Prenatal exposure to airborne polychlorinated biphenyl congeners and male reproductive health.

STUDY QUESTION: Is fetal exposure to lower-chlorinated polychlorinated biphenyls (LC-PCBs) in indoor air of private homes built with PCB-containing materials associated with semen characteristics and testicular volume in adult men? SUMMARY ANSWER: We observed only marginal and inconsistent associations between maternal exposure to PCBs in indoor air and semen quality, testicular size and reproductive hormones in the adult offspring. WHAT IS KNOWN ALREADY: Recent studies have shown LC-PCBs to exhibit endocrine-disrupting properties and increase the risk of cryptorchidism. Although exposure to LC-PCBs in indoor air is relatively common, the long-term impact of prenatal exposure on male reproductive health has not yet been investigated. STUDY DESIGN, SIZE, DURATION: In this cohort study, participants were men (18+ years) whose mothers carried them while living in one of two residential areas where indoor air had been contaminated by LC-PCB evaporating from building materials in subsets of the apartments. Men were considered prenatally exposed if their mother had lived in a PCB-contaminated apartment and unexposed if their mother had lived in an uncontaminated apartment for a minimum of 1 year during the 3.6 years before conception or during the first trimester. Mothers of prenatally unexposed men could not have lived in a contaminated apartment at any point. Recruitment lasted from 2017 to 2019. In total, 73 exposed and 111 unexposed men gave a blood and semen sample. PARTICIPANTS/MATERIALS, SETTING, METHODS: Percentage differences in semen volume, sperm concentration, total sperm count, morphologically normal spermatozoa, progressively motile spermatozoa and DNA fragmentation index (DFI) between prenatally exposed and unexposed men were estimated using negative binomial regression. Associations with total and calculated free testosterone (CFT), LH and FSH were modeled using the linear regression. Odds of small testicular volume was estimated with logistic regression. MAIN RESULTS AND THE ROLE OF CHANCE: Overall, the results of this study were conflicting. No differences in semen volume, sperm concentration, testosterone and CFT were observed between the groups, but there were slight indications of lower total sperm count, increased FSH and risk of small testicles, alongside lower sperm DFI and a higher proportion of normal spermatozoa in men exposed to LCB-PCBs from indoor air during fetal life. There is no apparent biologically plausible explanation for the apparently improved measures of DNA fragmentation and morphology, and these findings may have occurred purely by chance. LIMITATIONS, REASONS FOR CAUTION: Owing to the indirect measure of exposure, lack of adjustment for paternal factors, the potential for self-selection due to known exposure status and fertility issues, inability to take time spent away from the residence, limited statistical power and lack of comparable literature, independent replication of the study in larger cohorts is warranted. WIDER IMPLICATIONS OF THE FINDINGS: While our findings may appear reassuring for the large number of people residing and/or working in buildings with indoor air contaminated with LC-PCBs, further efforts to understand the full range of health consequences of fetal LC-PCB exposure are needed. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by the Independent Research Fund Denmark (ref no. 6110-00085B), Bispebjerg Hospital, Landsbyggefonden, Realdania (ref. no. PRJ-2017-00176), Grundejernes Investeringsfond (ref. no. 18-58) and Helsefonden (ref. no. 16-B-01-22 and 21-B-0412). K.S.H. was supported by FFIKA, Focused Research Effort on Chemicals in the Working Environment, from the Danish Government. The authors declare that they have no financial, personal or professional competing interests. TRIAL REGISTRATION NUMBER: Not applicable.

Allergy and respiratory health effects of dampness and dampness-related agents in schools and homes: a cross-sectional study in Danish pupils.

