Plasma lipoprotein changes in suckling and weanling rabbits fed semipurified diets

The distribution and composition of the plasma lipoproteins were studied in suckling rabbits and in rabbits either weaned to or fed as young adults cholesterol-free, semipurified diets containing protein of animal (casein) or plant (soy protein isolate) origin. The raised cholesterol levels of the suckling period resulted in an increase of very low density and intermediate density lipoproteins in a manner similar to that seen in adult rabbits fed a high fat diet supplemented with cholesterol. Young rabbits fed the cholesterol-free, semipurified diet containing casein also became hypercholesterolemic but, in this case, the increased cholesterol was found primarily in lipoproteins of intermediate density. Cholesterol levels remained low in those rabbits fed the soy protein isolate diet, and the lipoprotein distribution was somewhat similar to that of chow-fed animals. It appears that the raised cholesterol levels during the suckling period result in different lipoprotein patterns to those produced in young adult animals by a cholesterol-free, semipurified diet.     

The influence of protein and carbohydrate type on serum and liver lipids and lipoprotein cholesterol in rabbits

The non-lipid portions of semi-synthetic diets appear to be important determinants of hypercholesterolemia and atherosclerosis in the rabbit. Serum and liver lipid concentrations were determined in rabbits which had been pair-fed various protein (casein or soy protein isolate) and carbohydrate (sucrose or dextrose) sources as part of low fat, low cholesterol, semi-synthetic diets. It was verified that caseincontaining diets render rabbits hypercholesterolemic, while soy protein caused a degree of hypocholesterolemia. Additionally, sucrose, when fed in conjunction with casein, appears to augment this hypercholesterolemic effect. The distribution of total cholesterol among lipoprotein subclasses was increased in both the intermediate density lipoprotein (IDL) (1.006–1.019 g/ml) and low density lipoprotein (LDL) (1.019–1.063 g/ml) fractions and decreased in the high density lipoprotein (HDL) (1.063–1.21 g/ml) fraction when casein is fed. Soy protein feeding caused relatively more cholesterol to appear only in the IDL fraction when compared with commercial chow fed rabbits. Reasons for these differences may involve the saturation or suppression of endogenous lipoprotein hepatic receptors.     

l-Carnitine effects on chemical composition of plasma lipoproteins of rabbits fed with normal and high cholesterol diets

l-Carnitine plays an important role in the mitochondrial uptake of long-chain fatty acids in mammals. It has recently been shown that this compound has a marked hypo-cholesterolemic effect when used in conjunction with lipid-rich diets. The aim of this study was to investigate the effects of l-carnitine on the fatty acid composition of plasma lipoproteins in rabbits fed with different diets. Four different groups were investigated: group I (standard diet), group II (standard diet supplemented with l-carnitine at 80 mg/kg), group III (standard diet supplemented with 0.5% cholesterol), and group IV (standard diet supplemented with 0.5% cholesterol plus l-carnitine at 80 mg/kg). The feeding period was 126 d. Total plasma cholesterol was indistinguishable in groups I and II, but increased nearly 40-fold in group III. This increment was reduced by 50% in group IV. Correspondingly, total cholesterol content in lipoprotein fractions [very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) separated by agarose gel chromatography was the same for groups I and II, while for animals fed a cholesterol-rich diet (III) total cholesterol in VLDL+LDL increased nearly 100-fold when compared with groups I and II but, again, the increment was reduced by 50% in group IV. In contrast, total cholesterol in HDL increased only fivefold for both groups III and IV when compared with groups I and II, indicating no effects of l-carnitine on this parameter. The reduction of total cholesterol in VLDL+LDL particles in animals fed a cholesterol-rich diet plus l-carnitine was associated with a marked decrease in the ratio of cholesteryl ester to free cholesterol and a dramatic increase in their phospholipid content; opposite effects were observed for HDL. l-Carnitine induced a marked decrease in the saturated to unsaturated C₁₆+C₁₈ fatty acid ratio in cholesteryl esters associated with VLDL and LDL from animals fed with both normal and cholesterol-rich diets. The opposite effect (a large increase in the saturated to unsaturated fatty acid ratio) was observed for both cholesteryl esters and phospholipids associated with HDL in animals fed with both diets. The results suggested that the hypocholesterolemic effects of l-carnitine could be associated with increased systemic breakdown of cholesteryl esters, a probable increase in reverse cholesterol transport, and the stabilization of a phospholipid-based structure of VLDL+LDL particles.     

