Diet-induced modifications to milk composition have long-term effects on offspring growth in rabbits

It has been clearly demonstrated that the maternal nutritional status during pregnancy and lactation has long-term effects on offspring health. In mammals, milk represents the first maternal support provided to the newborns so that its composition may play a major role in long-term programming. We therefore assessed the effects of maternal high-fat/high-sugar obesogenic (OD) or control (CD) diets on offspring growth and adiposity in the rabbit. Between 7 and 20 wk of age, the BW gain of OD milk-fed rabbits was higher than that of CD milk-fed rabbits ( < 0.05). Body fat mass measurements at 21 wk of age revealed a significant increase in body adiposity as a function of milk ingested during the neonatal period, in both female and male offspring ( < 0.05). A marked weight gain difference was observed according to the milk in both female and male offspring. Moreover, we investigated the composition in major proteins and leptin levels in milk from OD or CD diet-fed dams. Liquid chromatography-mass spectrometry analysis of individual CD skimmed milk samples enabled identification and quantification of the rabbit main milk proteins and of their main phosphorylated isoforms at 2 different stages of lactation (3 and 10 d). Here we show that the OD diet induced a reduction in the whey acidic protein content concomitantly with both an increase in serum albumin and lactoferrin contents and in the phosphorylated isoforms of the main milk proteins. Furthermore, a sharp rise in leptin levels was observed in the milk of OD diet-fed dams on Day 10 of lactation when compared with CD diet animals ( < 0.05). Taken together, these findings provide evidence that lactation is a critical window of development during which exposure to a deleterious diet is highly detrimental to long-term outcomes. Moreover, these insights suggest that it may be possible to prevent at least some of the adverse effects of inadequate maternal nutrition on the long-term metabolic outcomes of the offspring through nutritional interventions applied during the lactation period.

Milk from dams fed an obesogenic diet combined with a high-fat/high-sugar diet induces long-term abnormal mammary gland development in the rabbit

Alterations to the metabolic endocrine environment during early life are crucial to mammary gland development. Among these environmental parameters, the initial nutritional event after birth is the consumption of milk, which represents the first maternal support provided to mammalian newborns. Milk is a complex fluid that exerts effects far beyond its immediate nutritional value. The present study, therefore, aimed to determine the effect of the nutritional changes during the neonatal and prepubertal periods on the adult mammary phenotype. Newborn rabbits were suckled by dams fed a high-fat/high-sugar obesogenic (OD) or a control (CON) diet and then subsequently fed either the OD or CON diets from the onset of puberty and throughout early pregnancy. Mammary glands were collected during early pregnancy (Day 8 of pregnancy). Rabbits fed with OD milk and then subjected to an OD diet displayed an abnormal development of the mammary gland: the mammary ducts were markedly enlarged (P < 0.05) and filled with abundant secretory products. Moreover, the alveolar secretory structures were disorganized, with an abnormal aspect characterized by large lumina. Mammary epithelial cells contained numerous large lipid droplets and exhibited fingering of the apical membrane and abnormally enlarged intercellular spaces filled with casein micelles. Leptin has been shown to be involved in modulating several developmental processes. We therefore analyzed its expression in the mammary gland. Mammary leptin mRNA was strongly expressed in rabbits fed with OD milk and subjected to an OD diet by comparison with the CON rabbits. Leptin transcripts and protein were localized in the epithelial cells, indicating that the increase in leptin synthesis occurs in this compartment. Taken together, these findings suggest that early-life nutritional history, in particular through the milking period, can determine subsequent mammary gland development. Moreover, they highlight the potentially important regulatory role that leptin may play during critical early-life nutritional windows with respect to long-term growth and mammary function.

Técnica venográfica contrastada in vivo dos dígitos de ovinos e caprinos

Foram utilizados 10 membros torácicos e pélvicos de ovinos e caprinos hígidos, de raça e sexo variados, com idade entre dois e quatro anos e peso corpóreo médio de 53kg. A porção distal dos membros torácicos e pélvicos foi submetida à técnica venográfica contrastada e à contagem vascular venosa da mesma região, em ambas as espécies. Não foram observadas diferenças numéricas em relação às veias entre machos e fêmeas, nem entre os membros direito e esquerdo da mesma espécie. Os ovinos possuem maior número de veias em relação aos caprinos. A técnica venográfica distal anterógrada de ambos os membros em ovinos e caprinos se mostrou aplicável revelando a vasculatura distal e podal, a comunicação entre os vasos venosos e a quantidade dos vasos presentes na região.

Metal Ions Protect DNA Against Strand Breakage Induced by Fast Neutrons

Single and double strand breaks (SSB and DSB) are induced by fast neutrons in plasmid (pBR322) DNA in 1 mM potassium phosphate buffer (pH 7.25). Increasing the concentration of monovalent (Na+, Cs+, Li+), divalent (Mg2+, Ca2+) and trivalent (Al3+, Co3+ (NH3)6) metal cations strongly decreases the yield of DSB. The extent of the observed protection depends on the valence of the cation. The production of SSB is only slightly decreased, except for Al3+ and Co3+ (NH3)6, whose effects are particularly large (complete protection at 1 and 0.1 mM respectively). Circular dichroism spectra show that Al3+ induces an important structural change of DNA at the ion concentration where the protection becomes total. This change is probably a condensation (collapse), as in the well-known case of Co3+ (NH3)6. Our results suggest two mechanisms of protection by metal ions: (i) the induction of structural changes of DNA, that render less accessible the critical sites of attack by OH. radicals; and (ii) the stabilization of the double helical regions between two close-set nicks on opposite strands, that hinders the effective double strand breakage of DNA.

