Generative deep learning for the development of a type 1 diabetes simulator

BACKGROUND

Type 1 diabetes (T1D) simulators, crucial for advancing diabetes treatments, often fall short of capturing the entire complexity of the glucose-insulin system due to the imprecise approximation of the physiological models. This study introduces a simulation approach employing a conditional deep generative model. The aim is to overcome the limitations of existing T1D simulators by synthesizing virtual patients that more accurately represent the entire glucose-insulin system physiology.

METHODS

Our methodology utilizes a sequence-to-sequence generative adversarial network to simulate virtual T1D patients causally. Causality is embedded in the model by introducing shifted input-output pairs during training, with a 90-min shift capturing the impact of input insulin and carbohydrates on blood glucose. To validate our approach, we train and evaluate the model using three distinct datasets, each consisting of 27, 12, and 10 T1D patients, respectively. In addition, we subject the trained model to further validation for closed-loop therapy, employing a state-of-the-art controller.

RESULTS

The generated patients display statistical similarity to real patients when evaluated on the time-in-range results for each of the standard blood glucose ranges in T1D management along with means and variability outcomes. When tested for causality, authentic causal links are identified between the insulin, carbohydrates, and blood glucose levels of the virtual patients. The trained generative model demonstrates behaviours that are closer to reality compared to conventional T1D simulators when subjected to closed-loop insulin therapy using a state-of-the-art controller.

CONCLUSIONS

These results highlight our approach's capability to accurately capture physiological dynamics and establish genuine causal relationships, holding promise for enhancing the development and evaluation of therapies in diabetes.

An ensemble machine learning approach for the detection of unannounced meals to enhance postprandial glucose control

BACKGROUND

Hybrid automated insulin delivery systems enhance postprandial glucose control in type 1 diabetes, however, meal announcements are burdensome. To overcome this, we propose a machine learning-based automated meal detection approach; METHODS:: A heterogeneous ensemble method combining an artificial neural network, random forest, and logistic regression was employed. Trained and tested on data from two in-silico cohorts comprising 20 and 47 patients. It accounted for various meal sizes (moderate to high) and glucose appearance rates (slow and rapid absorbing). To produce an optimal prediction model, three ensemble configurations were used: logical AND, majority voting, and logical OR. In addition to the in-silico data, the proposed meal detector was also trained and tested using the OhioT1DM dataset. Finally, the meal detector is combined with a bolus insulin compensation scheme; RESULTS:: The ensemble majority voting obtained the best meal detector results for both the in-silico and OhioT1DM cohorts with a sensitivity of 77%, 94%, 61%, precision of 96%, 89%, 72%, F1-score of 85%, 91%, 66%, and with false positives per day values of 0.05, 0.19, 0.17, respectively. Automatic meal detection with insulin compensation has been performed in open-loop insulin therapy using the AND ensemble, chosen for its lower false positive rate. Time-in-range has significantly increased 10.48% and 16.03%, time above range was reduced by 5.16% and 11.85%, with a minimal time below range increase of 0.35% and 2.69% for both in-silico cohorts, respectively, compared to the results without a meal detector; CONCLUSION:: To increase the overall accuracy and robustness of the predictions, this ensemble methodology aims to take advantage of each base model's strengths. All of the results point to the potential application of the proposed meal detector as a separate module for the detection of meals in automated insulin delivery systems to achieve improved glycemic control.

Optimizing Noninvasive Vagus Nerve Stimulation for Systemic Lupus Erythematosus: Protocol for a Multicenter Randomized Controlled Trial

BACKGROUND

Systemic lupus erythematosus is a chronic, multisystem, inflammatory disease of autoimmune etiology occurring predominantly in women. A major hurdle to the diagnosis, treatment, and therapeutic advancement of this disease is its heterogeneous nature, which presents as a wide range of symptoms such as fatigue, fever, musculoskeletal involvement, neuropsychiatric disorders, and cardiovascular involvement with varying severity. The current therapeutic approach to this disease includes the administration of immunomodulatory drugs that may produce unfavorable secondary effects.

OBJECTIVE

This study explores the known relationship between the autonomic nervous system and inflammatory pathways to improve patient outcomes by treating autonomic nervous system dysregulation in patients via noninvasive vagus nerve stimulation. In this study, data including biomarkers, physiological signals, patient outcomes, and patient quality of life are being collected and analyzed. After completion of the clinical trial, a computer model will be developed to identify the biomarkers and physiological signals related to lupus activity in order to understand how they change with different noninvasive vagus nerve stimulation frequency parameters. Finally, we propose building a decision support system with integrated noninvasive wearable technologies for continuous cardiovascular and peripheral physiological sensing for adaptive, patient-specific optimization of the noninvasive vagus nerve stimulation frequency parameters in real time.

METHODS

The protocol was designed to evaluate the efficacy and safety of transauricular vagus nerve stimulation in patients with systemic lupus erythematosus. This multicenter, national, randomized, double-blind, parallel-group, placebo-controlled study will recruit a minimum of 18 patients diagnosed with this disease. Evaluation and treatment of patients will be conducted in an outpatient clinic and will include 12 visits. Visit 1 consists of a screening session. Subsequent visits up to visit 6 involve mixing treatment and evaluation sessions. Finally, the remaining visits correspond with early and late posttreatment follow-ups.

RESULTS

On November 2022, data collection was initiated. Of the 10 participants scheduled for their initial appointment, 8 met the inclusion criteria, and 6 successfully completed the entire protocol. Patient enrollment and data collection are currently underway and are expected to be completed in December 2023.

CONCLUSIONS

The results of this study will advance patient-tailored vagus nerve stimulation therapies, providing an adjunctive treatment solution for systemic lupus erythematosus that will foster adoption of technology and, thus, expand the population with systemic lupus erythematosus who can benefit from improved autonomic dysregulation, translating into reduced costs and better quality of life.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05704153; https://clinicaltrials.gov/study/NCT05704153.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/48387.

