Proteome dataset of subcutaneous adipose tissue obtained from late pregnant dairy cows during summer heat stress and winter seasons.

Adipose tissue has a central role in the regulation of metabolism in dairy cows, and many proteins expressed in this tissue are involved in metabolic responses to stress (Peinado et al., 2012) [1]. Environmental heat stress is one of the main stressors limiting production in dairy cattle (Fuquay, 1981; West, 2003) [2], [3], and there is a complex interaction between heat stress and the transition period from late pregnancy to onset of lactation, which is manifested in heat-stressed late-gestation cows (Tao and Dahl, 2013) [4]. We recently defined the proteome of adipose tissue in peripartum dairy cows, identifying 586 proteins of which 18.9% were differentially abundant in insulin-resistant compared to insulin-sensitive adipose tissue (Zachut, 2015) [5]. That study showed that proteomic techniques constitute a valuable tool for identifying novel biomarkers in adipose tissue that are related to metabolic adaptation to stress in dairy cows. The objective of the present work was to examine the adipose tissue proteome under thermo-neutral or seasonal heat stress conditions in late pregnant dairy cows. We have collected subcutaneous adipose tissue biopsies from 10 late pregnant dairy cows during summer heat stress and from 8 late pregnant dairy cows during winter season, and identified and quantified 1495 proteins in the adipose tissues. This dataset of adipose tissue proteome from dairy cows adds novel information on the variety of proteins that are abundant in this tissue during late pregnancy under thermo-neutral as well as heat stress conditions. Differential abundance of 107 (7.1%) proteins was found between summer and winter adipose. These results are discussed in our recent research article (Zachut et al., 2017) [6].

Seasonal heat stress affects adipose tissue proteome toward enrichment of the Nrf2-mediated oxidative stress response in late-pregnant dairy cows.

Environmental heat stress and metabolic stress during transition from late gestation to lactation are main factors limiting production in dairy cattle, and there is a complex interaction between them. Many proteins expressed in adipose tissue are involved in metabolic responses to stress. We aimed to investigate the effects of seasonal heat stress on adipose proteome in late-pregnant cows, and to identify biomarkers of heat stress. Late pregnant cows during summer heat stress (S, n=18), or during the winter season (W, n=12) were used. Subcutaneous adipose tissue biopsies sampled 14days prepartum from S (n=10) and W (n=8) were analyzed by intensity-based, label-free, quantitative shotgun proteomics (nano-LC-MS/MS). Plasma concentrations of malondialdehyde and cortisol were higher in S than in W cows. Proteomic analysis revealed that 107/1495 proteins were differentially abundant in S compared to W (P<0.05 and fold change of at least ±1.5). Top canonical pathways in S vs. W adipose were Nrf2-mediated oxidative stress response, acute-phase response, and FXR/RXR and LXR/RXR activation. Novel biomarkers of heat stress in adipose tissue were found. These findings indicate that seasonal heat stress has a unique effect on adipose tissue in late-pregnant cows. SIGNIFICANCE: This work shows that seasonal heat stress increases plasma concentrations of the oxidative stress marker malondialdehyde and cortisol in transition dairy cows. As many proteins expressed in the adipose tissue are involved in metabolic responses to stress, we investigated the effects of heat stress on the proteome of adipose tissue from late-pregnant cows during summer or winter seasons. We demonstrated that heat stress enriches several stress-related pathways, such as the Nrf2-mediated oxidative stress response and the acute-phase response in adipose tissues. Thus, environmental heat stress has a unique effect on adipose tissue in late-pregnant cows, as part of the regulatory adaptations to chronic heat load during the summer season. In addition, this study presents the widest available dataset of adipose tissue proteome in dairy cows, and revealed several novel biomarkers of heat stress in adipose tissue of dairy cows, the use of which awaits further validation.

Effects of high dietary crude protein on the characteristics of preovulatory follicles in dairy heifers.