Little is known about the health effects of school-related indoor dampness and microbial exposures. In this study, we investigated dampness and dampness-related agents in both homes and schools and their association with allergy and respiratory health effects in 330 Danish pupils. Classroom dampness was identified based on technical inspection and bedroom dampness on parents' self-report. Classroom and bedroom dust was analyzed for seven microbial components. Skin prick testing determined atopic sensitization. Lung function was expressed as z-scores for forced expiratory volume in one-second (zFEV1 ), forced vital capacity (zFVC) and the ratio zFEV1 /zFVC using GLI-2012 prediction equations. The parents reported children's allergies, airway symptoms, and doctor-diagnosed asthma. High classroom dampness, but not bedroom dampness, was negatively associated with zFEV1 (ß-coef. -0.71; 95% CI -1.17 to -0.23) and zFVC (ß-coef. -0.52; 95% CI -0.98 to -0.06) and positively with wheezing (OR 8.09; 95% CI 1.49 to 43.97). No consistent findings were found between any individual microbial components or combination of microbial components and health outcomes. Among other indoor risk factors, environmental tobacco smoke (ETS) decreased zFEV1 (ß-coef. -0.22; 95% CI -0.42 to -0.02) and zFEV1 /zFVCratio (ß-coef. -0.26; 95% CI -0.44 to -0.07) and increased upper airway symptoms (OR 1.66; 95% CI 1.03-2.66). In conclusion, dampness in classrooms may have adverse respiratory health effects in pupils, but microbial agents responsible for this effect remain unknown.

Exposure to 27 polychlorinated biphenyls in the indoor environment of a workplace: a controlled bio-monitoring study.

PURPOSE: To assess the exposure to a broad-spectrum of polychlorinated biphenyl congeners (PCBs) from the indoor environment through bio-monitoring of people working in a building with PCB-containing materials and elevated PCB levels in the indoor air. METHODS: A cross-sectional study comparing the plasma concentration of 27 PCB congeners in 15 people working in a PCB-contaminated building and 30 matched controls. RESULTS: Median concentration of eight low-chlorinated PCB congeners was significantly higher in the exposed than in the control group. The sum of median concentrations of tri + tetra-chlorinated PCB was almost ten times higher in the exposed group than in the unexposed, and sums of dioxin-like and non-dioxin-like PCB were both relatively increased by 60 % in the exposed group. CONCLUSIONS: The occupational indoor environment may significantly add to PCB exposure, especially to the lower-chlorinated congeners. Health effect from this little-acknowledged exposure has not yet been documented, but data supporting lack of effect are sparse and research generating information on effect of exposure to specific congeners including at levels relevant for the indoor environment should be encouraged.

Determinants of house dust, endotoxin, and ß-(1→3)-D-glucan in homes of Danish children.

Little is known about the geographic variation and determinants of bacterial endotoxin and ß-(1,3)-D-glucan in Danish house dust. In a population of 317 children, we: (i) described loads and concentrations of floor dust, endotoxin, and ß-(1→3)-D-glucan and (ii) their correlations and (iii) assessed their determinants; (iv) Finally, we compared our findings with previous European studies. Bedroom floor dust was analyzed for endotoxin content by the kinetic limulus amoebocyte lysate assay and for ß-(1→3)-D-glucan by the inhibition enzyme immunoassay. The parents answered questions regarding potential determinants. We found: geometric means (geometric standard deviations) 186 mg/m(2) (4.3) for dust; 5.46 × 10(3) EU/m(2) (8.0) and 31.1 × 10(3) EU/g (2.6) for endotoxin; and 142 µg/m(2) (14.3) and 0.71 × 10(3) µg/g (7.3) for ß-(1→3)-D-glucan. High correlations (r > 0.75) were found between floor dust and endotoxin and ß-(1→3)-D-glucan loads, while endotoxin and ß-(1→3)-D-glucan concentrations were moderately correlated (r = 0.36-0.41) with the dust load. Having a carpet was positively associated with dust load and with endotoxin and ß-(1→3)-D-glucan concentrations. Pet keeping, dwelling type, and dwelling location were determinants of endotoxin concentrations. No other determinants were associated with ß-(1→3)-D-glucan concentrations. Compared with other European studies, we found lower ß-(1→3)-D-glucan loads and concentrations but higher endotoxin loads and concentrations suggesting a geographically determined different composition of Danish floor dust compared with other European regions.

Building-related symptoms and stress indicators.

