Effects of low density lipoproteins and mevinolin on cholesterol content and muscarinic cholinergic responsiveness in cultured chick atrial cells. Regulation of levels of muscarinic receptors and guanine nucleotide regulatory proteins

Cultures of myocytes from embryonic chick atria grown in medium supplemented with fetal calf serum from which lipoproteins had been removed demonstrated a nearly 10-fold increase in sensitivity of beating to the muscarinic cholinergic agonist carbamylcholine compared to cells grown with control serum. This effect was reversed by growth of cells in medium supplemented with lipoprotein-depleted serum (LPDS) reconstituted with the low density lipoprotein fraction from fetal calf serum. In cells grown in LPDS, total cell cholesterol was increased 32% over control levels and returned to control levels in cells grown with LPDS reconstituted with low density lipoprotein. Growth of cells in LPDS plus mevinolin, an inhibitor of endogenous cholesterol synthesis, also reversed the effects of LPDS on cholesterol content and sensitivity of beating to carbamylcholine. The ability of mevinolin (30 microM) to reverse the effect of LPDS on sensitivity of beating to carbamylcholine was inhibited by mevalonic acid, a metabolic precursor to cholesterol, with an IC50 of 7 x 10(-5) M. These data suggest that mevinolin reverses the effects of LPDS by altering cellular cholesterol levels. Enhanced responsiveness of embryonic chick heart cells to muscarinic stimulation was associated with a 2-fold increase in the number of muscarinic receptors with high affinity for agonist from 82 +/- 10 fmol/mg protein in media containing fetal calf serum to 175 +/- 12 fmol/mg protein in cells grown in the presence of LPDS. The distribution of receptors between high affinity (RH) and low affinity (RL) forms changed from 41% RH and 59% RL in cells grown in control serum to 66.5% RH and 33.5% RL in cells grown in LPDS. Quantitation of the effect of growth in LPDS on the levels of guanine nucleotide regulatory proteins No and Ni which couple the muscarinic receptor to a physiologic response, demonstrated that the relative levels of the 39-kDa alpha subunits of No and 41-kDa alpha subunits of Ni determined by ADP ribosylation with pertussis toxin and immunoblotting increased 2-fold compared to control cells grown with fetal calf serum. Growth of cells with medium supplemented with LPDS plus mevinolin reduced the levels of alpha 39 and alpha 41 to below the levels in control cells. Levels of the beta subunit of No and Ni were unaffected by growth with LPDS.(ABSTRACT TRUNCATED AT 400 WORDS)     

Genetic variation in immune parameters and associations to survival in Atlantic salmon

Lysozyme activity, haemolytic activity, total level of IgM, and levels of antibodies against A-layer from Aeromonas salmonicida and O-antigen from Vibrio salmonicida , respectively, were determined in 77 full-sib groups of Atlantic salmon in order to evaluate their possible use as immune parameters for indirect selection to improve disease resistance. Fish from parallel full-sib groups had previously been challenged with Aeromonas salmonicida (causing furunculosis), Renibacterium salmoninarum (causing bacterial kidney disease, BKD) and Vibrio salmonicida (causing cold-water vibriosis). Heritabilities were estimated for each of the immune parameters and correlations between the least square means of the full-sib groups for the different immune parameters and survival rates in the parallel full-sib groups were determined. A significant genetic variation in lysozyme activity was found, as well as an apparent genetic association between low lysozyme activity and high survival rates. Low heritabilities and low univariate correlations with survival in the full-sib groups were estimated for all of the other immune parameters. An analysis of the multivariate associations between the full-sib mean values of the complete set of immune parameters, and survival rates in the parallel full-sib groups in each of the challenge tests, revealed that, at low levels of lysozyme activity and with low antibody titres against V. salmonicida O-antigen, increased IgM levels seemed to increase survival from furunculosis.     