Bolus Insulin calculation without meal information. A reinforcement learning approach

In continuous subcutaneous insulin infusion and multiple daily injections, insulin boluses are usually calculated based on patient-specific parameters, such as carbohydrates-to-insulin ratio (CR), insulin sensitivity-based correction factor (CF), and the estimation of the carbohydrates (CHO) to be ingested. This study aimed to calculate insulin boluses without CR, CF, and CHO content, thereby eliminating the errors caused by misestimating CHO and alleviating the management burden on the patient. A Q-learning-based reinforcement learning algorithm (RL) was developed to optimise bolus insulin doses for in-silico type 1 diabetic patients. A realistic virtual cohort of 68 patients with type 1 diabetes that was previously developed by our research group, was considered for the in-silico trials. The results were compared to those of the standard bolus calculator (SBC) with and without CHO misestimation using open-loop basal insulin therapy. The percentage of the overall duration spent in the target range of 70-180 mg/dL was 73.4% and 72.37%, <70 mg/dL was 1.96 and 0.70%, and >180 mg/dL was 23.40 and 24.63%, respectively, for RL and SBC without CHO misestimation. The results revealed that RL outperformed SBC in the presence of CHO misestimation, and despite not knowing the CHO content of meals, the performance of RL was similar to that of SBC in perfect conditions. This algorithm can be incorporated into artificial pancreas and automatic insulin delivery systems in the future.

Generation of Individualized Synthetic Data for Augmentation of the Type 1 Diabetes Data Sets Using Deep Learning Models

In this paper, we present a methodology based on generative adversarial network architecture to generate synthetic data sets with the intention of augmenting continuous glucose monitor data from individual patients. We use these synthetic data with the aim of improving the overall performance of prediction models based on machine learning techniques. Experiments were performed on two cohorts of patients suffering from type 1 diabetes mellitus with significant differences in their clinical outcomes. In the first contribution, we have demonstrated that the chosen methodology is able to replicate the intrinsic characteristics of individual patients following the statistical distributions of the original data. Next, a second contribution demonstrates the potential of synthetic data to improve the performance of machine learning approaches by testing and comparing different prediction models for the problem of predicting nocturnal hypoglycemic events in type 1 diabetic patients. The results obtained for both generative and predictive models are quite encouraging and set a precedent in the use of generative techniques to train new machine learning models.

A Machine Learning Approach to Minimize Nocturnal Hypoglycemic Events in Type 1 Diabetic Patients under Multiple Doses of Insulin

Nocturnal hypoglycemia (NH) is one of the most challenging events for multiple dose insulin therapy (MDI) in people with type 1 diabetes (T1D). The goal of this study is to design a method to reduce the incidence of NH in people with T1D under MDI therapy, providing a decision-support system and improving confidence toward self-management of the disease considering the dataset used by Bertachi et al. Different machine learning (ML) algorithms, data sources, optimization metrics and mitigation measures to predict and avoid NH events have been studied. In addition, we have designed population and personalized models and studied the generalizability of the models and the influence of physical activity (PA) on them. Obtaining 30 g of rescue carbohydrates (CHO) is the optimal value for preventing NH, so it can be asserted that this is the value with which the time under 70 mg/dL decreases the most, with almost a 35% reduction, while increasing the time in the target range by 1.3%. This study supports the feasibility of using ML techniques to address the prediction of NH in patients with T1D under MDI therapy, using continuous glucose monitoring (CGM) and a PA tracker. The results obtained prove that BG predictions can not only be critical in achieving safer diabetes management, but also assist physicians and patients to make better and safer decisions regarding insulin therapy and their day-to-day lives.

Machine Learning Techniques for Hypoglycemia Prediction: Trends and Challenges

(1) Background: the use of machine learning techniques for the purpose of anticipating hypoglycemia has increased considerably in the past few years. Hypoglycemia is the drop in blood glucose below critical levels in diabetic patients. This may cause loss of cognitive ability, seizures, and in extreme cases, death. In almost half of all the severe cases, hypoglycemia arrives unannounced and is essentially asymptomatic. The inability of a diabetic patient to anticipate and intervene the occurrence of a hypoglycemic event often results in crisis. Hence, the prediction of hypoglycemia is a vital step in improving the life quality of a diabetic patient. The objective of this paper is to review work performed in the domain of hypoglycemia prediction by using machine learning and also to explore the latest trends and challenges that the researchers face in this area; (2) Methods: literature obtained from PubMed and Google Scholar was reviewed. Manuscripts from the last five years were searched for this purpose. A total of 903 papers were initially selected of which 57 papers were eventually shortlisted for detailed review; (3) Results: a thorough dissection of the shortlisted manuscripts provided an interesting split between the works based on two categories: hypoglycemia prediction and hypoglycemia detection. The entire review was carried out keeping this categorical distinction in perspective while providing a thorough overview of the machine learning approaches used to anticipate hypoglycemia, the type of training data, and the prediction horizon.

Understanding the Interplay Between Food Structure, Bacterial Fermentation and Appetite Sensing: A Randomized Crossover Human Trial

Objectives

Complex food structures can act like barriers towards digestive enzymes and reduce nutrient bioavailability. Nutrients that escape digestion in the upper gut (mainly fibre), becomes available for bacterial fermentation in the distal gut and generates short chain fatty acids (SCFA) which stimulate the release of appetite suppressing hormones Glucagon like peptide 1 (GLP-1) and Peptide YY (PYY). Processing can alter food structures, leading to more digestible products, but reducing nutrients reaching the distal gut, fermentation and appetite suppression. This study aimed to investigate the impact of food structures on the level of carbohydrate reaching the distal ileum and its subsequent effect on SCFA production and appetite hormone release.

Methods

Healthy volunteers (n = 10, 18–65 years) attended three separate 4-day inpatient visits. A nasoenteric tube was inserted into their distal ileum. During each visit, participants had one of three dietary interventions: Low fibre, processed diet (LF); High fibre, unprocessed diet (HF); same as HF but domestically processed (HFP). On day 4, ileal, blood and breath hydrogen (BH) samples were collected at baseline and hourly following food intake for 8 h. Blood samples were analyzed for appetite hormones and SCFAs using radioimmunoassay and GC-MS. Ileal samples were analyzed for metabolic profiling using 1H-NMR spectroscopy, partial least squares discriminant analysis with Monte-Carlo cross-validation and repeated-measures design.

Results

HFP but not HF had higher PYY levels than the LF (P = 0.004). BH and serum total SCFAs were higher in HF and HFP than LF indicating a higher bacterial fermentation (P = 0.021, 0.015 and P = 0.000, 0.003). HFP group had higher total SCFA than HF (P = 0.015). Distinct metabolic differences were identified in ileal samples from groups (e.g., time = 2 h, HF vs HFP R2Y: 0.99, Q2Y: 0.65). Ileal samples will be analysed for microbial profile (16 s rRNA, Illumina MiSeq), glucose and starch (spectroscopy) and SCFAs (GC-MS).

