Growth of Corynebacterium bovis in mammary secretions during physiological transitions of the bovine mammary gland

An in vitro microassay was used to evaluate growth of five strains of Corynebacterium bovis in mammary secretions collected from quarters of five Holstein cows at 0, 14, and 28 d of involution, at parturition, and 14 d after parturition. Variation in growth among different strains of Corynebacterium bovis was observed. Corynebacterium bovis grew well in mammary secretions obtained at the last milking of lactation, at parturition, and 14 d after parturition. However, growth of four strains of Corynebacterium bovis in mammary secretions obtained at 14 and 28 d of involution was reduced significantly. In contrast, a streptomycin-resistant strain of Corynebacterium bovis grew well in mammary secretions obtained during involution. These data suggest that mammary secretions support growth of Corynebacterium bovis during lactation but inhibit growth during the nonlactating period. Inhibition of growth in secretions collected during the nonlactating period may be associated with the high rate of spontaneous elimination of Corynebacterium bovis intramammary infection from cessation of milking to parturition. Conversely, enhanced growth in milk may be related to persistent Corynebacterium bovis intramammary infections during lactation.     

Modulation of bovine mononuclear cell proliferation during physiological transitions of the mammary gland

Mammary secretions and blood were collected from five primiparous Holstein cows 14 d following cessation of milking and 14 d prior to parturition for preparation of serum and mammary secretion skim fractions. Mammary secretions and blood were collected from the same animals 15 to 18 d following cessation of milking and 2 to 13 d prior to parturition for isolation of mononuclear cells. Effects of serum on mammary gland mononuclear cell proliferation and skim fractions from mammary secretions on blood mononuclear cell proliferation were evaluated. Mononuclear cell proliferation was evaluated in a mitogen-induced lymphocyte proliferation assay and in a mixed leukocyte assay. Proliferative responses of blood and mammary gland mononuclear cells did not vary significantly between the two time periods evaluated. Mammary secretion skim fractions obtained at both time periods significantly suppressed blood mononuclear cell proliferation. In contrast, exogenous serum enhanced mammary gland mononuclear cell proliferation in response to mitogens and allogeneic cells. Ability to enhance in vitro proliferation of mammary mononuclear cells isolated during physiological transitions of the mammary gland may suggest the potential for enhancing mammary mononuclear cell proliferation in vivo to reduce incidence of new intramammary infections at times when the mammary gland is highly susceptible.     

Thymidine incorporation by lactating mammary epithelium during compensatory mammary growth in beef cattle

Ten Hereford cows, 100 d into first lactation, were assigned to treatment or control groups to study compensatory growth of mammary glands. The right udder half of treatment cows was covered to prevent suckling by the calf, whereas control cows were suckled on all quarters. Milk production was estimated the day treatment began and 4 d later by machine milking following removal of calves for 12 h and i.v. injection of oxytocin. Five to 7 d after beginning treatment, cows were killed and mammary tissue was obtained from three regions within left and right glands for in vitro incubation with [3H]thymidine. Deoxyribonucleic acid of lactating udder halves did not increase in response to treatment although RNA: DNA ratio and milk production tended to increase. Incorporation of [3H]thymidine was greater in lactating quarters of treated cows than control cows (35,000 vs. 19,000 cpm/mg of DNA) with greatest incorporation in the basal regions of each gland. Furthermore, greatest incorporation of [3H]thymidine occurred in non-suckled glands. Autoradiographic analyses confirmed incorporation data and indicated that 81% of proliferating cells were epithelial. Data suggest that proliferation of mammary epithelial cells, within both the lactating and nonlactating glands, occurred in response to milk stasis.     

Phosphorylation of casein by the lactating mammary gland: a review.

The lactating mammary gland synthesizes and secretes large amounts of phosphoproteins that mainly are associated with the casein fraction of milk. The free amino acids and inorganic phosphate of blood serve as building materials for casein, and the final product appears in milk as a colloidal-sized particle, the casein micelle. According to our present concept, the biosynthesis of casein occurs in two steps: synthesis of the polypeptide chain, followed by phosphate addition. Phosphate groups are transferred to the nascent casein by a protein kinase localized in the Golgi apparatus. The enzyme uses adenosine 5'-triphosphate as the phosphate donor and requires divalent cations. Neighboring amino acids may be important in determining which serine residues in casein are phosphorylated. This review discusses historical and current research on the phosphorylation of casein.     