Qualitative and quantitative study of the growth and cell surface properties of Huntington's disease fibroblasts and age-matched controls

Summary Different growth-and cell surface properties of cells grown from skin biopsy samples from 25 Huntington's chorea patients, 22 at risk patients, and agematched controls were examined in a blind study. The number of explants obtained from each biopsy was carefully controlled. The nature (epithelial or fibroblastic) of the initial outgrowth was scored on all explants and the mean number of cells obtained from each explant after 3 weeks in culture was determined after trypsinization. During the next 15 passages, various parameters characterizing cell growth were studied. Maximal cell densities and growth rates were examined using a standard plating density of cells at each passage. These growth properties were also examined in three media: DME-NCS, DME-FCS, and Ham's F10 fetal calf serum (FCS). In addition, the effects of high temperature (40°C) and the addition of insulin to the medium on the growth and protein content of the cells was examined. These results, containing 152 measurements on 81 cases, were examined using a phased multivariate analysis. Blind cluster analysis showed that the clusters were nonrandomly determined. Factor analysis indicated the initial growth parameters to be among the most discriminating. Discriminant analysis, however, did not prove to be of any diagnostic use, since the external factors masked any possible genetic difference. Two possible sources of bias were identified: the size of the biopsy and the type of culture medium. The cell surface properties of HD and control fibroblasts were further investigated using two different techniques. The adhesion of single HD cells to either HD cell layers or normal cell layers revealed no significant differences. Intradermal immunization of rabbits with whole fibroblasts resulted, with both cell lines, in a polyspecific antiserum containing antibodies directed against a number of surface components. When HD and control fibroblasts were compared with the two antisera, no qualitative or quantitative differences in the precipitation patterns obtained using crossed immunoelectrophoresis, (CIE) were found. Our investigations did not allow us to discriminate HD cultures from controls by any of the qualitative and quantitative parameters tested.     

Reduction of lactic acid secreted from SV3T3 cells by a serum factor and biotin and its relationship to cell growth

Supplementation of media containing a low concentration (0.15–0.30% $\text{v}\text{>v}$) of calf serum with biotin or a low molecular weight serum growth factor (Peak III) reduces the amount of lactic acid secreted by simian virus 40-transformed 3T3 cells. While biotin and Peak III (which has been tentatively identified as biotin) can stimulate “stationary phase” cells to resume viable cell division, this growth promotion is not due to an alleviation of lactic acid toxicity per se. This conclusion is based on the finding that, although higher concentrations of lactic acid are cytotoxic, lactic acid added at concentrations found during “stationary phase” to cells plated in fresh medium is not growth inhibitory. These results suggest, instead, a possible major role for biotin and Peak III in energy production.     

Demographics of an Experimentally Released Population of Elk in Great Smoky Mountains National Park

ABSTRACT We assessed the potential for reestablishing elk (Cervus elaphus) in Great Smoky Mountains National Park (GSMNP), USA, by estimating vital rates of experimentally released animals from 2001 to 2006. Annual survival rates for calves ranged from 0.333 to 1.0 and averaged 0.592. Annual survival for subadult and adult elk (i.e., ≥ 1 yr of age) ranged from 0.690 to 0.933, depending on age and sex. We used those and other vital rates to model projected population growth and viability using a stochastic individual-based model. The annual growth rate (λ) of the modeled population over a 25-year period averaged 0.996 and declined from 1.059 the first year to 0.990 at year 25. The modeled population failed to attain a positive 25-year mean growth rate in 46.0% of the projections. Poor calf recruitment was an important determinant of low population growth. Predation by black bears (Ursus americanus) was the dominant calf mortality factor. Most of the variance of growth projections was due to demographic variation resulting from the small population size (n = 61). Management actions such as predator control may help increase calf recruitment, but our projections suggest that the GSMNP elk population may be at risk for some time because of high demographic variation.     

Proteolytic enzymes and arachidonic acid metabolites produced by MRC-5 cells on various microcarrier substrates

