Axial ablation versus terminal interruption of the reflux source (AAVTIRS): a randomised controlled trial

BACKGROUND

Treatment of superficial venous reflux has been shown to improve ulcer healing time and reduce the risk of ulcer recurrence. Terminal ablation of the reflux source (TIRS) is an alternative to formal endovenous ablation or surgery which can be performed by injecting sclerosant foam into the peri-ulcer plexus of the veins. TIRS has been shown to be successful and in our experience is the option preferred by many patients, when offered as an alternative to axial ablation (AA).

AIM

To determine if the proportion of ulcers healed within 6 months of endovenous treatment differs between patients undergoing AA of varicose veins or TIRS by peri-ulcer foam sclerotherapy.

METHODS

AAVTIRS is an assessor-blinded randomised controlled trial. Patients will be recruited from a dedicated ulcer clinic in Roscommon University Hospital and from the vascular surgical clinics in University Hospital Galway. All patients attending the ulcer clinic will be screened for eligibility.

RANDOMISATION

Random computer-generated sequence is stratified by ulcer size. Allocation will be concealed using sealed opaque envelopes.

BLINDING

Assessors reviewing wounds at follow -p visits will be blinded to patient allocation.

PRIMARY ENDPOINT

The proportion of ulcers healed within 6 months of enrolment.

DISCUSSION

This will be the first time that TIRS has been evaluated with a properly powered randomised trial in the setting of venous ulcer management. Streamlining the management of venous ulcers has broad health economic benefits. If it is found that TIRS is superior or non-inferior to AA, then a less expensive, less invasive injection can be offered as an alternative to AA in an attempt to encourage the healing of venous ulcers. If AA is found to be superior to TIRS, then this would suggest that all patients undergoing ablation in the management of venous ulcers should have their superficial reflux fully treated, building on the evidence of the EVRA trial.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04484168. Registered on 23 July 2020.

Diabetes care and pregnancy outcomes for women with pregestational diabetes in Ireland

AIMS

Pre-gestational diabetes mellitus (PGDM) is associated with adverse outcomes. We aimed to examine pregnancies affected by PGDM; report on these pregnancy outcomes and compare outcomes for patients with type 1 versus type 2 diabetes mellitus; compare our findings to published Irish and United Kingdom (UK) data and identify potential areas for improvement.

METHODS

Between 2016 and 2018 information on 679 pregnancies from 415 women with type 1 Diabetes Mellitus and 244 women with type 2 diabetes was analysed. Data was collected on maternal characteristics; pregnancy preparation; glycaemic control; pregnancy related complications; foetal and maternal outcomes; unscheduled hospitalisations; congenital anomalies and perinatal deaths.

RESULTS

Only 15.9% of women were adequately prepared for pregnancy. Significant deficits were identified in availability and attendance at pre-pregnancy clinic, use of folic acid, attaining appropriate glycaemic targets and appropriate retinal screening. The majority of pregnancies (n = 567, 83.5%) resulted in a live birth but the large number of infants born large for gestational age (LGA) (n = 280, 49.4%), born prematurely <37 weeks and requiring neonatal intensive care unit (NICU) admission continue to be significant issues.

CONCLUSIONS

This retrospective cohort study identifies multiple targets for improvements in the provision of care to women with pre-gestational DM which are likely to translate into better pregnancy outcomes.

Effect of an anti-gonadotropin-releasing factor vaccine on sexual and aggressive behaviour in male pigs during the finishing period under Australian field conditions

OBJECTIVE

The objective of this study was to evaluate the effectiveness of an anti-gonadotropin-releasing factor vaccine in controlling sexual and aggressive behaviour of male pigs in the late finishing period under Australian field conditions.

METHODS

Male pigs from four consecutive batches over a 4-month period were randomly assigned to two groups: an untreated control group (n = 434) or a group treated with Improvac® (n = 433). The vaccine was administered at 10 and 16 weeks of age. Pigs were housed under commercial conditions in ecoshelters, a commonly used housing system in Australia in which pigs are kept in large pens often containing >100 animals. The occurrence of sexual and aggressive behaviours was recorded and evaluated after second vaccination until slaughter at 22 weeks of age.

