Use of glucose-lowering drugs in Hungary between 2008 and 2017: the increasing use of novel glucose-lowering drug groups

AIMS

To analyse glucose-lowering drug utilization, focusing on the novel glucose-lowering drug groups dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists and sodium-glucose co-transporter-2 inhibitors, and the financial burden they entail.

METHODS

Crude reimbursed national drug utilization and expenditure data for the entire population of Hungary were obtained from the National Health Insurance Fund for the study period: 2008 to 2017. Data were analysed using the WHO's Anatomical Therapeutic Chemical Classification/defined daily dose system and were expressed in defined daily dose per 1000 inhabitants per day.

RESULTS

Total glucose-lowering drug consumption in Hungary showed an 18% increase over the study period, reaching 74.7 defined daily doses per 1000 inhabitants per day, while novel glucose-lowering drug use increased to 11.7 defined daily doses per 1000 inhabitants per day (16% of total glucose-lowering drug use) by 2017. Dipeptidyl-peptidase 4 inhibitor consumption grew to 7.4 defined daily doses per 1000 inhabitants per day by 2017. The most widely used dipeptidyl-peptidase 4 inhibitor was sitagliptin. Glucagon-like peptide-1 receptor agonists were used the least, but by 2017 rose to 1.5 defined daily doses per 1000 inhabitants per day, led by liraglutide. Sodium-glucose co-transporter-2 inhibitors appeared in the utilization data in 2014 and their consumption, mainly empagliflozin, reached 2.8 defined daily doses per 1000 inhabitants per day by 2017. The total expenditure on glucose-lowering drugs increased 94% between 2008 and 2017, and the total cost of novel glucose-lowering drug utilization comprised 44% of the total glucose-lowering drug expenditure in 2017.

CONCLUSIONS

Both the use of and the financial burden posed by novel glucose-lowering drugs in Hungary increased steadily between 2008 and 2017. This increase is expected to continue.

Copper-induced peroxidation of phosphatidylserine-containing liposomes is inhibited by nanomolar concentrations of specific antioxidants

Copper-induced peroxidation of liposomal palmitoyllinoleoyl-phosphatidylcholine (PLPC) is inhibited by alpha-tocopherol at micromolar concentrations. In our previous study we found that when the liposomes contain phosphatidylserine (PS), nanomolar concentrations of Toc were sufficient to inhibit peroxidation. In an attempt to gain understanding of the origin of this extreme antioxidative potency, we tested the antioxidative potency of 36 additional antioxidants and the dependence of their potency on the presence of PS in the liposomes. The results of these studies reveal that only 11 of the tested antioxidants possess similar antioxidative potency to that of Toc. These include trolox, butylated hydroxytoluene (BHT), curcumin, nordihydroguaiaretic acid (NDGA), diethylstilbestrol (DES), 2 of the 13 tested flavonoids (luteolin and 7,3',4'-trihydroxyflavone; T-414), alpha-naphthol, 1,5-, 1,6- and 1,7-dihydroxynaphthalenes (DHNs). Propyl gallate (PG), methyl syringate, rosmarinic acid, resveratrol, other flavonoids, as well as beta-naphthol, 1,2-, 1,3-, 1,4-, 2,3-, 2,6-, and 2,7-DHNs were either moderately antioxidative or pro-oxidative. For liposomes made of PLPC (250 microM) and PS (25 microM) the "lag" preceding copper-induced peroxidation (5 microM copper) was doubled upon addition of 30-130nM of the "super-active" antioxidants. We propose that the mechanism responsible for the extreme antioxidative potency against copper-induced peroxidation in PS-containing liposomes involves replenishment of the antioxidant in a ternary PS-copper-antioxidant complex. Based on structure-activity relationship of the 37 tested antioxidants, the "super-antioxidative potency" is attributed to the recycling of relatively stable semiquinone or semiquinone-like radicals.

Oxidation of liposomal cholesterol and its effect on phospholipid peroxidation

Lipid peroxidation is believed to play an important role in the pathogenesis of many diseases. Much research has therefore been devoted to peroxidation of different lipids in biomembranes and in model systems (liposomes) of different compositions. Yet, in spite of the relative simplicity of the liposomes, the existing literature is insufficient to reach definite conclusions regarding basic questions including the susceptibility of cholesterol to oxidation, its effect on the peroxidation of polyunsaturated phospholipids such as palmitoyllinoleoylphosphatidylcholine (PLPC) and how cholesterol influences the effect of water-soluble antioxidants such as urate on the peroxidation. The aim of the present study was to clarify these issues. Its major findings are that: (i) AAPH-induced peroxidation of cholesterol is slow and independent of the peroxidation of PLPC. In turn, AAPH-induced peroxidation of PLPC is not affected by cholesterol, independent of the presence of urate in the system. (ii) Cholesterol is not susceptible to copper-induced oxidation, but its inclusion in PLPC liposomes affects the peroxidation of PLPC, slowing down the initial stage of oxidation but promoting later stages. (iii) Addition of urate accelerates copper-induced peroxidation of PLPC in the absence of cholesterol, whereas in cholesterol-containing liposomes it inhibits PLPC oxidation. We attribute the complexity of the observed kinetics to the known cholesterol-induced rigidization of liquid crystalline bilayers.

Expression of foreign genes in chicks by hydrodynamics-based naked plasmid transfer in vivo

The study of gene function in vivo is considered one of the top achievements of modern biology, inasmuch as it provides tools to study gene function in the context of the whole animal. In chickens, techniques of DNA-mediated gene transfer are less advanced than in other animal or livestock models, and remain a significant challenge. The study presented here is the first to show that a hydrodynamics-based gene-transfer technique, originally developed for naked DNA transfer in mice, can be applied to chickens. Rapid injection of naked plasmids containing expression cassettes into the jugular vein of 6- to 10-day-old chicks resulted in specific expression of the transgenes. A CMV promoter-driven luciferase reporter gene was expressed at significant levels in the liver during the first 3 days post-injection with lower levels also detected in the kidney. Significantly, all injected birds showed detectable levels of luciferase expression. Similarly, injection of a plasmid containing the secreted human coagulation factor IX (hFIX) gene under the control of human alpha-1-anti-trypsin promoter resulted in detectable levels of the hFIX in the plasma during the first 2 days post-injection. The method described herein has the potential for a quick and simple route for gain and loss-of function experiments in chicken liver and kidney, as well as for studying systemic effects of secreted proteins and hormones.

