E. Douglas Rees

A study of the mechanism of intestinal absorption of benzo(a)pyrene

Abstract 1. 1. Benzo(a)pyrene and other polynuclear aromatic hydrocarbons are readily absorbed from the gut when fed to rats, but little is known about the mechanism of the absorption. To study the mechanism, everted sacs of small intestine were incubated in a medium containing a lipid emulsion of benzo(a)pyrene (50–1500 μM). After incubation, the concentration of benzo(a)pyrene in the sac tissue and in the medium inside the sac was determined by spectrofluorimetric analysis of chloroform extracts. 2. 2. For incubation medium concentrations above 200 μM, accumulation of benzo(a)pyrene in the sac tissue increased exponentially with increase in incubation medium concentration. The transfer of benzo(a)pyrene from sac tissue to the inside medium was proportional to the concentration in the sac tissue. The regression lines were not greatly influenced by fasting, rat age, or sex. Comparison of incubation at 0, 23 and 42° with that at 37° showed a lowered sac accumulation at 0° and an increase in accumulation with temperature. Anaerobiosis and/or 0.1 M iodoacetate did not appreciably influence sac tissue accumulation. Benzo(a)pyrene also accumulated in strips of small and large intestine and slices of liver and kidney and epididymal fat. The feature of exponential accumulation was not limited to tissue, for adsorption isotherms and time curves for string incubated in the same media has the same forms as those obtained for the sacs. Intragastric doses of benzo(a)pyrene appeared quickly in thoracic duct lymph and reached a peak in 3–4 h, but no more than 20% of the dose was recovered in the lymph. An exponential relationship between size of intragastric dose and concentration in adipose and mammary tissue, 18 h later, was noted. 3. 3. The data are in accord with a mechanism of physical adsorption of benzo(a)pyrene to the intestinal mucosal surfaces and them passive diffusion into and through the intestinal wall. Two phases of adsorption are postulated: first, unilayer (Langmuir) adsorption, then multilayer (Polanyi) adsorption which would account for the exponential nature of the accumulation.

NORMAL SERUM-LIPIDS IN RENAL-TRANSPLANT PATIENTS

In contrast to previous reports, most patients (78%) with a successful renal transplant being followed up at the University of Kentucky Medical Center had a normal serum-lipid profile. The patients with hyperlipidaema (22%) had normal fasting insulin levels; they received similar immunosuppressive therapy but were significantly older and more obese than those with normal lipids. This lower prevalence of hyperlipidaemia and the absence of fasting hyperinsulinaemia are tentatively attributed to the use of alternate-day corticosteroid therapy in stable renal-transplant patients. If confirmed, the relative infrequency of hyperlipidaemia in patients of alternate-day corticosteroid therapy would be an additional advantage of that therapy over a daily regimen.

The helical content of zein, a water insoluble protein, in non-aqueous solvents.

The conformation of zein, a seed protein from corn, was determined by optical rotary dispersion measurements in a wide variety of nonaqueous solvents. Over a wide range of dielectric constants, in pure and mixed solvent systems, the helical content was independent of dielectric constant. Determination of the helical content of insulin and ribonuclease in several of these solvents indicated a variation in secondary structure comparable of that of zein. Though virtually insoluble in water, zein not only is a globular protein in nonaqueous solutions, but has conformational properites characteristic of more conventionally behaving globular proteins.

Influence of five anti-cancer drugs on the induction and growth of experimental mammary cancers: comparison with ovariectomy.

The effects of cyclophosphamide, thiotepa, methotrexate, vinblastine, and 5‐fluorouracil on mammary carcinomas induced in female rats by 3‐methylcholanthrene were assessed. In one factorial experiment a group of rats received drugs concurrently with 3‐methylcholanthrene; a second (delay) group received drugs in the postcarcinogen period during which cancers became palpable. Mortality was less and drug effectiveness greater in the delay group. Methotrexate and 5‐fluorouracil significantly prolonged time of tumor appearance but combination of the two showed a negative interaction. In a second experiment simultaneous administration of drugs and 3‐methylcholanthrene was shown to increase mortality, especially in older rats. Drugs delayed tumor appearance but elicited more tumors than expected in older (relatively resistant) rats. Some rats receiving drugs (but not 3‐methylcholanthrene) developed mammary carcinomas. In a study of the effect on established carcinomas of cyclophosphamide, 5‐fluorouracil, 3‐methylcholanthrene and ovariectomy, ovariectomy elicited more rapid regressions in more tumors. Drug treatment prior to ovariectomy did not affect hormone dependency.

Halofenate in the treatment of type II hyperlipoproteinemia. Double blind comparison with clofibrate.