RESULTS

Male pigs treated with Improvac demonstrated significant reductions in mounting, fighting, pushing, head butting and tail manipulation when compared with control animals.

CONCLUSION

This study confirms that vaccination with Improvac can improve the welfare of entire male pigs by inhibiting sexual and aggressive behaviour.

Obesity-related chronic lymphoedema-like swelling and physical function

BACKGROUND

People with severe obesity (body mass index [BMI] > 40 kg/m(2)) have an 85% higher mortality than people with a healthy BMI. Poor physical function may contribute to this excess mortality. Lymphoedema-like swelling can affect the legs of severely obese people with normal lymphoscintigraphy.

AIM

We sought to determine the relationship between the presence of lymphoedema-like swelling and physical function in the severely obese.

DESIGN AND METHODS

In people with severe obesity, we ascertained whether lower leg lymphoedema-like swelling was present and determined the circumference of the lower leg, time taken to ascend and descend a 17-cm step 50 times and time taken to walk 500 m.

RESULTS

The 330 participants, 33% of whom were male, were aged 43.4 ± 12.7 years (mean ± standard deviation) and had a BMI of 51.7 ± 8.4 kg/m(2). Lymphoedema-like swelling was present in approximately one-third (n = 108) in whom a prior history of cellulitis and venous thromboembolism was more common (relative risks 6.16 and 3.86, respectively) than in those without lymphoedema-like swelling. Participants with lymphoedema-like swelling, compared with non-affected counterparts, had a higher lower leg circumference (35.0 ± 7.1 vs. 32.4 ± 4.8 cm), a slower step speed (0.40 ± 0.12 vs. 0.43 ± 0.10 steps/s) and a slower walking speed (0.97 ± 0.37 vs. 1.08 ± 0.30 m/s, P < 0.05 for all comparisons).

CONCLUSIONS

In this cross-sectional study, 33% of our severely obese participants had lymphoedema-like swelling. Participants with lymphoedema-like swelling had worse physical function than those without. This association was independent of BMI. The presence of obesity-related chronic lymphoedema-like swelling should lead to interventions that improve physical function.

Glucocorticoid prescriptions and breast cancer recurrence: a Danish nationwide prospective cohort study

BACKGROUND

Treatment with synthetic glucocorticoids (GCs) depresses the immune response and may therefore modify cancer outcomes. We investigated the association between GC use and breast cancer recurrence.

MATERIALS AND METHODS

We conducted a population-based cohort study to examine the risk of breast cancer recurrence associated with GC use among incident stage I-III female breast cancer patients aged >18 years diagnosed 1996-2003 in Denmark. Data on patients, clinical and treatment factors, recurrence, and comorbidities as well as data on GC prescriptions and potential confounders were obtained from Danish population-based medical registries. GCs were categorized according to administrative route: systemic, inhaled, or intestinal. Women were followed for up to 10 years or until 31 December 2008. We used Cox proportional hazards regression models to compute hazard ratios (HRs) and associated 95% confidence intervals (95% CIs) to evaluate the association between GC use and recurrence. Time-varying drug exposures were lagged by 1 year.

RESULTS

We included 18 251 breast cancer patients. Median recurrence follow-up was 6.9 years; 3408 women developed recurrence during follow-up. Four thousand six hundred two women filled at least one GC prescription after diagnosis. In unadjusted models, no association was observed among users of systemic, inhaled, and intestinal GCs (HRsystemic = 1.1, 95% CI 0.9-1.3; HRinhaled = 0.9, 95% CI 0.7-1.0; and HRintestinal = 1.0, 95% CI 0.9-1.2) versus nonusers. In adjusted models, the results were also near null (HRsystemic = 1.1, 95% CI 0.9-1.2; HRinhaled = 0.8, 95% CI 0.7-1.0; and HRintestinal = 1.0, 95% CI 0.8-1.2).