The effect of alfalfa-corn diets on cholesterol metabolism and gallstones in prairie dogs

Cholesterol gallstones were present in prairie dogs fed alfalfa plus corn with and without exogenous cholesterol (0.4%). The diets fed to the animals for eight weeks contained alfalfa plus corn in fixed proportions of 50∶50, 85∶15 and 15∶85 (w/w). At sacrifice, all animals were healthy but had not gained weight; no deaths occurred during the experiment. Cholesterol gallstones were present in all groups. In the absence of exogenous cholesterol, the highest stone incidence was found in the animals which received the lowest fiber (highest corn) diets (alfalfa plus corn, 50∶50, 67%; alfalfa plus corn, 15∶85, 83%). Cholesterol gallstone incidence was 100% when exogenous cholesterol was added to the alfalfa plus corn diets (50∶50 and 15∶85). No pigment gallstones were detected in any animal. Liver and plasma cholesterol concentrations were highest in the animals receiving alfalfa plus corn (15∶85) plus 0.4% cholesterol (4.29 mg/g, and 356 mg/dl, respectively). These values were lowest in animals receiving 85% alfalfa plus 15% corn without cholesterol (2.19 mg/g and 88 mg/dl, respectively). Lithogenic indices were below 1.00 in all groups. Biliary bile acids were mainly amidates of cholic acid and chenodeoxycholic acid, with the former predominating. Thus, gallstones can be formed in prairie dogs in the absence of exogenous cholesterol; gallstone incidence is reduced by dietary fiber.     

Nutritive value of diets based on tubers and legumes consumed in 3 different proportions

This study was an attempt to determine the nutritional value of diets based on mixtures of manioc and cowpea flours. The proportions analyzed were 87/13, 70/30 and 50/50, respectively. The effect of supplementing these diets with methionine was also investigated. The nutritional value of the diets was evaluated using as a basis the percentage of utilizable protein. Findings revealed that the protein was best utilized when the percentages of manioc and cowpea flours were 50/50, with significant differences observed among the proportions analyzed. In contrast, no significant differences were observed with methionine supplementation to diets of manioc and cowpea flours mixed in the proportion of 87/13. However, when the proportions were 70/30 and 50/50, the addition of methionine induced significant differences, with the highest protein value in both mixtures. It was also observed that the percentage of utilizable protein increased as the proportions of cowpea in the diets also increased.     

Effects of diets high in saturated fat and cholesterol on the lipid composition of canine platelets

The phospholipid composition of platelets from dogs on various experimental diets was determined. Thyroidectomized foxhounds were fed a control diet or the control diet supplemented with (1) beef tallow, (2) beef tallow and cholesterol, or (3) beef tallow, cholesterol, and safflower oil for 23 weeks prior to isolation of platelets. Platelets from animals fed the control diet contained 36.7% phosphatidylcholine (PC), 22.8% phosphatidylethanolamine (PE), 18.4% sphingomyelin (Sph), 11.8% phosphatidylserine (PS), 6.3% phosphatidylinositol (PI), and 2.2% lysophosphatidylcholine. The PE was 77.6% in the plasmalogen form. No highly significant changes in the phospholipid class composition resulted from the experimental diets. Cholesterol supplementation of the diets, however, caused consistent alterations in the fatty acid compositions of the platelet phospholipids including increases in the percentages of 18∶1ω9 (oleic acid), 18∶2ω6 (linoleic acid), and 20∶3ω6 (homo-gamma linolenic acid) and a decrease in the percentage of 20∶4ω6 (arachidonic acid). Addition of safflower oil to the tallow-cholesterol diet partially reversed these effects. These cholesterol-induced alterations in fatty acid composition could be due to exchange with plasma lipids, de novo synthesis, or altered platelet metabolism. The mechanism remains to be determined. Der. Nelson’s current affiliation is the Lipid Metabolism Branch, Division of Heart and Vascular Diseases, National Heart, Lung, and Blood Institute.     