The objectives were to examine the effect of high dietary crude protein on characteristics of preovulatory follicles in dairy heifers. Eight Israeli-Holstein heifers, 4 fitted with rumen fistula and 4 intact, were assigned to 1 of 3 treatments in a replicated (n=2) 4 × 3 incomplete Latin square design with 39-d periods. Treatments were: low (6.0%; LP), moderate (13.0%; MP), and high (20.0%; HP) crude-protein diets, containing 1.27 Mcal NE(L)/kg dry matter. Diets were based on approximately 66% wheat straw and various proportions of ground corn grain and soybean meal. The estrous cycles of the heifers were synchronized, and 14 d after behavioral estrus, heifers received PGF(2 α) injections. After a further 40 h, at d 39 of each period, follicular fluid (FF) was aspirated from follicles of diameter >7 mm. The intake of the LP diet was 9% lower than that of MP and HP diets. Rumen ammonia and plasma urea nitrogen concentrations were highest in the HP and lowest in the LP, with intermediate levels in MP diets. No differences were found between treatments in plasma and FF concentrations of glucose and nonesterified fatty acids. High-protein diets increased urea concentrations very similarly in preovulatory FF and in plasma. No differences were observed between diets, in preovulatory follicle diameters and concentrations of androstenedione. However, higher estradiol and progesterone concentrations in FF were observed under the HP than under the MP diet, with no difference between diets in estrogen to progesterone ratio. It can be concluded that high concentrations of urea in plasma, caused by high dietary crude protein, penetrated into preovulatory follicles, but did not impair preovulatory characteristics. This lack of detrimental effects might be attributed to the use in this study of nonlactating heifers, which have fewer nutritional and physiological constraints and eliminate negative effects of potential interactions with high urea on dairy cows' reproductive systems.

Effects of increased supplementation of n-3 fatty acids to transition dairy cows on performance and fatty acid profile in plasma, adipose tissue, and milk fat.

The objective of this study was to determine the effects of feeding an increased amount of extruded flaxseed with high proportions of n-3 fatty acids (FA) to transition dairy cows on performance, energy balance, and FA composition in plasma, adipose tissue, and milk fat. Multiparous Israeli-Holstein dry cows (n = 44) at 256 d of pregnancy were assigned to 2 treatments: (1) control cows were fed prepartum a dry-cow diet and postpartum a lactating-cow diet that consisted of 5.8% ether extracts; and (2) extruded flaxseed (EF) cows were supplemented prepartum with 1 kg of extruded flaxseed (7.9% dry matter)/cow per d, and postpartum were fed a diet containing 9.2% of the same supplement. The EF supplement was fed until 100 d in milk. On average, each pre- and postpartum EF cow consumed 160.9 and 376.2g of C18:3n-3/d, respectively. Postpartum dry matter intake was 3.8% higher in the EF cows. Milk production was 6.4% higher and fat content was 0.4% U lower in the EF group than in the controls, with no differences in fat and protein yields. Energy balance in the EF cows was more positive than in the controls; however, no differences were observed in concentrations of nonesterified fatty acids and glucose in plasma. Compared with controls, EF cows had greater proportions of C18:3n-3 in plasma and adipose tissue. The proportion of n-3 FA in milk fat was 3.7-fold higher in the EF cows, and the n-6:n-3 ratio was decreased from 8.3 in controls to 2.3 in the EF cows. Within-group tests revealed that the C18:3n-3 content in milk fat in the EF cows was negatively correlated with milk fat percentage (r = -0.91) and yield (r = -0.89). However, no decrease in de novo synthesis of less than 16-carbon FA was found in the EF group, whereas C16:0 yields were markedly decreased. It appears that the enrichment of C18:3n-3 in milk fat was limited to approximately 2%, and the potential for increasing this n-3 FA in milk is higher for cows with lower milk fat contents. In conclusion, feeding increased amounts of C18:3n-3 during the transition period enhanced dry matter intake postpartum, increased milk production, decreased milk fat content, and improved energy balance. Increased amounts of EF considerably influenced the FA profile of plasma, adipose tissue, and milk fat. However, the extent of C18:3n-3 enrichment in milk fat was limited and was negatively correlated with milk fat content and yield.

Long-term effects of ad libitum whole milk prior to weaning and prepubertal protein supplementation on skeletal growth rate and first-lactation milk production.