Carrying the FecB (Booroola) mutation is associated with lower birth weight and slower post-weaning growth rate for lambs, as well as a lighter mature bodyweight for ewes

The present study was conducted in an Assaf flock in which the FecB (Booroola) mutation was segregated to determine whether the FecB mutation affects birthweight and the pre- and post-weaning growth rate of ewe lambs, as well as the mature bodyweight of ewes. Significant differences (P = 0.01) in birthweight (mean ± s.e.m.) were found between BB ewe lambs (4.03 ± 0.08 kg) and B+ and ++ ewe lambs (4.16 ± 0.04 and 4.32 ± 0.07 kg, respectively), which themselves did not differ significantly (P > 0.05). An FecB-associated maternal effect on the birthweight of ewe lambs was also detected, with the birthweight of lambs born to BB mothers (3.93 ± 0.08 kg) being significantly (P < 0.0001) different from the birthweight of lambs born to B+ and ++ mothers (4.26 ± 0.04 and 4.33 ± 0.07 kg, respectively), which did not differ significantly. The genotypes of the lambs did not affect their preweaning growth rate. However, the post-weaning growth rate of ewe BB lambs (274 ± 5 g day−1) was significantly (P = 0.05) different from the similar (P > 0.05) post-weaning growth rates of B+ and ++ lambs (284 ± 3 and 290 ± 4 g day−1, respectively). The genotype at the FecB locus also affected the mature bodyweight of ewes, with that of BB ewes (67.3 ± 1.4 kg) being significantly (P < 0.001) different from the similar mature bodyweight of B+ and ++ ewes (70.8 ± 1.1 and 70.1 ± 1.7 kg, respectively).

Oocyte recovery, embryo development and ovarian function after cryopreservation and transplantation of whole sheep ovary

BACKGROUND

Successful cryopreservation of a whole ovary may provide a solution for women with premature ovarian failure. The aim of this study was to evaluate the function of cryopreserved whole sheep ovaries both in vitro and in vivo.

METHODS

Transplantation of frozen-thawed intact ovaries was performed on eight sheep by artery and vein anastomosis to the contralateral ovarian artery and vein. The remaining ovary was removed. Oocyte aspiration was performed 1 and 4 months post-transplantation. Serum progesterone levels were measured after 24 and 36 months. Magnetic resonance imaging (MRI) was carried out 12 months after transplantation.

RESULTS

Progesterone activity was detected in three sheep from 24 to 36 months post-transplantation. Oocyte retrieval was successful in two sheep and parthenogenic activation has resulted in embryonic development up to the 8-cell stage. MRI revealed an intact ovary with small follicles and intact blood vessels.

CONCLUSIONS

Whole ovaries, and the follicles and blood vessels they contain, are able to survive cryopreservation. In addition, MRI has shown that blood vessels were intact and that normal blood flow had resumed to the transplant. We conclude that immediate and long-term hormonal restoration and normal ovulation is possible after cryopreservation and transplantation of whole ovaries in sheep.

Effect of treatment with follicle-stimulating hormone or bovine somatotropin on the quality of oocytes aspirated in the autumn from previously heat-stressed cows

Conception in dairy cows during autumn remains low even after summer temperatures decline. This is possibly a residual effect of heat stress on oocyte quality. Lactating Holsteins previously heat-stressed during summer were used in two experiments (n = 8 and 16 cows) in autumn to examine hormonal strategies for improving quality of oocytes. Follicles (3 to 8 mm in diameter) were aspirated by the ovum pick-up procedure on d 4 of two consecutive estrous cycles of treated and control cows. Oocytes were classified morphologically, matured in vitro, chemically activated, and cultured for 8 d. In Experiment 1, FSH (2 x 200 mg, at a 12-h interval) was injected on d 5 and 12 of cycle 1 (treated cycle). Before FSH, the percentage of good quality oocytes (grade I) and the cleavage rate averaged 52 and 24%, respectively, in both groups. During the FSH-treated cycle, more 6- to 9-mm follicles were observed. In the subsequent cycle, rates of grade I oocytes and cleavage were significantly higher in FSH-treated than in control cows (89 vs. 51% and 85 vs. 31%, respectively). In Experiment 2, recombinant bovine somatotropin (bST, 500 mg) was injected on d 4 and 18 of the treated cycle. The bST treatment increased the number of 3- to 5-mm follicles. Before bST, grade I (39%) and cleaved oocytes (40%), were similar across treatment groups. In the subsequent cycle, the percentage of grade I oocytes was significantly higher in treated than in control cows (72 vs. 26%), but cleavage rates were similar. Neither FSH or bST improved blastocyst formation, and regardless of treatment, few blastocysts were formed. Treatment with bST improved oocyte morphology, whereas FSH improved both oocyte morphology and cleavage rates during autumn following summer heat stress.

Improvement of quality of oocytes collected in the autumn by enhanced removal of impaired follicles from previously heat-stressed cows

The fertility of dairy cows decreases during the summer and remains low during the cooler autumn although the animals are no longer under heat stress. The aim of this study was to characterize a delayed effect of summer heat stress on oocyte quality in the autumn and to improve oocyte quality by enhanced removal of follicles damaged during the previous summer. Lactating cows (n = 16) were subjected to heat stress during the summer. In autumn, ovarian follicles (3-7 mm in diameter) were aspirated by an ultrasound-guided procedure during four consecutive oestrous cycles. Follicles were aspirated from control cows on day 4 and from treated cows on days 4, 7, 11 and 15 of each oestrous cycle. All cows received PGF(2alpha) and GnRH injections on days 19 and 21, respectively, and maintained cyclicity, as indicated by plasma progesterone concentrations. On day 4 of each cycle, the oocytes recovered were examined morphologically, matured and activated in vitro, and cultured for 8 days. In cycle 1 (early October) both groups showed low percentages of grade 1 oocytes, cleavage, four- and eight-cell embryos, morulae and parthenogenetic blastocysts. Subsequently, the number of grade 1 oocytes increased earlier (cycle 2) in treated than in control cows (cycle 3; P < 0.05). The cleavage rate in the control group remained relatively low throughout (32-58%), whereas in the treated group it increased from 40% (cycle 1) to 75% (cycles 3 and 4; P < 0.05). The number at each stage of embryo development increased slightly but remained low throughout in the control group, whereas in the treated group significant (P < 0.05) increases of all stages were observed in cycles 3 and 4. The results show a delayed effect of summer heat stress on oocyte quality and embryo development in the autumn. Enhanced removal of the impaired cohort of follicles led to earlier emergence of healthy follicles and high quality oocytes in the autumn.

Improvement of quality of oocytes collected in the autumn by enhanced removal of impaired follicles from previously heat-stressed cows

The fertility of dairy cows decreases during the summer and remains low during the cooler autumn although the animals are no longer under heat stress. The aim of this study was to characterize a delayed effect of summer heat stress on oocyte quality in the autumn and to improve oocyte quality by enhanced removal of follicles damaged during the previous summer. Lactating cows (n = 16) were subjected to heat stress during the summer. In autumn, ovarian follicles (3-7 mm in diameter) were aspirated by an ultrasound-guided procedure during four consecutive oestrous cycles. Follicles were aspirated from control cows on day 4 and from treated cows on days 4, 7, 11 and 15 of each oestrous cycle. All cows received PGF(2alpha) and GnRH injections on days 19 and 21, respectively, and maintained cyclicity, as indicated by plasma progesterone concentrations. On day 4 of each cycle, the oocytes recovered were examined morphologically, matured and activated in vitro, and cultured for 8 days. In cycle 1 (early October) both groups showed low percentages of grade 1 oocytes, cleavage, four- and eight-cell embryos, morulae and parthenogenetic blastocysts. Subsequently, the number of grade 1 oocytes increased earlier (cycle 2) in treated than in control cows (cycle 3; P < 0.05). The cleavage rate in the control group remained relatively low throughout (32-58%), whereas in the treated group it increased from 40% (cycle 1) to 75% (cycles 3 and 4; P < 0.05). The number at each stage of embryo development increased slightly but remained low throughout in the control group, whereas in the treated group significant (P < 0.05) increases of all stages were observed in cycles 3 and 4. The results show a delayed effect of summer heat stress on oocyte quality and embryo development in the autumn. Enhanced removal of the impaired cohort of follicles led to earlier emergence of healthy follicles and high quality oocytes in the autumn.

