Open-air sprays for capturing and controlling airborne float coal dust on longwall faces.

Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening.

Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport.

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Thrombin generation and bleeding in haemophilia inhibitor patients during immune tolerance induction.

BACKGROUND: Inhibitor formation complicates haemophilia treatment and requires immune tolerance induction to rid inhibitors over 5 BU. In the prospective, randomized International Immune Tolerance Study, immune tolerance induction was equally effective with high-dose (HD) (200 IU kg-1 day-1 ) and low-dose (LD) (50 IU kg-1 3× per week) factor VIII, but haemorrhages were twofold higher in the LD arm. This finding was unexpected as inhibitors neutralize FVIII activity. We hypothesized that the thrombin generation assay (TGA), a global measure of clot formation, might predict bleeding better than FVIII levels. METHODS: We evaluated TGA using relipidated tissue factor (TF) on 83 thawed, recalcified corn trypsin inhibitor/citrate plasma samples from 31 subjects (17 HD, 14 LD) who participated on the ITI study, and who had sufficient sample available and appropriate informed consent. RESULTS: There were no significant differences in peak thrombin, estimated thrombin potential, maximum rate or lag time between HD and LD arms; between pre-, during and post-ITI time points, or after FVIII spiking. In 19 subjects (12 HD, 7 LD) with anti-FVIII<1.0 BU, the prevalence of non-neutralizing antibody (NNA) and neutralizing antibody (NA) was 89.5% (17/19), and the latter strongly correlated with anti-VIII titer, r = 0.73 [95% CI: 0.55, 0.88]. CONCLUSION: In haemophilia inhibitor patients, thrombin generation is present, but does not predict bleeding risk. Following tolerance induction, NNA remains detectable in the majority.

Blood lead concentrations in a remote Himalayan population.

The lead content in the air at the foothills of the Himalayas in Nepal was found to be negligible. The concentration of lead in the blood of 103 children and adults living in this region was found to average 3.4 micrograms per deciliter, a level substantially lower than that found in industrialized populations.

Erythrocyte adenosine deaminase deficiency without immunodeficiency. Evidence for an unstable mutant enzyme.

Inherited deficiency of the purine salvage enzyme adenosine deaminase (ADA) gives rise to a syndrome of severe combined immunodeficiency (SCID). We have studied a 2.5-yr-old immunologically normal child who had been found to lack ADA in his erythrocytes during New York State screening of normal newborns. His erythrocytes were not detectably less deficient in ADA than erythrocytes of ADA(-)-SCID patients. In contrast, his lymphocytes and cultured long-term lymphoid cells contained appreciably greater ADA activity than those from patients with ADA(-)-SCID. This residual ADA activity had a normal molecular weight and K(m) but was markedly unstable at 56 degrees C. His residual erythrocytes-ADA activity also appeared to have diminished stability in vivo. ADA activity in lymphoid line cells of a previously reported erythrocyte-ADA-deficient!Kung tribesman was found to contain 50% of normal activity and to exhibit diminished stability at 56 degrees C. ATP content of erythrocytes from both partially ADA-deficient individuals was detectably greater than normal (12.3 and 6.1 vs. normal of 2.6 nmol/ml packed erythrocytes). However, the dATP content was insignificant compared to that found in erythrocytes of ADA(-)-SCID patients (400-1,000 nmol/ml packed erythrocytes). The New York patient, in contrast to normals, excreted detectable amounts of deoxyadenosine, but this was <2% of deoxyadenosine excreted by ADA(-)-SCID patients. Thus, the residual enzyme in cells other than erythrocytes appears to be sufficient to almost totally prevent accumulation of toxic metabolites.

Erythropoietic protoporphyria and lead intoxication: the molecular basis for difference in cutaneous photosensitivity. I. Different rates of disappearance of protoporphyrin from the erythrocytes, both in vivo and in vitro.

