bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissemination of staphylococci in mice with experimental mastitis
Authors: Anderson James C. 
Published: June 2009

SummaryDuring the course of an acute, fatal mastitis in mice caused by intra-mammary injection of ∼ 105 cfu of Staphylococcus aureus, small numbers of staphylococci were detected in liver, spleen, kidney and heart. Transport from the mammary gland was by the venous blood system with no evidence of lymph node involvement. Intravenous injection of 100 times more staphylococci (∼107 cfu) than were fatal by the intramammary route failed to kill the mice and small numbers of staphylococci were found in the visceral organs. However, intravenous injection of ∼ 108 cfu of Staph. aureus was fatal and large numbers of staphylococci were found in the visceral organs. Treatment with cloxacillin (500 μg) by the intramammary or subcutaneous routes, or equally divided between these two routes, cleared the visceral organs of staphylococci; subcutaneous therapy had a limited and variable effect on numbers of staphylococci in the mammary gland while intramammary and divided treatments significantly reduced the numbers of staphylococci. Thus, staphylococci are disseminated to visceral organs during acute staphylococcal mastitis, but this makes a negligible contribution to the clinical disease.
Quantitative fractionation of casein mixtures by fast protein liquid chromatography
Authors: Davies D. Thomas , Law Andrew J. R. 
Published: June 2009

SummaryAlkylation of whole casein samples by reaction with cysteamine and cystamine in a bis-tris-propane–urea buffer (pH 7·0) followed by fast protein liquid chromatography (FPLC) at 20°C on a Mono Q HR5/5 column in the same buffer and using a NaCl gradient led to good resolution of the whole casein into fractions representing (i) γ2- plus γ3-caseins, (ii) κ-caseins, (iii) β-casein, (iv) αs2-caseins and (v) αsl-caseins, together with small amounts of unidentified materials. Quantitatively the FPLC values agreed well with those for αs1-, β-, αs2- and γ2- plus γ3-caseins obtained by ion-exchange chromatography on DEAE cellulose, Whatman DE52 and with those for º-caseins obtained by gel-permeation chromatography on Sephadex G–150.
Heat-induced association-dissociation of casein micelles preceding coagulation
Authors: Mohammad Kais S. , Fox Patrick F. 
Published: June 2009

SummaryHeating milk at 140 °C caused an initial increase in the percentage of total casein sedimented at 10000 g for 1 h and in the relative viscosity, but as heating continued both parameters decreased before increasing again just before the onset of visible coagulation. This suggests that heating milk at high temperatures caused an initial aggregation of casein micelles with a concomitant increase in particle size and weight, followed by dissociation of these aggregates with reaggregation just before coagulation. Chromatography of heated milk on controlled pore glass confirmed the above suggestion. Calcium appeared to play a major role in the initial association of casein micelles which was also influenced by the initial pH and total solids concentration but whey protein had no effect.
Comparison of a simple butterfat agar medium with other media used for isolation and enumeration of lipolytic bacteria from dairy products
Authors: Shelley Arthur W. , Deeth Hilton C. , MacRae Ian C. 
Published: June 2009

SummaryA nutrient agar medium containing 0·1 % of a low melting point fraction of butterfat was shown to be suitable for detection, enumeration and isolation of lipolytic bacteria from milk. Bacterial growth was not inhibited by the butterfat and lipolytic reactions were clearly visible and easily interpreted. Lipolytic counts on the butterfat agar compared favourably with lipolytic counts obtained with other commonly used media.
Interspecies variation in milk composition among horses, zebras and asses (Perissodactyla: Equidae)
Authors: Oftedal Olav T. , Jenness Robert 
Published: June 2009

SummaryMilk samples of four species of wild equids (onager, Equus hemionus onager; mountain zebra, E. zebra hartmannae; plains zebra, E. burchelli; Przewalski horse, E. caballus przewalskii) and two domesticated equids (ass, E. asinus; pony, E. caballus) were analysed. At mid to late lactation the milks of all species were very similar, containing on average 10–12% total solids, 1–2% fat, 1·6–1·8% true protein, 6–7% ‘lactose’, 0·3–0·5% ash, 0·08–0·12% calcium, 0·04–0·07% phosphorus and a calculated energy content of 2·0–2·4 kJ/g. Milk samples collected in the first 2 weeks after birth showed elevated levels of total solids and protein, and some had reduced ‘lactose’ levels, but there were no observable trends in milk composition during mid to late lactation (1–12 months post partum). It was concluded that these closely related species produce milks that are nearly identical in gross composition and that the domestic horse is a representative model for the study of equid lactation.
Dissociation during dialysis of casein aggregates cross-linked by colloidal calcium phosphate in bovine casein micelles
Authors: Aoki Takayoshi , Yamada Nagisa , Kako Yoshitaka , Imamura Tsuneaki 
Published: June 2009

