen responses. Application of the model allows the estimation of the following constants; the size of the responding clone, the rate of entry of committed cells into the initial cell cycle, the duration of the lag period before uptake of thymidine increases above background and the average duration of thymidine uptake in responding lymphocytes (Ts). If we analyze the experimental results of mitogen stimulation experiments in these terms we can show that the first three constants are sensitive functions of both the dose of mitogen and the source of the responding lymphocytes. The most interesting finding may be the fact that low doses of mitogen seem to decrease the rate of entry of committed lymphocytes into cell cycle. This would imply that the rate determining step in this process is not of an all or none type.