A model of subcutaneous pramlintide pharmacokinetics and its effect on gastric emptying: Proof-of-concept based on populational data

Pramlintide, an amylin analog, has been coming up as an agent in type 1 diabetes dual-hormone therapies (insulin/pramlintide). Since pramlintide slows down gastric emptying, it allows for easing glucose control and reducing the burden of meal announcements. Pre-clinical in silico evaluations are a key step in the development of any closed-loop strategy. However, mathematical models are needed, and pramlintide models in the literature are scarce. This work proposes a proof-of-concept pramlintide model, describing its subcutaneous pharmacokinetics (PK) and its effect on gastric emptying (PD). The model is validated with published populational (clinical) data. The model development is divided into three stages: intravenous PK, subcutaneous PK, and PD modeling. In each stage, a set of model structures are proposed, and their performance is assessed using the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). In order to evaluate the modulation of the rate of gastric emptying, a literature meal model was used. The final pramlintide model comprises four compartments and a function that modulates gastric emptying depending on plasma pramlintide. Results show an appropriate fit for the data. Some aspects are left as open questions due to the lack of specific data (e.g., the influence of meal composition on the pramlintide effect). Moreover, further validation with individual data is necessary to propose a virtual cohort of patients.

Modeling the effect of glucagon on endogenous glucose production in type 1 diabetes: On the role of glucagon receptor dynamics

This paper validates a glucoregulatory model including glucagon receptors dynamics in the description of endogenous glucose production (EGP). A set of models from literature are selected for a head-to-head comparison in order to evaluate the role of glucagon receptors. Each EGP model is incorporated into an existing glucoregulatory model and validated using a set of clinical data, where both insulin and glucagon are administered. The parameters of each EGP model are identified in the same optimization problem, minimizing the root mean square error (RMSE) between the simulation and the clinical data. The results show that the RMSE for the proposed receptors-based EGP model was lower when compared to each of the considered models (Receptors approach: 7.13±1.71 mg/dl vs. 7.76±1.45 mg/dl (p=0.066), 8.45±1.38 mg/dl (p=0.011) and 8.99±1.62 mg/dl (p=0.007)). This raises the possibility of considering glucagon receptors dynamics in type 1 diabetes simulators.

Near-optimal feedback control for postprandial glucose regulation in type 1 diabetes

This paper is focused on feedback control of postprandial glucose levels for patients with type 1 Diabetes Mellitus. There are two important limitations that make this a challenging problem. First, the slow subcutaneous insulin pharmacokinetics that introduces a significant lag into the control loop. Second, the positivity constraint on the control action, meaning that it is not possible to remove insulin from the body. In this paper, both issues are explicitly considered in the design process using the internal model control framework, to derive a near-optimal feedback controller. Optimality is understood here as minimizing the blood glucose peak after a meal intake and, at the same time, preventing glucose values below a prescribed threshold. It is shown how the proposed controller approaches the optimal closed-loop performance as a limit case. The theoretical results are supported by a numerical example and the feasibility of the overall strategy under uncertainties is illustrated using an extended version UVa/Padova metabolic simulator.

Assessment of Seasonal Stochastic Local Models for Glucose Prediction without Meal Size Information under Free-Living Conditions

Accurate blood glucose (BG) forecasting is key in diabetes management, as it allows preventive actions to mitigate harmful hypoglycemic/hyperglycemic episodes. Considering the encouraging results obtained by seasonal stochastic models in proof-of-concept studies, this work assesses the methodology in two datasets (open-loop and closed-loop) recorded in free-living conditions. First, similar postprandial glycemic profiles are grouped together with fuzzy C-means clustering. Then, a seasonal stochastic model is identified for each cluster. Finally, real-time BG forecasting is performed by weighting each model’s prediction. The proposed methodology (named C-SARIMA) is compared to other linear and nonlinear black-box methods: autoregressive integrated moving average (ARIMA), its variant with input (ARIMAX), a feed-forward neural network (NN), and its modified version (NN-X) fed by BG, insulin, and carbohydrates (timing and dosing) information for several prediction horizons (PHs). In the open-loop dataset, C-SARIMA grants a median root-mean-squared error (RMSE) of 20.13 mg/dL (PH = 30) and 27.23 mg/dL (PH = 45), not significantly different from ARIMA and NN. Over a longer PH, C-SARIMA achieves an RMSE = 31.96 mg/dL (PH = 60) and RMSE = 33.91 mg/dL (PH = 75), significantly outperforming the ARIMA and NN, without significant differences from the ARIMAX for PH ≥ 45 and the NN-X for PH ≥ 60. Similar results hold on the closed-loop dataset: for PH = 30 and 45 min, the C-SARIMA achieves an RMSE = 21.63 mg/dL and RMSE = 29.67 mg/dL, not significantly different from the ARIMA and NN. On longer PH, the C-SARIMA outperforms the ARIMA for PH > 45 and the NN for PH > 60 without significant differences from the ARIMAX for PH ≥ 45. Although using less input information, the C-SARIMA achieves similar performance to other prediction methods such as the ARIMAX and NN-X and outperforming the CGM-only approaches on PH > 45min.

Internal model control based module for the elimination of meal and exercise announcements in hybrid artificial pancreas systems

BACKGROUND AND OBJECTIVES

Hybrid artificial pancreas systems outperform current insulin pump therapies in blood glucose regulation in type 1 diabetes. However, subjects still have to inform the system about meals intake and exercise to achieve reasonable control. These patient announcements may result in overburden and compromise controller performance if not provided timely and accurately. Here, a hybrid artificial pancreas is extended with an add-on module that releases subjects from meals and exercise announcements.

METHODS

The add-on module consists of an internal-model controller that generates a "virtual" control action to compensate for disturbances. This "virtual" action is converted into insulin delivery, rescue carbohydrates suggestions, or insulin-on-board limitations, depending on a switching logic based on glucose measurements and predictions. The controller parameters are tuned by optimization and then related to standard parameters from the open-loop therapy. This module is implemented in a hybrid artificial pancreas system proposed by our research group for validation. This hybrid system extended with the add-on module is compared with the hybrid controller with carbohydrate counting errors (hybrid) and the hybrid controller with an alternative unannounced meal compensation module based on a meal detection algorithm (meal detector). The validation used the educational version of the UVa/Padova simulator to simulate the three controllers under two scenarios: one with only meals and another with meals and exercise. The exercise was modeled as a temporal increase of the insulin sensitivity resulting in the glucose drop usually related to an aerobic exercise.