Interferon-τ upregulates prolactin receptor mRNA in the ovine endometrium during the peri-implantation period

Our objective was to determine the effect of ovine interferon-τ (IFN-τ) on prolactin receptor (PRL-R) gene expression in the ovine endometrium. IFN-τ is an embryonic cytokine which, via its paracrine anti-luteolytic activity, plays a critical role in maternal recognition of pregnancy in ruminants. Using ribonuclease protection assay procedures, we compared endometrial PRL-R mRNA levels in ewes that were intrauterine injected with either 2 mg bovine serum albumin or 2 mg recombinant ovine IFN-τ on day 10 of the oestrous cycle (day 0 = day of oestrus). IFN treatment significantly increased the abundance of both the long and short forms of PRL-R mRNA in the ovine uterus, but had no effect on the long:short form ratio.In situhybridization experiments revealed that the increase in abundance of PRL-R mRNA in the uterus was localized to the glandular compartment of the endometrium. In pregnant ewes, a similar increase in PRL-R mRNA abundance was found to occur in ovine endometrium on days 14–15 post conception. Collectively, these data provided strong evidence that IFN-τ modulates the level of lactogenic hormone receptor mRNA in the ovine uterus. Whether the effect of IFN-τ on PRL-R expression is mediated directly or influenced, at least in part, by progesterone remains to be elucidated.

DNA radiolysis in DNA-protein complexes: a stochastic simulation of attack by hydroxyl radicals

PURPOSE

To propose an improved version of RADACK, a stochastic simulation of radiolytic attack on DNA, that takes into account the reactivity of each amino acid of a specifically bound protein with hydroxyl radicals. To apply it to the natural lactose operator-repressor complex taking advantage of recently reported structures. To compare the obtained probabilities of DNA strand break induction with those calculated with the previous versions and with an experimental pattern of strand break probabilities.

MATERIALS AND METHODS

Models of complexes close to the natural ones, derived from crystallography- and NMR-based structures recently available in the PDB databank, were used. The specific chemical reactivity of each amino acid was introduced in the new version of RADACK (the reactivity model). The probabilities of strand break induction by the irradiation of the complex were calculated with this new version as well as with previous ones.

RESULTS

The patterns of probabilities of strand break induction calculated with the improved version of RADACK were partially different from those obtained with previous versions. The patterns obtained for both, using putative models of natural complexes, were consistent with the experimental results, but some discrepancies were suggestive of slight differences between these structures and the real natural system. The crystallographic structure agreed best with the experimental results.

CONCLUSIONS

A new version of RADACK was validated that took into account the reactivity of atoms in both DNA and protein. The putative modelled structures of a natural lactose operator-repressor complex were discussed.

Visuoperceptual impairment in MS patients: nature and possible neural origins

Failures on visuoperceptual neuropsychological tasks (on neuropsychological tests of visuo-spatial perception or on tests concerning semantic properties of visual objects), may indicate focal deficits of visuoperceptual function, or could be the result of (an)other (peripheral) visual deficit(s), or be the effect of a more general cognitive decline. In multiple sclerosis (MS) patients exhibiting sufficient visual acuity and not showing severe cognitive deterioration, impairment on a comprehensive set of 31 visuoperceptual neuropsychological tasks was compared with spatial resolution deficits (SRD), temporal resolution deficits (TRD) for visual stimuli, abnormal pattern shift visual evoked potential (PSVEP) responses, and failing scores on neuropsychological tasks other than visuoperceptual tasks. Impairment on the visuoperceptual neuropsychological tasks was highly independent from the other abnormal visual and cognitive neurological impairments examined, suggesting that it mostly represented focal deficits. Only TRD in both eyes related to this impairment and this relationship was rather weak. Thus in some MS patients a slowed visual information processing may be one of the combined deficits underlying visuoperceptual neuropsychological task impairment. Given that SRD and TRD were not related to another stage of MS and reflect disturbances of a P (parvocellular channel and ventral stream projections) and M (magnocellular channel and dorsal stream projections) visual-system function respectively, demyelination of a certain M pathway may become a co-determinant of visuoperceptual neuropsychological task impairment more rapidly than damage to a certain P pathway.

RADACK, a stochastic simulation of hydroxyl radical attack to DNA

RADACK was conceived to simulate the radiation-induced attack to different DNA forms and complexes. It allows to separately calculate the probability of attack to each reactive atom of the sugar and of the base and takes into account the sequence-dependent structure of DNA as known from crystallographic or NMR studies or resulting from molecular modelling. The calculations are aimed to assess sequence-, structure- and ligand-dependent modulation of damages of sugar and bases, leading to single strand breaks (frank strand breaks, FSB) and alkali-labile base modifications (alkali-revealed breaks, ARB), respectively. The modelling procedure and the results of simulations for some representative structures (B, Z and quadruplex forms) are here described and discussed. The calculated relative probabilities of OH* radical attack to all reaction sites are compared to experimental FSB and ARB values. By a fitting procedure, the relative efficiencies of conversion of the C4' and C5'-centred radicals into FSB, epsilon (C4'): epsilon (C5'), and the relative efficiencies of base radicals- to- ARB conversion, epsilon(T) : epsilon(A) : epsilon(C) : epsilon(G), are then deduced for each DNA form. The ability of the model to account for the distribution of damages in DNA-ligand complexes is proven by its successful application to two DNA-protein systems : the lac repressor-lac operator complex and the nuclcosome core.

Radiation disrupts protein-DNA complexes through damage to the protein. The lac repressor-operator system

Eon, S., Culard, F., Sy, D., Charlier, M. and Spotheim-Maurizot, M. Radiation Disrupts Protein-DNA Complexes through Damage to the Protein. The lac Repressor-Operator System. Radiat. Res. 156, 110-117 (2001). Binding of a protein to its cognate DNA sequence is a key step in the regulation of gene expression. If radiation damage interferes with protein-DNA recognition, the entire regulation process may be perturbed. We have studied the effect of gamma rays on a model regulatory system, the E. coli lactose repressor-operator complex. We have observed the disruption of the complex upon irradiation in aerated solution. The complex is completely restored by the addition of nonirradiated repressor, but not by the addition of nonirradiated DNA. Thus radiation disrupts the DNA-protein complex by affecting the binding ability of the protein. This interpretation is supported by the dramatic loss of binding ability of a free irradiated repressor toward nonirradiated DNA. Interestingly, the dose necessary for the disruption of the irradiated complex is higher than that for inducing the complete loss of the binding ability of the free irradiated repressor. This may be due to the protection of key amino acids by the bound DNA. As seen from calculations of the accessibility of amino acids to radiolytic OH(.), the protection is due to both masking and conformational effects.