Conclusions

Current data suggests a potential benefit of domestically processed food structures on appetite suppression as measured by postprandial PYY levels. This may be related to the different metabolic profiles generated in the ileum. Better understanding of this link can aid the design of diets that enhance appetite suppression and reduce food intake.

Funding Sources

BBSRC.

Prediction of Nocturnal Hypoglycemia in Adults with Type 1 Diabetes under Multiple Daily Injections Using Continuous Glucose Monitoring and Physical Activity Monitor

(1) Background: nocturnal hypoglycemia (NH) is one of the most challenging side effects of multiple doses of insulin (MDI) therapy in type 1 diabetes (T1D). This work aimed to investigate the feasibility of a machine-learning-based prediction model to anticipate NH in T1D patients on MDI. (2) Methods: ten T1D adults were studied during 12 weeks. Information regarding T1D management, continuous glucose monitoring (CGM), and from a physical activity tracker were obtained under free-living conditions at home. Supervised machine-learning algorithms were applied to the data, and prediction models were created to forecast the occurrence of NH. Individualized prediction models were generated using multilayer perceptron (MLP) and a support vector machine (SVM). (3) Results: population outcomes indicated that more than 70% of the NH may be avoided with the proposed methodology. The predictions performed by the SVM achieved the best population outcomes, with a sensitivity and specificity of 78.75% and 82.15%, respectively. (4) Conclusions: our study supports the feasibility of using ML techniques to address the prediction of nocturnal hypoglycemia in the daily life of patients with T1D on MDI, using CGM and a physical activity tracker.

Minimizing postprandial hypoglycemia in Type 1 diabetes patients using multiple insulin injections and capillary blood glucose self-monitoring with machine learning techniques

BACKGROUND

Diabetic patients treated with intensive insulin therapies require a tight glycemic control and may benefit from advanced tools to predict blood glucose (BG) concentration levels and hypo/hyperglycemia events. Prediction systems using machine learning techniques have mainly focused on applications for sensor augmented pump (SAP) therapy. In contrast, insulin bolus calculators that rely on BG prediction for multiple daily insulin (MDI) injections for patients under self-monitoring blood glucose (SMBG) are scarce because of insufficient data sources and limited prediction capability of forecasting models.

METHODS

We trained individualized models that can predict postprandial hypoglycemia via different machine learning algorithms using retrospective data from 10 real patients. In addition, we designed and tested a hypoglycemia reduction strategy for a similar in silico population. The system generates a bolus reduction suggestion as the scaled weighted sum of the predictions. We evaluated the general and postprandial glycemic outcomes of the in silico population to assess the systems capability of avoiding hypoglycemias.

RESULTS

The median [IQR] sensitivity and specificity for hypoglycemia cases where the BG level was below 70 mg/dL were 0.49 [0.2-0.5] and 0.74 [0.7-0.9], respectively. For hypoglycemia cases where the BG level was below 54 mg/dL, the median [IQR] sensitivity and specificity were 0.51 [0.4-0.6] and 0.74 [0.7-0.8], respectively.

CONCLUSIONS

The results indicated a decrease of 37% in the median number of postprandial hypoglycemias median decrease of 44% for hypoglycemias of 70 mg/dL and 54 mg/dL, respectively. This dramatic reduction makes this method a good candidate to be integrated into any Decision Support System for diabetes management.

Treatment, outcomes and costs of asthma exacerbations in Chilean children: a prospective multicenter observational study

OBJECTIVE

To describe potential regional variations in therapies for severe asthma exacerbations in Chilean children and estimate the associated health expenditures.

METHODS

Observational prospective cohort study in 14 hospitals over a one-year period. Children five years of age or older were eligible for inclusion. Days with oxygen supply and pharmacological treatments received were recorded from the clinical chart. A basic asthma hospitalization basket was defined in order to estimate the average hospitalization cost for a single patient. Six months after discharge, new visits to the Emergency Room (ER), use of systemic corticosteroids and adherence to the controller treatment were evaluated.

RESULTS

396 patients were enrolled. Patients from the public health system and from the north zone received significantly more days of oxygen, systemic corticosteroids and antibiotics. Great heterogeneity in antibiotic use among the participating hospitals was found, from 0 to 92.3% (ICC 0.34, 95% CI 0.16-0.52). The use of aminophylline, magnesium sulfate and ketamine varied from 0 to 36.4% between the different Pediatric Intensive Care Units (ICC 0.353, 95% CI 0.010-0.608). The average cost per inpatient was of $1910 USD. 290 patients (73.2%) completed the follow-up six months after discharge. 76 patients (26.2%) were not receiving any controller treatment and nearly a fourth had new ER visits and use of systemic corticosteroids due to new asthma exacerbations.

CONCLUSIONS

Considerable practice variation in asthma exacerbations treatment was found among the participating hospitals, highlighting the poor outcome of many patients after hospital discharge, with an important health cost.

Impact of Use Frequency of a Mobile Diabetes Management App on Blood Glucose Control: Evaluation Study

Background

Technology has long been used to carry out self-management as well as to improve adherence to treatment in people with diabetes. However, most technology-based apps do not meet the basic requirements for engaging patients.

Objective

This study aimed to evaluate the effect of use frequency of a diabetes management app on glycemic control.

Methods

Overall, 2 analyses were performed. The first consisted of an examination of the reduction of blood glucose (BG) mean, using a randomly selected group of 211 users of the SocialDiabetes app (SDA). BG levels at baseline, month 3, and month 6 were calculated using the intercept of a regression model based on data from months 1, 4, and 7, respectively. In the second analysis, the impact of low and high BG risk was examined. A total of 2692 users logging SDA ≥5 days/month for ≥6 months were analyzed. The highest quartile regarding low blood glucose index (LBGI) and high blood glucose index (HBGI) at baseline (t1) was selected (n=74 for group A; n=440 for group B). Changes in HBGI and LBGI at month 6 (t2) were analyzed.