RESULTS

For the scenario with only meals, the three controllers achieved similar time in range (proposed: 85.1 [77.9,88.1]%, hybrid: 84.0 [75.9,86.4]%, meal detector: 81.9 [79.3,83.8]%, median [interquartile range]) with low time in moderate hypoglycemia. Under the scenario with meals and exercise, the proposed module reduces 4.61% the time in hypoglycemia achieved with the other controllers, suggesting an acceptable amount of rescues (27.2 [23.7, 31.0] g).

CONCLUSIONS

The proposed add-on module achieved promising results: it outperformed the meal-detector-based controller, even achieving a postprandial performance as good as the hybrid controller (with carbohydrate counting errors). Also, the rescue suggestion feature of the module mitigated exercise-induced hypoglycemia with admissible rescue amounts.

Comparison of Artificial Intelligence Control Strategies for a Peristaltically Pumped Low-Pressure Driven Membrane Process

Peristaltic pumping is used in membrane applications where high and sterile sealing is required. However, control is difficult due to the pulsating pump characteristics and the time-varying properties of the system. In this work, three artificial intelligence control strategies (artificial neural networks (ANN), fuzzy logic expert systems, and fuzzy-integrated local models) were used to regulate transmembrane pressure and crossflow velocity in a microfiltration system under high fouling conditions. A pilot plant was used to obtain the necessary data to identify the AI models and to test the controllers. Humic acid was employed as a foulant, and cleaning-in-place with NaOH was used to restore the membrane state. Several starting operating points were studied and setpoint changes were performed to study the plant dynamics under different control strategies. The results showed that the control approaches were able to control the membrane system, but significant differences in the dynamics were observed. The ANN control was able to achieve the specifications but showed poor dynamics. Expert control was fast but showed problems in different working areas. Local models required less data than ANN, achieving high accuracy and robustness. Therefore, the technique to be used will depend on the available information and the application dynamics requirements.

Super-twisting-based meal detector for type 1 diabetes management: Improvement and assessment in a real-life scenario

BACKGROUND AND OBJECTIVE

Hybrid automated insulin delivery systems rely on carbohydrate counting to improve postprandial control in type 1 diabetes. However, this is an extra burden on subjects, and it introduces a source of potential errors that could impact control performances. In fact, carbohydrates estimation is challenging, prone to errors, and it is known that subjects sometimes struggle to adhere to this requirement, forgetting to perform this task. A possible solution is the use of automated meal detection algorithms. In this work, we extended a super-twisting-based meal detector suggested in the literature and assessed it on real-life data.

METHODS

To reduce the false detections in the original meal detector, we implemented an implicit discretization of the super-twisting and replaced the Euler approximation of the glucose derivative with a Kalman filter. The modified meal detector is retrospectively evaluated in a challenging real-life dataset corresponding to a 2-week trial with 30 subjects using sensor-augmented pump control. The assessment includes an analysis of the nature and riskiness of false detections.

RESULTS

The proposed algorithm achieved a recall of 70 [13] % (median [interquartile range]), a precision of 73 [26] %, and had 1.4 [1.4] false positives-per-day. False positives were related to rising glucose conditions, whereas false negatives occurred after calibrations, missing samples, or hypoglycemia treatments.

CONCLUSIONS

The proposed algorithm achieves encouraging performance. Although false positives and false negatives were not avoided, they are related to situations with a low risk of hypoglycemia and hyperglycemia, respectively.

Glucose Prediction under Variable-Length Time-Stamped Daily Events: A Seasonal Stochastic Local Modeling Framework

Accurate glucose prediction along a long-enough time horizon is a key component for technology to improve type 1 diabetes treatment. Subjects with diabetes might benefit from supervision and control systems that accurately predict risks and trigger corrective actions early enough with improved mitigation. However, large intra-patient variability poses big challenges to glucose prediction. In previous works by the authors, clustering and local modeling techniques with seasonal stochastic models proved to be efficient, allowing for good glucose prediction accuracy for long prediction horizons. Continuous glucose monitoring (CGM) data were partitioned into fixed-length postprandial time subseries and clustered with Fuzzy C-Means to collect similar behaviors, enforcing seasonality at each cluster after subseries concatenation. Then, seasonal stochastic models were identified for each cluster and local predictions were integrated into a global prediction. However, free-living conditions do not support the fixed-length partition of CGM data since daily events duration is variable. In this work, a new algorithm is provided to overcome this constraint, allowing better coping with patient's variability under variable-length time-stamped daily events in supervision and control applications. Besides predicted glucose, two real-time indices are additionally provided-a crispness index, indicating good representation of current glucose behavior by a single model, and a normality index, allowing for the detection of an abnormal glucose behavior (unusual according to registered historical data). The framework is tested in a proof-of-concept in silico study with ten patients over four month training data and two independent two month validation datasets, with and without abnormal behaviors, from the distribution version of the UVA/Padova simulator extended with diverse sources of intra-patient variability.

Consequences of canceling elective invasive cardiac procedures during Covid-19 outbreak

BACKGROUND

During COVID-19 pandemic in Spain, elective procedures were canceled or postponed, mainly due to health care systems overwhelming.

OBJECTIVE

The objective of this study was to evaluate the consequences of interrupting invasive procedures in patients with chronic cardiac diseases due to the COVID-19 outbreak in Spain.

METHODS

The study population is comprised of 2,158 patients that were pending on elective cardiac invasive procedures in 37 hospitals in Spain on the 14th of March 2020, when a state of alarm and subsequent lockdown was declared in Spain due to the COVID-19 pandemic. These patients were followed-up until April 31th.

RESULTS

Out of the 2,158 patients, 36 (1.7%) died. Mortality was significantly higher in patients pending on structural procedures (4.5% vs. 0.8%, respectively; p < .001), in those >80 year-old (5.1% vs. 0.7%, p < .001), and in presence of diabetes (2.7% vs. 0.9%, p = .001), hypertension (2.0% vs. 0.6%, p = .014), hypercholesterolemia (2.0% vs. 0.9%, p = .026) [Correction added on December 23, 2020, after first online publication: as per Dr. Moreno's request changes in p-values were made after original publication in Abstract.], chronic renal failure (6.0% vs. 1.2%, p < .001), NYHA > II (3.8% vs. 1.2%, p = .001), and CCS > II (4.2% vs. 1.4%, p = .013), whereas was it was significantly lower in smokers (0.5% vs. 1.9%, p = .013). Multivariable analysis identified age > 80, diabetes, renal failure and CCS > II as independent predictors for mortality.

CONCLUSION

Mortality at 45 days during COVID-19 outbreak in patients with chronic cardiovascular diseases included in a waiting list due to cancellation of invasive elective procedures was 1.7%. Some clinical characteristics may be of help in patient selection for being promptly treated when similar situations happen in the future.