Radiosensitivity of DNA in a specific protein-DNA complex: the lac repressor-lac operator complex

PURPOSE

To calculate the probability of radiation-induced frank strand breakage (FSB) at each nucleotide in the Escherichia coli lac repressor-lac operator system using a simulation procedure. To compare calculated and experimental results. To asses the contribution of DNA conformational changes and of the masking by the protein to DNA protection by the repressor.

MATERIALS AND METHODS

Two structures of the complex were extracted from the PDB databank: crystallography- and NMR-based structures. Calculations were made of the accessibility of the atoms mainly involved in strand breakage (H4' and H5') to O&Hdot; and of the FSB probabilities, along: (1) DNA in the complex; (2) DNA in the complex depleted of the repressor; and (3) a linear DNA having the same sequence. An 80bp fragment bearing the operator was irradiated alone or in presence of the repressor. The relative probabilities of FSB at each nucleotide were determined using sequencing gel electrophoresis.

RESULTS

Calculations predict modulation of the accessibility of H4' and H5' atoms and of the probabilities of FSB along the DNA fragments of complexes. This is due to the protein-induced conformational change and to masking by bound protein. The best agreement with the experimental FSB was observed for calculations that use the crystallography-based structure.

CONCLUSIONS

For specific DNA-protein complexes, our calculations can predict the protein radiolytic footprints on DNA. They show the significant contribution of the protein-induced DNA conformational change to DNA protection.

Enhanced strand break induction of DNA by resonant metal-innershell photoabsorption

We determined The number of single and double strand breaks (ssb and dsb) in a DNA-chloroterpyridine platinum complex induced by resonant photoabsorption in the LIII innershell of a platinum atom. The number of ssb and dsb were measured in supercoiled plasmids (AG30) versus the chloroterpyridine platinum concentration, i.e., the ratio of intercalated molecules to the number of phosphate sites in DNA. A significant increase in the number of ssb and dsb was observed when the DNA contained intercalated molecules. This technique is an efficient way to induce ssb and dsb triggered by the atomic Auger effect.Key words: DNA breaks, Auger effect, resonant photoabsorption, intercalated molecules.

Enhanced strand break induction of DNA by resonant metal-innershell photoabsorption

We determined the number of single and double strand breaks (ssb and dsb) in a DNA-chloroterpyridine platinum complex induced by resonant photoabsorption in the L(III) innershell of a platinum atom. The number of ssb and dsb were measured in supercoiled plasmids (AG30) versus the chloroterpyridine platinum concentration, i.e., the ratio of intercalated molecules to the number of phosphate sites in DNA. A significant increase in the number of ssb and dsb was observed when the DNA contained intercalated molecules. This technique is an efficient way to induce ssb and dsb triggered by the atomic Auger effect.

Radiolysis of nucleosome core DNA: a modelling approach

PURPOSE

To calculate the expected pattern of frank strand breaks (FSB) induced in the DNA of a nucleosome core particle (NCP) by the attack of radiolytic OH* radicals and to compare this with the experimental pattern of FSB induced by the in vitro irradiation of chicken NCP.

MATERIALS AND METHODS

The structure of NCP was obtained from the PDB databank. Using molecular modelling, the structure of a linear DNA fragment with the central 60 bp sequence of NCP-DNA was determined. The accessibility of the sugar attack sites to OH* radicals at each nucleotide of the linear fragment or of the NCP-DNA was calculated. The probability of reaction of OH* with each sugar reactive site was calculated using a Monte-Carlo method-based stochastic model.

RESULTS

The accessibility of attack sites in the NCP-DNA and the calculated probabilities of sugar attack are mainly modulated through masking by histones, and only slightly through bending. The periodicity of the calculated FSB probabilities is identical to that of the experimental FSB probabilities in chicken NCP (period 10.4 +/- 0.1 bp).

CONCLUSIONS

The good agreement between the calculated and experimental results recommends the presented modelling procedure as a tool in predicting the radiosensitivity of DNA in DNA-ligand complexes of known structure.

Visuoperceptual impairment in multiple sclerosis patients diagnosed with neuropsychological tasks

A comprehensive set of 31 binocular neuropsychological tasks assessing a series of spatial and non-spatial visuoperceptual abilities was used to study visuoperceptual impairment in a representative group of 49 MS-clinic patients exhibiting neither diagnosed ophthalmological afflictions nor major psychiatric diagnoses. Among these patients, true frequency rate of visuoperceptual impairment, i.e. of subjects failing four or more tasks, was estimated at 26%. The pattern of visuoperceptual impairment was non-uniform, non-selective, restricted and idiosyncratic. Only four tasks yielded significant rates of impairment. They concerned colour discrimination, the perception of the Müller-Lyer illusion and object recognition in two separate conditions. Each of the four factors identified by factor analysis had an important representative (with factor loading >0.35) among these four tasks. Failures on these tasks correlated poorly. Together, the four tasks satisfactorily predicted visuoperceptual impairment as defined by the comprehensive set of tasks (sensitivity 86.7%; specificity 81.3%), but with regard to an uncontaminated criterion, their aggregate sensitivity and specificity was only 75 and 56% respectively. Visuoperceptual neuropsychological task performance related significantly but weakly to cognitive status, physical disability and to pyramidal, cerebellar and brain stem neurological signs, and did not correlate with other clinical neurological signs, disease duration, type of MS, a history of optic neuritis, depression or medication status Multiple Sclerosis (2000) 6 241 - 254

Strand break induction by photoabsorption in DNA-bound molecules

Dried samples of a DNA-chloroterpyridine platinum complex were irradiated with monochromatic X rays tuned to the photoabsorption resonance of the L(III) inner shell of the platinum atom. The number of single- and double-strand breaks (SSBs and DSBs) triggered by the Auger effect in supercoiled DNA plasmids was measured by the production of circular nicked and linear forms. To probe the specific contribution of the L(III) inner-shell excitation of the platinum atom, photon wavelengths were tuned on the resonance energy (on peak) and below (off peak). The quantum yields of the resonance radiation were typically found to be 11 for the SSBs and 1 for the DSBs. The DSB-to-SSB ratio increased by 20% when switching from off-resonance to on-resonance irradiation.

