Anna Skoczyńska

Lipid abnormalities in rats given small doses of lead

Previous human and experimental studies have demonstrated that lead exposure may modify the metabolism of lipids. Several studies have indicated that exposure to lead produces an increase in lipid peroxidation and inhibits blood superoxide dismutase activity. Recently, lipid peroxides have been shown to impair tissue membranes and to be a risk factor for vascular diseases. The aim of the present investigation was to evaluate the impact of subclinical lead poisoning on rat lipids in the context of atherosclerosis. The degree of poisoning was analogous to that in populations exposed to lead in a contaminated environment. Experiments were performed on male Buffalo rats with body weights of 150–200 g. The experimental animals received lead acetate intragastrically in doses of 35 mg lead/kg body wt. (Pb/kg) once weekly or 70 mg Pb/kg twice weekly for 7 weeks. Control rats were fed in the same manner with sodium acetate equimolar to the acetate in the lead acetate solution. One day after the feeding was over, venous blood samples, under ether anesthesia, were collected. The animals were killed by exsanguination and the liver was excised for determination of the metal (lead, copper, and zinc) content. A segment of the abdominal aorta was excised for histological examination. In venous blood the following were estimated: triglycerides, total cholesterol, high-density lipoprotein (HDL)-cholesterol fraction, serum lipid peroxides, and blood superoxide dismutase activity. Metal content (lead, copper, and zinc) in blood and liver was determined by means of atomic absorption spectrophotometry. In rats poisoned with small doses of lead, decreases in the plasma cholesterol level and the HDL-cholesterol fraction were observed. In parallel with the decrease in the cholesterol concentration, lead increases the serum triglyceride level, this increase being dependent upon lead levels in blood. In our studies a significant influence of lead on serum lipid peroxide level or blood superoxide dismutase activity was not found. In the histological examination, atrophy of the elastic fibers in the aorta was observed. The possible significance of the inhibitory effect of lead on lipoprotein lipase activity is discussed.

Response of the cardiovascular system to catecholamines in rats given small doses of lead

Experiments were done in order to assess the influence of low level lead poisoning in rats upon the responses of the rat cardiovascular system to perturbation by norepinephrine, epinephrine, and isoproterenol administration. Wistar rats were given lead acetate (50.0 mg/kg) via stomach tube once weekly for 5 weeks. Control rats were given sodium acetate similarly; both groups of rats were on a regular animal food diet during the experiment. At the end of the sixth week 2 types of responses were determined. Under urethane anesthesia, the response of mean arterial pressure and heart rate in control and lead-poisoned animals to various catecholamines was measured. Also the response of perfusion pressure in isolated mesenteric vessels, to catecholamines, was measured for vessels having been obtained from control and lead poisoned animals. Our results indicate that lead-treated rats, as compared to controls, have augmented and prolonged pressor responses to epinephrine and norepinephrine; less pronounced depression of arterial pressure in response to epinephrine and isoproterenol; and more pronounced tachycardia in response to isoproterenol. In the lead-treated rats, more pronounced vasoconstriction was observed in the perfusion studies upon administration of exogenous norepinephrine. Small doses of lead intensified alpha receptor response, diminished beta receptor response in blood vessels, and increased positive chronotropic action of isoproterenol.

Carotid sinus reflexes in rats given small doses of lead

The effect of low level lead poisoning on the carotid sinus reflex in rats was studied. The reflex was evoked by carotid artery clamping, in control and lead-poisoned animals. Wistar rats were given lead acetate trihydrate (50 mg/kg) via stomach tube once weekly for 5 weeks; control animals were given equimolar amounts of sodium acetate. Both groups were fed a regular animal food diet. At the end of the 6th week, and under urethane anesthesia, mean arterial blood pressure and heart rate were continuously recorded for both groups, before and after clamping, and after unclamping the left common carotid artery. In other experiments, some animals were pre-treated with dopamine, 0.040 mg/kg; practolol, 3 mg/kg; propranolol, 0.1 mg/kg; or atropine, 0.1 mg/kg. In animals not given drugs, lead produced a less pronounced rise in mean arterial blood pressure after clamping, and a more pronounced decrease in heart rate after unclamping, compared to control animals. Some drugs altered this response pattern. Atropine led to a more pronounced tachycardia in the lead-poisoned rats, whereas practolol led to a more pronounced bradycardia in the lead-poisoned rats. Propranolol pretreatment led to a less pronounced decrease in heart rate for lead-poisoned rats, again as compared to the controls. Atropine and beta-adrenergic receptor blocking agents produced similar carotid sinus reflex responses in control and lead-poisoned animals.