Summary Human diploid fibroblasts were cultured on microcarriers made from DEAE-dextran, denatured collagen, DEAE-dextran linked to denatured collagen, and glass. Cells grown on these four substrates were examined for the production of proteolytic enzymes and arachidonic acid metabolites. Culture fluids from cells grown on the DEAE-dextran microcarriers contained the highest amounts of proteolytic enzyme activity. Both plasminogen-independent and plasminogen-dependent fibrinolytic activities were present and the plasminogen-dependent activity seemed to result from the presence of both urokinase and tissue plasminogen activator. Culture fluid from the cells grown on the glass microcarriers contained the least amount of protease activity, and nearly all of the plasminogen-activator activity seemed to be of the urokinase type. Protease activity in the culture fluids of cells grown on the other two substrates were intermediate. With regard to arachidonic acid metabolites, cells grown on the DEAE-dextran microcarriers produced the highest amounts of cyclooxygenase products but very low levels of lipoxygenase metabolites. Cells grown on the other three substrates produced comparable amounts of various cyclooxygenase products (lower than that produced by cells on the DEAE-dextrans substrate). Cells grown on the glass microcarriers also produced detectable amounts of two lipoxygenase metabolites—leukotriene B₄ and leukotriene C₄. Inasmuch as both proteolytic enzymes and arachidonic acid metabolites regulate basic cell properties, the differential amount of these metabolites observed in the culture fluids on the various substrates may contribute to the biological differences that exist on these substrates. This study was supported in part by grants R44 CA 36656 and IK08HL01332-01 from the Public Health Service, U. S. Department of Health and Human Services and by grant BC-512 from the American Cancer Society. JDH is a research fellow of the American Lung Association.     

Combined ACTH and glucocorticoid treatment improves survival and organ maturation in premature newborn calves

Glucocorticoids play an important role in prenatal organ maturation in many species. In humans, maternal treatment with synthetic glucocorticoids improves neonatal adaptation of prematurely born infants. In cows, pre-term calf survival is improved following a single maternal glucocorticoid administration. We hypothesized that stimulation of endogenous cortisol secretion by adrenocorticotropin (ACTH) treatment combined with maternal dexamethasone treatment, would be even more efficient in stimulating organ maturation in the prematurely delivered calf. Three groups of premature calves were delivered by caesarian section at 90% of gestation length from dams which were either untreated or injected with dexamethasone before delivery, combined with either prenatal or postnatal ACTH treatment to the calf. During the first 24h after birth, thermoregulation, blood chemistry, liver values and organ weights were recorded. In the untreated calves, survival was significantly correlated with blood oxygenation, sodium and calcium levels at the moment of birth. There were marked maturational effects of the treatments on body temperature regulation, blood acid-base status, oxygenation, glucose, insulin, IGF-1 levels, weight of the heart, liver, gastrointestinal tract and thymus weight. For many of the measured metabolic, endocrine and organ weight parameters, the intrauterine ACTH treatment was associated with improved values relative to the postnatal ACTH treatment, which appeared to have no immediate effect on calf viability. In conclusion, the premature calf delivered by caesarian section at 90% of gestation length showed blood chemistry, metabolic, endocrine and organ growth characteristics that indicated severe prematurity. However, the maturation of organ function in newborn premature calves following maternal glucocorticoid injections was further enhanced if is was preceded by intra-fetal injections of ACTH.     

Growth stimulation of Escherichia coli in serum by iron(III) aerobactin. Recycling of aerobactin

Abstract Growth of wild-type strains and K-12 derivatives of Escherichia coli in calf serum was strongly enhanced by the iron(III) aerobactin supply system specified by certain ColV plasmids. Aerobactin was superior over enterochelin in stimulating growth. In contrast to enterochelin and ferrichrome, aerobactin seemed not to be hydrolyzed or modified during delivery of iron to cells.     

Genetic differentiation and phenotypic plasticity in Plantago major ssp major. I. The effect of differences in level of irradiance on growth, photosynthesis, respiration and chlorophyll content

Growth, root respiration, photosynthesis, dark respiration, chlorophyll content and chlorophyll alb ratio were followed in two genotypes of Plantago major L. ssp major L., originating from an exposed and a shaded habitat, respectively, at two levels of irradiance. In addition, responses of these processes to a transfer of plants from one light condition to the other were studied. Genetic differentiation between the two genotypes was reflected in growth rate, photosynthetic activity, dark respiration and chlorophyll content. Individuals of the genotype originating from a shaded habitat were less inhibited by low irradiance: growth was less depressed at low irradiance, while the genotype of the exposed habitat seemed to be more restricted to exposed conditions. The adaptive plastic response of growth and physiological parameters upon an alteration in irradiance was very small. The shoot to root ratio was a stable plant characteristic in these experiments. Plants of both genotypes were probably damaged after a transfer from the low to the high level of irradiance; the growth of these plants was not stimulated by high irradiance, and the photosynthetic activity was even decreased. Plants, which were transferred to the low level of irradiance, showed an immediate effect of the change and no adaptive response was observed. Obviously, the ability to perform adaptive plastic responses, which was demonstrated in the non-transferred plants after pretreatment, had been lost during the experiment and was confined to the seedling stage of individuals of the two genotypes.     