A questionnaire assessment of unmet needs for rehabilitation services and resources for people with multiple sclerosis: results of a pilot survey in five European countries. Needs Task group of MARCH (Multiple Sclerosis and Rehabilitation, Care and Health Services Research in Europe)

OBJECTIVE

To develop an international services and needs assessment instrument (SUN) for people with multiple sclerosis and their carers and to pilot this in different countries of the European Community.

DESIGN

Interview study of people with multiple sclerosis, their carers and nominated key professionals examining the unmet needs of patients and carers.

SETTING

Belgium, Estonia, Greece, Italy and the United Kingdom.

MAIN OUTCOME MEASURES

Needs assessment questionnaire.

RESULTS

The study comprised 137 people with multiple sclerosis, 125 carers and 111 professionals. Patients reported on average 2.9 unmet needs for themselves; their carers and professionals reported on average 2.4. Needs were categorized into seven broad categories. Due to difficulties experienced by the local researchers in distinguishing between needs and objectives a large proportion of needs had to be assigned to the 'other' category.

CONCLUSIONS

The SUN is a valuable and practicable tool for the identification of unmet needs for people with multiple sclerosis and their carers. Formal validation and reliability testing of the different language versions is recommended.

Effect of ethidium bromide intercalation on DNA radiosensitivity

PURPOSE

To assess the influence of the intercalating drug ethidium bromide (EtBr) on the yields of single strand breaks (ssb) induced by fast neutrons in supercoiled pBR322 plasmid and in a linear DNA restriction fragment.

MATERIALS AND METHODS

The yield of ssb in the plasmid was measured by agarose gel electrophoresis. The proportion of fragments bearing one ssb and the probability of breakage at each nucleotide site was determined using sequencing gel electrophoresis. The volume variations due to the intercalation of EtBr were calculated. The expected radio-modifying effect at each nucleotide site of the linear fragment was evaluated using a reported simulation procedure.

RESULTS

The ssb yield in the plasmid increased for concentrations up to 0.04 drug/bp and fell back in the range 0.04-0.1 drug/bp. For the linear DNA, only a slight protective effect was observed over the whole concentration range. The effect was almost the same at all nucleotide sites.

CONCLUSION

For the linear DNA fragment, radioprotection was mainly due to scavenging of OH* radicals by the intercalated drug. For the plasmid, the radio-modifying effect results mainly from the variation of its effective volume, due to the modification of superhelicity.

Increase in prolactin receptor (PRL-R) mRNA level in the mammary gland after hormonal induction of lactation in virgin ewes

In order to examine the hormonal regulation of the prolactin-receptor (PRL-R) gene expression during mammary gland development, ewes were treated to induce lactation via an estrogen-progesterone-hydrocortisone and ovine growth hormone treatment. In situ hybridization analysis was used and revealed that sex steroids increased PRL-R mRNA levels in the mammary gland. Using RNase protection assay we showed that the estradiol + progesterone treatment increased both the levels of the long and the short forms of PRL-R mRNA. Addition of hydrocortisone increased the level of alphaS1-casein transcripts and the level of the ratio of the long to the short form of the PRL-R mRNA. This ratio can be further enhanced by addition of ovine growth hormone to the latter treatment. This suggests a role of hydrocortisone and ovine growth hormone in the alternative splicing that leads to the preferential expression of the long form of the PRL-R mRNA. In conclusion, the present experiments suggest that estrogen, progesterone and hydrocortisone are the major regulators of the PRL-R gene expression during pregnancy and prepare the mammary gland for its differentiation.

Radioprotection of DNA by spermine: a molecular modelling approach

PURPOSE

To observe and explain the sequence-dependence of DNA radioprotection by spermine.

MATERIALS AND METHODS

Sequencing gel electrophoresis was used to analyse the probability of frank strand break (FSB) induction at each nucleotide site. Molecular modelling of complexes of DNA with spermine molecules and of a curved electrically null DNA has been performed.

RESULTS

The effect of spermine on radiation-induced strand breakage varied significantly along the studied fragment. At low spermine concentration, some sequences were protected while others were unprotected. Molecular modelling calculations show that the most electro-negative sites are located in the minor or in the major groove of DNA. The positively charged spermine (Z=+4) should preferentially bind to such sites. When bound in the minor groove, spermine triggers a reduction of the accessibility of radiolytic attack sites to OH* radicals. This is due to induced structural modifications and to the masking of attack sites. In the case of major groove binding, no reduction of accessibility occurs. This type of binding can explain the lack of protection of sequences with electro-negative sites in the major groove. At high spermine concentration, the fragment is strongly protected. A nucleosome-like pattern of breakage with periodically distributed regions of protection was observed. Molecular modelling calculations show that the accessibility of the attack sites in a curved electrically null DNA is also periodically reduced.

CONCLUSIONS

Molecular modelling of DNA-spermine complexes that takes into account the electrostatic properties of DNA, allows an explanation of the experimentally observed effects of spermine on DNA radiosensitivity.

Temporal resolution deficits in the visual fields of MS patients

We assessed the relationship between temporal resolution and MS-induced neuropathy. A diagnostic strategy comprising assessments of temporal resolution at 16 points in the extra-foveal visual field up to 12 degrees from the fovea was first compared with foveal temporal resolution and with a standard VEP procedure in the same MS patients. At the group level, foveal temporal resolution was less sensitive to demyelination than the 16-point diagnostic strategy, the detection rate of which was comparable to that of the VEP procedure. Cross-sensitivity of the VEP and the 16-point diagnostic procedure was low. Subsequently, the average severity of MS-induced temporal resolution deficits was studied at three retinal loci of the same size but different eccentricities. Foveal deficits were not significantly greater than more peripheral deficits within the central 12 degrees.

Monte Carlo simulation of radiolytic attack to 5'-d[T4G4]4 sequence in a unimolecular quadruplex

PURPOSE

To extend to a quadruplex the stochastic model of radiolytic attack previously applied to a quasi-random duplex DNA.