The effect of neurotensin on the concentration of cholesterol and bile acids in the guinea pig

In guinea pigs, total plasma cholesterol concentrations increased above the control values after single intravenous injections and after 3 days of continuous subcutaneous administration of neurotensin (NT). A high dose of NT (125 pmol/100 g body weight) induced tachycardia and severe respiratory distress; the lowest dose (1.25 pmol/100 g body weight) had the greatest hypercholesterolemic effect 15 min after the injections. The bulk of the total plasma cholesterol was in low density lipoprotein fractions. Cholesterol increased in the same fractions after intravenous administrations of NT. NT induced a decrease in the cholesterol content in the ileum but did not affect significantly the cholesterol content in the liver, kidneys or adrenals. In 48-hr fasted controls, plasma cholesterol concentration and cholesterol content in the liver, kidneys, adrenals and terminal ileum increased; after intravenous injections of NT, plasma cholesterol concentration further increased but cholesterol content of the liver, kidneys and ileum decreased. In fed animals, the concentration of the biliary taurochenodeoxycholic acid increased above the control values 5 and 35 min after the intravenous injections of NT. In fasted controls, the total concentration of bile acids was higher than in fed controls, but only the concentration of taurochenodeoxycholic acid further increased after the injections of NT. Proportionately more taurochenodeoxycholic acid than cholesterol was present in bile after the intravenous injections of NT. These data are consistent with the hypothesis that NT has a regulatory role in intestinal cholesterol transport.     

Effects of ethanol diets on cholesterol content and phospholipid acyl composition of rat hepatocytes

Chronic treatment of adult male rats with ethanol liquid diets resulted in alterations in phospholipid and cholesterol contents as well as the acyl composition of phosphatidylethanolamine (PE), phosphatidylinositol (PI)-phosphatidylserine (PS) mixture, and phosphatidylcholine (PC) of isolated hepatocytes. The influence of ethanol on these lipids was largely dependent on the proportion of dietary fat. Phospholipid and total cholesterol contents were elevated 23 and 27%, respectively, by ethanol when offered in a low-fat diet (5% corn oil). Only the percentage of arachidonic acid from PI-PS was significantly reduced in the low-fat ethanol group. Exposure to a high-fat (34% corn oil) diet in the presence of ethanol for 4–5 weeks resulted in a significant decrease in arachidonate/linoleate ratios of hepatic PE, PS-PI and PC, while total phospholipid content remained constant. In the high-fat, ethanol-treated group, hepatic cholesterol content was increased 2-fold. These results suggest that the level of dietary fat plays an important role in determining the effects of chronic ethanol consumption on hepatic cholesterol content and phospholipid acyl composition.     

Low-density lipoprotein turnover in inbred strains of rabbits hypo- or hyperresponsive to dietary cholesterol

In two inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol, low density lipoprotein (LDL) apolipoprotein (apoLDL) kinetics were determined with the use of a heterologous tracer isolated from a Watanabe heritable hyperlipidemic (WHHL) rabbit. On a diet without added cholesterol, the total clearance of apoLDL (which equals apoLDL production) did not differ significantly between rabbits of both strains. After the feeding of a diet containing 0.1% cholesterol for six weeks, plasma LDL cholesterol, plasma apoLDL and liver cholesterol concentrations rose significantly in the hyperresponsive but not in the hyporesponsive rabbits. Cholesterol feeding depressed the total fractional catabolic rate (FCR) of apoLDL in the hyper- but not in the hyporesponsive rabbits; this was attributed to a decrease of receptor-dependent FCR while receptor-independent FCR was similar in the two strains. On the diet containing cholesterol, the receptor-mediated absolute catabolic rate (ACR) of apoLDL did not differ between hyper- and hyporesponsive rabbits but receptor-independent ACR of apoLDL was higher in hyperresponders. It is concluded that the higher plasma apoLDL levels in hyperresponsive rabbits fed the 0.1% cholesterol diet are caused by a higher production of apoLDL and not by a lower flux of apoLDL through the receptor-mediated pathway.     