Na<Superscript>+</Superscript> gradient-dependent transport of hypoxanthine by calf intestinal brush border membrane vesicles

The properties of hypoxanthine transport were investigated in purified brush border membrane vesicles isolated from calf proximal and distal jejunum. Hypoxanthine uptake in the vesicles was stimulated by a transmembrane Na(+) gradient and an inside negative potential resulting in a transient accumulation of intravesicular hypoxanthine, especially in the proximal jejunum. Na(+)-dependent hypoxanthine uptake at this site seemed to occur by two saturable transport systems, a high affinity (K(m)=0.33 micromol/l) and a low affinity (K(m)=165 micromol/l) transporter. Guanine, hypoxanthine, thymine and uracil inhibited intravesicular hypoxanthine uptake, whereas adenine and the nucleosides inosine and thymidine were without effect. These findings represent the first demonstration of active Na(+) gradient-dependent nucleobase transport in intestinal brush border membrane vesicles.     

Routine heat inactivation of serum reduces its capacity to promote cell attachment

Summary Heat inactivation (56°C for 40 min) of bovine calf serum was shown to diminish its capacity to promote the attachment of cells to plastic or glass surfaces. This effect was not observed in stationary cultures (culture dishes) but became manifest under conditions in which the cells were subjected to a small amount of liquid shear force, i.e. by growing cells in roller bottles or culture tubes. Of four cell lines tested on bovine calf serum (SV-BHK, BALB-3T3, CV-1, and FS-4) SV-BHK and CV-1 cells showed the greatest sensitivity to loss of attachment-promoting activity. Fetal bovine serum also seemed to be affected by heat inactivation but to a lesser degree than bovine calf serum. Treatment of vessel surfaces with either unheated calf serum or specific attachment factors (gelatin, poly-d-lysine, and fibronectin) greatly increased cell attachment in the presence of heat inactivated serum. Heat inactivation did not seem to affect the ability of cells to grow after attachment. Of the four cell lines tested, the normal human fibroblast line (FS-4) was shown to be most effective at conditioning medium and restoring its capacity to promote the attachment of all four cell lines. This research was supported in part by VECOL, Inc., Bogata, Columbia and by grant SRC 5 U24 RR02557-02 from the National Institutes of Health, Bethesda, MD.     

The effect of calf jacket usage on performance,behaviour and physiological responses of group-housed dairy calves

Poor performance and ill-health of calves in the pre-wean period can affect future productivity. Increasing numbers of producers are opting to use calf jackets as a means of mitigating the potential negative effects of low ambient temperatures, wind speed and precipitation on growth and health. This study aimed to use a range of noninvasive monitoring technologies to investigate the effects of using calf jackets in the first 3 weeks of life on calf performance and behavioural and physiological parameters. Ninety Holstein-Friesian calves were allocated to one of the two treatments: (i) Jacketed until 21 days of age and (J; n = 44) ii. Nonjacketed (NJ; n = 46). Calves were group housed and fed milk replacer (MR) and concentrate solid feed via automatic feeders. Calves were weaned at day 56, and the experiment was completed at day 63. Health assessments were conducted on a daily basis throughout the experiment using predefined faecal and respiratory scoring protocols. A range of novel, noninvasive monitoring technologies were used to examine the activity, heart rate and thermal profiles of calves on an individual basis throughout the experimental period. There were no differences in calf live weight (LWT), average daily gain (ADG) or feed conversion efficiency (FCE) in J and NJ calves between days 5 to 20. However, NJ calves consumed more MR and had more unrewarded visits to the milk feeder than J calves during this period. Although calf LWT was comparable across treatments in the week following jacket removal (days 21 to 28), both ADG and FCE tended to be greater in NJ calves. There were no treatment differences in calf LWT at the end of the study (d63). When measured over a period of 24 h and at a mean ambient temperature of 7.7°C, skin surface temperature was 6.37°C higher in J calves. Core body temperature was higher in J calves between days 5 to 20; however, there were no differences in IR eye or IR rectal temperature. No differences in lying behaviour occurred, with calves spending 18 and 17 h/day lying between days 5 to 20 and days 21 to 28, respectively. Under the climatic and management conditions described, no significant benefits to calf performance were found as a result of the provision of calf jackets to group-housed calves in the first 3 weeks of life. The higher frequency of unrewarded visits to the milk feeder in NJ calves during the first 3 weeks of life could be suggestive of a lack of satiety in these calves.     