MATERIALS AND METHODS

The quadruplex structure is obtained from the PDB databank (first structure from 201D entry). The probabilities of OH* radical attack at all sugar and base reaction sites are calculated using a stochastic model based on the Monte Carlo method.

RESULTS

Good agreement between the calculated and experimental frank strand break (FSB) probabilities is obtained using the relative efficiencies of conversion of the C4' and C5'-centred radicals into FSB determined for the quasi-random duplex (2.8:1 respectively). Efficiencies of base radicals-to-alkali-revealed breaks (ARB) conversion are determined by fitting the calculated probabilities of base attack to the previously reported experimental probabilities for ARB. The efficiency of conversion of thymine radical into an ARB is 3.4+/-0.7 times higher than for guanine radical.

CONCLUSIONS

This paper supports the calculation method and allows evaluation of the relative efficiencies of thymine and guanine radicals-to-ARB conversion.

Cellular localization and evolution of prolactin receptor mRNA in ovine endometrium during pregnancy

In this study, we have investigated the expression of the prolactin receptor gene in ovine endometrium during oestrus cycle and pregnancy. Using reverse transcription-PCR analysis, we provided evidence that the prolactin receptor gene is specifically transcribed in this tissue. As shown by Northern blot analysis, the level of the prolactin receptor transcripts increased dramatically during late pregnancy. In situ hybridization experiments revealed that prolactin receptor mRNA was specifically expressed in the glandular compartment and confirmed the dramatic increase of its expression that occurs at the end of pregnancy. Taken together, these findings are consistent with a putative role of prolactin and/or related molecules in the regulation of the proliferation of the glandular compartment and/or in the control of the secretory activity of the endometrium.

Developmental expression and localization of the prolactin receptor (PRL-R) gene in ewe mammary gland during pregnancy and lactation: estimation of the ratio of the two forms of PRL-R messenger ribonucleic acid

In this study, we have analyzed the developmental expression of the prolactin receptor (PRL-R) gene in the ewe mammary gland during pregnancy and lactation. Using Northern and slot-blot analysis and in situ hybridization, we showed that the level of PRL-R mRNA in mammary epithelial cells increased during the second half of pregnancy, decreased at the end of pregnancy, and remained relatively stable during lactation with a level above that observed at the beginning of pregnancy. As shown by RNase protection assay, the ratio of the long to the short form of the PRL-R mRNA was always above 1. This ratio increased between Day 70 of pregnancy and term and decreased progressively during lactation. The high level of PRL-R mRNA before the induction of alphaS1-casein gene expression suggests that PRL may be involved in the growth and development of the mammary gland. More precisely, the increase of the ratio of the long to the short form of the PRL-R during lactogenesis suggests that the latter form may have a dominant negative action in the activation of milk protein gene transcription. Thus the long/short-form ratio of the PRL-R may play a key role in the shift between growth and differentiation of the mammary gland.

Radiosensitivity as support for the structure of a unimolecular DNA quadruplex

PURPOSE

To search for possible variations of radiosensitivity along a unimolecular DNA quadruplex and to use them as support for choosing one of the two possible structures proposed by NMR studies.

MATERIALS AND METHODS

The probability of radiation-induced frank strand breaks (FSB) and of alkali-revealed breaks (ARB) at each nucleotide site along the oligomer AATTCGTGGAGCACC (T4G4)4, was determined by sequencing gel electrophoresis as has been previously described in the literature. The oligomer was irradiated as a unimolecular quadruplex (QS) or paired to its complementary oligonucleotide in a double-stranded B-helix (DS).

RESULTS

The oligomer globally presents the same radiosensitivity in the quadruplex or in the double-stranded helix. FSB occur with the same probability at each nucleotide site in both QS- and DS-DNA. More ARB are induced at T- and less at G-sites in QS-DNA. The probability of ARB induction in the second T-run is lower than in the first and the third one.

CONCLUSION

Intrastrand radiosensitivity variations support the folding of the studied oligomer into a quadruplex with two lateral loops and one central loop of T-runs spanning the diagonal of the terminal G-quartet.

Sequence-dependent variations of DNA structure modulate radiation-induced strand breakage

Using a 80 base pair DNA fragment, the sequence-dependence was compared for: (i) the probability of fast neutrons induced strand breakage, (ii) the accessibility of the H4'- and H5'-atoms to OH. attack, (iii) the width of the minor groove, and (iv) the probability of OH. reactions with H4'- or H5'-atoms. The probability of strand breakage was measured using sequencing gel electrophoresis. The accessibility and the probability of reaction were calculated for the energy-minimized modelled DNA fragment. A Monte-Carlo simulation was used for calculating the probabilities of H-atom abstraction by OH.. It was observed that reduced breakage occurs in sequences exhibiting low accessibility of H4' and H5'2 and low probability of H-atom abstraction by OH., due to a narrow, minor groove. This shows that the breakage probability at a given nucleotide site is not determined by the chemical nature of the nucleotide (A, T, G or C), but mainly by the local sequence-modulated intrinsic structure. Fitting the experimental results with the calculated probabilities of reaction suggests that a C4'-centered radical evolves towards a strand break three times more efficiently than the C5' one, and that half of the breaks occur via the 4'-path and half via the 5'-path.

Thiol WR-1065 and disulphide WR-33278, two metabolites of the drug ethyol (WR-2721), protect DNA against fast neutron-induced strand breakage

The main metabolites of the cytoprotective drug Ethyol (Amifostine, WR-2721) are the thiol WR-1065 and the disulphide WR-33278 (formed by the oxidation of WR-1065). Both metabolites are well-known protectors against DNA damage induced by gamma-rays. Using supercoiled plasmid DNA and restriction fragments we show that they protect efficiently also in the case of fast neutrons. In anoxic conditions WR-1065 (Z = +2) protects by scavenging of OH. and by 'chemical repair' (by H donation from its SH function). WR-33278 (Z = +4) protects by scavenging of OH. and, in the case of the supercoiled plasmid DNA, by reducing the accessibility of radiolytic attack sites via the induction of packaging of DNA in liquid-crystalline condensates (observed by circular dichroism). Because of this second mechanism, the plasmid DNA is more efficiently protected by WR-33278 than by WR-1065, at concentration ratios > 1 drug/4 nucleotides. Moreover, using sequencing gel electrophoresis of irradiated fragments of known sequence, we show that the protection by the two metabolites is non-homogeneously distributed along the DNA sequence, with 'hot spots' of protection and with unprotected regions. Based on presented molecular modelling results we explain the sequence dependence of radioprotection by structural variations induced by the binding of the drugs.

