bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of acetate and of pyruvate on the pathways of glucose catabolism in lactating mammary tissue: 1. Rat tissue
Authors: Smith R. W. , Glascock R. F. 
Published: June 2009

SummaryA study was made of the changes in the pathways of glucose catabolism in slices of lactating rat mammary gland which occurred when acetate or pyruvate was added to the medium.When acetate was added there was an increase in the rates of oxidation of the C(2)and C(6)atoms of glucose but little change in that of the C(1)atom. The amounts of these carbon atoms which were incorporated into fatty acids, lactic acid and glyceride glycerol were reduced, but the results showed that the relative proportion of the glucose converted to these substances which passed through the pentose phosphate pathway was increased.When pyruvate was added, the rates of oxidation of the C(1), C(2)and C(6)atoms were all reduced to about the same extent. The incorporation of the glucose carbon into fatty acids was almost abolished and its incorporation into lactic acid and glyceride glycerol was very much reduced. The results showed that most of the glucose incorporated into these compounds under these conditions passed through the pentose phosphate pathway.Evidence is presented which suggests that the triose phosphates are not in complete isotopic equilibrium in lactating rat mammary tissue.These results are discussed in relation to the existence of 2 pools of acetyl coenzyme A, one intra- and the other extra-mitochondrial, and to the possible inhibition of certain steps of the glycolytic pathway.
The effects of acetate and of pyruvate on the pathways of glucose catabolism in lactating mammary tissue. II. Sheep tissue
Authors: Smith R. W. , Glascock R. F. 
Published: June 2009

SummaryA study was made of the changes in the rates of oxidation of the C(1), C(2) and C(6) atoms of glucose and in the pathways of glucose catabolism in sheep udder tissue in vitro which occurred when acetate and pyruvate were added.Whereas in rat mammary tissue the rate of oxidation of the C(1) atom of glucose was very much greater than that of the C(6) atom, the ratio of the rates of oxidation of these 2 atoms in sheep tissue was less than 2 when glucose was the only substrate.The addition of acetate resulted in an unequal stimulation of the oxidation of these 2 atoms, with the result that the ratio of their rates of oxidation was about doubled. The rate of oxidation of the C(2) atom was also increased.Acetate also increased the participation of the pentose phosphate pathway in glucose catabolism as measured by the incorporation of the C(1) and C(6) atoms of glucose into fatty acids, lactic acid and glycerol.Pyruvate produced little effect on the rate of oxidation of the C(1) atom but somewhat depressed that of the C(6) atom of glucose. At the same time, it caused a large increase in the participation of the pentose phosphate pathway.These results are discussed with reference to re-cycling of glucose carbon in the pentose phosphate pathway and to the relationship between that pathway and fatty acid synthesis. It is noted that the incorporation of glucose carbon into the 3 intermediates used gave values for the participation of that pathway which were in better agreement than was obtained in rat tissue. It is concluded that triose phosphates are more nearly in equilibrium in sheep than in rat mammary tissue.
Utilization of citrate by lactobacilli isolated from dairy products
Authors: Fryer T. F. 
Published: June 2009

SummaryTwenty-five strains of lactobacilli isolated from dairy products, includingLactobacillus casei, Lactobacillus plantarumandLactobacillus brevisspecies, were grown in semi-defined media and examined for their ability to ferment citrate and produce formate. Of 7 strains ofL. casei, all utilized citrate to varying extents, as did 9 of 10 strains ofL. plantarumand 3 of 8 strains ofL. brevis.L. caseiproduced 19–35% of the theoretical yield of formate from the citrate utilized,L. plantarum0–11% andL. brevis0–28%. Of 2 strains ofL. caseitested for their abilities to ferment citrate in the presence of 2% lactose, strain C 5 was unaffected by lactose whereas strain C 2 showed a 45% decrease in the citrate utilized. However, lactose used at 2% concentration greatly reduced formate production byL. caseiC 5, which produced 62% of the theoretical yield of formate from citrate after 35 days in the absence of lactose and only 8% in its presence. The yield of diacetyl produced byL. caseiC 5 from citrate plus lactose (both at 2% concentration) was 145 times that produced from citrate alone, and 800 times that from lactose alone.
Observations on the use of 2,4-dinitrophenylhydrazine and of 2,6-dichlorophenolindophenol for the determination of vitamin C in raw and in heat-treated milk
Authors: Toothill Joyce , Thompson S. Y. , Edwards-Webb J. 
Published: June 2009

