A framework for reconstructing transmission networks in infectious diseases

In this paper, we propose a general framework for the reconstruction of the underlying cross-regional transmission network contributing to the spread of an infectious disease. We employ an autoregressive model that allows to decompose the mean number of infections into three components that describe: intra-locality infections, inter-locality infections, and infections from other sources such as travelers arriving to a country from abroad. This model is commonly used in the identification of spatiotemporal patterns in seasonal infectious diseases and thus in forecasting infection counts. However, our contribution lies in identifying the inter-locality term as a time-evolving network, and rather than using the model for forecasting, we focus on the network properties without any assumption on seasonality or recurrence of the disease. The topology of the network is then studied to get insight into the disease dynamics. Building on this, and particularly on the centrality of the nodes of the identified network, a strategy for intervention and disease control is devised.

Experience of field testing in Lebanon during the COVID-19 pandemic, January to August 2021

Soon after detection of the first COVID-19 case in Lebanon, a testing strategy was developed aiming to early detect new cases and identify close contacts in order to implement isolation and quarantine measures, thus limiting disease transmission. Field-testing activities were initiated in March 2020, focusing on suspected cases and close contacts. The objective of this paper is to present data collected between the 1st and the 35th week of 2021 and discuss challenges and lessons learned. During the study period, testing activities were conducted in field sites covering all Lebanese districts and following a fixed schedule. Testing was provided free of charge for suspected/probable patients with COVID-19 and close contacts of positive cases. Nasopharyngeal specimens were collected and sent to designated laboratories for reverse transcription polymerase chain reaction testing. Results were received on a timely manner, within 48 hours. From the 1st to the 35th week of 2021, 1244 field-testing activities were conducted with an average of 37 testing activities per week. During this period, 71 542 samples were collected with an average of 2104 specimens per week. On average, activities covered 78% of the Lebanese districts. The average positivity rate for this period was 24% (15%–33%) in line with the virus circulation levels in the country. Timely development and implementation of a testing strategy is crucial during epidemics. The success of Lebanon’s field-testing experience was mainly due to the timely adapted approach that covered all national territories, targeting all residents as well as high-risk groups in suburbs and remote areas.

Sodium monochloroacetate causes cytotoxic effects, an increased lactate and pyruvate level and induces ultra structural and cytoskeletal alterations in cultured kidney and liver epithelial cells

1. Monochloroacetic acid (MCAA) and its sodium salt, sodium monochloroacetate (SMCA) are widely used in chemical industries as intermediates in the synthesis of carboxymethylcellulose, phenoxyacetic acid, thioglycolic acid, glycine, indigoid dyes and others. Moreover, MCAA has been found as a by-product of the chlorination disinfection of drinking water and as an environmental contaminant of the atmosphere from the photodechlorination reactions of chlorinated hydrocarbons. Little is known about the mode of action of both compounds on the cellular level. From cases of accidental poisoning of man it is known that MCAA accumulates in liver and kidney. 2. In this study, the cytotoxicity of SMCA on cultured liver (Chang liver cells) and kidney epithelial cells of the proximal tubule (Opossum kidney cells) was investigated and its effect on metabolism, ultrastructure and organization of cytoskeleton was examined. 3. Independent from the growth state of the cells (proliferating or quiescent), the results clearly show that SMCA causes a dose-dependent decrease in cell viability after an exposure period of 24 h. In all experiments, proliferating cells were more sensitive than quiescent and confluent cells. Liver cells were less sensitive against SMCA treatment than kidney epithelial cells. In contrast to liver cells, kidney cells exhibited a dose-dependent decrease in cell volume. The decrease in cell viability was accompanied by an increase of lactate and pyruvate concentrations released into the culture medium. In the case of Opossum kidney cells, lactate and pyruvate levels increased 5 - 6-fold, whereas in the case of Chang liver cells the increase was approximately twofold. While the ultrastructure of liver cells remained unaltered after drug treatment, kidney cells exhibited cytoplasmic vacuolization, membraneous disruption and especially mitochondrial alterations. In accordance with the changes in the ultrastructure of Opossum cells, was the reorganization of cytoskeletal elements with an increased stress fiber network at the basolateral surface as well as a partial depolymerization of microtubules and vimentin filaments. A cytoskeletal reorganization was not observed for Chang liver cells after SMCA treatment. 4. The results demonstrate that SMCA causes a dose-dependent cytotoxicity which is accompanied by metabolic, mitochondrial and cytoskeletal alterations in the cells.