SummaryCasein micelles separated by ultracentrifugation of raw skim milk were dispersed at a casein concentration of 2·5% in simulated milk ultrafiltrate and dialysed against 10 mM-imidazole buffer (pH 7·0) at 5 °C. The amounts of colloidal Ca and inorganic P decreased from 77 to 11 mg and from 31 to 2 mg respectively in 100 ml during 72 h of dialysis. Micellar casein content was reduced to 43 and 11% after 48 and 72 h of dialysis respectively. In high-performance gel chromatography of casein micelles in the presence of 6 M-urea, fraction 1, consisting of the casein aggregates cross-linked by colloidal Ca phosphate (CCP) decreased during dialysis and the retention time of the peak of fraction 1 was prolonged, suggesting that the cross-linkage between CCP and casein molecules was disrupted. The dissociation rates of the individual casein constituents from the casein aggregates cross-linked by CCP during dialysis were in the order β-> αs1 - > αs2-casein. The higher the ester phosphate content, the slower was the dissociation rate of the individual casein constituent. It is suggested that the strength of interaction between CCP and casein molecules depends on the ester phosphate content.
Inorganic constituents of cheese: analysis of juice from a one-month-old Cheddar cheese and the use of light and electron microscopy to characterize the crystalline phases
Authors: Morris Howard A. , Holt Carl , Brooker Brian E. , Banks Jean M. , Manson William 
Published: June 2009

SummaryA method of extracting cheese juice is described. Juice from a single one-month-old Cheddar cheese was used to investigate the relationship between the composition of the cheese juice and the occurrence of crystalline aggregates in the cheese. Two classes of crystalline aggregates were identified by light microscopy and also by electron microscopy in combination with X-ray microanalysis: the larger class contained both Ca and P whereas the smaller class contained Ca but not P. Concentrations of ions in the cheese and cheese juice were determined and corrected for the excluded volume of co-solutes and other phases present. When this was done, comparison of the concentrations of Na, K, Cl and lactate in the cheese and the cheese juice indicated that they were virtually entirely in solution, whereas appreciable amounts of the total Ca, P and P1 in the cheese were not extracted in the cheese juice. The amounts of the non-extractable salts were consistent with the volume fractions of the crystalline aggregates found by microscopy; calculations of the ion equilibria in the cheese juice showed that it was supersaturated with respect to various Ca phosphate salts and to tricalcium citrate. It is concluded that the physicochemical origin of the crystalline aggregates was the nucleation and growth of crystals from a supersaturated solution, though the sites of nucleation may have been formed by the microbial activity in the cheese. Of the free amino acids found in the juice, none was at a sufficiently high concentration to form a saturated solution, indicating that in this relatively young cheese the crystalline aggregates were not formed from amino acids.
Effect of a shielded liner on new mastitis infection
Authors: Binde Martin , Melby Hans Peter , Ask Asbjørn , Lund Andreas , Vangdal Svein AA. 
Published: June 2009

SummaryResults from a field trial involving 23 Norwegian dairy herds support the theory that deflector shields inserted into the teatcup liner can reduce the risk of intramammary infection. However, the effectiveness of this measure is questionable in cows already infected and in problem herds.
Catecholamines, oxytocin and milk removal in dairy cows
Authors: Blum Jürg W. , Schams Dieter , Bruckmaier Rupert 
Published: June 2009