SummaryA study has been made of methods using 2,4-dinitrophenylhydrazine (DNPH) or 2,6-dichlorophenolindophenol (DCP) for the determination of vitamin C (ascorbic acid+dehydroascorbic acid) in raw, UHT processed, evaporated and sterilized milk.Interfering substances were not detected in milk that had received a heat treatment no more severe than 145°C for 4 s (UHT process), so that either reagent could be used.With more drastic heat treatment, interfering substances were formed and only the DNPH method with column and thin layer chromatography of the DNPH derivatives was specific for vitamin C. With in-bottle sterilized milk, the values for ascorbic acid were (in mg/100 ml) 1·16 (DCP method with H2S reduction); 0·58 (DCP method withEscherichia colireduction); 0·64 (DNPH method); 0·33 (DNPH method combined with chromatography).In our experience the DNPH method combined with chromatography of the derivatives is highly specific for vitamin C and should be used to check the results obtained by other and simpler methods.
The estimation of diacetyl in the presence of other carbonyl compounds
Authors: Lees G. J. , Jago G. R. 
Published: June 2009

SummaryAn examination of the spectra of some volatile carbonyl semicarbazones indicated that only compounds containing vicinal carbonyl groups formed semicarbazones which absorbed at 270 nm. This observation was used for the quantitative estimation of diacetyl. The presence of both acetaldehyde and acetoin did not interfere with the estimation of diacetyl by this method.
A rapid bioassay for penicillin residues in milk
Authors: Cogan T. M. , Fox P. F. 
Published: June 2009

SummaryA new bioassay for the detection of penicillin in milk which can be completed in 1½ h has been developed. The test depends on measurement of pH changes in milk produced by an antibiotic sensitive organism, Streptococcus thermophilus BC. To measure the changes potentiometrically would require a very sensitive pH meter. Change in the enzymic coagulation time, which is extremely dependent on pH, was used in the present study to measure small changes in pH. The test is highly reliable and should be suitable as a milk selection test.
Metabolism of [1-14C]palmitate and [1-14C]oleate by the isolated perfused mammary gland of the sheep or goat
Authors: Massart-Leën Anne-Marie , Florescu S. , Verbeke R. , Peeters G. 
Published: June 2009

SummaryLactating mammary glands of sheep and goats were perfused for several hours in the presence of [1-14C]palmitate or [1-14C]oleate. Adequate quantities of acetate, glucose, amino acids and chylomicrons were added to the perfusate.The fall in specific activity of [1-14C]palmitic acid or [1-14C]oleic acid across the gland and the labelling of milk triglyceride fatty acids indicates an extensive transfer of radioactivity from plasma free fatty acids (FFA). The plasma triglycerides showed large arterio-venous differences in concentration. The small [14C] incorporation in plasma triglycerides decreased across the gland. In a control experiment triglycerides were also slightly labelled.There were no significant arterio-venous differences in cholesterol esters and their fatty acid composition showed only slight changes during passage through the gland. Their specific activity showed a small rise across the gland.In milk components, the [14C] was mainly localized in the triglycerides. An appreciable proportion of the palmitoleate is derived from palmitate by dehydrogenation within the gland, while there is no evidence for the hydrogenation of oleic acid to stearic acid. Elongation of palmitic acid to C18-acids does not occur to any important extent. FFA are catabolized to a variable extent by the gland.The role of FFA in labelling of milk and blood plasma fatty acid fraction is discussed.
The effects of dietary soybean oil on milk-fat composition in the cow
Authors: Steele W. , Noble R. C. , Moore J. H. 
Published: June 2009