Recent developments and potentialities for reducing embryo mortality in ruminants: the role of IFN-tau and other cytokines in early pregnancy

This review considers the potential reduction of embryo mortality in vitro and in vivo in ruminants. Data on cytokines provided by different fields of reproductive immunology and biology were collated. Because of the crucial importance of the local interactions between the embryo and its dam, the expression of growth-factor and cytokine genes was analysed in the embryo proper, trophoblast, oviduct and endometrium by reverse transcriptase polymerase chain reaction in sheep and in cattle during the pre- and periimplantation periods. Many deleterious cytokines, such as tumour necrosis factor-alpha, interferon-gamma (IFN-gamma), interleukin-2 (IL-2), and beneficial cytokines, such as transforming growth factor-beta, leukaemia inhibiting factor, colony-stimulating factor-1 (CSF-1), granulocyte-macrophage CSF, IL-1, IL-3, IL-4, IL-6, IL-10 and IFN-tau appeared to be involved in embryo survival in ruminants and other species. Their administration is efficient in a murine experimental model (CBA/J x DBA/2) of embryonic and fetal mortality. For instance, recombinant ovine IFN-tau (roIFN-tau) injected at the moment of implantation drastically reduces embryonic mortality in this model. In ruminants, roIFN-tau and recombinant bovine IFN-tau are very efficient in maintaining progesterone luteal secretion in cyclic animals. The involvement of IFN-tau in the mechanisms of maternal pregnancy recognition are particularly detailed in relation to inhibition of 13,14 dihydro-15-keto-prostaglandin F2 alpha (PGFM) pulses and oxytocin uterine receptivity. A synthetic model of the anti-luteolytic effects of IFN-tau on the endometrial cell is proposed. Finally, the particular potential of serum pregnancy-specific proteins (PSPs: PSPB, PSP60, pregnancy-associated glycoprotein) for monitoring embryo survival, with examples given for cattle and sheep is underlined.

Sequence-modulated radiosensitization of DNA by copper ions

Plasmid DNA and restriction fragments of 80 and 120 base pairs were irradiated with fast neutrons in the presence of CuCl2. The number of single and double strand breaks is higher in the presence than in the absence of Cu2+ ions. The radiosensitizing effect was lower for solutions of high compared with low ionic strength, and also lower for deoxygenated than for aerated solutions. This effect was inhibited by EDTA, catalase and Tris, but not by ethanol. Superoxide dismutase partially inhibited the effect of low copper concentrations (< 1 Cu2+/nucleotide). Saturation of the solutions with N2O removed the effect for these concentrations of copper. The sensitization occurred preferentially at pyrimidines (thymines > cytosines) situated 5' to one or several purines (guanine > adenine) or located between two purines, at runs of purines (guanine > adenine), and at combinations of such sequences. The results can be only partially explained by a Fenton-like mechanism involving radiation induced hydrated electrons and hydrogen peroxide, which produces OH. radicals at the sites of binding of copper on DNA. The regions around these binding sites may undergo conformational changes. A second path for sensitization could be the enhancement of the efficiency of cleavage by the radiolytically produced OH. radicals in these conformationally modified regions.

DNA breakage upon K-shell excitation of phosphorus as a model for direct effects in radiation biology

Single-strand breaks (SSBs) and double-strand breaks (DSBs) induced in DNA under phosphorus K-shell resonant absorption have been studied using supercoiled plasmids. The kinetics of the production of SSBs and DSBs exhibits a linear and a quadratic dependence, respectively, on photon fluence. Cross sections and quantum yields have been measured. The resonant photoexcitation of the phosphorus atoms was found to increase the DSB/SSB ratio compared to the off-resonance excitation. This enhancement factor can be related to the measured enhancement of the rate of cellular death and gene mutation in yeast under similar experimental conditions reported previously in the literature. Such resonant excitation of a specific atom belonging to DNA turns out to be an elegant method to investigate pure direct effects.

Comparative study of DNA radiolysis by fast neutrons and gamma-rays

The effect of fast neutrons on cells is different from that of gamma-rays: the relative (to gamma) biological effect (RBE) is higher than one and the oxygen enhancement ratio (OER) is lower than that of gamma-rays. We searched for differences between the effects of the two radiations on DNA, the critical target of radiations. Using a model plasmid DNA we observed that for the same absorbed dose, fast neutrons induce twice fewer single strand breaks (SSB) and 1.5 more double strand breaks (DSB) than gamma-rays. A transition metal ion, the Cu++, is a better sensitizer of DNA breakage with fast neutrons than with gamma-rays. In anoxia, cysteamine, a positively charged thiol, is a better radioprotector against neutrons than against gamma-rays. In presence of cysteamine, the OER is lower for neutrons than for gamma-rays. These results are discussed in terms of different physical properties of the two types of radiation.

Calculation of hydroxyl radical attack on different forms of DNA

A stochastic model of hydroxyl radical reaction with the DNA macromolecule in dilute aqueous solution is presented. It is based on the Monte Carlo method, the model of Smoluchowski, the model of the regular DNA atomic structure and the knowledge of reaction rate constants for .OH radical reaction with DNA constituents. The calculated respective overall probability of .OH radical reaction with sugar or base moiety dependents on DNA form (A, B or Z), base composition (AT/GC content) and strandedness (single and double). While for all three DNA forms studied (A, B and Z) as well as for both single- and double-stranded B-DNA, the specific probability of .OH radical attack on nucleobases is modulated by their sequence, the attack on deoxyriboses is only slightly sequence dependent (except for Z-DNA). The model predictions are compared to the experimental patterns of strand breaks and alkali revealed breaks for single and double stranded DNA in B-form and discussed in terms of molecular mechanisms of DNA damage induced by hydroxyl radical.