SummaryExperiments were designed to study the effects of catecholamines on oxytocin responses and milk removal in dairy cows. Adrenalin, noradrenalin, dopamine, isoproterenol (a β-adrenoceptor agonist), phentolamine (an α-adrenergic blocker) and propranolol (a β-adrenergic blocker) were infused intravenously. In addition, adrenalin was infused together with phentolamine and/or propranolol. Infusions started 8 min before milking and lasted until the end of milking. In some cases electroshocks (for 5 s) were applied immediately before milking in the absence and presence of phentolamine and propranolol. Adrenalin, noradrenalin and dopamine reduced milk removal, but only if administered in supraphysiological amounts. The effect of adrenalin and electroshocks on milk removal could be inhibited by α-, but not by β-adrenergic blockade. The effect of dopamine could be inhibited only partly by phentolamine. Inhibition of milk removal was not mediated by reduced oxytocin responses. Enhanced local release of catecholamines from sympathetic nerves was presumably responsible for lowered milk removal in response to electroshocks. Milk removal was facilitated during α-adrenergic blockade and during β-adrenoceptor stimulation.
Observations on the heat-induced salt balance changes in milk I. Effect of heating time between 4 and 90°C
Authors: Pouliot Yves , Boulet Marcel , Paquin Paul 
Published: June 2009

SummaryMilk permeate was separated at various temperatures by means of a hollow fibre ultrafiltration unit coupled to a stainless steel heat exchanger. Milk samples conditioned at 4°C were heated to 20, 40, 60, 80, 85 or 90°C prior to ultrafiltration. Ca, P, Mg, Na, K and citrate concentrations were measured in the permeate samples. Ca and P contents of the permeate decreased as the temperature increased. The pH was measured after cooling the permeate to room temperature. Smaller losses of Mg and citrate were also observed with increase in temperature. Na and K levels were not affected. A two-step time-concentration relationship was apparent for the species under study. An initial sharp decrease in concentration occurred in the first minute of holding time and was followed by a slower reaction. The possible occurrence of a two-step mechanism in the heat-induced salt balance changes is discussed. Dicalcium phosphate precipitation is believed to be coupled with tricalcium citrate precipitation upon heating.
Observations on the heat-induced salt balance changes in milk II. Reversibility on cooling
Authors: Pouliot Yves , Boulet Marcel , Paquin Paul 
Published: June 2009

SummaryMilk which had been heated to 85°C for 40 min was examined for changes to milk salts taking place upon cooling to 4, 20, 40 and 60°C. The time-concentration curves showed a two-step reaction for Ca, Pi and pH. The effect of the heat treatment in milk heated to 85°C for 40 min was to produce greater changes in the second step of the reaction. Because of the variability of the results for other species (Mg and citrate), the reversibility was calculated only for Ca and P. It was 90–95% and 93–99% respectively depending on the cooling temperature. The reversibility of the heat-induced changes and especially of the possible dissolution equilibrium between Ca phosphate and citrate precipitates on cooling are discussed.
Fatty acid composition and milk quality related to feeding Ca-saponified palm acid oil to different breeds of dairy cows
Authors: Hermansen John E. , Lund Pia 
Published: June 2009

SummaryThe effect of supplementing a normal dairy feed ration (3–4% fatty acid of DM) with saponified palm acid oil (soap) was investigated in two experiments. The first experiment was carried out in eight herds (four Jersey, four heavy breeds), where the diet was supplemented with 1·0 and 0·5 kg soap for cows in the first and last part of lactation, respectively. Taste and acid degree of milk were not affected, and no breed × soap interaction was found. Fatty acid composition in milk was only slightly but significantly affected. The content of short and medium chain fatty acids was reduced (3·5% unit) and was followed by an increase in the content of 16:0 and 18:1. The increase in 16:0 by the soap supplementation was smaller in Jersey cows than in the other breeds. In the second experiment the effect of supplementing diets either with 0·5 or 1·0 kg Ca-soap to cows in the first part of lactation was investigated in two herds of Danish Black and White cows. Acid degree and time for curd formation on renneting (K20) were significantly lowest at the highest soap inclusion. No general effect on the proportion of short and medium chain fatty acids in the milk fat was observed as a function of level of Ca-soap, but the proportion of 16:0 was increased. It is assumed that the very small effect on milk fatty acid composition obtained when the daily allowance of fatty acids was increased from 600 to ~ 1400 g per cow, is more or less a specific effect of dietary fat rich in palmitic acid and given in excess to the basic diet.
Detection of cows' milk in ewes' milk and cheese by an indirect enzyme-linked immunosorbent assay (ELISA)
Authors: Rodríguez Elena , Martín Rosario , García Teresa , Hernández Pablo E. , Sanz Bernabé 
Published: June 2009