SummaryThe effects of the isocaloric replacement of starch in a low-fat concentrate mixture by 8% soybean oil on the yield and composition of milk fat were investigated in a feeding experiment with 6 cows in mid lactation. Two high-fat concentrate mixtures were given to the cows. In one the requisite amount of soybean oil was given by including 50% coarsely ground soybeans in the concentrate mixture. In the other an equal amount of soybean oil was added directly to the concentrate mixture. The concentrate mixtures were given with a high-roughage diet that supplied 5·5kg hay and 2·7kg of sugar-beet pulp/day.When the 2 high-fat rations were given to the cows there were reductions in the percentages and yields of 10:0, 12:0, 14:0, 14:1, 16:0 and 16:1 fatty acids and increases in the concentrations and yields of 18:0, 18:1 and 18:2 fatty acids in the milk fat. The direct addition of the soybean oil to the diet also reduced the percentage and yield of 6:0 and 8:0 whilst the inclusion of the soybeans increased the percentage of 4:0 and the yields of 4: 0 and 6:0 in the milk fat.When both high-fat rations were given to the cows there were increases in the yields and concentrations of as-9–18:1 in the milk fat, whilst inclusion of the soybean oil in the diet increased also the concentration and yield oftrans-11–18:1.The implications of these findings are discussed.
The relationship between plasma lipid composition and milk fat secretion in cows given diets containing soybean oil
Authors: Steele W. , Noble R. C. , Moore J. H. 
Published: June 2009

SummaryThe effects on the composition of the plasma lipids of the isocaloric replacement of starch in a low-fat concentrate mixture by 8 % soybean oil were investigated in a feeding experiment with 6 cows in mid-lactation. Two high-fat concentrate mixtures were given: in one, the soybean oil was incorporated into the diet by the inclusion of the appropriate amount of coarsely ground soybeans; in the other, the soybean oil was incorporated directly in the concentrate mixture. The concentrate mixtures were given with a high-roughage diet that supplied daily 5·5kg hay and 2·7kg of sugar-beet pulp.When the cows were given the 2 high-fat diets there were increases in the concentrations of total plasma fatty acids and in the concentrations of fatty acids circulating in the plasma as phospholipids and cholesteryl esters. There were increases in the concentrations of plasma unesterified fatty acids and triglyceride fatty acids when the cows were given the diet containing soybeans but there were decreases in the concentrations of these 2 fractions when the cows were given the diet containing soybean oil.The inclusion of soybeans in the diet increased the concentration of 18:0 in the plasma triglycerides and unesterified fatty acids whilst the inclusion of soybean oil in the diet increased the concentrations of 18:0 and 18:1 but decreased the concentration of 18:2 in the plasma unesterified fatty acids.When the cows were given the 2 high-fat diets there were decreases in the concentrations of 16:0 and 16:1 and increases in the concentration of 18:2 in the plasma cholesteryl esters. The inclusion of soybeans in the diet also reduced the concentrations of 18:1 and 20:3 in the plasma cholesteryl esters but increased the concentrations of 18:0 and 18:2 in the plasma phospholipids.The major fatty acid circulating in the plasma of the cows was 18:2 (46·4–55·3%) on all diets but only about 1% (0·40–1·04%) of the total plasma 18:2 occurred in the plasma triglycerides.The results are discussed in relation to the changes in the composition of the milk fatty acids produced by the cows when they were given the experimental diets.
Determination of alkaline phosphatase activity in cheese using phenolphthalein monophosphate as substrate
Authors: Rammell C. G. , Joerin M. M. 
Published: June 2009

SummaryA method is described for determining alkaline phosphatase activity in cheese using phenolphthalein monophosphate as substrate. Results are read with a Lovibond comparator after 1 h incubation. Advisory standards are proposed based on a minimum pasteurization for 15 s at 71°C of the milk used for cheese-making.
A note on the influence of stage of lactation on the response in the lactose content of milk to a change of plane of energy nutrition in the cow
Authors: Dawson R. R. , Rook J. A. F. 
Published: June 2009

SummaryThree groups of Friesian cows, one of cows in early lactation, one of cows in mid-lactation and one of cows in late lactation, received over successive 4-week periods according to a double changeover Latin square design, rations providing a low, a normal and a high plane of energy nutrition. With the group of cows in early lactation the treatments were repeated again in mid-lactation and in late lactation.In all experimental groups there were increases and decreases in the treatment mean values for milk yield and solids-not-fat, protein and lactose contents, in response respectively to overfeeding and to underfeeding. The responses in lactose content in early and mid-lactation were small (overfeeding, 0·00 to +0·06 percentage units; underfeeding, −0·01 to −0·08 percentage units) and less than those in protein content, whereas in late lactation they were larger (overfeeding, +0·09 to +0·14 percentage units; underfeeding, −0·13 to −0·19 percentage units) and of the similar size to those in protein content.
Growth studies on the lactic streptococci: II. The effect of agitation on the growth characteristics ofStreptococcus lactisML8in batch culture
Authors: Keen A. R. 
Published: June 2009