Microplate methods for determination of serum cholesterol,high density lipoprotein cholesterol,triglyceride and apolipoproteins

Microtiter plate methods were developed for the enzymatic determination of serum total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and triglyceride (TG), and for the turbidometric determination of apolipoproteins. The micromethods resulted in accurate, precise values that were in good agreement with the conventional spectrophotometric assays. The coefficient of variation for TC determinations was 4.5% or less and bias was 5% or less. The lipid micromethod assays are sensitive to 10 mg/dL or less, and the apolipoprotein assay to 1 mg/dL. Less than 100 μL of serum suffices for TC, TG and apoprotein assays; HDL-C requires an additional 100 μL of serum. Advantages of the micromethods include reductions in assay time and in the amount of reagents required.     

Lipoprotein composition and serum cholesterol ester fatty acids in nonwesternized melanesians

In this study, the relationships between dietary fat [as measured by serum cholesterol ester fatty acids (CE-FA)], age, smoking, body mass index, and serum lipids were analyzed in 151 subsistence horticulturalists, aged 20–86 yr, from Kitava, Trobriand Islands, Papua New Guinea. Their diet consists of tubers, fruit, coconut, fish, and vegetables with a negligible influence of western food and alcohol. Total fat intake is low [21% of energy (en%)], while saturated fat intake from coconuts is high (17 en%, mainly lauric and myristic acid). In multivariate analysis, 11–43% of the variation of the serum lipoprotein composition was explained by CE-FA, age, and smoking habits. The proportion of CE20∶5n-3 explained much of the variation of triglycerides (TG, negative relation) and high density lipoprotein-cholesterol (HDL-C, positive) in both sexes and serum apolipoprotein A1 (ApoA1, positive) in the males. CE16∶0 was positively related to TG and negatively related to HDL-C and ApoA1 in both sexes, and in males it related negatively to total cholesterol (TC) and low density lipoprotein-cholesterol (LDI-C). In males, negative relationships were present between CE18∶2n-6 and TC and between CE14∶0 and serum lipoprotein(a). Smoking was independently associated with lower ApoA1 in both sexes and with lower HDL-C and higher TG, TC, LDL-C, and apolipoprotein B in males. In conclusion, marine n-3 fatty acids and linoleic acid showed the same potentially beneficial relationships with lipoproteins and apolipoproteins as in western populations. The relations of palmitic acid to serum lipids may be explained in terms of endogenous fat synthesis at a low-fat intake, rather than reflecting its relative intake.     

Influence of cholesterol feeding and dietary restriction on cholesterol absorption in rabbits

Plasma cholesterol and cholesterol absorption were measured in rabbits given either a standard or cholesterol-rich diet which were fed either ad libitum or reduced to 50% of the control ration. The results confirmed the aggravating effect of dietary restriction on the plama cholesterol response to cholesterol feeding. Hypercholesterolemia was doubled when cholesterol feeding was associated with reduced dietary intake. The percentage of cholesterol absorbed increased significantly in cholesterolfed rabbits on normal caloric ration, while dietary restriction had no effect on this parameter either with the standard or the cholesterol-rich diet. These data indicate that the mechanisms by which plasma cholesterol increases in response to cholesterol feeding involve increased cholesterol absorption. Nevertheless the aggravating effect of dietary restriction cannot be attributed to increased cholesterol absorption.     

Effect of garlic (Allium sativum linn) on serum lipoproteins and lipoprotein cholesterol levels in albino rats rendered hypercholesteremic by feeding cholesterol

The hypocholesteremic activity of garlic was tested by incorporating freeze-dried garlic powder at 0.5, 1.0, 2.0 and 3.0% levels in an atherogenic diet fed to rats. It was observed that 0.5 and 1.0% levels were not effective whereas the other 2 levels were. The group fed 2.0% garlic powder had much lower serum cholesterol level than the one fed 3%. The increased levels of low density lipoproteins (LDL) and LDL-cholesterol in rats fed the atherogenic diet were partly reversed in rats receiving a supplement of 2% garlic powder. On a cholesterol-containing diet, high density lipoproteins (HDL) and HDL-cholesterol levels were decreased. Inclusion of garlic powder in the atherogenic diet enhanced the percentage of HDL whereas no change was observed in HDL cholesterol levels. Commercial garlic pearls (equivalent to 0.15% garlic powder in the diet) produced a significant decrease in serum and liver cholesterol levels in rats fed the atherogenic diet. On the other hand, asafoetida at 1.5% level failed to reduce the serum cholesterol levels in the cholesterol-fed rats.     