Results

For analysis 1, baseline BG results for type 1 diabetes mellitus (T1DM) groups A and B were 213.61 (SD 31.57) mg/dL and 206.43 (SD 18.65) mg/dL, respectively, which decreased at month 6 to 175.15 (SD 37.88) mg/dL and 180.6 (SD 40.47) mg/dL, respectively. For type 2 diabetes mellitus (T2DM), baseline BG was 218.77 (SD 40.18) mg/dL and 232.55 (SD 46.78) mg/dL, respectively, which decreased at month 6 to 160.51 (SD 39.32) mg/dL and 173.14 (SD 52.81) mg/dL for groups A and B, respectively. This represents a reduction of estimated A_1c (eA_1c) of approximately 1.3% (P<.001) and 0.9% (P=.001) for T1DM groups A and B, respectively, and 2% (P<.001) for both A and B T2DM groups, respectively. For analysis 2, T1DM baseline LBGI values for groups A and B were 5.2 (SD 3.9) and 4.4 (SD 2.3), respectively, which decreased at t2 to 3.4 (SD 3.3) and 3.4 (SD 1.9), respectively; this was a reduction of 34.6% (P=.005) and 22.7% (P=.02), respectively. Baseline HBGI values for groups A and B were 12.6 (SD 4.3) and 10.6 (SD 4.03), respectively, which decreased at t2 to 9.0 (SD 6.5) and 8.6 (SD 4.7), respectively; this was a reduction of 30% (P=.001) and 22% (P=.003), respectively.

Conclusions

A significant reduction in BG was found in all groups, independent of the use frequency of the app. Better outcomes were found for T2DM patients. A significant reduction in LBGI and HBGI was found in all groups, regardless of the use frequency of the app. LBGI and HBGI indices of both groups tend to have similar values after 6 months of app use.

Phaco-non-penetrating deep sclerectomy in ocular hypertension secondary to dexamethasone intravitreal implant

PURPOSE

To evaluate the characteristics and progression of patients treated with a 0.7mg dexamethasone intravitreal implant (Ozurdex^®) and required glaucoma filtering surgery (phaco-non-penetrating deep sclerectomy) to control ocular hypertension (OHT).

METHODS

A retrospective observational study including patients treated with Ozurdex^® in a tertiary-care university hospital from May 2011 to April 2016.

RESULTS

In five years of follow-up, 1.10% (4/363) of patients treated with 0.7mg dexamethasone intravitreal implant required phaco-non-penetrating deep sclerectomy (PNPDS) to control OHT refractory to topical treatment. All four patients started or increased previous antihypertensive topical treatment since the first dexamethasone intravitreal implant. Three or more dexamethasone intravitreal implants were injected in the four cases before intraocular pressure (IOP) became uncontrolled and PNPDS was performed. All four patients have a successfully controlled IOP without treatment after PNPDS. Two patients required additional treatment with dexamethasone intravitreal implants after PNPDS, maintaining IOP under control without treatment.

CONCLUSIONS

To the best of our knowledge, this is the first study describing the successful results of PNPDS in OHT secondary to dexamethasone intravitreal implant. All four patients have achieved controlled IOP without treatment. Re-treatment with dexamethasone intravitreal implant in those patients who underwent PNPDS is also possible, and IOP remains controlled.

Hospitalizations for asthma exacerbation in Chilean children: A multicenter observational study

BACKGROUND

Asthma hospitalization rates in Chilean children have increased in the last 14 years, but little is known about the factors associated with this.

OBJECTIVE

Describe clinical characteristics of children hospitalized for asthma exacerbation.

METHODS

Observational prospective cohort study in 14 hospitals. Over a one-year period, children five years of age or older hospitalized with asthma exacerbation were eligible for inclusion. Parents completed an online questionnaire with questions on demographic information, about asthma, indoor environmental contaminant exposure, comorbidities and beliefs about disease and treatment. Disease control was assessed by the Asthma Control Test. Inhalation technique was observed using a checklist.

RESULTS

396 patients were enrolled. 168 children did not have an established diagnosis of asthma. Only 188 used at least one controller treatment at the time of hospitalization. 208 parents said they believed their child had asthma only when they had an exacerbation and 97 correctly identified inhaled corticosteroids as anti-inflammatory treatment. 342 patients used the wrong spacer and 73 correctly performed all steps of the checklist.

CONCLUSIONS

Almost half of the patients were not diagnosed with asthma at the time of hospitalization despite having a medical history suggestive of the disease. In the remaining patients with an established diagnosis of asthma potentially modifiable factors like bad adherence to treatment and poor inhalation technique were found. Implementing a nationwide asthma program including continued medical education for the correct diagnosis and follow up of these patients and asthma education for patients and caregivers is needed to reduce asthma hospitalization rates in Chilean children.

Artificial Intelligence for Diabetes Management and Decision Support: Literature Review

Background

Artificial intelligence methods in combination with the latest technologies, including medical devices, mobile computing, and sensor technologies, have the potential to enable the creation and delivery of better management services to deal with chronic diseases. One of the most lethal and prevalent chronic diseases is diabetes mellitus, which is characterized by dysfunction of glucose homeostasis.

Objective

The objective of this paper is to review recent efforts to use artificial intelligence techniques to assist in the management of diabetes, along with the associated challenges.

Methods

A review of the literature was conducted using PubMed and related bibliographic resources. Analyses of the literature from 2010 to 2018 yielded 1849 pertinent articles, of which we selected 141 for detailed review.

Results

We propose a functional taxonomy for diabetes management and artificial intelligence. Additionally, a detailed analysis of each subject category was performed using related key outcomes. This approach revealed that the experiments and studies reviewed yielded encouraging results.

Conclusions

We obtained evidence of an acceleration of research activity aimed at developing artificial intelligence-powered tools for prediction and prevention of complications associated with diabetes. Our results indicate that artificial intelligence methods are being progressively established as suitable for use in clinical daily practice, as well as for the self-management of diabetes. Consequently, these methods provide powerful tools for improving patients’ quality of life.

Apoptosis inhibition of Atlantic salmon (Salmo salar) peritoneal macrophages by Piscirickettsia salmonis

To improve the understanding of the piscirickettsiosis pathogenesis, the in vivo apoptosis modulation of peritoneal macrophages and lymphocytes was studied in juvenile Salmo salar intraperitoneally injected with Piscirickettsia salmonis. Five fish were sampled at post-exposure days 1, 5, 8 (preclinical), 20 (clinical) and 40 (post-clinical period of the disease), and the leucocytes of their coelomic washings were analysed by flow cytometry (using the JC-1 cationic dye), TUNEL and cytology to detect apoptotic cells. A selective and temporal pattern of apoptosis modulation by P. salmonis infection was observed. Apoptosis in lymphocytes was not affected, whereas it was inhibited in macrophages but only during the preclinical stage of the induced piscirickettsiosis. Hence, it is postulated that P. salmonis inhibits macrophage apoptosis at the beginning of the disease development to survive, multiply and probably be transported inside these phagocytes; once this process is complete, macrophage apoptosis is no longer inhibited, thus facilitating the exit of the bacteria from the infected cells for continuing their life cycle.

