Casein and lactose concentrations in milk of 31 species are negatively correlated

Summary Casein and lactose concentrations in milks of various species vary by at least 1–2 orders of magnitude, yet no single species secretes both components at either the high or the low end of the ranges. This pattern of variation could result from evolutionary adaptations in a single secretory mechanism.     

Prolactin concentrations in mouse milk during lactation

Summary Prolactin levels in mouse milk increased from the day of parturition to give a concentration of 230 ng/ml on days 2 and 3 of lactation. Thereafter, levels dropped to 140 ng/ml by day 6 and were maintained at this concentration until weaning.Acknowledgments. Mouse PRL and its antiserum was the generous gift of Y.N. Sinha (Scripps Clinic and Research Foundation, La Jolla, California). J.M.B. was in receipt of a Liverpool University Studentship.     

Plasma adenosine concentrations are elevated in Dahl salt-sensitive rats

We measured plasma levels of adenosine in Dahl salt-sensitive rats (DS) and Dahl salt-resistant rats (DR) to examine the potential role of adenosine in cardiovascular regulation in this type of hypertension. Plasma adenosine concentrations were significantly higher in DS than in DR. The NaCl content in the diet did not affect plasma adenosine concentration in either DS or DR. Significant positive correlation was found between adenosine concentrations and systolic blood pressure when the data for DS and DR were analyzed together. These results suggest that adenosine may play an important role in the pathophysiology of hypertension in DS.     

氧化酪蛋白对小鼠组织抗氧化能力及血液肽组成的影响

目的研究酪蛋白经过加热氧化和脂质过氧化物MDA氧化后,对小鼠体内氧化还原状态及小鼠血液中肽组成的影响。方法酪蛋白经100℃加热（0、30、60、90min）和丙二醛（MDA）氧化（MDA终浓度0、0．2、20、200mmol／L）处理,测定其羰基、巯基含量及表面疏水性的变化。小鼠分为四组,分别灌胃生理盐水、正常酪蛋白、加热90rain、MDA氧化酪蛋白,测定0、30、60、90、120、160min血液中自由基水平,并采用HPLC-MS分析灌胃后120min小鼠血浆肽组分的变化,测定小鼠的肝脏、空肠、十二指肠组织抗氧化能力指标（总抗氧化能力T—AOC、丙二醛MDA、还原型谷胱甘肽GSH）。结果酪蛋白经过两种氧化处理,羰基含量均随氧化程度呈显著上升,巯基含量呈下降趋势。加热氧化后酪蛋白表面疏水性比正常酪蛋白低,而MDA氧化导致疏水性上升。小鼠血液中自由基最高峰出现在灌胃后160min。灌胃两种方式处理的酪蛋白,血液中自由基的含量均显著高于灌胃正常酪蛋白组（P〈0．05）,肝脏、空肠、十二指肠还原型谷胱甘肽（GSH）含量和总抗氧化能力（T-AOC）均低于正常酪蛋白组,丙二醛（MDA）含量显著提高（P〈0．05）。HPLC—MS分析显示,灌胃MDA氧化酪蛋白组血液中肽组成与对照组不同,出现c7H15N4O含羰基类的物质：结论氧化会导致酪蛋白理化性质的改变,摄入氧化酪蛋白引起机体的氧化应激,降低组织抗氧化能力。     

The effect of lactose and iron on strontium absorption

Summary In rats fed on a milk diet with or without the addition of lactose and/or iron the transileal strontium-85 transfer was higher by 14–38% and the intestinal strontium retention lower by 6–23% than in control rats fed on standard laboratory food.Presented, in part, at the 12th Yugoslav Symposium for Radiation Protection, Ohrid 1983, and at the 11th Regional Congress of IRPA (Austrian — Hungarian — Yugoslav Radiation Protection Meeting), Wien 1983. Acknowledgments. This work was supported by a research grant from the Scientific Research Council of the Socialist Republic of Croatia. The author thanks Mrs M. Buben for her technical assistance.     

The effect of lactose and iron on strontium absorption

In rats fed on a milk diet with or without the addition of lactose and/or iron the transileal strontium-85 transfer was higher by 14-38% and the intestinal strontium retention lower by 6-23% than in control rats fed on standard laboratory food.     

Immune electrophoretic analysis of bovine milk and purified bovine milk protein fractions

Zusammenfassung Immunoelektrophoretisch liessen sich aus Kuhmilch mit Hilfe einiger Kaninchen-Anti-Milchseren mindestens 12 Immunpräzipitate nachweisen. Von diesen waren 6 Präzipitate serologisch mit Blutserumproteinen verwandt (u. a. Albumin und-Globulin). Ferner wurden Präparate von-Kasein,-Laktoglobulin und-Laktalbumin analysiert.     

