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SummaryA method for assay of lipolytic activity in platelet-poor plasma (PPP), platelet-rich plasma (PRP) and washed human platelets is presented. The lipolytic activity in PRP was about twice the activity in PPP. A significant correlation between lipolysis in platelets and platelet number was established. Molar sodium chloride strongly inhibited lipolytic activity in platelets and a washing procedure did not significantly change the lipolysis. The results indicate that a lipoprotein lipase is bound to human platelets and may play a role in metabolism of triglyceride in platelets.

Lipid studies were performed on fasting plasma samples in 214 healthy adolescent boys, 11-19 years of age. Ranges of normal values for plasma cholesterol and triglyceride concentrations, and normal lipoprotein patterns were established for this age group. The boys were grouped according to puberty rating. A significant increase in triglyceride values was obtained with adolescent maturity. Plasma cholesterol values did not change with age or puberty rating. One boy had hypercholesterolemia and a lipoprotein pattern consistent with Type II hyperlipoproteinemia (Fredrickson). Seventeen boys, all of whom had reached adolescent maturity, had elevated triglyceride values and a marked increase in pre-beta-lipoprotein. It appears from this study that increased concentrations of triglyceride and Type IV hyperlipoproteinemia of Fredrickson may be detected as boys reach maturity at adolescence.

Pig aorta glycerol ester hydrolase activity has been measured against a glyceryl tripalmitate hydrosol. The pattern of fatty acid release and the effect of some reagents known to modify lipase activity suggest that the glycerol ester hydrolase present in the pig aorta wall is a lipoprotein lipase.

Approximately half of the lipovitellin of stored shell eggs laid by hens fed a diet containing crude cottonseed oil was in a granule fraction which was not soluble in 0.7 M sodium acetate solution. The lipovitellins of this granule fraction were not isolated in the preparation of lipovitellin. The lipovitellins isolated from stored eggs contained slightly more β-lipovitellin than those isolated from fresh eggs. During storage of the eggs, some of the α-lipovitellin was converted to a lipoprotein which was eluted differently from an hydroxylapatite column than either α- or β-lipovitellin.

Lp(a), a polymorphic lipoprotein of human serum, has been isolated from strongly positive normal sera. The described procedure utilizes a serum pool of several liters. The purified lipoprotein has been investigated in its intact and totally delipidized form. Protein constituents could be characterized as apolipoprotein-B, apolipoprotein-AIII, and the Lp(a)-specific, dissociable polypeptide. Albumin could only be found in some of the preparations. The Lp(a)-specific polypeptide could be separated and characterized by its amino acid composition.

The light and, to a lesser extent, the dark cells of the cortical collecting tubules in mouse kidney contain a great number of granules which according to histochemical tests are composed of phospholipids and proteins. These granules are bounded by a triple-layered membrane measuring approximately 75 A across, and contain one or several crystals with a hexagonal or square lattice. These crystals are built up of rod-shaped units, which appear dense after osmium fixation, measure about 48 A in diameter, and are separated by a light interspace of similar dimensions. The mean center-to-center distance of the rods is about 96 A. The structure is explained as a lipoprotein crystallized within a membrane-bounded vacuole. No relationship between these granules and mitochondria was found. The physiological significance of the granules remains unknown.

Rennin is regarded as being similar to viruses such as vaccinia and phage in its physical and chemical properties. Rennet activity is carried by a lipoprotein existing in particles or micells of very great dimensions.

Summary1. Elinin, a lipoprotein fraction of the red cell exhibiting Rh activity has been isolated in relatively pure form largely by physical methods.2. Injection of elinin from Rh positive cells into animals has so far failed to yield a measurable titer of anti-Rh antibodies.3. Injection of elinin into human subjects who have been sensitized to the Rh factor by pregnancy or transfusion failed to increase the titer of Rh antibodies in the serum. Two of the subjects injected showed subsequent response to injection of whole Rh positive cells.4. Injection of 1 to 1.5 g of active elinin intramuscularly failed to effect a change in titer of circulating antibodies.