Divergence for residual feed intake of Holstein-Friesian cattle during growth did not affect production and reproduction during lactation

Residual feed intake (RFI) is the difference between actual and predicted dry matter intake (DMI) of individual animals. Recent studies with Holstein-Friesian calves have identified an ~20% difference in RFI during growth (calf RFI) and these groups remained divergent in RFI during lactation. The objective of the experiment described here was to determine if cows selected for divergent RFI as calves differed in milk production, reproduction or in the profiles of BW and body condition score (BCS) change during lactation, when grazing pasture. The cows used in the experiment (n=126) had an RFI of −0.88 and +0.75 kg DM intake/day for growth as calves (efficient and inefficient calf RFI groups, respectively) and were intensively grazed at four stocking rates (SR) of 2.2, 2.6, 3.1 and 3.6 cows/ha on self-contained farmlets, over 3 years. Each SR treatment had equal number of cows identified as low and high calf RFI, with 24, 28, 34 and 40/11 ha farmlet. The cows divergent for calf RFI were randomly allocated to each SR. Although SR affected production, calf RFI group (low or high) did not affect milk production, reproduction, BW, BCS or changes in these parameters throughout lactation. The most efficient animals (low calf RFI) lost similar BW and BCS as the least efficient (high calf RFI) immediately post-calving, and regained similar BW and BCS before their next calving. These results indicate that selection for RFI as calves to increase efficiency of feed utilisation did not negatively affect farm productivity variables (milk production, BCS, BW and reproduction) as adults when managed under an intensive pastoral grazing system.     

Comparison of growth curves of mice selected and unselected for postweaning gain

Summary Mice were sampled from a line selected for increased postweaning weight gain from three to six weeks and from a randombred control line originating from the same base population. Body weights were recorded at each of 14 ages from day 5 to day 98. The Richards and logistic growth functions were fitted to the growth trajectories of each individual mouse by a generalized non-linear least squares procedure. Estimated growth parameters (asymptotic weight, rate, shape of curve, age and weight at inflection, mean absolute growth rate and mean relative growth rate) were computed for each individual. The effects of line, litter within line, sex and line × sex interactions on these estimated parameters were then studied.Both the Richards and logistic functions fitted the data equally well and the plotted trajectories coincided over most of the growth curve. There was excellent agreement between the estimates of asymptotic weight and both age and weight at inflection based on the different functions. However, both functions apparently underestimated the asymptotic weight.Analyses of the line differences showed that selection for postweaning gain increased the mean absolute growth rate over the entire curve but had no effect on the relative growth rate or the shape of the growth curve. Full-sib analyses suggested the presence of considerable genetic variation and some high genetic correlations among the estimated growth parameters.Paper number 2942 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. This research was supported in part by Public Health Service Research Grant GM 11546. Computing services were supported by NIH Grant FR-00011.     

Glutamine-limited batch hybridoma growth and antibody production: experiment and model

The influence of glutamine (a major energy source) on both hybridoma growth and monoclonal antibody production was examined. A series of batch experiments were performed in T-flasks containing initial glutamine levels ranging from 0.5 to 4.0 mM in RPMI 1640 with 20% v/v fetal calf serum. The maximum final cell concentration increased with initial glutamine levels in the range of 0.5-2 mM; further glutamine increases had little or no effect. Earlier studies in our laboratories demonstrated that serum component(s) strongly influence the maximum specific growth rate. Here, the present studies reveal also the stoichiometric limitation by glutamine in the later stages of growth when its concentration is drastically reduced. For 0.5 to 1.5 mM initial glutamine, complete substrate utilization coincided with the cessation of cell growth and the onset of the death phase. For initial glutamine concentrations higher than 2.0 mM, growth halted prior to glutamine exhaustion, presumably because serum or RPMI component(s) were exhausted. The specific antibody secretion rate was essentially non-growth-associated above a critical low glutamine concentration in both the growth and death phases. At or below this critical value, an apparent emergence of stoichiometnc or energy limitation resulted in a dramatic drop in the secretion rate to zero. A simple unstructured model was developed that simulates these trends well. All parameters were determined using only subsets of the data. Nevertheless, these parameter values provided simulations in good agreement with all the glutamine-limited cultures.     