Results of bevacizumab as the primary treatment for retinal vein occlusions

BACKGROUND

The purpose of this study is to evaluate the efficacy of intravitreal bevacizumab as the primary treatment of macular oedema due to retinal vein occlusions.

METHODS

Patients diagnosed as having central retinal vein occlusion (CRVO) or branch retinal vein occlusion (BRVO) with visual acuity of less than 20/40 and macular oedema with more than 300 microm central retinal thickness were recruited. Patients that had received any prior treatment were excluded. After an initial intravitreal injection of bevacizumab, re-treatment was performed if intraretinal or subretinal fluid with distortion of the foveal depression was found in optical coherence tomography.

RESULTS

18 eyes with CRVO and 28 eyes with BRVO were included. During a 6-month period, the mean number of injections per patient was 3.7 (BRVO group) and 4.6 (CRVO group). In the BRVO group, mean baseline logMAR visual acuity was 0.80 (SD 0.38) and macular thickness was 486.9 microm (SD 138.5 microm). After 6 months, mean logMAR visual acuity improved significantly to 0.44 (SD 0.34), p<0.001. Mean macular thickness decreased significantly to 268.2 microm (SD 62.5 microm), p<0.001. In the CRVO group, mean baseline logMAR visual acuity was 1.13 (SD 0.21) and macular thickness was 536.4 microm (SD 107.1 microm). Mean final logMAR visual acuity improved significantly to 0.83 (SD 0.45), p<0.001. Mean macular thickness decreased significantly to 326.17 microm (SD 96.70 microm), p<0.001.

CONCLUSIONS

Intravitreal bevacizumab seems to be an effective primary treatment option for macular oedema due to retinal occlusions. Its main drawback is that multiple injections are necessary to maintain visual and anatomic improvements.

[Anatomical and functional outcomes of vitrectomy for the treatment of pseudophakic regmatogenous retinal detachment]

PURPOSE

To report the results obtained in a non-comparative series of pseudophakic patients with retinal detachment (RD) treated with vitrectomy with no associated scleral procedures.

METHODS

The clinical records of all pseudophakic patients with RD treated with vitrectomy were evaluated by one of the authors. Patients with primary regmatogenous RD with no signs of proliferative vitreoretinopathy were included. Patients with associated ocular pathologies or with less than 3 months follow-up were excluded. Main outcome measures were anatomical reattachment rate after one surgery, visual acuity change and surgical complications. The surgical procedure consisted of 20 g pars plana vitrectomy, with removal of peripheral vitreous up to the ora serrata. Laser photocoagulation of all retinal breaks was performed and 14% C3F8 was used as tamponade.

RESULTS

Thirty-one patients were included in the study. In 18 patients the macula was affected. Mean follow-up was 6.45 months (range 3 to 18). Retinal reattachment was achieved in all patients and only one patient experienced a re-detachment, 3 months after surgery. Visual acuity improved by a mean of 2.5 Snellen lines and 61.3% of patients reached a final visual acuity of 0.5 or better. Eight patients had an intraocular pressure rise after surgery, which was controlled with topical medication. No other complications were recorded.

DISCUSSION

Our results support the hypothesis that vitrectomy alone is a useful technique for the treatment of RD in pseudophakic eyes.

[Evaluation of trypan-blue toxicity in macular hole surgery with electroretinography]

PURPOSE

Concern has been raised about the retinal toxicity of vital dyes. We designed a prospective study to determine the possible toxicity of trypan-blue (TB) in macular hole surgery with TB-assisted internal limiting membrane (ILM) peeling through the performance of electroretinograms (ERGs).

METHODS

Patients diagnosed with a macular hole underwent ophthalmological evaluation prior to surgery and at 6 months follow-up. All patients underwent vitrectomy and ILM-staining under air. All phakic patients underwent phacoemulsification and IOL implantation simultaneously. There were two study groups: In group 1, ILM-staining was performed with 0.06% TB, while in group 2 the procedure was performed with 0.15% TB. Preoperative ERG recordings were measured in the week prior to surgery. Postoperative ERGs were measured 3 to 6 months after surgery. The ERG data between eyes with macular hole and fellow eyes were compared in the pre- and post-operative stages. Visual acuity (VA) changes in both groups were evaluated.

RESULTS

Nine patients were recruited in each group. VA improved significantly in both groups, with more than 65% of patients improving more than 2 lines. There were no statistical differences in VA gain between groups or in ERG values between affected and fellow eyes.

CONCLUSION

No significant retinal toxicity of TB staining could be clinically detected.

[Use of optical coherence tomography to measure prevalence of epiretinal membranes in patients referred for cataract surgery]

PURPOSE

To evaluate, using optical coherence tomography (OCT), the prevalence of epiretinal membranes (ERM) in patients referred for phacoemulsification, and the frequency of new ERM development in the first six months after surgery.

METHODS

Patients referred by general ophthalmologists for cataract surgery underwent a new, complete ophthalmological evaluation. OCT scanning was performed using the Macular Thickness Map acquisition protocol (StratusOCT, Carl Zeiss Meditec). This baseline examination was used to determine the prevalence of ERM in patients referred for cataract surgery. All patients underwent uneventful phacoemulsification. If an ERM was already present in one eye, the other eye was chosen for cataract surgery. If no ERM was present, the eye with the poorest visual acuity was operated. Operated eyes were followed-up for six months in order to study the influence of phacoemulsification on the development of ERM.

RESULTS

Forty-five patients were prospectively evaluated. In the baseline visit, ERM were detected by OCT in 7 patients (15.6%). Both eyes were affected in one patient, with the ERM being apparent on funduscopy only in her left eye. Fundus examination was unremarkable in all other cases. After six months follow-up, no new cases of epiretinal membranes were detected in the eyes that had undergone phacoemulsification, neither by fundus evaluation nor by OCT.

CONCLUSIONS

Epiretinal membranes, previously thought to be secondary to cataract surgery, may be present before phacoemulsification and can be diagnosed by OCT.

[Surgical treatment of Duane's syndrome type I by recession of the medial rectus of the affected eye and faden operation of the contralateral medial rectus]

PURPOSE

Different surgical approaches have been described for the treatment of Duane's syndrome. The purpose of our study is to report the results of patients undergoing recession of the medial rectus (MR) muscle of the affected eye and placement of contralateral MR faden posterior fixation sutures.

METHODS

Retrospective study of 11 patients treated by a 4-7 mm recession of the MR of the affected eye and 13 mm faden posterior fixation suture of the contralateral MR in order to correct abnormal head position and esotropia in primary position.