Production of pharmaceutical proteins in milk

There is every reason to expect that it will be possible within the next few years to begin to use farm animals to produce large quantities of some of the human proteins that are needed for the treatment of disease. Revolutionary new opportunities for the production of novel proteins in milk have been created by the development of methods for gene transfer. Exploitation of these opportunities depends upon selection and cloning of milk protein genes and identification of the sequences that govern tissue specific hormonally induced expression in the mammary gland. Studies with three genes, ovine -lactoglobulin, rat -casein and whey acidic protein of rat and mouse, suggest that they may all meet this requirement. Fragments of the ovine -lactoglobulin, murine whey acidic protein and rabbit -casein genes have directed production of novel proteins in the milk of transgenic mice, sheep, rabbits and pigs. The proteins were biologically active and usually co-migrated with authentic proteins. In early experiments, protein concentration was low, but our recent observations suggest that fusion genes containing genomic clones direct production of concentrations of protein that are suitable for commercial exploitation. In the longer term, two approaches may offer the potential of more reliable expression. Control elements capable of directing expression that is independent of site of insertion of the gene, but dependent on the number of copies of the gene, have been identified for a small number of genes. The availability of such elements for the milk protein genes would increase the reliability of gene expression considerably. Alternatively, targeted mutation of genes may allow the insertion of coding sequences within an existing gene so avoiding position effects.     

Production of pharmaceutical proteins in milk

There is every reason to expect that it will be possible within the next few years to begin to use farm animals to produce large quantities of some of the human proteins that are needed for the treatment of disease. Revolutionary new opportunities for the production of novel proteins in milk have been created by the development of methods for gene transfer. Exploitation of these opportunities depends upon selection and cloning of milk protein genes and identification of the sequences that govern tissue specific hormonally induced expression in the mammary gland. Studies with three genes, ovine beta-lactoglobulin, rat beta-casein and whey acidic protein of rat and mouse, suggest that they may all meet this requirement. Fragments of the ovine beta-lactoglobulin, murine whey acidic protein and rabbit beta-casein genes have directed production of novel proteins in the milk of transgenic mice, sheep, rabbits and pigs. The proteins were biologically active and usually co-migrated with authentic proteins. In early experiments, protein concentration was low, but our recent observations suggest that fusion genes containing genomic clones direct production of concentrations of protein that are suitable for commercial exploitation. In the longer term, two approaches may offer the potential of more reliable expression. Control elements capable of directing expression that is independent of site of insertion of the gene, but dependent on the number of copies of the gene, have been identified for a small number of genes. The availability of such elements for the milk protein genes would increase the reliability of gene expression considerably. Alternatively, targeted mutation of genes may allow the insertion of coding sequences within an existing gene so avoiding position effects.     

Occurrence of DDT and BHC residues in human milk in India

Summary Samples of human milk from Punjab, India have shown the presence of DDT and BHC residues in amounts greater than those reported from most of the other countries.This research has been financed in part by a grant made by the United States Department of Agriculture, Agricultural Research Service authorized by Public Law 480.     

Occurrence of DDT and BHC residues in human milk in India

The presence of pesticide residue of DDT and of BHC were determined in 1979 in samples of milk from 75 lactating mothers from Punjab, within a week after delivery. DDT and BHC residues were found present in all 75 samples collected. Recovery of isomers of BHC and metabolites/isomers of p.p'-DDT from the spiked samples was above 80%. The mean level of DDT residue was 0.51 ppm, which is more than the level reported from the U.S., Canada, Europe and Australia, but less than the level found in Guatemala. BHC residues also were higher than those found in other countries, with the exception of Japan. DDT level of 0.5 ppm in milk represents an infant intake of 0.09 mg/kg/day, which is 18 times the acceptable daily intake (0.005 mg/kg/day) recommended by the WHO. Acceptable daily intake of BHC has not yet been established.     

The effect of dietary lactose on the ileal absorption of sodium taurocholate in rats]

When Rats were fed a lactose containing diet, both the absorption rate of sodium taurocholate at the level of ileum and the contents of bile acids of the small intestine were increased. On the contrary, feeding of lactose did not modify the daily fecal excretion of bile acids. It therefore appears that dietary lactose increases the intestinal pool of bile acids by increasing their ileal absorption rate and that this effect of lactose is not subordinated to a modification of bile acid synthesis.     

The site of triglyceride biosynthesis in milk.

THe triglyceride biosynthesis which occurs in freshly secreted goat skim milk can be localized predominantly to large (1-8 mum) pieces of membrane-bounded cytoplasm. These contain the usual cytoplasmic organelles (but no nucleus) plus one or more large lipid droplets.