The impact of subchronic lead poisoning on the vascular effect of nitric oxide in rats

Lead-induced arterial hypertension is suggested to have resulted mainly from a reduction in nitric oxide (NO) bioactivity in vessel walls. The aim of this study was to evaluate the impact of poisoning by lead in so-called hypertensive doses on the basal and stimulated released NO effect in the rat mesenteric bed. Male Buffalo rats were given lead in a dose of 50 or 100ppm in drinking water for three months. The isolated mesenteric bed preconstricted by norepinephrine (0.5μg/ml) was used to determine the changes in vascular resistance induced by N-ω-nitro-l-arginine injected in increasing doses from 1.0 to 200.0μg or by acetylcholine administered in doses from 0.05 × 10(-10) to 5.0 × 10(-10)mol. These changes were measured as an increase or decrease in perfusion pressure in the constant flow system. In comparison with controls rats given 50ppm of lead, an increase in maximal response to N-ω-nitro-l-arginine (P < 0.01) and acetylcholine (P < 0.05) and a shift to the left of the dose-response curve for acetylcholine were demonstrated. Vascular responses in rats, who were given 100ppm of lead, were similar to those observed in the control group. It is concluded that lead induces NO-mediated changes of vascular tone and vascular reactivity only in the small range of doses known as hypertensive.

Serum angiotensin‐converting enzyme levels in patients with silicosis

In a group of control subjects, the mean serum angiotensin-converting enzyme (ACE) level was 38.1 +/- 10.6 nmol/min X ml (n = 30), and in a group of silicosis patients the mean serum ACE level was 45.2 +/- 16.0 (n = 26). Thirteen of these patients were classified as having nodular silicosis, and their mean serum ACE level was 44.2; 10 of these patients were classified as having progressive massive fibrosis, and their mean serum ACE level was 39.4. Three of these patients had confirmed silicotuberculosis, and their serum ACE levels were 63, 67, and 77 (mean = 69); these serum ACE levels are somewhat higher than those having been reported for patients with acute sarcoidosis. Thus, when serum ACE levels are being used to assist in distinguishing between silicosis and sarcoidosis, the possibility of silicotuberculosis must be also considered when high serum ACE levels are encountered.

Heart function in magnetic resonance imaging and the mesenteric artery reactivity in rats receiving lead-contaminated drinking water.

The aim of this study was to evaluate the effect of lead (Pb)-contaminated drinking water on magnetic resonance imaging (MRI)-estimated cardiac function, vascular reactivity, and serum lipids in rats. For 3 months, male Wistar rats, aged 4–6 weeks, were given drinking water with the addition of lead acetate at a concentration of 100 ppm Pb (10 rats) or water free from Pb (8 control rats). The cardiac MRI was performed at rest and under β-adrenergic stimulation on a 4.7 T scanner using electrocardiogram-triggered gradient echo (FLASH) cine sequence. After 1–2 weeks of the MRI test, experiments were performed ex vivo. After stabilization of perfusion pressure (PP), norepinephrine at doses from 0.01 to 5.0 μg was dissolved in Krebs solution, injected in a volume of 100 μl, and next infused at a concentration of 0.5 μg/ml into the isolated mesenteric artery. In this manner, preconstricted mesenteric bed was used to determine PP changes induced by acetylcholine, given at doses from 0.05 to 5.0 μg, before and during the infusion of nitric oxide synthase inhibitor (1.0 μg/ml). At the end, dobutamine (5 mg), followed by potassium chloride (10.5 mg), was injected. Lipid levels were determined enzymatically, blood Pb level was measured by the atomic absorption spectrophotometer. This study showed that Pb impairs the left ventricular systolic and diastolic function. Pb-induced changes in response to resistance of vessels to vasoactive agents may be secondary to the reduced left ventricular ejection fraction. The high-density lipoprotein subfraction 2 (HDL2) is involved in the cardiovascular effect of Pb.

Low-Level Exposure to Lead as a Cardiovascular Risk Factor

Cardiovascular diseases are the main cause of death in many developed and developing countries around the world. Cardiovascular end points (myocardial infarction, stroke or sudden death) are strictly connected with prevalence of classic cardiovascular risk factors, such as smoking, sedimentary lifestyle, obesity, atherosclerotic lipid pattern and arterial hypertension. Also, many ‘new’ factors have been identified, e.g. hyperhomocysteinemia, increased fraction of small, dense LDL or lipoprotein (a), increased C-reactive protein, increased apo-B/apo-A ratio or some enzymes’ increased activities (Skoczynska, 2006). However, traditional risk factors alone (nonmodifiable and modifiable alike) do not fully explain high incidence and mortality from these diseases. The effectiveness of different strategies concentrating on reducing known risk factors does not translate to a satisfactory reduction of incidence and mortality from myocardial infarction or stroke. It is essential to introduce strategies concerning ‘new’ risk-factors, as well as to identify those that remain unknown.