UNLABELLED: This study aims to study physiological stress indicators in relation to prevalence of building-related symptoms (BRS) among teachers employed in three selected schools in Copenhagen. Three hypotheses were studied: (i) Perceived psychosocial work environment was associated with BRS; (ii) Perceived psychosocial work environment (job strain) was associated with physiological strain; (iii) BRS was associated with physiological strain. We found a tendency among women of an association between job strain and being BRS positive. Also an association between job strain and physiological strain was observed among women. Being BRS positive was not associated with single physiological stress indicators with the exception of a higher level free testosterone in serum among BRS-positive women. PRACTICAL IMPLICATIONS: Including physiological stress indicators may be a supplementary measure to questionnaires when studying the association between the psychosocial work environment and building-related symptoms (BRS). In this study, job strain was associated with physiological strain among women. Being BRS positive was not associated with single physiological stress indicators with the exception of a higher level free testosterone in serum among BRS-positive women. This study should be regarded as a preliminary study because of its small number of participants.

Pretransition-ripples in bilayers of dipalmitoylphosphatidylcholine: undulation or periodic segments? A freeze-fracture study.

Freeze-fracture analysis of ripple structures of 1,2-dipalmitoylphosphatidylcholine bilayers leads to the conclusion that the asymmetric ripple is the basic structure formed by periodic segments with different tilt direction. The molecules are tilted by about 30 degrees from the bilayer normal but arranged in two positions. Symmetric ripples are also formed by an alternation in tilt direction of the segments but the succession is more complex. A ridge in their valleys or a cleft at their crests may indicate structures formed or deformed during preparation (replication, etching). The freeze-fracture method reveals transition structures in ripple formation which are helpful in interpretation, but does not support a model consisting of an undulation of the bilayer by periodic fluid-like and gel-like domains.

The structure and thermotropic phase behaviour of dipalmitoylphosphatidylcholine codispersed with a branched-chain phosphatidylcholine.

The structure and thermotropic phase behaviour of a fully hydrated binary mixture of dipalmitoylphosphatidylcholine and a branched-chain phosphatidylcholine, 1, 2-di(4-dodecyl-palmitoyl)-sn-glycero-3-phosphocholine, were examined using differential scanning calorimetry, synchrotron X-ray diffraction and freeze-fracture electron microscopy. The branched-chain lipid forms a nonlamellar phase when dispersed alone in aqueous medium. Mixed aqueous dispersions of the two phospholipids containing less than 33 mol% of the branched-chain lipid form lamellar phases over the whole temperature range were studied (4 degrees C to 60 degrees C). When present in proportions greater than 33 mol% it induces a hexagonal phase in mixed aqueous dispersions with dipalmitoylphosphatidylcholine at temperatures above the fluid phase transition. At temperatures below 35 degrees C a hexagonal phase coexists with a gel bilayer phase. The lamellar<-->nonlamellar transition can be explained satisfactorily on the basis of the shape of the molecule expressed in terms of headgroup and chain cross-sectional areas. At temperatures below 35 degrees C macroscopic phase separation of two gel phases takes place. Freeze-fracture electron microscopy revealed that one gel phase consists of bilayers with a highly regular, periodic superstructure (macro-ripples) whereas the other phase forms flat, planar bilayers. The macro-ripple phase appears to represent a relaxation structure required to adapt to the packing constraints imposed by the incorporation of the branched-chain lipid into the dipalmitoylphosphatidylcholine host bilayer. The data suggest that structural changes that take place on cooling the mixed dispersion below the lamellar<-->nonlamellar phase transition temperature cannot be adequately described using the molecular form concept. Instead it is necessary to take into account the detailed molecular form of the guest lipid as well as its physical properties.

Convex-concave curvatures in bilayers of dipalmitoylphosphatidylcholine and cholesterol induced by amphotericin B/deoxycholate after prolonged storage.

Freeze-fracture investigations on the influence of amphotericin B/deoxycholate on multilamellar vesicles (MLV) of DPPC containing cholesterol have revealed a new phase structure. Alternating convex and concave curvatures are observed after storage of the vesicles at temperatures below 25 degrees C for at least 4 weeks. Three types of these patterns occur, a small-dimensional (repeat distance approximately 100 nm), an intermediate-dimensional (repeat distance approximately 400 nm) and a large-dimensional (repeat distance approximately 700 nm). The types can be formed on the same bilayer side by side. Additionally, the types differ in the morphology of the tops. In the case of the small-dimensional type the shape of the top can be described as a circular flat plane or opening and in the other cases as a hemispherical cap. The large dimensional type differs from the others by involvement of bilayer stacks. The formation of this new phase after prolonged storage could be confirmed by DSC measurements. The new structure can be explained in the framework of bicontinuous cubic phases and periodically curved bilayer structures. From the electron micrographs a lo (liquid ordered) phase is suggested.