An electrophoretic study of a lipoprotein from calf thymus and calf liver is presented. Each of the lipoproteins studied revealed the presence of only one component. Isoelectric points lie between pH 4.65 – 4.85.

SummaryMouse brains were extracted with a variety of solutions composed of inorganic salts, organic solvents, or mixtures of each. During these experiments, it was noted that a differential effect of certain salts and solvents on isozyme patterns could be demonstrated. These effects of isozyme systems [lactic dehydrogenase (LDH) and nonspecific esterase] could best be explained on the basis of lipid-enzyme complexes. Circumstantial evidence is provided for viewing LDH as a lipoprotein catalyst.

In cattle with J blood-group substance both on erythrocytes and dissolved in serum, J activity was found in the total lipids extracted from erythrocytes, but not in the proteins precipitated by lipid extraction and not in the mucoproteins prepared from erythrocytes. Serum from these animals, however, does not only exhibit J activity of its total lipid, but also of its mucoproteins and of its residue after lipid extraction. This serum, therefore, contains the J substance in at least two different forms, as a lipoprotein and as a mucoprotein. Only the J lipoprotein is able to coat bovine erythrocytes during a postnatal period. It is suggested that hydrophobic groups are responsible for the attachment of the J substance to the erythrocytes. In cattle with J substance only in serum, coating of erythrocytes is missing. This is apparently due to the finding that the serum from these animals contains J mucoproteins, but virtually no J lipoprotein. Since the determinant of the J lipoprotein has been found in the glycosphingolipid fraction the genetically fixed difference between animals which have J substance on erythrocytes and in serum and those which have it only in serum seems to consist in the inability of the latter animals to synthesize a glycosphingolipid containing the sequence of sugars which is responsible for J specificity.

SUMMARY Cow’s milk has been found to contain a lipoprotein lipase similar to those previously demonstrated in post-heparin plasma, adipose tissue, and heart. Upon separation of the milk, most of the enzyme was found in the skim milk, although some was present in the cream from which it could be isolated with a relatively high specific activity. The triglycerides of cream were not hydrolyzed by the lipoprotein lipase, and it is supposed that the enzyme does not function in milk but rather in the lactating mammary gland.

SummaryIt has been demonstrated with the use of a functionally hepatectomized preparation and in the presence of a lipoprotein lipase inhibitor, Triton WR 1339, that, in the chicken, long chain fatty acids are absorbed in the form of triglycerides as the major component of a lipoprotein of density less than 1.006.

The histological anatomy of the female reproductive system of an oxyuroid nematode,Aspiculuris tetraptera, Schulz, has been described.The process of egg-shell formation in this animal has been followed in detail while the structural and chemical characteristics of the egg-shell have been studied by histochemical and other methods. It is shown that there are three layers: a lipoprotein layer, a ‘chitinous’ layer and the so-called vitelline (glycosidal) membrane. Evidence is presented for the exogenous origin of the lipoprotein layer: this being formed by the cells of the upper uterus which are shown to be secretory.The question of quinone-tanning in the egg-shell ofA. tetrapteraand in other oxyuroids and ascarids is considered. It is shown that neither a polyphenol oxidase nor a high concentration of phenolic substances (apart from protein tyrosine) exists in this system. The significance of these and other observations is discussed in relation to the mechanism of tanning as elucidated in insects and trematodes.I have to acknowledge with gratitude the support of many during these investigations. To Dr P. Tate for his encouragement and provision of facilities at the Molteno Institute; to Dr D. L. Lee, for much useful discussion and permission to refer to some of his unpublished electron micrographs of nematodes; to Professor J. D. Smyth, who kindly read through the manuscript; to the Cambridge Philosophical Society for a grant that made possible the translation of Fauré-Frémiet's classical study onAscaris;and to the Department of Technical Cooperation for financial assistance.