Inadequate response to imatinib treatment in chronic myeloid leukemia due to a drug interaction with phenytoin

Imatinib mesylate and the newer BCR-ABL tyrosine kinase inhibitors are the standard therapy for chronic myeloid leukemia. Although these are remarkably effective drugs, some mechanisms of resistance have been identified including drug-to-drug interactions. Here we present the case of a chronic myeloid leukemia patient with an inadequate response to imatinib due to concurrent phenytoin administration. Conspicuously low imatinib plasma trough levels were documented. Imatinib dose was increased from 400 to 800 mg with good response. In conclusion, drug-to-drug interactions should be ruled out in cases of resistance to tyrosine kinase inhibitor treatment. Potent inducers of cytochrome P450 isoenzyme CYP3A4, as phenytoin, could induce inadequate responses due to increased imatinib clearance and low imatinib trough plasma levels. Thus, this interaction should be avoided. When this is not possible, dose escalation of imatinib and measurement of plasma levels, if available, is recommended.

Stochastic Seasonal Models for Glucose Prediction in the Artificial Pancreas

BACKGROUND

Linear empirical dynamic models have been widely used for glucose prediction. The extension of the concept of seasonality, characteristic of other domains, is explored here for the improvement of prediction accuracy.

METHODS

Twenty time series of 8-hour postprandial periods (PP) for a same 60g-carbohydrate meal were collected from a closed-loop controller validation study. A single concatenated time series was produced representing a collection of data from similar scenarios, resulting in seasonality. Variability in the resulting time series was representative of worst-case intrasubject variability. Following a leave-one-out cross-validation, seasonal and nonseasonal autoregressive integrated moving average models (SARIMA and ARIMA) were built to analyze the effect of seasonality in the model prediction accuracy. Further improvement achieved from the inclusion of insulin infusion rate as exogenous variable was also analyzed. Prediction horizons (PHs) from 30 to 300 min were considered.

RESULTS

SARIMA outperformed ARIMA revealing a significant role of seasonality. For a 5-h PH, average MAPE was reduced in 26.62%. Considering individual runs, the improvement ranged from 6.3% to 54.52%. In the best-performing case this reduction amounted to 29.45%. The benefit of seasonality was consistent among different PHs, although lower PHs benefited more, with MAPE reduction over 50% for PHs of 60 and 120 minutes, and over 40% for 180 min. Consideration of insulin infusion rate into the seasonal model further improved performance, with a 61.89% reduction in MAPE for 30-min PH and reductions over 20% for PHs over 180 min.

CONCLUSIONS

Seasonality improved model accuracy allowing for the extension of the PH significantly.

Preventing parastomal hernias with systematic intraperitoneal specifically designed mesh

BACKGROUND

Parastomal hernia is a very common complication after stoma formation. Current surgical techniques for repairing parastomal hernia have unsatisfactory results. We aim to assess our preliminary experience with prophylactic mesh placement at the time of stoma formation.

METHODS

Data were prospectively recorded. A specifically designed mesh made of polyvinyl fluoride with central conduit (Dynamesh IPST®) was fixed using an intra-peritoneal onlay technique. Safety was evaluated by means of surgical data and frequency of mesh-related complications, efficacy by the rate of parastomal hernias.

RESULTS

Thirty-four patients were included in the study. Three of them died before a year of follow up (not related to the stoma), so they were excluded. The other 31 patients (11 women and 20 men) were prospectively followed up after different pathologies resulting in a permanent colostomy. Twelve months after surgery CT-Scan imaging revealed two (6.4%) parastomal hernias, one of them already clinically suspected. During the follow up, 29% of the patients (n = 9) developed another type of hernia (incisional, inguinal or both). In five patients (16.1%) a light stomal retraction of the otherwise slightly prominent ostomy was observed. Median clinical follow-up was 17.5 months (range 12-34).

CONCLUSION

Prophylactic parastomal mesh placement might be a safe and effective procedure with a potential to reduce the risk of parastomal hernia. Routine use of this technique should be further analysed.

Relapse of chronic myeloid leukemia after allogeneic stem cell transplantation: outcome and prognostic factors: the Chronic Myeloid Leukemia Subcommittee of the GETH (Grupo Español de Trasplante Hemopoyético)

In order to analyze the outcome of patients with chronic myeloid leukemia (CML) who relapse after allogeneic stem cell transplantation (SCT), we investigated data from 107 patients reported to the Spanish Registry, GETH. In all, 93 (87%) patients were treated after relapse; 36 out of 49 that failed to achieve a response received a second relapse-treatment, and seven a third one. At the last follow-up, the number of patients in molecular or cytogenetic remission was 29 and 13, respectively. Overall survival and progression-free survival after relapse were 53.6% (95% CI: 42.9--64.2) and 52% (95% CI: 41-63) at 5 years, respectively. In multivariate analysis, survival was significantly related to CML phase at relapse (cytogenetic or chronic phase vs advanced phases) and time from transplant to relapse (<1 vs >or=1 year). Patients with no adverse factors had a better survival compared with patients with one or two adverse features (65 vs 35 vs 0%, respectively). We conclude that a significant proportion of CML patients that relapse after transplantation can regain complete and long-lasting remissions with one or more salvage therapies. Disease stage at relapse and time from transplant to relapse should be taken into account when comparing results of different salvage treatments.

Type A behavior pattern today: relevance of the JAS-S factor to predict heart rate reactivity

The authors used 89 undergraduate students' scores in the S-factor of the Jenkins Activity Survey, a measure of speed and impatience, to classify 45 participants as high scorers and 44 as low scorers. They then measured the students' tonic and phasic heart rates during an examination, a genuinely stressful situation. The experiment consisted of three phases: adaptation, task, and recovery. The findings confirmed the authors' hypothesis that the high-S scorers would show higher cardiac reactivity values than the low-S scorers. The authors also observed that the high-S scorers took more time than the low-S scorers to recover their initial heart rate values after being exposed to the stress situation. This finding led the authors to suggest that each group may have different response patterns. They call for further research on individuals with "fast activation-fast recovery" and "fast activation-slow recovery" profiles.