In lead intoxication photosensitivity is usually absent, despite concentrations of protoporphyrin in the erythrocytes equal to or greater than in erythropoietic protoporphyria. Profound differences in the distribution of protoporphyrin in aging erythrocytes were demonstrated by age-dependent fractionation of cells on discontinuous density gradients. In erythropoietic protoporphyria the concentration of protoporphyrin declined extremely rapidly with erythrocyte age; the bulk of the protoporphyrin was lost in less than 3 days and the concentration of fluorescent erythrocytes in the gradient paralleled the decline of protoporphyrin. In lead intoxication the protoporphyrin concentration declined only slightly with cell aging and erythrocytes of all ages fluoresced. In the bone marrow from a patient with erythropoietic protoporphyria all reticulocytes, but only occasional late normoblasts, fluoresced, suggesting a single population. Sterile incubation in plasma (pH 7.5) demonstrated rapid diffusion of protoporphyrin from the erythrocytes in erythropoietic protoporphyria, but not in lead intoxication. Plasma protoporphyrin was elevated in erythropoietic protoporphyria, but not in lead intoxication. Estimates of the daily loss of protoporphyrin from erythropoietic tissue in erythropoietic proporphyria suggested an order of magnitude similar to the total blood protoporphyrin. Therefore, it is not necessary to postulate a preponderant extraerythropoietic source to explain the amount of fecal excretion. A significant amount of the diffused protoporphyrin probably reaches the skin with resulting photosensitivity. In contrast, in lead intoxication protoporphyrin remains within the erythrocyte throughout its life span ; there is no diffusion into the plasma and hence no photosensitivity.

Heterogeneity of the molecular lesions in inherited phosphofructokinase deficiency.

Human phosphofructokinase (PFK; EC 2.7.1.11) exists in tetrameric isozymic forms. Muscle and liver contain the homotetramers M4 and L4, whereas erythrocytes contain five isozymes composed of M (muscle) and L (liver) subunits, i.e., M4, M3L, M2L2, ML3, and L4. Inherited defects of erythrocyte PFK are usually partial and are described in association with heterogeneous clinical syndromes. To define the molecular basis and pathogenesis of this enzymopathy, we investigated four unrelated individuals manifesting myopathy and hemolysis (glycogenosis type VII), isolated hemolysis, or no symptoms at all. The three symptomatic patients showed high-normal hemoglobin levels, despite hemolysis and early-onset hyperuricemia. They showed total lack of muscle-type PFK and suffered from exertional myopathy of varying severity. In the erythrocytes, a metabolic crossover was evident at the PFK step: the levels of hexose monophosphates were elevated and those of 2,3-diphosphoglycerate (2,3-DPG) were depressed, causing strikingly increased hemoglobin-oxygen affinity. In all cases, the residual erythrocyte PFK consisted exclusively of L4 isozyme, indicating homozygosity for the deficiency of the catalytically active M subunit. However, presence of immunoreactive M subunit was shown in cultured fibroblasts by indirect immunofluorescence with monoclonal anti-M antibody. The fourth individual was completely asymptomatic, had normal erythrocyte metabolism, and had no evidence of hemolysis. His residual erythrocyte PFK showed a striking decrease of the L4, ML3, and M2L2 isozymes, secondary to a mutant unstable L subunit. Identical alterations of erythrocyte PFK were found in his asymptomatic son, indicating heterozygosity for the mutant unstable L subunit in this kindred. These studies show that, except for the varying severity of the myopathic symptoms, glycogenosis type VII has highly uniform clinical and biochemical features and results from homozygosity for mutant inactive M subunit(s). The absence of anemia despite hemolysis may be explained by the low 2,3-DPG levels. The hyperuricemia may result from hyperactivity of the hexose monophosphate shunt. In contrast, the clinically silent carrier state results from heterozygosity for mutant M or L subunit. Of the two, the M subunit appears to be more critical for adequate glycolytic flux in the erythrocyte, since its absence is correlated with hemolysis.

Characterization of neogenin-expressing neural progenitor populations and migrating neuroblasts in the embryonic mouse forebrain.

Many studies have demonstrated a role for netrin-1-deleted in colorectal cancer (DCC) interactions in both axon guidance and neuronal migration. Neogenin, a member of the DCC receptor family, has recently been shown to be a chemorepulsive axon guidance receptor for the repulsive guidance molecule (RGM) family of guidance cues [Rajagopalan S, Deitinghoff L, Davis D, Conrad S, Skutella T, Chedotal A, Mueller B, Strittmatter S (2004) Neogenin mediates the action of repulsive guidance molecule. Nat Cell Biol 6:755-762]. Here we show that neogenin is present on neural progenitors, including neurogenic radial glia, in the embryonic mouse forebrain suggesting that neogenin expression is a hallmark of neural progenitor populations. Neogenin-positive progenitors were isolated from embryonic day 14.5 forebrain using flow cytometry and cultured as neurospheres. Neogenin-positive progenitors gave rise to neurospheres displaying a high proliferative and neurogenic potential. In contrast, neogenin-negative forebrain cells did not produce long-term neurosphere cultures and did not possess a significant neurogenic potential. These observations argue strongly for a role for neogenin in neural progenitor biology. In addition, we also observed neogenin on parvalbumin- and calbindin-positive interneuron neuroblasts that were migrating through the medial and lateral ganglionic eminences, suggesting a role for neogenin in tangential migration. Therefore, neogenin may be a multi-functional receptor regulating both progenitor activity and neuroblast migration in the embryonic forebrain.