In order to identify the chemical nature of the membrane receptor sites involved in general anesthesia the apparent free energy of binding of methylene groups of n-alcohols in anesthetic systems was evaluated and compared with data from model systems. It was concluded that the sites may consist either of (i) the non-polar portions of lipids, (ii) a non-polar region of a lipoprotein made up of non-polar portions of the protein and lipid moieties or (iii) protein. However, if the site consists only of protein it is possible that this material undergoes a ligand-induced conformation change on binding the anesthetic. Some reasons for the use of caution in employing temperature effects to identify the chemical nature of the receptor sites are outlined.

The bactericidal substance present in mitochondrial extracts from rat leucocytes was found to be non-dialyzable, fractionated at 30 per cent (NH4SO4 saturation and was able to withstand temperatures up to 100°C. The tentative identification of a lipoprotein as the responsible bactericidal substance is based on various observations; an ultraviolet absorption at a peak associated with alpha, beta unsaturated fatty acids, 205 to 208 mµ, inactivation of the bactericidal substance by ether treatment at –70°C. but not at 0°C. and inhibition of the bactericidal activity with lipase treatment as well as with trypsin.

Agents capable of accelerating the conversion of prothrombin into thrombin in the presence of Ca+ may be said to have thromboplastic activity. Early studies of thromboplastic activity were carried out with materials derived from tissues. Wooldridge (1, 2), in 1886, produced intravascular clotting in animals by the intravenous administration of aqueous extracts of red blood cells, white blood cells, and tissues. He was of the opinion that the active factor in these extracts was a protein-lecithin compound. In 1912, Howell (3) also reported that a lipoprotein was responsible for the thromboplastic activity of aqueous tissues extracts. The lipid portion was a phosphatide which could be separated from the protein with fat solvents, and had the properties of "cephalin." He assumed that the thromboplastic activity of certain lecithins tested was due to contamination with cephalin. McLean (4, 5) extended these observations and showed that the potency of the cephalin preparation varied directly with the degree of unsaturation of the constituent fatty acids. Gratia and Levene (6) confirmed the work of Howell, using their own cephalin preparations. Wadsworth, Maltaner and Maltaner (7-9) prepared cephalin free of lecithin and showed that the lecithin had no thromboplastic activity. Cohen and Chargaff (10) and Chargaff (11) verified that the tissue thromboplastic factor was a lipoprotein and that the lipid portion was associated with the phosphatides. It became of interest to determine whether plasma contained a thromboplastic factor analogous to that found in the tissues. Wooldridge (12) suggested that a thromboplastic substance existed in plasma ("Fibrinogen-B") which united

A lipoprotein-X (LP-X) test has been performed in normal subjects and in patients with hepatobiliary diseases and haemolytic anaemia. Statistical analysis revealed a correlation between the occurrence of LP-X and increase of conjugated bilirubin and alkaline phosphatase. The LP-X test makes it possible to differentiate obstructive from non-obstructive jaundice but it fails to demonstrate or exclude cholestasis in all cases and cannot distinguish between intrahepatic and extrahepatic cholestasis.

When a high molecular weight dextran sulfate solution was added to serum in the presence of calcium ions, a lipoprotein complex was precipitated that contained the total serum cholesterol. The incorporation of this precipitation step in the procedure for total cholesterol determinations eliminated errors due to high serum bilirubin levels.

Lysosomes, as isolated and defined by biochemists, are particles in which acid lytic enzymes are contained by a lipoprotein membrane; they are inert until the membrane has been rendered permeable. Previously it has not been possible to demonstrate cytochemically organelles which meet all these criteria, since all the preparatory procedures have affected the membrane permeability. The controlled temperature freezing-sectioning method has permitted the demonstration of granules which are inactive for acid phosphatase until subjected to agents that will disrupt lipid-protein structures, such as heat, formalin, and ‘triton X-100’. Hence such organelles may be identified with the biochemists lysosomes.