RESULTS

After surgery, there was no torticolis in 81.8% of patients, with less than 10 degrees of torticolis in the remainder. In all patients, postoperative esotropia was less than 5 prismatic dioptres.

CONCLUSION

This is a safe and effective procedure in Duane's syndrome type I to treat moderate esotropia and torticolis.

[Rebound tonometry in a clinical setting. Comparison with applanation tonometry]

PURPOSE

Rebound tonometry has recently been modified for its use in humans. The purpose of our study was to determine the precision of the ICare(R) rebound tonometer (RBT) as compared with the Goldmann applanation tonometer (GAT).

METHODS

Patients were recruited from our Hospital's Glaucoma Unit. In each patient, intraocular pressure (IOP) was measured without anaesthesia using the RBT and ten minutes later using the GAT. Central corneal thickness (CCT) was measured by pachymetry.

RESULTS

Sixty-eight patients were recruited (132 eyes). Mean IOP readings with RBT were 18.9 +/- 7.2 (SD) mmHg and were 15.5 +/- 5.7 mmHg with GAT (p<0.001). There was a good correlation between both instruments (r = 0.87, p<0.001). In most cases (84.6%) the IOP measured with the RBT was greater than that measured with the GAT. The mean difference between both instruments was 3.4 +/- 3.6 mmHg. There was a trend towards greater differences between those obtained using the RBT than the GAT when IOP values were higher. A statistically significant correlation was found between IOP readings with both tonometers and CCT, with higher differences being seen as the CCT increased.

CONCLUSION

The RBT can be employed in a clinical setting taking into account that it usually overestimates IOP as compared with the GAT. It could be especially useful in glaucoma screening campaigns since it can be operated by a trained technician.

[Plasma concentrations of beta-endorphins in the children of alcoholic patients]

BACKGROUND

Of the factors identified in different studies as the possible causes of alcoholism, heredity appears to be the most important. However, environmental factors can increase or decrease the risk of an individual developing alcohol dependence.

METHOD

To clarify the possible influence of heredity on alcoholism, we studied the plasma concentration of beta-endorphins in 25 families with alcoholic members: 27 children whose father was alcoholic and 7 whose father and mother were both alcoholics. The results were compared with finding in an age-matched control group of no-drinking adults and normal children in non-drinking families.

RESULTS

The children of alcoholic parents had significantly lower beta-endorphin levels (p < 0.001) than control individuals, and concentrations were especially low when both parents were alcoholics.

CONCLUSION

We conclude that plasma beta-endorphin concentration may have predictive value in identifying persons likely to become alcoholics.

Effects of Breed on Follicular Dynamics and Oestradiol Secretion during the Follicular Phase in Sheep

Current study evaluates effects from breed and management background on follicular dynamics and endocrine output during the follicular phase of sheep oestrous cycle. Follicular phases were synchronized with three cloprostenol doses, 10 days apart, in three groups of 10 females of different non-prolific Spanish breeds (Manchega, Rubia del Molar and Negra de Colmenar). Development of all follicles reaching antral diameters >or=2 mm was assessed by daily transrectal ultrasonographies, whereas follicular function was evaluated by measurement of plasma oestradiol concentrations. All the ovulatory follicles were present at induced luteolysis in Manchega sheep, while a 93.7% were detected in Rubia del Molar and Negra de Colmenar ewes. The mean size of these ovulatory follicles was similar between breeds at 0 h, but their growth rates were higher in Manchega ewes, reaching a larger size at oestrous detection than in Negra de Colmenar and Rubia del Molar sheep (p < 0.05). Conversely, the oestradiol levels increased with time in Rubia del Molar and Negra de Colmenar (p < 0.05); whilst remained stable in Manchega females. However, the patterns of follicular turnover were similar between breeds. These results indicate that, though differences in follicular size and size distribution, patterns of follicular turnover in sheep are affected neither by the breed nor by the background of management and selection.

[Apical orbital inflammation in giant cell arteritis]

CASE REPORT

Our purpose is to describe a case of an acute optic neuropathy with apical muscle thickening in a patient already diagnosed with giant cell arteritis. Loss of visual acuity and perimetric concentric constriction responded rapidly to intravenous glucocorticoid therapy. There has been no relapse during continued long-term therapy with cyclophosphamide.

DISCUSSION

Giant cell arteritis is a systemic, idiopathic vasculitis; among its less frequent complications is orbital pseudotumor. Our patient required urgent treatment to avoid visual acuity loss due to compressive neuropathy and perineuritis.

[Ultrasound biomicroscopy in deep sclerectomy with a new acrylic implant]

OBJECTIVE

To describe the ultrasound biomicroscopic (UBM) characteristics seen in patients who have undergone deep phaco-sclerectomy with a new acrylic implant (Esnoper).

SUBJECTS, MATERIAL AND METHODS

UBM exploration was performed 12 months after deep phaco-sclerectomy in three patients with chronic open angle glaucoma.

RESULTS

One year after surgery, all three patients had intraocular pressure levels under 15 mmHg and were on no treatment. All of them had an intrascleral space in UBM, in which the hyperechogenic implant was visible.

CONCLUSIONS

The new non-absorbable implant has proven to be effective in these cases. Information provided by UBM is useful and assists in understanding the mechanism of action of deep sclerectomy.

[Side-effects of triamcinolone in young patients]

CASE REPORTS

Intravitreal triamcinolone is being increasingly employed for the treatment of macular diseases. We report two cases of intraocular pressure elevation and cataract formation after intravitreal triamcinolone therapy, and wonder if these complications are more likely when this agent is used in young patients. Intravitreal triamcinolone was injected into both eyes of the two young patients with chronic posterior and intermediate uveitis refractory to peribulbar and oral corticosteroid therapy. Chronic cystoid macular edema improved in both patients, however the intraocular pressure increased, requiring topical antihypertensive therapy, and this was followed by accelerated cataract formation.

DISCUSSION

Young age and chronic inflammation could be associated with an intraocular pressure rise and subsequent cataract development after intravitreal triamcinolone.

New ways to look at an old problem

A 32-year-old man presented with optic neuritis (papillitis). A discussion of optic neuritis, the role of magnetic resonance imaging, and possible treatment options are presented. The role of optical coherence tomography in following patients with optic neuritis is discussed.