CONCLUSION

We found no evidence of an effect of GC use on breast cancer recurrence.

Association between vitamin D status and physical function in the severely obese

CONTEXT

Mortality is 85% higher in severely obese subjects (body mass index [BMI] > 40 kg/m(2)) than in subjects with a healthy BMI; poor physical function may be contributory. Hypovitaminosis D is common in obese subjects and is associated with physical dysfunction in the elderly.

OBJECTIVE

We determined the relationship between vitamin D status and physical function in severely obese subjects.

DESIGN, SETTING, AND PATIENTS

We conducted a clinic-based, cross-sectional study of severely obese subjects. Participants were stratified into three groups according to the Institute of Medicine (IOM) vitamin D status categorization.

MAIN OUTCOME MEASURES

We compared levels of self-reported activity and times taken to walk 500 m and to ascend and descend a 17-cm step 50 times.

RESULTS

We recruited 252 subjects (age, 43.7 ± 11.2 y; BMI, 50.7 ± 9.7 kg/m(2)); 25-hydroxyvitamin D (25OHD) concentrations were less than 30 nmol/L in 109 participants. Participants with a 25OHD > 50 nmol/L, compared to those with a 25OHD < 30 nmol/L, had the highest activity levels (3.1 ± 3.4 h/wk versus 1.5 ± 2.5 h/wk; P = .015) and the shortest 500-m walk times (6.2 ± 1.1 min versus 7.4 ± 1.5 min; P = .003). Serum 25OHD concentrations had a weakly positive association with activity level (r = 0.19; P = .008) and a moderately negative association with 500-m walk time (r = -0.343; P < .001).

CONCLUSIONS

Vitamin D status had a significant relationship with physical activity and physical function in this cohort of severely obese subjects. Low activity levels are likely to perpetuate the problem of hypovitaminosis D due to less time spent outdoors. Studies exploring the effects of vitamin D supplementation in this population are warranted.

Glucagon-like peptide-1 analogue therapy for psoriasis patients with obesity and type 2 diabetes: a prospective cohort study

BACKGROUND

Diabetes and obesity are more prevalent amongst psoriasis patients as is disturbance of the innate immune system. GLP-1 analogue therapy considerably improves weight and glycaemic control in people with type 2 diabetes and its receptor is present on innate immune cells.

OBJECTIVE

We aimed to determine the effect of liraglutide, a GLP-1 analogue, on psoriasis severity.

METHODS

Before and after 10 weeks of liraglutide therapy (1.2 mg subcutaneously daily) we determined the psoriasis area and severity index (PASI) and the dermatology life quality index (DLQI) in seven people with both psoriasis and diabetes (median age 48 years, median body mass index 48.2 kg/m(2) ). We also evaluated the immunomodulatory properties of liraglutide by measuring circulating lymphocyte subset numbers and monocyte cytokine production.

RESULTS

Liraglutide therapy decreased the median PASI from 4.8 to 3.0 (P = 0.03) and the median DLQI from 6.0 to 2.0 (P = 0.03). Weight and glycaemic control improved significantly. Circulating invariant natural killer T (iNKT) cells increased from 0.13% of T lymphocytes to 0.40% (P = 0.03). Liraglutide therapy also effected a non-significant 54% decrease in the proportion of circulating monocytes that produced tumour necrosis factor alpha (P = 0.07).

CONCLUSION

GLP-1 analogue therapy improves psoriasis severity, increases circulating iNKT cell number and modulates monocyte cytokine secretion. These effects may result from improvements in weight and glycaemic control as well as from direct immune effects of GLP-1 receptor activation. Prospective controlled trials of GLP-1 therapies are warranted, across all weight groups, in psoriasis patients with and without type 2 diabetes.