Left ventricular diastolic function in workers occupationally exposed to mercury vapour without clinical presentation of cardiac involvement

The aim of the study was to evaluate left ventricular diastolic function in workers occupationally exposed to mercury vapour without clinical presentation of cardiac involvement. The studies included 115 workers (92 men and 23 women) occupationally exposed to mercury vapour without clinical presentation of cardiac involvement (mean age: 47.83±8.29). Blood samples were taken to determine blood lipid profile, urine was collected to estimate mercury concentration (HgU) and echocardiographic examination was performed to evaluate diastolic function of the left ventricle. In the entire group of workers occupationally exposed to mercury vapour without clinical presentation of cardiac involvement, Spearman correlations analysis demonstrated the following significant linear relationships: between body mass index (BMI) and ratio of maximal early diastolic mitral flow velocity/early diastolic mitral annular velocity (E/E`) (r=0.32, p<0.05), between serum HDL concentration and E/E` (r=-0.22, p<0.05), between HgU and E/E` (r=0.35, p<0.05), between HgU and isovolumetric relaxation time (IVRT`) (r=0.41, p<0.05), between HgU and ratio of maximal early diastolic mitral flow velocity/maximal late diastolic mitral flow velocity (E/A) (r=-0.31, p<0.05) and between serum HDL concentration and E/A (r=0.43, p<0,05). In logistic regression analysis it as shown that independent factors of left ventricular diastolic dysfunction risk in the study group included a higher urine mercury concentration, a higher value of BMI and a lower serum HDL concentration (OR(Hg-U)=1.071, OR(BMI)=1.200, OR(HDL)=0.896, p<0.05). Summing up, occupational exposure to mercury vapour may be linked to impaired left ventricular diastolic function in workers without clinical presentation of cardiac involvement.

Global emergence and population dynamics of divergent serotype 3 CC180 pneumococci

Streptococcus pneumoniae serotype 3 remains a significant cause of morbidity and mortality worldwide, despite inclusion in the 13-valent pneumococcal conjugate vaccine (PCV13). Serotype 3 increased in carriage since the implementation of PCV13 in the United States, while invasive disease rates remain unchanged. We investigated the persistence of serotype 3 in carriage and disease, through genomic analyses of a global sample of 301 serotype 3 isolates of the Netherlands3–31 (PMEN31) clone CC180, combined with associated patient data and PCV utilization among countries of isolate collection. We related genotypic differences to phenotypic variations through assessment of capsule charge (zeta potential), capsular polysaccharide shedding, and susceptibility to opsonophagocytic killing, which have previously been associated with carriage duration, invasiveness, and vaccine escape. The recent success of CC180 was associated with a globally emerging lineage termed Clade II, which was estimated by Bayesian coalescent analysis to have first appeared in 1968 [95% HPD: 1939-1989]. Clade II isolates were divergent in non-capsular antigenic composition, competence, and antibiotic susceptibility compared with the pre-PCV13 serotype 3 population. Co-resistance to tetracycline, macrolide, and chloramphenicol resulted from the acquisition of a Tn916-like conjugative transposon harbouring tetM, ermB, and cat. Differences in recombination rates among clades correlated with variations in the ATP-binding subunit of Clp protease as well as amino acid substitutions in the comCDE operon. Opsonophagocytic killing assays elucidated the low observed efficacy of PCV13 against serotype 3. Variation in PCV13 use among sampled countries was not correlated with the emergence of Clade II, implicating genotypic and phenotypic differences. Our analysis emphasizes the need for routine, representative sampling of isolates from disperse geographic regions, including historically under-sampled areas. We also highlight the value of genomics in resolving antigenic and epidemiological variations within a serotype, which may have implications for future vaccine development. Author Summary Streptococcus pneumoniae is a leading cause of bacterial pneumoniae, meningitis, and otitis media. Despite inclusion in the most recent pneumococcal conjugate vaccine, PCV13, serotype 3 remains epidemiologically important globally. We investigated the persistence of serotype 3 using whole-genome sequencing data form 301 isolates collected among 24 countries from 1993-2014. Through phylogenetic analysis, we identified three distinct lineages within a single clonal complex, CC180, and found one has recently emerged and grown in prevalence. We then compared genomic difference among lineages as well as variations in pneumococcal vaccine use among sampled countries. We found that the recently emerged lineage, termed Clade II, has a higher prevalence of antibiotic resistance compared to other lineages, diverse surface protein antigens, and a higher rate of recombination, a process by which bacteria can uptake and incorporate genetic material from its surroundings. Differences in vaccine use among sampled countries did not appear to be associated with the emergence of Clade II. We highlight the need to routine, representative sampling of bacterial isolates from diverse geographic areas and show the utility of genomic data in resolving epidemiological differences within a pathogen population.

Molecular diversity and antimicrobial susceptibility of Listeria monocytogenes isolates from invasive infections in Poland (1997–2013)

The epidemiology of invasive listeriosis in humans appears to be weakly characterized in Poland, the sixth most populous member state of the European Union. We obtained antimicrobial susceptibility data, PCR-serogroups and genotypic profiles for 344 invasive isolates of Listeria monocytogenes, collected between 1997 and 2013 in Poland. All isolates were susceptible to the 10 tested antimicrobials, except one that was resistant to tetracycline and minocycline and harbored the tet(M), tet(A) and tet(C) genes. Overall, no increasing MIC values were observed during the study period. Four PCR-serogroups were observed: IVb (55.8%), IIa (34.3%), IIb (8.1%) and IIc (1.8%). We identified clonal complexes (CCs) and epidemic clones (ECs) previously involved in outbreaks worldwide, with the most prevalent CCs/ECs being: CC6/ECII (32.6%), CC1/ECI (17.2%), CC8/ECV (6.1%) and CC2/ECIV (5.5%). The present study is the first extensive analysis of Polish L. monocytogenes isolates from invasive infections.