Genomic rearrangements of the PRPF31 gene account for 2.5% of autosomal dominant retinitis pigmentosa.

PURPOSE: To determine whether genomic rearrangements in the PRPF31 (RP11) gene are a frequent cause of autosomal dominant retinitis pigmentosa (adRP) in a cohort of patients with adRP. METHODS: In a cohort of 200 families with adRP, disease-causing mutations have previously been identified in 107 families. To determine the cause of disease in the remaining families, linkage testing was performed with markers for 13 known adRP loci. In a large American family, evidence was found of linkage to the PRPF31 gene, although DNA sequencing revealed no mutations. SNP testing throughout the genomic region was used to determine whether any part of the gene was deleted. Aberrant segregation of a SNP near exon 1 was observed, leading to the testing of additional SNPs in the region. After identifying an insertion-deletion mutation, the remaining 92 families were screened for genomic rearrangements in PRPF31 with multiplex ligation-dependent probe amplification (MLPA). RESULTS: Five unique rearrangements were identified in the 93 families tested. In the large family used for linkage exclusion testing, an insertion-deletion was found that disrupts exon 1. The other four mutations identified in the cohort were deletions, ranging from 5 kb to greater than 45 kb. Two of the large deletions encompass all PRPF31 as well as several adjacent genes. The two smaller deletions involve either 5 or 10 completely deleted exons. CONCLUSIONS: In an earlier long-term study of 200 families with adRP, disease-causing mutations were identified in 53% of the families. Mutation-testing by sequencing missed large-scale genomic rearrangements such as insertions or deletions. MLPA was used to identify genomic rearrangements in PRPF31 in five families, suggesting a frequency of approximately 2.5%. Mutations in PRPF31 now account for 8% of this adRP cohort.

Netrin-3 protein is localized to the axons of motor, sensory, and sympathetic neurons.

The netrin family of axon guidance cues has been shown to play a pivotal role in the guidance of a variety of axon projections during embryonic development, both in the vertebrate and invertebrate. While the guidance potential of netrin-1 has been examined in depth in many regions of the developing mouse brain very little information is available on the expression and activity of netrin-3. Here we show that the netrin-3 protein is present on motor neurons and subpopulations of neurons within sensory and sympathetic ganglia. Moreover, significant levels of netrin-3 protein were found to be associated with the axons projecting from these neurons suggesting a role for netrin-3 in axon pathfinding and fasciculation within the peripheral nervous system.

Localization of the netrin guidance receptor, DCC, in the developing peripheral and enteric nervous systems.

Over recent years the secreted guidance cue, netrin-1, and its receptor, DCC, have been shown to be an essential guidance system driving axon pathfinding within the developing vertebrate central nervous system (CNS). Mice lacking DCC exhibit severe defects in commissural axon extension towards the floor plate demonstrating that the DCC-netrin guidance system is largely responsible for directing axonal projections toward the ventral midline in the developing spinal cord (Fazeli et al., Nature 386 (1997) 796). In addition, these mutants lack several major commissures within the forebrain, including the corpus callosum and the hippocampal commissure. In contrast to the CNS, the role of the DCC guidance receptor in the development of the mammalian peripheral and enteric nervous systems (PNS and ENS) has not been investigated. Here we demonstrate using immunohistochemical analysis that the DCC receptor is present in the developing mouse PNS where it is found on spinal, segmental, and sciatic nerves, and in developing sensory ganglia and their associated axonal projections. In addition, DCC is present in the ENS throughout the early developmental phase.

Lack of an association between the angiotensin-converting enzyme insertion/deletion polymorphism and intracranial aneurysms in a Caucasian population in the United States.