Effects of breed on kinetics of ovine FSH and ovarian response in superovulated sheep

Embryo production is a useful tool for ex situ conservation of endangered species and breeds, despite a high variability in the ovarian response to superovulatory treatments. The current study evaluated the incidence and mechanisms of genetic factors in such variability, by determining the pharmacokinetics and pharmacodynamics of a standard treatment with ovine FSH (oFSH) in two endangered Spanish sheep breeds (Rubia del Molar, R, and Negra de Colmenar, N) in comparison to Manchega ewes (M, control group). In the first experiment, pharmacokinetics of an i.m. single dose of 1.32 mg of oFSH was evaluated in seven animals of each breed. Plasma FSH concentrations reached their maximum at 4h post-administration in all the ewes, but several of the kinetic parameters (plasma FSH concentration at 4h post-administration, maximum plasma FSH concentration, C(max), and both the area under the plasma concentration-time curve extrapolated to the infinite, AUC(inf), and to the last moment of sampling, AUC(last)) were higher in the N group. In the second trial, 10 animals of each breed were superovulated using eight decreasing doses of oFSH (3 x 1.32 mg, 2 x 1.10 mg, and 3 x 0.88 mg). The R group, when compared to N and M, showed both a higher number of corpora lutea (13.7+/-0.6 versus 10.0+/-0.4 in N and 9.8+/-0.6 in M, P<0.05 for both) and embryos (7.9+/-0.8 versus 4.3+/-0.4 in N, P<0.05, and 6.7+/-0.5 in M, n.s.). Evaluation of pharmacokinetic and dynamic parameters showed that, although there was a trend for a higher hormone availability in R sheep, mean FSH plasma concentrations were similar between breeds (0.54+/-0.08 ng/ml for R, 0.45+/-0.05 ng/ml for N and 0.35+/-0.05 ng/ml for M). However, differences were found in the number of preovulatory follicles growing in response to the FSH treatment between R (24.4+/-2.2), M (18.9+/-1.5, n.s.) and N sheep (14.1+/-1.4; P<0.01). Thus, differences in embryo yields between breeds would be related to differences in the pattern of follicular growth in response to FSH treatment.

A comparison between Humphrey and frequency doubling perimetry for chiasmal visual field defects

PURPOSE

To evaluate and compare the diagnostic ability of frequency doubling technology perimetry (FDT) with standard automated perimetry (SAP) using Humphrey Field Analyser for the detection of visual field defects produced by chiasmal lesions.

METHODS

Fifteen patients with documented chiasmal disease and previously diagnosed of bitemporal hemianopia with Humphrey perimetry were prospectively evaluated. All of them underwent a new SAP (SITA 24-2) followed by FDT tests (C-20 threshold). Diagnostic criteria for hemianopia were established according to the total deviation plot and the threshold values of FDT. A patient was diagnosed with hemianopia if one or both criteria were met. Based on these criteria, FDT sensitivity was calculated. Testing time and global indexes for both perimetric strategies were compared.

RESULTS

The sensitivity of FDT was 75.0% (18 out of 24 eyes); the criterion based on threshold values was met more often (70.83%) than the criterion based on the total deviation plot (50.0%). Linear correlation was better for the external column than for the internal column of the visual field. Testing time with FDT was 122.16 seconds shorter than with SAP (p<0.001). The mean value for mean deviation (MD) was -13.62 dB (SD 6.88) for SAP and -8.83 dB (SD 5.94) for FDT (p<0.001).

CONCLUSIONS

Compared with standard automatic perimetry, FDT has a low sensitivity for detecting temporal hemianopias and also has more difficulty in defining the vertical limits of the defects. Therefore, it does not appear to be an adequate method for the detection of chiasmal visual field defects.

Genetic analysis of antibiotic-resistance determinants in multidrug-resistant Shigella strains isolated from Chilean children

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of bla(OXA) in S. flexneri and with bla(TEM) in S. sonnei. The bla(OXA) gene but not bla(TEM) was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and bla(OXA) genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and bla(TEM), dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.

[Utility of bronchoalveolar lavage in immunocompromised children: diagnostic yield and complications]

OBJECTIVE

Immunocompromised children are at high risk for developing pneumonia due to opportunistic pathogens. The role of bronchoalveolar lavage (BAL) in the evaluation of such patients is still controversial.

MATERIAL AND METHOD

We reviewed the hospital records of immunosuppressed patients with respiratory symptoms who had undergone BAL in the pediatric department of the Hospital Clinico de la Pontificia Universidad Católica of Chile.

RESULTS

Sixty-eight BAL were performed on 54 children (mean age: 7.5 years) receiving wide-spectrum antibiotic treatment. The most frequent respiratory signs and symptoms were fever (90%) and cough and respiratory distress (81%); 18% had neutropenia and 43% thrombocytopenia. A specific pathogen was identified in BAL samples for 25 patients (37%). The pathogens isolated were bacteria in 21 cases, viruses in 6, Pneumocystis carinii in 5, fungi in 4, and Mycobacterium tuberculosis in one. Fourteen (19%) of the children who underwent BAL were on mechanical ventilation. Outcome was satisfactory in all cases. Twenty-one complications were recorded, 17 of which were minor (mild hypoxemia or fever) and 4 major, requiring tracheal intubation. No deaths were recorded.

CONCLUSIONS

Evaluation by fiberoptic bronchoscopy together with BAL proved to be a safe procedure with an adequate diagnostic yield that made it possible to determine the etiology of the pulmonary infiltrates seen in chest x-rays. Both positive and negative results of BAL were useful for treating the patients.

[IOP spikes following contact transscleral diode laser cyclophotocoagulation]

PURPOSE

To evaluate the incidence of intraocular pressure (IOP) spikes after contact transscleral diode laser cyclophotocoagulation (cyclodiode) and to identify related risk factors.

METHOD

Retrospective study of 116 eyes (110 patients) with refractory glaucoma who underwent cyclodiode. IOP measurement was obtained immediately before and one hour after cyclodiode. We defined an IOP spike as an increase equal or superior to 5 mmHg after laser treatment. We evaluated several potential pre-, intra- and post-operative factors related to the IOP spike occurrence.

RESULTS

Mean IOP decreased one hour after cyclodiode 6.96 mmHg (SD: 8.36) (p<0.001). Overall, we observed 10.8% of IOP spikes. Age, sex, mean energy delivered, pop occurrence and iris colour were not associated with the postoperative IOP spike occurrence. The percentage of IOP spikes was higher in neovascular glaucoma (p=0.074). The IOP spike rate was also higher after retreatment, but the difference compared to the eyes which underwent cyclodiode for the first time was not significant.