The number of donor CD3(+) cells is the most important factor for graft failure after allogeneic transplantation of CD34(+) selected cells from peripheral blood from HLA-identical siblings

This study analyzed the characteristics of 257 HLA-identical sibling transplants of granulocyte colony-stimulating factor-mobilized peripheral blood progenitor cells depleted of T cells by CD34(+) positive selection (allo-PBT/CD34(+)) for their effect on the incidence of graft failure. Twenty-four patients developed graft failure (actuarial probability, 11%; 95% confidence interval, 7.1-14. 9). Prognostic factors considered were sex and age of donor and recipient, donor-recipient blood group compatibility, diagnosis, disease status at transplant, conditioning regimen, cytomegalovirus serology, number of CD34(+) and CD3(+) cells infused, and cryopreservation. The major factor associated with graft failure was the number of CD3(+) cells in the inoculum. Twenty-three of 155 patients receiving a T-cell dose in the graft less than or equal to 0.2 x 10(6)/kg experienced graft failure, compared with only one of 102 patients receiving more than 0.2 x 10(6)/kg (actuarial probability 18% vs 1%, respectively; P =.0001). The actuarial probability of graft failure progressively increased as the number of CD3(+) cells in the graft decreased, which was determined by grouping the number of CD3(+) cells in quartiles (log-rank P =.03; log-rank for trend P =.003). In the multivariate analysis by the proportional hazard method, 2 covariates entered into regression at a significant level: CD3(+) cells less than or equal to 0.2 x 10(6)/kg (risk ratio = 17; P <.0001), and patients with chronic myelogenous leukemia (CML) conditioned with busulphan-based regimens (risk ratio = 4.8; P =.001). From these results it appears that the number of CD3(+) cells in the inoculum-with a threshold of 0.2 x 10(6)/kg or less-is the most critical factor in maintaining a sustained engraftment in allo-PBT/CD34(+) from HLA-identical siblings. In addition, for patients with CML receiving 0.2 x 10(6)/kg or less CD3(+) cells, total body irradiation might be better than busulphan-based regimens.

Skeletal effects of selective oestrogen receptor modulators (SERMs)

Women suffer a higher incidence of osteoporosis than men, in part due to oestrogen deficiency after menopause. In fact, the administration of oestrogen to post-menopausal women is associated with a decrease of bone resorption. Tamoxifen is a widely used selective oestrogen receptor modulator in women with breast cancer, which has been shown an agonistic profile in bone. However, tamoxifen seems less effective than oestradiol as an anti-resorptive agent and has no effect when the endogenous production of oestrogen is normal. Additionally, tamoxifen exhibits agonistic activity on the endometrium and has been suggested an oncogenic potential on that tissue. Raloxifene, a selective oestrogen receptor modulator from the benzothiophene family, behaves also as an agonist on the bone in both laboratory and clinical studies. Ongoing clinical trials confirm a protective effect of raloxifene similar to oestrogens. The Multiple Outcome of Raloxifene Evaluation (MORE) study is a prospective, randomized trial which, in a recent 2 year interim analysis, has shown that women suffering from osteoporosis receiving raloxifene had 42% fewer vertebral fractures than women receiving a placebo.

Histochemical localization of reverse transcriptase in polytene chromosomes of chironomids

The localization of a reverse transcriptase-related protein in salivary gland polytene chromosomes was investigated by immunohistochemistry in two species of Chironomus. The antibodies used were raised against a recombinant protein containing phylogenetically conserved motifs of reverse transcriptases and derived from an abundant non-LTR element previously identified in Chironomus. Immunoreactive protein was found in some telomeres, in a centromeric region, in a few interstitial bands and in Balbiani ring 3. The telomeric signal was probably dependent on transcription and increased dramatically when telomeric heat shock puffs were induced. A correlation with transcription was also seen in Balbiani ring 3, the immunobinding of which disappeared after inhibition of transcription with actinomycin D.

Specific intranucleolar distribution of Hsp70 during heat shock in polytene cells

Hsp70, the most abundant and conserved heat shock protein, has been described as strongly concentrating in the nucleolus during heat shock. The important metabolic processes that take place in the nucleolus, rDNA transcription, processing, and assembling with ribosomal proteins, and the nucleolar architecture itself are very sensitive to temperature changes. In this work, we have analyzed in detail the nucleolar changes, in structure and activity, induced by temperature in Chironomus thummi salivary gland cells and the fine subnucleolar localization of Hsp70 during heat shock. The optimum temperature chosen to induce the heat shock response was 35 degrees C. Under these conditions transcription of heat shock genes, inactivation of previously active genes and maximum synthesis of Hsps take place, while survival of larvae and recovery were ensured. After 1 h at 35 degrees C, nucleoli change from a uniform control pattern to a segregated pattern of nucleolar components that can be observed even at the light microscopic level. The dense fibrillar component (DFC) and the granular component appeared perfectly differentiated and spatially separated, the former occupying mainly the central inner region surrounded by a rim of granular component. Hsp70 was specifically localized within the DFC upon heat shock as shown by immunolocalization by both light and electron microscopy. Pulse labeling with [3H]uridine proves that rRNA transcription continues during heat shock. The pattern of Hsp70 distribution within the nucleolus correlates with that of newly produced rRNA transcripts. Hsp70 also colocalizes with RNA polymerase I, both being restricted to the DFC. These data show that the DFC seems to be the intranucleolar target for Hsp70 in heat-shocked cells. We discuss these results in relation to the possible function of Hsp70 in the first steps of preribosome synthesis.

Epstein-Barr virus associated B-cell lymphoma after autologous bone marrow transplantation for T-cell acute lymphoblastic leukaemia

Epstein-Barr virus associated lymphoproliferative disease after autologous bone marrow transplantation (ABMT) has rarely been reported. We report a case of B-cell lymphoma following ABMT for T-acute lymphoblastic leukaemia; bone marrow was purged in vitro with monoclonal antibodies to remove T cells. Immunoglobulin and T-cell receptor gene rearrangement studies were used to demonstrate clonality and to show that this patient developed a second neoplasm after ABMT. EBV proteins and genome (type A) were present in post-transplantation lymphoma, suggesting a causative role in its development.

[Maximum static respiratory pressures in adults. The reference values for a Mediterranean Caucasian population]

The aim of this study was to establish reference values for PImax and PEmax for the Mediterranean adult population. Male and female individuals between 18 and 83 years old meeting the criteria for consideration as references and residing in the metropolitan area of Valencia were assigned by decades to six subgroups, each containing at least 20 men and 20 women. PEmax was obtained from the point of maximum expiration (residual volume) and PImax was the point of maximum inspiration (total lung capacity). The cohort, which finally included 264 subjects (129 men and 135 women), was separated a priori by sex for data analysis. The following types of variables were studied: sociological (employment, educational level and exercise), biometric (age, height and weight) and spirometric results. A linear correlation analysis was performed for each pair of variables and a Kolmogorov-Smirnov test of normality was performed. In order to check the accuracy of PImax and PEmax readings, intra-individual variability was determined by performing three consecutive procedures over 3 days in 39 randomly selected individuals (18 men and 21 women). Significant inter-day and inter-test effects for respiratory pressures were thus ruled out. Predictive equations were worked out using a simple linear model including all predictive variables and eliminating weaker variables in a stepwise manner. Mathematical goodness of fit was assessed by a coefficient for multiple determinations (R2); also determined were the estimated standard error and statistical significance. We also compared observed and estimated values and the behavior of residual values in terms of their independence, normality and homoscedasticity. Reference limits were established by defining percentiles. The equations finally arrived at for men were as follows: PImax (-cmH2O) - 1.03 x Age + 0.59 x Weight + 133.07, PEmax (cmH2O) - 1.31 x Age + 263.12. The equations for women were PImax (-cmH2O) - 0.64 x Age + 125.18, PEmax (cmH2O) - 0.57 x Age + 0.65 x Weight + 116.26. Agreement with the usual references (the Black and Hyatt equations) was analyzed.