The developing cuticle ofPeriplanetashows some resistance to chemical attack even before the onset of the phenolic tanning which gives it its final hardness and colour. This early resistance is due to the impregnation of the cuticle with a lipoprotein complex. Histological and histochemical examination suggest that the combination of the sterol and protein moieties of the complex is dependent on the occurrence of some degree of aromatic bonding of the protein even before final tanning takes place. During this initial or primary aromatic bonding no marked colour is developed, and the active agent is not derived from a dihydroxyphenol, as it is in final tanning, but is a quinone formed by the oxidation insituof the tyrosine component of the protein moiety. No free dihydroxyphenol is involved, and the protein may be referred to as ‘self-tanning’. During the process of final hardening the protein of the impregnating complex undergoes further tanning. There is some evidence that the sterol also may be involved in this process, not merely through its association with the protein, but directly owing to its combination with the tanning agent.

SUMMARY: An inositol-dependent yeast Kloeckera brevis was grown in a medium limited in inositol and the fate of the inositol determined. All of the inositol was taken in by the yeast and combined in an organic form. Fractionation of the yeast after disruption in a Hughes press showed that 31-38% of the combined inositol was soluble in trichloroacetic acid solution and 43-65% was soluble in neutral or acidified lipid solvents. The trichloroacetic acid extract contained three inositol components; one minor one was identified as inositol monophosphate. The major component was a neutral derivative of mesoinositol which was not identified as any known naturally-occurring form of combined inositol. The lipid extracted with neutral solvents contained an inositide whose properties were those of phosphatidyl inositol. The lipid inositol extracted with acidified solvents appeared to be present in a lipoprotein.

Lp(a)-lipoprotein of human serum, when isolated by ultracentrifugation and gelfiltration on Sepharose 4 B, may disaggregate into several components either spontaneously or by mild treatment with detergents

Plasma proteins, as separated by zone electrophoresis, of coho salmon have been investigated from an early age to spawning and death. A protein fraction which may be similar to γ-globulin in other vertebrates increased throughout the period studied. Smolt transformation was associated with a temporary disappearance of the fastest migrating protein fraction. A lipoprotein fraction, presumably serum vitellin, was associated with egg formation. Serum vitellin was absent from the plasma of males, immature females, spawning females and spawned-out females.

Durch Subtraktion der Rontgenkleinwinkelstreuung gelber Blatter von der Rontgenkleinwinkelstreuung gruner Blatter kann die unspezifische Streuung der Blatter eliminiert und dadurch die spezifische Streuung des Lamellarsystems der Chloroplasten erhalten werden. Eine Analyse der spezifischen Streuung fuhrt auf eine Lipoproteinlamelle, die aus zwei Schichten, einer Lipid- und einer Proteinschicht, aufgebaut ist. Jeweils zwei derartige Lipoproteinlamellen sind so angeordnet, das die beiden Lipidschichten benachbart verlaufen. Der Raum zwischen den beiden Lipidschichten ist mit Wasser ausgefullt. Die Abgrenzung der Lipid- gegen die Proteinschichten erfolgt durch die Porphyrinringe des Chlorophylls, die in einer monomolekularen Schicht angeordnet sind. Die Proteinschicht besteht aus einer zweidimensionalen Anordnung von Proteinmolekulen. By subtraction of the small angle X-ray scattering of yellow leaves from the small angle X-ray scattering of green leaves it is possible to eliminate the non-specific scattering of the leaves and to obtain thereby the specific scattering of the lamellar system of the chloroplast. The analysis of the specific scattering indicates a lipoprotein lamella which is built up by two layers, one lipid and one protein layer. Two lipoprotein lamellae are arranged in pairs so that the two lipid layers are neighbours. The space between the two lipid layers is filled by water. The boundary between the lipid and protein layers is formed by a monomolecular layer of the porphyrin rings of chlorophyll. The protein layer consists of a twodimensional arrangement of protein molecules.