Our objectives were to determine the effects of rapid growth rate during the preweaning period and prepubertal protein supplementation on long-term growth pattern and milk production during the first lactation. Forty-six Israeli Holstein heifer calves were fed either milk replacer (MR) or whole milk (WM) from 4 to 60 d age. Calves had free access to WM or MR for 30 min twice daily and free-choice water and starter mix for the entire day. From weaning until 150 d of age, all heifers were fed the same ration. At 150 d of age the heifers were divided into 2 subgroups, with one subgroup supplemented with an additional 2% protein until 320 d of age. Thereafter, all heifers were housed and fed together until calving. Another cluster of 20 heifers was raised on MR and WM treatments and 3 animals from each nursery treatment were slaughtered at 60 d and 10 mo age to determine effects of nursery treatment on organ and adipose tissue mass. Prior to weaning, the MR heifers consumed 0.12 kg/d more DM than the WM heifers, but metabolizable energy intake was not different. Body weight at weaning and average daily gain during the preweaning period were 3.1 kg and 0.074 kg/d higher, respectively, in the WM treatment than in the MR treatment, with no differences in other measurements. Nursery feeding treatment and added protein had no effect on growth rate in the prepubertal period, but the postweaning difference in BW between the WM and MR heifers remained throughout the entire rearing period. The age at first insemination was 23 d earlier and age at pregnancy and first calving was numerically lower for the WM heifers than for the MR heifers. Adipose tissue weights at weaning were doubled in the WM calves. First-lactation milk production and 4% fat-corrected milk were 10.3 and 7.1% higher, respectively, for WM heifers than for MR heifers, whereas prepubertal added protein tended to increase milk yield. In conclusion, preweaning WM at high feeding rates appears to have long-term effects that are beneficial to future milk production. The positive long-term effects of feeding WM on first-lactation milk production were independent of their effects on skeletal growth. Enhanced milk production observed with WM treatment may be related to the milk supply, paracrine or endocrine effects of fat tissues on mammary parenchyma, or a combination of both factors.

Effects of dietary fats differing in n-6:n-3 ratio fed to high-yielding dairy cows on fatty acid composition of ovarian compartments, follicular status, and oocyte quality.

The objectives were to determine the incorporation of dietary encapsulated fats differing in n-6:n-3 ratio into milk fat, plasma, and various ovarian compartments and to examine the effects on ovarian follicular status, preovulatory follicle characteristics, and oocyte quality. Twenty-four multiparous Israeli Holstein cows, averaging 114 d in milk, were assigned to 1 of 3 treatment groups: 1) control (n=7), in which cows were fed a lactating cow diet; 2) E-FLAX (n=8), in which cows were fed a lactating cow diet that consisted of 1kg/d of encapsulated fat (3.8% of dry matter) containing 40.8% flaxseed oil, providing 242.2g of C18:3n-3 (low n-6:n-3 ratio); or 3) E-SUN (n=9), in which cows were fed a lactating cow diet that consisted of 1kg/d of encapsulated fat (3.8% of dry matter) containing 40.8% sunflower oil, providing 260.0g of C18:2n-6 (high n-6:n-3 ratio). Ovaries were monitored by ultrasonography for follicular status, and after synchronization, follicles >7mm were aspirated and evaluated. Ovum pickup was performed (19 sessions for the control and E-FLAX groups and 11 for the E-SUN group), and in vitro maturation and oocyte fertilization were conducted. The E-FLAX treatment increased the proportions of C18:3n-3 (5.8 fold), C20:5n-3, and C22:5n-3 (approximately 4-fold) in milk fat as compared with the other 2 treatments. The proportion of C18:3n-3 fatty acid in plasma increased dramatically with the E-FLAX treatment, from 1.43 and 1.49% in the control and E-SUN groups, respectively, to 7.98% in the E-FLAX group. Consequently, the n-6:n-3 ratio in plasma was reduced from approximately 42 in the control and E-SUN groups to 6.74 in the E-FLAX group. Proportions of C18:3n-3 in follicular fluid and granulosa cells were approximately 5-fold higher in the E-FLAX group than in the other 2 groups. The percentage of C18:2n-6 in cumulus-oocyte complexes of cows in the E-SUN group was 54% higher than that in the E-FLAX group and was 2.4-fold higher than that in the control group; the proportion of C18:3n-3 in the E-FLAX group was 4.73% and was not detected in the other groups. The average numbers of 2- to 5-mm follicles on d 5 and 9 of the cycle were higher in the E-FLAX group than in the E-SUN group, whereas the average numbers of follicles > or =10mm on d 5, 9, and 13 were higher in the E-SUN group than in the other 2 groups. The estrous cycles of the cows were synchronized and PGF(2alpha) was injected on d 16 to 17 of the cycle. The interval from PGF(2alpha) injection to behavioral estrus was longer in the E-FLAX group than in the E-SUN group, and the beginning of the luteal phase of the subsequent cycle was delayed. Concentrations of estradiol in follicular fluid of the preovulatory follicles were higher in the E-SUN group than in the E-FLAX group. The number of follicles aspirated by ovum pickup was higher in the E-FLAX group than in the control group, and the cleavage rate in the E-FLAX group was higher than in the control group, but not the E-SUN group. In conclusion, dietary n-3 fatty acids influenced the follicular status and increased the cleavage rate of oocytes as compared with those of control cows. These findings could be related to modifications of the fatty acid composition in plasma and ovarian compartments in response to dietary supplementation.