Radioprotection of DNA by polyamines

Putrescine, spermidine and spermine are natural polyamines bearing at neutral pH the net electrical charges +2, +3 and +4 respectively. We report here the radioprotective effect of these polyamines on the radiolysis of pBR322 plasmid DNA. We observe a very efficient protection against fast neutron-induced single and double-strand breakage in the presence of spermine and spermidine, and a significantly less efficient protection in the presence of putrescine. An ionic strength dependence is observed for spermidine and spermine, but not for putrescine. Circular dichroism measurements show spermidine- and spermine-induced structural modifications of DNA, i.e. the formation of tightly packaged condensates in the concentration range corresponding to radioprotection. No structural change is observed for concentrations of putrescine affording radioprotection. We explain the radioprotection by: (1) the scavenging of OH radicals in the bulk, essentially observed in the case of putrescine; (2) a local scavenging at the sites of binding of polyamines; and (3) the reduced accessibility of the attack sites in the condensed structures induced by spermine or spermidine.

Radiation-induced damages in single- and double-stranded DNA

In the present study, we searched for possible effects of DNA strandedness (single and double), on two types of damages, frank strand breaks (FSB, observed at neutral pH) and alkali labile sites (ALS, leading to breaks at alkaline pH) induced by irradiation with gamma-rays (60Co) or fast neutrons (p34,Be). Sequencing gel electrophoresis allowed us to follow the occurrence of these damages at each nucleotide site in single (ss-ss), double (ds-ds), and half single-half double (ss-ds and ds-ss) stranded oligonucleotides. Globally, in DNA with random sequences of bases, no differences in FSB and ALS yield between the single and the double-stranded conformations were observed. One observes, however, an increased alkaline lability at some guanine sites belonging to single-stranded region of ss-ds or ds-ss. Nevertheless, strandedness influences the radiosensitivity of some particular sequences, i.e. the 5'-AATT sequences. This region is less radiosensitive than the rest of DNA in the double helical, but not in the single-stranded conformation. The results are discussed in terms of DNA conformation.

Radiolytic signature of Z-DNA

Ionizing radiations induce various damages in DNA via the hydroxyl radical OH. generated by the radiolysis of water. We compare here the radiosensitivity of B- and Z-DNA, by using a Z-prone stretch included in a plasmid. In the supercoiled plasmid, the stretch is in the Z-form, whereas it is in the B-form when the plasmid is relaxed. Frank strand breaks (FSB) and alkali-revealed breaks (ARB) were located and quantified using sequencing gel electrophoresis. We show that B- and Z-DNA have the same mean sensitivity towards radiolytic attack, for both FSB and ARB. Nevertheless, the guanine sites are more sensitive, and the cytosine sites less sensitive in Z- than in B-DNA, leading to a characteristic signature of the Z-form. The comparison of experiments with the outcome of a Monte Carlo simulation of OH. radical attack suggests that transfer of initial damage from a guanine base to its attached sugar or the adjacent 3' cytosine is more important in Z-DNA than in B-DNA.

Radiosensitivity of DNA minicircles

DNA minicircles of 207 bp were constructed by the ligation of linear restriction fragments in the presence of various concentrations of ethidium bromide. Three topoisomers characterized by linking numbers (Lk) of 20, 19 and 18, and with helical repeats of 10.35, 10.9 and 11.5 bp/turn respectively, were obtained. They are called, respectively, relaxed minicircle or topoisomer 0, topoisomer -1 and topoisomer -2. Owing to the limited flexibility of such small circles, the stress created by the lack of 1 or 2 turns cannot be eliminated by a spatial circle-axis writhing (supercoiling) of the circular molecules. These two undertwisted, stressed topoisomers have to adopt a flat, non-crossed shape, similar to that of the relaxed minicircle. The three minicircles were irradiated with gamma-rays or fast neutrons. The same yields of single-strand breaks, double-strand breaks and alkali-induced single-strand breaks were observed for the three topoisomers showing that their base and sugar moieties are attacked equally by gamma photon- or fast neutron-induced radicals. We conclude that untwisting of a B helix does not modify the radiosensitivity of DNA.

Sites of strand breakage in DNA irradiated by fast neutrons

Therapeutic fast neutrons are densely ionizing particles, with a high relative biological effectiveness relative to 60Co gamma rays (RBE) and a low oxygen enhancement ratio (OER). The molecular basis of their properties is not yet entirely understood. In a previous work, we have shown that neutrons induce a different number of DNA frank strand breaks as compared to gamma photons, and we have revealed the presence of breaks due to the direct effects of neutrons. In the present work, we searched for eventual differences in the chemical nature of the attacked sites in DNA irradiated in oxygenated diluted solution. We compare our results with neutrons to those previously reported by other authors using gamma- or X-rays. Using sequencing gel electrophoresis of short natural DNA restriction fragments, or synthetic oligonucleotides, we have shown that, in the case of neutrons, the attack occurs with almost the same probability, at each nucleotide, as reported for gamma- and X-rays. The doubling of bands in the bottom of gels shows the presence of two types of termini, the 3'-phosphate and the 3'-phosphoglycolate. Upon neutron irradiation, the 3'-phosphate end appears with a higher yield than the 3'-phosphoglycolate, whereas equal amounts were obtained with gamma- or X-rays.

Identification of the DNA-interacting sites of proteins: microsequencing of the peptides cross-linked to 5-bromouracil substituted DNA

Photochemical induced cross-links between protein and nucleic acids are useful tools in the study of the protein-DNA interactions. The substitution of thymine by 5-bromouracil in DNA increases the photocross-linking yield, and reduces the direct damages to both DNA and proteins. Using the lac repressor-DNA non-specific interaction system, we have developed a procedure to identify the interaction site on the protein. Sensitive, accurate and inexpensive in time and material, this procedure is based on the possibility of sequencing peptides in the presence of a large excess of DNA. The obtained result (the implication of His 29) agrees with previous work.