SummaryΔ1-Testololactone administration caused no protein anabolic or androgenic effects in 4 subjects. Serum cholesterol and phospholipid levels fell, however, as did a lipoprotein lipids in three. The a lipoprotein effect is typical of testosterone and suggests a separation of lipoprotein from androgenic-anabolic properties in a testosterone derivative

The Lp(a) lipoprotein was originally suggested to be a qualitative autosomal dominant genetic marker confined to about 35% of Caucasian populations, when these were screened by a gel-diffusion technique. Using a more sensitive and quantitative immunochemical technique, the Lp(a) lipoprotein is found to be detectable in 75% of a random British population and to show quantitative variation in concentration between individuals. In hyperlipidaemic subjects (with the exception of subjects with the Type V abnormality) there is an overall increase in Lp(a) reactivity with a tendency for higher individual values to occur, regardless of the type of hyperlipidaemia. In individuals with coronary heart disease, hypertriglyceridaemia and the presence of a pre-beta-lipoprotein band on electrophoresis, no evidence was obtained to suggest that the electrophoretic abnormality was directly due to the increased frequency of Lp(a) reactivity found in such subjects. Using the immunofluorescent technique, the Lp(a) antigen has been demonstrated in the arterial atherosclerotic lesions of Lp(a) reactors in a topographic distribution closely similar to that of LDL.

The present study of 100 patients (46 of whom were included in a previous study) with suspected or proven coronary heart disease (CHD) confirms that Lp(a) lipoprotein and pre-beta1-lipoprotein are closely related, if not identical, and that Lp(a) lipoprotein/pre-beta-lipoprotein occurs more frequently in patients with CHD than in healthy people. Analysis of this lipoprotein component may have predictive value with respect to CHD.

A strong, positive association (P smaller than 0.0001) was found between the presence in serum of pre-beta1-lipoprotein upon electrophoresis in 0.5% agarose and the Lp(a+) phenotype in a series of 103 males aged 50-52 years participating in a health control study and in a series of 58 patients with sustained myocardial infarction. Both lipiprotein phenomena were more prevalent in the 58 patients than in the 103 presumably healthy males. The lack of any significant difference between total cholesterol values in the patients and the controls, despite the higher frequency of phenotype Lp(a+) in the former group, argues against the suggestion by Walton et al. (1974) that the increased Lp(a+) frequency in patients with coronary artery disease may be caused by a general increase in the concentration of low density lipoproteins (LDL).

To assess the relationship between the Lp(a) and the "sinking pre-beta" (d smaller than 1.006) lipoprotein, the concentration of Lp(a) was quantified by radial immunodiffusion and the presence or absence of sinking pre-beta was assessed by agarose electrophoresis in overnight fasting plasma samples from 485 adults, comprised of 320 with normal lipid levels, 48 with type IIa, 40 with type IIb, and 77 with type IV lipoprotein phenotypes. The median Lp(a) level was 7.6 mg/100 ml, 89% (433 of 485) having detectable Lp(a) levels. Twenty-two per cent (107 of 485) had detectable pre-beta lipoprotein in the d greater than 1.006 plasma fraction (sinking pre-beta). Of the sinking pre-beta positive plasma samples, 96% (102 and 107) exceeded the median Lp(a) level, and sinking pre-beta was detected in all 44 samples with an Lp(a) concentration exceeding 40 mg/100 ml. The relationship of Lp(a) and sinking pre-beta to lipoprotein phenotype was assessed. Compared to the normolipidemic group, the type IIa group had higher Lp(a) percentile values (p smaller than 0.02), whereas the IIb and type IV groups had significantly lower Lp(a) values than the normolipidemic group. Ninety-two per cent (296 of 320) of the normolipidemic subjects had detectable levels of Lp(a) and 22% (70 of 320) had detectable sinking pre-beta lipoprotein. Ninety-four per cent (45 of 48) of the type IIa plasmas had detectable Lp(a) levels and 27% (13 of 48) had sinking pre-beta lipoproteins. Contrasted with the IIa group, only 80% (32 of 40) of the IIb plasmas had detectable Lp(a) levels and 18% (7 of 40) had sinking pre-beta lipoprotein. In the type IV plasmas 78% (60 of 77) had detectable Lp(a) and 22% (17 of 77) had sinking pre-beta lipoprotein. Lp(a) or log Lp(a) levels were not correlated with apolipoprotein B levels (n = 485, r = 0.002 or 0.037, respectively). Furthermore, Lp(a) levels remained essentially constant in three subjects whose aprptein B levels were altered in response to pharmacological and/or dietary manipulation. A fourth subject had a 50% increase in Lp(a) but this change did not correlate with apoprotein B changes. Thus, these findings suggest that Lp(a) is metabolically independnet of low density lipoprotein even though it shares the same structural protein, apoprotein B.