Glucagon-like peptide-1 (GLP-1) and the regulation of human invariant natural killer T cells: lessons from obesity, diabetes and psoriasis

AIMS/HYPOTHESIS

The innate immune cells, invariant natural killer T cells (iNKT cells), are implicated in the pathogenesis of psoriasis, an inflammatory condition associated with obesity and other metabolic diseases, such as diabetes and dyslipidaemia. We observed an improvement in psoriasis severity in a patient within days of starting treatment with an incretin-mimetic, glucagon-like peptide-1 (GLP-1) receptor agonist. This was independent of change in glycaemic control. We proposed that this unexpected clinical outcome resulted from a direct effect of GLP-1 on iNKT cells.

METHODS

We measured circulating and psoriatic plaque iNKT cell numbers in two patients with type 2 diabetes and psoriasis before and after commencing GLP-1 analogue therapy. In addition, we investigated the in vitro effects of GLP-1 on iNKT cells and looked for a functional GLP-1 receptor on these cells.

RESULTS

The Psoriasis Area and Severity Index improved in both patients following 6 weeks of GLP-1 analogue therapy. This was associated with an alteration in iNKT cell number, with an increased number in the circulation and a decreased number in psoriatic plaques. The GLP-1 receptor was expressed on iNKT cells, and GLP-1 induced a dose-dependent inhibition of iNKT cell cytokine secretion, but not cytolytic degranulation in vitro.

CONCLUSIONS/INTERPRETATION

The clinical effect observed and the direct interaction between GLP-1 and the immune system raise the possibility of therapeutic applications for GLP-1 in inflammatory conditions such as psoriasis.

The IL-6 G-174C polymorphism may be associated with ischaemic stroke in patients without a history of hypertension

BACKGROUND

Recent data suggest that inflammatory reactions are involved in the pathogenesis of cerebral ischaemia.

AIM

To investigate whether certain inflammatory genetic polymorphisms are associated with the occurrence of ischaemic stroke.

METHODS

We investigated the prevalence of six polymorphisms in cytokine genes (IL-6, TNF-alpha, TNF-beta, IL-1beta, IL-10, and IL-1Ralpha) in a group of ischaemic stroke patients (n = 105) and in a control population (n = 389). We analysed the prevalence of these polymorphisms in different stroke subtypes and in relation to outcome six months post-stroke.

RESULTS

There was no significant variation in cytokine gene polymorphism frequencies between control and stroke populations or for different stroke subtypes. Subgroup analysis demonstrated that the prevalence of the IL-6 -174 CC genotype was significantly lower in stroke patients without a history of hypertension compared to controls.

CONCLUSION

The IL6 -174 CC genotype may be protective against stroke in those patients who have no history of hypertension. Further studies are required to verify these findings.

A cardiac evoked response algorithm providing threshold tracking: a North American multicenter study. Clinical Investigators of the Microny-Regency Clinical Evaluation Study

The purpose of this study was to evaluate a pacing system using the recognition of cardiac evoked response for the automatic adjustment of pacing output. Patients were prospectively followed after primary implantation of VVIR pacemakers using AutoCapture (St. Jude Medical CRMD). Sensing and pacing thresholds, polarization signal, evoked response, and AutoCapture performance were evaluated with serial visits and 24-hour Holter monitoring. Three hundred ninety-eight patients (mean age 71 +/- 15 years) were followed for an average duration of 1 year (3 days-1.75 years) with the algorithm functional in > 90% of patients. Backup pacing in the event of exit block was confirmed in all patients. Pacing thresholds remained stable at 0.89 +/- 0.34 V with a pulse width of 0.31 ms (with chronic output autoset at 0.3 V above the actual threshold). Evoked response exhibited a small but statistically significant increase with time (8.92 mV at implant, 9.60 mV at 12 months), however, this finding did not result in any change in AutoCapture function during our follow-up period. The polarization signal remained stable with minimal variation (1.12 mV at implant, 1.18 at 12 months). No clinical adverse events were observed using the AutoCapture algorithm. In this initial experience with the AutoCapture algorithm the evoked response and polarization measurements remained adequate, allowing the system to function in the majority of patients with safe, low output pacing. High energy backup pacing provided an added safety feature over fixed output devices in cases of unexpected threshold rises. Longer follow-up is required for continued long-term validation of the algorithm.