Periodically curved bilayer structures observed in hyphal cells or stable L-form cells of a Streptomyces strain, and in liposomes formed by the extracted lipids.

Periodically curved bilayer structures showing a tetragonal pattern were revealed by freeze-fracture electron microscopy in hyphal cells, stable L-form cells, and liposomes prepared from extracted lipids of Streptomyces hygroscopicus NG 33-354. The pattern is formed by alternating convex and concave curvatures of the bilayer. It has been found with different repeat distances (multiples of about 15 nm) and with a different degree of expression (from just visible to very pronounced). An interpretation as infinite periodic minimal surface (IPMS) structures is more probable than an inducement of the pattern by underlying small vesicles. The occurrence of nonbilayer textures and the similarity of the tetragonal pattern with a 'bilayer sector' from a cubic phase structure (Anderson, S. et al. (1988) Chem. Rev. 88, 221-242) support such an interpretation.

The phase diagram of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/sucrose in the dry state. Sucrose substitution for water in lamellar mesophases.

The phase diagram of the binary system, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/sucrose, was determined by DSC. In contrast to dry DPPC, which exhibits chain melting at 342.5 K, the main feature of the DPPC/sucrose system is eutectic melting at 320 K. This was supported earlier by Crowe, J.H., Crowe, L.M. and Chapman, D. (Science 223 (1984) 701-703), who reported a drastic decrease in the chain-melting temperature of the dry lipid in the presence of some mono- and disaccharides. Electron microscopy suggests that the phase structures on either side of the phase transition are of the lamellar type. Definite sugar saturation concentrations can be derived from this phase diagram. Up to about 17 mol% sucrose, i.e., 1 mol of sucrose per 5 mol of lipid is adopted by DPPC in the low-temperature phase Lc. In the high-temperature phase Lm the saturation concentration is well above 90 mol% sucrose at 320 K (eutectic point) but decreases with increasing temperature. The lower limit of 50 mol% sucrose is reached at 455 K. At this temperature, peritectic melting of sucrose occurs. Because of some similarities in the phase diagrams of DPPC/sucrose and DPPC/water, it is possible to understand the sucrose substitution for water in dry lamellar mesophases.

The influence of poly(ethylene glycol) on the molecular dynamics within the glycocalyx.

Interaction of polymers with cell surfaces is a question of general interest for cell aggregation and fusion. The molecular dynamics within the surface coat of human erythrocytes as well as alterations of membrane protein arrangement (IMPs) in the presence of poly(ethylene glycol) (PEG) were investigated by EPR spin labeling techniques and freeze-fracture electron microscopy, respectively. AT PEG concentrations which induce aggregation of erythrocytes the surface coat and the protein arrangement is not disturbed by the polymer. This implicate an exclusion of the polymer from the cell surface.

Hyperosmotic relaxation lysis of chromaffin granules is caused by interactions between the granular membrane and intragranular vesicles.

Bovine chromaffin granules undergo irreversible structural changes during osmotic shrinkage in hypertonic sucrose and salt solutions, such that, on reexposure to isoosmotic conditions they do not regain their original morphology, but undergo lysis ('hyperosmotic relaxation lysis'). Irreversible alterations of granules were induced by hypertonic incubations lasting for as little as 1 min. Fluorescence and EPR membrane labelling experiments showed that hypertonicity did not induce membrane loss for instance by inwardly or outwardly directed pinching off of membrane material. The mean sizes of chromaffin granules as a function of increasing and subsequently decreasing osmotic pressure were measured by photon correlation spectroscopy; there was no significant difference in sizes of hyperosmotically pretreated granules as compared with controls. Freeze-fracture electron micrographs showed the formation of 'twins' and 'triplets' under hypertonic conditions. They also revealed intragranular vesicles of 50-200 nm in diameter in both hypertonically and isotonically suspended granules. 'Twin' and 'triplet' granules were formed by the attachment of intragranular vesicles to the granule membranes. We suggest that hyperosmotic relaxation lysis is caused by the fact that this adhesion partly prevents the granule membrane from reexpanding, thus, leading to its rupture.