Summary In rooks we have found high serum lipid values, a macroscopically visible lipemia, without, by morphological examinations, any symptoms of atherosclerosis. The hyperlipemia was accompanied by lipoproteins of high electrophoretic mobility. Reasons for not finding atherosclerosis in rooks despite high plasma lipid levels are discussed.

Recent chemical and physical studies have clearly shown that visual pigments are an integral part of a lipoprotein membrane whose apparent role is to initiate cation exchange flow across its boundaries, when illuminated, giving rise, thereby, to a neural receptor potential. As membrane structures visual pigments are unique in that they contain, as the principal prosthetic group, a chromophore whose rather singular absorption spectrum serves as a sensitive probe of its molecular environment and whose spectral changes provide an essentially non-perturbative method of monitoring molecular events occurring within the membrane.

A lipoprotein which has lethal effects when injected into recipient animals has been isolated from mouse skin which has been exposed to controlled thermal energy. The toxic activity served as a means to monitor the isolation procedure. The properties of this product were found to be identical with those of the corresponding non-toxic compound obtained from native skin according to the same isolation procedure. Both products were comprised of the same six lipid classes and six oligomeric polypeptides. The toxin differed from the native product in molecular size and density. It would appear that thermal energy induces polymerization of a normal membraneous cell wall unit.

Apresentação de um caso de síndrome de Hunter-Hurler (gargoilismo); o diagnóstico foi firmado com base no quadro clínico, embora a paciente não apresentasse ura dos aspectos característicos que é o facies grotesco. A presença de alterações vertebrais características e da opacidade leitosa difusa da córnea, permitem o diagnóstico. A análise eletroforética das frações protêicas do sôro não permitiram tirar conclusões definidas, por se tratar de caso isolado; entretanto, deve ser destacada a existência de uma lipoproteína sem mobilidade eletroforética que, indicando a presença no sangue de um complexo lipoprotêico instável, poderia sugerir a possibilidade de formação de depósitos de lipóides. Case report of a Hunter-Hurler syndrome (gargoylism). The diagnosis was based on the clinical picture, although the grotesque facies, one of the main characteristics, was missing. The presence of typical vertebral alterations and the milk diffused opacity of the cornea, are sufficient to assure the diagnosis. The electrophoretic analysis of the serum proteins do not allow the authors to make definite statements because only one case was studied; however they point out the fact, considered very important by them, that there was a lipoprotein without electrophoretic mobility which indicating the presence of an instable lipoprotein complex in the blood, may suggest the possibility of lipoid deposit formation in the cells.

The apoprotein of human erythrocyte membranes was covalently spin-labelled with nitroxide-maleimide and mixed anhydride labels, before and after removal of sialic acids. The e.s.r. spectra and pH-induced spectral changes were compared with the reported spectra of native membranes. Interactions between the apoprotein and other lipids were examined using lipids containing spin probes. Lysolecithin was shown to bind more strongly than other lipids to membrane apoprotein. This binding was compared with the binding of lysolecithin to bovine serum albumin and acid casein. The formation of a lipoprotein complex between positively charged sialic acid free apoprotein and negatively charged sonicated dispersions of membrane lipid in an aqueous medium was examined using spin labels and spin probes. The data demonstrate that both polar and apolar interactions between the lipid and protein are involved in stabilisation of the complex.

