Enzymatic basic for DDE-induced eggshell thinning in a sensitive bird

Elastic Moduli of Avian Eggshell

We analyze 700 freshly-laid eggs from 58 species (22 families and 13 orders) across three orders of magnitude in egg mass. We study the elastic moduli using three metrics: (i) effective Young's modulus, EFEM, by a combined experimental and numerical method; (ii) elastic modulus, Enano, by nanoindentation, and (iii) theoretical Young's modulus, Etheory. We measure the mineral content by acid-base titration, and crystallographic characteristics by electron backscatter diffraction (EBSD), on representative species. We find that the mineral content ranges between 83.1% (Zebra finch) and 96.5% (ostrich) and is positively correlated with EFEM-23.28 GPa (Zebra finch) and 47.76 GPa (ostrich). The EBSD shows that eggshell is anisotropic and non-homogeneous, and different species have different degrees of crystal orientation and texture. Ostrich eggshell exhibits strong texture in the thickness direction, whereas chicken eggshell has little. Such anisotropy and inhomogeneity are consistent with the nanoindentation tests. However, the crystal characteristics do not appear to correlate with EFEM, as EFEM represents an overall "average" elasticity of the entire shell. The experimental results are consistent with the theoretical prediction of linear elasticity. Our comprehensive investigation into the elastic moduli of avian eggshell over broad taxonomic scales provides a useful dataset for those who work on avian reproduction.

David S. Miller: Scientist, Mentor, Friend-a tribute and thank you

David S. Miller was Acting Scientific Director of the Division of Intramural Research at the National Institute of Environmental Health Sciences, National Institutes of Health, and Head of the Intracellular Regulation Group in the Laboratory of Toxicology and Pharmacology before he retired in 2016. David received his Ph.D. in biochemistry from the University of Maine in 1973. David was a Group Leader at the Michigan Cancer Foundation before joining the NIEHS in 1985. His research covered a wide range from renal excretory transport mechanisms to regulation of transporters at the blood–CSF and blood–brain barriers, from fish, amphibians and birds to mammals. David was an outstanding scientist with irresistible enthusiasm for science and an incredible ability to think outside the box while being an exceptional mentor and friend.

Dichlorodiphenylchloroethylene elevates cytosolic calcium concentrations and oscillations in primary cultures of human granulosa-lutein cells

1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), a metabolite of DDT (1,1-dichlorodiphenyltrichloroethane), is a persistent hormonally active environmental toxicant that has been found in human serum and follicular fluid. The objective of this study was to determine whether DDE can alter free calcium ion concentrations in the cytosol ([Ca(2+)](cyt)) of human granulosa cells. Changes in [Ca(2+)](cyt) in single cells loaded with Fura-2 were studied using a dynamic digital Ca(2+) imaging system. At a concentration of 100 ng/ml, DDE stimulated small elevations of [Ca(2+)](cyt) accompanied by Ca(2+) oscillations. At 1 microg DDE/ml, there was a biphasic Ca(2+) response with marked elevations of [Ca(2+)](cyt) over time. In Ca(2+)-free medium, cells showed an initial small elevation of [Ca(2+)](cyt), which was magnified after addition of Ca(2+) to the medium. Washing the cells after DDE treatment failed to remove the elevated [Ca(2+)](cyt) and oscillations, both of which were eliminated by addition of EGTA. ATP also induced [Ca(2+)](cyt) elevations and oscillations, and these effects were potentiated when DDE was added. FSH induced transient [Ca(2+)](cyt) elevations, whereas hCG caused a prolonged elevation and marked oscillations in [Ca(2+)](cyt). These results suggest that DDE at concentrations normally found in human tissues induces elevations in [Ca(2+)](cyt) in granulosa-lutein cells. Our data therefore highlight a novel mechanism through which DDE can alter endocrine homeostasis and possibly act as an endocrine toxicant.