Preovulatory follicular status and diet affect the insulin and glucose content of follicles in high-yielding dairy cows

Insulin and glucose may be limiting factors for ovarian function in dairy cows genetically selected for high milk yield. The effects of nutrition on the intrafollicular content of insulin and glucose were investigated in Israeli Holstein dairy cattle fed a basic total mixed ration and producing 34-39kg of milk daily. In experiment 1, carried out in 11 oestrus-synchronised cows, little variation in insulin concentration was found in plasma sampled during the luteal phase, but high variation was found in plasma sampled during the follicular phase. Therefore, in order to prevent confounding the effects of diet and of phase in cycle in the following experiments, experimental diets were fed during the luteal phase of synchronised oestrus cycles. In experiment 2, designed as Latin-Square, six cows received sequentially diets containing 17.1 (control) or 19.7% of crude protein, using two sources of supplementary protein, i.e. soyabean meal (SBM) and corn gluten meal (CGM), differing in ruminal degradability and leucine content. When dry matter intake was used as covariant, plasma insulin on day 16 was 29.5 and 26.4% higher in cows fed diets containing SBM and CGM than in the control (P<0.05). In experiment 3, 17 cows were individually fed the basic diet and then switched to isoenergetic diets containing SBM (n=5), CGM (n=6) or corn grain (CG, n=6) given from day 10 to 16 of the synchronised oestrus cycle. On the eve of day 16, and in the morning of day 17, they were administered PGF(2alpha) and the content of 26 largest follicles was aspirated by using the transvaginal ovum pick-up technique. Follicles were sorted into two classes (preovulatory and subordinate) according to oestradiol concentration and the progesterone:oestradiol ratio in follicular fluid (FF). Higher concentrations of insulin (0.282 versus 0.127ng/ml, P<0.0001) and of glucose (0.614 versus 0.386g/l, P<0.002), were found in FF from preovulatory follicles. The insulin concentration in the FF of cows fed the CG diet was 26% higher than in their counterparts fed CGM (P<0.04), SBM being intermediate. Dietary effects did not reach significance in subordinate follicles. The finding that preovulatory follicular status is associated with increased intrafollicular insulin and glucose suggests that insulin is involved in follicular maturation. The nutritional effect on intrafollicular glucose and insulin may have practical implications to optimise feeding in dairy cows during phases of the oestrus cycle.

Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturition a control diet, a control diet plus 0.55 kg/d of calcium soaps of fatty acids, or a control diet with 500 mg of bST injected every 14 d. Fourteen days after a synchronized or natural estrus, cows were injected with a PGF2 alpha analogue; 48 h later, follicular fluid from all ovarian follicles > 8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both treatments changed the proportion of estradiol-active follicles (> 400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fluid estradiol concentration and the total number large follicles per cow. In follicles aspirated between 60 and 90 DIM the percentage of estradiol-active follicles was 67, 40, and 0 for cows on the control, calcium soaps of fatty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at follicle aspiration (r = 0.51). The proportion of oleic acid in free fatty acids in plasma at 50 DIM was lower in control cows and was lower in follicular fluid of estradiol-active follicles. Both calcium soaps of fatty acids and bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.

Susceptibility of serum lipids to copper-induced peroxidation correlates with the level of high density lipoprotein cholesterol

As a first step in evaluating the significance of our recently developed method of monitoring the kinetics of copper-induced oxidation in unfractionated serum, we recorded the kinetics of lipid oxidation in the sera of 62 hyperlipidemic patients and analyzed the correlation between oxidation and lipid composition of the sera [high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides]. We used six factors to characterize the kinetics of oxidation, namely, the maximal absorbance of oxidation products (ODmax), the maximal rate of their production (Vmax), and the time at which the rate was maximal (t(max)) at two wavelengths (245 nm, where 7-ketocholesterol and conjugated dienic hydroperoxides absorb intensely, and 268 nm, where the absorbance is mostly due to dienals). The major conclusions of our analyses are that: (i) Both ODmax and Vmax correlate positively with the sum of concentrations of the major oxidizable lipids, cholesterol, and cholesteryl esters. (ii). The value of t(max), which is a measure of the lag preceding oxidation and therefore reflects the resistance of the serum lipids to copper-induced oxidation, exhibits a negative correlation with HDL cholesterol. Although this finding accords with the observation of shorter lags for HDL than for LDL, it is apparently inconsistent with the role of HDL as an antirisk factor in coronary heart diseases.

Differential expression pattern of inhibin alpha and betaA subunits in the ovaries of postnatal and prepubertal lambs

The aim of the present study was to characterize gene and protein expression of follistatin, inhibin alpha (alpha) and inhibin betaA (betaA) subunits in the ovaries of postnatal (3-week-old) and prepubertal (14 and 20-25-week-old) lambs. Northern blot analysis revealed the presence of two alpha and two betaA mRNAs. In postnatal ovary the a 1.2-kb transcript was abundant, its amount gradually falling, while the 2.0-kb mRNA increased and became a major band at 20-25 weeks. Both betaA mRNAs, 4.5 kb and 6.0-7.5 kb, were weakly expressed in postnatal ovary, but whereas the 4.5-kb mRNA expression remained at a low level, that of the 6.0-7.5 kb mRNA increased about five fold in prepubertal ovary. The ratio of total alpha mRNAs to the dominant betaA form (6.0-7.5 kb) varied from 1.27 at 3 weeks to 0.33 at 20-25 weeks of age. One major follistatin mRNA of 2.5-3.6 kb was recognized and was constitutively expressed during ovarian growth. Several molecular-mass forms of alpha and betaA subunits with different compositions were seen in prepubertal compared with postnatal ovaries, the latter exhibiting more active follicular growth. In summary, ovine ovaries undergo distinct changes early in life, both morphological and functional, and show a changing pattern of inhibin subunit expression.