SummaryAn indirect enzyme-linked immunosorbent assay was successfully developed for the detection of defined amounts of cows' milk (1–50%) in sheeps' milk and cheese. The assay used polyclonal antibodies raised in rabbits against bovine caseins (BC). The anti-BC antibodies were recovered from the crude antiserum by immunoadsorption and elution from a column containing BC. The antibodies were biotinylated and rendered cows' milk specific by mixing them with lyophilized ovine and caprine caseins. ExtrAvidin-peroxidase was used to detect the biotinylated anti-BC antibodies bound to BC immobilized on 96-well plates. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying mixtures of sheeps' milk and cheese containing variable amounts of cows' milk.
An improved method for determining the nitrogen solubility of caseinates
Authors: Kneifel Wolfgang , Beurel Anne 
Published: June 2009

SummaryThe nitrogen solubility index (NSI) method for the examination of caseinates was evaluated. It was found that widely scattering NSI values are mainly due to ineffective centrifugation and filtration of the caseinate dispersion. In order to avoid this, an improved combined centrifugation–filtration procedure was developed as an alternative to the original NSI method, using an Amicon micropartition system MPS-1 equipped with discs of filter paper. The micropartition devices can be centrifuged in a Gerber centrifuge of the type used for butyromctric fat determination. Several types of caseinates were evaluated with the new method and yielded a markedly smaller range of single values than were obtained with the NSI method.
Prolidase activity ofLactococcus lactissubsp.cremorisAM2: partial purification and characterization
Authors: Booth Mary , Jennings Vincent , Fhaolain Ide Ní , O'Cuinn Gerard 
Published: June 2009

SummaryProlidase activity from cytoplasm ofLactococcus lactissubsp.cremoris (Streptococcus cremoris)AM2 was partially purified. The enzyme hadMr42000 and optimum activity between pH 7·35 and 8·25 in citrate, phosphate and borate buffers while in a universal buffer system an optimum pH between 8·3 and 9·0 was observed. The activity was strongly inhibited by the chelating agents E.DTA, 1,10-phenanthroline and 8-hydroxyquinoline. Inhibition was also noted with dithio-threitol,N-ethylmaleimide and bacitracin. The enzyme was active on all amino-acylproline substrates tested except Gly-Pro and Gip-Pro and also showed activity against Pro-Pro. While most prolyl amino acids tested were not hydrolysed, hydrolysis was noted with Pro-Ala and Pro-Val.Kmvalues of 20 mM and 10 mM were obtained with Phe-Pro and Met-Pro respectively; however, substrate inhibition was observed with Ile-Pro and Leu-Pro.
The effect of udder preparation before milking and contamination from the milking plant on bacterial numbers in bulk milk of eight dairy herds
Authors: McKinnon Charles H. , Rowlands G. John , Bramley A. John 
Published: June 2009

SummaryThe effect of teat washing and drying on bacterial numbers in bulk milk was compared with that of no teat preparation in eight commercial herds over one year. Using in-line milk samplers, milk was collected at various points during its passage through the milking plant and the samples were used to establish the relative significance of the sources of contamination of raw milk. Teat washing and drying of cows housed during winter reduced the total counts by 40% and streptococcal and coliform counts by 50%. Bacterial counts were significantly lower in cows at pasture during the summer and there was no reduction in count due to teat washing and drying. Bacteriological counts increased at each stage as the milk passed through the milking machine. The milking equipment significantly increased the total colony count by between 2000 and 3000/ml, and the bulk tank added a further 1500 to 2000/ml. The mean rinse bacterial counts of the milking equipment were higher in summer than winter, averaging 4·4 x 107bacteria/m2compared with 3·5 x 107/m2respectively. Although this level of bacterial contamination of the equipment is high by current standards, very low bulk milk bacterial counts were nevertheless achieved, particularly in the summer. This confirms that organisms from this source are not a major contaminant of the bulk milk. There was a very poor correlation between rinse counts and the bulk milk bacterial count, but a strong correlation (0·98) between total and streptococcal counts of the bulk milk. The unreliability of the use of rinse techniques to assess the contribution of milking equipment to bacterial counts of raw milk is emphasized.
Changes in the concentrations of glucose and galactose in the peripheral blood of sucking piglets
Authors: Holmes Mark A. , Arthur Peter G. , Hartmann Peter E. 
Published: June 2009