四川泡菜发酵过程中大肠杆菌消长规律的定量系统评价

目的探究四川泡菜发酵过程中大肠杆菌的消长规律。方法根据相关关键词在CNKI数据库中检索相关文献。对检索结果 13篇文献的50批次四川泡菜发酵过程中大肠杆菌消长数据进行定量系统评价。结果四川泡菜发酵过程中,大肠杆菌在数量上大体呈现为前升后降的动态变化模式;尽管乳酸菌生长及发酵产酸总体上对大肠杆菌产生抑制作用,但发酵过程中的多种参数和因素对大肠杆菌的消长具有显著影响。此外,泡菜发酵中,大肠杆菌数量的峰值与初始值之间有显著的正向相关关系;而发酵温度与泡菜发酵中大肠杆菌消失时间之间呈现反向相关关系。结论本研究可为进一步探讨四川泡菜发酵对大肠杆菌的抑制机制及风险评估提供参考。     

Effect of recombinant cytokines on leucocytes and physiological changes in bovine mammary glands during early involution

We examined the effects of administering recombinant bovine cytokines to non-lactating dairy cows and measured mammary gland leucocytes and the involution process. After the final milking, groups of cows were given an intramammary infusion of cytokine in two quarters. These cytokines were recombinant bovine interleukin-2 (rbolL-2) (2 x 10(5) units, n = 6), recombinant bovine granulocyte-macrophage colony stimulating factor (rboGM-CSF) (500 microg, n = 4) and recombinant bovine interleukin-1beta (rbolL-1beta) (10 microg, n = 10). Each animal also received an infusion of phosphate-buffered saline (PBS) in the other two quarters as controls. The rbolL-2 and rboGM-CSF were produced in a yeast expression system, while rbolL-1beta was produced in Escherichia coli. Leucocyte numbers, bactericidal activity of leucocytes, and concentrations of citrate and lactoferrin in quarter secretion samples were monitored after infusion of cytokine or PBS. Infusion of rbolL-2 had minimal effect on leucocyte numbers and concentrations of citrate and lactoferrin. Both rboGM-CSF and rbolL-1beta induced a rapid increase in the number of neutrophils and macrophages compared with control PBS quarters. Concentrations of lactoferrin in secretions were increased by rboGM-CSF and rbolL-1beta compared with control PBS quarters. In addition, infusion of glands with rbolL-1beta lowered the citrate:lactoferrin molar ratio compared with PBS control quarters. The results indicate that intramammary infusion of either rboGM-CSF or rbolL-1beta at cessation of milking immediately increased the number of phagocytic cells in the gland. These cytokines, in particular rbolL-1beta, also increased the rate of mammary gland involution during the early dry period.     

根皮素的制备、结构修饰及生理活性研究进展

根皮素是属于黄酮类中的二氢查尔酮类化合物,具有抑菌、抗氧化和抗酪氨酸酶等一系列生物活性,在食品、药品、化妆品等领域中均有巨大的应用前景。目前研究多集中在根皮素的制备、结构修饰、生物活性及机理研究方面,针对根皮素研究的综述较少。因此,该文在参考国内外研究文献的基础上,对根皮素的制备,包括从天然产物中提取分离、化学法半合成及全合成制备、生物合成;化学结构修饰,如酯化修饰、醚化修饰以及缩合反应等;生物活性,包括抗氧化、抑制肿瘤细胞增殖、免疫抑制及抗炎等及其作用机制等方面进行了综述,并对目前根皮素开发研究中面临的问题及对策进行了探讨。以期为未来根皮素的研究应用提供参考借鉴。     

Hormones, mammary growth, and lactation: a 41-year perspective

When I was a beginning graduate student 41 yr ago it had been established that estrogen caused mammary duct growth; a combination of estrogen and progesterone was required for lobule-alveolar development of the mammary glands; and prolactin and growth hormone were essential for mammary growth. In laboratory species exogenous prolactin, glucocorticoids, and estrogen would initiate secretion of milk provided the mammary glands had a well-developed lobule-alveolar system. It was not known with certainty that progesterone inhibited the process. For some species, prolactin and thyroxine had been shown to stimulate lactation, while glucocorticoids suppressed lactation. Definitive roles for growth hormone and insulin during lactation had not been established. Studies of hormonal control of mammary growth and function in cattle were few. In vitro methods to study hormonal regulation of the mammary glands were in their infancy. Quantitative measures of changes in mammary cell numbers and specific components of milk in response to hormones were rare. The concepts for quantification of hormone concentrations, hormone receptors, growth factors, and binding proteins in blood; hormonal regulation of nutrient partitioning; and hormonally induced mechanisms of action within mammary cells were waiting to be discovered. And eventually they were. However, lest we become too enamored with our current understanding of the hormones that control mammary growth and lactation, it remains a fact that the greatest physiological stimulus for milk yield is pregnancy, not some cocktail of exogenous hormones, growth factors, receptor agonists/antagonists, or gene therapies. Viva la mom!     