Effect of the synchronization of the degradation of dietary crude protein and organic matter and feeding frequency on ruminal fermentation and flow of digesta in the abomasum of dairy cows

Four Holstein cows in midlactation were equipped with ruminal and abomasal cannulas and used to study the effect of synchronized degradation of crude protein (CP) and organic matter (OM) and feeding frequency on digestion and outflow of nutrients. A 4 x 4 Latin square design was used. Diets were arranged in a 2 x 2 factorial design; the four diets contained high ruminally degradable OM and high ruminally degradable CP, high ruminally degradable OM and low ruminally degradable CP, low ruminally degradable OM and high ruminally degradable CP, and low ruminally degradable OM and low ruminally degradable CP. In each period, cows were fed four times daily from d 1 to 14 and two times daily from d 15 to 28. Mean daily ruminal ammonia N concentration was reduced by high ruminally degradable OM, low ruminally degradable CP, and twice daily feeding. Fluctuation in ruminal ammonia N was lower when cows were fed four times daily than when cows were fed twice daily. Plasma urea N concentrations were lower for cows fed diets that were high in ruminally degradable CP. Higher CP flow in the abomasum was found for cows fed the diet containing high ruminally degradable OM and low ruminally degradable CP. Microbial dry matter and CP flow to the abomasum were higher for cows fed twice daily than for cows fed four times daily. Flow of OM in the abomasum was not altered by concentrations of ruminally degradable OM or CP. These results suggest that the available energy in the rumen (ruminally degradable OM) is the most limiting factor for ruminal N utilization under our experimental conditions. Use of these data may improve the prediction of plasma urea N.

Lipid oxidation in unfractionated serum and plasma

In an attempt to develop an assay for the susceptibility of plasma lipids to oxidation, we have studied the kinetics of copper-induced oxidation in diluted serum and plasma prepared with different anticoagulants (heparin, citrate and EDTA) by monitoring the absorbance of oxidation-products at several wavelengths. These studies revealed the complex and interrelated effects of the water-soluble antioxidant ascorbic acid, citrate and chloride ions on the kinetics of copper-induced oxidation of plasma lipids. Specifically, the onset of oxidation induced by copper-citrate chelates is only slightly affected by chloride ions and is accelerated upon increasing the copper concentration. By contrast, in the absence of citrate, the lag preceding oxidation in diluted serum or plasma (but not the maximal rate of oxidation) depends markedly on the chloride concentration in the diluting medium. In the absence of Cl-, the lag preceding oxidation is a decreasing saturable function of copper concentration, whereas in a normal phosphate-buffered saline solution (PBS), the lag shows a biphasic dependence on copper concentration such that at copper concentrations above 10-30 microM (depending on the extent of plasma dilution), increasing the concentration of copper results in prolongation of the lag. This dependence of copper-induced oxidation on the concentration of copper is not observed for dialyzed serum unless ascorbic acid is added. Our interpretation of these results is that water-soluble reductants and chloride ions act synergistically to stabilize Cu+, on the expense of Cu2+. Quenching of free radicals by Cu+ may be responsible for the prolongation of the lag at high copper concentrations, with no reduction of the maximal rate of oxidation. In spite of the complex dependencies described above, spectrophotometric monitoring of the kinetics of oxidation of plasma lipids, under 'optimized conditions' (50-fold diluted serum, in PBS containing 720 microM sodium citrate and 100 microM copper), agrees with independent measurements of the consumption of polyunsaturated fatty acids. Hence, the spectroscopic method may become useful for evaluation of the susceptibility of plasma lipids to oxidation. This possibility, however, has yet to be elucidated through investigations of the correlation between the susceptibility of serum lipids to copper-induced oxidation in vitro and clinical factors of significance.

Factors affecting success of embryo collection and transfer in a transgenic goat program

During a goat transgenic program that took place in Israel from July 1995 to February 1996, Saanen (n = 343) and Nubian x Damascus (n = 378) crossbred goats of mixed ages were used as donors (n = 433) and recipients (n = 288). The effects of season, age, number of surgical procedures, previous hormonal treatments and ovulation rate on the number of microinjectable embryos collected were studied. Likewise, the effects of these parameters on the pregnancy rate as well as the number of embryos transplanted, endogenous progesterone concentrations and exogenous progesterone supplementation were studied in recipient does. Following superovulation with ovine follicle stimulating hormone, 85% of the does responded with 13.6 +/- 5.7 (mean +/- S D) ovulations/doe. Age, month and number of previous hormonal treatments significantly affected the ovulation rate. The average recovery rate was 70%, and it was affected only by the ovulation rate. Pronuclei were visualized in about 30% of the flushed embryos (including unfertilized ova), and those were microinjected with human serum albumin gene construct. About 68% of the injected embryos underwent at least one division during an overnight incubation, and those embryos were transferred, giving about 2.0 transferred embryos per ovulated donor. Of the recipients, 86% responded following synchronization with 3.1 +/- 1.6 (mean +/- S D) ovulations per doe. Breed and month had a significant effect on the ovulation rate. Two or three microinjected embryos were transferred to each recipient, resulting in more than a 40% pregnancy rate during September to November. Lower pregnancy rates were obtained before and after that period. By monitoring plasma progesterone concentrations in the recipients it was found that progesterone concentration was correlated with the ovulation rate. However, the pregnancy rate was not affected by progesterone concentration. During January and February, 30 to 50% of the recipients failed to develop functional corpora lutea (CL) following embryo transfer, which explained the lower pregnancy rate in those months. Of the 86 kids born 4 were transgenic.

The use of commercially available lipid emulsions for the preparation of amphotericin B-lipid admixtures

The use of Intralipid as a dilution medium for Fungizone, previously proposed by several groups to reduce the toxicity of amphotericin B, is limited by the instability of amphotericin B-lipid admixtures. We have shown that Fungizone-lipid admixtures with three different lipid emulsions can be stabilized by vigorous agitation. Unlike in preparations made by gentle shaking, in stable emulsions made by agitation for 18 h, most of the amphotericin B remains associated with the lipid phase for at least 1 month at 4 degrees C. The MICs of all the admixtures against various Candida spp. were similar to that of Fungizone and did not change following storage for at least 2 weeks at 4 degrees C. Furthermore, the toxicity of the admixtures, as evaluated by their haemolytic activity and amphotericin B-induced K+-leakage from human red blood cells, was much lower than that of Fungizone. Hence, amphotericin B-containing lipid emulsions made by extended agitation may be advantageous in clinical practice as they are efficient, stable, non-toxic and can be easily produced at low cost from commercially available ingredients approved for clinical use.