Production performance and pattern of milk fat depression of high-yielding dairy cows supplemented with encapsulated conjugated linoleic acid.

Several processes have been suggested to protect lipids from bioactivity of the rumen microorganisms. The majority of experiments with conjugated linoleic acid (CLA) were conducted using calcium salts of CLA. The objectives of this study were to determine the effects of encapsulated CLA (E-CLA) that was supplemented during days 21 to 100 post partum (PP), on milk fat depression, recovery rate and performance parameters. Forty-two multiparous Israeli-Holstein cows were divided at day 21 PP into two treatment groups: (i) control - supplemented with 43 g/day per cow of calcium salts of fatty acids (FAs). (ii) E-CLA - supplemented with 50 g/day per cow of encapsulated lipid supplement providing 4.7 g/day per cow of trans-10, cis-12 CLA. Post-treatment cows were followed for recovery rate until 140 days PP. Dry matter intake (DMI) during the treatment period was reduced by 2.5%, and milk yield was enhanced by 4.5% in the E-CLA cows. Milk fat percentage and yield were reduced by 13% and 9%, respectively, in the E-CLA treatment as compared with the control. The energy-corrected milk output was 3.6% higher in the control group than in the E-CLA group. Yields of trans-10, cis-12 CLA isomer in milk was 2.13-fold higher in the E-CLA cows than in the controls. Full recovery to milk fat percentage of the control group occurred 4 to 5 weeks after cessation of the E-CLA supplementation. No differences between groups were observed in any fertility parameter that was tested. In conclusion, the E-CLA supplement decreased DMI, enhanced milk yield, and decreased energy output in milk, and was effective in depressing milk fat. Full recovery to the milk fat content, but not yield, of the control group in the E-CLA group was relatively slow and occurred 4 to 5 weeks after termination of the supplementation.

The effects of live yeast supplementation to dairy cows during the hot season on production, feed efficiency, and digestibility.

The current study examined the effects of live yeast (LY) supplementation to dairy cows during the summer season on milk production, feed efficiency and ration digestibility. Forty-two dairy cows (14 primiparous and 28 multiparous) were fed either a control lactating diet or supplemented with 1 g of LY (Saccharomyces cerevisiae, Biosaf, Lesaffre) per 4 kg of dry matter consumed. The LY amounts were adjusted twice a week. Four rumen samples were taken from 30 cows in 2-h periods and ammonia concentrations were determined. Fecal grab samples from 30 cows were collected during 3 consecutive days, to determine the apparent digestibility of diets. The daily dry matter intake in the LY group was 2.5% greater compared with the control group (24.7 and 24.1 kg, respectively). The daily average milk yield of the LY group was greater by 1.5 kg (4.1%) compared with the control group (37.8 vs. 36.3 kg, respectively). There were no significant differences in the milk fat and protein percentages, but fat yield was greater in the LY group than in the control. The fat-corrected milk 4% was 2.0 kg (6.1%) greater in the LY group than in the control group (34.8 vs. 32.8 kg, respectively). The efficiency of using dry matter to produce 4% fat-corrected milk was 3.7% greater in the LY group compared with the control group. The ruminal ammonia concentrations after feeding were greater in the control group than in the LY group (151.9 vs. 126.1 mg/l, respectively). No differences were observed among groups in the total tract apparent digestibility of dry matter and other diet components. The pH values in the rumen that were determined in a companion trial using 4 fistulated cows tended to be higher in cows that were supplemented with LY than in the control (6.67 vs. 6.54, respectively). It may be concluded that LY supplementation to dairy cows during the hot season improved the rumen environment in a way that increased the dry matter intake and in consequence enhanced the productivity and efficiency.

Role of peripartum dietary propylene glycol or protected fats on metabolism and early postpartum ovarian follicles.