Ku-related antigens are associated with transcriptionally active loci in Chironomus polytene chromosomes

Antigens of Chironomus reactive with human sera containing anti-Ku antibodies and also with specific antibodies to each Ku subunit were characterized by immunoblot analysis. Three main antigen species were identified in nuclear-enriched extracts from salivary gland cells of Chironomus thummi, ranging in Mr from 55000 to 67000. The nuclear localization of Ku-related antigens in the dipteran Chironomus was studied by immunofluorescent labeling in polytene chromosomes of the salivary glands. Balbiani rings, loci highly active in transcription, were found to be strongly labeled by anti-Ku antibodies. Sugar-induced changes in the activity of the Balbiani ring genes were accompanied by the redistribution of Ku-related antigens as visualized by their absence in regressed Balbiani ring loci, and continued presence only in those that were transcriptionally active. A drastic change in the distribution of Ku-related antigens was also observed when C. thummi larvae underwent heat treatment as the immunofluorescent staining was restricted to previously described heat shock puffs. Anti-Ku sera reacted in addition with several chromosomal bands in which the presence of RNA polymerase II was also immunologically detected. The results show that Chironomus antigens reactive with anti-Ku antibodies are related to transcription in polytene chromosomes.

HLA haploidentical cord blood cell transplant in a 15-year-old, 50 kg weight patient: successful treatment for chronic myeloid leukemia after myeloid blastic transformation

A 15-year-old, 50 kg weight patient with CML had a myeloblastic transformation which reverted to Ph negative remission with intensive chemotherapy 5 years after diagnosis. Umbilical cord blood (UCB) from an HLA-haploidentical sister had been frozen 2 years and 9 months before, as she had no HLA-identical sibling and no suitable unrelated donor had been found. UCB transplant was selected on the basis of previous general experience with this kind of transplant, lack of a better choice of donor, and likelihood of a prompt relapse of the disease without delay and the patient developed grade II aGVHD as well as severe CsA toxicity which required discontinuation of the drug, anti-IL2r being given instead. Subsequently she only had histologic evidence of cGVHD and 1.5 years after the transplant she remains in complete hematologic remission with full chimerism and without evidence of the bcr/abl fusion gene. This case illustrates further possibilities of allo-transplantation using UCB.

[Obstructive and non-obstructive hypertrophic cardiomyopathy: clinical, electrocardiographic, and echocardiographic differences]

AIM

The purpose of the study was to analyse echocardiographic, electrocardiographic and clinical variables in patients with hypertrophic cardiomyopathy, as well as to compare the possible differences between the non-obstructive (NOHCM) and the obstructive form (OHCM).

METHOD

44 consecutive patients were studied and diagnosed with hypertrophic cardiomyopathy (NOHCM 26 and OHCM 18). The following variables were analysed: 1) echocardiographic: right ventricle (RV), interventricular septum (IVS), posterior wall (pW), telediastolic and telesystolic diameter of the left ventricle (TDD-LV and TSD-LV), size of the left atrium (LA), systolic anterior motion of the mitral valve (SAM), mitral insufficiency and direction of the jet (MI and MIpW), mitral anular calcium (MAC), filling pattern (A > E); 2) electrocardiographic: repolarization disorders (RD), left ventricular hypertrophy (LVH), negative "T" waves in the precordial leads (T-), pathological "q" waves, super or ventricular arrhythmias (SA or VA), short PR, right or left bundle branch block (RBBB and LBBB), and 3) clinical: presence of dyspnea, angina, syncope, palpitations and response to treatment with beta-blockers (B-b) or Calcium-antagonists (C-A).

RESULTS

There were no differences in age or sex between the obstructive and non-obstructive groups: 1) echocardiographic differences: there were none in RV, pW, TDD-LV, LA nor A > E wave. Significant differences were found (p < 0.05) in the rest of the variables; IVS (16 +/- 3 mm in NOHCM vs 22 +/- 5 mm in OHCM), TSD-LV (26 +/- 5 mm in NOHCM vs 22 +/- 6 mm in OHCM), SAM (38% in NOHCM vs 89% in OHCM), MI (19% in NOHCM vs 78% in OHCM), MIpW (20% in NOHCM vs 79% in OHCM), MAC (15% in NOHCM vs 44% in OHCM); 2) electrocardiographic differences: there were none in the presence of RD, pathological "q", VA, short PR, RBBB nor LBBB. The presence of "T" negatives was on the limit of significance in the precordial leads (31% in NOHCM vs 11% in OHCM; p = 0.09). Differences were found in the rest of the variables; LVH (58% in NOHCM vs 83% in OHCM), SA (50% in NOHCM vs 17% in OHCM); 3) clinical differences: there were none in the presence of dyspnea, angina, syncope or palpitations. Differences were found in the improvement with treatment; B-b (60% in NOHCM vs 57% in OHCM), C-A (100% in NOHCM vs 100% in OHCM).

CONCLUSIONS

1) in our patients, the most frequent cardiomyopathy is the non-obstructive one, with no predominance of age or sex; 2) in OHCM, IVS is much wider, with smaller TSD-LV, there is a greater incidence of MI, generally directed towards the posterior wall of the left atrium, and a larger tendency to calcify the mitral annulus; 3) the most frequent electrocardiographic abnormality is the alteration of repolarization. NOHCM has a greater incidence of SA and a lower degree of LVH with more prevalence of negative "T" waves in the precordial leads; 4) there are no clinical parameters differentiating the two groups, although the sustained improvement obtained with treatment is more likely to be produced by the calcium-antagonists than by beta-blockers in both types of cardiomyopathy.