The effect of albumin on copper-induced LDL oxidation

In an attempt to gain deeper understanding of the mechanism or mechanisms responsible for the protective effect of serum albumin against Cu(2+)-induced peroxidation of low density lipoprotein (LDL), we have examined the influence of the concentrations of bovine serum albumin (BSA), Cu2+ and LDL on the kinetics of peroxidation. Since the common method of monitoring the oxidation by continuous recording of the absorbance of conjugated dienes at 234 nm cannot be used at high BSA-concentrations because of the intensive absorption of BSA, we have monitored the time-dependent increase of absorbance at 245 nm. At this wavelength, conjugated dienes absorb intensely, whereas the background absorbance of BSA is low. Using this method, as well as the TBARS assay for determination of malondialdehyde, over a large range of BSA concentrations, we show that in many cases the influence of BSA on the kinetics of oxidation can be compensated for by increasing the concentration of copper. This reconciles the apparent contradiction between previously published data. Detailed studies of the kinetic profiles obtained under different conditions indicate that binding of Cu2+ to albumin plays the major role in its protective effect while other mechanisms contribute much less than copper binding. This conclusion is consistent with the less pronounced effect of BSA on the oxidation induced by the free radical generator AAPH. It is also shown that the copper-albumin complex is capable of inducing LDL oxidation, although the kinetics of the latter process is very different from that of copper-induced oxidation. Nevertheless, when compared to copper induced oxidation at similar concentration of the oxidation-promotor, the kinetics of oxidation induced by copper-albumin complex is very different and is consistent with a tocopherol mediated peroxidation, characteristic under low radical flux. Similar kinetics was observed for copper-induced oxidation only at much lower copper concentrations.

Exogenous insulin-like growth factor II enhances post-infarction regional myocardial function in swine

OBJECTIVES

Insulin-like growth factor II (IGF-II) promotes cardiac myocyte growth and contractility in vitro. This study was designed to investigate the effect of exogenous IGF-II on regional myocardial function at the area of infarct in the pig.

METHODS

Myocardial infarction was induced in 12 female anaesthetized pigs by affigel blue beads, embolizing microvessels of the left anterior descending coronary artery distribution. In the experimental group (n = 6), IGF-II (0.12 microgram.kg-1 in two animals and 0.6 microgram.kg-1 in four) was incorporated into the beads and delivered by them to the infarct area. Myocardial function was followed echocardiographically, and the excised heart was analysed immunohistochemically and histopathologically.

RESULTS

Myocardial function in injured zones, inversely related to an echocardiographic segmental wall motion score (mean +/- SEM), was similar between the two groups at baseline, but at 4 weeks post-infarction was significantly (P = 0.008) reduced in the control group (0.58 +/- 0.38 vs 3.42 +/- 0.84), in contrast to nearly baseline values in the experimental group (0.58 +/- 0.33 vs 1.17 +/- 0.42, P = 0.41). Cardiac performance in injured segments was significantly better after myocardial injury in the experimental group (P = 0.04). Tissue samples from both groups (4 weeks post-infarction), stained with haematoxylin and eosin demonstrated peri-infarct myocyte hypertrophy, corresponding to regions selectively stained by an antibody for CD56, which highlights growing cardiac myocytes. By image analysis semi-quantification, staining for CD56 was significantly (P = 0.04) higher in the peri-infarct region of the experimental group, as compared with controls (106.5 +/- 2.8 vs 92 +/- 4.4 gray level units). Microvessels stained for von-Willebrand factor were similar in number in both groups (P = 0.8), as were mesenchymal cells stained for vimentin (P = 0.7).

CONCLUSIONS

Exogenous IGF-II, delivered to the infarct area ameliorates regional cardiac function in the pig, perhaps by inducing peri-infarct myocyte growth.

Cholesterol precipitation from cholesterol-supersaturated bile models

Bile-model systems containing cholesterol (CH), phosphatidylcholine (PC) and sodium cholate (NaC) at concentrations similar to those found in supersaturated human gall bladder bile ([CH]/[PC] = 0.60 +/- 0.01; CH saturation index, CSI = 1.58 +/- 0.03) were prepared by mixing PC-CH vesicles with NaC micellar solutions. Following mixing, the dispersion became transparent and gave rise to high resolution 1H-NMR spectra typical of mixed micellar systems. Cryo-transmission electron micrographs of specimens vitrified at that stage support the conclusion that the vesicles had become completely micellized. Following micellization, the metastable (cholesterol-supersaturated) bile-models spontaneously underwent a series of reorganizational steps: first, cholesterol-rich vesicles with a [CH]/[PC] ratio of 1.57 +/- 0.69 were formed, in co-existence with a mixed micellar system with [CH]/[PC] = 0.43 +/- 0.01 and CSI = 1.12 +/- 0.03. The resultant cholesterol-rich vesicles subsequently aggregated and cholesterol crystals of varying sizes and shapes appeared within the aggregates: needle-like structures were first observed, followed by clusters of those crystals and of helical crystals. Eventually, typical plate-like cholesterol crystals appeared, at which time some of the PC returned to the non-particulate (isotropic) phase. Consequently, the system contained cholesterol crystals coexisting with mixed micelles, whose composition was close to the limit of saturation (CSI = 1.08). These findings confirm the sequence of events preceding the appearance of cholesterol crystals, as previously proposed in our less detailed studies ((1990) Hepatology 12, 149S) and support the relevance of the morphologically similar results of Konikoff et al. ((1992) J. Clin. Invest. 90, 1155) obtained in a very dilute supersaturated bile-model.

Effect of lactation on single-dose pharmacokinetics of norfloxacin nicotinate in ewes

In a three-way crossover trial, six healthy Finnish-Merino-Awassi ewes were given a single intravenous injection of norfloxacin nicotinate (in a dose equivalent to 25 mg of norfloxacin base per kg of body weight) during nursing, 1 day after weaning, and 1 month after weaning. Blood and milk samples were collected at different time intervals following dosing, and norfloxacin concentrations were determined by a high-performance liquid chromatography assay. The serum drug concentration versus time data were analyzed by a noncompartmental approach which was based on the statistical-moment theory. The total body clearance values were 4.2 +/- 1.3 (injection during nursing), 1.6 +/- 0.3 (injection 1 day after weaning), and 3.1 +/- 0.8 ml/min/kg (injection 1 month after weaning). The mean residence times were 335 +/- 83, 797 +/- 129, and 481 +/- 102 min and terminal half-lives were 266 +/- 51, 603 +/- 94, and 372 +/- 68 min for the respective treatments. The estimated volumes of distribution at steady state were 1.3 +/- 0.1, 1.2 +/- 0.1, and 1.4 +/- 0.2 liter/kg for the respective treatments. Milk norfloxacin concentrations were up to 40 times higher than the corresponding concentrations in serum during lactation. Accordingly, in ewes with 1.5 liter of milk in the udder more than half of the drug in the animal appeared to be in the milk. Therapeutic concentrations of norfloxacin could be detected in the sera of suckling lambs, implicating that fluoroquinolone therapy should be discouraged during breast feeding. In lactating ewes and in ewes with full udders, moment analysis calculations did not show a significant difference between the system moment mean residence time and the system matrix mean residence time values. Thus, the pharmacokinetics of norfloxacin in the three groups could be described by the classical two-compartment open-body model with input and output occurring from the central compartment. The results did not support the existence of a distinguishable milk compartment. Milk secretion seemed to act as one of the clearance processes of the drug when milk was continuously removed.