Effects of nutritional stress during lactation on immunity costs and indices of future reproduction in Iberian red deer (Cervus elaphus hispanicus)

Nutrition may affect the balance between immunity and traits such as reproduction or growth. This study examines the effect of low nutrient availability on immunity indices and lactation in captive Iberian red deer. Twelve hinds and their calves were allotted to a food-restricted (50-60% daily energy requirements) or a control group just after calving. Low calorie intake exerted a greater effect on the immunity of calves than on that of hinds. Whereas no difference was found for hinds, calves of the low intake group showed mean immunoglobulin (Ig) levels higher than those on a standard diet, which suggests that Ig level may indicate the level of fighting against pathogens. Serum indices of body condition in calves showed generally positive correlations with milk nutrient production. In contrast, Ig level within each group showed a pattern inverse to that of the other group for early lactation: in the standard diet group, the greater the milk nutrient produced and calf growth, the lower the Ig level; this relationship was inversed in the low-nutrition group. These results suggest that, on a standard diet, high Ig levels may indicate high levels of pathogen fighting paired to poorer body condition. Inversely, once the first barriers of innate immunity are surpassed, only those calves on the low-nutrition group with greater resources would be able to spend more resources to fight infection. Thus, low calorie intake might boost its slowing effect on growth by increasing the costs of infection fighting.     

Effects of black bear relocation on elk calf recruitment at Great Smoky Mountains National Park

Previous research from 2001 to 2006 on an experimentally released elk (Cervus elaphus) population at Great Smoky Mountains National Park (GSMNP or Park) indicated that calf recruitment (i.e., calves reaching 1 yr of age per adult female elk) was low (0.306, total SE = 0.090) resulting in low or negative population growth (λ = 0.996, 95% CI = 0.945–1.047). Black bear (Ursus americanus) predation was the primary calf mortality factor. From 2006 to 2008, we trapped and relocated 49 bears (30 of which were radiocollared) from the primary calving areas in the Park and radiomonitored 67 (28 M:39 F) adult elk and 42 calves to compare vital rates and population growth with the earlier study. A model with annual calf recruitment rate correlating with the number of bears relocated each year was supported (ΔAIC_c = 0.000; β = 0.070, 95% CI = 0.028–0.112) and a model with annual calf recruitment differing from before to during bear relocation revealed an increase to 0.544 (total SE = 0.098; β = −1.092, 95% CI = −1.180 to −0.375). Using vital rates and estimates of process standard errors observed during our study, 25-yr simulations maintained a mean positive growth rate in 100% of the stochastic trials with λ averaging 1.118 (95% CI = 1.096–1.140), an increase compared with rates before bear relocation. A life table response experiment revealed that increases in population growth were mostly (67.1%) due to changes in calf recruitment. We speculate that behavioral adaptation of the elk since release also contributed to the observed increases in recruitment and population growth. Our results suggest that managers interested in elk reintroduction within bear range should consider bear relocation as a temporary means of increasing calf recruitment. © 2011 The Wildlife Society.     

Serum glucocorticoids have persistent and controlling effects on insulinlike growth factor i action under serum-free assay conditions in cultured human fibroblasts