A double-blind study comparing halofenate, a new lipid-lowering investigation drug, with an established drug, clofibrate, was conducted on 33 clinic patients with Type II hyperlipoproteinemia for a period of 48-96 weeks. All but 10 patients had some type of symptomatic major vascular disease. With respect to serum cholesterol levels, a comparable proportion (56-59%) of patients in each group responded to the respective treatment but the magnitude of lowering was substantially less for the halofenate responders (12% mean decrease versus 25%). Type IIa patients in both groups were more likely than Type IIb patients to have a favorable cholesterol-lowering response. Weight gain of 5% or greater was prejudicial to cholesterol lowering. In the case of serum triglycerides, the proportion of patients responding to clofibrate treatment was somewhat greater (87% versus 57% for halofenate) but the mean magnitude of lowering (27-34%) was comparable for responders in the two groups. Weight gain did not influence appreciably the triglyceride-lowering effect. Elevated concentrations of triglyceride (Type IIb) in the control period favored a triglyceride lowering response by clofibrate but was only a moderate influence on the response to halofenate.

Hormonal Influence on Fatty Acid Composition of Sterol Ester and Phospholipid Fractions of Experimental Mammary Carcinomas

Summary The fatty acid compostions of the sterol ester and phospholipid fractions of mammary carcinomas and a derived, transplantable sarcoma were determined; the composition of the sarcoma differed from that of the carcinoma. Hormonal modification (ovariectomy plus 50 μg estradiol-17β with or without progesterone) of hosts bearing mammary carcinomas did not per se result in changes in the fatty acid composition of the phospholipid fraction of the carcinomas, except in those carcinomas which became laden with fat. The phospholipid and sterol ester fractions of fat-laden carcinomas had increased proportions of the shorter chain (C10-14) fatty acids and decreased proportions of polyunsaturated fatty acids but differences were not as great as in the triglycerides.

Effects of Estradiol-17β and Progesterone on Experimental Mammary Carcinoma Lipid

Like the parent mammary epithelium, many of the mammary carcinomas induced by the polycyclic hydrocarbons, 3-methylcholanthrene (3-MC) and 7,12-dimethylbenz(a)anthracene (DMBA), respond to hormonal changes in the host. Two kinds of responsiveness have been demonstrated: a) regression after ovariectomy, and b) lipid accumulation following high doses of estradiol-17β with or without progesterone. Shay et al (1,2) showed the frequent occurrence of mammary carcinomas in the Wistar rat following intragastric administration of 3-MC dissolved In olive oil, and they also demonstrated that the carcinomas regress after ablation of the ovaries. Huggins and his associates (3,4) later discovered the marked sensitivity of the breast tissue of the young, female Sprague-Dawley rat to 3-MC and DMBA. Dose schedules have been worked out by Huggins so that mammary carcinomas now can be induced with virtual certainty in 1007. of these animals. Most of the animals bear several tumors and though some tumors may become very large (100 gms or more), the hosts generally survive for several months. Most of the carcinomas are strikingly hormone dependent in that they regress rapidly after ovariectomy or hypophysectomy.

Optimal selection of flasks for the indirect method of manometry

Abstract The selection, on the basis of flask volume and fluid volume, of the members of a flask pair for the indirect method of manometry is very important. A poor choice yields erratic results even with flawless experimental technique. In order to determine optimal combinations, formulae of the indirect method were analyzed, and an expression for the statistical variance associated with different combinations of flask and fluid volumes was derived. Graphs and a table were constructed and can be used to select suitable combinations. As a general rule, in order to obtain the minimum variance, flasks of equal volumes should be selected and used with the maximum practical difference in fluid volumes. It was also found that the choice of flask and fluid volumes does not depend on γ; an optimal combination has a minimum variance for all values of γ.

Mammary Gland Fatty Acids in Rats of Different Susceptibility to Mammary Carcinoma Induction

Summary Although young female rats of the Sprague-Dawley and Osborne-Mendel strains are quite vulnerable to the induction of mammary cancer by intragastric instillation of 7,12-dimethylbenz (a) anthracene and rats of Fischer, Marshall, and Long-Evans strains are relatively resistant, the fatty acid composition of mammary glands from rats of these five strains were comparable. A sex difference was noted in three strains with males having a somewhat greater proportion of 18:2 (linoleic acid) and a lower proportion 16:1 (palmitoleic acid) than females. The phospholipid levels of the breasts tissue of both male and females in all five strains were quite low relative to the total lipid.

Vulnerability of the Subterminal Chromosomes of Cultured Rat Mammary Cancer Cells to Alterations.

Summary Permanent lines of cells cultured from a 3-methylcholanthrene and a 7,12 -dimethylbenzanthracene induced rat mammary cancer have been obtained. Although the most common chromosome number of cells in both lines was the diploid number, the 3-MC line had many hypodiploid cells and the DMBA line had many tetraploid and hypotetraploid cells. Deviations from the normal rat karyotype were the rule even in diploid cells. The most common alteration was absence of subterminal chromosomes.