Obesity and serum lipids: an evaluation of the relative contribution of body fat and fat distribution to lipid levels

The association of obesity and hyperlipidemia does not mean that fatness per se is the primary determinant of the lipid abnormality. To evaluate the contribution of fatness to fasting levels of serum triglycerides (TG), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C), we analyzed data on 368 caucasian adults (286 women, 82 men) consecutively entering a weight control program. Although most subjects were overweight, the population represented a wide spectrum of body weights and lipid levels. Study variables included body fat mass (by total body water), fat free mass (FFM), body build (chest to height ratio), fat cell size and number (from bilateral buttock biopsy specimens), upper-lower body fat pattern by arm to thigh circumference ratio, central-peripheral fat pattern by subcapsular to triceps skinfold ratio, waist to hip ratio, and the presence or absence of diabetes. Our results concurred with previously noted correlations of body weight with TG (r = 0.29, P less than 0.0001) and with HDL-C (r = -0.28, P less than 0.0001) at least in the larger sample of women, but there was no significant correlation with LDL-C (r = -0.06). In order to evaluate the relative contribution of the various components of body composition and fat distribution to lipid levels, stepwise regression analyses were performed on the subgroups of women and men. Among women: TG level was predicted best by FFM, upper body fat pattern, age, and diabetes (explaining 30 percent of TG variance); LDL-C level was predicted by age only (explaining 12 percent of variance); and HDL-C level was predicted by body build only (8 percent). Among men: TG level was predicted best by central and upper body fat patterns and diabetes (31 percent of variance); LDL-C and HDL-C levels were not significantly predicted by any of the 11 study variables. These results, obtained from cross-sectional analysis of a predominantly obese sample, suggest that lipid levels may be more directly related to body fat pattern, fat free mass and body build than to body fatness itself.

A mechanism by which atrial natriuretic factor mediates its glomerular actions

Differential in vivo glomerular effects of atriopeptin I (AP I) and atriopeptin III (AP III) were studied in parallel with in vitro physiological and biochemical parameters. In anesthetized Sprague-Dawley rats, AP III, but not AP I, significantly increased glomerular filtration rate. Image analysis microscopy was used to assess the effect of AP I and AP III on angiotensin II (ANG II)-induced contraction of cultured rat glomerular mesangial cells. AP III, but not AP I, inhibited ANG II-induced mesangial cell contraction in a concentration-dependent manner. Additional inhibitory agents included exogenous DBcGMP, 8-BrcGMP, Na nitroprusside, and DBcAMP. AP III stimulated mesangial cell cGMP with a lower threshold and greater maximum stimulation than AP I. Neither agent stimulated cAMP accumulation. Since mesangial cell contractility may regulate the glomerular capillary surface area, these results suggest that AP III partially mediates its glomerular effects through inhibition of ANG II-induced mesangial cell contraction. Whereas cGMP is not clearly implicated as the mediator of this effect, it appears that both cGMP and cAMP may regulate the state of mesangial cell contractility.

Regulation of fibronectin receptor distribution by transformation, exogenous fibronectin, and synthetic peptides

Recent studies have shown that fibronectin and its 140K membrane receptor complex are spatially associated with microfilaments to form cell surface linkage complexes which are thought to mediate adhesive interactions between fibroblasts and their substrata. We examined the regulation of the organization of these cell surface structures in transformed and fibronectin-reconstituted cells as well as in cells treated with a competitive synthetic peptide inhibitor of fibronectin binding to its receptor. Correlative localization experiments with interference reflection microscopy and double-label or triple-label immunofluorescence revealed a concomitant loss of fibronectin, 140K receptor, and alpha-actinin colocalization at cell substratum extracellular matrix contact sites after transformation of chick fibroblasts by wild-type or temperature-sensitive Rous sarcoma viruses (RSV). Western and dot immunoblot analyses established that although similar total quantities of intact 140K molecules were present in the transformed cell cultures, significantly more was released into the culture medium of transformed cells. The 140K molecules on transformed cells were available for interaction with exogenously added fibronectin, which could reconstitute fibronectin-140K linkage complexes. In such fibronectin reconstitution experiments, many cells expressed both fibronectin-140K-actin linkage complexes and RSV pp60src, indicating that the morphological reversion could occur even in the continued presence of RSV transformation. The synthetic peptide Gly-Arg-Gly-Asp-Ser derived from the sequence of the cell-binding region of fibronectin could also prevent the organization of fibronectin-140K linkage complexes. Our results suggest that fibronectin interaction with cells regulates the organization of fibronectin receptor complexes and cytoskeletal components at the cell surface.

[Mechanism of cell damage by hematoporphyrin derivatives (HPD) plus light--I. Photooxidation of hepatoma cell membrane by HPD plus light]

Ascitic hepatoma cells of mice were incubated with three HPD. After the cell-bound HPD was treated by visible light, the product of membrane lipid peroxidation--malondialdehyde (MDA) was determined. The results showed that the MDA level increased with HPD concentration and exposure time, but it was unchanged in the control. Beta-carotene, a quencher of singlet oxygen, could inhibit the lipid photooxidation of the membrane of cell-bound HPD resulting in a decrease of MDA level which decreased with increase of beta-carotene concentration. Adding vitamin E in vitro and vivo, formation of the product of membrane lipid peroxidation of cell-bound HPD by light was inhibited and the MDA level decreased with the increase of vitamin E concentration. These results show that the singlet oxygen, produced by HPD bound cells following light activation, reacts directly with the polyunsaturated fatty acids on cell membrane to produce lipid peroxides leading to cellular damage.