Eighty multiparous cows were used to test the effects of feeding a supplement containing 55% dry propylene glycol (PGLY), prilled fat (PrFA) containing a low proportion of unsaturated fatty acids (FA), or calcium soaps of long-chain FA (CaLFA) containing a high proportion of unsaturated FA on energy balance (EB), blood metabolites, and early postpartum (PP) ovarian follicles. Dry cows (256 d pregnant) were divided into 6 groups and began the following dietary treatments: 1) control group, fed a dry cow diet and fed a lactating cow diet PP; 2) PGLY group, diet supplemented with 500 g/d per cow of dry PGLY prepartum through 21 d in milk; 3) PrFA:control group, diet supplemented with 230 g/d per cow of PrFA prepartum and fed the control diet PP; 4) PrFA:PrFA group, diet supplemented with 230 g/d per cow of PrFA prepartum through 21 d in milk; 5) CaLFA:control, supplemented with 215 g/d per cow of CaLFA prepartum and fed the control diet PP; 6) CaLFA:CaLFA, supplemented with 215 g/d per cow of CaLFA prepartum through 21 d in milk. Follicular fluid was aspirated from follicles > or = 6 mm on d 12 PP. The daily average calculated EB during the first 21 d in milk was lower in the PrFA:PrFA (-4.16 Mcal/d) and CaLFA:CaLFA (-3.64 Mcal/d) groups than in the control (-1.71 Mcal/d) and PGLY (-2.19 Mcal/d) groups. Postpartum plasma beta-hydroxybutyrate was higher, and insulin concentrations were lower in the PrFA:PrFA (6.2 mg/dL and 126.1 pg/mL, respectively) and CaLFA:CaLFA (7.0 mg/dL and 130.7 pg/mL) groups than in the control (4.5 mg/dL and 274.5 pg/mL) and PGLY (4.3 mg/dL and 272.6 pg/mL) groups, whereas nonesterified FA concentrations were higher only than the control group. Postpartum nonesterified FA were 21% lower and insulin plasma concentrations were 86% higher in the CaLFA:control group as compared with the PrFA:control group. The progesterone concentrations in the follicular fluid of estradiol-active follicles were higher in the CaLFA:CaLFA (200.7 ng/mL) group than in all other groups (57.3 to 92.4 ng/mL), and androstenedione and estradiol concentrations were higher (54.2 and 1,049.1 ng/mL, respectively) than in the PGLY (15.5 and 440.1 ng/mL), PrFA:control (22.6 and 314.1 ng/mL), and CaLFA:control (17.5 and 451.9 ng/mL) groups. In conclusion, supplementation of protected fat during the peripartum period negatively affected the EB status of the cows. Neither fat supplementation nor PGLY influenced the development of ovarian follicles during the early PP period, but feeding fat containing a high ratio of unsaturated FA (CaLFA) increased progesterone concentrations in estradiol-active follicles that were aspirated at 12 d in milk.

Transmission-line model for myelinated nerve fiber.

Herein, the well-known cable equation for non-myelinated axon model is extended analytically for myelinated axon formulation. The classical cable equation is thereby modified into a linear second order ordinary differential equation with periodic coefficient, known as Hill's equation. Hill's equation exhibits periodic solutions, known as Floquet's modes. The Floquet's modes are recognized as the nerve fiber activation modes, which are conventionally associated with the nonlinear Hodgkin-Huxley formulation. They can also be incorporated in our linear model.

Interaction of array of finite electrodes with layered biological tissue: effect of electrode size and configuration.

A hybrid scheme, combining image series and moment method has been utilized for the calculation of the intramuscular three-dimensional (3-D) current density (CD) distribution and potential field transcutaneously excited by an electrode array. The model permits one to study the effect of tissue electrical properties and electrode placement on the CD distribution. The isometric recruitment curve (IRC) of the muscle was used for parameter estimation and model verification, by comparison with experimentally obtained IRCs of functional electrical stimulation (FES)-activated quadriceps muscle of paraplegic subjects. Sensitivity of the calculated IRC to parameters such as tissue conductivity, electrode size, and configuration was verified. The resulting model demonstrated characteristic features that were similar to those of experimentally obtained data. The model IRCs were insensitive to the electrode size; however, the inclusion of the bone-fascia layer significantly increased the intramuscular CD and, consequently, increased the IRC slope. Of the different configurations studied, a four-electrode array proved advantageous because, in this case, the CD between the electrodes was more evenly distributed, providing better resistance to fatigue. However, due to the steeper linear portion of the IRC, this configuration suffered from a somewhat reduced controllability of the muscle.

The effect of sarcomere shortening velocity on force generation, analysis, and verification of models for crossbridge dynamics.