In vitro growth of enterococci of bovine origin in bovine mammary secretions from various stages of lactation

In vitro growth responses of Enterococcus faecium and Enterococcus faecalis were tested in cell-free, fat-free bovine mammary secretions. Mammary secretions were collected during the dry period, and during early, late, and extended lactation. Sixty-three enterococcal isolates from aseptically collected bovine quarter milk samples and bedding samples from a commercial dairy herd were tested. Isolates from bovine quarter milk samples originated from mammary glands with clinical mastitis, cows with composite somatic cell score >4, postpartum milk samples, or from routine milk samples submitted to a mastitis diagnostic laboratory. Source of enterococcal isolates and the species significantly contribute to the ability of organisms to multiply in mammary secretions from various stages of lactation. Isolates collected from milk samples of the commercial herd and isolates from milk submitted to a mastitis diagnostic lab did not display enhanced growth in mammary secretions compared with isolates from bedding. Growth responses of E. faecalis were greater than those for E. faecium in secretions collected during the dry period, late lactation, and extended lactation. Bacterial growth did not differ between enterococcal species in mammary secretion collected from cows in early lactation. Differences in bacterial growth between E. faecalis and E. faecium in mammary secretions may indicate differences between species in susceptibility of mammary glands during the lactation cycle.     

Mammary-derived growth inhibitor protein and messenger ribonucleic acid concentrations in different physiological states of the gland.

Expression of mammary-derived growth inhibitor in tissue from lactating and involuting bovine mammary glands was investigated. Seventeen lactating, pregnant (220 to 272 d in gestation) cows were divided in two groups of 8 and 9 cows each. Cows of the first group were slaughtered while in lactation. Cows of the second group (9 involuting cows) were slaughtered at 13 to 52 d following sudden cessation of milking. High concentrations of mammary-derived growth inhibitor (.63% of the total protein) were detected in mammary tissue of lactating cows. Mammary-derived growth inhibitor (less than .10% of the total protein) was dramatically reduced during most of the involution period (13 to 45 d following cessation of milking). Mammary-derived growth inhibitor was again detected (.28% of the total protein) during the last stage of the involution (46 to 53 d after cessation of milking), which coincided with colostrum formation. When steady state concentrations of mammary-derived growth inhibitor mRNA were examined, the results obtained mirrored those obtained at the protein concentration. These data suggest that regulation of mammary-derived growth inhibitor occurs via modulation of the steady state concentration of its mRNA. Furthermore, there is a strong correlation between mammary-derived growth inhibitor expression and lactation in dairy cows.     

Black pepper and its pungent principle-piperine: a review of diverse physiological effects

Black pepper (Piper nigrum) is one of the most widely used among spices. It is valued for its distinct biting quality attributed to the alkaloid, piperine. Black pepper is used not only in human dietaries but also for a variety of other purposes such as medicinal, as a preservative, and in perfumery. Many physiological effects of black pepper, its extracts, or its major active principle, piperine, have been reported in recent decades. Dietary piperine, by favorably stimulating the digestive enzymes of pancreas, enhances the digestive capacity and significantly reduces the gastrointestinal food transit time. Piperine has been demonstrated in in vitro studies to protect against oxidative damage by inhibiting or quenching free radicals and reactive oxygen species. Black pepper or piperine treatment has also been evidenced to lower lipid peroxidation in vivo and beneficially influence cellular thiol status, antioxidant molecules and antioxidant enzymes in a number of experimental situations of oxidative stress. The most far-reaching attribute of piperine has been its inhibitory influence on enzymatic drug biotransforming reactions in the liver. It strongly inhibits hepatic and intestinal aryl hydrocarbon hydroxylase and UDP-glucuronyl transferase. Piperine has been documented to enhance the bioavailability of a number of therapeutic drugs as well as phytochemicals by this very property. Piperine's bioavailability enhancing property is also partly attributed to increased absorption as a result of its effect on the ultrastructure of intestinal brush border. Although initially there were a few controversial reports regarding its safety as a food additive, such evidence has been questionable, and later studies have established the safety of black pepper or its active principle, piperine, in several animal studies. Piperine, while it is non-genotoxic, has in fact been found to possess anti-mutagenic and anti-tumor influences.     