Influence of organochlorine pesticides on ATPase activities of microsomal fractions of bovine oviductal and endometrial cells

In the present study the effects of organochlorine pesticides: o,p'-DDT, p,p''-DDT, methoxychlor, and lindane on ATPase activities of microsomal fractions of bovine oviductal and endometrial cells were investigated. We were not able to characterize a Ca2+ stimulated ATPase, whereas 57 and 15% of the total ATPase activity were sensitive to Mg2+ in the oviductal and endometrial fractions, respectively. After 10 min preincubation with the four organochlorines, a significant inhibition was found only with o,p''-DDT at 32 microM (27.9%) and 64 microM (35.6%) in the oviductal microsomal fraction and at 64 microM (32.2%) in that of the endometrium. Increasing the preincubation time to 30 min, the Mg2+ ATPase in the endometrial fraction was significantly inhibited by all four pesticides at 64 microM, but in the oviductal fraction only at 64 microM o,p''-DDT. It is suggested that organochlorine pesticides can have an influence on cells responsible for reproduction.

DDE-induced eggshell thinning in birds: effects of p,p'-DDE on the calcium and prostaglandin metabolism of the eggshell gland

1. The focus of this review is the effects and mechanism of action of p,p'-DDE on eggshell formation in birds. Inhibition of prostaglandin synthesis in the eggshell gland mucosa is a probable mechanism for p,p'-DDE-induced eggshell thinning. 2. The duck is sensitive to p,p'-DDE-induced eggshell thinning but the domestic fowl is not, and studies comparing the two species in regard to the calcium and prostaglandin metabolism of the eggshell gland have shown that eggshell thinning induced by p,p'-DDE in ducks is accompanied by reduced activity of prostaglandin synthetase, reduced levels of prostaglandin E2, and reduced uptake of 45Ca by the eggshell gland mucosa. The content of calcium, bicarbonate, chloride, sodium, and potassium are also reduced in the eggshell gland lumen in ducks exhibiting eggshell thinning. None of these effects are seen in the domestic fowl. 3. Inhibition of prostaglandin synthesis is a specific effect of p,p'-DDE. The detrimental effects of p,p'-DDE on the eggshell gland seem to be unique when comparing the compound with structurally related substances, i.e., similar treatment regimens with o,p'-DDE, p,p'-DDT, o,p'-DDT, and p,p'-DDD do not cause eggshell thinning in ducks. Neither do they inhibit prostaglandin synthesis in the eggshell gland mucosa. 4. Administration of other compounds that do inhibit prostaglandin synthesis, e.g., indomethacin, does cause the same effects as those seen with p,p'-DDE, i.e., eggshell thinning and the described effects on the calcium and prostaglandin metabolism of the eggshell gland.

Effects of DDE on the fluidity of model and native membranes: implications for the mechanisms of toxicity

2,2-Bis(p-chlorophenyl)-1,1-dichloroethylene (DDE) interaction with model and native membranes was studied by means of fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), probing the bilayer core, and by intramolecular excimerization of 1,3-di(1-pyrenyl) propane (Py(3)Py), probing the outer regions of the bilayer. In the gel phase of DMPC bilayers, DDE induces concentration-dependent fluidizing effects into the hydrophobic core, but no effects are detected in the outer regions of the membrane, as evaluated by DPH and Py(3)Py, respectively. Regarding the fluid phase, DDE has no apparent effect on the bilayer center, but it induces a limited ordering effect on the outer regions. Similar effects are described for bilayers of DPPC and DSPC. Unlike DPH, Py(3)Py is very sensitive to DPPC and DSPC pretransitions, not abolished by DDE (50 microM), as opposite to the effects observed with lindane (Antunes-Madeira, M.C., Almeida, L.M. and Madeira, V.M.C. (1990) Biochim. Biophys. Acta 1022, 110-114), but similar to those observed with DDT (Antunes-Madeira, M.C., Almeida, L.M. and Madeira, V.M.C. (1991) Pestic. Sci. 33, 347-357). DDE inhibits to some extent the cholesterol-induced ordering in DMPC bilayers and high cholesterol concentrations (> or = 30 mol%) do not prevent DDE interaction, as evaluated by DPH. On the other hand, the effects of DDE reported by Py(3)Py depend on temperature and cholesterol contents of DMPC bilayers. For cholesterol levels ranging from 10 to 50 mol% and temperatures below the phase transition of DMPC, Py(3)Py fails to detect any significant effect. Nevertheless, above the phase transition, Py(3)Py detects either ordering effects of DDE at low cholesterol contents (< 30 mol%) or fluidizing effects at high cholesterol levels (> or = 30 mol%). The results in native membranes correlate reasonably with those obtained in models of synthetic lipids. Thus, DPH does not detect any apparent effect of DDE in relatively fluid native membranes of sarcoplasmic reticulum, but detects moderate disordering effects in membranes of brain microsomes and erythrocytes, i.e., membranes with high cholesterol. On the other hand, Py(3)Py reports ordering effects of DDE in fluid membranes of sarcoplasmic reticulum, an effect similar to that observed in fluid systems of synthetic lipids without or with low cholesterol. Additionally, as described for models, Py(3)Py detects disordering effects of DDE in cholesterol rich membranes, namely, brain microsomes.