CONCLUSIONS

These preliminary results suggest that IOP spike prevention could be considered in neovascular glaucoma scheduled for cyclodiode

Epithelial cell contact-induced alterations in Salmonella enterica serovar Typhi lipopolysaccharide are critical for bacterial internalization

The invasion of Pseudomonas aeruginosa and Salmonella enterica serovar Typhi into epithelial cells depends on the cystic fibrosis transmembrane conductance regulator (CFTR) protein as an epithelial receptor. In the case of P. aeruginosa, the bacterial ligand for CFTR is the outer core oligosaccharide portion of the lipopolysaccharide (LPS). To determine whether serovar Typhi LPS is also a bacterial ligand mediating internalization, we used both P. aeruginosa and serovar Typhi LPS as a competitive inhibitor of serovar Typhi invasion into the epithelial cell line T84. P. aeruginosa LPS containing a complete core efficiently inhibited serovar Typhi invasion. However, neither killed wild-type Typhi cells nor purified LPS were effective inhibitors. LPS from mutant Typhi strains defective in O side-chain synthesis, but with an apparently normal core, was capable of inhibiting invasion, but LPS obtained from a deeper rough mutant strain with alterations in fast-migrating core oligosaccharide failed to inhibit invasion. Lastly, exposure of wild-type serovar Typhi to T84 cultures before heat killing resulted in a structural alteration in its LPS that allowed the heat-killed cells to inhibit invasion of wild-type serovar Typhi. These data indicate that the serovar Typhi LPS core, like the P. aeruginosa LPS core, is a ligand mediating internalization of bacteria by epithelial cells, and that exposure of this ligand on wild-type Typhi is induced by the bacteria's interaction with host cells.

The rfaH gene, which affects lipopolysaccharide synthesis in Salmonella enterica serovar Typhi, is differentially expressed during the bacterial growth phase

We have cloned and sequenced the rfaH gene from Salmonella enterica serovar Typhi strain Ty2. The gene showed a high degree of similarity to the rfaH genes from Escherichia coli K-12 and S. enterica serovar Typhimurium. A rfaH mutant was constructed by site-directed mutagenesis. This mutant produced a rough lipopolysaccharide (LPS), with an incomplete core region. The defect in LPS expression that results from the rfaH mutation was corrected by a plasmid carrying the intact gene. The plasmid-borne rfaH gene also restored normal LPS synthesis in a rfaH mutant of E. coli. Reverse transcription-polymerase chain reaction analyses were performed to determine the effects of various environmental conditions on the expression of rfaH. The transcription of rfaH showed a growth-phase-dependent regulation, with maximal expression at the late exponential phase. Other environmental conditions, such as temperature or medium osmolarity, did not affect transcription of rfaH.

Uptake of endocytic markers by rice cells: variations related to the growth phase

Endocytosis is now considered a basic cellular process common to plant cells. Although both non-specific and receptor-mediated endocytosis appear to take place in plant cells, the physiological role of the latter remains unclear. We have investigated the endocytic process in rice cell suspensions using two biotinylated proteins, peroxidase and bovine serum albumin (bHRP and bBSA), as markers. First, we show that markers are internalized by rice cells and appear in intracellular membranes. The uptake of the two markers is temperature dependent, saturable with time and markers dose and it is competed by free biotin. Thus, it shows the properties of a receptor-mediated process. We also show that uptake of markers is strongly influenced by growth phase as optimal uptake occurs during the lag phase, but the initiation of the exponential growth phase decreases uptake drastically. Arrest of the cell cycle by starvation of either a nutrient (phosphate) or a growth regulator (2,4-dichlorophenoxyacetic acid), both components of the culture medium, does not modify the rate of bBSA uptake. Subsequent readdition of these components results in growth recovery and a dramatic decrease in bBSA uptake. On the other hand, nocodazole treatment, a method to arrest the cell cycle by microtubule depolymerization, inhibited bBSA uptake. The possible causes for this arrest of endocytosis are discussed.

Estrogen replacement therapy and the prevention of coronary heart disease in postmenopausal women

The use of estrogen replacement therapy (ERT) for the prevention of coronary heart disease (CHD) is discussed. Cardiovascular disease is the number one cause of death in women. It is believed that the loss of estradiol production at menopause increases the risk of CHD. Theoretically, ERT should decrease CHD risk in postmenopausal women by maintaining at premenopausal levels the metabolic factors that affect CHD. Many mechanistic studies of the effects of estrogen on lipoproteins, hemostasis, carbohydrate metabolism, and vessel wall tone and reactivity support a cardioprotective role for estrogen. In addition, observational studies have found that ERT, with or without progesterone, significantly reduces the risk of CHD. However, mechanistic and observational studies can establish only an association, not a cause-and-effect relationship. Furthermore, bias may influence the risk estimates. The Heart and Estrogen/Progestin Replacement Study (HERS), published in 1998, was the first large, randomized, controlled trial to evaluate the efficacy of estrogen and progesterone replacement therapy in reducing CHD risk. Overall, the study found that continuous hormone replacement therapy (HRT) in women with CHD did not reduce cardiovascular risk at an average of 4.1 years of follow-up. In addition, there was an early increase in the risk of thromboembolic events. Although many mechanistic and observational studies suggest that ERT reduces the risk of morbidity and mortality from CHD in postmenopausal women, the only large, randomized, controlled study of this question to date failed to confirm this. Until data from ongoing studies are available, health care providers must reconsider prescribing ERT or HRT solely for the secondary prevention of CHD.

Characterization of Cop I coat proteins in plant cells

Membrane traffic in eukaryotic cells is mediated by COP (coat protein)-coated vesicles. Their existence in plant cells has not yet been unequivocally demonstrated, although coated vesicles (probably with a COP coat) can be seen by electron microscopy. At the gene level, plant cells seem to contain all the components necessary to form COP-coated vesicles. In this paper, we have used antibodies raised against mammalian COPI coat proteins to detect putative homologues in rice (Oryza sativa) cells. Using these antibodies, we have found that rice cells contain alpha-, beta-, beta'-, and gamma-COP, as well as ADP-ribosylation factor (ARF) 1 protein. In addition, we show that antibodies against mammalian beta'-COP can immunoprecipitate not only beta'-COP but also alpha-, beta-, and gamma-COP, suggesting that COPI components in rice cells exist as a complex (or coatomer) in the cytosol, as in mammalian cells. Finally, we show that COP binding to membranes is GTP-dependent, and that ARF1 also binds to membranes in a GTP-dependent manner.