A closed-chest pig model of sustained ventricular tachycardia

The goal of this study was to develop and explore a closed-chest animal model of sustained VT. Seven of 11 domestic pigs had successful induction of myocardial infarction by injection of agarose gel microbeads into the left anterior descending coronary artery through an inflated balloon angioplasty catheter. Four of the first five pigs died and seem to represent a "learning experience." During a 3- to 50-day follow-up period, each pig underwent 1-3 electrophysiological studies. Sustained, monomorphic VT was induced 1-4 times in 5 of the 7 pigs (a total of 19 episodes), was reproducible during the same study in all pigs, and could be repetitively induced during successive studies in some. Ventricular fibrillation was induced less frequently (nine episodes) and was successfully terminated by DC shock in eight episodes. We conclude that a closed-chest pig model of VT is feasible and is associated with a relatively high induction rate of sustained, monomorphic, and reproducible VT and a relatively low mortality rate.

Intracoronary injection of basic fibroblast growth factor enhances angiogenesis in infarcted swine myocardium

OBJECTIVES

This study was performed to examine the effect of intracoronary exogenous basic fibroblast growth factor (bFGF) on angiogenesis in infarcted myocardial regions.

BACKGROUND

Exogenous bFGF is a potent promoter of angiogenesis. Little information is available on its effect on myocardial angiogenesis.

METHODS

Myocardial infarction was induced in 10 pigs by intracoronary injection of microscopic beads. Four pigs served as a control group; in six pigs slow-release bFGF was delivered by the beads. Cardiac performance was evaluated by repeated echocardiographic measurement and angiogenesis was evaluated by immunohistochemical studies 14 days later.

RESULTS

As compared with control pigs, pigs treated with bFGF had higher microvessel counts (mean +/- SEM) in both viable tissue (141 +/- 27 per field vs. 39 +/- 4, p = 0.01) and nonviable tissue (329 +/- 26 per field vs. 95 +/- 7, p < 0.001) within the infarct area. No significant differences in total regional left ventricular wall motion were noted between the two groups throughout the 14-day study period.

CONCLUSIONS

In the swine, direct intracoronary application of bFGF to infarcted myocardium enhances myocardial neovascularization within 2 weeks.

Plasma immunoreactive inhibin and FSH in prepubertal Assaf and Booroola-Assaf ewe lambs

Plasma immunoreactive inhibin (i-inhibin) was measured in Assaf and Booroola-Assaf (1/2 Booroola-1/2 Assaf) ewe lambs between the ages of 2 and 15 weeks and correlated with plasma FSH. I-inhibin concentrations were similar in both genotypes and was maximal at 2 weeks of life and decreased thereafter. These levels (mean +/- s.e.) were 1.28 +/- 0.12 and 1.14 +/- 0.10 ng/ml at 2 weeks and 0.55 +/- 0.06 and 0.45 +/- 0.05 ng/ml at 15 weeks of age in Assaf (n = 13) and Booroola-Assaf (n = 13) respectively. In Assaf ewes an inverse correlation between plasma inhibin and FSH was observed at 4 and 15 weeks but not at 2 weeks of age. In Booroola-Assaf ewes, no significant correlation was found at any age studied. At 4 weeks of age, Assaf and Booroola-Assaf ewe lambs had very different ovarian morphology. Assaf lambs had large ovaries with a mean diameter of 1.00 +/- 0.09 cm (mean +/- s.e.) and many preantral and antral follicles present, while Booroola-Assaf had much smaller ovaries (0.66 +/- 0.03 cm, p < 0.05) with only a few antral follicles. It seems likely that the FecB allele from the Boorola Merino influenced the structure of the ovary although the contribution of other Booroola genes cannot be ruled out. In summary, the plasma i-inhibin concentrations decreased between 2 and 15 weeks of age irrespective of genotype. It is speculated that in prepubertal ewe lambs the ratio of bioactive to immunoreactive inhibin varies with age and between the genotypes with different ovarian development.

Monitoring ovarian response of Booroola Assaf ewe lambs to PMSG, using ultrasonography and serum estradiol

Ovarian size was determined for 30-day-old ewe lambs treated with pregnant mare serum gonadotropin (PMSG; 1000 IU) using ultrasonography and was compared with direct measurement at laparotomy. Ultrasonography was found to be an accurate and reliable method for estimating ovarian size, and a significantly high correlation was found between the methods (R=0.96, P<0.01). Forty-eight hours following PMSG treatment, serum estradiol levels increased from below detectable levels to a value of 72.8+/-27.4 pg/ml (mean+/-SEM). A high correlation was found also between estradiol levels and ovarian size measured at laparotomy and by ultrasound, with a correlation coefficient of 0.94 and 0.80, respectively. It is suggested that a differential increase in ovarian size and estradiol secretion in immature ewe lambs treated with PMSG may reflect the different stages of ovarian development in individual animals. Noninvasive methods such as ultrasonography and measurements of serum estradiol may be utilized in the estimation of ovarian response.

Differential pituitary response to GnRH in pregnant Booroola-Assaf and Assaf ewes

Pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was examined at a late stage of pregnancy in 10 Booroola-Assaf ewes heterozygous at the FecB locus (FecBFec+) and in 11 Assaf ewes that were non-carriers (Fec+Fec+). Basal plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations were similar in the two genotypes. Administration of 100 micrograms of GnRH resulted in a significant increase (P < 0.05) in plasma LH and FSH concentrations in most of the ewes treated. Maximal responses were observed 105-135 min after GnRH treatment. Pituitary responses to GnRH were significantly lower (P < 0.05) in Booroola-Assaf than in Assaf ewes. The decreased pituitary responsiveness observed in FecB gene carriers compared with Fec+Fec+ ewes might be due to differences in the concentrations of ovarian or uterine hormones modulating the release of gonadotrophin. The results suggest that FecB-specific differences can be observed at the pituitary level.

Cardiomyopathy in cattle induced by residues of the coccidiostat maduramicin in poultry litter given as a feedstuff

An experimental feeding trial was conducted in order to substantiate an hypothesis on the aetiology of a previously unrecorded cardiomyopathic syndrome in beef cattle in Israel. It was believed that residues of the ionophore maduramicin (Cygro; American Cyanamid) in poultry litter fed to cattle, after the maduramicin had been incorporated into broiler feed as a coccidiostat, were the cause of the cardiomyopathy. Three groups of 5 heifers were fed for several weeks (1) poultry litter from a field case, containing 4.8 ppm maduramicin; (2) poultry litter to which maduramicin was added to give a concentration of 12 ppm; (3) poultry litter with no maduramicin (control). Clinical, biochemical, necropsy and histopathological findings showed that maduramicin residues are cardiotoxic, even at the lower level of maduramicin fed, which is commonly encountered in poultry litter in Israel.