Immunohistochemical localization of a calcium pump and calbindin-D28k in the oviduct of the laying hen

The localization of a plasma membrane calcium pump in the oviduct of the laying hen was investigated by immunohistochemical techniques, utilizing a monoclonal antibody (5F10) produced against the human erythrocyte calcium pump. This antibody was shown to react with an epitope of the pump in oviductal tissue, and prominent staining was observed on the microvilli of the tubular gland cells of the hen shell gland (uterus) and the isthmus. The Ca2+ pump was not detectable in the infundibulum or the magnum. Calbindin-D28k, also localized by immunohistochemical means, was observed to be present in the tubular gland cells of the shell gland and the distal isthmus (adjacent to shell gland) but not in either the proximal isthmus (adjacent to the magnum), the magnum or the infundibulum. The localization of the Ca2+ pump in the oviduct corresponds to known sites of mineral deposition during egg shell formation. The distribution of calbindin-D28k differed, co-localizing with the Ca2+ pump in the shell gland and distal isthmus but not in the proximal isthmus. This might reflect a greater rate of active Ca2+ secretion in the distal isthmus and shell gland as compared to the proximal isthmus.

Role of magnesium in egg shell formation in the domestic hen

1. The effects of feeding diets containing various amounts of magnesium on plasma concentration of calcium and magnesium in the domestic hen were investigated. 2. Plasma concentrations of calcium and magnesium decreased during shell formation in all birds. 3. Plasma magnesium content and egg shell thickness were severely reduced in birds given diets containing either 207 or 132 mg Mg++/kg. 4. Using electron microscopy, a precise correlation was observed between the normal distributions of magnesium and organic material across the egg shell of the domestic hen.

Human placental Ca2+-ATPase: in vitro inhibition by DDT homologs

In vitro inhibition of Ca2+-ATPase by DDT homologs was studied using maternal brush-border membranes from human term placentas as an enzyme source. At 10 microM concentration many of the compounds tested inhibited this enzyme. The order of effectiveness of inhibition was as follows: p,p'-DDE greater than p,p'-DDD greater than p,p'-DDT greater than methoxychlor(mec). Both p,p'-DDOH and p,p'-DDA did not inhibit the placental Ca2+-ATPase. Assays using varying concentrations (0.3 microM to 0.1 mM) of p,p'-DDT were also performed. The inhibition of human placental Ca2+-ATPase ranged from 12% for 0.3 microM p,p'-DDT to 69% for 30 microM p,p'-DDT. Higher concentrations of this pesticide failed to cause further enzyme inhibition.

Histochemical studies of Ca-ATPase, succinate and NAD+-dependent isocitrate dehydrogenases in the shell gland of laying Japanese quails: with special reference to calcium-transporting cells

In order to elucidate the problem of which cells are involved in calcium transport and to estimate the role of mitochondria in calcium transport in the avian shell gland, the fine structure and the Ca-ATPase, succinate dehydrogenase (SDH) and nicotinamide adenine dinucleotide (NAD+)-dependent isocitrate dehydrogenase (NAD+-ICDH) activity of the shell gland of egg-laying Japanese quails were examined. The surface epithelial cells, consisting of ciliated cells with cilia and microvilli and non-ciliated cells with microvilli, had many large and electron-dense granules. The tubular-gland cells occupied the proprial layer and lacked secretory granules. When an egg was in the shell gland, the well-developed mitochondria of tubular-gland cells characteristically tended to accumulate in the apical cytoplasm, while they were scattered throughout the cytoplasm when an egg was not in the shell gland. Intense Ca-ATPase activity was found on the microvilli of tubular-gland cells, and moderate activity was found on the lateral-cell surface. In the surface epithelial cells, the basolateral cell surface showed moderate enzymatic activity. Both SDH and NAD+-ICDH activity were found in tubular-gland cells when an egg was in the shell gland. These results strongly suggest that calcium for eggshell calcification is actively transported by the tubular-gland (depending on Ca-ATPase activity) and that the mitochondria of gland cells may play an important role in this process as an energy source.