Efficacy and safety of ibutilide fumarate for the conversion of atrial arrhythmias after cardiac surgery

BACKGROUND

Atrial arrhythmias occur commonly after cardiac surgery and are a cause of significant morbidity and increased hospital costs, yet there is no well-studied treatment strategy to deal with them expeditiously. The purpose of this study was to determine the efficacy and safety of ibutilide fumarate, an approved drug for the rapid conversion of atrial fibrillation and flutter, in patients after cardiac surgery.

METHODS AND RESULTS

Patients with atrial fibrillation or flutter occurring 1 to 7 days after surgery and lasting 1 hour to 3 days were randomized to receive two 10-minute blinded infusions of placebo or 0.25, 0.5, or 1.0 mg of ibutilide fumarate. Treatment was considered successful if sinus rhythm was restored for any period of time by hour 1.5. A total of 302 patients were randomized, 201 with fibrillation and 101 with flutter. Treatment with ibutilide resulted in significantly higher conversion rates than placebo, and efficacy was dose related (placebo 15%; ibutilide 0.25 mg 40%, 0.5 mg 47%, and 1.0 mg 57%). Conversion rates at all doses were higher for atrial flutter than for atrial fibrillation. Mean time to conversion decreased as the dose was increased. Polymorphic ventricular tachycardia was the most serious adverse effect and occurred in 1.8% of the ibutilide-treated patients compared with 1.2% of patients who received placebo.

CONCLUSIONS

Ibutilide is a useful and safe treatment alternative for the atrial arrhythmias that occur after cardiac surgery.

Comparative reproducibility of defibrillation threshold and upper limit of vulnerability

The upper limit of vulnerability (ULV) is the strength at or above which VF is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. Previous studies have demonstrated a statistically significant correlation between the ULV and the defibrillation threshold (DFT) in groups of patients. However, the correlation between ULV and DFT may not be close in individual patients. This imperfect correlation may be due to physiological factors or to limitations of the measurement methods. The reproducibility of either DFT or ULV has not been studied critically. The purpose of this study was to compare the reproducibility of clinically applicable methods for determination of DFT and ULV. We prospectively studied 25 patients with a transvenous implantable cardioverter defibrillator (Medtronic 7219D) at postoperative electrophysiological study. DFT was defined as the lowest energy that defibrillated after 10 seconds of VF. The ULV was defined as the lowest energy that did not induce VF with three shocks at 0, 20, and 40 ms before the peak of the T wave in ventricular paced rhythm at a cycle length of 500 ms. Both the DFT and the ULV were determined twice for biphasic pulses using a three-step, midpoint protocol. There was no significant difference between the two determinations of DFT (10.1 +/- 5.9 J vs 10.4 +/- 5.8 J), the two determinations of ULV (13.4 +/- 6.8 J vs 13.8 +/- 6.6) or the DFT-ULV Pearson correlation coefficients for each determination (0.84, P < 0.001 vs 0.75, P < 0.001). To analyze reproducibility, Lin concordance coefficients for second determination versus first determination were constructed for both ULV and DFT. This coefficient is similar to the Pearson correlation coefficient, but measures closeness to the line of identity rather than the line of regression. The Lin concordance coefficient for ULV was higher than that for DFT (0.93, 95% CI 0.85-0.97 vs 0.64, 95% CI 0.33-0.82; P < 0.01). For paired comparison of defibrillation efficacy under different experimental conditions, the sample sizes required to detect differences of 2 J, 3 J, and 4 J (80% power, P < 0.05) were 52, 24, and 15 for DFT versus 15, 8, and 6 for ULV. We conclude that a simple, clinically applicable method for determination of ULV is more reproducible than the single point DFT. Measured correlations between the ULV and single point are limited by the reproducibility of the DFT measurement.

Upper limit of vulnerability is a good estimator of shock strength associated with 90% probability of successful defibrillation in humans with transvenous implantable cardioverter-defibrillators

OBJECTIVES

The goals of this study were to determine the probability of successful defibrillation at the upper limit of vulnerability and to evaluate a minimal safety margin for implantable cardioverter-defibrillator first shocks based solely on the upper limit of vulnerability.