Shoot growth on de-fruited grapevines: a physiological indicator for irrigation scheduling

A simple and inexpensive but biologically meaningful way of gauging grapevine water status that can guide irrigation scheduling is described. The growth rate of shoots on grapevines from which all fruit has been removed (de-fruited shoot growth) is presented as a sensitive indicator of vine and soil water status and we propose a procedure for irrigation scheduling based on monitoring de-fruited shoot growth and soil moisture. These guidelines were derived from corresponding measurements of de-fruited shoot growth and soil moisture potential that were undertaken at frequent intervals (generally 1 to 2 days). De-fruited shoot growth rate between 48 and 71 days after anthesis was linearly correlated with the mean moisture potential of the soil at depths of 60 cm and 90 cm in the centre of the drip-irrigated zone (r = 0.94). De-fruited shoot growth effectively ceased when soil moisture potential at these points had decreased to -70 kPa, although much of the root zone would have been even drier. De-fruited shoot growth thus shows an integrated and dynamic response to vine-available soil water that could aid irrigation scheduling.     

钛营养对烤烟生长过程中生理特性的影响

研究了不同浓度钛溶液灌根对烤烟生长过程中各种生理特性的影响.结果表明:在伸根期用适量的钛肥灌根,能增加烤烟叶片中叶绿素、类胡萝卜素含量和转化酶活性,可以促进烤烟的光合作用,有利于烟草同化产物的转化和利用,同时也能够提高烤烟叶片中SOD和POD活性,降低MDA含量,明显降低烟叶中细胞膜脂过氧化程度,提高烤烟抗衰老能力和抗逆性.上述作用,在钛肥灌根的短期内,效果尤为明显,其中富钛增效剂稀释600倍灌根效果最好.     

Invited review: Genomic analysis of data from physiological studies

Physiology deals with the functions of living organisms and their systems, and its scientific endeavors can be viewed as having temporally occurred in 3 phases. The first phase of physiology studies focused on determining the functions of particular organs and tissues and their functional differences according to physiological status. The second phase of studies focused on characterizing differences in these functions according to the environment, or productivity. The third phase of studies focuses on determining the physiological causes of differences in productivity. Distinguishing cause from effect in physiological systems of inter-related processes is problematic, such that science has struggled to identify the root physiological mechanisms and their role in the network of genes leading to differences in productivity. Genomics is the study of the entire genome and provides powerful new tools that will accelerate third-phase discoveries of causal physiological processes. That research exploits information on DNA polymorphisms known as markers, complete DNA sequence, RNA sequence, and RNA expression in particular tissues at specific life stages. Physiologists can determine the genetic cause of mutant animals, identify genetic differences between cases and controls, and identify genes responsible for differences in performance between average and above-average animals. In some species, physiologists can leverage genomic data being used to predict genetic merit in elite seedstock populations, as a starting point to identify genes that will then motivate detailed physiological studies in the organs or tissues and stages of life in which those genes are expressed. Such work will increase our knowledge of biology and may lead to novel approaches to manipulate animal performance.     

Symposium review: Environmental effects on mammary immunity and health

Environmental effects on pathogen abundance and access are precursors to mastitis. Indeed, high heat and humidity, and unsanitary housing and equipment, are associated with greater pathogen load and exposure. Although less is known about effects of environment on a cow's ability to resist infection, several indicators suggest that it can affect pathogen responses. Mastitis incidence and bulk tank somatic cell count vary with season, typically peaking in summer. Recent controlled studies have revealed that heat stress exposure results in changes in the microbiome of the cow and her environment, which may relate to negative effects on milk quality and cow health. Alternatively, specific pathogen loads may vary based on housing dynamics rather than associations with physical environment. Indeed, housing-related stressors, such as overcrowding and social group challenge, influence secretion of glucocorticoids, thus affecting pathogen resistance in the cow. Two key seasonal variables are photoperiod and temperature, specifically the heat stress consequent to elevated temperature and humidity. Shifts in light duration regulate immune function in other species, but apparently have limited effect on udder health of lactating cows. In contrast, in dry cows, short days increase peripheral blood mononuclear cell number and are associated with lower somatic cell count in the next lactation, compared with long days. With heat stress, elevated body temperature directly affects expression of immune-related genes in mammary tissue. Responses depend on duration of exposure and feature acute upregulation of immune-signaling pathways, followed by enrichment of other immune-related pathways after prolonged exposure. Most responses are transient and recover within 1 wk. Functionally, heat stress impairs some aspects of acquired immunity in dry cows, including antigen responses and lymphocyte proliferation, but apparently not innate immune function. However, heat stress in late gestation reduces neutrophil phagocytosis and killing in vitro, and neutrophils in circulation are reduced in vivo as are responses to pathogen challenge in the subsequent lactation. A holistic understanding of the complex interplay of environment, pathogens, and host is needed to inform advances in this area.     