Protective effect of Crataegus oxyacantha against reperfusion arrhythmias after global no-flow ischemia in the rat heart

The protective effect against reperfusion arrhythmias of a 3-month oral pretreatment with a dried extract of Crataegus oxyacantha (LI 132)(standardized to 2.2% flavonoids) was studied with the Langendorff heart of the rat after global no-flow ischemia. The heart was perfused with a modified Krebs-Henseleit solution in which the K+ content was reduced to 3.4 mmol/l in order to lower the fibrillation threshold. According to pilot experiments which considered various durations of global no-flow ischemia ranging from 10 to 20 minutes, two durations were chosen for the present study: 20 minutes (group 20) in which ventricular fibrillation (VF) was the predominant form of arrhythmias, and 18 minutes (group 18) in which the prevalence of VF was markedly lower despite the small difference in the duration of ischemia. Crataegus pretreatment significantly (p = 0.02) reduced the average prevalence of malignant arrhythmias (VF + Flutter) as observed during the 20-min-period of reperfusion as follows: group 20: from 89% (control, n = 9) to 51% (LI 132, n = 7), group 18: from 48% (control, n = 8) to 8% (LI 132, n = 8). In group 20, ventricular tachycardia (VT) could be observed only in the treated group, because of the predominance of VF in the control group. LI 132 pretreatment reduced the average prevalence of VT in group 18 in spite of the identical percentage of occurrence (6 out of 8 rats, with and without treatment) due to a shorter duration of the VT episodes. Thus, under the conditions of our experiments, effective prevention against reperfusion arrhythmias by Crataegus pretreatment was evident.

Myocardial protection by pretreatment with Crataegus oxyacantha: an assessment by means of the release of lactate dehydrogenase by the ischemic and reperfused Langendorff heart

The effect of the pretreatment with the powder of crataegus oxyacantha on the release of lactate dehydrogenase (LDH) during ischemia and reperfusion was studied in an isolated rat heart model. Male Wistar rats were divided into control and crataegus group (for which the standard diet was mixed with a 2% crataegus powder standardized to 2.2% flavonoids). The investigations started 3 months after commencing the treatment. The hearts were isolated and a retrograde perfusion was performed at constant pressure according to the technique of Langendorff. The experimental protocol comprised 10 min equilibration, according to the technique of Langendorff. The experimental protocol comprised 10 min equilibration, according to the technique of Langendorff. The experimental protocol comprised 10 min equilibration, 110 min occlusion of the left anterior descending coronary artery, and 30 min reperfusion. The coronary effluent was sampled for the LDH determination after 5, 30, 90, 120 and 150 min. The LDH activity, which was initially very low in both groups (control, 16.5 +/- 4.3; crataegus, 26.0 +/- 8.8 mU/min) increased slightly during the ischemia, and very strongly as soon as the heart was reperfused. However, the increase in the crataegus group was significantly lower (1777.3 +/- 451.9 vs control 3795.3 +/- 511.9 mU/min, p = 0.01). At the end of the reperfusion period, LDH activity decreased markedly but did not reach the ischemic values. The attenuation of the LDH release by crataegus pretreatment suggests a preservation of the cell membrane and a protection from myocardial damage.

Myocardial protection by ischemic preconditioning: the influence of the composition of myocardial phospholipids

It was the aim of this study to investigate (1) whether preconditioning modifies the fatty acid (FA) composition of myocardial phospholipids (PL), (2) whether a previous modification of membrane PL composition by the administration of coconut oil or fish oil influences the preconditioning, and (3) to compare the protective effects of preconditioning to those of dietary fish oil. To this end, three groups of rats were given during 10 weeks either a standard diet, or a standard diet + 10% coconut oil, or a standard diet + 10% fish oil. The preconditioning was performed in situ in the anesthetized open-chest rats by 2 cycles of 3 min left anterior descending coronary artery occlusion and 10 min reperfusion. It was followed by a 40 min ischemia and a 60 min reperfusion. ECG was recorded and used for the continuous count of the salves of extrasystoles, ventricular flutter and fibrillation. These rhythm disturbances were subsequently added and evaluated as total arrhythmias. The FA of tissue PL were analyzed in a sample of the ischemic zone the size of which was determined by means of malachite green. Coconut oil diet (rich in saturated FA) modified slightly the myocardial PL by increasing oleic acid and decreasing linoleic acid and resulted in the highest incidence of arrhythmias. Fish oil diet had the opposite effect in modifying drastically the PLFA (replacement of the n-6 FA by the n-3 FA) and minimizing significantly the arrhythmias in comparison with the standard diet group.(ABSTRACT TRUNCATED AT 250 WORDS)

n-3 versus n-6 fatty acid incorporation into the phospholipids of rat heart sarcolemma. A comparative study of four different oil diets

The fatty acid (FA) composition of the phospholipids of rat heart sarcolemma was studied after a 10-week feeding period of diets containing 10% of each of coconut oil, corn oil, linseed oil, and fish oil in comparison to a low fat diet. The major modifications observed were the following: (1) a general increase of the n-6 FA family upon corn oil administration; (2) a dual effect of linseed oil in increasing 18:2 n-6 (more than did corn oil) and decreasing 20:4 n-6 and 22:4 n-6. At the same time n-3 FA increased significantly; and (3) a significant fall in the n-6 FA following fish oil, and a marked rise in the n-3 FA. The 10-fold increase in 22:6 n-3 supports the hypothesis of an inhibition of arachidonate synthesis, as well as that of the competition for the incorporation sites of phospholipids. In general, the n-3 FA diets produced the replacement of the n-6 FA by the n-3 FA in membrane phospholipids, and led to a significant increase of the double bond index (DBI).