Effect of liposome-encapsulated hemoglobin on triglyceride, total cholesterol, low-density lipoprotein, and high-density lipoprotein cholesterol measurements

The present study investigated the effect of liposome-encapsulated hemoglobin (LEH), an experimental oxygen-carrying resuscitation fluid, on triglyceride, total cholesterol, and low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol measurements. In vivo, the intravenous infusion of LEH (5.6 mL/kg, n=6) elevated serum triglycerides (+92% vs. baseline, P<.05), total cholesterol (+25% vs. baseline, P<.01), LDL cholesterol (+72% vs. baseline, P<.01) and had no effect on serum HDL cholesterol. In addition, LEH did not alter the elevation in serum triglycerides (+302% vs. baseline, P<.01) and LDL cholesterol (+86% vs. baseline, P<.01) induced by lipopolysaccharide (3.6 mg/kg, i.v., n=6). Ex vivo, measurements of triglycerides and total cholesterol as well as LDL and HDL cholesterol in whole blood from naive rats were not changed by the addition of LEH (0–50%, n=6). In vitro, the addition of a fixed concentration of LEH (50%, n=6) to varying concentrations of cholesterol solution (0–50%), or vice versa, had no effect on cholesterol determination. It is therefore concluded that LEH only minimally affects serum levels of triglycerides, total cholesterol, LDL cholesterol, and HDL cholesterol and does not interfere with their measurement.     

The use of the computer in serum lipid and lipoprotein analysis

The usefulness of computers in data evaluation is generally recognized; however, the problem of utilizing a computer in the most intelligent manner deserves careful consideration. Several programs are described which aid in serum lipid and lipoprotein analysis. Two programs requiring a minimum of manual measurements have been developed to analyze gas-liquid chromatograms. These programs perform many operations including corrections for baseline, linearity, Gaussian resolution, and variation in column conditions. The presentation in some detail of one of these programs for NCH elemental analysis illustrates the development and refinement of a program for a specific instrument. Finally, a general purpose statistical analysis program has been developed which greatly aids in summarizing and correlating data from these programs, as well as other sources, such as ultracentrifugal data.     

Minimal effective dose on serum cholesterol concentration and the safety evaluation of dressing containing plant sterol in Japanese subjects

We examined the minimal effective dose on serum cholesterol concentration and the safety of dressing containing plant sterol in humans. EXP.1: Sixty-eight healthy Japanese males (total cholesterol (TC) > or = 170 mg/dL) were randomly divided into four groups, and were given 0, 400, 800 or 1200 mg/day of plant sterol in 15 g dressing for 4 weeks followed by the washout period of 4 weeks. Although there were no significant differences in serum TC and low-density lipoprotein cholesterol (LDL-C) concentrations among all groups after feeding plant sterol for 4 weeks, in 36 subjects with TC > or = 220 mg/dL, serum LDL-C concentration tended to reduce when received 800 or 1200 mg of plant sterol, and the difference between 0 and 1200 mg groups was statistically significant. The difference between 0 and 800 mg groups was near significant (p=0.053). Intake of 400 mg of plant sterol did not change serum LDL-C concentration. EXP.2: Twenty-one healthy Japanese subjects (TC > or = 180 mg/dL, 10 men, 11 women) were given 2400 mg/day of plant sterol in 45 g dressing for 4 weeks. Clinical data were all remained normal. These results indicated that minimal effective dose of the plant sterol on serum cholesterol concentration in healthy male subjects is around 800 mg/day, and intake of 2400 mg/day of plant sterol is regarded to be safe.     

Simulation of the composition and proportions of anions in polymerized silicate melts