SummaryChanges in the concentrations of glucose and galactose were measured in the peripheral blood of ten piglets after they had ingested milk during a natural sucking. In addition, the mild stress associated with the experimental procedure was determined by sampling nine fasted piglets over a period of 9 to 12 min. During this period there was a significant increase in the concentration of glucose in the blood of the piglets but no change in the concentration of galactose. After milk ingestion during a natural sucking the concentrations of both glucose and galactose increased from 5·7 mM and 19μM to reach peak values of 7·7 mM and 122μM, respectively, by 30 to 35 min. The concentrations of glucose and galactose returned to initial values in 60–80 min and 80–100 min, respectively, after sucking. Since the change in the concentration of galactose in the peripheral blood was much lower than the change in the concentration of glucose, we conclude that galactose was rapidly removed by the livers of sucking piglets. However, after the ingestion of milk the percentage increase (from initial to peak values) in the concentration of galactose in the blood was much larger (650%) than the increase in the concentration of glucose (43%). Thus, we propose that the determination of galactose in the peripheral blood may provide a qualitative method for monitoring the digestion and absorption of milk lactose in sucking piglets.
Transepithelial potential difference in the goat mammary gland and its change during hand milking, and administration of oxytocin and catecholamines
Authors: Alekseev Nikolaj P. , Markov Alexander G. , Tolkunov Yuri A. 
Published: June 2009

SummaryThe reaction of secretory epithelium and myoepithelial cells in the alveoli to hand milking and i.v. injection of oxytocin and catecholamines was studied in lactating goats. The reaction of secretory cells was assessed by changes in the transepithelial (blood–milk) potential difference (PD), and the contractile reaction of myoepithelial cells by the growth of intramammary pressure (IP). The initial value of PD was 24·6 ± 0·6 mV, that of IP 3·32 ± 0·08 kPa (24·9 ± 0·6 mmHg). Milking and oxytocin administration caused a rise in PD and an increase in IP. After noradrenaline and adrenaline injections two-phase PD changes and a short-term rise in IP were recorded. Isoproterenol, a β-agonist, caused a rise in PD but did not affect IP. Phenylephrine, an α-agonist, caused two-phase and one-phase changes in PD. Simultaneously, a rise in IP was recorded. The results show that the reaction of the mammary gland to the substances administered is complex. Myoepithelial and secretory cells respond differently to short-term rises in the level of mediators and hormones in the blood.
Ultrafiltration of defatted whey: improving performance by limiting membrane fouling
Authors: Daufin Georges , Michel Françoise , Labbé Jean-Pierre , Quemebais Auguste , Grangeon André 
Published: June 2009

SummaryDefatted whey was obtained by aggregating residual fat to calcium phosphate precipitates and separating the precipitate by membrane microfiltration (pore diameter 0·2 μm). When ultrafiltering this defatted whey the performance of an inorganic membrane (molecular mass cut-off, 10 kDa) was limited by the large concentration of Ca and phosphates. Consequently, the influence of the aggregation pH (either decreasing or constant) on membrane fouling has been studied for ultrafiltration (UF) of defatted sweet whey and defatted whey UF retentates (protein content up to 30g l–1). In all experiments protein rejection was 100%. When pH was kept constant during the pretreatment, membrane fouling was significantly lowered. Hydraulic resistances ascribed to irreversible fouling were in good agreement with fouled membrane analyses performed by i.r. and X-ray photoelectron spectroscopies. They showed that provided a low Ca and phosphate content was maintained in the microfiltrate, which was achieved at constant pH, no apatite was detected within the membrane, and proteins were less fouling. On the other hand, the amount of fouling material depended on the transmembrane pressure gradient along the hydraulic path. On the membrane surface, the higher the pressure, the higher the fouling. In the membrane bulk, the fouling heterogeneity depended on the ability of the defatted whey to precipitate apatite. If it did, the higher the pressure, the higher the calcium phosphate and the protein fouling. With other phosphate structures, the bulk fouling depended on the barrier formed by surface fouling layers and the protein concentration polarization layer, which were more resistant to solute and solvent transfer under higher pressure, where they were thicker.