Diagnosis of transfusion-associated graft-versus-host disease by polymerase chain reaction in fludarabine-treated B-chronic lymphocytic leukaemia

Transfusion-associated graft-versus-host disease (TA-GVHD), has rarely been reported associated with B-chronic lymphocytic leukaemia (B-CLL). We report a patient diagnosed with B-CLL, previously treated with fludarabine, who developed TA-GVHD after being transfused during surgery for splenectomy. Diagnosis was confirmed by polymerase chain reaction (PCR) detection of donor DNA in the patient, by amplification of Y-chromosome sequence and analysis of minisatellite polymorphisms. B-CLL patients treated with fludarabine appear to be at risk for TA-GVHD and should be regarded as candidates for transfusions with irradiated blood products. This case illustrates that PCR is a rapid technique for the early diagnosis of TA-GVHD.

[The usefulness of the isovolumetric relaxation time of both ventricles in detecting acute rejection in the heart transplant patient]

AIMS

The purpose of our study was to evaluate the usefulness of the isovolumetric relaxation time in both ventricles when diagnosing acute rejection in transplanted patients.

METHOD

68 endomyocardial biopsies were performed on a total of 38 patients. An echocardiographic study was carried out within the first 24 hours of each biopsy. All registrations were made by the same person. The isovolumetric relaxation time was measured in the left and right ventricles. The patients were divided according to two criteria: according to the degree of rejection (0-I, II, III) and according to whether the rejection was treatable (III) or non-treatable (0, I and II).

RESULTS

In both ventricles, there was a progressive decrease of the isovolumetric relaxation time corresponding to higher degrees of rejection: in the left ventricle (0-I = 90 +/- 16; II = 74 +/- 16; III = 70 +/- 26; significant differences of II and III in relation to 0-I) as well as in right ventricle (0-I = 43 +/- 16; II = 37 +/- 14; III = 29 +/- 8; significant difference of III in relation to 0-I). The patients with treatable and non-treatable rejection were compared: no differences were found in the isovolumetric relaxation time of the left ventricle (0, I and II = 85 +/- 16 vs III = 70 +/- 26), but they were found in the right ventricle (0, I and II = 41 +/- 15 vs III = 29 +/- 8).

CONCLUSIONS

Acute heart rejection induces a decrease of the isovolumetric relaxation time in both the left ventricle and the right ventricle. However, the isovolumetric relaxation time of the right ventricle seems to be a more useful parameter than isovolumetric relaxation time of the left ventricle, as it permits to detect whether an acute heart rejection is treatable or non-treatable.

[The incidence of major histocompatibility system antigens in dilated and ischemic myocardiopathies]

AIM

The purpose of this study was to analyze the frequency of the different antigens of HLA in patients with diagnosis of very advanced dilated cardiomyopathy and ischemic heart disease by comparing them with a control group of supposedly healthy subjects.

MATERIAL AND METHOD

The group of dilated cardiomyopathy consisted of 35 patients (8 women and 27 men) aged between 14 and 60 years. The group of ischemic heart disease included 32 patients (4 women and 28 men) aged between 34 and 64 years. The control group comprised 1337 subjects of the Spanish Mediterranean area, supposedly healthy and recruited from paternity studies.

RESULTS

In dilated cardiomyopathy we found a higher incidence in comparison with the control group of the A-2 (62.86% vs 46.22%), B-12 (60.00% vs 32.38%) and DQ-3 (82.86 vs 49.96%) antigens, and a lower incidence of B-51 (0.00% vs 12.49%). In ischemic heart disease we found, when comparing to the control group, a higher incidence of A-11 (31.25% vs 13.08%) and A-29 (34.38% vs 14.58%) antigens and a lower incidence of DQ-2 (15.63% vs 49.88%).

CONCLUSIONS

In the Spanish Mediterranean area, the presence of A-2, B-12 and DQ-3 antigens, as well as the absence of B-51 would favour the appearance of advanced dilated cardiomyopathy. The presence of the A-11 and A-29 antigens would predispose to ischemic cardiomyopathy while the presence of DQ-2 would have a protective effect on the appearance of this cardiopathy.

[Changes in lipoprotein(a) after heart transplantation]

AIM

The purpose of this study was to analyze the evolutionary changes of lipoprotein (a) levels occurring in heart transplant and to evaluate the possible relationship between the plasma concentration of this lipoprotein and the immunosuppressor drugs normally used in this type of transplant.

METHOD

17 patients undergoing heart transplant and with no history of dyslipemia or dysglucemia were studied. Patients with metabolic alterations after the transplant were excluded (except when these alterations occurred during the first week), as well as those who showed intercurrent processes near to the determinations. These were performed before the transplant, and 1, 2, 4 and 6 months later.

RESULTS

An increase of lipoprotein (a) was observed after the transplant, with a subsequent progressive decrease. Significant differences were found between the levels prior to the transplant (9.18 +/- 8.66) and 6 months later (7.53 +/- 8.86), with no differences found between the previous concentrations and the determinations after one month (10.29 +/- 7.58), two months (8.06 +/- 7.90) and four months (8.82 +/- 7.84). Differences were also observed between the values of the first month in relation to the subsequent months, as well as between the 4th and the 6th month. No relationship was noticed between the levels of this lipoprotein and those of cyclosporin (r = 0.10), azatioprine (r = 0.17) and deflazacort (r = 0.19).

CONCLUSIONS

The lipoprotein (a) levels increase after heart transplant, with a subsequent gradual decrease even below the previous figures. These levels bear no relationship with the dose of immunosupressors normally used in heart transplant.

Chronic myeloid leukaemia and allogenic bone marrow transplantation in a patient with toxic oil syndrome

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[Efficacy of various treatments in the management of idiopathic thrombocytopenic purpura in the adult]

PURPOSE

To evaluate the ITP treatment modalities and their results in a series of 30 adult patients.

PATIENTS AND METHODS

30 patients, age 15-74, were diagnosed of ITP in our institution between 1988 and December 1991. We defined the ITP as: mild (platelets > or = 50 x 10(9)/L and < or = 120 x 10(9)/L), moderate (platelets 25-50 x 10(9)/L) and severe (platelets < or = 25 x 10(9)/L). Treatment was initiated when the platelet count reached a level < 50 x 10(9)/L. Initial therapy was oral prednisone or methyl-prednisolone in all patients. In 12 unresponsive patients the treatment included splenectomy. Patients who fail steroid therapy and splenectomy received additional lines of therapy, that included: vincristine (n = 2), vinblastine (n = 1), danazol (n = 5), anti D immunoglobulin (n = 6), methotrexate (n = 2), intravenous immunoglobulin (n = 3).

RESULTS

Complete remission was obtained in 19 patients with a follow-up of 3 to 55 months (median, 30 months). Partial remission was achieved in 4 patients, that was sustained for 9 to 39 months (median, 22.5 months) after initial therapy. One unresponsive patient died of infection. Six mild ITP patients did not require therapy with a follow-up of 14 to 56 months (median, 33.1 months).