OBJECT: The identification of polymorphisms associated with an increase in the risk of developing disease is integral to the development of genetic biomarkers to identify individuals at risk. Based on reports indicating a role for angiotensin-converting enzyme (ACE) in the pathogenesis of intracranial aneurysms (IAs) as well as hypertension, an independent risk factor for IAs, the authors investigated the association between an insertion/deletion (I/D) polymorphism in the ACE gene and IAs in a Caucasian population in the US. METHODS: The patient population consisted of 162 randomly selected Caucasian patients who underwent surgical repair of an IA at Memorial-Hermann Hospital (Houston, TX) and had no family history of the disease. The ACE I/D polymorphism was typed using polymerase chain reaction amplification of genomic DNA, and allele and genotype frequencies were compared between the patients with IAs and 143 healthy Caucasian volunteers (control group) by performing logistic regression and chi-square tests. The ACE I/D allele frequencies did not differ significantly between the patient and control populations. There were similar allele and genotype frequencies in male and female study participants in both patient and control populations. The authors found no evidence of an association between the allelic or genotypic distribution of the ACE I/D polymorphism and aneurysmal subarachnoid hemorrhage or unruptured IAs. CONCLUSIONS: Contrary to findings in two European Caucasian populations (one British and one Polish), this polymorphism did not contribute to the risk of developing IAs in a Caucasian population in the US.

Does deficiency of von Willebrand factor protect against cardiovascular disease? Analysis of a national discharge register.

INTRODUCTION: von Willebrand factor (VWF) plays a critical role in platelet adhesion and aggregation after vascular injury and at sites of high shear rate. Elevated VWF levels are associated with an increased risk of ischemic cardiovascular events; however, it is unclear whether VWF deficiency is protective against atherosclerosis. We aimed to compare the prevalence of cardiovascular disease (CVD) among patients with and without von Willebrand disease (VWD). METHODS: A cross-sectional analysis was performed on discharge data for adults from the Nationwide Inpatient Sample (NIS) between the years 2009 and 2011. CVD was defined as ischemic heart disease, myocardial infarction, ischemic cerebrovascular disease, or peripheral vascular disease. For prevalence calculations and statistical analyses, we used discharge-level weights provided by the NIS to reflect national estimates. CVD was compared across groups by use of the Rao-Scott chi-square test. Multivariable logistic regression was used to estimate the likelihood of CVD in VWD patients after adjustment for age, gender, and CVD-related risk factors. RESULTS: The prevalence of CVD in VWD patients was less than the prevalence of CVD in non-VWD patients (15.0% versus 26.0%). VWD was associated with a decreased likelihood of CVD after adjustment for age, gender, and CVD-related risk factors (odds ratio 0.85; 95% confidence interval 0.79-0.92). DISCUSSION: These findings indicate that the risk of CVD is decreased among VWD patients, and that VWF deficiency may be protective against CVD.

Expression of the netrin-1 receptor, deleted in colorectal cancer (DCC), is largely confined to projecting neurons in the developing forebrain.

Axon guidance mechanisms are crucial to the development of an integrated nervous system. One family of molecules that may be important in establishing axonal connectivity in mammals is the Netrins, and their putative receptors DCC (deleted in colorectal cancer), Neogenin, and Unc-5. Knockout and mutational analyses of some of these genes have shown that they are critically involved in the development of several specific pathways in the developing brain. However, previous expression analyses of these genes have largely been confined to the developing spinal cord. In the present study, we analyzed the expression of DCC in the developing mouse forebrain. We found that DCC protein is expressed in specific axonal populations projecting from the developing olfactory bulb, neocortex, hippocampus, and epithalamus/habenular complex. In the developing olfactory bulb and neocortex, DCC expression is particularly evident during the targeting phase of axon outgrowth and is then rapidly downregulated. As predicted from the knockout and mutational analyses of this gene, DCC is expressed in axonal commissures, in particular the corpus callosum, hippocampal commissure, and the anterior commissure. In addition, we found that DCC is expressed in the habenular commissure, the fasciculus retroflexus, and the stria medularis. Therefore, this analysis implicates a function for DCC in additional axonal guidance systems not predicted from the knockout and mutational analyses.

Randomized, placebo-controlled trial of iron supplementation in infants with low hemoglobin levels fed iron-fortified formula.