Invited review: Modelling quality changes of fruits and vegetables during drying: a review

Fruits and vegetables have received much attention as these materials have been reported to contain various phytochemicals, which are claimed to exert many health benefits. When extraction of bioactive compounds cannot be performed on fresh fruits and vegetables, drying needs to be conducted to keep the materials for later use. Dried fruits and vegetables have also been regarded as alternative fat‐free snacks and received more attention from the food industry during the past decade. This implies that not only nutritional changes, but also other changes including physical and microstructural changes are of importance and need to be optimised, preferably through the use of various modelling approaches. The objective of this article is to provide a brief review of some advances in modelling quality changes of fruits and vegetables during drying. These include modelling of nutritional, colour and selected physical changes. Approaches to monitoring and modelling microstructural changes are also mentioned.     

Milk yield and mammary growth effects due to increased milking frequency during early lactation

Increased milking frequency (IMF) at the beginning of lactation has been shown to increase milk yield not only during IMF but also after its cessation. The objectives of this experiment evaluated the effects of increased milking frequency initiated during early lactation on mammary growth and effects on milk yield (MY). Thirty-one cows were divided into treatment groups: 1) 2X: cows milked twice daily (2X) beginning at parturition (d 1), 2) IMF1: cows milked four times daily (4X) from d 1 to 21 postpartum (PP) and 3) IMF4: cows milked 2X d 1 to 3 and 4X d 4 to 21 PP. The 4X cows were milked immediately before 2X cows and again approximately 3 h later, at the end of the normal milking routine. All cows were milked 2X from d 21 to 305 postpartum. Milk yields were 34.5, 37.8 and 37.6 kg/d during wk 1 to 44 for 2X, IMF1 and IMF4, respectively. Mammary biopsies from four cows per treatment were obtained on d 7 and 14 PP to evaluate mammary cell proliferation. Tritiated-thymidine incorporation tended to increase on d 7 in IMF1 cows, and arithmetic means of the percentage of cells expressing Ki-67 proliferation antigen were consistent with a proliferative response to IMF though not significant. Blood was sampled three times per wk during the first 2 wk and then once per wk during wk 3, 4, 5, 6, 8, and 10. Plasma insulin-like growth factor-1 (IGF-1) averaged 20.1 ng/ml in IMF cows vs. 24.2 in 2X but was not accompanied by a change in bST. Prolactin was also not affected by treatment. Neither milk yield nor potential effects on mammary cell proliferation were correlated with systemic IGF-1. Implementing an IMF routine increases MY during treatment and elicits a carryover effect on the remainder of lactation. Milk yield responses after an IMF routine may be the result of increased mammary cell proliferation.     

Organization and growth of mammary epithelia in the mammary gland fat pad

Mammary gland development consists of a series of very highly ordered events involving interactions among a number of distinct cell types. An important aspect of mammary gland development is that the mammary gland consists of a fat pad of mesodermal origin into which epithelial cells of ectodermal origin proliferate. This proliferation of epithelial cells into the mammary fat pad is the subject of this review. The nature of the stroma into which epithelial cells proliferate is of considerable importance in determining the structure of the resulting gland. In mice, white adipose tissue appears to be required for normal mammary development. Transplantation of mammary epithelia to other types of stroma does not support epithelial growth or result in abnormal growth. To date, a synthetic substratum capable of mimicking white adipose tissue has not been developed. Although collagen gel cultures are generally considered superior to glass or plastic substratum in supporting near normal epithelial growth, the technique has not advanced to the point that the in vivo growth pattern is duplicated. Recent research on the generation of chimeric mammary tissue (by transplanting mammary epithelia from rats, cows, and women to the mammary fat pads of athymic nude mice) suggests that there are important species differences in the stromal requirements for mammary gland development. In particular, extensive and expansive growth of rat mammary tissue is observed in mouse mammary fat pads. However, the mouse mammary fat pad appears incapable of supporting expansive growth of bovine or human mammary epithelia. The reason for this difference is not clear. However, human and bovine mammary epithelia may require the presence of more fibrous (collagenous) tissue than rodent mammary epithelia for normal proliferation.