Relation between Ca metabolism and ATPase activities in the subcellular fractions from duck eggshell gland mucosa after DDE administration during different stages of eggshell formation

The ATP-dependent Ca2+ uptake by and the Ca2+-Mg2+-activated ATPase activity in the subcellular fractions from the eggshell gland of two varieties of ducks, Indian Runner ducks (IRD) and the cross-breed of Swedish and Rouen ducks (SRD), showed functional changes during eggshell formation in relation to the values in the resting state. DDE inhibited the Ca2+ uptake (Ca) but increased the Ca2+-Mg2+-ATPase activity (P) of fractions from active but not of those from resting glands. DDE reduced the Ca/P ratio of several fractions from active glands. DDE inhibited the functional increase in Ca2+-Mg2+-ATPase in the IRD homogenate, however. The effect of DDE on the eggshell index of mature eggshell was greater in IRD than in SRD, the reason for this being that the effect was exerted during a shorter time period in the latter variety.

Relation between Ca2+ uptake and ATPase activity in the particulate fractions of the eggshell gland mucosa of the domestic fowl and duck

The relation between the rates of ATP-dependent Ca2+ uptake and ATP hydrolysis was studied in homogenates of eggshell gland mucosa and its subcellular fractions from the domestic fowl and duck. The Ca2+-Mg2+-ATPase activity was 5-10% of that of the "basal" Mg2+-ATPase at an optimal Ca2+ concentration in the subfractions. The presence of K+ and/or Na+ increased the rate of Ca2+ uptake and the Ca2+-Mg2+-ATPase activity; the effects of K+-Na+ were not inhibited by ouabain. The Ca/P ratio varied with the experimental conditions. At 10(-4) M Ca2+ and in the absence of K+ Na+ it was 0.8, and in their presence 0.4.

Renal sulfate transport at the basolateral membrane is mediated by anion exchange

The transport of sulfate was studied in basolateral membrane (BLM) vesicles isolated from rat kidney cortex by centrifugation on a Percoll self-generating gradient. In contrast to sulfate transport at the luminal membrane, sulfate uptake by BLM vesicles was not sodium dependent. However, imposition of an inside greater than outside bicarbonate gradient stimulated BLM sulfate uptake nearly 10-fold and produced a transient overshoot of about 4-fold. This process appeared to become saturated at high concentrations of either bicarbonate or sulfate. Sulfate itself, thiosulfate, and hydroxyl, but not chloride or thiocyanate, were able to substitute for bicarbonate. None of these anions was as effective as bicarbonate. The sulfate/bicarbonate exchange was unaltered by manipulation of membrane potential, suggesting that it was electroneutral. Both bicarbonate stimulation and overshoot could be prevented by known inhibitors of anion transport, including mercuric chloride, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, and phloretin. Bicarbonate-stimulated sulfate uptake also was inhibited by thiosulfate, probenecid, and acetazolamide. Thus, rat kidney BLM vesicles showed carrier-mediated anion exchange. Its properties indicate that this carrier may participate in both reabsorptive and secretory sulfate transport.

Role of phospholipids in the DDT-induced efflux of potassium in human erythrocytes

Incubation of human erythrocytes for 1-2 h at 37 degrees C in a suspension of dipalmitoylphosphatidylcholine (DDPC) liposomes results in a phospholipid enrichment of erythrocyte membranes by 45-55% and a depletion of cholesterol by 19-24%. The enrichment by DPPC was time and concentration dependent. By contrast, dioleoylphosphatidylcholine (DOPC) liposomes were less effective in enriching the membranes with phospholipid and in depleting the membranes of cholesterol. Concomitantly, the DDT-induced efflux of K+ was reduced in the case of DPPC-enriched erythrocytes but enhanced in DOPC-enriched erythrocytes. These results suggest that DDT partitions more readily into the unsaturated than the saturated phospholipids of the erythrocyte membrane. It is concluded that the extent to which DDT affects the flux of K+ across the membrane is dependent on the fluidity of the lipid phase. We also report here a rapid method for cholesterol depletion of red blood cells in comparison to previously reported methods.