Physico-chemical characterization of Intralipid emulsions

Fat emulsions containing soy triacylglycerols (100-300 g/l) and egg-yolk phospholipids (12 g/l) are often used for intravenous feeding. Previous studies have shown that these emulsions contain chylomicron-like emulsion particles of diameters of 300-400 nm and excess phospholipids aggregated as vesicles (liposomes), which remain in the infranatant upon floatation of the emulsion particles by ultracentrifugation. This work is devoted to the characterization of the commercial lipid emulsions commonly denoted Intralipids, with special emphasis on the presently ill-defined liposomes. The lipid particles composing commercial lipid emulsions (10%, 20% and 30% Intralipids, Kabivitrum Nutrition) were characterized by the combined use of physical and chemical methods. Each of the emulsions was fractionated by ultracentrifugation in saline into a 'cream' layer which floats to the top of the dispersion upon ultracentrifugation and a relatively transparent infranatant. The cream layer contains large emulsion particles of diameters ranging from 300 to 400 nm, in agreement with theoretical considerations based on their chemical composition as determined by chemical analysis. The infranatants contain about 1 g/l triacylglycerols in addition to phospholipids (from 7.2 g/l in 10% Intralipid to 2.4 g/l in 30% Intralipid) in the form of smaller particles of 70-100 nm diameter. Cryo-transmission electron microscopy shows that the infranatants contain vesicles (mostly unilamellar) at the side of residual small emulsion particles. This conclusion is also consistent with the distribution of phospholipids between outer and inner lamellae, as determined by 31P-NMR.

Eumycetoma caused by Curvularia lunata in a dog

Curvularia lunata was cultured from black granules found in granulomatous tumefactions excised from the subcutis of a three year old Medium Schnauzer dog. Draining sinuses were present in some of the tumefactions. Accordingly the diagnosis of eumycotic mycetoma was made. This diagnosis was confirmed by histopathological examination. During the four years following the first surgical intervention, several more similar tumefactions were excised on three different occasions. The dog died of chronic renal failure at the age of 8 years. There was no bone involvement or visceral diffusion of the fungus. The granules were examined by scanning electron microscopy. Immunoglobulins in the dog's serum, assessed by a qualitative test, proved to be equal to immunoglobulins in the serum of a control dog. Precipitating antibodies against C. lunata were not found. The dog was treated for 150 days with itraconazole. In spite of good initial results, recurrence of the fungal lesions were observed after the treatment's interruption. Further treatment with itraconazole for 45 days proved ineffective. No side effects of the drug were observed. This is, to the best of our knowledge, the first case in which C. lunata is identified as the causative agent of an animal eumycetoma.

Stability of mixed micellar systems made by solubilizing phosphatidylcholine-cholesterol vesicles by bile salts

Complete solubilization of phosphatidylcholine and cholesterol by bile salts in the form of stable mixed micelles requires that the effective ratio of bile salt/lipids in the mixed micelles (Re = ([bile salt] - critical micellar concentration)/([phosphatidylcholine] + [cholesterol]) will exceed a critical value. This equilibrium solubilizing ratio is an increasing function of the cholesterol/phosphatidylcholine ratio. In contrast, the concentration of sodium cholate required for solubilization of vesicles made of phosphatidylcholine and cholesterol does not increase by increasing the cholesterol/phosphatidylcholine ratio. Consequently, the latter solubilization procedure yields metastable mixed micelles whenever the cholate concentration is higher than that required for vesicle solubilization but lower than that needed for establishing a micellar equilibrium. These metastable mixed micelles undergo partial revesiculation to form cholesterol-rich vesicles that subsequently aggregate. Cholesterol crystallization appears to occur through its reorganization within these aggregated vesicles. The overall rate of the above series of processes increases sharply with the total lipid concentration and with the cholesterol/phosphatidylcholine ratio. The dependence of the rate on the effective ratio of bile salts/lipids is very complex: at any given ratio of cholesterol/phosphatidylcholine within the range of 0.3 to 0.5, increasing the cholesterol/phosphatidylcholine ratio requires higher cholate concentrations for the formation of stable mixed micelles (higher equilibrium solubilizing ratio). On the other hand, the metastable mixed micellar larsystems are long-lived whenever the effective ratio of cholate/lipids is lower than a critical value.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-clinical intramammary infection in lactating ewes and its association with clinical mastitis

A bacteriological survey for the study of non-clinical intramammary infection in the sheep udder was carried out in 88 Assaf ewes. A mean infection prevalence in the first few weeks of lactation was 55%. The most common bacterial isolates were Micrococcus spp. followed by coagulase negative staphylococcus, together accounting for 93% of the total number of isolates. An infection prevalence of 54% was found in ewelambs 2 days after their first lambing, indicating a marked new infection rate around lambing. Generally, the course of lactation was characterized by dynamic changes of new infection and spontaneous resolution. About 5% of half udders examined developed clinical mastitis. The comparison of bacteriological data from mastitic milk samples and from samples taken from the same half udders before the appearance of the clinical disease could not support the theory that in sheep, mastitis is a clinical exacerbation of a non-clinical intramammary infection.

Stability of mixed micellar bile models supersaturated with cholesterol

The maximal equilibrium solubility of cholesterol in mixtures of phosphatidylcholine (PC)1 and bile salts depends on the cholesterol/PC ratio (Rc) and on the effective ratio (Re) between nonmonomeric bile salts and the sum (CT) of PC and cholesterol concentrations (Carey and Small, 1978; Lichtenberg et al., 1984). By contrast, the concentration of bile salts required for solubilization of liposomes made of PC and cholesterol does not depend on Rc (Lichtenberg et al., 1984 and 1988). Thus, for Rc greater than 0.4, solubilization of the PC-cholesterol liposomes yields PC-cholesterol-bile salts mixed micellar systems which are supersaturated with cholesterol. In these metastable systems, the mixed micelles spontaneously undergo partial revesiculation followed by crystallization of cholesterol. The rate of the latter processes depends upon Rc, Re, and CT. For any given Rc and Re, the rate of revesiculation increases dramatically with increasing the lipid concentration CT, reflecting the involvement of many mixed micelles in the formation of each vesicle. The rate also increases, for any given CT and Re, upon increasing the cholesterol to PC ratio, Rc, probably due to the increasing degree of supersaturation. Increasing the cholate to lipid effective ratio, Re, by elevation of cholate concentration at constant Rc and CT has a complex effect on the rate of the revesiculation process. As expected, cholate concentration higher than that required for complete solubilization at equilibrium yields stable mixed micellar systems which do not undergo revesiculation, but for lower cholate concentrations decreasing the degree of supersaturation (by increasing [cholate]) results in faster revesiculation. We interpret these results in terms of the structure of the mixed micelles; micelles with two or more PC molecules per one molecule of cholesterol are relatively stable but increasing the bile salt concentration may cause dissociation of such 1:2 cholesterol:PC complexes, hence reducing the stability of the mixed micellar dispersions. The instability of PC-cholesterol-cholate mixed systems with intermediary range of cholate to lipids ratio may be significant to gallbladder stone formation as: (a) biliary bile contains PC-cholesterol vesicles which may be, at least partially, solubilized by bile salts during the process of bile concentration in the gallbladder, resulting in mixtures similar to our model systems; and (b) the bile composition of cholesterol gallstone patients is within an intermediary range of bile salts to lipids ratio.