Electron microscopic visualization of the arrangement of the two protein components of (Na+ + K+)-ATPase.

The information obtained by electron microscopic examination of highly purified membrane preparations of (Na+ + K+)-ATPase after freeze-fracturing or negative staining suggests the following conclusions. The catalytic 100 000 dalton protein component penetrates with its greater 'globular' mass the plasma membrane and protudes with its smaller mass from the protoplasmic surface by a stalked knob carrying the catalytic centre. The 40 000 dalton glycoprotein component is anchored in the membrane interior by a non-pom the outer membrane surface forming a surface coat of ill-definable substructure.

The appearance of cytoplasmic membranes of Escherichia coli cells in freeze-fracture electron microscopy after stringent and relaxed response.

Guanosine-5'-diphosphate-3'-diphosphate (ppGpp), an effector for many metabolic pathways, is synthesized by the relA gene product after amino acid limitation. Studies of stringent controlled Escherichia coli CP78 (relA+) and relaxed controlled E. coli CP79 (relA-) were carried out to test whether these strains differ in the appearance of their cytoplasmic membranes after induction of stringent and relaxed response. Cytoplasmic membrane structures of the cells were investigated by freeze-fracture electron microscopy after cooling the cells. The obtained micrographs showed a net-like distribution of the particles in the cytoplasmic membranes of relaxed controlled cells whereas such a pattern was not detectable in the stringent controlled counterparts.

Morphological transitions of brain sphingomyelin are determined by the hydration protocol: ripples re-arrange in plane, and sponge-like networks disintegrate into small vesicles.

The phase transition of hydrated brain sphingomyelin occurs at around 35 degrees C, which is close to the physiological temperature. Freeze-fracture electron microscopy is used to characterize different gel state morphologies in terms of solid-ordered and liquid-ordered phase states, according to the occurrence of ripples and other higher-dimensional bilayer deformations. Evidently, the natural mixed-chain sphingomyelin does not assume the flat L beta, phase but instead the rippled P beta, phase, with symmetric and asymmetric ripples as well as macroripples and an egg-carton pattern, depending on the incubation conditions. An unexpected difference was observed between samples that are hydrated above and below the phase transition temperature. When the lipid is hydrated at low temperature, a sponge-like network of bilayers is formed in the gel state, next to some normal lamellae. The network loses its ripples during cold-incubation, which indicates the formation of a liquid-ordered (lo) gel phase. Ripples re-appear upon warming and the sponge-like network disintegrates spontaneously and irreversibly into small vesicles above the phase transition.

Characterization of the nonlamellar cubic and HII structures of lipid A from Salmonella enterica serovar Minnesota by X-ray diffraction and freeze-fracture electron microscopy.

The aggregate structures of lipid A, the 'endotoxic principle' of bacterial lipopolysaccharide (LPS), from rough mutant Salmonella enterica sv. Minnesota R595 was analyzed at different water content, cation (Mg2+) concentration, and temperature applying synchrotron radiation X-ray diffraction and, in selected cases, freeze-fracture electron microscopy. The X-ray diffraction spectra prove the existence of different lamellar, mixed lamellar/cubic, various cubic, and inverted hexagonal (HII) structures depending on ambient conditions. The three mainly bicontinuous cubic phases Q224, Q229, and Q230 can be observed between 30 and 50 degrees C in narrow water and cation concentration ranges. Above 50 degrees C, Q212 an intermediate phase between bicontinuous and micellar is adopted. In freeze-fracture electron microscopic experiments, cubic structures of these symmetries are not readily detected, which can be understood in the light of changes in hydration during freezing and the metastability of these phases. However, 'lipidic particles' closely related to cubic phases are observed. Above 65-70 degrees C, the existence of the HII phase with hexagonal periodicities dH between 4.0 and 6.0 nm for different hydration states is shown using both techniques. Possible biological implications for the preference of lipid A for nonlamellar structures are discussed.

Hydration of DMPC and DPPC at 4 degrees C produces a novel subgel phase with convex-concave bilayer curvatures.