A new statistical model is proposed for describing an equilibrium structure of polymer complexes in a silicate melt. The model makes it possible to calculate the molecular-mass distributions of polyanions of the general formula (Si _i O_{3i + 1 ? j} )^{2(i + 1 ? j} )^?, where i is the number of silicon atoms and j is the number of intramolecular closures of bridging bonds. The proposed model is implemented as the STRUCTON computer program (version 1.1, 2006) intended for calculating the composition and proportions of polyanions at different degrees of polymerization of the system. The executable code is implemented on personal computers. The distributions of Q ⁿ structons, which are obtained experimentally from Raman and NMR spectroscopic data or evaluated theoretically, are used as input parameters for the computer program. The testing calculations are performed with the STRUCTON program for three arbitrary distributions of Q ⁿ particles corresponding to different degrees of polymerization 0.25 ≤ α ≤ 0.49 for the model system containing 104 initial structons. The results of the statistical simulation have demonstrated that a limited ensemble of polymer complexes is formed in the system, so that the mean number of different types of complexes varies from 46 to 141. This result correlates with an increase in the mean size of anions from 1.87 to 8.60 and with a decrease in the total number of polymer particles from 5320 to 1166 in the aforementioned range of degrees of polymerization α.     

Susceptibility of serum lipids to copper-induced peroxidation correlates with the level of high density lipoprotein cholesterol

As a first step in evaluating the significance of our recently developed method of monitoring the kinetics of copper-induced oxidation in unfractionated serum, we recorded the kinetics of lipid oxidation in the sera of 62 hyperlipidemic patients and analyzed the correlation between oxidation and lipid composition of the sera [high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides]. We used six factors to characterize the kinetics of oxidation, namely, the maximal absorbance of oxidation products (OD_max), the maximal rate of their production (V _max), and the time at which the rate was maximal (t _max) at two wave-lengths (245 nm, where 7-ketocholesterol and conjugated dienic hydroperoxides absorb intensely, and 268 nm, where the absorbance is mostly due to dienals). The major conclusions of our analyses are that: (i) Both OD_max and V _max correlate positively with the sum of concentrations of the major oxidizable lipids, cholesterol, and cholesteryl esters. (ii). The value of t _max, which is a measure of the lag preceding oxidation and therefore reflects the resistance of the serum lipids to copper-induced oxidation, exhibits a negative correlation with HDL cholesterol. Although this finding accords with the observation of shorter lags for HDL than for LDL, it is apparently inconsistent with the role of HDL as an antirisk factor in coronary heart diseases.     

The effect of dietary supplementation of cholesterol and its subsequent withdrawal on the liver lipids and serum lipoproteins of chickens

Two groups of male chickens were fed either a control diet (group N) containing a standard poultry ration admixed with 10% corn oil or a cholesterol diet (group C) in which the control diet was supplemented with 1% cholesterol. After 6 weeks on the diets, a negligible amount of very low density lipoprotein (VLDL) was found in the serum from control animals. On the other hand, the serum VLDL from the cholesterol-fed birds was the predominant lipoprotein and carried 72% of the total serum lipids. Surprisingly this lipoprotein from cholesterol-fed animals was very low in triglycrides (6%) and high in total cholesterol (77%). While the level of serum low density liporotein was unaffected by the ingestion of cholesterol, the concentration of total lipids and phospholipids in the high density lipoprotein decreased in cholesterol-fed animals. The greatest change in liver lipids from animals fed cholesterol was found in the cholesterol esters, whereas the unesterified cholesterol, triglyceride and phospholipid varied slightly or remained constant. In normal animals the distribution of cholesterol between the liver and the serum was about equal, whereas in the cholesterol-fed birds the liver accounted for 80% of the cholesterol found in the liver-serum pool. In order to determine how the hypercholesterolemic bird responds to the withdrawal of cholesterol from the ration, a diet-exchange experiment was conducted. In this study the birds that were originally fed the cholesterol diets (group C) for 6 weeks were placed on the control diet (group CN) and the birds fed the control diet (group N) for 6 weeks were given the cholesterol diet (group NC). At periodic intervals, 1, 3, 7 and 14 days following the change of diets, 3–5 animals from each group were sacrificed, and analyses performed on their serum lipoproteins and liver lipids. Within one day after the diet substitution, there was a 31-fold increase and a 46% decrease, respectively, in the serum VLDL concentration in groups NC and CN as compared with their corresponding steady state values (groups N and group C, respectively). The liver cholesterol increased 4-fold and decreased 40%, respectively, in the two groups NC and CN as compared with the values obtained before the diet substitution. It is suggested that the concentration of cholesterol in the liver is the principal factor controlling cholesterol metabolism in chickens fed a hypercholesterolemic diet. This represents a portion of a Ph.D. thesis submitted by A.W. Kruski to the University of Illinois in February 1971.