CONCLUSION

In adult patients with mild ITP, therapy is not required. Steroid therapy remains the initial therapeutic choice for moderate and severe ITP. In unresponsive patients useful alternative choices are splenectomy, danazol, anti D immunoglobulin and methotrexate.

[Treatment with fludarabine of chronic refractory lymphoid leukemia]

PURPOSE

New antimetabolic drugs, purine-analogous, have been introduced in the treatment of advanced or refractory cases of chronic lymphocytic leukaemia (CLL), fludarabine (FLU) being one of such drugs. The results attained with FLU in 6 cases of refractory CLL are reported.

PATIENTS AND METHODS

The efficacy and toxicity of FLU was evaluated in 6 patients (median age 63 years) between March 1993 and March 1994. Five patients were in stage III-IV and one in stage II of the Rai's system, and they were refractory to the usual treatment. The dosis used here was 30 mg/sq m/day, for 5 days every 4 weeks, up to a total of 6 therapeutic courses. The response was assessed after 3 and 6 courses. Anti-infectious prophylaxis was made with co-trimoxazole, monthly benzathine penicillin G and isoniazid in Mantoux-positive patients. The response criteria were those given by the NIC Working Group for CLL.

RESULTS

The patients received 2 to 6 courses. None of them attained complete remission: 1 had nodular remission, 2 had partial remission, 2 responded partially although not reaching criteria for partial remission (1 died of pancytopenia), and 1 had disease progression and died after the second course. Fast and important reduction of the lymphocyte count as well as the CD4 lymphocytes was present in all cases. Bone-marrow infiltration decreased strikingly in 2 cases and the platelet count improved in 3 cases and worsened in 2 others. The following toxicity was recorded: 2 patients had nausea, 5 had neutropenia (below 500 x 10(9)/L in 3 instances) and 4 had thrombocytopenia (lower than 40 x 10(9)/L in one case). In 26 therapeutic courses there were 10 febrile episodes (1 for pneumonia, 1 for gastroenteritis and 8 without any septic foci); 1 patient developed pulmonary tuberculosis after completing the treatment and one patient died of posttransfusion graft versus host disease after splenectomy once she had completes six courses.

CONCLUSION

This experience confirms the efficacy of FLU in the treatment of refractory B-CLL patients and is in agreement with previous reports as no response is initiated after the 3rd course. The lymphocyte count decreases quickly and strikingly. Depletion of CD4 lymphocytes along with neutropenia and hypogammaglobulinaemia make these patients highly sensitive to all types of infection, chiefly by opportunistic germs, so adequate anti-infectious prophylaxis is of great importance. The two patients with pre-treatment haemoglobin and platelet values lower than 10 g/dL and 40 x 10(9)/L, respectively, were the only ones in need of transfusion. No cumulative myelosuppression was appreciated.

Heat shock activation of telomeric sequences in different tissues of Chironomus thummi

The heat shock transcription factor (HSF) has been found by immunocytochemistry using the Drosophila HSF antibody at T-BRIII, a telomeric heat shock-induced puff in polytene chromosomes of Chironomus thummi salivary glands. Other heat shock-activated loci were also positively stained by the antibody. Neither the telomeres nor other heat shock loci were labeled under control conditions. These results support the presence of a heat shock gene at T-BRIII despite its peculiar location and molecular organization, different from other well-characterized heat shock genes in Diptera. This locus is similarly induced and transcribed under heat shock in Malpighian tubules, another larval polytenic tissue. Transcription from telomeric-associated sequences has also been found in control polytenic and diploid tissues. The meaning of transcription and heat shock activation of telomeric sequences is discussed in relation to the organization of telomeres and compared to possible equivalents in other known heat shock loci.

Heat-shock induction and cytoplasmic localization of transcripts from telomeric-associated sequences in Chironomus thummi

Transcription of telomeric-associated sequences has been detected in the salivary gland cells of the larvae Chironomus thummi. In this species, a heat shock induces puffing at some telomeres, especially at one of the telomeres of chromosome III. We found that this process was concomitant with an increase in the overall telomeric transcript levels. Transcription was also observed in all the telomeres under control conditions, by in situ hybridization, even when these telomeres appeared to be in a nonpuffed state. The telomeric transcripts were found in both, the nuclei and, at higher levels, in the cytoplasmic extracts of salivary gland cells. The heat-shock activation, however, appeared to be restricted to the nuclear level. Telomeric transcription and the peculiar behavior of C. thummi telomeres after a heat shock are discussed.

Comparative analysis of four parameters involved in puffing activity along chromosome arm 2L of D melanogaster

Autoradiographic and immunofluorescent techniques have been used to analyse the relationship between puffing, transcription and occurrence of DNA/RNA hybrids in D melanogaster salivary gland chromosome 2L. Experiments of 3H-uridine incorporation have indicated that similar rates of RNA synthesis are observable in well developed puffs as well as in some diffuse bands and interbands. On the other hand, puffs of similar size incorporate 3H-uridine at quite different rates. The presence of RNA polymerase II seems to follow a coincident pattern with that of 3H-uridine incorporation. Our results indicate that the rate of transcription does not determine either the formation of a puff or its potential size. Instead, we have found a positive correlation between the amount of DNA/RNA hybrids and puff size, independently of the transcription rates. Transient accumulation of transcribed RNAs in their chromosomal compartment could therefore play a relevant role in the determination of puff size.

Identification of the spI products of Balbiani ring genes in Chironomus thummi

The spI fraction of high molecular weight secretory proteins was analysed in Chironomus thummi. These proteins are encoded by giant Balbiani ring (BR) genes which develop specifically in salivary gland cells. Each component of the spI fraction was studied electrophoretically from early and middle 4th instar larvae and prepupae, as well from galactose-treated larvae where changes in the relative puffing pattern of BR1 and BR2 are known to occur. The spI fraction consists of at least two bands with electrophoretic mobilities slower than those of the spI components of Camptochironomus. The slow migrating component remains throughout the 4th larval instar, while the amount of the faster component changes, being abundant in early 4th instar and prepupae, but not present (or very weak) in middle 4th instar. The correlated shifts in BR puffing pattern during these developmental stages suggest that the slow and fast components are encoded by BR2 and BR1. The spI fraction is modified by galactose treatment, the fast component being induced in parallel with a decrease in the slow component. These changes are correlated with changes in the steady-state levels of RNA: an increase in BR1 RNA and a decrease in BR2 RNA, and of proteins. These proteins could correspond to the spIb and spIa fractions allocated to BR2 and BR1, respectively, in Camptochironomus. After galactose treatment a new faster band sometimes appears, that could correspond to the spIc fraction of Camptochironomus. A possible spId equivalent was also identified. In conclusion the main features of the spI family in C. thummi are similar to those of spI in Camptochironomus.