In spite of the declining prevalence of iron-deficiency anemia, a large proportion of low-income infants have "low-normal" (11-11.5 g/dL) and "low" (less than 11 g/dL) hemoglobin (Hgb) values. Because most of these infants are fed iron-fortified formulas, it was of interest whether additional iron supplementation would enhance Hgb values. A cohort of 334 healthy, inner-city, minority, 6-month-old infants, fed iron-fortified formulas, with Hgb values ranging from 9 to 11.5 g/dL, participated in a double-blind, randomized, placebo-controlled trial of supplemental iron at 0, 3, and 6 mg/kg per day for 3 months. Hemoglobin values increased significantly with age, regardless of assignment to placebo or supplemental iron (means for the entire cohort: 6 months 10.9 g/dL, 8 months 11.2, 10 months 11.3, and 12 months 11.4). The proportion of "responders" (Hgb level increased greater than or equal to 1 g/dL) was 34% and did not differ significantly by placebo or iron dose. There were no significant differences in mean corpuscular volume or levels of erythrocyte porphyrins or serum ferritin between treatment groups. The implications of this clinical trial are twofold: (1) screening healthy infants fed iron-fortified formula at the age of 6 months is not justified, regardless of socioeconomic status; (2) the clinical practice of routinely treating low-income, "low-Hgb" infants with iron supplementation, without regard to dietary considerations, is unwarranted.

Long-term tolerability, pharmacokinetic and preliminary efficacy study of lamotrigine in patients with resistant partial seizures.

Four adult men with resistant partial seizures underwent an intensive open-label protocol designed to evaluate long-term add-on lamotrigine (LTG) therapy. Following an 8-week baseline, LTG was added to their background medication(s) (carbamazepine in three; carbamazepine and phenytoin in one). Incremental LTG doses of 50, 100, 150, and 200 mg every 12 h were given on days 58-60, 61-63, 64-127, and 128-176, respectively. The patients were hospitalized during and after each of the dose increases for a total of 25 days. Frequent outpatient visits were performed biweekly, weekly, or monthly, depending on the phase of the protocol. Frequent clinical, electrocardiographic (ECG), and laboratory evaluations were performed. Serial blood levels and 24-h urine collections were performed sequentially. In patients 1, 2, and 3, LTG was well tolerated at 200 mg b.i.d. Patient 4 did not tolerate 150 mg, b.i.d., but tolerated and maintained complete seizure control on 100 b.i.d. All four patients tolerated LTG and continued to receive it for 39, 46, 105, and 104 weeks, respectively. Serial 12-h plasma LTG levels were obtained on days 63, 70, and 133. On these days, the mean (+/- SD) LTG clearances (dose/AUC) were 0.0436 +/- 0.0171, 0.0468 +/- 0.0093, and 0.0575 +/- 0.0160 L/h/kg, respectively. Some 43-87% of the LTG was recovered in the urine, predominantly as the glucuronide metabolite. In the four patients, the mean weekly seizure frequency per patient was 6.5 in baseline, 5.0 on submaximal LTG doses, and 3.5 on the maximum administered doses. Three of the four patients eventually experienced a greater than 50% decrease in seizure frequency. In conclusion, when given for long periods of time (9.5 months to 2 years), LTG was well tolerated in doses up to 400 mg/day and mean trough levels of 3.0 +/- 0.6 microgram/ml; LTG has a favorable pharmacokinetic profile and appears to exhibit first-order linear kinetics during long-term chronic dosing; LTG shows preliminary evidence of efficacy during long-term administration; and to date, our patients represent the longest reported experience of continuous and closely monitored LTG therapy in the literature.

Study of the cardiotoxic potential of pharmaceutical compounds in chick myocardial myocyte reaggregate cultures.

Cardiotoxicity produced by doxorubicin in vivo is considered to be due to a direct effect on the myocardium and this is also a major component with toxicity of isoprenaline and digoxin. In the case of the cardiotoxicity produced at high doses by the antihypertensives hydralazine and pinacidil, an indirect mechanism operating by way of their exaggerated pharmacological effects is believed to be responsible. These compounds were examined for their cardiotoxic potential in vitro using chick myocardial myocyte reaggregate (MMR) cultures; allylamine HCl was used as a positive control. Cultures were incubated for up to 24 hr with each compound; parameters analysed were: spontaneous beating activity (SBA), lactate dehydrogenase (LDH) leakage and microscopic evidence of cytotoxicity. Allylamine, doxorubicin, digoxin and to a lesser extent isoprenaline were highly toxic to MMR cultures, as demonstrated by their effects on SBA, LDH leakage and morphology. Hydralazine showed very mild cytotoxicity at the highest concentrations with no LDH leakage; pinacidil was not cytotoxic but showed a dose-related inhibition of SBA. These results confirm the direct toxic action of doxorubicin and digoxin on myocardial cells and indicate that this is also an important mechanism in vivo for isoprenaline. The lack of any significant toxicity with hydralazine and pinacidil accords with an indirect mechanism based on their pharmacology.