Ultracentrifugal studies of whole serum and crude Fraction IV to which 131I thyroxine had been added have revealed more than 89% of the radioactivity in the D>1.21 (“bottom”) material. Precipitation with antisera against alpha-1, alpha-2 and beta-lipoproteins resulted in no radioactivity in the precipitates. Analysis of a subtraction of Fraction IV-4 rich in TBG revealed no detectable lipid. These findings indicate that thyroxine binding alpha-globulin is not a lipoprotein of the major lipoprotein classes. (Endocrinology 77: 398, 1965)

It has been established that a lipid-soluble selenium compound is enriched in high molecular weight (m.w. ≥5000) extracts from fish. The selenium compound is also enriched in oil extracted from fish by a mixture of non-polar and polar organic solvents (hexane-isopropanol) as compared to the oil extracted with non-polar solvents (hexane) only. When raw fish material is stored it gradually deteriorates and the selenium content in oil produced by boiling of the raw fish material, increases with time. The results indicate that at least part of the lipid-soluble selenium is bound as a lipoprotein.

Doctors' wives who browse through medical journals have recently become anxious about the toxicity and carcinogenic potential of the polyunsaturated fatty acids they use in preparing Jolliffe's "Prudent Diet" for their husbands. They have read an editor's suggestion that "linoleic acid acts by diverting energy required for the synthesis of body constituents" and that "unsaturated fatty acids are potent uncouplers" of oxidative processes from adenosine triphosphate production, and that the "effect of unsaturated fatty acids on the incidence, growth and spread of tumors" should be studied before using them as foods.1 Perusal of the references given by the editor seems to dispel the ghosts which so alarm him. Microsomes, the metabolic centers of the cells, do contain a lipoprotein which potentiates their enzymes for splitting adenosine triphosphate. This lipoprotein does contain polyunsaturated and, in larger quantities, saturated fatty acids and those with one double bond. The fatty acids alone

Growing rats were fed diets containing a lipoprotein concentrate prepared from niger seeds, as the sole source of protein. Protein efficiency ratio (PER) and productive protein value (PPV) were calculated for two levels of protein in the diet, 11.1 % and 22.4 %, respectively. When the protein content of the diet was 11.1 % the PER was 2.37 (for a feeding period of three weeks). The corresponding PPV was 42.0. A short term toxicological feeding study was carried out on rats fed with these diets for a 90-day period. No significant diet-related changes were observed in the growth, appearance, behaviour and survivals of the animals. Hematological findings were normal. The histopathological examinations of the main organs gave normal results. Electron microscopy showed an increased amount of multi-vesicular bodies (possibly lysosomes) as well as an increased content of fat droplets in the cytoplasm of liver cells. The significance of these changes remains unclear.

Certain properties of the atypical serum lipoprotein, referred to as pre-β1-lipoprotein, suggested that it might be identical to the lipoprotein carrying the Lp(a) antigen: Lp(a) lipoprotein. Both lipoprotein phenomena are under genetic control and occur in a certain proportion of healthy people. Pre-β1-lipoprotein occurs more frequently in patients with coronary heart disease (CHD) than in the healthy population. The present study of Finnish CHD patients was undertaken to investigate whether a close relationship could be revealed between pre-β1-lipoprotein and Lp(a) lipoprotein, as well as between Lp(a) lipoprotein and CHD. Both expectations were realised, and we conclude that pre-β1-lipoprotein is very closely related, if not identical to Lp(a) lipoprotein. If the present results are confirmed in future studies, serum analysis for Lp(a) lipoprotein/pre-β1-lipoprotein may become a useful tool for the identification in early life of members of a subpopulation which is particularly at risk for developing CHD.