Precipitation of calcium palmitate from bile salt-containing dispersions

Addition of calcium chloride to mixed micellar systems composed of sodium salts of palmitic acid and high concentrations of different bile acids results in precipitation of Ca(palmitate)2 only when the palmitate concentration exceeds a critical value, which is dependent on the concentrations of Ca2+, Na+ and bile salt, and on the type of bile salt used. All these dependencies, as well as the complex and interrelated effects of the various parameters on the kinetics of Ca(palmitate)2 precipitation are consistent with the following mechanism: (i) calcium binds to palmitate-bile salt mixed micelles and promotes their aggregation, at a rate governed by the concentration ratio between bound calcium and micelles (here denoted "binding ratio"). (ii) Ca(palmitate)2 precipitation occurs within the aggregate of micelles only if those micelles include sufficient amounts of Ca2+ and palmitate to allow for the formation of large enough crystal units of Ca(palmitate)2 which can serve as nucleation "seeds". Both the concentrations of micelles and Na+ have dual effects on the rate of precipitation. Increasing micelle concentration, by itself, accelerates aggregation but at the same time leads to a decrease of the binding ratio, thus reducing the rate of precipitation. Na+ which reduces the binding ratio through competitive binding also reduces the surface charge, thus assisting micelle aggregation. Our model also explains the facilitation of precipitation observed when phosphatidylcholine is contained in the palmitate-bile salt mixed micelles and the inhibitory effect of the water soluble bovine serum albumin.

On the solubility of calcium deoxycholate: kinetics of precipitation and the effect of conjugated bile salts and lecithin

In view of the low solubility of calcium deoxycholate and the possible induction of cholesterol precipitation in the gallbladder by calcium insoluble salts, we find it of interest to study the precipitation of calcium deoxycholate and its dependence on other bile components. The findings of these studies were as follows: (i) Precipitation of calcium deoxycholate from mixtures of calcium chloride and monomeric deoxycholate (at concentrations below the critical micelle concentration (CMC] is very slow even at relatively high CaCl2 concentrations (more than 20 days at 50 mM CaCl2). (ii) At higher deoxycholic acid (DOC) concentrations, precipitation of micellar DOC is faster and requires much lower calcium chloride concentrations. For any given calcium concentration, the rate of precipitation is maximal at an optimal DOC concentration. In solutions containing 150 mM NaCl, the maximal rate of precipitation occurs at about 10 mM DOC, almost independent of Ca2+ concentration. At lower ionic strength (10 mM NaCl), the optimal DOC concentration is 30 mM. These observations suggest that the most important factors in determining the rate of Ca(DOC)2 precipitation are (a) the ratio between calcium ions bound to the surface of a DOC micelle, and the [DOC] (the Ca2+/DOC binding ratio) and (b) the concentration of DOC micelles. (iii) In the presence of conjugated deoxycholates, the crystallization of calcium deoxycholate is inhibited. Phosphatidylcholine has a similar, although smaller, inhibitory effect. Upon precipitation of calcium deoxycholate from a mixed micellar system containing sodium deoxycholate, phosphatidylcholine and cholesterol, the latter two components spontaneously form vesicles. The anti-nucleating effect of PC and conjugated bile salts is explained in terms of "poisoning" of the crystallization process. In view of the latter results we conclude that under normal conditions calcium deoxycholate is not likely to precipitate in the gallbladder.

Clavulanate-potentiated amoxycillin: in vitro antibacterial activity and oral bioavailability in calves

The minimal inhibitory concentrations (MIC) of amoxycillin and clavulanate-potentiated amoxycillin (amoxycillin:clavulanic acid, 4:1 by weight) were compared for 171 Salmonella, 170 Escherichia coli, and 32 Pasteurella isolates recovered from infected neonatal calves. In the presence of clavulanic acid, the MIC of amoxycillin was reduced to levels less than or equal to 12.5 micrograms/ml for all the Salmonella group B, all the Pasteurella, and for 12 out of the 44 E. coli isolates which were resistant to amoxycillin (MIC greater than or equal to 100.0 micrograms/ml). For isolates sensitive to amoxycillin (MIC less than or equal to 1.56 microgram/ml) there was no change in MIC values in the presence of clavulanic acid. A small proportion of Salmonella and E. coli isolates were resistant to clavulanate-potentiated amoxycillin. In a cross-over trial involving 10 preruminant (2 weeks old) calves, amoxycillin trihydrate and clavulanate-potentiated amoxycillin were administered orally at 10 mg/kg. An analysis of serum amoxycillin level data showed that the pharmacokinetic parameters t1/2ab, Cmax, t1/2 beta, AUC, Cp degree, and f' (estimated drug absorption ratio) were the same after treatment with amoxydrate and clavulanate-potentiated amoxycillin. Administration of clavulanate-potentiated amoxycillin and probenecid resulted in elevation and prolongation of serum amoxycillin levels. Computations showed that in preruminant calves serum amoxycillin concentrations sufficient to inhibit sensitive pathogens can be maintained by oral clavulanate-potentiated amoxycillin treatment at 10 mg/kg TID. At two times that dose rate serum drug concentrations capable of inhibiting 50% of all types of pathogens examined can be maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacology of mecillinam in calves

The minimal inhibitory concentrations (MIC) of mecillinam, a novel beta-amidinopenicillanic acid derivative with unusual activity against Gram-negative bacteria, were compared with the MIC of cephazolin, cephalothin, amoxycillin, oxytetracycline, chloramphenicol, dihydrostreptomycin, neomycin, kanamycin, gentamicin and sulfadoxin/trimethoprim (TMP) against pathogenic Gram-negative bacteria recovered from neonatal calves. The MIC values of mecillinam ranged between 0.05 microgram/ml and 12.5 micrograms/ml, and the MIC90 values were 1.56 micrograms/ml and 3.12 micrograms/ml. The activity of mecillinam against salmonella, Escherichia coli and Pasteurella multocida was similar to or slightly greater than the activities of the first-generation cephalosporins, gentamicin and sulfa/TMP. Mecillinam concentrations less than or equal to 3.12 micrograms/ml inhibited the growth of the majority of isolates which were resistant (MIC90 greater than 100 micrograms/ml) to the other antibiotics studied. The minimum bactericidal concentration (MBC) values of mecillinam were two- to three-fold higher than the MIC values. The two-compartment open model was appropriate for the analysis of serum mecillinam concentrations measured after intravenous administration. The distribution half-life (t1/2 alpha) was 11.7 min, the elimination half-life (t1/2 beta) was 53.3 min, and the apparent volume of distribution (Vd (area)) and the distribution volume at steady state (Vd (ss)) were 0.568 and 0.896 l/kg, respectively. The drug was quickly absorbed after intramuscular (i.m.) injection; peak serum drug concentrations were directly related to the dose administered. They were obtained 30 min after treatment and the i.m. t1/2 was approximately 65 min.(ABSTRACT TRUNCATED AT 250 WORDS)