Anti-tumor properties of lymphocytes activated by the oxidizing mitogens

Human peripheral blood mononuclear cells when activated with the oxidizing mitogens, neuraminidase/galactose oxidase or sodium periodate, express cytolytic activity for freshly isolated tumor cells and for a variety of cell lines, including NK-resistant solid tumor lines. Normal lymphoid cells are not targets for cytotoxicity and do not inhibit lysis of susceptible targets mediated by the oxidizing mitogen-activated mononuclear cells. The cytotoxic response is rapidly generated and reaches peak levels at 48 hr. The oxidizing mitogens induce expression of IL 2 receptors on peripheral blood mononuclear cells. Combined treatment of cells with IL 2 and the oxidizing mitogens results in a marked enhancement of cytotoxicity. Enhancement is achieved at levels of IL 2 that alone result in minimal generation of cytotoxic cells. Growth of a human renal cancer cell line in nude mice was inhibited when the renal cancer cells were injected together with oxidizing mitogen-activated human mononuclear cells. These studies indicate that oxidizing mitogen-activated cells provide a potentially valuable source of material for the adoptive immunotherapy of tumors.

Anti-tumor properties of lymphocytes activated by the oxidizing mitogens

Human peripheral blood mononuclear cells when activated with the oxidizing mitogens, neuraminidase/galactose oxidase or sodium periodate, express cytolytic activity for freshly isolated tumor cells and for a variety of cell lines, including NK-resistant solid tumor lines. Normal lymphoid cells are not targets for cytotoxicity and do not inhibit lysis of susceptible targets mediated by the oxidizing mitogen-activated mononuclear cells. The cytotoxic response is rapidly generated and reaches peak levels at 48 hr. The oxidizing mitogens induce expression of IL 2 receptors on peripheral blood mononuclear cells. Combined treatment of cells with IL 2 and the oxidizing mitogens results in a marked enhancement of cytotoxicity. Enhancement is achieved at levels of IL 2 that alone result in minimal generation of cytotoxic cells. Growth of a human renal cancer cell line in nude mice was inhibited when the renal cancer cells were injected together with oxidizing mitogen-activated human mononuclear cells. These studies indicate that oxidizing mitogen-activated cells provide a potentially valuable source of material for the adoptive immunotherapy of tumors.

Chronic measurement, using a Doppler probe, of uterine artery flow in the gravid guinea-pig

A chronic animal model is described which permits for the first time the continuous measurement of uterine artery blood flow velocity in the pregnant guinea-pig by using a miniaturized Doppler flow probe. Preliminary validation revealed that alterations in actual blood flow are directly and proportionally related to the change in the Doppler shift (r = 0.984) from 0 to 100 ml/h. The velocity signal baseline was as stable as that of systemic blood pressure. Depending upon the individual animal's flow velocity, a deviation of 2-5% from baseline was statistically significant. With experience, greater than 90% of preparations were successful and a 30-day interval was often available for study. Uterine artery flow velocity increased steadily between 45 and 55 days of gestation. Instrumentation did not result in fetal growth retardation. A reduction in flow velocity occurred during general anaesthesia using ketamine and the antianxietal xylazine. In agreement with the reports of other investigators using a different model, both hydralazine and angiotensin II increased uterine blood velocity and adrenaline reduced it.

Quantitation of myelination and demyelination by the measurement of myelin basic protein by ELISA

Utilizing a competitive inhibition enzyme-linked immunosorbent assay (ELISA) we measured the amount of myelin basic protein (MBP) in brain, liver, and kidney of newborn mouse and compared these values with myelinated cerebellar explant cultures under various conditions. Explant cultures demyelinated with anti-myelin serum showed a 90% decrease in MBP when compared with controls. These results correlated with myelination and demyelination as observed by light microscopy. Newborn tissues including brain showed only negligible activity for MBP. This technique provides a sensitive and objective method for quantitating in-vitro demyelination.

Rhodopsin's amino terminus is a principal antigenic site

Antisera and monoclonal antibodies to rhodopsin were examined for their binding specificity to rhodopsin by using peptides from the rhodopsin sequence as competitors for antibody binding to rhodopsin in an enzyme-linked immunoassay. Monoclonal antibodies tested were raised in mice against bovine and rat rhodopsin. Antisera tested were raised in sheep against bovine rhodopsin and in rabbits against human rhodopsin. Peptides were synthesized from the bovine rhodopsin sequences 2-32, 1-12, 13-23, 24-34, 5-11, 231-252 and 331-348 for use as competitors in the immunoassay. A mixture of soluble CNBr peptides, and the purified CNBr peptide representing the sequence 2-39 were also employed. The monoclonal antibodies were all anti-amino-terminal in their binding specificity, although each recognized slightly different regions of the amino terminus. Each of the three antisera was predominantly directed against rhodopsin's amino terminus. We conclude that the amino-terminal 30 or more amino acids, and particularly the amino-terminal 15 amino acids, represent a principal antigenic region of the rhodopsin molecule.