BACKGROUND

The upper limit of vulnerability is the strength at or above which ventricular fibrillation is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. It has been proposed as an estimate of defibrillation efficacy because it correlates with the defibrillation threshold and can be determined with a single episode of fibrillation.

METHODS

We studied 40 patients prospectively at implantation of transvenous cardioverter-defibrillators. Defibrillation threshold was defined as the weakest biphasic shock that defibrillated after 10 s of ventricular fibrillation. The upper limit of vulnerability was defined as the weakest biphasic shock that did not induce ventricular fibrillation when given at 0, 20 and 40 ms before the peak of the T wave in ventricular paced rhythm at cycle length 500 ms. After determination of the upper limit of vulnerability and defibrillation threshold, patients underwent six additional fibrillation-defibrillation episodes. The strength of five of the defibrillation shocks was equal to the upper limit of vulnerability; the strength of one of the six shocks was randomly selected to be equal to the upper limit of vulnerability plus 3 J. The implantable cardioverter-defibrillator was tested at the upper limit of vulnerability plus 3 J in 28 patients.

RESULTS

The defibrillation threshold was 8.8 +/- 5.0 J (mean +/- SD), and upper limit of vulnerability was 11.3 +/- 4.6 J; the defibrillation threshold and upper limit of vulnerability were highly correlated (r = 0.89, p < 0.001). The success rate for the 200 defibrillation shocks with strength equal to the upper limit of vulnerability was 90% (95% confidence intervals based on proportion of successes in 40 patients: 86% to 94%). All five defibrillation test shocks at the upper limit of vulnerability were successful in 24 patients (60%); four of five were successful in 12 patients (30%); and three of five were successful in 4 patients (10%). All 40 test shocks and 28 implantable cardioverter-defibrillator shocks with a strength equal to the upper limit of vulnerability plus 3 J were successful.

CONCLUSIONS

The upper limit of vulnerability is a good estimator of the shock strength associated with 90% probability of successful defibrillation (DFT90). A strength of 3 J above the upper limit of vulnerability is a good estimate of the minimal acute safety margin for implantable cardioverter-defibrillator first shocks.

Underdetection of ventricular tachycardia by algorithms to enhance specificity in a tiered-therapy cardioverter-defibrillator

OBJECTIVES

The goal of this study was to determine the incidence and clinical significance of underdetection in 125 patients treated with a tiered-therapy cardioverter-defibrillator, the Medtronic PCD.

BACKGROUND

Underdetection, distinct from undersensing, is a unique, potential complication of new algorithms that enhance specificity in tiered-therapy cardioverter-defibrillators. These algorithms may delay or prevent recognition of ventricular tachycardia even though electrograms are sensed accurately and RR intervals meet the programmed interval criterion.

METHODS

Underdetection was defined as delay in detection > 5 s at electrophysiologic study or symptomatic delay or detection failure at follow-up of 15 +/- 8 months.

RESULTS

We identified six specific mechanisms of underdetection caused by algorithms to discriminate sustained ventricular tachycardia from sinus tachycardia, atrial fibrillation, ventricular fibrillation and nonsustained ventricular tachycardia. Underdetection caused detection delays in 13 (1.9%) of 677 induced ventricular tachyarrhythmia episodes in 12 patients (9.6%). During follow-up, underdetection occurred in 7 (9.9%) of 71 patients in whom ventricular tachycardia therapies were programmed. Failure to detect ventricular tachycardia occurred in 6 (0.6%) of 988 spontaneous ventricular tachycardia episodes in four patients (5.6%); 2 episodes required external cardioversion. After defibrillator reprogramming, underdetection did not occur.

CONCLUSIONS

Algorithms to enhance specificity cause underdetection of ventricular tachycardia in a significant minority of patients with tiered-therapy cardioverter-defibrillators. Optimal programming can minimize underdetection.