Hydration of dimyristoyl- and dipalmitoylphosphatidylcholines at 4 degrees C results in the formation of a characteristic subgel phase designated Pcc. Examination of the phase by freeze-fracture electron microscopy shows convex-concave deformations of the planar bilayer which are of two types. A smaller type with a radius of curvature of about 20 nm predominates in DMPC, and a larger type with about 70 nm radii of curvatures dominates in DPPC. The Pcc phase can also be formed in samples hydrated at temperatures above the main phase transition if the dispersion is frozen slowly and subsequently incubated at 4 degrees C for several days. The subgel Pcc phase was distinguished from the subgel Lc phase by the temperature of transition, packing of the acyl chains on the basis of wide-angle X-ray diffraction, and 2H-NMR spectra characteristic of a 'solid-ordered' phase. Vibrational spectra of the carbonyl and phosphate regions are consistent with a partially reduced hydration state. The origin of the convex-concave bilayer deformation is believed to result from constraints imposed by limiting hydration of the headgroup and a frustration arising from the spontaneous curvature of both monolayers.

Freeze-fracture studies on lipids and membranes.

Freeze-fracture electron microscopy is especially useful for investigation of lipid structures by the advantageous fracture course within hydrophobic zones. Freezing is, on the other hand, a restriction because the structures of lamellar and non-lamellar phase states with disordered acyl chains (L(alpha), H(II,) cubic) are difficult to preserve. An important aspect of this method is therefore the lipid structure of phase states with ordered acyl chains (crystal, gel), and with a different degree of hydration. Freeze-fracture of pure lipid systems creates a valid representation of the structure of non-lamellar phases and of the general structure of the "lamellar" lipid bilayer, and lamellar phases with characteristic deformations (ripples, curvatures, plane sectors) can be identified. Fracture through the hydrophobic bilayer centre of biological membranes reveals characteristic protein components, the intramembraneous particles (IMPs). The lateral distribution of the IMPs is a helpful marker for fluid and rigid phase states, also without deformation of the lamella. The overall history and the present state of knowledge concerning the different structures revealed by the freeze-fracture and freeze-etch techniques in lipid systems, and to a limited extent in biological membranes, is reviewed, taking into account studies from our own laboratory.

Quantitative estimation of non-lamellar structures in membranes. A 31P-nmr and electron microscopical study of the influence of linolic acid on the erythrocyte membrane.

The influence of linolic acid on the phase behaviour of erythrocyte membranes has been studied using the 31P-nmr spectroscopy and freeze-fracture electron microscopy. For untreated membranes a lamellar arrangement is found in the nmr spectra as well as in electron micrographs. Incubation of erythrocytes with vesicles from linolic acid yields dramatic changes in membrane structure. Besides the lamellar structure there are non-lamellar phases of phospholipids. The percentage of lipids arranged in these structures can be estimated from the nmr spectra by computer simulation. A combination of freeze-fracture and nmr experiments indicates that hexagonal and micellar structures are involved in the non-lamellar phase.

Alteration of the enucleating erythroblast glycocalyx.

Plasmalemmal differentiation of the enucleating normoblast of rabbit and rat was studied by means of cytochemical methods and freeze-etching. Staining with colloidal iron revealed about identical amounts of iron particles bound to various areas of the normoblast membrane. Cationized ferritin and ruthenium red, likewise, failed in the demonstration of significant changes of the enucleating normoblast glycocalyx. Despite these findings the topo-optical staining with toluidine blue showed the plasmalemmal envelope of the protruding normoblast nucleus moderately birefringent, clearly discriminated from the intense anisotropic staining of the future reticulocyte membrane. The ferritin-labeled snail lectin anti AHP localized a great number of binding sites at the plasmalemmal envelope of the nucleus under extrusion. That is in sharp contrast with rather low lectin binding to the future reticulocyte membrane which amounts to about 30 to 50% of the nuclear envelope label. The findings provide evidence of unmasking of bindings sites of the normoblast membrane. Apparently, the effect is due to conformational changes of the cell membrane, rather than it could be attributed to degradation of glycoproteins. Moreover, enucleation kinetics may also be related to supramolecular changes of membrane structure albeit missing evidence for the rearrangement of membrane particles.