Correlation between the activity of a 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-insensitive puff and the synthesis of major heat-shock polypeptide, hsp70, in Chironomus thummi

The induction of puff III-A3b, a major heat-shock puff in Chironomus thummi salivary cells, was insensitive to the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), whereas no transcriptional activity could be detected at the other heat-shock puffs in the presence of this drug. In these conditions, a polypeptide with the same Mr and isoform pattern as those of the major heat-shock polypeptide, hsp70, was synthesized. These results suggest that hsp70 is encoded by locus III-A3b. In addition to DRB insensitivity, incorporation of [3H]UTP on puff III-A3b took place in an in vitro transcription assay under low-salt conditions (100 mM NaCl); no labelling could be detected at the other heat-shock puffs under these conditions. Although DRB has been reported as a specific inhibitor of RNA polymerase II-directed transcription, and although the low-salt conditions were not propitious for the activity of this enzyme, RNA polymerase II was detected on puff III-A3b and on the other heat-shock puffs by immunofluorescence with anti-RNA polymerase II antibodies.

Induction of the heat-shock response by carbon dioxide in Chironomus thummi

The effects of a set of stress treatments on gene expression of Chironomus thummi salivary gland cells have been analyzed. Among the treatments assayed, only during recovery from carbon dioxide have we observed a response similar to that previously described after heat-shock treatment: induction of the heat-shock puffs and synthesis of the heat-shock polypeptides. In these conditions, puffing and transcription of telomeric regions were observed, which led to the appearance of the temperature-inducible telomeric Balbiani ring T-BR-III. Other treatments failed to induce the heat-shock response, despite promoting real stress conditions to C. thummi larvae or salivary gland cells.

Telomeric DNA sequences differentially activated by heat shock in two Chironomus subspecies

The patterns of puffing, transcription and protein synthesis under heat shock were analysed in polytene nuclei of Chironomus thummi piger, in comparison with those obtained in the closely related subspecies C. th. thummi. Most chromosomal heat shock puffs, as well as heat shock induced polypeptides, in C. th. piger paralleled those previously reported for C. th. thummi. Nevertheless, we found a striking difference in behaviour in the induction of telomeric Balbiani rings by heat shock in the two subspecies. Although homologous sequences were present at all the telomeres in both subspecies, they were not always transcriptionally activated by heat shock. The most frequently puffed telomeres were that of chromosome III R in C. th. thummi and that of chromosome IV R in piger. Transcription of the same sequences from both telomeric Balbiani rings (T-BR-III and T-BR-IV) occurred under heat shock. The enigmatic behaviour of telomeres and the functional significance of T-BRs are discussed in relation to possible equivalents in other Diptera.

Temperature-induced Balbiani rings in Chironomus thummi

The formation of a new telomeric Balbiani ring in the right arm of chromosome III (T-BR III) has been induced in Chironomus thummi larvae by applying a wide range of temperature treatments (33 degrees - 39 degrees C). In this paper we present some kinetic and functional characteristics of this structure. T-BR III incorporates tritiated uridine, and during its formation accumulation of acidic proteins takes place. However, induction and maintenance of this puff structure appear to be insensitive to Actinomycin treatment. An additional T-BR can be induced in chromosome I by employing the most drastic temperature treatments (37 degrees - 39 degrees C). We also report the existence of a group of puffs active after heat treatments in Chironomus polytene chromosomes which could be homologous with the T-puffs of Drosophila.

Dependence of Balbiani ring puffing on protein synthesis

The possible dependence of puffing of the Balbiani rings (BRs) on the protein synthesis has been investigated by studying the response of these structures to protein synthesis inhibition induced by cycloheximide and anisomycin. When larvae of Chironomus thummi belonging to middle IV instar (BR1 repressed, BR2 expanded) are subjected to short treatment (3--6 h) with these drugs, BR1 and BR2 puffing states remain essentially unaffected. But when the same treatments are applied to galactose-pretreated larvae (BR1 expanded, BR2 repressed), selective reactivation of the collapsed BR2 occurs. These observations suggest that maintenance of a given puffing state can be dependent, to a variable extent, on the supply of newly synthesized proteins. In particular, selective re-expansion of galactose-repressed BR2 induced by the drugs seem to indicate the existence of repressor-like factor whose activity would be triggered by the galactose treatment.

The formation of ribonucleoprotein droplets in Chironomus salivary gland nuclei

The appearance of RNP droplets associated with specific regions of polytene chromosomes from Chironomus larvae has been studied, systematically by light microscopy using glutarladehyde fixation and lactic acid squashing of the salivary gland. During the fourth larval instar the highest frequency of nuclei which contained droplets (over 50%) was observed in late prepupae. Several treatments (heat and cold shock, cycloheximide) were found to stimulate the formation of a large number of droplets whose features under the light and electron microscopes seemed to be identical to those observed in untreated larvae. Droplets could be observed either in a free state in the nuclear sap or grouped around specific regions of the chromosome such as some Balbiani rings and puffs. Kinetic studies suggest that droplets first appear in a free state and later group themselves on specific chromosome regions. Transcriptional activity seems to be essential for the process of droplet accumulation in the chromosome, since it does not take place if RNA synthesis is inhibited. Cytochemical tests showed striking similarities between the staining reactions of droplets and those of the fibrillar component of the nucleolus. These observations indicate that droplets probably originate from, or share a common component with, nucleolar material and that this component has a preferential affinity for some active chromosomal loci, where it accumulates.

Galactose induced Balbiani-ring-like structures in chromosomes I and II of Chironomus thummi

In one strain of Chironomus thummi, galactose feeding of the larvae induced the appearance of 2 Balbiani-ring-like structures on salivary gland chromosomes I and II. This phenomenon may be related to the galactose induction of BR6 in C. pallidivittatus.

Effect of galactose treatment in the puffing pattern of Chironomus thummi Balbiani rings

Galactose feeding of Chironomus thummi larvae induces the regression of Balbiani ring c (BRc) and the full expansion of BRb, both localized in the IV salivary gland chromosome. This effect coincides with that described on BR2 and BR1 of Ch. pallidivittatus and Ch. tentans. The puffing changes of BRb and BRc throughout develoment have been studied and also show identical variations as in BR1 and BR2 of Ch. pallidivittatus and Ch. tentans. The similar behaviour of BRb and BR1, and of BRc and BR2 respectively after galactose treatment and throughout development strongly suggests that these BRs play the same physiological role in the three Chironomus species, with BRb = BR1 and BRc= BR2.