Effect of p-p'-DDE administered in vivo and in vitro on Ca2+ binding and Ca2+-Mg2+-ATPase activity in egg shell gland mucose of ducks

Thinning of the egg shell is produced by p-p'-DDT and DDE in several species of birds. A study was made of the effect of DDE administered in vitro and in vivo on the Ca2+ binding and Ca2+-Mg2+-activated ATPase of a homogenate of the egg shell gland of ducks (Anas platyrhynchos var.). The concentration of Ca2+ was 1 X 10(-4) M and that of MgATP 1 X 10(-3) M. In vitro, DDE in concentrations of 2-16 micrograms/ml of incubation medium inhibited the Ca2+-Mg2+-activated ATPase in a concentration-dependent manner, whereas Mg2+-activated ATPase was not affected by these concentrations. The Ca2+ binding by the homogenate was reduced by DDE in the same concentrations. The sodium azide sensitive Ca2+ binding was most sensitive. In vivo, DDE administered in a concentration of 40 mg/kg dry weight of the food for 45 days reduced the egg shell index by 18% in comparison to controls. After 45 days of treatment the DDE concentrations in the egg shell gland mucosa was 1.20 +/- 0.16 micrograms/g of wet weight, while no DDE was detected in the controls. The Ca2+-Mg2+-activated ATPase was reduced by 32%, whereas the Mg2+-ATPase was not changed. The Ca2+ binding by the homogenate was reduced by 29%, the sodium azide sensitive part being most vulnerable, DDE increased the total Ca content of the egg shell gland mucosa by 44%. Since Ca is transported against a concentration gradient between blood plasma, and the lumen of the shell gland, it is suggested that DDE, by inhibiting the Ca2+-Mg2+-activated ATPase, decreased the Ca translocation over the egg shell gland mucosa.

Functionally abnormal Na+-K+ pump in erythrocytes of a morbidly obese patient

The Na(+)-K(+) pump in the erythrocytes of a mordibly obese patient shows a unique constellation of functional abnormalities. The number of pump units, measured by [(3)H]ouabain binding to intact cells, as well as the enzymatic activity of the (Na(+)-K(+))-dependent ATPase in erythrocyte membranes were found to be markedly increased compared with control cells (18-fold and 14-fold, respectively). There was a concomitant fivefold increase in the rate of pump-mediated uptake of (86)Rubidium (a K analogue); this was balanced by an increased rate of (86)Rb efflux. In striking contrast to normal cells, however, a major portion of this efflux (80%) was inhibited by ouabain, and thus appeared to be mediated by the Na(+)-K(+) pump. Erythrocytes from this patient had elevated levels of intracellular K(+) and reduced levels of intracellular Na(+). This finding, taken together with the ouabain inhibition of K(+) efflux and the absence of associated abnormalities, argues against the possibility that the increased number of Na(+)-K(+) pump units was a compensation for a primary increase in the permeability of the erythrocyte membrane to monovalent cations, as is seen in a variety of erythrocyte disorders. Further evidence for a primary abnormality of the enzyme was our observation that the cardiac glycoside ouabain bound to these cells with reduced affinity and had a right shifted dose response for pump inhibition. The markedly increased number of Na(+)-K(+) pump units in these cells did not appear to extend to mononuclear leukocytes.In conclusion, the erythrocytes from this patient have a very large number of functionally abnormal Na(+)-K(+) ATPase units. A unique abnormality of the erythrocyte Na(+)-K(+) ATPase of these cells is the most likely explanation for these findings.