The study tests the hypothesis that the transition rate (G) of the cardiac cross-bridge (XB) from the strong force generating state to the weak state is a linear function of the sarcomere shortening velocity (V(SL)). Force (F) was measured with a strain gauge in six trabeculae from the rat right ventricle in K-H solution [(Ca]0 = 1.5 mM, 25 degrees C). Sarcomere length (SL) was measured with laser diffraction techniques. Twitch F at constant SL and the F response to shortening at constant V(SL) (0-8 microm/s; deltaSL 50-100 nm) were measured at varied times during the twitch. The F response to shortening consisted of an initial fast exponential decline (tau = 2 ms), followed by a slow decrease of F. The instantaneous difference (deltaF) between the isometric F (F(M)) and F during the slow phase depended on the duration of shortening (deltat), the instantaneous F(M) and V(SL). deltaF = G1 x F(M) x deltat x V(SL) x (1 -V(SL)/V(MAX)), where V(MAX) is the unloaded V(SL) and G1 was 6.15+/-2.12 microm(-1) (mean +/- s.d.; n=6). DeltaF/F(M) was independent of the time onset of shortening. The linear interrelation between deltaF and V(SL) is consistent with the suggested feedback, whereby XB kinetics depends on V(SL). This feedback provides a more universal description of the interrelation between shortening and force, as well as the observed linear relation between energy consumption and the mechanical energy output.

Current distribution in skeletal muscle activated by functional electrical stimulation: image-series formulation and isometric recruitment curve.

The present work develops an analytical model that allows one to estimate the current distribution within the whole muscle and the resulting isometric recruitment curve (IRC). The quasistatic current distribution, expressed as an image series, i.e., a collection of properly weighted and shifted point-source responses, outlines an extension for more than three layers of the classical image theory in conductive plane-stratified media. Evaluation of the current distribution via the image series expansions requires substantially less computational time than the standard integral representation. The expansions use a unique recursive representation for Green's function, that is a generic characteristic of the stratification. This approach permits one to verify which of the tissue electrical properties are responsible for the current density distribution within the muscle, and how significant their combinations are. In addition, the model permits one to study the effect of different electrode placement on the shape and the magnitude of the potential distribution. A simple IRC model was used for parameter estimation and model verification by comparison with experimentally obtained isometric recruitment curves. Sensitivity of the model to different parameters such as conductivity of the tissues and activation threshold was verified. The resulting model demonstrated characteristic features that were similar to those of experimentally obtained data. The model also quantitatively confirmed the differences existing between surface (transcutaneous) and implanted (percutaneous) electrode stimulation.

Frequency of the F508 deletion in cystic fibrosis patients from the European part of the USSR.

The frequency of the F508 deletion (delta F508) has been analyzed in 189 cystic fibrosis (CF) patients from the European part of the USSR, viz. 127 northern Slavonians (Leningrad region), 30 southern Slavonians (the Ukraine), 10 central Slavonians (Moscow region), 14 Moldavians (Kishenev region) and 8 Lithuanians (Vilnius region). The distribution of CF+ chromosomes with and without delta F508 varied significantly in the different ethnic groups studied and correlated with the clinical manifestation of CF. The overall frequency of delta F508 in Slavonian patients is equal to 62.5%, approximately 90% of them being heterozygous or homozygous for this mutation. The frequency of the deletion among 99 Slavonian patients with severe disease manifestation (pancreatic insufficiency, PI) is equal to 67.5%, only 12 patients having pancreatic sufficiency (PS, 17.5%). The highest value of delta F508 (77.4%) is registered in PI/CF patients of the southern Slavonian group; it is much less frequent (about 57%) in relevant groups of Slavonians from the northern and central parts of the country. Unusually low frequencies (24% and 26%) of delta F508 are detected in a few samples of Lithuanian and Moldavian CF patients, respectively. All delta F508+CF-chromosomes of Slavonian origin are associated with haplotypes 2.2.2. defined by the restriction fragment length polymorphism sites KM19/PstI, CS.7/Hin6I and MP6d-9/MspI, although a high proportion (about 25%) of unknown mutations is associated with the same haplotype. Haplotype B (allele 1XV2c/TaqI; allele 2 KM19/PstI) accounts for 91% of delta F508+CF chromosomes. Our data are consistent with the hypothesis of a single origin and subsequent diffusion of this major CF mutation; however, its interpopulational dissemination in Eastern Europe does not follow the suggested south-east to north-west gradient in Western Europe. The significance of these data for prenatal diagnosis and carrier screening of CF mutations is briefly discussed.