SummaryInvestigations on the growth characteristics ofStreptococcus lactisML8in skim-milk medium have indicated that agitation of the medium may decrease the growth rate of the organism by decreasing the availability of CO2(CO2effect) and of soluble nitrogen (soluble nitrogen effect). The former effect was observed only when the CO2concentration was depleted by heat sterilization; the latter occurred when a certain threshold level of agitation was exceeded. Results suggested that the soluble nitrogen affect was caused by an alteration in the rate of diffusion of substances formed in the immediate vicinity of the bacterial cell by the proteolytic enzyme system.
Growth studies on the lactic streptococci: IV. Some observations on redox potential
Authors: Keen A. R. 
Published: June 2009

SummaryRedox potential changes at 30°C in anaerobic reconstituted skim-milk cultures ofStreptococcus cremorisAM1and AM2andStreptococcus lactisML8have been investigated in batch cultures and continuous cultures maintained at constant pH by the addition of fresh medium.Str. lactisML8was more strongly reducing than eitherStr. cremorisAM1or AM2. The positiveEhvalues which can arise in dense continuous cultures of lactic streptococci are not likely to affect either the lactic acid formation or proteolytic activity of the resultant bacterial concentrate. An electrolytic reduction cell is described which allows variations in redox potential in cultures to be controlled simply and effectively.
Formaldehyde-treated casein–safflower oil supplement for dairy cows: I. Effect on milk composition
Authors: Pan Y. S. , Cook L. J. , Scott T. W. 
Published: June 2009

SummaryThe effects of feeding lactating cows a daily supplement of 1 kg formaldehyde-treated casein–safflower oil (1:1, w/w) on the milk composition are reported. Three breeds, Jersey, Sahiwal and Sahiwal × Jersey crossbred were used.The formaldehyde treatment not only eliminated the suppressing effect on the milk, fat and protein yields and on the fat and protein contents usually encountered when such a level of unsaturated oil is fed to lactating cows, but also resulted, on the average, in 15 and 6% increases in the fat and protein contents respectively.The formaldehyde-treated dietary supplement also caused a decline of 5% in the solids-not-fat content, presumably due to a decrease in the lactose content.It is suggested that the formaldehyde treatment protects the casein from the ruminal proteolysis and this in turn prevents the encapsulated unsaturated oil from biohydrogenation and eliminates the diverse effects on rumen microflora and environment.
Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning
Authors: Walker N. J. 
Published: June 2009

SummaryTwo chemical tests were used to measure the extent of lactose degradation by Maillard browning in casein and skim-milk powder during storage. At the same time these products were evaluated organoleptically. Highly significant correlations between age, flavour score and level of browning in skim-milk powder were in contrast to the lack of any relationship between the flavour score or age of casein and its level of browning. Maillard browning occurring during storage of skim-milk powder was accompanied by increasing levels of cereal and malty flavours. A stale flavour, which closely resembled the musty flavour common to casein, was not observed in skim-milk powder until after storage for 9 months. A distinct difference in the flavour stability of rennet casein and acid casein could not be accounted for in terms of the relative extent of lactose degradation. Evaluation of casein samples with different lactose contents suggested that Maillard browning does not contribute to flavour defects during storage unless the curd is so insufficiently washed during manufacture as to produce an abnormally high level of lactose in the dried product.
Metabolism of [U-14C]-l-threonine and [U-14C]-l-phenylalanine by the isolated perfused udder
Authors: Verbeke R. , Roets E. , Massart-Leën Anne-Marie , Peeters G. 
Published: June 2009

SummaryA lactating mammary gland of a goat was perfused for 9 h in the presence of [U-14C]-l-threonine and received adequate quantities of glucose, acetate and amino acids. Two lactating sheep udders were likewise perfused in the presence of [U-14C]-l-phenylalanine: the plasma levels of phenylalanine in the first of these experiments were 4 times higher than in the second.In the [14C]threonine experiment, 4 % of the casein and 0·4 % of the expired CO2were derived from threonine; 85 % of the threonine and 1·6 % of the glycine residues in casein originated from plasma threonine. Small14C levels were found in glutamic acid, aspartic acid and serine of casein. The relative specific activities amongst the casein amino acids and the appearance of appreciable labelling in plasma glycine are consistent with the view that threonine is split by threonine aldolase.In the [14C]phenylalanine experiments virtually no radioactivity was detected in CO2, lactose or citric acid, indicating that this substrate is not broken down by mammary tissue. In the second experiment, 96 % of the phenylalanine and 0·3 % of the tyrosine of casein originated from plasma phenylalanine. In the first experiment, a 30-fold higher14C incorporation into casein tyrosine relative to phenylalanine was observed. The possible significance of the phenylalanine concentration in the plasma on the degree of conversion of phenylalanine into tyrosine within the mammary gland is discussed.
The composition of milk of British Alpine and Anglo–Nubian goats imported into Trinidad
Authors: Devendra C. 
Published: June 2009