Study of the effects of cardiovascular drugs in heart cell cultures.

Compounds that produce myocardial pathology in vivo can be separated into two main classes-those that are directly toxic to the myocardium and those that are considered to act by way of an indirect vascular or neurologically based mechanism. An in vitro model of myocardium without nervous or systemic influences can be used to differentiate between direct myocardial cytotoxic effects and indirect cardiac pathology arising in vivo from exaggerated vascular or neural pharmacological effects of a number of drugs. In this study direct-acting cardiotoxic compounds are distinguished from those causing cardiac pathology by indirect mechanisms by their different pattern of effects in chick embryonic myocardial myocyte reaggregates (MMRs) cultures. The toxicity of the direct-acting cardiotoxic drugs allylamine (positive control, 50 mum) and doxorubicin were compared with digoxin and isoprenaline, which show both direct and indirect mechanisms in vivo, and the indirectly acting hydralazine and pinacidil. Changes in spontaneous beating activity (SBA), leakage of lactate dehydrogenase (LDH) and cell morphology by light and transmission electron microscopy were used to assess toxicity. The MMRs were cultured for up to 24 hr in a series of concentrations of the five compounds in the range 0.1 to 10,000 mum. Allylamine, doxorubicin, digoxin and, to a lesser extent, isoprenaline were highly toxic to the MMRs, as shown by alterations in SBA, LDH leakage and cellular morphology. In contrast, hydralazine showed a very mild degree of toxicity at the highest concentrations in the absence of LDH leakage; treatment with pinacidil did not show any evidence of morphological degeneration but did cause a dose-related inhibition of SBA. These results are consistent with the view that doxorubicin and digoxin are directly toxic to myocardial cells and also suggests that this is an important mechanism in vivo for isoprenaline. The absence of a significant degree of toxicity with hydralazine and pinacidil is consistent with an indirect toxic mechanism.

The Lack of Toxicity of Potassium ChannelActivators in Heart Cell Cultures.

High doses of the potassium channel activators (KCAs) BRL 44269, levcromakalin and pinacidil in a number of laboratory animal species cause a profound reduction in blood pressure which results in reflex tachycardia, ischaemia and myocardial necrosis. Thus, it is considered that the in vivo cardiac pathology seen with KCAs is an indirect effect as a consequence of excessive pharmacological effects rather than direct myocardial toxicity. This hypothesis was tested, in vitro, in the chick embryonic myocardial myocyte reaggregate (MMR) model system. Changes in spontaneous beating activity (SBA), leakage of lactate dehydrogenase (LDH) and cell morphology by light and transmission electron microscopy were used to assess toxicity. The MMRs were cultured for up to 24hr in a series of different concentrations of the three KCAs in the range 1-10,000mum. In addition to an untreated control, allylamine (50mum), a known direct acting myocardial cytotoxin, was used as a positive control. Incubation with allylamine caused clear evidence of toxicity and permanent cessation of SBA. In contrast, KCAs caused changes in SBA and significant toxicity was only seen at the highest concentration (10,000mum) of BRL 44269. These results are supportive of the view that KCA-induced cardiac pathology in vivo is due to an indirect pharmacological action rather than a direct, cytotoxic mechanism.

Elevated blood lead in a population near a lead smelter in Kosovo, Yugoslavia.

A survey of residents of a community surrounding a lead smelter has revealed an alarming incidence of elevated blood lead and erythrocyte protoporphyrin concentrations. In particular, children who were less than 3 yr of age were severely affected. Of those children tested in December, 1980, 35% had blood lead concentrations between 50-69 microgram/dl, while an additional 12% had concentrations greater than or equal to 70 microgram/dl, and are, therefore, at risk for severe neurological sequelae.