Incidence and timing of activity parameter changes in activity responsive pacing systems

The incidence and timing of rate response parameter reprogramming in activity responsive pacing systems during the year after implantation was evaluated in two groups of patients: 24 patients in whom a VVI,R system was implanted (Activitrax, Medtronic, Inc.), and 21 patients in whom a DDD,R system was implanted (Synchrony, Siemens Pacesetter, Inc.). Activity parameter changes in Activitrax patients were made based on the presence of symptoms, while in Synchrony patients, changes were based on objective data obtained using a sensor indicated rate histogram with a slow and fast walk protocol. No significant difference in the incidence of activity parameter reprogramming was noted at various time intervals during the first year in Activitrax patients; in Synchrony patients a greater incidence of reprogramming changes was noted at the 1-month follow-up visit compared to later follow-up visits (P less than 0.02). Further, the incidence of changes at 1 month was greater for Synchrony compared to Activitrax patients (P less than 0.001), while no difference was detected between groups at subsequent follow-up intervals. Use of the slow and fast walk protocol, by permitting serial evaluation of sensor response, demonstrated alterations in sensor drive rates with similar levels of activity over the initial 4 to 6 postimplant weeks. This may result from postoperative changes at the pacemaker insertion site. Based on this experience, predischarge programming may not predict long-term rate response requirements. We recommend evaluation of sensor function using an exercise protocol performed at 4 to 6 postimplant weeks in all rate responsive pacing systems that utilize a piezoelectric crystal.

An evaluation of an assay for DNA synthesis in lymphocytes with [3H]thymidine and harvesting on to glass fibre filter discs

Different grades of glass fibre filter paper have been compared for harvesting cells labelled with tritium using a semi-automatic harvester. Grade GF/C (Whatman Ltd) was selected for routine use although GF/B was found to be useful for whole blood cultures. The factors affecting the choice of thymidine concentration and activity are discussed and 1 mjCi or [3H]thymidine (5 Ci/mMol)/0.2 ml culture is shown to give a linear relationship with total DNA synthesis for up to 22 h.

Stimulation of lymphocytes by antigen in microplate cultures; absence of an effect of transfer factor in vitro

The best conditions for the optimum stimulation of human leucocytes by antigens, including protein purified derivative (PPD), streptokinase-streptodornase varidase (SKSD) and tetanus toxoid have been studied in microplate cultures. The leucocytes of each donor have their own characteristic response to antigen which depends on the culturing conditions such as antigen concentrations, cell concentrations and the time of measuring the rate of DNA synthesis. Thus, no conditions provide a universal optimum for antigen stimulation in vitro. Leucocyte dialysates, i.e. potential transfer factors, have been prepared from donors, who between them are strongly positive to the antigens PPD, SKSD, tetanus toxoid, diphtheria toxoid and Keyhole limpet haemocyanin. In contrast to some previous reports these leucocyte dialysates had no effect on the thymidine incorporation by leucocytes grown in the presence of these antigens. It is suggested that the selection of optimal conditions for the response to antigen may have obscured the effect of any non-specific enhancement of reactivity b lyeucocyte dialysates.

The control of protein synthesis during the stimulation of lymphocytes by phytohaemagglutinin. III. Poly(U) translation and the rate of polypeptide chain elongation

1. Cell-free systems from phytohaemagglutinin-stimulated pig lymphocytes are much more active in both endogenous protein synthesis and the translation of poly(U) than those from unstimulated lymphocytes. 2. Addition of tRNA stimulates the translation of poly(U) and greatly reduces the difference between systems from stimulated and unstimulated lymphocytes. Endogenous protein synthesis is not increased by added tRNA. 3. Systems from stimulated lymphocytes have an increased capacity to form aminoacyl-tRNA with several different amino acids. This reaction is limited by the amount of tRNA present in the cell-free system. 4. The rate of polypeptide elongation is not affected by lymphocyte stimulation. The increased rate of protein synthesis must therefore be due to an increase in the frequency of initiation of the synthesis of protein molecules.