Summary The biological actions of insulinlike growth factor I (IGF-I) measured under serum-free assay conditions were found to be significantly influenced by prior subculture conditions for adult human fibroblasts. Glucocorticoids seemed to be the major medium variable affecting IGF-I action. IGF-I added to serum-free cultures had little or no effect on [¹⁴C]aminoisobutyric acid uptake or [³H]thymidine incorporation in human fibroblasts previously maintained in media containing serum with low glucocorticoid levels or in serum stripped of endogenous steroids. However, a 48-h preincubation with dexamethasone resulted in a marked synergistic increase in IGF-I stimulation of [¹⁴C]aminoisobutyric acid uptake and [³Hthymidine incorporation in these cultures. In contrast, IGF-I in serum-free medium seemed to be a potent mitogenic and metabolic stimulus for human fibroblasts which had been subcultured in media with a high glucocorticoid content, either endogenous, or supplemented. After these culture conditions, a 48-h preexposure to dexamethasone had no further enhancing effect on IGF-I action. Dexamethasone also potentiated IGF-I, insulin, and epidermal growth factor stimulation of fibroblast replication depending on the earlier subcultivation conditions. Thus, glucocorticoids are important modulators of IGF-I bioactivity in cultured human fibroblasts. Serum glucocorticoids can exert a profound influence on the biological phenomena measured in cell culture, even when the serum has been removed before the actual experiment, and must be carefully taken into account for accurate evaluation of the biological function of IGF-I and other growth factors. This work was supported in part by grants DK28229, DK36054, CA42106, RCDA01275, and DK24085 from the National Institutes of Health, Bethesda, MD.     

新生牛肝中低分子抑瘤物影响白血病细胞生长的实验研究

新生牛肝经匀浆、离心和分级超滤后,得到分子量≤1.0kDa的、耐热的成分——新生牛肝抑瘤物(new-bom calfliver suppressor,BLS-1)。对BLS-1的生物学活性进行了检测,结果表明在体外液体和半固体琼脂培养条件下,它对人和小鼠白血病细胞系(如HL-60、L833 和 P388 等)的生长均有明显的抑制作用,并存在着一定的量效关系;与同样条件下BLS-1对人和小鼠正常粒-巨噬系祖细胞的抑制作用相比较,BLS-1对白血病细胞生长的抑制作用具有较强的选择性。进一步观察了BLS-1对5例急性非淋巴细胞白血病病人骨髓的原代白血病细胞集落(leukemic blast progenitor,L-CFU)生成的影响,结果表明,当BLS-1的浓度达到500μg/ml时,L-CFU的生成受到明显抑制。上述研究结果提示,在新生牛肝中可能存在类似于人胎儿肝脏中的一类低分子天然抑瘤物。     

Beef cow reproduction as affected by postpartum nutrition and temporary calf removal

Data were collected on 306 multiparous cows over a 3-yr period (1984-1986) to evaluate the effect of postpartum nutrition and temporary calf removal on reproductive performance. All cows calved in a body condition score (BCS) of >/= 5 and were randomly allotted at parturition to an experiment with a 2 x 2 factorial arrangement of treatments. The factors consisted of high or low-flush levels of postpartum nutritional management, with or without temporary calf removal for 48 h prior to the breeding season. The high diet contained 26.0 Mcal metabolizable energy. The low regimen of the low-flush diet contained 14.7 Mcal metabolizable energy, with the flushing regime consisting of a diet of 36 Mcal metabolizable energy. The flushing diet was offered 2 wk prior to breeding through the first 30 d of breeding. Interval to estrus was 45 and 44 d for high and low-flush, respectively (P>0.05), while interval to estrus with temporary calf removal and without temporary calf removal was 47 and 42 d, respectively (P<0.05). Means for the cumulative percent in estrus at 20, 40 and 60 d of breeding, respectively, were high, 93, 97 and 98; low-flush, 95, 96 and 98; with temporary calf removal, 92, 96 and 99; and without temporary calf removal, 96, 97 and 98 (P>0.05). Interval to pregnancy was 81 and 82 d for high and low-flush, respectively (P>0.05), while interval to pregnancy with temporary calf removal and without temporary calf removal was 82 and 81 d, respectively (P>0.05). Cumulative percentages of animals pregnant at 20, 40 and 60 d of breeding, respectively, were high, 59, 83 and 91; low-flush, 59, 80 and 90; with temporary calf removal, 58, 83 and 91; and without temporary calf removal, 60, 80 and 90 (P>0.05). Calf performance in response to dam nutrition and temporary calf removal was not affected at weaning or at intervals prior to weaning (P>0.05). Interactions between nutrition level and removal of calf factors were not significant (P>0.05) for any of the parameters measured. The data suggest cows calving in BCS >/= 5 have equivalent reproductive performance whether receiving high levels of energy postpartum or low levels of energy early postpartum, followed by a flushing diet fed immediately proceeding and continuing through the first 30 d of breeding. No beneficial effect of temporary calf removal was observed for cows calving with BCS >/= 5.