Comparison of p-p'-DDE and o-p'-DDE on eggshell thickness and Ca binding activity of shell gland in ducks

One of the main ecotoxicological effects of DDT and its stable metabolite DDE is to reduce the reproductive success in several species of birds by decreasing the thickness of the eggshell. In two different strains of ducks (Anas platyrhynchos var.) addition of 40 mg/kg dry weight of p-p'-DDE to the diet for 45 days produced a significant and long-lasting reduction of the shell thickness, measured as eggshell index. The reduction was more marked in Indian Runner Ducks (IRD; 30 +/- 3%) than in a Swedish X Rouen breed (SR; 10 +/- 2%. The p-p'-DDE residues in the egg yolk + egg white were almost similar in the two strains; 38 +/- 2 and 51 +/- 6 p.p.m. (wet weight) respectively. In the IRD 40 mg/kg of o-p'-DDE in the diet for 45 days was much less potent in reducing the eggshell index (8 +/- 3%) than the p-p' isomer; the amount of residue of the o-p' isomer in the eggs (2.2 +/- 0.1 p.p.m.) was also smaller. A homogenate of the shell gland from the SR breed accumulated 45Ca2+ in the presence of ATP. The accumulation was inhibited about 50% by 5 mM sodium azide and 100% by 3 mM mersalyl. p-p'- and o-p'-DDE in the incubation medium both reduced the Ca2+ binding, in a similar and dose-dependent manner. The threshold concentration was about 20 p.p.m.; 40 p.p.m. reduced the accumulation by about 40%. DDE may reduce eggshell thickness by inhibiting the Ca binding to the membranes of the cells of the eggshell gland.

The effect of DDT on vitamin D metabolism and calcium binding activity in the chick

The mechanism of DDT impaired calcium absorption was studied in control, DDT fed and starved chicks. The metabolism of [3H]cholecalciferol was the same in the 3 groups, but the DDT fed and starved chicks had less intestinal calcium binding activity than the control chicks. These results suggest that DDT impaired calcium absorption and intestinal calcium binding activity may be a result of DDT induced anorexia.

Estrogenic activities of chlorinated hydrocarbons

Some DDT analogs are estrogenic, particularly o,p'-DDT, which comprises approximately 15-20% of the commercial DDT mixture. Whether this compound or its metabolites are active has not been established. In fact, the data obtained thus far are more confusing than enlightening. For example, CCl4 pretreatment of immature female rats has been reported to inhibit or enhance estrogenic activity of o,p'-DDT, and SKF-525A pretreatment has been reported to enhance or not alter the estrogenic effect. Although o,p'-DDT inhibits binding of estradiol to the estrogen receptor from rat or human at low levels (approximately 1-10 micrometer) in vitro, higher levels are required to inhibit nuclear binding of [3H] estradiol in incubated whole uteri. Futhermore, o,p'-DDT appears to be neither estrogenic nor antiestrogenic in an in vitro estrogen assay. Methoxychlor appears to be "activated" by metabolism, and it is probable that phenolic metabolites are responsible for its estrogenic activity. Since chlorinated hydrocarbons often enhance the metabolism of steroids and may reduce circulating levels of steroids, interactions of the exogenous hormonally active agents with steroid receptors may be self-potentiating in vivo.

Ingestion of crude oil: sublethal effects in herring gull chicks

A single small oral dose of Kuwait or South Louisiana crude oil caused cessation of growth, osmoregulatory impairment, and hypertrophy of hepatic, adrenal, and nasal gland tissue in herring gull chicks living in a simulated marine environment. These findings suggest that ingesting crude oil causes multiple sublethal effects that might impair a bird's ability to survive at sea.

Effects of DDT on eggshell quality and calcium adenosine triphosphatase

Adult mallard ducks were fed a diet containing 50 ppm DDT for 6 months. Eggs laid during this period were collected and eggshell weight, thickness, and calcium were determined. Chronic ingestion of DDT resulted in production of eggshells that were significantly thinner and lighter than those of controls. Total calcium of thinned eggshells was also reduced; however, calcium per gram of eggshell was not altered, indicating that other eggshell constituents were not incorporated as well. Calcium adenosine triphosphatase activity in the microsomal fraction of eggshell gland epithelium was assayed in control and DDT-fed ducks. Enzyme activity in DDT-fed ducks was reduced to 65% of control values. Since Ca-ATPase has been shown to be associated with calcium transport, enzyme inhibition may be responsible for decreased eggshell weight and thickness. Electron microscopic evaluation of microsomal fractions showed elements of the plasma membrane, including cilia and microvilli, as well as rough and smooth endoplasmic reticulum. Inhibition of calcium transport at the plasma membrane of mucosal epithelium is proposed as a possible mechanism of DDT-induced eggshell thinning.