Cloning and structural analysis of four genes encoding interferon-omega in rabbit

By using an ovine interferon-tau (IFN-tau) cDNA probe, four recombinant phages were isolated from a rabbit genomic library and sequenced from nucleotides -450 to 1,300 relative to the CAP site. Each of the four rabbit genes contains an open reading frame of 595 nucleotides and code for proteins that exhibit structural characteristics of the interferon-omega (IFN-omega) family. They display more than 98% identity in their coding regions. The deduced amino acid sequences share > 96% sequence similarity. In contrast, the 5' and 3' noncoding regions have diverged considerably (approximately 50% identity). Amino acid comparisons of rabbit IFN-omega with IFN-omega of other species reveal the highest degree of identity with human (72%), followed by porcine (68%) IFN-omega. Rabbit IFN-omega displays only 57% sequence similarity with ovine IFN-tau. The coding regions of the four genes subcloned in a cytomegalovirus eukaryotic expression vector and transfected in monkey COS-7 cells direct the production of proteins that protect bovine and rabbit cells against vesicular stomatitis virus infection, thus demonstrating that these genes encode fully active IFN proteins. The expression of these genes was studied in Sendai-induced rabbit leukocytes. A single band of poly(A)+RNA hybridized with a rabbit IFN-omega probe under stringent conditions, whereas no IFN-omega transcript was detected with RNA isolated from uninduced leukocytes. Southern blot analysis suggest the existence of at least eight IFN-omega genes or pseudogenes in the rabbit genome.

Radioprotection of DNA by a DNA-binding protein: MC1 chromosomal protein from the archaebacterium Methanosarcina sp. CHTI55

The archaebacterial chromosomal protein MC1 binds tightly and unspecifically to DNA; binding protects DNA against radiolysis by fast neutrons. At low covering of pBR322 plasmid DNA, one bound protein protects some 50 attack sites (phosphate-sugar moieties) against both single (ssb) and double strand breaks (dsb). At high covering of plasmid, protection against dsb becomes almost complete, although about half of the attack sites remain accessible to ssb. DNA restriction fragments were used to investigate the organization of the complexes, and its consequences on DNA radiolysis. Sequencing gel electrophoresis of the radiolytically-broken fragments are almost regular in the absence of protein, showing that breakage occurs at every base. In the presence of the protein, a periodic protection pattern is observed. The period of 11 base pairs is interpreted as the minimum distance between two adjacent MC1 proteins.

Radiolytic footprinting. Beta rays, gamma photons, and fast neutrons probe DNA-protein interactions

Ionizing radiations induce numerous damages in DNA, especially strand breaks. The hydroxyl radical OH., produced by the radiolysis of water, is mainly responsible for this effect. The fact that strand breakage occurs at all nucleotides and that bound proteins may locally radioprotect DNA at the binding site lead us to develop a radiolytic footprinting method to study DNA-protein interactions. Three different radiations were used: beta rays, gamma photons, and fast neutrons. In order to validate this technique, three well-known interaction systems were tested: the lac repressor-lac operator of Escherichia coli, the cyclic AMP receptor protein (CRP) of E. coli and its specific site in the lac regulation region, and the core nucleosome. Radiolytic footprinting gives results similar to those obtained by more classical probes: DNase I, complexes of orthophenanthroline (OP) and copper, complexes of ethylenediaminetetraacetate ion (EDTA) and iron, and UV light. For the same system (lac repressor), irradiation with either gamma photons or fast neutrons gives identical results.

Photo-cross-linking of CRP to nonspecific DNA in the absence of cAMP. DNA interacts with both the N- and C-terminal parts of the protein

Adenosine cyclic 3',5'-phosphate receptor protein (CRP or CAP) is a regulatory protein involved in the transcription of several operons in Escherichia coli. cAMP-independent, nonspecific complexes of CRP and DNA were investigated by photochemical cross-linking of the protein to nonspecific DNA, whose thymines are substituted by 5-bromouracil (BrUra). The cross-linked protein was completely digested by trypsin, and the covalently bound peptides were sequenced. We identified two regions of the protein in close contact with DNA: one in the C-terminal part, overlapping the canonical helix-turn-helix motif, and the other one in the N-terminal part, which is usually not considered to belong to the DNA-interacting domain of CRP. This result lead us to propose models for nonspecific interaction, where the DNA is in contact with both the N- and C-terminal parts of the protein.

N-acetylcysteine and captopril protect DNA and cells against radiolysis by fast neutrons

N-Acetylcysteine and captopril, respectively mucolytic and antihypertensive drugs, contain free sulfhydryl groups. Since in general thiols have well-established radioprotective abilities, we sought putative radioprotective effects of these drugs against therapeutic fast neutrons. We show that pBR322 plasmid DNA is indeed protected against radiolytic strand breakage by both drugs. The oxygen independent protection is consistent with a hydroxyl radical scavenging mechanism. A clonogenicity assay reveals an increase of the survival of SCL-1 cultured keratinocytes irradiated in the presence of the drugs compared with cells irradiated without drugs. Our results suggest possible interferences between treatment with drugs bearing-SH groups and radiotherapy.

Addition of a dipeptide spacer significantly improves secretion of ovine trophoblast interferon in yeast

Yeast has been analysed for its potential to secrete an ovine member of the type-I interferon (IFN) family, trophoblastin (oTP-1). The processing potential of the yeast KEX2 gene product (KEX2p) was evaluated using gene oTP-1 fused to the pre-pro sequence encoding the pre-pro peptide of the yeast alpha-factor precursor. High-level accumulation of nonprocessed (unmatured) recombinant oTP-1 (re-oTP-1) was observed in the medium. In order to short-circuit the limiting activity of KEX2p and to obtain a fully matured re-oTP-1, secretion was directed using a pre::oTP-1 fusion, relying only on signal peptidase-dependent processing. However, secretion of oTP-1 was impaired. High-level secretion was restored when the gene product contained a peptide spacer between oTP-1 and the signal peptidase cleavage site. The oTP-1 variant was shown to have an extended N terminus. An N-extended form was examined further and shown to have the correct size. Surprisingly, the variant retained its in vitro and in vivo biological activities. This system is likely to represent a general method for high-level secretion of type-I IFNs.