SummaryThe variations in the composition of milk over an 18-week period from lactating British Alpine and Anglo–Nubian goats imported into Trinidad are reported. The animals were fed Napier grass (Pennisetum purpureum) ad lib. and 2 lb of a proprietary concentrate mixture daily.The mean percentage contents of the milks of British Alpine and Anglo–Nubian goats were: total solids 11·49±0·22, 12·17±0·28; butterfat 3·42±0·18, 4·06±0·22; total N 0·462±0·04, 0·530±0·07; ash 0·78±0·02, 0·79±0·03 and ‘lactose’ 4·38±0·28, 4·05±0·55. Anglo–Nubian goats had a higher content of percentage total solids, fat, total N and ash. For all constituents the coefficient of variation between weeks was higher for Anglo–Nubian goats. No significant trends were found between weeks for each of the components analysed for both breeds. Statistically significant correlations (P < 0·01) were found between percentage fat and percentage total N for both breeds.The mean mineral contents (mg/100ml) for the milks of British Alpine and Anglo–Nubian goats were: Na 52·6±4·6, 55·5±1·9; K164·0±8·4, 133·4±11·4; Ca 85·5±11·6, 89·9±9·8; Mg 13·2±3·8, 10·2±1·6 and P 74·7±3·9, 82·1±3·9. British Alpine goat's milk had a higher content of K and that of Anglo–Nubian goats had a higher content of P; both differences were statistically significant (P < 0·01).The milk composition figures in this study together with those from a similar study in Guadeloupe suggest that the values are low and considerably lower in comparison with the same breeds of goats in a temperate environment. This could be a feature of dairy goats imported into the tropics due perhaps to inadequate nutrition. Much more information is needed to verify this possibility.
Location of proteins within the milk fat globule membrane
Authors: Anderson M. , Cheeseman G. C. , Knight Dorothy J. 
Published: June 2009

SummaryRadioactive labelling of intact fat globules with125I gave at least one labelled protein in each of the 4 fractions of the fat globule membrane. Similar treatment of isolated membrane gave extensive labelling of all membrane proteins in each fraction.It was concluded that all fractions are partially exposed at the membrane surface and the existence of well-defined layers is unlikely.
The differentiation of curd made from heated and raw milk
Authors: Guha K. C. , Roy B. R. 
Published: June 2009

SummarySince Indian law requires curds to be made from heat-treated milk, a means for distinguishing between curds made from raw and from heat-treated milks was sought. Curds contain whey proteins that are partly or completely denatured by heat treatment; the kinetics of the reaction are first order. The concentrations of native whey proteins in raw and heat-treated milks and in curds made from those milks were measured. No difference was found between the concentrations in heattreated milk and in the curds made from it, so that identical values were obtained for the half-life on heating and for the activation energy of denaturation. The acidity and microbial growth occurring during the production of curd did not affect the whey proteins. On electrophoresis, curd from raw milk gave a few whey protein bands, but curd from milk boiled for 10 min gave none, showing complete denaturation of the whey proteins.
Metabolite levels and enzyme activities in the bovine mammary gland at different stages of lactation: I. Metabolite levels related to energy production
Authors: Waldschmidt Marianne 
Published: June 2009

SummarySamples of the mammary gland were obtained from heifers, lactating and dry cows by a freeze-clamping technique. Amounts of lactate, pyruvate, malate, ATP, ADP and AMP were determined in the sample extracts and calculated per g fresh weight and per mg DNA. Pyruvate, lactate and AMP amounts showed only minor changes at different stages of lactation, whereas quantities of malate, ATP and ADP were significantly higher in cows giving high milk yields. Pyruvate levels showed seasonal variations parallel to changes in milk composition. NAD: NADH ratios in mammary cytoplasm showed no significant differences between different groups of cattle, whereas ATP: AMP ratios in mammary gland samples were highest in lactating animals.